Effect of applied sustained load and severe environments on durability performance of carbon-fiber composite cables

Abstract

The research work reported in this paper involves investigation of the mechanical and durability performance of unstressed and stressed Tokyo Rope carbon-fiber composite cables for prestressing applications. This research is critical in order to establish the critical (allowable) stress and safety factors for the use of carbon-fiber composite cable tendons for prestressed precast-concrete members. The carbon-fiber composite cable specimens were exposed to simultaneous high alkali environment and sustained loading at different elevated exposure temperatures (22℃ and 60℃) for 3000, 5000, and 7000 h. The high alkali environment (12.8 pH) simulated the concrete pore solution and the elevated temperature was used to accelerate the aging process. The applied sustained stress on the carbon-fiber composite cable strands was equivalent to 40% and 65% of their guaranteed tensile strength. This was achieved through testing 171 carbon-fiber composite cable specimens subjected to stress levels of 0%, 40%, and 65% of their guaranteed strength, under tensile load. Also, 136 carbon-fiber composite cable specimens were tested to investigate the transverse shear strength. In addition, the durability characteristics of the constituent materials of the carbon-fiber composite cable strands were assessed to understand the long-term behavior of these materials. The results showed the effect of sustained stress on the degradation of carbon-fiber composite cable strands. Under sustained stress of 40% and 65%, the reductions in tensile strength were 10.6% and 12.3%, respectively. Scanning electron microscope results on epoxy resin indicated that no degradation is detected since the surface remains smooth without any pitting or loose material.

Long-Term Durability of Carbon-Reinforced Concrete: An Overview and Experimental Investigations

“…The long-term durability is affected by environmental factors such as stress, temperature, moisture and alkalinity (e.g., [17,20]). These factors are not only used to simulate the environmental conditions, but also for artificial aging, as it is not possible to carry out long-term tests over a service life of up to 100 years [17,[21][22][23][24][25].…”

Electrochemical impedance spectroscopy characteristic of degradation process for carbon fiber/vinyl ester composites in salt water

“…It can be seen that, the value of |Z| 0.01 Hz at OCP is the highest with the smallest change. After 205 days of immersion it decreases less than one order of magnitude from the beginning and maintains around 1.0×10 6 V cm 2 with no big variation during 100 days-205 days stage, which probably is related to a slower penetration rate of the electrolyte through the composite and the moisture uptake nearly approaches to saturation. The initial value of |Z| 0.01 Hz at cathodic polarization (2.0×10 6 V cm 2 at À0.6 V SCE , 3.4×10 5 V cm 2 at À0.12 V SCE ) is obviously lower than that at OCP (5.0×10 6 V cm 2 ).…”

“…After 205 days of immersion it decreases less than one order of magnitude from the beginning and maintains around 1.0×10 6 V cm 2 with no big variation during 100 days-205 days stage, which probably is related to a slower penetration rate of the electrolyte through the composite and the moisture uptake nearly approaches to saturation. The initial value of |Z| 0.01 Hz at cathodic polarization (2.0×10 6 V cm 2 at À0.6 V SCE , 3.4×10 5 V cm 2 at À0.12 V SCE ) is obviously lower than that at OCP (5.0×10 6 V cm 2 ). This is because carbon fibers are good conductors, the cathodic reaction (O 2 + 2H 2 O + 4e → 4OH À ) is initiated on the fibers immediately upon application of cathodic polarization.…”

“…Initially, people generally thought that CFRP materials would not suffer corrosion damage, but later found that some aggressive media, high temperature, or galvanic couple action would decrease the stability of the composites and cause the mechanical properties to degrade. [1][2][3][4][5][6][7][8] Since carbon fiber is a good electronic conductor with the potential more positive than most engineering metals, when a CFRP is in contact with a metal there will be a galvanic process between the CFRP and the metal, which could cause corrosion damage to the anodic metal. Meanwhile, the degradation of the CFRP due to the chemical reactions between some functional groups in the polymer and oxygen reduction products (hydroxyl ions, peroxide et al) at the surface of the carbon fiber cathode occurs.…”

Behavior of Piles Reinforced by Geosynthetics Under Lateral Load

“…The use of fiber-reinforced polymer (FRP) bars and geosynthetic geogrids (G) as pile reinforcement materials was discovered to be a promising strategy, due to their high strengthweight ratio, durability, and high ability to anti-corrosion [7] [8]. Composite piles are commonly used as waterfront barriers, fenders, and bearing piles for light structures in ports due to the ongoing creation of novel composite materials [9][10][11][12][13]. They were also used in bridge rehabilitation work as load-bearing substructures [14].…”