REVIEW OF LITERATURE

9

CHAPTER 2

REVIEW OF LITERATURE

2.1 Introduction

A detailed review of literature on the performance of different types of concrete

specimens that were exposed to higher temperature is reported in this chapter.

Shape of specimen, size of specimen, magnitude of temperature load applied on the

specimen, duration of heating, time temperature curve, rate of heating, rate of

cooling, time taken for hot test after curing period, time taken for load test after

heating, stressed/unstressed test on hot members, type of cooling adopted on heated

specimens etc are the parameters that influence the test results. To completely

understand the behavior of concrete under elevated temperature, it is necessary to

consider all the key factors involved while designing the experimental setup. Grade

of concrete, type of cement, type of admixture, type of aggregate, water cement

ratio, density of concrete, reinforcement percentage, cover to the reinforcement etc

are some of the important factors that influence the performance of concrete at

elevated temperature. However it is difficult to carry out experimental

investigations considering all the parameters that influence the performance of

concrete exposed to elevated temperatures. Hence different researchers considered

different sets of parameters. This chapter summarizes the salient features of the

experimental and analytical investigations reported in the literature. The analysis of

the data indicates that the behaviors of Normal Compacting Concrete and Self

Compacting Concrete are different. The effects of elevated temperatures on the

properties of concrete such as compressive strength, tensile strength, flexural

strength and spalling reported in the literature are summarized.

A review of methods used by various investigators for testing concrete at elevated

temperature indicates that, the tests can be categorized into three types namely

stressed test, unstressed test and unstressed residual strength test. In stressed tests, a

preload is applied to the specimen prior to heating and the load is sustained during

the heating period. Heat is applied at a constant rate until a target temperature is

reached, and this temperature is maintained for a time until a thermal steady state is

10

achieved. Load is then increased at a prescribed rate until the specimen fails. In the

unstressed test, the specimen is heated, without preload at a constant rate to the

target temperature, which is maintained until a thermal steady state is achieved.

Load is then applied at a prescribed rate until failure occurs. In unstressed residual

strength test, the specimen is heated without preload at a prescribed rate to the

target temperature, which is maintained until a thermal steady state is reached

within the specimen. The specimen is then allowed to cool, following a prescribed

rate to room temperature. Load is applied on the specimen at room temperature until

the specimen fails. The first two types of test are suitable for accessing the strength

of concrete during high temperatures, while the later is excellent for finding the

residual properties after the high temperature. It is reported by Abrams [1973]1 that

the last method gives the lowest strength and is therefore more suitable for getting

the limiting values of strength.

2.2 Review of Literature

2.2.1 Development of Self Compacting Concrete

Bertil Persson (2001)10

carried out an experimental and numerical study on

mechanical properties, such as strength, elastic modulus, creep and shrinkage of self

compacting concrete and the corresponding properties of normal compacting

concrete. The study included eight mix proportions of sealed or air cured specimens

with water binder ratio (w/b) varying between 0.24 and 0.80. Fifty percent of the

mixes were SCC and rests were NCC. The age at loading of the concretes in the

creep studies varied between 2 and 90 days. Strength and relative humidity were

also found. The results indicated that elastic modulus, creep and shrinkage of SCC

did not differ significantly from the corresponding properties of NCC.

Nan Su et al (2001)73

proposed a new mix design method for self compacting

concrete. First, the amount of aggregates required was determined, and the paste of

binders was then filled into the voids of aggregates to ensure that the concrete thus

obtained has flowability, self compacting ability and other desired SCC properties.

The amount of aggregates, binders and mixing water, as well as type and dosage of

super plasticizer to be used are the major factors influencing the properties of SCC.

11

Slump flow, V-funnel, L-flow, U-box and compressive strength tests were carried

out to examine the performance of SCC, and the results indicated that the proposed

method could be used to produce successfully SCC of high quality. Compared to

the method developed by the Japanese Ready Mixed Concrete Association

(JRMCA), this method is simpler, easier for implementation and less time

consuming and requires a smaller amount of binders and saves cost.

Bouzoubaa and Lachemi (2001)12

carried out an experimental investigation to

evaluate the performance of SCC made with high volumes of FlyAsh (FA). Nine

SCC mixtures and one control concrete were made during the study. The content of

the cementitious materials was maintained constant (400kg/m3), while the

water/cementitious material ratios ranged from 0.35 to 0.45. The self compacting

mixtures had a cement replacement of 40%, 50%, and 60% by Class F flyash. Tests

were carried out on all mixtures to obtain the properties of fresh concrete in terms

of viscosity and stability. The mechanical properties of hardened concrete such as

compressive strength and drying shrinkage were also determined. The SCC mixes

developed a 28 day compressive strength ranging from 26 to 48 MPa. They reported

that economical SCC mixes could be successfully developed by incorporating high

volumes of Class F flyash.

Sri Ravindrarajah et al (2003)89

made an attempt to increase the stability of fresh

concrete (cohesiveness) using increased amount of fine materials in the mixes. They

reported about the development of self compacting concrete with reduced

segregation potential. The systematic experimental approach showed that partial

replacement of coarse and fine aggregate with finer materials could produce self

compacting concrete with low segregation potential as assessed by the V-Funnel

test. The results of bleeding test and strength development with age were

highlighted by them. The results showed that flyash could be used successfully in

producing self compacting high strength concrete with reduced segregation

potential. It was also reported that flyash in self compacting concrete helps in

improving the strength beyond 28 days.

12

Hajime Okamura and Masahiro Ouchi (2003)30

addressed the two major issues

faced by the international community in using SCC, namely the absence of a proper

mix design method and jovial testing method. They proposed a mix design method

for SCC based on paste and mortar studies for super plasticizer compatibility

followed by trail mixes. However, it was emphasized that the need to test the final

product for passing ability, filling ability, flowability and segregation resistance was

more relevant.

Mohammed Sonebi (2004)67

developed medium strength self compacting concrete

(MS-SCC) by using pulverised fuel ash (PFA) with a minimum amount of super

plasticizer. A factorial design was carried out to mathematically model the influence

of key parameters on filling ability, passing ability, segregation resistance and

compressive strength, which are important for the successful development of

medium strength self compacting concrete incorporating PFA. The parameters

considered in the study were the contents of cement and PFA, water to powder

(cement + PFA) ratio (w/p) and dosage of SP. The responses of the derived

statistical models are slump flow, fluidity loss, Orimet time, V-funnel time, L-box,

rheological parameters, segregation resistance and compressive strength at 7, 28 and

90 days. Twenty one mixes were prepared to derive the statistical models, and five

were used for the verification and the accuracy of the developed models. The

models are valid for mixes made with 0.38 to 0.72 w/p, 60 to 216 kg/m3 of cement

content, 183 to 317 kg/m3 of PFA and 0% to 1% of SP, by mass of powder. The

influences of w/p, cement and PFA contents, and the dosage of SP were

characterised and analysed using polynomial regression equations, which can

identify the primary factors and their interactions on the measured properties. The

results showed that MS-SCC can be achieved with a 28 day compressive strength of

30 to 35 MPa by using up to 210 kg/m3 of PFA.

Mustafa Sahmaran et al (2006)71

evaluated the effectiveness of various mineral

additives and chemical admixtures in producing Self Compacting Mortars (SCM).

For this purpose, four mineral additives (flyash, brick powder, limestone powder

and kaolinite), three super plasticizers and two viscosity modifying admixtures were

13

used. Within the scope of the experimental program, 43 mixtures of SCM were

prepared keeping the amount of mixing water and total powder content (portland

cement and mineral additives) constant. Workability of the fresh mortar was

determined using mini V-Funnel and mini slump flow tests. The setting time of the

mortars, was also determined. The hardened properties that were determined

included ultrasonic pulse velocity and strength at 28th

and 56th

days. It was

concluded that among the mineral additives used, flyash and limestone powder

significantly increased the workability of SCMs. On the other hand, especially

flyash significantly increased the setting time of the mortars, which can be

eliminated through the use of ternary mixtures, such as mixing flyash with

limestone powder. The two polycarboxyl based SPs yield approximately the same

workability and the melamine formaldehyde based SP was not as effective as the

other two.

Mustafa Sahmaran and Ozgur Yaman (2007)72

studied the fresh and mechanical

properties of a fiber reinforced self compacting concrete incorporating high volume

flyash that does not meet the fineness requirements of ASTM C 618. A poly

carboxylic based super plasticizer was used in combination with a viscosity

modifying admixture. In mixtures containing flyash, 50% of cement by weight was

replaced with flyash. Two different types of steel fibers were used in combination,

keeping the total fiber content constant at 60 kg/m3. Slump flow time and diameter,

V-funnel, and air content were found to assess the fresh properties of the concrete.

Compressive strength, splitting tensile strength, and ultrasonic pulse velocity were

determined for the hardened concrete. The results indicated that high volume coarse

flyash can be used to produce fiber reinforced self compacting concrete, even

though there is some reduction in the strength because of the use of high volume

coarse flyash.

Burak Felekoglu et al (2007)14

made an investigation on five self compacting

concrete mixtures with different combinations of water/cement ratio and super

plasticizer dosage levels. Slump flow, V-funnel and L-box tests were carried out to

determine the optimum parameters for the self compactibility of mixtures.

14

Compressive strength development, modulus of elasticity and splitting tensile

strength of mixtures were also studied. It was reported that optimum water/cement

ratio for producing SCC was in the range of 0.84 to 1.07 by volume. The ratios

above and below this range may cause blocking or segregation of the mixture. The

Splitting tensile strengths of the SCC mixes were found to be higher and the values

of Modulus of elasticity were found to be lower than those of NCC.

Binu Sukumar et al (2007)11

replaced high volume flyash in the powder, based on

a rational mix design method to develop self compacting concrete. High flyash

content necessitated the study on the development of strength at early ages of curing

which is a significant factor for the removal of formwork. Rate of gain of strength at

different periods of curing such as 12 h, 18 h, 1 day, 3 days, 7 days, 21 days and 28

days were studied for various grades of different SCC mixes and suitable relations

were established for the gain in strength at the early ages in comparison to the

Conventional Concrete (CC) of same grades. Relations were also formulated for the

compressive strength and the split tensile strength for different grades of SCC

mixes. It was observed that the rate of gain in strength for different grades of SCC

was slightly more than the expected strength of conventional concrete of the same

grades.

Burak Felekoglu and Hasan Sarıkahya (2007)13

synthesized three Poly

Carboxylate (PC) based super plasticizers by using radical polymerisation

techniques. The effect of these admixtures on setting time of cement pastes, time

dependent workability and strength development of SCC was investigated. Test

results showed that, from the viewpoint of chemical structure, workability retention

performance of PC based super plasticizers could be manipulated by modifying the

bond structure between main backbone and side chain of copolymer. PC based SPs

with ester bonding were found to be ineffective in maintaining the workability of

fresh concrete workability due to the alkali attack vulnerability of this bond

structure. It was also reported that, by directly bonding the polyoxyethylene side

chain to the backbone of copolymer, the workability of fresh concrete can be

effectively maintained at least for a period of 2 h. It was found that, in addition to

15

the types of SP, water/powder ratio of SCC mixtures were also responsible for the

long workability retention performances. Best results were derived from mixtures

incorporating 2.3 weight % of SP.

Ahmadi et al (2007)2 studied the development of Mechanical properties up to 180

days of self compacting and ordinary concrete mixes with rice husk ash (RHA),

from a rice paddy milling industry. Two different replacement percentages of

cement by RHA, 10%, and 20%, and two different water/cementitious material

ratios (0.40 and 0.35) were used for both of self compacting and normal concrete

specimens. The results were compared with those of the self compacting concrete

without RHA. SCC mixes show higher compressive and flexural strength and lower

modulus of elasticity rather than the normal concrete. Replacement up to 20% of

cement with rice husk ash in matrix caused reduction in utilization of cement and

expenditures, and also improved the quality of concrete at the age of more than 60

days. It was concluded that RHA provides a positive effect on the Mechanical

properties after 60 days.

Halit Yazici (2007)31

developed self compacting concrete by replacing cement with

a Class C FA in various proportions from 30% to 60%. Durability properties of

various self compacting concrete mixtures such as, freezing and thawing, and

chloride penetration resistance were found. Similar tests were carried out with the

incorporation of 10% Silica Fume (SF) to the same mixtures. Test results indicated

that SCC could be obtained with a high volume FA. Addition of 10% SF to the

system improved both the fresh and hardened properties of high performance high-

volume FA SCC. These mixtures had good mechanical properties, freeze thaw and

chloride penetration resistance. Moreover, these mixtures also had great

environmental and economical benefits. The heat of hydration and shrinkage of

these mixtures were lower than those of the SCC mixtures made with high volume

Portland cement.

Khatib (2008)52

investigated the influence of including flyash on the properties of

self compacting concrete. Portland cement was partially replaced with 0–80% FA.

