Post Date:22,Jan,2024
1.The dosage of polycarboxylate superplasticizer water-reducing agent is too large, and there are too many bubbles on the surface of the concrete structure.
From the perspective of pumpability and durability, it is beneficial to appropriately increase the air-entraining properties. Many polycarboxylate water-reducing agents have high air-entraining properties. Polycarboxylic acid-based water-reducing admixtures also have a saturation point like naphthalene-based water-reducing admixtures. For different types of cement and different cement dosages, the saturation points of this admixture in concrete are different. If the amount of admixture is close to its saturation point, the fluidity of the concrete mixture can only be improved by adjusting the amount of slurry in the concrete or using other methods.
Phenomenon: A certain mixing station has been using polycarboxylic acid-based water-reducing agent to prepare concrete for a period of time. Suddenly one day, a construction site reported that after removing the formwork of the shear wall, it was found that there were too many bubbles on the surface of the wall and the appearance was too poor.
Reason: On the day of pouring concrete, the construction site reported many times that the slump was small and the fluidity was poor. The staff on duty in the laboratory of the concrete mixing station increased the amount of admixtures. The construction site used large shaped steel formwork, and too much material was added at one time during pouring, resulting in uneven vibration.
Prevention: Strengthen communication with the construction site, and recommend that the feeding height and vibration method be operated strictly in accordance with the specifications. Improve the fluidity of the concrete mix by adjusting the amount of slurry in the concrete or using other methods.
2.Polycarboxylate water-reducing agent is over-mixed and the setting time is prolonged.
Phenomenon: The slump of concrete is large, and it takes 24 hours for the concrete to finally set. At a construction site, 15 hours after the structural beamconcrete was poured, it was reported to the mixing station that part of the concrete had not yet solidified. The mixing station sent an engineer to check, and after heating treatment, the final solidification took 24 hours.
Reason: The amount of water-reducing agent is large, and the ambient temperature is low at night, so the concrete hydration reaction is slow. The unloading workers at the construction site secretly add water to the concrete, which consumes a lot of water.
Prevention: The amount of admixture should be appropriate and the measurement should be accurate. We remind you to pay attention to insulation and maintenance when the temperature at the construction site becomes low, and polycarboxylic acid admixtures are sensitive to water consumption, so do not add water at will.
Post time: Jan-24-2024