Revisiting the Mechanism of Carbonation Shrinkage of Autoclaved Aerated Concrete

Abstract

In the article the analysis with the generalization of experimental and theoretical studies of foreign and Russian scientists is given in order to compare, substantiate and refine existing scientific theories and statements on the nature and mechanism of carbonation factor effect on shrinkage properties and creep of cement stone and aerated concrete. It is pointed out that according to the existing opinions of foreign scientists (such as Powers, Ramachandran, Feldman, Swenson and Sereda), the mechanism of carbonation shrinkage of cement stone is considered as a topochemical process and consists in dilution of calcium hydroxide at the points of contact of crystals and formation of additional bonds during the precipitation of reaction products in new zones. The mechanism of the shrinkage of autoclaved aerated concrete during carbonation processes is explained in the framework of the scientific theories of Russian scientists E.S. Silayenkov and E.N. Chernyshov. This mechanism is classified as heterogeneous reaction, referring to its kinetic and diffusion component, where the main causes of shrinkage deformations are the intrinsic stresses of the crystalline intergrowth and the polymerization of silica gel, resulting from the interaction of hydrated calcium silicate with carbonic acid.