Stone decay induced by fire on historic buildings: the case of the cloister of Lisbon Cathedral (Portugal)

• Published in: Building Stone Decay - From Diagnosis to Conservation Vol. 271; no. 1; pp. 87 - 98
• Main Author: Dionísio, A.
• Format: Book Chapter Journal Article
• Language: English
• Published: The Geological Society of London 2007; The Geological Society, London; Geological Society of London
• Series: Geological Society, London, Special Publications
• Subjects: Civil Engineering; Civil Engineering & Construction Materials; Patterns and monitoring of decay
• ISBN: 9781862392182; 1862392188
• ISSN: 0305-8719; 2041-4927
• DOI: 10.1144/GSL.SP.2007.271.01.10

Lisbon Cathedral, built in Late Romanesque style, is one of the most ancient Portuguese monuments. Its cloister was severely damaged by a fire that occurred in 1755 right after an earthquake. The aim of this investigation is to study stone thermal damage through the application of in situ and laboratory techniques. With this study it is possible to identify and characterize (chemically and mineralogically) the main thermal decay forms. Special attention is given to colour modification and granular disintegration. Through the application of an indirect ultrasound method it is verified that only a small number of stone blocks are relatively sound (11%). In terms of chromatic alteration, two factors are considered to explain heat-induced colour modification: the transformation of goethite into hematite and an increase in hematite single crystalline domains. It is also established that the most probable high-temperature range to which the cloister stones were subjected during the fire was 300–350 °C.