investigation of high performance fiber …docs.trb.org/prp/17-03129.pdf · 8 a very early...

Khakimova, Ozyildirim, Harris 1

INVESTIGATION OF HIGH PERFORMANCE FIBER REINFORCED CONCRETE 1

PROPERTIES: VERY EARLY STRENGTH, TOUGHNESS, PERMEABILITY, AND 2

FIBER DISTRIBUTION 3 4

Evelina Khakimova, M.S., E.I.T., Corresponding Author 5 Virginia Transportation Research Council 6

530 Edgemont Road, Charlottesville, VA 22903 7

Telephone: (434) 293-1977; Fax: (434) 293-1990; Email: [email protected] 8

9

H. Celik Ozyildirim, Ph.D., P.E. 10 Virginia Transportation Research Council 11

530 Edgemont Road, Charlottesville, VA 22903 12

Telephone: (434) 293-1977; Fax: (434) 293-1990; Email: [email protected] 13

14

Devin K. Harris, Ph.D. 15 University of Virginia, Department of Civil and Environmental Engineering 16

351 McCormick Road, Charlottesville, VA 22904 17

Telephone: (434) 924 – 6373; Fax: (434) 982 – 2951; Email: [email protected] 18

19

20

Word Count: 4478 words text + 12 tables/figures x 250 words (each) = 7476 words 21

22

Submission Date: November 15, 2016 23


ABSTRACT 1 Concrete cracking, high permeability, and leaking joints allow for the intrusion of harmful 2

solutions, resulting in concrete deterioration and corrosion of reinforcement. The development of 3

durable concrete with limited cracking is a potential solution for extending the service life of 4

concrete structures. Optimal design of very early strength (VES) durable materials will facilitate 5

rapid and effective repairs, reducing traffic interruptions and maintenance work. 6

The purpose of this study was to develop low-cracking durable materials that can achieve 7

a very early compressive strength of 3,000 psi within 10 hours. Various proportions of silica 8

fume and fly ash, and steel fibers and polypropylene fibers were used to evaluate concrete 9

durability and post-cracking performance. In addition, toughness, residual strength, permeability 10

of cracked concrete, and fiber distribution were examined. 11

VES durable concretes can be achieved with proper attention to mixture components 12

(amounts of portland cement and accelerating admixtures), proportions (water–cementitious 13

material ratio), and fresh concrete and curing temperatures. Permeability values indicated that 14

minor increases in crack width, above 0.1 millimeter, greatly increase infiltration of solutions. 15

Adding fibers can facilitate crack width control. An investigation of fiber distribution showed 16

preferential alignment and some clumping of fibers in the specimens and highlighted the need for 17

sufficient mixing and proper sequencing of concrete ingredients into the mixer to ensure a 18

uniform random fiber distribution. Results indicated that VES and durable fiber-reinforced 19

concrete materials can be developed to improve the condition of existing and new structures and 20

facilitate rapid effective repairs and construction. 21

22

23

Keywords: very early strength, durability, fiber-reinforced concrete, steel, polypropylene, 24

toughness, residual strength, permeability, fiber distribution 25


INTRODUCTION 1 New construction and rehabilitation of existing structures are in need of high-performance durable 2

materials that facilitate the extension of the service life of structures with minimal maintenance. 3

The National Bridge Inventory estimated that in 2014 about 10% of U.S. structures were 4

structurally deficient. In comparison, 6.2% of Virginia Department of Transportation (VDOT) 5

structures were considered structurally deficient at the end of Fiscal Year 2015 (1). The 6

percentage of structurally deficient structures is being reduced; however, there is still a large 7

number of structures requiring immediate rehabilitation. Therefore, the use of high-performance 8

concretes, preferably with high early strength and high durability, that facilitate extension of 9

service life of transportation structures is essential. 10

The Federal Highway Administration started the implementation of high performance 11

concrete (HPC) in 1991. In the transportation industry, early HPC developments were commonly 12

described as concretes with low permeability and high strength (2). Further, the use of VES 13

concretes has become common within state departments of transportation. The development of 14

VES depends on the cement type, amount of paste, water-cementitious material ratio (w/cm), 15

fresh concrete and curing temperatures, and the addition of supplementary cementitious materials 16

(SCMs) and chemical admixtures (3). There are no minimum strength criteria for VES concretes; 17

however, a compressive strength of 2,000 psi was reported to be sufficient for regular traffic loads 18

(4). Punurai et al. (5) conducted a study on VES concretes using high proportions of Type I 19

cement, an accelerating admixture, and fresh concrete temperatures above 82 °F to achieve the 20

required early strength. The VES concretes reached a compressive strength of more than 2,250 21

psi and a flexural strength of more than 350 psi in about 6.5 hours. VDOT has successfully used 22

latex-modified concrete (LMC) with rapid set cement (LMC-VE) in concrete overlays to obtain 23

