Concrete is one of the most popular construction materials due to benefits like being readily available, economical, and versatile.
Yet, environmentalists have concerns about the effects of CO2 emissions during concrete production.
Concrete construction in the past indeed left much to be desired by way of its carbon footprint. That said, technological advances and new discoveries in the concrete industry have since changed this fact.
We’ll explain how concrete is more sustainable than damaging when applying the right methods and considerations.
First off, concrete has several sustainable properties on its own.
These properties often prompt project owners choose to use concrete in their commercial projects.
The strength of concrete makes it a useful material for holding heavy loads.
The type of cement used to make your concrete, and the standards met during construction, will determine its strength. Concrete structures have a compressive strength of around 2,500 to 5,000 psi.
However, a new type of concrete with much higher strength capabilities exists. We call this UHPC (or “ultra-high-performance concrete”). This concrete has a potential strength of up to ten times the normal range.
Due to its strength, we can use concrete in all aspects of construction where safety is of increased concern. If you’ll notice, concrete is a common material for tunnels, bridges, roads, and — of course — buildings.
Since concrete is so strong, less material is necessary to construct a building. Additionally, the end product will last many years without needing reconstruction or repairs.
Closely related to strength, concrete is extremely durable. It’ll last through years of exposure to harsh conditions, such as high winds, snow, and even some flooding.
This ability to endure common problematic conditions for another material means less maintenance. Plus, when needed, it requires less material for repairs.
Concrete can withstand damage from unexpected conditions. Therefore, less concrete ends up in rubble brought to landfills.
Unlike wood, cement is resistant to fire. As a result, concrete won’t melt, burn, or emit dangerous greenhouse gases when exposed to high temperatures.
As a result, concrete structures will remain standing through fires. In fact, concrete walls can act as a barrier to the spread of a fire throughout a building, containing the fire to its location.
As we’ve discussed, structures made from concrete can withstand various natural disasters. This reduces the need for demolition and reconstruction of concrete structures.
Concrete is wind resistant, surviving hurricanes, tornadoes, and blizzards.
It’s also water-pressure resistant. So flooding, hurricanes, and tsunamis will have a less damaging effect on concrete than some other types of materials.
Autogenous healing is a complicated way to define self-healing concrete pavements.
In some concrete, superabsorbent polymers absorb water and swell to heal cracks within the slab.
Calcium carbonate coats bacteria cells, expanding and acting as an extra filler to these cracks.
Encapsulated polymers within the concrete mixture can open when the concrete suffers damage. This causes it to spill out its contents. These contents settle in the cracks and harden, bonding the sides together.
The production of concrete does emit CO2 into the air. However, the concrete structure reabsorbs much of that carbon after construction.
As time passes, concrete reacts with the CO2 in the air, absorbing a large amount back into the concrete mass.
Of course, some parameters will reduce the amount of carbon concrete can reabsorb. That includes the thickness of the concrete, the type of concrete used, and the application of any sealing component.
When demolishing reinforced concrete structures, the newly exposed concrete rubble will absorb a significant amount of CO2 as it sits for reuse.
Now, let’s look beyond concrete’s natural sustainable properties.
Project owners can extend the sustainability of concrete through environmentally conscious production and design methods.
The tactics below help to reduce:
The less energy-intensive method of making concrete sustainable is to find a way to reuse concrete for any worthwhile purpose. However, there are more in-depth ways to improve the sustainability of concrete.
Let’s continue our list …
One simple way to make concrete more sustainable:
Substitute the cementitious materials used in your concrete mix for something with less of an impact.
Clinker is the original material used to make concrete out of cement. Still, the production of clinker is one of the main proponents of carbon emissions in concrete production.
Using an SCM in place of clinker reduces the carbon footprint of concrete. Most of the SCMs below would otherwise be “waste” as a by-product of another industry but have found a new purpose.
These dust-like particles come from the coal-firing process. You add them to the cement mixture to reduce the need for clinker in the final product.
Fly ash helps to reduce the carbon emissions from the production of clinker. Also, adding it to your cement mixture will increase your concrete structures’ strength and chemical resistance.
However, fly ash does have its limitations.
Due to the nature of this additive, concrete made with cement containing fly ash is unsuitable for precast structures. It also requires a longer curing time, slowing down construction progress.
Another by-product, silica fume, is a great substitute for clinker. Silica provides extra strength and chemical resistance.
Silica fume is usually best for projects needing higher-strength concrete because it’s often in limited supply.
Rice husk is abundant; discarded during rice processing. This waste product contains about 20% silica, which you can harness when burning off the remaining product.
This rice husk ash can then serve as a substitute for clinker. In addition, it contains similar properties and benefits for concrete as silica fume and fly ash.
GGBS is also a by-product. Yet, this material is slightly different than the others mentioned here.
This is a by-product of the steel industry and is a hydraulic material that provides a higher ability to be substituted for clinker.
