摘要
为研究工程水泥基复合材料(ECC)与锈蚀螺纹钢筋的黏结破坏机理,采用中心拉拔试验方法,分析钢筋锈蚀率、黏结锚固长度、钢筋直径和纤维掺量等因素对黏结性能的影响。结果表明,ECC与锈蚀钢筋的黏结应力-滑移曲线可分为微滑移阶段、滑移阶段、破坏阶段和残余阶段,试件破坏类型为剪切拔出破坏;黏结强度随钢筋锈蚀率的增加先增大后减小,存在临界锈蚀率使得黏结性能最好;钢筋锈蚀率为10%时,试件黏结强度随钢筋锚固长度和钢筋直径的增大而减小;随着纤维体积掺量的增加,黏结韧性指数和黏结强度先增大后减小,纤维体积掺量为2%时,纤维的增韧和阻裂效果最明显。
关键词
工程水泥基复合材料(engineered cementitious composite, ECC)是一种具有拉伸应变硬化行为且极限拉伸应变超过3%的高性能材
笔者以银川地区的腾格里沙漠砂为细集料制备ECC,并对其进行了单轴拉伸、单轴压缩力学性能试验和耐久性试
ECC所用材料分别是普通硅酸盐水泥、腾格里沙漠砂、PVA纤维、粉煤灰、聚羧酸高效减水剂和水,纤维主要参数由厂家提供,如
纤维名称 | 长度/mm | 直径/µm | 极限抗拉强度/MPa | 密度/(kL· | 弹性模量/GPa |
---|---|---|---|---|---|
PVA | 12 | 40 | 1 600 | 1 300 | 40 |
钢筋型号 | 直径/mm | 屈服强度平均值/MPa | 抗拉强度平均值/MPa | 伸长率/% |
---|---|---|---|---|
HRB400 | 10 | 439 | 625 | 24 |
12 | 465 | 625 | 22 | |
14 | 465 | 605 | 25 | |
16 | 465 | 636 | 24 | |
18 | 420 | 608 | 24 |
混凝土种类 | 纤维体积掺量/% | 抗压强度/MPa | ||
---|---|---|---|---|
E1 | 2.00 | 53.25 | 52.34 | 53.24 |
E2 | 1.75 | 54.04 | 54.59 | 54.80 |
E3 | 2.25 | 49.03 | 48.36 | 49.27 |
C1 | — | 53.59 | 54.51 | 53.89 |
注: E1、E2、E3分别是3种纤维掺量不同的ECC;C1是普通混凝土。
对12组ECC与锈蚀钢筋中心拉拔试件和1组混凝土与锈蚀钢筋的对比试件进行黏结性能试验,每组3个试件,控制变量是钢筋锈蚀率、黏结锚固长度、钢筋直径和纤维掺量,试件主要设计参数,如
试件编号 | 钢筋直径/mm | 锚固长度/mm | 理论钢筋锈蚀率/% | 实际钢筋锈蚀率/% | 极限黏结荷载/kN | 极限黏结应力/MPa |
---|---|---|---|---|---|---|
E1-5 d12-10 | 12 | 60 | 10 | 9.95 | 47.53 | 21.02 |
E1-8 d12-10 | 12 | 96 | 10 | 10.32 | 62.48 | 17.27 |
E1-12 d12-10 | 12 | 144 | 10 | 10.24 | 63.56 | 11.72 |
E2-5 d12-10 | 12 | 60 | 10 | 9.68 | 38.81 | 17.17 |
E3-5 d12-10 | 12 | 60 | 10 | 9.85 | 37.13 | 16.42 |
E1-5 d10-10 | 10 | 50 | 10 | 9.76 | 38.65 | 24.61 |
E1-5 d14-10 | 14 | 70 | 10 | 9.68 | 75.31 | 18.74 |
E1-5 d16-10 | 16 | 80 | 10 | 10.35 | 50.79 | 16.50 |
E1-5 d18-10 | 18 | 90 | 10 | 10.28 | 64.10 | 12.60 |
E1-5 d12-0 | 12 | 60 | 0 | 0 | 48.87 | 21.61 |
E1-5 d12-5 | 12 | 60 | 5 | 5.16 | 49.78 | 23.02 |
E1-5 d12-15 | 12 | 60 | 15 | 14.79 | 41.43 | 18.32 |
C1-5 d12-10 | 12 | 60 | 10 | 9.84 | 43.04 | 19.02 |
注: E1-5 d12-10表示E1-黏结锚固长度(5 d)钢筋直径(12 mm)-钢筋理论锈蚀率(10%);d是钢筋直径。

