NCAT Report 99-3: Design of New-Generation Open Graded Friction Courses provides a recommended mix design procedure for OGFCs. OGFC is more expensive per ton than dense-graded HMA, but the unit weight of the mix when in-place is lower, which partially offsets the higher per-ton cost.
The lack of fines in the open-graded aggregate does not allow for it to hold on to the water. Instead, the water permeates through the base material. This base is typical in a permeable base installation and has since been introduced and used in any patio and walkway installation to allow for the permeation of water.
There are two types of open-graded mixes typically used in the U.S.: 1 Open-graded friction course (OGFC). Typically 15 percent air voids, no minimum air voids specified, lower aggregate... 2 Asphalt treated permeable bases (ATPB). Less stringent specifications than OGFC since it is used only under dense-graded... More ...
Open-Graded An open-graded HMA mixture is designed to be water permeable (dense-graded and SMA mixes usually are not permeable). Open-graded mixes use only crushed stone (or gravel) and a small percentage of manufactured sands. There are two types of open-graded mixes typically used in the U.S.:
Open graded friction courses (OGFCs) are a type of pavement that have been built across the United States since the 1950's. These asphalt mixes contain only a small portion of fine aggregate, creating a pavement with a relatively large percentage of air voids.
An open graded cold mix is a coarse aggregate mix (very small amount of fine aggregate) with a large amount of air voids to allow for water to drain. These mixes can be used as a base or surface course and show excellent resistance to fatigue, reflection cracking, rutting, and shoving.
SMA is generally more expensive than a typical dense-graded HMA because it requires more durable aggregates, higher asphalt content, modified asphalt binder and fibers. In the right situations it is cost-effective because of its increased rut resistance and improved durability.
Hot Mix Asphalt (HMA) is a combination of approximately 95% stone, sand, or gravel bound together by asphalt cement, a product of crude oil. Asphalt cement is heated aggregate, combined, and mixed with the aggregate at an HMA facility.
An open-graded HMA mixture is designed to be water permeable (dense-graded and SMA mixes usually are not permeable). Open-graded mixes use only crushed stone (or gravel) and a small percentage of manufactured sands.
Open-graded (clean) aggregates: are “porous” with notable air voids between individual stones, and little to no “fines”. These mixtures drain effectively, but do not compact well to form a dense conglomerate. Road applications include use as base material and for subsurface drainage.
Open Graded Asphalt is a porous asphalt mix formulated to provide large voids (in excess of 20 per cent) to allow surface water to drain away and hence increase safety for the motorist. The demand for low traffic noise surfacing has greatly increased in the last few years, especially in urban areas.
Open Graded Asphalt (OGA) is a porous asphalt material that produces a highly textured surface. It provides a safer wet weather surfacing by reducing the amount of surface water leading to improved visibility and skid resistance. It also generates lower tyre noise compared to other bituminous surfacings.
Stone mastic asphalt (SMA), also called stone-matrix asphalt, was developed in Germany in the 1960s with the first SMA pavements being placed in 1968 near Kiel. It provides a deformation-resistant, durable surfacing material, suitable for heavily trafficked roads.
Asphalt Surface Course refers to an aggregate, sand, and asphalt cement mixture used as the final surface course placed in a lift (often above the intermediate asphalt pavement course), in a roadway application, driveways, parking lots, and trails.
In general the asphalt layers are paved on a bound or unbound road base layer. Starting at the road surface, the first layer is called the surface course. The second layer is mostly called the binder course. The lower layers are the base courses.
Type A hot mix requires that at least 90% of the coarse aggregate and 70% of Fine aggregate used contains crushed particles while Type B hot mix only requires 25% and 20% respectively.