Concrete construction of large photovoltaic grid-connected system

After completing the requirements and preparations for civil construction of large-scale photovoltaic grid-connected systems, even if the concrete is constructed.

Before the concrete is poured, a construction measure plan for the concrete project shall be submitted, which includes: the supply plan of cement, steel bar, aggregate and formwork, as well as the concrete pouring procedure drawing and construction progress plan, etc. The concrete pouring procedure drawing shall be in accordance with the requirements of the construction drawings, and the construction methods and procedures for the concrete pouring of each project part, the binding and welding of steel bars, the installation of embedded parts, etc. shall be compiled in detail. During the construction process, provide the supervisor with the detailed construction records and reports of the concrete project in a timely manner, the contents of which shall include: variety and quality inspection results of various raw materials; mix ratio of concrete; operation records of heat preservation, maintenance and surface protection of concrete; temperature during pouring, pouring temperature of concrete outlet and pouring point; formwork operation records and the date of demolding of each component; reinforcement operation records and actual reinforcement consumption of each component and block; test results of concrete specimens; concrete quality inspection records and quality accident handling records, etc.

Concrete materials must be strictly controlled. The cement complies with current industry standards. Before each batch of cement leaves the factory, the quality of the cement of the manufacturer shall be inspected and re-inspected. After each batch of cement is transported to the construction site, the supervisor has the right to conduct warehouse inspection and sampling testing of the cement. In the process of cement transportation, pay attention to its varieties and labels not to be mixed, and take effective measures to prevent the cement from being damp. The arrived cement is stored in special warehouses or storage tanks according to different varieties, labels, factory batch numbers, bags or bulk, etc., to prevent cement deterioration due to improper storage.

Water use. All water suitable for drinking can be used, and untreated industrial wastewater shall not be used. When drinking water is used, the water quality should comply with current industry standards. The substances contained in the mixing water should not affect the growth of workability and strength of concrete, and cause corrosion of steel bars and concrete.

Aggregate. The quality of the coarse and fine aggregates conforms to the current industry standards. According to the actual local conditions, the basic aggregates are selected from standard stones. Aggregates of different particle sizes are stored separately, and it is strictly forbidden to mix with each other and soil; when loading and unloading, avoid serious crushing of the aggregates. Aggregates containing active ingredients must be demonstrated by special tests.

Admixtures. According to the performance requirements of concrete, combined with the selection of concrete mix ratio, the amount of admixture is determined through tests, and the test results should be reported to the supervisor. The quality and application technology of the admixture used in concrete conform to the current national standard “Concrete Admixture” GB8076–2008, “Concrete Admixture Application Technical Specification” GB50119-2013 and relevant regulations on environmental protection.

Mix ratio. The concrete mix ratio must be selected through the test, and the test is based on the relevant provisions of the current national standard “Ordinary Concrete Mix Proportion Design Regulations” JGJ55-2011. Before the concrete mix ratio test, the ingredients for various mix ratio tests and the mix ratio test plans for mixing, mould making and curing should be submitted to the supervisor.

Concrete sampling test. In the process of concrete pouring, according to the relevant provisions of “Code for Acceptance of Construction Quality of Concrete Structure Engineering” GB50204-2015 and the instructions of the supervisor, conduct concrete sampling tests on site and submit the following materials: ①Selected materials and product quality certificate; ②Ingredients, mixing and overall dimensions of the test piece; ③Manufacture and maintenance instructions of the test piece; ④Test results and their description; ⑤ Test data such as bulk density, compressive strength, tensile strength, ultimate tensile value, elastic modulus, Poisson’s ratio, slump and initial setting and final setting time of concrete of various ages.

Mix. When mixing cast-in-place concrete, strictly follow the approved concrete batching list for batching. Yachou changed the ingredient list without authorization. Unless otherwise stipulated in the contract, fixed mixing equipment shall be used, and the productivity of the equipment shall meet the requirements of the peak pouring strength of this project. All weighing, indicating, recording and control equipment should have dust-proof measures, the equipment should be accurately weighed, and its weighing deviation should not exceed the relevant provisions of the “Concrete Structure Engineering Construction Quality Acceptance Specification” GB50204-2015, and the accuracy of the weighing equipment should be checked regularly according to the instructions. After the installation of the mixing equipment is completed, the operation and operation inspection of the equipment shall be carried out together with the supervisor. Concrete mixing is in accordance with the relevant provisions of the “Concrete Structure Engineering Construction Quality Acceptance Specification” GB50204-2015, and the mixing procedure and time should be determined by tests.

Transportation. After the concrete is out of the mixer, it should be quickly transported to the pouring site. The transportation time should not exceed 45 minutes. There should be no separation, slurry leakage, serious bleeding and excessive slump reduction during transportation. When concrete is put into the warehouse, segregation should be prevented.

