Compressive strength of clay brick walls
Bureau of Standards Journal of Research
Compressive tests of 168 walls of common brick, each 6 feet long and about 9 feet high and of 129 wallettes, about 18 inches long and 34 inches high, were made. Four kinds of brick, 3 mortar mixtures, 2 grades of workmanship, different curing conditions, and 10 different types of masonry (3 solid and 7 hollow) were the variables. Wall strengths were more closely related to the shearing strength of the single brick than to any other strength property of the brick. On the average, the compressive
... ge, the compressive strength of the wallettes was by far a better measure of the strength of the walls than any of the brick strength values. The use of cement mortar gave higher wall strengths than of cement-lime mortar and much higher than if lime mortar was used. For the solid walls the strength varied about as the cube root of the compressive strength of the mortar cylinders, 2-inch diameter and 4-inch length, cured on the walls. Large differences in strength due to differences in workmanship were found. The walls having smoothed-off spread-mortar beds and filled joints were much stronger than walls in which the horizontal mortar beds were furrowed by the mason's trowel. Some of this difference in strength might be ascribed to difference in the filling of the vertical joints. Some of the walls laid in cement mortar were kept damp for seven days after construction. These walls were not stronger than similar walls cured under ordinary conditions in the laboratory. The solid walls were stronger than the hollow types. With bricks of rectangular cross section the hollow wall strengths varied about as the net areas in compression. When the bricks were not truly rectangular in section, the strength of the hollow walls was found to be less than that expected from the net area. Construction data are given which show the relative saving in materials and time for the hollow types. The results of the wallette tests confirm, in general, the conclusions deduced from the wall tests.