Concrete – the defined structure of our built world. It is the most used construction material in the world and manifests itself in a variety of ways – from large high-rise buildings to small sidewalks. With usage comes responsibility. The concrete industry is responsible for nearly 8% of global carbon dioxide emissions.
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This is an astonishing statistic when we consider the range of environmental issues with which we already contend. The question is, how do we make concrete more sustainable?
To be clear, we don’t produce more sustainable concrete just by changing a recipe or supplying a new chemical. Sustainability is not a one-step answer for concrete but a multi-layered approach that includes selection of better materials, innovative chemistry, construction processes, and demolition/recycling methods.
In this blog, we will cover these phases and options. But don’t worry, we will also be looking at impactful products, such as pumping aid, Addage VMA powder that play a significant role in the quest towards more sustainable concrete.
The Problem With Traditional Concrete
First things first. Concrete is composed of three main ingredients: water, cement, and aggregates (sand and gravel). Cement – Portland cement specifically – has the highest environmental damage potential of the three.
Cement production consists of heating limestone with other materials at temperatures as high as 1450°C in kilns. This process releases a substantial amount of CO₂ into the atmosphere as it uses fossil fuels in the process of heating, and the chemical process also releases CO₂.
Here are some more stats to put some context around things:
Every ton of cement production releases about 0.9 tons of CO₂ into the atmosphere.
The global usage of cement is around 4.1 billion tons (yes with a B) per year.
The usage of concrete is predicted to double by 2060, as a function of urbanization and increasing population.
Clearly, not only can we not do “business as usual”.
1. Supplementary Cementitious Materials (SCMs)
One of the best ways to mitigate the carbon footprint of concrete is to replace a portion of the cement with Supplementary Cementitious Materials (SCMs). SCMs can be industrial byproducts or naturally occurring pozzolans.
Common SCMs include:
Fly Ash: A byproduct of coal-fired power plants, Fly Ash can improve both workability and long-term strength while reducing CO₂ emissions.
Ground Granulated Blast Furnace Slag (GGBFS): A byproduct from the steel industry, GGBFS reduces permeability and enhances durability.
Silica Fume: A byproduct of silicon metal production, the finer Silica Fume can increase strength and reduce porosity.
Benefits:
Substitutes for a less energy-intensive Portland cement.
Utilizes industrial waste to reduce impact on landfills.
Improves particular performance characteristics.
It is possible to reduce CO₂ emissions by 30–50% using SCMs, depending on the content and type of SCM used. This is a large step towards reducing the overall carbon footprint of concrete.
2. Using Alternative Binders
Cement has been around for 2,000 years and is the most commonly used material in urban construction. However, a recognized problem with cement has points been the irreversible greenhouse gases associated with its production processes.
SCMs (Supplemental Cementing Materials) are generally less damaging for a slightly lower performance but still count on traditional cement. Other materials are also being studied with the potential to entirely replace cement in construction.
Some examples include:
Geopolymer Concrete: Geopolymer concrete is made from fly ash and slag and is activated with alkaline solutions. This, and the superior durability, is a great contributor to a far lower carbon footprint.
Limestone Calcined Clay Cement (LC3): A hybrid of calcined clay and limestone, is a great alternative cement that reduces emissions up to 40% while sustaining similar strength.
Alternative binders are no longer merely a research endeavor, but actually already in construction products and being utilized in projects, with most codes and production methods permitting their use.
3. Recycled Aggregates and Materials
Sustainability may also rely on what we already have in our environmental footprint. By using recycled aggregates from demolished concrete in demolished residential or commercial structures, or recycled aggregates from industrial waste, we lessen the need to use virgin resources and lessen the environmental footprint of the industry as a whole (we are all aware of the costs of quarrying).
Some practices are:
– Crushed concrete is being used as an aggregate in new concrete mixes (in part, this is our weaker and less damaging environment/environment practice).
– Glass and rubber particles added as aggregate in mixes for specialized applications.
– Plastics are being used as (added) aggregates as fillers for lightweight filler applications.
Minimizing the destruction of natural aggregate resources is, of course, a good practice for the environment. With the added benefit of less landfill, a very good thing for the environment.
4. Carbon Capture and Storage (CCS) in Concrete
One of the most promising developments is turning concrete from a carbon emitter to a carbon sink.
Here is how this works:
CarbonCure and other technologies inject CO₂ (captured from an industrial source) into the concrete mix. In the concrete, the CO₂ reacts with the calcium ions to form calcium carbonate, effectively locking the gas into a stable, solid state and trapping it forever.
This process actually strengthens the concrete, while lowering the CO₂ emissions count.
