ABSTRACT
Concrete is a human-made substance, with a key ingredient being Portland hydraulic cement. Cement itself is created through a chemical reaction induced between clay and limestone. The calcium oxide mixture is mixed, dried and then fired in large kilns until it breaks down into a fine dry powder. Concrete was used long ago by the Romans and indeed the dome of the mighty Pantheon in Rome is all Roman-era concrete, still in excellent condition and the world record holder for largest unreinforced concrete dome in the world. Concrete is good in compression, as hard to crack as stone. Concrete is not good in tension, so we add rods of reinforcing steel to it–the two materials work well together. The steel performs excellently in tension and is woven in a matrix that a bond together with the concrete as it sets. There are various ways of applying concrete to a surface of course, with one particular method known as ‘shotcrete’.
