微波照射下砂浆-骨料多场耦合的数值研究

Numerical analysis of multi-field coupling between mortar-aggregate under microwave radiation

摘要

新建筑的建造和旧建筑的拆除产生了大量废弃混凝土，从废弃混凝土中提取再生骨料已成为一种缓解资源危机、实现骨料循环利用的方案。微波加热因其选择性加热、高效、绿色的特点被逐渐应用于再生骨料的回收中。为了探究微波照射下砂浆-骨料沿界面分离与多场耦合之间的关系，利用COMSOL Mulitphysics软件建立了三维砂浆-骨料二相模型，分析了电磁场、温度场、应力场的分布情况。通过与微波加热试验对比，验证了数值分析的可靠性。数值模拟结果表明:电场强度和温度梯度在砂浆-骨料界面处达到最大值；骨料的外侧受拉，内侧受压。加热条件为3 kW，200 s时，在砂浆-骨料界面处，第一主应力超过砂浆的极限抗拉强度，界面处出现裂纹，随着时间的延续，裂纹逐渐从界面处向试件边缘扩展并相互连接，最终砂浆与骨料在界面处发生分离。

Abstract

The construction of new buildings and the demolition of old buildings have led to significant amounts of waste concrete. Therefore, extracting recycled aggregates from this waste concrete has emerged as a solution to mitigating resource crisis and achieving aggregate recycling. Microwave heating has been gradually applied to the recovery of recycled aggregates due to its characteristics of selective heating, high efficiency, and environmental friendliness. In order to investigate the relationship between mortar-aggregate interface separation and multi-field coupling under microwave irradiation, a three-dimensional mortar-aggregate biphasic model was established using COMSOL Mulitphysics software, the distribution of the internal electromagnetic field, temperature field, stress field was analyzed, and the reliability of numerical analysis was verified through microwave heating experiments. The numerical simulation results indicate that the electric field intensity and temperature gradient reach their maximum values at the mortar-aggregate interface. The outer side of the aggregate is subjected to tension, while the inner side is subjected to compression. Under heating condition of 3 kW, 200 s, the first principal stress exceeds the ultimate tensile strength of the mortar at the mortar-aggregate interface, and cracks appear at the interface. With the passage of time, the cracks gradually propagate from the interface to the edge of the specimen and connect with each other, eventually leading to the separation of the mortar and aggregate at the interface.

关键词

微波 / 骨料 / 多场耦合 / 温度 / 热应力

Key words

microwave / aggregate / multi-field coupling / temperature / thermal stress

参考文献

[1] 肖建庄, 马旭伟, 刘琼, 等. 全再生混凝土概念的衍化与研究进展[J]. 建筑科学与工程学报, 2021, 38(2): 1-15.

[2] XIAO Jianzhuang, MA Xuwei, LIU Qiong, et al. Evolvement and research progress of concept for full recycled concrete[J]. Journal of architecture and civil engineering, 2021, 38(2): 1-15(in Chinese).

[3] DIMITRIOU G, SAVVA P, PETROU M F. Enhancing mechanical and durability properties of recycled aggregate concrete[J]. Construction and building materials, 2018, 158: 228-235.

[4] KIM Y, HANIF A, USMAN M, et al. Slag waste incorporation in high early strength concrete as cement replacement:environmental impact and influence on hydration & durability attributes[J]. Journal of cleaner production, 2018, 172: 3056-3065.

[5] GRABIEC A M, KLAMA J, ZAWAL D, et al. Modification of recycled concrete aggregate by calcium carbonate biodeposition[J]. Construction and building materials, 2012, 34: 145-150.

[6] LAW M C, LIEW E L, CHANG S L, et al. Modelling microwave heating of discrete samples of oil palm kernels[J]. Applied thermal engineering, 2016, 98: 702-726.

[7] LIU H L, E J Q, DENG Y W, et al. Experimental study on pyrolysis characteristics of the tobacco stem based on microwave heating method[J]. Applied thermal engineering, 2016, 106: 473-479.

[8] 高经纬, 程绍桐, 范立峰. 加热方式对花岗岩力学性能影响的试验研究[J]. 应用力学学报, 2024, 41(3): 567-574.

[9] GAO Jingwei, CHENG Shaotong, FAN Lifeng. Effects of heating methods on the mechanical properties of granite[J]. Chinese journal of applied mechanics, 2024, 41(3): 567-574(in Chinese).

[10] 邵珠山, 魏玮, 陈文文, 等. 微波加热岩石与混凝土的研究进展与工程应用[J]. 工程力学, 2020, 37(5): 140-155.

[11] SHAO Zhushan, WEI Wei, CHEN Wenwen, et al. Research progress and industrial applications of microwave heating processing on rock and concrete[J]. Engineering mechanics, 2020, 37(5): 140-155(in Chinese).

[12] TEIMOORI K, COOPER R. Multiphysics study of microwave irradiation effects on rock breakage system[J]. International journal of rock mechanics and mining sciences, 2021, 140: 104586.

[13] CHOI H, LIM M, CHOI H, et al. Using microwave heating to completely recycle concrete[J]. Journal of environmental protection, 2014, 5(7): 583-596.

[14] 魏玮, 张宏亮, 邵珠山, 等. 微波和传统加热下混凝土劈裂抗拉性能分析[J]. 工程力学, 2024, 41(5): 134-145.

