The costs of manufacture of some types of formwork can be very high, but as with steel, they are capable of very long life spans. It is said that timber formwork may have re-use on a site of not more than 10 times, but this would depend upon workmanship, supervision etc. The opportunity to create complex shapes however still exists and many designers have taken advantage of this with irregular plan shapes and floors which cantilever beyond the perimeter columns. Concrete Comprises, cement, coarse aggregate, fine aggregate, and water. Admixtures can often be used to enhance characteristics, accelerators, retarders, sulphate resisting, anti-freeze, plasticisers etc.
Bars can be plain round, deformed round, square, rectangular, ribbed etc.
Bars vary from 6 mm to 40 mm, usually 12 metres maximum length and to BS 4449. Fabric reinforcement or mesh is usually manufactured from smaller size bars welded together to form a grid. The fabrics which are available are manufactured from different diameter bars, different configurations, and different weights per square metre, capable of performing different functions. The sizes of fabric reinforcement vary, but a standard sheet is approximately 4800 mm x 2400 mm. Fabric reinforcement is usually used in slabs, but can be used in beams and columns as a wrap-around measure to make a reinforced cage.