The influence of silanes on hydration and strength development of cementitious systems

Abstract

The influences of three types of silane (tetraethoxysilane (TEOS), 3-aminopropyltriethoxysilane (APTES), N-2-aminoethyl-3-aminopropyltrimethoxysilane (AEAPTMS)) on flowability, strength development and hydration kinetics of cement pastes and mortars are systematically investigated. Results show that: 1) three silanes exhibit a dispersing effect on cement pastes indicated by the increased flowability of fresh cement pastes, among which AEAPTMS shows the strongest dispersing power; 2) AEAPTMS and APTES retard cement hydration by extending the induction period and reducing the hydration degree at certain ages determined by isothermal calorimetry, measurements of non-evaporable water amount and portlandite content in hydration products at ages before 90 days; 3) AEAPTMS and APTES show positive effect on the toughness of mortars after 7 day curing; and 4) three silanes act differently on strength growth at various ages, which should be a result that is counterbalanced by their influences on hydration kinetics, pore structure, composition and morphology of hydration products.