International Concrete Abstracts Portal

This paper presents an experimental investigation into the bond behavior between basalt FRP (BFRP) sheet and concrete substrate under coupled effects of freeze-thaw cycling and sustained load. Specially designed double-lap shear specimens were exposed to up to 200 freeze-thaw cycles with sustained load. After exposure, the specimens were tested to failure. Digital Image Correlation (DIC) test method was applied to capture the full-field strain in the study. Nonlinear constitutive law of FRP-concrete interface was determined based on full-field deformation and strain analysis. Test results show that freeze-thaw cycling leads to significant decreases in load carrying capacity, ultimate slip, shear strength and increases in effective stress transfer length of FRP-concrete interface. Additional damage is generated when the load condition is taken into account during freeze-thaw cycling test. Moreover, apparent changes in failure mode were found with the increasing number of freeze-thaw cycles.

In current International Codes for FRP Reinforced Concrete, an environmental reduction factor is applied to the tensile strength of GFRP bar to account for its long-term durability. In this paper, the approaches for the durability design of GFRP bars are discussed and corresponding limitations are addressed, followed by presentation of a newly developed design approach, which incorporates the effects of relative humidity, exposure temperature, and design life. By using time extrapolation and time-temperature shift approaches, a new equation for design strength of GFRP bar under various exposure time and temperature was proposed. The effect of moisture, in the form of relative humidity, was incorporated into the new equation by investigating the relationship between the relative humidity and concrete pore water. On the basis of reported durability data for E-glass/VE GFRP bars embedded in moist concrete, reduction factors linked to service life, temperature and relative humidity were obtained. By utilizing the new approach presented in this paper, more refined and accurate design values for long-term tensile strength of a GFRP bar could be achieved.

This paper presents research that uses novel clamp anchors and a simple mechanical stressing device for post-tensioning carbon FRP (CFRP) composite rods. The CFRP system was used in the repair of prestressed and normal reinforced concrete beams controlled by flexural and shear failure, respectively. The scaled specimens were designed to simulate concrete bridge girders with two different types of field-observed damage—end cracking and damage to internal steel prestressing tendons caused from vehicle collision. The CFRP repair system increased the ultimate strength and proved to be a practical and feasible method of repairing concrete girders with reduced shear or flexural capacity.

Common FRP rebars or plates used for reinforcing or strengthening in civil engineering are made by fiber reinforced thermosetting polymer (FRSP) materials. FRSP can not be reshaped after being cured so that many of the bent shapes cannot be easily obtained and handled at site. In view of this, glass fiber reinforced polypropylene (GFRPP) were developed in according to fiber reinforced thermoplastic polymer systems. This paper is focused on the experimental and theoretical studies on the corrosion resistance of GFRPP rebar in alkali, acid and salt solution at various temperatures. And some durability life prediction was concluded through FHWA method, which may be valuable to understand the durability of GFRPP rebars in practice. The results reveal that these kinds of GFRPP rebars exhibits a bad resistance in alkali solution, may due to the vulnerable glass reinforcement. And further studies should be carried on to optimizing this kind of GFRPP rebar.

The bridge deck slab is a prime example where FRP bars are used as main concrete reinforcement. In Canada, bridge deck slabs are usually subjected to a variation of cold and hot weathering while directly sustain the traffic loads. Both fatigue and thermal loading are expected to adversely affect the overall performance of such structural elements. In this research, a total of 4 large-scale bridge deck slabs totally reinforced with glass FRP bars were constructed and tested under simulated long-term loading and environmental conditions. The slabs were subjected to 3,000,000 cycles of sinusoidal waveform fatigue loading combined with either 100 freeze-thaw cycles or continuous cold temperature for one month. The test parameters included the environmental conditioning and the reinforcement ratio. It was concluded that the overall behavior of GFRP-reinforced bridge deck slabs after being subjected to simulated long-term fatigue load cycles and freeze-thaw or cold temperature is satisfactory according to the current design codes.