Investigating the effect of base material on silica-alkaline reaction in geopolymer concretes

Concrete is the most widely used material in the construction industry and this material can be damaged under aggressive conditions. Among the destructive and aggressive factors of concrete, the existence of reactive aggregates and the occurrence of the phenomenon of alkaline reaction of aggregates is an important issue. In fact, this reaction is a chemical reaction that occurs in concrete between alkaline oxides in cement and reactive silica in aggregates and can have serious consequences on the performance of the structure in terms of durability. Weakening of mechanical properties of concrete and brittle fracture of rebars, internal expansion, creation of cracks, reduction of strength, and possible failure of a concrete structure can be among the consequences of this reaction. The use of geopolymer concretes, apart from reducing the production of carbon dioxide gas and environmental effects, with better durability and proper performance, can guarantee the stability of these concretes against the consumption of reactive aggregates. In this study, the effect of fly ash and slag as the base material of geopolymer mixtures on the durability of these concretes against the alkaline reaction of aggregates is investigated.