Title: RECENT DEVELOPMENTS IN PERVIOUS MACADAM SURFACES --BITUMEN, FLEXIBLE AND DURABLE. 3RD EUROBITUME SYMPOSIUM 1985, THE HAGUE, NETHERLANDS, SEPTEMBER 11-13, 1985
Abstract: Earlier work on pervious macadam surfacings had indicated that they possess a number of advantages over the more traditional impervious surfacings such as asphaltic concrete and hot rolled asphalt. In wet road conditions the ability for water to drain through the surface leads to substantial reductions in tyre induced spray, the tendency for vehicles to aquaplane, and surface reflections from the lights of oncoming vehicles at night. The reduction in rolling noise between tyres and the road surface, under both wet and dry conditions, is of great environmental benefit in urban and other noise sensitive areas. However, in practice it has been found that due to the very open nature of the mix (15%-25% voids) the binder film on the surface of the aggregate is continuously exposed to the effects of air, sunlight and water which can accelerate ageing effects with subsequent reduction in service life. Other observed problems have been the tendency to gradually compact under heavy traffic and blockage of the voids with road dirt. Recent work has concentrated upon ways of reducing these effects, principally by modifying the binder with the addition of thermoplastic polymers or thermosetting epoxy resins. As part of a joint research programme developed by bacmi, rba and TRRL a series of trial stretches each 150 metres long have been laid on a principal road (a38) in staffordshire near burton-on-trent. A 20 mm grading has been selected to optimise the drainage properties of the mix and it has been laid to a nominal thickness of 45 mm. The various sections contain bitumens that have been modified by the addition of natural rubber, eva, sbs rubbers and epoxy resins. There is also one section containing a proportion of inorganic mineral filler. The materials were all manufactured on a batch plant, and apart from close attention to temperature control to minimise any degradation effects on the binders, no special problems were encountered in mixing and laying. Over a period of years measurements will be made on skid resistance, surface deformation, noise and spray levels, and general condition to determine, if possible, the most cost effective mix. In another experiment the free draining properties of the mix have been enhanced by an overspraying technique to produce smooth surfaces throughout the interconnected void system of the mix. The contribution of the pervious macadam surfacing to the structural strength of the pavement as a whole has been studied and found to vary considerably depending on binder type. For a standard 100 pen bitumen the contribution is approximately 10% of an equivalent thickness of hra, whereas for the epoxy bitumen binder the contribution is equal to that of the hra. The results for the binders containing various polymers lie between these two extremes.(a) for the covering abstract of the symposium see IRRD 815173.
Publication Year: 1985
Publication Date: 1985-01-01
Language: en
Type: article
Access and Citation
AI Researcher Chatbot
Get quick answers to your questions about the article from our AI researcher chatbot