How often have you heard the words sustainability and concrete together? Probably not often, if ever. These terms seem to go together like water and fire — one puts the other out. But it doesn’t have to be this way.
Concrete is the biggest contributor to CO² in the built environment, and the industry has to look at ways to make concrete more sustainable.
Residential, commercial and industrial building does not look to be slowing down, and with the Infrastructure Investment and Jobs Act (IIJA) there will be more projects underway that require concrete.
Concrete is literally everywhere you look above ground and below ground — it is everywhere the world works, lives and plays.
These days, there are various efforts for post-concrete production, including recycling waste and reusing wastewater. But what if the concrete production itself was more eco-friendly?
One path for producing concrete more sustainably is not a new technology, but it has been picking up steam over the last few years in the U.S. — concrete produced by volumetric mixers. These mixers produce on demand concrete at the jobsite — pouring exactly what is needed when it is needed.
Why is this important to sustainability and concrete production? Good environmental management practices do more than preserve the natural environment — they can save your business money.
Minimizing waste, increasing resource efficiency and adopting cleaner production methods have been shown to reduce operating costs. The following takes a look at waste, water and emissions and how volumetric concrete mixers can help your business control its concrete and its costs.
Reducing Waste Management
Volumetric concrete mixers feature virtually no waste because only the exact amount of concrete is produced for each pour. All the materials — sand, stone, cement, admixtures and water — are carried on the volumetric mixer in separate compartments to the jobsite.
The mix design can even be changed at the jobsite, if needed, without wasting any materials, and completely eliminates hot loads. Dealing with leftover concrete has become an environmental issue because of the limited places for safe disposal, so there is value in avoiding excess concrete production.
By mixing and delivering exactly the right amount of fresh concrete, waste is limited to a couple of shovels of concrete versus potentially yards of material.
This saves the operator and the customer money because you pay only for what is produced. It also limits the amount of waste.
While wasted material is certainly not sustainable, doing our part to limit waste moves us in the direction of better sustainability. Volumetric mixers limit waste and that is one part of the equation that make them an environmentally friendly option.
Water savings are important for several reasons. First and foremost, water is limited in some areas and it wasting it benefits no one. According to the standards organization CSA Group, it takes about 200 gallons of water to wash out a traditional drum mixer compared to 8 to 10 gallons of water for a volumetric mixer. This is a massive savings in water that does not have to be wasted or run through a waste stream in some way.
Volumetric mixers reduce both emissions and the CO² that result from the concrete production process. With concrete produced on the jobsite, volumetric mixers do not have the travel time and fuel usage that barrel trucks do. They do not need to go back and forth to the jobsite from the batch plant, they will not have to be washed out or stopped at any time because they can be continually loaded with sand, stone, cement and water. To illustrate the environmental benefits, compare a fairly large pour at 6,500 cubic yards continuous-pour project for the traditional barrel and volumetric mixers. According to the U.S. Energy Information Administration, the barrel truck would produce approximately 470 to 820 metric tons of CO², versus the 11.9 metric tons of CO² produced by a volumetric truck. This calculation takes into account diesel fuel and waste concrete at 5% to 10% for barrel trucks. It does not include loaders, generators, chillers or the batch plant.
This article will not go into the sustainability effects of batch plants, but a quick comparison of barrel trucks and volumetric concrete mixers shows that to meet production rates of 230 cubic yards per hour on a continuous-pour jobsite, it would take one batch plant and 33 barrel trucks — making trips to and from the batch plant 20 to 30 minutes from the project — or four volumetric mixers.
While there is certainly a role for both barrel and volumetric trucks, it is important to understand the environmental impact of both.
Putting Volumetric Trucks Into Action
For Bauman Landscape & Construction, a green approach to concrete has helped the company win business. “When you start working with bigger contractors, the generals who are fighting for the Leadership in Energy and Environmental Design (LEED) credits on jobs, it makes you more appetizing to them. They want to use someone who is going to help them meet the credits and help them look better to their client,” said Mike Bauman, owner and president of Bauman Landscape & Construction.
Bauman, along with his daughter, Angela, have been in business since 1978, specializing in public works. Ninety percent of the work the company does is for the city of San Francisco.
“The city loves our volumetric mixers. They like the mix better than the barrel mixers,” said Bauman. The company was one of the first to use 100% recycled aggregate in its mix. They use a blended stone mixing about 50% of the concrete dust with virgin sand so 75% of the concrete is recycled.
“You have to send in a monthly report when you do a job for the city about how much you recycled — what you have done with all the waste materials and how you used it. So, it is a big part of the contract. If you don’t send that in, you don’t get paid,” said Bauman.
Since the city of San Francisco has embraced his volumetric truck, he has noted other interested parties.
“We have a lot of people who see us using our mixers. [They] call us, and we end up selling to a lot of the competition, because right now we always have availability with these trucks.”
Helping the Environment & Saving You Money
With more projects more frequently requiring concrete, it is important to address how to sustainably produce concrete to preserve the natural environment. From reducing waste to conserving water and minimizing emissions, volumetric mixers can help your business reduce costs and be more environmentally friendly.