Abstract

GAMA-CASTRO, Jorge E et al. Architecture of earth: adobe as construction material in the Prehispanic epoch. Bol. Soc. Geol. Mex [online]. 2012, vol.64, n.2, pp.177-188. ISSN 1405-3322.

Adobe has been used as a building material for thousands of years by indigenous peoples of America, in the southwestern United States, Mesoamerica, and Andean South America. Currently, fifty percent of the houses in the world are built with soil-derived materials. These materials may thus represent a viable solution to the problem of homelessness, by proposing a means for low-cost self-built homes. However, a limitation to developing such an alternative is that the processing techniques of building materials made from soil are the result of empirical knowledge. Such knowledge is often unsystematic, varies in each culture and region, and lacks an interdisciplinary terminology, thus precluding the recognition of universal standards for technological evaluation. The aim of this paper is to contribute to the formal knowledge related to the intrinsic nature of one of the most widely used pre-Hispanic construction materials: adobe. In order to do so, techniques for the quantitative measurement of the characteristics and diagnostic properties of the material were implemented. For this purpose six samples of adobe were selected and analyzed from the pre-Hispanic archaeological sites Zethé and Sabina Grande, both located near Huichapan, Hidalgo. The samples of adobe were formally characterized by internationally accepted analytical methods used by the Society of Soil Science and by the American Society for Testing and Materials. Here, methods included routine physical and chemical analysis supplemented by selected tests, including: (i) quantitative determination of particle size, (ii) micromorphological analysis, (iii) X-ray diffraction, and (iv) X-ray fluorescence. The samples are characterized by the following variables: (i) predominance of a loamy matrix; (ii) low to moderate content of non-expansive clay; (iii) predominance of a high bulk density; (iv) a low coefficient of linear expansion; (v ) stable consistency; (vi) moderate water retention (33 and 1500 kPa); (vii) predominantly alkaline; (viii) low to moderate reaction to phenolphthalein; (ix) poor to moderately poor content of organic matter and total carbon; (x) low content of total CaO; (xi) sand fraction dominated by primary volcanic glass and minerals; (xii) clay fraction dominated by quartz, feldspar and halloysite; and (xiii) micromorphological and mineralogical composition similar to that of a volcanogenic alluvium. We consider that these characteristics give acceptable physical and mechanical building properties to the studied adobes. Furthermore, it is notable that the characteristics of the adobe samples are very similar to each other. This similarity suggests the likelihood that these materials were developed under controlled conditions. This specialization in adobe manufacture required a certain amount of knowledge concerning soil properties and their transformation into construction elements.

Keywords : adobe; earthen architecture; pre-Hispanic construction materials.

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