An Assessment of Pore Size Distribution Changes of the Andesite (Iscehisar, Turkey) Used as Building Stone of Cultural Heritages in Relation to the Artificial Accelerated Ageing Factors

摘要

The aim of this study is to assess pore size distribution changes of the Iscehisar (Turkey) andesite in relation to the six artificial accelerated ageing factors such as salt crystallization, freezing-thawing, thermal shock, SO(2)action in the presence of humidity, water vapour transmission, and capillary water absorption. The andesite has a bimodal pore size distribution mainly between 0.1 and 2-3 mu m. This work found that artificial accelerated ageing factors have a significant influence on change in pore size distribution of andesite used as building stone. Among six artificial accelerated ageing tests, the highest porosity level recorded for the andesite was 15.603% in salt crystallization test, and the rate of increase of porosity was determined as 28.41%. The effects of all ageing tests resulted in a change in pore size distribution in the andesite. According to the experimental results, the porosity value decreased with the presence of crystallized salts in pores and increased with the growth of existing fissures and the expansion of the pores. These results concluded that the selection of stones for the restoration works of historic monuments or modern use should be made after performing than one destructive test to avoid anomalous results that may arise owing to the influence of individual ageing factors.