Zero Carbon Concrete

Concrete is affordable, durable, recyclable, and strong. It resists water and extreme weather, provides foundations, and is one of the building blocks of climate-resilient infrastructure. Concrete is key for meeting various sustainability goals throughout the world.

Concrete is the second most consumed material in the US. The only substance in the world that is consumed more than concrete is water. Concrete is also one of the most consumed materials throughout the world, and the use of concrete and cement is expected to go up. This means that finding a way to make concrete less destructive for the world we live in can have massive benefits. Concrete is not great for the environment, it is responsible for 4-8% of the world’s carbon dioxide production, and uses 1/10th of the world’s industrial water. If we can decrease the environmental impact of concrete production, then we can significantly decrease climate change, pollution, and environmental degradation. As the world urbanizes, we can expect the amount of concrete used to grow up. In modern cities, concrete is the foundation as well as one of the primary building blocks.

Why bother decreasing carbon dioxide emission?

Carbon dioxide, or CO2, is a greenhouse gas. This means that when the sun’s light enters the atmosphere, it CO2 and other greenhouse gasses trap it, causing a heating effect. CO2 is not the most dangerous greenhouse gas, others, like methane, are far more effective at trapping the sun’s heat. However, CO2 is vastly overproduced. Yes, almost every breathing animal (including people) inhales oxygen and exhales CO2. Yes, decomposing plants emit CO2. But, human interaction with nature has resulted in too much CO2 being produced. The natural world has had ways of balancing its own CO2 production. But as 80% of the greenhouse gas emitted by human activity is CO2, that production over the years has been enough to tip the world’s ability to handle the gas. This is why you will find CO2 reduction as a major goal of climate change.

How concrete can become CO2 neutral

What parts of the concrete production process produce the most carbon dioxide?

In order to understand exactly how concrete can not be a producer of carbon dioxide, we need to know how it produces the stuff. What parts of the concrete manufacturing process produce CO2? What parts produce the most, and how can they be improved?

Turning limestone into cement

The process of making limestone into cement involves a chemical reaction at extremely high temperatures. It must be heated to 1500° F, which requires immense amounts of fuel. This is the main factor in cement CO2 production, and the area where it can best be made more efficient. Some estimates deduce that as much as 2/3 of the CO2 produced during the cement-making process happens during this chemical reaction.

Transportation

Of course, raw and finished materials have to be transported. As the main engine for moving around our world is internal combustion, this means more gasses are produced in moving concrete.

The challenges

Reducing the carbon footprint of transportation is the easy part

Fortunately, transportation is already moving in a greener direction. More and more electric cars, trucks, and trains are being produced and used. Electric and wind-powered shipping vessels are moving things across the oceans as well. The US is already — slowly but surely — on the way to making all of its transportation carbon-neutral. As battery technology and electric motors improve, it will only get easier.

It’s the cement production process that poses the real problems

Most of the cement made in the US is Portland Cement. It is effective, durable, and has all the other positive qualities that makes cement so ubiquitous. The problem with it is that it was invented nearly 200 years ago. As such, it’s manufacturing process hasn’t changed much since.

Besides the manufacturing process requiring huge amounts of fuel, the chemical reaction used to make cement leaves behind calcium oxide. When the other substances exit limestone to make calcium oxide, where do you think they go? Into the atmosphere, as CO2.

The main greenhouse emitting agent in cement is called clinker. Clinker is a nodular substance used in the kilning stage of cement and is also a binder in many cement products. It is produced by heating limestone and clay to liquefaction in a kiln (around 1400-1500° F).

The solutions

  • Electric kilns for heating the cement are beginning to be implemented. These use lower carbon or renewable energy sources for heating cement to its required temperature.
  • Alternative fuels and electricity-powered vehicles are already driving CO2 out of the transportation process of cement.
  • Clinker is being substituted with alternative materials in some cases. It can be replaced with recycled byproducts like chemically treated steel slag and fly ash.
  • Concrete can be made from upcycling, that is captured CO2 from other industrial activities. This “Co2ncrete” shows much promise in creating carbon-neutral (or even negative) concrete.
  • Concrete itself naturally absorbs CO2. So the longer concrete lasts, the more CO2 it sucks out of the atmosphere. Longer-lasting concrete is a great way to facilitate this process.

Of course, there is a lot more work to do in order to decrease concrete’s global emissions. The Global Cement and Concrete Association even has a climate ambition plan. Concrete, may be one of the worst construction materials for the environment. However, the production of concrete is slowly moving towards reducing, or even neutralizing it’s greenhouse emissions.

Paving the way for a better future

If you have a paving project in mind, but would rather keep it lower-emission, then Reliable Paving has got you covered. We are am experienced, professional, and large paving contractor, who already recycles the vast majority of the asphalt we use. Our asphalt paving and concrete is built to last which saves our clients time and money. It also decreases the strain on the Earth from constant material consumption. If you’d like to get started on your paving project, let us know today.