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The ties for the anchored bulkhead shown in Figure 9-16 are located four feet from the top of the sheetpiling and are spaced at fifteen feet centers. The end of the tie is secured to two anchor piles raked as indicated. The active earth pressure may be assumed equivalent to a fluid pressure of 30 pounds per square foot per foot and passive pressure may be assumed equivalent to a fluid pressure of 400 pounds per square foot per the depth of penetration indicated, calculate the value of the total active pressure on the back of the wall, the value of the total passive pressure on the front of the wall, and the moment of all forces about the tie point. Determine the forces in the tie, the maximum shear and the maximum moment in the wall, and the forces in the compression and tension anchor piles. The fill behind the retaining wall in Figure 9-17 has a unit weight of 110 pounds per cubic foot with an equivalent fluid pressure of 30 pounds per square foot per foot. Passive earth pressure may be assumed equivalent to a fluid pressure of 300 pounds per square foot per foot and the coefficient of friction at the underside of the base is . All concrete has a compressive strength of 3000 pounds per square inch and reinforcement consists of Grade 60 deformed bars. Neglecting the effects of the shear key, determine the factor of safety against overturning and the bearing pressure distribution under the base. Using factored loading, determine the reinforcement, calculate the minimum depth of the shear key to provide a factor of friction against mass concrete gravity dam shown in Figure 9-18 is 20 feet high. Determine the minimum base width if no tensile stresses are allowed in the concrete and the water level is at the top of the dam wall. Details of a counterfort retaining wall are shown in Figure 9-19. The fill behind the wall has an equivalent fluid pressure of 40 pounds per square inch and reinforcement consists of Grade 60 determined bars. Determine the horizontal reinforcement required at the base of the stem in the front and earth faces, the reinforcement required at the base of the the required penetration of the sheetpile retaining wall shown in Figure 9-20 if active earth pressure may be assumed equivalent to a fluid pressure of 35 pounds per square foot per foot and passive pressure may be assumed equivalent to a fluid pressure of 450 pounds per square foot per foot. Calculate the force in the tie and the location and magnitude of the maximum shear and the maximum moment in the shestpiling. 翻译：由于对土木工程方面没有研究，所以很多专业术语是靠GOOLE差找和个人猜测，可能会不尽准确，甚至有所错误，但是本着学习的态度，我还是很认真地翻译了。我猜测，这可能是某本英文版建筑教材后面的习题吧？所以我用了习题的语气做的翻译。望对你有所帮助。图9-16所示的防水隔层定点的联结点位于板桩顶部4英尺处，且以15英尺为间隔居中隔开。联结点的末端被两个锚杆斜拉以保证安全。设松软土层的主动压力等同于30磅每平方英尺每英尺的液压，被动压力等同于400磅每平方英尺每英尺的液压。在必要灌注深度的条件下，求墙体背面主动压力总值，墙体正面被动压力总值，以及所有连接点的扭矩力。测定联结处所受的力，墙体的最大抗减承载力，最大瞬间扭矩力，和锚杆的压拉力。图9-17所示的挡土墙后填充物单位重量为110磅每立方英尺，具有约等于30磅每平方英尺每英尺的液压的压力。设被动土压约等于300磅每平方英尺每英尺的液压以及底部摩擦系数为；所有混凝土抗压强度为3000磅每立方英寸并且由级别60的不规则钢筋加固；忽略剪切键。求底部填充物的抗破坏及承压安全系数。 用你所计算的系数，求加固强度，计算在抗滑动摩擦系数为情况下，剪切键的最小深度。图9-18所示的的混凝土浇筑拱坝的高为20英尺。假设混凝土中不允许出现拉力、且水位高度刚好在大坝顶部，求其底宽的最小值。图9-19中给出了拱柱型挡土墙的具体数值，墙后填充物具有约等于40磅每平方英尺每英尺的液压的压力，且由级别60的不规则钢筋加固。求正面茎干底部以和地面水平加固要求、以及拱柱底部加固要求。求图9-20所示的板桩挡土墙的必要灌注深度。假设其中：主动土压约等于35磅每平方英尺每英尺的液压、被动压力约等于450磅每平方英尺每英尺的液压。计算板桩最大剪切和最小剪切情况下，接点处受的力，以及接点位置和数量
Traditional Construction ProceduresAs mentioned before, construction under the traditional construction procedure is performed by contractors. While they would like to satisfy the owner and the building designers, contractors have the main objective of making a profit. Hence, their initial task is to prepare a bid price based on an accurate estimate of construction costs. This requires development of a concept for performance of the work and a construction time schedule. After a contract has been awarded, contractors must furnish and pay for all materials, equipment, power, labor, and supervision required for construction. The owner compensates the contractors for construction costs and general contractor assumes overall responsibility for construction of a building. The contractor engages subcontractors who take responsibility for the work of the various trades required for construction. For example, a plumbing contractor installs the plumbing, an electrical contractor installs the electrical system, and an elevator contractor installs elevators. Their contracts are with the general contractor, and they are paid by the general , in addition to a general contractor, the owner contracts separately with specialty contractors, such as electrical and mechanical contractors, who perform a substantial amount of the work require for a building. Such contractors are called prime contractors. Their work is scheduled and coordinated by the general contractor, but they are paid directly by the also, the owner may use the design-build method and award a contract to an organization for both the design and construction of a building. Such organizations are called design-build contractors. One variation of this type of contract is employed by developers of groups of one-family homes or low-rise apartment buildings. The homebuilder designs and constructs the dwellings, but the design is substantially completed before owners purchase the of the construction procedure often is difficult. Consequently, some owners seek assistance from an expert, called a professional construction manager, with extensive construction experience, who receives a fee. The construction manager negotiates with general contractors and helps select one to construct the building. Managers usually also supervise selection of subcontractors. During construction, they help control costs, expedite equipment and material deliveries, and keep the work on schedule. In some cases, instead, the owner may prefer o engage a construction program manager, to assist in administrating both design and contractors employ labor that may or may not be unionized. Unionized craftspeople are members of unions that are organized by construction trades, such as carpenter, plumber, and electrician unions, Union members will perform only the work assigned to their construction, all work should be inspected. For this purpose, the owner, often through the architect and consultants, engages inspectors. The field inspectors may be placed under the control of an owner’s representative, who may be titled clerk of the works, architect’s superintendent, engineer’s superintendent, or resident engineer. The inspectors have the responsibility of ensuring that construction meets the requirements of the contract documents and is performed under safe conditions. Such inspections may be made at frequent addition, inspections also are made by representatives of one or more governmental agencies. They have the responsibility of ensuring that construction meets legal requirements and have little or no concern with detailed conformance with the contract documents. Such legal inspections are made periodically or at the end of certain stages of construction. One agency that will make frequent inspections is the local or state building department, whichever has jurisdiction. The purpose of these inspections is to ensure conformance with the local or state building is a description of the basic traditional construction procedure for a multistory the award of a construction contract to a general contractor, the owner may ask the contractor to start a portion of the work before signing of the contract by giving the contractor a letter of intent or after signing of the contract by issuing a written notice to proceed. The contractor then obtains construction permits, as required, form governmental agencies, such as the local building, water, sewer, and highway general contractor plans and schedules construction operations in detail and mobilizes equipment and personnel for the project. Subcontractors are notified of the contract award and issued letters of intent or awarded subcontracts, then are given, at appropriate times, notices to construction starts, the general contractor orders a survey to be made of adjacent structures and terrain, both for the record and to become knowledgeable of local conditions. A survey is then made to lay out offices for the contractor are erected on or near the site. If desirable for safety reasons to protect passersby, the required to be removed from the site are demolished and the debris is carted , the site is prepared to receive the building. This work may involve grading the top surface to bring it to the proper elevations, excavating to required depths for basement and foundations, and shifting of utility piping. For deep excavations, earth sides are braced and the bottom is construction starts with the placement of foundations, on which the building rests. This is followed by the erection of load-bearing walls and structural framing. Depending on the height of the building, ladders, stairs, or elevators may be installed to enable construction personnel to travel from floor to floor eventually to the roof. Also, hoists may be installed to lift materials to upper levels. If needed, temporary flooring may be placed for use of the building rises, pipes, ducts, and electric conduit and wiring are installed. Then, permanent floors, exterior walls, and windows are constructed. At the appropriate time, permanent elevators are installed. If required, fireproofing is placed for steel framing. Next, fixed partitions are built and the roof and its covering are put is place,Finishing operations follow. There include installation of the following: ceilings; tile; wallboard; wall paneling; plumbing fixtures; heating furnaces; air-conditioning equipment; heating and cooling devices for rooms; escalators; floor coverings; window glass; movable partitions; doors; finishing hardware; electrical equipment and apparatus, including lighting fixtures, switches, transformers, and controls; and other items called for in the drawings and specifications. Field offices, fences, bridges, and other temporary construction must be removed from the site. Utilities, such as gas, electricity, and water, are hooked up to the building. The sit is landscaped and paved. Finally, the building interior is painted and owner’s representatives then give the building a final inspection. If they find that the structure conforms with the contract documents, the owner accepts the project and gives the general contractor final payment on issuance by the building department of a certificate of occupancy, which indicates that the completed building meets building-code requirements.传统的施工程序众所周知，在传统的施工程序中进行施工的承包商。尽管他们想满足业主和建筑设计师的要求，但是最终还是以赚取利润为主要目标的。因此，他们最初的任务是对编写投标价格的建筑成本进行准确的估计。这就需要进行前期调查的工作并且做出施工时间表。等合约批出后，施工方必须提供所有材料并支付其费用，设备，电力，劳动力。业主此时需要进行必要的监督。一个总承包商承担一个建筑整体的责任。从事分包的承建商则需承担建造工程所需的各个工作。例如，管道承包商安装水管，电业承办商安装电气系统，电梯则由电梯承包商安装。他们与总承包商签订合同，费用由总承包商支付。有时候，除了一个总承包商，还有各种专业承包商，如电气和机械承包商，执行工作时需要与业主签订合同。这种承包商被称为间接承包商。他们的工作，由总承包商协调，但它们都是由业主直接联系。还有些时候，业主可以使用设计建造方法同时兼有设计和建筑施工单位的职能。这些单位被称为设计建造承包商。这方面的一个类型的合同聘用的变化是由一户住宅或低层住宅建筑群的开发。在房屋建筑设计和建造的住房，但设计之前需要由购买房屋的业主完成。施工过程管理往往是困难的。因此，一些业主会去寻求专家的协助，这些专家被称为专业施工经理，他们具有丰富的施工经验。施工经理与总承包商进行谈判，并选择其中一个项目。施工经理通常还监督分包商。在施工期间，它们有助于控制成本，加快运送设备和材料，并保持工作的进度。在依法行政，协助设计和建设的情况下，业主可以选择从事建筑项目经理。建筑承包商雇用的劳动力，一般有大工和小工。大工再建筑工程中从事技术活，如木工，管道工，工会成员和电工工会，小工则执行了分配给他们的工作。在施工期间，一切工作都要验收。因此，业主通过建筑师和监理经常进行督查。可能是名为工程员，建筑师或驻地工程师。作为业主的代表实地视察。核查人员必须确保工程符合合同文件的要求，并在安全的条件下进行的责任。这种检查可作出重复。此外，验收还是需要一个或多个政府机构的代表。他们必须确保工程符合法律要求，并负责检查与合同文件是否一致。这种视察一般定期或在某些阶段施工结束以后进行。地方或国家建设部门具有管辖权。这些检查的目的是确保符合当地或国家的建筑规范。以下是传统多层建筑施工的基本程序。建造开始后合同授予开发商，业主可要求开发商开始施工之前签约给或之后签约发出书面通知的同时另一部分工作继续进行。紧接着施工方根据需要获取建筑许可证，例如当地的建设，供水，污水处理，政府机构和公路部门。总承包商的计划和进度详细施工作业以及动员项目设备和人员。分包商得到通知后，做出签订合同的意向或授予分包合同书，然后给出在适当的时候进行通知。在施工前启动，总承包商要进行的一项调查就是邻近结构和地形，这些都要记录在案，并要熟悉当地情况。这项调查结束以后，随即进行布局建设。承建商的现场办事处都建在施工现场或附近。为了安全起见，必须从脚手架上移除的东西，产生的碎片都要运走。下一步，该网架是为建设工程准备的。这项工作为地下室开挖和基础开挖的深度，以及公用事业管道转移找到正确的标高。深挖掘，土方支撑，底部排出。建筑开始于基础上，然后是承重墙和结构框架的施工。梯子，楼梯，或电梯的安装，可让施工人员往返于各个楼层。此外，可安装卷扬机来运送材料。由于建筑高度的上升，管道，电力管道和线路安装以及永久地板，外墙，窗户和构造的影响。在适当的时候，永久的电梯安装。再需要的情况下可以安装防火卷帘。其次，屋顶等地方也需要安装。精加工工序安装有包括以下内容：天花板，瓷砖，墙板，墙壁镶板，水管装置，加热炉，空气调节设备，加热和冷却室装置;自动扶梯;地板，窗户玻璃;活动板，门;电气设备和仪器，包括照明灯具，开关，变压器，控制器，遵照项目的图纸和规格。外地办事处，围栏，桥梁和其他临时建筑，公共设备，如天然气，电力管道，水管，都连接到建筑上。最后，是建筑物内部的打扫和清洗。业主的代表，会给建设工程作最后检查。如果他们满意并认为符合合同文件，那么业主接受该项目，并交给总承包商的一个占用证书，这表明，总承包商已完成建设，建设部门再根据建筑规范的要求发放最后付款。