Pouring. 8 hours before the start of concrete pouring and 12 hours for concealed works, the supervisor must be notified to inspect the preparation of the pouring site. The inspection contents include: foundation treatment, cleaning of the poured concrete surface, and burying and installation of formwork, steel bars, embedded parts and other facilities; after passing the inspection, concrete pouring can be carried out. Before the concrete is poured, the batching list for the concrete pouring in the part shall be submitted for review and approval, and then the concrete can be poured.

Foundation surface concrete pouring. Concrete pouring work can only be carried out after the foundation surface of the building has passed the acceptance inspection. The temporary protective layer of the foundation should be treated before the vertical formwork on the soft foundation binds the steel bars, and if necessary, the concrete back cover of the same strength level as the base plate should be poured according to the requirements of the construction drawings; when operating on a soft foundation, efforts should be made to avoid damaging or disturbing the undisturbed soil, and if necessary, pour the bottom plate with the same number of concrete back cover as required by the construction drawings. Concrete pouring should be carried out by means of pump truck pressing and feeding. The pouring of concrete is carried out continuously, and it is formed at one time, and the concrete is vibrated and compacted.

Conservation. After the concrete is poured, it should be sprinkled in time for curing to keep the concrete surface often wet. The curing of the concrete surface should generally start within 12 to 18 hours after the concrete is poured, but it should be cured in advance in hot and dry climates. In the low temperature season and the season of sudden temperature drop, early surface curing should be carried out. The curing time of concrete should not be less than 14 days, and in dry and hot climate conditions, the curing time should not be less than 28 days. Concrete maintenance work should be in charge of a special person, and maintenance records should be made.

Embedded parts. Seven days before the concrete is poured, according to the structural shape drawing and the drawings of various embedded parts, draw a list of the embedded parts of the listed projects and submit them for approval. Submit the acceptance materials for embedded parts according to the specified content. The deviation between the position of the embedded parts and the design drawings should not exceed ±5mm, and the exposed metal embedded parts should be treated with anti-corrosion and rust prevention. When the same support foundation is concreted and poured, the intermittent time of concrete pouring should not exceed 2h; if it exceeds 2h, it should be treated according to the construction joint. Before welding the top embedded parts and the steel support legs, the foundation concrete curing should reach 100% strength.

If it is a static pressure pile foundation, the construction should meet the following requirements: ① The pile in place should be kept vertical, so that the axes of the jack, the pile section and the pile driving hole are coincident, and the eccentric pressure should not be applied. The pile head of the static pressure prefabricated pile shall be equipped with a steel pile cap. ② During the pile pressing process, the pressure, the verticality of the pile and the pressing depth should be checked. The deviation of the pile position plane should not exceed ±10mm, and the deviation of the verticality of the pile should not exceed 1% of the length of the pile. ③ The pile pressing should be carried out continuously, and the interval between the same pile should not exceed 30min. The pile pressing speed should generally not exceed 2m/min.

Masonry works. Submit a construction measure plan including the following: construction floor plan; masonry work construction methods and procedures; configuration of construction equipment; site drainage measures; quality and safety assurance measures; construction schedule; material test reports for masonry; quality inspection records and reports.

During the masonry construction process, the contractor shall submit construction quality inspection records and reports as instructed by the supervisor. The following completion materials shall be submitted when the completion acceptance is completed: masonry project completion drawing; masonry material test report; geological surveying and mapping data of the foundation of the masonry project; masonry quality report of the masonry project; other completion materials required by the supervisor.

Material requirements. The variety and strength grade of the bricks meet the design requirements, and there are factory certificates and test sheets. The mixing ratio of cementitious materials shall meet the strength and construction and workability requirements specified in the construction drawings. For mixing cementitious materials, ingredients should be made strictly according to the ingredients list determined by the test. It is strictly forbidden to change without authorization. The allowable weighing error of ingredients should meet the following requirements: cement is ±2%: sand and gravel are ±3%; water and admixtures are ±1%. During the mixing process of the cementitious material, the stability of the moisture content of the coarse and fine aggregates is maintained. According to the change of the moisture content of the aggregate, the water consumption can be adjusted at any time to ensure the accuracy of the water-cement ratio. Mixing of cementitious materials: mechanical mixing is not less than 2~3min; manual mixing is dry mixing at least three times, and then wet mixing until the color is uniform before use. The cementitious material can be used as needed.

Support foundation construction process. The base of the bracket adopts microporous cast-in-place piles. Construction sequence: positioning → steel cage processing → micro-hole forming → lower steel cage → pouring concrete → curing. Bracket installation and construction process: the bracket adopts a steel structure, which is factory-produced and transported to the construction site for installation. Only a small number of steel components are processed on site, and the brackets are connected by bolts.

Related Posts