What Is Concrete Crack? 什么是混凝土裂缝？
Cracking is a phenomenon of “ a complete or incomplete separation of either concrete or masonry into two or more parts produced by breaking or fracturing”. This definition is given by American Concrete Institute (ACI). In this article, we will discuss various concrete crack repair methods.
开裂是一种现象，即“混凝土或砖石完全或不完全分离成两个或多个部分，由断裂或破裂产生”。该定义由美国混凝土协会 （ACI） 给出。在本文中，我们将讨论各种混凝土裂缝修复方法。
A structure is subjected to cracking or crack formation due to one or more factors like:-
由于一个或多个因素，结构会出现开裂或裂缝形成，例如：
·Temperature and plastic shrinkage.温度和塑性收缩。
·Thermal variations. 温度变化。
·Drying shrinkage. 干燥收缩。
·Chemical reactions. 化学反应。
·Weathering process. 老化过程。
·Construction overload, and施工超载，以及
·Poor construction practices like improper curing, inadequate water content in concrete mixture, inadequate formwork support, etc.
施工方法不当，如养护不当、混凝土混合物含水量不足、模板支撑不足等。
The development of cracks in structures is an indication of structural distress or a lack of durability. Due to cracks, the structure may face problems like weakening of structure, water leakage through cracks, etc.
结构中出现裂缝是结构不良或缺乏耐久性的迹象。由于裂缝，结构可能会面临结构弱化、裂缝漏水等问题。
The development of cracks is a big deal if observed and examined from a structural perspective. Other than the structural aspects, it also affects the interior as well as the exterior aesthetics of the structure.
如果从结构角度观察和检查，裂纹的发展是一件大事。除了结构方面，它还会影响结构的内部和外部美感。
Cracks affect the structure in many ways. So it is important to examine and repair the cracks as soon as possible. Crack repairs can be done by various methods, which depend upon the nature of cracks and the type of structure. There are many other factors on which suitable crack repair methods are chosen.
裂缝以多种方式影响结构。因此，尽快检查和修复裂缝很重要。裂缝修复可以通过各种方法完成，这取决于裂缝的性质和结构类型。选择合适的裂纹修复方法还有许多其他因素。
Concrete Crack Repair Methods
混凝土裂缝修复方法
Crack repair can be done using different methods and techniques. They are as follows:-
裂缝修复可以使用不同的方法和技术来完成。它们如下：
1.Epoxy injection grouting 环氧树脂注浆
2.Routing and sealing 布线和密封
3.Flexible sealing 柔性密封
4.Stitching 拼接
5.Providing additional reinforcement提供额外的加固
6.Drilling and plugging 钻孔和封堵
7.Prestressing steel 预应力
8.Grouting 灌浆
Let us learn each method of crack repair in detail below:
让我们在下面详细了解每种裂缝修复方法：
1. Epoxy Injection 1. 环氧树脂注射
Epoxy compounds possess properties like high compressive strength, tensile strength, and bond strength. They are widely used for making repair mortar.
环氧化合物具有高抗压强度、拉伸强度和粘结强度等特性。它们广泛用于制造修补砂浆。
Epoxy compounds are not suitable for concrete crack repairs, especially for external applications. It is because epoxy compounds are not compatible with various weather conditions and temperature changes.
环氧化合物不适用于混凝土裂缝修复，尤其是外部应用。这是因为环氧化合物与各种天气条件和温度变化不相容。
Epoxies can also be used on wet surfaces. Wet surfaces require some special grade of epoxy. It is way too costly than the normal epoxy compounds.
环氧树脂也可用于潮湿的表面。潮湿的表面需要一些特殊等级的环氧树脂。它比普通的环氧化合物贵得多。
Epoxy compounds can be used to seal cracks as narrow as 0.002 inch which is approximately 0.05 mm. It is an effective method for crack repair. The procedure for crack repair by epoxy injection grouting is as follows:-
环氧化合物可用于密封窄至 0.002 英寸（约 0.05 毫米）的裂缝。是裂纹修复的有效方法。环氧树脂注浆修复裂缝的程序如下：
·Clean the cracks. 清洁裂缝。
·Seal the surfaces. 密封表面。
·Install the entry and venting points.安装入口和通风点。
·Mix the epoxy compound. 混合环氧化合物。
·Inject the epoxy. 注入环氧树脂。
·Remove the surface seal. 拆下表面密封。
2. Routing And Sealing 2. 布线和密封
The crack sealers used for repair of cracks should ensure structural integrity and serviceability. Additionally, they should be able to protect from ingress of harmful substances.
