Self-compacting concrete incorporating steel and polypropylene fibers_ Compressive and tensile...

8/13/2019 Self-compacting concrete incorporating steel and polypropylene fibers_ Compressive and tensile strengths, moduli

1/13

Self-compacting concrete incorporating steel and polypropylene fibers:

Compressive and tensile strengths, moduli of elasticity and rupture,

compressive stressstrain curve, and energy dissipated under

compression

Farhad Aslani , Shami Nejadi

Centre for Built Infrastructure Research, School of Civil and Environmental Engineering, University of Technology, Sydney, Australia

a r t i c l e i n f o

Article history:

Received 6 August 2012

Received in revised form 12 March 2013

Accepted 7 April 2013

Available online 25 April 2013

Keywords:

B. Mechanical properties

A. Fibers

C. Analytical modelling

D. Mechanical testing

a b s t r a c t

Fiber-reinforced self-compacting concrete (FRSCC) is a high-performance building material that com-

bines positive aspects of fresh properties of self-compacting concrete (SCC) with improved characteristics

of hardened concrete as a result of fiber addition. Considering these properties, the application ranges of

both FRSCC and SCC can be covered. A test program is carried out to develop information about the

mechanical properties of FRSCC. For this purpose, four SCC mixes plain SCC, steel, polypropylene,

and hybrid FRSCC are considered in the test program. The properties include compressive and splitting

tensile strengths, moduli of elasticity and rupture, compressive stressstrain curve, and energy dissipated

under compression. These properties are tested at 3, 7, 14, 28, 56, and 91 days. Relationships are estab-

lished to predict the compressive and splitting tensile strengths, moduli of elasticity and rupture, com-

pressive stressstrain curve, and energy dissipated under compression. The models provide predictions

matching the measurements.

2013 Elsevier Ltd. All rights reserved.

1. Introduction

Self-compacting concrete (SCC) can be placed and compacted

under its own weight with little or no vibration and without seg-

regation or bleeding. SCC is used to facilitate and ensure proper

filling and good structural performance of restricted areas and

heavily reinforced structural members. It has gained significant

importance in recent years because of its advantages[1].Recently,

this concrete has gained wider use in many countries for different

applications and structural configurations. SCC can also provide a

better working environment by eliminating the vibration noise.

Such concrete requires a high slump that can be achieved by

superplasticizer addition to a concrete mix and special attention

to the mix proportions. SCC often contains a large quantity of

powder materials that are required to maintain sufficient yield va-

lue and viscosity of the fresh mix, thus reducing bleeding, segre-

gation, and settlement. As the use of a large quantity of cement

increases costs and results in higher temperatures, the use of min-

eral admixtures such as fly ash, blast furnace slag, or limestone

filler could increase the slump of the concrete mix without

increasing its cost[2].

Fiber-reinforced self-compacting concrete (FRSCC) is a rela-

tively recent composite material that combines the benefits of

the SCC technology with the advantages of the fiber addition to a

brittle cementitious matrix. It is a ductile material that in its fresh

state flows into the interior of the formwork, filling it in a natural

manner, passing through the obstacles, and flowing and consoli-

dating under the action of its own weight. FRSCC can mitigate

two opposing weaknesses: poor workability in fiber-reinforced

concrete (FRC) and cracking resistance in plain concrete. A few

studies have been carried out on optimization of the mix propor-

tion for the addition of steel or polypropylene fibers to SCC. Mean-

while, there is insufficient research on the mechanical properties of

FRSCC. In mechanical terms, the greatest disadvantage of cementi-

tious material is its vulnerability to cracking, which generally oc-

curs at an early age in concrete structures or members. Cracking

may potentially reduce the lifetime of concrete structures and

cause serious durability and serviceability problems.

The most beneficial properties with the fiber addition to the

concrete in the hardened state are the impact strength, the tough-

ness, and the energy absorption capacity. A detailed description of

the benefits provided by the fiber addition to concrete can be found

elsewhere [3,4]. The fiber addition might also improve the fire

resistance of cement-based materials, as well as their shear

resistance. The possible applications of FRSCC include highways;

industrial and airfield pavements; hydraulic structures; tunnel

1359-8368/$ - see front matter 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.compositesb.2013.04.044

Corresponding author. Tel.: +61 434419460.

E-mail address: [email protected](F. Aslani).

Composites: Part B 53 (2013) 121133

Contents lists available atSciVerse ScienceDirect

Composites: Part B

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c o m p o s i t e s b
http://dx.doi.org/10.1016/j.compositesb.2013.04.044mailto:[email protected]://dx.doi.org/10.1016/j.compositesb.2013.04.044http://www.sciencedirect.com/science/journal/13598368http://www.elsevier.com/locate/compositesbhttp://www.elsevier.com/locate/compositesbhttp://www.sciencedirect.com/science/journal/13598368http://dx.doi.org/10.1016/j.compositesb.2013.04.044mailto:[email protected]://dx.doi.org/10.1016/j.compositesb.2013.04.044http://-/?-http://-/?-http://-/?-http://-/?-http://crossmark.dyndns.org/dialog/?doi=10.1016/j.compositesb.2013.04.044&domain=pdfhttp://-/?-


2/13


3/13

developments of mechanical properties with time are investigated.

