Reinforced concrete, as a high-quality engineering material, is gradually used in major engineering industries, and this is especially true for water conservancy projects. However, reinforced concrete has certain drawbacks in engineering construction due to its structural characteristics, which is the cracking phenomenon that affects its quality. The cause of the cracking phenomenon of concrete is caused by the corresponding problems, only in the engineering operation will be effective control of quality supervision and supervision, and through the standardization of the construction environment for reasonable operation, can to a certain extent reduce the occurrence of cracking phenomenon.
For the cracks that have been formed, you can use professional means to make up for it, to minimize the loss.
The main points of reinforced concrete construction technology in water conservancy project
1. In general, reinforced cement soil technology has three components, which are dialectically unified and cannot be separated, that is, the technology of effective combination through reinforcement, the technology of operation through the formwork, and the technology of combination through reinforcement. Reinforcement technology can be combined with the internal structure of the concrete, while the formwork is to create a platform for concrete forming, concrete is the most important link in the construction of the project, its construction quality determines the quality of the completion of the water conservancy project.
(1) The construction of reinforcement is to be done before the concrete is placed.
The reinforcement work consists of handling the reinforcement, connecting it to each other, and assembling it in several points. In the construction, the most important part is to check the basic materials of the reinforcement first, the quality of the reinforcement must be strictly in accordance with the production requirements of the standardized operation, and issue a quality assurance certificate for the reinforcement. The processing techniques should be refined in a targeted manner, with different requirements for different processing.
Rebar, as a raw material of steel nature, can be welded with equipment or tied with materials in order not to destroy its recyclability during the connection operation. Finally, the assembly of the reinforcing steel is done according to the construction environment and its own installation requirements. After the reinforcement assembly meets the specification requirements and the quality inspection is passed, the formwork can be fixed and finally the concrete can be poured.
(2) the formwork body for the concrete pouring platform, its structural composition is usually by the formwork structure and used to support the weight of the part of the common existence.
In the application of the formwork in water conservancy projects, the formwork can basically be made of wood and steel. Due to the different composition characteristics of the formwork, the functional composition of the assembly is not the same.
The support system of the formwork directly determines the completion quality of the formwork for concrete work, and the use of the completed concrete is also reserved, so the formwork is an important guarantee for the quality of concrete placement, and should be placed in strict accordance with the requirements in the construction.
Before construction, the staff needs to check the surface of the formwork to ensure that there is no debris on the surface and keep the layout neat and dry, make a comprehensive comparison of the formwork parameters to confirm that its support parameters are proportional to the weight of the concrete pour, and keep the width between the formwork arranged according to the pouring requirements to avoid leakage during the pouring process. After the successful completion of the formwork and its support work, it is just as necessary to put the quality inspection in the first place before the final reduction of the penal pouring construction.
The overall quality of the project is determined by the perfect cooperation of each part, and only by strengthening its internal overall connectivity can we ensure that the quality of the project meets the standard requirements. In the construction process of water conservancy project, the material composition ratio of concrete is more important and needs to be compared and optimized through the analysis of data to make it more functional. After the construction of concrete pouring is completed, timely maintenance operations are essential. Keeping the intermittency of pouring is the most effective preventive measure to prevent cracking.
Control techniques of reinforced concrete in construction
1. Before admission should check a variety of human field materials unqualified not to enter; strictly according to the construction ratio notification list to mix concrete, water reducing agent must be weighed and then loaded into plastic bags. On-site concrete mixing, – generally measured raw materials are first gathered in the loading hopper from the loading hopper into the mixing cylinder.
Water and liquid admixtures are measured and fed directly into the mixing cylinder at the same time as they are fed into the mixing cylinder. Concrete construction batching is one of the important links to ensure the quality of concrete must be strictly controlled. Construction batching when the quality of concrete is affected by two main factors: First, inaccurate weighing.
2. not according to the actual moisture content of sand, stone material changes in the construction ratio of the conversion will inevitably change the original theoretical ratio of water-cement ratio, gravel ratio and slurry bone ratio. These directly affect the cohesiveness, fluidity, compactness and strength level of concrete. The order of raw materials gathered into the hopper: when there is no admixture and mixes into the hopper in the order of stone, cement, sand.
