微波照射下砂浆的电磁响应与强度劣化规律试验研究

Experimental study on electromagnetic response and strength deterioration of mortar under microwave heating

摘要

微波作用下混凝土的破碎效率主要取决于砂浆的破碎，研究微波作用下砂浆强度劣化规律具有重要的意义。为了揭示微波作用下砂浆强度的劣化规律，首先对砂浆块体及其原材料的介电性能进行测试，介电性能是电磁能转化为热能的主要影响参数。借助矢量网格分析仪获得了水泥、砂子、水和砂浆块体的复介电常数，探讨了频率、温度等因素对介电常数和升温速率的影响，进一步分析了微波加热时长对不同强度等级砂浆抗压强度的影响。研究结果表明:温度对介电常数的影响较明显，随着温度的升高，水的介电性能明显降低。砂浆的强度越高，介电性能越强，升温速率越快。由升温规律、质量损失及抗压强度的变化规律综合分析表明，5 kW微波加热60 s后，M20、M25和M30这3种强度的砂浆内部裂纹均进入快速扩展阶段，强度明显降低。加热100 s后，3种砂浆的强度分别降低了25%、18%、16%。本研究可为微波破碎砂浆及强度弱化提供参考，进一步为微波法混凝土破碎技术的推广应用提供技术指导。

Abstract

The crushing efficiency of concrete under microwave action mainly depends on the crushing of mortar，so it is of great significance to study the deterioration law of mortar strength under microwave action. In order to reveal the deterioration law of mortar strength under microwave action，firstly，the dielectric properties of mortar block and its raw materials are tested，which is the main parameter affecting the conversion of electromagnetic energy into heat energy. The complex dielectric constants of cement，sand，water and mortar blocks were obtained by vector grid analyzer. The effects of frequency，temperature，and other factors on the dielectric constants and heating rates were analyzed. The influences of microwave heating time on compressive strength of mortar with different strength grades were further analyzed. The results show that the effect of temperature on the dielectric constant is significant，and the dielectric properties of the water decrease significantly with the increase of temperature. The higher the strength of mortar，the stronger the dielectric property and the faster the heating rate. According to the comprehensive analysis of the heating law，mass loss and the variation trend of compressive strength，after 60 s of 5 kW microwave heating，the internal cracks of M20，M25 and M30 mortar entered a stage of rapid expansion，and the strength decreased significantly. After heating for 100 s，the strength of the three mortars was reduced by 25%，18% and 16%，respectively. This study can provide reference for microwave mortar crushing and strength weakening，and further provide technical guidance for the popularization and application of microwave concrete crushing technology.

关键词

微波 / 砂浆 / 介电性能 / 温度 / 抗压强度

Key words

microwave / mortar / dielectric properties / temperature / compressive strength

参考文献

[1] Ghaemi S Z， Amidpour M. The effect of standardization of industries on life cycle embodied energy of residential buildings in Iran[J]. Energy Efficiency, 2019， 12（6）: 1529-1545.

[2] Kaptan K， Cunha S， Aguiar J. A review:construction and demolition waste as a novel source for CO₂ reduction in Portland cement production for concrete [J]. Sustainability, 2024， 16（2）: 585.

[3] Ouyang K， Liu J H， Liu S H， et al. Influence of pre-treatment methods for recycled concrete aggregate on the performance of recycled concrete:a review[J]. Resources Conservation and Recycling, 2023， 188: 106717.

[4] Lippiatt N， Bourgeois F. Investigation of microwave-assisted concrete recycling using single-particle testing[J]. Minerals Engineering, 2012， 31: 71-81.

[5] 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.

[6] 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.

[7] 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）.

[8] Wei W， Shao Z S， Zhang Y Y， et al. Fundamentals and applications of microwave energy in rock and concrete processing - a review[J]. Applied Thermal Engineering, 2019， 157: 113751.

[9] Zhang P J， Wei W， Shao Z S， et al. Effect of moisture on concrete damage and aggregate recycling under microwave irradiation[J]. Journal of Building Engineering, 2022， 46: 103741.

[10] 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.

[11] 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）.

[12] Akbarnezhad A， Ong K C G. Thermal stress and pore pressure development in microwave heated concrete[J]. Computers and Concrete, 2011， 8（4）: 425-443.

[13] Singh C， Khanna V， Singh S. Sustainability of microwave heating in materials processing technologies[J]. Materials Today: Proceedings, 2023， 73，Part 2: 241-248.

[14] Wei W， Shao Z S， Zhang P J， et al. Experimental assessment of microwave heating assisted aggregate recycling from dried and saturated concrete[J]. Materials and Structures, 2021， 54（4）: 142.

