The paper presents a study on the performance of some current consolidation products when applied in volcanic tuffs from Azores. Two blocks were taken from a deposit, coming from dismantled buildings, in the Terceira Island. Three consolidating products, one ethyl silicate, one epoxy and one acrylic resins and two application methods, by brushing and by capillary absorption, were selected. The study consisted of characterising a set of specimens before and after treatment aiming at obtaining information for assessing the effectiveness, and durability of the tested products. Mechanical properties, such as the drilling resistance and ultrasonic velocity (P wave), were taken into account in the assessment of products performance. Salt crystallisation was used for comparing treated and non-treated specimens in order to get an insight into the treatments long term behaviour.
The volcanic tuffs here studied were once used as dimension stone in buildings of unknown type and importance. Similar materials can be found in buildings of cultural significance where decay may force the implementation of conservation and restoration actions. The high porosity and low mechanical resistance of these tuffs lead to fast decay rates and consolidation may be required to counteract the acting decay processes. The study reported in this paper aimed at contributing to assess the effectiveness of some current stone consolidants and to get an insight in their long term behaviour in this particular stone material. The data presented here focus mainly the physical and mechanical characterisation of treated and non treated specimens, with special attention to the ultrasonic velocity and the drilling resistance. The consolidants include one ethyl silicate, and one epoxy and one acrylic resins, all of them with widespread use in monuments conservation.
Terceira Island belongs to Azores Archipelago situated near the Mid-Atlantic Ridge. Zbyszewski et al (1971) state that Terceira's main rocks are lava flows, such as basalts, trachytes and andesites, tuffs and ignimbrites. The latter two are the main building stones of pyroclastic origin. Several outcrops with volcanic tuffs show well-defined bedding planes. The samples tested in this study were collected in a deposit of blocks from dismantled buildings, in Praia da Vitória, Terceira Island. They correspond to the grey and brown types of tuffs.
Two blocks, named Band C, were cut in 112 specimens of cubic and prismatic shapes, with sizes: 5×5×10 [cm]; 5×5×5 [cm], 2.5×2.5×10 [cm], and 5×5×1 [cm]. The specimens were prepared without having any concern about anisotropy. However, many of them show lineations of clasts more or less parallel to their faces, meaning that bedding planes are approximately coincident with the prismatic faces. The laboratory tests were performed to characterise mechanical and hygric parameters according to ISRM (1981) and RILEM (1980) suggested methods. Application methods and absorbed amounts All applications were carried out at laboratory environment conditions. The three consolidants were applied by brushing on top of cubic specimens, while TG and PB were also applied by capillary absorption in some prismatic specimens.
