Effect of a temperature rising inhibitor on the hydration kinetics of white cement pastes containing slag at different temperatures

Abstract

This study systematically investigates the effects of a starch-based thermal rise inhibitor (TRI) on the hydration kinetics of white cement-slag blended pastes under 23 °C, 40 °C, and 60 °C conditions, aiming to address thermal cracking issues in mass concrete caused by hydration heat. The hydration exothermic process was monitored by isothermal calorimetry, while microstructural evolution and hydration products were analysed using MIP, TGA/DTG, and BSE-IA. The results demonstrate that TRI significantly reduces the exothermic rate at the main hydration peak and delays its occurrence. Based on reaction kinetic analysis, this behavior is speculated to originate from TRI adsorption onto cementitious surfaces, which inhibits C-S-H growth, with an enhanced inhibitory effect at elevated temperatures. The incorporation of slag synergizes with TRI to regulate the hydration kinetics via both dilution effects and pozzolanic reaction. TRI preferentially modulates early-stage hydration kinetics by reducing reaction rates in NG and induction I stages, while exerting negligible effects on the D stage. Additionally, TRI modifies pore distribution by facilitating transitions of multiple harmful pores rather than uniformly reducing the quantity. Although TRI slows the precipitation of early-stage C-S-H and ettringite, the retarding effect of TRI decreases progressively as hydration progresses. BSE-IA confirmed that TRI significantly retarded early hydration, increasing sample porosity and the proportion of unreacted phases in slag-blended systems. In conclusion, the above findings establish an adsorption-mediated modulation mechanism of TRI on white cement-slag composite binder, which provides a theoretical framework for mitigation of thermal cracking in mass WPC concrete.