20 Years Experience of Porous Concrete Pavements on Roadways in Japan

Porous concrete pavement (POC) is a concrete pavement with drainage and noise reduction functions by forming continuous voids in the concrete. In Japan, POC was developed in the 1970s and applied on sidewalks in the 1980s. After that, research on admixtures as binders progressed, and it became possible to achieve the POC design flexural strength of 4.4 MPa along with continuous voids. Therefore, POC could be applied on roadways. In the 2000s, POC began to be applied at expressway toll gates. The reason for this is that the porous asphalt pavement (POA) has severe rutting due to repeated starting and stopping movements of vehicles, while POC has higher resistance to the rutting distress comparing with POA. In order to confirm the long-term performance of POC, the Japan Cement Association (JCA) constructed POC test sections on actual roadways in various places. This paper reports the results of field surveys on two of the test POC sections that were in service for about 20 years. The performances of the road surface (faulting at transverse joints, raveling, slip resistance, roughness) meets the target values for maintenance and repair guidelines. However, relatively severe crackings were observed in some sections, which did not meet specified criterions of maintenance and repair guidelines. The reason for this is considered to be the effect of increased temperature stress due to the wide transverse joint spacing of 20 m in the test sections. The degree of cracking was lower on the 25 cm thickness sections than that on the 20 cm thickness sections. On the other hand, drainage and noise reduction functions have declined over time due to clogging of the voids, which similar declines were also observed on the POA sections. These results demonstrate that POC has a sufficient durability and can be used on roadways, although cleaning clogged voids is still required to maintain specific drainage and noise reduction functions.