Water availability near the surface dominates the evaporation of pervious concrete

Abstract

In field trials of pavements, pervious concrete has been found to be both hotter and cooler than conventional concrete. There is much speculation on the cooling effect of pervious concrete, but specific measurements and modeling to confirm this are deficient. This study presents a model for the evaporation rate of pervious concrete pavements. The model is validated by the temperature observed from an experimental section and by documented data on the evaporation of pervious concrete. The model is then implemented into a one-dimensional pavement temperature model to simulate the temperature evolution of the pervious pavement system. It is found that the water availability (surface resistance) near the pavement surface dominates the evaporation rate of the pervious concrete. Rewetting the surface can keep the pervious concrete surface cool for 12–24h during a typical hot summer day. After this period, the pervious concrete surface is hotter than a conventional concrete pavement. Rewetting the pervious concrete can keep it cooler than convectional concrete, especially when it is replenished with water around mid-day. Therefore, it should be cautious to deem pervious pavement as a cool pavement alternative unless it is re-wetted periodically.