The water to binder ratio was maintained at 0.36 for all mixes. Properties like

16

workability, compressive strength, ultrasonic pulse velocity, absorption and

shrinkage were found. The results indicated that high volume FA can be used to

produce high strength and low shrinkage SCC. Replacing 40% of Portland cement

with FA resulted in a strength of more than 65 N/mm2

at 56 days. High absorption

values were obtained with increasing amount of FA. There is a systematic reduction

in shrinkage as the FA content increases and at 80% FA content, the shrinkage at 56

days reduced by two third compared with the control. A linear relationship existed

between the 56th

day shrinkage and FA content. Increasing the admixture content

beyond a certain level led to a reduction in strength and increase in absorption. The

correlation between strength and absorption indicated a sharp decrease in strength

as absorption increased from 1 to 2%. Beyond 2% absorption, the reduction in the

strength was found to be at a slower rate.

Shazim Ali Memon et al (2008)90

studied the use of Rice Husk Ash (RHA) to

increase the amount of fines and hence achieving self compacting concrete in an

economical way. They compared the properties of fresh SCC containing varying

amounts of RHA with that containing commercially available viscosity modifying

admixture. The comparison was done at different dosages of super plasticizer

keeping cement, water, coarse aggregate, and fine aggregate contents constant. Test

results substantiate the feasibility to develop low cost SCC using RHA. Cost

analysis showed that the cost of ingredients of specific SCC mix is 42.47 percent

less than that of control concrete.

Paratibha Aggarwal et al (2008)80

presented a procedure for the design of self

compacting concrete mixes based on an experimental investigation. At the

water/powder ratio of 1.180 to 1.215, slump flow test, V-funnel test and L-box test

results were found to be satisfactory, i.e. passing ability, filling ability and

segregation resistance are well within the limits. SCC was developed without using

VMA in this study. Further, compressive strength at the ages of 7, 28, and 90 days

was also determined. By using the Ordinary Portland Cement (OPC) 43 grade,

normal strength of 25 MPa to 33 MPa at 28 days was obtained, keeping the cement

content around 350 kg/m3 to 414 kg/m

3.

17

Seshadri Sekhar and Srinivasa Rao (2008)86

studied the properties like

compressive strength, split tensile strength and flexural strength of SCC mix

proportions ranging from M30 to M65 grades of concrete. An attempt was made to

obtain a relationship among the splitting tensile strength, flexural strength and

compressive strength from the test results. The increase in the compressive strength

for all the grades of SCC mixes compared with the 28th

day compressive strength

varied between 20 and 30%. The increase in flexural strength for all the grades of

SCC mixes compared with the 28th

day flexural strength varied between 15 and

25%. The increase in split tensile strength for all the grades of SCC mixes

compared with the 28th

day split tensile strength varied between 15 and 25%.

Al-Feel and Al-Saffar (2009)3 carried out an experimental investigation to study

the effect of curing methods on the compressive, splitting, and flexural strengths

(modulus of rupture) of self compacting concrete and compared the same with that

of normal concrete. The self compacting concrete was made with Portland cement,

limestone powder, sand, gravel and super plasticizer. The specimens were cured in

the air and water, for the period of 7, 14, and 28 days. Three specimens were tested

for each point of each property. It is reported that the compressive strength, splitting

tensile strength and flexural strength of the water cured specimens were 11%, 10%

and 11% respectively more than those of the specimens cured in air. From the failed

specimens it was found that there was no segregation and the bond between

aggregate and matrix was good.

Kursat Esat Alyamac and Ragip Ince (2009)61

studied the relationship between

properties of the fresh SCC and the hardened SCC containing marble powder. For

this purpose, the mix design approach based on monogram developed by Monteiro

and co-workers for normal vibrated concrete was adapted to SCC mixes. In order to

obtain this monogram, a series of SCC mixes with different water/cement ratios and

water/powder ratios were prepared. Several tests such as slump-flow, T50 time, L-

box, V-Funnel and sieve segregation resistance were applied for fresh concrete and

tests such as compressive strength and split tension strength at 7,28 and 90 days

18

were performed for hardened concrete. They reported that the mix design method

based on monogram can be used for preliminary design of SCC mixes.

Ilker Bekir Topcu et al (2009)39

developed self compacting concrete, using waste

Marble Dust (MD) as a filler material. MD was used directly without any additional

processing. MD was used to replace the binder of SCC in proportions of 0, 50, 100,

150, 200, 250 and 300 kg/m3. Slump flow test, L-box test and V-funnel test were

carried out on the fresh concrete. Compressive strength, flexural strength, ultrasonic

velocity, porosity and compactness were also determined at 28 days. The effect of

waste MD usage as filler material on capillarity properties of SCC was also

investigated. It was concluded that the workability of fresh SCC has not been

affected up to 200 kg/m3 MD content. However, the mechanical properties of

hardened SCC were found to decrease while using MD, especially when the content

of MD was more than 200 kg/m3.

Hemant Sood et al (2009)35

highlighted the use of European standards for testing

self compacting concrete in Indian conditions. They carried out an experimental

investigation of self compacting concrete using flyash and Rice husk ash as mineral

admixtures and testing rheological properties as per European Standards. Addition

of flyash in SCC increased the filling and passing ability of concrete, whereas rice

husk ash imparted viscosity to concrete improving segregation resistance of

concrete mix. From this experimental study it was inferred that flyash and RHA

blend improved the overall workability, which is the prime important characteristic

of SCC. Increase in Rice husk ash content increased the water demand and reduced

the compressive strength of concrete.

Girish et al (2010)28

presented the results of an experimental investigation carried

out to find out the influence of paste and powder content on self compacting

concrete mixtures. Tests were conducted on 63 mixes with water content varying

from 175 l/m3 to 210 l/m

3 with three different paste contents. Slump flow, V-funnel

and J-ring tests were carried out to examine the performance of SCC. The results

indicated that the flow properties of SCC increased with increase in the paste

volume. As powder content of SCC increased, slump flow of fresh SCC increased

19

almost linearly and in a significant manner. They concluded that paste plays an

important role in the flow properties of fresh SCC in addition to water content. The

passing ability as indicated by J-ring improved as the paste content increased.

Nicolas Ali Libre et al (2010)76

studied the effect of chemical and mineral

admixtures, including super plasticizer, viscosity modifying agent, limestone

powder and flyash with different w/c ratios on fluidity, viscosity, and stability of

self consolidating mortar. The results indicated that w/c is the most significant

parameter influencing the rheological properties of cementitious mixtures, specially

their stability. Furthermore, the maximum allowable w/c ratio for preventing

inhomogeneity could not be a fixed value for all the mixtures and should be

adjusted for the target fluidity. They reported that addition of VMA was an effective

method for stabilizing self consolidating mortars and preventing any kinds of

instability. Limestone powder and flyash mainly affected bleeding and aggregate

blockage. Besides, these mineral admixtures improved the fluidity of the mixtures

to some extent.

Venkateswara Rao et al (2010)94

developed standard and high strength self

compacting concrete with different sizes of aggregate based on Nansu’s mix design

procedure. The results indicated that Self Compacting Concrete can be developed

with all sizes of graded aggregate satisfying the SCC characteristics. The

mechanical properties such as compressive strength, flexural strength and split

tensile strengths were found at the end of 3, 7 and 28 days for standard and high

strength SCC with different sizes of aggregate. The optimum size of aggregate was

found to be 10mm for standard self compacting concrete (M30), while it was 16mm

for high strength self compacting concrete (M70) though all other sizes also could

develop properties satisfying the criteria for SCC. A comparison of M30 and M70

grade concrete confirmed that the filling ability, passing ability and segregation

resistance were better for higher grade concrete for the same size of aggregate. This

is due to the higher fines content in M70 concrete. It was noted that 10mm size

aggregate and 52% flyash resulted in highest mechanical properties in standard

20

SCC, whereas 16 mm size aggregate with 31% flyash content resulted in highest

strength in case of high strength SCC.

Mucteba Uysal and Kemalettin Yilmaz (2011)69

studied the benefits of using

limestone powder (LP), basalt powder (BP) and marble powder (MP) as partial

replacement of Portland cement to develop the self compacting concrete.

Furthermore, LP, BP and MP were used directly without any additional processing

in the production of self compacting concrete. The water to binder ratio was

maintained at 0.33 for all mixtures. The examined properties include workability,

air content, compressive strength, ultrasonic pulse velocity, static and dynamic

elastic moduli. Workability of the fresh concrete was determined by using both the

slump flow test and the L-box test. The results proved that it is possible to

successfully utilize waste LP, BP and MP as mineral admixtures in producing SCC.

It was reported that the employment of waste mineral admixtures improved the

economical feasibility of SCC production.

2.2.2 Experimental Investigations on the Behaviour of Concrete Materials

Under Elevated Temperatures

Abrams.M.S (1973)1 determined the compressive strength of 7.5x15cm cylindrical

specimens that were heated for short duration to temperatures of 200 to 1600° F (93

to 871°C). Carbonate, siliceous, and lightweight aggregates were used in the

experiment. Three different types of tests (heated without load and tested hot,

heated with load and tested hot, and tested cool after heating) were carried out on

the specimens. Carbonate aggregate concrete and lightweight concrete specimens

when tested hot without prior loading retained about 75 percent of their original

strength (strength prior to heating) at 1200°F (649°C). Above that temperature,

reduction in the strength was observed. Specimens heated while loaded had the

highest strengths, while the strength of specimens heated, cooled, and then tested

were the lowest throughout the temperature range. Original strength of concrete had

little effect on the percentage of strength retained at high temperatures. The

lightweight concrete had strength characteristics at high temperatures similar to

those of carbonate concrete. At temperatures above 800°F (427°C), the siliceous

21

aggregate concrete had lower strength than the other concretes. The salient features

of the test are shown in Table 2.1.

Table 2.1 Salient Features of Test Carried out by Abrams M.S

Size of the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cylinder

(0.076 x

0.152)

21 to 871oC

Peak

temperature

maintained

for 3 to 4

hours

Furnace

temperature

curve

- -

Stressed,

Unstressed,

Un stressed

residual

strength

test

Moetaz M. El-Hawaryet al (1996)65

studied the effect of fire on the flexural

behaviour of Reinforced Concrete (RC) beams. Four groups of RC beams were cast,

exposed to fire at 650°C for time durations of 0, 30, 60 and 120 min and then

cooled by water. Reduction in ultimate load, increase in deflection, increase in both

compressive and tensile strains and reduction in concrete compressive strength were

observed for the heated specimens. The salient features of the test are shown in

Table 2.2.

Table 2.2 Salient Features of Test Carried out by Moetaz M. El-Hawary et al

Size of the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Beam

(1.8x0.12

x0.2)

650°C

Peak

temperature

maintained

for 30min,

60min,

120min

Furnace

temperature

curve

-

Sprayed

with water

immediately

Un

stressed

residual

strength

test

Moetaz M. El-Hawary and Sameer A. Hamoush (1996)66

carried out an

experimental investigation to determine the effect of high temperature on the

interfacial bond shear modulus between concrete and reinforcement. Steel bars of

different diameters were embedded in concrete cylinders for a depth less than that

required for total development to assure failure by loss of bond. Specimens were

then kept in an oven for different time durations and different temperatures.

22

Specimens were then cooled by either keeping cylinders at room temperature or

immersing them in water. The interfacial bond shear modulus between concrete and

steel reinforcement was calculated using an experimental analytical technique. The

pull out test was applied, and loads and displacements were recorded. Results from

the pull out test were then used along with an analytical model to calculate the bond

shear modulus. The analytical model was based on the physical representation of

the pull out test, assuming linear elastic behavior of both steel and concrete. The

effects of temperature, duration of heating, size of steel bar and the method of

cooling on the bond shear modulus were investigated. The bond shear modulus was

found to be independent of the diameter of the reinforcing bars and was found to be

much lower for concrete cooled by water than for concrete cooled gradually in air.

Specimens heated to about 100°C for short durations and cooled in air experienced

an increase in the bond shear modulus. For all other specimens, a reduction in the

bond shear modulus was noticed. The reduction increased with the increase of the

heating temperature or duration of heating. The salient features of the test are shown

in Table 2.3.

Table 2.3 Salient Features of Test Carried out by Moetaz M. El-Hawary and

Sameer A. Hamoush

Size of

the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cylinder

(0.1 x

0.2)

100,300

500oC

Peak

temperature

maintained

for 2,4 & 8

hours

Furnace

temperature

curve

-

Natural

cooling by

air,

immersion

in water

Un

stressed

residual

strength

test

Moetaz M. El-Hawary et al (1997)22

studied the effect of duration of fire exposure

and the concrete cover thickness on the behaviour of RC beams subjected to fire in

shear zone and cooled by water. Investigation was carried out on eight reinforced

concrete beams of size 1800 x 200 x 120 mm. The beams were divided into two

groups. Group (1) consisted of four beams with a cover thickness of 20 mm and

group (2) consisted of four beams with a cover thickness of 40 mm. Each group was

subjected to a temperature of 650°C for different periods of time, i.e. 0, 30, 60. 120

23

min. The compressive strength of the beams was determined non-destructively

using a Schmidt hammer on the next day after exposure to fire. The beams were

tested by applying two transverse loads incrementally. Strains and deformations

were measured at each load increment. Cracking loads, crack propagation and

ultimate loads were recorded for each beam. The behaviour of the beams exposed to

fire in the shear zone was found to be highly affected by the fire exposure time and

the change of the cover thickness. The salient features of the test are shown in Table

2.4.