Concrete, when it cures, actually absorbs small amounts of CO₂ from the surrounding atmosphere — a process called carbonation.
The thought of concrete absorbing greenhouse gases like a sponge? Now we’re talking about really cool innovation in the space.
5. Smart Mix Design and Optimization
Mix design is where science becomes art. When engineers consider how to optimize the mix design of concrete, it is possible to create additional benefits of reduction in material use, waste, and embodied energy.
Modern methodologies can be employed that leverage tools such as AI-based algorithms and simulation software that can help engineers to:
Increase cement content without loss to engineered strength.
Optimize the water-to-cement ratio, thus minimizing cracking and shrinking.
Facilitate workability and pumping characteristics without compromising on water use.
And this is where our secondary keyword, pumping aid, comes in.
6. ADDAGE VMA: The Unsung Hero of Sustainable Concrete
When considering sustainable concrete, VMA likely isn’t the first thought that comes to mind. But this little additive does more than you may think.
What is ADDAGE VMA?
ADDAGE VMA is a Viscosity Modifying Admixtures added to concrete to enhance its ability to be pumped, especially when pumping long distances or heights. VMA improves the cohesiveness of the concrete mix, which reduces segregation and provides a more consistent flow through pumps, pipes, and hoses.
Why is this important for sustainability?
1. Reduces the Need for Excess Water
In the past, when concrete needed to be pumped, extra water was added to make the mix easier to pump. Additional water will weaken the mix and add additional shrinkage. Our Viscosity Modifying Admixtures allows the concrete mix to remain workable without sacrificing strength.
2. Improves Efficiency on the Job Site
Efficiency in concrete pumping ultimately leads to fewer stoppages, less rework, and quicker placement. This all saves energy, fuel, and time to complete the job, which has environmental costs.
Enables Use of Eco-Friendly Mixes
Allows for High content SCM & recycled materials to be pumped sustainable mixes with larger amounts of SCM or recycled materials can be difficult to pump at times. VMA allows these mixes to flow more easily without sacrificing the pumpability of concrete, eventually making sustainable mixes more practical for actual construction.
Reduces Material Waste
Improved pumping definitely reduces the chance for material waste and blockages, which further reduces the environmental footprint.
In summary, VMA may not be glamorous, but the product plays an important role in keeping construction practices greener.
7. 3D Concrete Printing
Talk about the future – 3D printing is starting to be an innovative way to make the production of concrete more sustainable.
Allows exact placement for the materials – no formwork and therefore no wastage.
Can use a non-traditional eco-friendly mixture of concrete.
Less labour and quicker construction.
Can be set up to maximize strength with lower quantities of material.
Eventually, 3D concrete printing could be standard across eco-friendly construction practices.
8. Better Practices and Maintenance
Even if you use the greenest concrete mix in the world, if you waste it on-site, or if you engage in poor practices to maintain the structure later, you are not truly sustainable.
Here are some ways better practices can assist in sustainability actions:
Reducing material waste through accurate batching would result in using less concrete, which is more sustainable.
Using methods of curing that conserve water consumption and energy.
Designing structures with longevity in mind means that fewer demolitions/rebuilds will occur.
Taking care of and maintaining structures should prevent premature deterioration and extends serviceability.
Sustainability should not just be viewed as a material choice, but should be a way of thinking in all actions through the life of a building/structure.
9. Demolition and Circular Economy
Sustainability, it’s a new life at the end of the building’s end of life.
Selective demolition is when an asset is demolished to recover usable materials like steel, aggregates, and in some cases, certain admixtures.
Concrete crushing creates new basmaterial or recycled aggregates from the rubble.
To have cyclical forms of reuse from a building’s life (re-usable at the end of its life), requires cradle to cradle thinking – and not Landfill to landfill thinking.
What we are experiencing is a transition to a circular economy in the construction space and an imperative to curb waste and preserve materials.
Final thoughts: A Greener Future Foundation
The concrete industry has a large footprint – but a larger opportunity. We can make concrete more sustainable, without losing performance, or affordability. Through innovation, smarter materials, processes, and culture.
From tech solutions such as carbon-capture mixes and 3D printing, to everyday assists such as pumping aids. To create smoother and less wasteful construction, the path toward green concrete is set. Literally.
However, sustaining change will only happen through collaboration – engineers, architects, policy makers, and builders, and a willingness to reform habits. As you walk upon a sidewalk, drive across a bridge, or look across your city’s skyline, remember, sustainability is built bottom up.
We’re not building a sustainable environment with every sustainable choice we make; we’re building a sustainable future.
