Concrete is one of the most ubiquitous products on the planet. It’s used for roads, parking areas, bridges, dams, walls, and even entire buildings. It’s so common, according to some reports, that next to water, it’s the most used substance in the world.
Valued for its durability, concrete resists the forces of winds, floods, fires, and bug infestations. It doesn’t harbor rot or mold, and offers natural temperature control to structures.
In some respects, the case can be made that concrete is a sustainable material. After all, its durability means whatever it's used for will stand for many years without succumbing to the forces that might take out a weaker material.
Having said that, concrete as it's been made historically has a major environmental impact. It doesn’t get as much attention as the micropolastics in our food supply and the toxins in our water, but classic-edition concrete has some serious drawbacks.
Why Is Old Concrete Bad for the Environment?
Both cement and the concrete it goes into impact the global environment fairly heavily. Starting at the roots, mining products from the ground scars the Earth and contributes to water pollution. According to ScienceMuseum.org, “Cement production alone generates around 2.5 billion tonnes of carbon dioxide (CO2) per year—about 8% of the global total.”
Once in a kiln, the conversion of the materials into cement releases high amounts of carbon into the air. Worse, cement production is depleting some types of usable sand and is highly water consumptive.
What’s the Difference Between Cement and Concrete?
These two terms are often used interchangeably, but cement is actually an ingredient in concrete (usually about 10-15% of the total material).
Cement is made from natural ingredients. However, those ingredients have to be mined for use. It’s made up of about 85% lime and silica, but may also include shale, iron ore, clay, and rock.
These materials go into a kiln where they are heated to extremely high temperatures until they form a ball called “clinker”. That ball is then ground down to produce what is commonly known as portland cement.
To make concrete, portland cement is mixed with water and an aggregate such as gravel or stone. The mixture hardens, and actually continues to harden for years.
What Can We Use Instead of Cement?
With the impact cement has on the environment, it’s easy to see we should be on the hunt for more eco-friendly options. But, we are so dependent on cement in concrete, it won’t be an overnight switch.
However, there are several cement alternatives already on the market, and new technologies coming out every year.
One way we can think of alternatives is as a replacement for cement in the concrete recipe. There are many materials on the market that partially or completely replace cement in this scenario.
Hemp is an incredibly useful plant. It got a bad wrap many decades ago because of its relationship to the marijuana plant, but now that hemp is once again legal in all 50 US states, it’s being used in myriad products from textiles to biodegradable plastic to insulation.
As hemcrete, the plant's fibers are pressed into a material substitute for concrete. It’s renewable, fast growing, and lightweight, so it’s easy to work with and creates fewer emissions during transport.
As a plant, hemp naturally captures carbon from the air and releases oxygen as it grows. That carbon remains trapped inside when it’s converted to hempcrete.
Eliminate concrete from the mix with wood instead. Use it for a deck instead of pouring a patio. Frame a house instead of making concrete walls.
Timbercrete is another wood-based material that can lighten the concrete footprint. It’s a mixture of waste sawdust and concrete, along with a binder. It’s lighter than traditional concrete and actually traps carbon rather than releasing it.
Timbercrete is a versatile material that can be formed into blocks, bricks, panels, or paver stones. It can be used indoors or outdoors, is heat resistant (unlike heat-absorbing concrete), and is much easier to screw or hammer into when used as a building material.
Timbercrete is actually stronger than concrete, even though it’s lightweight, and is fire-resistant, unlike traditional wood. It also functions as an excellent insulator, saving energy and money.
3. Straw Bales
Straw is a natural material that has been used as a building material for a long time. People have stuffed their walls with straw with the knowledge it’s a great insulator of both sound and heat.
Straw bales are endlessly renewable and also help with the emissions problem since, like all plants, they store carbon.
Obviously, straw bales may not be the most durable option. If not properly cared for, they can be susceptible to pests and mold, and they don’t offer fire resistance.
However, with proper protection, a straw bale structure can last a century or more. Better yet, the materials can be easily composted back into the land with no waste.
Beyond traditional straw bales, straw can also be combined with concrete to lighten the carbon footprint of the latter.
Some of the first examples of concrete were found in Syria, dating back to 6500 BCE. Similarly, the ancient Romans made a concrete mixture out of volcanic ash around 125 CE that still stands in the Pantheon today.
The modern use of ash is as an additive to cement, more than a replacement for it. Inasmuch, it creates a cement that uses less water and reduces shrinkage.
The most beneficial part of this process is that the ash used is known as fly ash, and it’s a by-product left behind at coal-burning power plants.
While burning coal doesn’t do anyone a favor, since it’s happening we can at least make use of these recycled materials instead of sending them to the landfill. This is a case of progress, not perfection.
Yes, paper. The concept of Papercrete has been around since the late 1920’s. Once again, this is a combination of paper pulp and cement, so it lightens the load of concrete but doesn’t entirely replace it.
