Microwave-Accelerated Curing of Reinforced Concrete Prepared by Recycled Concrete Aggregate

This chapter presents a rapid, early-stage curing method for reinforced self-compacting concrete prepared with recycled concrete aggregate (RCA) using a continuous conveyor microwave and hot-air system. Each of these magnetrons produced a power of 800 Watt (W) and combined with up to 70 °C convective hot air, thereby reducing demolding time to enhance the development of strength in the early stages of curing in an integrated curing system. Two concrete mixtures were prepared under natural coarse aggregate (NCA) or recycled concrete aggregate (RCA), with a water-to-cement ratio of 0.45 w/c and 450 kg/m³ hydraulic cement. After a 30-minute primary curing stage (delay period), the concrete specimens were subjected to microwave curing in two 10-minute periods. Infrared thermography, moisture sensors, flexural strength testing, and network analysis tools were used to monitor temperature profiles and variations, moisture reduction, and dielectric properties. Central temperatures of the specimens also rose by around 35-55 °C, and free water content decreased by 15% in weight over 20 min, improving hydration. Flexural strength increased by as much as 85%, and the curing time was 2 h.