VES and low-permeability mixtures. LMC-VE can achieve a minimum compressive strength of 24

2,500 psi in 3 hours, which allows for rapid repairs and early lane opening to traffic (6). 25

Some of the main drawbacks of VES concretes are increases in thermal and autogenous 26

shrinkage and elastic modulus. In addition, there is a high risk of cracking, potentially leading to 27

a decrease in concrete durability. The long-term strength is also negatively affected by the high 28

temperatures at early ages (7, 8). Associated increases in fresh concrete temperature also cause a 29

decrease in slump and an increase in water demand (7). 30

The addition of SCMs generally enhances concrete ultimate strength; reduces concrete 31

permeability; and improves resistance to corrosion, alkali-silica reactivity, and sulfate attack. 32

Further, the addition of fibers minimizes cracks and reduces crack widths, leading to a lower 33

permeability compared to concretes without fibers (9, 10). Cracks less than 0.1-millimeter-wide 34

do not have a great effect on permeability, whereas a rapid permeability increase is seen for 35

concrete with cracks wider than 0.1 millimeter (11). Further, the American Concrete Institute 36

considers 0.1 millimeter as a reasonable crack width for water-retaining structures (12). 37

The lower the permeability of concrete, the better it resists cycles of freezing and thawing, 38

penetration of chlorides, corrosion of reinforcement, sulfate attacks, and alkali-silica and other 39

harmful reactions (13). In addition, large volumes of steel (S) or polypropylene (PP) fibers (0.5% 40

to 2.0% by volume) are expected to improve the post-cracking performance of concrete, 41

increasing its durability, tensile and flexural strengths, residual strength, and toughness (14). 42

Further, it has been shown that S fibers do not exhibit any corrosion with crack widths less than 43

0.1 millimeter (15). Light corrosion occurs with wider cracks and the corrosion product does not 44

penetrate more than 1 millimeter into concrete. Mangat et al. (16) demonstrated that corrosion 45

does not occur with a crack width less than 0.15 millimeter for low carbon steel FRC. 46


The distribution of fibers in concrete mixtures can considerably influence the performance 1

of concrete. Fiber clumping causes the formation of sections without fibers, which act as defects 2

and detrimentally affect the mechanical performance of FRCs (17-19). At the same time, because 3

of random fiber distribution, only a certain fraction of the fibers is optimally oriented and aligned 4

to resist tensile and flexural stresses efficiently (20). It has been determined that the longitudinal 5

fiber alignment is beneficial to the post-cracking concrete flexural and tensile capacities (21-23). 6

Further, statistical spatial point pattern analysis can be used to examine the fiber distribution. 7

Akkaya et al. (19) used statistical K- and F-functions to examine the fiber clumping tendency and 8

describe areas without fibers, respectively. The first several cracks occurred in the areas with 9

fewer fibers. These areas formed because of fiber clumping in the other areas of the specimen. 10

The clumping of fibers is indicated by higher statistical K-function and lower F-function values. 11

12

PROBLEM STATEMENT 13 Concrete cracking and high permeability allow for the intrusion of harmful solutions, resulting in 14

concrete deterioration and corrosion of reinforcement. The use of low-permeability durable 15

concretes with controlled cracking for repairs and new construction would improve the service 16

life of the structures. Further, the use of VES materials would facilitate rapid and effective repairs 17

and reduce traffic interruptions. 18

The purpose of this study was to develop durable VES concrete mixtures with resistance 19

to cracking. The target minimum compressive strength was 3,000 psi within 10 hours. The 20

mixtures included SCMs for durability and different types and volumes of fibers for crack 21

resistance. Compressive and flexural strengths and drying shrinkage were determined. Other 22

characteristics such as toughness, residual strength, permeability of cracked concrete, and fiber 23

distribution were also examined. 24

25

MATERIALS AND METHODS 26

Overview 27 The study was divided into three main stages. The first stage focused on the development of VES 28

fiber-reinforced concrete (VES-FRC) mixtures that can reach a compressive strength of 3,000 psi 29

within 10 hours. Concrete batches without fibers were prepared and tested for compressive 30

strength to attain the very early strengths. When satisfactory strengths were obtained, batches 31

with fibers were prepared to determine characteristics other than compressive strength, such as 32

flexural strength, toughness, residual strength, drying shrinkage, permeability of cracked 33

specimens, and fiber distribution. The second stage focused on testing of the water permeability 34

of cracked FRCs. Controlled crack widths of 0.1 to 0.5 millimeters (0.004 to 0.020 inch) were 35

formed in FRC cylinders using the splitting tensile test in accordance with ASTM C496; the 36

cylinders were then tested using the falling head permeability equipment. The third stage 37

investigated the fiber density and distribution in the concrete mixtures, and spatial fiber dispersion 38

was examined at the cross sections of the crack location. Laboratory testing was completed at the 39

