Although concrete admixtures can effectively improve the performance of concrete, they sometimes produce negative effects, especially when used improperly. Some abnormal phenomena will occur. This should be paid attention to and find out. Causes and solutions. The following causes and solutions are for readers’ reference.
(1) Concrete slump loss is large
Cause: admixtures and cement or other raw materials Poor adaptability; low admixture dosage; high cement or ambient temperature, fast hydration rate; improper use of concrete mix ratio.
Solution: Notify admixture manufacturers to adjust the adaptability of admixtures to cement, replace unqualified raw materials; increase the amount of admixtures and increase the content of mineral admixtures Quantity; adjust the concrete mix ratio.
(2) The setting time is too long
Cause: excessive dosage of retarder or sudden cooling The amount of retarder was not adjusted in time, and the amount of admixture was not adjusted according to the temperature and retarder conditions during production; the quality of the cement changed; there were quality problems with the mineral admixtures; uneven mixing or the mixing time was too short, and the admixtures were not Disperse evenly.
Solution: Adjust the amount of admixture according to weather conditions; notify the admixture supplier to reduce the amount of retarder or change the type of coagulant; replace cement or minerals Admixture; production is to adjust the concrete production mix ratio in time according to changes in temperature.
(3) False coagulation
Cause: Anhydrite or industrial gypsum is used as a setting regulator Cement encounters cement containing calcium lignin or calcium sugar; the admixture contains sodium carbonate early strength agent; the amount of triamine exceeds 0.1%; the temperature of the cement is too high; the amount of early strength agent is too large.
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