Bond Strength of Fiber Reinforced Polymer (FRP) Bars in Autoclaved Aerated Concrete (AAC)

A new type of HFRP hybrid bars (hybrid fiber reinforced polymer) was introduced to increase the rigidity of FRP reinforcement, which was a basic drawback of the FRP bars used so far. Compared to the BFRP (basalt fiber reinforced polymer) bars, modification has been introduced in HFRP bars consisting of swapping basalt fibers with carbon fibers. One of the most important mechanical properties of FRP bars is compressive strength, which determines the scope of reinforcement in compressed reinforced concrete elements (e.g., column). The compression properties of FRP bars are currently ignored in the standards (ACI, CSA). The article presents compression properties for HFRP bars based on the developed compression test method. Thirty HFRP bars were tested for comparison with previously tested BFRP bars. All bars had a nominal diameter of 8 mm and their nonanchored (free) length varied from 50 to 220 mm. Test results showed that the ultimate compressive strength of nonbuckled HFRP bars as a result of axial compression is about 46% of the ultimate strength. In addition, the modulus of elasticity under compression does not change significantly compared to the modulus of elasticity under tension. A linear correlation of buckling load strength was proposed depending on the free length of HFRP bars.

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Thermal effect on fiber reinforced polymer reinforced concrete slabs

Canadian Journal of Civil Engineering ◽

10.1139/l07-110 ◽

2008 ◽

Vol 35 (3) ◽

pp. 312-320 ◽

Cited By ~ 9

Author(s):

A. Zaidi ◽

R. Masmoudi

Keyword(s):

Thermal Effect ◽

Concrete Cover ◽

Fiber Reinforced Polymer ◽

Concrete Slabs ◽

Fiber Reinforced ◽

Reinforced Concrete Slabs ◽

Reinforced Polymer ◽

Frp Bar ◽

Frp Bars ◽

Concrete Interface

The difference between the transverse coefficients of thermal expansion of fiber reinforced polymer (FRP) bars and concrete generates radial pressure at the FRP bar – concrete interface, which induces tensile stresses within the concrete under temperature increase and, eventually, failure of the concrete cover if the confining action of concrete is insufficient. This paper presents the results of an experimental study to investigate the thermal effect on the behaviour of FRP bars and concrete cover, using concrete slab specimens reinforced with glass FRP bars and subjected to thermal loading from –30 to +80 °C. The experimental results show that failure of concrete cover was produced at temperatures varying between +50 and +60 °C for slabs having a ratio of concrete cover thickness to FRP bar diameter (c/db) less than or equal to 1.4. A ratio of c/db greater than or equal to 1.6 seems to be sufficient to avoid splitting failure of concrete cover for concrete slabs subjected to high temperatures up to +80 °C. Also, the first cracks appear in concrete at the FRP bar – concrete interface at temperatures around +40 °C. Comparison between experimental and analytical results in terms of thermal loads and thermal strains is presented.

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Utilizing alkali-activated materials as ordinary Portland cement replacement to study the bond performance of fiber-reinforced polymer bars in seawater sea-sand concrete

Advances in Structural Engineering ◽

10.1177/13694332211065186 ◽

2022 ◽

pp. 136943322110651

Author(s):

Ruiming Cao ◽

Bai Zhang ◽

Luming Wang ◽

Jianming Ding ◽

Xianhua Chen

Keyword(s):

Tensile Strength ◽

Bond Strength ◽

Ordinary Portland Cement ◽

Concrete Strength ◽

Fiber Reinforced Polymer ◽

Bond Performance ◽

Reinforced Polymer ◽

Sea Sand ◽

Frp Bars ◽

Alkali Activated

Alkali-activated materials (AAMs) are considered an eco-friendly alternative to ordinary Portland cement (OPC) for mitigating greenhouse-gas emissions and enabling efficient waste recycling. In this paper, an innovative seawater sea-sand concrete (SWSSC), that is, seawater sea-sand alkali-activated concrete (SWSSAAC), was developed using AAMs instead of OPC to explore the application of marine resources and to improve the durability of conventional SWSSC structures. Then, three types of fiber-reinforced polymer (FRP) bars, that is, basalt-FRP, glass-FRP, and carbon-FRP bars, were selected to investigate their bond behavior with SWSSAAC at different alkaline dosages (3%, 4%, and 6% Na2O contents). The experimental results manifested that the utilization of the alkali-activated binders can increase the splitting tensile strength ( ft) of the concrete due to the denser microstructures of AAMs than OPC pastes. This improved characteristic was helpful in enhancing the bond performance of FRP bars, especially the slope of bond-slip curves in the ascending section (i.e., bond stiffness). Approximately three times enhancement in terms of the initial bond rigidity was achieved with SWSSAAC compared to SWSSC at the same concrete strength. Furthermore, compared with the BFRP and GFRP bars, the specimens reinforced with the CFRP bars experienced higher bond strength and bond rigidity due to their relatively high tensile strength and elastic modulus. Additionally, significant improvements in initial bond stiffness and bond strength were also observed as the alkaline contents (i.e., concrete strength) of the SWSSAAC were aggrandized, demonstrating the integration of the FRP bars and SWSSAAC is achievable, which contributes to an innovative channel for the development of SWSSC pavements or structures.

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