The Binder Index – A Parameter That Influences the Strength of Geopolymer Concrete

Geopolymer concrete (GPC) is an environmentally friendly material in the sense that it uses industrial by-products such as ground granulated blast furnace slag (GGBS) and fly ash (FA), which are activated by an alkaline solution. This paper presents an experimental investigation concerning the strength of the GPC and its relation to a new parameter called the ‘Binder Index (BI)’. The parameters considered in the investigation include GGBS to fly ash ratios (0.25 0.43, 0.67, 1.0, 1.5, and 2.3) and the molarity of the alkaline activator (6, 8, 10, and 12). The binder index combines the effect of the GGBS to the fly ash ratio and the molarity of the alkaline activator. The results have shown that the strength of the GPC is significantly influenced by varying the binder index. The results indicate that a nonlinear relation exists between the binder index and the compressive strength of the GPC and the binder index and the modulus of rupture.