Also, since only a few correlations among the mechanical proper-

ties of FRSCC have been reported and are unclear. In the presented

study regression analyses are conducted on existing experimental

data to propose splitting tensile strength, moduli of elasticity and

rupture, energy dissipated under compression models that on

compressive strength and age of concrete. Also, compressive

stressstrain relationships for SCC and FRSCC are compared with

the test results.

3. Experimental study

3.1. Materials

3.1.1. Cement

In this experimental study, Shrinkage Limited Cement (SLC) cor-

responding to the ASTM C183-08[5] (AS 3972[6]) standard was

used. SLC is manufactured from specially prepared portland ce-

ment clinker and gypsum. It may contain up to 5% of AS 3972 ap-

proved additions. The chemical, physical, and mechanical

properties of the cement used in the experiments are shown inTa-

ble 1. The chemical, physical, and mechanical properties adhere to

the limiting value or permissible limits specified in AS 2350.2, 3, 4,

5, 8, and 11[7].

3.1.2. Fly ash

It is important to increase the amount of paste in SCC because

fly ash is an agent to carry the aggregates. Eraring Fly Ash (EFA)

is a natural pozzolan. It is a fine cream/grey powder that is low

in lime content. The chemical and physical properties of EFA used

in the experimental study are given inTable 1. The chemical, phys-

ical, and mechanical properties of the EFA used adhere to the lim-

iting value or permissible limits specified in ASTM C311-11b[8]

(ACI 232.2R-03 [9], AS 2350.2 [7], AS 3583.1, 2, 3, 5, 6, 12, and

13[10]).

3.1.3. Ground granulated blast furnace slag

Granulated Blast Furnace Slag (GGBFS) is another supplemen-

tary cementitious material that is used in combination with SLC.

GGBFS used in the experiment originated in Boral, Sydney, and it

conformed to ASTM C989-06 [11] (ACI 233R-95 [12] and AS

3582.2 [13]) specifications. The chemical and physical properties

of GGBFS are given inTable 1.

Table 3

The physical and mechanical properties of fibers.

Fiber type Fiber name Density (kg/

m3)

Length

(l)

Diameter

(d)

Aspect ratio

(l/d)

Tensile strength

(MPa)

Modulus of elasticity

(GPa)

Cross-section

form

Surface

structure

Steel Dramix RC-80/

60-BN

7850 60 0.75 80.0 1050 200 Circular Hooked end

Polipropylene

(PP)

Synmix 65 905 65 0.85 76.5 250 3 Square Rough

Table 4

The proportions of the concrete mixtures (based on SSD condition).

Constituents N-SCC D-SCC S-SCC DS-SCC

Cement (kg/m3) 160 160 160 160

Fly ash (kg/m3) 130 130 130 130

GGBFS (kg/m3) 110 110 110 110

Cementitious content (kg/m3) 400 400 400 400

Water (l/m3) 208 208 208 208

Water cementitious ratio 0.52 0.52 0.52 0.52

Fine aggregate (kg/m3)

Coarse sand 660 660 660 660

Fine sand 221 221 221 221

Coarse aggregate (kg/m3) 820 820 820 820

Admixtures (l/m3)

Superplasticiser 4 4.86 4.73 4.5

VMA 1.3 1.3 1.3 1.3

High range water reducing agent 1.6 1.6 1.6 1.6

Fiber content (kg/m3)

Steel 30 15

PP 5 3

Table 5

The SCC mixes workability characteristics.

Workability charact eristics N-SCC D-SCC S-SCC DS- SCC

Average spreading diameter (mm) 680 670 700 650

Flow timeT50cm (s) 2.7 3.8 2.5 3.2

Average J-Ring diameter (mm) 655 580 570 560

Flow timeT50cm J-Ring (s) 3.2 5 6 5

L-box test 0.87 Blockeda Blocked Blocked

Flow time V-funnel (s) 6 7 Blocked Blocked

V-funnel at T5min (s) 4 5 Blocked Blocked

Entrapped air (%) 1.3 1.2 1.2 1.0

Specific gravity (kg/m3) 2340 2274 2330 2385

a Fibers are the main reason for blockage.

Table 6

Compressive strength, tensile strength, modulus of elasticity, and modulus of rupture of SCC mixtures at different ages.