Table 2.4 Salient Features of Test Carried out by Moetaz M. El-Hawary et al

Size of the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Beam

(1.8x0.2

x0.12)

650°C

Peak

temperature

maintained

for 30min,

60min,

120min

Furnace

temperature

curve

-

Sprayed

with water

immediately

Un

stressed

residual

strength

test

Y.N.Chan et al (1999)17

carried out an investigation on the fire resistance of

Normal Strength Concrete (NSC) and High Strength Concrete (HSC), with

compressive strengths of 39, 76 and 94 MPa respectively. After exposure to

temperatures upto 1200°C, compressive strength and tensile splitting strength were

determined. The pore structure in HSC and in NSC was also investigated. Results

indicated that HSC lost its mechanical strength in a manner similar to that of NSC.

The range between 400 and 800°C was found to be critical to the strength loss.

High temperatures had a coarsening effect on the microstructure of both HSC and

NSC. On the whole, HSC and NSC suffered damage to almost the same degree,

although HSC appeared to suffer a greater worsening of the permeability related

durability. The salient features of the test are shown in Table 2.5.

24

Table 2.5 Salient Features of Test Carried out by Y.N.Chan et al

Size of

the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cube

(0.1x0.1

x0.1)

20, 400,

600, 800,

1000 &

1200°C

Peak

temperature

maintained

for

1 hour

Furnace

temperature

curve

-

Natural

cooling

by air

Un

stressed

residual

strength

test

Y.N.Chan et al (2000)16

carried out an experimental investigation to study the

mechanical properties and pore structure of high performance concrete and normal

strength concrete after exposure to high temperature. After the concrete specimens

were subjected to a temperature of 800°C, their residual compressive strength was

measured. The porosity and pore size distribution of the concrete were investigated

using mercury intrusion porosimetry. Test results indicated that HPC had higher

residual strength than the normal strength concrete after exposure to high

temperature. It was reported that the changes in pore structure could be used to

indicate the degradation of mechanical property of HPC subjected to high

temperature. The salient features of the test are shown in Table 2.6.

Table 2.6 Salient Features of Test Carried out by Y.N.Chan et al

Size of the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cube

(0.1x0.1x0.1)

800°C

Peak

temperature

maintained

for

1 hour

Furnace

temperature

curve

5 to

7°C/min

Natural

cooling

by air

Un

stressed

residual

strength

test

Chi-Sun Poon et al (2001)18

investigated the strength and durability performance

of normal and high strength pozzolanic concrete incorporating silica fume, flyash

and blast furnace slag at elevated temperatures up to 800ºC. The strength properties

were determined using an unstressed residual compressive strength test, while

durability was investigated by rapid chloride diffusion test and crack pattern

25

observations. It was found that pozzolanic concrete containing flyash and blast

furnace slag gave the best performance particularly at temperatures below 600ºC as

compared to the pure cement concrete. Explosive spalling occurred in high strength

concrete containing silica fume. A distributed network of fine cracks was observed

in all flyash and blast furnace slag concrete, but no spalling or splitting occurred.

The high strength pozzolanic concrete resulted in a severe loss in permeability

related durability than the loss in the compressive strength. Thirty percent

replacement of cement by flyash in HSC and 40% replacement of cement by blast

furnace slag in normal strength concrete were found to be optimal to retain

maximum strength and durability after high temperatures. The salient features of the

test are shown in Table 2.7.

Table 2.7 Salient Features of Test Carried out by Chi-Sun Poon et al

Size of the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cube

(0.1x0.1x0.1)

(0.1x0.05)

200°C,

400°C,

600°C&

800°C

Peak

temperature

maintained

for 1 hour

Furnace

temperature

curve

2.5°C/min

Natural

cooling

by air

Un

stressed

residual

strength

test

Chi-Sun Poon et al (2003)19

carried out an experimental investigation to evaluate

the performance of Metakaolin (MK) concrete at elevated temperatures up to

800°C. Eight normal and high strength concrete mixes incorporating 0%, 5%, 10%

and 20% MK were prepared. The residual compressive strength, chloride-ion

penetration, porosity and average pore sizes were measured and compared with

silica fume, flyash and pure ordinary portland cement concretes. It was found that

after an increase in compressive strength at 200°C, the MK concrete suffered a

more severe loss of compressive strength and permeability related durability than

the corresponding SF, FA and OPC concretes at higher temperatures. Explosive

spalling was observed in both normal and high strength MK concretes and the rate

of spalling increased with higher MK contents. The salient features of the test are

shown in Table 2.8.

26

Table 2.8 Salient Features of Test Carried out by Chi-Sun Poon et al

Size of the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cube

(0.1x0.1x0.1)

Cylinder

(0.1x0.2)

200°C,

400°C,

600°C&

800°C

Peak

temperature

maintained

for 1 hour

Furnace

temperature

curve

2.5°C/min

Natural

cooling

by air

Un

stressed

residual

strength

test

Kumar A and Kumar V (2003)60

carried out an investigation to find the residual

strength of reinforced cement concrete beams exposed to higher temperature for a

long duration. Six Reinforced Cement Concrete (RCC) beams were cast with same

reinforcement, length, grade of concrete and clear cover. Four beams were exposed

to fire for durations of 1 h, 1.5 h, 2 h and 2.5 h. These beams exposed to fire for

2.5 h and tested at room temperature failed in serviceability criteria. The reduction

in stiffness was found to increase with the increase in the duration of fire exposure.

The following conclusions were drawn by the authors from the test carried out on

RCC beams. RCC beam of grade M20 with 25 mm clear cover was unable to resist

a fire exposure of about 2.5h as it failed in serviceability criterion. Spalling of

concrete was observed at many places, which increased further with the time. Even

2 h fire duration was found to be critical as the beam was able to take only about

50% load of the companion beam. The behavior of M20 RCC beam exposed to fire

of 1 h duration was found to be satisfactory as its strength was found to be about

83% of the companion beam. The salient features of the test are shown in Table 2.9.

Table 2.9 Salient Features of Test Carried out by Kumar A and Kumar V

Size of the

specimen

(m)

Temperature

range Time duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Beam

(3.96x0.2

x0.3)

1000ºC

1hr,1.5hr,2hr,

2.5hr

(IS 3809-

1979)

Furnace

temperature

curve

-

Natural

cooling

by air

Un

stressed

residual

strength

test

Fu-Ping Cheng et al (2004)26

investigated the effects of high temperature on the

strength and stress-strain relationship of high strength concrete. Stress-strain curve

27

tests were conducted at various temperatures (20, 100, 200, 400, 600 and 800°C) for

four types of HSC. The variables considered in the experimental study included

concrete strength, type of aggregate, and the addition of steel fibers. From the

results of stress-strain curve tests it was found that plain HSC exhibited brittle

properties below 600°C, and ductility above 600°C. HSC with steel fibers exhibited

ductility above 400°C. The compressive strength of HSC decreased by about a

quarter of its room temperature strength within the range of 100 to 400°C, the

strength further decreased with the increase of temperature and reached about a

quarter of its initial strength at 800°C. The strain at peak load also increased with

temperature, from 0.003 at room temperature to 0.02 at 800°C. Further, the increase

in strains for carbonate aggregate HSC was found to be more than that of the

siliceous aggregate HSC. The salient features of the test are shown in Table 2.10.

Table 2.10 Salient Features of Test Carried out by Fu-Ping Cheng et al

Size of the

specimen

(m)

Temperature

range Time duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cylinder

(0.1x0.2)

20,100,200,

400,600&

800oC

Peak

temperature

maintained for

1 hour

Furnace

temperature

curve

2°C/min -

Un

stressed

residual

strength

test

Min Li et al (2004)64

investigated the effect of temperature exposure on

compressive strength, splitting tensile strength and flexural strength of normal and

high strength concrete. Oil furnace was used in this study for heating the specimens.

The temperature time curve was close to the standard curve, which conforms to

Chinese standard GB/T 9978-1999. After being heated to temperatures of 200, 400,

600, 800 and 1000°C respectively, the mechanical properties of HSC were found.

The influence of temperature, water content, specimen size, strength grade and

temperature profiles on mechanical properties of HSC were discussed. They

concluded that the larger the specimen size, the lesser the strength loss. The salient

features of the test are shown in Table 2.11.

28

Table 2.11 Salient Features of Test Carried out by Min Li et al

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Beam

(0.415x0.1x0.1)

Cube

(0.1x0.1x0.1)

Cube

(0.15x0.15x0.15)

200, 400,

600, 800&

1000°C

90min

Furnace

temperature

curve

(GB/T

9978-1999)

-

Natural

cooling

by air

Un

stressed

residual

strength

test

B.Persson (2004)82

made a comparison between the performance of vibrated

concrete and that of self consolidating concrete under elevated temperature.

Cylinders and columns were tested by compressive loading with high temperature.

Polypropylene fibers were used to avoid the spalling of concrete. Hydrocarbon and

ISO 384 fire curves were used. Rate of heating was maintained at 240°C and 480°C

per hour. Specimens were heated in the temperature range of 20 to 800°C and

specimens were slowly cooled upto room temperature and tested. It was observed

from the test results that explosive spalling took place for columns with SCC but

not for columns with vibrated concrete, even through the vibrated concrete columns

were cured exactly as SCC columns. It was reported that spalling mainly depended

on the stress in the concrete, cement powder ratio and w/c ratio. Lower elastic

modulus at fire temperature was observed in SCC than that in vibrated concrete.

The salient features of the test are shown in Table 2.12.

Table 2.12 Salient Features of Test Carried out by B.Persson

Size of the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cylinder

(0.1x0.2)

Prestressed

column

(2x0.2x0.2)

20, 200, 400,

600 & 800°C 2hours

ISO 384 &

modified

hydro carbon

fire curve

240°C/hr&

480°C/hr

60°C/hr

Un

stressed

residual

strength

test

Xudong Shi et al (2004)97

carried out an experimental investigation on flexural

members exposed to fire load to understand the effect of cover thickness on the

resistance of members. They varied the cover from 10mm to 30mm. The bottom

29

surface and the two lateral surface of the specimen were heated. They reported that

the bottom concrete cover had significant influence on the ultimate loading capacity

of the specimens, but the extent of this influence decreased with an increase in the

concrete cover thickness. It was found that, it is improper to excessively increase

the bottom concrete cover thickness to improve the fire resistance of the specimens.

Also the beneficial effect of the lateral concrete cover was found to be lower than

that of the bottom concrete cover. The salient features of the test are shown in Table

2.13.

Table 2.13 Salient Features of Test Carried out by Xudong Shi et al

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type

of

test

Beam

(1.3x0.1x0.18

1.3x0.1x0.19

1.3x0.1x0.20)

900°C 150 min

Furnace

temperature

curve

- - -

A.Ferhat Bingol and Rustem Gul (2004)25

investigated the effect of high

temperature on compressive strength of concrete with the aim to produce a fire

resistant concrete. Concrete was made by replacing ordinary aggregate with pumice

in the ratios of 25, 50, 75 and 100% in volume. The temperature values were chosen

as 150, 300,450,600 and 750°C. The effect of heating duration over the

compressive strength was also examined and different types of concrete mixtures

were heated for durations of one hour, three hours and five hours for each of

temperature values. It was observed that the quality of concrete deteriorated at

150°C and specimen began to lose some strength at this temperature. Though the

considerable strength loss was not noticed from 150 to 300°C, all types of concrete

mixtures continued to lose their compressive strength after 300°C. Every concrete

mixture lost a significant part of their initial strength when the temperature reached

750°C. It was reported that the heating duration did not affect the strength loss

significantly but a high temperature was found to be a significant parameter on the

strength loss. The salient features of the test are shown in Table 2.14.

