Compressive strength and pore structure studies of clamp-fired waste powdered clay brick as a supplementary cementitious material

Abstract

Clamp-firing system is a cost-effective technology used to produce burnt clay bricks in many West African countries including Ghana. However, this firing system generates between 7%- 15% of waste in a form of burnt broken bricks and with time creates disposal problems. In this work, burnt clay broken bricks were sampled and pulverised to 75 microns and used as a partial replacement of cement between 10-40 wt. %. Two different sets of mortars were prepared, one from Portland cement as the binder whereas the other set using Portland cement-pulverised bricks as their binders. Compressive strength test was performed on the mortars after moisture exposure at 3, 7 and 28 days. Water absorption test was used to study the pore structure of the optimum mortar mix. The results of the Portland cement-pulverised bricks mortars were compared with the Portland cement mortars. The results of the study indicated that 30 wt.% of the pulverised brick used to replace Portland cement gave the optimum mortar mix. The pore structure of the cement-pulverised brick mortar mixture showed a significant reduction compared to the Portland cement mortars. Si and Al MAS NMR studies revealed that pore structure reduction was due to polymerisation of aluminosilicate hydrates. The study recommends the use of waste powdered burnt clay brick as a supplementary cementitious material and possible means to provide alternative solutions to the disposal of waste burnt broken bricks.