Compression Tests of Hollow Brick Units and Prisms

It is customary to relate the compressive strength of the masonry to that of its components: mortar and units. The correlation between solid unit compressive strength, mortar type and assemblage compressive strength is well documented, and is generally independent of unit coring. The relationships of prism components and prism dimensions to assembly compressive strength and modulus of elasticity for hollow brick are presented in this paper.

Hollow brick meeting the requirements of ASTM C 652 in four widths were selected. Portland cement-lime mortars, Type N, S, M by proportions, were used. Both face-shell and full mortar bedding were used to construct prisms with height to thickness ratios from 2 to 5. Mortar, brick and prisms were tested in compression. Deformations measured during prism testing permitted the determination of modulus of elasticity in compression.

Hollow unit masonry prisms fail by tensile splitting of the crosswebs, regardless of their aspect ratio. Prism compressive strength and modulus of elasticity are influenced least by fully bedded, stack bond prims. Compressive strengths of prisms made from hollow brick have similar relations to h/t and mortar strength as prisms of solid brick, but less dependence on unit strength.