Strength and durability of concrete with crushed sand
B Balapgol*, Indian Institute of Technology Bombay, India
S A Kulkarni, Indian Institute of Technology Bombay, India
K M Bajoria, Indian Institute of Technology Bombay, India
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Strength and durability of concrete with crushed sand
B Balapgol*, Indian Institute of Technology Bombay, India
5 A Kulkarni, Indian Institute of Technology Bombay, India
K M Bajoria, Indian Institute of Technology Bombay, India
Abstract
This paper presents the results of an experimental study on strength and durability
of concrete with crushed basalt stone fine aggregates as a substitute to diminishing
natural sand. The strength and durability properties of concrete viz. compressive
strength, flexural strength and permeability of hardened concrete were investigated. An
experimental study was performed to observe the performance of concrete
incorporating crushed basalt stone fine aggregates replacing the natural sand. The test
results indicate that the performance of concrete with crushed basalt stone fine
aggregates were excellent. The compressive strength of concrete for different grades
increased from 8 % to 26 %, the flexural strength was increased from 1 % to 5 % and
coefficient of permeability was decreased significantly. The test results indicated that
strength and durability of concrete would be better with crushed sand replacing natural
sand .
.
1. Introduction
The natUral sand is one of the main constituents of the concrete making about 35% of volume of
concrete used in building construction industry. It is mainly excavated from the riverbeds . Due to the
construction of dams on rivers, these natural resources are erasing fast. In hilly areas and other such
places where sand is not abundantly available this becomes a good substitute. Natural sand always
contains high percentages of inorganic salts of chlorides, sulphates and other deleterious organic salts
and impurities. Chlorides and sulphates adversely affect the strength and durability of concrete and
reinforcing steel thereby reducing life of the structure.
Due to excessive excavation, silt in natural sand has been found more in volume . The salt
percentage further increases in rainy season . Excessive silt causes reduction in strength of concrete
affecting durability. Crushed sand is different in shape, grading and content of very fine sand compared
with river sand, and it is well known that the material properties of crushed sand concrete are also
different from those of river sand concrete [2,6]. It is also responsible for shrinkage cracks in concrete
works. Thus the use of crushed sand as a substitute to the diminishing natural sand has become
essential keeping in view of technical , commercial and environmental requirements.
There is a little available published data on the use of crushed sand as a SUbstitute to natural sand.
Ahmed et al in 1989 have studied the performance of concrete with limestone crushed sand as a
substitute to the natural sand . The results indicated that the concrete with crushed sand improved the
physical properties of concrete [1]. Sangamnerkar in 1999 reported that the dust content upto 10% as a
partial replacement of fine aggregates improved the strength properties of concrete [2] .
179
The investigation presented here in evaluates the performance of hardened concrete with crushed basalt
stone fine aggregates as a substitute to the natural sand. The experimental work was carried out on four
concrete mixtures to study compressive strength, flexural strength and permeability of concrete.
2. Materials properties
The constituents of concrete were tested as per Indian Standards [4,5] are summarized as follows.
The properties of the materials used in the experimental work are given below.
2.1 Cement
The Birla Super ordinary Portland cement of 53 Grade is used.
Specific gravity = 3.15,
Fineness modulus
=3066.3 cm 3 /gm,
Consistency
= 31.2%,
Initial setting time
=200 minutes,
Final setting time = 600 minutes, Soundness of cement =1 mm,
Compressive strength of cement: 3 days= 31.01 N/mm 2 , 7 days = 48.98 N/mm 2 ,
28 days= 64.62 N/mm 2 .
2.2 Fine Aggregates
Crushed basalt stone passing 4.75 mm sieve is used.
Specific gravity
=2.70,
Fineness modulus =3.26,
Free surface water =1.91 %,
Water absorption =4.90 %,
3
Bulk density
=1.75 gm/cm , Bulking
=8.0%.
2.3 Course Aggregates
Crushed basalt stone passing through 25 mm and retaining on 4.75 mm sieve is used ..
a) 10 mm size aggregates
Fineness modulus =2.10,
Specific gravity
= 3.01 ,
Water absorption
=1.62%,
Free surface water =1.40%.
Bulk density
= 1.42 gm I cm 3 .
b) 20 mm size aggregates
Fineness modulus =3.55,
Specific gravity
= 3.01 ,
Water absorption
=1.62%,
Free surface water =1.40%.
Bulk density
= 1.48 gm I cm 3
Super plasticizer
= MC-Bauchemic Zentrament FBV.
Drinking water is used for preparation of concrete.
3. Testing program and results
A total of eight mixes were prepared and studied to investigate the properties of concrete with
crushed basalt fine aggregates and natural sand. Four mixes with crushed stone fine aggregates and four
mixes with natural sand called control mixes were prepared. The concrete mixes were made with water­
to-cement ratios of 0.38,0.41,0.55 and 0.60.
