Arab International University

Faculty of civil engineering

Student Work Report

Strength of Lightweight Concrete

Prepared By:

Jaber Hasan Al-Sodi

Under the Supervision of:

Dr. Basem Ali

2015

1

Abstract

The purpose of this report is to investigate the types, advantages, mechanical properties

of LWC. And what additions act in the strength of LWC.

This report presents the results of the Investigation of the response of lightweight

concrete to elevated temperature. Also this report investigates the effects of steel fibers

on some properties of light weight concrete as compressive strength, splitting tensile

strength and flexural strength.

Also this report investigates the effect of porous aggregate on strength of concrete.

And investigated influence of pre-wetting Aggregate on mechanical properties of

concrete.

But the performance of structural lightweight aggregate concrete could be further studied

with various cement content at constant w/c ratio.

2

Acknowledgements

I would like to express my sincere gratitude to Dr.Basem Ali for his perfect assistance guidance, recommendations and support throughout this report and preparation of this thesis.

3

Table of Contents

1. Introduction: ------------------------------------------------------------------------------------------ 7

2. Types of Lightweight Concrete ----------------------------------------------------------------- 9

2.1 No-Fines Concrete --------------------------------------------------------------------------------- 9

2.2 Lightweight Aggregate concrete ---------------------------------------------------------------10

2.3 Aerated Concrete ---------------------------------------------------------------------------------11

3. Advantages and Disadvantges of Lightweight Concrete -------------------------------12

4. Mechanical Properties of Structural Lightweight Concrete -----------------------------13

4.1 Compressive strength (unheated specimens) ---------------------------------------------13

4.2 Compressive strengths (heated specimens) -----------------------------------------------15

5. Effect of reinforcement by steel fibers on behavior of lightweight concrete : ------18

5.1 Materials:------------ --------------------------------------------------------------------------------18

5.1.1 Cement -----------------------------------------------------------------------------------------------18

5.1.2 Fine Aggregate-------------------------------------------------------------------------------------19

5.1.3 Crushed Bricks as Light Weight Coarse Aggregate--------------------------------------20

5.1.4 Steel Fibers -----------------------------------------------------------------------------------------21

5.1.5 High-Range Water Reducing Admixture (Super plasticizer) ---------------------------21

5.2 Mix Proportions ------------------------------------------------------------------------------------22

5.3 Mixing of Concrete --------------------------------------------------------------------------------22

5.4 Casting, Compactions and Curing ------------------------------------------------------------23

5.5 Testing of Concrete -------------------------------------------------------------------------------23

5.6 Results 24

5.6.1 Equilibrium Density of Light Weight Concrete ---------------------------------------------24

5.6.2 Compressive Strength ---------------------------------------------------------------------------24

5.6.3 Flexural Strength ----------------------------------------------------------------------------------26

5.6.4 Splitting Tensile Strength ------------------------------------------------------------------------28

6. Effect of mineral admixture on properties of lightweight concrete: -------------------30

7. Examples about using of LWC: ----------------------------------------------------------------31

8. Creep and Shrinkage of Lightweight Concrete: -------------------------------------------32

9. Effect of Porous Lightweight Aggregate -----------------------------------------------------34

4

10. Effect of Aggregate Pre-wetting ---------------------------------------------------------------36

11. Conclusion:- ----------------------------------------------------------------------------------------39

12. Recommendations --------------------------------------------------------------------------------39

13. Findings:------------- --------------------------------------------------------------------------------40

14. Refrences:-- -----------------------------------------------------------------------------------------42

5

List of Figures

Figure 1: No-fines concrete ........................................................................................ 9

Figure 2: Lightweight Aggregate Concrete ............................................................... 10

Figure 3: Aerated Concrete ...................................................................................... 11

Figure 4: Variation of Strength with Age at Ambient Temperature (Balogun 1986). . 14

Figure 5: Variation of Strength with Temperature for Different Mix Ratios. .............. 16

Figure 6: Variation of Strength with Temperature for Different Mix Ratios. .............. 17

Figure 7: Light weight coarse aggregate .................................................................. 20

Figure 8: Steel Fiber ................................................................................................. 21

Figure 9: Curing of light weight concrete .................................................................. 23

Figure 10: Compressive Strength at 7 and 28 days( Zinkaah 2014) ........................ 26

Figure 11: Show the shape of concrete crush with Fibers and without Fibers .......... 26

Figure 12: Flexural Strength at 28 days( Zinkaah 2014) .......................................... 27

Figure 13: Show the shape of concrete failure with Fibers and without Fibers ......... 28

Figure 14: Show the shape of concrete splitting with steel Fibers ............................ 29

Figure 15: Splitting tensile strength at 28 days( Zinkaah 2014) ................................ 29

Figure 16: Relationship between the steel Fibers content and increasing in splitting

tensile strength( Zinkaah 2014). ............................................................................... 29

Figure 17: SEM View of LWC Showing the LWA Closely Bonded with Cement Matrix

(x75) ......................................................................................................................... 34

Figure 18: BSEI View of LWC Showing Diffusion of Cement Paste into Aggregate

Surface (x75) ............................................................................................................ 35

Figure 19: Aggregate Shell and IZ of the Concrete Composite (x2000) ................... 35

Figure 20: Porous Aggregate as Interlocking sites for HCP at the IZ (x5000) .......... 36

6

List of Tables

Table 1: Advantages and Disadvantages of Lightweight Concrete(Samidi 1997). ... 12

Table 2: Average Compressive Strength of Unheated Test Specimens ( N/mm2)

(Balogun 1986). ........................................................................................................ 13

Table 3: Chemical Analysis of Cement( Zinkaah, 2014)........................................... 18

Table 4: Physical properties of Cement( Zinkaah 2014) ........................................... 18

Table 5: Grading of fine aggregate( Zinkaah 2014) .................................................. 19

Table 6: Grading of light weight coarse aggregate( Zinkaah 2014) .......................... 20

Table 7: Physical properties of light weight coarse aggregate( Zinkaah 2014) ........ 20

Table 8: Properties of steel fiber( Zinkaah 2014) ..................................................... 21

Table 9: Details of the mixtures( Zinkaah 2014) ....................................................... 22

Table 10: Compressive Strength at 7 and 28 days( Zinkaah 2014) ......................... 25

Table 11: Flexural Strength at 28 days( Zinkaah 2014) ........................................... 27

Table 12: splitting tensile at 28 days( Zinkaah 2014) ............................................... 28

Table 13 Summary the results of the "high strength" mix( Kenneth & Harmon) ....... 33

Table 14: Mix Proportions of LWAC(Lo et al 2004) ................................................. 37

Table 15: Workability and Density of LWAC (Lo et al 2004) .................................... 37

Table 16: Compressive Strength of LWAC(Lo et al 2004) ....................................... 38

7

1. Introduction:

Concrete is a composite material that consists of a cement paste within which various

sizes of fine and course aggregates are embedded. It contains some amount of

entrapped air and may contain purposely-entrained air by the use of air-entraining

admixtures.

