Scc Containing Coal Fly Ash and Bottom Ash

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Influence of water/powder ratio on strength properties of self-compacting

concrete containing coal fly ash and bottom ash

Rafat Siddique a, Paratibha Aggarwal b,, Yogesh Aggarwal b

a Civil Engineering Department, Thapar University, Patiala 147 004, Indiab Civil Engineering Department, National Institute of Technology, Kurukshetra, India

a r t i c l e i n f o

Article history:

Received 9 January 2011

Received in revised form 5 September 2011

Accepted 2 October 2011

Available online 24 November 2011

Keywords:

Self-compacting concreteWaterpowder ratio

Compressive strength

Split tensile strength

Bottom ash

Fly ash

a b s t r a c t

The paper deals influence of water/powder ratio on strength properties of self-compacting concrete (SCC)containing coal bottom ash. SCC was made with coal bottom ash as replacement of fine aggregates in

varying percentages of 0%, 10%, 20% and 30% and fly ash as replacement of cement in varying percentagesof 1535%. Strength properties tests were carried out at the ages of 28, 90 and 365 days for the variousmixes.

Results indicatethe behaviour similar to normal SCC of increase in strength on decrease of waterpow-der ratio. A comparison between SCC with various fly ash contents and with various replacements of fine

aggregates with bottomash showed that SCC obtained strengthincreaseon decreaseof w/p from 0.439 to0.414 for 0% bottomash, 0.500.47 for 10% bottomash, 0.580.51 for 20% bottomash and 0.6200.546for

30% bottom ash. All mixes showed strength gain beyond 28 days and the mixes with 15% and 35% fly ashmixes gained strength of the order of 60 MPa and 40 MPa, respectively at 90 days. However, it was pos-

sible to produce SCC with a compressive strength of 4050 MPa with 1535% fly ash replacement. Thebottom ash could be used up to 20% keeping in view the decrease of strength of about 1520% (if flyash percentages with 15% and 20% are not taken into consideration), as they show higher decrease of

strength. Thus, the optimum fly ash percentage was 2535% and bottom ash percentage was up to 20%

in the present study.2011 Elsevier Ltd. All rights reserved.

1. Introduction

Self-compacting concrete (SCC) has gained significant impor-

tance in recent years because of the advantages it offers [16].SCC was developed in Japan [1]in the late 1980s to be mainly usedfor highly congested reinforced structures. Recently, this concretehas gained wide use in many countries for different applications

and structural configurations.SCC requires a high slump that can easily be achieved by

superplasticizer addition to a concrete mix and special attention

has to be paid to mix proportioning. SCC often contains a largequantity of powder materials which is required to maintain suffi-ciently low yield stress to provide flowability at a plastic viscositywhich is high enough to effectively avoid segregation. As, the use ofa large quantity of cement increases cost and results in greater

temperature rise, the use of mineral admixtures such as fly ash,bottom ash, blast furnace slag, or limestone filler could increasethe slump of the concrete mixture without increasing its cost.

A research[7]was aimed at evaluating the usage of Rice HuskAsh (RHA) as viscosity modifying agent in SCC, and to study the rel-ative costs of thematerials used in SCC. Test results substantiatethe

feasibility to develop low cost SCC using RHA. In the fresh state ofconcrete, the different mixes of concrete have slump flow in therange of 595795 mm, L-box ratio ranging from 0 (stucked) to 1and flowtime ranging from 2.2to 29.3 s. Thecompressive strengths

developed by the SCC mixes with RHA were comparable to the con-trol concrete. Cost analysis showed that the cost of ingredients ofspecific SCCmix is 42.47% less than that of control concrete. A study

[8] investigated compressive strength and particularly dryingshrinkage properties of self-compacting concretes containing bin-ary, ternary, and quaternary blends of Portland cement, fly ash(FA), ground granulated blast furnace slag (GGBFS), silica fume(SF), and metakaolin (MK). Based on the findings of this study, the

following conclusions may be drawn: There was a marked reduc-tion in the compressive strength of the concretes with increasingFA content while the concretes having GGBFS had comparablestrength values to that of the control concrete. The SF and MK con-

cretes, on the other hand, had consistently higher compressivestrength than the control concrete. The negative effect of FA onthe compressive strength was relatively diminished with the ter-nary and quaternary use of mineral admixtures. According to the

0950-0618/$ - see front matter 2011 Elsevier Ltd. All rights reserved.doi:10.1016/j.conbuildmat.2011.10.035

Corresponding author. Tel.: +91 1744 225741; fax: +91 1744 238050.

