荷载作用下结构型纤维对混凝土裂缝渗透率演化的影响

曾伟; 丁一宁

doi:10.13801/j.cnki.fhclxb.20191213.001

荷载作用下结构型纤维对混凝土裂缝渗透率演化的影响

doi: 10.13801/j.cnki.fhclxb.20191213.001

曾伟,
丁一宁^,

大连理工大学　海岸与近海工程国家重点实验室，大连 116024

基金项目: 国家自然科学基金(51578109)

详细信息

通讯作者:
丁一宁，博士，教授，博士生导师，研究方向为高性能混凝土　E-mail：ynding@hotmail.com

中图分类号: TU528.572
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出版历程
- 收稿日期: 2019-10-23
- 录用日期: 2019-12-06
- 网络出版日期: 2019-12-13
- 刊出日期: 2020-09-15

Effects of macro fibers on crack permeability evolution of concrete under loading

ZENG Wei,
DING Yining^,

State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China

摘要

摘要: 为研究荷载作用下结构型钢纤维和结构型聚丙烯纤维对混凝土裂缝渗透率演化的影响，通过劈拉试验引入混凝土裂缝，同时利用真空渗水试验装置对不同裂缝宽度下混凝土裂缝渗透率进行实时测量和分析。借助激光扫描仪对混凝土裂缝表面形态进行信息采集和形态重构。对比分析了结构型钢纤维、结构型聚丙烯纤维及混杂纤维(包括结构型钢纤维和结构型聚丙烯纤维)对混凝土裂缝渗透率及裂缝表面形态的影响。研究表明：结构型纤维可通过增大裂缝表面粗糙程度降低混凝土裂缝渗透率，且随着纤维掺量的增高，混凝土裂缝渗透率随之减小。对比单掺纤维混凝土，混杂纤维混凝土具有更粗糙的裂缝表面，且展现出更显著的裂缝抗渗性能；随着裂缝的扩展，混凝土裂缝渗透率更接近于泊肃叶渗流模型；相比于泊肃叶渗流模型修正系数ξ，本文所用渗透率参数α更适合量化结构型纤维对混凝土裂缝渗透率的影响。
- 结构型纤维 /
- 裂缝渗透率 /
- 裂缝表面形态 /
- 泊肃叶渗流模型 /
- 粗糙度
Abstract: In order to study the effects of macro fibers on the crack permeability evolution of concrete under loading, the splitting test was adopted to generate cracks on the concrete specimens. The crack permeability of different crack widths was measured in real time using the vacuum permeability test. The laser scanning equipment was adopted for the measurement of information and the reconstruction of the topography of crack surface. The effects of macro steel fiber, macro polypropylene fiber and hybrid fiber(including macro polypropylene fiber and macro steel fiber) on the crack permeability of concrete and the topography of crack surface were analyzed and compared. The results show that the macro fibers increase the crack surface roughness of concrete and indirectly decrease the crack permeability of concrete. With the increasing of fiber content, the crack permeability decreases. Compared to mono fiber reinforcement, the crack surface of hybrid fiber reinforced concrete is rough and the crack permeability of hybrid fiber reinforced concrete is small. With the increase of crack width, the crack permeability is closer to the value predicted by the Poiseuille flow model. Compared to modified factor ξ of Poiseuille flow model, parameter α of permeability is suitable for quantifying the effect of macro fibers on the crack permeability of concrete.
- macro fiber /
- crack permeability /
- crack surface topography /
- Poiseuille flow model /
- roughness number

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图 1 结构型钢纤维(SF)和结构型聚丙烯纤维(PP)的形状

Figure 1. Geometry of macro steel fiber(SF) and macro polypropylene fiber(PP)

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图 2 混凝土劈拉试验

Figure 2. Splitting tensile test of concrete

LVDT—Linear variable differential transformer

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图 3 混凝土裂缝面积测量

Figure 3. Measuring crack area of concrete

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图 4 混凝土真空渗水试验

Figure 4. Vacuum permeability test of concrete

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图 5 混凝土有效裂缝宽度计算方法^[18]

Figure 5. Computational method of effective crack width of concrete^[18]

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图 6 混凝土试件裂缝中心扩展宽度(D_COD)与有效裂缝面积(A_f^eff)的统计关系

Figure 6. Statistical relationship between crack opening displacement(D_COD) and effective crack area( A_f^eff) of a representative concrete sample

