Influence of Hydroxypropyl methylcellulose (HPMC) on the hydration characteristics and early phase composition of C3S-gypsum binary paste

To further understand the influence of HPMC on cement-based material (CBM) hydration, this study investigates the hydration characteristics and early product formation of C3S-gypsum binary pastes with HPMC. Results demonstrated that HPMC significantly delayed heat release peak occurrence, with the most pronounced effect on induction period duration, which was increased by 1-2 times with adding HPMC. Calculations employing the Krstulovic-Dabic hydration kinetic model show that HPMC most significantly extended the nucleation and crystal growth (NG) stage, increasing the duration by 21% in the 0.05% HPMC group. Additionally, the 0.035% HPMC group showed a 2.6% decrease in CSH gel and 14% in Ca(OH)2 generation after 1 day, while also reducing the chemically bound water (CBW) content by 20%, with CBW relative content variations correlating with hydration stage rate constants. This study confirms that HPMC delays C3S-gypsum hydration and reduces early product generation, aiding future regulation of CBM hydration processes.