In some countries, fired clay bricks (FCBs) are widely used for construction, but their production is energy-intensive, relies largely on firewood, and contributes to deforestation and carbon emissions. This study explores unfired clay bricks stabilised with cement and rice husk ash (RHA) as a sustainable alternative, using Dakawa ward in the Morogoro Region, Tanzania, as a case study. The bricks, with a clay of plasticity index 17%, were stabilized with 6%, 10%, and 14% cement by mass, moulded into 40 mm cubes, and cured for 28 days. The compressive strengths achieved were 1.5, 3.6, and 4.1 MPa with water absorption values of 9.8%, 11.1%, and 15.2%, respectively. The FCBs of the same size had a compressive strength of about 3.2 MPa but a high water absorption of 20.2%. The results show that approximately 10% cement stabilisation is sufficient to produce better-performing bricks than FCBs. To minimise cement use, RHA was introduced by partially replacing cement at ratios of 20:80, 35:65, and 50:50 (total binder: 10%). After curing, compressive strengths of 3.6, 3.3, and 2.5 MPa were achieved, with corresponding water absorption values of 11.4%, 13.5%, and 17.0%. These results indicate that cement-RHA stabilisation can reduce cement use while maintaining a performance comparable to FCBs.
Samson et al. (Fri,) studied this question.