Aspects of the tensile strength of brick-mortar joints.

The main purpose of this work is to assess the factors which affect the tensile bond strength of brick mortar joints and to verify their relative importance, both by reference to the literature, and by experimentation. From these investigations the most important aspects are seen to be the absorption of water from the mortar by the brick, and the grade of the mortar.Almost one thousand tensile bond couplets were tested using a newly devised apparatus which has several advantages over existing test methods. Four experimental programmes were carried out, each of which was designed to investigate one or more of the factors which were judged either to be of particular importance, or to be inconclusive, or both.Arising out of the main section of the work was the tensile strength hypothesis. This is capable of showing, in a qualitative way, how the tensile strength and mode of failure of a brick-mortar joint can be related to the properties of the mortar and the brick. The hypothesis draws upon concepts from other disciplines, such as soil physics, in order to describe the physical processes which are important. Accordingly, it is the way that a brick absorbs water from the mortar that will have the most profound effect on the subsequent processes of hydration and strength development within the mortar.In order to provide some evidence in favour of the hypothesis, pilot studies were carried out to determine the moisture characteristics of mortar and to furnish data on the hydration products within the joint. Whilst, these pilot studies had their limitations, the results were encouraging.Recommendations are made regarding future developments of the hypothesis from a theoretical and a practical viewpoint.