What should pay attention to when using bulk concrete as a prefabricated component?
(1) Insufficient strength or uneven strength of concrete, large deviation of strength, is a frequent quality problem, and is a quality problem affecting structural safety. To prevent this quality problem, comprehensive management is required. In addition to strict control in concrete transportation, pouring, maintenance and other aspects, special attention should be paid during the concrete mixing stage. It is necessary to control the quality of various raw materials. It is necessary to carefully implement the mix ratio and strictly measure the ingredients of raw materials.
(2) Cracks in concrete structures are a common quality problem. There are many reasons for this. In the mixing stage, if the sand, stone contains a large amount of mud, the water consumption is large, the use of expired cement or excessive cement, etc., may cause concrete shrinkage cracks. Therefore, the yellow sand in the concrete is controlled to be medium sand, and the sand content is not more than 40%. Therefore, in the mixing stage, it is still necessary to strictly control the quality of raw materials, carefully implement the mix ratio, and strictly measure.
(3) The concrete mixture has poor workability and the slump does not meet the requirements. There are many reasons for this type of quality problem. Among them, the water-cement ratio has the greatest influence; the second is the gradation of the stone, the excessive content of the needle and the flaky particles; the third is that the stirring time is too short or too long. The solution should start from the above three aspects.
(4) Concrete in winter construction is prone to freezing damage. The solution is to carefully implement the relevant regulations of winter application, pay attention to the heating temperature of aggregate and water in the mixing stage, ensure the temperature of the concrete, and strengthen the maintenance.
(5) Pay attention to the storage and storage of cement, admixtures and mixed materials. Cement should have a cement store to prevent rain and moisture; cement that has been shipped for more than three months should be retested. Admixtures and mixes should be protected from moisture and deterioration. They should be stored separately according to specifications and varieties to prevent misuse.