Cold Foam In-Place Recycling: How San Jose Saved $400,000 on Monterey Road

Cold foam in-place recycling is an increasingly popular pavement rehabilitation method that reuses existing materials directly on the roadway, cutting costs and project timelines dramatically. This article examines the Pavement Construction and Asphalt Equipment a Complete Guide context through a landmark project: FMG’s cold foam in-place recycling work on Monterey Road in San Jose, California, where the city saved $400,000 and cut construction time by half compared to conventional methods.

1. Understanding Cold Foam In-Place Recycling and Its Benefits

What Is Cold Foam In-Place Recycling?

Cold foam in-place recycling is a technique that recycles the existing asphalt layer directly on the roadway. Unlike traditional methods that require milling, hauling to a plant, and importing new materials, this process grinds the existing surface, mixes it with foamed asphalt binder and cement, and places it as a new structural base in a single pass. The term “cold” means no heat is applied to the aggregates, unlike hot mix recycling. The “foam” describes liquid asphalt injected with water, causing it to expand and create a foamed binder that coats the recycled material.

Key Environmental and Economic Advantages

The benefits of cold foam in-place recycling extend well beyond simple cost savings. Agencies and contractors gain multiple advantages:

• Zero material waste: All existing asphalt is reused on site, eliminating the need to truck debris to landfills.
• Reduced carbon footprint: No hauling of old materials out or new aggregates in translates to fewer truck trips and lower emissions.
• Conservation of natural resources: Aggregates are a declining natural resource. Recycling preserves them for future use.
• Faster project completion: Projects are completed in roughly half the time of conventional overlay operations.
• Lower cost: Savings typically range from 20 to 40 percent compared to traditional patch-and-overlay methods.
• Improved structural section: The recycled layer creates a new structural base that is stronger than a simple overlay.

Comparing Cold Foam Recycling to Conventional Methods

2. The Monterey Road Project: A Case Study in Sustainable Pavement Rehabilitation

Project Background and Road Conditions

Monterey Road in San Jose, California, presented a classic case of a failing urban arterial. The 2.2-mile stretch suffered from alligator cracking, raveling, potholes, and advanced oxidization. The city faced a familiar dilemma: how to restore the road without exhausting the annual pavement budget.

The city elected to pursue two bids for the project: one using a conventional patch-and-overlay approach and the other using cold foam in-place recycling followed by a surface overlay. This dual-bid strategy allowed San Jose to compare costs directly and make an informed decision based on real numbers rather than estimates.

The Numbers Behind the Decision

The cold foam in-place recycling bid came in $400,000 lower than the conventional alternative. That 20 to 30 percent savings was only the beginning. The city also benefited from:

1. A reduction in construction duration from 18 days to 9 days, cutting lane closure impacts on local businesses and commuters by half.
2. Elimination of 780 truckloads of material import and off-hauling, reducing traffic congestion and road wear from heavy vehicles.
3. Diversion of 15,600 tons of aggregate material from the landfill, supporting the city’s sustainability goals.
4. Elimination of the need to purchase approximately 15,000 tons of new asphalt concrete, saving both money and natural resources.

For more on the broader toolkit for road restoration, see our coverage of Asphalt Pavement Rehabilitation Strategies Techniques and Best Practices for Restoring Road Performance.

Feasibility Assessment and Mix Design

Not every road is a candidate for cold foam in-place recycling. Mike McElroy, owner and President of FMG, explains: “Some roads are failed deeper than 6 inches, have base failures or have huge depressions in the asphalt. We are going 3 to 6 inches.” Monterey Road passed the feasibility assessment. FMG extracted core samples and sent them to an independent laboratory that developed a custom mix design. “You’re going to take the bad existing roadway and design a new mix,” McElroy says. This step is critical because recycled roads often contain patched areas and varying aggregate sizes.

3. Step-by-Step Process of Cold Foam In-Place Recycling

Materials and Proportions

The cold foam in-place recycling process typically uses three ingredients blended with the existing pavement material:

1. Liquid asphalt (2.5 percent): PG 64-10 grade binder that is foamed by injecting water.
2. Bulk cement (1 percent): Added dry to improve early strength and moisture resistance.
3. Water (variable): Used to create the foaming action and achieve proper compaction moisture content.

These proportions are adjusted by the laboratory mix design based on the existing pavement composition, traffic loading, and environmental conditions at the project site.