In concrete construction, the concrete represents a very large proportion of the

total load on the structure, and there are clearly considerable advantages in

reducing its density. One of the ways to reduce the weight of a structure is the

use of lightweight aggregate concrete (LWAC) (Mouli & Khelafi 2008).

Lightweight concrete can be defined as a type of concrete which includes an

expanding agent in that it increases the volume of the mixture while giving additional

qualities such as nailibility and lessened the dead weight ( Zakaria 1978).

It is lighter than the conventional concrete with a dry density of 300kg/��up to 1840

kg/m� 87 to 23% lighter. It was first introduced by the Romans in the second century

where ‘The Pantheon’ has been constructed using pumice ,the most common type of

aggregate used in that particular year (Samidi 1997). From there on, the use of

lightweight concrete has been widely spread across other countries such as USA, United

Kingdom and Sweden.

The lower density and higher insulating capacity are the most obvious characteristics

of Lightweight Aggregate Concrete (LWAC) by which it distinguishes itself from ‘ordinary’

Normal Weight Concrete (NWC). However, these are by no means the only

characteristics, which justify the increasing attention for this (construction) material. If

that were the case most of the design, production and execution rules would apply for

LWAC as for normal weight concrete, without any amendments. Lightweight Aggregate

(LWA) and Lightweight Aggregate Concrete are not new materials.

8

In recent years, more attention has been paid to the development of lightweight

aggregate concrete (Lo et al.2007). The specific gravity of concrete can be lowered

either by using porous, therefore lightweight aggregates instead of ordinary ones, or

introducing air into the mortar, or removing the fine fractions of aggregate and

compacting concrete only partially. In all cases, the main goal is to introduce voids into

the aggregate and the mortar or between mortar and aggregate. A combination of these

methods can also be made in order to reduce further the weight of concrete. The

use of lightweight aggregates is by far the simplest and most commonly used method of

making a lightweight concrete (Gündüz & Uǧur 2005).

9

2. Types of Lightweight Concrete

Lightweight concrete can be prepared either by injecting air in its composition or it

can be achieved by omitting the finer sizes of the aggregate or even replacing them by a

hollow, cellular or porous aggregate. Particularly, lightweight concrete can be

categorized into three groups:

i) No-Fines Concrete

ii) Lightweight Aggregate Concrete

iii) Aerated/Foamed Concrete

2.1 No-Fines Concrete

No-fines concrete can be defined as a lightweight concrete composed of cement

and fine aggregate. Uniformly distributed voids are formed throughout its mass. The

main characteristics of this type of lightweight concrete is it maintains its large voids and

not forming laitance layers or cement film when placed on the wall. Figure 1 shows one

example of No-fines concrete.

fines concrete-: No1Figure

10

No-fines concrete usually used for both load bearing and non-load bearing for

external walls and partitions. The strength of no-fines concrete increases as the cement

content is increased. However, it is sensitive to the water composition. Insufficient water

can cause lack of cohesion between the particles and therefore, subsequent loss in

strength of the concrete. Likewise too much water can cause cement film to run off the

aggregate to form laitance layers, leaving the bulk of the concrete deficient in cement

and thus weakens the strength.

2.2 Lightweight Aggregate Concrete

The lightweight aggregate concrete can be divided into two types according to its

application. One is partially compacted lightweight aggregate concrete and the other is

the structural lightweight aggregate concrete. The partially compacted lightweight

aggregate concrete is mainly used for two purposes that is for precast concrete blocks or

panels and cast in-situ roofs and walls. The main requirement for this type of concrete is

that it should have adequate strength and a low density to obtain the best thermal

insulation and a low drying shrinkage to avoid cracking (Samidi 1997).

Structurally lightweight aggregate concrete is fully compacted similar to that of the

normal reinforced concrete of dense aggregate. It can be used with steel reinforcement

as to have a good bond between the steel and the concrete.

The concrete should provide adequate protection against the corrosion of the steel. The

shape and the texture of the aggregate particles and the coarse nature of the fine

aggregate tend to produce harsh concrete mixes. Only the denser varieties of

lightweight aggregate are suitable for use in structural concrete ( Samidi 1997 ). Figure 2

shows the feature of lightweight aggregate concrete.

: Lightweight Aggregate Concrete2Figure

11

2.3 Aerated Concrete

Aerated concrete does not contain coarse aggregate, and can be regarded as an

aerated mortar. Typically, aerated concrete is made by introducing air or other gas into a

cement slurry and fine sand. IN commercial practice, the sand is replaced by pulverized

fuel ash or other siliceous material, and lime maybe used instead of cement (Samidi

1997).

There are two methods to prepare the aerated concrete. The first method is to inject

the gas into the mixing during its plastic condition by means of a chemical reaction.

The second method, air is introduced either by mixing-in stable foam or by whipping-

in air, using an air-entraining agent. The first method is usually used in precast concrete

factories where the precast units are subsequently autoclaved in order to produce

concrete with a reasonable high strength and low drying shrinkage. The second method

is mainly used for in-situ concrete, suitable for insulation roof screeds or pipe lagging.

Figure 3 shows the aerated concrete.

: Aerated Concrete3Figure

12

3. Advantages and Disadvantges of Lightweight

Concrete

Table 1 shows the advantages and disadvantages of using lightweight concrete as

structure (Samidi 1997).

(Samidi 1997).Advantages and Disadvantages of Lightweight Concrete :1Table Advantages Disadvantages

i) rapid and relatively simple construction.

ii) Economical in terms of transportation as

well as reduction in manpower.

iii) Significant reduction of overall weight

results in saving structural frames, footing

or piles.

iv) Most of lightweight concrete have better

nailing and sawing properties than heavier

and stronger conventional concrete.

i) Very sensitive with water content in the

mixtures.

ii) Difficult to place and finish because of

the porosity and angularity of the

aggregate. In some mixes the cement

mortar may separate the aggregate and

float towards the surface.

iii) Mixing time is longer than conventional

concrete to assure proper mixing.