Age (days) N-SCC D-SCC S-SCC DS-SCC Age (days) N-SCC D-SCC S-SCC DS-SCC

Compressive strength (MPa) Tensile strength (MPa)

3 12.45 18.50 13.65 14.30 3 1.65 2.32 1.16 1.76

7 21.80 25.30 22.50 26.30 7 2.26 3.38 1.93 2.51

14 29.05 34.30 32.45 38.10 14 2.80 3.87 3.05 3.54

28 33.30 38.00 38.10 45.00 28 3.60 4.54 3.56 4.09

56 40.60 50.50 42.90 50.75 56 4.17 5.35 4.02 4.33

91 46.40 51.15 47.65 52.00 91 4.57 5.44 4.41 4.80

Modulus of elasticity (GPa) Modulus of rupture (MPa)

3 25.23 24.45 25.36 26.78 3 2.50 3.35 3.13 2.47

7 27.84 26.57 27.87 30.13 7 3.35 4.10 4.26 3.81

14 32.24 29.14 29.68 31.26 14 4.66 5.40 4.60 4.80

28 35.39 35.76 35.76 36.10 28 5.00 6.37 5.00 5.40

56 35.58 36.44 36.32 37.03 56 5.87 6.72 6.50 6.52

91 37.79 37.58 37.47 38.12 91 7.13 7.23 6.76 7.21

F. Aslani, S. Nejadi / Composites: Part B 53 (2013) 121133 123
http://-/?-http://-/?-http://-/?-http://-/?-


4/13

3.1.4. Aggregate

In this study, crushed volcanic rock (i.e., latite) coarse aggregate

was used with a maximum aggregate size of 10 mm. Nepean river

gravel with a maximum size of 5 mm and Kurnell natural river

sand fine aggregates were also used. The sampling and testing of

aggregates were carried out in accordance with ASTM C1077-13

[14](AS 1141[15]and RTA[16]) and the results for coarse and fine

aggregates are shown inTable 2, respectively.

Fig. 1. Flexural loaddeflection curve of N-SCC mixture at different ages (a) 3 days, (b) 7 days, (c) 14 days, (d) 28 days, (e) 56 days, and (f) 91 days.

Fig. 2. Flexural loaddeflection curve of D-SCC mixture at different ages (a) 3 days, (b) 7 days, (c) 14 days, (d) 28 days, (e) 56 days, and (f) 91 days.

124 F. Aslani, S. Nejadi/ Composites: Part B 53 (2013) 121133


5/13

3.1.5. Admixtures

The superplasticiser, Viscosity-Modifying Admixture (VMA),

and high-range water-reducing agent were used in this study.The new superplasticiser generation Glenium 27 complies with

AS 1478.1 [17] type High Range Water Reducer (HRWR) and

ASTM C494 [18]types A and F are used. The Rheomac VMA 362

viscosity modifying admixture that used in this study is a ready-to-use, liquid admixture that is specially developed for producing

Fig. 3. Flexural loaddeflection curve of S-SCC mixture at different ages (a) 3 days, (b) 7 days, (c) 14 days, (d) 28 days, (e) 56 days, and (f) 91 days.

Fig. 4. Flexural loaddeflection curve of DS-SCC mixture at different ages (a) 3 days, (b) 7 days, (c) 14 days, (d) 28 days, (e) 56 days, and (f) 91 days.

http://-/?-http://-/?-http://-/?-


6/13

concrete with enhanced viscosity and controlled rheological prop-

erties. Pozzolith 80 was used as a high-range water-reducing agent

in the mixes. It meets AS 1478[17]Type WRRe, requirements for

admixtures.

3.1.6. Fibers

In this study, two commercially available fibers, Dramix RC-80/

60-BN type steel fibers and Synmix 65 type polypropylene (PP) fi-

bers were used. The mechanical, elastic and surface structure prop-

erties of the steel and PP fibers are summarized inTable 3.

3.2. Mixture proportions

One control SCC mixture (N-SCC) and three fiber-reinforced SCC

mixtures were used in this study. Fiber-reinforced SCC mixtures

contain steel (D-SCC), PP (S-SCC), and hybrid (steel + PP) (DS-SCC)

fibers. The content proportions of these mixtures are given inTa-

ble 4. These contents were chosen to attempt to keep compressive

strength to a level applicable to construction. As shown inTable 4,

cement, fly ash, GGBFS, water, fine and coarse aggregates, VMA,

and high range water reducing agent constituents amount are

same for four mixes. But, fiber amount and superplasticiser that

are used in the mixes are different.

A forced pan type of mixer with a maximum capacity of 150 lwas used. The volume of a batch with fibers was kept constant at

50 l. First, powders and sand are mixed for 10 s and water and

superplasticiser are added and mixed for 110 s and the coarse

aggregate is added and at the end fibers are added to the pan

and mixed for 90 s.

3.3. Samples preparation and curing conditions

We used six /150 mm 300 mm molds for the determination

of compressive and splitting tensile strengths per each age, and

three cylindrical molds /150 mm 300 mm are used for the

determination of the modulus of elasticity per each age. Mean-

while, three 100 mm 100 mm 350 mm molds are used for

the determination of modulus of rupture per each age. Specimens

for testing the hardened properties are prepared by direct pouringof concrete into molds without compaction. The specimens are

Fig. 5. Compressive stressstrain curve of (a) N-SCC, (b) D-SCC, (c) S-SCC, and (d) DS-SCC mixes at different ages.

