Effect of AMPS-based polycarboxylate superplasticizer on early hydration of cement and its mechanism

2-acrylamide-2-methylpropanesulfonic acid (AMPS) has attracted much attention in the field of admixture design because of its highly electronegative sulfonic acid groups. However, the number of AMPS introduced has different effects on the early strength of cement-based materials, and its role in the early hydration of cement and the mechanism are still unclear. In this study, inducing early strength polycarboxylate superplasticizer (IES-PCEs) was synthesized from 2-hydroxyethyl poly (ethylene glycol) vinyl ether (EPEG), acrylic acid (AA) and AMPS at different molar ratios. The results showed thatIES-PCE-5 % performed excellent water reduction performance and early strengthening effect, which could increase the compressive strength of mortar by 89.93 % at 1 d and increase the cumulative heat release by 43.03 % at 3 d hydration. It was interesting that the appropriate introduction of AMPS could convert the sulfonic acid group (-SO 3 − ) into SO 4 2− in the cement pore solution environment, forming "secondary gypsum" with Ca 2+ . This can prolong the induction period and acceleration period of hydration, significantly promote the production of early ettringite (AFt). AFt and hydration products such as calcium hydroxide (CH) and calcium silicate hydrate (C-S-H) form a complex three-dimensional network structure, which promotes the development of early strength of cement-based materials. The aim of this study is to provide the research basis for the development of high-performance polycarboxylate superplasticizer materials that meet the requirements of early strength of cement-based materials in railway engineering construction.