Influence of gypsum and limestone, used as mineral additives, on autoclaved aerated concrete properties

Abstract

AbstractGypsum is a very popular mineral additive used in autoclaved aerated concrete (AAC) technology. In many studies, tobermorite can be synthesized from calcium‐silicate‐hydrate (C‐S‐H) phase under hydrothermal conditions in the presence of gypsum, and its impact on the tobermorite content in the AAC blocks has been discussed. It has been found in a previous study that tobermorite can be synthesized from katoite (Ca3Al2[SiO4]3‐x(OH)4x, where x = 1.5–3.0). Probably, it is the reason why Al additives accelerated tobermorite formation in the AAC process. Another very popular mineral additive is limestone. Calcite, in particular limestone, accelerates the reaction between alite with water and forms C‐S‐H phase, which may have an impact on tobermorite formation under hydrothermal treatment. The impact of limestone and gypsum as additives on phase composition and properties of AAC was determined. In the initial study on the laboratory scale, influence of limestone on the microstructure of AAC was determined. Later, on a technical scale, properties such as compressive strength, dry density, thermal conductivity coefficient, drying shrinkage, and phase composition for blocks of AAC containing gypsum additive or calcite additive were studied.