That said, it provides many of the same benefits and drawbacks as the other SMCs on this list.
You can also improve the sustainability of concrete by the amount and type of energy used in its production. Therefore, finding a renewable energy source to tap into is key.
Whenever possible, less energy used can reduce the carbon footprint of the concrete used in our infrastructure.
You can apply this concept to the transportation of concrete as well. For example, if you use locally sourced concrete, the energy used to transport the concrete to your job site will decrease.
Aggregate materials help to make the concrete stronger without using any extra concrete or water. Aggregates also make concrete less permeable, helping to reduce the likelihood of cracks and needed repairs.
Asphalt removed from roads or other paved areas is reusable, often as aggregates in concrete.
Crushing and blending this material with another aggregate will keep it from clumping, especially in hot weather.
There are some design considerations to be aware of as well. The DOT provides a full guide for engineers and contractors.
As the name implies, this aggregate is crushed concrete from demolished concrete structures.
You simply reuse this concrete as an add-in to your concrete mix. These can vary in size from small pebbles to large chunks.
This is a by-product of melting iron in a blast furnace for steel fabrication. It crystallizes after cooling it with water.
There are two admixtures developed to help improve the sustainability and durability of concrete:
This hardening admixture developed by Kryton increases the strength of concrete. Yet, it also boosts its resistance to erosion and abrasion.
This admixture can replace sealers and hardeners applied to the surface of the concrete.
Another product by Kryton, the Krystol Internal Membrane (KIM), makes concrete permanently waterproof.
Concrete structures often don’t need repairs due to the concrete becoming weak. Instead, it’s because of the corrosion in the reinforcing steel within the concrete.
This waterproof sealing on the concrete has one main benefit. KIM ensures that corrosion to the reinforcements in concrete is much less of an occurrence.
Using new types of concrete developed to address the common environmental issues posed by concrete structures can be a good way to make your concrete structure more sustainable.
This type of concrete comes from the same ingredients as regular concrete but has a drier consistency.
You’d compact it with the same machinery used to lay asphalt, making it unnecessary to use forms, dowels, or reinforcement.
RCC is a great substitute for asphalt in roads and parking lots. It’s tough, resistant to potholes and rutting, and much more cost-effective.
This concrete addresses the concern of the heat island effect in urban areas, where pavement covers most of the land area. We also call it “cool pavement.”
Most concrete in America is impervious or impermeable. That means it traps water at the surface, which can cause flooding, erosion, and stagnant puddles.
However, one of the biggest concerns with so much impervious concrete surface is that it traps heat. This causes a “heat island,” raising temperatures in cities and causing climate change.
Cool pavement allows water to pass through and absorb into the ground below, along with the heat.
This type of pavement reduces flooding and erosion and is cool to the touch, making summertime in the city much more bearable.
Using sustainable construction methods can also reduce energy consumption when building concrete structures.
Methods such as precast concrete slabs use much fewer man hours and supplementary materials than on-site casting.
Sustainable design methods can also improve the sustainability of concrete. For example: creating a design for disassembly in the future for easy reuse.
The world now sees the importance of protecting our planet from the destructive effects of industrialization. Society is also banding together to find new ways to minimize this.
With new developments on the horizon, the sustainability of concrete is only expected to improve.
So how does the world plan to further improve and enforce the sustainability of concrete?
Well, let’s look at some of the exciting developments and current programs:
The CSHub is a team of researchers dedicated to finding new ways to make concrete a more sustainable building material. They recognize that concrete is the most produced material on earth.
If they can improve its sustainability, they’ll be making a positive impact on the sustainability of construction as a whole.
They delve into ways to:
All objectives of this group of innovative minds go back to reducing the environmental impact of the cement industry.
They’re also dedicated to finding ways to improve concrete’s resilience to the effects of natural disasters.
This council founded LEED (Leadership in Energy and Environmental Design). The program promotes green building practices and incentivizes sustainable development.
This program is always finding new ways to encourage urban areas to practice sustainable concrete construction. They also aim to keep our built environment as carbon-neutral as possible throughout the life cycle of the project.
The LEED rating system is globally recognized. That means earning certification for your concrete building will be globally respected.
Consumers are now more environmentally conscious and request greener concrete buildings. This motivates companies to practice sustainable construction to deliver. What better way than to get LEED certified?
Yet, the LEED system goes beyond just reducing carbon emissions.
It’s a holistic program that considers every aspect of the building when deciding on the rating. That includes air quality and water use.
Imagine if all contractors, architects, and engineers aim to excel in their LEED ratings. If they did, the built environment would become a much greener industry.
The sustainability benefits of concrete as a building material aren’t hard to identify. Project owners can make concrete more sustainable through sustainable design and building methods.
Here at FMP, we believe that sustainable building methods and materials help reduce our environmental impact. We also think they’re smart business moves.