30

Table 2.14 Salient Features of Test Carried out by A.FerhatBingol and RustemGul

Size of

the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cylinder

(0.1 x 0.2)

150,

300,450,600

and 750°C

Peak

temperature

maintained

for 1,3 and 5

hours

Furnace

temperature

curve

-

Natural

cooling

by air

Un

stressed

residual

strength

test

Gai-FeiPeng et al (2006)27

carried out an investigation to explore the relationship

between occurrence of explosive spalling and residual mechanical properties of

fiber toughened high performance concrete exposed to high temperatures. The

residual mechanical properties measured were compressive strength, tensile

splitting strength and fracture energy. A series of concretes were prepared using

ordinary Portland cement and crushed limestone. Steel fiber, polypropylene fiber,

and hybrid fiber (polypropylene fiber and steel fiber) were added to enhance the

fracture energy of the concrete. After exposure to high temperatures ranged from

200 to 800 °C, the residual mechanical properties of fiber toughened high

performance concrete were investigated. For fiber concrete, although residual

strength was decreased by exposure to high temperatures over 400 °C, residual

fracture energy was significantly higher than that before heating. Incorporating

hybrid fiber seems to be a promising way to enhance the resistance of concrete to

explosive spalling. The salient features of the test are shown in Table 2.15.

Table 2.15 Salient Features of Test Carried out by Gai-FeiPeng et al

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cube

(0.1x0.1

x0.1)

Beam

(0.3x0.1x0.1)

200, 400,

600 &

800°C

Peak

temperature

maintained

for 1 hour

Furnace

temperature

curve

10°C/

min

Natural

cooling

by air

Un

stressed

residual

strength

test

Metin husem (2006)63

examined the variation of compressive and flexural

strengths of ordinary and high performance micro concrete at high temperature.

31

Compressive and flexural strengths of ordinary and high performance micro

concrete which were exposed to high temperatures (200, 400, 600, 800 and 1000°C)

and cooled differently (in air and water) were obtained. Compressive and flexural

strengths of these concrete samples were compared with each other and then

compared with the samples which had not been heated. Strength loss curves of these

concrete samples were compared with the strength loss curves given in the codes.

The results indicate that strength of concrete decreases with increasing temperature

and the decrease in the strength of ordinary concrete was more than that of the high

performance concrete. The type of cooling was found to affect the residual

compressive and flexural strength, the effect being more pronounced as the

temperature increases. Strength loss curves obtained from this study were found to

be in agreement with the strength loss curves given in the Finnish Code. The salient

features of the test are shown in Table 2.16.

Table 2.16 Salient Features of Test Carried out by Metin husem

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cylinder

(0.15x0.3)

Beam

(0.04x0.04

x0.16)

200, 400,

600, 800&

1000°C

-

Furnace

temperature

curve

5.5&

6.67°C/min

Air and

water

Un

stressed

residual

strength

test

A.Noumowe et al (2006)77

carried out an investigation to understand the behavior

of conventional vibrated high strength concrete and self compacting high strength

concrete at high temperature. Based on the results they concluded that, the residual

mechanical properties of self compacting high strength concretes were similar to

those of conventional high strength concrete. The risk of spalling for self

compacting high strength concrete was greater than that of conventional high

strength concrete. The tests showed that severe spalling could occur with self

compacting high strength concrete even at a heating rate as low as 0.5°C/min. The

salient features of the test are shown in Table 2.17.

32

Table 2.17 Salient Features of Test Carried out by A.Noumowe et al

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate

of

heating

Rate of

cooling/

coolant

Type of

test

Cylinder

(0.16x0.32)

Beam

(0.4x0.1x0.1)

400, 600°C -

Furnace

temperature

curve

0.5°C/

min

Cooling

as per

(RILEM

TC-129)

Un

stressed

residual

strength

test

Y.F.Chang et al (2006)15

carried out an investigation to obtain complete

compressive stress–strain relationship for concrete after heating to temperatures of

100 to 800°C. All concrete specimens were standard cylinders of diameter 150 mm

and height 300 mm, made with siliceous aggregate. The heated specimens were

tested at 1 month after they were cooled to room temperature. From the results of

108 specimens with two original unheated strengths, a single equation for the

complete stress–strain curves of heated concrete was developed. Through the

regression analysis, the relationships of the mechanical properties with temperature

were proposed to fit the test results, including the residual compressive strength,

peak strain and elastic modulus. The equation proposed is applicable to unheated

and heated concrete specimens at different temperatures. In addition, the split

cylinder tests of 54 specimens were also found and a relationship between splitting

tensile strength and temperature was established. The salient features of the test are

shown in Table 2.18.

Table 2.18 Salient Features of Test Carried out by Y.F.Chang et al

Size of the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cylinder

(0.15x0.3)

100,200,300,

400,500,600,

700& 800°C

Peak

temperature

maintained

for 1.5 to 2.5

hours

Furnace

temperature

curve

1 to

4.5°C/min

Natural

cooling

by air

Un

stressed

residual

strength

test

Kosmas K. Sideris (2007)58

carried out an investigation on the mechanical

properties of self consolidating concrete subjected to elevated temperatures up to

700°C. Eight different concretes (four self consolidating and four conventional)

33

having different strength categories were produced. At the age of 120 days,

specimens were placed in an electrical furnace and heated at a rate of 5°C/min until

the desired temperature was reached. Temperatures of 100, 300, 500, and 700°C

were maintained for 1 h. Specimens were then allowed to cool in the furnace and

tested for compressive strength, splitting tensile strength, and ultrasonic pulse

velocity. Similar tests were also performed at room temperature (20°C) for the

reference specimens. Residual strengths of both SCC and Conventional concrete

were reduced almost in a similar manner upto the maximum temperature reached.

Explosive spalling occurred in both SCC and CC of the highest strength category at

temperatures greater than 380°C. The residual compressive strength of SCC

mixtures was higher than the one of CC mixtures for the same strength class. The

tentative spalling behaviors of SCC and CC were the same and depended only on

the strength category. The salient features of the test are shown in Table 2.19.

Table 2.19 Salient Features of Test Carried out by Kosmas K. Sideris

Size of the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cube

(0.1x0.1

&0.15x0.15)

Cylinder

(0.15x0.3)

100,300,

500 &

700oC

Peak

temperature

maintained

for 1hour

Furnace

temperature

curve

5°C/min

Natural

cooling

by air

Un

stressed

residual

strength

test

Esref Unluoglu et al (2007)23

investigated the mechanical properties of structural

reinforcement after the exposure to high temperatures. Plain steel and reinforcing

steel bars embedded into mortar and plain mortar specimens were prepared and

exposed to 20, 100, 200, 300, 500, 800 and 950 °C temperature for 3 hours

individually. The S420 deformed steel bars with diameters of B10, B16 and B20

were used. The tension tests on reinforcements taken from cooled specimens and

the variations in yield strength, ultimate strength and in resilience of three different

dimensioned reinforcements were determined. For the temperatures upto 500°C, the

reinforcing steel specimens with cover had the same yield strength and tensile

strength with that of the reinforcing steels without high temperature exposure.

34

However, when the temperature exceeded 500°C, the reinforcing steel with cover

was found to lose the strength. It was observed that 25 mm cover thickness was not

sufficient to protect the mechanical properties of reinforcing steel when the

structure is exposed to temperatures over 500°C. It is required to provide sufficient

concrete cover thickness to protect reinforcements from fire reaching the

temperatures over 500°C. The salient features of the test are shown in Table 2.20.

Table 2.20 Salient Features of Test Carried out by Esref Unluoglu et al

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Mortar

(0.06x0.06x0.3

0.066x0.066x0.3

0.07x0.07x0.37)

20°C,

100°C,

200°C,

300°C,

500°C,

800°C&

950°C

Peak

temperature

maintained

3 hours

Furnace

temperature

curve

-

Natural

cooling

by air

Un

stressed

residual

strength

test

Omer Arioz (2007)78

presented the effects of elevated temperatures on the physical

and mechanical properties of various concrete mixtures prepared using ordinary

Portland cement, crushed limestone, and river gravel. Specimens were subjected to

elevated temperatures ranging from 200 to 1200ºC. After exposure, weight losses

and the compressive strength were found out. Test results indicated that weight of

the specimens significantly reduced with an increase in temperature. This reduction

was very sharp beyond 800ºC. The effects of water/cement ratio and type of

aggregate on losses in weight were not found to be significant. The results also

revealed that the relative strength of concrete decreased as the exposure temperature

increased. The salient features of the test are shown in Table 2.21.

Table 2.21 Salient Features of Test Carried out by Omer Arioz

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cube

(0.07x0.07x0.07)

200°C to

1200°C 2 hours

Furnace

temperature

curve

20°C/min

2°C/min

Un

stressed

residual

strength

test

35

Serdar Aydin and Bulent Baradan (2007)85

investigated the effects of high

temperature on the mechanical properties of cement based mortars containing

pumice and flyash. Four different mortar mixtures with varying amounts of flyash

were exposed to high temperatures of 300, 600, and 900°C for 3 h. The residual

strength of these specimens was determined after cooling by water or air.

Microstructure formations were investigated by X-ray and SEM analyse. The

pumice mortar incorporating 60% flyash was found to have the best performance

particularly at 900°C. This mixture did not show any loss in compressive strength at

all test temperatures when cooled in air. The superior performance of 60% FA

mortar may be attributed to the strong aggregate cement paste interfacial transition

zone and ceramic bond formation at 900°C. However, all mortar specimens were

found to have severe losses in terms of flexural strength. Furthermore, specimens

cooled in water showed greater strength loss than the air cooled specimens.

Nevertheless, the developed pumice, flyash and cement based mortars seemed to be

a promising material in reducing high temperature hazards. The salient features of

the test are shown in Table 2.22.

Table 2.22 Salient Features of Test Carried out by Serdar Aydin and Bulent Baradan

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

0.04x0.04x1.6

300°C,

600°C&

900°C

Peak

temperature

maintained

for three

hours

Furnace

temperature

curve

10°C/min

Water

soaking

&Air

cooling

Un

stressed

residual

strength

test

Ilker Bekir Topcu and Cenk Karakurt (2008)38

carried out an experiment on hot

rolled S220 and S420 reinforcement steel rebars that were subjected to high

temperatures and subsequently cooled to room temperature to understand the

behaviour of these materials under fire. The deterioration of the mechanical

properties of yield strength and modulus of elasticity is considered as the primary

element affecting the performance of steel structures under fire. It was aimed to

determine the residual mechanical properties of steel rebars after exposing them to

36

elevated temperatures. Steel bars were subjected to 20, 100, 200, 300, 500, 800 and

950oC temperatures for 3 hours and tensile tests were carried out. Effects of

temperature on mechanical properties of S220 and S420 were determined. All

mechanical properties of the steel rebars were reduced due to the temperature

increase. It is seen that mechanical properties of S420 steel were affected more than

those of S220 steel at elevated temperatures. The authors suggest that the protective

cover thickness should be higher for increasing the fire safety of reinforced concrete

members. The salient features of the test are shown in Table 2.23.

Table 2.23 Salient Features of Test Carried out by Ilker Bekir Topcu

and Cenk Karakurt

Size of the

specimen (m)

Temperature

range Time duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

S220 and

S420 Steel

Rebars

(10mm and

16mm dia&

200mm

Length)

20,100,200,

300,500,800

&

950oC

Peak

temperature

maintained for

three hours

Furnace

temperature

curve

-

Natural

cooling

by air

Un

stressed

residual

strength

test

M.C.Alonso et al (2008)4 carried out an experimental investigation on Self

Compacting Concrete reinforced with polymeric fibers (Polypropylene fibers, PPF).

First, the mechanical and micro structural characterization was determined. Further

the influence of the presence of the PPF in the SCC durability properties of the

material was studied at laboratory, using different indicators. Finally, the response

of both types of material with respect to resistance at high temperature was

evaluated through micro structural analysis. The results indicated that porosity,

capillary suction, transport of chloride and depth of carbonation for the self

compacting concrete with and without fibers are very similar. The salient features

of the test are shown in Table 2.24.

37

Table 2.24 Salient Features of Test Carried out by M.C.Alonso et al

Size of the

specimen

(m)

Temperature

range Time duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

SCC Beams

(0.4 x 0.1 x

0.1)

Cylinder

(0.075 x

0.1)

20,200,300,

500 &

700oC

Peak

temperature

maintained

for two hours

Furnace

temperature

curve

2oC/min

<1oC/min

Natural

cooling

by air

Un

stressed

residual

strength

test

R.H. Haddad et al (2008)29

evaluated the bond behavior between fiber reinforced

concrete and 20mm reinforcing steel rebars under elevated temperatures. Fifty

modified pullout specimens (100x100x400 mm) were prepared using high strength

concrete with basalt aggregate and different volumetric mixtures of three types of

fibers, namely brass coated steel fibers, hooked steel fibers, and high modulus

polypropylene fibers. Specimens, designated for heat treatment, were then subjected

to elevated temperatures, ranging from 350 to 700oC, whereas unheated (control)

ones were kept in the laboratory. The overall response of control and heat damaged

specimens, cracking extent and the continuity were described. Standard cubes

(100x100x100) were cast, cured, and heat treated under similar conditions and then

tested to evaluate the compressive and splitting tensile strengths. The results

indicated significant reduction in the residual compressive, splitting and steel–

concrete bond under high temperatures with dramatic changes in bond stress free

end slip trend behavior. Use of fibers minimized the damage in steel–concrete bond

under elevated temperatures and hence the reduction in bond strength. Specimens

which incorporated hooked steel fibers attained the highest bond resistance against

elevated temperatures followed, in sequence, by those prepared with the mixture of

hooked and brass coated steel, the mixture of hooked steel and polypropylene, and

brass coated steel fibers. Statistical models were developed to describe the

relationship between the bond strength and exposure temperature. The salient

features of the test are shown in Table 2.25.

