International Journal of Current Trends in Engineering & Research (IJCTER)
e-ISSN 2455–1392 Volume 2 Issue 5, May 2016 pp. 181 – 187
Scientific Journal Impact Factor : 3.468
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STRENGTH CHARACTERISTICS OF HOLLOW SANDCRETE
BLOCKS PRODUCED IN WADATA-MAKURDI, NIGERIA
OBAM OGAH1, EJEMBI LUCY IGBE2
1,2
Department of Civil Engineering, University of Agriculture Makurdi
1
Corresponding Author Email: [email protected]
2
Email: [email protected]
Abstract—The spate of building collapse in Nigeria has put in the front burner the need to investigate
the quality of buildings. Collapse and heavy cracks are the frequent features of many buildings in
Makurdi, Nigeria. There are many causes for collapse of buildings; one of which is weak and poor
quality walling units, for example hollow sandcrete blocks. This piece of research work is to find out
the compressive strength, density and water absorption qualities of hollow sandcrete blocks produced
in Wadata-Makurdi, Nigeria. Laboratory experimental procedures were used for the methods. Five
block industries were randomly selected. Test results showed that the mean compressive strength of
all blocks (9 inches blocks) tested from the six industrial sites is 0.54N/mm2. This is far below the
1.8 N/mm2 recommended by Nigerian Industrial Standard (NIS). Block industry A has the greatest
average value of compressive strength of 0.71N/mm2 while block industry C has the least strength of
0.38 N/mm2. There was no appreciable difference in water absorption value of the blocks produced
at the six industrial sites. However, for the six inches blocks, the water absorption value from site A
has the least mean value of 2.3 percentage water absorption. The research results showed that the
blocks do not meet the minimum requirements and therefore, cannot be used for construction of
buildings.
Key Words—Compressive Strength, Hollow Sandcrete Block, Housing, Water Absorption
I.
INTRODUCTION
The necessity for shelter has always been one of the most important needs of man. The major
component of any kind of shelter is its wall. Block is indispensable material predominantly used as
walling unit in construction of building.
Over 90 percent of houses and many other types of building in Nigeria are constructed using
sandcrete blocks (Baiden and Tuuli, 2004). It is a load bearing and non-load bearing wall unit. The
blocks are supposed to have adequate compaction pressure so that they can confidently be used in
building of walls and other structures at various levels during construction. Considering the three
main types of concrete block i.e. solid, cellular and hollow, the hollow sandcrete block is more
economical in terms of weight, density and compressive strength and is commonly used in
construction work (Hamzaet, 2009). The British standard 6073:1981 part1 defines block as a
masonry unit of large size in all dimension specified for bricks but no dimension should exceed
650mm nor should the height exceed either its length or Six times its thickness. In harden state,
sandcrete block has high compressive strength and this strength increases with density. According to
NIS (2001), hollow sandcrete blocks are classified as:
Type A: dense aggregate concrete blocks, density of 1500kg/m3.
Type B: light weight aggregate blocks for load bearing walls, density greater than 625kg/m 3.
Type C: light weight aggregate blocks, for non-load bearing position, density is less than 625 kg/m3.
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International Journal of Current Trends in Engineering & Research (IJCTER)
Volume 02, Issue 05; May – 2016 [Online ISSN 2455–1392]
Nigerian Industrial Standard (NIS) 87:2001 defines sandcrete block as a composite material made up
of cement, sand and water. It is usually rectangular in shape, hollow or solid. It is used to construct
wall in building and other structures. Wall serves as protection, aid privacy to man and his properties
(Edward, 1895). Hollow blocks were first used in the United States as a substitute for stone and
wood in building. The earliest known example of house built entirely of hollow block was in 1837 on
Stalen Island, New York. The homes built of hollow block showed a creative use of common
inexpensive material to replace the more expensive and traditional framed stone masonry building
(Lancaster, 2005).
