The durability of mechanical properties of flexible waterproofing membranes used on ventilated terraces under long term exposure to high temperatures

Abstract

Abstract The paper analyses the influence of high temperatures (70 °C for three months) on the durability of the mechanical properties of waterproofing membranes used on ventilated terraces. The test kits consisted of a concrete substrate, waterproofing membrane (reinforced bitumen sheet or EPDM membrane), and the top layer spot-supported by plastic pedestals. The stress transferred by the pedestals to the substrate was determined through calculations. The changes after ageing were evaluated in the areas between the pedestals and in their locations for their ability to maintain the mechanical load-transferring function, including but not limited to resistance to continuous or instant spot loads. The action mechanism of the ageing processes was investigated by analysing the microstructure of the cross-sections of the tested samples using SEM. After three months of exposure to + 70 °C, the resistance to spot loads of a reinforced bitumen sheet was higher than that of a flexible EPDM sheet. Simultaneously, the tensile values are more favourable for the first sheet type. The impact resistance of the reinforced bitumen sheet increased by 36%, whereas that of the EPDM membrane decreased by 25%. The static puncture resistance of the reinforced bitumen sheet before and after ageing remained at the same level; for the EPDM membrane, the value dropped by 20%. In both cases, microscopic images of the cross-sections of the tested items revealed structural changes in the form of microcracks.