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Building with Low Carbon Concrete: Techniques and Benefits

Aug. 13, 2024
11 min read

Concrete is one of the most widely used construction materials, but its production is a significant source of carbon emissions due to the energy-intensive process of cement manufacturing. As the construction industry seeks to decarbonize concrete and adopt more eco-friendly materials, low carbon concrete has emerged as a promising alternative. In this blog, we will explore the techniques and benefits of using low carbon concrete in building projects, exploring how it can revolutionize the way we build for a more sustainable future.

 

What is low carbon concrete?

Low carbon concrete, also known as green concrete or eco-friendly concrete, is engineered to reduce the carbon footprint associated with traditional concrete. It incorporates alternative materials and innovative production techniques to minimize greenhouse gas emissions without compromising concrete's strength, durability, or versatility.

What is low carbon concrete made of?

Low carbon concrete is made by partially or completely substituting traditional cement with alternative binders and incorporating supplementary cementitious materials (SCMs). Some key components of low-carbon cement include:

  • Fly ash: A byproduct of coal combustion, fly ash is used to replace a portion of cement, reducing the carbon footprint.
  • Ground Granulated Blast Furnace Slag (GGBS): This byproduct of steel manufacturing is another effective cement substitute.
  • Silica fume: A byproduct of silicon and ferrosilicon alloy production, it enhances strength and durability.
  • Recycled aggregates: Using recycled concrete or industrial byproducts as aggregates reduces the need for virgin materials.
  • Geopolymers: Inorganic polymers that can replace cement, made from materials like fly ash and metakaolin.

Why traditional concrete has a large carbon footprint

Traditional concrete has a large carbon footprint primarily due to the production of Portland cement. This process involves heating limestone (calcium carbonate) in kilns to produce lime (calcium oxide) and releasing carbon dioxide (CO2) as a byproduct. This reaction accounts for around 60% of the cement industry's CO2 emissions, with roughly 0.9 tons of CO2 emitted per ton of cement. Additionally, the high energy required for kiln operations, often fueled by coal or natural gas, adds significantly to carbon emissions.


Further emissions arise from transportation and grinding. Cement plants are frequently distant from raw material sources and construction sites, increasing fuel consumption and CO2 emissions from transport. The energy-intensive grinding of clinker also contributes to the overall carbon footprint.
 

Increasing demand for lower-carbon concrete

Global decarbonization trajectories suggest that the construction industry must cut emissions by 50% by 2030 to achieve net zero by mid-century and meet the climate goals of the Paris Agreement. As a result, the demand for low-carbon concrete is stronger than ever due to several interrelated factors, each driving the construction industry towards greener practices. 


Firstly, the demand for low-carbon cement is driven by regulatory pressures and corporate sustainability goals. Governments worldwide are implementing stricter carbon emission regulations and upgrading building codes, pushing industries to adopt greener practices. 


Companies are also setting ambitious sustainability targets to reduce their carbon footprints and enhance their environmental credentials. For instance, building projects must often meet specific green standards to gain approval or funding, driving the shift toward low-carbon cement. 


Secondly, consumer awareness and financial incentives further boost this demand. With growing public concern about environmental issues, consumers and investors increasingly favor sustainable building materials. Lastly, governments and organizations offer grants and tax breaks for using eco-friendly materials, making low-carbon cement a more attractive option for developers and builders. 
 

What are the benefits of building with low carbon concrete?

