Evaluation of the crack bridging ability of waterproofing membranes using indirect tensile test and digital image correlation

Abstract

Adhered waterproofing membranes are often subject to cracks that emerge from the substrate, which can result in loss of watertightness. A test that simulates this situation allows evaluating the maximum crack opening and consequent performance of waterproofing systems. The ability of the material to bridge cracks and maintain the watertightness performance is known as crack bridging ability (CBA). This study aimed to evaluate an indirect tensile test to study the CBA of waterproofing materials adhered to a concrete substrate. Three waterproofing materials with different mechanical characteristics were tested: acrylic membrane, modified-bitumen sheet, and cementitious membrane. Pull-off tests were also performed before and after the crack ability tests. Digital Image Correlation (DIC) analysis were used to measure the deformation on the membrane surface during the tests and precisely detect the crack transfer from the substrate. The results demonstrate that materials with greater elongation at ruptures, such as the modified-bitumen sheet and acrylic membrane, are more resistant to crack opening. Fragile materials, as the cement-based membranes, even if polymers are added, may crack and lose their watertightness when subjected to tensile stresses. Relationships between CBA and the adhesion strength were noticed. The modified-bitumen sheet, with lower adhesion, resists greater crack openings. The indirect tensile test used to assess the CBA allows determining the waterproof materials performance, especially with the use of the DIC technique that enables quantitative measurements.