A Study on the Hydrothermal Synthesis of Calcium Silicate Products by Calcination of Full-Component Waste Concrete

Famao Mao and Hongmei Ai ()
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Famao Mao: School of Civil Engineering, Dalian University of Technology, Dalian 116024, China
Hongmei Ai: School of Civil Engineering, Dalian University of Technology, Dalian 116024, China

Sustainability, 2023, vol. 15, issue 23, 1-13

Abstract: In order to achieve the reuse of waste concrete, the hydrothermal synthesis of low-temperature calcined calcium silica products with an ideal admixture of fly ash and waste concrete as raw materials was investigated and various properties were studied. The findings suggest that the optimal method involves adding 10% fly ash to waste concrete to lower the temperature at which calcium carbonate decomposes. The compressive strength of the specimens generally increases with increasing calcium–silicon ratio and pressure can reach up to 43.98 MPa. Nevertheless, the duration of holding requires adjustment in line with autoclave pressure: the higher the pressure, the shorter the holding time, and vice versa for lower pressure. Most of the specimens are water-resistant with softening coefficients above 0.6 and up to 0.91. The macroscopic strength is determined by the way in which the microstructure of the hydration products forms under different conditions. The optimum design for the experimental conditions should be that the pressure, holding time and calcium–silica ratio should be 1.0 MPa, 9 h and 1.0, respectively. Due to their potential for resource conservation and environmental improvement, autoclaved silicate materials manufactured from waste concrete may be a viable alternative as a green construction material.

Keywords: waste concrete; autoclave system silicon calcium products; hydrothermal synthesis; silicon calcium products (search for similar items in EconPapers)
JEL-codes: O13 Q Q0 Q2 Q3 Q5 Q56 (search for similar items in EconPapers)
Date: 2023
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