38

Table 2.25 Salient Features of Test Carried out by R.H. Haddad et al

Size of the

specimen

(m)

Temperature

range Time duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Beam

(0.4x0.1x0.1)

Cube

(0.1x0.1x0.1)

350, 500,

600&700oC

Peak

temperature

maintained

for two hours

Furnace

temperature

Curve

-

Natural

cooling

by air

Un

stressed

residual

strength

test

Ilker Bekir Topcu and Burak IsIkdag (2008)37

studied the mechanical properties

of structural rebars after exposure to elevated temperatures. The mortar was

prepared with CEM I 42.5N cement and fired clay. The S420a, B16 mm ribbed

steel bars were used to prepare the specimens with the covers of 20, 30, 40 and 50

mm against elevated temperatures up to 800°C. The rebars were embedded in

mortars and then specimens were exposed to 20, 100, 200, 300, 500 and 800°C

temperatures for 3 h, individually. The mechanical tests were conducted on cooled

specimens, and the ultimate tensile strength, yield strength and elongation of mortar

specimens at various temperatures were also determined at the end of the

experiments. It was observed that 20–30–40–50 mm cover thickness was not

sufficient to protect the mechanical properties of rebars when exposed to above

500°C temperature. Therefore required cover thickness of concrete must be

calculated regarding protection of reinforcement up to peak temperatures. The

salient features of the test are shown in Table 2.26.

Table 2.26 Salient Features of Test Carried out by Ilker Bekir Topcu

and Burak IsIkdag

Size of the

specimen (m)

temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Beam

(0.056x0.056

x0.29

0.076x0.076

x0.31

0.096x0.096

x0.33

0.116x0.116

x0.35)

20°C,

100°C

200°C,

300°C,

500°C&

800°C

Peak

temperature

maintained

for 3 hours

Furnace

temperature

Curve

-

Natural

cooling

by air

Un

stressed

residual

strength

test

39

Anagnostopoulos et al (2009)5 carried out an investigation to determine the

influence of different fillers on the properties of SCC of different strength classes

when exposed to high temperatures. They reported that explosive spalling occurred

in both the cases of SCC and NCC when the oven peak temperature of 600°C is

maintained. SCC was found to spall more compared to NCC due to lower

permeability and higher moisture content. SCC with ladle furnace slag in its

composition was found to have higher compressive strength at the age of 28 days

due to slag’s cementitious behavior, but was more susceptible to spalling effects

after fire exposure compared to other mixtures. SCC produced with glass filler had

greater rheological characteristics at fresh state condition, but did not perform well

after exposure to high temperatures. SCC produced with limestone filler was found

to have better performance compared to mixtures prepared with different filler

materials. The salient features of the test are shown in Table 2.27.

Table 2.27 Salient Features of Test Carried out by Anagnostopoulos et al

Size of the

specimen

(m)

Temperature

range Time duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cube

(0.1x0.1

x0.1)

Cylinder

(0.15x0.3)

300& 600°C

Peak

temperature

maintained for

one hour

Furnace

temperature

curve

10°C

/min

Natural

cooling

by air

(24 hrs)

Un

stressed

residual

strength

test

Udaya kumar et al (2009)92

carried out an investigation to generate experimental

data on residual flexural strength of heated RCC beams and their strengthening

using various repair techniques. A total of 25 RCC beams were cast with similar

cross sectional details, length, grade of concrete and clear cover. Twenty beams

were tested after fire exposure and the remaining five were used as companion

beams. The beams were heated in two stages. In the first stage, two beams were

kept at each temperature for 3 h between 100°C and 1000°C, in increments of

100°C. Beams exposed to temperature ranging between 100 and 500°C were

repaired by applying paint. The beams exposed to temperature ranging between 600

and 1000°C were repaired for spalling. In the second stage, all repaired specimens

40

were again heated. These test specimens were tested for flexural strength after

bringing them to room temperature. The variation of flexural strength of repaired

RCC beams with increase in temperature was studied and the flexural strength of

beams before and after the repair was compared. The salient features of the test are

shown in Table 2.28.

Table 2.28 Salient Features of Test Carried out by Udayakumar et al

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Beam

(1.2x0.112x0.24)

100 to

1000°C

Peak

temperature

maintained

for three

hour

ISO 834

fire curve -

Natural

cooling

by air

Un

stressed

residual

strength

test

Tayfun Uygunoglu and Ilker Bekir Topcu (2009)91

Studied the effects of

aggregate type on the coefficient of thermal expansion of self consolidating

concrete produced with normal and lightweight aggregate at elevated temperature.

Two types of aggregates namely crushed limestone and pumice were used.

Different combinations of water/powder ratio and super plasticizer dosage levels

were prepared for the SCC and Self Consolidating Lightweight Concrete (SCLC)

mixtures. The total powder content (cement and mineral additives) was constant in

the experiments. Thermal test was performed to accurately characterize the

Coefficient of Thermal Expansion (CTE) of SCC and SCLC aged 28 days using the

dilatometer. The CTEs of SCC and SCLC were defined by measuring the linear

change in length of concrete specimens subjected to a range of temperatures. Test

temperatures were varied from 20 to 1000°C at a heating rate of 5°C/min. The

results, in general, showed that SCC has higher CTE than normal weight concrete

and that lightweight aggregate reduced the CTE of SCC due to their porous

structure. The aggregate type has significant influence on the thermal expansion of

SCC. The salient features of the test are shown in Table 2.29.

41

Table 2.29 Salient Features of Test Carried out by Tayfun Uygunoglu

and Ilker Bekir Topcu

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type

of

test

Cube

(0.07x0.07x0.07)

Cylinder

(0.15x0.3)

20 to 1000°C -

Furnace

temperature

curve

5°C

/min - -

Hanaa Fares et al (2009)32

carried out an experimental study on the performance

of self consolidating concrete subjected to high temperature. Two SCC mixtures

and one vibrated concrete were tested. Mechanical and micro structural properties

were studied at ambient temperature and after heating. Compressive strength,

flexural strength, bulk modulus of elasticity, porosity and permeability of these

concretes were found. For each test, the specimens were heated at a rate of 1 °C/

min upto desired target temperatures (150, 300, 450 and 600°C). In order to ensure

a uniform temperature throughout the specimen, the temperature was held constant

at the target temperature for 1 h before cooling. In addition, the specimen mass was

measured before and after heating in order to determine the loss of water during the

test. The salient features of the test are shown in Table 2.30.

Table 2.30 Salient Features of Test Carried out by Hanaa Fares et al

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cylinder

(0.16×0.32)

Prism

(0.1x0.1x0.4)

150, 300,

450 &

600oC

Peak

temperature

maintained

for one hour

Furnace

temperature

curve

1°C/

min

Natural

cooling

by air

Un

stressed

residual

strength

test

Jin Tao et al (2010)51

reported the results of laboratory investigations carried out to

study the effects of high temperatures ranging from room temperature to 800°C on

the compressive strength of SCC and HSC. It was reported that the hot compressive

strength of SCC decreased with increase in temperature. It was found that grade of

concrete had an effect on the strength loss of concrete, especially in the temperature

range below 400°C. Higher grades of SCC resulted in higher loss of strength. But

42

this difference was found to be less in the permanent strength loss stage. Compared

with normal strength SCC, high strength SCC was found to possess a larger

compressive strength when exposed to high temperature. It was also reported that

addition of polypropylene fibers decreased the strength .However the addition

reduced the probability of explosive spalling. The salient features of the test are

shown in Table 2.31.

Table 2.31 Salient Features of Test Carried out by Jin Tao et al

Size of the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cylinder

(0.15x0.3)

200 to

800°C -

Furnace

temperature

curve

5°C/min &

30°C/min

above

500°C

-

Un

stressed

residual

strength

test

Sivaraja (2010)87

studied the effect of high temperature on mechanical strength

properties of five different self compacting concrete mixes. Initially five different

SCC mixes such as normal concrete, SCC (Self Compacting Concrete) with flyash,

SCC with silica fume, SCC with rice husk ash and SCC with 20% quarry sand were

designed. The fresh concrete properties such as filling ability and passing ability

were ascertained. Specimens were subjected to high temperature up to 500°C and

1000°C for 1 hour in hot furnace. Mechanical properties such as compressive

strength, split tensile strength and modulus of rupture were obtained by conducting

respective tests as per Indian Standards. Results of specimens subjected to high

temperature were compared with those of conventional specimens. The salient

features of the test are shown in Table 2.32.

Table 2.32 Salient Features of Test Carried out by Sivaraja

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cube

(0.15x0.15

x0.15)

Cylinder

(0.15X0.3)

Beam

(0.5x0.1x0.1)

500 and

1000°C

Peak

temperature

maintained

for one

hour

Furnace

temperature

curve

5°C

/min

Natural

cooling

by air

Un

stressed

residual

strength

test

43

Subhash C. Yaragal et al (2010)88

tested the cube samples subjected to elevated

temperatures ranging from 100oC to 800

oC, in steps of 100

oC with a retention

period of 2 hours. After exposure, weight losses and the residual compressive

strength retention characteristics were studied. Test results indicated that weight and

strength significantly reduced with an increase in temperature. As the exposed

temperature increased, loss in weight of specimen increased, above 200oC. With

increase in grade of concrete, there was a decrease in loss of weight of specimen

after subjecting it to elevated temperatures. In general there was a substantial loss

(74%) in strength from 100oC to 800

oC for M20, M25 & M30 grades of concretes.

However for M35, M40 & M45 grades, strength loss was 80%. The observed

minimum residual strength was 18% for M45 at 800oC. Residual compressive

strength prediction equations for two ranges of temperature were derived for normal

strength concretes. The salient features of the test are shown in Table 2.33.

Table 2.33 Salient Features of Test Carried out by Subash C. Yaragal et al

Size of the

Specimen(m)

Temperature

Range

Time

Duration

Time-

Temperature

Curve

Rate of

Heating

Rate of

Cooling/

Coolant

Type of

test

Cube

(0.15

x0.15x0.15)

100oC to

800oC

Peak

temperature

maintained

for two hour

Furnace

temperature

curve

2oC/min

Natural

cooling

by air

Un

stressed

residual

strength

test

I.K. Fang et al (2010)24

designed three full scale beam exterior column sub

assemblage specimens, according to ACI 318 seismic provisions and these

specimens were subjected to ISO 834 fire test to check the fire resistance. Two

specimens were made of self compacting concrete and one was made of Normal

Concrete (NC). Analysis based on thermal properties of materials suggested in

Eurocode 2 and ANSYS software was carried out to predict the temperature

distribution of specimens. The specimens performed satisfactorily after subjecting

them to three hours of fire as per ISO 834 fire curve. The significant explosive

spalling occurred in about 25 minutes after heating. The beam deflection at the end

of heating was approximately 10 times that before heating. Most of the concrete

44

spalling occurred along the bottom edge of beams and corner of lower column

during the early twenty five minutes of heating. Relatively more spalling was

observed at bottom of the beam for the normal concrete specimen. Most of the

vertical displacements in the beam occurred in the first thirty minutes of heating,

and then the increase of vertical displacement decreased during the thirty to sixty

minutes due to the low temperature rise in beam. The normal and self compacting

concrete specimens behaved quite closely in their load displacement relationships at

load in the residual strength test. Two specimens failed in ductile flexural mode and

one specimen failed in unfavorable diagonal shear after exhibiting significant yield

behavior in beams. The salient features of the test are shown in Table 2.34.

Table 2.34 Salient Features of Test Carried out by I.K. Fang et al

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Column

(0.5 x 0.5 x

2.86)

Beam

(7.68x 0.4 x 0.5)

1193oC 180 min

ISO 834

Standard

Temperature

Curve

-

Natural

cooling

by air

Un

stressed

residual

strength

test

Bahar Demirel and Oguzhan Kelestemur (2010)6 investigated the effect of

elevated temperature on the mechanical and physical properties of concrete

specimens obtained by substituting cement with Finely Ground Pumice (FGP) at

proportions of 5%, 10%, 15% and 20% by weight. To determine the effect of silica

fume on the mechanical and physical properties of concrete containing FGP, SF

was added to all specimens except the control specimen. The specimens were

heated in an electric furnace up to 400, 600 and 800°C and kept at these

temperatures for one hour. After the specimens were cooled, Ultrasonic Pulse

Velocity (UPV), compressive strength and weight loss values were determined. The

results demonstrated that addition of the mineral admixtures to concrete decreased

both unit weight and compressive strength. It was also found that elevating the

temperature above 600°C affected the compressive strength to a larger extent. The

weight loss of concrete was more pronounced for concrete mixtures containing both

45

FGP and SF. SEM investigations conducted on the specimens confirmed the

deformation of well-developed Ca(OH)2 crystals and the C-S-H gel at temperatures

beyond 600°C. This study demonstrates that the critical temperature for concrete

specimens containing FGP or FGP and SF was 600°C, because all the hydrated

phases including C-S-H and Ca(OH)2 appeared to have amorphous structures at this

temperature instead of their characteristic crystal structures. The salient features of

the test are shown in Table 2.35.

