chapter3 preliminary investigation -...

CHAPTER 3

PRELIMINARY INVESTIGATION

3.1 GENERAL

Self Compacting Concrete is an innovative concrete for the design of which no codal

recommendations are available. Researchers across the world have developed many

methods for mix proportioning of sec. Similarly different test methods have been

developed to characterise the workability properties of Sec. So far no single method

or combination of methods has achieved universal approval.. So each mix should be

tested by more than one test method for the different workability parameters.

Laboratory trials should be done to verify properties of the initial mix composition.

When the advantages of see such as capability of Hawing through congested

reinforcement are combined \"v1th that of steel fibres such as increase in ductility and

toughness, the resulting material, steel fibre reinforced self compacting concrete

(SFRCC) would be a promising material for extending the applications of sec to

structures in seismic zones. Fibres are known to bridge cracks, retard their

propagation and improve the properties of sec.

This chapter deals w1th the tests on constituent materials, mix proportioning for the

development of 40MPa see mix, use of lvI-Sand in sec, study on int1uence of steel

fibres on fresh and hardened properties of sec. The volume fraction of fibres was

varied from 0%, 0..25%, 0.5%,0.75% and 1% with aspect ratio (lid) 30, 50 and 70. To

study the fresh properties slump flow test, V-funnel test, V-box test and L-box test

were conducted. Hardened properties like cube and cylinder compressive strength,

split tensile strength, flexural strength and modulus of elasticity were determined. For

comparisol4 eve mix of similar strength was studied. Studies on the durability

properties ofsce were also carried out and compared with CVC.

3.2 TESTS ON MATERIALS

The constitutive materials used in this study are cement, flyash, manufactured sand

(M-Sand); river sand, coarse aggregate, water, superplasticizers, steel fibres and

54

HYSD bars. These materials were tested as per the standard testing procedures to

check the acceptability of the materials and the properties of the same obtained are

given below.

3.2.1 Cement

Ordinary Portland Cement 53 grade conforming to IS 12269:1999 was used.

Laboratory tests were conducted on cement to determine standard consistency, initial

and final setting time, and compressive strength as per IS 269: 1998 and IS 4031 :2000

and its results are tabulated in Table 3.1. The results conforms to the IS

recommendations.

Table 3.1 Properties of Cement

Sl. No Test conducted Result

1 Standard consistency 32%

2 Initial setting time 170 minutes

3 Final setting time 480 minutes

4 3 day compressive strength 27.67N/mmk

5 7 day compressive strength 39.93 N/mmk

6 28 day compressive strength 54.22 N/mmk

3.2.2 Flyash

Fly ash is a fine inorganic material with pozzolanic properties, which can be added to

cement to improve its cementitious properties. A high quality flyash generally permits

a reduction in water content of a concrete mixture, without loss of workability. The

flyash of specific gravity 2.1 obtained from Hindustan Newsprint Limited, Kottayam,

was used for experiments. The test results collected from the manufacturer are given

in Table 3.2.

Table 3.2 Chemical Composition of Fly Ash

Sl. No. Constituents Quantity (%)

1 Silica (Si02) 59.42

2 Alumina (Ah03) 32.36

3 Ferric Oxide (Fe203) 4.07

4 Calcium oxide (CaO) 0.18

5 Loss of ignition 3.75

55

3.2.3 Fine Aggregate

In see, the quantity of fine aggregate is normally more than that of coarse aggregate.

Presently, there is an acute shortage of river sand and quite often the river sand

obtained from local vendors does not meet all the requirements of fine aggregate. In

this circumstance manufactured sand (M-Sand) offers a viable alternative to river

sand. A combination of river sand and M-Sand was used as fine aggregate in this

study.

