Reinforced Concrete Mixture
Reinforced concrete is a material of civil construction that became one of the most important elements of the civil engineering and architecture of the 20th century. It is used in the structures of the buildings, and it is differentiated from normal concrete because it receives a metallic frame for resisting tractive efforts, whereas the concrete itself resists compression.
It is composed of a compact mixture of:
- medium aggregates: broken rocks, rolled pebbles, etc
- small aggregates: sand, pebbles
- binders: cement and/or whitewash
- additives: dye, accelerators, staple fibres, etc.
For attainment of a good concrete in accordance with its purpose, the basic production operations of the material must be executed with perfection, which influences greatly the properties of the concrete.
The basic operations of the production of the concrete are:
- Dosage: Study, indication of the ratios and quantification of the component materials of the mixture, similar to get a concrete with definitive characteristics previously established
- Mixture: To give homogeneity to the concrete, with the objective of which is to make it so that it presents the same composition in any point of its mass
- Transport: To take the concrete of the point where it was prepared to the place where will be applied, being able to be inside of the workmanship or for it, when mixed in plant or is of it
- Casting: of the mass in the armed steel beams
- Launching: Rake of the concrete in the application place, in general, in the forms (wood or metal formworks). It starts to harden after four hours of the addition of the water
- Dense: Compacting of the concrete mass, looking to remove the maximum volume of emptiness (number of voids) possible (increasing the resistance). In USA it is usual to vibrate the mass with mechanical vibrators, preventing the emptiness excess
- Cure: Set of measures with the objective to prevent the loss of water (evaporation) for the concrete in the first days of age, water that is necessary for reaction with the cement (hydration). Wet blankets of felt with water are used in this operation. In very cold climates the mixture is heated with vapor. Normally the project resistance is reached 28 days after the application.
Reinforced concrete is a useful and complex material that requires lots of attention and time to use it properly, but it is indispensable in modern civil construction.