Thermal characteristics of porous concrete in a hydronic road heating system

Abstract Porous road concrete is an important part of the hydronic road heating system to avoid icing on the road. The thermal characteristics of porous concrete are obtained in the heating process to evaluate the microstructure effects and predict the road conditions. This study applied the Monte Carlo method to generate a two-dimensional heterogeneous porous concrete model. The porous concrete is a mixture of aggregates, bonding interfaces, cement pastes, and air voids. The thermal characteristics (average road surface temperature and road surface temperature distribution) of porous concrete were simulated. The average road surface temperatures were validated with the experiment results. The thermal characteristics of porous concrete as affected by the aggregate areal ratio, air void size, and air void ratio were compared and analyzed. The results indicate that the average road surface temperature at 8 h increased by 1.07 K and the preheating time decreased by 1.05 h when the aggregate areal ratio was increased from 40 % to 60 %. The road surface temperature fluctuation for the aggregate areal ratio of 50 % was the highest (274.34 ∼ 275.96 K). The average road surface temperature at 8 h decreased by 0.39 K and the preheating time increased by 0.51 h with the air void size changing from 1 ∼ 3 mm to 1 ∼ 5 mm. The road surface temperature fluctuation for the air void size of 1 ∼ 5 mm was the highest (273.80 ∼ 274.50 K). The average road surface temperature at 8 h decreased by 4.48 K and the preheating time increased by 4.03 h with the air void ratio increasing from 0 to 10 %. The road surface temperature fluctuation of none air void was the lowest (277.88 ∼ 278.12 K), indicating that the air void had a significant impact on the road surface temperature.