Virginia Transportation Research Council (VTRC). Table 1 shows the ASTM and other test 40

methods and specimen sizes used during this study. 41

Two types of fibers were considered for this study: PP and S. The 2-inch-long PP fibers 42

were crimped in shape to facilitate a mechanical bond to concrete. The S fibers were straight with 43

hooked ends for improved anchorage, with the total fiber length of 2.4 inches. 44

45


TABLE 1 Fresh and Hardened Concrete Test Methods

Property Test Method Specimen Size No. of Test

Specimens

Fresh Concrete Properties

Air content ASTM C231-14 - -

Slump ASTM C143-15 - -

Unit weight ASTM C138-14 - -

Temperature ASTM C1064-12 - -

Hardened Concrete Properties

Compressive strength ASTM C39-15 4 by 8 in cylinder 1 or 2 per test age

Elastic modulus ASTM C469-14 4 by 8 in cylinder 2 at 28 days

Flexural strength ASTM C1609-12 4 by 4 by 14 in beam 1 or 2 per test age

Shrinkage (length change) ASTM C157-08 3 by 3 by 11 in beam 2 per FRC mixture

Splitting tensile strength (crack formation) ASTM C496-11 6 by 2 in cylinder Total of 66

Water permeability (falling head) Virginia Test Method 120 6 by 2 in cylinder Total of 66

Maturity test, Method 1 ASTM C1074-11 - -

Maturity test, Method 2 ASTM C918-13 - -

- = not applicable.

1

Stage I: Development of VES-FRCs 2 The VES-FRC mixtures that can achieve a compressive strength of 3,000 psi within 10 hours 3

were developed. Initially, concrete batches without fibers were tested to achieve the very early 4

strengths; then mixtures with fibers were made. 5

The development of VES concretes mainly focused on the use of the following: 6

increased cement content 7

reduced w/cm 8

increased fresh concrete temperature 9

accelerating admixtures 10

insulating the specimens during curing. 11

The VES concretes with silica fume (SF) were developed based on the ongoing research at 12

VTRC and by consultation with the industry. The mixture design of VES with fly ash (FA) was 13

adopted from existing VDOT patching mixtures typically used for pavement repairs, which 14

require a compressive strength of 2,000 psi within 6 hours. The Class F FA and SF met the 15

ASTM C618 and ASTM C1240 standards, respectively. 16

The VES with SF concrete batches without fibers were made at three temperatures: 72, 84, 17

and 90 °F. The temperatures were recorded using multiple thermocouples with a data logger. 18

Two VES with FA concrete batches were made with fresh concrete temperatures at 75 and 85 °F. 19

To obtain elevated fresh concrete temperatures, the hot mix water was used; the aggregates and 20

cementitious materials were kept at a room laboratory temperature of about 73 °F. 21

After successful mixing of the VES concretes without fibers, two batches with PP or S 22

fibers for each mixture with VES-FRC with SF and VES-FRC with FA were made. Based on the 23

fiber manufacturers’ recommended dosages, 15 lb/yd3 of PP and 66 lb/yd3 of S fibers were 24

considered. The fiber dosages were as recommended by the manufacturer and limited by proper 25

mixing and workability (upper limit) and desired properties (lower limit). The cost will depend 26

on the amount of used fibers for properties and project needs. The 15 lb/yd3 of PP fibers appeared 27

to be the maximum amount that can be added without any major mixing problems, such as fiber 28

balling. The S fibers could be added at higher amounts; however, cost should be considered. 29

Therefore, a small increase to 80 lb/yd3 was tried to ensure improvements in the post-cracking 30

behavior. Table 2 shows the VES-FRC mixture designs. Two types of FRC were used having a 31


different cementitious content, SCM, and w/cm to achieve the desired strength, permeability, and 1

shrinkage. 2

TABLE 2 VES-FRCs Mixture Designs

Component (lb/yd3) VES-FRC w/ SF VES-FRC w/ FA

Cement Type I/II 750 750

Silica fume (6%)* 50 -

Class F fly ash (15%) - 132

Water 272 265

Fine aggregate 1437 1364

Coarse aggregate 1407 1407

Total cementitious material 800 882

w/cm 0.34 0.30

PP (% by volume) 15 (1.0) - 15 (1.0) -

S (% by volume) - 80 (0.6) - 80 (0.6)

Admixture (oz/cwt)

Set accelerating 24 24

Hardening accelerating 20 20

- = not applicable; VES = very early strength; FRC = fiber-reinforced concrete; SF = silica fume; FA = fly ash; 3 PP = polypropylene; S = steel. 4 *SF is 6% of total cementitious content. 5 6

