Environmental Bad Boy
When it comes to environmental sustainability, concrete gets a bad rap. It is commonly regarded as being environmentally destructive, exacerbated by its closed-loop life cycle. Cement production is allegedly responsible for 8% of global emissions, making it the world’s single biggest industrial cause of carbon pollution.
Limestone, the key raw material, releases carbon dioxide as it is heated in a cement kiln. There are also issues due to the overuse of water in the concrete process.
On the flip side, concrete has a very low embodied energy per unit mass. This means that associated carbon impacts from transport or construction methodology are low.
Furthermore, concrete alleviates the need to remove carbon-sequestering forests for timber construction. And thirdly, concrete is very long-lasting, and it may be helpful to compare the lifetime environmental impact of any given structure with alternative building methods.
So it’s complicated.
What Would We Use If We Didn’t Have Concrete?
Concrete is an extremely versatile, cheap, and durable building material. Unfortunately, there isn’t yet a viable alternative to ‘swap out’ for concrete in every situation, although of course a lot of research is being done in this area.
However due to the costs of implementing alternatives and the difficulty of changing industry habits, concrete will remain in very common use for some time yet.
Can We Do Anything to Alleviate the Impact?
One thing we can do is to make the structures last longer – get more service life out of any given structure so it can be reused rather than demolished and replaced. This effectively reduces the amount of new concrete required – one concrete structure at a time. At MARKHAM, we call this “Adding Life to Concrete”. This approach reduces the lifetime environmental impact of the structure.
How Can This Be Achieved?
It’s one of MARKHAM’s core observations, that moisture, and the reactive contaminants it carries in solution, is the driving factor in a very broad range of concrete deterioration issues.
For a commonly recognized example, chlorides entering the porosity of the concrete will destroy the protective passivation zone around the reinforcing steel, leading to premature corrosion and concrete cracking. This is commonly seen in marine environments. However, if the moisture couldn’t enter the porosities, the process would be arrested.
Concrete impermeability is known to be connected to its durability, and this example shows why. To make the concrete more durable, we need to make it less permeable. So how can we enhance the impermeability, and therefore the durability, of existing concrete?
Nanoparticle Catalyst Technology
Fact: the application of nanoparticle silica colloid, with the appropriate catalyst, will induce the formation of a C-S-H hydrogel within the concrete. This process uses existing uncured lime within the concrete and immobilises the moisture within the pores. The process penetrates deep – depths up to 170mm have been achieved – and leaves nothing on the surface. The net result is to effectively waterproof the concrete, stopping water from entering or moving through the concrete. This in turn arrests the movement of reactants, and the reactions themselves (which require moisture to proceed).
It all sounds too easy? One of the key benefits of this treatment is its simplicity, with minimal downtime required of the site. The product is also nil VOC, making it extremely safe for working around waterways and sensitive environments.
MARKHAM has the case studies to prove that this technology works. One classic example being Bledisloe Wharf, which was scheduled for demolition about 20 years ago, but thanks to hydrogel treatments is still standing and in active use!
If you’re interested in other case studies or would like to see some independent reports, please get in touch!
Or better still, reach out to discuss your own project – let’s add life to your concrete!
Banner photo by Andreas Brücker on Unsplash.
Corrosion photo by Jarrod Erbe on Unsplash.