Accelerated microwave curing of concrete: A design and performance-related experiments |
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| Affiliation: | 1. Department of Building Technology, Faculty of Industrial Technology, Phranakhon Rajabhat University, Changwattana Road, Bangkhen, Bangkok 10220, Thailand;2. Center of Excellence in Electromagnetic Energy Utilization in Engineering (CEEE), Department of Mechanical Engineering, Faculty of Engineering, Thammasat University Prathum Thani, 12121, Thailand;1. Department of Civil Engineering, National Research Centre, Egypt;2. Structural Engineering Department, Faculty of Engineering, Ain Shams University, Egypt;3. Structural Engineering Department, German University in Cairo, Egypt;4. Structural Engineering Department, Cairo University, Egypt;1. Center of Excellence in Electromagnetic Energy Utilization in Engineering (CEEE), Department of Mechanical Engineering, Faculty of Engineering, Thammasat University Prathum Thani, 12121, Thailand;2. Building Technology Program, Faculty of Industrial Technology, Phranakhon Rajabhat University, 3 Moo 6 Changwattane Road, Anusaowari Sub District, Bang Khen District, Bangkok 10220, Thailand;1. Department of Building Technology, Faculty of Industrial Technology, Phranakhon Rajabhat University, Changwattana Road, Bangkhen, Bangkok 10220, Thailand;2. Center of Excellence in Electromagnetic Energy Utilization in Engineering (CEEE), Thammasat University (Rangsit Campus), Khlong Luang, Prathum Thani 12121, Thailand;3. Materials Research Institute, Pennsylvania State University, University Park, PA 16802, USA;1. China West Construction Academy of Building Materials, Chengdu 610017, China;2. State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan 430072, China;3. School of Materials Science and Engineering, Tongji University, Shanghai 200092, China |
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| Abstract: | Microwave (MW)-accelerated curing has emerged as an innovative and popular curing method for concrete materials. This paper reports the results of a study to model the horn antenna used for the MW irradiation of a workpiece with a mobile MW-accelerated concrete curing unit, based on a coupled thermal and electromagnetic analysis. The mathematical models were useful for evaluating the heat generation within a horn antenna and as a basis for constructing a mobile MW-accelerated curing unit with an operating frequency of 2.45 GHz and a MW power level of 800 W. Further, the early-age compressive strength development and volume stability of MW-cured concrete were investigated in terms of its shrinkage and compared to the properties of autoclave-cured concrete. The design results showed that under the concept of the allowable maximum temperature for the concrete workpiece, which was controlled to less than 80 °C, a horn antenna that was 216.70 mm wide, 333.68 mm long, and 273.0 mm high produced a uniform thermal distribution in a concrete workpiece. Moreover, experimental investigations showed that the application period for curing using a mobile MW-curing unit was considerably shorter than that in autoclave curing methods. The appropriate delay time (time after concrete mixing) was 30 min, and MW irradiation for 45 min could improve the maximum 8-h early-age compressive strength of MW-cured concrete, whereas an application time of 15 min produced the 28-day compressive strength. When a concrete workpiece was cured at high temperature using MW energy for more than 15 min at a temperature greater than 80 °C, the effect was a continuous increase in the early-age compressive strength, which was greater than that achieved by autoclave curing. In terms of volumetric stability, MW-curing for 30 and 45 min increased the ultimate shrinkage to a greater extent than that by autoclave curing and vice versa in the case of a MW application time of 15 min. |
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| Keywords: | Microwave Concrete Curing Prototype design Compressive strength: volume stability |
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