Building with low-carbon cement offers numerous benefits that extend beyond environmental sustainability. Let’s take a look at its benefits below:

  • Significant reduction in greenhouse gas emissions: Traditional concrete production, particularly the manufacture of Portland cement, is responsible for approximately 8% of global CO2 emissions. By using alternative materials and production methods, low-carbon cement can reduce the carbon footprint associated with concrete production by at least 30%
  • Improved durability and longevity: Many low-carbon concrete formulations enhance the durability of structures, leading to longer lifespans and reduced maintenance and replacement costs. For example, concrete containing fly ash or slag can exhibit greater resistance to sulfate attack, reducing the likelihood of deterioration in harsh environments. 
  • Resource efficiency: Using industrial byproducts and recycled materials in low-carbon cement conserves natural resources and reduces landfill waste. For instance, incorporating fly ash into concrete reduces the need for new cement and diverts waste from landfills. This practice not only conserves raw materials but also minimizes the environmental impact of waste disposal.
  • Energy savings: Some formulations offer improved thermal insulation properties, reducing the energy required for heating and cooling. For example, concrete with enhanced thermal mass can help regulate indoor temperatures, maintaining a more stable and comfortable environment. This can lead to lower energy bills and reduced reliance on heating and cooling systems, contributing to overall energy efficiency.
  • Compliance with green building standards: Many building certification programs, such as LEED (Leadership in Energy and Environmental Design) and BREEAM (Building Research Establishment Environmental Assessment Method), award points for using sustainable materials. Incorporating low-carbon concrete can help projects achieve higher certification levels, which can enhance marketability and attract eco-conscious clients.

8 Techniques for building with low carbon concrete

Photo by Glenov Brankovic from Unsplash

Tackling decarbonization in the U.S. building sector will necessitate an extensive, unified effort. That’s why implementing low carbon concrete in construction requires specific techniques to maximize its benefits. It not only reduces environmental impact but also contributes to long-term sustainability goals. Here are eight techniques that can revolutionize the way you build with low-carbon cement:

1. Mix design optimization

Mix design optimization is crucial for achieving a balance between environmental benefits and structural performance in low carbon concrete. This technique involves carefully selecting and proportioning materials to reduce the carbon footprint while maintaining the concrete's required properties. The process starts with replacing a portion of traditional Portland cement with SCMs such as fly ash, GGB, or silica fume. 


These SCMs not only lower CO2 emissions but also enhance certain properties of the concrete, such as its workability, strength, and durability. This optimization process requires a thorough understanding of the materials' interactions and the specific requirements of the construction project, ensuring that the final mix achieves both sustainability goals and performance standards.
 

2. Switch the fuel source

To reduce emissions, switch to a fuel that generates less pollution. This includes transitioning from traditional fuels like coal to lower-carbon options such as renewable natural gas. Another option is to use waste fuels like non-recyclable plastics, tires, and rail ties. Carbon-neutral fuels such as biofuels or biogas could also be a potential option.

3. Adequate curing 

Proper curing methods are essential for ensuring that low-carbon cement develops its full strength and durability. Curing affects the hydration process of the cement, which is critical for the concrete's long-term performance. Several methods can be employed to maintain adequate moisture and temperature during curing:

  • Wet curing: This method involves moistening the concrete surface by covering it with water-soaked burlap, mats, or wet sand. This is particularly effective in preventing the evaporation of water from the surface, which can lead to surface cracking and reduced strength. Wet curing can be maintained for several days, depending on the ambient conditions and the specific requirements of the concrete mix.
  • Curing compounds: These are chemical solutions applied to the surface of the concrete that form a film to retain moisture. This method is beneficial in preventing rapid evaporation and maintaining the hydration process. Curing compounds are often used in conjunction with other curing methods to ensure optimal conditions.
  • Curing blankets: Insulated curing blankets can be used to cover the concrete and maintain a stable temperature. This is especially useful in cooler climates or colder months to prevent the concrete from freezing and ensure proper curing.

4. Implement energy-efficient equipment

Implementing energy-efficient technologies and practices in cement production, such as upgrading kilns and optimizing processes, along with using renewable energy sources like wind energy systems or solar panels, significantly reduces the carbon footprint of concrete manufacturing.

5. Innovative construction methods 

Techniques like 3D printing and prefabrication can optimize material use and reduce waste. For instance, 3D printing concrete structures can create complex geometries with minimal material waste. By using computer-controlled systems to print concrete layer by layer, 3D printing can create intricate designs and reduce the amount of material required. 


