Mechanical properties of concrete reinforced with macro fibres recycled from waste GFRP
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摘要: 树脂基纤维增强复合材料(简称“复材”)具有轻质、高强、耐腐蚀等突出优点，广泛应用于建筑、交通、能源、航空航天及体育等行业。复合材料生产过程和寿命终端产生了大量的复材固体废弃物，其中95%以上为玻璃纤维增强复合材料(简称“玻纤复材”)。玻璃纤维附加值较低且力学性能易在回收处理后显著降低，因此玻纤复材固废的回收经济性不强。本研究团队此前提出了通过机械切割将玻纤复材固废加工成粗纤维，并用于制备粗纤维混凝土(Macro fibre reinforced concrete, MFRC)。本文通过一系列轴压和劈拉试验，研究粗纤维体积掺量、厚度、长度对两种配比混凝土的力学性能的影响。试验结果表明，粗纤维的掺入能显著提升混凝土的劈拉强度，体积掺量为1.5%时，配比二混凝土的劈拉强度提高40%。评估了现有FRC劈拉强度预测公式对MFRC劈拉强度的预测效果，并基于试验结果提出了粗纤维混凝土劈拉强度预测公式。Abstract: Fibre-reinforced polymer (FRP) composites have been widely used in many sectors, such as construction, transportation, energy, aerospace and sports, due to their advantages such as lightweightness, high strength, and excellent durability. A large amount of FRP wastes arises from the production process and at the end-of-life of FRP products, of which 95% is glass fibre reinforced polymer (GFRP) composites. Existing GFRP recycling methods are not economical owing to the low added value of glass fibres and significant degradation of glass fibre properties due to the recycling process. The authors’ research team has previously proposed a mechanical method to process decommissioned wind turbine blades into macro fibres, which can then be used to produce macro fibre reinforced concrete (MFRC). This paper presents an experimental study in which the effects of fibre volume fraction, fibre thickness, fibre length, and concrete mix on the compression and splitting tensile properties of MFRC were investigated. The test results show that the splitting tensile strength of the concrete can be significantly enhanced by the addition of macro fibres, e.g., by 40% when the macro fibre volume fraction in mix 2 concrete is 1.5%. The applicability of existing equations for predicting the splitting tensile strength of fibre reinforced concrete (FRC) to MFRC is evaluated, and a new equation for predicting the splitting tensile strength of MFRC is proposed based on the test data.
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Key words:
- GFRP /
- wastes /
- mechanical recycling /
- macro fibres /
- fibre reinforced concrete
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图 1 玻纤复材风机叶片的粗纤维化方法
Figure 1. Mechanical processing of a wind turbine blade into macro fibres
图 6 MFRC轴压试件典型破坏模态
Figure 6. Typical failure modes of MFRC cylinders under compression
图 9 MFRC劈拉试件典型破坏模态
Figure 9. Typical failure modes of MFRC splitting tensile test specimens
图 11 MFRC劈拉强度实验值和预测值的比较
Figure 11. Predicted vs test values of MFRC splitting tensile strength
表 1 回收粗纤维统计参数
