MR-2 Pavement Reuses - GreenroadsGreenroads Manual v1.5 Materials & Resources MR-2 Pavement Reuse DOCUMENTATION A calculation that shows the computed percent of material reused including

Greenroads™ Manual v1.5 Materials & Resources

MR-2 Pavement Reuse

PAVEMENT REUSE GOAL Reuse existing pavement and structural materials.

CREDIT REQUIREMENTS Reuse at a minimum, a percentage of existing pavement materials or structural elements by estimated volume or weight as shown in Table MR‐2.1. The materials considered in volume calculations can include but are not limited to hot mix asphalt (HMA), portland cement concrete (PCC), unbound granular base material, stabilized base material, reinforced concrete, structural steel, and timber. In general, pavement materials will be easier to calculate by volume while structural materials should be calculated in terms of weight, unless material volumes are adjusted for density.

Table MR‐2.1: Points for Estimated Volume or Weight of Reused Materials

Credit MR‐2 Points 1 2 3 4 5

% Reuse of Existing Pavement Materials or Structural Elements 50 60 70 80 90

Details

“Reuse” is defined as a continued use or repurposing of existing materials within the project limits. Specifically, this means the material in question has not been transported beyond the project limits at any time during project construction and that it has been minimally processed or changed from its original condition.

This definition differentiates “reuse” from “recycle.” Pavement reuse methods are intentionally used to extend the life of the existing pavement structure in place. Similarly, in most cases, reuse of structures, such as bridges or retaining walls, is typically known as a “retrofit,” where specific methods are implemented to extend the life of the existing structure in place. Reused materials may be used in place, or they may be temporarily removed from their original location if:

1. The materials substantially remain in the same condition as they were removed. 2. The materials are replaced in the same location on the project or are moved to

a new location on the project and repurposed without processing. “Retrofit” is defined as the reinforcement of structures to become more resistant and resilient to the forces of natural hazards and other environmental factors such as aging and weathering. It involves the consideration of changes in the mass, stiffness, damping, load path and ductility of materials, as well as radical changes such as the introduction of energy absorbing dampers and base isolation systems.

“Recycle” is defined as recovering a portion of a used product or material from the waste stream for reprocessing and/or repurposing with minimal or no transport offsite or within the project limits. A “recycled material” is any material, from any project, that has been:

1. Processed at a location outside of the roadway project limits 2. Processed at a location inside of the project limits, but substantially displaced or

otherwise moved or removed from its existing location specifically in order to process the material, such as temporary or mobile on‐site recycling facilities.

MR-2

1-5 POINTS

RELATED CREDITS

PR‐2 Lifecycle Cost Analysis

PR‐9 Asset Management Plan

MR‐3 Earthwork Balance

MR‐4 Recycled Materials

PT‐1 Long‐Life Pavement

PT‐6 Pavement Performance Tracking

SUSTAINABILITY COMPONENTS

Ecology Economy

BENEFITS

Reduces Raw Materials

Reduces Fossil Fuel Use

Reduces Air Emissions

Reduces Greenhouse Gases

Reduces Solid Waste Reduces Manmade

Footprint Increases Service Life Reduces Lifecycle

Costs

Materials & Resources Greenroads™ Manual v1.5

Pavement Reuse MR-2

3. Material from any outside source that has been repurposed for use on the roadway project, even if salvaged and still its original condition.

“Existing pavement material” is defined as all material within the project limits in the existing pavement structure (including surfacing and base material). This includes travelled lanes and shoulders, and pavement structures for physically separated bicycle and pedestrian pathways.

“Existing structural material” is defined as all material within the project limits in existing non‐pavement structures such as bridges (including overpasses), retaining walls, and stormwater infrastructure such as vaults, pipes and culverts. All existing structural materials include their foundations, for which volumes may be difficult to estimate. Where actual weights are not available, reasonable estimates may be used or volume may be estimated. To compute volume of hollow structural sections such as prefabricated members or corrugated steel, estimate the mass of the material and adjust for material density to determine volume. Note that for typical reinforced concrete sections, the steel does not need to be separated from the composite section for purposes of volume calculations and a composite density may be used.

In order to achieve credit, some activity must be done to either the pavement or a structure such that the materials or assembly is improved or upgraded in some way. Cleaning, regular maintenance and minor repairs done as part of routine operations and maintenance do not qualify for this credit.

This credit is NOT appropriate for construction of an entirely new roadway or bridge replacement, nor does it apply to materials in existing subgrade (natural in‐situ material), fill material or sidewalks that are not explicitly part of the pavement structure or structural element. Additionally, this reuse credit does not include minor structural elements such as luminaires, signs, or signals because they do not make up a significant amount of the total volume of materials on the project and they do not bear regular loads of people or vehicles.