Table 7

The energy dissipated under compression.

Mix Age (days)

3 7 14 28 56 91

Gc (MPa)

N-SCC 0.658 0.833 1.228 1.255 1.544 1.612

D-SCC 0.747 1.117 1.327 1.494 1.683 1.825

S-SCC 0.701 0.988 1.304 1.421 1.617 1.745

DS-SCC 0.762 1.239 1.359 1.535 1.700 1.865



7/13

kept covered in a controlled chamber at 20 2C for 24 h until

demolding. Thereafter, the specimens are placed in water presatu-

rated with lime at 20C. These specimens are tested at 3, 7, 14, 28,

56, and 91 days. For each test, separated specimens are used and

surface of specimens are smoothed.

3.4. Samples test methods

The compressive strength test, performed on /150 mm

300 mm cylinders, followed AS 1012.14 [19] and ASTM C39 [18]

tests for compressive strength of cylindrical concrete specimens.

The cylinders were loaded in a testing machine under load control

at the rate of 0.3 MPa/s until failure. The splitting tensile test, run

on /150 mm 300 mm cylinders, was in accordance with the AS

1012.10 [20] and ASTM C496 [18] tests for splitting tensile strength

of cylindrical concrete specimens, although ACI committee 544.2R

[4]hardly recommends the use of the test on fiber-reinforced con-

crete. The running arose because the ratio of fiber length to cylinder

diameter took a low value of 0.23 in the work and because some

investigators have shown that the ASTM C496 test is applicable to

fiber-reinforced concrete specimens.

The modulus of elasticity test that followed the AS 1012.17[21]and ASTM C469 was done to /150 mm 300 mm cylinders. The

flexural strength (modulus of rupture, MOR) test, conducted using

100 mm 100 mm 350 mm test beams under third-point load-

ing, followed the AS 1012.11[22]and ASTM C1018 test for flexural

toughness and first-crack strength of fiber-reinforced concrete. The

mid-span deflection was the average of the ones detected by the

transducers through contact with brackets attached to the beam

specimen.

3.5. Properties of fresh concrete

The experiments required for the SCC are generally carried

out worldwide under laboratory conditions. These experiments

test the liquidity, segregation, placement, and compacting of

fresh concrete. Conventional workability experiments are not

sufficient for the evaluation of SCC. Some of the experiment

methods developed to measure the liquidity, segregation, place-ment, and compaction of SCC are defined in the European

guidelines [23] and ACI 237R-07 [24] for SCC, including specifi-

cation, production and use as slump-flow, V-funnel, U-box,

L-box and fill-box tests.

This study performed slump flow, T50cmtime, J-ring flow, V-fun-

nel flow time, and L-box blocking ratio tests. In order to reduce the

effect of loss of workability on the variability of test results, the

fresh properties of the mixes were determined within 30 min after

mixing. The order of testing is as follows: 1. Slump flow test and

measurement ofT50cmtime; 2. J-ring flow test, measurement of dif-

ference in height of concrete inside and outside the J-ring and mea-

surement of T50cm time; 3. V-funnel flow tests at 10 s T10s and

5 minT5min; and 4. L-box test[25].

4. Experimental results

4.1. Properties of fresh concrete

The results of various fresh properties tested by the slump flow

test (slump flow diameter andT50cm); J-ring test (flow diameter);

L-box test (time taken to reach 400 mm distance T400mm, time

taken to reach 600 mm distance T600mm, time taken to reach

Fig. 6. Energy dissipated under compression (Gc) versus strain of (a) N-SCC, (b) D-SCC, (c) S-SCC, and (d) DS-SCC mixes at different ages.

http://-/?-http://-/?-


8/13

800 mm distance TL, and ratio of heights at the two edges of L-box

[H2/H1]); V-funnel test (time taken by concrete to flow through V-

funnelafter 10 s T10s); the amount of entrapped air; and the specific

gravity of mixes are given in Table 5. The slump flow test judges the

capability of concrete to deform under its own weight against the

friction of the surface with no restraint present. A slump flow value

ranging from 500 to 700 mm for self-compacting concrete was sug-

gested [23]. At a slump flow>700 mm theconcretemight segregate,and at


9/13

investigation indicated that all mixes met the requirements of

allowable flow time. About V-funnel flow time test results for the

N-SCC mix was 6 s and for the D-SCC was 7 s and for other fiberrein-

forced SCC mixes are blocked, obviously.

The maximum size of coarse aggregate was restricted to

10 mm to avoid a blocking effect in the L-box for N-SCC mix.

