Recent development of microwave applications for concrete treatment
TL;DR: A comprehensive review of the scientific and technical achievements of microwave-assisted concrete treatment can be found in this article, where the theoretical fundamentals for the microwave assisted concrete heating process are investigated in detail, covering areas such as the microwave heating characteristics, governing equations, dielectric properties and multi-field coupling effects.
About: This article is published in Construction and Building Materials.The article was published on 2021-02-01. It has received 35 citations till now. The article focuses on the topics: Concrete recycling.
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TL;DR: In this article , the intrinsic effect of microwave pre-curing on the hydration kinetics and microstructure development of UHPFRCs is investigated. And the observed experimental results show that the microwave treatment can create a dense shell around the cured UHPC's periphery, which can resist the lateral deformation of the specimen and guarantee the excellent mechanical properties of the treated sample.
Abstract: This research aims to clarify the intrinsic effect of microwave pre-curing on the hydration kinetics and microstructure development of Ultra-High Performance Concrete (UHPC). Six hours after casting, the UHPC samples are subjected to microwave pre-curing for 60–240 s. Then, the macro and micro characteristics of the cured UHPC are evaluated. The observed experimental results show that the microwave treatment can create a dense shell around the cured UHPC's periphery, which can resist the lateral deformation of the specimen and guarantee the excellent mechanical properties of the treated sample. Moreover, when steel fibres are included into UHPC, the reflection and shielding effect of the 3D fibres network can significantly block the promotion effect of microwave on the strength development of UHPFRC. Additionally, due to the high energy of microwave, high polymerization hydration products and advanced pore structure (micro and meso scales) can be observed in the pre-cured UHPC.
25 citations
TL;DR: In this paper , a comprehensive study of the different effects of different curing methods on the strength development of normal concrete and UHPC is presented. But, it is not practical to specify the peak curing regimes for concrete or UHC since the best results need critical monitoring of curing parameters.
25 citations
TL;DR: In this article , the most commonly used curing regimes for AAMs are conducted in thermal or ambient temperature environments, adopted in the form of immersion of the AAM in water, ambient and high humidity, sealing, oven and, more recently, microwave curing.
23 citations
TL;DR: In this paper, the authors investigated the heating process of aggregate-mortar interfaces under microwave irradiation and provided a contribution and reference for the further application of microwave-assisted aggregates recycling.
14 citations
TL;DR: In this paper , a review of the latest knowledge on the recycling techniques for different GFRP and CFRP composites is presented, and the high value applications of the composites remanufactured through recycled fibers are outlined.
Abstract: ABSTRACT There is an urgent need to recycle glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) composites due to environmental challenges caused by incineration and traditional landfilling. This review incorporates an overview of the latest knowledge on the recycling techniques for different GFRP and CFRP composites. The applications of these chopped fibers are limited due to significant depreciation in their mechanical properties after recycling. The high-value applications of the composites remanufactured through recycled fibers are outlined. This review also incorporates the present challenges and modern trends in the recycling of fiber-reinforced composites. It is expected that further innovations in recycling technologies will be helpful to establish a circular economy and sustainable benign environment. Graphical abstract
14 citations
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TL;DR: In this paper, the fundamentals of electromagnetic theory, dielectric response, and applications of microwave heating to materials processing, especially fiber composites, are reviewed in this article, and a knowledge of electromagnetic theories and dielectrics is essential to optimize the processing of materials through microwave heating.
Abstract: In microwave processing, energy is supplied by an electromagnetic field directly to the material. This results in rapid heating throughout the material thickness with reduced thermal gradients. Volumetric heating can also reduce processing times and save energy. The microwave field and the dielectric response of a material govern its ability to heat with microwave energy. A knowledge of electromagnetic theory and dielectric response is essential to optimize the processing of materials through microwave heating. The fundamentals of electromagnetic theory, dielectric response, and applications of microwave heating to materials processing, especially fiber composites, are reviewed in this article.
1,296 citations
TL;DR: Microwave sintering has emerged as a new method for sinterding a variety of materials that has shown significant advantages against conventional sinterging procedures as mentioned in this paper. But microwave sinterings are not suitable for all materials.
911 citations
TL;DR: In this article, a review of microwave heating applications in environmental engineering is presented, which identifies the areas of potential commercial development as contaminated soil vitrification, volatile organic compounds (VOC) treatment and recovery, waste sludge processing, mineral ore grinding and carbon in pulp gold recovery.
Abstract: This paper presents a review of microwave heating applications in environmental engineering A number of areas are assessed, including contaminated soil remediation, waste processing, minerals processing and activated carbon regeneration Conclusions are presented, which identify the areas of potential commercial development as contaminated soil vitrification, volatile organic compounds (VOC) treatment and recovery, waste sludge processing, mineral ore grinding and carbon in pulp gold recovery Reasons are detailed why other areas have not seen investment into and implementation of microwave heating technology These include difficulties associated with the scaling up of laboratory units to industrial capacities and a lack of fundamental data on material dielectric properties This has meant that commercialisation of microwave heating processes for environmental engineering applications has so far been slow In fact, commercialisation is only deemed viable when microwave heating offers additional process-specific advantages over conventional methods of heating
847 citations
TL;DR: In this article, a brief account of results generated from microwave-assisted mineral treatments tests is given, which demonstrate that microwave energy has potential in mineral treatment and metal recovery operations such as heating, drying, carbothermic reduction of oxide minerals, leaching, roasting/smelting, pretreatment of refractory gold ore and concentrate, spent carbon regeneration and waste management.
747 citations
TL;DR: In this article, a free-space measurement system was developed for measurements of dielectric properties of planar slabs of ceramic and composite materials, in the frequency range of 14.5-17.5 GHz.
Abstract: For measurements of dielectric properties of planar slabs of ceramic and composite materials, the authors have developed a free-space measurement system in the frequency range of 14.5-17.5 GHz. The key components of the measurement system are a pair of spot-focusing horn lens antennas, a network analyzer, and a computer. Because of the far-field focusing ability of horn lens antennas, the free-space measurements can be made at microwave frequencies in a relatively compact and simple measurement setup. The time-domain gating feature of the network analyzer and the thru, reflect, and line calibration technique were used to eliminate the effects of undesirable multiple reflections. The dielectric constants and loss tangents were measured for standard materials such as fused quartz, Teflon, and polyvinylchloride (PVC). Dielectric properties for Teflon and PVC were also measured in a waveguide medium for purposes of comparison with the free-space method. >
643 citations