Crack Initiation and Propagation in Fiber-Glass Reinforced Mortars

Abstract

Reinforced cement-based rendering mortars are used as the protection layer in External Thermal Insulation Composite Systems (ETICS). Thermal insulations, when used in renovation, have a big impact on the reduction of CO2 emissions. The interactions with the environment changing temperature and relative humidity lead to thermal and hygral strains, which when restrained, may lead to stresses that can attain the tensile strength of the material causing then the mortar cracking. The eventual penetration of water inside the cracks may cause the insulator to lose partially its efficiency and durability. Here, we focus on the cracking development in the reinforced mortar layer using experimental techniques. To understand the crack initiation and propagation in the reinforced mortar layer, and the role of the fiber-glass mesh as reinforcement inside the mortar, a new mechanical setup is developed. This setup is designed to perform 3-point bending tests using in-situ X-ray tomography. The latter allows observing the cracks inside the mortar sample shedding lights on the reinforcement mechanisms of the fiber-glass mesh and its impact on the initiation and the propagation of the cracks. The role of the mortar heterogeneities is also analyzed and information about cracks characteristics such as openings and lengths may be extracted.