An influence of thermally-induced micro-cracking under cooling treatments: mechanical characteristics of Australian granite

Isaka, Badulla Liyanage Avanthi and Gamage, Ranjith Pathegama and Rathnaweera, Tharaka Dilanka and Perera, Mandadige Samintha Anne and Chandrasekharam, Dornadula and Kumari, Wanniarachchige Gnamani Pabasara (2018) An influence of thermally-induced micro-cracking under cooling treatments: mechanical characteristics of Australian granite. Energies, 11 (6 - Article 1338).

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Abstract

The aim of this study is to characterise the changes in mechanical properties and to provide a comprehensive micro-structural analysis of Harcourt granite over different pre-heating temperatures under two cooling treatments (1) rapid and (2) slow cooling. A series of uniaxial compression tests was conducted to evaluate the mechanical properties of granite specimens subjected to pre-heating to temperatures ranging from 25–1000◦C under both cooling conditions. An acoustic emission (AE) system was incorporated to identify the fracture propagation stress thresholds. Furthermore, the effect of loading and unloading behaviour on the elastic properties of Harcourt granite was evaluated at two locations prior to failure: (1) crack initiation and (2) crack damage. Scanning electron microscopy (SEM) analyses were conducted on heat-treated thin rock slices to observe the crack/fracture patterns and to quantify the extent of micro-cracking during intense heating followed by cooling. The results revealed that the thermal field induced in the Harcourt granite pore structure during heating up to 100◦C followed by cooling causes cracks to close, resulting in increased mechanical characteristics, in particular, material stiffness and strength. Thereafter, a decline in mechanical properties occurs with the increase of pre-heating temperatures from 100◦C to 800◦C. However, the thermal deterioration under rapid cooling is much higher than that under slow cooling, because rapid cooling appears to produce a significant amount of micro-cracking due to the irreversible thermal shock induced. Multiple stages of loading and unloading prior to failure degrade the elastic properties of Harcourt granite due to the damage accumulated through the coalescence of micro-cracks induced during compression loading. However, this degradation is insignificant for pre-heating temperatures over 400◦C, since the specimens are already damaged due to excessive thermal deterioration. Moreover, unloading after crack initiation tends to cause insignificant irreversible strains, whereas significant permanent strains occur during unloading after crack damage, and this appears to increase with the increase of pre-heating temperature over 400◦C. © 2018 by the authors.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
Faculty/School / Institute/Centre: Current - Faculty of Health, Engineering and Sciences - School of Agricultural, Computational and Environmental Sciences
Date Deposited: 01 Mar 2019 04:55
Last Modified: 05 Mar 2019 01:10
Uncontrolled Keywords: acoustic emission; cooling; granite; high temperature; loading; mechanical properties; microstructural analysis; unloading; acoustic emissions; compression testing; concrete aggregates; crack initiation; cracks; deterioration; elasticity; heating; scanning electron microscopy; compression loading; fracture propagation; irreversible strain; loading and unloading; mechanical characteristics; uni-axial compression tests; acoustic emission testing
Fields of Research : 09 Engineering > 0914 Resources Engineering and Extractive Metallurgy > 091402 Geomechanics and Resources Geotechnical Engineering
Identification Number or DOI: 10.3390/en11061338
URI: http://eprints.usq.edu.au/id/eprint/35965

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