Overview and quality assessment of volcanic tuffs in the Mexican building heritage

Many cultural heritage sites in Mexico have been built with volcanic tuff rocks from the earliest Central American civilizations to the time of the Spanish conquest and up to the present. Throughout this long period of time, the stones have been subjected to progressive weathering as evidenced by different types of damage phenomenon such as scaling, sanding, crumbling, sugaring and salt efflorescence. This study utilizes a collection of 53 tuffs from different regions in Mexico that show a diverse range of colors, rock compositions and mineralogy, and heterogeneous rock fabrics indicative of their volcanic origin. Comprehensive investigations have been done that include detailed petrographic analyses, cathodoluminescence, clay mineral analyses, and the determination of a wide range of petrophysical properties (e.g., porosity, capillary water uptake, water absorption, sorption, hydric and thermal expansion, and mechanical properties). All analyzed data combined are used for derivation of some general trends concerning the suitability/durability of tuffs applied as natural building stones.