Anywhere you go, you’ll likely see concrete as part of buildings, homes and other structures. That’s because it’s the most commonly used building material. With that said, it comes at a cost.
The Problems With Concrete
Although concrete has been the most popular building tool for decades, it takes a toll on the environment in a few different ways.
1. Carbon Dioxide
Cement is the biggest ingredient in making concrete, but it involves a certain percentage of greenhouse gas emissions. It adds up to contribute about 8% of the world’s total carbon dioxide (CO2) emissions. The process emits CO2 in two different ways.
First, it requires heating a kiln to high temperatures, which uses energy. Second, in the process of mixing cement into concrete, another transformation takes place — calcination. This is when limestone gets heated, turning it into quicklime.
2. Increase in Production
The world’s population is growing. This means more buildings. Cement production continues to rise each year, which entails only more CO2 emissions.
3. Resource Damage
Cement production requires a large amount of energy use. But the smaller ingredients, like sand and stone, come from mining natural resources and habitats. It also causes a high demand for fresh water, making up about 20% of the world’s industrial water consumption.
These reasons show why finding alternatives to concrete must help lessen some, or all, of these consequences.
Substitutes and Alternatives for Greener Concrete
You’ll see plenty of concrete wherever you go. However, you’ll also start to see some new alternatives and substitutes.
Researchers and architects understand the need for a viable concrete replacement. Here are some potential solutions they’ve found.
1. Coal Waste
The process of burning coal dust produces a waste called fly ash. This waste product often ends up in landfills, where it can impact the local environment.
In 2018, researchers at the Washington State University discovered a way to incorporate fly ash into concrete through molecular engineering. By reusing the waste, this new process would not involve the heating or cement requirements.
While strategies like this are still under development, as long as coal waste is around, using it is a greener concrete construction process with plenty of potential. It’s easy to imagine how much less CO2 this process would emit.
2. Geopolymer Concrete
Australian researchers found in a study that geopolymer concrete can replace 50% of traditional concrete in use. Geopolymer concrete is an alternative that doesn’t use limestone.
Instead, this concrete uses things like fly ash, clay or slag, combining environmentally friendly materials in a low-energy process.
3. Biomass Fuel and Tires
If geopolymer concrete helps with the limestone emissions, the kiln emissions still pose a problem. How can alternative fuel sources help with the production process?
Kilns use coal in the heating process, and they need to reach extremely high temperatures. Heating tries and biomass fuel can reduce the amount of CO2 emissions that come with this process. Combining this with something like geopolymer concrete would reduce emissions greatly.
4. Fiber Cement
Fiber cement uses water, minerals and air, plus fire to heat the mixture in a filtration process. Fiber cement is a durable option that reduces the need for replacement parts and materials over a span of decades.
In its implementation, fiber cement offers a sustainable option that has already become common. For example, it can be seen in the construction of high-profile structures like the Tiroler Festival Hall in Erl, Austria. The design creates a striking aesthetic without using materials that produce harmful gas emissions.
5. Graphene-Infused Concrete
At the University of Exeter, researchers tested adding graphene into concrete. Graphene is about 200 times stronger than steel and provides a lightweight and flexible alternative. It also conducts heat and electricity well.
Because of its strength and durability, using graphene-infused concrete would cut the required materials needed in half. This would help substantially reduce CO2 emissions.
6. Root Veggies
You heard that right! At Lancaster University, researchers have found ways to use vegetables like carrots or beets in concrete mixes. They take nanoplatelets from the fibers of these vegetables and combine them in the cement.
The nanoplatelets strengthen the mixture, which would then require less cement in total. This alternative would also be cheaper than graphene because food waste would have a new use.
7. Recycled Plastic
In Queensland, Australia, a Ph.D. student at James Cook University, Shi Yin, won an innovation award for his use of recycled plastic in concrete. Since concrete often requires steel to reinforce it, which uses a lot of energy, Yin replaced it with recycled plastic.
This replacement can cut CO2 emissions in half. This is on top of already slashing emissions by 50% by using recycled plastic instead of virgin plastic.
8. Old Concrete
Something as simple, and cost-effective, as using old concrete can also help reduce emissions. While waste from demolition sites usually goes to landfills, reusing the old concrete can be a nifty cost-cutting and environmentally friendly trick.
9. Adapt Buildings to Use Less Concrete and Cement
Another solution is to adapt buildings to use less concrete and cement. The problem is concrete is cheap and versatile, with no need for fireproofing. Builders appreciate these qualities while constructing durable structures.
Fortunately, architects and construction companies with a focus on green building are leading the charge. The Windhover Contemplation Center at Standford University, for example, is built with rammed earth walls — a combination of locally-sourced clay, sand and gravel.
The feasibility of such measures depends on the building’s location, however. Natural disasters such as earthquakes can still devastate buildings with minimal concrete, so it takes careful design consideration to make a new structure durable.
Future Hopes for Greener Concrete
There are even more ideas on the horizon that haven’t come to fruition yet. Something like capturing CO2 during production is a promising idea similar to carbon capture during coal-fired electricity generation.
Hopefully, another alternative will be carbon-negative cement, which would replace quicklime with magnesium oxide. Neither of these has quite gotten the momentum they need.
But researchers know the potential of these ideas. The next steps are to get clients and contractors to use the newer, greener options. Keep an eye out for these alternatives! You can find sustainable options for just about everything.