An Influence of Thermally-Induced Micro-Cracking under Cooling Treatments: Mechanical Characteristics of Australian Granite

Badulla Liyanage Avanthi Isaka, Ranjith Pathegama Gamage, Tharaka Dilanka Rathnaweera, Mandadige Samintha Anne Perera, Dornadula Chandrasekharam and Wanniarachchige Gnamani Pabasara Kumari
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Badulla Liyanage Avanthi Isaka: Department of Civil Engineering, Monash University, Building 60, Melbourne, VIC 3800, Australia
Ranjith Pathegama Gamage: Department of Civil Engineering, Monash University, Building 60, Melbourne, VIC 3800, Australia
Tharaka Dilanka Rathnaweera: Department of Civil Engineering, Monash University, Building 60, Melbourne, VIC 3800, Australia
Mandadige Samintha Anne Perera: Department of Civil Engineering, Monash University, Building 60, Melbourne, VIC 3800, Australia
Dornadula Chandrasekharam: Indian Institute of Technology Hyderabad, Telangana 502285, India
Wanniarachchige Gnamani Pabasara Kumari: Department of Civil Engineering, Monash University, Building 60, Melbourne, VIC 3800, Australia

Energies, 2018, vol. 11, issue 6, 1-24

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.

Keywords: high temperature; cooling; mechanical properties; granite; acoustic emission; loading and unloading; microstructural analysis (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2018
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (7)

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