【作者】 程红强；

【导师】 高丹盈；

【作者基本信息】 郑州大学 ， 水工结构工程， 2007， 博士

【摘要】 新老混凝土粘结是混凝土工程中经常涉及到的一个问题，对二者之间粘结界面性能的研究具有十分重要的理论意义和实际应用价值。本文结合国家基础性研究重大项目(攀登计划B)<<重大土木与水利工程安全性与耐久性基础研究>>之5．2(1)子课题：“新老混凝土的粘结机理和测试方法研究”，在普通混凝土与老混凝土粘结性能研究的基础上，对纤维混凝土与老混凝土的粘结性能进行系统地试验研究，探讨了纤维混凝土与老混凝土粘结剪切、劈拉基本力学性能及粘结面抗冻、抗渗耐久性能，同时运用断裂力学方法对纤维混凝土与老混凝土粘结Ⅱ型断裂性能进行了试验研究及理论分析，并通过约束收缩试验分析了纤维混凝土与老混凝土的粘结性能。本文的主要工作如下：1．进行了93个纤维混凝土与老混凝土Z型粘结试件及整体试件的直接剪切试验，主要考察纤维类型、纤维掺量、界面粗糙度、界面剂类型等对纤维混凝土与老混凝土粘结剪切性能的影响。结果表明，纤维的加入能明显改善新老混凝土粘结剪切性能，在纤维掺量的一定范围内，随着纤维掺量的增加，新老混凝土粘结剪切强度不断增加；同时，纤维的加入，改善了新老混凝土粘结面的剪切变形性能，剪切破坏时极限变形也逐渐增大。在试验基础上，探讨了纤维混凝土与老混凝土粘结剪切机理，得到了新老混凝土粘结面的剪应力～剪切滑移关系曲线，提出了纤维混凝土与老混凝土粘结剪切强度的计算公式。2．进行了111个纤维混凝土与老混凝土粘结立方体试件的劈拉试验，探讨了纤维类型、纤维掺量、界面粗糙度、界面剂类型、粘结界面方位等因素对粘结劈拉强度的影响。在钢纤维体积率的一定范围内，随着钢纤维体积率的增加，粘结劈拉强度不断增加，钢纤维体积率为1.5％(S3)时，粘结劈拉强度提高14.1％；钢纤维的加入，改善了新老混凝土粘结面的劈拉变形性能，劈拉破坏时极限变形也逐渐增大。随着聚丙烯纤维掺量的增加，粘结劈拉强度不断提高，聚丙烯纤维掺量为1.5Kg／m~3(P4)时，粘结劈拉强度提高18.1％。不同的粘结界面方位对纤维混凝土与老混凝土粘结性能有一定影响，新混凝土水平浇筑(粘结界面水平)时粘结劈拉强度较侧向浇筑(粘结界面竖直)时粘结劈拉强度要高，分析试验数据，建立了二者之间的关系表达式。在试验基础上，提出了纤维混凝土与老混凝土粘结劈拉强度计算公式。3．进行了219个纤维混凝土与老混凝土粘结立方体试件冻融循环后的劈拉试验，探讨了纤维混凝土与老混凝土粘结面的冻融损伤机理，分析了纤维类型、纤维掺量、界面粗糙度、界面剂类型等因素对粘结面抗冻劈拉性能的影响。结果表明，冻融循环作用下，钢纤维混凝土与聚丙烯纤维混凝土损伤不断累积，主要表现为随冻融循环次数的增加，相对动弹模逐渐下降、质量损失率增大和强度的不断降低。冻融循环对纤维混凝土与老混凝土粘结劈拉性能有较大影响。随冻融循环次数的增加，粘结劈拉强度急剧降低。纤维的加入，能有效提高新老混凝土粘结面冻融劈拉强度，当冻融循环次数一定时，在纤维掺量的一定范围内，随新混凝土中纤维掺量的增加，新老混凝土粘结劈拉强度不断增加；对不同的冻融循环次数，纤维对粘结劈拉强度的增加影响幅度不一样，冻融次数较大时，纤维对粘结劈拉强度的影响更加明显。根据对试验数据的分析，建立了冻融循环作用下纤维混凝土与老混凝土粘结劈拉强度计算公式。4．采用纤维混凝土与老混凝土粘结复合圆台体试件，进行了114个粘结试件的抗渗试验，主要考察纤维类型、纤维掺量、界面粗糙度、界面剂类型等因素对粘结面渗透性的影响，对粘结面的渗流特性及层面力学参数，如粘结面等效水力隙宽、渗透系数以及渗透规律进行了探讨。结果表明，老混凝土表面处理方式对纤维混凝土与老混凝土粘结面抗渗性能有一定影响；界面剂的使用有利于纤维混凝土与老混凝土粘结面抗渗性能的改善。纤维的加入能改善新老混凝土粘结面抗渗性能，随着纤维掺量在一定范围内的增加，粘结面抗渗性能不断增加，钢纤维体积率为1.5％时，钢纤维对粘结面抗渗性能的增益比达27％；聚丙烯纤维掺量为1.5Kg／m~3时，聚丙烯纤维对粘结面抗渗性能的增益比达60％。在试验基础上，提出了纤维混凝土与老混凝土粘结面平均渗透系数的计算公式。5．设计了适用于Ⅱ型断裂的带切口的双面直接剪切试件，进行了57个纤维混凝土与老混凝土粘结试件的Ⅱ型断裂试验及144个整体试件冻融循环条件下的Ⅱ型断裂试验，分析了纤维类型、纤维掺量、界面粗糙度、界面剂等因素对粘结面Ⅱ型断裂性能的影响及冻融循环次数对纤维混凝土Ⅱ型断裂性能的影响。结果表明，老混凝土表面处理方式对纤维混凝土与老混凝土粘结面Ⅱ型断裂性能有一定影响，随老混凝土表面粗糙度的增加，粘结面Ⅱ型断裂韧度逐渐增加；界面剂的使用能提高纤维混凝土与老混凝土粘结面Ⅱ型断裂韧度。新混凝土中加入一定量的纤维能有效改善新老混凝土粘结面的Ⅱ型断裂性能，随纤维掺量的增加，新老混凝土粘结面Ⅱ型断裂韧度逐渐增加，新混凝土中钢纤维体积率为2.0％时，粘结面Ⅱ型断裂韧度较普通混凝土与老混凝土粘结面Ⅱ型断裂韧度提高25％；新混凝土中聚丙烯纤维掺量为1.5Kg／m~3时，粘结面Ⅱ型断裂韧度较普通混凝土与老混凝土粘结Ⅱ型断裂韧度提高16.3％。冻融循环作用下纤维对混凝土Ⅱ型断裂韧度的提高影响更加明显。冻融循环对纤维混凝土Ⅱ型断裂韧度有较大影响，随冻融循环次数的增加，断裂韧度逐渐下降。在试验基础上，探讨了粘结面断裂损伤机理，提出了纤维混凝土整体试件在冻融循环作用下Ⅱ型断裂韧度计算公式及纤维混凝土与老混凝土粘结Ⅱ型断裂韧度计算公式。6．进行了162个纤维混凝土整体试件的自由收缩试验及162个纤维混凝土与老混凝土粘结试件的约束收缩试验，探讨了新、老混凝土收缩差异对粘结性能的影响以及纤维类型、纤维掺量等因素对粘结约束收缩的影响。结果表明，在新混凝土中加入一定量的钢纤维或聚丙烯纤维，能有效减小新老混凝土之间的收缩差异(且随纤维含量的增加，收缩差异减小效果逐渐明显)，从而减小粘结界面的收缩力，提高新老混凝土粘结性能。根据纤维混凝土自由收缩应变符合双曲线函数形式的试验结果，建立了纤维混凝土自由收缩应变的统一计算模式，提出了纤维混凝土与老混凝土粘结试件约束收缩力学模型。更多还原

【Abstract】 Bonding Fresh concrete to old concrete is a discussible question that often related to actual project of concrete engineering. The study on behavior of adherence interface has important value in terms of theory and engineering application. Referenced to the subject "Research on mechanism of adherence and measure method of young on old concrete", which is sub-subject of national momentous foundational research subject(Climbing Project B)—《The foundational study on safety and durability of huge civil and water conservancy engineering》, a systemic study of bonding fresh fiber reinforced concrete on old concrete is carried out in the thesis. A series of experiments and research on the mechanical properties of the bonding interface between fresh fiber concrete and old concrete, such as shearing and splitting tensile strength, has been conducted. And the durability of freezing-thaw resistance and impermeability on bonding interface has also been studied. The theory of fracture mechanics are adopted in the analysis, and some analysis have been carried out in shrinkage difference between fresh concrete and old concrete through restriction shrinkage test.The main contents of research are as follows:1. Using Z-shape specimens, the bonding shear property of fresh fiber reinforced concrete to old concrete was explored. 