Weathering effects on physical–chemical properties of external plaster mortars exposed to different environments

• All physical and chemical properties were changed under ageing, both in simulated and natural environment.
• Compression strength, vapour permeability and total porosity are getting worse the most during weathering.
• Changes of porosity and density are inconsistent, depend on a kind of plaster mortar binder.
• Lower amount of 0.1–1.0 μm pores and lower initial absorption below 9% influence greater on weathering resistance in time.
• For plasters on resin binders, the ageing does not result in significant changes, which proves their greater resistance.

The paper presents results of a research on various types of external plasters, traditional and thin-layered, subjected to ageing tests, both in simulate and natural environment. A special ageing chamber for simulating of climate influences on building materials was implemented. The aim of the carried out study was to investigate a way of influence of artificial ageing and weathering process on basic physical and mechanical properties and to provide a comparison between them. Simultaneously attention was focused on the pore microstructure which was analysed by the mercury intrusion method (MIP). Additionally, the specimens were characterized from the crystal-chemical (X-ray diffraction, XRD), chemical (TG analysis) and morphological (SEM) point of view. On this ground ageing characteristics of the tested materials were possible to be defined, which describe occurred changes and can be useful for durability assessment. The results show that all tested properties were changed under ageing, both in simulate and natural environment.