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图 7 连续位移加载与持载下混凝土裂缝渗透率的对比

Figure 7. Comparison of crack permeability of concrete taken between continuous displacement loading and constant load

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图 8 激光扫描仪

Figure 8. Experimental set-up of the laser scanning equipment

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图 9 扫描线路

Figure 9. Scanning path

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图 10 混凝土裂缝表面形态示意图

Figure 10. Schematic view of crack surface topography of concrete

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图 11 NC、SF/NC、PP/NC和SF-PP/NC缝渗透率随有效裂缝宽度变化关系

Figure 11. Relationship between crack permeability and the effective crack width of NC, SF/NC, PP/NC and SF-PP/NC

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图 12 NC、SF/NC、PP/NC和SF-PP/NC修正系数ξ随有效裂缝宽度变化关系

Figure 12. Relationship between modified factor ξ and effective crack width of NC, SF/NC, PP/NC and SF-PP/NC

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图 13 NC、SF/NC、PP/NC和SF-PP/NC裂缝表面重构图

Figure 13. Reconstruction views of crack surface of NC, SF/NC, PP/NC and SF-PP/NC

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表 1 混凝土基准配比

Table 1. Basic mix proportion of concrete kg·m⁻³

Cement	Fly ash	Fine aggregate	Coarse aggregate	Water	Superplasticizer
390	155	822	848	272.5	5.5

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表 2 结构型SF和结构型PP的性能参数

Table 2. Properties of macro SF and macro PP

Type	Length/mm	Diameter/mm	Aspect ratio	Tensile strength/MPa	E-modulus/GPa	Number/(pieces·kg⁻¹)
Macro SF	35	0.54	65	1 345	200.0	14 500
Macro PP	30	0.67	45	490	3.9	96 000

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表 3 结构型SF和结构型PP掺量

Table 3. Contents of macro SF and macro PP

Type	Macro SF	Macro PP
NC	—	—
SF20/NC	20 kg/m³ (0.25vol%)	—
SF40/NC	40 kg/m³ (0.50vol%)	—
SF60/NC	60 kg/m³ (0.75vol%)	—
PP6.9/NC	—	6.9 kg/m³ (0.75vol%)
SF40-PP2.3/NC	40 kg/m³ (0.50vol%)	2.3 kg/m³ (0.25vol%)

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表 4 普通混凝土(NC)、结构型钢纤维增强混凝土(SF/NC)、结构型聚丙烯纤维增强混凝土(PP/NC)和混杂纤维增强混凝土(SF-PP/NC)的D_COD与A_f^eff的拟合曲线参数的对比

Table 4. Comparison of fitted parameter between D_COD and A_f^eff of normal concrete(NC), macro steel fiber reinforced concrete(SF/NC), macro polypropylene fiber reinforced concrete(PP/NC) and hybrid fiber reinforced concrete(SF-PP/NC)

NC	SF20/NC	SF40/NC	SF60/NC	PP6.9/NC	SF40-PP2.3/NC
0.02906 (R²=0.99)	0.03256 (R²=0.99)	0.03551(R²=0.95)	0.04039 (R²=0.98)	0.03016 (R²=0.96)	0.04237 (R²=0.97)
Note: R²—Coefficient of determination.

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表 5 NC、SF/NC、PP/NC和SF-PP/NC拟合曲线的参数

Table 5. Fitted parameters of curves of NC, SF/NC, PP/NC and SF-PP/NC

Parameter β	Fitted parameter α
Parameter β	NC	SF20/NC	SF40/NC	SF60/NC	PP6.9/NC	SF40-PP2.3/NC
1.541	171 465.3(C_v=6.1%)	66 963.0(C_v=8.9%)	18 477.5(C_v=5.4%)	1 942.1(C_v=7.6%)	10 020.3(C_v=3.8%)	1 431.0(C_v=5.1%)
Note: C_v—Coefficient of variation.

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表 6 NC、SF/NC、PP/NC和SF-PP/NC裂缝粗糙度

Table 6. Crack roughness number of NC, SF/NC, PP/NC and SF-PP/NC

NC	SF20/NC	SF40/NC	SF60/NC	PP6.9/NC	SF40-PP2.3/NC
1.133 (C_v=1.9%)	1.214 (C_v=3.6%)	1.299 (C_v=6.9%)	1.430 (C_v=4.7%)	1.304(C_v=3.7%)	1.480(C_v=4.1%)

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