Table 2.35 Salient Features of Test Carried out by Bahar Demirel and

Oguzhan Kelestemur

Size of the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cube

(0.1 x 0.1 x

0.1)

20,400,600,

800oC

Peak

temperature

maintained

for one

hour

Furnace

temperature

curve

2.5oC/min

Natural

cooling

by air

Un

stressed

residual

strength

test

Hanaa Fares et al (2010)33

carried out an experimental study on the properties of

self compacting concrete subjected to high temperature. Two SCC mixtures and one

vibrated concrete mixture were tested. These specimens were heated at a rate of

1°C/min upto temperatures of 150, 300, 450 and 600°C. In order to ensure a

uniform temperature distribution throughout the specimens, the temperature was

held constant at the maximum temperature for 1h before cooling. Physicochemical

properties and the micro structural characteristics were studied. Thermo gravimetric

analysis, thermo differential analysis, X-ray diffraction and SEM observations were

made. It was observed from the results that the residual compressive strength

increased between 150 and 300°C. The salient features of the test are shown in

Table 2.36.

Table 2.36 Salient Features of Test Carried out by Hanaa Fares et al

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cylinder

(0.16×0.32)

Prism

(0.1x0.1x0.4)

150, 300,

450 &

600oC

Peak

temperature

maintained

for one hour

Furnace

temperature

curve

1°C/

min

Natural

cooling

by air

Un

stressed

residual

strength

test

46

Ilker Bekir Topcu et al (2011)36

studied the effect of high temperatures on the

mechanical properties of the reinforcement bars placed between 3 and 5 cm covers

inside the mortar specimens. These reinforced mortar specimens were exposed to

20, 100, 200, 300, 500 and 800°C temperatures. Then these bars were taken out of

these mortar specimens and the mechanical properties were found. The results of

the study indicated that larger covers gave better protection to the steel bars against

high temperatures. The salient features of the test are shown in Table 2.37.

Table 2.37 Salient Features of Test Carried out by Ilker Bekir Topcu et al

Size of

the specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Beam

(0.076x0.076

x0.31

0.116x0.116

x0.35)

20°C,

100°C,

200°C,

300°C,

500°C&

800°C

Peak

temperature

maintained

for three

hour

Furnace

temperature

curve

-

Natural

cooling

by air

Un

stressed

residual

strength

test

S. Bakhtiyari et al (2011)9 evaluated the fire resistance of self compacting concrete

(SCC) containing limestone and quartz powders, with two different compressive

strengths, and compared with normal concrete. The residual mechanical strength of

the mixes at different temperatures was measured. The changes in the phase

composition of the cement pastes at high temperatures were examined with thermal

analysis and X-ray diffractometry methods. The SCC mixes showed a higher

susceptibility to spalling at high temperatures but the NC mixes suffered a higher

strength loss. Both the powder types and the compressive strength notably

influenced the fire behavior of the SCC. The quartz powder accelerated the

hydration of the SCC cement paste at high temperatures, up to 500°C. However, the

quartz contained SCC showed the highest risk of spalling among all the mixes. The

results showed that the thermal analysis could be a useful device for evaluating the

fire behavior of building materials. The salient features of the test are shown in

Table 2.38.

47

Table 2.38 Salient Features of Test Carried out by S. Bakhtiyari et al

Size of the

Specimen(m)

Temperature

Range

Time

Duration

Time-

Temperature

Curve

Rate of

Heating

Rate of

Cooling/

Coolant

Type of

test

Cube

(0.15x0.15

x0.15)

Cylinder

(0.15x0.3)

150°C,

500°C,

750°C&

1000°C

Peak

temperature

maintained

for two

hour

Furnace

temperature

curve

-

Natural

cooling

by air

Un

stressed

residual

strength

test

S. Bakhtiyari et al (2011)8 developed self compacting concrete specimens with

limestone (L) and quartz (Q) powder. The influence of this type of the powder on

the properties of fresh and hardened concrete was evaluated. Dense packing theories

were used for the mix design of samples. The equation of Fuller and Thompson for

Particle Size Distribution (PSD) of aggregates was modified considering fine

particles and a proper PSD curve was obtained for SCC. Experimental results

showed that this method needs use of less powder content and results in higher

strength/cement ratio compared to traditional mixing methods. No significant

difference was observed between the compressive strengths of specimens

containing limestone (L-specimens) and quartz (Q-specimens) powder, with similar

proportions of materials. The residual compressive strength of specimens was

examined at 500°C and contradictory behavior was observed. The type of powder

played an important role in the behavior of SCC at high temperatures. The use of

the quartz powder accelerated the hydration process and led to the development of

strength at high temperatures, around 500°C. The reason for this phenomenon is the

partial pozzolanic effect of the quartz, at an internal autoclaved condition produced

at these temperatures. Therefore, the porosity of concrete decreased and

consequently the pore pressure increased, which in turn increased the tendency of

spalling of concrete. However, as the mechanical strength of sample also increased

with development of hydration, it might overcome the produced pore pressure. In

this situation, if tensile strength of the concrete prevails over the pore pressure and

thermal stresses, spalling will not occur and the compressive strength of the

concrete will considerably increase. Such a behavior can be also seen for concretes

48

containing silica fume, because of its high pozollanic activity. The SCC containing

limestone powder has a lower risk for spalling, but its mechanical strength is

decreased with increasing temperature. About 15% reduction of the compressive

strength can be expected at temperatures around 500°C. The salient features of the

test are shown in Table 2.39.

Table 2.39 Salient Features of Test Carried out by S. Bakhtiyari et al

Size of the

Specimen(m)

Temperature

Range

Time

Duration

Time-

Temperature

Curve

Rate of

Heating

Rate of

Cooling/

Coolant

Type of

test

Cube

(0.15x0.15

x0.15)

Cylinder

(0.15x0.30)

500°C

Peak

temperature

maintained

for two hour

Furnace

temperature

curve

10°C/

min

Natural

cooling

by air

(24 hrs)

Un

stressed

residual

strength

test

Wasim Khaliq and Venkatesh Kodur (2011)95

presented the effect of temperature

on thermal and mechanical properties of self consolidating concrete and Fiber

Reinforced SCC (FRSCC). Specific heat, thermal conductivity and thermal

expansion of the specimens were measured. Compressive strength, tensile strength

and elastic modulus were found in the temperature range of 20–800°C. Four SCC

mixes, plain SCC, steel, polypropylene and hybrid fiber reinforced SCC were

considered in the test program. Temperature was found to have a significant

influence on thermal conductivity, specific heat and thermal expansion of SCC and

FRSCC. The thermal conductivity generally decreased with temperature, while the

thermal expansion increased with temperature up to 800°C. However, specific heat

remained almost constant up to about 400°C, and then increased with presence of

steel fibers. Data from mechanical property tests indicated that the presence of steel

fibers increased the high temperature splitting tensile strength and elastic modulus

of SCC. Thermal expansion of FRSCC was found to be slightly higher than that of

SCC in 20–1000°C range. Data generated from these tests were utilized to develop

simplified relations for expressing thermal and mechanical properties of SCC and

FRSCC as a function of temperature. The salient features of the test are shown in

Table 2.40.

49

Table 2.40 Salient Features of Test Carried out by Wasim Khaliq

and Venkatesh Kodur

Size of the

Specimen(m)

Temperature

Range

Time

Duration

Time-

Temperature

Curve

Rate of

Heating

Rate of

Cooling/

Coolant

Type of

test

Cylinder

(0.1x0.2

0.075x0.15)

Prism

(0.10x0.10

x0.30)

20°C to

800°C

Peak

temperature

maintained

for two

hour

RILEM

Technical

committee

TC-129

(Furnace)

5°C/

min &

2°C/

min

Natural

cooling

by air

Un

stressed

residual

strength

test

Manolia Abed Al-Wahab Ali (2011)62

investigated the residual mechanical

properties (compressive strength, modulus of rupture and dynamic modulus of

elasticity) of self compacting concrete exposed to elevated temperatures ranging

from 100-800oC. Also he studied the influence of High Reactivity Metakaolin

(HRM), as a partial replacement of cement, for improving the mechanical properties

before and after exposure to elevated temperatures. The concrete specimens were

subjected to a temperature of 100, 200, 400, 600 and 800°C with exposure duration

of 2 hours. The performance of SCC containing HRM was found to be better than

that of SCC without HRM. The residual compressive strength of SCC with HRM

after an exposure to a temperature of 800oC was found to be 73.2% while for the

normal SCC the residual strength was only 65% of the original strength. At the

same exposure temperature of 800oC, the reduction in the modulus of rupture was

found to be more than that of compressive strength, the difference being in the

range 2% - 12.4%. The reduction in the dynamic modulus of elasticity was found to

be higher than that of the compressive strength and modulus of rupture. The salient

features of the test are shown in Table 2.41.

Table 2.41 Salient Features of Test Carried out by Manolia Abed Al-Wahab Ali

Size of the

Specimen(m)

Temperature

Range

Time

Duration

Time-

Temperature

Curve

Rate of

Heating

Rate of

Cooling/

Coolant

Type of

test

Cube

(0.15x0.15x0.15)

Prism

(0.10x0.10x0.5)

100°C,200°C,

400°C,

600°C&

800°C

2 hr

Furnace

temperature

curve

2°C/

min

Natural

cooling

by air

Un

stressed

residual

strength

test

50

J.E. Park et al (2011)81

investigated the behavior of high strength concrete

columns at elevated temperatures including temperature distributions and spalling.

Seven short HSC columns having different design parameters were fabricated and

placed in a heating chamber for fire tests. The design parameters are cross sectional

areas, cover thicknesses, and arrangements of reinforced bars. The columns were

heated using temperature control system following ISO 834 time temperature curve.

Temperature distributions were obtained from temperature gauges located inside the

columns during the fire tests, and the spalling depths of the columns were measured

after the fire tests in order to examine the reduction in the cross sectional area due to

spalling. They reported that cross sectional area, cover thickness, and reinforcement

arrangements, affected the temperature distribution and spalling of HSC columns.

The column with the larger cross sectional area and thinner concrete cover showed

the higher temperature distributions. Even with a same reinforcement ratio, the

more distributed arrangement of reinforcing bars resulted in the higher temperature

distributions of the HSC column. Spalling of the HSC column was found to be

highly related to the temperature distribution; that is the HSC column showing the

higher temperature distributions resulted in the larger spalling. However, the effect

of cross sectional area of the column on area loss was not significant. The salient

features of the test are shown in Table 2.42.

Table 2.42 Salient Features of Test Carried out by J.E. Park et al

Size of the

Specimen(m)

Temperature

Range

Time

Duration

Time-

Temperature

Curve

Rate of

Heating

Rate of

Cooling/

Coolant

Type

of

test

HSC Column

1.5x0.35x0.35

1.5x0.45x0.45

1.5x0.55x0.55

1193oC 160 min

ISO 834

Standard

Temperature

Curve

-

- -

Jayasree.G et al (2011)50

carried out an investigation to determine the residual

characteristics of RC beams subjected to elevated temperature under unstressed and

stressed conditions. The RC beams were of size120mmx120mmx1500mm and

designed with single and double reinforcement and designated as Type I and Type

II respectively. M20 grade of concrete was used. The temperatures were kept as

51

100°C, 200°C, 300°C, 400°C and 500°C and the duration of exposure was 4 hours.

The specimens were cooled in air and the residual properties were tested by

conducting two point bending test on RC beams and their behavioral parameters

were compared with those of the reference specimens. The extent of damage

suffered was measured by the damage factor and was found to be around 32 % for

Type I beams and 48% for the Type II beams when tested under unstressed test

condition and exposed to 500°C. The damage factor was around 33% for Type I

beams and 49% for Type II beams in stressed test condition for the same exposed

temperature. The degradation in stiffness at 50% of ultimate load was nearly 36%

and 35% for Type I and Type II beams in unstressed test and 49% and 76.6%

respectively for stressed test when exposed to 500°C. The ultimate load of RC

beams tested in stressed condition was only 5% lower than that of the beams under

unstressed test condition. The salient features of the test are shown in Table 2.43.

