Leaching prediction for vertical test panels coated with plaster and mortars exposed under real conditions by a PHREEQC leaching model

A requirement of the Construction Products Regulation (CPR) in the European Union states that construction works must be designed in such a way that throughout their entire life cycle, they have no exceedingly high environmental impact. The objective of the current work was to simulate the leaching of selected metals and sulfate in vertical test panels (VTPs) covered by plaster and mortar. The investigation is based on 18-month leaching outdoor tests (LOT) under real weather conditions. A leaching model was developed using the geochemical model PHREEQC with the Lawrence Livermore National Laboratory (LLNL) thermodynamic data base and coupled with MATLAB in order to optimize the run-off and weather parameters. The model was calibrated by comparing the data from laboratory Dynamic Surface Leaching Tests (DSLT) with simulation results up to an acceptable fit. The parameters obtained were then used in the LOT simulations and validated. The model allows predictions on the substance discharge from various plasters and mortars under real weather conditions. Physical characteristics of the material (e.g., thickness and absorption capacity) play an important role in the leaching of substances in façades covered with plaster and mortar. The lower the thickness and absorption capacity of the material applied, the greater the run-off and discharge of leached substances.