Bond strength of Autoclaved Aerated Concrete (AAC) masonry using various joint materials

Autoclaved Aerated Concrete (AAC) blocks are used for both load bearing and non-load bearing masonry walls. The tensile and shear strengths of such walls are greatly affected by the bond strength of block-mortar interface. This article investigates the bond strength of AAC block-mortar interface made of ordinary sand-cement mortar of different compositions and polymer modified mortars. A method of improving the bond strength (both tensile and shear) of ordinary sand-cement mortar without altering the block surface characteristics is proposed. In this method, the block surfaces are coated with a thin cement-slurry coating before applying a thick sand-cement mortar. For all types of interfaces, the shear bond strength of the masonry was studied using a triplet test, while the tensile bond strength was determined based on a cross-couplet test. The failure patterns during the bond strength tests were studied. Subsequently, costs were estimated for AAC walls of different types of interfaces. Considering the bond strength as well as cost, using a weak mortar along with cement-slurry coating was found superior to the ordinary sand-cement mortar and polymer modified mortar.