Hydration and microstructure of cement-based materials under microwave curing

• Microwave curing improves the early strength when compared to steam curing.
• Microwave curing reduces the pores in the range of >100 nm.
• Microwave curing forms short-rod AFt and diminishes the particle size of CH.
• Microwave curing increases the absorption of S, Mg and K by C-S-H gel.

By reducing the curing time, microwave curing can enhance the productivity, save the capital and decrease the plant areas for precast concrete when compared with the steam curing. Based on the results of 6-h and 24-h compressive strength tests the optimum curing regime was selected. The sample microwave cured using the selected curing regime was then compared against samples cured using (a) normal curing (b) steam curing at 40 °C for 10 h and (c) steam curing at 80 °C for 4 h by performing the compressive strength, XRD, TG-DSC, SEM-EDS and MIP. The results indicate that, compared with the steam curing at 80 °C, microwave curing improves the compressive strength of mortar before the age of 28 days, increases the porosity of mortar slightly, while reduces the pores in the range of >100 nm greatly, forms short-rod AFt and smaller particle size of calcium hydroxide, and increases the adsorption of K, S and Mg by C-S-H gel.