This credit IS appropriate for:

Pavement rehabilitation actions that place new material over the existing pavement structure such as hot mix asphalt (HMA) overlays, PCC overlays (either bonded or unbounded) and pavement surface treatments (e.g., chip seals, slurry seals).

In‐place reprocessing operations (even though some are referred to as “recycling”) such as hot in‐place recycling, cold in‐place recycling, full depth reclamation, portland cement concrete (PCC) crack‐and‐seat and rubblization.

Repurposing of existing material for other purposes in the same project. The material must not leave the project boundary to be considered. If it does leave the project boundary it may still be considered in the Recycled Materials credit.

Any of several bridge retrofit methods:

Stainless steel wire mesh (SSWM) composites

Full height steel jackets

Elastomeric bearings

Steel restrainer cables

Shear keys

Fiber reinforced polymers (FRP) wraps

Shape memory alloy (SMA) devices

Metallic and viscoelastic dampers

Pipe seat extenders

Reuse and repairs of structural foundations

Retaining wall retrofits such as leveling, seismic retrofits, and slope stabilization methods that leave a majority of the original wall in place.


MR-2 Pavement Reuse

DOCUMENTATION A calculation that shows the computed percent of material reused including the following four items at minimum:

1. Total volume of existing pavement structure 2. Total volume of reused pavement structure 3. The computed percentage of the total reused volume, and 4. A short written description of how the structure was reused.

APPROACHES & STRATEGIES

Where feasible, undertake pavement preservation efforts (e.g., overlays, diamond grinds, etc.) that preserve a majority of the existing pavement structure. Pavement structure should not be reused if its engineering properties are inadequate for the pavement’s intended function. In this instance, this credit serves as a reward for an agency maintaining an active pavement preservation program that addresses deteriorated pavement early enough so as to avoid a total reconstruction as the only viable remedy.

Use in‐place recycling techniques such as hot in‐place recycling, cold in‐place recycling and full depth reclamation. These methods qualify as reuse because the material has not crossed project boundaries.

Use a crack‐and‐seat or rubblization option for deteriorated PCC rather than removing and replacing the existing PCC. Such operations usually involve paving additional structure over the cracked‐and‐seated or rubblized PCC; therefore, additional considerations would be bridge clearance, drainage flows and matching grades for cross‐streets, ramps and other access roads.

Retrofit or refurbish existing structures. There are a variety of methods available for retrofits depending on existing issues.

Perform a lifecycle cost analysis of retrofit options for bridges when considering design alternatives.

Reuse the pavement on bridges where it exists.

Plan to reuse foundations because it reduces environmental impacts, especially for in‐water work.

Reuse subassemblies and components of structures if the entire structural element cannot be reused.

Evaluate the structural condition of existing elements such as bridges and retaining walls. This is typically determined by a structural engineer. Do not reuse elements that have been damaged by corrosion or natural hazards without review by a structural engineer.

Where structural elements are determined to be inadequate for reuse, consider salvaging them or deconstructing them for use on another project or purpose.

Example: “Reuse” versus “Recycle”

Greenroads makes a distinction between the terms “reuse” and “recycle.” The following discussion provides more details for distinguishing between the two.

Reused materials: These materials originate from within the project limits and are either maintained in place (such as existing pavement structure) or disturbed/removed but are not transported outside the project limits. Examples include:

Overlaying an existing pavement structure with new pavement material. The existing structure is counted as reused material. This is specific to pavements since, for instance, a stop sign that remains undisturbed during a roadway project does not count as being reused.

Removing crushed aggregate base course from one location and reusing it as crushed aggregate base course in another location within the project.

Hot in‐place recycling (HIR). The processing and treatment of an existing HMA pavement section (usually 1‐2 inches of the surface only). Treatment involves heating the existing HMA surface, the addition of bituminous and/or chemical additives and, often, some additional new HMA. The existing pavement materials remain in place and essentially serve their original purpose.


Pavement Reuse MR-2

Cold in‐place recycling (CIR). The processing and treatment with bituminous and/or chemical additives of an existing HMA pavement section without heating to produce a restored pavement layer. The existing pavement materials remain in place and essentially serve their original purpose. In many cases the resultant product is used as a stabilized base course that may or may not be subsequently overlaid with a new surface course.

Full‐depth reclamation (FDR). The processing and treatment with bituminous and/or chemical additives of an existing HMA pavement (may also include base material) without heating to produce a restored pavement layer. The existing pavement materials remain in place and essentially serve their original purpose. In many cases the resultant product is used as a stabilized base course that may or may not be subsequently overlaid with a new surface course.

