Key Takeaways & Executive Findings
- •• Chlorite, amphibole, and altered plagioclase are highly microwave-sensitive, showing rapid heating (>2.5 °C/s) and violent rupture. • Surface temperature non-uniformity (VT) evolves through increasing, decreasing, and stabilizing phases, reflecting heat accumulation and transfer dynamics. • Temperature gradients spatially correlate hotspots with rupture points, with shallow melting affecting surface temperature distribution. • Findings enable prediction of microwave heating in hard rocks and deepen understanding of microwave-induced weakening mechanisms.
Abstract
Microwave fracturing offers significant potential for efficient hard rock fragmentation. This study investigates real-time heating and fracture characteristics of ten granitoid minerals under 2 kW microwave irradiation for 3 min. Chlorite, amphibole, and altered plagioclase were identified as highly microwave-sensitive, exhibiting high mass and P-wave velocity decay, rapid heating rates (>2.5 ℃/s) and violent rupture. Mineral surface temperature non-uniformity, quantified by the coefficient of variation (VT), evolved through distinct increasing, decreasing, and stabilizing phases, reflecting shifts in dominance between heat accumulation and transfer. Temperature gradients revealed the spatial relationship between hotspots and rupture points, with shallow melting influencing surface temperature distribution. Undamaged minerals exhibited significant temperature gradient spatiotemporal variability but ultimately stabilizing. These results enable prediction of microwave heating behavior in hard rocks containing analogous minerals and enhance our understanding of microwave-induced weakening mechanisms.
1. Introduction
Deep resource exploitation in mining and tunneling faces challenges due to the non-linear strength increase of hard rock with depth and limitations of traditional mechanical breakage methods, including high ground disturbance and rapid tool wear, leading to inefficient excavation. Microwave-assisted breaking presents a promising alternative, offering rapid heating and precise control.
While microwave fracturing feasibility is established, the basic weakening mechanisms remain unclear. Researchers have consistently identified the dielectric properties of rocks as the primary factor governing their heterogeneous microwave response. However, the inherent heterogeneity of rocks, arising from variations in constituent mineral species, structure, distribution, and grain size, presents a significant challenge: studying the bulk dielectric properties of rocks alone offers limited insight into the fundamental mechanisms governing localized heating and damage initiation. Therefore, investigating individual rock-forming minerals is essential to understand the inhomogeneous heating and microwave-induced fracturing mechanisms.
Mineral microwave sensitivity classifications include chemical groupings and optical analogies (dark minerals absorb better). However, these face limitations: chemical classifications lack universality (e.g., magnetite vs. hematite), and optical analogies are complicated by dependencies on crystal structure and elemental composition within mineral groups. Direct dielectric property measurement offers accuracy but is challenged by potential errors, especially for high-loss minerals using common techniques like resonant cavity. Consequently, microwave heating rate tests are widely adopted for quantifying mineral absorption. Critically, while measuring bulk heating, this method inherently obscures the spatiotemporal evolution of temperature fields and the dynamic interplay between localized heating and the initiation and progression of damage modes (e.g., cracking, melting) within individual minerals.
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BAI Yan-bo, YANG Ben-gao, WANG Jing-yu, XIE Jing, TANG Rui-feng, GAO Ming-zhong, YUAN Liang (2026). Heating and fracture spatiotemporal evolution characteristics of key granite minerals under microwave irradiation. Journal of Central South University. https://doi.org/10.1007/s11771-026-6207-4
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Frequently Asked Questions
What are the key granite minerals that are highly sensitive to microwave irradiation?
Chlorite, amphibole, and altered plagioclase were identified as highly microwave-sensitive, exhibiting rapid heating rates (>2.5 °C/s) and violent rupture under 2 kW microwave irradiation for 3 minutes.
How does surface temperature non-uniformity evolve during microwave irradiation?
The coefficient of variation (VT) of surface temperature evolves through distinct increasing, decreasing, and stabilizing phases, reflecting shifts in dominance between heat accumulation and transfer.
What is the significance of temperature gradients in microwave-induced fracturing?
Temperature gradients reveal the spatial relationship between hotspots and rupture points, with shallow melting influencing surface temperature distribution, which is crucial for understanding damage initiation.
How can these findings be applied in engineering practice?
The results enable prediction of microwave heating behavior in hard rocks containing analogous minerals, enhancing the understanding of microwave-induced weakening mechanisms and aiding in efficient hard rock fragmentation.
What is the DOI of this research article?
The DOI is 10.1007/s11771-026-6207-4.
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