This report discusses different types of lightweight concrete, including no-fines concrete, lightweight aggregate concrete, and aerated concrete. It describes their key characteristics and composition. The report also examines the mechanical properties and compressive strengths of structural lightweight concrete specimens at various curing ages and temperatures. The main findings are that compressive strength decreases with higher water-cement ratios, increases with curing age, and decreases significantly as temperature rises. Reinforcement and mineral admixtures can improve the flexural, tensile and compressive strengths of lightweight concrete.

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Arab International University
Faculty of civil engineering
ReportStudent Work
Lightweight concrete
Dr. Basem Ali:Supervisors
Student :Jaber Hasan Al-Sodi

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Table of Contents
List of tables…………………………………………………………………………………………………………………….3
List of figures …………………………………………….…………............................................................4
1.Introduc on........................................................................................................................... 5
2.TYPES OF LIGHTWEIGHT CONCRETE ..........................................................................................6
. 2.1. NO-FINES CONCRETE .......................................................................................................6
2.2. LIGHTWEIGHT AGGREGATE CONCRETE……………………………….…………………………………………….….6
2.3. AERATED CONCRETE …………………….………………………………………………………………………………….….7
3.ADVANTAGES AND DISADVANTAGES OF LIGHTWEIGHT CONCRETE …………………………………….……….8
4.Mechanical Properties of Structural Lightweight Concrete ……………………………….…………………………..9
4.1. Compressive strength (unheated specimens) ……………………………………………………………..9
4.2. Compressive strengths (heated specimens) ……………………………………………………………………..10
5.Effect of reinforcement on behavior of lightweight concrete ………………………………………………………13
5.1.Compressive Strength…………………………………………………………………………………………………...…. 13
5.2.Flexural Strength…………………………………………………………………………………………………………………14
5.3. Splitting Tensile Strength………………………………………………………………………………………….………..16
6.Effect of mineral admixture on properties of lightweight concrete ………………………………………..……17
References…………………………………………………………………………………………………………………….……18

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List of Tables:
Table 3.1: Advantages and Disadvantages of Lightweight Concrete ……………………………….8
Table 4.1 Average Compressive Strength of Unheated Test Specimens ……………………..…...9
Table 5.1. Compressive Strength at 7 and 28 days ………………………………………………………..……13
Table 5.2. Flexural Strength at 28 days ………………………………………………………………………..……...15
Table 5.3. Spli ng tensile at 28 days………………………………………………………………………………………………16

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List of Figures:
Figure 2.1 No-fines concrete……………………………………………….……………….………….…….6
Figure 2.2 Lightweight Aggregate Concrete………………………………………………….………..7
Figure 2.3. Aerated Concrete………………………………………………………………………………...8
Figure 4.1. Varia on of Strength with Age at Ambient Temperature……………………………....10
Fig. 4.2.Varia on of Strength with Temperature for Different Mix Ra os. …………..11 ,12
Figure 5.1 Compressive Strength at 7 and 28 days………………………………………………….13
Figure 5.1.2 Show the shape of concrete crush with Fibers and without Fibers……..13
Figure 5.2.1 Flexural Strength at 28 days……………………………………………………………………………14
Figure 5.2.2 Show the shape of concrete failure with Fibers and without Fibers…...14
Figure 5.3.1 Spli ng tensile strength at 28 days………………………………………………………………….16
Figure 5.3.2 Rela onship between the steel fibers content and increasing in tensile splitting
strength………………………………………………………………………………………………………………………………..16

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1.Introduction
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 and Khelafi, 2008)
Lightweight concrete (LWC) has been used for more than 2,000 years (ACI 213R) (American
Concrete Ins tute [ACI], 2003). Early notable LWC structures include the Port of Cosa, the Pantheon
Dome, and the Coliseum.
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 [1].
. It is lighter than the conven onal concrete with a dry density of 300kg/m3up to 1840 kg/m3; 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
[2]. 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.
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 and Ugur, 2005).

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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 2.1 shows one example of No-fines concrete.
Figure 2.1 No-fines concrete
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
Porous lightweight aggregate of low specific gravity is used in this lightweight concrete instead
of ordinary concrete. The lightweight aggregate can be natural aggregate such as pumice, scoria and
all of those of volcanic origin and the artificial aggregate such as expanded blast-furnace slag,

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vermiculite and clinker aggregate. The main characteristic of this lightweight aggregate is its high
porosity which results in a low specific gravity [4].
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 [2].
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 [2].
. Figure 2.2 shows the feature of lightweight aggregate concrete.
Figure 2.2 Lightweight Aggregate Concrete.
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 [2].

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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 2.3 shows the aerated concrete.
Figure 2.3. Aerated Concrete
3. ADVANTAGES AND DISADVANTAGES OF LIGHTWEIGHT CONCRETE
Table 2 shows the advantages and disadvantages of using lightweight concrete as structure [2].
Table 3.1: Advantages and Disadvantages of Lightweight Concrete
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.