[15] WEI Wei, ZHANG Hongliang, SHAO Zhushan, et al. Analysis of splitting tensile properties of concrete under microwave and conventional heating conditions[J]. Engineering mechanics, 2024, 41(5): 134-145(in Chinese).

[16] WEI W, SHAO Z S, QIAO R J, et al. Workability and mechanical properties of microwave heating for recovering high quality aggregate from concrete[J]. Construction and building materials, 2021, 276: 122237.

[17] CHEN W W, SHAO Z S, WEI W. Experimental study of the heating potential of mortar-aggregate under microwave irradiation[J]. Journal of materials in civil engineering, 2021, 33(7): 04021153.

[18] EVERAERT M, STEIN R, MICHAUX S, et al. Microwave radiation as a pre-treatment for standard and innovative fragmentation techniques in concrete recycling[J]. Materials, 2019, 12(3): 488.

[19] LIPPIATT N, BOURGEOIS F. Investigation of microwave-assisted concrete recycling using single-particle testing[J]. Minerals engineering, 2012, 31: 71-81.

[20] HAQUE K E. Microwave energy for mineral treatment processes-a brief review[J]. International journal of mineral processing, 1999, 57(1): 1-24.

[21] 张鹏举. 微波照射下不同湿度混凝土热力响应研究[D]. 西安: 西安建筑科技大学, 2021.

[22] LIANG C G, GUO Z S, YUE X, et al. Microwave-assisted breakage of basalt:a viewpoint on analyzing the thermal and mechanical behavior of rock[J]. Energy, 2023, 273: 127225.

[23] 周航, 邵珠山, 乔汝佳, 等. 工业微波照射下混凝土砂浆-骨料界面力学性能与多场效应数值分析[J]. 材料科学与工程学报, 2023, 41(1): 30-38.

[24] ZHOU Hang, SHAO Zhushan, QIAO Rujia, et al. Numerical analysis on mechanical properties and multi-field effects of concrete mortar-aggregate interface under industrial microwave irradiation[J]. Journal of materials science and engineering, 2023, 41(1): 30-38(in Chinese).

[25] 李勇. 微波场中混凝土劣化机理研究[D]. 西安: 西安科技大学, 2017.

[26] AKBARNEZHAD A, ONG K C G, ZHANG M H, et al. Microwave-assisted beneficiation of recycled concrete aggregates[J]. Construction and building materials, 2011, 25(8): 3469-3479.

[27] PITTS M. Thermal properties of the Cobourg limestone[D]. Kingston:Queen's University, 2017.

[28] MOUNANGA P, KHELIDJ A, BASTIAN G. Experimental study and modelling approaches for the thermal conductivity evolution of hydrating cement paste[J]. Advances in cement research, 2004, 16(3): 95-103.

[29] TANG B N, ZHU C Q, XU M, et al. Thermal conductivity of sedimentary rocks in the Sichuan Basin, Southwest China[J]. Energy exploration & exploitation, 2019, 37(2): 691-720.

[30] HASSANI F, NEKOOVAGHT P M, GHARIB N. The influence of microwave irradiation on rocks for microwave-assisted underground excavation[J]. Journal of rock mechanics and geotechnical engineering, 2016, 8(1): 1-15.

[31] ZEIML M, LACKNER R, PESAVENTO F, et al. Thermo-hydro-chemical couplings considered in safety assessment of shallow tunnels subjected to fire load[J]. Fire safety journal, 2008, 43(2): 83-95.

[32] ZHU J Y, YI L P, YANG Z Z, et al. Three-dimensional numerical simulation on the thermal response of oil shale subjected to microwave heating[J]. Chemical engineering journal, 2021, 407: 127197.

[33] FIA A Z, AMORIM J. Heating of biomass in microwave household oven-a numerical study[J]. Energy, 2021, 218: 119472.

[34] MOHD MOKHTA Z, ONG M Y, SALMAN B, et al. Simulation studies on microwave-assisted pyrolysis of biomass for bioenergy production with special attention on waveguide number and location[J]. Energy, 2020, 190: 116474.

[35] HUANG J X, XU G, HU G Z, et al. A coupled electromagnetic irradiation, heat and mass transfer model for microwave heating and its numerical simulation on coal[J]. Fuel processing technology, 2018, 177: 237-245.

[36] HONG Y D, LIN B Q, LI H, et al. Three-dimensional simulation of microwave heating coal sample with varying parameters[J]. Applied thermal engineering, 2016, 93: 1145-1154.

[37] CHEN F Y, WARNING A D, DATTA A K, et al. Susceptors in microwave cavity heating:modeling and experimentation with a frozen pie[J]. Journal of food engineering, 2017, 195: 191-205.

[38] PITCHAI K, CHEN J J, BIRLA S, et al. Modeling microwave heating of frozen mashed potato in a domestic oven incorporating electromagnetic frequency spectrum[J]. Journal of food engineering, 2016, 173: 124-131.

[39] XIAO Y H, SHAO Z S, WEI W, et al. Study on mechanism of strength weakening of concrete subjected to microwaves in microwave-assisted concrete recycling[J]. International journal of heat and mass transfer, 2023, 213: 124353.

[40] BRU K, TOUZÉ S, BOURGEOIS F, et al. Assessment of a microwave-assisted recycling process for the recovery of high-quality aggregates from concrete waste[J]. International journal of mineral processing, 2014, 126: 90-98.

基金资助

国家自然科学基金青年项目(12202333)

中国博士后科学基金资助项目(2021MD703868)