Papercrete is a sustainable option because it is made from recycled paper. We love recycling. It can be used for anything from making a planter to insulating walls.
Plastic certainly gets a lot more media coverage as a perpetrator of environmental sabotage than the equally damaging cement.
The well-identified primary issues with plastic are that it’s a petroleum-based material (look for bio-based plastic instead!) which means it requires oil drilling, transport, and energy intensive treatment, and that it never, ever, ever, goes away.
Plastic breaks down into microplastics, eventually, but never biodegrades completely. Those microplastics are so small they travel right through processing plants and down the streams and rivers to the ocean, touching every living thing along the way.
Microplastics have been found in everything from the fish we eat to baby food. Just a few months ago, scientists found microplastics in 80% of human blood tested, spawning a new phrase—microplastic pollution.
Waste plastic is being used in the construction industry as a replacement for a portion of the aggregate material in concrete. This makes great use of an otherwise toxic material and helps reduce the impact of concrete at the same time.
Glass is another natural material, made from sand, soda ash, and limestone. It’s endlessly recyclable and stable enough for long-term storage.
However, glass production still leaves its environmental mark from mining those raw materials and using high heat to process the glass.
Using post-consumer glass as an aggregate in concrete continues the lifecycle of the material and enhances the durable aspects of concrete.
If you think about it, glass is one of the oldest building materials, so it’s actually been used as a cement substitute for a long time.
It’s used for passive solar energy collection, makes a great insulator, and of course, allows us to see the outside world from the inside. Glass is so ubiquitous that it can even be used for floors and ceilings.
8. Composite Cement
We hit on this one earlier, in a sense. Composite cement is made with a blend of materials, most commonly reducing the amount of clinker used to make portland cement by combining it with fly ash.
That combination is then mixed with either limestone or blast furnace slag—a material sourced from molten iron slag in a furnace. On its own, blast furnace slag is stable and strong enough to replace 70-80% of the cement content in concrete.
Composite cements take advantage of this, sometimes combining blast furnace slag and limestone with portland cement in lieu of fly ash.
Any of these combinations significantly reduce the carbon emissions from the production of clinker.
9. Recycled Concrete
When concrete is broken up, there’s no need to send it to the landfill. Instead, it’s a valuable resource in making more of the same.
In addition to lengthening the life cycle of concrete already on the planet, recycling concrete results in a reduction in sourcing virgin materials.
Bamboo is often used in the same ways as timbercrete. It can reinforce concrete or operate as a stand-alone wood-type material.
It has its own category because, in case you didn’t know, bamboo isn’t a wood, it’s a grass. That means it grows quickly and is renewable.
It requires few resources to grow or harvest, making it inexpensive, especially if you live in a region where bamboo grows.
Metal is a durable and long-lasting option for everything from roofing to framing.
When it comes to DIY projects, steel is especially lightweight for its strength, as well as versatile and easy to maneuver.
Ferrock is made from waste steel dust (we love recycling) and silica from ground glass. It’s a fairly new material, launching onto the scene in the past five years or so, more than a decade after the initial lab accident that resulted in its discovery.
Reports suggest it’s more flexible than concrete, which makes it less likely to crack. It’s also reportedly up to five times stronger than concrete when it comes to compression. That’s a lot of strength.
Ferrock is carbon negative, meaning it traps more carbon than it releases during manufacturing.
Unlike other materials, Ferrock is strengthened by exposure to saltwater, making it a great concrete substitute in coastal regions. Plus, Ferrock dries in a fraction of the time of traditional portland cement.
So far, Ferrock is made in limited quantities, partially due to the fact it relies so heavily on waste products from other industries.
13. Micro Silica
Also known as “Silica Fumes,” micro silica is a powder made from another manufacturing byproduct from ferrosilicon alloy and silicon production.
It’s a result of the condensation of silicon dioxide and can replace around 10% of the cement traditionally used in concrete.
Like some other materials, micro silica is credited with improving the compression strength and durability of concrete.
It’s made a name for itself as a product suitable for structures with exposure to harsh chemicals. Perhaps eliminating those production facilities should be the next place we look as we strive toward a more sustainable future. But again, I digress.
Although prolific, concrete’s days are numbered as the world gains increasing awareness of its damaging characteristics. Fortunately, innovative technologies have stepped in to pave the way for that transition away from cement.
The Future of Cement Alternatives
It’s an exciting time in the world of innovations, and the construction industry is right in the middle of the mix. Scientists are working on ways to capture carbon and subsequently inject it into concrete or concrete substitutes.
This is a way of removing carbon from the air, storing it for the life of the concrete. Think of it as carbon offsetting for the cement industry.
Ongoing research and development projects are examining the cement alternatives mentioned here, as well as a host of other options.