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Glass Fiber Reinforced Polymer (GFRP)
CONCRETE IN
CONCRETE IN
Electromagnetic Applications
Masonry Strengthening
Physical Properties - Aslan 100, 101 GFRP Rebar
Cross Sectional AreaThe cross sectional area of the rebar may be determined by immersing a sample in water and measuring the volume displacement of the piece. When calculating the cross sectional area, the cross section is assumed to be a circle. Per ASTM D7205.Nominal DiameterThe nominal diameter of the rebar is the average diameter and assumes the shape of the rebar is a circle. Nominal diameter should be used for design.Tensile StressTensile stress values shown are determined as the average failure load divided by the cross sectional area based on nominal bar diameter, less three standard deviations. Tensile stress varies as diameter increases due to shear lag which develops between the fibers in the larger sizes. For AC1440.1R-06 design, this value is the guaranteed tensile strength, ffu*.  Certification of Measured Mechanical PropertiesTest reports from an independent lab are available on request for each production lot. Reports show the tensile strength of the sample population, average tensile modulus and the calculated ultimate strain for each tensile test based on the average modulus. Per ASTM D7205.II. Modulus of ElasticityThe variation in the Modulus of Elasticity of different diameter bars is much smaller than that of the tensile stress.Modulus of Elasticity ....... 40.81 G PA (5.92 X 106 psi) Published values are an average modulus from a population of samples.  III. Bond Stress to ConcreteThe bond stress to concrete shown is based on pull out tests performed using test methods proposed in ACI 440.3R-04 Method B.3. This method is used as it is easily repeatable and gives an indication of relative performance.Forms constructed out of plywood are used to cast a concrete block around one meter long rods as shown below.
In order to control the embedment length within the block, the rods are prepared with a bond breaker which consists of soft plastic tubing placed around the rods to prevent contact between the rod and concrete. The embedment length is 5 bar diameters. The concrete used is a high early strength portland cement, fine aggregate (all purpose sand) and water (49.89 kg cement, 45.36 sand and, 12.5 l water). The 14 day compressive strength of cylinders is typically 45MPa. Previous research has shown that bond strength does not vary significantly with varying concrete strength, provided the concrete block is properly sized to prevent splitting. Loads are measured by the electronic load cell of a test frame and the slip between the rod & concrete is measured by six DC voltage LVDT's, three at each end. While the free end LVDT's measure direct indication of free end slip, the loaded end measurements need to be adjusted for elongation of the rod between the actual loaded end of the embedment length and the attachment point of the LVDT's.
Bond of GFRP to concrete is controlled by the following internal mechanisms: chemical bond, friction due to surface roughness of the GFRP rods, mechanical interlock of the GFRP rod against the concrete, hydrostatic pressure against 
IV. Coefficient of Thermal Expansion:
Transverse Direction
18.7 x 10-6/°F
33.7 x 10-6/°C
Longitudinal Direction
3.66 x 10-6/°F
6.58 x 10-6/°C V. Barcol Hardness:50 min. per ASTM D2583VI. Glass Fiber Content by Weight:70% minimum per ASTM D2584VII. Specific Gravity:2.0 per ASTM D792VIII. Shear Stress:Shear stress ACI 440.3R-04 Method B.3; 22,000 psi (152 MPa)
Durability
Potential durability versus traditional steel reinforcement is one of the chief benefits of GFRP Rebar. However, being a relatively new material for use as a concrete reinforcement, decades of performance data are not available. Therefore, durability or longevity is one of the key issues concerning GFRP reinforcement. In environments that would degrade steel reinforcement, there is little concern that these same agents (low pH solutions) will degrade the quality of GFRP rebar. High pH or alkaline solutions will, however, degrade glass fibers. Research has focused on encapsulating the glass fibers in a resin matrix that protects them from potential alkaline degradation. Aslan 100 is produced using a vinylester resin matrix. Typical portland concrete pour water is very alkaline with a pH of approximately 13. It is presumed that any water that hydrates through the concrete also creates a high pH solution that could potentially degrade the rebar. Most durability studies have focused on subjecting GFRP Rebars to alkaline solutions of 13pH at elevated temperatures to simulate service lives on the order of 50 years. Fortunately, research from the ISIS network in Canada which involved extracting GFRP bars from several bridges and structures across Canada that have been in service from between 5 and 8 years reveals NO DEGRADATION of the GFRP bars. (Durability of GFRP Reinforced Concrete from Field Demonstration Structures ? M. Onofrei University of Manitoba May 2005). This performance matches that of GFRP dowel bars that had been extracted from service in Ohio after 20 years. If used in polymer concrete, a plastic matrix, or as temporary reinforcing in portland concrete, a separate GFRP rebar formulation, Aslan 101, is available. 
