Investigation of un-calcined coal gangue together with ground granulated blast furnace slag and fly ash to ambient-curing production high-strength geopolymer

Aim of this work is to exploit an ambient-curing method to produce high-strength geopolymers by applying un-calcined coal gangue (G). An optimized alkaline activator solution with a mixture proportion of 1.2 M, 8% AE, and 0.32 liquid-solid ratio was adopted to stimulate the mixture of G, ground granulated blast furnace slag (S), and fly ash (A). The geopolymer totally composed of S displayed the highest strength, which was more than 70 MPa at 28 d. Compressive strengths dramatically decreased from 55 MPa to 20 MPa when the content of G changed from 25% to 55% in S-G binary geopolymers. The strength of S-A-G ternary geopolymers did not significantly influence by the content of G until 17%, and the strengths decreased with the increasing G content as it exceeded 22%. Appropriate contents of G resulted in aluminosilicate gel formation in the ternary S-A-G geopolymers, and compressive strengths of the ambient-curing ternary geopolymers can reach similar to 65 MPa at 28 d. (c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The aim of this study was to produce high-strength geopolymers using an ambient-curing method and un-calcined coal gangue (G) as an additive. The results showed that the geopolymer composed solely of ground granulated blast furnace slag (S) exhibited the highest strength, while the strength dramatically decreased with an increase in the content of G in the S-G binary geopolymers. In the ternary S-A-G geopolymers, the strength was not significantly affected by the content of G until it exceeded 17%, and decreased as the G content exceeded 22%. Suitable content of G resulted in the formation of aluminosilicate gel in the ternary geopolymers, and the compressive strength of the ambient-curing ternary geopolymers reached approximately 65 MPa at 28 days.