E-mail addresses: [email protected] (P. Aggarwal), yogesh.24@rediff

mail.com(Y. Aggarwal).

Construction and Building Materials 29 (2012) 7381

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GLM-ANOVA result, FA appeared to be most effective factor on thecompressive strength; however, the effect of GGBFS appeared to be

insignificant. The contribution of FA, MK, and SF were 26.7%, 12.7%,and 9.7%, respectively.

An investigation [9]presented the transport and mechanicalproperties of self consolidating concrete that contained high per-centages of low-lime and high-lime fly ash (FA). Self consolidating

concretes (SCCs) containing five different contents of high-lime FAand low-lime FA as a replacement of cement were examined alongwith a control SCC mixture without any FA for comparison. Thefresh properties of the SCCs were observed through, slump flow

time and diameter, V-funnel flow time, L-box height ratio, and seg-regation ratio. The hardened properties included the compressivestrength, split tensile strength, drying shrinkage and transportproperties (absorption, sorptivity and rapid chloride permeability

tests) up to 365 days. Test results conformed that it was possibleto produce SCC with a 70% of cement replacement by both typesof FA. The use of high volumes of FA in SCC not only improvedthe workability and transport properties but also made it possible

to produce concretes between 33 and 40 MPa compressivestrength at 28 days, which exceeds the nominal compressivestrength for normal concrete (30 MPa).

Previous studies have shown that the use of mineral admixturessuch as fly ash and blast furnace slag could increase the slump ofthe concrete mixture without increasing its cost, while reducingthe dosage of superplasticizer needed to obtain similar slump flowcompared to concrete made with Portland cement only[10]. Also,

the use of fly ash improves rheological properties and reduces thecracking potential of concrete as it lowers the heat of hydration ofthe cement [11]. Kim et al. [12] studied the properties of superflowing concrete containing fly ash and reported that the replace-

ment of cement by 30% (40% for only one mixture) fly ash resultedin excellent workability and flowability. Other researchers [13]evaluated the influence of supplementary cementitious materialson workability and concluded that the replacement of cement by

30% of fly ash can significantly improve rheological properties.

The use of fly ash reduces the demand for cement, fine fillers andsand[14], which are required in high quantities in SCC. Moreover,the incorporation of fly ash also reduces the need for viscosity-

enhancing chemical admixtures.The objective of this paper is to measure the fresh properties

and strength properties like compressive and split tensile strengthat the ages of 28, 90 and 365 days for the various mixes, incorpo-

rating bottom ash as partial replacement of fine aggregates in vary-ing percentages of 10%, 20% and 30% and fly ash as replacement ofcement in varying percentages of 1535% along with the effect ofwater/powder ratio on the strengths.

2. Materials used

2.1. Cement

Ordinary Portland cement (Grade 43) with normal consistency 28% and initial

and final setting times as 75 and 215 min was used. It had specific gravity as 3.15

and 7-day compressive strength as 37 MPa and conformed to BIS: 8112-1989specifications.

2.2. Fly ash and coal bottom ash

Class F Fly ash obtained from Panipat Thermal Power Station, Panipat, Harya-

na with specific gravity 2.13, wasused. In addition to fly ash, there arevast amounts

of substandard (coarse) bottom ash that can be utilized in the concrete industry.

Coal bottom ash was also obtained from Panipat Thermal Power Station, Panipat,

Haryana. Specific gravity of bottom ash was 1.93 and fineness modulus was ob-

served to be 1.6, as shown in Fig. 1, with bulk density loose and compacted as

776 and 948 kg/m3, respectively. The chemical properties of fly ash and bottomash are presented inTable 1.

2.3. Admixtures

A polycarboxylic ether based superplasticizer complying withASTM C-494 type

F, with density approximately 1.10 and pH approximately 5.0 was used.