The gap between rebars in the L-box test was 35 mm. The

L-box ratio H2/H1 for the N-SCC mix was above 0.8 which is,according to the European guidelines and, obviously, for other

mixes is blocked. A total spread over 700 mm was measured

and no sign of segregation or considerable bleeding in any of

the mixtures was detected as the mixtures showed good homoge-

neity and cohesion.

4.2. Compressive strength

Table 6 presents the compressive strength of N-SCC, D-SCC, S-

SCC, and DS-SCC mixes achieved at different ages. Compressive

strength samples with fiber mixes are higher than N-SCC mix. Sam-

ples with the S-SCC mix have lower compressive strength unlike

the D-SCC and DS-SCC mixes. The average compressive strength

of the DS-SCC mix is 19%, 4%, and 13% higher than the N-SCC,D-SCC, and S-SCC mixes, respectively. The results show that the

D-SCC mix at three days was 32%, 26%, and 22% higher than the

N-SCC, S-SCC and DS-SCC mixes respectively. Furthermore, the re-

sults indicate that the compressive strength of the DS-SCC mix at

91 days is 11%, 1%, and 8% higher than the N-SCC, D-SCC, and S-

SCC mixes, respectively.

4.3. Tensile strength

Table 6presents the splitting tensile strengths of N-SCC, D-SCC,

S-SCC, and DS-SCC mixes determined at different ages. The tensile

strengths of the D-SCC and DS-SCC samples are higher than those

of the N-SCC and S-SCC. The S-SCC mix has a lower tensile strength

than N-SCC. The average tensile strength of the D-SCC mix is 23%,

27%, and 15% higher than that of the N-SCC, S-SCC, and DS-SCCmixes, respectively. Moreover, the results indicate that the tensile

strength of the D-SCC mix at 91 days is 16%, 19%, and 12% higher

than that of the N-SCC, S-SCC, and DS-SCC mixes, respectively.

4.4. Modulus of elasticity

Table 6presents the modulus of elasticity of N-SCC, D-SCC, S-

SCC, and DS-SCC mixes attained at different ages. The average

modulus of elasticity of DS-SCC mix is 2%, 4% and 3%, higher than

that of the N-SCC, D-SCC, and S-SCC mixes, respectively. The results

show that the N-SCC mix at 14 days age is 9%, 8%, and 3% higher

than D-SCC, S-SCC, and DS-SCC mixes, respectively. Additionally,

the results indicate that the tensile strength of the DS-SCC mix at

91 days is 0.8%, 1%, and 1% higher than that of the N-SCC, D-SCC,

and S-SCC mixes, respectively.

4.5. Modulus of rupture (flexural tensile strength)

Table 6andFigs. 14present the flexural tensile strengths and

flexural loaddeflection curve of N-SCC, D-SCC, S-SCC, and DS-SCC

Fig. 8. Predicted compressive strength-related mechanical properties values versus experimented values (a) tensile strength, (b) modulus of elasticity, and (c) modulus ofrupture.

http://-/?-http://-/?-


10/13

mixes determined at different ages. The average flexural tensile

strength of the D-SCC mix is 14%, 9%, and 9% higher than that of

the N-SCC, S-SCC, and DS-SCC mixes, respectively. The results show

that the S-SCC mix at seven days is 21%, 4% and 10% higher than the

N-SCC, D-SCC, and DS-SCC mixes, respectively. Also, the results

indicate that flexural tensile strength of D-SCC mix at 91 days is

1%, 6%, and 0.2% higher than that of the N-SCC, S-SCC, and DS-

SCC mixes, respectively.

4.6. Compressive stressstrain curve

Complete stressstrain curves of the concrete of specimens

were obtained from the compression tests of the cylinders with a

controlled displacement rate. For each mix, three cylinders were

tested. As the test results reproduced well, each stressstraincurves shown inFig. 5represents the average results of the three

tests. It should be noted that the axial strains of the concrete in

compression were obtained from the full height shortening of the

cylinders using LVDTs. To assure stable tests in the softening phase

the testing equipment should have enough stiffness and sophisti-

cated PID control should be available. During the test, the strains

were obtained from the relative displacement of the loading plat-

ens. For this purpose three LVDTs were disposed around the test

sample forming an angle of 120between consecutive LVDTs. This

test set up avoids that the deformation of the test equipment is

added to the displacements read by the LVDTs. This arrangement

of the transducers also allows that the specimen deformation in

the longitudinal axis, can be computed simply by the average read-

outs of the three transducers. There is no need to attend to therotation of the upper loading paten, since the computed deforma-

tion is at the longitudinal axis of the specimen. The strain was cal-

culated from the average displacement readings divided by the

height of the specimen.

The used testing rig has these features and the tests were car-

ried out in displacement control. The compression stressstrain

curves at increasing ages of N-SCC, D-SCC, S-SCC, and DS-SCC

mixes are shown inFig. 5.All the fibrous SCC mixes verified more

substantial ductility than the corresponding N-SCC mix. Com-

monly, the nature of failure in compression for the N-SCC mix

tended to be more sudden and brittle as the age of the concrete in-

creased. On the other hand, with the increasing age, the majority of

the fibrous SCC mixes maintained their ductility and gradual fail-

ure mechanism.

