Fiber reinforced bituminous mix
Addition of various kinds of fibers to the binder and aggregates during mix preparation process results in fiber reinforced bituminous mix (FRBM). Fibers are generally blended with bitumen binder before mixing it with the aggregates to achieve complete coating and even distribution throughout the mix. Research shows that FRBMs develop good resistance to aging, fatigue cracking, moisture damage, bleeding, reflection cracking etc. (Serfass and Samanos, 1996; Maurer et al., 1989). Ultra-thin whitetopping
Overlaying technique of pavement
rehabilitation is well known and widely practiced.
However, ultra thin whitetopping (UTW) of concrete
over existing bituminous pavement is a relatively
new concept. UTW can be designed for low-speed, low
volume traffic areas such as street intersections,
aviation taxiways and runways, bus stops and tollbooths.
In this technique, a thin layer of
high-strength, fiber-reinforced concrete is placed
over a clean, milled surface of distressed bituminous
concrete pavement to achieve a full or partial bonding.
Bonding makes the two layers behave as a monolithic
unit and share the load. Due to bonding, the neutral
axis in concrete shifts from the middle of concrete
layer towards its bottom. This results in a lowering
of stresses at the bottom of concrete layer. Thick
composite section behaviour causes the corner stresses
to decrease. On the other hand, downward shifting
of neutral axis may cause critical load location
to shift from edges to corners thus increasing the
corner stresses. Short joint spacing is used to decrease
the slab area that can curl or warp thus minimizing
the corresponding stresses (MTTP
2004). A schematic diagram of UTW have been presented
in Figure-9.
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Figure -9 Flexible composite pavement using UTW |
UTW is an excellent resurfacing option for deteriorated bituminous pavements which otherwise require frequent repair or overlays.
Following are some of the advantages of a UTW system (CAC 2004, Murison 2002):
• It is beneficial for repair of roads and intersections having problems of rutting, cracks, and poor drainage.
• It provides improved skid resistance.
• Its light colour reflects more light than bituminous pavement.
• Its heat-reflecting property can help to lower the average city temperature.
• It is less costly to maintain, than conventional flexible pavements, and does not require frequent resurfacing and repairs.
• The UTW concrete resists bitumen aging.
• The UTW concrete prevents degradation of bituminous surface due to fuel spills.
• It causes minimal traffic disruption due to faster construction and repair procedure.
• Its small panels are ideal for utility maintenance.
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