Abstract
Due to the potential for significant process benefit, microwave assisted concrete recycling is highlighted by many scholars and engineers over the world recently. In this paper, a multi-field model is established to simulate the microwave heating process of concrete specimen with single-particle aggregate by using of COMSOL Multiphysics. The validation of this model is verified by comparison with temperature from experiment. Mechanical properties of aggregate-mortar interface during microwave heating process was experimentally investigated. Electric, temperature, stress field evolution and moisture transformation during microwave heating process are discussed in detail. Temperature and stress gradient at mortar-aggregate interface influenced by microwave heating power, frequency and duration are analyzed and graphically presented, which are the dominant factors to achieve the interface debonding. Based on the comparison between concrete absorbed energy and temperature variation, energy efficiency for microwave heating concrete is also briefly discussed. Results of this investigation could provide a multi-field understanding for the microwave treatment on concrete.
Highlights
Microwave is an electromagnetic radiation with frequencies varies from 300MHz to 300GHz, which showed great potential in industrial and scientific practical applications [1]–[5]
Four physical fields are used in numerical simulation, the mechanical field, electromagnetic field, thermal field and mass transfer field to illustrate the complex and more practical multi-field heating process of concrete
Prior work has achieved to give an insight into the complex multi-field coupling of microwave treatment process under various circumstance through the numerical simulation
Summary
Microwave is an electromagnetic radiation with frequencies varies from 300MHz to 300GHz, which showed great potential in industrial and scientific practical applications [1]–[5]. When concrete is irradiated under microwave, mortar, aggregate and water could be heated under electromagnetic field. Four physical fields are used in numerical simulation, the mechanical field, electromagnetic field, thermal field and mass transfer field to illustrate the complex and more practical multi-field heating process of concrete. METHODOLOGY The COMSOL Multiphysics is employed to simulate the multi-field heating process in mortar-granite concrete under microwave irradiation. The heat and mass transfer process and the mechanical field evolution for granite and mortar phases could be both simulated through the model. A) The walls of the oven and the waveguide are perfectly conducting; b) The initial temperature distribution of sample and air are homogeneous; c) Granite and mortar are considered as homogeneous porous media; d) Chemical reaction is not considered in the heating process
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