For each batch, the compressive strength was tested starting from 6 hours after casting and 7

about every hour until a compressive strength of 3,000 psi was reached. Then the rest of the 8

cylinders were tested at 1, 7, and 28 days. In addition, samples for flexural strength, drying 9

shrinkage, and falling head permeability tests were made. The first-peak and peak flexural 10

strengths, residual strengths, toughness, and equivalent flexural strength ratio were determined in 11

accordance with ASTM C1609 (24). All specimens were covered with plastic and insulating 12

material and kept inside Styrofoam containers for the first 24 hours or until a compressive 13

strength of 3,000 psi was reached. Then the samples were demolded and moved to a moisture 14

room for 28 days. The moisture room relative humidity was maintained above 95% with an air 15

temperature of 73 ± 3 °F. During curing, the temperatures of the specimens were monitored. 16

17

Stage II: Permeability of Cracked FRC Specimens 18 For each FRC batch with S or PP fibers, eight to ten 6 by 2 inch cylinders were tested. ASTM 19

C496 splitting tensile testing procedure was followed to form the cracks widths of 0.1 to 0.5 20

millimeter (0.004 to 0.020 inch). The MTS laser extensometer was used to capture the horizontal 21

displacement between two reflective pieces of tape mounted at the center on one side of the 22

specimen. In addition, an optical magnifier, with a 20-millimeter scale (in 0.1-millimeter 23

increments, numbered every 1.0 millimeter), was used to measure the crack widths with and 24

without the applied load. Figure 1 shows the splitting tensile test setup and the magnifier. The 25

correlation between the results of the two measurement methods revealed a difference of about 26

10% on average, which was deemed to be acceptable because of the irregularity of the crack 27

widths. The crack widths were measured at the top, middle, and bottom sections on both sides of 28

the specimen. The crack width formed in the middle section of the specimen was the most 29

observed width and was used as a final crack width of that specimen. The relaxation of the crack 30

width after unloading was also determined. All VES-FRC specimens followed a similar trend of 31

crack width recovery with an average of 43%. 32


1 FIGURE 1 (a) Splitting tensile test setup with MTS laser; (b) test specimen; (c) magnifier with scale. 2

3

ASTM C1202 was followed to saturate the cracked specimens for the permeability testing. 4

Virginia Test Method 120, a falling head permeability test, was used to measure the coefficient of 5

water permeability (CWP), i.e., the laminar water flow rate through the cracked saturated sample. 6

The test was performed three times for each sample, and the average CWP, k, was determined in 7

accordance with Equation 1 (25): 8

9

𝑘 = 𝑎 ∙ 𝑙

𝐴 ∙ 𝑡∙ ln (

ℎ1

ℎ2) (1)

10

where k = CWP, a = standpipe area, A = average specimen area, l = average sample thickness, t = 11

average flow time, h1 = initial hydraulic head, and h2 = final hydraulic head. 12 13

Stage III: Fiber Distribution Analysis 14 To investigate fiber distribution, the flexural beams with PP and S fibers were sliced along the 15

transverse and horizontal directions into 1-inch-thick sections. Figure 2 shows the schematic of 16

the ASTM C1609 test method with a third-point flexural loading and the transverse (T) and 17

horizontal (H) cutting orientations for the two slicing methods: HTH and THTHT. At least two 18

specimens were analyzed for each method for each mixture type. 19

20

21 FIGURE 2 Schematic of the flexural test setup, and two slicing methods: (a) HTH, and (b) THTHT. 22 H = horizontal cut; T = transverse cut. 23

24

Digital images of the cross sections were taken and analyzed in MATLAB through image 25

processing to determine fiber coordinates. Outputs of the MATLAB analysis code for a steel 26

fiber specimen are displayed in Figure 3, with steps illustrating (a) an inverse grayscale of an 27

original image, (b) a binary image after thresholding, (c) an image with removed pixels out of set 28

1

(a) (b) (c)

H T H T H T H T

(a) (b)

1


limits, and (d) the original image with overlaid calculated fiber coordinates. Optimal orientation 1

was taken into consideration; hence only fibers oriented at the 45° angle or less were included in 2

the fiber count. 3

4

5 FIGURE 3 Image analysis process: (a) inverse; (b) binary; (c) pixel removal; (d) final. 6

7

Fiber density was calculated, and spatial point pattern trends through statistical K- and F-8

functions were determined (26). Typically, there are three types of spatial point patterns: 9

clustered, regular (ordered), and random. The K-function represents the tendency of fiber 10

clumping and measures the distance between fibers. The F-function can be used to measure the 11

empty spaces between the fibers. The calculated K- and F-function values were compared to the 12

