Quantification of volume change of AAC blocks for various environmental conditions

Autoclaved Aerated Concrete (AAC) masonry systems are widely used as partition walls in framed structures. Cracking is often reported in such walls after a certain duration of construction. Dimensional changes occurring in the masonry system under varying temperature and relative humidity (RH) conditions are some of the primary reasons for such distress. Past studies show that bedding mortar can significantly contribute to dimensional changes due to shrinkage behaviour. Most of the literature focus on characterising the influence of raw materials on the microstructure, strength, and performance characteristics of AAC blocks. In the current study, experimental studies on AAC blocks with and without bedding mortars are conducted under controlled and ambient environmental conditions to understand the impact of temperature and RH on the dimensional change behaviour of these wall systems. Furthermore, the dimensional changes observed for AAC blocks are compared with conventional clay and fly ash bricks to understand the intrinsic properties of these materials. In the experimental studies under ambient conditions, small and large-scale AAC masonry units are built and monitored for dimensional change over a period of one month. Results show that the AAC block undergoes significant dimensional change along with the bedding mortar, which is greatly influenced by the boundary conditions of the masonry system, relative humidity, and temperature. In the end, recommendations are given at the component and system levels to reduce the crack development in AAC masonry.