Influence of Amorphous Nanodispersive SiO2 Additive on Structure Formation and Properties of Autoclaved Aerated Concrete

Abstract

The influence of surfactant concentration and pozzolanic amorphous nanodispersive SiO2 (ANS) additive on formation of autoclaved aerated concrete (AAC) structures and properties was investigated. It was established that in the AAC forming mixture the replacement of 1.0 % milled sand by ANS accounts for considerably higher crystallinity of hardened binding material, and that the plate-like shape of crystals generated in this case is typical to hydrosilicates with lower ratio C/S. The formation of such AAC structure conditioned increase in compressive strength by 20.0 %, bending strength by 31.0 and decrease in shrinkage at temperature of 700 °C by 0.1 % versus AAC without surfactant and ANS. Basing on the results of investigations, a hypothesis was framed to say that ANS added to AAC forming mass serve as nucleators during the hardening of concrete, stimulating higher crystallinity in the hardened structure of binding material than that without this additives and improving AAC mechanical properties. In addition to this impact, the ANS additive helps to form the crystalline structure, in this way evidencing existence of compounds with lower ratio C/S in AAC hardening structure, as well as to increase thermal resistance of concrete.