[15] Zhang P J， Wei W， Shao Z S. Multifield coupling study on random aggregate concrete under microwave irradiation[J]. Construction and Building Materials, 2022， 318: 126025.

[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] Wang Z J， Zhang T， Zhou L. Investigation on electromagnetic and microwave absorption properties of copper slag-filled cement mortar[J]. Cement and Concrete Composites, 2016， 74: 174-181.

[19] Guo H Y， Wang Z J， An D D， et al. Collaborative design of cement-based composites incorporated with cooper slag in considerations of engineering properties and microwave-absorbing characters[J]. Journal of Cleaner Production, 2021， 283: 124614.

[20] Tiegoum W J， Mambou N L L， Elat A M E， et al. Physical，mechanical properties and microstructure of concretes made with natural and crushed aggregates:application in building construction[J]. Cleaner Materials, 2023， 7: 100173.

[21] 邵珠山, 王维涛, 赵冬, 等. 微波照射下附着砂浆对再生混凝土粗骨料强度的影响[J]. 材料科学与工程学报, 2024， 42（1）: 27-34.

[22] Shao Zhushan， Wang Weitao， Zhao Dong， et al. Influence of adhesive mortar on the strength of recycled concrete coarse aggregate under microwave irradiation[J]. Journal of Materials Science and Engineering, 2024， 42（1）: 27-34（in Chinese）.

[23] 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.

[24] Lippiatt N R， Bourgeois F S. Recycling-oriented investigation of local porosity changes in microwave heated-concrete[J]. Kona Powder and Particle Journal, 2014， 31: 247-264.

[25] Zheng Y L， Su Z Q， Fu H Y， et al. Thermal behaviors of cement and mortar under microwave treatment and the influencing factors:an experimental study[J]. Construction and Building Materials, 2024， 411: 134191.

[26] 邵珠山, 吴丹丹, 袁媛, 等. 多模微波场中玄武岩加热及内部损伤机理研究[J]. 应用力学学报, 2022， 39（1）: 129-136.

[27] Shao Zhushan， Wu Dandan， Yuan Yuan， et al. Research on heating characteristics and internal damage emergence of basalt in multimode microwave field[J]. Chinese Journal of Applied Mechanics, 2022， 39（1）: 129-136（in Chinese）.

[28] 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.

[29] 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）.

[30] 中华人民共和国住房和城乡建设部. 建筑砂浆基本性能试验方法标准:JGJ/T 70-2009[S]. 北京: 中国建筑工业出版社， 2009.

[31] Xiao Y H， Xue Y H. A review on application of microwave in cement life cycle[J]. Renewable and Sustainable Energy Reviews, 2024， 199: 114498.

[32] Yao J H， Tao M， Zhao R， et al. Effect of microwave treatment on thermal properties and structural degradation of red sandstone in rock excavation[J]. Minerals Engineering, 2021， 162: 106730.

[33] Zhang H L， Wei W， Shao Z S， et al. The investigation of concrete damage and recycled aggregate properties under microwave and conventional heating[J]. Construction and Building Materials, 2022， 341: 127859.

[34] Xiao Y H， Shao Z S， Wei W， et al. Effect of microwave pretreatment on mechanical behavior of concrete and aggregate recovery[J]. Construction and Building Materials, 2023， 387: 131647.

[35] Xiao Y H， Shao Z S， Wei W. Investigation of thermally-induced separation in mortar-aggregate under microwave irradiation[J]. Composite Structures, 2023， 316: 117035.

[36] Lee N K， Koh K T， Park S H， et al. Microstructural investigation of calcium aluminate cement-based ultra-high performance concrete（UHPC）exposed to high temperatures[J]. Cement and Concrete Research, 2017， 102: 109-118.

[37] 姚华彦, 姚家李, 方琦, 等. 微波作用对砂岩物理力学性质影响的试验[J]. 应用力学学报, 2023， 40（6）: 1335-1342.

[38] Yao Huayan， Yao Jiali， Fang Qi， et al. Experimental study on the effect of microwave on the physical and mechanical properties of sandstone[J]. Chinese Journal of Applied Mechanics, 2023， 40（6）: 1335-1342（in Chinese）.

[39] 鞠杨, 刘红彬, 田开培, 等. RPC高温爆裂的微细观孔隙结构与蒸汽压变化机制的研究[J]. 中国科学（技术科学）, 2013， 43（2）: 141-152.

[40] Ju Yang， Liu Hongbin， Tian Kaipei， et al. An investigation on micro pore structures and the vapor pressure mechanism of explosive spalling of RPC exposed to high temperature[J]. Scientia Sinica（Technologica）, 2013， 43（2）: 141-152（in Chinese）.

基金资助

国家自然科学基金资助项目(12432020)