2.4. Aggregates

Locally available natural sand with 4.75 mm maximum size was used as fine

aggregate, and crushed stone as coarse aggregate with 16 mm maximum size,

was used. Both fine aggregate and coarse aggregate conformed to Indian StandardSpecifications BIS: 383-1970. The coarse and fine aggregates had a specific gravity

of 2.67, andwater absorptionsof 0.95%and 0.90%,and fineness modulusas 6.86 and

2.32, respectively, as shown inFig. 1. The bulk density (loose and compacted) was

observed to be 1460 and 1540 kg/m3 for coarse aggregates and 1590 and 1780 kg/

m3 for fine aggregates, respectively.

3. Experimental program

3.1. Mixture proportions

The proportions of the concrete mixtures are summarized in Ta-

bles 2a and 2b. Twenty concrete mixtures were tested, with fivemixes for each percentage of replacement by bottom ash, whichhad total powder content to 550 kg/m3 (cement + fly ash). Coarseaggregate content was maintained at 39% by volume (590 kg/m3)

of concrete and fine aggregate content at 45% by volume of mortarin concrete (910 kg/m3), with air-content being assumed to be 2%.The various SCC mixes with fly ash as 15%, 20%, 25%, 30% and 35%

by weight of total powder content were developed, and their mixproportions and fresh properties are given inTable 2.

3.2. Preparation, and casting of specimens

For these mix proportions, required quantities of materials wereweighed and mixing of cement and fly ash in dry state and coarse

6

40.8

76.584.85

94.2599.45 100

0

20

40

60

80

100

100001000100

Sieve Size (microns)

Percenta

gePassing

Fine aggregate Bottom ash

Fig. 1. Grading curves for fine aggregates (sand and bottom ash).

Table 1

Chemical properties of fly ash and bottom ash.

Sr. no. Constituents wt.%

Fly ash Bottom ash

1. Loss on ignition 4.17 5.80

2. Silica (SiO2) 58.55 57.76

3. Iron oxide (Fe2O3) 3.44 8.56

4. Alumina (Al2O3) 28.20 21.585. Calcium oxide (CaO) 2.23 1.58

6. Magnesium oxide (MgO) 0.32 1.19

7. Total sulphur (SO3) 0.07 0.02

8. Alkalies: (a) Sodium oxide (Na2O) 0.58 0.14

(b) Potassium oxide (K2O) 1.26 1.08

The properties of fly ash and bottom ash conform to IS: 3812-2003.

74 R. Siddique et al. / Construction and Building Materials 29 (2012) 7381


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and fine aggregates were mixed dry separately. Add half of the

mixing water to coarse and fine aggregates and mix for 3 min. Mix-er is stopped and left covered for 15 min, then cement and fly ashadded evenly over the aggregate and mixed for 30 s. Add remainingwater over next 30 s and then mixing continued for 3 min after

adding all the materials together in a mixer to obtain homoge-neous mix. The casting immediately followed mixing, after carry-ing out the tests for fresh properties. The top surface of thespecimens was scraped to remove excess material and achievesmooth finish. The specimens were removed from moulds after

24 h and cured in water till testing. The cubes of size 150 mm werecast for determination of compressive strength and 150 300 mmcylinders for split tensile strength. All test measurements were ta-ken as the average of three readings for strength tests.

3.3. Testing of the specimens

3.3.1. Properties of fresh concrete and strength

For determining the self-compactibility properties (slump flow,

T50cmtime, V-funnel flow times, L-box blocking ratio, U-box differ-ence in height) tests were performed. All fresh test measurements

were duplicated and the average of measurements was given. In

order to reduce the effect of workability loss on variability of testresults, fresh state properties of mixes were determined within aperiod of 30 min after mixing. The order of testing was as below,respectively.

1. Slump flow test and measurement ofT50cmtime;2. V-funnel flow tests at 10 s T10sand 5 minT5min;3. L-box test;4. U-box test

The slump flow represents the mean diameter of the mass ofconcrete after release of a standard slump cone; the diameter ismeasured in two perpendicular directions. According to Nagataki

and Fujiwara[15] a slump flow ranging from 500 to 700 mm isconsidered as the slump required for a concrete to be self-com-pacted. At more than 700 mm the concrete might segregate, andat less than 500 mm the concrete is considered to have insufficientflow to pass through highly congested reinforcement. The stability

of SCC mixtures was evaluated through the V-shaped funnel test.According to Khayat and Manai [16], a funnel test flow time less

Table 2a

Mix composition for 0% and 10% bottom ash mixes.

