CLEAN

For some suburban and urban roads in modern cities, maintenance works are less and less sustainable, because of the induced traffic disruptions and associated social costs. This question was addressed by an international OECD working group called Long-Life Pavement (LLP). According to LLP conclusions, it would be desirable to construct pavement with a 30-40 year lifespan, while, nowadays, wearing courses do not last longer than 7 to 15 years. Therefore, the aim of the project is to optimise and to validate a new wearing course concept for long-life pavement called High-Performance Cementitious Material (HPCM). Currently this material consists in a thin layer of ultra-high performance fibre-reinforced mortar, in which hard, polishing-resistant chippings are embedded. In the framework of LLP working group (phase II), HPCM was subject of numerous laboratory tests. It is now time to extend the study up to the construction site. The design of the material will be first optimised, refining some mix parameters and detailing a number of options. In the first one, a de-polluting function will be added, thanks to the photocatalytic action of titan dioxide (Ti02). This product is known to enhance the degradation of urban pollutants (NOx, VOC) by ultra-violet radiations. Given the product cost, incorporation of Ti02 in a thin, high durability coating applied in high pollutant emission areas appears to be relevant. Another option consists in suppressing the chippings embedment; here, the texture is controlled by moulding the fresh mortar with an impression matrix. This would allow applying current knowledge of the relationships between wearing course micro- and macro-texture, on one hand, and road surface characteristics (skid resistance, acoustic emission and mechanical durability) on the other hand. Then, industrial application processes will be developed and validated through two HPCM demonstration sites. A suburban roundabout will be built in the Sarthe department at the beginning of the project, in order to display the material behaviour under a real traffic. In parallel, a construction facility will be designed and built. Also, another potential construction site area (in Montoire, Loire-Atlantique) will be studied, where the Ti02 option HPCM could be applied with a pre-industrial process. Attention will be paid to air pollution (pollutant types and emission time distribution) and climate (wind, rain etc.). An environmental instrumentation plan will be then carried out. After construction of this experimental street, the pavement will be characterized with regard to classical pavement properties – evenness, skid-resistance, noise generation – and to de-pollution ability, through a one-year monitoring. The technology will be assessed during the end of the project. First, the expected absence of degradation will be checked, as a normal feature for a long-life pavement. As far as economics is concerned, initial costs of the construction sites will be recorded. Then the theoretical cost of the disseminated technology, and the total cost over the lifecycle will be evaluated, and compared to those of current (bituminous) techniques. Social impact of HPCM will be addressed through the de-polluting efficiency, regarding both N0x and other types of pollutant as benzene compounds, an aspect not yet examined in previous projects. Social acceptability and architectural quality will be also studied through a survey towards city authorities. As for the environmental aspect, energy and green-house gas emissions linked with the use of HPCM will be quantified. Economy in non-renewable resource associated with one centimetre of non-oil products lasting 30 years, as compared to several centimetre current bituminous wearing courses lasting less than 15 years, will be assessed. Yet this option looks very sustainable, under the hypothesis that the practical implementation appears feasible (main subject of the project). Finally, the whole project will be carried out in the framework of OECD LLP works (phase III), in which about 20 developed countries are working together.