The experimental study was carried out on specimens of four concrete mixes with crushed sand and
10% stone dust as part replacement to crushed sand and the test results were compared with
corresponding four control specimens of concrete mixes having same proportions of constituents with
natural sand. The mix proportions designed as per Indian Standards [3]. For comparison of behavior of
natural sand and crushed sand, natural sand was sieved and used in the same proportions as the
percentages of fraction observed in crushed sand. The gradation of aggregates is reported in Table no 1.
The course <;3ggregates, crushed sand and natural sand were separated into different size fractions and
recombined to a specific gradation as shown in Table no.1 The other constituents of concrete viz.
cement, course aggregates, plasticizer, water-to-cement ratios were kept same for each concrete mix and
corresponding control mix. The adopted mix proportions for four grades of mixes are summarized in Table
no.2. The required slump of concrete was obtained by using super plasticizer FBV Zentrament as percent
of weight of cement. The concrete mixes were proportioned to have slump within permissible limits of
Indian Standards [3]. The following tests were conducted to study the strength and durability of concrete
180
I .
Ta bl e no. 1 G ra da t'Ion 0 fA\g_grega es b)Y sieve analysIs
Course Aggregates
12.5 mm passing
Sieve
Cumulative
size
% retained
25 mm passing
Sieve
Cumulative
size
% retained
Natural Sand
Crushed Sand
Sieve
size
(mm)
Cumulative
% retained
Sieve
size
Cumulative %
retained
12.5
0.0
25
0.0
4.75
15.20
4.75
040
10
40.6
20
65.04
2.36
32.60
2.36
5.00
6.3
70.2
16
92 .08
1.18
69.10
1.18
59.60
4.75
98 ,8
12.5
98 .52
0,60
86.30
0,60
78.70
Pan
100.0
10
99,86
0,30
96.30
0,30
89.10
-­
-­
6.3
100
0.15
99 .10
0.15
9340
-­
-­
-­
-­
pan
100
pan
100
Fineness modulus
Fineness modulus
Fineness modulus
Fineness modulus
=2 .10
=3.55
=3,26
=3.99
Ta bl e no. 2Adopte d mixture proportions for different grades of concrete
Mixture No
Cement
Crushed
Sand
M15
1
3.5
M20
1
2.92
M35
1
1.58
M40
1
145
Course Aggregates
10 mm
20 mm
1.75
249
4,24
1,55
WIC Ratio
Plasticizer
by % wt , of
cement
0.60
1,5
0,55
1.5
041
2,7
0.38
2.7
2.22
3.77
0.94
2.14
3,68
2,09
0.89
2.98
3.1 Compressive strength
The compressive strength of the concrete was determined in accordance with Indian Standards [4] ,
To find compressive strength 30 cubes of size 150 x 150 x150 mm for each of eight mixes were casted .
The cube specimens were tested under uniaxial compression . The average compressive strength results
are reported at the age of 7 days and 28 days in Table no,3,
3.2 Flexural strength
The flexural strength of concrete was determined by bending test in accordance with Indian
Standards [4]. To find flexural strength three beam specimens of size 700 x 150 x150 mm for each of
eight mixes were tested after 7 days and 28 days curing under universal testing machine with two-point
loading, The average flexural strengths for concrete with crushed sand and natural sand were reported in
Table 4.
181
Table no. 3 Constituents of Concrete for specimens ( per one cu. m)
Mixture
No.
Cement
(N)
Fine Aggregates
(N)
Course
Aggregates (N)
Natural
Sand
Crushed
Sand
20 mm
10 mm
ActualW
ater
Stone
Dust
(N)
(N)
Plasticizer
(N)
M15-N
2550 .6
8932.7
-­
6352.2
4467.6
182.9
-­
38.26
M15-C
2550.6
-­
8040.0
6352.2
4467.6
182.9
892.9
38.26
M20-N
2943 .0
8588.7
-­
6543.3
4565.7
191.1
-­
44.15
M20-C
2943.0
-­
7729.8
6543.3
4565.7
191.1
858 .9
44.15
M35-N
4169 .3
6600.8
-­
8930.1
3902.8
190.1
-­
112.60
M35-C
4169 .3
-­
5940.0
8930.1
3902 .8
190.1
858 .9
112.60
M40-N
4316.4
6295.5
-­
9003.0
3802 .8
182.0
-­
116.50
M40-C
4316.4
-­
5665.9
3802.8
9003.0
182.0
629.6
Where, M15-N represents mixture with natural sand and M15-C, with crushed sand .
116.50
T a bl e no. 4C ompresslve s reng th , flexura I s treng th an d coe ff'
IClen t 0 f J)ermea blt
I/!l'
Mixture no .
