Degradation mechanism of tensile properties and life prediction of hybrid carbon/basalt fiber reinforced polymer bars in seawater sea-sand concrete
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摘要: 为了研究海水浸泡下海水海砂混凝土(SSC)中以环氧树脂为基体的混杂碳-玄武岩纤维复材筋(CF-BF/Epoxy)拉伸性能退化规律,在不同温度(25℃、40℃和55℃)下对SSC中的CF-BF/Epoxy进行海水浸泡,周期为60天、90天和120天,通过拉伸试验对CF-BF/Epoxy在SSC中的拉伸性能进行了研究,并利用SEM和FTIR对其微观结构的变化进行了分析。结果显示:环境温度对CF-BF/Epoxy的拉伸性能有明显影响,在55℃下浸泡120天后,抗拉强度下降了13.84%,弹性模量在3%范围内轻微波动,CF-BF/Epoxy出现伪延性;玄武岩纤维和碳纤维混杂延缓了SSC中OH−进一步向CF-BF/Epoxy内部侵蚀,而外层玄武岩纤维区域的树脂水解和树脂-纤维界面退化是CF-BF/Epoxy拉伸性能退化的主要原因。最后基于Arrhenius方程预测,嵌入SSC中的CF-BF/Epoxy的抗拉强度保持率将在584~803天内降至70%。
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关键词:
- 混杂碳-玄武岩纤维复材筋 /
- 海水海砂混凝土 /
- 抗拉强度 /
- 退化机制 /
- 寿命预测
Abstract: To investigate the degradation pattern of tensile properties of epoxy resin-based hybrid carbon-basalt fiber reinforcing bars (CF-BF/Epoxy) in seawater sea-sand concrete (SSC) under seawater immersion, the CF-BF/Epoxy in SSC were soaked in seawater at different temperatures (25℃, 40℃, and 55℃) for durations of 60, 90 and 120 days. The tensile performance of the CF-BF/Epoxy in SSC was examined through tensile tests, and the changes in their microstructure were analyzed by SEM and FTIR. The results indicate that ambient temperature significantly affects the tensile properties of CF-BF/Epoxy. After 120 days of immersion at 55℃, the tensile strength decreases by 13.84%, the elastic modulus experiences a slight fluctuation within a 3% range, and pseudo-ductility is observed in the CF-BF/Epoxy. Additionally, blending of basalt fibers and carbon fibers delay the further intrusion of OH− from SSC into CF-BF/Epoxy, while the hydrolysis of the resin in the outer basalt fiber region and the degradation of the resin-fiber interface are identified as the primary causes of the decline in the tensile properties of CF-BF/Epoxy. Lastly, based on the Arrhenius equation, it is predicted that the tensile strength retention rate of CF-BF/Epoxy embedded in SSC will drop to 70% between 584 and 803 days.-
Key words:
- CF-BF/Epoxy /
- seawater sea-sand concrete /
- tensile strength /
- degradation mechanism /
- life prediction
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表 1 海水海砂混凝土(SSC)配合比
Table 1. Mixing ratio of seawater sea sand concrete (SSC)
Cement/(kg·m−3) Artificial seawater/(kg·m−3) Coarse aggregate/(kg·m−3) Sea-sand/(kg·m−3) Water reducer/(kg·m−3) 370 185 1113 682 0.111 表 2 人工海水的化学成分
Table 2. Chemical composition of artificial seawater
NaCl/(g·L−1) MgCl2/(g·L−1) Na2SO4/(g·L−1) CaCl2/(g·L−1) KCl/(g·L−1) NaHCO3/(g·L−1) 24.53 5.20 4.09 1.16 0.695 0.201 表 3 嵌入SSC中CF-BF/Epoxy的加速老化试验
Table 3. Accelerated aging test of CF-BF/Epoxy embedded in SSC
Type of FRP bars Test environment Exposure temperature/℃ Exposure period/d Number of tensile
test specimensCF-BF/Epoxy Artificial seawater immersion 25 60, 90, 120 5 40 60, 90, 120 5 55 60, 90, 120 5 表 4 CF-BF/Epoxy拉伸性能测试结果
Table 4. Test results of tensile properties of CF-BF/Epoxy
Specimen of FRP bars Tensile strength Elastic modulus Ultimate strain/% Average/MPa Retention/% CV/% Average/GPa Retention/% CV/% Average Retention HFRP 2437.41 100 1.2 146.87 100 3.3 1.66 100 HT25D60 2390.00 98.05 1.3 144.84 98.62 1.6 1.65 99.40 HT25D90 2278.19 93.47 3.6 144.76 98.56 3.4 1.57 94.81 HT25D120 2260.69 92.75 4.4 143.18 97.49 1.6 1.58 95.12 HT40D60 2373.33 97.37 4.7 142.49 97.02 3.2 1.67 99.34 HT40D90 2267.46 93.03 6.6 143.22 97.51 2.0 1.58 95.37 HT40D120 2217.14 90.96 5.1 142.52 97.04 2.2 1.56 93.72 HT55D60 2360.00 96.82 1.5 143.60 97.78 2.3 1.64 99.00 HT55D90 2186.67 89.71 4.2 145.03 98.75 3.9 1.51 90.83 HT55D120 2100.00 86.16 1.7 145.13 98.82 1.0 1.45 87.17 Note: CV—Coefficient of variation. 表 5 CF-BF/Epoxy在SSC中寿命预测的时移因子(FTS)参数
Table 5. Time shift factor (FTS) parameters for life prediction of CF-BF/Epoxy wrapped by SSC
Type of FRP bars Solution temperature/℃ FTS Qingdao (12.3℃) Fuzhou (20.1℃) Haikou (23.8℃) CF-BF/Epoxy 25 1.33 1.11 1.03 40 1.81 1.51 1.39 55 2.39 2.00 1.84 表 6 不同文献中FRP筋拉伸试验结果和寿命预测结果
Table 6. Tensile test results and life prediction of FRP bars in different literatures
Parameters of
FRP barExposure condition Tensile test results Life prediction Ref. Duration/d Tensile strength retention/% Tensile strength retention/% Service-life/years Location 8 mm CF-BF/Epoxy SSC (pH=13.3) 120 (25℃) 92.75 70 2.6 Qingdao (12.3℃) This study 90 (40℃) 93.03 70 1.8 Fuzhou (20.1℃) 90 (55℃) 89.71 70 1.6 Haikou (23.8℃) 8 mm BFRP SMSSC (pH=12.5) 180 (25℃) 86.88 70 5.1 Qingdao (12.3℃) [15] 90 (40℃) 75.42 70 2.4 Fuzhou (20.1℃) 90 (55℃) 60.81 70 1.7 Haikou (23.8℃) 6 mm BFRP Simulated SSC pore
solutions (pH=13.4)63 (32℃) 92.7 70 20.4 Hall's Harbor Quay (7.6℃) [16] 63 (40℃) 81.7 63 (55℃) 26 70 14.6 Waterloo Creek Bridge (9.9℃) Natural environments — 91.6 5 Hall's Harbor Quay (7.6℃) 86.4 6 Waterloo Creek Bridge (9.9℃) GFRP
(E-glass in a vinylester matrix)Natural environments — No significant degradation 5-8 Halls Harbor Wharf [37] Joffre Bridge Chatham Bridge Growchild Trail Bridge Waterloo Greek Bridge Note: SMSSC—Seawater sea sand concrete. -
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