New Cementitious Materials Based on Alkali-Activated Fly Ash: Performance at High Temperatures

Abstract

This paper reports on a comparative study of the mechanical performance at different temperatures of a commercial Portland cement, used as a control, and a new cementitious material made from an 8M-NaOH activated fly ash and containing no OPC. Two types of mechanical tests were conducted: (i) high temperature mechanical tests, to determine the strength and fracture toughness of the two materials between 25° and 600°C, and (ii) post-thermal treatment tests, to evaluate the residual strength after 1 h of exposure to different temperatures (200°, 400°, 600°, 800°, and 1000°C). In both cases, the results showed that the new cementitious material performed significantly better at high temperatures than the Portland cement control. Differential thermogravimetry (DTG)/TG, Fourier transform infrared (FTIR), and X-ray diffraction analyses were also conducted to analyze the mineralogical and microstructural variations taking place in the material as a result of high temperature exposure. The results of these tests were correlated with the mechanical behaviour observed.