用于修复裂缝的裂缝密封剂应确保结构完整性和可维护性。此外，它们应该能够防止有害物质进入。
This technique of crack repair is used in conditions where remedial repair is required and structural repair is not needed. In this method, the original crack formed on the surface is enlarged, which is known as routing, and then after the crack is sealed using a suitable joint sealant.
这种裂缝修复技术用于需要补救性修复和不需要结构修复的条件下。在这种方法中，将表面形成的原始裂纹扩大，称为布线，然后在裂纹密封后使用合适的接缝密封胶进行密封。
This method is commonly used as its procedure is relatively simple and requires no special training for repairing the cracks. It is mostly used for flat surfaces like floors and pavements, respectively. It can be used on vertical and curved surfaces.
这种方法是常用的，因为它的程序相对简单，不需要特殊的培训来修复裂缝。它主要用于地板和人行道等平面。它可用于垂直和曲面。
This method is suitable for repairing both, fine cracks and large cracks as well. The sealants used for the treatment of concrete may be of several materials, including epoxies, silicones, and asphaltic materials.
这种方法适用于修复细裂纹和大裂纹。用于处理混凝土的密封剂可以是多种材料，包括环氧树脂、有机硅和沥青材料。
Cement grouts are generally avoided as they are likely to crack. The sealant should be applied depending upon the use of the area on which it is applied.
通常避免使用水泥灌浆，因为它们可能会开裂。密封剂的应用应根据其应用区域的用途而定。
In this method, a groove of 6 mm to 25 mm depth is prepared by means of concrete saw a hand tool or a pneumatic tool. Then the groove is cleaned by water blasting or air blasting.
在这种方法中，通过混凝土锯、手动工具或气动工具制备 6 mm 至 25 mm 深的凹槽。然后通过喷水或空气喷射清洁凹槽。
The groove is allowed to dry. Once it is completely dried, the sealant is placed in the groove and is allowed to cure. After the surface is cured properly, it can again be used.
让凹槽干燥。完全干燥后，将密封剂放入凹槽中并使其固化。表面固化后，可以再次使用。
3. Flexible Sealing 3.
柔性密封
In this method, a recess is cut along the line of the crack and it is filled up with a suitable flexible material. The breadth of recess and the sealant’s strength capacity determine the joint movement that can be accommodated.
在这种方法中，沿着裂缝线切割一个凹槽，并用合适的柔性材料填充。凹槽的宽度和密封胶的强度能力决定了可以容纳的关节运动。
So, the sealant bond must have a suitable width and shape for the expected movement. A bond breaker should be used to prevent the sealing material from bonding to the bottom of the recess.
因此，密封胶粘接必须具有适合预期运动的宽度和形状。应使用断接器防止密封材料粘接到凹槽底部。
4. Stitching 4. 缝合
In this technique, holes are drilled on both sides of the crack. The holes are cleaned up, and the legs of stitching dogs are anchored in it using either a non-shrink grout or an epoxy-resin-based bonding system. The stitching dogs should be variable in length and/ or orientation.
在这种技术中，在裂缝的两侧钻孔。这些孔被清理干净，缝合狗的腿被固定在其中，使用非收缩灌浆或基于环氧树脂的粘合系统。缝合狗的长度和/或方向应可变。
It should be located in such a way that the tension transmitted across the crack is spread over an area and not applied to a single point. This method is preferred when the tensile strength is to be re-established across major cracks.
它的位置应使穿过裂缝的张力分布在一个区域上，而不是施加到单个点上。当要在主要裂纹上重新建立抗拉强度时，这种方法是首选。
5. Providing Additional Reinforcement
5. 提供额外的加固
a) By Conventional Reinforcement
a） 通过常规加固
This method of crack repair is used to repair the cracks in reinforced cement concrete. In this method, first of all, the crack is sealed using a sealant. Then, holes of approximately 20 mm in diameter are drilled so that it intersects the crack plane at approximately 90 degrees.