The compressive strength of sandcrete block is affected by mix proportion, mode of manufacture;
physical conditions such as curing method and duration and temperature etc. The strength of
structure partly depends on its wall. Walls built with poor quality blocks that fail to meet standard
often collapse, causing severe damage to structure and loss of lives (Dhir, 1980).
The most popular size recommended by the Nigerian Industrial standard (NIS) 87 (2001) is 450mm
and 225mm and are available in thickness of 63, 95, 100, 140, 190 and 225mm. British Standard
(BS) 2028 and 1364 also allow the size of 150 x 450mm, 200 x 450mm, 300 x 450mm, 200 x
600mm and 225 x 600mm block (Nene, 2009).
The frequent collapse of buildings in Nigeria has been attributed to two main causes, the poor quality
of construction work and poor quality of building materials (Tagher et al, 2007).
Joan et al., (2014) carried out a research on assessment of the quality of Sandcrete Blocks in use in
Owerri, South-east Nigeria. Ten sandcrete block samples with nominal dimensions 450 x 225 x
225mm were randomly obtained from each of the four manufacturers. Only two out of the four
industries satisfied the requirements of Nigerian National Building Code (2006). The code stipulates
that the average strength of six blocks should not be less than 2.0N/mm2 and the lowest strength of
individual block should not be less than1.75N/mm2.
Anosike and Oyebade (2011) carried out a research on Sandcrete Block and quality management in
Nigeria building industry. The study revealed very low compliance with standards. The average
strength of the blocks was 0.66N/mm2 and 16.95% water absorption capacity.
Onwuka et al., (2013) carried out a study on the structural characteristics of Sandcrete blocks
produced in south-east, Nigeria. The experimental results showed that most of the blocks produced
were generally substandard.
Yusuf and Hamza (2011) carried out a study on the compressive strength of six (450x150x225mm)
and nine (450x225x225mm) inches manually produced sandcrete blocks. The found the 7day
average compressive strength of 6 inches blocks to be 2.55N/mm2 and that of 9 inches blocks to be
2.59N/mm2. The both satisfied the NIS requirements of 1.8N/mm2 at the age 7days and 2.5N/mm2 at
the age of 28days. The block could cope with thermal and moisture conditions and the problem of
algae growth on the face of block work during construction is unlikely to affect the strength of block
(Edward, 1985).
Compressive strength (
is the ratio of crushing load (P) to area (A, as cast area) of block.
(1)
The fire resistance of hollow sandcrete block wall depends on the geometry and density of the block.
The geometry affects the effective thickness. The fire resistance of a block wall increases as the
block density increases. Hollow sandcrete blocks are non-combustible material with class ‘Zero’
rating of flame speed. An un-plastered thickness of 100mm gives two hours of fire resistance with a
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International Journal of Current Trends in Engineering & Research (IJCTER)
Volume 02, Issue 05; May – 2016 [Online ISSN 2455–1392]
wide range of material including block work (Samson et al, 2002). One rule of thumb is to consider
all pink colored blocks as damaged; fire will expose hollow block to gases and liquid that can be
harmful to them, among other salts and acids that can be formed when gases produced by fire come
in contact with water (Samson et al, 2002). When plastered and painted to fill the cavities in the
texture, hollow blocks serve as good barriers to sound transmission (George, 1980).
According to Neville (1996), the rate of water absorption of aggregate influences the bond between
aggregate and cement paste, the resistance of concrete to freezing and thawing, chemical stability,
resistance to abrasion and specific gravity.
II.
MATERIALS AND METHOD
Twenty sandcrete hollow blocks (6 and 9 inches each) were obtained from five block industries in
Wadata-Makurdi, Nigeria. The size of the 9 inches block is 450 x 225 x 225mm while that of the 6
inches block is 450 x 150 x 225mm.
2.1 Density Test
Each sample of the hollow block samples was weighed as collected and the mass (M) recorded.