4.7. Energy dissipated under compression

The energy absorption per unit volume under compression was

determined as the area under the stress (r)/strain (e) curve, the va-lue can be calculated using Eq. (1):

Gc

Z eu0

r de 1

TheGcvalue was always determined until a ultimate deformation,

eu, of 0.05, where it was expected that the residual strength wouldbe small.Table 7 includes the average values ofGc. In general, the

concrete energy absorption increased with age. The major part of

the energy is released in the softening phase that is too dependent

on the fiber reinforcement mechanisms provided by fibers crossing

the cracks. The efficiency of those mechanisms depend considerablyon the fiber bond length and fiber orientation towards the cracks

Fig. 9. Comparison between experimented (a) N-SCC, (b) D-SCC, (c) S-SCC, and (d) DS-SCC mixes compressive stressstrain curve results with proposed relationship.



11/13

they bridge, whose homogeneity cannot be assumed between two,

apparently, equal batches. The variation of the energy dissipated

under compression with the strain is represented inFig. 6. In gen-

eral,Gcincreased with strain more quickly for the older specimens,

56 and 91 days than for the specimens with 3, 7, 14 and 28 days.

5. Analytical relationships for the mechanical properties

5.1. Time-related mechanical properties relationships

To estimate the SCC mixes compressive strength, tensile

strength, modulus of elasticity, modulus of rupture, and energy

dissipated under compression at various ages, Eqs.(2)(6)are pro-

posed based on regression analyses of the experimental data.Fig. 7

shows that the proposed time-related relationships of compressive

strength, tensile strength, modulus of elasticity, modulus of rup-

ture, and energy dissipated under compression are in good agree-

ment with the experimental results. Also, R2 (correlation

coefficient) of proposed models in comparison with experimental

results is shown inFig. 7.

5.1.1. Compressive strength

fcmt f0calnt b 2

Mix f0c a b

N-SCC f0cN 3.47 2.54

D-SCC f0cfD 3.75 6.66

S-SCC f0cfS

3.84 3.87

DS-SCC f0cfDS 3.96 4.54

where f0

cN is the N-SCC mix compressive strength, f0

cfD is the D-SCCmix compressive strength, f0cfS is the S-SCC mix compressive

strength, f0cfDS is the DS-SCC mix compressive strength, and a andbare the empirical constants.

5.1.2. Tensile strength

fctmt fctc lnt k 3

Mix fct c k

N-SCC fctN 4.09 0.60

D-SCC fctfD 4.87 1.43

S-SCC fctfS 3.69 0.19

DS-SCC fctfDS 4.60 0.91

where fctNis the N-SCC mix tensile strength, fctfD is the D-SCC mix

tensile strength, f0ctfS is the S-SCC mix tensile strength, f0

ctfDS is the

DS-SCC mix tensile strength, and c and k are the empiricalconstants.

5.1.3. Modulus of elasticity

Ecmt

Ec

g lnt l 4

Mix Ec g l

N-SCC EcN 9.47 21.42

D-SCC EcfD 8.40 19.20

S-SCC EcfS 9.30 20.83

DS-SCC EcfDS 10.47 23.15

whereEcN is the N-SCC mix modulus of elasticity, EcfD is the D-SCC

mix modulus of elasticity, EcfSis the S-SCC mix modulus of elasticity,

EcfDSis the DS-SCC mix modulus of elasticity, and g and l are theempirical constants.

5.1.4. Modulus of rupture

fcrmt fcrwlnt u 5

Mix fcr w /

N-SCC fcrN 3.89 1.00

D-SCC fcrfD 5.39 2.07

S-SCC fcrfS 4.75 1.96

DS-SCC fcrfDS 3.99 1.08

where fcrNis the N-SCC mix modulus of rupture, fcrfD is the D-SCC

mix modulus of rupture, fcrfSis the S-SCC mix modulus of rupture,

fcrfDS is the DS-SCC mix modulus of rupture, and w and / are theempirical constants.

5.1.5. Energy dissipated under compression

Gcmt Gcx lnt q 6

Mix Gc x q

N-SCC GcN 4.33 0.340

D-SCC GcfD 4.91 0.476

S-SCC GcfS 4.69 0.411

DS-SCC GcfDS 5.16 0.541

where GcN is the N-SCC mix energy dissipated under compression,

GcfD is the D-SCC mix energy dissipated under compression, GcfS isthe S-SCC mix energy dissipated under compression, and GcfDS is

the DS-SCC mix energy dissipated under compression.

