A sustainable alternative to traditional building materials: assessing stabilised soil blocks for performance and cost in Malawi

Within Malawi, and across the Global South, the adoption of stabilised soil blocks (SSBs) as a sustainable alternative to burnt clay bricks, has been hindered by the high cost of stabilisers. The purpose of this article is to evaluate the performance of cement as a stabiliser in soil stabilised blocks, and to propose cement ratios which both reduce the material cost while meeting building requirements for local applications. Using a brick production method replicable within a rural African context, we tested a range of cement contents for dry compressive strength, flexural strength, and water absorption properties. Our findings suggest that a cement content of 3.6% is adequate for single-story building applications, four times lower than that currently used in compressed brick production within the study area. Moreover, the elimination of the firing process - which represents half of burnt brick production costs - and the proposed cement ratios correspond to large cost savings, ranging from 20% to 77% depending on building application, for brick producers. These results suggest that the cost of manufacturing stabilised soil blocks can be considerably reduced and thus become financially viable; however further innovation is needed to achieve a sustainable means of production and use.