Table 1. Statistical properties of recycled macro fibres
Designation MF-1 MF-2 MF-3 MF-4 MF-5 Nominal dimensions/mm 90×4.5×0.5 90×4.5×1.2 90×4.5×2.2 60×4.5×0.5 30×4.5×0.5 Length/mm Average 91.20 90.57 87.60 58.25 33.30 Standard deviation 1.94 4.56 2.97 1.94 1.20 Width/mm Average 4.49 4.57 4.57 4.63 4.81 Standard deviation 0.43 0.36 0.75 0.80 0.48 Thickness/mm Average 0.54 1.26 2.26 0.54 0.50 Standard deviation 0.16 0.26 0.53 0.19 0.12 Tensile strength/MPa Average 554 Standard deviation 135 Elastic modulus/GPa Average 37.7 Standard deviation 7.3 
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表 2 试件设计
Table 2. Specimen design
No. Mix Water/cement ratio Fibre length/mm Fibre thickness/mm Fibre volume fraction/% No. of specimens Compression Splitting 1-1 S1 W0.32 L0 V0%T0 0.32 - - 0 3 3 1-2 S1 W0.32 L90 V0.5%T0.5 0.32 90 0.5 0.5 3 3 1-3 S1 W0.32 L90 V1%T0.5 0.32 90 0.5 1 3 3 1-4 S1 W0.32 L90 V1.5%T0.5 0.32 90 0.5 1.5 3 3 1-5 S1 W0.32 L90 V2%T0.5 0.32 90 0.5 2 3 3 2-1 S2 W0.32 L90 V1.5%T1.2 0.32 90 1.2 1.5 3 3 2-2 S2 W0.32 L90 V1.5%T2.2 0.32 90 2.2 1.5 3 3 2-3 S2 W0.32 L60 V1.5%T0.5 0.32 60 0.5 1.5 3 3 2-4 S2 W0.32 L30 V1.5%T0.5 0.32 30 0.5 1.5 3 3 2-5 S2 W0.47 L90 V1.5%T0.5 0.47 90 0.5 1.5 3 3 2-6 S2 W0.47 L0 V0%T0 0.47 - - 0 3 3
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表 3 混凝土基体配合比
Table 3. Mix proportions of concrete matrix
Mix Strength grade Fresh water/
Cement ratioFresh water/
(kg·m−3)Cement/
(kg·m−3)Fine Aggregate/
(kg·m−3)Coarse Aggregate/
(kg·m−3)Water reducer/% 1 C60 0.32 160 500 795 970 0.45 2 C40 0.47 185 395 715 1075 0.19
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表 4 MFRC轴压实验结果
Table 4. Key results of MFRC compression tests
No. Group fc,m/ MPa CoV/ % εco,m/ % CoV/ % Em/ GPa CoV/ % vm CoV/ % 1-1 S1 W0.32 L0 V0%T0 51.7 2.1 0.223 13.7 35.5 5.9 0.18 6.2 1-2 S1 W0.32 L90 V0.5%T0.5 46.0 6.4 0.175 10.6 36.2 0.7 0.19 0.0 1-3 S1 W0.32 L90 V1%T0.5 49.1 4.7 0.183 3.8 35.4 3.6 0.20 5.0 1-4 S1 W0.32 L90 V1.5%T0.5 37.4 5.3 0.167 9.0 32.7 6.8 0.19 11.2 1-5 S1 W0.32 L90 V2%T0.5 38.0 7.3 0.194 6.2 28.6 6.7 0.17 3.5 2-1 S2 W0.32 L90 V1.5%T1.2 74.5 1.6 0.264 4.7 39.7 1.2 0.17 0.0 2-2 S2 W0.32 L90 V1.5%T2.2 65.5 1.2 0.245 11.9 39.5 1.9 0.21 4.8 2-3 S2 W0.32 L60 V1.5%T0.5 57.4 1.0 0.236 16.2 37.1 5.4 0.19 6.0 2-4 S2 W0.32 L30 V1.5%T0.5 60.2 2.7 0.208 1.7 40.2 2.5 0.19 5.3 2-5 S2 W0.47 L90 V1.5%T0.5 50.9 2.9 0.272 0.7 32.4 4.6 0.19 16.6 2-6 S2 W0.47 L0 V0%T0 50.1 2.4 0.218 7.2 36.0 2.9 0.22 16.2 Note: fc,m = Average compressive strength; εco,m = Average value of strain at compressive strength; Em = Average value of modulus of elasticity in compression; vm = Average Poisson's ratio; CoV = Coefficient of variation.
