The quantification of physico-mechanical properties and durability of onyx-travertines from Santa Ana de los Rios de Cuenca, Ecuador

Abstract

In this study, physico-mechanical properties and durability of 4 onyx-travertines from Sinincay (Ecuador) were investigated. These onyx-travertines are commonly used for decorative purposes in buildings in the Historic Center of Santa Ana de los Rios de Cuenca. The aim of this work was to characterize these stones and determine the variation of their physico-mechanical properties, such as mass loss and water absorption, after being subjected to four durability tests: salt crystallization (S-C), freeze-thaw (F-T), thermal shock (T-S) and acid attack (A-A). In addition, Scanning Electron Microscopic (SEM) analyses were carried out to record weathering patterns and understand the deterioration mechanism. Results show that these stones' sedimentary structure is stratified. Two specimens exhibit geometrical features consistent with porous laminated facies and the remaining two have slightly porous cryptolaminated ones. Facies' structure orientation is also found to determine mechanical strength, exhibiting the normal to lamination orientation the lowest value. As for durability, the statistical interpretation of the results suggests that the level of severity of each test follows S-C > F-T > A-A > T-S. In addition, laminated facies are more vulnerable to accelerated aging tests. Impact of S-C, F-T and T-S tests is mainly explained by differences in porosity and damage produced by A-A is related to the available effective area for the reaction to take place. Thus, the onyx-travertine is more than a wonderful material, it represents an interesting case study for development of future research on heritage stone in Ecuador and the world by employing normalized tests that are rarely used or published.