Mix 0% Bottom ash 10% Bottom ash

M01 M02 M03 M04 M05 M101 M102 M103 M104 M105

Cement (kg/m3) 465 440 415 385 355 465 440 415 385 355

Fly ash (kg/m3) 85 110 135 165 195 85 110 135 165 195

Fly ash (%) 15 20 25 30 35 15 20 25 30 35C.A. (kg/m3) 590 590 590 590 590 590 590 590 590 590

F.A. (kg/m3) 910 910 910 910 910 819 819 819 819 819

B.A. (kg/m3) 91 91 91 91 91

S.P. (%) 1.95 2.00 1.80 1.80 1.80 1.85 1.80 1.50 1.60 1.70

w/p 0.41 0.41 0.42 0.43 0.44 0.472. 0.48 0.48 0.49 0.50

Slump flow

Dia. (mm) 675 690 605 675 635 675 605 625 605 645

T50cms 4.5 3.0 4.5 3.0 4.0 3.5 2.5 2.2 3.5 3.8

L-box (H2/H1) 0.9 0.9 0.6 0.95 0.92 0.8 0.82 0.8 0.7 0.9

U-box (H1H2) (mm) 20 10 50 15 20 25 20 65 50 30

V-funnel

T10ss 7.5 4.5 7 5 10 6.6 7.5 5.2 8.9 9

T5mins 15 5 8.5 9.5 18 12.5 12.5 6.8 16 18

Room temp. 31 32 32 33 32 29 32 33 30 32

Conc temp. 30 29 28 29 28 27 29 29.5 28 28.5

Table 2b

Mix composition for 20% and 30% bottom ash mixes.

Mix 20% Bottom ash 30% Bottom ash

M201 M202 M203 M204 M205 M301 M302 M303 M304 M305

Cement (kg/m3) 465 440 415 385 355 465 440 415 385 355

Fly ash (kg/m3) 85 110 135 165 195 85 110 135 165 195

Fly ash (%) 15 20 25 30 35 15 20 25 30 35

C.A. (kg/m3) 590 590 590 590 590 590 590 590 590 590

F.A. (kg/m3) 728 728 728 728 728 640 640 640 640 640

B.A. (kg/m3) 182 182 182 182 182 270 270 270 270 270

S.P. (%) 1.9 1.3 1.4 1.4 1.6 1.8 1.2 2.0 1.3 1.3

w/p 0.51 0.52 0.54 0.56 0.58 0.55 0.55 0.56 0.61 0.62

Slump flow

Dia. (mm) 590 645 600 600 590 625 600 590 610 590

T50cms 6.0 3.0 1.5 2.5 2.7 2.5 3.0 2.0 1.8 4L-box (H2/H1) 0.95 0.95 0.6 0.9 0.8 0.82 0.7 0.6 0.87 0.86

U-box(H1-H2) mm 30 30 45 30 50 30 55 30 20 40

V-funnel

T10ss 6.5 4.5 7 6.5 8 4 4.8 4.2 5.4 6.1

T5mins 8.8 7.0 7.9 12.7 16 6.5 5.8 9.7 9.5 10.5

Room temp. 32 30 32 31 32 34 30 33 32 32

Conc temp. 28 27 28 28 28 28 27 30 29 28

R. Siddique et al. / Construction and Building Materials 29 (2012) 7381 75


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than 6 s is recommended for a concrete to qualify for an SCC. Foreach mixture, the compressive strength was determined on three

cubes, and split tensile strength test on three cylinders at 28, 90,and 365 days, as per IS 516:1959.

4. Results and discussion

4.1. Properties of fresh concrete

The slump flow test judges the capability of concrete to deformunder its own weight against the friction of the surface with no re-

straint present. A slump flow value ranging from 500 to 700 mmfor a concrete to be self-compacting was suggested[15]. At slumpflow >700 mm, the concrete might segregate, and at


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age for all mixes and also with percentages of fly ash varying from35% to 15% at a particular age.