Recycled materials: These materials may originate within or external to the project limits and are diverted from final disposal (i.e. landfill) and are reprocessed or repurposed for use in the project. The essential difference between “recycling” and “reuse” is that recycling involves reprocessing/repurposing and, usually, substantial transportation (usually to and from the reprocessing facility and sometimes to and from the project site). Also, a recycled material can often originate from outside the project limits before use on the project, whereas reused material does not. Examples include:

HMA from the project in question or another project, commonly called reclaimed asphalt pavement (RAP), is transported to a storage location or HMA plant location and included as a constituent of a new HMA mixture for the project in question.

An existing concrete structure from the project in question or another project is demolished and crushed into an appropriate gradation and used as a crushed aggregate base material or an aggregate component in new PCC on the project in question.

An industrial byproduct (e.g., coal fly ash, silica fume, ground granulated blast furnace slag) is incorporated as a component in a new material (e.g., PCC).

Diverted waste material (e.g., discarded rubber tires, crushed glass) is incorporated as a component in a new material (e.g., HMA, PCC).

Example: What Is and What Is Not “Existing Pavement Structure”

Figures MR‐2.1 through MR‐2.4 show examples of what should and should not be included in this calculation.

Figure MR‐2.1: This bicycle path should NOT be counted as existing pavement structure because it is a separate bicycle/pedestrian path that is not accessible to automobiles.

Figure MR‐2.2: This bicycle lane should be counted as existing pavement structure because although it is marked as a bicycle lane, it is accessible to automobiles. Specifically, it must be crossed by vehicles accessing curbside parking.

Figure MR‐2.3: This paved median should NOT be counted as existing pavement structure because it is separated from the travelled way by a curb structure and is not accessible to automobiles.

Figure MR‐2.4: This paved median area should be counted as existing pavement structure because it is accessible to automobiles even though the double yellow line implies that they should stay out.


MR-2 Pavement Reuse

Figure MR‐2.1: A bicycle path in Auburn, AL. Figure MR‐2.2: A bicycle path as part of the roadway (image from Google Maps).

Figure MR‐2.3: A paved non‐accessible median

(image from Bing Maps).

Figure MR‐2.4: A paved accessible median on US 101

in Washington State.

Example: Calculation for Widening an Existing Roadway

Description: Four miles of an existing two‐lane road with 12‐foot wide lanes and no shoulders is to be widened to include a 10‐foot wide two‐way left turn lane and 8‐foot shoulders. The existing pavement structure consists of 5 inches of HMA over 8 inches of crushed aggregate. The existing pavement is kept in place except that the top 1.5 inches of HMA is removed by a milling machine. New pavement of the same structure is built on either side of the existing pavement structure to accommodate the wider final alignment.

Calculation logic: All 8 inches of the base material and 3.5 inches of the HMA are reused. The 1.5 inches removed by the milling machine is not considered “reused.” If it is recycled then it may qualify for consideration under MR‐4 Recycled Materials.

Calculation: Total volume of existing pavement:

Reused volume of existing pavement:

craig

Stamp

craig

Stamp


Pavement Reuse MR-2

Percentage of existing pavement reused:

17,991 20,338

0.88 88%

This project would qualify for 4 points.

Example: Calculation for Bridge Retrofit Project – State Route 99 Aurora Bridge

Description: The landmark Aurora Bridge in the City of Seattle was built in 1932 and has undergone several rehabilitation activities. Currently, it is scheduled for additional retrofit of 18 of its 48 unique columns, as well as its supporting trusses, girders and beams starting in late 2010. The columns are “cruciform” shaped, which makes it difficult to use traditional retrofit options such as steel column jackets. The Washington State Department of Transportation intends to spend $2.1 million to complete the upgrade the seismic capacity of the bridge.

Figure MR‐2.5: Aurora Bridge, Seattle, WA (Photo Courtesy of WSDOT)

Calculation logic: The entire bridge structure is to remain in place for the planned 2010 retrofit, therefore 100% of it is reused.

Calculation: None needed. All existing structural materials are reused.


Example: Calculation for Bridge Retrofit Project – State Route 104 Hood Canal Bridge

Description: The Hood Canal Bridge is the longest floating bridge over saltwater in the world. At 1.5 miles, the bridge is comprised of two approaches, two transition spans and 36 pontoons. The west “half” of the bridge has 19 pontoons and the east has 17. The west approach span of the bridge and some of the existing pontoon structures were retrofitted. This portion of the bridge had been replaced in 1982 after sinking in 1979. The east “half” of the bridge was completely replaced with construction completing in early 2010.


