Effect of chemical protective treatments on durability of building stones for used in restoration

ABSTRACT M.Sc. Thesis EFFECT OF CHEMICAL PROTECTIVE TREATMENTS ON DURABILITY OF DÖĞER TUFF FOR USED IN RESTORATION Özlem GÜVEN Afyon Kocatepe University Graduate School of Natural and Applied Sciences Department of Mining Engineering Supervisor: Assoc. Prof. Mustafa Yavuz ÇELİK The tuffs have been used as building stones since the Ottoman period in the Afyonkarahisar region. The historical buildings that were built with the Döğer tuffs and which have survived to the present day have started to decompose because of atmosphere and environmental factors and have been subjected to restoration process from time to time. Water is one of the most important reasons of deterioration of natural building stones. Water enters natural building stones in different ways. One of the most important of these ways is the capillary water absorption mechanism. Water entering in the natural building stones through capillary water absorption can lead to wetting-drying, freezing-thawing and salt crystallization. In this study, a 3-stage study was carried out in order to examine these deterioration mechanisms in the Döğer tuffs. In the first stage, chemical, petrographic-mineralogical (polarizing microscope, XRD), physico-mechanical properties and pore diameter distribution of material were determined. In the second step, aging tests such as water absorption due to capillary action, resistance to frost effects and determination of resistance to salt crystallization (with sodium chloride (NaCl) and sodium sulfate decahydrate (Na2SO410H2O) solution) were carried out in accordance with the relevant standards. The experiments were repeated on the treated samples with surface protection chemicals as well as untreated samples. The protective effect of surface protection chemicals was determined against the destructive damages of these tuffs. In the third stage, the amount of deterioration of the Döğer tuff samples was determined with the help of changes in some physical and mechanical parameters such as weight loss, ultrasound speed change and uniaxial compressive strength. In the freeze-thaw experiments, the mass loss value was 17.18% for the untreated samples and 5.73% for the treated samples. The compressive strength values were decreased by 11.44% in the untreated samples, whereas the compressive strength decreased by 9,55% in the untreated samples. In the NaCl solution, after the salt crystallization experiments, the compressive strength decreased by an average of 36.75% in the samples not applied the surface protection, whereas the compressive strength in the untreated samples decreased by 5. 61%. In the experiments conducted with Na2SO4 10H2O solution, the compressive strength decreased by 72.58% on the samples without surface protection, while the compressive strength increased by 1.79% in the samples with surface protection. According to the experimental studies, it can be said that if these tuffs are coated with a surface protective chemical, they will be more resistant to the aging effects. 2019, xv + 100 pages Keywords: Döğer tuff, Durability, Surface protect chemical, Restoration, Freeze-thaw, Salt crystallization, Water capillarit