3.2.3.1 River sand

Laboratory tests were conducted on river sand to determine the different physical

properties as per IS 383:1970. River sand passing through 4.75 mm sieve was used for

the experiments. Sieve analysis was done to determine the fineness modulus and grain

size distribution. The gradation curve is shown in Fig. 3.1. The test results conforms

river sand to zone II of the IS recommendations and are tabulated in Table 3.3 and

Table 3.4

Table 3.3 Properties of River Sand

SI. No. Test conducted Result

1 Specific gravity 2.58

2 Bulk density( glee) 1.76

3 Void ratio 0.45

4 Porosity (%) 30.80

5 Fineness modulus 2.95

6 Moisture content at maximum bulking (%) 6.00

7 Percentage of maximum bulking (%) 43.00

Table 3.4 Sieve Analysis of River Sand

IS sieve Weight % Weight Cumulative %% Passing

(mm) retained (kg) retained weight retained4.75 0 0 0 100

2.36 0.218 14.533 14.533 85.466

1.18 0.399 26.600 41.133 58.866

0.60 0.311 20.733 61.867 38.133

0.30 0.333 22.200 84.067 15.933

0.15 0.153 10.200 94.267 5.733

56

120

100 .,A--,,80 /Cl

s: /'i)ell 60 /".",A.

~ /40 /

/"" /'20 /'

" /

o -I. ./~-

0.1 1 10

Log sieve opening In mm

--..-5arrple

-.- Upper Urrit

-.- Lower ~rrit

Fig. 3.1 Gradation Curve ofRiver Sand

3.2.3.2 Manufactured sand (M-Sand)

Commercially available M-Sand was used. Laboratory tests were conducted on

M-Sand to determine its physical properties as per IS 383:1970. M-Sand passing

through 4.75mm sieve was used tor the experiments. Sieve analysis was done to

determine the fineness modulus and grain size distribution. The gradation curve tor

M-Sand is shown in Fig. 3.2. The test results conforms M-Sand to zone II of the IS

recommendations and are tabulated in Table 3.5 and 3.6

Table 3.5 Properties of Manufactured Sand



2 Bulk density (glee) 1.81

3 Void ratio 0.36


5 Fineness modulus 2.53

6 Moisture content at maximum bulking (%) 10.00

7 Maximum bulking (%) 61.48

57

Table 3.6 Sieve Analysis of Manufactured Sand

IS sieve Weight %Weight Cumulative %% Passing

(mm) retained (kg) retained retained

4.75 0 0 0 100

2.36 0.117 7.800 7.800 92.200

1.18 0.352 23.467 31.267 68.733

0.60 0.285 19.000 50.267 49.733

0.30 0.333 22.200 72.467 27.533

0.15 0.278 18.533 91.000 9.000

-...--sallllle

-.- \.%lper firrit

- It!- Low er IlIlit

10

-

1Log sieve opening in mm

,,"",."/

/,./'

//

//

_/O+-----;liI""'---------r----------.

0.1

20

120 ]

100 I

~ 80.~"iii III) 60:.'ifl.

40

Fig. 3.2 Gradation Curve of Manufactured Sand

3.2.4 Coarse Aggregate

Locally available gravel was used as coarse aggregate. For proper gradation,

combination of 6mm and 12.5mm aggregates were used. Laboratory tests were

conducted on coarse aggregate to determine the different physical properties as per IS

383:1970. Experiments include sieve analysis and determination of specific gravity.

The test results are given in Table 3.7 and Table 3.8 and corresponding gradation

curve in Fig. 3.3 which conforms to IS recommendations.

58

Table 3.7 Properties of Coarse Aggregate



2 Bulk density (glee) 1.604

3 Void ratio 0.726


5. Fineness modulus 6.48

Table 3.8 Sieve Analysis of Coarse Aggregate.

IS sieve size Weight % Weight Cumulative % %

(mm) retained (kg) retained retained Passing

12.50 0.45 15 15.00 85.0

10.00 0.85 28.33 43.33 56.7

4.75 1.4 46.67 90.00 10.0

120

100 ,80 ;

C»Il: --+-saftllte'I 60 I -��_ Upper finell

Q. , -.... Lower Iirriltf!.

40 II. /

20 ;-/

01 10 100

Log sieve opening in mm

Fig. 3.3 Gradation Curve of Coarse Aggregate

3.2.5 Chemical Admixture

see is considered as a high perfoffilance concrete and to achieve its fresh properties a

number of ingredients are necessary. Workability, filling ability and flowabilty of

59

sec without segregation can be achieved by the proper addition of chemical

admixtures. The admixtures used for SCC are mainly superplasticisers and viscosity

modifying agents. Superplasticisers are an essential component of SCC.