The use of lightweight aggregate in concrete has many advantages. These include:

(a) Reduction of dead load that may result in reduced footings sizes and lighter

and smaller upper structure. This may result in reduction in cement quantity and

possible reduction in reinforcement.

(b) Lighter and smaller pre-cast elements needing smaller and less expensive handling

and transporting equipment.

(c) Reductions in the sizes of columns and slab and beam dimensions that result in

larger space availability.

(d) High thermal insulation.

(e) Enhanced fire resistance (Kayali 2007 & ACI 213,2003).

13

4. Mechanical Properties of Structural Lightweight

Concrete

4.1 Compressive strength (unheated specimens)

Table 2 shows summary of average compressive strength of unheated test

specimens. It is observed that at 7-day curing age, the compressive strength values of

the unheated concrete specimens with 1:2:2 mix and w/c ratios of 0.6 and 0.8 were

2.85 and 2.60 N/mm2respectively. At 21-day curing age, average compressive

strength of specimens with w/c ratio of 0.6 and 0.8 were 4.46 and 3.65N/mm2

respectively. At 90-daycuring age, concrete with 1:2:2 mix and water/cement ratio of 0.6

showed an average compressive strength value of 4.69 N/mm2 while for 1:2:2 mix and at

0.8 water/cement ratio, the average strength was 4.56 N/mm2 (Balogun 1986).

)2Average Compressive Strength of Unheated Test Specimens ( N/mm :2Table (Balogun 1986).

Curing Age (days)

w/c

Ratio

Mix Ratio

1:2:2

Mix Ratio

1:2.5:2

0.6

0.8

7

2.85

2.6

21

4.46

3.95

90

4.69

4.56

7

5.34

4.88

21

6.00

5.62

90

7.34

6.52

Compressive

Strength

(N/mm2)

In all test cases, the average compressive strengths of test specimens with w/c of

0.6 were higher than the corresponding values for test specimens with 0.8 w/c ratio. The

decrease in strength of test specimens with w/c = 0.8 relative to test specimens

prepared with w/c = 0.6 could be attributed to presence of excess moisture for

hydration process in the specimens prepared with 0.8 w/c ratio (Balogun 1986).

14

The results of strength variation with curing age for different mixes at 21oC laboratory

temperature (unheated specimens) are presented in Figure. 4 The figure indicates that

the test specimens for 1:2 ½:2 mix at w/c ratio of 0.6 have the highest

compressive strength values. At 7-day curing age, the average values for compressive

strength are 5.34N/mm2and 4.88 N/mm2for 0.6 and 0.8 w/c ratios respectively. This

indicates a 9.20% more than the strength of the specimens with 0.8 w/c ratio. At 90 day

curing age, the strength values are7.34 N/mm2 and 6.52 N/mm2 at w/c ratio of 0.6 and

0.8. This indicates a difference of 12.42% in strength values an indication that the

smaller the w/c ratio value, the higher the strength of the mixes provided the mix were

prepared under the same condition (Balogun 1986 ).

Also, for test specimens prepared from 1:2:2 mix with w/c ratio of 0.6, the

average compressive strength at 7-day curing age was 2.85 N/mm2as against 2.60

N/mm2 for specimens with 0.8 w/c ratio. This indicates a reduction of 8.77% of

compressive strength of test specimens with 0.6 w/c ratio. This trend of decrease in

strength values for mix with 0.6 w/c ratio when compared with the mix with 0.8 w/c ratio

was also observed at 21- and 90-day curing ages (Balogun 1986 ).

(Balogun 1986). : Variation of Strength with Age at Ambient Temperature4Figure

15

4.2 Compressive strengths (heated specimens)

Figures 4 present results of compressive strengths with increase in temperature. It

is observed that the compressive strengths of test specimens reduced with increase in

temperature. At 7-day curing age, the 1:2½:2 mix test specimens cast with 0.6 w/c ratio

have average compressive strength of 5.34 N/mm2 at ambient (21oC) teWmperature

while at 800oC temperature, the average compressive strength of test specimens

reduced to 3.67N/mm2 at the same age. This shows 31.27% reduction in strength. An

average of 3.48% reduction in compressive strength with every 50oC increase in

temperature was recorded.

At 21-day curing age, between 21oC and 800oC temperature range, the

compressive strength values are 5.90 N/mm2 and 4.21 N/mm2 respectively. This gives a

reduction in strength values of 28.64%. An average of 3.18% reduction in compressive

strength with every 50oC increase in temperature was recorded (Balogun 1986 ).

At 90-day curing age a reduction in strength value of 35.10% corresponding to an

average loss in strength of 3.9% for every 50oC increase in temperature was observed.

The investigation further showed that at 8000C/hour, in most specimens the periwinkle

shells disintegrated considerably and had all broken into pieces.

The rate of loss of strength by the test specimens was higher at the early stages of

drying as the periwinkle shells tend to experience change in their structure due to

temperature increase. This perceived structural change as a result of heat effect is

responsible for rapid loss of compressive strength of the test specimens. As the

temperature increased, the effect reached its peak, hence, the rate of influence on the

compressive strength reduced.

This trend in loss of compressive strength by test specimens with increase

in temperature is also observed for all other mixes as indicated in Figures.5,6.(ii), (iii)

and (iv).In all cases, as the temperature increases, there is a gradual loss in strength of

the specimens. At the temperature of 800oC/hr, heated specimens lost between 26%

and 40% of initial strength values before the heating process commenced (Balogun

1986).

16

Also, the rate of loss in strength evaluated by the slope of Figures 5,6 (i), (ii), (iii) and

(iv) curves tends to be higher in 1:2.5:2 mixes when compared to 1:2:2 mixes,

irrespective of the water/cement ratio and the curing age. The compressive

strengths of the test specimens were reasonably maintained up to 300oC, there

after as temperature increases there is a severe and progressive decrease in

strength. This is attributed to the formation of cracks in the specimens, coupled with poor

bonding of the concrete matrix. The loss in strength is considerably lower before

attainment of 400oC temperature level, but at 600oC most of the periwinkle shells

(aggregate) in the test specimens were fractured. This accounts for higher strength loss

at higher temperatures (Balogun 1986 ).

ature for Different Mix Ratios.: Variation of Strength with Temper5Figure (i) 1:2.5:2 mix with w/c ratio = 0.6, (ii) 1:2:2 mix with w/c= 0.6.