93 bonding specimens were experimented and the main influence factors were researched, such as the type of fiber, the content of fiber, roughness of interface and adhesive agent. The test results indicated that the bonding shear behavior of fresh to old concrete is improved with the using of fiber in fresh concrete. In some range of fiber content, with the increase of fiber content, the bonding shear strength of fresh to old concrete continuously increase, the shear deformation property of bonding interface is improved and the utmost deformation is increscent when the shear failure of bonding specimens occurred. Based on experiments, the relation curve of shear stress-deformation on bonding interface of fresh fiber concrete to old concrete and the calculating formulae of shear strength of fresh fiber concrete to old concrete were put forward.2.111 composite cubic specimens of fresh fiber concrete to old concrete were test for behavior researching of bonding splitting tensile and the main influence factors were analyzed. In some range of steel fiber volume fraction, with the increase of steel fiber content, the test results indicated that the bonding splitting tensile strength continuously increase and for steel fiber volume fraction being 1.5%, bonding splitting tensile strength of fresh steel fiber concrete to old concrete increase 14.1% compared with ordinary concrete to old concrete. On the other hand, the using of steel fiber in fresh concrete can improve behavior of deformation on splitting tensile testing. Polypropylene fiber in fresh concrete can increase bonding splitting tensile strength similar to steel fiber but for polypropylene fiber content being 1.5Kg/m~3, bonding splitting tensile strength of fresh polypropylene fiber concrete to old concrete increase 18.1% compared with ordinary concrete to old concrete. The orientation of adhesive interface has some influence on bonding strength that the bonding splitting tensile strength of level adhesive interface is higher than vertical adhesive interface. Based on experiments, the calculating formulae of splitting tensile strength of fresh fiber concrete to old concrete were put forward.3. Subjected to freeze-thaw cycle, splitting tensile test of 219 composite cubic specimens of fresh fiber concrete to old concrete were carried out. The freeze-thaw damage mechanism and main influence factors were analyzed. It was found that the damage of fiber concrete were continue cumulate under freeze-thaw cycle and the relative dynamic modulus and strength were reduced, but the mass losing of specimens were increase. The freeze-thaw cycle have important influence on bonding splitting tensile property of fresh fiber concrete to old concrete. With the increase of freeze-thaw cycle, the bonding splitting tensile decrease rapidly. The using of fiber in fresh concrete can increase bonding splitting tensile strength of bonding specimens subjected to freeze-thaw cycle. For certain freeze-thaw cycle, in some range, with the increase of fiber content in fresh concrete, the bonding splitting tensile strength continually increase and when the times of freeze-thaw cycle is higher, the influence of fiber is more prominent. Based on experiments, the calculating formulae of splitting tensile strength of new fiber concrete to old concrete subjected to freeze-thaw cycle were put forward.4. The composite impervious specimen was designed and 114 bonding specimens were presented. The main influence factors on bonding seepage properties of fresh fiber concrete to old concrete were discussed. Also the seepage properties and