Service life assessment of renders on the basis of changes of physical and mechanical properties during simulated weathering

The article presents a method for the estimation of service life of renders for selected physical and mechanical properties whereof values have been determined in the accelerated ageing tests. The ageing tests were performed in simulated conditions with 500 cycles, and for comparison, in natural conditions for the period of 2 years. To describe the ageing characteristics, specific qualities were applied for which the changes demonstrated a monotonic character and which enabled at the same time to determine a limit performance value, which is required when formulating models of durability. The above quality demonstrated changes in bulk density and adhesion to the substrate. Statistical models of durability based on time series were developed for those qualities. The optimal fit of the models was demonstrated by means of a statistical test confirming the normal distribution of random residuals. In addition to the description of the degradation process, a modified model of concrete surface degradation determining mass losses was adopted. The empirical values of such qualities as: compressive strength, porosity, adhesive strength and vapor permeability were used as auxiliary parameters of the model. The experimental verification of mass losses allowed for a successful application of the model. (C) 2019 Elsevier Ltd. All rights reserved.