Asphalt friction course

At least 9 million scrap tires are processed into ground rubber annually. Ground tire rubber is used in rubber products (such as floor mats, carpet padding, and vehicle mud guards), plastic products, and as a fine aggregate addition (dry process) in asphalt friction courses. Crumb rubber has been used as an asphalt binder modifier... 

The most beneficial applications were found by the review to be thin asphalt friction course overlays over portland cement concrete or aged asphalt pavements, to provide quieter and safer ride... 

Two of the more recent innovations for using sulfur modified binders are in conjunction with recycling old asphalt pavements and the construction of open graded friction courses (OGFC). 

Saylak, D., "Design of Open Friction Courses with Sulfur-Extended Asphalt Binders", Final Report on FHWA Contract No. DOT-FH-11-9588, May, 1981. 

The influence of highway pavement surface type on tire/pavement noise was studied (Bennert et al., 2006). It was found that the open-graded friction course (OGFC) with the hot mix GRT-modified asphalts attained the lowest noise levels. Also, the GRT-modified OGFC mixes exhibited finer aggregate gradations than the traditionally used OGFC. 

For the surface layer, in particular, the asphalts most commonly used nowadays are (a) asphalt concrete for very thin layers (AC-VTL), (b) porous asphalt (PA), (c) open-graded friction course mixture (OGFC), (d) stone mastic asphalt (SMA), (e) single or double surface dressing (S-SD or D-SD) and (f) micro-surfacing (MS). Table 10.17 gives the comparative properties/characteristics for all the abovementioned surfacing materials. 

Three types of RA have been used traditionally porous friction course, and gap and open graded asphalt concretes. 

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