There are four main types of steel bars used in reinforced concrete (commonly known as ‘rebar’ for short). They have different properties, including slightly different appearance, load-bearing tensile strength and price, so it’s often a question of budget vs. expected load. Here’s our quick summary of the four types of steel bars and what they are commonly used for.
Hot Rolled Deformed Bars
‘Deformation’ is usually not a word you want to hear in construction, but it’s an important feature of hot rolled deformed steel bars. Steel bars are rolled while still hot, giving them a textured surface finish. The ribbed deformations along the length of the bars allows them to bond better with concrete, making them a popular choice for reinforcement and achieving a tensile strength of around 60,000 psi.
Cold Worked Steel Bars
Cold worked steel bars again have tensile strength of approx. 60,000 psi, but the manufacturing process is different. Instead of being rolled when they are hot, cold steel bars are worked at room temperature. They may be twisted or manipulated in some other way to give them a ribbed texture, which again improves their adhesion to the concrete around them. The benefit of cold working is that the finished steel bars can meet extremely tight tolerances, especially in terms of the straightness of the bar along its full length.
Mild Steel Plain Bars
Mild steel plain bars do not have the ribbed deformations to enhance bonding with the surrounding concrete. Instead, hooks are sometimes used on the ends to provide extra purchase. The smooth surface of these steel bars inevitably means lower strength when used in reinforced concrete – typically about 40,000 psi – but they are also cheaper, so if they are unlikely to encounter loads at or above that limit, they’re an economical option.
Prestressing Steel Bars
Prestressing steel bars consist of multiple threads of steel – sometimes two or three strands, but sometimes six spun in a helical spiral around a seventh thicker core strand. The cold-drawn wires together offer very high tensile strength of over 250,000 psi, and this is why prestressing steel bars are used to reinforce concrete that must carry the largest loads, for example in concrete building slabs and bridge decks. A solid concrete foundation is a prerequisite for the installation of a steel building frame, visit our blog post for a guide on how to build your own steel framed house.
