Abstract
To increase the quality of recycling, a new demolition technique is required that can work in parallel with existing crushing methods, which use large equipment with high crushing efficiency. Moreover, the efficient collection of the remains from the fractional dismantling method needs to be considered based on its procedure, and the technology for partial dismantling that is efficient in remodeling, maintenance, and reinforcement has to be developed. In this study, the temperature-increasing characteristics of rebars inside ferroconcrete with respect to their arrangement was investigated by partial rapid heating through high-frequency induction heating. Based on this, the chemical and physical vulnerability characteristics of ferroconcrete due to the thermal conduction generated on the rebar surface and the cracks caused by the thermal expansion pressure of the rebar were verified. In addition, the objective of this study was to verify the applicability of the technology by specifying the vulnerability range of ferroconcrete based on the heating range with adequate consumption of energy.
Highlights
Concrete is a material composed of aggregates, cement, and water
For D10 reinforcing bars, the size of the thermal expansion pressure is smaller owing to the reduction in crosssectional area compared to other reinforcing bars, the changes in the occurrence of cracks appeared differently
Calcium hydroxide (Ca(OH)2 ) in the hardened cement body is disassembled at 530 ◦ C, while CSH gel, which has a large effect on the physical properties of concrete, is disassembled at temperatures of 600 ◦ C or higher
Summary
Concrete is a material composed of aggregates, cement, and water. After hydration reactions, 60–70% of the mass is composed of C-S-H(CaO-SiO2 -H2 O) gel, and the remaining 20–30% is calcium hydroxide (Ca(OH)2 ).When concrete is exposed to high temperatures, the chemical and physical structures change, resulting in the dehydration of calcium hydrate and thermal expansion of the aggregates, which cause cracks in the concrete at temperatures above 300 ◦ C.Calcium hydroxide (Ca(OH)2 ) in the hardened cement body is disassembled at 530 ◦ C, while CSH gel, which has a large effect on the physical properties of concrete, is disassembled at temperatures of 600 ◦ C or higher. Concrete is a material composed of aggregates, cement, and water. When concrete is exposed to high temperatures, the chemical and physical structures change, resulting in the dehydration of calcium hydrate and thermal expansion of the aggregates, which cause cracks in the concrete at temperatures above 300 ◦ C. Calcium hydroxide (Ca(OH)2 ) in the hardened cement body is disassembled at 530 ◦ C, while CSH gel, which has a large effect on the physical properties of concrete, is disassembled at temperatures of 600 ◦ C or higher. Concrete melts at a temperature of 1150 ◦ C or higher [53]. Concrete is a porous structure composed of hardened cement bodies and voids, which contain aggregate, cement, chemically bonded water, and gel water, and the voids are filled with free water and air
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