Water was poured into a graduated cylinder container and the initial volume (V1) noted. The block
was then immersed in the cylinder container and the new level (volume V2) of water taken. The same
process was repeated for the remaining block samples. The density (D) is given by equation (2).
D=
(2)
2.2 Water Absorption Test
Each sample of the hollow block samples was weighed as collected and the mass (M1) recorded.
They were immersed in water for 24 hours. They blocks were removed from water and immediately
weighed individually and the mass (M2) recorded. The percentage water absorption (W.A.) is given
by equation (3).
W.A. =
(3)
2.3 Compressive Strength Test
Smooth surface plate of wood was placed at the bottom and top of block specimen, so as to ensure
uniform distribution of load, and the block was then crushed, using compressive testing machine,
1500KN capacity. The procedure was repeated for the remaining samples. The process used the
Nigerian Industrial Standard (NIS 87: 2007) as guide. Equation (1) was used to calculate
compressive strength.
III.
RESULTS AND DISCUSSION
3.1 Density Test Results
The results of density tests are shown in Tables 1 and 2 for 6 and 9 inches blocks respectively. As
can be observed from Table 1, factory A blocks have the highest average density of 1237kg/m3 while
factories B and C have the least average density of 1172kg/m 3 each. The 9 inches blocks produced
similar results as indicted in Table 2. Density is a function of strength and the low compressive
strength as indicated in Tables 3 and 4 accounts for the relative low densities of the blocks.
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International Journal of Current Trends in Engineering & Research (IJCTER)
Volume 02, Issue 05; May – 2016 [Online ISSN 2455–1392]
3.2 Water Absorption Test Results
The results of the water absorption tests of the blocks are shown in Table 3 and 4. As expected,
factory A has the least average value of water absorption of 2.3 percent and factories B and C with
the worst mean value of about 6 percent.
3.3 Compressive Strength Test Results
The results of the compressive strength tests of the blocks are shown in Tables 5 and 6. Statistical
ANOVA (Analysis of variance) tests indicated a significant difference between the compressive
strengths across the factories. Factory A has the highest average compressive strength of 0.72 and
0.39 N/mm2 for both 6 and 9 inches blocks. Factory D has the lowest average compressive strength
of 0.32 and 0.23 N/mm2 for the 6 and 9 inches blocks respectively. All the strengths fall below the
1.8 N/mm2 minimum recommended for building blocks by the Nigeria Industrial Standard. The
implication is that the blocks being produced in these factories are not fit to be used as building
blocks.
Table 1: The Block Density Values (6 inches blocks)
Block Factory
A
B
C
D
E
Average Density of Dry
Block (Kg/m3)
1237
1172
1172
1175
1189
Average Density of Wet (24
hour soak) Blocks (Kg/m3)
1211
1106
1107
1118
1136
Table 2: The Block Density Values (9 inches blocks)
Block Factory
A
B
C
D
E
Average Density of Dry
Blocks (Kg/m3)
7789
7390
7390
7449
7551
Average Density of Wet (24
hour soak) Blocks (Kg/m3)
7233
6795
6795
6868
8733
Table 3: Results of Water Absorption Test (6 inches blocks)
Block Factory
A
B
C
D
E
Average Dry
Weight of Blocks
(M1) (Kg)
18394
16804
16808
16980
17246
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Average Wet
Weight of
Blocks (M2) (Kg)
18790
17800
17800
17842
18058
Average Water Absorption (%)
2.3
5.9
5.9
5.1
4.7
184
