Abstract
The petrographic and petrophysical characteristics of three varieties of ignimbrites used in the architectural heritage of Arequipa (southwest Peru) are analyzed. The modal classification QAFP and TAS diagram discriminate their dacitic nature. Mercury injection porometry revealed very high porosity: 46.5% for white and beige ignimbrites, and 35.5% for the pink variety. Ignimbrites contain intrusions of vulcanodetrital fragments and vacuoles that influence their predominantly non-linear mechanical behavior. The results of water absorption by capillarity (C) and ultrasound pulse velocity (UPV) demonstrate a slight anisotropy for the beige variety and near isotropy for white and pink ignimbrites, which justify the randomness of the application of the ashlars in the masonry and in the selection of the faces to carve. Surfaces with hollows in the white and beige ignimbrites are the result of the erosion of the acicular pumice that fills the vacuoles.
Highlights
Arequipa ignimbrite began to be used in vaulted constructions in the 17th century [1], the city was founded in the middle of the 16th century during the Spanish viceroyalty
This result is associated with consolidation and compaction processes, which lead to sintering and compression of the pyroclastic material by quenching [32], which are conditioned by the crystallochemical composition of the glass phase [6]
In the ignimbrite varieties studied, differences in the petrological and physico-mechanical properties were detected, which enables them to be selected based on the destination of the ashlar in the building
Summary
Arequipa ignimbrite began to be used in vaulted constructions in the 17th century [1], the city was founded in the middle of the 16th century during the Spanish viceroyalty. The abundance of white ignimbrite called “sillar de Arequipa” [2] made it possible to cut ashlars, voussoirs and pavement tiles measuring 40 × 40 × 20 cm , which were dimensions based on the Spanish yard (vara de Castilla, 0.835905 m). The ignimbrites are associated with volcanic trends of variable petrological series in terms of their composition [4,5,6], which affects their petrophysical and mechanical properties. These properties are in turn conditioned by their degree of consolidation [7], which determines their suitability as construction materials [8,9,10]. Areas of the now-dormant quarry fronts are open to tourists
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