17

Variation of Strength with Temperature for Different Mix Ratios. :6Figure mix with w/c= 0.8.(iii) 1:2.5:2 mix with w/c ratio = 0.8, (iv) 1:2:2

18

5. Effect of reinforcement by steel fibers on behavior

of lightweight concrete :

5.1 Materials:

5.1.1 Cement

Ordinary Portland cement type ALDOUH has been used in this investigation. The

chemical analysis of cement are given in the Table 3 and 4 and these results

completes with ASTM Specif. C150-02a/2002(ASTM C 150-02a ,2002)

2014)Zinkaah, (Chemical Analysis of Cement :3Table Compound

composition CaO SiO2 Al2O3 Fe2O3 SO3 MgO L.O.I L.S.F I.R C3A

Percentage

by weight 63.2 18.9 3.8 4.6 1.5 1.7 1.9 0.9 0.4 2.32

Limit of ASTM

Specif .C150-

02a/2002

----- ----- ----- ----- ≤2.3 ≤6.0 ≤3.00 ----- ≤0.75 ≤5.

0

)Zinkaah 2014 (Physical properties of Cement :4Table Physical properties Test results Limit of ASTM Specif.

C150-0.2a/2002

Initial setting (vicat) 75 min 45 min.(Min)

Final setting (vicat) 165 min 375 min. (Max)

Compressive strength of

mortar(MPa)

3-days 19.5 15 (Min)

7-days 29.3 21 (Min)

19

5.1.2 Fine Aggregate

A normal weight washed sand with a (4.75mm) maximum size is used as fine

aggregates. The grading of the sand conformed to the requirement of ASTM C33-01

(ASTM C 33 – 01,2001).The sieve analysis results are given in Table 5.

2014)Zinkaah (Grading of fine aggregate: 5Table Sieve size Cumulative Passing % Limit of ASTM C33-01

9.5 mm 100.00 100

4.75 mm 95.58 95 – 100

2.36 mm 73.50 80 – 100

1.18 mm 70.03 50 – 85

600 µm 51.50 25 – 60

300 µm 16.40 5 – 30

150 µm 2.14 0 - 10

20

5.1.3 Crushed Bricks as Light Weight Coarse Aggregate

In this experiment a crushed hole-clay bricks with dimensions (235*115*75) mm

were used as coarse light weight aggregate .The bricks crushed and graded

according to ASTM C330-04(ASTM C 330-04)for light weight aggregate with19 mm

maximum size. Bricks before crushing have the compressive strength (12.3 MPa) and

(22.4 %) absorption. Table (6) and (7) shows the grading and physical properties of

coarse LWA respectively. ( Zinkaah 2014)

2014)( Zinkaah Grading of light weight coarse aggregate :6Table Sieve size Cumulative Passing % Limit of ASTM C330-04

25 mm 100 100

19 mm 100 90 – 100

9.5 mm 40 10 – 50

4.75 mm 10 0 – 15

75 µm 2 0 – 10

2014)( Zinkaah Physical properties of light weight coarse aggregate :7Table Property Test results Limit of ASTM C330-04

Bulk density (Kg/m3) 852 880

Absorption 27.4 % ------

Specific gravity 1.75 ------

Figure 7: Light weight coarse aggregate

21

5.1.4 Steel Fibers

The steel fibers used in this test experiment were straight steel fibers; Table (8)

shows the properties of steel.

2014)( Zinkaah Properties of steel fiber :8Table Property Specifications

density 7800 kg/m3

Tensile strength 2850 MPa

Length 15 mm

Diameter 0.2 mm

Aspect ratio 75

: Steel Fiber8Figure

5.1.5 High-Range Water Reducing Admixture (Super plasticizer)

Sika viscocrete-5930 is used to reduce the water and to get higher compressive

strength. It is a third generation Superplasticizer for concrete and mortar and meets

the requirements for super plasticizer according to ASTM-C- 494 Types G and F and BS

EN 934 part 2: 2001( Zinkaah 2014).

22

5.2 Mix Proportions

The reference mixture (A) is designed according to the Standard Practice

for Selecting Proportions for Structural Lightweight Concrete (ACI 211.2-98)(1).

A series of five concrete mixtures were made including reference

mixture(A), while other four mixtures contain steel fibers there are (1%, 0.75%,

0.5%, and 0.25%) for mixes (B, C, D, and E) by volume of concrete respectively.

Superplasticizer was added to give the slump within (200-250) for all mixtures. The

light weight coarse aggregate and fine aggregate was flooded with water, 24h prior

to mixing, then this was drained before mixing to get saturated surface dry

aggregate (S.S.D). Table (9) shows the mixture proportions of light weight

concrete ( Zinkaah 2014).

2014)( Zinkaah Details of the mixtures: 9Table

Mix Percent of S.F

by volume of

concrete

Cement (

Kg/m3)

Sand

(Kg/m3)

Aggregate(Kg/m3) W/C S.P % of

cement

A 0 385 500 690 0.3 0.6

B 1 385 500 690 0.3 0.8

C 0.75 385 500 690 0.3 0.75

D 0.5 385 500 690 0.3 0.70

E 0.25 385 500 690 0.3 0.65

*S.F: Steel Fibers, * S.P: Superplasticizer

5.3 Mixing of Concrete

Firstly, the quantities of gravel and sand were placed in a concrete mixer and dry

mixed for 1 min. Secondly, the cement is spread and dry mixed for 1 min. After which,

fibers were slowly added by hand spraying, while the mix was rotating .Mixing was

continued for 3 minutes to encourage a uniform distribution of fibers throughout the

concrete. Lastly, adding of water and the Superplasticizer to the mix. The mixing time

was ranging between (2-3) minutes to get a uniform mix without segregation ( Zinkaah

2014).

23

5.4 Casting, Compactions and Curing

The freshly mixed fiber-reinforced concrete is fed into the molds, the molds were

lightly coated with mineral oil before use, according to ASTM C 192-88 (ASTM

C192-88, 1989), concrete casting was carried out in different layer each layer of 50

mm. Each layer was compacted by using a vibrating table for (15-30) second until no

air bubbles emerged from the surface of the concrete, and the concrete is

leveled off smoothly to the top of the molds. Then the specimens were kept covered in

the laboratory for about (24) hours. After that the specimens remolded carefully, marker

and immersed in water until the age of test ( Zinkaah 2014).

light weight concreteCuring of : 9Figure

5.5 Testing of Concrete

To investigate the behavior of light weight concrete with steel fibers the following

specimens were cast for each mix.

- Six (100 mm) cubes to measure the compressive strength at 7 and 28 days

according to BS 1881 part116:1989.

