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A Mathematical Model For Prediction Of The Strength Of Sancrete Cement Block
[APPLICATION OF HENRY SCHEFFE’S AND OSADEBE’S CONCRETE OPTIMISATION THEORY]
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Sandcrete blocks are mostly produced in Nigeria by the small scale
manufacturers who as business people have profit as their main motive
and therefore often use sub-standard materials and improper procedures
in the production of the blocks. This results in the output of poor
quality blocks with poor strength properties. Whereas Nigerian burnt
bricks are reported to have compressive strength in the range of
11.5N/mm2 to 26.0N/mm2, the corresponding range for sandcrete blocks was
only found to be 1.45M/mm2 to 3.5N/mm2 (Graham, 1990; Danso, 1994).
This problem tends to limit the application of the material and could
also be a major factor in relation to the structural failure of
buildings in the event of earthquakes.
As mentioned above, apart from
the compressive strength of the unit, very little is known about the
other properties of the block such as the Young’s Modulus, tensile,
flexural and transverse strengths which are required by structural
engineers and other scientists for design computations. The lack of
information on these strength properties of sandcrete blocks leaves room
for much speculation and approximation, which could be detrimental to
the design of structures.
Virtually all the numerous research and
publications on the material seem to focus on the strength properties of
the material. Very little exist in literature on the durability of
sandcrete blocks. In recent years however, reports from around the globe
indicate that the premature deterioration of concrete and other
cementitious materials is a major problem. For instance it has been
reported that significant proportions of national budgets have been
expended on the maintenance of concrete structures in the US and Europe.
Thus the philosophy that a strong concrete is a durable concrete has
failed as this is not always the case. It can therefore be argued that
to avoid huge maintenance costs of structures constructed from concrete
and for that matter sandcrete blocks, the basic masonry units must be
durable as well as strong.
Closely linked with permeation
(durability) and strength properties of cementitious materials is the
water-cement ratio. Most researchers agree that water cement ratio has a
profound impact on the durability and strength of these materials but
few researchers of sandcrete blocks have examined the effect of
water-cement ratio on the properties of the blocks.
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