CIR Around the U.S.

A look at some case studies were cold in-place recycling was successfully used to rehab pavements

Redmond Ave., San Jose, CA
Redmond Ave., San Jose, CA

Cold in-place recycling (CIR) is a fast, economical asphalt pavement rehabilitation technique that reuses existing pavement materials. CIR involves the processing and treatment with bituminous and/or chemical additives of an exiting asphalt pavement without heat to produce a restored pavement layer.

All work is completed while on the pavement being recycled and is therefore less disruptive than other rehab techniques. It is also environmentally preferable because transportation of material, except the recycling additive being used, is not normally required.

Below are some case studies were CIR was successfully used to rehab asphalt pavements.

Redmond Ave., San Jose, CA

Redmond Avenue in San Jose, CA, is a highly trafficked road used by cars, buses, vans and delivery trucks. The existing pavement was in need of repair and the cold in-place recycling (CIR) process was selected as the preferred method, mainly to accommodate high-traffic levels.

The contractor used a Wirtgen 3800 CR with integrated Vogele screed and a recycling width of 12.5 ft. Before recycling the pavement, 1% cement was prespread in front of the 3800 CR.

Recycling pass 1: The 3800 CR recycled the pavement in-place to a depth of 4 in., simultaneously adding 2.2% foamed bitumen. The recycled material was paved directly behind the recycler using the integrated screed, and finish compaction was achieved using Hamm rollers.

Recycling pass 2: This pass required a total width of 13.5 ft. As the 3800 CR was fitted with a 12.5 ft. cutter, a Wirtgen W 150 pre-milled a section of pavement ahead of the CR and windrowed the milled material between the 3800 CR’s front tracks. This material was introduced into the mixing chamber along with the material cut by the 3800 CR, providing sufficient material to pave to a width of 13.5 ft.

The on-board mixing computer was adjusted to compensate for this additional material to maintain the mix design requirements.

Project data

Recycling width                                 12.5 ft.

Recycling depth                                                4 in.

Percentage cement                        1.0%

Percentage foamed bitumen     2.2%

Production rate                                > 400 tph

Highway 15, Mason County, IL

In accordance with the Mason County bid documents, CIR was the designated rehabilitation method for Highway 15. The existing pavement was highly distressed, being over 40 years old, with extensive alligator cracking and areas of cold-mix patching. In addition, this section of the highway suffered high levels of transverse cracking with affected driving conditions.

The contractor for this project selected the Wirtgen 3800 CR with a working width of 12.5 ft.  and integrated Vogele screed. This unit features the ability to hydraulically open both the right and left end gates to discharge material to the sides in case of excessive material build up at the screed head.

The mix design and pavement investigation were carried out by the emulsion supplier. The design called for the project to be divided into two sections, with a recycling depth of 3 in. for the first 2 miles and a depth of 4 in. for the remaining 6 miles. The emulsion content was calculated on a range of coarse to medium gradation at 2.25% to 3.75%.

The 3800 CR pushed the bitumen tanker. Simultaneously, the 3800 CR milled the existing pavement to the required thickness, added the design percentage of emulsion proportional to the working speed and added metered amounts of compaction moisture to suit varying in-situ conditions.

The 3800 CR paved the recycled material immediately with the integrated Vogele AB425T screed. No windrowing or pick-up machine or additional paver was required. Compaction was carried out right behind the screed using a Hamm HD 120 roller.

Project Data

Recycling width                                 12.5 ft.

Recycling depth                                                0-6 in.

Percentage emulsion                     2.25-3.75%

Total area                                            93.646 square meters

Production rate                                410 tph

Route 17, Hampton, VA

Route 17 in Hampton, VA, runs with two lanes in each direction. As a result of continuously increasing traffic volumes (approximately 15,000 vehicles per day, 3% trucks), the pavement surface was covered with extensive areas of patching and transverse and longitudinal cracks extending throughout the pavement structure.

The rehabilitation method chosen for Route 17 was CIR using foamed bitumen as the binding agent. A Wirtgen WLB 10 S foam lab delivered the mix design and pavement investigation.

First, a Wirtgen W 2000 milling machine pre-milled the exiting asphalt pavement to a depth of 2 in. Then the compact recycling train reported for duty.

Preceding tanker trucks deliver hot bitumen and water to the 3800 CR Rear Load via hose connections. The cold recycler milled off and granulated the damaged asphalt layer down to a depth of 5 in. in a single pass while the milling and mixing rotor mixed in foamed bitumen and water at the same time.

The 3800 CR Rear Load forwarded the recycled material directly to the Vogele Super 2100-2 paver. Hamm HD 120 and HD 130 rollers compacted the new pavement right behind the paver. Down-cutting recycling thus produced a bituminous base layer of superior quality – no crushing or screening plant was required.

PROJECT DATA

Recycling width                                 12.5 ft.

Recycling depth                                                5 in.

Percentage cement                        1.0%

Percentage foamed bitumen     2.2%

Average working speed                                28 ft./min.

Production rate                                520 tph­­

Baileysville Road, Freeport, IL

Baileyville Road in Freeport, IL, is a highly trafficked business road. The distressed pavement showed extensive alligator and transverse/longitudinal cracking, with irregular and unstable shoulder widths. CIR was selected to renew the road, mainly to accommodate high-traffic levels.

The contractor used a Wirtgen 3800 CR cold recycler with a recycling width of 12.5 ft.  and foamed bitumen as the binding agent. The 3800 CR stabilized the pavement to a depth of 4 in. in a single pass and across the full width of the traffic lane, adding 2.5% foamed bitumen and 1.5% water. The 3800 CR then loaded the recycled material into the paver’s receiving hopper.

A Vogele paver worked behind the 3800 CR, paving the recycled material to the required grade. Final compaction of the recycled lane was achieved using Hamm rollers. Traffic was guided past the construction site on the adjacent lane.

PROJECT DATA

Recycling width                                 12.5 ft.

Recycling depth                                                4 in.

Percent foamed bitumen             2.5%

Percentage added water              1.5%

Average working speed                                22 ft./min.

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