Brief Note on Precast Concrete
Precast concrete is employed to define individual concrete members of varied shapes which are designed during a way that might slot in parts of the entire structure. Before placing them within the desired position of the structure they're constructed in separate forms. Whereas, the word cast-in-situ concrete is employed to define concrete members, cast or poured, in formwork found out at the ultimate position of the structure.
The new technique called prefabrication construction of which precast concrete may be a part.
Advantages of precast concrete over cast-in-situ concrete:
- Just in case of casting identical members, it's advantageous for an equivalent framework to be used.
- Superior quality of concrete are often produced as better-quality control check are often practiced within the factory or yard site.
- With this process smoother exposed surfaces are often produced hich could not require plastering.
- With adequate protection within the casting yard precasting work are often administered under all weather .
- it's not difficult to form precast unit consistent with the specified shape.
- If necessary, they will be dismantled with none breakage.
- The curing process are often completely more effectively and economically.
- Under all weather constructions are often erected.
- Construction of a building are often done at an excellent speed.
Precast Concrete: Disadvantages
For handling, transportation and erection special sorts of equipment are required. Especially for beams, slabs, columns, etc.
Due to the need of skilled labor the value of construction may increase. During loading, transporting, and erection there's an opportunity of injury .
It is difficult to mix different units and to form them functional especially if differing types of units are involved.
Modification within the future to the building constructed using precast units is difficult.
Precast Elements: Dimensions
Given below are the preferred dimensions for different elements of a building:
Flooring and roofing scheme- Precast slabs along with other precast structural flooring unit:
Length: the normal length must be in multiples of 3M.
Width: the normal width must be in multiples of 1M.
Total thickness: The overall thickness must be in multiples of M/4.
Beams: (1) Length: The normal length must be in multiples of 3M. (2) Width: The normal length must be in multiples of M/4.
Total depth: The overall depth of the floor zone must be in multiples of M/4.
Columns: (1) The overall depth (which is floor-to-floor or the clear height) must be in multiples of 1M for height which is up to 2.8M, for height above 2.8M it must be in multiples of 2M. (2) Lateral dimension: The average lateral dimension or diameter of columns must be in multiples of M/4.
Walls: The thickness of wall on an average must be multiples of M/4.
Staircase: The normal width of stairs should be in multiples of 1M.
Lintels: (1) length: The minimum length should be in multiples of 1M. (2) The minimum width should be in multiples of M/4. (3) The minimum depth should be in multiples of M/4.
Sunshades Projection: (1) The minimum length must be in multiples of 1M.