Superplasticiser improves the workability of mix without addition of water whereas

viscosity modifying agents helps to reduce segregation of SCC mix. Viscosity

modifying agents were not used in this study.

Superplasticiser: Modified polycarboxylic ether based superplasticiser(Glenium

B233) was used in this experimental study. Use of this superplasticizer speeds up

construction, increases workability and cohesion and aids pumping by reducing

friction between the particles and dry packing. The properties of superplasticiser as

reported by the manufacturer are given in Table 3.9

Table 3.9 Properties of Superplasticiser

SI. No. Properties Test Values

1 Appearance Yellowish free flowing liquid

2 Specific Gravity 1.1 at 25uC

3 Chloride ions content <0.2%

4 pH 7

5 Normal Dosage 500 to 1200ml/100kg ofcementitious material

3.2.6 Steel Fibres

To enhance the ductile behaviour and energy absorption characteristics of SCC, Gl

wires of 0.5 mm diameter cut into appropriate length was used as steel fibres. The

steel fibres were tested and the ultimate tensile strength was obtained as 530 N/mm2.

Photo.3.1 Steel fibres

60

3.2.7 Reinforcement

HYSD steel reinforcement of 6mm diameter was used as reinforcement for both self

compacting concrete and conventionally vibrated concrete slabs. It was tested to

determine its mechanical properties and the average values of the test result are given

in Table 3.10. The stress strain plot for the steel reinforcement is given in Fig. 3.4.

Table 3.10 Properties of Reinforcement

Tests Results

Proof Stress 443.00 N/mmL

Ultimate Stress 583.00 N/mmL

Young's modulus of elasticity 2.05 x 10' N/mmL

Elongation 28.33 %

Reduction in area 64.04%

i

!1 i + ! ~ 1 ~...•..:.~ +.... j ...... ·········· •..,l ·················· ••.,r : : I : : ············1,1········· :' o.

j 1 : ! J", I j I I .. J i_

0.050 0.100 0;150 0.200 0.250 0.300 0.350 0."00 0.-450 0:500~>Str8in %

Fig. 3.4 Stress Strain Curve for Steel

3.2.8 Water

Potable water directly drawn from the water supply line of laboratory was used for the

study.

3.3 MIX PROPORTIONING OF SCC USING RIVER SAND

In the absence of codal provision for see mix design, the methodology available in

literature [Ganesan et al (2006), Jagadish Vengala and Ranganath (2004),

61

Debashish Das et al. (2006)] and the guidelines given by EFNARC has been used for

mix proportioning. In designing the mix it is most useful to consider the relative

proportions of the key components by volume rather than by mass. Indicative typical

ranges of proportions and quantities in order to obtain self-compactability

recommended by EFNARC are given below. Further modifications will be necessary

to meet strength and other performance requirements.

· Water/powder ratio by volume of 0.80 to 1.10

· Total powder content - 160 to 240 litres (400-600 kg) per cubic meter.

· Coarse aggregate content normally 28 to 35 per cent by volume of the mix.

· Water cement ratio is selected based on requirements. Typically water

content does not exceed 200 litre/m3•

· The sand content balances the volume of the other constituents

The design mix was obtained after extensive trials by varying the quantities of coarse

aggregate, fine aggregate, fly ash and super plasticizer to develop a 40MPa SCC mix.

The ingredients were varied as shown in Table 3.11 for obtaining the design mix. For

comparison Conventionally Yibrated Concrete (CYC) with same 28 day strength was

also developed. The details of both the mixes are given in Table 3.12.

