Microwave heating of hardened concrete: Parameter effects and empirical model study

This study investigates the effect of microwave exposure on hardened concrete and develops a predictive model to estimate concrete temperature rise. Experimental tests were conducted on concrete cylinders with varying dimensions (50 ×100 mm, 75 ×150 mm, 100 ×200 mm, and 150 ×150 mm), water-to-cement (w/c) ratios (0.36, 0.43, and 0.50), and moisture conditions (saturated-surface-dry and oven-dry). Specimens were exposed to three microwave power levels (300 W, 600 W, and 1000 W) for different durations ranging from 30 s to 10 min. The internal temperature was continuously measured in several locations using embedded thermocouples and a thermal camera. Results show that the heating rate decreased with increasing specimen volume (concrete sample geometry) and w/c ratio, whereas higher microwave power accelerated the temperature rise. Saturated specimens experienced explosive failure due to internal steam pressure buildup, and dry specimens exhibited deeper microwave penetration, reaching the entire depth of specimens over 150 mm, compared with only about 100 mm for saturated concrete. The developed empirical model demonstrated reliable predictive capability across all experimental conditions.