The principle of the analysis of concrete structures, the implementation of the correct application of the project, and grasp of the Xu-shaped concrete shrinkage and creep of the process, control of harmful cracks in concrete to enhance the structural safety and durability.
Abstract: In the modern construction of concrete plays an important role, but the concrete cracks are more common. This article analyzes the causes of concrete cracks is proposed measures to control and prevent the cracks, and curing of the concrete problems early. Key words: concrete crack; cracks; Cracks; conservation First, micro-cracks in concrete Cracks in reinforced concrete structures is to work with. Rather, the hardening process of concrete in the condensation, there exist micro-cracks, because the concrete in the cement and aggregate changes in temperature and humidity conditions to produce the volume of non-uniform deformation, and they bonded together and can not free-form deformation, so the formation of mutual restraint stress; Once the cement and aggregate constraint between the stress is greater than the bond strength and tensile strength of cement itself, will produce micro-cracks. Second, the causes of concrete cracks Concrete cracks are the result of the development of micro-cracks. Concrete cracks for many reasons, for its part, considered to be bound by the deformation of concrete due to tensile stress than the material's sake. 1. Optional inappropriate material defects and the formation of cracks. Expired cement, aggregate excess mud, with active SiO 2 , high alkali cement, limestone aggregate, cement hydration heat and so on. 2. Construction of mishandling the formation of defects and cracks. Plastic concrete sink, was the top bar of the resistance, the formation of cracks along the reinforcement; concrete vibration is not dense, there cellular, easy to form the starting point for a variety of stress fractures; concrete mixer, transit time is too long, so that water evaporation, causing low slump concrete pouring, making the concrete volume in the mesh irregular cracks; rapid drying of concrete made when the initial curing of concrete contact with the atmosphere in the irregular mesh surface cracks; early form removal, concrete not yet established sufficient strength to impose its own components in the actual gravity load, prone to all kinds of stress cracks. 3. Because of the force components, deformation and crack formation of defects. Center tension; center compression; bending; shear; by punching; beam concrete shrinkage and temperature deformation; plate of concrete shrinkage and temperature deformation; in reinforced concrete, the tensile stress is mainly borne by the reinforced concrete is exposed stress. In plain concrete or reinforced concrete on the edges if the tensile stress within the structure there shall be to rely on concrete to bear. General design requirements in both the tensile stress does not appear or appear only very small tensile stress. However, the maximum temperature of concrete in construction to the operation of the cooling period of steady temperature, often caused by a large concrete internal tensile stress. 4. Because of environmental factors affect the formation of defects and cracks. Mainly temperature and humidity changes, the brittleness of concrete and uneven, as well as unreasonable structure, failure of raw materials (such as alkali-aggregate reaction), template deformation, differential settlement of foundation. Concrete dissolution cycles many times by the freeze, the stress generated in the concrete, and promote the development of existing cracks, loose structure, surface cracks, surface spalling or overall collapse. Third, measures to control and prevent the cracks 1. Of cement, water, aggregate, admixtures, reinforcement materials, the improper selection of the formation of cracks on the entry of raw materials must be in accordance with national standards for strict inspection and acceptance of the approach to prevention, where the unqualified use of defective materials shall be , or reduce the level of test use; of these have occurred due to improper selection of materials defects or cracks in concrete produced must be observed in detail for the long term (due to some problems take a while to find), carefully identify its causes and Quality of the problem, study and formulate their treatment and reinforcement. This is because once occurred due to improper material selection, quality problems, often with the universal reason. 2. As long transport time of concrete mixing, pouring too fast, the vibration is not real, it is improper construction joint, move the template the formation of cracks and other reasons can follow the "concrete order" strict implementation of concrete mixing, transport, pouring, vibration pound set and the old concrete construction joint connection. Templates, and form removal, and conservation requirements to prevent, the occurrence of such cracks in the component have been, but also distinguish the type of component, component of the force characteristics of the site where the cracks and the extent of serious cracks were commonly used in concrete cracks reinforcement measures or by filling concrete, steel anchor reinforcement, and even stick steel reinforcement, prestressed reinforcement remedial measures. 3. Due to dry weather, the initial maintenance is not good, the early cold concrete and large changes in temperature and humidity of the cracks were used to enhance the natural hardening process of concrete Results conservation, conservation of heat storage, the use of air-entraining agent to uniform distribution of air bubbles inside the concrete, measures such as temperature expansion joint repair reserved. Severe cold components, some should be removed, some should be reinforced before being used. 4. Because the components have to withstand loads too wide cracks, reasonably designed to prevent the emergence of these cracks; cracks have been too broad component appears to be reinforced by strengthening measures. 5. The foundation of unequal settlement of large cracks too broad and reasonably in the design of the building when checking in the use phase of the settlement to prevent the emergence of these cracks, these cracks have occurred on the structure, to use ground-based control measures proper handling of the foundation, then building the structure reinforcement measures adopted to solve. 6. On the environmental conditions and changes in the use of the crack occurred, according to different properties to different control measures, such as: (1) the use of temperature and humidity changes during the formation of cracks, usually difficult to eradicate, to adopt the protection of reinforced concrete measures to reduce atmospheric humidity changes of the component is appropriate; (2) The cracks resulting from repeated freezing and thawing, in addition to defects and damage has been formed in part to be reinforced or reinforced, but should add insulation on the cold concrete measures; (3) The corrosive medium in the resulting defects and damage a large area, in addition to corrosion and damage should be removed by the site to be reinforced or reinforced, shall use the acid water glass slag cement concrete or concrete overlay to protect; (4) damage due to earthquake seismic structural measures should be adopted to prevent; have been generated by the earthquake damage is not severe earthquake damaged buildings may refer to repair and reinforcement of the solution to the problem. In addition, temperature control and improved from the constraints of the two aspects. Used to improve the aggregate gradation, with a dry hard concrete, mixed with mixture, add air-entraining agent or a plasticizing agent measures to reduce the amount of cement in concrete; water when mixing concrete or gravel with water cooling to reduce the concrete pouring temperature; hot days when the pouring of concrete pouring to reduce the thickness of heat by pouring level; in the concrete laying pipes, pass into the cold water temperature; set reasonable removal time, the surface heat when temperatures plunged to avoid dramatic concrete surface temperature gradient ; Construction of Concrete Blocks and long-term exposure to surface or thin-walled structure, insulation measures taken in the cold season. Measures to improve the constraints are: a reasonable parting block; to avoid excessive fluctuations basis; reasonable arrangements for the construction process, to avoid the excessive height and long-term exposure to the side. In addition, to improve the performance of concrete and improve the crack resistance, enhance conservation, to prevent surface shrinkage, in particular, to ensure the quality of concrete is very important to prevent fractures, special attention should be avoided through the cracks, appears to restore its structural integrity is difficulties, so the construction should be to prevent the occurrence of cracks in the main cross-cutting. Fourth, early curing of concrete Practice shows that cracks in concrete common, most of the surface cracks of different depth, mainly because of the temperature gradient caused by the sudden drop in temperature in cold areas are also easy to form cracks. Therefore, the concrete surface of the insulation to prevent early cracking is particularly important. From the viewpoint of thermal stress, thermal insulation should meet the following requirements: (1) prevent the concrete and the concrete surface temperature difference between inside and outside the gradient, to prevent surface cracks; (2) to prevent the concrete super cool, should try to try to make concrete the construction period of not less than the minimum temperature on the stability of the temperature of concrete used; (3) to prevent cold and old concrete to reduce the constraints between the new and old concrete. Early curing of concrete, the main purpose is to maintain proper temperature and humidity conditions in order to achieve the effect of two aspects, one of the concrete from adverse temperature and humidity deformation of the invasion, to prevent the harmful shrinkage and shrinkage. On the one hand to smooth the cement hydration in order to meet the design strength and crack resistance. V. Conclusion Cracks in concrete above the relationship between the various effects of the theory and practice discussed, although the academic cracks in the concrete and calculation methods are different theories, but for specific advice for prevention and improvement measures more unified, but in practice of effects are good, concrete construction depends on our seeing much comparison, more analysis after problems, and more sum up, with a variety of preventive treatment measures, concrete cracks are completely avoidable.
