Twenty-Years Experience of Porous Concrete Pavements on Roadways in Japan

AUTHORS: Nakamura, H., Koyanagawa, M., and Nishizawa, T.

ABSTRACT: Porous Concrete Pavement (PoCP) is a concrete pavement with drainage and noise reduction functions by forming continuous voids in the concrete. In Japan, porous concrete was developed in the 1970s and applied on sidewalks in the 1980s. After that, research on admixtures and binders progressed, and it became possible to achieve the flexural strength of 4.4 MPa for porous concrete with continuous voids and apply PoCP on roadway pavements. In the 2000s, PoCP began to be used in expressway toll gates. The reason for this is that porous asphalt pavement (PoAP) in the toll gates had severely rutted due to repeated deceleration and acceleration of vehicles, while PoCP has higher resistance to the rutting comparing with PoAP. In order to confirm the long-term performances of PoCP, the Japan Cement Association (JCA) constructed PoCP test sections on actual roadways in various places. This paper reports the results of field surveys on two sites that have served for about 20 years. The performances of road surface (faulting at transverse joints, smoothness, rutdepth) were confirmed to meet the target values for maintenance and repair guidelines. However, relatively severe cracking 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 thermal stress due to the long transverse joint spacing of 20 m in the test sections. The degree of cracking was lower in the 25 cm slab thickness sections than that in the 20 cm slab thickness sections. On the other hand, drainage and noise reduction functions have declined over time due to clogging of the void and similar declines also observed on PoAP sections. These results demonstrate that PoCP has a sufficient durability and can be used on roadways, although cleaning clogged voids is still required to maintain sufficient drainage and noise reduction functions.