Workability and Strength Properties of Class C Fly Ash-Based Geopolymer Mortar

Abstract

Fly ash-based geopolymer mortar normally achieves expected properties by heat curing. This becomes one of the obstacles for in-situ applications. The development of high calcium fly ash-based geopolymer mortar, suitable for ambient curing, will gain the applicability of such a material in civil structures. This article reports the results of an experimental study on mortar workability and the increasing of compressive strength of class C fly ash-based geopolymer mortar created in ambient curing condition. The main synthesis parameters such as alkali to the cementitious mass ratio varied from 30% to 40% by an increment of 5% and absolute volume of paste to absolute volume of voids of the aggregate ratio varied from 1 to 2 by an increment of 0.25. These parameters were designed to figure out their individual effects on mortar workability and the mechanical properties for the production of geopolymer mortar. The results suggested that the workability of mortar generally increased by using alkali to the cementitious mass ratio. The compressive strength of 60 MPa and the direct tensile strength of 2.8 MPa, the ratio of alkali to the cementitious mass of 0.35 and absolute volume of paste to absolute volume of voids of the aggregate ratio was 1.5; it was obtained at ambient temperature after 28 days of age. The results will be useful for developing the knowledge for the use of class C fly ash in producing geopolymer concrete, which is currently in progress. Hopefully, this contribution of research will improve the applications of such new binding material in the future.