MR-2 Pavement Reuse

Calculation logic: Use weight as an indicator for actual material volume of the pontoons. (Total volume of materials can be computed from WSDOT data, but density information is not available.) The east portion of the bridge (17 pontoons) weighs 107,111 tons with an approach slab weighing 3,800 tons. The west portion of the bridge weighs 127,817 tons with an approach slab weighing 1,000 tons. There are two transition spans (steel truss) that are 800 tons each.

Calculation: Compute the total weight of the bridge.

[107,111 + 127,817 + 3,800 + 1,000 + 2(800)] = 241,328 tons

Compute the total weight of the retrofitted sections. (Note this calculation presumes 100% of the west half features were retrofitted for ease of calculation.)

[127,817 + 1,000 +800] = 129,617 tons

Compute the percentage of the total bridge weight of the retrofitted section.

129,617 tons/241,328 tons = 53.7%

This project would qualify for 1 point. Additionally, the pontoons were sold to a company in Canada and they have been reborn as marina structures. The replaced bridge trusses were not able to be reused but were salvaged for scrap.

Figure MR‐2.6: Hood Canal floating bridge retrofit and replacement project. (Photo Courtesy of WSDOT)

Example: Calculation for Preservation Overlay of an Existing HMA Pavement

Description: Six miles of an existing four‐lane highway with 12‐foot wide lanes and 8‐foot shoulders is to be overlaid with 2 inches of additional HMA. All of the exiting pavement structure is to remain in place.


Pavement Reuse MR-2

Calculation logic: All of the existing pavement structure is to remain in place therefore 100% of it is reused.

Calculation: None needed. All existing pavement is reused.


Example: Calculation for Rubblization of an Existing PCC Roadway

Description: Three miles of a four‐lane highway with 12‐foot wide lanes and 8‐foot shoulders is to be rubblized and overlaid with 6 inches of HMA. The existing pavement structure across all lanes and shoulders consists of 9 inches of PCC over 12 inches of crushed aggregate.

Calculation logic: All of the existing pavement structure is to remain in place therefore 100% of it is reused.



Example: Calculation for Hot In-Place Recycling of an Existing HMA Roadway

Description: Two miles of a two‐lane highway with 12‐foot wide lanes and 4‐foot shoulders is to be hot in‐place recycled. Hot in‐place recycling will be done on the top 2 inches of HMA pavement using a heater scarification approach (http://pavementinteractive.org/index.php?title=HIPR). This method uses a plant that heats the pavement surface (typically using propane radiant heaters), scarifies the pavement surface using a bank of non‐rotating teeth, adds a rejuvenating agent to improve the asphalt binder viscosity, then mixes and levels the mix using a standard auger system. The pavement is then compacted using conventional compaction equipment.

Calculation logic: All of the existing pavement structure is reprocessed and reused on the project, therefore 100% is reused.



Example: Calculation for Reconstruction of One Lane of an Existing Roadway

Description: One mile of the outside southbound lane of an existing six‐lane arterial with 12‐foot wide lanes is to be removed and replaced with PCC to accommodate a bus rapid transit lane. The arterial has no shoulders and has a raised vegetated median that is not accessible to automobiles. The existing pavement structure consists of 7 inches of HMA over 9 inches of crushed aggregate. The outside southbound lane construction requires a pavement structure of 12 inches of PCC over 7 inches of crushed aggregate. Therefore, all the pavement structure in the outside lane must be removed and a further three inches of excavation must be done to accommodate the thicker pavement section. Once the excavation is done, 7 inches of the previously removed crushed aggregate is placed. Then, 12 inches of new PCC is placed. The project scope includes all southbound lanes because other median work and restriping is to be done. The project scope does not include the northbound lanes.

Calculation logic: The project scope only includes the southbound lanes; only material in these lanes shall be included in the calculation. Also, since 7 inches of the existing crushed aggregate was reused as base course for the new PCC lane, it can be included.

Calculation: Total volume of existing pavement in the southbound lanes:


MR-2 Pavement Reuse

36 7 9 1

12 1

5,280 1 27

9,387

Reused volume pavement in the two left‐hand existing lanes (those not reconstructed):

24 7 9 1

12 1

5,280 1 27

6,258

Reused volume of crushed aggregate in the reconstructed right‐hand lane:

12 7 1

12 1

5,280 1 27

1,368

Percentage of existing pavement reused:

6,258 1,368 9,387

0.81 81%


If the project did not reuse the existing aggregate in the right lane, the calculation would be as follows:

6,258 9,387

0.66 66%

The project would qualify for 2 points.

