Common carbon steel reinforcements used in building construction works consists of deformed steel bars and welded steel mesh fabrics. These reinforcements usually come in the classes of;
i. Plain round hot-rolled mild-steel bars (BS4449/BS EN 10080) with minimum characteristics strength of 250 N/mm2 and its use being phased out in the new harmonized Eurocode.
ii. Deformed mild-steel bars (BS 4449/ BS EN 10080) with higher strength than round mild bars.
iii. Hot-rolled deformed (high-bond) high-yield-stress bars (BS4449/ BS EN 10080) with characteristics strength of 460 N/mm2 for bars up to 16 mm inclusive and 425 N/mm2 for bars more than 16 mm size.
iv. Cold-worked bars (BS4461) that are usually mild-steel bars of which the yield point has been eliminated by cold working, and
v. Fabric reinforcement (BS4483) which the reinforcement is generally steel wire mesh, the wire complying with BS4482 (this usually comes in four types: Type A is a square mesh with identical long bars and cross bars, commonly used in ground slabs. Type B is a rectangular (structural) mesh that is particularly suitable for use in thin one-way spanning slabs. Type C is a rectangular (long) mesh that can be used in pavements, and in two-way spanning slabs by providing separate sheets in each direction. Type D is a rectangular (wrapping) mesh that is used in the concrete encasement of structural steel sections. The stock size of standard fabric sheets is 4.8 m x 2.4 m, and merchant size sheets are also available in a 3.6 m x 2.0 m size).
These bars rely on adequate concrete cover protection to enable good alkaline environment and prevent the reinforcements from rusting/corrosion. In special situations, especially in exposed surfaces that have greatest chances of chloride attacks, that can lead to rusting/corrosion, galvanised, epoxy-coated or stainless steel which are products of alloying of steel using elements like chromium, nickel, manganese, molybdenum and titanium can be used. Such faces where this type of steel can be applicable are: splash zones usually of marine structures, abutments, parapet edges and soffits.
Pros of stainless-steel reinforcement
- Significant reduction in the whole life cycle cost of the structure.
Cons of stainless-steel reinforcement
- High initial cost of construction as much as 650% of cost of normal reinforcement.
Types/ranges of stainless-steel reinforcement
Austenitic stainless steels (BS 6744): chromium and nickel are the main alloying elements. They are corrosion resistance and suitable for most applications.
Duplex stainless steels: these have high chromium and low nickel contents, provide greater corrosion resistance for the most demanding environments.
Note: stainless steel can be supplied in lengths up to 6m for all sizes, and up to 8m for larger bar sizes.
