Interpretation of the instantaneous loss of slump in concrete using polycarboxylate superplasticizer

Use concrete water-reducing agent to improve the cohesion of concrete, but improper use will damage the slump retention of concrete. In recent years, due to the rapid development of sulfamate water-reducing agent technology, product costs have been significantly reduced, resulting in a rapid increase in the number of users using polysulfamate water-reducing agents, and the specific problems using sulfamate water-reducing agents have also become more and more serious. highlight. Let’s talk about a few points about the problems encountered:

1. Incoming factory inspection

(1) After the batch of sulfamate water-reducing agent is weighed, sampling should be taken first experiment. During the experiment, be sure to use the manufactured mortar mix (the sand and gravel can be dried), and do not use the cement slurry method for the experiment; the storage time of the concrete sample cannot be too long; the slag powder and coal ash should also be the most recently removed samples. .

(2) During the experiment, if it is found that the concrete mixture has good cohesion and the slump loss over time does not exceed 50mm, the goods can be loaded and unloaded. If it is found that the concrete mixture oozes slurry after mixing and grips the ground, the situation after 1 hour needs to be checked. If the concrete has no longer segregated after 1 hour and the slump loss over time does not exceed 50mm, it will be considered qualified and cargo can be loaded and unloaded. .

2. Temperature control of concrete entering the factory

(1) When the temperature is high in summer, the temperature of the concrete entering the factory should be controlled not to exceed 60°C, and the concrete mix should be discharged from the machine The temperature cannot exceed 30℃. If the above standards can be exceeded, it will be less likely to collapse too quickly.

(2) When the concrete temperature cannot exceed the specified limit, surface water can be used to clean the sand and gravel to reduce the temperature; cover the pool with aluminum-platinum reflecting sunlight to control the water temperature at 20°C under.

3. The adaptability of sulfamate water-reducing agents

Compared with other water-reducing agents, sulfamate water-reducing agents have weaker adaptability to concrete raw materials. It is particularly sensitive to the temperature of concrete, the mud content of sand and gravel, the composition of mineral admixtures, and the intake of water reducing agent. Therefore, before using sulfamate superplasticizer, it is necessary to conduct experiments in batches commonly used in production, and then put into production after passing the test.

</p