Concrete

Today concrete is the most widely used engineering material. It comes in many different types but the basic composition is the same eg portland cement, sand, stone or other aggregates and water. The surface is very highly alkaline when wet. A common problem often experienced with reinforced concrete is corrosion of the reinforcement. Concrete can be broken down in two ways:

• By chlorides. These may be present in the concrete or penetrate the concrete from the outside.
• By carbonation. A process which reduces the alkalinity of the concrete to below pH 1O, the level which can sustain the passive film.

Fibrous concrete is very similar to normal concrete but has fibrous aggregate such as asbestos or sawdust instead of sand for lightness.

Glass reinforced concrete is a factory made precast concrete reinforced with alkali-resistant glass fibre. The normal use for this type of concrete is in cladding panels, sewer pipes, cable ducts, etc.