At 20% replacement with bottom ash, strengths were observedto be in the range of 2329 MPa, 3240 MPa, and 3845 MPa at28, 90, and 365 days respectively. A gain of strength of about 23%at 28 days and 18% at 365 days was observed with the decreasein fly ash contents from 35% (M205) to 15% (M201).

For 30% replacement with bottom ash the strength of M301 wasobserved to be 25.77 MPa at the age of 28 days. The findingsregarding the gain of strength at 28 days and 365 days of 41%and 14%, respectively, with the decrease in fly ash contents from

35% (M305) to 15% (M301), are similar to the ones [20], whereinthey concluded that when the bottom ash content was increased,the decrease in compressive strength could be attributed to the in-crease in water demand. In normal concrete also, reduction in

strength was observed up to 30% replacement of fine aggregatewith bottom ash.

28-day compressive strength for percentages of fly ash (1535%) and mixes at 10% bottom ash showed 0.314% strength de-

crease, 1820% strength decrease with 20% bottom ash and 2638% decrease with 30% bottom ash in comparison to correspondingmixes with 0% bottom ash. Similarly, 90-day compressive strength

for mixes with 10% bottom ash showed 1521% strength decrease,1833% strength decrease with 20% bottom ash and 2238% de-crease with 30% bottom ash in comparison to corresponding mixeswith 0% bottom ash. Also, 365-day compressive strength for mixeswith 10% bottom ash showed the 720% strength decrease, 1126%

strength decrease with 20% bottom ash and 1632% decrease with30% bottom ash, in comparison to corresponding mixes with 0%bottom ash.

4.3. Split tensile strength

Tensile strength is one of the most important fundamentalproperties of concrete. An accurate prediction of tensile strength

of concrete will help in mitigating cracking problems, improveshear strength prediction and minimise the failure of concrete intension due to inadequate methods of tensile strength prediction.Split tensile strength developed for mixes with bottom ash per-

centages varying from 0% to 30% is shown in Figs. 69, respectively,with 0% bottom ash varied from 1.55 to 2.40, and 1.762.68, 2.122.96 MPa at 28, 90, and 365 days. The gain of split tensile strengthfor various mixes was observed to be between 4.3% and 5% at 28

and 90 days, increasing with increase in cement content. The ten-sile strength values were observed to be between 4.3% and 6.8% ofcompressive strength.

At 10% replacement of fine aggregates with bottom ash,

strengths were observed to be in the range of 1.482.26 MPa,1.692.40 MPa 1.972.82 MPa at 28, 90 days and 365 days, respec-

tively. As the percentage of fly ash in 10% bottom ash mixes de-creased the split tensile strength increased at all ages. The gainof strength for various mixes was observed to be 55.6% between

28 and 90 days, increasing with increase in cement content. At20% replacement with bottom ash, strengths were observed to bein the range of 1.412.12 MPa, and 1.552.26 MPa, 1.822.54 MPa at 28, 90, and 365 days respectively, on decrease of fly

ash from 35% to 15%. An increase of about 50% strength at 28 daysand 39% at 365 days was observed with the decrease of the fly ashcontents from 35% (M205) to 15% (M201). The gain of strength forvarious mixes was observed to be between 4.7% and 5.7% between

28 and 90 days, increasing with increase in cement content.The split tensile strength for M305 with 35% fly ash of total

powder content was obtained as 1.27MPa, 1.48 MPa and1.69 MPa respectively at the ages of 28, 90, and 365 days,

0% Bottom ash

1

2

3

Age (days)

SplitTensileStrength

(MPa)

35% fly ash 30% fly ash 25% fly ash

20% fly ash 15% fly ash

28 90 365

Fig. 6. Split tensile strength (0% bottom ash) at various fly ash contents.

