① In concrete projects, the following retardants or retarding water reducing agents can be used, sugars, lignosulfonates, hydroxycarboxylic acids and their salts, inorganic salts and other amine salts.
② Retarder and retarding water-reducing agent can be used for large-volume concrete, concrete constructed in hot climate conditions, and concrete that needs to be parked for a long time or transported over long distances of concrete.
③ Retarder and retarder water-reducing agent should not be used for concrete construction where the daily minimum temperature is below 5℃, nor should they be used alone for concrete with early strength requirements. Concrete and steam-cured concrete.
④ Retarder such as citric acid and sodium methyl tartarrate should not be used alone in ash-lean concrete with low cement content and large water-cement ratio.
⑤ When adding sugar retarder to cement using anhydrite or industrial waste gypsum as the setting agent, a cement adaptability test should be carried out first. It can only be used after passing the test.
⑥ The type and dosage of retardant and retarding water-reducing agent should be based on the setting time, transportation distance, parking time, strength and other requirements of the concrete. to make sure.
Generally, the dosage of retarder should be within 0.1-0.3%, and the dosage of hydroxycarboxylate should be between 0.03-0.1%.
⑦ Retarder and retarding water-reducing agent should be added in solution, and the amount of water in the solution should be deducted from the mixing water. When there are many insoluble or insoluble substances, it must be stirred thoroughly before use.
⑧ Retarder or retarding water-reducing agent can be used in combination with other admixtures, but must be determined through testing. When preparing solutions, if flocculation or precipitation occurs, the solutions should be prepared separately and added to the mixer separately.
⑨ The pouring, vibrating and curing of concrete mixed with retarder and retarded water-reducing agent can be the same as those without additives. However, watering and curing should be done after final setting, and early local concentrated loads should be avoided. </p
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