With the development of science and technology, modern bridge engineering tends to be more and more large-scale, mechanized and complex. In order to reduce the self-weight of the structure, reduce the cross-section, improve the load-bearing capacity and increase the span, the application of high-strength concrete provides an effective way for this purpose. The application of expansion joints in road and bridge construction can not only improve the level of construction technology, but also improve the overall quality of road and bridge construction. Under the new situation, the market competition is becoming more intense, give full play to the role of road and bridge expansion joints, is to ensure the core competitiveness of the construction unit and the decisive factor in the road of sustainable development. In the construction of road and bridge projects, should be familiar with the basic factors affecting the amount of expansion and construction technology points, in order to provide a reliable guarantee for the healthy development of the construction unit.
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The road bridge expansion joint construction material preparation
- Cement material control work. In order to ensure the quality of the project, this project specially selects the 52.5 grade silicate or ordinary silicate cement which meets the national standard. The cao, mgo, so3 content of cement should meet the requirements of the design documents, in addition, the alkali content is also strictly controlled to reduce the excessive alkali aggregate reflection produced by cement in mixing concrete. Cement fineness specific surface area indicators to meet 350 to 380m2/kg.
- Aggregate control. Concrete requires the use of coarse and fine aggregates, the following analysis of the control of coarse aggregates in concrete. Coarse aggregate selection of limestone gravel with a nominal maximum particle size of not more than 20mm, the performance indicators of this gravel should meet the design requirements: Mud content needs to be within the limits, the gravel should be cleaned with water before use, in order to control the mud content. The alkali activity test of the aggregate should be strictly carried out, and the stone crushing can be done with a hammer crusher. Crushed stone shape also has special requirements, its needle flake content should be less than 5%, crushing value should be less than 9%, and its result should not be less than 2 times the compressive strength of the concrete to be prepared. Crushed stone solidity test, the quality loss should be less than 4%. The fine aggregate in the concrete should be used as far as possible without clay in the sand, the alkali content of which should also meet the relevant technical requirements, the fineness modulus should be less than 3%, and the mud content should be controlled within 4%.
- The reasonable use of admixtures. The admixtures used in this project shall be tested by the relevant technical inspectors and shall be used only after passing the test, and the use of untested or unqualified products is strictly prohibited. Additive manufacturers should provide product specifications, product specifications should identify the main additive components and content, factory inspection reports and certificates of compliance, as well as the performance report of the concrete after the addition of admixtures. Water reducing agent selection of high-performance polycarboxylic acid composite water reducing agent.
- The quality control of other materials. This project before pouring the concrete in the seam, between the old and new interface coated with foreign imports of concrete interface agent, to meet the requirements of the project use. The chloride ion content in concrete should also be effectively controlled, and the amount of various materials added should not exceed 4.0kg/m3. In addition, the amount of concrete admixture should also be controlled within the requirements of the design documents, and the use of excessive concrete admixture for the convenience of construction is strictly prohibited. Additives additive equipment and instruments should be clearly marked, accurate measurement, the error should be controlled within the appropriate range.
Highway bridge construction technology points analysis of expansion joints
The type of expansion joint is selected by the designer considering the road grade, length of the beam and structural characteristics, etc. Different types of expansion joint have different characteristics. Although different types of expansion joint are designed to meet the requirements from the viewpoint of beam expansion, the effect on traffic and durability of the expansion joint itself are different from the viewpoint of use. This paper analyzes the construction technology of expansion joints of a highway bridge. According to the construction sequence, the expansion joint installation process can be divided into two processes: Paving after the installation of joints and paving after the installation of joints. In this construction, paving first and then installation process is chosen, i.e. The asphalt pavement is saved at the bridge expansion joint first, and the road surface is removed and the expansion joint is installed after the roller has fully compacted to reach the traffic condition. This process can ensure the smoothness of the expansion joints and overcome the problem of not easy to compact on both sides of the expansion joints than the process of installing joints and then paving. Its specific construction process is as follows.
