The most destructive material on earth, let's look at the harmful effects of concrete
In February 2019 an article in The Guardian described concrete as ‘The most destructive material on earth’ and they’d be right, the environmentally harmful effects of concrete are massive. Concrete is also incredibly difficult to work with.
Common usage of concrete
The most common use of concrete is as a pad or series of piles which form the foundation/s of an individual house. Before we get to pouring concrete pads and or piles let’s look at how concrete’s key ingredient, cement is made.
How is concrete made?
To make cement, limestone (calcium carbonate – CaCO3) is heated to temperatures approaching 10000C, along with other silicates bearing materials such as clay. At these temperatures, the limestone breaks down into Calcium Oxide (known as Lime – CaO), Silicon Oxides and Carbon dioxide. The two oxides combine to produce di & tri-calcium Silicate, which is then ground to a fine powder known as ‘clinker’. Gypsum is added to the clinker (to prevent flash setting), and this is ground further to produce cement. During these processes huge amounts of CO2 are released from fossil fuels which are used to heat the limestone in order for the chemical reactions to take place and further from the transformation of calcium carbonate into calcium oxide.
Time to get busy
OK, so you want to build a house using traditional methods. Best start preparing now, because you’ve got a lot of work to do before you can even consider a concrete pour. Ground works first, concrete needs to be poured on a level, well-drained and compacted surface. This means excavation to remove soft top soil as well as any tree roots that may interfere with the concrete both now and in the future. Your site then must be levelled, removing material is common but in some cases you might need to add material in order to achieve a level surface. You’ll then need to add a couple of inches of gravel across the entire site which will need to be well compacted to prevent the concrete from shifting and cracking.
Water, water, everywhere
Whilst water is a key component of concrete it’s also one of its worst enemies, your compacted gravel will hopefully also act to soak away any water which finds its way under your completed pad, if not the ground below could swell causing the concrete to crack and fail, so it’s wise to you dig a drainage channel around your site to help water flow away from your precious concrete.
Concrete forms and shuttering
Let’s talk about forms. Concrete forms provide a container to trap the concrete as its poured and maintain its shape as it dries. Forms have to have tight joints to prevent concrete from leaking and must be rigid to prevent the concrete from bowing, and strong enough to hold the concrete firmly in place. Your forms must also be dead level and have the right support and bracing as it’s key the finished pad is the correct shape or the overall strength and durability of your pad will be compromised. You’ll also need to treat forms with light bodied petroleum oil (just one more of the many harmful effects of concrete) which not only prevents the concrete from sticking to the forms, but also prevents wooden forms from absorbing water, which could lead to the concrete warping whilst drying.
Concretes major weakness is that it is highly prone to cracking. So your site may require the use of reinforcement in the form of Rebar, steel mesh, steel fibre, cellulose fibre. Not only to try to prevent cracking but also to bear the weight of your completed structure. Such reinforcement must be positioned in the centre of your concrete, not near the top or the bottom but in the centre, tricky, good luck with that.
So you’ve cleared your site, it’s level (we hope) your forms and reinforcement is ready, you’ve got your finger crossed the calculations for the amount of concrete required are correct and its time for your pour. What about the weather? You’ll ideally need three consecutive days when it warm and rain free. Not too hot, not too cold, but just right.
The Great British weather
The temperature of the concrete within the first 24 to 48 hours determine whether it will achieve its required strength. If it freezes the concrete will weaken badly, so you’ll have to provide some form of insulation. If it’s too hot too much water will evaporate from the surface of the concrete adversely affecting the finished product. If its raining, well, you’re in trouble. It’s a very fine line to ensure the correct water content of your concrete, too much or too little and you’ve got problems. Where do we live again? That’s right, the UK, think on that one.
How long does concrete take to dry?
Now its poured we can just leave the pad and it’ll dry no problem right? Wrong, you’ve got to help your concrete to cure. Some water needs to evaporate from your pad in order for the concrete to harden fully, but not too much, it needs to retain just the right quantity of water, so you’ll need to monitor that for up to 14 days.
The alternative to concrete
An MMC Ark Haus does not require the use of an environmentally harmful, sensitive and time costly material like concrete. Rather an MMC home sits on industrial steel screw piles designed specifically to bear the load of the individual house. It’s a simple process and one which does not create huge environmental damage. Moreover, screw piles for a single house can be drilled in a day. So if you’re using concrete, by the time you’ve brought your gear on site to start the ground clearance, we’ve finished our foundations and are ready to build up.
We hope you now understand the harmful effects of concrete on the environment and the time taken by using this material when it’s just not necessary. For more information on MMC and our unique approach to the housing sector please contact us.