Damaged and Healthy Ignimbrites from the Surroundings of Morelia, Mexico; Uses for Restoration of the Colonial Inheritance

Abstract

The historic centre of Morelia, Mexico has over a thousand architectonic monuments catalogued. This allowed the city to become part of the list of world heritage site by UNESCO in the 90s of 20th century. The location of Michoacan, the State in which Morelia is the capital, allowed it to have an abundance of acidic extrusive igneous rocks such as the ignimbrite quarry stones. The ignimbrites were carved into blocks to build vertical elements such as the walls and the foundations. Cases of carved and sculpted blocks were not designed to be coated with mortars, non sculpted ignimbrites were used in the case of buildings that were designed to carry coatings mortars and/or paintings; constructions in which the time to build was small, the money was scarce or the destination was not particularly important. These monuments are colonial ones, the European brought building techniques in vogue in Europe; books written by Vitruvius, Palladio and Alberti were adapted to local conditions as ethnic and regional materials and costumes. Ignimbrites, after exposed to the environment have begun to damage on the blocks posted as facades. In cases of severe exfoliation or acute devitrifying of the matrix in the ignimbrites, it is necessary to replace the damaged blocks by healthy rocks earned from the quarry stones of the surrounding places but it has not been able to find full match between rocks; sometimes do not match the resistance, porosity, durability, color or geographical location in the historical archives. Results to date show matches and the discrepancies between the different quarry stones and uses that are targeting in heritage buildings.