Compressive Strength and Durability of Geopolymer Concrete

The impacts of using Ground Granulated Blast Furnace Slag (GGBFS) and fly ash as a replacement to Ordinary Portland Cement (OPC) are evaluated. A total of 120 concrete cubic and cylindrical samples were casted and tested for four different binder compositions. Compressive strength testing conducted on cubes and cylinders at various ages revealed that incorporation of fly ash as binder reduces the compressive strength at various ages. In addition, it is also observed that geopolymer concrete provides late strength gain which is a major drawback of the usage of such concrete. Furthermore, it was noted that GGBFS- and fly ash- based concrete gain compressive strength at later ages compared to conventional concrete. This is due to the late activation process. On the other hand, durability testing of geopolymer concrete, represented by rapid chloride penetration test (RCPT), suggests that replacing OPC with GGBFS and fly ash in concrete provides massive improvements in durability at the various testing ages. In contrast, adding further fly ash reduces overall durability by increasing the water absorbed and water penetration depth. Finally, it is concluded that environment friendly materials such as GGBFS and fly ash can serve as appropriate alternatives to OPC in the binding material of concrete mixes.