Table 2.43 Salient Features of Test Carried out by Jayasree.G et al

Size of the

Specimen

(m)

Temperature

Range

Time

Duration

Time-

Temperature

Curve

Rate of

Heating

Rate of

Cooling

/Coolant

Type of test

Beam

(1.5x0.12

0.12)

100oC,

200oC,

300oC, 400

oC

& 500oC

4 Hours

Furnace

temperature

curve

-

Natural

cooling

by air

Stressed &

Un stressed

residual

strength test

Krishna Rao M.V et al (2011)59

investigated the effect of sustained elevated

temperature on the properties of ordinary concrete of M40 grade containing

different types of cements and cured by two different methods. The specimens were

heated to150°C, 300°C and 450°C for 1 hour duration in a muffle furnace.

Compressive strength of the specimens was found after air cooling to the room

temperature. The variables considered in the study were types of cementing

material, temperature and method of curing. Results indicated the losses of strength

due to high temperature exposure and the presence of 10% silica fume as a cement

replacement seemed to have no significant effect. The compressive strength of

concrete and the weight of concrete decreased with increasing temperature.

52

Specimens subjected to conventional water curing performed relatively better than

those of membrane curing. The salient features of the test are shown in Table 2.44.

Table 2.44 Salient Features of Test Carried out by Krishna Rao M.V et al

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cube

(0.15x0.15x0.15)

150°C,

300°C&

450°C

Peak

temperature

maintained

for one

hour

Furnace

temperature

curve

-

Natural

cooling

by air

Un

stressed

residual

strength

test

Yining Ding et al (2011)98

analyzed the effect of various fibres on the residual

compressive strength, the ultimate load, flexural toughness, the failure pattern and

the fracture energy of Self Compacting High Performance Concrete (SCHPC) after

exposure to various high temperatures. The micro Polypropylene Fibre (PP fibre)

could mitigate the spalling of SCHPC member significantly, but did not show clear

effect on the mechanic properties of concrete. The macro steel fibre reinforced

SCHPC showed higher flexural toughness and ultimate load before and after high

temperatures. The mechanical properties of Hybrid Fibre reinforced concrete

SCHPC (HFSCHPC) were better than those of mono fibre reinforced SCHPC after

exposure to higher temperature. The failure mode changed from pull out of steel

fibres at lower temperature to breaking down of steel fibres at higher temperature.

The use of hybrid fibre can be effective in providing the residual strength and in

improving the toughness and fracture energy of SCHPC after high temperature. The

combination of steel fibres and PP fibres resulted in positive composite effect on the

post peak behaviour of SCHPC materials before and after exposure to high

temperature. During the high temperature, PP fibre can mitigate or prevent the

explosive spalling, enhance the residual strength and fracture energy, but does not

increase the toughness of SCHPC. Steel fibres were found to improve the residual

compressive strength, enhance the ductility of SCHPC subjected to different high

temperatures, but it was not able to mitigate the spalling of concrete at high

temperature. This observation supports the use of fibre cocktail in SCHPC as a fire

53

resistant material. They concluded that the use of fibre cocktail reinforced SCHPC

material can be very effective in reducing thermal stress and in improving

composite effect of hybrid fibres on the post crack behaviour during heating process

at high temperature. The salient features of the test are shown in Table 2.45.

Table 2.45 Salient Features of Test Carried out by Yining Ding et al

Size of the

specimen

(m)

Temperature

range Time duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cube

(0.1x0.1x

0.1)

Beam

(0.1x0.1x

0.4)

300,600,

900°C

Peak

temperature

maintained for

three hour

Furnace

temperature

curve

6°C/min

Natural

cooling

by air

Un

stressed

residual

strength

test

S. Bakhtiyari et al (2011)7 investigated the influence of permanently expanded

polystyrene formwork on the fire resistance of self compacting concrete. SCC was

produced and cured by two different conditions, one by the traditional method and

the other inside expanded polystyrene forms. Normal vibrated concrete with similar

characteristic strength was also produced and cured under the same conditions for

comparison. The specimens were exposed to different high temperatures. The

residual mechanical strengths, phase composition and porosity changes at high

temperatures were investigated. The SCC was found to be more susceptible to

spalling than the normal vibrated concrete. This is due to more packing of the SCC,

giving rise to higher pore pressure at high temperatures. The insulating permanent

forms raised the risk of spalling of concretes and had significant influence on the

residual mechanical strengths of the concrete. The relative residual strength of the

SCC was higher than that of the NC at high temperatures. Hence, if the spalling can

be controlled, for example using polypropylene fibers, the fire resistance of the SCC

can be higher than that of the NC. The loss of residual strength of concrete was not

very significant until 500°C. The relative residual strength of the SCC was

considerably increased around 500°C. It was due to acceleration of hydration at

medium high temperatures, which was confirmed with XRD and porosimetry tests.

The salient features of the test are shown in Table 2.46.

54

Table 2.46 Salient Features of Test Carried out by S. Bakhtiyari et al

Size of the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cube

(0.15 x 0.15

x 0.15)

Cylinder

(0.15 x 0.30)

150,500,

750 &

1000°C

Peak

temperature

maintained

for two

hour

Furnace

temperature

curve

-

Natural

cooling

by air

(24 hrs)

Un

stressed

residual

strength

test

E.G. Choi and Y.S. Shin (2011)20

investigated the effects of concrete compressive

strength and cover thickness on the structural behavior of reinforced concrete beams

under fire. For this purpose, four normal strength and high strength concrete beams

were fabricated and tested under the ISO 834 standard fire curve to point of the

failure. The test setup was designed to evaluate the heat distribution and

displacement changes of simply supported beams subjected to sustained loads under

fire. Test results for normal strength and high strength concrete beams were

compared for each of the test variables. The test results indicated that the

relationships between time and temperature distributions in the beam sections are

very similar and are unrelated to the strength of the concrete, with the exception of

the upper part of the beam section. It was also found that the rate of increase in the

deflection for both normal strength and high strength concrete beams were very

similar before spalling but became remarkably high for high strength concrete

beams after spalling. A simplified model was proposed to determine the effect of

spalling on the temperature gradient of a high strength concrete beam. The results of

Finite Difference Method (FDM) analysis using this proposed model indicated

temperature gradient that was similar to that of the test results. The salient features

of the test are shown in Table 2.47.

Table 2.47 Salient Features of Test Carried out by E.G. Choi and Y.S. Shin

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Beam

(0.25 x 0.4 x

4.7)

- -

ISO 384

Time

Temperature

Curve

- - Stressed

test

55

Kiang Hwee Tan and Yuqian Zhou (2011)53

investigated the flexural behavior of

Fiber Reinforced Polymer (FRP) strengthened beams after exposure to elevated

temperatures. Twenty five specimens making up un-strengthened beams and FRP

strengthened beams were fabricated. Glass and basalt FRP systems were used with

and without protective systems, which included a cement mortar overlay and two

types of commercially available intumescent coatings. Typical temperature time

histories at the surface of FRP laminates, FRP concrete interface, internal steel bars

and center of beams were monitored by using two specimens. The other specimens

were tested to failure under three point bending after subjecting them to elevated

temperatures. Test results indicated a general decrease in the initial stiffness and

ultimate strength of the specimens with an increase in the exposed temperature. The

protective systems appeared to preserve the structural integrity of glass FRP

systems when the elevated temperature was less around 700°C. Basalt FRP

strengthened beams exhibited less deterioration in ultimate strength than glass FRP

strengthened beams. The salient features of the test are shown in Table 2.48.

Table 2.48 Salient Features of Test Carried out by Kiang Hwee Tan

and Yuqian Zhou

Size of the

specimen (m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Beam

(0.4x0.1x0.1)

950oC

Peak

temperature

obtained

after one

hour

ASTM

E119

(Furnace)

-

Natural

cooling

by air

Un

stressed

residual

strength

test

Neelam Pathak and Rafat Siddique (2012)75

studied the properties of self

compacting concrete such as compressive strength, splitting tensile strength, rapid

chloride permeability, porosity, and mass loss when exposed to elevated

temperatures. Mixes were prepared with three percentages of class F flyash ranging

from 30% to 50% and for comparison; one controlled mixture without flyash

was also produced. The specimens were heated to 20oC, 100

oC, 200

oC, and 300

oC.

Ordinary Portland cement was used for making SCC mixes. The 28th

day

compressive strength ranged between 21.43 and 40.68 MPa and splitting tensile

56

strength ranged from 1.35 to 3.60 MPa. Test results clearly show that there is little

improvement in compressive strength within temperature range of 200–300oC as

compared to 20–200oC but there is little reduction in splitting tensile strength

ranging from 20 to 300oC with the increase in percentage of flyash. The salient

features of the test are shown in Table 2.49.

Table 2.49 Salient Features of Test Carried out by Neelam Pathak

and Rafat Siddique

Size of the

Specimen(m)

Temperature

Range

Time

Duration

Time-

Temperature

Curve

Rate of

Heating

Rate of

Cooling/

Coolant

Type of

test

Cube

(0.15x0.15

x0.15)

Cylinder

(0.15x0.3

0.1x0.05)

20°C

100°C,

200°C&

300°C

Peak

temperature

maintained

for one

hour

RILEM

Technical

committee

TC-129 (39)

1°C/min

Natural

cooling

by air

(24hrs)

Un

stressed

residual

strength

test

Neelam Pathak and Rafat Siddique (2012)74

studied the use of foundry sand and

flyash on the properties of self compacting concrete such as compressive strength,

splitting tensile strength, modulus of elasticity, rapid chloride permeability, porosity

and mass loss when exposed to elevated temperatures. The influence of flyash as

partial replacement of cement and foundry sand as partial replacement of sand on

the properties of SCC was investigated. Mixes were prepared with three percentages

of flyash ranging from 30% to 50% and one controlled mix without flyash was also

prepared for comparison. Fine aggregate was replaced with 10% of foundry sand.

The specimens were heated up to 27oC, 100

oC, 200

oC, and 300

oC and in order to

ensure a uniform temperature distribution throughout the specimens, the

temperature was kept constant for a period of 1 h before cooling. Using ordinary

portland cement, an increase of about24–25% in compressive strength, 18–22% in

splitting tensile strength was observed at 28 days when flyash content was

decreased from 50% to 30%. Also test results clearly show that there is little

improvement in compressive strength within the temperature range of 200–300oC as

compared to 27–200oC. But the rate of splitting tensile strength and modulus of

elasticity loss were found to be higher than those of the compressive strength loss at

elevated temperatures. The salient features of the test are shown in Table 2.50.

57

Table 2.50 Salient Features of Test Carried out by Neelam Pathak

and Rafat Siddique

Size of the

Specimen(m)

Temperature

Range

Time

Duration

Time-

Temperature

Curve

Rate of

Heating

Rate of

Cooling/

Coolant

Type of

test

Cube

(0.15x0.15

x0.15)

Cylinder

(0.15x0.3

0.1x0.05)

27°C

100°C,

200°C&

300°C

Peak

temperature

maintained

for one

hour

RILEM

Technical

committee

TC-129

1°C/min

Natural

cooling

by air

(24hrs)

Un

stressed

residual

strength

test

Ozge Andic-Cakır and Selim Hizal (2012)79

prepared Self Consolidating

Lightweight Concrete (SCLWC) mixtures using two different lightweight coarse

aggregates and by replacing normal weight crushed coarse limestone aggregate at a

constant water/powder ratio. One of the SCLWC mixtures was also prepared at a

different water/powder ratio. All the mixtures were exposed to 300, 600 and 900°C,

respectively. Type of lightweight aggregate and water/powder ratio were found to

affect the water transport characteristics and resistance of the mixtures subjected to

elevated temperatures. Compressive strength and modulus of elasticity of the

mixtures were found to be affected by the type of the aggregate and w/c (or w/p)

ratio, while splitting tensile strength was mainly affected by the type of the

aggregate alone. Type and porosity of the aggregates and w/c (or w/p) ratio of the

mixtures were the main factors that affect the porosity and thus, the water

absorption capacity of self consolidating lightweight concrete samples. The porosity

of concrete was found to adversely affect the resistance of self consolidating

lightweight concrete subjected to elevated temperatures. Even though the specimens

were pre dried at 105oC for 24 h before the exposure to elevated temperature, the

pores in hardened concrete still acting as water reservoirs during exposure was

attributed to be the main reason for this behaviour. Such exposure cracks were

observed in the micro structural analysis of deteriorated pumice containing

specimens after exposure to elevated temperatures. For a given lightweight

aggregate type, the decrease in w/c (or w/p) ratio decreased the permeability of

concrete which is expected to have an adverse effect during exposure to elevated

temperatures; however, this serves as a protection against high temperature by

58

decreasing the moisture content of specimens. The salient features of the test are

shown in Table 2.51.

