Thermogravimetric analysis (TGA) is commonly used to quantify cement hydration by attributing mass loss to decomposing hydration products or carbonates. However, as binder systems become more complex, assuming a single gas evolves within a temperature range becomes unreliable. This work introduces a novel method for calibrating and directly measuring chemically bound water quickly in complex cementitious systems by coupling TGA with infrared spectroscopy (TG-IR). Type IL and ordinary portland cement (OPC) pastes were examined, including OPC blended with 20% fly ash (FA) or slag (SL), or 5% biochar (BC). For OPC, SL, and FA, TG-IR and the Bhatty TGA-only method agreed within 1%; however, TGA-only methods were found unreliable for high-LOI BC and IL pastes, deviating by 5–20% compared to TG-IR. TG-IR thus provides more broadly applicable framework for quantifying decomposition products in modern blended cements where the assumptions of TGA-only methods become invalid. • A method is proposed for quantifying IR absorbance to determine bound water. • TG-IR can deconvolute and quantify simultaneous gas release during thermal decomposition. • TG-IR can quantify products of complex systems without relying on prescriptive assumptions.
Hylton et al. (Mon,) studied this question.