values obtained under the complete spatial randomness (CSR) condition: K-CSR and F-CSR, 13

respectively. For the K-function, the clustering is observed for values greater than K-CSR, 14

whereas the F-function values that drift below the F-CSR curve indicate a more clustered pattern, 15

with more fiber-free areas. 16

17

RESULTS AND DISCUSSION 18 19

Stage I: VES-FRCs Development 20 VES Concretes Without Fibers 21

The laboratory batches with VES concretes with SF were made at 72, 84, and 90 °F fresh concrete 22

temperatures and reached a compressive strength of 3,000 psi over 13, 8, and 7 hours, 23

respectively (Figure 4a). ASTM C918 and ASTM C1074 maturity test methods, using the Nurse-24

Saul function, indicated the time the mixture with the fresh concrete temperature of 72 °F reached 25

the required strength (Figure 4b). Further, the successful results of the VES with FA concrete 26

patching mixtures led to the implementation of the mixtures in this project, with the compressive 27

strength requirement of 3,000 psi within 10 hours. 28

1

(a) (b) (c) (d)


1 FIGURE 4 (a) Trial VES w/ SF temperature developments; (b) strength-maturity relationship for the 72 °F 2 batch. 3 VES = very early strength; SF = silica fume. 4 5

Further, the time of initial set was about 5, 4, and 3 hours for the 72, 84, and 90 °F 6

mixtures, respectively. The temperature rise after the set was greater for the mixtures with higher 7

initial fresh concrete temperatures, which indicates faster strength development. The trial VES 8

with FA mixtures reached a compressive strength of 2,000 psi within 7 hours. Therefore, based 9

on maturity predictions, it was expected that these mixtures would gain the desired 3,000 psi 10

compressive strength within 10 hours. 11

12

VES Concretes with Steel and Polypropylene Fibers 13

The PP and S fibers were added to the optimized VES with FA and VES with SF concrete 14

mixtures. The VES-FRCs fresh concrete properties are presented in Table 3. The air content 15

values were within the VDOT specifications (27). The slump values were low, ranging from 2 to 16

5 inches. The mixtures with FA had lower values than the ones with SF attributed to a lower 17

dosage of high-range water-reducing admixture, the type of fiber, and a lower w/cm. However, 18

the mixtures remained sufficiently workable for easy placement in the molds. The molds were 19

then capped to limit evaporation. The shrinkage specimens during drying were kept in a special 20

room with the relative humidity set to 50% ± 4% as required by ASTM C157. 21

(a)

(b)

1

60

70

80

90

100

110

120

130

140

150

0 2 4 6 8 10 12 14 16 18 20 22 24

Te

mp

era

ture

[ F

]

Age [hours]

VES w/ SF @ 90°F VES w/ SF @ 84°FVES w/ SF @ 72°F

3,000 psi reachedInitial Set Time


TABLE 3 VES-FRCs Fresh Concrete Properties

Properties VES-FRC w/ SF VES-FRC w/ FA

w/ PP w/ S w/ PP w/ S

Air content (%) 5.5 5.9 5 6.4

Unit Weight (lb/ft3) 145 148 148 149

Slump (in) 4 5 2 3

Mix temperature (°F) 85 90 97 94

Air temperature (°F) 75 75 75 75

VES = very early strength; FRC = fiber-reinforced concrete; 1 SF = silica fume; FA = fly ash; PP = polypropylene; S = steel. 2

3

All VES-FRC specimens reached a compressive strength of over 3,000 psi within 8.5 4

hours (Table 4). Typical VES-FRCs flexural load-deflection plots are presented in Figure 5. The 5

increase in first-peak and residual flexural strengths with age is shown. 6

7 TABLE 4 VES-FRCs Hardened Properties

Test Age VES-FRC w/ SF VES-FRC w/ FA

w/ PP w/ S w/ PP w/ S

Compressive strength (psi)

6.5 hours 1,890 950 2,930 2,540

7.5 hours 2,530 2,780 3,860 2,840

8 hours - - - 3,160

8.5 hours 4,150 3,220 - -

24 hours 6,700 7,540 5,240 4,380

7 days 7,730 7,880 7,260 5,690

28 days 8,780 8,880 8,860 8,890

First-peak / peak flexural strength

(psi)

7.5-8.5 hours 490 460 / 620 375 465 / 475

24 hours 690 715/ 1,030 660 665 / 1,135

7 days 985 1,000 985 1,010 / 1,090

28 days 1,075 1,100 / 1,380 1,095 1,115 / 1,290

Elastic modulus (106 psi) 28 days 4.82 5.17 4.13 3.92

Drying shrinkage (%) 35 days* 0.04 0.05 0.06 0.07

4 Months 0.07 0.06 0.07 0.08

* Length change values at 35 days after casting, including the first 7 days of moist curing.

