Low-carbon and recycled materials in road construction

States are exploring the use of low-carbon and recycled materials in road construction for the purposes of lowering carbon emissions, enhancing the durability and longevity of roads, and saving on costs associated with materials, repairs, and environmental impacts. Plastic has emerged as a recent innovation to reduce the amount of cement required in concrete or asphalt mixtures; however, rubber and other materials are also being examined.

“While cement makes up only a small portion of the concrete mix by volume, it accounts for up to 90 percent of the total carbon embodied in the material due to the energy required to make clinker,” writes Rebecca Esau and Audrey Rempher for the Rocky Mountain Institute. “Concrete producers can reliably substitute approximately 40 percent of traditional cement with low-carbon alternatives.”

State and local governments are also examining their procurement processes. In certain cases, they are mandating the use or study of low-carbon materials, establishing maximum allowable carbon limits for mixtures, and requiring or incentivizing manufacturers to submit Environmental Product Declarations (EPDs).

“Nearly one-third of all concrete used for construction in the United States is procured by state and local governments,” writes Chris Neidl and Caleb Woodall for the National Resources Defense Council.

The release of microplastics into the surrounding areas as a result of using plastic for road construction is a vital concern being studied in various pilot programs. The extent to which this occurs is not yet fully known.

In 2024, the Federal Highway Administration awarded $1.2 billion to 39 state DOTs as part of its Low Carbon Transportation Materials Grant. However, the program was rescinded in 2025 as part of the One Big Beautiful Bill Act, and many or all states never received the funding. Still, states remain engaged in pilot programs and research.

As one example of cross-state collaboration, eight state DOTs have pooled funds together to launch the Transportation Materials Resource Center in 2025. The Iowa DOT is the lead agency, while other participating states include Maryland, Michigan, Minnesota, Missouri, Nebraska, Pennsylvania, and Texas. “The primary objective of the TMRC is to champion the identification and evaluation of innovative materials for use in transportation infrastructure,” according to the project description.

Another similar initiative including collaboration by 30 state DOTs is the Technology Transfer Concrete Consortium, which states, “The purpose of this pooled fund project is to identify, support, facilitate and fund concrete research and technology transfer initiatives.”

Pilot Projects and Initiatives

The California Department of Transportation (Caltrans) engaged in multiple initiatives to reduce carbon emissions from road pavement. Caltrans repaved a one-mile section of Highway 162 using 100% recycled materials, a mixture of recycled asphalt pavement and liquid plastic made from single-use bottles. The department also approved the use of low-carbon cement in road construction and maintenance projects after funding the research conducted at Oregon State University. Caltrans maintains a list of Low-Carbon Materials Initiatives and Sustainable Pavement Ideas Repository.

The Hawai’i Department of Transportation paved a stretch of road using 1,950 tons of plastic modified asphalt – the equivalent of 195,000 plastic bottles – as part of a pilot project enabling researchers at the University of Hawai’i at Manoa and Hawai’i Pacific University to evaluate the performance of the plastic modified asphalt and the potential for the release of microplastics into the surroundings.

The Iowa Department of Transportation evaluated the effectiveness of a cornstarch hydrogel additive in concrete mixtures to reduce the cracking and deterioration of roads during freeze-thaw cycles. The agency also partnered with Iowa State University to study the use of eggshell waste as a replacement for lime and cement to stabilize the soil in freezing conditions for pavement and gravel road construction.

The Maryland Department of Transportation launched a pilot project to use rubber-modified asphalt (RMA), a mix of recycled tire rubber with asphalt, to pave a stretch of northbound lanes on Maryland Route 650. “The environmental and economic advantages were clear – RMA could extend the life of roads, reduce long-term maintenance costs, and repurpose scrap tires that might otherwise end up in landfills,” according to the Tire Industry Association. Researchers at the University of Missouri are currently studying RMA’s ability to reduce greenhouse gas emissions.

The Missouri Department of Transportation partnered with the University of Missouri’s Asphalt Pavement and Innovation Lab to test the effectiveness of 9 types of recycled materials, including scrap tires and plastic waste, in asphalt mixes used for road construction along a portion of Interstate 155. “We currently utilize recycled asphalt, pavement, recycled asphalt shingles and ground tire rubber in our mixtures. Expanding to utilize plastic reduces the amount of virgin material needed, which is a winning situation for the environment and overall cost,” said Dave Ahlvers, a state design engineer at MoDOT.

The New York City Department of Transportation tested three strips of pavement on Staten Island using a mix of recycled plastic and recycled asphalt pavement. NYC DOT also announced a pilot project that will utilize an asphalt mix made with 50 percent of recycled roadway material.

The Port Authority of New York and New Jersey established maximum allowable carbon limits for concrete mixes used in various projects, which include roads and bridges. Ground glass and Portland-limestone cement are two examples of permissible low-carbon materials being used. The Port Authority has also identified 18 concrete mixes utilizing low-carbon materials as the result of a pilot program launched in collaboration with local universities.

The Pennsylvania Department of Transportation used plastic pellets made from grocery bags, milk jugs, and other recycled plastics in a pilot project, which tested the performance of high- and low-density polyethylene in two quarter-mile sections of road reconstruction.

The Virginia Department of Transportation studied the use of recycled plastic-modified (RPM) asphalt mixtures in road construction, and whether this use would result in microplastics leeching into the surrounding environment.

State Legislation

California A.2446 (2022; enacted) requires the Air Resources Board to establish a framework for reducing the carbon intensity of building materials with exemptions based on substantial cost increases.

Colorado S.25-182 (2025; enacted) adds embodied carbon improvements to the Industrial Clean Energy Tax Credit and the list of energy improvements eligible for funding by the Colorado New Energy Improvement District.

Connecticut H.6027 (2025; referred to committee) creates a state procurement standard for the use of low-embodied carbon construction materials in certain state construction projects.

Maryland H.781 (2024; referred to committee) requires the use of rubber modified asphalt in the construction and repair of state highways.

Massachusetts H.4849 (2022; did not pass) concerns provisions in state procurement contracts involving the use of low embodied carbon concrete.

New Mexico H.153 (2026; vetoed) “Low-Carbon Construction Material Rebate Act” provides rebates and other financial incentives to buyers of low-carbon construction materials.

New Jersey S.287 (2023; enacted) provides corporate business taxes and gross income tax credits for certain deliveries of low carbon concrete and for the costs to conduct environmental product declaration analyses of low carbon concrete.

New York S.542A (2021; enacted) “Low Embodied Carbon Concrete Leadership Act” establishes procurement guidelines for low embodied concrete.

New York S.7648A (2025; referred to committee) “Sustainable Building Materials Act” provides a sales tax exemption for certain low-carbon building materials and establishes a grant program for manufacturers of concrete for environmental product declarations.

Pennsylvania H.R.83 (2025; referred to committee) commissions a study on the feasibility and implementation of expanding construction requirements to use more sustainable building products in state-funded and private construction projects.