Cement is the most utilised construction material and the second most consumed
commodity in the world after water. It has been reported that the heavily energy-intensive
processes that are involved in its production contribute about 7 to 10% (per cent) to the
total global anthropogenic carbon dioxide (CO2), which is the main cause of global
warming; and are expensive economically. It is however possible, that energy and cost
efficiency can be achieved by reducing on the amount of cement, and in its place utilising
Supplementary Cementitious Materials (SCMs), which require less process heating and
emit fewer levels of CO2. This research aimed to provide an original contribution to the
body of knowledge by investigating the suitability of Corncob Ash (CCA), Anthill Soil (AHS)
and Rice Husk Ash (RHA) as SCMs by testing them for pozzolanic or hydraulic properties.
Cement was replaced in concrete with these materials by weight, as well as by the volume
of RHA at 0%, 5%, 7.5%, 10%, 15%, 20%, 25% and 30% steps at the point of need.
Durability was investigated using the water absorption and sulfate tests. Results of the
chemical analysis by X-Ray Diffraction (XRD) showed that CCA, AHS and RHA contained
the required chemical composition for SCMs, and the mean compressive strengths (fcm)
achieved, when converted to characteristic compressive strengths (fck,cube), were for those
classes that are listed as being durable and suitable for structural applications. The
behavior of these materials in workability, density, gain in compressive strength over time,
water absorption and sulfate tests were also consistent with the characteristics of SCMs.
The good repeatability observed across the range of tests that were carried out indicates
a high level of confidence in the results obtained, and highlights the great potential of
using CCA, AHS and RHA to enhance the durability of hardened concrete, mitigate on
environmental nuisance, reduce the cost of construction and improve the overall
properties of concrete.