Table 3.11 Details of Study for Mix Proportioning

Material Limiting values

Powder content 500kg/mJ to 600kg/mJ

Fly ash 10% to 50% of the total powder content

Coarse aggregate 35% to 45% of the volume of concrete

Water powder ratio 0.35 to 0.36

Superplasticiser 0.8% to 1.5% of binder

Table 3.12 Mix Proportion of SCC and CVC Mixes

Cement Flyash Fine Coarse Water Water SuperplasticizerMix

(kg/m3) (kg/m3

)aggregate aggregate (kg/m3

)binder (% by weight of

(l{g/m3) (kg/m3

) ratio binder)

SCC 420 180 875.21 559.78 216 0.36 0.8-1

CVC 420 - 612.80 1226.35 168 0.4 0.25-0.5

62

3.4 MIX PROPORTIONING OF see USING M-SAND

Trials were done in the laboratory to obtain see mix with 20, 40, 50 and 60 % of

river sand replaced with M-Sand and workability test such as slump flow, V funnel

and V tube for each percentage of replacement was carried out. The hardened

properties such as cube compressive strength, cylinder compressive strength, split

tensile strength, flexural strength and modulus of elasticity of concrete for each

percentage of replacement of M-Sand were studied. The mix designations for various

percentage replacement of river sand by M-Sand are shown in Table 3.13.

Table 3.13 Designation of see Mixes

Mix % replacement of riverdesignation sand with M-Sand

MSO 0

MS20 20

MS40 40

MS50 50

MS60 60

3.4.1 Tests on see with M-Sand

3.4.1.1 Tests on fresh properties of see with M-Sand

The workability of see mixes with various percentage of replacement of river sand

by M-Sand were determined by conducting slump test, V-box and V-funnel test and

the results obtained are shown in Table 3.14.

Table 3.14 Fresh Properties of see with M-Sand

Slump v- V-funnel U-box RemarkMix flow funnel T5 minute value

(mm) (s) (s) (mm)MSO 780 8 9.03 16 see

MS20 760 8.06 9.08 17 seeMS40 710 10 11.06 18 seeMS50 680 12 14.12 22 seeMS60 630 12.03 15 27 NOT see

63

Experimental result reveals that the see mixes retained its properties as see up to

50% replacement of river sand by M-Sand without an additional dosage of

superplasticiser. The workability of see was decreasing with increase in M-Sand.

3.4.1.2 Tests on hardened properties of SCC with M-Sand

The see replaced with various percentage of M-Sand has been tested to study its

hardened properties by carrying out standard tests on cubes, cylinders and prisms. The

hardened properties such as cube and cylinder compressive strength, split tensile

strength, flexural strength and modulus of elasticity obtained out of this investigation

are given in Table 3.15.

Table 3.15 Hardened Properties of SCC with M-Sand

Mix Cube compressive Cylinder SplitFlexural Modulus ofstrength (N/mm2

) compressive tensilestrength Elasticitystrength strength(N/mm2

) (N/mm2)7 day 28 day (N/mm2

) (N/mm2)

MSO 32.80 42.00 34.32 3.69 4.52 2.8x 10'1

MS20 33.33 45.66 35.06 4.64 4.73 2.8x 10'1

MS40 37.77 48.22 38.00 4.80 4.83 3.34x 104

MS50 33.77 43.00 34.15 4.49 4.54 3.2x 10'1

MS60 31.11 41.33 33.23 3.58 4.40 2.5 x 104

It can be noted that the i h day and 28th day cube compressive strength increases upto

40% replacement of river sand by M-Sand. Further replacement of river sand

decreases the compressive strength of see as shown in Fig. 3.5. It is also found that

28-day cylinder compressive strength, split tensile strength, flexural strength and

modulus of elasticity increases upto 40% replacement of river sand by M-Sand but

decreases on further replacement by M-Sand. MS 20 mix was selected for further

study so as to enable fibre addition.