5.2. Compressive strength-related mechanical properties relationships

Eqs.(5)(7)are proposed based on regression analyses of the

experimental data to predict the SCC mixes tensile strength, mod-

ulus of elasticity, and modulus of rupture based on the compres-

sive strength. The bases of the proposed relationships are

captured from Aslani and Nejadis [1]study. Fig. 8 indicates the

proposed compressive strength-related relationships of tensile

strength, modulus of elasticity, and modulus of rupture are in good

agreement with the experimental results. Moreover, R2 (correla-

tion coefficient) of proposed models in comparison with experi-mental results is shown inFig. 8.

http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-


12/13

5.2.1. Tensile strength

fct g1f0cg2 7

Mix fct f0c g1 g2

N-SCC fctN f0cN 0.204 0.8047

D-SCC fctfD f0cfD

0.237 0.7999

S-SCC fctfS f0

cfS 0.067 1.0889

DS-SCC fctfDS f0

cfDS 0.226 0.7585

5.2.2. Modulus of elasticity

Ec j1f0cj2 8

Mix Ec f0c j1 j2

N-SCC EcN f0

cN 10.913 0.3226

D-SCC EcfD f0cfD 6.649 0.4383

S-SCC EcfS f

0

cfS 10.395 0.3271DS-SCC EcfDS f

0

cfDS 12.895 0.2651

5.2.3. Modulus of rupture

fcr d1f0c

d2 9

Mix fcr f0

c d1 d2

N-SCC fcrN f0cN 0.325 0.7871

D-SCC fcrfD f0cfD 0.376 0.7511

S-SCC fcrfS f0

cfS 0.670 0.5818

DS-SCC fcrfDS f0cfDS 0.309 0.7714

5.3. Compressive stressstrain relationship

In this study, a compressive stressstrain relationship (Eqs.

(10)(17)) for SCC mixes that is based on authors [1,26] model

was developed by using the proposed compressive strength (Eq.

(2)) and elastic modulus (Eqs.(4), (8)) relationships.Fig. 9 shows

that the proposed stressstrain relationship fits the experimental

results well. InFig. 9, typical 91 days age compressive stressstrain

curve results are selected to compare with the proposed compres-

sive stressstrain relationship.

rcf0c

n ece0c

n 1 ece0c

n 10

n n1 1:02 1:17Esec=Ec0:74

ifec6 e0c 11

n n2 n1 - 28 f ifecP e0c 12

- 135:16 0:1744f0c0:46 13

f 0:83exp911=f0c 14

Esec f0c=e

0c 15

e0c f0cEc

mm 1

16

m f0

c17 0:8 17

where rcis concrete stress, f0c maximum compressive strength ofconcrete, n material parameter that depends on the shape of the

stressstrain curve, e concrete strain, e0cstrain corresponding withthe maximum stress f0c, n1 modified material parameter at the

ascending branch, n2 modified material parameter at the descend-

ing branch, Ecmodulus of elasticity, Esecsecant modulus of elastic-

ity, n1 modified material parameter at the ascending branch, n2modified material parameter at the descending branch, and q,

xcoefficients of linear equation.

6. Conclusions

The following conclusions can be drawn from this study:

Experimental investigation and analytical study were per-

formed to develop a simple and rational mathematical

model for the prediction of mechanical properties and

complete stressstrain curves of concrete under compres-

sive load. Four different SCC mixes were used in the

experiment. These mixes include N-SCC (normal SCC),

D-SCC (steel fiber-reinforced SCC), S-SCC (PP fiber-rein-

forced SCC), and DS-SCC (hybrid fiber-reinforced SCC). Based on the experimental results: (a) the average com-

pressive strength and modulus of elasticity of the DS-

SCC mix is higher than that of the N-SCC, D-SCC, and S-

SCC mixes, respectively; (b) the average tensile strength

of the D-SCC mix is higher than that of the DS-SCC, N-

SCC, and S-SCC mixes, respectively; (c) the average mod-

ulus of rupture of the D-SCC mix is higher than that of the

N-SCC, S-SCC, and DS-SCC mixes, respectively.

The proposed analytical expressions to predict the most

significant mechanical properties (i.e., compressive

strength, tensile strength, modulus of elasticity, modulus

of rupture, and energy dissipated under compression) of

the developed SCC mixes are in a good agreement com-

pare to experimental results. The proposed compressive stressstrain model based on

the authors model with several modifications (i.e., chang-

ing the ascending and descending portions) is developed

by using the proposed compressive strength and elastic

modulus models that are in good agreement with the

experimental results for the developed SCC mixes.

Acknowledgements

This work was supported by Centre for Built Infrastructure Re-

search, School of Civil and Environmental Engineering, University

of Technology Sydney, Australia. The authors would like to express

their sincere gratitude and appreciation to Boral, BOSFA, and Con-

crite companies.

References

[1] Aslani F, Nejadi S. Mechanical properties of conventional and self-compactingconcrete: an analytical study. Constr Build Mater 2012;36:33047.

[2] Aslani F, Nejadi S. Bond characteristics of steel fibre reinforced self-compactingconcrete. Canada J Civil Eng 2012;39(7):83448.

