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

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 degrees and 600 degrees C, and (ii) post-thermal treatment tests, to evaluate the residual strength after I h of exposure to different temperatures (200 degrees, 400 degrees, 600 degrees, 800 degrees, and 1000 degrees 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.