Trenching construction
After the completion of the bridge deck high-strength concrete paving operation, follow the relevant provisions of the expansion joint construction, the width of the slotting is determined. After measuring and placing the samples, the cutting machine is selected to cut the joints, which should ensure the neatness and straightness of the cut joints. The bridge deck debris cleaning is generally selected from equipment such as blowers, and the filling material is foam, etc. After slotting construction, in order to reduce the degree of damage to the 2 sides of asphalt concrete, the pre-buried steel in the slot should be adjusted, and to the top surface of the beam 1 cm position implantation of steel, when broken steel and other situations, should be timely repair. At the same time timely clean up the discarded materials that appear after slotting to ensure the neatness of the construction site.
Cutting construction
As a new construction material, high-strength concrete is widely used in large-span bridge structures for its superiority of high compressive strength, strong resistance to deformation, high density and low porosity. After completing the construction of road and bridge project pavement, the construction of cutting joints is carried out according to the width of the reserved slots, and the cutting machine is generally selected for the construction. In the seam cutting construction, must be strictly based on the bridge center position of the expansion joint centerline, and design regulations, from the centerline position to 2 sides of the construction width, should ensure the straightness and consistency of the line, and then follow the specific situation of the line through the seam cutting machine to cut the bridge deck pavement construction. Should ensure the accuracy of the position of the cut seam, and with the manual way, the brick paving layer cutting debris generated by the timely cleanup. In the construction of cutting joints, the road surface should be covered outside the cutting joints to avoid harm to the road surface and prevent the concrete pavement from loosening.
Pre-embedded reinforcement
Strictly control the quality of reinforcement, to avoid unqualified quality reinforcement materials for the construction site. Road and bridge expansion joint construction, because of a large amount of steel, processing should be centralized, and transported to the site. During construction, both ends of the reinforcement should be welded to the steel column to ensure that the length of the main reinforcement meets the construction requirements and the deviation cannot exceed the allowable range. Bury the steel bars to the exact position, so as to determine the position of the steel bars. Mark out each rebar point on it, and make sure that the rebar is not contaminated by the soil when filling for sand rebar in deep position. According to the relevant design requirements, calculate the length and thickness of the rebar weld. If the deformation or bending phenomenon occurs during the pre-burial of the reinforcement, it should be adjusted in time to ensure the accuracy of the pre-burial position of the reinforcement. Reinforcement implantation technology is generally used in the case of damaged reinforcement. In the construction of reinforcement implantation, it should be fully integrated with the anchorage direction of the expansion joint to ensure that the anchorage reinforcement of the expansion joint and the welding position of the implantation reinforcement are qualified and have high force capacity. When cleaning the surface rust of reinforcement, iron brush is generally selected for construction. If the misalignment occurs in the position of the pre-buried reinforcement and the anchorage ring of the expansion joint device, the anchorage ring of the expansion joint should be adjusted in time.
Installation of expansion joint device and welding construction
After completing the above links, the levelness of the bridge deck should be determined and the gap parts of the bridge should be cleaned up. When installing the expansion joint device, the expansion joint device is lifted into position first and combined with the length of the channel steel, the double limb type is selected to set the channel steel on the bridge deck, and the expansion joint device is lifted by nail bolts and finally fixed on the channel steel.
In the welding construction, it must be fully combined with the width of the expansion gap in order to carry out the welding time determination. Firstly, the positioning spot welding construction is carried out, that is, the matching anchor rings and anchor bars on 2 sides of the expansion joint device are spot welded sequentially along one end of the expansion joint device, and after finishing the spot welding, the flatness and straightness of the expansion joint device must be fully tested to ensure that its quality meets the construction requirements before the welding operation can be carried out. Secondly, after fixing the expansion joint, its elevation should be retested to ensure that deformation and deviation will not occur in the temporary fixing process, and the anchoring reinforcement and pre-buried reinforcement of the anisotropic steel beam should be welded on both sides at the same time to ensure its stability. Finally, after finishing all the welding work, the fixture should be dismantled in time, and the shrinkage and hanging seam devices should be lifted, followed by quality inspection again, and if problems are found, corresponding measures must be taken in time to deal with them, and finally the reinforcement should be tied.
Conclusion
To sum up, with the national economy development speed rising, in the road and bridge engineering construction, only according to the relevant construction requirements for construction, in order to improve the quality of highway engineering. Expansion joint construction as an important part of the construction of road and bridge engineering construction, only on the basis of understanding its construction points, in order to improve its technical level, in order to improve the quality of the project, and to achieve the maximum economic benefits of road and bridge engineering provides a reliable guarantee.