POTENTIAL ISSUES

1. A project may misclassify a material as “reused” instead of “recycled.” Usually this is a minor issue since both processes can receive Greenroads points. See MR‐4 Recycled Materials for more information.

2. Pavement thickness in older road sections may be highly variable; therefore estimating existing volume may be difficult. In such cases, it is important to clearly state assumptions and the sources of information you are using.

RESEARCH Reused materials are a valuable and cost‐effective resource that may be used to help reduce the ecological impacts and lifecycle costs of roadway construction. In many forms of roadway infrastructure (especially pavements) existing materials can be reused for their original intended purpose if they meet minimum engineering standards. Badly deteriorated hot mix asphalt (HMA) pavement, for example, may be ground up in place, stiffened with a binding agent and recompacted to form the base material for a new pavement. This process is typically referred to as cold in‐place recycling.

For the built environment, materials reuse typically refers to the idea of carefully deconstructing a building instead of demolishing it. Deconstruction means disassembling a building in such a way that the materials can be reused for new construction (BMRA, 2010). Thus, items like floor joists, windows, doors, plumbing fixtures and siding that still have remaining life can be reused for new construction rather than demolished and either sent to landfill or recycled as more basic materials (e.g., wood, steel, etc.). For instance, an assembly of materials like a door (possibly consisting of wood, aluminum, brass, glass, plastic and more) can be reused rather than disposed of or separated into its constituent components for recycling.


Pavement Reuse MR-2

Pavement Reuse Defined Pavement Reuse: the process by which pavement materials within the project limits are either maintained in place (such as existing pavement structure) or disturbed/removed but are not transported outside the project limits.

By this definition Greenroads distinguishes “reuse” from “recycle” because recycling is defined more broadly as the process by which materials within or external to the project limits are diverted from final disposal (i.e. landfill) and are reprocessed or repurposed for use in the project. The essential difference between “recycling” and “reuse” is that recycling involves reprocessing/repurposing and, usually, substantial transportation (usually to and from the reprocessing facility). Also, a recycled material need not originate from the project in question. Therefore, material reuse as defined by Greenroads offers the same sustainability benefits of recycling (see MR‐4 Recycled Materials for a discussion of benefits, current waste streams and diversion rates) with the added benefit of reduced transportation and an associated reduction in energy, emissions and cost.

This credit focuses exclusively on reuse of pavement materials because of (1) the dominance of pavements materials on roadway projects, and (2) the ability to reuse large percentages of existing pavement structures. First, pavements are the most prevalent structure in roadway construction, accounting for about 70% of state and local roadway expenditures (BTS, 2008). On most projects (except for perhaps bridges and tunnels) they make up a majority of the material by weight. Second, it is quite common to undertake a roadway construction project that keeps in place the entire existing pavement structure (essentially 100% reuse). This can occur in roadway expansion projects, projects that reprocess existing materials in‐place and, importantly, routine preservation projects that either add to the existing structure or only replace the top few inches of an existing pavement structure. For the purposes of Greenroads, these types of preservation “overlays” and “mill‐and‐fill” (remove a thin layer of pavement and replace with a comparable thickness) jobs are deemed to have reused the entire remaining pavement structure. In this way, the pavement reuse credit can serve as a reward for an owner that pursues a preservation program designed to maintain pavement network condition through timely periodic surface overlays or treatments rather than wholesale remove‐and‐replace procedures.

Pavement Reuse Methods This section briefly overviews some of the more common pavement reuse methods that meet the Greenroads “reuse” definition. These are:

Surface treatments

Overlay / Mill and Fill

Hot in‐place recycling (HIR)

Cold in‐place recycling (CIR)

Full‐depth reclamation (FDR)

Crack‐and‐Seat of PCC pavements

Rubblization of PCC pavements

In the cases of CIR, FDR, crack‐and‐seat and rubblization the existing material is effectively downcycled; that is it is reused for a lesser purpose (as an aggregate material instead of a bound concrete material). In all cases, these methods are considered “reuse” as defined by Greenroads because no existing material leaves the project site.

Surface Treatments Pavement surface treatments are materials placed on the existing pavement surface in order to correct minor surface defects, improve wear course characteristics (i.e., friction) and provide a waterproof covering. Surface treatments are generally quite thin (e.g., less than 1‐inch thick) and can consist of a number of different treatments including:

Fog seal (Figure MR‐2.7). A light application of a diluted slow‐setting asphalt emulsion to the surface of an aged (oxidized) pavement surface.