mechanical parameter, such as equivalent hydraulic fracture width, permeability coefficient and seepage law were explored. The test results indicated that the using of fiber in fresh concrete can improve the impermeability of fresh to old concrete. In some range, with the fiber content increase, the impermeability of bonding interface was enhanced. For steel fiber volume fraction being 1.5%, the increment ratio of steel fiber on bonding impermeability reached to 27% and for polypropylene fiber content being 1.5Kg/m~3, the increment ratio of polypropylene fiber on bonding impermeability reached to 60%. Based on experiments, the calculating formulae of average permeability coefficient of fresh fiber concrete to old concrete were put forward.5. The double direct shear specimen with notch was designed for the mode II fracture. 57 specimens of fresh fiber concrete to old concrete and 144 fiber concrete specimens subjected to freeze-thaw cycle were carried out mode II fracture test. The main influence factors on mode II fracture properties of fresh fiber concrete to old concrete were discussed. The test results indicated that the interfacial treatment method had some influence on mode II fracture properties of fresh fiber concrete to old concrete. With the interfacial roughness increase, the mode II fracture toughness of adhesive interface. The using of adhesive agent can improve the mode II fracture toughness of fresh fiber concrete to old concrete. Adding fiber to fresh concrete, the mode II fracture properties of fresh fiber concrete to old concrete were obviously improved. For steel fiber volume fraction being 2.0%, the mode II fracture toughness of fresh fiber concrete to old concrete increase 25% compared with ordinary concrete to old concrete, and for polypropylene fiber content being 1.5Kg/m~3, the increment was16.3%. Using of the fiber in concrete, the mode II fracture properties of concrete can be improved great. With the increase of fiber content, the mode II fracture toughness of concrete was continuously increased and this increment influence was more obvious under freeze-thaw cycle. The cycle of freeze-thaw has great influence on the mode II fracture toughness of fiber concrete and with the increase of cycle, the mode II fracture toughness was decrease. Based on experiments, the calculating formulae of the mode II fracture toughness of fiber concrete subjected to freeze-thaw cycle and adhesive interface of fresh fiber concrete to old concrete were put forward.6. Tests of free shrinkage of 162 specimens of fiber concrete and restriction shrinkage of 162 specimens of fresh fiber concrete to old concrete were carried out. The influence of shrinkage difference between fresh concrete and old concrete on adhesive property of fresh fiber concrete to old concrete was explored, and the influences of main factors on adhesive interface restriction shrinkage were discussed, such as the type of fiber and the content of fiber in fresh concrete. The experiment result indicated that the shrinkage difference between fresh concrete and old concrete can been effectively reduced by adding steel or polypropylene fiber to fresh concrete. These decreases of shrinkage difference can reduce shrinkage force on adhesive interface, as a result, the adhesive property of fresh fiber concrete to old concrete can been improved and these influence was more obviously with the increase of fiber content. The test results indicated that the free shrinkage strain of fiber concrete has a mode of hyperbola function and the unification calculating formulae of free shrinkage strain of fiber concrete were put forward. Based on experiments, a mechanics model about restriction shrinkage of fresh fiber concrete to old concrete has been found.更多还原