Terms & Definitions
Fibre Reinforced Concrete
Fibre reinforced concrete (FRC) is any concrete that is produced with a fibrous material in addition to its typical components (cement, aggregate, water, fillers, admixtures). The fibrous material can be steel, plastic (e.g. polypropylene) or organic (e.g. hemp).
The fibres in FRC bring it numerous benefits in terms of toughness, durability and ductility. The main advantage of FRC over traditional concrete is in its post-cracking resistance. Traditional concrete has a low tensile strength compared with its compressive strength and once it cracks its bearing capacity in tension drops to zero. However, in FRC, once a crack appears, fibres “bridge” the crack and continue carrying tensile stress.
Because of these advantages and great potential that it offers, FRC is being increasingly used in different structural and non-structural applications: round-supported slabs, pavements, roads, tunnel linings, pipe sewer lines and flat slabs. Its properties allow designers to reduce crack widths of concrete structures in service, as well as to reduce (or even eliminate) reinforcement. Most importantly, many studies employing multi-criteria decision making methods have shown that FRC is more sustainable than traditional reinforced concrete for many applications.
Waste and Recycled Materials in Concrete
Believe it or not, but concrete is the most produced material on earth! Over 25 billion tons of concrete are made each year and it makes up most of the built environment around us. This also means that we need a lot of natural resources to produce concrete – minerals and stone for cement and aggregates. Of course, this places a large strain on the environment.
One challenge is the large emission of CO2 from cement production: 5–7% of annual anthropogenic CO2 emissions come from cement production! Another problem is what happens to concrete structures after their service life is over? They are still mostly demolished and deposited in landfills. This leads to almost 850 million tons of construction and demolition waste being generated in the EU every year!
What can we do about this?
First, we can recycle construction and demolition waste to produce recycled aggregates and replace natural and river stone used in concrete!
Second, we can use a lot of industrial by-products to replace cement used in concrete! These can be fly ash (from coal combustion), steel slag (from steel production), red mud (from aluminium production), and many more.