- = data not available; VES = very early strength; FRC = fiber reinforced concrete; SF = silica fume;

FA = fly ash; PP = polypropylene; S = steel.

8

The flexural strength values met the strength requirements of 260 to 400 psi reported by 9

Van Dam et al. (28) for the 6 to 8-hour concrete repair materials. The VES-FRCs with S fibers 10

had better post-cracking performance than the VES-FRCs with PP fibers, with deflection 11

hardening behavior and higher residual strength and toughness values. Toughness values, 𝑇150𝐷 , 12

were almost double for the S fiber samples (440 inch-pounds) compared to the samples with PP 13

fibers (230 inch-pounds). The flexural capacity, represented by the equivalent flexural strength 14

ratio (24), 𝑅𝑇,150𝐷 , of the VES-FRCs with S fibers was 93% on average after the first-peak, 15

whereas the capacity of VES-FRCs with PP fibers was about 49% on average. 16


1 FIGURE 5 VES-FRCs with PP (left) and S (right) fibers for mixtures with (a) SF and (b) FA. 2 VES = very early strength; FRC = fiber-reinforced concrete; PP = polypropylene; S = steel; 3 SF = silica fume; FA= fly ash. 4

5

High paste and cement contents for VES-FRCs result in higher shrinkage values. At 4 6

months, the systems had length change values up to 0.07% on average, which satisfied the 7

suggested limit of 0.07%; however, the shrinkage values after 28 days of drying were greater than 8

the recommended value of 0.04% (29). VDOT uses a maximum value of 0.035% for low 9

cracking bridge decks (27). In addition, the paste content, amount of cement paste expressed as 10

percent volume of the whole mixture (30), was determined. The values of 0.32 and 0.33 for VES-11

FRCs with SF and with FA, respectively, exceeded the recommended 0.27 paste content limit 12

(31). 13

14

Stage II: Permeability of Cracked FRC Specimens 15 Figure 6 shows the CWP results for the cracked VES-FRCs. The CWP values follow 16

approximately the same trend for all concretes, and the observed variation could be due to the 17

irregularity of crack size and pattern. As expected, a large increase in the CWP for increased 18

crack widths was observed. The increase of CWP by 20 times on average (except for the VES-19

FRC with FA and PP) was observed for crack widths increasing from 0.1 to 0.2 millimeter. 20

(a)

(b)

1


The CWP values for the solid samples without cracks were on the order of 10-10 cm/s, 1

corresponding to the typical CWP values of normal strength concrete (8). The CWP values for 2

crack widths greater than 0.1 millimeter were above 10-6 cm/s and for widths greater than 0.2 3

millimeter were above 10-3 cm/s. In this case, the corrosion of primary reinforcement attributable 4

to leakage through cracks wider than 0.1 millimeter is highly probable. 5

6

7 8 FIGURE 6 CWP versus crack width. 9 Conversion factors: 100 µm = 0.1 mm = 0.0039 in. 10 VES = very early strength; FRC = fiber-reinforced concrete; SF = silica fume; 11 FA = fly ash; PP = polypropylene; S = steel. 12

13

Stage III: Fiber Distribution Analysis 14 The image analysis of the cross sections with steel fibers indicated a tendency of long rigid fibers 15

to align parallel along the length of the beam. This alignment is beneficial to the flexural and 16

tensile capacities of the specimens because of a greater number of fibers at the beam crack face 17

effectively resisting the applied normal stresses after cracking. The flexible PP fibers were more 18

equally distributed in all directions. Figure 7 illustrates the average fiber density for transverse 19

and horizontal cross sections for S and PP fibers. 20

21

22 FIGURE 7 Fiber density per cross-section side for HTH and THTHT: (a) S and (b) PP. 23 H = horizontal cut; T = transverse cut; VES = very early strength; FRC = fiber-reinforced concrete; 24 SF = silica fume; FA= fly ash; PP = polypropylene; S = steel. 25

26 27

1E-06

1E-05

1E-04

1E-03

1E-02

1E-01

1E+00

0 100 200 300 400 500 600

Coe

ffic

ien

t o

f W

ate

r P

erm

ea

bili

ty, k

[cm

/s]

Crack Width [µm]

VES-FRC w/ SF - S VES-FRC w/ FA - S

VES-FRC w/ SF - PP VES-FRC w/ FA - PP

(a) (b)

1


The calculated K-function and F-function average values were compared to the theoretical 1

functions values under the CSR condition, K-CSR and F-CSR, respectively. Here, values of the 2

K-functions are presented in the form of (𝐾(𝑠)

𝜋)

1/2

. For the S fiber specimens, the VES-FRC with 3

SF samples displayed more fiber clumping compared to the samples with FA. The VES-FRC 4

with FA displayed values closer to the K-CSR curve, indicating more of a random distribution 5

