Development of sustainable geopolymer composites for repair application: Workability and setting time evaluation

Abstract

One of the most used construction materials worldwide is concrete. It has a lot of advantages over the other construction materials. However, the production process of concrete produces a huge amount of carbon dioxide. Geopolymer composites are gained attention as eco-friendly alternative to traditional cement. In this research an attempt has been done to optimize a sustainable geopolymer mortar made of ground-granulated blast furnace slag (GGBS) and fly ash (FA). The optimized geopolymer mortar is designed to be convenient and practical for repairing damaged reinforced concrete members. Accordingly, this research is focused on improving setting time and workability of an ambient cured geopolymer mortar. In this research an attempt has been done to study the impact of using different superplasticizer dosages, different GGBS percentages, and different alkaline activator solution ratios on the setting time and flowability of an ambient cured geopolymer mortar. The obtained findings of this study showed that, alkaline activator ratio is one of the most significant parameters that affect workability and setting time of the geopolymer mortar. In this study, fifteen different mixes were tested and evaluated. Modified Vicat apparatus and Flow Table test were used to evaluate setting time and workability for the mortars. The outcome of the optimization showed that, the most convenient and practical mix which provided the highest setting time and reasonable flowability contained of 25% GGBS, 75% FA and 5% superplasticizer. The obtained workability for the optimum mix was about 156.25 mm and the achieved setting time was about 30 min.