How Can Concrete Be Environmentally Friendly?

The Importance of sustainability

The challenge is that currently, based on U.S. Environmental Protection Agency (EPA) carbon emissions data, the manufacturing of cement alone accounts for 1.25% of U.S. CO2 emissions. As that demand is projected to increase, it is important to investigate building more sustainably, including utilizing innovative approaches and technology.

Together, the cement and concrete industry has developed a Roadmap to Carbon Neutrality which outlines the opportunities and actions to reach carbon neutrality. Spearheaded by the Portland Cement Association, the Roadmap involves the entire construction process, starting at the cement plant and extending through the entire life cycle of the built environment to incorporate the circular economy. This view looks at relationships at each step, demonstrating how the concrete industry can address climate change, one project at a time. One of the biggest points from this Roadmap is that a conversation must occur between architects, engineers, contractors, and producers to determine how to improve the environmental impact of the concrete for each project. It’s through the sharing of knowledge and information that sustainable solutions will become more commonplace.

A variety of environmental alternatives are available to help you reduce the carbon emissions of your concrete projects. 

improving concrete's sustainability

Consider these alternatives to increase the sustainability of your next project.

Portland-Limestone Cement. By replacing up to 15 percent of the clinker in ordinary portland cement (OPC) with ground limestone added to portland-limestone cement (PLC), up to a 10 percent reduction in the carbon footprint can be achieved. PLC performs just like the cement you’re used to using, with the same durability and resilience, and follows the same specifications and mix design. Another advantage of PLC, beyond its reduction in the carbon profile, is a 1:1 cement replacement with OPC.

Supplementary cementitious materials. Supplementary cementitious materials (SCMs) are used to boost the performance of a concrete mix while at the same time, reducing its carbon footprint through decreasing the amount of portland cement used. The advantages of using SCMs are more economical concrete mixtures, reduced permeability, increased strength, and positive effects on other concrete properties. Using these materials also can help with LEED credits for green building projects. The most common SCMs include:

• Fly ash. A popular SCM since the mid-1900s, it can decrease concrete’s carbon footprint—and its cost—while increasing its strength and workability.
• Slag cement. This hydraulic cement reduces the environmental impact of concrete mixtures as well as reduces permeability while increasing durability.
• Silica fume. This highly pozzolanic material is used to enhance mechanical and durability properties of concrete. It can improve concrete’s compressive strength, bond strength, and abrasion resistance.

Additionally, concrete mixtures using these SCM’s that are industrial by-products lower disposal needs and conserve natural resources. It’s important to remember that concrete is 100 percent recyclable and can be used in new concrete, base materials, or controlled fill.

Concrete Additives. Another way to increase the sustainability of your projects is to take steps to ensure the concrete has a longer lifespan. Concrete additives can increase the sustainability by making the concrete stronger, less susceptible to cracks, easier to place and finish, and more cost-efficient. You can collaborate with your concrete producer to create a combination of chemical admixtures, fibers, supplementary cementitious materials, and color pigments to meet your project’s needs. Types of admixtures that will increase the sustainability of your concrete, while enhancing other features include:

• Air entraining agents. These increase the freeze-thaw durability of concrete, increase resistance to scaling caused by deicing chemicals, and improve workability.
• Water-reducing chemicals. Workability can be increased without increasing water content. These are used in many different situations, including high-strength and high-performance mixtures, and to improve concrete pumping and placing.
• Retarders. Used to slow the rate of setting of concrete. By slowing the initial set time, the concrete mixture can stay in its fresh mix state longer and achieve higher ultimate strengths.
• Accelerators: These can speed up the setting time and reduce the time needed to wait for strength to develop. This also allows concrete to be placed in winter with a reduced risk of frost damage.
• Superplasticizers or High Range Water Reducers. Water requirements can be reduced anywhere from 12 percent to up to 40 percent. These can help achieve high-performance mixtures that improve workability, speed finishing, increase strength, conserve cement, and help reduce shrinkage and thermal cracking.

Optimized gradations. By using a blend of aggregates that have particles of every size represented in the mixture, we can use less cement and achieve higher strengths and better durability. This simple technique can result in a concrete mixture with up to 15% less cementitious material that outperforms the old standard “stone and sand” aggregate blend.

CarbonCure™ Technology. Producers that partner with CarbonCure™ technologies can reduce the carbon footprint of the concrete. This is achieved with technology that recycles the waste carbon dioxide (CO2). The result is improved compressive strength and reduced cement content without impacting strength or performance.

Optimized design thickness. Reduce costs and CO2 emissions by minimizing the amount of materials needed to construct a given pavement or structure. The economic and environmental benefits can be significant.

By leveraging the options that work best for your project, the results can render many advantages, including a longer life and lower carbon footprint. Remember to optimize concrete mixes and use only the materials necessary for the project, to avoid excess emissions. And equally important, by increasing your use of recycled materials, you can help decrease what goes into landfills.

What's next for Sustainable Concrete

Increased analysis and reporting are now required for many construction projects. To achieve environmentally friendly, long-term solutions, all those involved should look at the economic and environmental costs over the lifetime of a project. This can be done through methodologies known as life cycle cost analysis (LCCA) and life cycle assessment (LCA). Increasingly Environmental, Social, and Governance (ESG) reporting is also being requested as part of the analysis process to identify material risks and growth opportunities.

The future may hold changes for sustainable concrete construction. Already, companies are facing demands to adapt business models to reflect how they are addressing the environmental impact of concrete. And ESG reporting may only be the beginning of accountability. Now is the time to be a leader by seeking sustainable solutions for each project by working to find the best solutions to improve structural performance, energy efficiency, resiliency, and carbon reduction.