(Figure 8a). The specimens with VES-FRCs with PP fibers displayed similar spatial fiber 6

dispersion for both SF and FA mixtures, indicating some degree of fiber clumping (Figure 8b). 7

Further, during mixing, concretes with PP fibers exhibited more fiber clumping compared to the 8

mixtures with S fibers. From the F-function results it is apparent that all specimens displayed 9

fiber clumping and some number of empty areas without fibers, with the slopes less steep than the 10

F-CSR curves slopes. 11

FIGURE 8 Spatial Fiber Distribution Analysis for K- (left) and F-function (right): (a) S, (b) PP. K-CSR = K-function under CSR condition; F-CSR = F-function under CSR condition; VES = very early strength;

FRC = fiber-reinforced concrete; SF = silica fume; FA = fly ash; PP = polypropylene; S = steel.

(a)

(b)

1


CONCLUSIONS 1

VES-FRCs with different fiber types and dosages and SF or FA can provide durable 2

concretes, facilitate rapid and effective repairs, and reduce traffic interruptions and maintenance 3

work. 4

A compressive strength of 3,000 psi within 10 hours can be achieved with the use of 5

increased cement contents, a low w/cm, increased fresh concrete temperatures above 80 °F, 6

accelerating admixtures, and insulated curing. 7

High residual strengths and resistance to cracking can be achieved with the addition of 8

fibers. VES-FRCs with S fibers had superior post-cracking performance compared to VES-FRCs 9

with PP fibers. 10

VES-FRCs had high paste contents and high shrinkage values, making them prone to 11

cracking. However, the addition of fibers is expected to facilitate crack control through residual 12

flexural strength and toughness. 13

Water permeability increases with increase in crack width. Cracks wider than 0.1 14

millimeter allow for the intrusion of harmful solutions. 15

The long rigid steel fibers had a tendency to align parallel along the length of the 16

beam, which is beneficial to the flexural and tensile capacities of the specimens; flexible PP fibers 17

were more equally distributed in all directions. All FRC systems, especially the mixtures with PP 18

fibers, had a tendency for fiber clumping to various degrees. 19

20

ACKNOWLEDGMENTS 21 The authors thank VTRC research and technical staff for their assistance and guidance in this 22

study, specifically William Ordel, Michael Burton, Kenneth Herrick, Andrew Mills, Troy Deeds, 23

Stephen Lane, James Copeland, Xuemeng “John” Xia, and Keith Peres. The authors also thank 24

the industry for their input and assistance with this study. The authors thank the University of 25

Virginia, specifically Muhammad Sherif, and personnel of VDOT’s Materials Division and 26

Structure and Bridge Division, VDOT’s Staunton District, and the Federal Highway 27

Administration. 28

REFERENCES 29 1. Virginia Department of Transportation. State of the Structures and Bridges Report. 30

Richmond, 2015. 31

2. Ozyildirim, C. High-Performance Concrete for Transportation Structures. Concrete 32

International, January, 1993, pp. 33–38. 33

3. Kosmatka, S. H., and M. L Wilson. Design and Control of Concrete Mixtures. Portland 34

Cement Association, Skokie, Ill., 2011. 35

4. Parker, F., and W. L. Shoemaker. PCC Pavement Patching Materials and Procedures. 36

Journal of Materials in Civil Engineering, Vol. 3, No. 1, 1991, pp. 29–47. 37

5. Punurai, S., W. Punurai, and C.-T. T Hsu. A Very Early Strength Concrete for Highway 38

Construction. Journal of Testing and Evaluation, Vol. 35, No. 6, 2007, pp. 1–9. 39

6. Sprinkel, M. M. Very Early Strength Latex-Modified Concrete Bridge Overlays. 40

Transportation Research News, Vol. 247, December, 2006, pp. 34–35. 41

7. Klieger, P. Effect of Mixing and Curing Temperature on Concrete Strength. Journal of the 42

American Concrete Institute, Vol. 54, No. 62, 1958, pp. 1063–1081. 43

8. Nawy, E. G. Fundamentals of High-Performance Concrete. John Wiley & Sons, Inc., New 44

York, 2001. 45


9. Rappaport, J., C.-M. Aldea, S. P. Shah, B. Ankenman, and A. Karr. Permeability of Cracked 1

Steel Fiber-Reinforced Concrete. National Institute of Statistical Sciences, Durham, NC, 2

2001. 3

10. Ozyildirim, C., C. Moen, and S. Hladky. Investigation of Fiber-Reinforced Concrete for Use 4

in Transportation Structures. Publication VTRC 97-R-15. Virginia Transportation Research 5

