Microwave processing of cement and concrete materials – towards an industrial reality?

Buttress, Adam; Jones, Aled; Kingman, S.W.

doi:10.1016/j.cemconres.2014.11.002

Cited by 92 publications

(23 citation statements)

References 73 publications

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“…High-frequency electromagnetic heating, such as microwave curing, is able to reduce such nonuniformity due to its superior penetration depth. In addition, microwave curing exhibits the characteristics of energy saving, rapid stripping for precast concrete [ 2 , 3 ] or concrete repair [ 4 ], which is effective in accelerating the hydration of cement [ 5 , 6 , 7 , 8 ] or improving the pozzolanic reaction of supplementary cementitious materials (SCMs) [ 9 , 10 , 11 , 12 , 13 , 14 ]. According to the research of Wu et al, microwave curing increases the early strength without any detrimental effect at later ages [ 15 ].…”

Section: Introductionmentioning

confidence: 99%

SEM Analysis of the Interfacial Transition Zone between Cement-Glass Powder Paste and Aggregate of Mortar under Microwave Curing

et al. 2016

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In order to investigate the effects of microwave curing on the microstructure of the interfacial transition zone of mortar prepared with a composite binder containing glass powder and to explain the mechanism of microwave curing on the improvement of compressive strength, in this study, the compressive strength of mortar under microwave curing was compared against mortar cured using (a) normal curing at 20 ± 1 °C with relative humidity (RH) > 90%; (b) steam curing at 40 °C for 10 h; and (c) steam curing at 80 °C for 4 h. The microstructure of the interfacial transition zone of mortar under the four curing regimes was analyzed by Scanning electron microscopy (SEM). The results showed that the improvement of the compressive strength of mortar under microwave curing can be attributed to the amelioration of the microstructure of the interfacial transition zone. The hydration degree of cement is accelerated by the thermal effect of microwave curing and Na+ partially dissolved from the fine glass powder to form more reticular calcium silicate hydrate, which connects the aggregate, calcium hydroxide, and non-hydrated cement and glass powder into a denser integral structure. In addition, a more stable triangular structure of calcium hydroxide contributes to the improvement of compressive strength.

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Section: Introductionmentioning

confidence: 99%

SEM Analysis of the Interfacial Transition Zone between Cement-Glass Powder Paste and Aggregate of Mortar under Microwave Curing

et al. 2016

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“…This period of curing also provides the best compromise between the rate of strength gain and the long term strength of concrete, which has to be made in most practical applications. Application of microwave curing during the middle and final phases, on the other hand, will be more disruptive to the internal structures formed by hydration and result in greater reduction in long term strength [5,7].…”

Section: Casting and Curingmentioning

confidence: 99%

“…Unlike conventional heating, microwave curing generates heat from within concrete or a repair patch to provide uniform heating across its depth. Less than 1 h of microwave exposure applied in the first stage of hydration is sufficient to achieve the desired curing temperature [5][6][7]. There is already considerable research [8][9][10][11][12] on the use of early age microwave curing to accelerate strength development of concrete.…”

Section: Introductionmentioning

confidence: 99%

Bond of steel reinforcement with microwave cured concrete repair mortars

2017

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This paper investigates the effect of microwave curing on the bond strength of steel reinforcement in concrete repair. Pull-out tests on plain mild steel reinforcement bars embedded in four repair materials in 100 mm cube specimens were performed to determine the interfacial bond strength. The porosity and pore structure of the matrix at the steel interface, which influence the bond strength, were also determined. Test results show that microwave curing significantly reduces the bond strength of plain steel reinforcement. The reduction relative to normally cured (20°C, 60% RH) specimens is between 21 and 40% with low density repair materials and about 10% for normal density cementitious mortars. The corresponding compressive strength of the matrix also recorded similar reduction and microwave curing resulted in increased porosity at the interface transition zone of the steel reinforcement.A unique relationship exists between bond strength and both compressive strength and porosity of all matrix materials. Microwave curing reduced shrinkage but despite the wide variation in the shrinkage of the repair mortars, its effect on the bond strength was small. The paper provides clear correlations between the three parameters (compressive strength, bond strength and porosity), which are common to both the microwave and conventionally cured mortars. Therefore, bond-compressive strength relationships used in the design of reinforced concrete structures will be also valid for microwave cured elements.

