Paper contribution

Damage characteristics of thermally treated sandstone using the block punch index test

Sourav Das; Ratan Das; Debasish Mazumder

Proceedings
EUROCK 2026
Pages
315-323
Submitted
28 January 2026
Accepted
15 June 2026
Published
12 August 2026

Summary

Abstract

The strength characteristics of rock represent an important parameter in geotechnical and engineering applications. While the uniaxial compressive strength (UCS) test is widely utilized, it requires extensive sample preparation and difficulties in evaluating the strength properties of weak, foliated rocks. As an alternative, the Block Punch Index (BPI) test is suitable for thinly bedded rocks, however effect of BPI on thermally treated rock remained unexplored. This research investigates BPI strength variations on calcareous sandstone that have been heated under range of temperatures upto 800° C, maintained in a muffle furnace for 6 hours, and then cooled to room temperature. The results indicated that with the increase in temperature, the BPI value of the rock decreases, from 15.13 MPa at room temp to 5.75 MPa at 800 °C. A maximum BPI strength around 22.21 MPa was recorded for the sample treated at 500 °C, as grain expansion fills pores and fissures, making the rock denser and thereby increasing the strength of the specimen. Beyond that, the strength reduction continued till 800° C due to the development of microcracks, as confirmed with linear crack density analysis of the microphotographs. The mechanical degradation of the rock exhibited a non-linear pattern across the entire temperature range tested. Moreover, the porosity of the specimen has increased from 3.16% (room temperature) to 11.76% at 800 °C. In addition, colour transitions from grey to rust red were observed, due to iron oxidation. Furthermore, an endothermic peak was observed around ~760-780 °C, which must be due to the decomposition of CaCO₃ into CaO. These findings will provide essential information into the physico-mechanical properties of sandstone, which has practical implications for engineering applications such as geothermal energy extraction, nuclear waste disposal, and underground coal gasification projects

Contributors

Authors

  1. Sourav Das Rock Mechanics and Rock Engineering Laboratory, Department of Geology, Cotton University, Guwahati, Assam 781001, India ORCID 0000-0002-9623-9408
  2. Ratan Das Rock Mechanics and Rock Engineering Laboratory, Department of Geology, Cotton University, Guwahati, Assam 781001, India
  3. Debasish Mazumder Rock Mechanics and Rock Engineering Laboratory, Department of Geology, Cotton University, Guwahati, Assam 781001, India

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