The influence of aminosilanes on macroscopic properties of cement paste

In this work the authors present the results obtained by studying the influence of γ-aminopropyltriethoxysilane or (CH3CH2O)3Si(CH2)3NH2, (APTES), and N-β-aminoethyl-γ-aminopropyltrimethoxylsilane or (CH3O)3Si(CH2)3NH(CH2)2NH2, (AEAPTES), on macroscopic properties of fresh and hardened cement pastes and mortars prepared from ordinary Portland cement. The mixing ability of aminosilane substances with water is an advantage in comparison to other types of organofunctional silanes when used as an admixture to the cement system. This enables direct blending with water and cement and homogeneous distribution of aminosilane molecules through the bulk of the cement material. The highly polar amine and alkoxide groups of aminosilane molecules exhibit strong chemical interactions with cement matrix which are reflected in modified macroscopic properties of the cement system. The effect of APTES and AEAPTES on (a) properties of fresh cement paste and mortar as workability, setting time, water/cement ratio, air content and density, and on (b) properties of hardened cement paste and mortar as compressive and flexural strength, was studied.