Abstract: In the modern construction of concrete plays an important role, but the concrete cracks are more common. This article analyzes the causes of concrete cracks is proposed measures to control and prevent the cracks, and curing of the concrete problems early. Key words: concrete crack; cracks; Cracks; conservation First, micro-cracks in concrete Cracks in reinforced concrete structures is to work with. Rather, the hardening process of concrete in the condensation, there exist micro-cracks, because the concrete in the cement and aggregate changes in temperature and humidity conditions to produce the volume of non-uniform deformation, and they bonded together and can not free-form deformation, so the formation of mutual restraint stress; Once the cement and aggregate constraint between the stress is greater than the bond strength and tensile strength of cement itself, will produce micro-cracks. Second, the causes of concrete cracks Concrete cracks are the result of the development of micro-cracks. Concrete cracks for many reasons, for its part, considered to be bound by the deformation of concrete due to tensile stress than the material's sake. 1. Optional inappropriate material defects and the formation of cracks. Expired cement, aggregate excess mud, with active SiO 2 , high alkali cement, limestone aggregate, cement hydration heat and so on. 2. Construction of mishandling the formation of defects and cracks. Plastic concrete sink, was the top bar of the resistance, the formation of cracks along the reinforcement; concrete vibration is not dense, there cellular, easy to form the starting point for a variety of stress fractures; concrete mixer, transit time is too long, so that water evaporation, causing low slump concrete pouring, making the concrete volume in the mesh irregular cracks; rapid drying of concrete made when the initial curing of concrete contact with the atmosphere in the irregular mesh surface cracks; early form removal, concrete not yet established sufficient strength to impose its own components in the actual gravity load, prone to all kinds of stress cracks. 3. Because of the force components, deformation and crack formation of defects. Center tension; center compression; bending; shear; by punching; beam concrete shrinkage and temperature deformation; plate of concrete shrinkage and temperature deformation; in reinforced concrete, the tensile stress is mainly borne by the reinforced concrete is exposed stress. In plain concrete or reinforced concrete on the edges if the tensile stress within the structure there shall be to rely on concrete to bear. General design requirements in both the tensile stress does not appear or appear only very small tensile stress. However, the maximum temperature of concrete in construction to the operation of the cooling period of steady temperature, often caused by a large concrete internal tensile stress. 4. Because of environmental factors affect the formation of defects and cracks. Mainly temperature and humidity changes, the brittleness of concrete and uneven, as well as unreasonable structure, failure of raw materials (such as alkali-aggregate reaction), template deformation, differential settlement of foundation. Concrete dissolution cycles many times by the freeze, the stress generated in the concrete, and promote the development of existing cracks, loose structure, surface cracks, surface spalling or overall collapse. Third, measures to control and prevent the cracks 1. Of cement, water, aggregate, admixtures, reinforcement materials, the improper selection of the formation of cracks on the entry of raw materials must be in accordance with national standards for strict inspection and acceptance of the approach to prevention, where the unqualified use of defective materials shall be , or reduce the level of test use; of these have occurred due to improper selection of materials defects or cracks in concrete produced must be observed in detail for the long term (due to some problems take a while to find), carefully identify its causes and Quality of the problem, study and formulate their treatment and reinforcement. This is because once occurred due to improper material selection, quality problems, often with the universal reason. 2. As long transport time of concrete mixing, pouring too fast, the vibration is not real, it is improper construction joint, move the template the formation of cracks and other reasons can follow the "concrete order" strict implementation of concrete mixing, transport, pouring, vibration pound set and the old concrete construction joint connection. Templates, and form removal, and conservation requirements to prevent, the occurrence of such cracks in the component have been, but also distinguish the type of component, component of the force characteristics of the site where the cracks and the extent of serious cracks were commonly used in concrete cracks reinforcement measures or by filling concrete, steel anchor reinforcement, and even stick steel reinforcement, prestressed reinforcement remedial measures. 3. Due to dry weather, the initial maintenance is not good, the early cold concrete and large changes in temperature and humidity of the cracks were used to enhance the natural hardening process of concrete Results conservation, conservation of heat storage, the use of air-entraining agent to uniform distribution of air bubbles inside the concrete, measures such as temperature expansion joint repair reserved. Severe cold components, some should be removed, some should be reinforced before being used. 4. Because the components have to withstand loads too wide cracks, reasonably designed to prevent the emergence of these cracks; cracks have been too broad component appears to be reinforced by strengthening measures. 5. The foundation of unequal settlement of large cracks too broad and reasonably in the design of the building when checking in the use phase of the settlement to prevent the emergence of these cracks, these cracks have occurred on the structure, to use ground-based control measures proper handling of the foundation, then building the structure reinforcement measures adopted to solve. 6. On the environmental conditions and changes in the use of the crack occurred, according to different properties to different control measures, such as: (1) the use of temperature and humidity changes during the formation of cracks, usually difficult to eradicate, to adopt the protection of reinforced concrete measures to reduce atmospheric humidity changes of the component is appropriate; (2) The cracks resulting from repeated freezing and thawing, in addition to defects and damage has been formed in part to be reinforced or reinforced, but should add insulation on the cold concrete measures; (3) The corrosive medium in the resulting defects and damage a large area, in addition to corrosion and damage should be removed by the site to be reinforced or reinforced, shall use the acid water glass slag cement concrete or concrete overlay to protect; (4) damage due to earthquake seismic structural measures should be adopted to prevent; have been generated by the earthquake damage is not severe earthquake damaged buildings may refer to repair and reinforcement of the solution to the problem. In addition, temperature control and improved from the constraints of the two aspects. Used to improve the aggregate gradation, with a dry hard concrete, mixed with mixture, add air-entraining agent or a plasticizing agent measures to reduce the amount of cement in concrete; water when mixing concrete or gravel with water cooling to reduce the concrete pouring temperature; hot days when the pouring of concrete pouring to reduce the thickness of heat by pouring level; in the concrete laying pipes, pass into the cold water temperature; set reasonable removal time, the surface heat when temperatures plunged to avoid dramatic concrete surface temperature gradient ; Construction of Concrete Blocks and long-term exposure to surface or thin-walled structure, insulation measures taken in the cold season. Measures to improve the constraints are: a reasonable parting block; to avoid excessive fluctuations basis; reasonable arrangements for the construction process, to avoid the excessive height and long-term exposure to the side. In addition, to improve the performance of concrete and improve the crack resistance, enhance conservation, to prevent surface shrinkage, in particular, to ensure the quality of concrete is very important to prevent fractures, special attention should be avoided through the cracks, appears to restore its structural integrity is difficulties, so the construction should be to prevent the occurrence of cracks in the main cross-cutting. Fourth, early curing of concrete Practice shows that cracks in concrete common, most of the surface cracks of different depth, mainly because of the temperature gradient caused by the sudden drop in temperature in cold areas are also easy to form cracks. Therefore, the concrete surface of the insulation to prevent early cracking is particularly important. From the viewpoint of thermal stress, thermal insulation should meet the following requirements: (1) prevent the concrete and the concrete surface temperature difference between inside and outside the gradient, to prevent surface cracks; (2) to prevent the concrete super cool, should try to try to make concrete the construction period of not less than the minimum temperature on the stability of the temperature of concrete used; (3) to prevent cold and old concrete to reduce the constraints between the new and old concrete. Early curing of concrete, the main purpose is to maintain proper temperature and humidity conditions in order to achieve the effect of two aspects, one of the concrete from adverse temperature and humidity deformation of the invasion, to prevent the harmful shrinkage and shrinkage. On the one hand to smooth the cement hydration in order to meet the design strength and crack resistance. V. Conclusion Cracks in concrete above the relationship between the various effects of the theory and practice discussed, although the academic cracks in the concrete and calculation methods are different theories, but for specific advice for prevention and improvement measures more unified, but in practice of effects are good, concrete construction depends on our seeing much comparison, more analysis after problems, and more sum up, with a variety of preventive treatment measures, concrete cracks are completely avoidable.
