The role of clay minerals in the deterioration of stone was the focus of two papers in yesterday’s session of the 12th International Congress on Deterioration and Conservation of Stone. Here are the highlights.
“Hydric Swelling of Clays in Brownstone” Timothy Wangler, Elaine Ngo, and George W. Scherer.
Timothy Wangler discussed how swelling pressures of clay minerals could be measured in brownstone. Two methods were used. In the first laboratory method, brownstone was restrained between two platens then wetted. The resulting swelling exerted measurable forces on the platen. Alternately, a warping test was devised to again show the significance of clay swelling in stone deterioration. Wet/dry cycles cause stresses from the swelling of clays which result in patterns like mud cracking or spalling. Wangler and his colleagues are now working on swelling inhibitor treatments for stone.
“Role of Swelling clay minerals in the spalling decay mechanism of the Pierre du midi Limestone (south east of France)” by Jeremie Berthonneau