Investigation of some atmospheric effects in the laboratory tests on deterioration of andesite (Iscehisar-Turkey) used as the building stone of cultural heritages

Abstract

Natural stones are exposed to long-term atmospheric effects in accordance with the area that they are used in. They are affected not only by salt crystallization, freezing-thawing, and heat effect, but also by the emissions into the atmosphere (air pollution, several gases, and vapour). These effects may cause negative changes on both physico-mechanical properties and exterior appearances of natural stones. The present paper has aimed to point out some atmospheric effects and their consequences on the durability of the andesite (Iscehisar, Turkey) used as the building stones for cultural heritages. For this purpose, the characterization of the tested andesite was determined by various analytical techniques such as petrographic, mineralogical (polarizing microscope, SEM-EDX and XRD), chemical (XRF), physical, and mechanical tests. Subsequently, the changes on andesite caused from atmospheric pollution such as SO2, salt, and water vapour were investigated through several laboratory experiments. These ageing tests consisted of the determination of resistance to ageing by SO2 action in the presence of humidity, determination of resistance to ageing by salt mist, and determination of water vapour transmission properties. These experiments were performed with untreated and treated andesite samples with siloxane-based water repellent applied. The total porosity ratio of the andesite was 19.73%, and it shows pore size ranges between 0.01 and 100 μm. The change in the weight of resistance to ageing by salt mist experiment was 0.488% for the untreated andesite samples, and for the treated andesites, it was 0.285%. The treatments with water repellents could generally be considered successful concerning their influence on SO2, salt, and water vapour effect on the andesite samples. After the experiment of resistance to ageing by salt mist, the ultrasonic P-wave velocity decrease was determined for the untreated andesite samples as 1.34% and for the treated samples as 0.67%. Water repellent material on the tested andesite was decreased water vapour transmission by 57.07% on average.