- Two (100 * 200 mm) cylinders to conduct the splitting tensile strength at 28 days,

accordance to ASTM C496-86.

- Two (100x100x400mm) prisms to evaluate the flexural strength at 28 days, according

to ASTM C 78 (2002).

-Two (150 * 300 mm) cylinders to conduct the splitting tensile strength at 28 days,

according ASTM C 469 (2002).

- Furthermore, two 100 mm cubes were cast to investigate the water absorption

according to B.S. ASTM C 642.

24

5.6 Results

5.6.1 Equilibrium Density of Light Weight Concrete

To measure the equilibrium density according ACI 211.2-98(ACI 211.2-98),

remove the cylinders have dimensions (150*300) mm from their curing condition on

the seventh day after molding and immerse in water at (23 ± 2 °C) for 24 h. Measure the

apparent mass of the cylinders while suspended and completely submerged in water

and record as (C). Remove from the water and allow draining for 1 min by placing the

cylinder on a coarser cloth. Remove visible water with a damp cloth, determine the mass

and record as (B). Dry the cylinders with all surfaces exposed, in a controlled

humidity until the mass of the specimen changes not more than 0.5 % and record as

(A). The equilibrium density of the light weight concrete can be calculated from the

following equation.

Em= (Ax997) / (B-C)

Where:

Em= measured equilibrium density, kg/m3

A = mass of cylinder as dried, kg (lb)

B = mass of saturated surface-dry cylinder, kg

C = apparent mass of suspended-immersed cylinder, kg

The equilibrium density of light weight concrete in this experiment equal to 1812

Kg/m³ and that satisfied the requirements of ACI committee 211.2-98; state that,

the equilibrium weight not exceeding (1842 kg/m³).( Zinkaah 2014)

5.6.2 Compressive Strength

Values of compressive strength for all mixes are shown in Table (10) and Figure

(10) at 7 and 28 days, results demonstrated that in general, all concrete

specimens exhibited an increase in compressive strength with increase the percent of

steel fibers. The percent of increasing in compressive strength at 7 days about

(27.18%, 43%, 30.32%, and 17.48%) for (1%, 0.75%, 0.5%, and 0.25%) steel

fibers respectively. While in 28 days, adding (1%, 0.75%, 0.5%, and 0.25%) steel

fibers lead to increasing in compressive strength by about (30.33%, 51.73%, 33.79%,

and 21.26%) respectively. It can be seen that the increase in compressive strength of

light weight steel fiber concrete at 28 days was greater than their corresponding

compressive strength at 7 days. Such increase in compressive strength was attributed to

25

the intensive product of hydration process around the steel fibers and in voids of

concrete ( Salih et al 2005 ).

From Figure (10) it may also be concluded that the addition of steel fibers

up to 0.75% of concrete volume improved the compressive strength of light weight

concrete due to the better mechanical bond strength between the fibers and the

cement matrix which delays micro-cracks formation ( Dawood & Ramli 2010 ).

However, Adding more steel fibers up to 1% of concrete volume reduces the

increasing in the compressive strength as compared with 0.75% but it remain higher

than the reference mix and this is attributed to the voids introduction in the mix due

to excessive fiber content that may lead to reduction in bonding and disintegration(

Dawood & Ramli 2009 ).

)( Zinkaah 2014Compressive Strength at 7 and 28 days :10Table

Mix

Compressive

strength

MPa-7 days

%Increase in

compressive

Strength -7 days

Compressive

strength

MPa-28 days

%Increase in

compressive

Strength -28 days

A-0.00%S.F 22.66

28.82

32.41

29.53

26.32

……….

27.18

43.00

30.32

17.48

29.77

38.8

45.17

39.83

36.1

………..

30.33

51.73

33.79

21.26

B-1.00%S.F

C-0.75%S.F

D-0.50%S.F

E-0.25%S.F

26

2014)( Zinkaah : Compressive Strength at 7 and 28 days10Figure

: Show the shape of concrete crush with Fibers and without Fibers11Figure

5.6.3 Flexural Strength

The test results of the flexural strength are reported in Table (11) and

Figure (12). The results indicated that in general, all types of concrete specimens

exhibited continued increase in flexural strength with increasing in steel fibers. The

increase in flexural strength for light weight concrete with steel fiber relative to

reference concrete mix were 20.91%, 29.25%, 41.67% and 54.24% for light weight

concrete with 0.25%, 0.5%, 0.75% and 1% steel fiber by volume of concrete

respectively ( Salih et al 2005 ).

27

This behavior is mainly attributed to the role of steel fiber in releasing

fracture energy around crack tips which is required to extent crack growing by

transferring stress from one side to another side. Also this behavior is due to the

increase in crack resistance of the composite and the ability of fibers to resist forces

after the concrete matrix has cracked ( Salih et al 2005 ).

2014)( Zinkaah : Flexural Strength at 28 days11Table

Mix

Flexural strength

MPa-28 days

%Increase in flexural

Strength

A-0.00%S.F

B-1.00%S.F

C-0.75%S.F

D-0.50%S.F

E-0.25%S.F

6.60

10.18

9.35

8.53

7.98

……….

54.24

42.67

29.24

20.91

2014)( Zinkaah : Flexural Strength at 28 days12Figure

28

: Show the shape of concrete failure with Fibers and without Fibers13Figure

5.6.4 Splitting Tensile Strength

The results of splitting tensile strength for the lightweight concrete mixes

are shown in Table (12) and plotted in Figure (15). It can be concluded that the

inclusion of steel fibers in concrete mix cause a considerable increase in splitting

tensile strength relative to reference mix (without fibers) ( Salih et al 2005 ).

Splitting tensile strength increases as the fiber volume fraction increases.

However, The increasing in splitting tensile strength of light weight steel fiber concrete

(LWSFC) relative to reference concrete at 28 days were 62.62%, 33.76% , 17.27%

and 5.93% for LWSFC with 1%, 0.75%, 0.5% and 0.25% steel fiber by volume of

concrete respectively, Figure (16). This increasing may be due to the excellent

mechanical anchorage of steel fibers at their surface which leads to high bond

strength between the fibers and the matrix ( Salih et al 2005 ).

2014)( Zinkaah splitting tensile at 28 days :12Table

Mix

Splitting Strength

MPa –28 days

% Increase in Splitting

Strength

A-0.00% S.F 3.88 ………….