BU HUI XIE YA
参考文献［1］徐荣年,徐欣磊.工程结构裂缝控制——“王铁梦法”应用事例集［M］.北京:中国建筑工业出版社,2005. ［2］何星华,高小旺.建筑工程裂缝防治指南［M］.北京:中国建筑工业出版社,2005.［3］韩素芳,耿维恕.钢筋混泥土结构裂缝控制指南［M］.北京:化学工业出版社,2005,12.［4］过镇海,时旭东.钢筋混凝土原理和分析［M］.北京:清华大学出版社,2003,5.［5］曲德仁.混凝土质量控制［M］.北京:中国工业出版社,2003.［6］鞠丽艳.混凝土裂缝抑制措施的研究进展［M］. 北京:清华大学出版社，2002. 5. ［7］郭仕万，肖欣，赵和平.混凝土施工中的裂缝控制［M］. 北京: 中国农业出版社，. ［8］鞠丽艳，张雄.混凝土裂缝防治的两种新方法［M］. 北京:中国建筑工业出版社，2002. 7. ［9］杨绍林,田加才,田丽.新编混凝土配合比使用手册[M].北京:中国建筑工业出版社,.
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水泥混凝土结构裂缝的影响、成因及防治策略论文
在平时的学习、工作中，大家都不可避免地会接触到论文吧，论文是进行各个学术领域研究和描述学术研究成果的一种说理文章。写起论文来就毫无头绪？以下是我精心整理的水泥混凝土结构裂缝的影响、成因及防治策略论文，欢迎大家借鉴与参考，希望对大家有所帮助。
摘要： 水泥混凝土，也称水泥砼，由水、水泥以及多种的混合材料组成，广泛地运用于工程施工。由于水泥混凝土结构施工会受到温度、水分、技术条件等多种因素的影响，所以在使用过程中非常容易出现裂缝。结合工程实际，简要分析了水泥混凝土结构工程施工中出现裂缝的原因，并提出了相关防治措施。
关键词： 工程施工；水泥混凝土结构；裂缝；结构病害；
水泥混凝土结构裂缝，是水泥混凝土施工过程中常见的结构病害。如果处理不及时，会使水泥混凝土出现严重结构性损坏，不仅增加了水泥混凝土结构的施工造价成本，同时也缩短了水泥混凝土结构的使用年限。由于部分水泥混凝土结构施工工期较紧，对水泥混凝土结构裂缝处理不够及时，导致水泥混凝土结构建筑物在使用过程中达不到预定要求。在实际施工过程中，应在分析水泥混凝土结构产生裂缝原因的基础上，及时制订施工防治技术方案，保证水泥混凝土结构施工的持续、有效开展。
1、工程施工中常见裂缝类型
由水泥混凝土集配问题引起的裂缝
现场施工人员经验主义作祟，未能及时掌握和调整施工现场水泥混凝土配比，一味地使用实验室配比，没有根据施工现场条件及时调整水泥混凝土结构配合比例，或者使用的原材料不合格，都极易造成水泥混凝土结构的裂缝。例如在水泥混凝土结构配比中，对各类原材料、水、外加剂等因素控制不当，结构物的强度达不到设计要求，就会产生裂缝[1]。
由环境原因引起的裂缝
水泥混凝土结构环境原因引起的裂缝，主要指的是由于水泥混凝土结构施工过程中温度、湿度等环境因素的变化对结构物引起的裂缝。施工过程中出现了较大的温、湿度等环境因素变化时，会导致水泥混凝土结构物理性能发生变化，进而出现裂缝。
由基础原因引起的裂缝
水泥混凝土结构基础原因引起的裂缝，主要是指在施工过程中没有对回填土进行挤密夯实而进行水泥混凝土结构施工所产生的裂缝；如果地基土质过于松软，在水泥混凝土结构施工前未进行夯实处理，同样也会出现水泥混凝土结构裂缝。如果水泥混凝土结构物长期被基础中的渗水浸泡，也会出现不均匀裂缝[2]。
由后期养护不当引起的裂缝
水泥混凝土施工过程中，应及时进行水泥混凝土养护。如果养护不及时，水泥混凝土面层将会出现干缩性裂缝，出现水泥混凝土表面“起皮”现象；或因温度不够达不到水泥混凝土终凝条件，水泥混凝土整体出现“断板”现象。
2、水泥混凝土结构裂缝带来的影响
容易埋下安全隐患，由于水泥混凝土结构裂缝的出现会影响到水泥混凝土建筑物原有的承载能力，进而缩短了水泥混凝土结构物的正常使用时间。在建筑施工过程中，裂缝的存在可能会造成大量的返修，浪费材料，延误工期，最终造成巨大的`经济和名誉损失。水泥混凝土结构裂缝会对建筑的外观质量造成极大的影响，影响工程的质量验收和后续款项的结算。
3、工程施工过程中，水泥混凝土结构裂缝产生的原因
在水泥混凝土结构施工过程中，受到温度、湿度、原材料本身以及施工技术等多方面因素的影响，会导致水泥混凝土结构出现裂缝。
原材料的影响
水泥混凝土中的原材料对水泥混凝土结构的质量起着至关重要的作用，一旦在施工过程中采用了不合格的原材料，就容易引起水泥混凝土裂缝现象：粗细集料含泥量过大会导致与水泥的黏合度不足；粗集料针片状比例过大、粗细集料配比不均会导致水泥混凝土密实度不足；水泥的最佳用水量及初、终凝时间等会对水泥混凝土结构的整体强度和水泥混凝土结构后期养护产生影响。
施工技术的影响
在水泥混凝土结构施工过程中，要采用科学的施工技术，加强对工程管理制度、施工组织设计的时间节点等关键要素的管理。在对水泥混凝土地面施工时，要对原地面进行找平、填土、分层夯实施工，不然会使水泥混凝土路面因受力不均而产生裂缝和“断板”现象。在水泥混凝土路面施工中，要将水泥混凝土路面振捣密实，切勿出现空洞而影响水泥混凝土路面的使用年限。在水泥混凝土施工养护的过程中，要及时观察和监测水分和温度变化情况，及时掌握水泥混凝土的初、终凝时间，实施喷水、覆盖保温设施。要保证水泥混凝土结构终凝后，才可以拆除模具，以免因水泥混凝土结构未达到强度而产生裂缝，影响水泥混凝土结构的正常使用。
物理性能的影响
由于水泥混凝土属于脆性材料，环境中温度、湿度对其影响较大。在温度、湿度数值出现较大变动时，水泥混凝土结构的应力也会出现相应的变化，导致水泥混凝土结构裂缝的产生。
4、工程施工中水泥混凝土结构裂缝的预防措施
水泥混凝土结构裂缝会对建筑物整体结构埋下隐患，有可能影响到人民群众的生命财产安全。通过对水泥混凝土结构裂缝产生原因的分析，需要对其做出积极的事前、事中、事后预防。
设计过程中的预防措施
科学制订水泥混凝土的配置比例。在水泥混凝土结构配比方案制订时，要合理控制水灰比，各类外加剂的添加要符合施工现场的实际情况。在实验室水泥混凝土配比符合施工要求的情况下，要在现场及时调整配比，不能一贯地依赖于实验室的配比结果。要根据水泥混凝土结构的高度、宽度、长度及时调整钢筋分布，使水泥混凝土结构应力分布均匀。加大对水泥混凝土原材料的质量监测力度，杜绝使用不合格的原材料。要根据实际情况，适时对水泥混凝土配比进行合理调整。
施工过程中的预防措施
水泥混凝土结构的施工过程是影响工程质量的关键步骤，科学的施工工序是决定水泥混凝土结构是否产生裂缝的重要因素。在施工前要注意水泥混凝土结构原基层的平整度；施工中要严格根据设计和工艺进行施工，保证水泥混凝土结构合理的施工配合比例，满足水泥混凝土结构设计强度与材料和易性的质量要求；在水泥混凝土运输过程中时，要对水泥混凝土采取保水、保温等相关的防护措施；在水泥混凝土浇筑过程中，要适时控制水泥混凝土的出料速度，并保证水泥混凝土结构浇筑过程中要振捣密实、均匀。要注重二次抹压在水泥混凝土施工工程中的重要作用，二次抹压能够减少水泥混凝土结构裂缝的出现。二次抹压时，要适时掌握水泥混凝土结构的初、终凝时间，如果抹压时间过晚，水泥混凝土结构已经逐渐凝固，即使抹压也不能使水泥混凝土结构物理外观形态变化；如果抹压时间过早，二次抹压后水泥混凝土结构才会产生裂缝，不会对水泥混凝土结构物理外观产生影响。所以，工程施工人员需对抹压的时机进行控制，介于水泥混凝土结构初凝和终凝之间的时间段进行抹压，方能减少裂缝的产生，提高水泥混凝土结构的质量[3]。
养护过程中的预防措施
