Dosage and water consumption of polycarboxylate superplasticizer:

Polycarboxylate superplasticizer has the characteristics of low dosage and high water reduction. When the dosage is 0.15-0.3%, the water-reducing rate can reach 18-40%. However, when the water-to-binder ratio is small (below 0.4), the dosage is more sensitive than when the water-binder ratio is high. The water-reducing rate of polycarboxylate superplasticizer varies with the amount of cementitious material. Under the same conditions, the water-reducing rate of the amount of cementitious material less than 3 is less than 400kg/m3, and this difference is easily ignored. However, in the process of use, it will be found that this traditional empirical method is not suitable for Polycarboxylate superplasticizer, mainly because Polycarboxylate superplasticizer are more sensitive to water consumption than traditional superplasticizers. When the water consumption is reduced, the expected workability of the concrete cannot be achieved; when the water consumption is high, although the slump becomes larger, there will be a lot of bleeding and even a little segregation, which has a negative impact on the overall performance of the concrete. This will cause a lot of inconvenience in the actual site construction. The temperature has a great influence on the amount of polycarboxylate superplasticizer. In practice, it is found that the amount of admixture used in normal production during the day is low at night (the temperature is lower than 15 ℃), and slump often occurs” Return to big”, even bleeding and segregation.

Concrete is very picky about the saturation point and water consumption of the water reducing agent. Once the excess amount is exceeded, the concrete will appear unfavorable phenomena such as segregation, bleeding, slurry running, hardening and excessive air content.

(1) The trial mix test should be carried out again with the changed raw materials to adjust the dosage to achieve the best effect;

(2) The dosage of polycarboxylate superplasticizer and the water consumption of concrete must be strictly controlled during use;

(3) In the concrete test of the water reducing agent for the raw materials, try to adjust the water reducing agent to the “sluggish” type to achieve the purpose of being insensitive to the raw materials and water consumption.