MR-2 Pavement Reuse

Slurry seal (Figure MR‐2.8). A homogenous mixture of emulsified asphalt, water, well‐graded fine aggregate and mineral filler used as a maintenance treatment or wearing course. Microsurfacing is an advanced form of slurry seal that uses the basic ingredients and combines them with polymer additives to achieve better engineering properties.

Chip seal (Figure MR‐2.9 and MR‐2.10). Also known as a seal coat or bituminous surface treatment, a chip seal is a thin protective wearing surface applied to a pavement surface. At its most basic, a chip seal consists of a layer of asphalt (often applied as an emulsion) applied to the existing pavement surface in which a single layer of aggregate is embedded. More exotic chip seals can use several layers (e.g., double chip seal), different stone sizes (e.g., racked‐in seal), and be combined with other surface treatments (e.g., cape seal – combined with a slurry seal) (Gransberg & James, 2005).

Figure MR‐2.7: No fog seal (left), fog seal (right). Figure MR‐2.8: Microsurfacing (from the Washington State Department of Transportation).

Figure MR‐2.9: Chip seal asphalt emulsion application.

Figure MR‐2.10: Chip seal aggregate application.

Overlay / Mill & Fill Overlays (Figure MR‐2.11) are operations where either PCC or HMA is placed over an existing pavement. Overlays can be used to add additional structure to the existing pavement (called “structural overlays”) or can be used to provide a new pavement surface free of defects (called “non‐structural overlays”). A “mill and fill” is a variation of an overlay where the existing pavement surface is partially removed by a pavement milling machine (cold planer, Figure MR‐2.12) before the overlay is applied. This is usually done to either:

1. Remove existing surface defects in order to improve overall pavement quality, or 2. Maintain existing pavement elevations after the overlay is complete.


Pavement Reuse MR-2

In many instances (especially the second) the milling depth is the same as the subsequent overlay depth. For HMA pavements, overlays and mill‐and‐fills are the most common form of pavement preservation and can constitute the majority of HMA placed for most owners (as opposed to new pavements). PCC overlays can consist of bonded or unbounded overlays. Bonded overlays, often referred to as “whitetopping” when placed on existing HMA pavements, consist of a thin PCC layer (usually 2 to 7 inches) that is bonded to the existing underlying pavement. An unbounded overlay is a PCC layer placed over an existing pavement without bonding. Since there is no bonding, the new PCC layer essentially performs like an independent structure and therefore must be thicker; often the minimum thickness for an unbounded overlay is 5 to 7 inches.

Figure MR‐2.11: 1.8‐inch overlay. Figure MR‐2.12: Milling machine.

Hot In‐Place Recycling (HIR) HIR involves in‐place reprocessing of the top of an existing HMA pavement. The process is accomplished by heating the existing pavement surface to aid in remixing, additive addition and removal of defects. Despite its name, Greenroads considers HIR to be reuse since the existing material does not leave the project site. There are generally three methods of HIR:

Heater scarification. Heats the pavement surface (typically using propane radiant heaters), scarifies the pavement surface using a bank of non‐rotating teeth, adds a rejuvenating agent to improve the recycled asphalt binder viscosity, then mixes and levels the recycled mix using a standard auger system. The recycled asphalt pavement is then compacted using conventional compaction equipment.

Repaving. Heats the pavement surface (typically using propane radiant heaters), removes (by scarification and/or grinding) the top 1 to 2 inches of the existing HMA pavement, adds a rejuvenating agent to improve the recycled asphalt binder viscosity, places the recycled material back on the remaining existing pavement using a primary screed, and may simultaneously place a HMA overlay.

Remixing (Figures MR‐2.13 and MR‐2.14). Similar to repaving but adds new virgin aggregate or new HMA to the recycled material before it is replaced.


MR-2 Pavement Reuse

Figure MR‐2.13: HIR heating equipment. Figure MR‐2.14: HIR equipment heating and removing the top layer of existing HMA.

Cold In‐Place Recycling (CIR) CIR (Figure MR‐2.15) involves milling and crushing the existing HMA pavement, mixing in measured amounts of emulsified liquid asphalt and lime slurry, and placing and compacting the reprocessed material to construct a new roadway base. Following CIR, the base is overlaid with HMA or, in some cases, a chip seal. The depth of milling is generally 2 to 4 inches and, importantly, does not extend beyond the existing HMA layer.

Figure MR‐2.15: CIR process train (photo from the Washington State Department of Transportation).

Full Depth Reclamation (FDR) FDR (Figures MR‐2.16 and MR‐2.17) involves pulverizing the full existing pavement structure and a portion of the underlying subgrade and combining the resultant material with water and/or a stabilizing agent to form a uniform stabilized base course (ARRA, n.d.). Typical FDR depths are 6 to 9 inches (ARRA, n.d.). After FDR, it is typical to pave either a thin HMA pavement or chip seal.


