Feasibility of producing sustainable geopolymer composites made of locally available natural pozzolan

The feasibility of using locally available natural pozzolanic materials as complete replacement of cement binder to produce sustainable geopolymer concrete was investigated. Compressive strength, flowability, and microstructure of geopolymer mortar were measured and compared to highlight the effect of various parameters such as sand/pozzolan ratio, water/pozzolan ratio, type and concentration of activators, presence of soluble silicates, and curing age on the behavior of natural pozzolan-based geopolymer mortar. Two types of activators, namely sodium and potassium hydroxides were used as an activating solution for geopolymerization. Experimental results revealed that the compressive strength of natural pozzolan-based geopolymer mortars was affected by the type and concentration of activators. The strength was enhanced with curing ages and presence of soluble silicates but reduced with increasing water/pozzolan ratio. The flowability of geopolymer mortar increased with increasing the water/pozzolan ratio and presence of soluble silicates but decreased with increasing the sand/pozzolan ratio. SEM images showed a well-packed and homogenous microstructure of geopolymer mortar.