International Journal of Current Trends in Engineering & Research (IJCTER)
Volume 02, Issue 05; May – 2016 [Online ISSN 2455–1392]
Table 4: Results of Water Absorption Test (9 inches blocks)
Factory
A
B
Average Dry weight
(Kg)
16478
15480
Average Wet weight
(Kg)
17698
16790
Average Water
Absorption (%)
7.4
7.6
C
D
E
15480
15646
19896
16790
16972
17202
8.5
8.5
8.2
Table.5: Compressive Strength (N/mm2) Results (6 inches blocks)
Block
No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
A
B
Factory
C
0.80
0.59
1.13
0.58
0.81
0.95
0.54
0.55
1.06
1.09
0.55
0.72
0.92
0.36
1.03
0.52
0.53
0.55
0.71
0.31
0.65
0.48
0.49
0.26
0.35
0.51
0.33
0.38
0.91
0.57
0.27
0.24
0.47
0.33
0.28
0.52
0.90
0.74
0.32
0.22
0.39
0.29
0.77
0.20
0.22
0.65
0.39
0.24
0.20
0.19
0.20
0.21
0.92
0.76
0.89
0.45
0.44
0.36
0.29
0.18
D
E
0.53
0.80
0.57
1,18
0.45
0.29
0.44
0.38
0.28
0.42
0.57
0.54
0.31
0.48
0.52
1.03
1.06
0.62
0.59
0.31
0.36
0.55
0.36
0.39
0.39
0.42
0.37
0.27
0.83
0.79
0.90
0.90
1.03
0.47
0.47
0.59
0.29
0.30
0.28
0.89
Table 6: Compressive Strength (N/mm2) Test Results (9 inches blocks)
Block
No.
1
2
3
4
5
6
7
8
9
10
11
A
0.59
0.30
0.30
0.25
0.29
0.41
0.46
0.20
0.20
0.32
0.36
B
0.48
0.17
0.25
0.38
0.62
0.27
0.18
0.30
0.39
0.32
0.31
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Factory
C
0.21
0.30
0.36
0.37
0.20
0.30
0.39
0.52
0.30
0.35
0.34
D
0.16
0.30
0.20
0.13
0.13
0.14
0.14
0.19
0.20
0.30
0.26
E
0.28
0.31
0.19
0.39
0.48
0.42
0.20
0.29
0.41
0.43
0.24
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International Journal of Current Trends in Engineering & Research (IJCTER)
Volume 02, Issue 05; May – 2016 [Online ISSN 2455–1392]
12
13
14
15
16
17
18
19
20
0.39
0.32
0.27
0.61
0.61
0.69
0.29
0.42
0.20
0.54
0.21
0.54
0.21
0.40
0.20
0.30
0.51
0.59
IV.
0.29
0.32
0.40
0.20
0.27
0.27
0.30
0.30
0.20
020
0.50
0.20
0.15
0.22
0.40
0.31
0.30
0.20
0.19
0.49
0.30
0.48
0.20
0.39
0.39
0.29
0.30
CONLUSION
Affordable and adequate housing needs continue to grow, especially in poor countries of the world.
Building blocks are one of the important parts of building. Building cracks and total collapse are
common features in Makurdi, Nigeria. Laboratory tests were carried out on some of the strength
properties of samples of building blocks produced in Makurdi. None of the block samples, from the
five selected factories, met the minimum strength requirement given by the Nigerian Industrial
Standard (NIS 87).
Five block industries were randomly selected. Test results showed that the mean compressive
strength of all blocks (9 inches blocks) tested from the five industrial sites is 0.54N/mm 2. Block
industry A has the greatest average value of compressive strength of 0.71N/mm2 while the block
industry D has the least strength of 0.38 N/mm 2. There was no appreciable difference in water
absorption value of the blocks produced at the five industrial sites. Based on the results the blocks
are not fit to be used as building blocks.
V.
RECOMMENDATIONS
I recommend the following actions to be taken, based on the results of the research:
i.
The relevant monitoring bodies such as NIS, Standard Organization of Nigeria (SON) etc,
should beam their search light on block manufacturing industries at Wadata-Makurdi, to
ensure compliance to standards.
ii. The local authorities should advise the people against the use of sub-standard building
blocks in the construction of their houses.
iii. The authority should prosecute individuals or companies that are fond of producing substandard building blocks in the locality.
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