64

... 50

1EEZ 45.5

fit 40c:~in 35~

i! 30CoE

25 j8l».Qa 20 -I

0 20 40

%M-Sand

60

--+-Average Q>npressive Strength- 7 days

___Average Coflllressive Strength- 28 days

80

Fig.3.5 Cube Compressive Strength of SCC with M-Sand

3.4.2 Hardened Properties of evcThe hardened properties of the eve mix were determined on standard specimens as

in the case ofsec and is shown in Table 3.16.

Table 3.16 Hardened Properties of CVC

Properties CVCMix

7 day cube compressive strength (N/mm2) 32.17

28 day cube compressive strength (N/mm") 46.66

Cylinder compressive strength (N/rom2) 40.57

Split tensile strength (N/mm') 3.53

Flexural strength (N/rom2) 4.85

Modulus ofElasticity (N/mmL) 3.36 x 104

3.5 INFLUENCE OF FIBRES IN SCC

Review of literature showed that increase in fibre addition could improve the ductility

and toughness characteristics, reduce the crack width etc. But increase in volume

fraction and aspect ratio of fibres were observed to drastically affect flow properties

of concrete. With smaller aspect ratios, more fibres can be added to see without

65

much loss of workability. Hence a study was conducted to optimize the volume

fraction and aspect ratio of steel fibres for producing SFRSee.

Table 3.17 Designation of SFRSCC Mix

SINo.Mix Percentage volume Aspect ratio of

Designation of fibre (Vr) Steel fibre (lId)

1 VORO 0% -

2 V0.25 R30 0.25% 30

3 VO.25 R50 0.25% 50

4 V0.25 R70 0.25% 70

5 VO.5 R30 0.50% 30

6 VO.5 R50 0.50% 50

7 VO.5 R70 0.50% 70

8 VO.75 R30 0.75% 30

9 VO.75 R50 0.75% 50

10 VI R30 1% 30

11 VI R50 1% 50

Note: 1. V represents volume fraction of fibres2. R represents aspect ratio of fibres

The volume fractions were varied from 0%,0.25%,0.5%,0.75% and 1% with aspect

(lId) ratios 30, 50 and 70. The designations of mixes used for the study are given in

Table 3.17.

3.5.1 Tests on Fresh SFRSeC

To ensure fresh properties such as filling ability, passing ability and stability, the

standard test methods like slump flow test, V-funnel test, V-box test, L- box test were

conducted. The test results are given in Table 3.18. Both slump flow and flow time

gave same trend on fibre addition. It was observed that increase in volume fraction

and aspect ratio of fibres reduce flowability of the mix. Better flow properties were

shown by mix with lower volume fraction of fibres. The maximum aspect ratio of

fibre that can be added without affecting self compactability was found to be 50. For

aspect ratio 50 the maximum volume fraction of fibre was observed to be 0.75% for

retaining the properties of sec. For aspect ratio 70 the slump flow requirement was

66

not achieved beyond 0.25% volume fraction. But the mix was observed to fill the

specimens without vibration.

Table 3.18 Fresh Properties of SFRSCC

Sl MixSlump Slump V-funnel Vrat U-Box L-Box

No. Designationflow flow time flow time T5min value pass Remarks

(mm) (sec) (sec) (sec) (mm) ratio

EFNARC limit 650-800 2 to 5 6 to 12 +3 0-30 0.8-1 -1 YORO 755 2.67 6.60 6.89 10 0.95 see2 VO.25 R30 725 2.99 6.72 6.94 18 0.92 see3 Y0.25 R50 708 3.12 6.91 7.21 21 0.85 see4 Y0.25 R70 680 3.87 8.20 10.30 - - Not see5 YO.5 R30 705 3.28 7.10 8.20 19 0.90 see6 YO.5 R50 690 3.60 8.84 11.30 22 0.82 see7 YO.5 R70 645 5.20 13.23 17.20 - - Not see8 YO.75 R30 690 3.40 8.20 9.83 21 0.85 see9 YO.75 R50 675 4.02 10.00 11.45 24 0.80 see10 Y1 R30 665 4.20 9.00 11.32 35 0.68 Not see11 Y1 R50 645 4.84 12.45 13.42 35 - Not see

