Densification of Fresh Concrete by Microwave

Concrete mixes with different fly ash replacement levels, namely 0%, 35% and 55% at a fixed water to binder ratio (W/B) of 0.6 were heated by a tailor-made microwave oven up to 50oC immediately after casting until initial setting in order to remove excessive free water. The compressive strengths of microwave densified samples after 7 days were 3.2%, 7.7% and 29.6% higher than those of oven heated batches. It demonstrated that higher density, lower water absorption and better microstructure were achieved after microwave heating, indicating microwave heating can be a promising technique for densifying fresh concrete