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“…These techniques require new parameters and operations that can enhance the SVM computational cost. In this regard, the first contribution of this study is to develop non-iterative SVM-based algorithms for analyzing the sensor (smart aggregate) data, which can improve the performance of SVM, rather than traditional SVM.Furthermore, the local structural health monitoring based on microwave and millimeter-wave imaging is an efficient approach for visualizing and localizing detected damage in structures [10][11][12][16][17][18]. These methods offer cost-effective methods of local inspection, to identify the exact location of the crack [19,20].…”

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confidence: 99%

Algorithm Development for the Non-Destructive Testing of Structural Damage

et al. 2019

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Monitoring of structures to identify types of damages that occur under loading is essential in practical applications of civil infrastructure. In this paper, we detect and visualize damage based on several non-destructive testing (NDT) methods. A machine learning (ML) approach based on the Support Vector Machine (SVM) method is developed to prevent misdirection of the event interpretation of what is happening in the material. The objective is to identify cracks in the early stages, to reduce the risk of failure in structures. Theoretical and experimental analyses are derived by computing the performance indicators on the smart aggregate (SA)-based sensor data for concrete and reinforced-concrete (RC) beams. Validity assessment of the proposed indices was addressed through a comparative analysis with traditional SVM. The developed ML algorithms are shown to recognize cracks with a higher accuracy than the traditional SVM. Additionally, we propose different algorithms for microwave-or millimeter-wave imaging of steel plates, composite materials, and metal plates, to identify and visualize cracks. The proposed algorithm for steel plates is based on the gradient magnitude in four directions of an image, and is followed by the edge detection technique. Three algorithms were proposed for each of composite materials and metal plates, and are based on 2D fast Fourier transform (FFT) and hybrid fuzzy c-mean techniques, respectively. The proposed algorithms were able to recognize and visualize the cracking incurred in the structure more efficiently than the traditional techniques. The reported results are expected to be beneficial for NDT-based applications, particularly in civil engineering. These algorithms have successfully been utilized to solve engineering problems [3][4][5][6][13][14][15]. The SVM method has been extensively used in many research studies, and it is accepted as an efficient classifier for detecting damage [7][8][9]. However, there had been a substantial increase in utilizing advice sets for enhancing SVM performance. However, applying and expressing this knowledge in terms of its constraints still has some difficulties. These techniques require new parameters and operations that can enhance the SVM computational cost. In this regard, the first contribution of this study is to develop non-iterative SVM-based algorithms for analyzing the sensor (smart aggregate) data, which can improve the performance of SVM, rather than traditional SVM.Furthermore, the local structural health monitoring based on microwave and millimeter-wave imaging is an efficient approach for visualizing and localizing detected damage in structures [10][11][12][16][17][18]. These methods offer cost-effective methods of local inspection, to identify the exact location of the crack [19,20]. Microwave-and millimeter imaging techniques are non-contact and one-sided techniques which can be efficiently applied for the non-destructive evaluation of non-transparent materials, as their signals can penetrate the dielectric materials and provid...

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Microwave processing of cement and concrete materials – towards an industrial reality?

Cited by 92 publications

References 73 publications

SEM Analysis of the Interfacial Transition Zone between Cement-Glass Powder Paste and Aggregate of Mortar under Microwave Curing

SEM Analysis of the Interfacial Transition Zone between Cement-Glass Powder Paste and Aggregate of Mortar under Microwave Curing

Bond of steel reinforcement with microwave cured concrete repair mortars

Algorithm Development for the Non-Destructive Testing of Structural Damage

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