[3] Balaguru PN, Shah SP. Fiber reinforced cement composites. NewYork: McGraw-Hill Inc.; 1992.

[4] ACI 544.2R. State-of-the-art report on fiber reinforced concrete. Technicalreport, American Concrete Institute; 1999.

[5] ASTM C183-08. Standard practice for sampling and the amount of testing ofhydraulic cement. ASTM standards 2000 (Annual book); 2000.

[6] AS 3972. General purpose and blended cements. Standards Australia; 2010.

[7] AS 2350. Methods of testing Portland and blended cements. StandardsAustralia; 2006.

http://-/?-http://-/?-http://-/?-http://refhub.elsevier.com/S1359-8368(13)00192-3/h0005http://refhub.elsevier.com/S1359-8368(13)00192-3/h0005http://refhub.elsevier.com/S1359-8368(13)00192-3/h0010http://refhub.elsevier.com/S1359-8368(13)00192-3/h0010http://refhub.elsevier.com/S1359-8368(13)00192-3/h0015http://refhub.elsevier.com/S1359-8368(13)00192-3/h0015http://refhub.elsevier.com/S1359-8368(13)00192-3/h0015http://refhub.elsevier.com/S1359-8368(13)00192-3/h0015http://refhub.elsevier.com/S1359-8368(13)00192-3/h0010http://refhub.elsevier.com/S1359-8368(13)00192-3/h0010http://refhub.elsevier.com/S1359-8368(13)00192-3/h0005http://refhub.elsevier.com/S1359-8368(13)00192-3/h0005


13/13

[8] ASTM C31-11b. Standard test methods for sampling and testing fly ash ornatural Pozzolans for use in Portland-cement concrete. ASTM Standards 2000(Annual book); 2000.

[9] AC1 232.2R-03. Use of fly ash in concrete. ACI Committee 232; 2004.[10] AS 3583. Methods of test for supplementary cementitious materials for use

with portland cement. Standards Australia; 1998.[11] ASTM C989-06. Standard specification for ground granulated blast-furnace

slag for use in concrete and mortars. ASTM Standards 2000 (Annual book);2000.

[12] ACI 233R-95. Ground granulated blast-furnace slag as a cementitious

constituent in concrete. ACI Committee 233; 2000.[13] AS 3582.2. Supplementary cementitious materials for use with portland and

blended cement Slag Ground granulated iron blast-furnace. StandardsAustralia; 2001.

[14] ASTM C1077-13. Standard practice for agencies testing concrete and concreteaggregates for use in construction and criteria for testing agency evaluation.ASTM Standards 2000 (Annual book); 2000.

[15] AS 1141. Methods for sampling and testing aggregates PARTICLE sizedistribution sieving method. Standards Australia; 2011.

[16] RTA (Regional Transportation Authority). Materials Test Methods, vol. 1.

[17] AS 1478.1. Chemical admixtures for concrete, mortar and grout admixturesfor concrete. Standards Australia; 2000.

[18] Annual book of ASTM standards 2000. Volume 04.02, Concrete and aggregates;2000.

[19] AS 1012.14. Method for securing and testing from hardened concrete forcompressive strength; 1991.

[20] AS 1012.10. Determination of indirect tensile strength of concrete cylinders;2000.

[21] AS 1012.17. Determination of the static chord modulus of elasticity andPoissons ratio of concrete specimens; 1997.

[22] AS 1012.11. Determination of modulus of rupture; 2000.[23] EFNARC. The European guidelines for self-compacting concrete. Specification,

Production and Use; 2005.[24] ACI 237R-07. Self-consolidating concrete. ACI Committee 237; 2007.[25]Maia L, Azenha M, Geiker M, Figueiras J. E-modulus evolution and its relation

to solids formation of pastes from commercial cements. Cem Concr Res2012;42:92836.

[26] Aslani F, Jowkarmeimandi R. Stressstrain model for concrete under cyclicloading. Mag Concr Res 2012;64(8):67385.

http://refhub.elsevier.com/S1359-8368(13)00192-3/h0020http://refhub.elsevier.com/S1359-8368(13)00192-3/h0020http://refhub.elsevier.com/S1359-8368(13)00192-3/h0020http://refhub.elsevier.com/S1359-8368(13)00192-3/h0025http://refhub.elsevier.com/S1359-8368(13)00192-3/h0025http://refhub.elsevier.com/S1359-8368(13)00192-3/h0025http://refhub.elsevier.com/S1359-8368(13)00192-3/h0025http://refhub.elsevier.com/S1359-8368(13)00192-3/h0020http://refhub.elsevier.com/S1359-8368(13)00192-3/h0020http://refhub.elsevier.com/S1359-8368(13)00192-3/h0020http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-http://-/?-

Self-compacting concrete incorporating steel and polypropylene fibers_ Compressive and tensile...

Documents

Transcript of Self-compacting concrete incorporating steel and polypropylene fibers_ Compressive and tensile...