Metal reinforcement is a vital element of concrete used for foundations and other major structures including columns and beams. It provides tensile strength to what then becomes known as reinforced concrete. When used in columns, reinforcing steel can also increase compressive strength.
Of course, the reinforcement must be suitable for the structure involved and it is essential that there is a good bond between the concrete and the steel otherwise the stresses won’t be transferred from the concrete to the steel. Also, the concrete must be fully compacted and the reinforcing steel must be clean with no traces of loose rust, oil, or paint that would reduce the bond.
There are a number of different types of reinforcing steel products as well as spacers that ensure correct concrete cover, from the surface of the concrete to the nearest reinforcing steel bar.
Types of Reinforcing Steel
Standard reinforcing steel is available in the form of steel bars and steel fabric or reinforcing mesh including:
- Mild steel reinforcing steel bars that typically have a minimum tensile strength of 250 MPa. They are rounded and easy to cut and bend. Plain round bar is commonly used for stirrups, links, and ligatures that separate layers of mesh in concrete slabs or for dowel bars that join concrete sections in pavements, for instance.
- Deformed high-yield reinforcing steel bars that typically have a minimum tensile strength of 450 MPa. Manufactured by hot rolling or cold working, they are used when extra reinforcing is needed for trench mesh or steel fabric sheets.
- Steel reinforcing fabric that is made from hand-drawn steel wire that is welded to various patterns including square and rectangular grids. Produced in flat sheets, it is used mainly as reinforcement in slabs and precast concrete elements to provide tensile strength and to prevent cracking. It may also be used in walls to reduce labour costs in terms of handling and fixing, but the material cost will tend to be higher.
- Special coated reinforcing steel is used when concrete will be exposed to extreme conditions, for instance in a marine environment where it can become corroded very quickly.
Types of Spacers
Different types of spacers, including those made from plastic and concrete, are manufactured for use with different types of reinforcing. Some are known as chairs. For instance:
- Plastic-tipped wire chairs are intended for use in suspended and on-ground slabs, beams, and vertical walls. While made of wire, they have legs that are protected with a plastic film to prevent the spacer from sinking into the ground.
- Plastic continuous bar chairs are used for on-ground and suspended slabs to speed up the placement of reinforcing steel.
- Plastic deck chairs are used for on-ground and suspended slabs but may also be used to manufacture precast panels and beams, as well as tilt-up panels.
- Plastic slab-on-ground spacers are manufactured to support reinforcing steel bar and reinforcing mesh. They feature a flat base that minimises penetration of the waterproof membrane laid under the concrete.
- Plastic trench mesh supports that can be clipped onto the steel mesh before it is lowered into place are another option. These spacers may also be used for Z-cages in raft slabs and strip footings.
- Plastic Clip Fast spacers are light and may be used for numerous applications including precast beams and panels, in-situ beams and walls, and suspended decks.
- Fastwheels are suitable for light reinforcing whether in the form of mesh or bar. They are particularly useful for column construction and manufacture of precast concrete.
- Concrete block spacers range in height from 25 mm to 28 mm and are considered high-load spacers. They have a flat base to prevent tilting or rolling and are ideal for slab-on-ground applications.
Reinforcing Steel from BlueScope Distribution
BlueScope Distribution supplies a comprehensive range of reinforcing steel products including reinforcing mesh, reinforcing steel bar, and Lysaght Bondek®, a highly efficient, robust and versatile formwork and reinforcement system designed for concrete slabs. All the necessary reinforcement accessories are also available from BlueScope Distribution including the spacers and chairs needed to provide support for reinforcing steel bar and mesh.
- Reinforcing steel bar products comprise:
- Plain round bar used for ligatures and dowel bars.
- Deformed bar up to 500 MPa that provides extra reinforcing for trench mesh and fabric sheets.
- Starter bars used to tie concrete walls to footings and slabs in accordance with an engineer’s designs. These can be cut and then bent to shape from deformed bars.
- Corner bars used to tie right-angled elements of a structure together, including walls, beams, and slabs. These can also be cut and bent from standard deformed bars.
- Ligatures that are manufactured from grade R250N round reinforcing steel bars for ultimate strength.
- Swimming pool reinforcing steel bar that is specially formulated for this use.
- Reinforcing steel mesh products are made from grade D500L ribbed reinforcing steel wire and comprise:
- Trench mesh that is designed for residential footing trenches. Sheets are manufactured in 6-mlengths and a variety of widths using longitudinal wires up to 12 mm in diameter.
- Square mesh is a general purpose product intended for reinforcing flat concrete walls and floor slabs. The wires are welded together with equal spaces to create square apertures. Available in two sheet sizes, 6 m x 2.4 m and 2 m x 4 m, it is intended for reinforcing flat concrete floor slabs and walls.
- Rectangular mesh is also welded but the spacing in each direction is different so that rectangular rather than square apertures are formed. It is designed for use in slabs and walls where more strength is needed in one direction.
- Formwork products are versatile and are not only for robust formwork but also designed as a reinforcement and ceiling system where concrete slabs are constructed. The system comprises profile steel sheeting that offers increased speed and efficiency of construction. Benefits and features include:
- Exceptional spanning capabilities for maximized strength and minimized deflection.
- The ability to act as permanent formwork with little propping and zero stripping required.
- Fast, easy installation.
- A saving on both reinforcing steel and concrete costs because it operates as a composite slab.
- A fire resistant design.
The Lysaght Bondek® formwork products available from BlueScope Distribution are backed by a BlueScope Steel warranty and have nationwide technical support.
Whether you need reinforcing steel mesh, bar, or formwork products, BlueScope Distribution is the company to contact. All products are manufactured in accordance with AS 1302-1991, the national Australian standard for Steel reinforcing bars for concrete.