Note: 1. V represents volume fraction of fibres2. R represents aspect ratio of fibres

V-funnel test results indicated reduction of filling ability on fibre addition. The results

indicated that similar to slump flow test, increase in fibre volume fraction and aspect

ratio reduce the filling ability of see. V-funnel at TSmin indicated the influence of

fibre addition on segregation resistance of the mix. Increase in the volume fraction

and aspect ratio of fibres reduced the segregation resistance of see. For mix with

aspect ratio 70, maximum amount of fibre that could be added without imparting

segregation was 0.25%. U-box and L-box values indicate the passing ability of see.Passing ability indicated by both tests decreased on increase in volume fraction and

aspect ratio. Except for fibres of aspect ratio 70, all the mixes showed required

passing ability upto fibre volume fraction 0.75%.

67

3.5.2 Tests on Hardened SFRSCC

To determine the mechanical properties, standard specimens were prepared using

see mix with fibres. The hardened properties of mix were determined by conducting

standard tests such as cube compressive strength, cylinder compressive strength, split

tensile strength, flexural strength and modulus of elasticity. The hardened properties

of all mixes are shown in Table 3.19.

Table 3.19 Hardened Properties of SFRSCC

Cubecompressive Cylinder Split

Flexural Modulus ofMix strength compressive tensile

strength Elasticity(N/mm2

) strength strength(N/mm2

) (N/mm2)

(N/mm2) (N/mm2

)7 28 Day

VORO 34.44 45.56 33.94 5.116 4.302 3.120xl04

VO.25 R30 34.53 45.82 38.01 5.366 4.420 3.123x104

VO.25 R50 37.50 47.39 42.73 5.956 4.553 3.144xl04

VO.50 R30 34.88 48.40 42.02 5.699 5.050 3.183xl04

VO.50 R50 42.58 52.97 45.72 6.112 5.317 3.434xl04

VO.75 R30 37.70 52.58 45.56 6.151 5.461 3.369xl0'l

VO.75 R50 44.24 53.24 50.52 6.860 6.840 3.673xl0'l

It was observed that addition of 0.25% volume fraction of fibres did not show much

influence in the hardened properties. Addition of higher volume fraction of fibres and

increased aspect ratio had shown enhancement in all the mechanical properties.

Presence of 0.75% fibres with aspect ratio 50 exhibited best results showing an

increase of 17% in cube compressive strength, 18% in modulus of elasticity, 59% in

flexural strength and 34% in split tensile strength. Test results on hardened properties

showed that all the mechanical properties of see increased considerably by fibre

addition. Enhancement in hardened properties was in rise when higher volume

fractions and larger aspect ratio of fibres were used. The notable increase in the

flexural strength and split tensile strength are of much importance when see is used

for flexural members.

68

3.5.3 Discussion of Results

Test results of fresh properties inferred that increase in volume fraction and aspect

ratio reduces the flow properties of see. Increase in fibre aspect ratio drastically

affected passing ability of see. The passing ability requirement of see limits the

aspect ratio of fibres as 50 at 0.75% volume fraction. Mix with fibre aspect ratio 70

showed 0% passing ability. For assuring all the fresh properties of see, the

maximum volume fraction had to be limited to 0.75% for fibres of aspect ratio 50.

Test results on hardened properties showed that all the mechanical properties of seehas been considerably increased by fibre addition. Enhancement in hardened

properties was considerable when higher volume fractions of fibres were used. It has

been observed that fibre aspect ratio beyond 50 causes the loss of both fresh and

hardened properties. Similarly the mix with volume fraction of I% failed in respect of

fresh properties. Fibres with aspect ratio 50 and volume fraction 0.75% exhibited best

results. 0.25% fibre addition did not influence any of the mechanical properties

significantly. Hence 0.25% fibre addition was not considered in further study.