10% Bottom ash

1

2

3

28 90 365

Age (days)

SplitTe

nsileStrength

(MPa)




20% Bottom ash

1

2

3

28 90 365

Age (days)

SplitTensileS

trength

(MPa)




30% Bottom ash

1

2

3

Age (days)


(MPa)



28 90 365




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respectively. With the increase in cement content the strength ofM301 increased gradually to 1.90 MPa at 28 days. An increase ofabout 50% strength at 28 days and 34% at 365 days was observed

with the decrease of the fly ash contents from 35% (M305) and15% (M301). The mixes at 10% bottom ash showed 3.58% strengthdecrease, 916% strength decrease with 20% bottom ash and 1820% decrease with 30% bottom ash at 28 days. At more advanced

age (90 days), 410% strength decrease at 10% bottom ash, 1218% strength decrease with 20% bottom ash, and 1623% decreasewith 30% bottom ash was observed and 48.5% strength decreasefor 10% bottom ash, 816% strength decrease with 20% bottom

ash and 1523% decrease with 30% bottom ash at 365 days in com-parison to corresponding mixes with 0% bottom ash.

Table 3 shows the computations of ratios of split tensile

strength (ft) to the compressive strength (fc0.6) of the experimental

values of present investigation and the theoretical values of splittensile strength (ft) based on expressions proposed by earlierinvestigators (1821). An average value so obtained for different

SCC mixes has been found to be 0.24. This, in general form, wouldgive an expression a

ft

0:24fc

0:6

1

Further, a comparison of experimental results has been madewith those of other authors and shown inFig. 10. The split tensile

results are observed to be close to the results of Parra et al. [21]maybe because the researchers have also conducted the experi-ments within the range of w/p of 0.45 and 0.65, with SCC mixescontaining crushed limestone aggregates. In the investigations car-

ried out [22,23], it is observed that no replacement of fine

Table 3

Comparison of experimental values of split tensile strength (ft) with the theoretical values predicted by other researchers.

Concrete mix 28 Days compressive strength,

fc (MPa)

Split tensile strength ft (MPa) Ratios based on experimental values ft/(fc)0.6

Exp. Theoretical values as per references

Parra et al.[21] Dinakar et al.[22] Sukumar et al.[23]

SCC350 29.62 1.55 1.68 2.78 3.31 0.21

SCC380 30.66 1.76 1.72 2.88 3.40 0.23

SCC410 31.47 1.83 1.75 2.96 3.47 0.23SCC425 32.38 1.97 1.79 3.04 3.55 0.25

SCC440 33.15 2.12 1.81 3.12 3.61 0.26SCC460 35.19 2.40 1.89 3.31 3.78 0.28

Average values = 0.24.

1.0

1.5

2.0

2.5

3.0

3.5

4.0

15 20 25 30 35 40 45

Compressive Strength (MPa)


(MPa)

present study Felekogula et al Parra et al.2007

Dinakar et a l,2007 Sukumar et al ,2007 ACI 318

ACI 318

Sukumar et al,2007

Felekoglu et al,2007

Dinakar et al,2007

Parra et al,2007

Present Study

Fig. 10. Split tensile strength and compressive strength by various authors.

28-Day Strength

0

20

40

60

0.3 0.4 0.5 0.6 0.7 0.8

Water/Powder

CompressiveStrength

(MPa)

0% bottom ash 10% bottom ash


Fig. 11. Variation of compressive strengthwith w/p ratio for various percentages ofbottom ash at 28 days.

90-Day Strength

0

20

40

60

80

100

Water/Powder

CompressiveStre

ngth

(MPa)



0.3 0.4 0.5 0.6 0.7 0.8

Fig. 12. Variation of compressive strengthwith w/p ratio for various percentages of

bottom ash at 90 days.

365-Day Strength

0

20

40

60

80

100

CompressiveStrength

Water/Powder

(MPa)



0.3 0.4 0.5 0.6 0.7 0.8



Fig. 13. Variation of compressive strengthwith w/p ratio for various percentages ofbottom ash at 365 days.



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aggregates is carried out and fly ash [0%, 10%, 30%, 70%, and 85%]has been used as replacement of cement in SCC mixtures [22]. Sim-ilar, observation was made in the mixes developed by Sukumar

et al., where replacement of cement with fly ash varied between25% and 85%. Also, on comparison with mixes developed by Feleko-glu et al. [24], where the replacement of cement is carried out bylimestone dust, it can be observed that when the replacement of

fine aggregates is carried out, the results tend to be on the loweras compared to the results obtained when only replacement of ce-ment with fly ash is done.

