Impact of curing temperatures and alkaline activators on compressive strength and porosity of ternary blended geopolymer mortars

Abstract

Impact of changing temperatures of curing (27, 60 and 90 °C) and types of alkaline activator solution on the properties of geopolymer mortars (GPMs) prepared by combining agricultural and industrial wastes including granulated-blast-furnace-slag (GBFS), fly-ash (FA), and palm-oil-fuel-ash (POFA) was examined. Sodium Hydroxide (NH), Sodium Silicate (NS) and NHNS alkaline solutions were used as alkali activators. Proposed GPMs were synthesized using NH solution of molarity 8 M, ratios of alkaline solution to binder were 0.30, NS to NH was 3.0 and binder to fine aggregate (sand) was 1.5. The mechanical properties of the studied GPMs and the products of reaction were greatly sensitive to the variation of mix compositions, alkaline activators type, and temperatures of curing. Furthermore, the formation of crystalline calcium silicate hydrate (C-S-H), calcium aluminium silicate hydrate (C-A-S-H) together with additional amorphous gel led to the compressive strength enhancement of the GPMs as the content of FA was increased and activated with NS solution. A linear correlation was established between compressive strength, ultrasonic pulse velocity and porosity of the proposed GPMs.