Experimental investigation on evaporation rate for enhancing evaporative cooling effect of permeable pavement materials

•A simple test method of evaporation rate was developed.•Evaporation rate were measured for six permeable pavement materials.•Main factors affecting evaporation rate were explored.•Methods to enhance evaporation rate were proposed.

Beyond the environmental function of stormwater management, permeable pavement is also a type of cool pavement that can help mitigate urban heat island effect through evaporative cooling. Evaporation rate is an important factor that influences the evaporative cooling effect of permeable pavements. A simple experiment method was used to initially explore the evaporation rates of different pavement materials under outdoor conditions. Experimental results of the evaporation rates were obtained for six different permeable pavement materials plus the bare water. The main factors influencing the evaporation rates were revealed. The findings imply that high water availability near the surface or large moisture exposure to the atmosphere are critical for the evaporation rate and consequent evaporative cooling effect of pavement materials. Increased air voids and permeability is one way to improve moisture exposure to the atmosphere and enhance the evaporation. Keeping the surface wet through enhanced capillary effect with finer gradations or directly sprinkling water on the surface is another way to produce a better evaporative cooling effect. An optimal design of materials with appropriately balanced pore size and capillary effect and adequate permeability is desired to maximize the evaporative cooling effect.