B-1.00% S.F 6.31 62.63

C-0.75% S.F 5.19 33.76

D-0.50% S.F 4.55 17.27

E-0.25% S.F 4.11 5.93

29

Show the shape of concrete splitting with steel Fibers :14Figure

2014)( Zinkaah Splitting tensile strength at 28 days :15Figure

Relationship between the steel Fibers content and increasing in splitting :16Figure 2014).( Zinkaah tensile strength

30

6. Effect of mineral admixture on properties of

lightweight concrete:

The use of mineral admixtures in concrete such as fly ash, silica fume, natural

pozzolan, meta kaolin and calcined clay has become widespread due to their pozzolanic

reaction and environmental friendliness (Erdogan 1997, Mehta 1986 & Neville

2003).These pozzolanic admixtures are used for reducing the cement content in mortar

and concrete production (Gleize et al 2007 & Sabir et al. 2001). Also, the use of

pozzolanic materials such as silica fume and fly ash are necessary for producing high

performance concrete. These materials, when used as mineral admixtures in high

performance concrete, can improve both the strength and durability properties of the

concrete (Poon et al. 2006 & Parande et al. 2008).

31

7. Examples about using of LWC:

Cores taken from a lightweight World War II ship at Port Charles near Annapolis

had a carbonation depth after 49 years exposure of less than 7 mm (Holm et al

1988).

Bridges built over the years with lightweight aggregates have been surveyed

and results show that they perform at least as well as normal weight concrete

bridges, and in some instances provide superior performance (FHWA 1985).

The use of lightweight concrete in the United Sates dates back to 1900s. Expanded

clays and shales were developed commercially by S.H. Hayde and were used for

shipbuilding during World War I. The Park Plaza Hotel in St. Louis was a early

example of lightweight concrete construction in the 1920s. Since 1950s, lightweight

concrete has been used regularly in multistory buildings and other large structures.

Some of the more notable structures are the Bank of America Corporate Center,

Cahrlotte; the Watergate Apartments, Washington D.C.; and the Lake Point Towers,

Chicago. Lightweight concretes are also used for applications as diverse as highway

bridges and offshore drilling platforms (Mindess et al 2003).

32

8. Creep and Shrinkage of Lightweight Concrete:

In 1989-1990 a study was conducted at North Carolina State University to determine

the shrinkage and creep potential of concrete made with expanded slate aggregate

(Leming 1990 ).

As part of this study, elastic modulus and other standard plastic concrete

characteristics were also determined. Four separate concrete mixes were produced for

this study. One mix was a conventional concrete using normal weight coarse aggregate

for comparison. Two mixes were “standard lightweight” mixes, and the fourth mix was a

relatively high strength mix. The author (Leming) noted that values of creep and

shrinkage strain for these lightweight concretes were low compared to national (United

States) averages. He also noted that values of the elastic modulus were significantly

higher than predicted by American Concrete Institute equations based on compressive

strength and unit weight. He noted that “this is almost certainly due to the superior

stiffness of the expanded slate aggregate compared to many other commercially

available lightweight aggregates The following table summarizes the results of the “high

strength” mix in this study(Leming1990).

33

)( Kenneth & HarmonSummary the results of the "high strength" mix 13Table Quantities

Cement (pcy)

Ground Blast Fumace Slag(psy)

Water (psy)

3/4" (19mm) Expanded Slate LWA(pcy)

Unit Weight Plastic

Unit Weight Dry

Slump

Air

Compressive Strength:

7 days

28 days

365 days

Splitting Strength:

7 days

28 days

365 days

Elastic Modulus :

7 days

28 days

365 days

Creep Data :

Specific Creep

Creep Coefficient

Shrinkage Data (at 365 days ):

Microstrain

1948 ��/��

1865��/��

171.5 mm

36.8 MPa

49.5 MPa

57.2 MPa

2.6 MPa

3.4 MPa

3.6 MPa

23.3 GPa

24.7 GPa

26.5 GPa

Mix S-4

536

342

323

940

121.6 pcf

116.4 pcf

6-3/4 in

1.5%

5340 psi

7180 psi

8290 psi

370 psi

495 psi

520 psi

3.38x10�psi

3.58x10�psi

3.84x10�psi

0.29

1.2

310

34

9. Effect of Porous Lightweight Aggregate

T.Y. Lo and H.Z. Cui have focused on the effect of porous aggregate on strength of concrete. They have examined the topography of the interfacial zone and the characteristic of the surface pores of the lightweight aggregate concrete. The experimental work in this research is based on LWC with cement content of 450 kg/m3 and water/cement ratio of 0.36. The lightweight aggregate was a synthetic aggregate manufactured from expanded clay. Sand was used as fine aggregate. The concrete compressive strengths at 7 and 28 days were measured to be 46.5 MPa and 51 MPa, respectively. The results of studies and Scanning Electron Microscope views showed that the porous surface of LWA improved the interfacial bond between the aggregate and cement paste by providing interlocking sites for the cement paste forming a dense and uniform interfacial zone. (Figure 17.). The “Wall Effect” that appears in the normal weight concrete does not occur on the interfacial zone of LWC (Figure18.). The resulting interfacial zone is about 5 µm –10 µm wide (Figure19), which is much smaller than normal weight concrete. The shell of lightweight aggregate of 20 µm thick can be identified. Some cement paste has infiltrated the surface pores of the lightweight aggregate to some depth (Figure 20.) (Lo &Cui 2004).

SEM View of LWC Showing the LWA Closely Bonded with Cement :17Figure Matrix (x75)

35

BSEI View of LWC Showing Diffusion of Cement Paste into Aggregate :18Figure Surface (x75)

: Aggregate Shell and IZ of the Concrete Composite (x2000)19Figure

36

for HCP at the IZ (x5000): Porous Aggregate as Interlocking sites 20Figure

10. Effect of Aggregate Pre-wetting

T.Y. Lo, H.Z. Cui and Z.G. Li have investigated influence of pre-wetting on

mechanical properties of concrete. The lightweight aggregate used in mixes

originated from expanded clay and medium sand was used. Six mixed were prepared

(Table 14.) which gives the total cementitious content from 420 kg/m3 to 450

kg/m3. The w/c ratios were between 0.54 to 0.56 and aggregate pre-wetting times

were 0, 30 min. and 60 min. The slumps of the fresh LWAC mixes with the aggregate

pre-wetted for 30 min. was found to be higher than those samples pre-wetted 60

min. and those without pre-wetting (Table 15.). According to test results (Table 16), the

compressive strength achieves its maximum value when the LWA pre-wetted for 30 min

( Lo et al 2004).

