STUDY ON THE FEASIBILITY OF USING SAWDUST AS PARTIAL REPLACEMENT FOR SAND IN CONCRETE

ABSTRACT
This experimental study considered the use of sawdust particles as substitute to fine
aggregate in the production of concrete. It investigated the physical properties of sawdust
as well as the workability, compressive and tensile strength properties of concrete
produced by replacing 5%, 10% and 25% by volume of sand with sawdust. It also aimed
to provide new knowledge on how to improve the construction industry methods by using
a sawdust concrete mixture that would guarantee product performance and contribute to
saving the environment.
A conventional concrete mixture was prepared as a reference mix and compared to
sawdust concrete mixture. Slump and compaction factor tests were carried out on the
fresh concrete and compressive and tensile strength on hardened concrete. Increased
sawdust proportions resulted in stiffer mixes thus reducing the workability of the concrete
produced. Cubes of 100mm by 100mm were prepared and their compressive strengths at
7 and 28 days were determined. Results showed that the compressive strength decreased
with higher sawdust content with replacements beyond 10% resulting in a considerable
strength decrease. Similarly, cylinders of diameter 150mm by 300mm height were
prepared and their tensile strength determined. As witnessed with compressive strength
there was a decrease in tensile strength with an increased replacement of sand with
sawdust.
It was concluded that 10% substitution offered an optimum replacement level. However,
the resulting concrete density was still beyond the maximum limit for lightweight
concrete hence a number of recommendations on modifications to the sawdust were made
to increase the amounts that can be incorporated in concrete. This would ultimately result
in lower density while maintaining the required strength.

 

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