Reinforcing steel for concrete
Reinforcing steel for concrete
Reinforcing mesh with single and double bars
Concrete has a very high compressive strength, i.e., that it can be subjected to high loads. However, it can only absorb tensile stresses to a very small extent. Concrete cracks, if these stresses exceed its tensile strength. Tensile stresses always occur in the concrete girder or in the concrete floor, therefore, steel is placed in these types of loaded construction elements, which accepts these stresses. The location of the reinforcement, its arrangement and the required steel diameters are determined on the basis of strength calculations, which are part of the technical documentation constituting the basis for obtaining a building permit. It cannot be estimated, and in the light of building regulations, it is not allowed. Inserting reinforcing steel into concrete without calculation is only allowed for secondary building elements, as long as no requirements are made for strength. An example of this could be a grill (barbecue) garden, in the foundation of which the reinforcement is placed, to prevent it from breaking under the weight of the grill. Reinforcing steel is not protected against rust, which is redundant anyway, because covering it with concrete effectively protects against it.
Reinforcing steel is delivered in 3 characters. These are:
• Reinforcing bars for concrete with a diameter 6-32 mm and length 12-15 m. These bars may have a ribbed surface to bond firmly to the concrete.
• Reinforcement meshes, in which rods with a diameter 4-12 mm are welded crosswise. The spacing between the bars is 100, 150 or 250 mm. There are single and double bars, composed of two tightly adjoining rods of the same diameter.
• Reinforcing wire with a diameter 4-12 mm. Wire with a smooth or profiled surface is available on the market, sold in circles. Ribbed reinforcing bars are supplied in several strength classes. Steel grade A-II has a characteristic tensile strength 355 MPa; steel grade A-III has a characteristic tensile strength 410 MPa. Characteristic tensile strength of the order 410 MPA stands for, that the steel wire of the cross section 1 mm2, before it breaks, may be loaded with force 410 N.
N (Newton) is a unit of force and mass.
10 N replies 1 kg, 410 So N replies 41 kg.