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表 5 纤维混凝土劈拉强度预测模型
Table 5. Models for predicting the splitting tensile strength of FRC
Source Parameters Equation Note WAFA and ASHOUR [39] $ f_{\rm{c}}^{\prime},{V_{\rm{f}}} $ $ {f_{\rm{spf}}} = 0.58{(f_{\rm{c}}^{\prime})^{0.5}} + 3.02{V_{\rm{f}}} $ $ f_{\rm{c}}^{\prime} \leqslant 100\;{\text{MPa}} $ BAE et al. [41] $ f_{\rm{c}}^{\prime},{V_{\rm{f}}},L,{d_{\rm{f}}} $ $ {f_{\rm{spf}}} = 0.83{(f_{\rm{c}}^{\prime})^{0.47}}\left(\dfrac{{ - 2}}{{1 + {{(0.125 Ri)}^{0.8}}}} + 3\right) $ $ \begin{gathered} Ri{\text{ = }}{V_{\rm{f}}}L/{d_{\rm{f}}} \\ f_{\rm{c}}^{\prime} \leqslant 150\;{\text{MPa}} \\ \end{gathered} $ SONG et al. [40] $ f_{\rm{c}}^{},{V_{\rm{f}}} $ $ {f_{\rm{spf}}} = 0.63{({f_{c} })^{0.5}} + 3.01{V_{\rm{f}}} - 0.02{V_{\rm{f}} }^2 $ $ {f_{\rm{c}}} \leqslant 100\;{\text{MPa}} $ AL AZZAWI and SARSAM [42] $ f_{\rm{c}}^{},{V_{\rm{f}}},L,{d_{\rm{f}}},{b_{\rm{f}} } $ $ {f_{\rm{spf}}} = 0.47{(f_{\rm{c}}^{})^{0.5}} + 4.2 F $ $ \begin{gathered} F{\text{ = }}{V_{\rm{f}}}{{\text{b}}_{\rm{f}}}L/{d_{\rm{f}}} \\ 41 \leqslant f_{\rm{c}}^{} \leqslant 115\;{\text{MPa}} \\ \end{gathered} $ MUSMAR [43] $ f_{\rm{cf} }^{},{V_{\rm{f}} },L,{d_{\rm{f}} } $ $ {f_{{s} {pf} }} = {({f_{\rm{cf} }})^{0.5}}\left(0.6 + 0.4{V_{\rm{f}}}\dfrac{L}{{{d_{\rm{f}} }}}\right) $ $ 4 \leqslant {f_{\rm{cf} }} \leqslant 120\;{\text{MPa}} $ EL DIN et al. [44] $ f_{\rm{cf} }^{},{V_{\rm{f}} },L,{d_{\rm{f}} },{b_{\rm{f}}} $ $ {f_{\rm{spf} }} = 0.095\left[{f_{\rm{cf} }} + 10\sqrt F \left(3 - \dfrac{{20}}{{{f_{\rm{cf} }}}}\right)\right] $ $ F{\text{ = }}{V_{\rm{f}} }{{\text{b}}_{\rm{f}}}L/{d_{\rm{f}}} $ LE HOANG [45] $ f_{\rm{cf} }^{},{V_{\rm{f}}},L,{d_{\rm{f}}},{b_{\rm{f}}} $ $ {f_{\rm{spf}}} = {({f_{\rm{cf} }})^{0.5}}\left(0.94{V_{\rm{f}} }\dfrac{L}{{{d_{\rm{f}}}}}{b_{\rm{f}} } + 0.67\right) $ $ 120 \leqslant {f_{\rm{cf} }} \leqslant 200\;{\text{MPa}} $ Notes: fc’= Characteristic compressive strength of plain concrete; fc = Measured compressive strength of plain concrete; fcf = Measured compressive strength of FRC.
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表 6 FRC模型对MFRC劈拉强度的预测效果
Table 6. Evaluation of FRC models for predicting the splitting tensile strength of MFRC
Source Predicted/Test IAE/% Average SD CoV/% WAFA and ASHOUR [39] 0.83 0.14 16 19.8 BAE et al. [41] 1.32 0.14 10 30.5 SONG et al. [40] 0.98 0.16 16 12.6 AL AZZAWI and SARSAM [42] 0.92 0.13 15 13.5 MUSMAR [43] 1.19 0.12 10 18.5 EL DIN et al. [44] 1.28 0.16 13 27.5 LE HOANG [45] 1.34 0.13 10 33.5 Equation (5) 1.00 0.08 8 6.0 Equation (6) 1.02 0.15 15 7.4 Notes: SD—Standard deviation; IAE—Integral absolute error.
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