37

et al 2004) Mix Proportions of LWAC(Lo :14Table

Group

No.

Mix

No.

Water

(kg/m3)

Cement

(kg/m3)

PFA

(kg/m3)

W/(C+PFA)

LWA(kg/m3)

Water reducing

Admixture (l/m3)

Pre-wetting time

Of LWA (min) Fine Coarse

1

1 230 420 0 0.55 710 560 2.6 0

2 230 420 0 0.55 710 560 2.6 30

3 230 420 0 0.55 710 560 2.6 60

2

4 245 450 0 0.54 710 560 2.6 0

5 245 450 0 0.54 710 560 2.6 30

6 245 450 0 0.54 710 560 2.6 60

3

7 250 450 0 0.56 569 488 0 30

8 250 382.5 67.5 0.56 569 488 0 30

9 250 337.5 112.5 0.56 569 488 0 30

2004) ty and Density of LWAC (Lo et al Workabili :15Table

Group

NO.

Mix

NO.

Slump

(mm)

Density

(kg/m3)

Pre-wetting

Time of LWA

1

1 155 1848 0

2 175 1851 30

3 130 1840 60

2

4 165 1757 0

5 185 1806 30

6 140 1771 60

3

7 142 1617 30

8 165 1622 30

9 172 1630 30

38

2004) trength of LWAC(Lo et al Compressive S :16Table

Group

NO.

Mix

NO.

Density

(kg/m3)

Compressive strength (MPa)

7-days 28-days 90-days

1

1 1848 31.33 (86%) 36.41 37.01 (102%)

2 1851 31.84 (83%) 38.58 40.13 (104%)

3 1840 33.10 (88%) 37.59 40.03 (106%)

2

4 1757 24.31 (83%) 29.19 30.32 (104%)

5 1806 35.88 (84%) 42.95 45.10 (105%)

6 1771 32.01 (82%) 39.04 41.55 (106%)

3

7 1617 28.21 (90%) 31.22 31.39 (101%)

8 1622 26.30 (82%) 32.16 35.75 (111%)

9 1630 24.94 (72%) 34.48 39.39 (114%)

39

11. Conclusion

The purpose of this report was to summarize the types and advantages of

Lightweight Concrete (LWC), the mechanical properties of LWC and what additions act

in the strength of LWC.

This report presents the results of the Investigation of the response of lightweight

concrete to elevated temperature. The variables are: mix proportion, water/cement

ratio, curing age and temperature. The parameter that was measured is: compressive

strength. The results showed that the compressive strength of concrete decreased

with increase in water/cement ratio and temperature but increased with increase in

curing age and cement content.

Also this report investigates the effects of steel fibers on some properties of light

weight concrete. The coarse aggregate used in this study made from crushed clay

bricks. The variables are: Steel Fiber/volume ratio and curing age. The parameters that

were measured are: compressive strength, splitting tensile strength and flexural

strength. Four proportions of steel fibers are used (0.25%, 0.5%, 0.75%, and 1%) by

volume of concrete, in addition, to reference mix (without steel fibers). The density

obtained from experimental work was 1812 Kg/m³.

The results showed that, in general, the adding of steel fibers led to increase the

compressive strength of light weight concrete. The enhancement in compressive

strength was about (17%-43%) at 7 days and (21%-51%) at 28 days as compared with

reference mix. Also, it is deduced that, the proportion (0.75%) of steel fibers is the

optimum one. On the other hand, splitting tensile strength increased by about 62.62%,

33.76%, 17.27% and 5.93% for light weight concrete with 1%, 0.75%, 0.5% and 0.25%

steel fibers by volume of concrete respectively. Furthermore, flexural strength improved

by about 54.24%, 41.67%,29.25% and 20.91% for light weight concrete with 1%, 0.75%,

0.5% and 0.25% steel fiber by volume of concrete respectively.

12. Recommendations

The performance of structural lightweight aggregate concrete could be further

studied with various cement content at constant w/c ratio.

40

13. Findings:

After this study we can conclude several results:

1- Using of Lightweight Concrete lead to reductions in the sizes of columns and

slab and beam dimensions that result in larger space availability.

2- For the same concrete mix, the strength was higher for samples with

lower water/cement ratio (0.6) than those with higher water/cement ratio (0.8).

The observed differences varied between 4.17 and 12.91%for unheated

specimens.

3- The results showed that with increase in temperature, there was a gradual

loss in strength of the test specimens. At the maximum temperature of

800oC/hr, most heated specimens lost between 24 and 40% of their

strength values depending on the mix proportion and curing age.

4- crushed bricks as coarse aggregate and steel fibers can be used together

to produce light weight concrete has acceptable properties and has

equilibrium density equal to 1812 Kg/m³.

5- the compressive strength of light weight concrete increase with adding

steel fibers, that increases in compressive strength varied (17%-43%) at 7

days and (21%-51%) at 28 days as compared with reference mix.

6- The experimental work indicated that, the optimum proportion of steel fibers

act on compressive strength was (0.75%), furthermore, increase steel

fibers from (0.75%) to (1%) by volume of concrete caused decrease in

compressive strength from (43%) to (27%) in 7 days, and from (51%) to

(30%) in 28 days as compared with reference mix (without steel fibers).

7- The splitting tensile strength of light weight concrete increased when

adding steel fibers. The increasing in splitting tensile strength of light

weight steel fiber concrete (LWSFC) relative to reference concrete at 28

days were 62.62%, 33.76% , 17.27% and 5.93% for LWSFC with 1%,

0.75%, 0.5% and 0.25% steel fiber by volume of concrete respectively.

8- Using steel fibers in light weight concrete led to significant effect on

flexural strength. The increase in flexural strength for light weight concrete

with steel fiber relative to reference concrete mix were20.91%, 29.25%,

41.67% and 54.24% for light weight concrete with 0.25%, 0.5%, 0.75%

and 1% steel fiber by volume of concrete respectively.

41

9- The slumps of the fresh Lightweight Aggregate Concrete ( LWAC) mixes with

the aggregate pre-wetted for 30 min. was found to be higher than those

samples pre-wetted 60 min. and those without pre-wetting.

10- the compressive strength achieves its maximum value when the Lightweight

Aggregate ( LWA) pre-wetted for 30 min.

42

14. Refrences:

ACI 213 R-03. (2003). Guide for Structural Lightweight-Aggregate Concrete, American Concrete Institute Report, Reported by Committee. p. 213

ACI committee 211, “Standard practice for selecting proportions for structural

lightweight concrete” (ACI 211.2-98) (Reapproved 2004), ACI manual of concrete practice, pp. 1-20.