Many researchers have developed relations for SCC compressive

strength and split tensile strength. In the present investigation,such a relations for SCC mixes made with varying percentages ofbottom ash has been developed.

4.3.1. Theoretical expressions for split tensile strength

ft= 0.18 fc2/3 MPa (Parra et al.[21])ft = 0.094 fc MPa (Dinakar et al.[22])ft = 0.0843 fc + 0.818 (Sukumar et al.[23])

4.4. Influence of waterpowder ratio on compressive strength

Figs. 1113show the compressive strength of SCC mixes versusthe waterpowder ratio (w/p) with different bottom ash contents

at ages of 28, 90 and 365 days. The relation between 28-day, 90-day and 365-day compressive strength and waterpowder ratio

for mixes without bottom ash and with various percentages is gi-ven inTable 4. It is observed that the results obtained from thepresent study, provide a good fit for most of the cases (R2 valueabove 0.8).

Although factors such as content of fine and coarse aggregate,material proportions, and curing age can affect the compressivestrength of SCC, the water-to-powder ratio (w/p) by weight is the

most prominent determinant of compressive strength [22]. A com-parison between SCC with various fly ash contents and with vari-ous replacements of fine aggregates with bottom ash showedthat SCC obtained strength increase on decrease of w/p from

0.439 to 0.414 for 0% bottom ash, 0.500.47 for 10% bottom ash,

0.580.51 for 20% bottom ash and 0.6200.546 for 30% bottomash. The trend of compressive strength on increase of water/pow-der ratio at various ages is clearly visible in various figures and it is

observed to be same for various ages i.e. 28-d, 90-d and 365-d, alsothat increase of water/powder ratio decreased the compressivestrength for all percentages of bottom ash at all ages.

4.5. Influence of water/powder ratio on split tensile strength

The influence of water/powder ratio on split tensile strength ofSCC mixes with various percentages of replacement of fine aggre-gate bottom ash at various ages is presented in Figs. 1416. The

split tensile strength also decreased with an increase in water/powder ratio. The water/powder ratio (w/p) by weight has the

most prominent effect on the strength of SCC. A comparison be-tween SCC mixes with different fly ash contents and at different

Table 4

Relationship for expected compressive strength from w/p ratio for various percentages of bottom ash.

Ages 28-Days 90-Days 365-Days

Bottom ash (%) Equation Regression coef. Equation Regression coef. Equation Regression coef.

0 0.65x4.51 0.86 0.62x5.01 0.61 0.96x4.58 0.83

10 0.69x5.16 0.82 0.84x5.27 0.76 2.77x3.80 0.84

20 1.38x4.67 0.96 2.16x4.51 0.95 4.62x3.46 0.9430 1.99x4.32 0.78 3.73x3.06 0.95 7.55x2.97 0.91

28-Day Strength

0

1

2

3

4

0.3 0.4 0.5 0.6 0.7 0.8 0.9Water/Powder


(MPa)

0% bottom ash 10% bottom ash20% bottom ash 30% bottom ash

Fig. 14. Variation of Split tensile strength with w/p ratio for various percentages of


90-Day strength

0

1

2

3

4

Water/Powder

SplitTensile

Strength

(MPa)



0.3 0.4 0.5 0.6 0.7 0.8 0.9

Fig. 15. Variation of split tensile strength with w/p ratio for various percentages of


365-Day Strength

0

1

2

3

4

0.3 0.4 0.5 0.6 0.7 0.8 0.9

Water/Powder


(MPa)


20% bottom ash 30% bottom ash0% bottom ash10% bottom ash


Fig. 16. Variation of Split tensile strength with w/p ratio for various percentages ofbottom ash at 365 days.



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replacements of fine aggregates by bottom ash showed that SCCmixes obtained split tensile strength increase on decrease ofwater/powder ratio from 0.44 to 0.41 with 0% bottom ash, 0.50

0.47 with 10% bottom ash, and 0.580.51 with 20% bottom ashand 0.6200.546 for 30% bottom ash.Figs. 1416clearly indicatethe trend shown by split tensile strength with increase of water/powder ratio. It was observed that increase of water-to-powder ra-

tio decreased the split tensile strength for all percentages of bot-tom ash at all ages. The relation between 28-day, 90-day and365-day split tensile strength and waterpowder ratio for mixeswithout bottom ash and with various percentages is given inTable

5. It is observed that the results obtained from the present study,

provide a good fit for most of the cases (R2 value above 0.8), asin the case of compressive strength.

