Recycling of the pavements

RECYCLING OF THE
PAVEMENTS
Pavement
Management System
Bhavya S. Jaiswal
Btech civil,
Mtech
Transportation
Engineering

RECYCLING OF THE PAVEMENTS
FLEXIBLE PAVEMENT
• India has a network of over 5,897,671 kilometers (3,664,643 mi) of roads as of
31 March 2017.
• This is the second-largest road network in the world, after the United States with
6,645,709 kilometers (4,129,452 mi).
• The Bituminous pavement rehabilitation alternatives are mainly overlaying,
recycling and reconstruction.
• In the recycling process the material from deteriorated pavement, known as
Reclaimed asphalt pavement (RAP), is partially or fully reused in fresh
construction.
• It is also reported that recycled mix has higher resistance to shearing and
scuffing, which in turn increase the rutting resistance.
• Chances of reflective cracking are found to be less with recycled mix.
Prepared by: Bhavya S. Jaiswal

FLEXIBLE PAVEMENT
• Bituminous pavement recycling technology is not yet a popular in India.
• However, in advanced countries, bituminous material is the most recycled material
in the construction industry.
Advantages:
1) less user delay
2) conservation of energy
3) preservation of environment
4) reduced cost of construction
5) conservation of aggregate and binder
6) preservation of existing pavement geometrics
Country RAP/year
USA 33 million tons
Sweden 0.84 million tons
Germany 7.3 million tons
Denmark 0.53 million tons
Netherland 0.12 million tons
Japan 20 million tons

FLEXIBLE PAVEMENT
Recycling Methods:
In-place
Recycling
Cold Process
Hot Process
Central plant
Recycling
Pavement
recycling
Hot Process
Cold Process

FLEXIBLE PAVEMENT
Hot in-place recycling:
• The pavement intended to be recycled is heated to a higher temperature
using suitable heating arrangement. This facilitates easier removal of materials.
• After heating ,the pavement surface is scarified to the required depth. Further,
depending on the requirement fresh aggregate and binder are added.
• The material is mixed well and compacted to the required thickness. As this
process consumes less time, least disruption to traffic is caused.
• The transportation cost is less, as materials need not be taken away.
• Machinery required for this purpose being bulky in nature, sufficient right-of-way
is required. This becomes an important consideration for in-place recycling
within the city areas.

FLEXIBLE PAVEMENT
Hot in-place recycling Assembly:

3. RECYCLING OF THE PAVEMENTS
FLEXIBLE PAVEMENT
Cold in place recycling:
• In cold in-place recycling process first, the pavement is scarified with a
scarifier. The scarified material is crushed to the required gradation.
• The required amount of fresh aggregates and binder in cold form (emulsion or
cutback) is added.
• It is compacted and left for aeration. During this process additives like,
cement, quick lime, fly ash may be used.
• The cold mix recycling takes care of local geometric correction, correction of
pavement distresses like surface cracks Being an in-situ process the hauling
cost is considerably low.
• The air quality related problems during construction is almost negligible as
compared to hot mix process.
• Moisture content (when bitumen emulsion is used) needs to be given
importance as it influences gradation control, mixing and workability of recycled
mix to a large extent.

FLEXIBLE PAVEMENT
Cold in place recycling Assembly:

FLEXIBLE PAVEMENT
Hot central plant recycling:
• In this process, RAP is combined with required quantity of bituminous binder, and fresh
aggregates in a hot mix plant.
• The resultant mix is heated to an elevated temperature and mixed thoroughly.
• The hot mix is transported to paving site, placed, and compacted to the required
compaction level.
• The mix properties and performance is high comparable to that of virgin mix. And also
have noted that the quality control in this process is better when compared to hot in-
place recycling.
• As RAP is susceptible to moisture, care needs to be taken while storing it.
• Less workspace is required for laying the recycled mix, hence this is suitable for the
roads where the right of way is somewhat restricted.
• The RAP should not be exposed to extremely high temperature as it causes pollution
due to smoke emission

FLEXIBLE PAVEMENT
Hot recycling central plant

FLEXIBLE PAVEMENT
Cold central plant recycling:
• This is the similar process as is the hot central plant mixing, except it does not involve any
heating, and therefore emulsion bitumen is used binder in most of the cases.
• Precise control on the mixing time is important, over-mixing may cause premature breaking of
emulsified bitumen, under-mixing results in insufficient coating of aggregates.
Cold recycling central plant

