Experimental Investigations and Prediction of Thermal Behaviour of Ferrosialate‑Based Geopolymer Mortars

摘要

This paper studies the thermal behaviour of ferrosialate geopolymer mortars. This is done by monitoring various factorsinfluencing the strength gain/loss, weight loss, enthalpy changes, physical and chemical transformations in the ferrosialategeopolymer structure using TG/DT analysis. This study proposed a novel predictive equation for estimating this parameterwith the help of gene expression programming (GEP). Fly ash is used as a raw feed for sialate geopolymer, and red mudalong with fly ash is used for ferrosialate geopolymer. Till 200 ℃, oven-cured samples showed maximum strength results.Whereas in later stages, i.e. after exposure to 400 ℃, ambient cured samples surpassed the former by 4.14%. Developmentof broad amorphous hump in the XRD patterns, presence of thicker geopolymer structure in the SEM images for 400 ℃samples, an exothermic peak in the DTA curves at 400 ℃ and increment in the compressive strength up to 400 ℃ exposure,all pointing to a conclusion that elevated temperature-favoured ferrosialate geopolymer formation till 400 ℃. After exposureto 800 ℃, maximum strength loss of 68.57% and 30.3% is observed for sialate and ferrosialate samples dehydroxylation,recrystallization, and melting of unreacted particles are the reasons for diminishing the strength at elevated temperatures.An equation using GEP model (r~2 = 0.913) having nine genes is proposed that can predict the residual compressive strengthof ferrosialate geopolymer mortars. Though this model is for ferrosialate geopolymer, a similar technique can be easilyadapted to other types of geopolymers.