Napier University
University of Edinburgh

Masonry codes under preparation by ISO and CEN are to use a formula for the calculation of characteristic compressive strength of masonry based on a reference or “normalised” unit size. The present investigation was carried out to derive an empirical formula for the shape factor, 5, by which the measured compressive strength should be multiplied to give the equivalent strength of a selected “normalised” sized unit. Solid concrete specimens of varying dimensions, sawn from solid blocks, were tested in compression to study the influence of the shape of the units on their compressive strength. The tested surfaces of the specimens were prepared by grinding to eliminate any effects of capping or packing materials on the apparent compressive strength. From the results of the investigation a formula for the shape factor was suggested and comparisons with previous formulae are presented.