Load strain properties and splitting of roof membranes

The load-strain properties of several bituminous membranes when tested in tension are examined and the effect of temperature on the breaking load, load-strain modulus, and breaking strain is considered. The shear properties of the bitumens used as adhesives in the production of the membranes are examined at temperatures from -15 F (-26 C) to 32 F (0 C) at a rate of shear of 0.21 per min. The observed transition in the shear modulus of the asphaltic material at 0 F (-18 C) is found to coincide with the glass transition temperature of this material. The development of a critical- thickness concept is described, and it is suggested that the performance of roofing membranes under deformation may be controlled by the load-strain properties of the membrane and the shear properties of the adhesive.