Civil Engineering 101: Why Should We Recycle Concrete?
Buildings and structures are left in rubble when they are demolished by men, shattered by wars, or destroyed by natural calamities like earthquakes. Every time any of that happens, there are lots of waste concrete lying around.
More often than not, these piles of waste concrete end up in landfills for disposal. That’s apart from the wastes made by construction activities. In the US, about 135 million tons of construction and demolition wastes are produced annually, which is 3lbs/person/day.
To be able to place these waste concrete to where they belong, it takes a considerable amount of money to transport the waste concrete to the landfill and dispose them properly.
But there is a better, more sustainable, and more economic way to make use of waste concrete instead of disposing them in landfills: recycle them.
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Concrete recycling is not an entirely new solution to the growing problem of concrete wastes around the world. It is not just widely adopted. Not too many companies want to invest in concrete recycling equipment and technology despite the advantages of the process.
When concrete is recycled, the landfills where they are supposed to be dumped are cleared, thus reducing the need for more landfills. Concrete is non-biodegradable and takes a lot of landfill space.
Recycling concrete into usable aggregate also consumes less energy compared with processing new stone for construction of buildings and structures. This means a lesser need for mining or more mining resources for other use.
Perhaps the greatest advantage of concrete recycling is its construction application. Rather than use fresh concrete, there are construction activities that utilize recycled concrete like in road foundation, landscape materials, soil stabilization, and pipe bedding.
Source: Geofabrika
Meanwhile, recycled concrete as aggregates can be combined with virgin aggregate when used in new concrete.
The process of concrete recycling is not a complicated science. It starts from crushing the concrete using equipment with jaws and impactors. Others suggest to pulverize the waste concrete but doing so makes it harder to separate the unnecessary components and to control the particle size distribution.
Dirt is separated from the aggregate by screening after the concrete is crushed. Next step is to get the steel, plastic, soil, and wood out of the concrete by magnet, water flotation, or air separator.
By-products of this process are aggregates of various grades and types.
A note worth taking is that recycled concrete as aggregates do not have the same properties as fresh aggregates. Typically, they have a higher absorption and lower specific gravity than natural aggregate, and produce concrete with slightly higher drying shrinkage and creep. Meanwhile, the crushing strength and impact resistance are lower in recycled concrete.
When it comes to strength, recycled aggregate concrete is about 10 to 15 per cent less as compared to concrete with fresh aggregate.
Sources: The Constructor | Concrete Thinker | The Balance
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