NV Implementing New Portland Cement Standards
The Nevada Department of Transportation recently announced that it will be allowing the use of Portland limestone cement on new highway construction projects to reduce its carbon footprint. According to reports, the agency anticipates reducing carbon dioxide emissions by about 4,000 tons per year, or the equivalent of 870 less cars on the road.
With traditional Portland cement, a binder is produced by heating limestone and clay in a rotary kiln and ground into a fine powder. This process reportedly emits about one pound of CO2 per pound of cement through fuel used to heat the kiln and thermal decomposition of the calcium carbonate.
However, Portland limestone cement replaces up to 15% of the binder material with raw, powdered limestone. This process reduces carbon emissions during production by about 9%.
The department notes that it is responsible for more than 5,000 miles of state roadways. Additionally, NDOT uses 45,000 tons (90 million pounds) of cement each year to build, maintain and upgrade projects using cement. These include pavement, bridges, sidewalks, curbs, retaining walls, culverts and more.
DYK: we will use Portland limestone cement on highway projects to reduce carbon dioxide emissions by 4,000 tons per year. That’s equivalent to 870 fewer cars on the road.— Nevada DOT (@nevadadot) June 25, 2022
It’s part of our dedication to reducing greenhouse gas emissions in Nevada transportation!@NevDCNR pic.twitter.com/4rPHy4Nds5
In Nevada, transportation reportedly contributes 35% of the state’s total greenhouse gas emissions and is projected to stay the leading GHG emitter. A GHG Reduction Strategic Plan was created by the agency to reduce transportation-related greenhouse gas emissions within highway operations, planning, design, construction and maintenance.
GHG emissions were recently reduced by 11% through reduced energy and fuel use, as well as recycling highway materials, Carson Now reports. NDOT said in its statement that it worked with industry experts and stakeholders, such as the Nevada Associated General Contractors and California Nevada Cement Association, to draft the new standards.
Other Recent Concrete Environmental Standards
Last month, the City of Portland, Oregon, announced the approval of recommendations to add Concrete Embodied Carbon Threshold requirements for city construction projects. The recommendations were approved by chief engineers from the Environmental Services, Water and Transportation infrastructure bureaus.
While cement is the largest component of concrete, cement production along reportedly generates 8% of global greenhouse gas emissions. Lower-carbon mixes can be designed to perform as well, or better, than conventional concrete and are competitive in cost, the city notes.
Concrete is used in a high volume of projects in Portland, including sidewalks and ADA ramps, bicycle and pedestrian paths, fire hydrant pads, retaining walls for parks, and large infrastructure projects such as the Water Bureau’s Bull Run filtration facility and the Bureau of Environmental Services’ wastewater and stormwater infrastructure. The new sustainability standards will accelerate the bureaus’ use of concrete that is durable but manufactured with lower climate impacts.
Projects that are currently underway and are using low-carbon concrete include:
Implementing the new threshold requirements will reportedly result in a range of 3%-35% reduction in greenhouse gas emissions over historically used concrete mixes. For example, a new water reservoir project would result in a 19% reduction in concrete-embodied carbon, saving approximately 3.5 kg-CO2e which is the equivalent of removing 754 gasoline-powered cars of the road.
The new city standards will take effect in January. Current Sustainable Procurement Initiatives, including the Low-Carbon Concrete Initiative and the new Embodied Carbon Thresholds for Concrete Mixes, can be found here.