Retarding admixtures are additives used in concrete to delay the setting time. By slowing down the hydration process, they extend the workability period, allowing more time for placement and finishing. This is particularly useful in hot weather or large construction projects where rapid setting can lead to challenges. Retarding admixtures improve concrete quality and facilitate better placement and finishing, ultimately enhancing construction efficiency.
The following retarders can be used in concrete works:
1. Glucose, sucrose, molasses, sugar calcium and other sugar compounds;
2. Hydroxycarboxylic acids and their salts such as citric acid (sodium), tartaric acid (sodium potassium), gluconic acid (sodium), salicylic acid and its salts;
3. Polyols such as sorbitol and mannitol and their derivatives;
4. Organic phosphoric acid and its salts such as 2-phosphonic acid butane-1,2,4-tricarboxylic acid (PBTC), amino trimethylene phosphonic acid (ATMP) and its salts;
5. Phosphate, zinc salt, boric acid and its salts, fluorosilicate and other inorganic salts.
6. Concrete engineering can use retarder compounded by different retarding components.
1. The retarder is suitable for concrete that delays the setting time.
2. The retarder is suitable for concrete that requires slump retention ability, concrete that has a long static stop time or long-distance transportation, and self-compacting concrete.
3. The retarder can be used for mass concrete.
4. The retarder should be used for concrete where the daily minimum temperature is above 5℃.
5. Retarders such as citric acid (sodium) and tartaric acid (potassium sodium) should not be used alone for lean concrete.
6. When the retarder containing carbohydrates is used in combination with the water reducing agent, the compatibility test can be carried out according to the method in Appendix A of this specification.
Zhengzhou, Henan, China