Microstructure of renovation plasters and their resistance to salt

•Durability of renovation plasters.•The resistance to salt crystallization.•Intensity of salts solutions.•Destructive effects of salts solutions.•Plasters with low porosity and monomodal pore size distribution. One of the most important factors which decide about the durability of the renovation plasters is the resistance to crystallization of salt which dissolves under the influence of moisture. This paper demonstrates the results of the research on the influence of the microstructure of pores in cement-lime mortars and their resistance to various cyclical salts. Six plasters differing in porosity and microstructure were selected for the study. The purpose of the study was to alternatively soak samples with three solutions of salts: NaCl at a concentration of 25.9%, Na2SO4 at 18.3% and NaNO3 at 45%, and then crystallize the salts. It was found that salts solutions have a various intensity of destructive effect on renovation plasters. It was demonstrated that the durability of plasters depends to a greater extent on the pore size distribution than on the total porosity Pc. Salts solutions do not have a destructive effect on plasters with a large variety of pores, whereas plasters with low porosity and monomodal pore size distribution were destroyed under the influence of Na2SO4 and NaNO3 solutions. Porosimetry and electron microscopy were used in the studies.