水泥混凝土结构的养护要严格按照水泥混凝土结构养护国家标准来实施，使水泥混凝土结构的裂缝降到最低。要加强温、湿度监控，严格按照水泥混凝土结构设计要求，对水泥混凝土养护的温度、湿度和技术条件进行把控；要采取措施，合理控制温度、湿度数值的变化范围，在施工中可采用水泥混凝土结构表面覆盖塑料薄膜、草席的方法，保证水泥混凝土结构物的温度，适时人工洒水来保证水泥混凝土所需的湿度。另外，在工程施工过程中，要保证水泥混凝土结构养护工作周期满足规范要求，通常情况下水泥混凝土结构养护周期为7～15d，工程施工过程中的具体养护时间应根据施工现场的实际风力、温湿度等情况而决定[4]。
5、结束语
目前，水泥混凝土结构施工已经普遍使用到了各类工程中，水泥混凝土结构的质量直接影响着工程质量。本文简要分析了水泥混凝土结构工程施工中出现裂缝的原因，并提出了防治水泥混凝土结构裂缝的措施。但是，水泥混凝土结构裂缝牵扯的因素较多，在实际工程施工中很难避免。要在水泥混凝土结构工程项目施工过程中，从施工的各个环节进行水泥混凝土结构裂缝的预防控制，使工程施工的质量和效率得到有效的保障，使建设物的使用年限得到有力的保证。
6、参考文献
[1]冯树合.工程施工中水泥混凝土结构出现裂缝的原因及预防[J].江西建材,2014(3):74.
[2]吴巍.基于工程施工中水泥混凝土结构出现裂缝的原因及预防措施的分析[J].中华民居(下旬刊),2014(6):333-334.
[3]赵晓春.工程施工中水泥混凝土结构出现裂缝的原因及预防[J].科技致富向导,2014(29):262.
[4]沈亚萍.房建施工中混凝土结构出现裂缝的原因及预防[J].四川水泥,2015(6):225.
水泥混凝土早期裂缝成因及防治
早期裂缝是水泥混凝土路面的关键问题，早期裂缝对于道路的使用寿命和运营安全具有重要影响，需要在施工过程中进行管理和控制。下面由我为大家分享水泥混凝土早期裂缝成因及防治，欢迎大家阅读浏览。
1 水泥混凝土路面早期裂缝的成因分析
分析水泥混凝土路面的施工全过程，早期裂缝的形成主要是在水泥混凝土养护过程中产生，但其形成原因却包含了水泥混凝土原材料质量、配比，施工和易性、振捣和养护的控制，施工中温度的影响等，这些成因是复杂的，但从裂缝形成的机理和呈现特点来看，早期裂缝的形成主要是水泥混凝土的塑性收缩、自收缩和温度收缩等效应形成，以下将从这三个方面剖析早期裂缝的成因特点和组成。
塑性收缩效应
塑性收缩是水泥混凝土在浇筑振捣过程中，由于水分蒸发引起混凝土表面收缩而形成的裂缝，这些裂缝的分布没有规律性，主要呈现网状或者斜向，与路面结构的受力特点无必然联系。塑性裂缝在水泥混凝土浇筑过程中或多或少会产生，其形成机理是水泥在硬化过程中，水分蒸发使得水泥混凝土的化学反应受到影响，导致水泥混凝土各个材料不能完全黏结，形成了细微的裂缝。一般塑性裂缝主要发生在面层表面，因此表面的水分蒸发速度是最快的，失水效率也是最高的，因此塑性裂缝的深度一般在0～50mm之间。塑性开裂的程度与浇筑过程中气温、湿度和浇筑温度等因素高度相关，气温越高、风速越大、湿度越低，则水分的`蒸发速度越快，裂缝也更容易产生。
自收缩效应
自收缩是指水泥混凝土中的水泥在水化过程中需要消耗水分，这个水化过程使得混凝土的相对湿度变低，造成毛细孔、凝胶孔等缺少，造成胶凝料体积变小，即混凝土内部部分材料收缩，而这种自收缩作用受到周边其他材料的限制并产生裂纹。这种自收缩完全是水泥混凝土的本身特性所致，因此一般的施工过程都需要加入缓凝剂，延缓水泥混凝土的凝结，降低水化效率，从而减少不必要的自收缩裂缝。大量研究表明：未加入缓凝剂的混凝土，在初凝开始就会进行自收缩，1d时间内自收缩值就能达到28d的50%～60%，说明了自收缩主要发生在早期。为了避免自收缩效应，需要加入一定量的缓凝剂以保证质量。
温度收缩效应
温度收缩是混凝土材料的一个关键问题。目前我国生产的水泥品种，其比表面都比较大，水泥的水化速度很快，这就使得水泥混凝土在浇筑过程中，在初凝的时间段内水泥产生水化作用大量放热，这些热量可以使得浇筑的路面温度上升6～10℃，而水化放热完成后，周围空气和热交换作用使得面层的温度降低，而面层内部的温度尚无法进行高效率的热交换，使得路面的表面和内部形成温度差，这个温度差的作用使得内部水泥混凝土约束表面的收缩，导致面层混凝土开裂。一般而言，面层厚度越大，温度收缩效应越明显，裂缝的数量、宽度和深度等也将越大，而水泥混凝土的水泥用量、周围气温对温度效应也有显著影响，例如水泥用量越大，则水化效应更显著，温度收缩效应也越大;周围气温越大、昼夜温差越大，则温度的收缩效应也越显著。
2 水泥混凝土路面早期裂缝防治措施
明确了水泥混凝土的早期裂缝特点和成因后，可以针对裂缝形成的源头建立防治措施和方法，保证水泥混凝土路面结构的施工质量。具体而言，可以从原材料控制、材料配比的控制、施工质量控制、混凝土板切缝等方面形成防治措施。
原材料控制
水泥混凝土的原材料质量是确保路面施工质量的关键，也是影响塑性收缩和自收缩效应的关键。首先，水泥材料的选择非常关键，为了降低早期裂缝，应该选择强度高、干缩性好及抗冻性能好的水泥材料，例如矿渣硅酸盐水泥的早期强度低、水化热又高，很容易产生早期裂缝，不宜采用。其次，混凝土骨料的级配和粒径等也是重要影响因素，骨料应该确保无风化、含泥量低且强度足够，骨料的粒径应该采用连续粒径级配，保证集料与水泥的黏结密实而不容易产生离析;最后，水泥混凝土的混合料中水的质量也需要保证，不能随便采用江河水，需要确保用水的质量满足混凝土浇筑要求。
材料配比的控制
原材料的配比同样影响水泥混凝土的早期性能，这其中水泥用量和水用量是需要特别关注的配比，除温度收缩效应外，塑性收缩和自收缩都是由于水分的蒸发或者水泥用量太多引起，因此需要控制混凝土在必要的潮湿状态下硬化。水泥在水化过程中需要少量的水，而大部分的水是为了保证混凝土的和易性，因此需要严格控制配比中的单位用水量。减水剂是一种较为有效的含水量控制方法，在水泥硬化过程中加入早强剂有利于减少裂缝形成。
施工质量控制
早期裂缝的形成因素之一是水泥混凝土各种配料之间连接不紧密，为了保证不均匀的收缩，需要在振捣过程中将水泥混凝土各种混合料振捣密实，在保证密实的情况下还需要确保振捣的均匀，一般振捣不好的部位也是最容易产生早期裂缝的部位。此外，振捣过程中还需要对混合料的含水量进行控制，根据实际的振捣情况以及混合料的运输距离、摊铺时间等进行合理调控。另外，水泥混凝土路面压实完成后，还需要进行必要的养护，养护也是避免早期裂缝的关键工序，养生的过程是要确保混凝土与周围环境温度差别不至于过大，同时要确保养护环境的湿度，避免早期裂缝的形成和发展，当水泥路面达到标准的抗拉强度后，可不再进行养护。
混凝土板切缝
由于水泥混凝土路面是面状结构，在浇筑完成后温度收缩效应是影响其质量的关键，即便养护完成，由于环境的昼夜温差等作用，都可能会在路面结构中产生早期裂缝，因此应该及时进行切缝处理。混凝土板的切缝应该结合环境的变化进行调整，基本原则是确保切缝的质量，不引起路面损坏，切缝的时机是混凝土板达到基本强度后开展。
3 结论
早期裂缝是水泥混凝土路面的关键问题，早期裂缝对于道路的使用寿命和运营安全具有重要影响，需要在施工过程中进行管理和控制。论文探讨了水泥混凝土路面早期裂缝的形成原因，剖析了塑性收缩、自收缩和温度收缩是早期裂缝产生的三个主要原因，并探讨了其内在影响机理，最后提出了处置早期裂缝的方法，应该从原材料、配比、施工管控和混凝土面板切缝等措施出发，以保证水泥混凝土路面的施工质量，降低早期裂缝的形成和发展。
参考文献：
[1] 胡敏玲，胡力群.水泥混凝土路面早期裂纹、裂缝成因及其防治措施[J].交通标准化，2006(1)：130-133.
