Abstract

The mechanical behaviour of rocks is one of the main research topics in rocks mechanics. More specifically, there is a large body of scientific literature focused on the effect of high temperatures on rock properties. Recent fires in tunnels and historic monuments have revived interest in this topic. Most of these studies are focused on the evaluation of the variation of strength, deformability, and physical properties against temperature. Obviously, the general conclusion of these studies is that strength decreases, and deformability increases, as the target temperature increases. However, there is usually for each rock a temperature threshold (TT) at which these characteristics change sharply. The changes show different behaviour. This paper focuses on the study of a temperature threshold of a limestone from the eastern Spain and its behaviour after exposure to high temperature. Samples of this rocks are exposed to different target temperatures (i.e. 200, 400, 600 and 800 °C) and their properties such as porosity, density, unconfined compressive strength, and Young modulus are obtained. The studied limestones exhibit different TT and differing developments of these properties after heating. A comprehensive compilation of relevant topics is performed to compare the TT of different types of sedimentary rocks with that tested in this work.

1 Introduction

Analysing the mechanical behaviour of rocks subjected to high temperatures is an issue of interest for evaluating the consequences of a fire in historical monuments and infrastructures, and assessing geothermal energy or the use of these materials in storage of radioactive waste.

Research has generally focused on the variations in the most commonly studied properties: porosity; density; compressive strength; and the elastic modulus. Many publications have discussed the relationship of these properties with the maximum temperature exposure of the rock and have even studied the relationships between them.

It has been shown that porosity increases with the target temperature (Yavuz, Demirdag and Caran, 2010; Brotóns et a.l, 2013; Wu et al., 2013; Tian, Ziegler and Kempka, 2014). Density, strength, and the deformability parameters decrease as temperature increases (Zhang, Mao and Lu, 2009; Ranjith et al., 2012; Ding et al., 2016). Some authors, have analysed the type of breakages in the samples (Chen et al., 2009; González-Gómez et al., 2015; Lü et al., 2017) and changes in colour and appearance (Koca et al., 2006; Kompaníková et al., 2014) produced by high temperatures. Furthermore, other authors (Simmons and Cooper 1978; Peng et al., 2019;) examined rock samples after several heating and cooling cycles, concluding that the number, width and length of thermally induced microcracks significantly increase.

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