Experimental study of one-part geopolymer using different alkali sources

Abstract

This paper investigates the feasibility of combining different solid alkali materials as activator to prepare one-part geopolymer mortars. The effects of different composite solid activators on aluminosilicate materials were studied and compared with the traditional water glass and sodium hydroxide composite solution activator through the measurement of fresh and harden properties and microstructural analysis. The results showed that sodium metasilicate pentahydrate was more suitable than quick-dissolving sodium silicate for preparation of geopolymer. The addition of sodium carbonate and calcium hydroxide in solid activator enhanced the compressive strength and decreased the setting time and flowability of the mixes. The highest compressive strength (47.4 MPa, 28 d) was obtained with the activators consisting of sodium metasilicate pentahydrate and sodium carbonate. While scanning electron microscope (SEM) analysis indicated that micro-pores left by the dissolution of metasilicate particles might have an adverse effect on the mechanical properties of mortar samples.