Study on the microstructure of thin-layer facade plasters of thermal insulating system during artificial weathering

Investigations involving the influence of simulate weathering on the microstructure of thin-layer plasters laid on foamed polystyrene are reported. In order to examine internal changes, two kinds of properties were examined in time per 100 cycles during 400 cycles. One of the properties is an open porosity connected with pore structure tested by the mercury intrusion method (MIP), and total porosity examined by helium intrusion technique (HIP). The other property is mineral composition analyzed on X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results have shown that changes of porosity, pore structure and chemical microstructure of plasters occured after successive weathering. In tested plasters, greater changes were noticed above the gaps of thermal insulation boards than beyond them. Porosimetry tests resulted in greater variations of open porosity over the gaps. Similarly, higher amounts of calcium carbonate were found in plasters and background mortars in places over the gaps of polystyrene boards.