ABSTRACT
Concrete in its simplest form is usually a mixture of cement powder, water, sand and gravel. A range of cement powders exist on the market which impart different characteristics to the material. The water is necessary as when cement comes into contact with water a chemical reaction commences which ultimately results in the paste hardening. The sand and gravel, sometimes termed fine and coarse aggregate, form a matrix of strong particles of differing sizes which when glued together by the cement paste form an extremely strong and durable engineering material. Modern concretes often include admixtures. The workability of concrete can be thought of as the ease with which concrete can be mixed, placed, compacted and finished. It must be durable and survive for the design life of a structure. Corrosion of steel reinforcement is likely to occur when loss of passivity takes place, which is usually due to either carbonation or chloride ingress.
