What would our world be like without concrete? Looking around we discover that houses, offices, schools, roads, bridges, dams and other structures are built with this material. And to think that concrete is made of the most ordinary materials such as sand, gravel, water and cement.
In concrete, cement and water mix to form a paste. This paste acts as a binder for the sand or gravel, and when it hardens, it forms a solid mass.
The concrete must be poured while it is still fresh. Trucks used to deliver concrete have huge drums with concrete inside. The drum spins continuously while pouring concrete to prevent concrete from hardening inside the drum. When fresh, the concrete can be poured into a mold in the desired shape. And when it hardens, it has great resistance against water, fire or weather.
Reinforced concrete has a steel bar skeleton. When concrete hardens, steel gives it extra strength. Most large concrete structures are made of reinforced concrete.
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