This document discusses various methods for rehabilitating asphalt pavements through recycling. It begins with an introduction to asphalt recycling and its advantages such as conservation of resources and reduced traffic disruption. Different recycling techniques are then outlined, including cold planning, full depth reclamation, cold in-place recycling, and hot in-place recycling. For each method, the key steps of the process are described. Examples of recycling projects in Pakistan are also provided.
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Existing Practice for Rehabilitation
For the rehabilitation process , existing practice is to mill the
pavement up to the required depth
After that the milled material is dumped at the dumping site.
Thus tons of material is wasted which can be reuse using different
recycling process
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Existing Practice for Rehabilitation
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Existing Practice for Rehabilitation
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Asphalt Pavement Recycling
Asphalt Pavement Recycling is one way to stretch
existing budgets to maintain, preserve, rehabilitate and
reconstruct more kilometers of roadways.
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Advantages of Asphalt
Recycling
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Advantages of Asphalt Recycling
Conservation of natural resources
Better pavement performance
Reduced traffic disruption, maintained pavement geometry and
thicknesses
Removes cracked and aged pavement layers
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Advantages of Asphalt Recycling
Improves pavement smoothness and cross‐slopes
Maintains curb heights, drainage inlets, and bridge clearances
Creates a rough texture that bonds better with the overlay
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Materials savings will depend on...
Virgin binder cost
Asphalt content of the mix design
Aggregate cost
RAP cost
Asphalt content of the RAP
Percentage of RAP
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Executive Summary of Maintenance /
Rehabilitation Expenditure on NHA Network
Serial No. Maintenance Activity Year
2007-08
Year
2008-09
Year
2009-10
1 Rehabilitation 1,416.55 2,248.23 4,413.93
2
Structural Overlay
(Periodic Maintenance)
1,637.92 1,898.59 1,425.70
3
Functional Overlay
(Periodic Maintenance)
1,676.43 1,812.60 1,973.12
4 Routine Maintenance 809.92 1,278.82 1,190.46
5 Highway Safety 410.00 469.0 650
6
Emergency Maintenance
Allocation
900.00 1,000.00 1,000.00
Total (1 to 6) Rs. Million 6,850.82 8,707.24 10,653.21
Network Length KM 9,893 11,569 11,897
Asphalt Production Cost Categories
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Energy Consumption Related to Road
Construction and Maintenance.
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Economical benefits
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RAP
(Reclaimed Asphalt Pavement)
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What is RAP
RAP= Reclaimed Asphalt Pavement
Removed and/or reprocessed pavement
materials containing:
binder (5%) and aggregates (95%)
Old asphalt pavement that has been removed
from the roadway by either full depth removal or
milling
High RAP is > 25% by weight of mix.
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RAP as a base material
Roughly equal to granular base with some additional value.
RAP as a Roadbeds
Value is roughly equal to granular
base Replacement Value Plus…
Reduced Haul if processed in place
Conservation of aggregate resources
Overall economics (Fuel Consumption
& Equip. Savings)
This historically accounted for the
largest recycling tonnage
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RAP used in Shoulders
Shoulders Value is greater than
granular material + increased structural
number.
Reduced Haul when processed and left
in place
Conservation of aggregate resources
Overall economic benefit and less
shoulder maintenance
Energy savings vs. paved shoulders
Safety of wider shoulder
RAP in new pavement
Replaces portion of expensive virgin binder and aggregate
Virgin aggregate + asphalt value
costs
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Use of Recycle Pavement in Pakistan
Hot-In-Place Recycling
In the initial instance, projects of Hot-In-Place Recycling were launched on
different locations of Motorway M-2 (M-2 Contract No 207-2006).
Hot Recycling Works on M-2 (Km 90 to 330), July 2007.
Cold In-Place Recycling was experimented on
Kharain–Rawalpindi Project (51 KM, Contract No 13),
Mian Channu-Sahiwal-Okara (72 Kms, Contract Package No.11b).
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Use of additives
Foamed Bitumen
Used as a binder for
Cold mixes with reclaimed Asphalt
pavement (RAP) materials.
Specialist surface dressing
Conventional cold mixes with good
quality or marginal aggregates
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Foamed bitumen
The product of hot bitumen meeting with
small amount of cold water ,
creating thin bubbles of bitumen to bond
with pulverized base materials.
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Emulsified Bitumen
A mixture of asphalt cement, water and emulsifying
agent (free flowing liquid at ordinary temperature).
These three constituents are fed simultaneously into
a colloid to produce extremely small globules (5-10µ)
of asphalt cement, which are suspended in water.
The emulsion contain about 50% - 65% bitumen.
Has low viscosity at ambient temperature, it
generally can be used without additional heat.
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Various Methods of Asphalt
Pavement Recycling
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Various Methods of Asphalt Pavement
Recycling
To describe the various asphalt recycling methods, six
broad categories have been defined by Asphalt Recycling
and Reclaiming Association (ARRA), U.S. Department of
Transportation, Federal Highway, Administration.
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Cold Planning (CP)
Cold planning is the controlled removal of an existing
pavement to a desired depth, longitudinal profile, and
cross-slope, using specially designed equipment. The
resulting textured surface can be immediately used as a
driving surface, can be further treated with one of the other
asphalt recycling methods, or once cleaned and tack coated,
overlaid with HMA or recycled mix. In addition, CP can be
used to roughen or texture pavements to restore low
friction numbers and eliminate slipperiness.
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Hot Mix Asphalt Recycling (Central Plant)
Hot recycling in central plant is the process of removing the
existing pavement, combining RAP with new or “virgin”
aggregates, new asphalt binder, and/or recycling agents (as
required) in a central plant to produce a recycled mix. Hot
recycling of RAP currently is the most widely used asphalt
recycling method in the world.
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Cold Mix Asphalt Recycling (Central Plant)
In this process RAP material is mixed with new asphalt binder
and new aggregate (if needed) to produce cold, recycled mix
without application of heat. Recycled mix is produced at a
central location using a stationary clod mix plant. The cold
central plant recycling mix can be used immediately or it can
be stockpiled for later use in such applications as maintenance
blade patching or pothole repair.
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Full Depth Reclamation (FDR)
The recycling method where all of an asphalt pavement section, and
a predetermined amount of underlying materials, are treated to
produce a stabilized base course. In this process existing pavement is
pulverized, introduce additive and mix, mixed material are compacted
and a wearing course is finally applied on it.
Distresses and problems like loss of bonding between pavement
layers, stripping loss of surface integrity due to raveling, potholes,
bleeding, excessive shoulder drop off, inadequate structural capacity
are effectively treated with this method.
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Cold In-place Recycling (CIR)
In this process existing pavement materials are removed,
mixed with stabilizing agents, virgin materials (if required) and
reused in place. Cold in-place recycling is undertaken on site
and generally uses 100 percent of the RAP generated during
the process.
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Cold in-place Recycling
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CIR Train at work
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Hot In-place Recycling (HIR)
In this process existing asphalt surface is heated, soften and
scarified to a depth, typically from 20 to 60 mm (25 mm most
common). Scarified material is combined with virgin aggregates,
asphalt binder, and/or recycling agent on the requirement basis
and finally compacted.
Mostly surface defects i.e. Raveling, Potholes, Bleeding, Friction
number, Rutting, Corrugations, Shoving, Slippage, longitudinal
transverse and reflection cracking, poor ride quality caused by
swells, bumps, sags, and depressions are effectively treated with
this method of recycling.
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