5. Conclusions

(i) The present investigation has shown that it is possible todesign an SCC incorporating fly ash and bottom ash on var-ious percentages. The SCCs having fly ash and bottom ashshowed all fresh properties with in the ranges specified for

the mix to be SCC mix.(ii) All mixes showed strength gain beyond 28 days and the

mixes with 15% and 35% fly ash mixes gained strength ofthe order of 60 MPa and 40 MPa, respectively at 90 days.

However, it was possible to produce SCC with a compressive

strength of 4050 MPa with 1535% fly ash replacement.The bottom ash could be used up to 20% keeping in viewthe decrease of strength of about 1520% (if fly ash percent-

ages with 15% and 20% are not taken into consideration), asthey show higher decrease of strength. Thus, the optimumfly ash percentage was 2535% and bottom ash percentagewas up to 20% in the present study.

(iii) The compressive strength and split tensile strengthincreased with a decrease in the percentage of the fly ashand the water-to-cementitious materials ratio. Increase inbottom ash content resulted in decrease in compressive

strength and split tensile strength with reference to mixwith 0% bottom ash for a specific age for particular fly ashcontent. Compressive and split tensile strength of SCC mixes

was found to increase with age for all mixes with varyingpercentages of fly ash and bottom ash. Increase in bottomash decreased the split tensile strength with reference tomix with 0% bottom ash for a specific age for particular flyash content.

(iv) A comparison between SCC with various fly ash contents and

at various levels of replacements of fine aggregates by bot-tom ash showed that SCC obtained strength increase ondecrease of w/p from 0.44 to 0.41 for 0%, 0.500.47 for10%, and 0.580.51 for 20% bottom ash.

(v) The economical SCC could be achieved with sufficientstrength as the conventional concrete. Based on the materi-als used in this study, the results suggested that it is techni-cally feasible to utilize bottom ash as a part of paste content

in the production of SCC. Besides environmental benefitssuch as reduction in the continued and expanding extraction

of natural aggregate which often leads to irremediable dete-rioration of the countryside. Also, Quarrying of aggregatesleads to disturbed surface area, etc., but the artificial aggre-

gates from industrial wastes are not only adding extra aggre-gate sources to the natural and artificial aggregate but alsoprevent environmental pollution. In addition to above, therecould be some technical and financial advantages as well as

it can be used as a low-cost replacement material for moreexpensive sand in SCC.

References

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[11] Kurita M, Nomura T. Highly-flowable steel fiber-reinforced concretecontaining fly ash. In: Malhotra VM, editor. Am. Concr. Inst. 1998;SP178(June):15975.

[12] Kim JK, Han SH, Park YD, Noh JH, Park CL, Kwon YH, Lee SG. Experimentalresearch on the material properties of super flowing concrete. In: Bartos PJM,Marrs DL, Cleland DJ, editors. Production Methods and Workability ofConcrete, E&FN Spon; 1996. p. 27184.

[13] Miura N, Takeda N, Chikamatsu R, Sogo S. Application of super workable

concrete to reinforced concrete structures with difficult constructionconditions. Proc. ACI SP; 1993;140:16386.[14] Khurana R, Saccone R. Fly ash in self-compacting concrete. In: Proc. of fly ash,

silica fume, slag and natural pozzolans in concrete. ACI SP-199; 2001. p. 25974.

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Table 5

Relationship for expected split tensile strength from w/p ratio for various percentages of bottom ash.

Ages 28-Days 90-Days 365-Days

Bottom ash (%) Equation Regression coef. Equation Regression coef. Equation Regression coef.

0 0.0086x6.27 0.86 0.0124x5.99 0.86 0.0551x4.39 0.70

10 0.011x7.032 0.83 0.0234x6.14 0.83 0.0387x5.62 0.76

20 0.0789x4.89 0.92 0.079x5.0 0.92 0.1071x4.77 0.9330 0.1054x4.85 0.96 0.1403x4.45 0.95 0.1565x4.48 0.95



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