[2] 王鹏.浅谈水泥混凝土路面早期裂缝危害及分类防治[J].北方交通，2008(6)：34-35.
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网址是：《商品混凝土》由中国建筑材料联合会主管，建筑材料工业技术情报研究所、中国硅酸盐学会科普工作委员会主办，是国内首家商品混凝土专业期刊，主要面向全国商品混凝土生产、管理、科研、应用、检测、教学等行业，是以专业技术为核心的综合类刊物。《商品混凝土》坚持为社会主义服务的方向，坚持以马克思列宁主义、毛泽东思想和邓小平理论为指导，贯彻“百花齐放、百家争鸣”和“古为今用、洋为中用”的方针，坚持实事求是、理论与实际相结合的严谨学风，传播先进的科学文化知识，弘扬民族优秀科学文化，促进国际科学文化交流，探索防灾科技教育、教学及管理诸方面的规律，活跃教学与科研的学术风气，为教学与科研服务。
为了提高自防水混凝土的抗渗能力，人们在防水材料的研究上倾注了巨大的精力，防水材料的性能有了很大的改善。如中国建筑材料科学研究院研制成功的U型膨胀剂就是一种良好的防水抗渗材料。在混凝土中掺入10％～14％U型膨胀剂，能使得混凝土抗渗能力提高1～2倍，达S 30，如此看来混凝土的自防水抗渗能力应该无可置疑了。但其实不然，自防水结构由于细部处理不当，仍然会在墙板施工缝、变形缝、后浇带、预理金属件及穿墙过管等部位产生渗漏，不仅影响建筑物的正常使用，而且给维修带来困难。那么，自防水混凝土结构为何会在结构细部出现渗漏呢？究其原因，在施工中对细部处理没有引起足够的重视，也没有采取有效的防治措施，是造成渗漏的主要原因。那么，在这些部位该怎样进行施工呢？ 墙板施工缝的施工按照地下防水工程施工及验收规范规定，墙板施工缝应留在底板表面不少于200 mm的墙体上，并在墙板混凝土中留置阶梯、凸凹和预板金属板等形式。除了在混凝土墙板上留置施工缝的高度应满足规范规定的条件外，为方便工程施工，当地板上设置有垂直墙板的地梁时，应使墙板施工缝的高度设在高于梁顶标高的位置；在墙与柱交接处，应利用柱箍筋的间隙保持凸缝的混凝土强度完全达到不缺楞掉角的强度时，方可拆除凸缝两侧模板；对于损坏了的凸缝部位，可在墙板上凿除部分混凝土重新形成凸缝；对于凸缝台阶处成型不密实的混凝土，应在安装上部墙模板之前凿去，直到肉眼观察无细小气孔为止，同时要将凸缝的凸出部分凿毛，除去表面浮浆层，并认真检查施工缝封口模板的密实性以及牢固性。铺设水泥砂浆的厚度以盖住凸缝为标准，铺浆长度要适应混凝土的浇筑速度，不宜过长或者间断漏铺。当混凝土砂浆在墙板中的卸料高度＞3 m时，可根据墙板厚度选用柔性流管浇灌，避免混凝土出现离析现象。变形缝的施工为避免止水带局部出现卷边或接头粘接不牢，在施工中应采取以下几项措施：（1）选购止水带时应按图纸要求选购长度能够满足底板加两侧墙板的长度尺寸，如长度不能满足要求而需接长时，可采用氯丁型801胶结剂粘结，并用木制的夹具夹紧，或者采用热挤压粘结方法，以保证粘结效果。（2）止水带安装过程中的支模和其他工序施工中，要注意不应有金属一类的硬物损伤止水带。（3）浇筑混凝土时，应先将底板处的止水带下侧混凝土振捣密实，并密切注意止水带有无上翘现象；对墙板处的混凝土应从止水带两侧对称振捣，并注意止水带有无相位移现象，使止水带始终居于中间位置。（4）为便于施工，变形缝中填塞的衬垫材料应改用聚苯乙烯泡沫塑料板或沥青浸泡过的木丝板。后浇带施工由于工程施工的需要，常在地下结构中留设后浇带，而渗漏常出现在后浇带两侧混凝土的接缝处。渗漏的主要原因：①后浇带部位的混凝土施工过早，且浇灌混凝土的落差较大，使得后浇带接缝处产生过大的拉应力；②浇灌前对后浇带混凝土接缝的截面局部遗留的混凝土残渣或碎片未能清除干净，或后浇带的底板位置的接缝处长时间的暴露沾了泥污未处理干净，严重影响了新老混凝土的结合所致；③设计中存在着局部不合理的现象。根据上面的分析，后浇带的施工时间宜在两侧混凝土成型6周后，混凝土的收缩变形基本完成后再进行。或者通过沉降观测，当两侧沉降基本一致，结合上部结构荷载增加情况以及底下结构混凝土浇筑后的延续时间确定。施工前，应将接缝面用钢丝刷认真清理，最好用錾子凿去表面砂浆层，使其完全露出新鲜混凝土后再浇筑。施工时可根据混凝土浇筑的速度在接缝面上再涂刷一遍素水泥浆，但每次涂刷的超前量不宜过长，以免失去结合层的作用。后浇带混凝土中还可掺入15％的明矾石膨胀剂，在混凝土硬化时起收缩补偿作用。混凝土浇筑应采用二次振捣法，以提高密实性和界面的结合力，设计中往往会对该部位配筋进行加强，针对配筋较密的特点，后浇带宜采用T型的形状，以方便拆除模板。钢筋的绑扎施工中必须注意将撑环、撑角设置在双排钢筋之间，对应的位置也应加设保护层垫块。撑环或撑角的每一端应有不少于2道绑扎，为了慎重可靠，宜采取焊接的方法固定在钢筋上。预埋的金属件及穿墙螺栓预埋的穿墙地脚螺栓、穿墙套管以及为安装模板设置的穿墙螺栓，设计和施工规范都规定要焊接止水环，但对施工中的止水环焊缝的检查要求不够严格，以致于施工中往往存在局部漏焊和严重夹渣现象，为渗水提供了通道。因此，要加强对止水环焊缝的检查，在满焊的条件下应逐个敲去焊缝检验，对不合格的要补焊后方可用到工程中。用于支模的穿墙螺栓也可采用汽压焊和电渣压力焊顶锻形成止水环工艺，但需注意顶锻后形成的止水环径部分应大于钢筋直径倍以上，而且止水环相对穿墙螺栓中心不得有严重偏移现象。当混凝土达到一定强度后，应在穿墙螺栓端头迎水面侧凿除20～30 mm深的混凝土，截去穿墙螺栓，用膨胀砂浆做墙面处理。对于较大的方形套管，管子的底部常因无法振捣而出现空洞蜂窝现象，我们对此类套管采取在止水环两侧分别开出直径不小于振捣棒直径的洞口，便于将振捣捧插入套管下部混凝土中振捣，同时排出气体，从而保证了这部分混凝土的密实性。结语前面简要论述了自防水混凝土结构中有关墙板施工缝、变形缝、后浇带、预埋金属件及穿墙过管部位产生渗漏的原因及其正确的施工方法，只要从这几个细部进行施工监控，就能最大限度地提高防水工程质量，使自防水混凝土结构达到良好的防水效果。
1. 前言� 混凝土是由水泥、砂、石和水拌合后，水泥水化反应形成凝胶，将砂、石胶结而成具有一定强度的固体复合材料。其内部结构为：水和水泥作用形成水泥浆，水泥浆包裹在砂的表面，并填充于砂的空隙中成为砂浆，砂浆又包裹在石子的表面，并填充砂子的空隙。水泥浆将砂、石牢固地胶结为一整体，使混凝土具有所需的强度、耐久性等性能。混凝由于土自身的特殊性能在水利水电工程、桥梁工程等土木工程领域发挥着极其重要作用。但是混凝土原材料质量、混凝土配合比、混凝土的搅拌和输送、混凝土浇筑、养护及拆模等施工工艺对混凝土质量有较大的影响，施工过程中需对其进行严格的质量控制。� 2. 原材料的质量控制� 原材料是组成混凝土的基础,原材料品质的优劣直接影响到混凝土质量的好坏,因此首先要把好原材料质量关。� 水泥的强度和体积安定性直接影响混凝土的质量。水泥的强度上下波动,混凝土的强度就会发生相应的变化;水泥的体积安定性差,就会使混凝土产生膨胀性裂缝。因此,要选择好水泥品种,根据经验,大水泥厂生产的水泥质量比较稳定可靠。� 石子主要控制好级配、针片状含量和压碎值。