N. DE VITIS* A.W. PAGE* and S.J. LAWRENCE** *The University of Newcastle, NSW **CSIRO-DBCE, North Ryde, NSW

Masonry bond strength is one of the most important and fundamental parameters required for the design of unreinforced masonry structures. Bond strength depends upon many parameters related to the properties of the masonry units and mortar. It is also expected to be a function of age, with initial bond being established as soon as the unit is laid, and the strength then increasing as hydration of the cementitious material in the mortar takes place. The investigation described in this paper was a preliminary experimental study to investigate the influence of age on bond strength for clay, concrete and calcium silicate units combined with typical mortars, Flexural bond strengths of masonry joints were determined at ages ranging from lh to 6 months. The results are reported, and trends examined. The final bond strength was found to be significantly greater than the 7d strength, indicating that the current use of 7d strength for design purposes by the Australian Masonry Code may be over conservative.