Q. How does the tensile strength of composite rebar compare to steel?

A. Tensile strength varies from manufacturer to manufacturer. mateenbar^TM is one of the highest strength composite rebars available, with a tensile strength of over 1000 MPa it is almost at the theoretical limit for an E-glass or ECR-glass reinforced composite rebar. This is over twice the tensile strength of steel rebar, which is typically 400 to 500 MPa.

Q. How does the modulus compare to steel rebar?

A. The modulus is lower than steel. Steel is typically 200 GPa, whereas mateenbar^TM is between 50 and 55 GPa, which is close to the theoretical limit for glass-reinforced composite rebar.

Q. How can the lower modulus be allowed for in the design?

A. The good news is that the lower modulus can be overcome. Because mateenbar^TM is so corrosion resistant, it does not require large coverages to provide protection, so can be placed much closer to the surface. The increased distance from the neutral axis increases the sectional modulus. Also, due to the non-corrosive nature of mateenbar^TM the crack-width allowance as defined by ACI is increased from 0.3mm to 0.7mm

Q. Can a higher modulus composite rebar be manufactured?

A. mateenbar^TM is at the theoretical limit for E-glass or ECR-glass reinforced rebar. Other reinforcements can be used, such as Carbon fibre, Aramid fibre or S-glass, but all these reinforcement options are very expensive, so these options are generally not practical due to the significant cost increase.

Q. Does composite rebar have ductile failure?

A. Composite rebar itself is elastic to the point of failure. But, with correct design, the structure can still exhibit the desirable ductile failure mechanism. This is achieved by a balanced reinforcement design. The higher tensile strength of the reinforcement then forces a mechanism of progressive bond-failure, which results in a ductile failure mode of the structure. This is outlined in the American Concrete Institute ACI 440 documents.

Q. Is mateenbar^TM affected by alkaline conditions?

A. Alkaline attack has been highlighted as a problem for composite rebar. E-glass reinforcement is prone to alkaline attack. However, mateenbar^TM is manufactured from ECR-glass, which is immune to alkaline attack.

Q. Can mateenbar^TM be bent on-site?

A. mateenbar^TM bends must be manufactured to shape. These are usually available ex-stock, but special shapes will need to be made to order for you.

Q. Are bends as strong as straights?

A. Rebar bends are not as strong as straights. It should be noted that this is also true of steel rebars. We recommend that wherever possible straights should be used, for example, if it is possible that a slight re-design will increase the quantity of straights and reduce the quantity of bends, this should be given serious consideration. The result is likely to be a cheaper and better outcome.

Q. Is FRP rebar cost competitive against steel?

A. Where corrosion is not an issue, then steel reinforcement is usually a cheaper option. However, when extra protection is required to reduce the corrosion rate within the rebar, mateenbar^TM is likely to be a more cost effective option. Savings can be made in one or more of the following ways:
• Reduced coverage. Extra thickness is not required to protect the rebar.
• No requirement for expensive concrete waterproofing additives.
• No allowances needed for diameter reduction caused by corrosion.
• mateenbar^TM is much cheaper than Stainless Steel, and has better longevity.
• Cathodic protection is not required with mateenbar^TM.
• Reduced maintenance costs.
• Longer life-span significantly reduces the life-cycle costs.

Q. Are there any special handling requirements for composite rebars ?

A. On-site handling of composite rebars is very similar to that of steel. Most reinforcement materials are by their very nature robust, but should all be treated with some degree of care. In this respect mateenbar^TM is no different to any other reinforcement.

Q. Does on-site damage need to be repaired?

A. With any rebar, including steel, significant damage must be addressed. However, minor damage will not affect the performance of mateenbar^TM. For example, mateenbar^TM is manufactured from corrosion resistant material, and does not rely on a coating to protect the rebar from the elements, so minor scratching of the surface will not have a significant effect, and will not cause accelerated corrosion.
Q. Do I need to design specifically for composite rebar?

A. You should design around the properties of mateenbar^TM. The American Concrete Institute ACI 440 committee is an excellent source of information, and designers should familiarise themselves with ACI 440.1R-06 or similar guides. Pultron has a support service, and can assist with or review designs, and are happy to work with design engineers to assist them in the transition from steel to mateenbar^TM

Q. When should I use mateenbar^TM?

A. Whenever you have to make considerations for corrosion protection of rebar, you should consider the use of mateenbar^TM instead. Additional corrosion protection may be in the form of coated rebar such as galvanised or epoxy coated, or it could be the use of special steels such as stainless. The use of cathodic protection or extra allowances on concrete coverage, or special additives to ensure the concrete is waterproof. All of these are indications that mild steel is not suitable, and any protection method is not actually solving the problem, but simply delaying the inevitable - which is rusty reinforcement. In these cases the use of mateenbar^TM should be considered for the performance / cost benefit it will offer.