Potential use of Shea nutshell ash as partial replacement of portland cement in interlocking earth blocks

Before the discovery of new building materials, earth was the basic building material. These buildings provided shelter and protected the people from weather. However, earth material is characterized with low strength, high shrinkage and sorptivity. To enhance the characteristics of earth blocks, several methods like cement and lime stabilisation of earth have been investigated. Due to the high cost and environmental impact of these stabilisers, a number of investigations have been carried out, including the possibility of using pulverized and combustible industrial and agricultural waste as partial replacement for cement in stabilised earth blocks. This study, therefore centered on analysing the potential use of Shea nutshell ash (SNSA) in stabilised interlocking earth blocks (IEBs). SNSA is obtained from the calcination of Shea nutshell, an agro-based waste. The quantity of cement used for the stabilisation of earth blocks was partially supplanted by SNSA from 0 to 6% by mass with a step of 2. The impacts of SNSA and cement on water absorption, dry density and compressive strength of IEBs were assessed. The results show a gain in compressive strength for 2% of replacement (4%C+2%SNSA) especially at 28 and 56 days (4.79% and 34.62% respectively). Moreover, SNSA improved the dry density of IEBs and the best result (1773.51 kg/m3) was obtained for blocks with (0C+6SNSA) at 56 days. Although SNSA enhanced the compressive strength and dry density of IEBs, it did not improve the resistance of IEBs to water. Water absorption of the blocks was not satisfactory. Based on these results, SNSA is suitable for use as a stabiliser in earth blocks. It is an environmental friendly and low carbon material, affordable and it can contribute to sustainable and low-cost houses construction.