Compressive Strength
Flexural Strength
Permeability
(N/mm2)
(N/mm2)
(m/sec)
(x 10-8
7 Days
28 Days
7 Days
28 Days
M15-N
13.84
20.91
2.83
4.22
-­
M15-C
1653
22.63
2.87
4.26
1.76
M20-N
21.94
32.76
2.98
4 .96
-­
M20-C
27.00
37.04
3.06
5.12
1.48
M35-N
23.30
34.74
2.89
4.22
-­
M35-C
30.48
41.85
2.98
4.26
1.26
M40-N
25 .53
38.00
3.76
5.41
-­
M40-C
35 .84
47.84
3.86
5.71
1.19
)
T a b Ie no. 5Variation 0 f compressive strenRt h an d flexura strenRth
Mixture No.
Percent increase in compressive
strenf th
Percent increase in flexural strength
7 Days
28 Days
7 Days
28 Days
M15-C
19.44
8.23
1.41
0.95
M20-C
23 .06
13.07
2.68
3.23
M35-C
30 .82
20.47
3.11
3.32
M40-C
40.38
25.90
3.48
5.55
182
3.3 Permeability
The permeability of concrete is related to durability of concrete in terms of its resistance against
progressive determination under exposure to sever climatic conditions and leaching due to prolonged
seepage of water. The permeability is measured in terms of coefficient of permeability, by permeability
test apparatus in accordance with Indian Standards [5]. To find coefficient of permeability of hardened
concrete a cube specimen of size 150 x 150 x 150 mm for each of eight mixes were casted. The
specimens were subjected to a known hydraulic pressure from one side in a permeability test apparatus
after 28 days of curing. Measuring the quantity of water percolated through it in 100 hours , the coefficient
of permeability were calculated and reported in Table 4.
60
_ 50
"'
0..
~ 40
.c
....
en
c 30
.......
a>
•
(f)
ci. 20
E
0
u 10
•
-+-7 Day-N
1 ......... 7 Day- C
- . . - 28 Day-N
1
28 Day-C I
1---
0
M15
M35
M20
M40
Grade of Concrete
4. Discussions
1. There was significant increase in compressive strength of concrete with crushed sand (refer Table 4
and Fig . 1)
2. The compressive strength was increased by 19.44% to 40 .38% at 7-day age and increased by 8.33
% to 25.9 % at 28-day age as the grade of concrete mixes were increased (refer Table 5)
3. There was significant gain in compressive strength at early age (Fig . 1)
4. The concrete mixes with crushed sand experienced marginal increase in the flexural strength (refer
Table noA).
5. The flexural strength was increased by 1.41 % to 3.48% at 7 day age and increased by 0.95% 5.55%
at 28 day age as the grade of concrete mix increased (refer Table no. 5).
8
8
6. The coefficient of permeability of concrete was gradually decreased from 1.76 x 10. m/s to 1.19 x10m/s as the grade of concrete mix increased (refer Table no. 4 and fig . 2) .
5. Conclusions
183
An experimental study was performed to examine the strength and durability of concrete with
crushed sand as replacement to the natural sand . The data assembled during the course of investigation
lead to the following conclusions;
• The performance of concrete with crushed sand was excellent. There was an increase in
compressive strength about 8 to 26 % and flexural strength about 1 to 5 % with as the grade of
concrete mix increased .
• The concrete with crushed sand performed better than concrete with natural sand as the grade of
concrete mix increased .
• The flexural strength of concrete with crushed sand was marginally increased on the strength of
concrete with natural sand .
• The permeability of concrete decreased as the grade of concrete mix increased . The concrete with crushed sand was found to be stronger and durable . The crushed sand may be used as a substitute to natural sand . References
1. Ahmed , A. E., and EI. Kourd A. A. , 1989. Properties of concrete incorporating natural sand and
crushed stone very fine sand . American Concrete Journal, , 86(4),417-424 .
2. Celik T. and Marar K. 1996. Effect of crushed stone dust on some properties of concrete. Cement
and Concrete Research, 26(7), 1121-1130.
3. Indian Standard code of practice for Recommended Guidelines for concrete mix-design I. S
10262-1982, Bureau of Indian Standards, New Delhi.
4. Indian Standard code of practice for Methods of Test for Strength of Concrete. I. S. 516-1959 ,
Bureau of Indian Standards, New Delhi.
5. Indian Standard code of practice for plain and reinforced concrete. I. S: 456-2000, Bureau of
Indian Standards, New Delhi.
6. Kim J. K. , Lee C. S., Park C. K. and Eo S. H., 1997. The fracture characteristics of crushed lime
stone sand concrete. Cement and Concrete Research , 27( 11), 1719-1729
184