SMALL-SCALE DIRECT TENSION TEST FOR THE DETERMINATION OF BOND STRENGTH AND MORTAR MICROSTRUCTURE IN MASONRY

摘要

This report describes the development and application of a small-scale test method for the determination of bond strength in masonry. The test procedure was developed to investigate the bond strength and the corresponding mortar macro/microconstituents in a given section of masonry. This small-scale test is able to measure the "local" rather than the "average" bond strength of mortar joints. The test involves coring masonry couplets using a hollow diamond impregnated drill bit to obtain cylindrical specimens with a length-to-diameter aspect ratio of 3:1. The mortar bed joint is located perpendicular to the longitudinal axis and in the centre of the specimen. Samples are tested in direct tension under controlled displacement conditions. This technique allows several bond strength results to be obtained from a single brickwork couplet or alternatively, the bond strength in specific regions of the joint may be assessed. The uniform stress distribution across the joint in the test specimen and the small size of the specimens makes this a useful technique to study mortar/unit bond interactions by allowing the failure surfaces to be examined in detail using optical and scanning electron microscopy techniques.