Studying the acoustic emission response of an Indian monumental sandstone under varying temperatures and strains

Study of rocks under high temperature and strain-rate condition can serve as vital information in the restoration process of fire damaged buildings. In this study, the mechanical response of thermally treated fine-grained Dholpur sandstone was observed under increasing strain rates. Dholpur sandstone, a popular construction material, has been used to build some of the iconic monuments in India, a list which includes the Parliament, House of Indian President and the Buddhist Stupas of Sanchi. Thermal treatment spanned across ten days which included heating of the samples (200, 400, 600, 800 and 1000 °C) for five days followed by cooling, in room condition, for the exact same duration. The samples were then tested to failure at three different strain rates (2 × 10−5, 1 × 10−4 and 2 × 10−4 S−1). The elastic modulus was measured using non-contact laser extensometer. Acoustic emission (AE) technique was used to observe the microcrack development under compressive loading. The results from AE were used to demarcate the various stress thresholds and the stress regimes. The result of the experimental analysis suggests that the strength and elastic properties of rocks tend to increase till 400-600 °C followed by a fall in the mechanical characteristics. Onset of plasticity can be observed at high temperature. Strength of the rocks decrease at high strain rates due to the influence of strain rate dependency. The threshold values follow the behaviour of the mechanical properties under the influence of temperature and strain rate.