Effects of joint thickness, adhesion and web shells to the face shell bedded concrete masonry loaded in compression

Prism tests are used to assess the strength of masonry in the Australian masonry structures standard, AS3700 (2011).Where no testing is done, the standard provides correction factors to account for the effect of the height of blocks to the mortar thickness; the primary driver of this correction factor is the usage of larger height units (for example, typical two cell hollow concrete blocks of 190mm height against typical solid clay bricks of 76mm height) with a constant mortar thickness of 10mm.In recent times, higher adhesive thin bed mortars of 2mm -4mm thickness are being introduced in masonry construction internationally.Further, for ease of construction of reinforced masonry, H blocks that have only the mid web shell are introduced.Although the web shells are not mortared and hence do not resist axial compression, they do offer lateral restraint to the face shells loaded in compression.The usage of H blocks and the thinner and higher adhesive mortars have renewed interest of the compression behaviour of hollow concrete masonry and hence is re-visited in this paper.This paper presents an experimental study carried out to examine the effects of the thickness of mortar joints, the type of mortar adhesives and the presence of web shells in the hollow concrete masonry prisms under axial compression.A noncontact digital image correlation (DIC) technique was used to measure the deformation of the prisms.The method quite adequately determined the strain field of the loaded face shells subjected to axial compression.The absence of end web shells consistently has lowered the compressive strength and stiffness of the prisms; thinner mortars and higher adhesive mortars have increased the compressive strength and stiffness, whilst lowering the Poisson's ratio.