Chemical weathering of archaeological monuments and their conservation

Abstract

Physical weathering is caused by parameters such as water, temperature variations, salt laden winds etc Water : It acts as a good solvent and transporting agent. Capillary rise of salt solutions from ground into the stone surface gives rise to crystallization of the salts within the stone pore. The increase in volume of the crystallized salt, builds up stress and thus ruptures the rock. Contact of the stone surface leads to loss of stone minerals leaving the stone surface more porous and rough. At sub zero temperatures, the water within the pores can freeze and expand to about 9% thus leading to rupturing of the stone. Air: Strong winds laden with sand particles have an abrasive action on the monumental stone surface. It also acts as a transporting agent for the dust, micro flora, pollen micro soot etc. Temperature: It is an ever existing factor accompanying almost all processes and bearing on several properties. A rock is a poor conductor of heat and hence the differential thermal expansion between the surface and the crust leads to exfoliation and micro cracks.