3.6 DURABILITY PROPERTIES

3.6.1 General

One of the important factors which influences the durability and long term

performance of concrete structures is the proper compaction of concrete. Proper

compaction eliminates air voids in the concrete mass making it impermeable and

durable. On many occasions, reinforced concrete elements contain heavy and

congested reinforcement necessitated either by structural requirement or

constructional need. The use of normal concrete in such situations may often result in

poor compaction and consequent defects in the placed concrete such as

honeycombing, bleeding, segregation etc. Self compacting concrete which possesses

superior flowability becomes an ideal material for such situations. In this

investigation, the durability properties of eve and see were compared by

conducting various tests like permeable voids and water absorption, acid attack,

sorptivity and alternate wetting and drying.

69

3.6.2 Permeable Voids and Water Absorption

It is a usual practice to find water permeability when assessing durability of concrete.

Permeability can be measured by conducting water permeability test, percentage of

water absorption test and initial surface absorption test. The absorption and permeable

voids were determined on 150 mm cubes. The surface dry cubes after 90 days

immersion in water were kept in a hot air oven at 105°e till a constant weight was

attained. The ratio of the difference between the mass of saturated surface dry

specimen and the mass of the oven dried specimen at 105° e to the volume of the

specimen gives the permeable voids in percentage as given below: (Dinakar et al.,

2008)

Permeable voids = [(A - B)/V]xl 00 (3.1)

where

A = weight of surface dried saturated sample after 90 days immersion period.

B = weight of oven dried sample in air.

V = Volume of sample

The oven dried cubes after attaining constant weight, were then immersed in water

and the weight gain was measured at regular intervals until a constant weight was

reached. The absorption at 30 min (initial surface absorption) and final absorption (at

a point when the difference between two consecutive weights at 12 hr interval was

almost negligible) was determined. The final absorption in all cases was determined at

96 hr. The absorption characteristics indirectly represent the volume of pores and their

connectivity. (Dinakar et al). The results of permeable voids and water absorption for

eve and see are presented in Table 3.20. From the result it can be seen that eve

has higher permeable voids and water absorption than see. The permeable voids are

influenced by the paste phase; primarily, it is dependent on the amount of

interconnected capillary pores present in the paste. Because of the self compacting

property and the presence of fly ash, the paste phase becomes denser. Thus the test

results indicate that there are less interconnected pores and less permeable voids in

see than in eve. According to the recommendations given by eoncrete Society

(CEB, 1989) initial absorption of "good concrete" is less than 5% for 30 min

70

absorption. This shows that eve and see had lower absorption than the limit

specified for "good" concrete.

Table 3.20 Permeable Voids and Water Absorption

Tests eve see

Initial absorption % 2.63 1.19

Final absorption % 10.13 7.38

% Permeable voids 23.15 16.79

3.6.3 Acid Attack

The chemical resistance of the concrete was studied by immersing them in an acid

solution of 3% H2S04• After 90days period of curing the specimens were removed

from the curing tank and their surface was cleaned with a soft nylon brush to remove

weak reaction products and loose materials from the specimen and the weight was

measured. Mass loss of specimens due to acid attack were determined and expressed

as a percentage of initial weight and the results are shown in Table 3.21.

Table 3.21 Acid Attack

Test Mass loss %

eve see

Acid attack 4.53 1.82

It can be seen that the mass loss of see is considerably lower than that of eve. This

may be attributed to puzzolanic property of fly ash by which ea(OH)2 present in

concrete is converted into cementitious material which makes the paste structure

dense. The see and eve after 90 days in acid is shown in Photo 3.2. It can be

inferred from the photos that eve is subjected to severe acid attack than see.

