Additions of Minerals in Clays of Morelia Region, Mexico: Effects on Volumetric Stabilization and Color
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Additions of Minerals in Clays of Morelia Region, Mexico: Effects on Volumetric Stabilization and Color W. Martínez Molina1, J. L. Ruvalcaba Sil2, E. M. Alonso Guzmán1, A. Flores Rentería1, M. Manrique Ortega2, A. A. Torres Acosta3 1 Facultad de Ingeniería Civil de la Universidad Michoacana de San Nicolás de Hidalgo, Edificio F de Ciudad Universitaria, Avenida Francisco J. Mújica s/n, Colonia Felícitas del Río, Morelia, Michoacán, Mexico CP 58040, Mexico. e-mail: [email protected]; [email protected] 2 Instituto de Física, Universidad Nacional Autónoma de México UNAM, Mexico. e-mail: [email protected] 3 Universidad Marista de Querétaro, Querétaro Centro Histórico, CP 76000, Querétaro, Mexico. ABSTRACT Clays were used intensively in cultural heritage’s monuments and objects. Conservation procedures can be performed specifically for earthen materials using stabilized clays, considering that the aesthetic features must be preserved in order to avoid drastic differences and the lost of their patrimonial value. This work presents the study of the mechanical behavior of clay stabilized with different materials following the norm ASTM D 6276 – 99ª, for lime stabilization. The effects of other stabilizers on the clay were studied as well. For these purposes, lime, gypsum, Portland cement (type II), sodium hydroxide, and dehydrated cactus fibers of white cactus opuntia in concentrations of 2, 4, 6, 8 and 10 wt% were added to a clay from Morelia region. Atterberg limits were determined to calculate the linear and volumetric stabilization. The best volumetric stabilization values were chosen to prepare samples to measure the mechanical behavior under compression, tension and flexion strengths. Colorimetric measurements were also performed on the stabilized clays to determine the best preparation with the most suitable aesthetic qualities to perform conservation treatments on monuments and cultural heritage constructions made with earthen materials. The highest values for compression were observed for gypsum and mucilage additions while the highest tension was obtained for mucilage ones. Gypsum addition had the bigger rupture module under flexion. On the other hand, the color of the stabilized clay is closer to the original clay color for cement, lime and mucilage preparations. INTRODUCTION In Michoacan region, Mexico, the Purepecha people developed, especially at the shores of the lakes of Patzcuaro, Zirahuen and Cuitzeo, where a significant concentration of historical constructions and monuments made of earthen materials (adobe) remain nowadays. Adobes were prepared using clays, very abundant in the 215
Pacific Coast of the country. The clays studied in this work are from the Santiago Undameo quarry, Michoacan, Mexico, at the shore of the Cointzio dam. Many of the historical buildings and monuments are still used for their original function: Churches, hospitals and housing. They are exposed to environmental conditions and the corresponding deterioration. For this reason, they required conservation
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