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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).
4. Mechanical Properties of Structural Lightweight Concrete
4.1. Compressive strength (unheated specimens)
Table 4.1 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 ra os of 0.6 and 0.8 were 2.85 and 2.60
N/mm2
respectively. At 21-day curing age, average compressive strength of specimens with w/c
ra o of 0.6 and 0.8 were 4.46 and 3.65 N/mm2
respec vely. At 90-day curing age, concrete with
1:2:2 mix and water/cement ra o 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 ra o, the average strength was 4.56 N/mm2
.
( 3)
Table 4.1 Average Compressive Strength of Unheated Test Specimens ( N/mm2
)
Curing Age (days)
w/c Ratio Mix Ra o 1:2:2 Mix Ra o 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 ra o. The decrease in
strength of test specimens with w/c = 0.8 rela ve 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 ra o. ( 3)
The results of strength variation with curing age for different mixes at 21o
C laboratory
temperature (unheated specimens) are presented in Fig. 4.1. The figure indicates that the test

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specimens for 1:2 ½:2 mix at w/c ra o of 0.6 have the highest compressive strength values. At
7-day curing age, the average values for compressive strength are 5.34N/mm2
and 4.88 N/mm2for
0.6 and 0.8 w/c ra os respec vely. This indicates a 9.20% more than the strength of the specimens
with 0.8 w/c ra o. At 90 day curing age, the strength values are7.34 N/mm2
and 6.52 N/mm2 at w/c
ra o of 0.6 and 0.8. This indicates a difference of 12.42% in strength values an indica on that the
smaller the w/c ratio value, the higher the strength of the mixes provided the mix were prepared
under the same condition. ( 3)
Also, for test specimens prepared from 1:2:2 mix with w/c ra o of 0.6, the average
compressive strength at 7-day curing age was 2.85 N/mm2
as against 2.60 N/mm2
for specimens with
0.8 w/c ra o. This indicates a reduc on 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. ( 3)
Figure 4.1. Varia on of Strength with Age at Ambient Temperature.
4.2. Compressive strengths (heated specimens)
Figures 4.2 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 ra o have average compressive
strength of 5.34 N/mm2
at ambient (21o
C) temperature while at 800o
C temperature, the average
compressive strength of test specimens reduced to 3.67N/mm2
at the same age. This shows 31.27%
reduc on in strength. An average of 3.48% reduc on in compressive strength with every 50o
C
increase in temperature was recorded. At 21-day curing age, between 21o
C and 800o
C temperature
range, the compressive strength values are 5.90 N/mm2
and 4.21 N/mm2
respectively. This gives a

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reduction in strength values of 28.64%. An average of 3.18% reduc on in compressive strength with
every 50o
C increase in temperature was recorded. ( 3)
At 90-day curing age a reduc on in strength value of 35.10% corresponding to an average loss in
strength of 3.9% for every 50o
C increase in temperature was observed. The investigation further
showed that at 8000
C/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 Figs. 4.2.(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
800o
C/hr, heated specimens lost between 26% and 40% of initial strength values before the heating
process commenced. ( 3)
Also, the rate of loss in strength evaluated by the slope of Figs. 4.2(i), (ii), (iii) and (iv) curves tends
to be higher in 1:2.5:2 mixes when compared to 1:2:2 mixes, irrespec ve of the water/cement
ratio and the curing age. The compressive strengths of the test specimens were reasonably
maintained up to 300o
C, 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
a ainment of 400o
C temperature level, but at 600o
C most of the periwinkle shells (aggregate) in the
test specimens were fractured. This accounts for higher strength loss at higher temperatures.( 3)

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Fig. 4.2.Variation of Strength with Temperature for Different Mix Ratios.
(i) 1:2.5:2 mix with w/c ra o = 0.6, (ii) 1:2:2 mix with w/c= 0.6,
Fig.4.2. Variation of Strength with Temperature for Different Mix Ratios.
(iii) 1:2.5:2 mix with w/c ra o = 0.8, (iv) 1:2:2 mix with w/c= 0.8.

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5. Effect of reinforcement on behavior of lightweight concrete :
5.1. Compressive Strength
Values of compressive strength for all mixes are shown in Table (5.1) and Figure (5.1) 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 respec vely. 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%) respec vely. 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 the intensive product of hydration process
around the steel fibers and in voids of concrete [5].
From Figure (5.1) it may also be concluded that the addi on 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 [6].
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[7].
Table 5.1. Compressive Strength at 7 and 28 days
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

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Figure 5.1 Compressive Strength at 7 and 28 days.
Figure 5.1.2 Show the shape of concrete crush with Fibers and without Fibers
5.2. Flexural Strength
The test results of the flexural strength are reported in Table (5.2) and Figure (5.2.1). 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 rela ve 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. 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 [5].

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Table 5.2. Flexural Strength at 28 days
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
Figure 5.2.1 Flexural Strength at 28 days.
Figure 5.2.2 Show the shape of concrete failure with Fibers and without Fibers.

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5.3. Splitting Tensile Strength
The results of splitting tensile strength for the lightweight concrete mixes are shown in Table
(5.3) and plotted in Figure (5.3.1). 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). 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 respec vely, Figure (5.3.2). 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.[5]
Table 5.3. Splitting tensile at 28 days
Figure 5.3.2 Rela onship between the steel
Figure 5.3.1 Spli ng tensile strength at 28 days Fibers content and increasing in splitting
. tensile strength.

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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,
metakaolin 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
and Cyr, 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).

18. 18
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[4] . Liew Chung Meng, Introduction to Lightweight Concrete.www.maxpages.com.
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