REFERENCES
• Bituminous pavement recycling, By Aravind K. and Animesh Das, Department of
Civil Engineering , IIT Kanpur:
https://documentcloud.adobe.com/link/review?uri=urn:aaid:scds:US:f83bc42b-1b75-
4617-bf62-9f01ffe8d079
• CHAPTER 13 IN-PLACE RECYCLING, MTAG Volume I Flexible Pavement
Preservation 2nd Edition, Caltrans Division of Maintenance, February 19, 2008
• Introduction To Pavement Recycling:
https://www.fhwa.dot.gov/pavement/recycling/98042/01.cfm
• Flexible Pavement Recycling: https://dot.ca.gov/programs/design/lap-landscape-
architecture-and-community-livability/lap-sus-b-resource-conservation/lap-sus-b-1-
flexible-pavement-recycling

RIGID PAVEMENT
• WHY CONCRETE PAVEMENT RECYCLING?
• Concrete recycling is a relatively simple process.
• It involves…
1) Breaking
2) removing
3) crushing
• Hardened concrete from an acceptable sources used to produce RCA(Recycled
Concrete Aggregate)
• Produced for use as a substitute for virgin aggregate in almost any application.
• Old concrete pavements (including parking lots, sidewalks, curb and gutter, etc.)
that are to be removed often are excellent sources of material for producing RCA
because they are generally of good quality and are free of the contaminating
materials.
• Concrete pavements are 100 percent recyclable (ACPA 2006) According To
American Concrete Pavement Association.

RIGID PAVEMENT
• WHY CONCRETE PAVEMENT RECYCLING?
• Virgin aggregate resources are vast, but finite; many high-quality, conveniently
located virgin aggregate resources are being depleted rapidly.
• In addition, environmental regulations, land use policies and urban/suburban
construction and settlement are further limiting access to known aggregate
resources.
• Virgin aggregate costs can be expected to rise with scarcity and increasing haul
distances.
• Concrete pavement recycling is a proven technology that offers an economical
and sustainable solution to environmental problems.
• Pavement recycling also may offer the opportunity to improve the potential
performance of the pavement (through material modifications) while addressing
other roadway deficiencies (e.g., geometrics, foundation corrections, etc.) during
reconstruction.

RIGID PAVEMENT
Foundation Stability:
• The angular, rough-textured nature of RCA results in excellent particle interlock,
resulting in highly stable layers for pavement foundation, pipe bedding, and
backfill applications.
• The use of fine RCA in pavement layers or soil stabilization applications offers
the additional potential benefit of the development of additional strength and
stiffness over time as the un and partially-hydrated cement in the RCA continues
to hydrate.
• This secondary cementing effect can be significant, turning an “unbound” layer
of dense-graded or fine RCA into a layer that behaves more like a cement-
stabilized subbase.
• The benefits of this stiffening should be considered in predicting pavement
performance, and pavement structural designs (e.g., joint spacing, slab
thickness, etc.) should be engineered accordingly.

RIGID PAVEMENT
Concrete Strength:
Several studies have shown that the strength and elastic modulus of concrete
produced using coarse RCA may be lower than those of concrete containing all
virgin aggregate if the RCA contains significant amounts of reclaimed mortar.
However, research has shown that the replacement of up to 80 percent of the
virgin fine aggregate with fine RCA can potentially increase the strength of the
resulting concrete, with the peak strength increase occurring at a replacement
rate of about 25 percent (Fergus 1981).

RIGID PAVEMENT
Production of Recycled Concrete Aggregate (RCA):
• EVALUATION OF SOURCE CONCRETE
• It is the First step in producing RCA to determine quality and overall
performance of the source concrete.
• Records of the original concrete components (aggregate sources and quality,
cement type, admixtures, and reinforcing type (including fibers) and quantity),
concrete strength and durability can be useful in determining the potential
applications for the RCA produced.
• High-quality, durable concrete may be suitable for producing RCA for use in
structural concrete or pavement surface layers.
• Lower quality materials may be best suited for subbases, fill or other
applications.