Council, Charlottesville, 1997. 6

11. Aldea, C.-M., S. P. Shah, and A. Karr. Permeability of Cracked Concrete. Materials and 7

Structures, Vol. 32, No. 5, 1999, pp. 370–376. 8

12. American Concrete Institute. Control of Cracking in Concrete Structures. Publication ACI 9

244R-01. Farmington Hills, Mich., 2001. 10

13. Shah, S. P., and K. Wang. Microstructure, Microcracking, Permeability, and Mix Design 11

Criteria of Concrete. Fifth International Conference on Structural Failure, Durability and 12

Retrofitting, 1997, pp. 260–272. 13

14. American Concrete Institute. Report on Fiber Reinforced Concrete. Publication ACI 14

544.1R-96. Farmington Hills, Mich., 2009. 15

15. Granju, J.-L., and S. Ullah Balouch. Corrosion of Steel Fbre Reinforced Concrete from the 16

Cracks. Cement and Concrete Research, Vol. 35, No. 3, 2005, pp. 572–577. 17

16. Mangat, P. S., and K. Gurusamy. Permissible Crack Widths in Steel Fibre Reinforced 18

Marine Concrete. Materials and Structures, Vol. 20, No. 5, 1987, pp. 338–347. 19

17. Akkaya, Y., J. Picka, and S. P. Shah. Spatial Distribution of Aligned Short Fibers in Cement 20

Composites. Journal of Materials in Civil Engineering, Vol. 12, No. 3, 2000, pp. 272–279. 21

18. Akkaya, Y., A. Peled, and S. P. Shah. Parameters Related to Fiber Length and Processing in 22

Cementitious Composites. Materials and Structures, Vol. 33, No. 8, 2000, pp. 515–524. 23

19. Akkaya, Y., S. P. Shah, and B. Ankenman. Effect of Fiber Dispersion on Multiple Cracking 24

of Cement Composites. Journal of Engineering Mechanics, Vol. 127, No. 4, 2001, pp. 311–25

316. 26

20. Portland Cement Association. Fiber Reinforced Concrete. Skokie, Ill., 1991. 27

21. Kang, S. T., and J. K. Kim. The Relation Between Fiber Orientation and Tensile Behavior in 28

an Ultra High Performance Fiber Reinforced Cementitious Composites (UHPFRCC). 29

Cement and Concrete Research, Vol. 41, No. 10, 2011, pp. 1001–1014. 30

22. Kang, S. T., and J. K. Kim. Investigation on the Flexural Behavior of UHPCC Considering 31

the Effect of Fiber Orientation Distribution. Construction and Building Materials, Vol. 28, 32

No. 1, 2012, pp. 57–65. 33

23. Kang, S. T., B. Y. Lee, J.-K. Kim, and Y. Y. Kim. The Effect of Fibre Distribution 34

Characteristics on the Flexural Strength of Steel Fibre-Reinforced Ultra High Strength 35

Concrete. Construction and Building Materials, Vol. 25, No. 5, 2011, pp. 2450–2457. 36

24. ASTM International. ASTM Standard C1609/C1609M-12: Flexural Performance of Fiber-37

Reinforced Concrete (Using Beam with Third-Point Loading. West Conshohocken, Penn., 38

2013. 39

25. Virginia Department of Transportation. Virginia Test Method 120: Method of Test for 40

Measurement of Permeability of Bituminous Paving Mixtures Using a Flexible Wall 41

Permeameter - (Asphalt Lab). Richmond, 2005. 42

26. Diggle, P. J. Statistical Analysis of Spatial Point Patterns. Hodder Education Publishers, 43

London, 2003. 44

27. Virginia Department of Transportation. 2016 Road and Bridge Specifications. Richmond, 45

2016. 46


28. Van Dam, T. J., K. R. Peterson, L. L. Sutter, A. Panguluri, J. Sytsma, N. Buch, R. Kowli and 1

P. Desaraju. Guidelines for Early-Opening to Traffic Portland Cement Concrete for 2

Pavement Rehabilitation. Publication NCHRP Report 540. Transportation Research Board, 3

Washington, D.C., 2005. 4

29. Babaei, K., and A. M. Fouladgar. Solutions to Concrete Bridge Deck Cracking. Concrete 5

International, Vol. 19, No. 7, 1997, pp. 34-37. 6

30. American Concrete Institute. ACI Concrete Terminology. Publication ACI CT-13. 7

Farmington Hills, Mich., 2013. 8

31. Darwin, D., J. Browning, and W. D. Lindquist. Control of Cracking in Bridge Decks: 9

Observations from the Field. Cement, Concrete, and Aggregates, Vol. 26, No. 2, 2004, pp. 10

148-154. 11

investigation of high performance fiber …docs.trb.org/prp/17-03129.pdf · 8 a very early...

Documents