When mixed with mixture, the order is stone, cement, mixture, sand. When mixed with dry powder admixture, the order of stone, admixture, cement, sand. Concrete mixing is not less than the minimum time specified for concrete mixing. Construction shall not arbitrarily increase or decrease the amount of material must be mixed concrete according to the specified slump, the unqualified concrete shall not be poured. During the mixing process, the mixing depth should be checked at any time, focusing on checking whether there is a “plain” sandwich at the bottom of the mix. Concrete meets the requirements when the fat compound is evenly mixed, consistent color, with good fluidity, cohesion and water retention, no water secretion, no segregation. If it does not meet the requirements, the reasons should be found and adjusted in time, and require a person responsible for picking out the soil, super-sized particles and other debris; concrete pouring to vibrate densely without leakage and over-vibration, especially in the inner mold vibration leakage phenomenon and formwork running slurry.
3. Concrete paving to the pouring site of the mixture, generally poured directly to the installation of the formwork of the slot and manual uniformity, there are obvious segregation should be mixed again. Paving should be a large iron handle to the mixture to put loose, and then use the shovel, scraper to put the material loose, paving.
In the vicinity of the formwork, you need to use the square shovel with the buckle shovel method to spread the mixture and insert the pounding several times to make the mortar pounding out, so as to avoid the phenomenon of hollow honeycomb. Paving loose concrete should be slightly higher than the top surface of the formwork design height of about 10%. Construction interval shall not be too long, – generally should not exceed lh, for reasons of stoppage within lh, can have been pounded concrete surface covered with sacks embedded in the work will be raked loose concrete and then continue to pave; such as stoppage of more than lh should be construction joints, such as in the middle of the rain when the plant stopped paving stock set construction joints, – side operators can continue to smear under the shed and other work.
Reinforced concrete in the construction of the problem and corrective measures
1. If the problem of exposed reinforcement is found, the concrete slag and rust remaining on the surface of the exposed reinforcement should be promptly removed, flushed and moistened with water, and smoothed and leveled with a cement mortar with a ratio of 0.4 to 0.5.
If the location of the exposed reinforcement is deeper, the weaker part of the concrete should be removed first, rinsed with water and moistened, and the exposed reinforcement should be re-pounded with more compacted fine concrete and carefully maintained again. To prevent the problem of exposed reinforcement, it is necessary to fully confirm that the reinforcement is in the right place and the thickness of the protective layer is moderate during the preparation stage of concrete filling construction. For the control of the thickness of the protective layer, it can be used in advance to tie the reinforcement on the mat and to fix the way, for the reinforcement density is too high can be appropriate in the concrete to add stones and other mixed materials.
2. surface repair is a relatively simple and widely used repair technology, more suitable for surface cracks structure is more stable or will not affect the bearing capacity of structural water conservancy projects of all kinds of surface cracks, but also applicable to some deep cracks.
The general treatment is to reapply cement slurry directly on the crack surface or directly on the concrete surface area coated especially or asphalt and other types of materials with good corrosion resistance. While taking protective measures, in order to avoid concrete cracking again due to external forces or existing cracks continue to expand, additional protective measures need to be added to the crack surface, such as sticking a layer of glass fiber square cloth and so on.
3. Some of the concrete cracks to the overall impact of water conservancy projects, there are some cracks to the water conservancy project seepage control performance caused by a large impact, for this type of cracks more grouting technology to repair.
In the actual construction, the use of pressure equipment, so that the cement filling material fully into the cracks, to be cemented material solidification hardening, can be integrated with the concrete structure, to achieve the purpose of sealing dense reinforcement. Grouting technology in the more common application of cementitious materials, including cement slurry, polyurethane and other materials, should be based on the scale of water conservancy projects and other characteristics, a reasonable choice.
4. If the cracks bring greater impact on the structural performance of concrete, then the corresponding implementation of reinforcement process for concrete structures.
In the implementation of the reinforcement process for the concrete structure, the common methods include: appropriate expansion of its cross-sectional area, and for the structural elements of the corner outsourcing steel, the use of prestressing method, adhesive steel plate, the addition of quality points or additional shotcrete reinforcement.