Pavement Reuse MR-2

Figure MR‐2.16: Road reclaimer used in FDR (photo from Grace Pacific, Inc.).

Figure MR‐2.17: Finished FDR material before overlay (photo from Grace Pacific, Inc.).

PCC Crack‐and‐Seat Crack‐and‐Seat is a method for rehabilitating failed plain jointed PCC pavement that involves breaking up the existing PCC pavement into small pieces (typically 1 to 4 foot pieces), seating those pieces with a heavy proof roller and then overlaying the cracked and seated PCC with new HMA. This method avoids removing the old PCC; instead using it as a high quality base material. Typically, PCC is cracked using a drop hammer truck (Guillotine Breaker, Figure MR‐2.18) that repeatedly drops a heavy weight onto the pavement surface.

Figure MR‐2.18: Guillotine breaker used for crack‐and‐seat.

Crack‐and‐seat projects have performed relatively well to date. For instance, Rajagopal et al. (2004) showed that the crack‐and‐seat technique reduced reflection cracking over at least a 9‐year period for the conditions analyzed.

PCC Rubblization Rubblization is a method for rehabilitating failed PCC pavement (typically plain jointed PCC pavement) that involves rubblizing the existing PCC pavement (particles sizes of 2 to 15 inches in diameter depending upon the specific method used) and then overlaying the rubblized PCC with HMA pavement. This method avoids removing the old PCC; instead using it as a high quality base material. Rubblization is typically accomplished by one of two methods:

Resonant breaker (Figure MR‐2.19). A machine that strikes the pavement at a high frequency (around 44 Hz, the resonant frequency of the PCC pavement) and low amplitude (0.5‐0.75 inches) using the resonant


MR-2 Pavement Reuse

frequency to fracture the existing PCC into small‐diameter particles. The breaking shoe can be 2 to 12 inches wide.

Multi‐head breaker (Figure MR‐2.20). A machine that strikes the pavement with a series of drop hammers (1 to 5 foot drop height) and uses the impact energy to fracture the existing PCC pavement into small‐diameter particles.

Figure MR‐2.19: RMI resonant breaker (photo from Resonant Machines, Inc.).

Figure MR‐2.20: Antigo multi‐head breaker (photo from Antigo Construction, Inc.).

Limited evidence suggests that rubblized pavements, if constructed properly, can perform well. Wolters et al. (2005) examined rubblized pavements in 2005 that were 3‐8 years old and found them to be in good condition with the exception of those sections that did not have well drained base layers.

GLOSSARY

CIR Cold in‐place recycling (sometimes CIPR)

Cold In‐Place Recycling In‐place reprocessing of a portion of existing HMA pavement (usually the top 204 inches) into a high quality base material by milling, crushing and stabilizing. Usually this base is then covered by a thin HMA layer or surface treatment.

Crack‐and‐Seat Method for rehabilitating failed plain jointed PCC pavement that involves breaking up the existing PCC pavement into small pieces (typically 1 to 4 foot pieces), seating those pieces with a heavy proof roller and then overlaying the cracked and seated PCC with new HMA.

Downcycling The recycling of a material to a material of lower quality or reduced functionality.

FDR Full depth reclamation

Full Depth Reclamation In‐place reprocessing of a HMA pavement structure (including the granular base course and some subgrade material) into a high quality base material by pulverizing and stabilization. Usually this base is then covered by a thin HMA layer or surface treatment.

HIR Hot in‐place recycling (sometimes HIPR)

HMA Hot mix asphalt

Hot In‐Place Recycling In‐place reprocessing of a thin top layer (usually less than 2 inches) of an existing HMA pavement by scarification, rejuvenation and repaving.

Mill and Fill A variation of an overlay for existing HMA pavements where the existing pavement surface is partially removed by a pavement milling machine before the overlay is applied.

Overlay A layer of either PCC or HMA that is placed over an existing pavement. Overlays can be used to add additional structure to the existing pavement (called “structural overlays”) or can be used to provide a new pavement surface free of defects (called


Pavement Reuse MR-2

“non‐structural overlays”).

PCC Portland cement concrete

Recycle A process that diverts materials within or external to the project limits from final disposal in a landfill by reprocessing or repurposing them for use in the project.

Reuse A process that maintains materials in place (such as existing pavement structure) or disturbs or removes them by means that does not include transport outside the project limits.