图1 拉拔试件尺寸(单位:mm)
Fig. 1 Size of specimen (unit: mm)

图2 拉拔试验装置
Fig. 2 Pull experiment device

图4 典型黏结应力-滑移曲线
Fig. 4 Typical bond stress-slip curves
1)微滑移阶段(OA):钢筋开始滑移,锈蚀层结构被挤压破坏,钢筋与ECC间的胶结力减小,此时黏结应力主要取决于机械咬合力和握裹力,黏结应力-滑移曲线基本呈线性上升趋势。
2)滑移阶段(AB):钢筋周围ECC产生不同程度的径向裂缝,锈蚀产物被挤压密实,钢筋与ECC间咬合齿逐渐被剪断挤压,ECC中的纤维被拔出或拉断,吸收耗散钢筋滑移过程中产生的能量,黏结应力-滑移曲线上升趋势放缓,直至黏结应力到达峰值点(黏结强度)。
3)破坏阶段(BC):钢筋与周围ECC间的咬合齿基本被破坏,钢筋与ECC的滑移量迅速增大,机械咬合力和摩擦力随之减小,接触界面也逐渐被磨平。试件内部破坏情况如

图5 试件内部破坏情况
Fig. 5 Internal damage of the specimens
4)残余阶段(CD):钢筋连同螺纹间ECC被缓缓拔出,黏结应力主要取决于拔出界面滑动摩擦力,由于钢筋的拔出界面趋向平滑,残余黏结应力变化较小。

图6 不同锈蚀率下平均黏结应力-滑移曲线
Fig. 6 Bond stress-slip curve under different corrosion rates

图7 不同锈蚀率下黏结强度对比
Fig. 7 bond strength under different corrosion rates

图8 不同锚固长度下平均黏结应力-滑移曲线
Fig. 8 Bond stress-slip curve under different anchorage lengths

图9 不同直径下平均黏结应力-滑移曲线
Fig. 9 Bond stress-slip curve under different rebar diameter

图10 不同钢筋直径黏结强度对比
Fig. 10 bond strength under different rebar diameter

图11 不同纤维掺量下平均黏结应力-滑移曲线
Fig. 11 Bond stress-slip curve under different fiber content
美国材料与试验协会(ASTM)C1018利用能量比值法计算黏结韧性指
, | (2) |
, | (3) |
式中:和分别为达到黏结强度时和黏结强度下降至 50%时,对应的黏结韧性指数,如