ASTM C 150-02a; “Standard Specification for Portland Cement”, Annual Book of

ASTM Standards, Vol. 04. 02, 2002. ASTM C 33 – 01. “Standard Specification for Concrete Aggregates”. “Annual book of

ASTM standards, 2001, pp. 1-8 ASTM C 330-04, “Standard specification for lightweight aggregate for structural

concrete “Annual book of ASTM standards, pp. 1-4. ASTM C192-88 “Standard Practice for Making and Curing Test Specimens in the

Laboratory”. Animal Book of ASTM Standard, Philadelphia, Vol.04-02, 1989, pp.112-118.

ASTM C496-86 “Standard Test Method for Splitting Tensile Strength of Cylindrical

Concrete Specimens”, Annual Book of ASTM Standard, Philadelphia, Vol. 04-02, 1989, pp. 259-262

ASTM C78-84 “Standard Test Method for Flexural Strength of Using Simple Beam with

Third-Point Loading”, Annual Book of ASTM Standard, Philadelphia, Vol. 04-02, 1989, pp.32-34.

ASTM C469, "Standard Test Method for Static Modulus of Elasticity and Poisson’s Ratio

of Concrete in Compression", Vol. 4, 2002, pp.1-5. ASTM C642-06,” Standard Test Method for Density, Absorption, and Voids in

Hardened Concrete”, Annual book of ASTM Standard, pp.1-3. American Concrete Institute. ACI 213R: Guide for Structural Lightweight-Aggregate

Concrete. Farmington Hills, MI, 2003. Balogun, L.A. (1986). Effect of temperature on the residual compressive strength of

laterized concrete. Building and Environment, 21(3-4), 221– 226. B.S. 1881, part 116, "Method of Determination of Compressive Strength of

Concrete Cubes", British Standards Institution, 1989 Dawood ,ET.& Ramli, M.(2010) “Proportioning of crushed brick concrete reinforced

by palm fibre ”. Journal of Materials Sciences and Engineering with Advanced Technology.2010; 2(1):77-96.

43

Dawood, ET.& Ramli, M.(2009) “Study the effect of using palm fiber on the properties of high strength flowable mortar”, CI Premier: 34th OWICs papers, Singapore. 2009; 93-101.

Erdogan ,TY .(1997). Admixtures for Concrete, Middle East Technical Univ. Press,

Ankara, Turkey FHWA Report on “ Criteria for Designing Lightweight Concrete Bridges”, Report

No. FHWA/RD-85/045, August, 1985, 146 pps. Gleize ,PJP. Cyr ,M. & Escadeillas ,G. (2007). Effects of metakaolin on autogenous

shrinkage of cement pastes, Cement Concrete Compos. 29(2):80-87 Gündüz, L. & Uǧur, I. (2005). The effects of different fine and coarse pumice

aggregate/cement ratios on the structural concrete properties without using any admixtures, Cement Concrete Res. 35: 1859-1864

Holm, T.A. . Bremner, T.W. .& Vaysburd, A.(1988), “Carbonation of Marine Structural

Lightweight Concrete”, Second International Conference on Performance of Concrete in Marine Environment, Saint Andrews, N.B., Canada, ACI SP 109, August 21-26, 11 pp. “Bridge Deck Survey”, Expanded Shale, Clay and Slate Institute, Washington, D.C., 1960, 24 pp.

Kayali, O. (2007). Fly ash lightweight aggregates in high performance concrete,

Construction and Building Materials, 22 (12): 2393-2399. Kenneth, S. &Harmon, PE .Engineering properties of structural lightweight concrete.

Carolina Stalite Company – United States . Liew Chung Meng, Introduction to Lightweight Concrete.www.maxpages.com. Lo ,TY. Tang, WC. & Cui ,HZ . (2007).The effects of aggregate properties on

lightweight concrete, Build. Environ. 42: 3025-3029. Lo, T.Y. & Cui ,H.Z.( 2004).“Effect of Porous Lightweight Aggregate on Strength of

Concrete”, Materials and Letters, Vol.58, pp. 916-919. Lo, T.Y., Cui, H.Z, Li, Z.G.(2004). “Influence of Aggregate Pre-wetting and Fly Ash on

Mechanical Properties of Lightweight Concrete”, Waste Management, Vol. 24, pp. 333-338.

Leming, M.L. (1990 )“Creep and Shrinkage of Lightweight Concrete”. Department of Civil

Engineering, North Carolina State University at Raliegh, North Carolina. Mouli , M.& Khelafi ,H. (2008).Performance characteristics of lightweight aggregate

concrete containing natural pozzolan, Build. Environ. 43:31-36. Mehta ,PK.(1986). Concrete: Structure, Properties, and Materials, Prentice- Hall,

Englewood, NJ.

44

Mindess, S. Young, J.F.& Darwin D., Concrete, 2nded., Prentice-Hall, New Jersey, 2003 Neville ,AM .(2003). Properties of concrete, Fourth and Final Edition, Pearson Prentice

Hall, England Poon, CS. Kou ,SC. & Lam ,L .(2006). Compressive strength, chloride diffusivity and

pore structure of high performance metakaolin and silica fume concrete, Const. Build.Mater. 20(10): 858-865.

Parande ,AK. Babu ,BR. Karthik ,MA. Deepak Kumaar ,KK. & Palaniswamy, N .(2008).

Study on strength and corrosion performance for steel embedded in metakaolin blended concrete/mortar. Const. Build.Mater. 22(3):127-134.

Samidi,M.R.(1997). First report research project on lightweight concrete, University

Teknologi Malaysia, Skudai, Johor Bahru. Salih, S. A., Rejeb, S. K., & Najem, K. B.(2005) “The Effect of Steel Fibers on the

Mechanical Properties of high Performance Concrete” 2005 Al-Rafidain Engineering Vol.13 No.4.

Sabir ,BB. Wild ,S. & Bai, J .(2001). Metakaolin and calcined clays as pozzolans for

concrete: a review, Cement Concrete Compos. 2001;23(6):441-454. Zakaria ,M.L.(1978). Bahan dan Binaan, Dewan Bahasa dan Pustaka. Zinkaah, O.H.(2014). Influence of Steel Fibers on the Behavior of Light Weight Concrete

Made from Crushed Clay Bricks. American Journal of Civil Engineering. Vol. 2, No. 4, 2014, pp. 109-116. doi : 10.11648/j.ajce.20140204.11