Influence of Microwave Energy on Thermal Conductivity and Compressive Strength of Concrete

Abstract

The objective of this research was to study the influence of microwave energy on thermal conductivity and compressive strength of concrete. The tested properties of cement paste include setting time, temperature from hydration reaction and compressive strength at the ages of 1, 3, and 5 days with the water-to-binder ratios were 0.22, 0.38, 0.45, 0.55 and 0.70. The tested results were used to analyze the curing conditions of concrete with microwave energy. 

From the tested results of cement paste properties, it was observed that setting time increased with the increase of water-to-binder ratios. The initial and final setting time of the cement pastes with 0.38, 0.45 and 0.55 water-to-binder ratios were in accordance to ASTM C 191 but the initial and final setting time of the cement pastes with 0.22 and 0.70 water-to-binder ratios were not in accordance to ASTM. For the tested results of the hydration reaction in cement paste, it was found that the highest temperature was 60  C. And the compressive strength of cement paste decreased with increasing the water-to-binder ratios. 

For the analysis of curing conditions, it was found that the optimum condition for curing concrete with microwave energy is that the temperature in concrete matrix should not be over 60 C. If temperature is over than 60 C, it will led to segregation of proportions in concrete. The optimal conditions were 100 watts of microwave power, 15 minutes for curing time and 30 minutes for delay time. Additionally, the concrete curing with microwave energy had high compressive strength but thermal conductivity were low when compared with concrete curing with water, due to water in concrete were decreased.