Ministry to Promote Water-Retentive Pavement for Heat Island Control

Japanese Minister of Land, Infrastructure and Transport Nobuteru Ishihara announced on July 23, 2004, that the ministry will include expenses for water-retentive road paving in its budget request for fiscal 2005. The Tokyo Metropolitan Government and several other municipalities have already started using this type of pavement to mitigate the heat island effect in urban areas.

The water-retentive pavement is designed to facilitate the storage of rainwater using asphalt mixed with highly water-retaining materials that are commonly used in disposable diapers. As the water stored in the pavement evaporates slowly into the air, it absorbs the surrounding heat and lowers the temperature. The experiment shows that this pavement can effectively reduce the temperature of a road surface by up to 25 degrees Celsius in mid-summer, when the surface temperature can be as high as 60 degrees. This results in reducing the sensible temperature by two to three degrees.

The Tokyo Metropolitan Government has been introducing this type of pavement on some of its roads on a trial basis since the summer of 2001. The study results to date show that the paving lowers the road surface temperature by about 10 degrees compared to conventional asphalt. Tokyo's Sewerage and Construction Bureaus are jointly conducting a feasibility study involving the spraying of treated sewage water over water-retentive pavement to enhance its cooling effect.



Posted: 2004/11/22 11:59:35 AM
Japanese version