open gradation of aggregate
lacks the mid-sized aggregates
Dense graded. Gap graded
• Open-graded and gap-graded aggregate
skeleton, nominal aggregate sizes of 12.5 mm or
less, and higher than normal asphalt binder
contents and are placed in thicknesses of less
than 1 in.
OGFC consists of an aggregate with relatively uniform grading
and little or no fine aggregate and mineral filler
OGFC is composed of open
Minimum 18% air voids
Where to use?
– High traffic to aid in cleaning mixture and justify
– Areas with high frequency of wet weather
– Balance against possible increase winter
– Should not be used on short segments or bridge
To provide high skid resistance and superior
surface drainage OGFC is used. So the ride
quality and safety is the main concern to
Their macro texture facilitates drainage of
water from the tire/pavement interface,
Reduce the potential for hydroplaning:
by providing drainage channels for water to
flow beneath the pavement surface
The sheet of surface water that causes
hydroplaning is drained through the mix to
the edge of the pavement.
Graded Aggregate Base
Dense Graded Asphalt
SKID RESISTANCE - Which pavement
would you rather drive on in a storm?
Quiet, it's smooth, silent
it feels like you're driving on sponge rubber
• Experiencing glare while driving is irritating
and dangerous for all drivers.
• visual acuity and peripheral vision are
reduced as people get older.
• Rain and night-time driving are the biggest
contributors to accidents.
"Low textured" surfaces reflect more light
and act like mirrors.
The color of the road surface affects daytime
visibility. The lighter the surface color, the
greater the potential for glare.
•Mitigation of Flushing and Bleeding: Its open void
structure increases the pavement friction and allows
absorption of free surface asphalt to overcome
Provide and maintain good high speed, frictional qualities
• durability and flexibility.
• increases resistance to moisture damage.
• increases resistance to bleeding.
• reduces aging of the mix.
• increased resistance to rutting.
• noise level decreases.
• the tolerance to higher stress and strains.
• maintain viscoelastic properties for a much
Asphalt rubber OGFC
• Freeze early and last to thaw
• Difficult to remove snow and ice
• icy areas where tire chains, or snowplows
are commonly used, OGFC has exhibited
• May need special deicing chemicals
• Require more treatments.
• Possible issue on bridge decks
• Problems with transitions to normal
The fines from mud and sand can fill the
voids and reduce the drainage capacity of
The OGFC must be kept clean to prevent
Measurements to improve its properties:
• Production temperatures are increased
to dry aggregate components and thus
improve AC adhesion.
• Coarser gradations and thicker layers
are used to improve permeability.
• Setting minimum percentages for air
voids at 18%.
How to improve the performance
of OGFC mixes
• Polymer additives:
– reduces premature oxidation.
• Hydrated lime:
– stripping agent
• Rubberized asphalt:
– improving durability
• Mineral fibers:
– increase the ability of asphalt to coat
• Raveling due to softened binder from oil
and fuel drippings.
• Raveling due to oxidation and hardening
of the binder.
• Raveling due to lack of compaction or low
• Delamination due to improper tack coat
OGFC overlays may exhibit the following
• Shear failures in high stress areas.
• Cracking due to fatigue.
• Cracking due to reflection from below