Creep
When subjected to a constant load, all structural materials, including steel, may fail suddenly after a period of time, a phenomenon known as creep rupture. Creep tests conducted in Germany by Bundelmann & Rostasy in 1993, indicate that if sustained stresses are limited to less than 60% of short term strength, creep rupture does not occur in GFRP rods. For this reason, GFRP rebars are not suitable for use as prestressing tendons. In addition, other environmental factors such as moisture can affect creep rupture performance. Based on ACI 440 design guidelines, sustained stress may not exceed 20% of minimum ultimate tensile stress. For a summary of the recommended design guidelines, refer to AC440.1R-06 or your controlling national guide. Stirrups, Shapes and BendsBends in Hughes Brothers GFRP Rebar are fabricated by shaping over a set of molds or mandrels prior to thermoset of the resin matrix. Field bends are not allowed.
Research has shown that bends typically maintain 38% of ultimate tensile strength through the radius. (Eshani, Rizkalla)
It is recommended that you work with the factory in the early stages of design, as not all standard bends and shapes are readily available. For example, a J-Hook at the end of a 10 meter length of rebar would be achieved by lap splicing a J-hook piece to the 10 meter rebar.
Due to the low E Modulus of GFRP bars, it is possible to field bend large radius shapes. Care must be taken to avoid bending stresses that exceed the ACI440 recommendation of 20% of ultimate sustained stress in the bar. For this reason, the minimum allowable radius for field curved GFRP bars is shown.  
Design Considerations
 One difference is that all FRP?s are linear elastic up to failure and exhibit no ductility or yielding. In traditional steel reinforced concrete design, a maximum amount of steel is specified so that the steel will yield and give warning of pending failure of the concrete member. ACI440.1R-06 gives the option of two failure modes to the designer, an over reinforced section where compression failure of the concrete is the preferred mode of failure. Or, failure by rupture of the FRP reinforcing in which case serviceability requirements, deflection and crack widths, must be satisfied in order to give a warning of pending failure. In either case, the suggested margin of safety against failure is higher than that used in traditional steel-reinforced concrete design. Another major difference is that serviceability will be more of a design limitation in GFRP reinforced members than with steel. Due to it's lower modulus of elasticity, deflection and crack widths will affect the design. Outside of North America, the ASCE Journal of Composites has published design guidelines for GFRP Reinforced Concrete for Construction (Aug 1997 Vol.1 No 3 ISSN 1090-0268 Code: JCCOF2) based on the extensive work performed in Japan for the Japanese Ministry of Construction. Additional design guidelines have been published by the Canadian Highway Bridge Design Code; Section 16 "Fibre Reinforced Structures" and "Commentary for Section 16" and the Canadian CSA S806 Code for Buildings. Modifications to Norwegian Standard NS3473 when using fiber reinforced plastic (FRP) reinforcement, April 29, 1998. From the United Kingdom, the Institution of Structural Engineers, "Interim Guidance on the Design of Reinforced Concrete Structures Using Fibre Composite Reinforcement", August 1999. Active efforts are also underway for a European Eurocode 2 under the efforts of FIB Task Group 9.3 "FRP (Fibre Reinforced Polymer) Reinforcement for Concrete Structures. Links to many of these activities can be found via the Hughes Brothers web site.  Hughes Brothers only guarantees the performance of its material to meet minimum ultimate requirements as listed. The use of competent experienced engineering personnel should always be employed in the design and construction of concrete reinforced structures. Subjects covered in the ACI440.1R-06 design guide include:
Current knowledge restricts the use of FRP bars for:
Lap Splice - Tension
Design AssistanceTo aid the designer unfamiliar with the new ACI440.1R- 06 guide, Hughes Brothers engineering staff are available to assist you.  Masonry Strengthening Aslan 100 GFRP bars can be used to increase the strength of existing unreinforced masonry walls in flexure (out-of-plane) and shear (in-plane). This has important implications in areas that are subject to new seismic codes, hurricane wind loading or even blast mitigation schemes. In addition, Aslan 100 GFRP bars can be used to restore or increase the structural strength of existing masonry walls that have already cracked. In many instances the strengthening procedure can maintain the visual appearance of the existing masonry, particularly in the case of shear reinforcing.
the technique used is known as "Near Surface Mount" or NSM strengthening. The procedure consists of:
  If hollow Concrete Masonry Units (CMU) are being strengthened, the groove depth should not exceed the thickness of the masonry unit shell to avoid local fracture of the masonry. It is also recommended to mask off the groove to avoid staining the surrounding masonry during the application of epoxy or cementitious pastes.
Handling and Placement
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