Life-prolonging preventive maintenance techniques for porous asphalt

<p align="LEFT"> </p> <p align="LEFT">The Dutch national roads agency Rijk swaterstaat (RWS) is constantly look ing for faster maintenance techniques and more cost effective maintenance measures, to extend the service life of Porous Asphalt (PA) with minimal traffic hindrance. End of service life of PA is determined by excessive loss of stones from the surface, called raveling. Raveling is caused by a complex of factors lik e possible drainage of the mortar (transport, construction, early life), direct loading via the stones, water pressure under the tire, accelerated ageing from the surface, clogging, etcetera. In the field raveling mainly occurs after the bitumen in the top of the PA layer is strongly aged. Due to the ageing of the bitumen, the mortar bonding bridges between the coarse aggregate become more brittle, which mak es them more sensitive for (micro) crack s and/or adhesion loss between stone and the mortar, which probably will lead to raveling. The service life of existing PA could be extended by adding bitumen from the surface, which could fill and heal micro-crack s, rejuvenate the aged bitumen in the mortar and add bitumen to the mortar bonding bridges. RWS has challenged the Dutch mark et to develop life-prolonging preventive maintenance techniques for PA. Three potential rejuvenating products, that could fulfill the requirements of RWS, were offered:<br />- Pentack &reg; of producer ESHA (emulsion system), applied by ESHA<br />- Modiseal&reg; ZX of producer Latexfalt (hot polymer modified bitumen), applied by contactor BAM<br />- Modimuls&reg; ZV of producer Latexfalt (emulsion system), applied by contractor Heijmans.<br />Whether these products actually contribute to the life extension of PA is investigated by InfraQuest (a partnership between RWS, Delft University of Technology and TNO). The three products were applied on existing PA road sections, which were not raveled, and extensive research was conducted on specimens obtained from these test sections for validation. Also a Life Cycle Analysis and Cost Benefit Analysis were performed to investigate whether the examined life extension maintenance measures were cost effective and satisfied the environmental requirements of RWS. In this paper an overview will be given of the approach to the validation studies and the conclusions that could be drawn from the results.</p> <p align="LEFT"> </p>