Rubblization Method for rehabilitating failed PCC pavement (typically plain jointed PCC pavement) that involves reducing the existing PCC pavement to small particles (2‐15 inches in diameter depending upon the specific method used) and then overlaying the rubblized PCC with HMA pavement.

Surface Treatment Materials placed on the existing pavement surface in order to correct minor surface defects, improve wear course characteristics (i.e., friction) and provide a waterproof covering.

REFERENCES Andrawes, B., & Desroches, R. (2007). Comparison between Shape Memory Alloy Seismic Restrainers and Other

Bridge Retrofit Devices. Journal of Bridge Engineering. 12 (6), 700. Asphalt Recycling and Reclaiming Association (ARRA). (n.d.). Full Depth Reclamation: A Century of Advancement for

the New Millennium. ARRA, Annapolis, MD.

Binici B. (2008). Design of FRPs in circular bridge column retrofits for ductility enhancement. Engineering Structures. 30 (3), 766‐776.

Building Materials Reuse Association (BMRA). (2010). Website. Available at http://www.bmra.org.

Bureau of Transportation Statistics (BTS). (2008). Transportation Statistics Annual Report 2007. TABLE G‐8 Public Expenditures on Construction of Highways and Streets: January 2006‐May 2007. Washington, DC: Research and Innovative Technology Administration (RITA), U.S. Department of Transportation (US DOT).

Choi, Jun‐Hyeok. (2008). Seismic retrofit of reinforced concrete circular columns using stainless steel wire mesh composite. Canadian Journal of Civil Engineering, 35(2), 140‐147.

Earthquake Engineering Research Center (EERC), University of California, Berkeley. (n.d.) Northridge Earthquake.

Accessed June 2, 2010. Available at http://nisee.berkeley.edu/northridge/

Gransberg, D. & James, D.M.B. (2005). NCHRP Synthesis 342: Chip Seal Best Practices. Washington, DC: National Cooperative Highway Research Program, Transportation Research Board.

International Strategy for Disaster Reduction (ISDR). (2004, March 31). ISDR : Terminology. Accessed June 5, 2010. Available at http://www.unisdr.org/eng/library/lib‐terminology‐eng home.htm

Padgett J.E., & DesRoches R. (2008). Three‐dimensional nonlinear seismic performance evaluation of retrofit

measures for typical steel girder bridges. Engineering Structures. 30 (7), 1869‐1878. Padgett, J. E., Dennemann, K., & Ghosh, J. (2010). Risk‐based seismic life‐cycle cost‐benefit (LCC‐B) analysis for

bridge retrofit assessment. Structural Safety. 32 (3), 165. Rajagopal, A., Minkarah, I., Green, R. & Morse, A. (2004). Long‐Term Performance of Broken and Seated

Pavements. Transportation Research Record. (869), 3‐15.


MR-2 Pavement Reuse

Stanton, J. F., Roeder, C.W., Mackenzie‐Helnwein, P., White, C., Kuester, C. et al. National Cooperative Highway Research Program (NCHRP). (2008). NCHRP Report 596 ‐ Rotation limits for elastomeric bearings. Washington, D.C.: Transportation Research Board.

Volpe, John A. Northridge Earthquake‐ Preliminary Summary Report. Effects of Catastrophic Events on

Transportation System Management. 22 Apr. 2002. Accessed June 2, 2010. Available at http://ntl.bts.gov/lib/jpodocs/repts_te/13775.html

Washington Department of Transportation (WSDOT). (2010). WSDOT – SR 99 – Aurora Bridge Seismic Retrofit

Project. Accessed August 20, 2010. Available at http://www.wsdot.wa.gov/Projects/SR99/AuroraBridgeSeismicRetrofit/projectPhotos

Washington Department of Transportation (WSDOT). (2010). WSDOT – SR 104 – Hood Canal Bridge – 2009

Frequently Asked Questions. Accessed August 20, 2010. Available at http://www.wsdot.wa.gov/Projects/SR104HoodCanalBridgeEast/faq.htm

Washington Department of Transportation (WSDOT). (2010). SR 104 – Hood Canal Bridge – By the Numbers.

Accessed August 20, 2010. Available at http://www.wsdot.wa.gov/Projects/SR104HoodCanalBridgeEast/numbers.htm

Wolters, A.S., Smith, K.D. & Peterson, C.V. 2007. Evaluation of Rubblized Pavement Sections in Michigan.

Transportation Research Record. (2005), 18‐26.


Pavement Reuse MR-2

Documents

MR-2 Pavement Reuses - GreenroadsGreenroads Manual v1.5 Materials & Resources MR-2 Pavement Reuse DOCUMENTATION A calculation that shows the computed percent of material reused including