The Recycling Train in Action

The core of the operation is the recycling train, led by the Wirtgen 3800CR Cold Recycler. FMG acquired this machine in April 2011, and the Monterey Road project was one of seven cold foam recycling projects the company completed in the San Francisco Bay Area. The process follows a carefully orchestrated sequence:

1. Obstruction lowering: Crews lowered iron manholes, vaults, and other surface obstructions below the planned recycling depth.
2. Dry cement application: Dry bulk cement was spread on the roadway surface at the rate specified by the mix design.
3. Recycling train assembly: A water truck and a tanker truck containing PG 64-10 liquid asphalt were pushed by the Wirtgen 3800CR as it moved forward.
4. Grinding and foaming: The Wirtgen 3800CR ground 4 inches of existing material. Its computerized pumping system injected oil and water into the drum housing based on the machine’s forward speed, creating foamed asphalt that coated the recycled aggregates.
5. Screed placement: The foamed asphalt mixture exited the back of the machine through a screed, placing the recycled material at the specified grade and cross-slope.
6. Compaction: Steel-drum rollers (15-ton) made 3 to 4 passes, achieving 98 to 105 percent density. Pneumatic rollers followed, bringing fines to the surface and kneading the material for a finished surface.

The recycling train operated at 20 to 30 feet per minute. Within a few hours, the surface was dry enough to accept a fog seal. For additional reading on these material processes, see Asphalt Pavement Recycling Technologies Methods and Sustainable Practices for Reclaimed Materials.

Fog Sealing and Surface Protection

A critical step FMG refined during this project was fog sealing. Crews applied a 10 to 12 hundredths of a gallon per square yard fog seal followed by sand. “It is imperative to put down sand and oil,” McElroy says. “The foam process leaves a crust on top that needs protection.” On earlier projects with light traffic, FMG had not used fog seals. Monterey Road’s high traffic volume caused slight raveling until the fog seal was applied, which eliminated the problem. FMG then handed the project to contractor Graniterock Pavex for the final surface overlay.

4. Lessons for Contractors Adopting Cold Foam Recycling Technology

Material Management and Grade Control

Cold foam in-place recycling presents unique material management challenges compared to conventional paving. “Unlike paving, if you go a little too thick or thin you have to add or remove material,” McElroy explains. “With what we’re doing we have a set amount of material. If we are grinding out 4 inches we have to put 4 inches back. If we start running out of material that means we’re going too thick and if we start gaining material that means we are going too thin.” FMG addressed this challenge by using a screed equipped with electronic grade control, enabling precise depth management throughout the recycling pass.

Traffic Management on High-Speed Corridors

Monterey Road carried freeway-speed traffic approaching 65 miles per hour with stop lights and turn lanes in the work zone. “The problem is you have stop lights in the middle of the job, and people driving 65 miles per hour to a stop,” McElroy says. “When you recycle, you are putting down a granular product. It takes four hours to cure.” FMG implemented rolling lane closures: one lane was closed, recycled, fog sealed, sanded, temporarily striped, and reopened within the same day.

Equipment Differences: Recycling vs. Milling

Contractors will notice key differences with the Wirtgen 3800CR. “The machine can be converted into a milling machine within a few hours,” McElroy says. “A conventional milling drum spins clockwise, breaking asphalt from underneath. The Wirtgen 3800RC drum turns counterclockwise. If you go slowly you take small bites; faster means bigger bites.” This downward-cutting action lets contractors manage aggregate size, affecting final mix gradation. For more on the equipment, refer to Road Construction and Asphalt Paving Equipment Machinery for Highway Street and Pavement Infrastructure.

The Business Case for Investing in Recycling

Mike McElroy speaks passionately about pavement recycling. “We’re a pretty small company. We went out on a limb, and we are taking a risk on it because it [recycling] has to happen,” he says. “The bottom line is cities, counties and states can’t afford to waste their resources anymore. Aggregates are a declining natural resource. We have to recycle because it is the right thing to do.” For contractors considering entering the cold foam recycling market, the Monterey Road project demonstrates that the technology is proven, the savings are real, and the demand is growing. As agencies increasingly require sustainable solutions, early adopters will have a competitive advantage.

Key Takeaways for Construction Professionals

• Cold foam in-place recycling can reduce project costs by 20 to 40 percent compared to conventional mill and overlay.
• Project timelines are cut by approximately 50 percent due to elimination of material hauling and plant processing.
• The process creates a new structural section, not just a surface treatment, extending pavement life significantly.
• Proper mix design by an independent laboratory is essential for project success.
• Fog sealing is critical on high-traffic roads to prevent surface raveling after recycling.
• Traffic management strategies must account for the 4-hour curing time of the recycled material.
• The Wirtgen 3800CR can be converted between recycling and milling configurations, providing equipment flexibility.

As road budgets continue to tighten and sustainability requirements become standard, cold foam in-place recycling offers a proven path forward. The Monterey Road project stands as a compelling example of how innovation, practical engineering, and environmental stewardship can come together to deliver better roads at lower cost.