AN INVESTIGATION OF THE PROPERTIES OF CONCRETE CONTAINING MACADAMIA SHELLS AS A PARTIAL REPLACEMENT OF COARSE AGGREGATES

Abstract
The world, especially Kenya, is faced with the problem of solid waste. This solid waste also
constitutes agricultural waste. This experimental research is focused on the use of macadamia
shells, which is an agricultural waste, as a partial replacement of coarse aggregates in concrete. It
also looks into reducing the cost of producing concrete by replacing conventional coarse
aggregates obtained from quarries with macadamia shells obtained from the local farmers. The
research investigated the properties of macadamia shells in comparison with the properties of
conventional coarse aggregates based on strength properties required in concrete and in other
forms of construction. It also observed the properties of concrete with the addition of macadamia
shells and compared it with the control normal conventional concrete.
It the laboratory, various aggregates tests were done on the macadamia shells and significant
differences and similarities were observed. Macadamia shells exhibits higher toughness than
conventional aggregates. This is observed in the aggregates impact value test and the ten percent
fines tests. The particle size distribution of the macadamia was to some extent similar to the one
of the conventional aggregates.
In concrete, the coarse aggregates were replaced with macadamia shells by percentage masses of
10%, 20%, 30% and 50%. As the percentage replacement increased, the compressive and tensile
strength reduced. The workability at 10% replacement was higher than in normal concrete using
a constant water/cement ratio of 0.45. At 50% replacement, an increase in water/cement ratio to
0.55 yielded a much stronger concrete than using a water/cement ratio of 0.45. This increase in
strength due to higher water cement is not observed in normal conventional concrete. An
increase in percentage replacement yielded less dense concrete showing that macadamia shells
can be used to produce lightweight high strength concrete which is much cheaper than the
conventional concrete.

 

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