Distribution and evolution of (micro)strain and stresses in flexible, waterproofing membranes using digital image correlation and finite element modelling

High performance of one-component, flexible, waterproofing membranes is fundamental to prevent crack propagation from concrete substrates into coatings and finishing layers. This study investigates the influence of air pores and mineral inclusions in a polymer-cement matrix on stress concentrations and crack propagation by combining physical testing with finite element modelling. During physical testing, surface deformation is investigated and mapped using Digital Image Correlation. Finite element simulations of internal deformation reveal that pores and inclusions retard the crack propagation. Pores delay crack propagation actively by blunting crack tips. Inclusions act as force chains distributing stresses and elasto-plastic deformation over larger volumes inside the membrane. Consequently, yield stresses are locally reached at larger bulk strains retarding crack initiation and propagation. Varying distribution, size and content of pores/inclusions exposes their respective influence on the crack-bridging behavior. Optimizing these parameters can significantly improve the crack -bridging ability and therefore the overall performance of waterproofing membranes.