Behavior of Concrete Block Masonry Under Axial Compression


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Title: Behavior of Concrete Block Masonry Under Axial Compression

Author(s): Robert G. Drysdale and Ahmad A. Hamid

Publication: Journal Proceedings

Volume: 76

Issue: 6

Appears on pages(s): 707-722

Keywords: axial loads; building codes; compression tests; compressive strength; failure; grouting; masonry; mortars (material); prisms; structural design; concrete blocks.

Date: 6/1/1979

The results of 146 axial compression tests of concrete block masonry prisms are reported. The results show that the strengths of grouted prisms are not affected much by the mortar joint. The average compressive strength for grouted prisms was less than for similar ungrouted prisms indicating that the concept of superposition of the strengths of grout and the ungrouted prism is not valid. An explanation for this phenomenon is suggested which indicates that the incompatibility of the deformation characteristics for the grout and the block contributes to this result. It is shown that the larger lateral tensile strains in the grouted prisms correspond to vertical compression strain levels in the grout which are associated with extensive microcracking and greatly increased Poisson’s ratios. It is argued that this large lateral expansion of the grout leads to a premature tensile splitting failure of the blocks’ shells. It is also shown that increasing the grout strength is not an efficient means for increasing the masonry compressive strength.