1 preface
With the continuous improvement of social living standards, people's requirements for travel safety are getting higher and higher. Therefore, in the process of road and bridge construction, we should constantly develop and apply new technologies to improve the quality of roads and bridges. The construction technology of steel fiber reinforced concrete is a construction mode of comprehensively optimizing materials and technology, and it is an important standard and core technology for road and bridge inspection in China at present, which has been highly valued. Make good use of steel fiber reinforced concrete construction technology, provide all kinds of personalized services to the maximum extent, and meet people's basic travel safety and smooth traffic. Therefore, the author will discuss the construction technology and quality control of steel fiber reinforced concrete in road and bridge construction.
2 theoretical basis
Compared with ordinary concrete, steel fiber reinforced concrete has better physical and chemical properties, mainly reflected in the control of cracks. Specifically, at the initial stage of loading, it is not only the concrete base material but also the steel fiber that bears the external pressure, but the base material is the main one. In the later stage, the base material cracked, while the steel fiber structure was intact and assumed external pressure. Analysis of the reinforcement principle of steel fiber reinforced concrete mainly includes the following two theories: one is the theory of composite mechanics, and the other is the theory of fiber spacing. Among them, the basis of fiber spacing theory is fracture mechanics. They have reinforced steel fiber reinforced concrete from different theoretical angles, and the specific analysis is as follows. From the perspective of composite mechanics theory, steel fiber reinforced concrete is regarded as a fiber reinforcement system, and then two important parameters, fiber direction coefficient and fiber length coefficient, are derived. The stress, elastic modulus and strength of steel fiber reinforced concrete are obtained by using the mixing principle, and the following formulas are obtained: FFT = ft (1-ρf)+η θ ρ lf ρ f/df, where f represents the volume ratio of steel fiber, lf represents the length of steel fiber and df represents the diameter of steel fiber. After a lot of theoretical and experimental verification, this formula has been recognized and widely used in the industry.
From the perspective of fiber spacing theory, steel fiber reinforced concrete mainly adopts linear elastic fracture mechanics theory to control the occurrence and development of cracks, and the obtained results are the same as those derived from composite mechanics theory. Under the theory of fiber spacing, the performance of steel fiber reinforced concrete is mainly determined by the following factors: the type of steel fiber, the content of steel fiber and the length-diameter ratio of steel fiber. The sand ratio, the maximum particle size ratio of coarse aggregate, water reducer and admixture also have some effects on the structural properties of steel fiber reinforced concrete. If the pavement material adopts steel fiber concrete, it will also be affected by underground drainage and other conditions.
3 Main construction techniques
3. 1 road construction
(1) Five aspects should be paid attention to in the leveling of steel fiber reinforced concrete pavement: first, steel fibers should be continuously and evenly laid in the panel; Secondly, the steel fiber is dispersed by a disperser and added into a blender; Thirdly, try to prevent the steel fiber from caking during the mixing process, which can be controlled from the sequence and time of feeding; The fourth is to ensure the consistency of slump of admixture; Fifth, try to achieve the continuity of paving and pouring work and avoid uneven distribution of steel fibers. Leveling is an essential process after paving, and the road should be pressed according to the specific conditions such as road arch and slope.
(2) Vibrating In the process of pavement steel fiber concrete construction, vibrating is also an important process. Mechanical vibration can improve the strength and density of steel fiber, and then improve the crack resistance of pavement. When vibrating, we must pay attention to the sequence, strictly control the frequency of vibrating at the same time, put an end to excessive vibration and vibration leakage, and control the incidence of steel fiber holes and grooves to zero. (3) A characteristic of the construction of the formed steel fiber reinforced concrete pavement is that the fibers will be gradually irregular, with high sand content and fine coarse aggregate. In the actual construction process, in order to avoid the exposure of steel fibers, the pavement needs to be leveled and shaped by mechanical action. Generally, embossing operation will be carried out by means of embossing machine, and the leakage or exposure of steel fiber can be well controlled by this means. In the process of using steel fiber concrete in pavement construction, we should pay attention to some matters: first, rapid construction and large amount of water will delay the setting and hardening of steel fiber; Secondly, the addition of additives must be based on scientific calculation; Finally, transportation and paving time must be strictly controlled and standardized to ensure pavement strength.
3.2 Construction Technology of Steel Fiber Concrete in Bridge Construction
(1) The steel fiber reinforced concrete pavement on the bridge deck can effectively improve the durability, crack resistance and comfort of the bridge deck, and enhance the stiffness and bending strength of the bridge. At the same time, this technology can reduce the thickness of pavement, thus reducing the weight of the structure, improving the stress condition of the bridge and prolonging the service life of the bridge deck. (2) Bridges with partially reinforced pier structures need maintenance in use. For piers, after bearing pressure for a period of time, there will be problems such as fracture and surface peeling. At this time, it is a good choice to repair with sprayed steel fiber concrete. This method can well meet the seismic requirements of the bridge and maintain the integrity of the bridge. (3) The upper bearing part of the bridge is the place where the upper bearing capacity is concentrated. The application of steel fiber reinforced concrete in this part can improve the structural mechanical properties of the bridge, improve the deformation problem and reduce the self-weight, which caters to the trend of lightweight and long-span bridge body.
4 Quality control measures
4. 1 Reasonable control ratio
According to the relevant regulations of building construction, the construction proportion of steel fiber reinforced concrete is determined by two key factors, one is the strength design of the project, and the other is the strength coefficient of construction preparation. Only by combining the above two factors scientifically can the compressive strength and flexural strength of steel fiber reinforced concrete be improved.
4.2 Use the correct construction method
In the process of steel fiber reinforced concrete construction, every link requires the operator to use the correct construction method. Once any link is omitted, it will have a negative impact on the whole project. The mixing of steel fiber concrete is the most important link in the construction process. When mixing steel fiber reinforced concrete, it is necessary to control the amount of single mixing to achieve uniform mixing. At the same time, the mixing work should follow certain procedures and principles, and should not be taken lightly. Only by mixing strictly according to the requirements can the propagated steel fibers solidify and agglomerate in the mixing process.
5 conclusion
To sum up, steel fiber reinforced concrete construction technology plays a very important role in road and bridge construction. The development and popularization of steel fiber reinforced concrete technology is not achieved overnight. Only by combining government departments, construction units and the masses with a positive attitude can this technology be popularized and used. For government departments, policies should be means, for construction units, projects should be benchmarks, and for the masses, scientific understanding should be guidance. It is believed that steel fiber reinforced concrete construction technology will play an increasingly important role in future road and bridge construction.
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