Table 2.51 Salient Features of Test Carried out by Ozge Andic-Cakır and Selim Hizal

Size of the

Specimen

(m)

Temperature

Range

Time

Duration

Time-

Temperature

Curve

Rate of

Heating

Rate of

Cooling/

Coolant

Type of

test

Cube

(0.15x0.15

x0.15)

(0.05x0.05

x0.05)

20°C

300°C,

600°C&900°C

Peak

temperature

maintained

for two

hour

Furnace

temperature

curve

15°C/

min&

5°C/

min

Natural

cooling

by air

Un

stressed

residual

strength

test

Mucteba Uysal (2012)68

carried out an experiment to evaluate the performance of

self compacting concrete subjected to elevated temperatures. For this purpose,

Portland cement (PC) was replaced with Limestone Powder (LP), Basalt Powder

(BP) and Marble Powder (MP) in various proportions. Polypropylene (PP) fibers

were added to 50% of the specimens to understand the effect of PP fibers on the

behavior of SCCs subjected to high temperatures. SCC mixtures were prepared with

water to cement ratio of 0.33 and polypropylene fibers content was 2 kg/m3 for the

mixtures containing polypropylene fibers. Specimens were heated up to

temperatures of 200, 400, 600 and 800oC. Tests were conducted to determine loss in

weight and compressive strength. Ultrasonic pulse velocity was determined and

surface crack observations were made after being exposed to elevated temperatures.

Experimental results indicated that a severe strength loss was observed for all of the

SCC mixtures after exposure to 600oC, particularly the specimens containing

polypropylene fibers though they reduce and eliminate the risk of the explosive

spalling. At higher replacement levels of LP, BP and MP, further lower residual

strength was observed. In terms of percent residual properties, control specimens

performed better than filler additive specimens for all heating cycles. The salient

features of the test are shown in Table 2.52.

59

Table 2.52 Salient Features of Test Carried out by Mucteba Uysal

Size of the

Specimen(m)

Temperature

Range

Time

Duration

Time-

Temperature

Curve

Rate of

Heating

Rate of

Cooling/

Coolant

Type of

test

Cube

0.10x0.10

x0.10)

200°C,

400°C,

600°C,

800°C

Peak

temperature

maintained

for three

hour

RILEM

Technical

committee

TC-129

(Furnace)

1°C/

min

Natural

cooling

by air

Un

stressed

residual

strength

test

Rahul P. Chadha et al (2012)84

carried out an experiment investigation to find out

the effect of fire on flexural strength of reinforced concrete beams. After heating,

the specimens were allowed to reach the room temperature and some samples were

quenched with water for rapid cooling. Flexural strength was determined after

cooling. Simultaneously, theoretical investigation of various parameters in relation

to fire was carried out. The flexural strengths of the beams exposed to fire at 550°C

& 750°C for 60 and 120 minutes were found to be less than those of the reference

beam by about 34.84% and 44.37% respectively. When the beams were exposed at

950°C there was a significant decrease in flexural strength and the reduction was

found to be 61.99% and 64.24% respectively. The reduction in strength for beams

exposed to fire with a cover thickness of 25mm & 30mm was around 35 % less than

that for the reference beam at 550°C. The reduction in strength for beams exposed

to fire with a cover thickness of 25mm & 30mm was found to be 60% and 47%

when compared with the reference beam at 750°C. The reduction was 64% and

61% respectively for beams exposed to 950°C. Spalling of concrete was observed in

the beam exposed to fire for 2 hr at 950°C at the time of removal from furnace,

which increased with time under normal weathering conditions. The salient features

of the test are shown in Table 2.53.

Table 2.53 Salient Features of Test Carried out by Rahul P. Chadha et al

Size of the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Beam

(0.15 x

0.15x 0.7)

550,750

950oC

1 hour,

2 hour

Furnace

temperature

Curve

-

Natural

cooling &

Water

quenching

Un stressed

residual

strength

test

60

Mucteba Uysal et al (2012)70

carried out an experimental investigation on the

performance of self compacting concrete subjected to high temperatures. For this

purpose, Portland cement was replaced with flyash and Granulated Blast Furnace

Slag (GBFS) in various proportions with and without polypropylene fibers. The PP

fiber content was 2 kg/m3 for the mixtures that contained fibers. When the

specimens were 56 days old, they were heated to elevated temperatures (200, 400,

600 or 800°C). Tests were conducted to determine the weight loss and the

compressive strength. The change in the ultrasonic pulse velocity was measured and

observations for surface cracks were made after the specimens were exposed to

elevated temperatures. A severe strength loss was observed for all of the specimens

after 600°C, particularly for the specimens that contained PP fibers; however, the

fibers reduced and eliminated the risk of explosive spalling. Based on the test

results, it was concluded that the performance of FA concrete is better than that of

the GBFS concrete. The salient features of the test are shown in Table 2.54.

Table 2.54 Salient Features of Test Carried out by Mucteba Uysal et al

Size of the

specimen

(m)

Temperature

range

Time

duration

Time-

temperature

curve

Rate of

heating

Rate of

cooling/

coolant

Type of

test

Cube

(0.1x0.1x0.1)

200, 400,

600&800oC

Peak

temperature

maintained

for three

hour

Furnace

temperature

curve

1°C/

min

Natural

cooling

by air

0.4ºC/min

Un

stressed

residual

strength

test

2.2.3 Analytical Investigations on the Behaviour of Concrete Materials Under

Elevated Temperatures

Kodur and Phan (2007)57

discussed about the material, structural detailing and fire

characteristics that influence the performance of HSC under fire conditions. Data

from earlier experimental and numerical studies were used to illustrate the impact of

the concrete mix design and the structural detailing on fire performance of HSC

systems. The fire characteristics, concrete mix properties and structural design

features were found to have an influence on the fire performance of HSC columns.

The intensity of fire, size of fire, heat output, and rate of heating were found to

61

influence the degree of spalling and the fire endurance duration of HSC members.

The main parameters that influence fire performance of HSC at material level were

found to be strength of concrete, silica fume content, concrete moisture content,

density of concrete, % of fibre reinforcement and type of aggregate. At the

structural level, tie spacing, confinement, tie configuration, load levels and size of

the members were found to play an important role in determining the fire

endurance. They reported that by adopting proper guidelines, both at material and

structural level, spalling in HSC members can be minimized to a significant level

and fire endurance can be enhanced. Adding polypropylene fibres to concrete mix

was found to be effective in minimizing the spalling in HSC under hydrocarbon

fires.

Kodur and Dwaikat (2008)54

developed a macroscopic finite element model to

investigate the effect of fire induced spalling on the response of reinforced concrete

beams. Spalling is accounted for in the model through pore pressure calculations in

concrete. The principles of mechanics and thermodynamics were applied to

compute the temperature induced pore pressure in the concrete structures as a

function of fire exposure time. The computed pore pressure was checked against the

temperature dependent tensile strength of concrete to determine the extent of

spalling. Using the model, case studies were conducted to investigate the influence

of concrete permeability, fire scenario and axial restraint on the fire induced

spalling and also on the response of RC beams. Results from the analysis indicate

that the fire induced spalling, fire scenario, and axial restraint have significant

influence on the fire response of RC beams. It was also shown that permeability of

concrete has a substantial effect on the fire induced spalling and thus on the fire

response of concrete beams. The fire resistance of high strength concrete beams can

be lower than that of normal strength concrete beams due to fire induced spalling

resulting from the low permeability of high strength concrete.

Kodur and Dwaikat (2008)55

presented a numerical model, in the form of a

computer program, for tracing the behavior of reinforced concrete beams exposed to

fire. The three stages associated with the numerical procedure for evaluating fire

62

resistance of RC beams were namely, fire temperature calculation, thermal analysis

and strength analysis. A simplified approach to account for spalling under fire

conditions was also incorporated in the model. The use of the computer program for

tracing the response of RC beams from the initial pre loading stage to collapse

stage, due to the combined effect of fire and loading, was demonstrated. The

validity of the numerical model was established by comparing the predictions from

the computer program with the results from full scale fire resistance tests. Through

the results of numerical study, it was shown that the type of failure criterion has

significant influence on predicting the fire resistance of RC beams.

Wu and Lu (2009)96

developed a beam element model to analyse reinforced

concrete beams at elevated temperature using the principle of virtual work. After

validating the model with the results of an available experimental program, a RC

beam with elastic axial and rotational restraints at beam ends was selected for

numerical parametric study. The parameters investigated included different spans,

different levels of applied load, different types of loads and different levels of axial

and rotational stiffness at beam ends. Through the parametric analysis, it was found

that axial restraint induced axially compressive force and increased the mid span

deflection when temperature was increased. The effect of the rotational restraint on

the generated axial force was found to be less.

R.A. Hawileh et al (2009)34

investigated the fire performance of Carbon Fiber

Reinforced Polymer (CFRP) strengthened members subjected to various

environmental exposure factors and their resistance to heat transfer. A detailed

finite element model of a CFRP strengthened reinforced concrete T-beam was

developed. The model accounts for the variation in the thermal and mechanical

parameters of the constituent materials with temperature, including CFRP and

insulation materials. Nonlinear time domain transient thermal stress finite element

analysis was performed using the commercial software ANSYS to study the heat

transfer mechanism and deformation within the beam for fire conditions initiating

from the bottom of the beam. To relate the simulation to an actual case, a reinforced

concrete T-beam strengthened with CFRP and fire tested by other investigators was

63

modeled. The progression of temperature in the beam, CFRP, reinforcing steel, and

along the CFRP concrete interface was compared with the observed fire test data.

The predicted results were found to be in good agreement with the measured ones.

In addition, the mid span deflection was found to increase nonlinearly during the

fire exposure time due to the increase in the total strain on the tension side of the

beams and due to concrete cracking.

Kodur et al (2009)93

developed a numerical model for tracing the response of Fiber

Reinforced Polymer (FRP) strengthened reinforced concrete beams under fire

conditions. The model was based on a macroscopic finite element approach and

utilized moment curvature relationships to trace the response of insulated FRP

strengthened RC beams from linear elastic stage to collapse under any given fire

exposure and loading scenarios. In the analysis, high temperature material

properties, load and restraint conditions, material and geometric nonlinearity were

accounted for, and a realistic failure criterion was applied to determine the failure of

beams. The model was validated against fire test data on FRP strengthened RC

beams and was applied to study the effect of FRP strengthening, insulation scheme

and failure criterion on the fire response of FRP strengthened RC beams. Results

from the model indicated that the fire behavior of FRP strengthened RC beams,

provided with supplemental fire insulation, was as good as that of unstrengthened

RC beams. A case study was also presented to illustrate the application of the model

for optimizing the fire insulation scheme to achieve required fire resistance in FRP

strengthened concrete beams.

Zhaohui Huang (2010)99

developed a nonlinear procedure to model the bond

characteristic between concrete and reinforcing steel for reinforced concrete

structures subjected to fire load. The accuracy and reliability of the model were

demonstrated by the analysis of one pull out test and one beam test at ambient

temperature. Four full scale beams were tested under two fire conditions. The model

was found to predict the response of reinforced concrete members and structures in

a fire with acceptable accuracy. It was reported that the bond condition between the

concrete and reinforcing steel bar has an important influence on the fire resistance

64

of reinforced concrete structures, especially when the temperature of the reinforcing

steel bar is high (more than 500°C).

Kodur and Dwaikat (2011)56

proposed an approach for evaluating the fire

resistance of reinforced concrete beams. A macroscopic finite element model was

applied to study the influence of various parameters on the fire resistance of RC

beams. Data from parametric studies were utilized to develop a simplified

expression for evaluating the fire resistance of an RC beam as a function of

influencing parameters. The validity of the proposed approach was established by

comparing the fire resistance predictions with those obtained from finite element

studies as well as from fire resistance tests. Predictions from the proposed equation

were also compared with fire resistance estimates from current codes of practice.

The applicability of the approach to design situations was illustrated through a

numerical example. The proposed rational approach expressed fire resistance in

terms of conventional structural and material design parameters, and thus facilitates

easy evaluation of fire resistance. The proposed approach yielded better estimates

than those from current codes of practice and thus can be used to evaluate the fire

resistance of RC beams with an accuracy that will be adequate for design purposes.

2.3 Conclusions Based on Review of Literature

Inspite of a few investigations carried out on fire resistance of SCC, further studies

on fire resistance of self compacting concrete elements are needed. Special attention

has to be paid to the material properties for analysis and evaluation of the residual

strength of structural elements exposed to fire. The considerable reduction in

compressive strength, tensile strength, flexural strength and Young’s modulus has

been observed for concrete specimens exposed to elevated temperatures. Since SCC

contains mineral and chemical admixtures, the behavior of SCC specimens

subjected to high temperatures may be different from that of Normal compacting

concrete and High performance concrete. The effect of grade of SCC, reinforcement

percentage, cover, type of cooling, rate of heating etc have to be clearly understood.

Hence an attempt has been made to understand the influence of the key parameters

that will affect the performance of SCC under elevated temperatures.