Performance of geopolymer concrete composed of fly ash after exposure to elevated temperatures

Alkaline activated concretes based on a mixture of fly ash (FA) and blast furnace slag (GBFS), as well as FA and Portland cement (OPC), both at a ratio of 80:20, were exposed to temperatures between 25 degrees C and 1100 degrees C. Then, the physicochemical and mechanical changes were evaluated. The results indicate that the activated concretes have better performance than the reference ones (100% OPC). At temperatures of 1100 degrees C, the residual strengths of the FA/GBFS and FA/OPC concretes are 15 and 5.5 MPa, respectively, unlike the OPC concrete that lost 100% of its strength. At temperatures above 900 degrees C, the activated matrix densified, and the crystalline phases, such as sodalite, nepheline, albite and akermanite, are identified. (C) 2017 Elsevier Ltd. All rights reserved.