The concrete retardation time is too long and the anti-segregation agent is used to solve the problem. Anhui segregation agent is selected from Yulong

Abnormalities in the setting time of concrete generally manifest as excessive retarding, rapid setting and false setting. There are many factors that influence the abnormal condensation of cement concrete. Concrete admixtures, cement, admixtures, ambient temperature and wind speed may ultimately lead to the occurrence of abnormal condensation of cement concrete. Judging from the quality of concrete projects at this stage, the type of retarder, improper retarder dosage, incompatibility between admixtures and cement, and ambient temperature are the main reasons for abnormal condensation of cement concrete and even accidents in concrete projects.
Anti-segregation agent should be used to solve the problem of excessive retarding time of concrete

Causes of excessive retarding of concrete

(1) Excessive retarder component in concrete admixture , especially when the sucrose content is high;

(2) Overmixing of concrete admixtures caused by human or mechanical failure;

(3) Mistaken into fly ash or mineral powder Use of cement;

(4) Improper concrete mix design and too many admixtures, especially when the temperature of the concrete pouring environment is low;

(5) Influence of temperature, excessive temperature Low;

(6) Insufficient maintenance, especially when the temperature is too low;

(7) The air content of concrete is too large, causing the air content of concrete to reach 8-10%;

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(8) The concrete slumps are too large or even segregate and bleed, resulting in high fly ash content and high water-cement ratio on the surface of the concrete;

Causes of rapid setting of concrete

(1) There is no retarder added to the concrete admixture or the amount of retarder is not enough;

(2) For cement that uses anhydrite and fluorogypsum as the setting regulator, lignin sulfonate should be used. When using salt water-reducing agents, it is easy to cause rapid concrete setting;

(3) The water-cement ratio is low, the maintenance is not in place, and the ambient temperature is too high, the wind will cause the concrete to lose water prematurely and accelerate the hardening of the cement. ;

(4) Sulphoaluminate cement or high alumina cement is used;

(5) C3A content in cement is high and alkali content is high;
Concrete retards setting If the time is too long, use anti-segregation agent to solve it

Causes of false setting of concrete

(1) The ambient temperature is too high, the wind is too strong, the concrete loses water prematurely, and the maintenance is not in place and it is not covered in time. , especially when carboxylic acid admixtures are used to prepare high-grade concrete, the surface of the concrete quickly loses water and becomes hard, while the concrete in the lower layer is still relatively soft and has not set;

(2) Cement, admixtures, sand The adsorption of concrete admixtures by stone aggregates and other materials suddenly increases with time, pump pressure, and ambient temperature conditions. The slump is quickly lost, and the concrete is scattered like tofu. The main reason is that the admixtures and their types are related to changes in the adsorption capacity of cement;

(3) The temperature of the cement is too high, and the dihydrate gypsum in the cement dehydrates and turns into hemihydrate gypsum or anhydrous gypsum;

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Solution:

(1) In summer, it is best not to use cement with a temperature exceeding 80°C to mix concrete in a concrete mixing station;

(2) In summer, use underground Cold water (add ice if necessary);

(3) Maintain concrete in time to prevent premature loss of water or freezing;

(4) Before construction, make cement and Adaptability test of concrete admixtures, mixing concrete to observe fluidity loss, and examining the setting time of concrete at the prevailing temperature. Determine the suitability of concrete admixtures;

(5) Maintenance of mixing station instruments and equipment for reliable operation;

(6) Concrete admixture products must be inspected, reliable, and of stable quality;

(7) Appropriate concrete mix ratio;

(8) When encountering abnormally solidified concrete, analyze the specific problems in detail and remove them as soon as possible if they endanger the quality of the project. The sooner the better. Generally speaking, if excessive retardation exceeds 4 days, the loss of concrete strength will be serious; when false concrete setting occurs, cement mortar of the same strength grade can be used to remix the concrete before pouring or use the mortar to plaster the concrete surface. Collect light. After the concrete is quickly set, if it is not poured into the formwork, it will be discarded. If it is poured into the formwork, it will be cut out or retained depending on the specific situation.

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