No matter if you are putting together a simple concrete pad for your backyard, or a major structural concrete development for a residential or commercial project, there are various products to choose from for general concrete reinforcement. Rebar and other concrete reinforcement products are essential to adding varying levels of structural support to concrete elements, more than just what concrete provides on its own.
There is more than just standard rebar, with corrosion resistant products, lightweight products, and fibre-products, these are just some of the options engineers have to choose from.
General Introduction
Rebar(steel reinforcement for concrete) is provided a numbering system that corresponds with the size of the steel rebar. The higher the number, generally speaking, the larger the rebar and more serious structural capacity it can provide up to a certain point. With larger sized rebar, considerations for adequate concrete cover from the rebar have to be addressed, so the size of concrete members are also expected to increase or, be large, if large rebar is used.
Steel rebar sizes vary from #3 to #18. This is the imperial system, and metric systems follow a similar precedent, with smaller rebar (10m size) being smaller in size than a rebar (20m size). Each sizing is nominal corresponding to an actual measurable diameter.
Different grades of rebar are provided from 40 to 100 and represent general strength of rebar. The higher the number, the higher the strength.
Some types of rebar are provided to prevent corrosion and cracking/deterioration of concrete.
Rebar that is exposed through migration of water or being exposed to elements in concrete can expand and rust, causing cracking and disrupting structural stability of concrete elements. So some types of rebar exist to prevent premature structural failures of concrete / steel-reinforced members like beams, columns, concrete slabs etc.
Concrete coring can be a way to inspect rebar quality in-situ for completed projects. Discoloration of rebar and reinforcement can be seen in cores from slabs or beams for example where warranted for inspection by and engineer.
The use of rebar for size and type, in addition to design characteristics(cage-rebar, U-bar, Z-bar etc.) is really dependent on the design considerations of structural engineers. However rebar detailing and reinforcement supply companies may also have insight for larger projects.
Standard Rebar
Standard rebar is also known as carbon steel rebar or black rebar.
If you have a simple concrete project, where exposure to moisture and serious structural implications are not a concern, standard rebar is the go to. It is most affordable out of reinforcement members, with exception, to some wire products. In climates where corrosion is of concern other rebar products with corrosion resistant can be used. Proper concrete cover is essential to preventing corrosion of standard rebar.
Photo Above: Concrete footing/pile-cap/beam-on-grade used with rebar projection. Standard rebar (carbon steel / black rebar) tied around vertical rebars. Appearing as 15m or 20m rebar.
Galvanized Rebar
Hot dip galvanized(HDG) rebar productions provider superior corrosion resistance than standard black rebar / carbon steel rebar products. The additional process of adding a galvanized coating protects the rebar from corrosion. Coating through HDG(hot-dip-galvanized) gives a zinc coating to rebar, bonding to the steel. The additional process involved in supplying the rebar means additional costs for any project, so, realistically, this product should only be used where absolutely required.
Zinc coated on the steel actually corrodes first prior to the steel itself. The coating of the zinc is also protective.
As galvanized rebar is a coating process, then any cuts and welds may require touch-up.
Galvanized rebar comes in a dull metallic appearance, as opposed to standard rebar, in black or dark-grey grey non-metallic.
Photo Above: Pool structure concrete can be another typical use case of a galvanized or other corrosion-resistant rebar.
Stainless Steel Rebar
Stainless steel rebar as the name implies is steel reinforcement made from stainless steel alloy which provides a similar intent of epoxy products or galvanized products, being, corrosion resistance. Stainless rebar grade options depend on alloy options such as 316LN for instance. An interesting benefit of stainless steel rebar is the lack of magnetic property, for some specific types of stainless steel rebar. That could be important for electrical devices.
A stainless steel rebar product could be used for, like galvanized rebar, structural elements that need to be constructed for resistance to corrosion.
As stainless steel rebar is the actual composition of the metal itself, being different than black carbon steel, it is not coated.
Epoxy Coated Rebar
The epoxy coated rebar product(s) are black rebar products that receive a secondary coating for additional corrosion resistance.
In the way that epoxy coated rebar gets a coating, it is like galvanized rebar, but, the coating is not bonded as strongly as the galvanizing process allows for. So while epoxy coated rebar can provide great protection against corrosion, there are disadvantages with the coating because it can be damaged easily. Care with install and transport of epoxy coated rebar is essential.
Epoxy coated rebar has different variants where, green/purple can identify varying levels of protection.
Ends and cuts of epoxy rebar would need be treated too.
Glass Fiber Reinforced Bars
Glass fiber reinforced rebar are products made of fiber composites and are a replacement material for steel rebar products. Due to having no metal product inherent in the design of the product, they are naturally resistant to corrosion. Fiberglass rebars are lighter than steel, which makes for easier hand installation and transportation.
Glass fibre reinforced bars cannot be bent on site like steel bars so installation from detailing to final placement/tying and ordering/shop-drawings is critical.
Sources note this product to have increased strength over typical steel products.
Welded Wire Mesh
Welded wire mesh is a product that is formulated of steel wires, welded to create a square mesh that can be inserted into structural items like housekeeping pads, concrete sidewalks, and other non-critical structural components. However, welded-wire mesh or grating can also be used in more structurally demanding concrete elements too, it just depends on the design.
Fibre Reinforcement
Steel fibres are used as an alternative to typical rebars to provide strength and stability to concrete items like concrete slabs. Steel fibres are added into the mix designs to provide additional strength, but, in lieu of rebar, so there is no placement of concrete rebar as is typical. Various sizes of fibres are available for selection and utilization within the concrete.
Non-steel fibre reinforcements can also be utilized for concrete reinforcement too.
Macro fibers or micro fibers (synthetic products) are introduced into concrete elements for structural reinforcement properties. Again, placement of rebar is not necessary unless specifically called for within the design.
Concrete Reinforcement Designs – Residential
There are various types of rebar that can be utilized in concrete reinforcement designs: U-bar, rebar cage, Z-bar, L-bar, etc. These are just some of the typical names, however, each manufacturer provides their own shape codes applicable for project requirements.
Rebar shapes fulfill various roles dictated by structural engineers.
Rebar comes in various sizes, shapes, and options, for utilization in a multitude of structures and concrete elements. Typically for residential construction projects in Calgary, AB, Canada, with concrete grade beams, concrete pile caps, concrete ramps, concrete walls and more, carbon steel rebar (black rebar) is used as the product. It is the most affordable and generally commonly specified.
However, for instance in and around pool areas, specialized rebar products resistant against corrosion may be warranted to be used.
Photo Above: Steel cage for concrete column with ‘ties’ spaced in intervals to encapsulate column vertical rebar. Nomenclature for reinforcement may vary from commercial to residential projects.
Conclusion
If you have requirements for corrosion resistance, because you are in an area with exposure to humid conditions or salts, consider a corrosion resistant product such as galvanized rebar, stainless steel rebar, or epoxy coated rebar may be warranted.
No matter the type of reinforcement you are using on your project, you need to have an inspection completed either by the lead hand, or a structural engineer. Omission of rebar or miss-alignment of structural reinforcement can have implications on structural stability. Always double check your project specifications or drawings to make sure the rebar you are using is correct, whether that be epoxy coated rebar, stainless steel rebar, galvanized rebar, etc
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