这种裂缝修复方法用于修复钢筋水泥混凝土中的裂缝。在这种方法中，首先使用密封剂密封裂缝。然后，钻出直径约为 20 毫米的孔，使其与裂纹平面相交约 90 度。
The holes are then filled up with epoxy reinforcement bars of 12 mm or 16 mm diameter are placed into that, extending at least 500 mm on each side of the crack. The spacing of reinforcement bars is decided on the severity of cracks or as suggested by engineers.
然后用直径为 12 毫米或 16 毫米的环氧树脂增强棒填充孔，在裂缝的每一侧延伸至少 500 毫米。钢筋的间距取决于裂缝的严重程度或工程师的建议。
b. By Prestressing Steel b.通过预应力钢
When a major part of a member is to be strengthened or a crack is to be treated, this method is often the preferred method. This method uses prestressing strands or reinforcement bars to apply a compressive force. Sufficient anchorage should be provided for the prestressing steel.
当要加固构件的主要部分或要处理裂纹时，这种方法通常是首选方法。这种方法使用预应力钢绞线或钢筋来施加压缩力。应为预应力钢提供足够的锚固。
6. Drilling And Plugging 6. 钻孔和封堵
In this method, a hole of 50 mm to 75 mm diameter is drilled down the length of the crack. The hole is thoroughly cleaned and filled with grout.
在这种方法中，沿着裂纹的长度钻一个直径为 50 mm 至 75 mm 的孔。彻底清洁孔并填充灌浆。
The grout key is responsible for preventing the transverse movements of the concrete sections adjacent to the crack. The key also helps to reduce heavy water leakage through the cracks and loss of soil from behind the leaking wall.
灌浆键负责防止裂缝附近混凝土部分的横向移动。灌浆键还有助于减少通过裂缝的大量漏水和漏水墙后面的土壤流失。
7. Grouting 7. 灌浆
Based on grout material used, there are three methods for crack repair by grouting. They are as follows:-
根据所使用的灌浆材料，灌浆修复裂缝的方法有三种。它们如下：
1.Portland cement grouting 硅酸盐水泥灌浆
2.Chemical grouting 化学灌浆
3.Epoxy grouting 环氧树脂灌浆
Portland Cement Grouting 硅酸盐水泥灌浆
Portland cement grout is used to repair wide cracks, especially in structures like gravity dams and thick concrete walls. Portland cement grout prevents water leakage, but it does not bond the cracks structurally.
波特兰水泥灌浆用于修复宽裂缝，特别是在重力坝和厚混凝土墙等结构中。硅酸盐水泥灌浆可防止漏水，但不会在结构上粘结裂缝。
The procedure for this method is as follows:
此方法的步骤如下：
• Clean the cracks by air jetting or water jetting.
• 通过喷气或喷水清洁裂缝。
• Installation of grout nipples at suitable intervals and sealing of the cracks with a suitable sealant.
• 以适当的间隔安装灌浆接头，并用合适的密封剂密封裂缝。
• Grout the affected area with Portland cement grout and let it dry.
• 用波特兰水泥灌浆灌浆受影响的区域灌浆并使其干燥。
• The Portland cement grout generally contains cement and water or cement, water, and sand. Sometimes additives such as water reducers are added to the grout mixture to improve its properties.
• 波特兰水泥灌浆通常含有水泥和水或水泥、水和沙子。有时在灌浆混合物中添加减水剂等添加剂以改善其性能。
Chemical Grouting 化学灌浆
For chemical grouting, chemicals such as sodium silicate, urethane, and acrylamide are used. Two or more chemicals are mixed to form a new chemical, which may be in the form of gel, a solid precipitate, or foam. The chemical grouts can be used in moist conditions also because of their properties to resist moisture.
对于化学灌浆，使用硅酸钠、氨基甲酸酯和丙烯酰胺等化学品。将两种或多种化学物质混合形成一种新的化学物质，其形式可以是凝胶、固体沉淀或泡沫。化学灌浆可以在潮湿条件下使用，因为它们具有防潮的特性。