Analysis of co-fired clay and palm kernel shells as a cementitious material in Ghana

•The calcination of palm kernel shells at the calcination temperature of clay which was at 800°C yielded less reactive crystalline phases.•Strength activity index of the calcined material that contained 20% of palm kernel shells by weight of clay was enhanced than the control mixture.•The optimum compressive strength of the co-fired material used to replace Portland cement was at 20%. The treatment of clay through a calcination process at high temperatures have been the usual and a common means of producing clay pozzolan as a supplementary cementitious material. However incorporating waste biomass as a component material in clay is very uncommon. This work analyzed the use of palm kernel shells as a component material in clay and were calcined at a high temperature of 800°C. The palm kernel shells were used to replace clay at 10%, 20% and 30% by weight. Strength activity index prescribed by ASTM C311 was used to determine the maximum mixture proportion between calcined clay and palm kernel shells. The calcined clay and palm kernel shell mixtures that gave the maximum strength were subjected to an incremental replacement dosage of Portland cement between 10% and 40% by weight. Test results indicated that the maximum strength mixture proportion between clay and palm kernel shells was obtained at 20% replacement of clay. Moreover the maximum value that showed a better strength performance through the incremental replacement by the calcined material was also at 20% Portland cement replacement. The study recommended the use of palm kernel shells to a limit of 20% clay replacement. The is because at higher content of palm kernel shells in clay calcined at a high temperature, more unreactive crystalline phases are formed that inhibit reactivity of pozzolanic active phases. The use of 20wt.% of palm kernel shells in clay to produce a supplementary cementitious material provides a sustainable means of waste disposal via construction application.