Valorising cassava pomace biosolid in fired clay bricks production: Physical, mechanical and thermal evaluation

In this study, the practicability of recovering cassava pomace biosolids (CPB) for use as pore forming materials in fired clay bricks was examined. The raw materials were characterized for their chemical, mineral and thermal properties and found suitable for fired clay brick production. Modelled test brick samples containing up to 15% CPB were fabricated and fired at 900 and 1000 degree celsius. Apparent porosity increased from 31.2% to 48.6% at 900 degree celsius. Bulk density reduced from 1.97 g/cm(3) to 1.58 g/cm(3) at 1000 degree celsius during firing with the progressive introduction of CPB in the brick bodies. Water absorption values of bricks fired at 1000 degree celsius ranged between 10.80% and 28.82%. Compressive strengths of bricks declined from 20.01 MPa to 6.3 MPa at 900 degrees C firing. However, this decline was compensated with an over 30% improvement in thermal insulation as thermal conductivities reduced from 0.84 W/mK to 0.54 W/mK. Phase analysis evidenced kaolinite transformation into metakaoline and mullite, geothite dehydroxylation into hematite and the formation of wollastonites in the fired brick samples. Morphological analysis of CB-15 brick series showed significant differentials in terms of the nature of pores developed and clay vitrification due to changes in firing temperatures. Overall, CB-10 brick series was considered suitable for load supporting structural construction whereas CB-15 were most apt for thermal insulation walling construction. Consequently, by adjusting the CPB content within 2.5-15 wt% in the bricks' bodies, the produced bricks could be applicable to a wide spectrum of construction applications.