Mechanical and physical properties of two volcanic tuffs used in traditional canary constructions

Abstract

The volcanic stones, especially basalts, phonolites and tuffs, are the most common material used in traditional buildings in Canary Islands. Masonries and decorative elements of façades were commonly made of this soft type of stones. However, in the last decade, the pathologic processes related to their degradation have become evident. The elimination of the render that preserve this stone to the exposition of the climatic agents is the main reason of such damages. This situation has provoked a disquieting deterioration of a huge number of buildings of the historic heritage of Gran Canaria. Hence, the search of solutions that afford to repair these constructions and so, guarantee their integrity is urgent. Regarding this, the materials analysis and characterization is essential to evaluate them and decide about the best options to preserve them. In this paper, we expose a part of the research project (mechanical and physical characterization) that goes on about these stone materials. The tuff quarries and outcrops had been largely studied from a geological point of view and from their engineering properties focused on mechanical and physical test and statistics, as well as their chemical or mineralogical analysis. In spite of their importance on the Canary Islands? heritage, there are not published researches of their properties and their relation to their use. Therefore, the main objective of this research is to study two types of volcanic tuffs used in Gran Canaria island building construction. These are a white-dark tuff used in Vegueta-Triana area from the 15th century (Las Palmas) named as ?Perojo? and a brown one used in San Francisco from 14-15th Century (Telde) named as ?Telde?. Both of them were obtained from masonries of buildings currently in restoration.