Microwave dielectric heating to disassemble a modified cementitious joint

摘要

According to existing theory on the deterioration of cement and concrete, a cement hardener undergoes a hydrate disassembly reaction at high temperatures of 300 °C or above; this increases the internal void volume and decreases the residual strength. This weakness mechanism has already been applied to manufacturing recycled aggregates and has reached the stage of practical application for removing adhered mortar from the aggregate surface. However, heating using an external heat source consumes a considerable amount of energy, and greenhouse gases are emitted during the recycling process because of low energy efficiency. In this study, a susceptor with outstanding microwave heating efficiency was selected, and the temperature elevation characteristics from the microwave heating of cementitious material containing the susceptor were analyzed. Through measurement, the bond strength of a cementitious joint including a modifier with the susceptor was found to weaken after microwave heating; thus, a new cementitious joint that can be reused or recycled as construction material and members is proposed. If the susceptor can selectively make cement material vulnerable in a short time by absorbing microwaves at the cementitious joint, the combined waste from the cementitious joint can be separated into single materials.