经调研,目前,好多混凝土厂家的石子级配都不是很好,因此,如何确保石子级配连续,且在生产中切实可行,还值得进一步探讨研究。� 砂最关键的是细度模数和含泥量,砂子太细或含泥过多, 会增加混凝土的干缩裂缝。另外,砂石中含泥量高,不仅影响混凝土的强度,而且影响抗冻性、抗渗性和耐久性。因此,混凝土最好采用中粗砂,且含泥量和有机质的含量必须满足规范要求。� 混凝土拌和所用的水中，不应含有影响水泥水化和混凝土质量的有害物质，如使用有机杂质的沼泽水、海水等拌制混凝土,则会在混凝土表面形成盐霜。� 在混凝土生产过程中，对原材料的质量控制，除经常性的检测外，还要求质量控制人员随时掌握其含量的变化规律，并拟定相应的对策措施，如：砂石的含泥量超出标准要求时，及时反馈给生产部门，及时筛选并采取能保证混凝土质量的其它有效措施；砂子含水率通过干炒法测定，及时根据测定的含水率来调整混凝土配合比中的实际用水量和集料用量；对于相同标号之间水泥活性的变异,通过胶砂强度试验快速测定，根据水泥活性结果予以调整混凝土的配合比。水泥、砂、石子各性能指标必需达到规范要求。� 3. 混凝土配合比� 混凝土配合比是指单位体积的混凝土中各组成材料的重量比例。水灰比、单位用水量和砂率是混凝土配合比设计的三个基本参数,它们与混凝土各项性能之间有着非常密切的关系。确定这三个基本参数的基本原则是：在满足混凝土强度和耐久性的基础上,确定混凝土水灰比,在满足混凝土施工要求的和易性基础上,根据粗骨料的规格确定混凝土单位用水量,砂在骨料中的数量应以填充石子空隙后略有富余的原则来确定。混凝土施工配合比必须通过实验，满足设计技术指标和施工要求，经审批后方可使用。混凝土施工配料必须经审核后签发，严格按签发的混凝土施工配料单进行配料，严禁擅自更改。在施工配料中一旦出现漏配、少配或者错配，混凝土将不允许进仓。� 4. 模板工程质量控制� 施工方案应根据主体工程的结构体系、荷载大小、合同工期及模板的周转情况等，综合考虑所选择的模板和支撑系统。保证工程结构和构件各部分形状尺寸和相关位置的正确，对结构节点及异型部位模板合理设计(是否采用专用模板)有重要意义。模板具有足够的承载能力、刚度和稳定性，能可靠地承受新浇混凝土的自重和侧压力，以及在施工过程中所产生的荷载。模板接缝处理方案要保证不漏浆，模板及支架系统构造要简单、装拆方便，便于钢筋绑扎、安装、清理和混凝土的浇筑、养护。� 目前施工中常用钢组合模板、木模板、胶合板模板、塑料模板等。应对模板质量(包括重复使用条件下的模板)、外型尺寸、平整度、板面的洁净程度、相应的附件(角模、连接附件)，以及支撑系统进行检查，确定模板规格。重要部位应要求预拼装。� 隔离剂选用质地优良和价格适宜的，隔离剂合理选用是提高混凝土结构、构件表面质量和降低模板工程费用的重要措施。因此,选用时应考虑脱模剂的干燥时间是否满足施工工艺要求。脱模剂的脱模效果与拆模时间有关,当脱模剂与混凝土接触面之间粘结力大于混凝土的内聚力时，往往发生表层混凝土被局部粘掉的现象，因此具体拆模时间应通过试验确定。� 5. 混凝土的搅拌及输送质量控制� 根据工程量的大小并结合施工单位自身设备条件选取相应拌和设备和运输设备，提前预测拌和设备和运输设备可能出现的故障和问题，及时安排机修人员做好设备的检查和修理工作。不能因为设备故障而停止混凝土的浇筑，确保施工过程中及时提供工程所需混凝土，满足工程的要求，保证施工进度。� 混凝土拌和质量控制要点。� （1）混凝土最小拌和时间。根据拌和容量、最大骨料粒径、拌和方式等具体确定。� (2)在混凝土拌和中应定时检测骨料含水量。� (3)混凝土掺和料在现场宜用干掺法，且必须拌和均匀。� (4)混凝土拌和物出现下列情况之一，按不合格处理。①错用配合比；②混凝土配料时，任意一种材料计量失控或漏配；③拌和不均匀或夹带生料；④出口混凝土坍落度超过最大允许范围。 混凝土运输过程中注意事项。� （1）运输中不致发生分离、漏浆、严重泌水、过多温度回升和坍落度损失。� （2）混凝土运输时间。根据运输时段平均气温等具体确定。� （3）低温天气应避免天气、气温等因素的影响，采取遮盖或保温设施。� （4）混凝土的自由下落度不宜大于，否则应设缓降措施，防止骨料分离。� （5）混凝土在运输过程中如果出现故障，必须及时处理。在混凝土初凝前想办法将混凝土运送到浇筑仓位，否则以不合格处理。� 6. 混凝土浇筑� 浇筑混凝土前，对模板及其支架、钢筋和预埋件必须进行检查，并做好记录，符合设计要求后，清理模板内的杂物及钢筋上的油污，堵严缝隙和孔洞，方能浇筑混凝土。� （1）混凝土浇筑前仓面要清理干净，浇筑面验仓合格后才允许进行混凝土浇筑。 � （2）为保证新老混凝土施工缝面结合良好，在浇筑第一层混凝土前，应铺与混凝土同标号的水泥砂浆2㎝～3㎝，铺设的砂浆面积应与混凝土浇筑强度相适应，铺设厚度要均匀，避免产生过厚或过薄现象。� （3）混凝土的浇筑应采用平铺法或台阶法施工，严禁采用滚浇法，应按一定厚度、次序、方向、分层进行，且浇筑层面平整，浇筑墙体时应对称均匀上升，浇筑厚度一般为30cm～50cm。 � （4）混凝土浇筑应先平仓后振捣，严禁以振捣代替平仓。振捣时间以混凝土粗骨料不再显著下沉，并开始泛浆为准，将混凝土内的气泡振捣出，避免振捣时间太短或过长，造成欠振、漏振及过振，振捣完应慢慢拔出，严禁速度过快。混凝土的振捣半径应不超过振捣器有效半径的倍，应将振捣器插入下层混凝土5cm左右，不应过深，以免造成下层混凝土的过振。 � （5）混凝土浇筑期间，如表面泌水较多，应及时清除，并采取措施减少泌水。严禁在模板上开孔赶水，以免带走灰浆。 � （6）在混凝土浇筑过程中，尤其是浇筑顶板，应设置位移变形观测点，设专人定期观测模板是否偏移，设专人检查、加固模板。 � （7）浇筑完的混凝土必须遮盖来保温或者防雨。� 7. 混凝土的养护及拆模质量控制� 混凝土的养护。 为使混凝土中水泥充分水化，加速混凝土的硬化，防止混凝土自型后因曝晒、风吹、干燥、寒冷等自然因素的影响出现不正常的收缩、裂缝破坏等现象。混凝土浇筑完毕后应及时洒水养护保持混凝土表面湿润。� 混凝土表面的养护要求：� (1) 塑性混凝土应在浇筑完毕后 6-18 小时内开始洒水养护，低塑性混凝土宜在浇筑完毕后立即进行洒水养护。� (2) 混凝土应该连续养护，养护期内必须确保混凝土表面处于湿润状态。� (3) 混凝土养护时间不宜少于 28 天。� 拆模。 拆模的迟早直接影响到混凝土质量和模板使用周转率。拆模时间应根据设计要求、气温和混凝土强度等级情况而定。对非承重模板，混凝土强度达到以上，其表面和棱角不因为拆模而损坏方可拆除。对承重模板达到规定的混凝土设计标号的百分率后才能拆模。� 8. 结束语� 混凝土工程质量的好坏，是由设计人员、监理人员和施工人员共同努力的结果。每一位负责质量的人员必需注意预防质量缺陷的发生或尽早地发现施工中可能出现的缺陷，以不误时机地采取补救措施，所有的施工人员、监理人员都应当随时监控混凝土的配制、搅拌、浇筑和养护等过程。
我国社会经济不断快速发展,特别是近些年来,土木工程的建设发展十分迅速。下文是我为大家搜集整理的关于土木工程大学本科毕业论文的内容，欢迎大家阅读参考!