RIGID PAVEMENT
PAVEMENT BREAKING AND REMOVAL:
 After the pavement slabs have been prepared for processing, the recycling
process continues with on-site demolition.
 The main purpose of pavement breaking is to size the material for ease of
handling and transport to the crushing plant.
 The slabs are broken into pieces small enough (typically 18 to 24 in. [45 to 60
cm]) to be lifted and transported easily.
 Where steel mesh reinforcing or rebar are present and have not been broken or
separated from the concrete by the breaking operation, a back hoe or bulldozer
with a “rhino horn” attachment curved and pointed steel pick, as shown in Fig.
often serves as an excellent loosening tool.

RIGID PAVEMENT
Gravity drop hammer
equipment for pavement
breaking.
Multi-head hydraulic
hammer pavement breaking
equipment.

RIGID PAVEMENT
“Rhino horn” for use in loosening
broken pavement fragments.

RIGID PAVEMENT
REMOVAL OF EMBEDDED STEEL:
• The removal of reinforcing steel, tie bars and dowels can occur during several phases of
the recycling process, but typically is accomplished during the breaking and removal
operation (particularly for continuous reinforcing steel)
• Following the primary and secondary crushing operations, where electromagnets often
are used to pick steel from the conveyor belts or Manual labor may be used to
supplement magnetic steel removal operations.
• Salvaged steel generally becomes the property of the contractor, who can typically sell it
as scrap metal.
• Wire mesh steel with large quantities of bonded concrete often is wasted.

RIGID PAVEMENT
Removal of reinforcing steel on the job site or after crushing.

RIGID PAVEMENT
Removal and transport of broken
pavement fragments using end
loader and dump truck.

RIGID PAVEMENT
CRUSHING AND SIZING:
• The same basic equipment used
to processes virgin aggregates
also can be used to crush, size
and stockpile the RCA (ECCO
1999), although equipment
modifications (e.g., the use of
more wear-resistant components
and the addition of
electromagnets) permit more
efficient processing of most
salvaged concrete pavements.

RIGID PAVEMENT
BENEFICIATION:
• Beneficiation can be described as the treatment of any raw material to improve
its physical or chemical properties prior to further processing or use.
• This can be a necessary step in some aggregate processing operations
(including concrete crushing to produce RCA) to eliminate accidentally included
organic material, excessive dust, and other contaminants that would cause
problems in the intended application of the aggregate.

RIGID PAVEMENT
STOCKPILING:
• Coarse RCA can be stockpiled using the same techniques and equipment as
are used with virgin coarse aggregate materials.
• Fine RCA stockpiles generally need to be protected from precipitation to reduce
the potential for secondary cementing due to hydration of exposed and
previously dehydrated (or partially hydrated) cement grains.
• As with virgin fine and coarse aggregates, more than two separate stockpiles
may be necessary to allow the production of aggregate blends that meet project
specifications.

RIGID PAVEMENT
RCA crusher, conveyor
and stockpiling
operation

RIGID PAVEMENT
IN-PLACE CONCRETE RECYCLING:
• When RCA is to be used in a subbase layer of the roadway and/or shoulders,
production can be accomplished using an in-place concrete recycling train.
• Such systems typically utilize primary and secondary crushers that have been
specially adapted for in-place recycling and are mounted on crawler tracks.
• Figure illustrates how the coarse RCA and fine RCA can be separated during
recycling operations, making it easy to use only the coarse RCA in the subbase
and/or shoulders.
• In-place recycling saves the cost of fuel and labor involved in hauling raw and
processed materials to and from the job site (in addition to the material and fuel
savings associated with using recycled materials instead of mining virgin
aggregates).

RIGID PAVEMENT
In-place recycling of an existing
concrete pavement with the coarse
and fine RCA being separated as
part of the process

REFERENCES
• Recycling Concrete Pavements:
http://wikipave.org/index.php?title=Recycling_Concrete_Pavements
• Recycling concrete pavements, By James W. Mack, Clinton E. Solberg, and Gerald
F. Voigt:
https://documentcloud.adobe.com/link/review?uri=urn:aaid:scds:US:0691e0bd-
12e2-45bc-ba96-7e0ca38e9c71
• Concrete Pavement Recycling and the Use of Recycled Concrete Aggregate in
Concrete Paving Mixtures:
https://documentcloud.adobe.com/link/review?uri=urn:aaid:scds:US:c19f5315-e772-
4490-935d-e9ef6e425c47

Recycling of the pavements

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