Stresses Due to Physical and Chemical Actions in Polymer Coatings on a Concrete Substrate

Abstract

Polymer coatings on concrete surfaces repeatedly exhibit blisters, cracks or delaminations. Various processes had been proposed to explain the causes of such damage. However, the magnitude of stresses acting on the interface between coating and substrate is relatively unknown. This is particularly true for stresses caused by chemical and physical actions. In a theoretical and experimental research program an attempt is made to quantify such stresses. Two processes causing stresses are described, osmotic pressure and capillary pressure. Two test set-ups were developed to determine the magnitude of such stresses. The results so far show that osmotic processes and capillary suction can result in pressures up to 45 and 2 bar respectively acting on the interface between concrete and coating. But also smaller pressures may cause blisters or delaminations due to stress concentrations at local defects.