Stress rate sensitivity of stone masonry units bound with fibre reinforced hydraulic lime mortar

摘要

It is well established that most construction materials behave differently under static and dynamic loading. However, the literature on the time-dependent response of masonry joints is scarce, particularly with regard to the bond behaviour in historical stone masonry. This paper describes the dynamic response of sandstone masonry units bound with hydraulic lime mortars (HLMs). A drop weight impact machine was used to generate stress rates up to 10~7 kPa/s. The dynamic impact factor and stress rate sensitivity were evaluated for the fiexural strength of the sandstone, mortar and for the bond strength of the unit and further, the pattern of failure was noted in the units for each mortar mix and loading rate. Based on a related study on the fracture toughness of HLM, polypropylene micro-fibres were incorporated at 0, 0.25 and 0.5% volume fraction into the mortar. Results show that the flexural bond strength was more sensitive to stress rate than the flexural strength of the mortar, at similar rates of loading. Further, the stress rate sensitivity of the bond strength decreased with an increase in the fibre content. Also, whereas the mode of failure in the masonry units under quasi-static loading was through fracture at the mortar-block interface, the failure plane transferred to within the mortar under dynamic loading, particularly in the presence of fibre reinforcement.