Meanwhile, prefabrication construction involves manufacturing concrete components in a controlled factory environment before transporting them to the construction site for assembly. This approach allows for better quality control, reduced construction time, and minimized waste. Prefabricated elements, such as panels or modular units, can be made with low-carbon cement, ensuring that the sustainability benefits are maintained throughout the construction process.


These innovative methods not only improve the efficiency of construction but also contribute to the overall sustainability of the project by reducing material waste and optimizing resource use.
 

6. Carbon capture and utilization


Implementing carbon capture and utilization (CCU) techniques can significantly lower concrete's carbon footprint. This involves capturing CO2 emissions from cement production and using them in the concrete curing process or converting them into useful products. For example, CO2 can be injected into fresh concrete, where it reacts with calcium ions to form calcium carbonate, enhancing the concrete's strength and durability while permanently sequestering the carbon. This technique not only reduces emissions from the cement industry but also adds value to the final concrete product.


7. Conduct localized production

Sourcing raw materials locally and producing concrete close to construction sites can minimize the carbon emissions associated with transporting materials over long distances. For instance, a construction project in a city might source aggregates from a nearby quarry and produce concrete on-site or at a local batching plant, reducing transportation-related emissions.


8. Quality control 


This is vital to ensure the performance and durability of low carbon concrete. Regular testing and monitoring during production and construction can help identify and address potential issues early on. For example, conducting compressive strength tests on concrete samples at various curing stages can ensure that the mix design meets the required specifications and performance criteria. Quality control measures of low-carbon cement include:
 

  • Testing concrete samples: Concrete samples are taken from the batch and tested for compressive strength, workability, and other key properties. Compressive strength tests, such as cylinder or cube tests, are performed at various curing intervals to assess the concrete’s ability to withstand loads. Workability tests, such as the slump test, ensure that the concrete can be properly placed and finished.
  • Monitoring production: During the production phase, monitoring involves checking the accuracy of material proportions, mixing procedures, and equipment calibration. Ensuring that the mix design is followed precisely helps maintain consistency and performance.
  • On-site inspection: Regular inspections during construction help identify and address potential issues such as improper mixing, placement, or curing. These inspections ensure that the concrete is applied correctly and that any deviations from the specified mix are corrected promptly.
     

Build towards a greener future with low carbon concrete with BD+C


Builders and designers are now turning to innovative solutions to reduce the environmental impact of their projects. Choosing to build with low-carbon concrete is a proactive step towards a greener future. BD+C is at the forefront of this movement, advocating for the adoption of eco-friendly practices in the built environment. Subscribe to our newsletter today and get unlimited access to expert strategies, practices, and insights on not only sustainability but everything about building, design, and construction!


FAQs about low carbon concrete


Understanding the ins and outs of low-carbon cement is essential for those in the construction field looking to adopt sustainable practices, making it essential to address common questions about it. Here are some of them below:

Is low carbon concrete more expensive?

Low-carbon cement and steel cost 25% more. However, this only adds 1% to the final cost of products like houses or cars. Despite the initial higher cost, low carbon concrete's durability and sustainability can lead to long-term savings. The environmental impact of traditional concrete is not factored into its cost, which is crucial as we move towards a Net Zero society.

How long does it take for low carbon concrete to cure?

Low carbon concrete typically takes the same amount of time to cure as traditional concrete, which is generally around 28 days. However, this can vary depending on the specific mix of materials used, environmental conditions, and curing methods employed. For instance, a concrete mix with 50% GGBS will be half as strong as a Portland cement mix in the first seven days after pouring. However, it should reach the same strength as the Portland cement mix within 28 days.

What are the challenges of using low carbon concrete?

Low-carbon concrete may have different properties and performance characteristics compared to regular concrete, requiring additional testing and research before widespread adoption. There may also be limitations on the availability of low-carbon concrete materials and expertise, making it less accessible for widespread use in construction projects.

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