Early Stage Hydration Process of Hydroxypropyl Methyl Cellulose Ether Modified Cement Pastes

Effect of hydroxypropyl methyl cellulose ether (HPMC) on early stage process of cement pastes and its mechanism were studied by hydration heat, chemical combined water, calcium ion concentration, TG-DTG and Ca (OH) 2 content. Results show that HPMC can significantly delay hydration acceleration period of cement pastes. Hydration acceleration period of cement pastes gradually goes back, with the dosage increasing. However, changes of HPMC dosage has little effect on deceleration period and stabilization period of cement hydration. When hydration time is less than 6 hours, chemical combined water slowly increases. Chemical combined water dramatically increases when hydration time is between 6 hours and 24 hours. After 4 hours hydration, calcium ion concentration reaches maximum 26.8mm/L in blank sample. Calcium ion concentration gradually decreases when hydration time is more than 4 hours and reach minimum 9.2 mm/L after 24 hours hydration. Calcium ion concentration of cement pastes which modified with HPMC showed the same change law. When hydration time is less than 4 hours, the content of Ca (OH) 2 in cement pastes slowly enlarges along with hydration time prolonging. The content of Ca (OH) 2 significantly increases when hydration time is more than 4 hours. At the same age, the more the dosage of HPMC is, the less the chemical combined water, calcium ion concentration and Ca (OH) 2 content.