During the production process, the materials must be fed in strict accordance with the mix proportion determined by the test without any randomness, the water cement ratio and mixing time shall be strictly controlled, the moisture content of sand and gravel shall be sampled in time with climate change, and the water consumption shall be adjusted.
In case of any error between the actual consumption and the drawing after pouring, the construction unit shall bear it by itself, which has nothing to do with the concrete company.
Gravel with high strength, 5 ~ 25mm particle size, good continuous grading, the same color, mud content less than 0.8% and no sundries shall be selected, and the place of origin, specification and color shall be determined.
(2) coarse aggregate (gravel).
preventive measures (1) the design adopts the “principle of dense fine reinforcement” , local reinforcement, such as mid span, slab column joint, post pouring belt, settlement belt and reinforcement belt.
(5) Admixtures.
Where there are people, there are rivers and lakes, and where there are interests, there are disputes.
2.
If there is no objection to the quantity during the random inspection, the delivery note shall be signed for confirmation.
Causes of strength: (1) unreasonable mix proportion design and insufficient strength of commercial concrete; (2) unstable control of concrete raw materials and processes and large fluctuation of commercial concrete quality; (3) random addition of water on site to change the water cement ratio and affect the strength; (4) loose vibration; (5) inadequate maintenance; (6) The specimen is not well formed and is not cured as required.
Preventive measures: (1) cement.
If it is found that the deviation is lower than the agreed deviation value in the process of spot check, it will be punished A batch of concrete supplied shall be signed in according to the minimum quantity.
Preventive measures (1) control the quality of incoming raw materials, resolutely reject unqualified raw materials, and ensure the qualified and stable quality of raw materials; the laboratory shall strengthen the certification of the trial mix of mix proportion, and timely adjust the mix proportion with the change of season to ensure the surplus rate of strength; (2) Strengthen the technical communication with the construction director and on-site supervision personnel, provide the operation manual of commercial concrete, eliminate illegal operation, standardize construction and ensure the project quality; (3) The curing after concrete pouring shall be effectively communicated with the construction unit and implemented in accordance with the specifications, and the effective curing shall not be abandoned due to trouble or increased cost, resulting in potential quality hazards of concrete; (4) the on-site test block production concrete company shall send technicians to cooperate with the on-site documenter according to the sampling system Conduct standard fabrication and timely curing to ensure uniform and qualified strength of concrete test block.
(3) Construction: the formwork support shall be firm; the stay time of the concrete mixer truck to the construction site shall not be too long to avoid adding water at will; the concrete vibration shall be dense; the concrete curing shall be timely.
(source: network, civil engineering inspection and sorting, and the copyright belongs to the original author)..
After the first batch of raw materials entering the site are sampled and retested by the supervisor, they shall be immediately “sealed”, and each batch of incoming materials entering the site in the future shall be consistent with the “sealed sample” If obvious color difference is found through comparison, it shall not be used.
Products with fineness above class II fly ash specified in technical code for application of fly ash concrete (gbj146-90) should be selected.
4.
(4) Fly ash.
It is best to select the same clinker.
3) causes of cracks (1) related to structural design and stress load: such as exceeding the design load range, structural settlement difference, insufficient member section size, insufficient reinforcement consumption, unreasonable reinforcement layout, etc.; (2) related to use and environmental conditions: such as environmental temperature, humidity change, reinforcement corrosion, impact, vibration, etc; (3) Related to raw materials and mix proportion: such as high cement consumption, high hydration heat, admixture problems (such as calcium content of fly ash), improper concrete mix proportion, etc; (4) Related to construction: for example, the water is added and tamped poorly on site, the slump is too large, the aggregate sinks and bleeding, the next process is carried out when the concrete surface strength is too low, the maintenance measures are improper or the maintenance is not timely, etc.
It is required to determine the manufacturer, strength grade and batch number.
Medium coarse sand shall be selected, with fineness modulus of more than 2.5 and mud content of less than 2%, without sundries, and the place of origin, sand fineness modulus and color shall be determined.
The supplier and fineness shall be determined, and shall not contain any sundries.
It is required to determine the manufacturer, brand and dosage.
The addition of fly ash can improve the fluidity and later strength of concrete.
(3) fine aggregate (sand).
Causes of color difference: (1) large color difference and instability of raw materials of concrete; (2) unstable slump of concrete; (3) construction operation reasons; (4) causes of formwork; (6) Reasons for on-site maintenance.
When the concrete mixer enters the construction site, the construction unit should organize personnel to weigh it, or spot check it.
How can we effectively prevent those quarrels between the mixing plant and the construction unit? 1.
Causes: (1) measurement problems of concrete enterprises; (2) waste of concrete enterprises in the unloading process (unloading to the ground, reversing of mixer truck, etc.); (3) drivers sell concrete secretly; (5) the construction site is moved to other parts for pouring; (6) the pouring thickness is not well controlled and over thick; (7) there is too much allowance in the pump truck pipe; (8) In order to avoid such disputes, we suggest that the concrete unit weight should be agreed upon when the contract is signed, and the concrete unit weight of each strength grade should be agreed.
(2) The mix proportion design must be reasonable; the raw materials must be selected correctly and scientifically; the mix proportion shall be adjusted according to the engineering characteristics, climatic conditions, structural design requirements and on-site construction conditions.
Portland cement is preferred.
