The Georgia Department of Transportation has evaluated and approved Fibrox 300 mineral fiber for use as an additive in asphaltic concrete mixes. With its ideal fiber length and its industry leading purity, Fibrox 300 is the mineral fiber of choice for use as a stabilizing additive in Stone Matrix Asphalt (SMA) and Open Graded Friction Course (OGFC) road surface applications. Fibrox 300 is readily available in 40lb bags and 650 lb bales.

Stone Matrix Asphalt (SMA)
SMA is a gap graded mix containing a higher percentage of coarse aggregate than that of conventional asphalt. The key ingredients aside from aggregate are Fibrox 300 mineral fibres, which assist in stabilizing the high asphalt content, mineral fillers and asphalt cement. The high concentration of coarse aggregate optimizes the stone on stone contact which results in SMA's superior performance and wearibility versus traditional asphalt mixes. SMA aggregates are bonded together by a thick film of asphalt cement. Fibrox 300 serves to stabilize and reduce "drain-down" of the high content asphalt mix. Additionally, Fibrox 300 will increase the film thickness and surface tension which enhances the wear and load bearing capacity of the road.

Open Graded Friction Course (OGFC)
An OGFC road surface construction is very porous. The "open" surface layer of 22 mm to 35 mm contains more voids than traditional asphalt roads thereby allowing water to be absorbed in the road and laterally migrate. Without the use of Fibrox Mineral Fiber, OGFC roads will exhibit poor wear characteristics. The increased voids will cause drain-down, resulting in picking and ravelling.

GDOT Office of Materials and Research (OMR)
The Department of Transportation for the State of Georgia (GDOT) maintains an Office of Materials and Research (OMR) that is recognized worldwide as being one of the finest of its kind. With a staff of 400, the OMR administers the GDOT research program, which is geared toward the implementation of new technology, including improved highway materials and processes that will be more economical and environmentally friendly.

Amongst other accomplishments, the OMR, in conjunction with Georgia Tech, has developed Stone Matrix Asphalt to improve rut resistance and increase service life; and Modified Open-Graded Friction Course to improve drainage and skid characteristics of surface mixes. Products which meet GDOT specifications are placed on the GDOT Qualified Products List. Only products included on this list or those which have been uniquely certified by this laboratory may be used in GDOT construction projects.

Fibrox 300 has been added to the Qualified Product List and is approved for use on GDOT projects.

• Back to the main Articles index.