浅析土木工程施工中混凝土技术的运用
摘要:混凝土技术是目前国内、外建筑领域工程项目施工建设过程中常用的一种技术手段，同时也是建筑行业快速发展的技术保障。实践中可以看到，混凝土是确保土木工程项目整体施工质量的重要影响因素，混凝土技术水平在很大程度上关系着整个工程项目施工建设质量和应用安全可靠性。因此，在当前的形势下，加强对混凝土技术及其在土木施工过程中的应用问题研究，具有非常重大的现实意义。本文将对土木工程施工建设过程中用到的几种混凝土技术进行分析，并在此基础上提出一些建设性建议，以供参考。
关键词:土木工程施工建设混凝土技术
1土木施工中的混凝土浇筑技术
土木工程项目施工建设过程中，对混凝土质量有标准和要求，土木工程施工建设中用到的混凝土，其强度一般在C20至C40之间，该范围内的土木工程项目施工建设用料(混凝土)选择过程中，还应当根据建筑构造要求、性能等，对混凝土进行合理的配筋作业;比如，针对土木工程项目中的大体积混凝土浇筑比例方法，对钢筋数量适当增加，而且钢筋可承受混凝土浇筑时中的温度应力，可以有效对混凝土裂缝等病害进行控制。土木工程项目施工建设过程中，尤其是混凝土浇筑前，应当对混凝土温度、产生的温度应力等进行全面预算，并且合理确定土木工程施工过程中的温度指标、混凝土温度变化情况。
在此基础上，还要制定温度变化管控措施，并且对土木工程项目施工建设过程中的各种混凝土裂缝病害问题进行预防，以此来确保土木工程项目整体施工质量。土木工程施工过程中，混凝土浇筑施工是一项比较难操作的的工程，主要是因为混凝土的成分是水、砂石，并且还有加入适量的外加剂。在混凝土施工过程在，通常因上述组成材料的比例控制不好，而容易出现施工质量问题。比如，因混凝土灌水量不足，而形成收缩性裂缝，该种情况容易发生在混凝土施工时地基受到限制的情况下。在具体的土木工程施工建设过程中，因内部拉应力比混凝土抗拉强度大，所以可能会产生内部裂缝病害。之所以会出现拉应力超标现象，主要原因在于水分、温度等参数不合理。
比如，温度性病害，主要是因为热胀冷缩，混凝土膨胀、收缩过程中，形成挤压应力、拉伸应力，进而导致混凝土结构内部产生裂缝。基于以上分析可知，混凝土施工过程中，应当把握好混凝土浇筑技术，具体分析如下:第一，全面分层技术。在土木工程施工过程中，混凝土结构施工时常用分层技术进行浇筑，首层浇筑后、初凝前，对第二层进行浇筑，然后以此类推，逐层进行浇筑施工操作，直到最终完成施工任务。同时，利用该技术手段，可以有效确保施工质量，而且建筑结构平面一定要避免过大，施工时从短边依次向长边进行施工操作。第二，分段分层技术。土木工程施工过程中，采用分层技术手段进行浇筑，其强度一般都非常的大，若现场施工机械难以有效满足施工质量要求，则建议采用分段分层技术进行浇筑施工作业。具体操作过程中，应当从底层开始，完成一段距离后，再对第二层进行浇筑，如此往复至浇筑完毕为止。第三，斜面分层技术。土木工程施工过程中，该技术适用于结构相对较长，超过厚度本身大约3倍的工况，将混凝土一次性浇筑到顶，混凝土可形成自然斜面坡1∶3，振捣时应当确保从浇筑层最底端开始施工，然后逐层上移。
2土木施工中的混凝土振捣技术
土木工程施工过程中，振捣是一个非常重要的环节，混凝土自吊斗口下落过程中，自由降落的有效高度应当控制在2米范围之内。实践中，若浇筑高度在3米以上，则需采取有效的保护措施，比如利用溜管、入串桶等。混凝土浇筑过程中，应当本着分段分层、不间断的原则进行施工作业，根据建筑结构的特点、钢筋材料的疏密程度等，合理确定浇筑层的有效高度。通常情况下，浇筑层有效高度为振捣器作用范围的倍时，最大高度也不能超过50厘米。实际振捣施工过程中，若所选用的是插入式振捣器设备，则应当保持快插、慢播。其中，插点的排列一定要均匀，而且依点移动，严格按照设计要求和顺序进行施工作业，不可出现遗漏，确保振实均匀性。在振捣过程中，对移动间距也提出了更高的要求，比如移动间距不能超过振捣半径的倍，一般在30至40厘米之间。在上层振捣过程中，建议插入下层大约5厘米位置，以此来有效避免两层间产生接缝问题。在布设表面振动器移动间距时，每一次移动间距均需确保底板完全覆盖已振捣的区域边缘，在结构衔接位置的混凝土可达到标准密实度要求。
3土木工程施工中的箍筋施工技术
土木工程混凝土施工过程中，各个梁柱节点位置的箍筋施工非常重要，箍筋施工时，钢筋分布比较密集，操作人员需高空作业，尤其是纵横交错处，箍筋绑扎操作难度比较大。在此过程中，若采用的是整体沉梁施工方式，则节点位置的下部箍筋绑扎难度非常的大，甚至会导致梁柱节点位置无法准确放置柱箍筋，产生安全隐患。在具体施工过程中，建议采用两个开口箍筋拼台方式，即在节点位置采用开口箍筋施工技术手段，通过规范箍筋封闭、箍筋末端弯钩构造，可确保箍筋对混凝土核心的有效约束作用。
然而，分层下箍施工方法的实际应用难度非常的大，建议拆除节点处的模板，只有这样才能保证节点箍筋间距、绑扎安全可靠性。梁板模板施工安装完毕后，方可对梁板钢筋进行安装，进而对整体沉梁进行施工作业。从施工效果来看，该种施工方法，钢筋堆放、运输以及绑扎，整体施工非常的安全，交叉工序也比较多。在施工过程中，应当避免支模与绑钢筋不发生冲突，施工效率高。在此过程中，针对节点箍筋少放、难以确保箍筋间距等问题，笔者建议采用以下技术措施进行处理。首先，下料施工时，每个节点位置均应当适当增加纵向短筋;其次，柱节点位置箍筋焊接过程中，在纵向短筋上构建骨架;同时，还要将整体骨架套入柱纵筋，并且将其布设在楼板模板面之上，用穿粱钢筋对其进行牢固绑扎。
4土木工程施工中的混凝土养护技术
混凝土施工技术在国内建筑行业发展过程中的应用非常的广泛，实际操作过程中多采用的是泵送混凝土施工模式。采用泵送混凝土施工技术，可有效缩短施工工期，改善混凝土性能。在土木工程项目施工建设过程中，应当做好原材料购置、配比以及振捣等环节的质量管控，以免混凝土强度不达标。土木工程施工中的混凝土养护过程中，主要的养护技术手段包括以下几个方面的内容。第一，墙板混凝土完成浇筑振捣以后，需带模养护7天以上。拆模以后，挂上两层麻袋将其严密的覆盖好，继续对其进行保温。在此过程中，需洒水养护到两周的时间;第二，顶板混凝土浇捣施工完成、终凝以后，6小时内不能浇水，以免出现起灰、起皮等问题;8至12小时内，用薄膜可将其严密覆盖，而且面层加盖两层麻袋进行保温和养护，确保7天内混凝土足够的湿润。3～4天以后，确认混凝土核心温度高峰期过去，再正常洒水养护至14d(满足UEA防水混凝土养护要求)。
5结语
土木工程施工过程中的混凝土施工技术应用非常的广泛，而且涉及到诸多方面的影响因素，因此实践中应当加强重视和技术创新，只有这样才能确保我国建筑行业的可持续发展。
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[2]张永存，李青宁.薄壁混凝土渡槽结构施工过程中的温度应力分析[J].混凝土与水泥制品，2015(10).
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