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Glass fiber-reinforced polymer

 Glass fiber-reinforced polymer (GFRP) reinforcement has emerged as a new opponent to conventional reinforcement. The GFRP owns a higher tensile strength, non-corrosive reinforcement, lighter weight, and higher strength-weight ratio. The corrosion of reinforcement can severely damage the structure by causing the concrete to cracks or spall. The Maintainance of damaged structures can significantly be costly. The GFRP is a non-corrosive reinforcement. Therefore, the use of GFRP can eliminate the deterioration of structure due to reinforcement corrosion. The use of GFRP has increased recently for many applications such as bridge deck, pavement, walls, and other applications. However, the use of GFRP is limited due to the lack of information about the long-term performance of GFRP.

Figure 1

GRFP bars have many advantages, such as tensile strength. The tensile strength of GRFP bars is higher than the conventional reinforcement. Table no:1 shows the mechanical properties of GRFP bars. We can notice that the tensile strength ranges from 896 to 413 MPa. the high tensile strength will reduce the area of reinforcement for a specific cross-section, resulting in cost saving.
Figure 2

Corrosion of reinforcement has always been a primary cause of concrete structure deterioration. Concrete structures located in harsh environments such as coastal areas or inside the water are vulnerable to reinforcement corrosion. The use of GFRP bars can be a good solution to this problem. Using GFRP reinforcement for structures in a harsh environment can be economical in the long term. Also, it will spare the client the headache of structure maintenance or rehabilitation. Slowing the corrosion of conventional reinforcement in concrete structures is done by implementing various measures. Increasing the concrete cover is one of these measures. The concrete cover will delay the effects of concrete carbonation, which can cause reinforcement corrosion. Also, the use of concrete with low permeability proves to be a good solution to avoid the ingress of chloride and other harmful chemicals. Other measures can be the use of waterproofing to prevent the ingress of harmful chemicals or the use of epoxy-coated reinforcement. These measures can significantly slow the corrosion of reinforcement for structure in a harsh environment. 

The handling of GFRP reinforcement is similar to epoxy-coated reinforcement. However, the GFRP weight is one-fourth of the conventional reinforcement, which makes it easier to handle the GFRP reinforcement.however, the bending of GFRP reinforcement is not possible at the site, and it should be done at the factory. The inability to bend the GFRP reinforcement at the site can result in inconvenience and delay in completing the work. 

Figure 2

A research project was done by Trejo to test the long term properties of GRFP reinforcement. 3 specimens were tested to evaluate the long term performance of GRFP. Three GRFP specimens were fabricated in 2000 and tested in 2007 to assess the tensile capacity and the modulus of elasticity (MOE) of GRFP bars. The researchers conclude that the mean stress capacity undergoes rapid decay in the first few years and gradually slows over time. Moreover, they found that the decay is more for smaller bars. The probability of bar #3 (9.5mm dia) not meeting the ACI 440 requirements is 0.44. The probability of bar #5 (15.80mm dia) not meeting the ACI 440 requirements is 0.25. We can conclude that the tensile strength of GFRP reinforcement is decaying over time, and we still lack sufficient data regarding the long-term performance of GFRP.



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