Physical and mechanical properties of Ignimbrite from Arucas, Canary Islands

Abstract

This research is a contribution to the mineralogical and physical–mechanical characterisation of the ignimbrites from Arucas (Gran Canaria Island), used as building stones under the commercial names of "Piedra de Arucas Lomo Tomás de León" and "Piedra de Arucas Rosa Silva". This stone has been used for more than five hundred years and is part of the local architectural heritage, but has also been exported to other regions of the world. To perform this characterisation, a chemical analysis was carried out using X-ray fluorescence (XRF), mineralogical and petrographic properties were obtained using polarised optical microscopy (POM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Several physical properties were determined, namely: apparent density (AP), open porosity (OP), water absorption at atmospheric pressure (WA), water absorption by capillarity (WAC), ultrasound velocity (PWV) and colour. Mechanical properties were obtained through compressive strength (UCS), bending strength (BS), point load (PLT), indirect tensile (BTS) and energy at break (IR) tests. To evaluate the durability, the samples were subjected to salt crystallisation cycles (CS), SO2 action (AS) and salt spray (SS) and the abrasion resistance (AR) was determined. The results obtained show that, although both samples share the same lithology and belong to the same geological formation (Salic Formation, trachytic-phonolitic), they show very different properties. Porosity stands out as the property with the higher difference among the two studied varieties. Therefore, the application of these ignimbrites should be done accordingly, avoiding environmental conditions that promotes the wettability and/or the salt crystallisation.