图12 韧性指数定义
Fig. 12 Definitions of toughness indices
试件 | 纤维掺量/% | |||||
---|---|---|---|---|---|---|
E2-5d12-10 | 1.75 | 8.36 | 16.30 | 40.17 | 1.95 | 4.81 |
E1-5d12-10 | 2.00 | 10.35 | 21.86 | 63.38 | 2.18 | 6.12 |
E3-5d12-10 | 2.25 | 7.28 | 13.75 | 28.78 | 1.89 | 3.96 |
1)ECC与锈蚀钢筋的典型黏结应力-滑移曲线可分为微滑移阶段、滑移阶段、破坏阶段和残余阶段。纤维的桥接作用大量吸收和耗散滑移过程中产生的能量,抑制了裂缝的发展,试件破坏类型为剪切-拔出破坏。
2)试件黏结强度和残余黏结应力随着钢筋锈蚀率的增加先增大后减小,存在临界钢筋锈蚀率使得锈蚀钢筋与ECC的黏结性能最好。
3)钢筋锈蚀率为10%时,试件黏结强度随钢筋锚固长度和钢筋直径的增大而减小,其中,锚固长度5 d试件的黏结强度是12 d试件的1.81倍。
4)随着纤维体积掺量的增加,黏结韧性指数和黏结强度先增大后减小,纤维体积掺量2%时纤维的增韧和阻裂效果最明显。
参考文献
Victor C, Li S W, Cynthia W. Tensile strain-hardening behavior of polyvinyl alcohol engineered cementitious composite (PVA-ECC)[J]. ACI Materials Journal, 2001, 98(6): 483-492 . [百度学术]
Li M, Li V C. High-early-strength engineered cementitious composites for fast, durable concrete repair-material properties[J]. ACI Materials Journal, 2011, 108(1):3-12. [百度学术]
Rokugo K, Kanda T, Yokota H, et al. Applications and recommendations of high performance fiber reinforced cement composites with multiple fine cracking (HPFRCC) in Japan[J]. Materials & Structures, 2009, 42(9):1197-1208. [百度学术]
陈文永, 陈小兵, 丁一. ECC高性能纤维增强水泥基材料及其应用[J]. 工业建筑, 2010, 40(S1): 768-772. [百度学术]
Chen W Y, Chen X B, Ding Y. ECC high performance fiber reinforced cement-based material and its application[J]. Industrial Construction, 2010, 40(S1): 768-772.(in Chinese) [百度学术]
林红威, 赵羽习. 变形钢筋与混凝土黏结性能研究综述[J]. 建筑结构学报, 2019, 40(1): 11-27. [百度学术]
Lin H W, Zhao Y X. Bond behavior between concrete and deformed steel bar: a review[J]. Journal of Building Structures, 2019, 40(1): 11-27.(in Chinese) [百度学术]
林红威, 赵羽习, 郭彩霞, 等. 锈胀开裂钢筋混凝土粘结疲劳性能试验研究[J]. 工程力学, 2020, 37(1): 98-107. [百度学术]
Lin H W, Zhao Y X, Guo C X, et al. Fatigue of the bond behavior of corroded reinforced concrete with corrosion-induced cracks[J]. Engineering Mechanics, 2020, 37(1): 98-107.(in Chinese) [百度学术]
刘曙光, 邓轶涵, 张菊, 等. PVA纤维水泥基复合材料与钢筋粘结性能研究[J]. 功能材料, 2016, 47(1): 1110-1116. [百度学术]
Liu S G, Deng Y H, Zhang J, et al. Research on bond behavior between PVA fiber reinforced cementitious composites and rebar[J]. Journal of Functional Materials, 2016, 47(1): 1110-1116.(in Chinese) [百度学术]
米渊, 潘金龙, 周青山. 钢筋与纤维增强水泥基复合材料粘结性能试验研究[J]. 建筑结构, 2016, 46(15): 69-73. [百度学术]
Mi Y, Pan J L, Zhou Q S. Experimental study on bond behavior between steel bars and patterned vertical alignment engineered cementitious composite[J]. Building Structure, 2016, 46(15): 69-73.(in Chinese) [百度学术]
Chao S H, Naaman A E, Parra-Montesinos G J. Bond behavior of reinforcing bars in tensile strain-hardening fiber-reinforced cement composites[J]. ACI Structural Journal, 2009, 106(6): 897-906. [百度学术]
Cai J M, Pan J L, Tan J W, et al. Bond behaviours of deformed steel rebars in engineered cementitious composites (ECC) and concrete[J]. Construction and Building Materials, 2020, 252: 119082. [百度学术]
Che J, Wang D, Liu H, et al. Mechanical Properties of desert sand-based fiber reinforced concrete (DS-FRC) [J]. Applied Sciences, 2019, 9(9):1857. [百度学术]
An X, Che J L, Liu H F, et al. Study on freeze-thaw resistance with NaCl of desert sand engineering cement composites[J]. Physics and Chemistry of the Earth, Parts A/B/C, 2021, 121: 102954. [百度学术]
白亮, 周枫, 谢鹏飞, 等. 高延性纤维增强水泥基复合材料力学性能试验研究[J]. 工业建筑, 2017, 47(6): 108-113. [百度学术]
Bai L, Zhou F, Xie P F, et al. Experimental research on mechanical properties of engineered cementitious composites[J]. Industrial Construction, 2017, 47(6): 108-113.(in Chinese) [百度学术]
生兆亮, 辛欣, 夏多田, 等. 纤维增强水泥基材料强度和微结构的影响因素研究[J]. 硅酸盐通报, 2020, 39(10): 3108-3114. [百度学术]
Sheng Z L, Xin X, Xia D T, et al. Influence factors of strength and microstructure of fiber reinforced cement-based materials[J]. Bulletin of the Chinese Ceramic Society, 2020, 39(10): 3108-3114.(in Chinese) [百度学术]
谢磊, 李庆华, 徐世烺. 纤维掺量对聚乙烯醇纤维增强水泥基复合材料动态压缩性能的影响[J]. 复合材料学报, 2021, 38(9): 3086-3100. [百度学术]
Xie L, Li Q H, Xu S L. Influence of fiber volume fraction on dynamic compressive properties of polyvinyl alcohol fiber reinforced cementitious composites[J]. Acta Materiae Compositae Sinica, 2021, 38(9): 3086-3100.(in Chinese) [百度学术]
ASTM C1018-97 Standard test method for flexural toughness and first-crack strength of fiber-reinforced concrete (using beam with third-point loading) [S]. West Conshohocken,USA: ASTM International, 1997. [百度学术]