71

Photo 3.2 see and eve Specimens After 90 Days in Acid

3.6.4 Sorptivity

Sorptivity test measures the rate of absorption of water by capillary suction of

unsaturated concrete placed in contact with water (Neville, 2005). The sorptivity test

determines the rate of capillary rise absorption by a concrete specimen which rests on

small supports in a manner such that only the lowest 2 to 5 mm of the specimen is

submerged. The increase in mass ofthe specimen with time is recorded. There exists a

relation ofthe form

(3.2)

where

i increase in mass in glmm2 since the beginning of the test per unit of

cross sectional area in contact with water; as the increase in mass is

due to the ingress of water, 19 is equivalent to 1 mm3, so that i can be

expressed in mm

t time, measured in minutes, at which the mass is determined, and

S sorptivity in mmlmin0.5

Test was conducted on samples of 50mm diameter and lOOmm long cylinders. The

samples were preconditioned to a certain moisture condition by drying in an oven for

7days at 500 C. After cooling, sides of the concrete samples were sealed using

72

electrician's tape. After taking initial weight, samples were kept in a tray such that 2

5mm depth was immersed in water as shown in Photo 3.3.

Photo 3.3 Sorptivity Test

At selected times (1, 4, 9, 16,25,36,49,64,81, 100 minutes and 24 hrs) the samples

were removed from water, excess water blotted off and weighed. It was again

replaced in water. A straight line is fitted to the plot of the increase in mass, or the rise

of the water front, versus the square root of time. The point of origin (and possibly

also the very early readings) is ignored because there is a small increase in mass at the

instant when the open surface pores in the lowest 2 to 5mrn of the specimen first

become submerged. The slope of the line of the best fit of these points is reported as

sorptivity. The result of sorptivity test is given in Table 3.22 and is plotted in Fig. 3.6.

Some typical values of sorptivity are: 0.09mm/min°'s for concrete with a water/cement

ratio of 0.4, and O.17mm/min°.5 at a water/cement ratio of 0.6 (Neville, 2005). It can

be seen that eve exhibits higher sorptivity than sec.

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Table 3.22 Sorptivity Test Resuls

Time Gain in mass/ unit area(min) (g/mm2

)

SCC CVC1 0.000746 0.0009734 0.001090 0.0017179 0.001233 0.00217116 0.001401 0.00259425 0.001541 0.00303236 0.001666 0,00335549 0.001842 0.00371564 0.001949 0.00402881 0.002071 0.004346100 0.002239 0.004670

y =0.0002x + 0.0007

y = O.0004x + 0.0009

10 128642

... 0.006EEt» 0.006c:

e0.004lU...'c 0.003:I{;;~ 0.002

.E 0.001c:'(ij

C) 0+---,...------.------.------.----.----..o

Square root of time in mino.5

Fig. 3.6 Comparison of Sorptivity of see and eve

3.6.5 Alternate Wetting and Drying

The test was carried out to study the effect of sea water on the durability of concrete.

150 mm cubes after 28days of curing were weighed and kept in marine water. After

60 days of alternate wetting and drying, they were taken out, weighed again and loss

in mass was found out. (Ganesan et at, 2006).

The result obtained for see and eve for alternate wetting and drying is given in

Table 3.23. From the result it can be seen that see is less liable to marine action

74

compared to eye. This is due to lower porosity and the presence of less reactive

compounds in the paste phase.

Table 3.23 Weight Loss Due to Alternate Wetting and Drying in Marine Water

TestsWeight loss

eve seeAlternate wetting and drying 0.39 0.24

3.7 SUMMARY

Self compacting concrete contains a number of constitutive materials and the

properties of these materials control its fresh and hardened properties. To develop an

see which satisfies all the fresh and hardened properties, study on the mechanical

properties of materials is necessary. This chapter discussed the details of materials

used, its testing for finding the physical, chemical and mechanical properties and

comparison with standard specifications. Test results revealed that all the materials

conforms to the IS specifications. Scope of use ofM-Sand in see was explored since

river sand is scarce due to the ban imposed on mining of river sand. The study

revealed that M-Sand can replace river sand in see. Influence of the presence of

fibres in see was studied by varying the fibre content and aspect ratio. It was

observed that a maximum of 0.75% fibres can be added in the design mix without

affecting self compactability. All the hardened properties were improved by the

addition of fibres and the maximum improvement was by the addition of 0.75% fibres

of aspect ratio 50. Studies on durability indicated better performance of see than

eye.

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chapter3 preliminary investigation -...

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