Superplasticizer affect bleeding and segregation of fresh concrete
Segregation is due to the different particle size and density of the concrete mixture of the components and the emergence of stratification. Bleeding is a manifestation of isolated form. Moderate bleeding is usually harmless, if excessive bleeding, it may affect the performance of hardened concrete.
When certain workability of concrete, when incorporated superplasticizer to reduce the water-cement ratio for the purpose of incorporation of superplasticizer can reduce the mixing water, so water will also reduce bleeding. However, if the effective reduction of water-containing form together into lime, calcium sulfate and calcium carbonate precipitate, increasing the likelihood of segregation phenomenon, this time, to increase the amount of cement to improve or remedy. When certain concrete water-cement ratio, the incorporation of superplasticizer to improve the workability for the purpose of superplasticizer can be mixed with fluid concrete mixing high slump while. Fresh concrete segregation does not occur, bleeding phenomenon, a little vibration or without vibration can be poured, so as to make large or complex concrete structures section, pumping process provides favorable conditions.
Studies have shown that mixed superplasticizer concrete slump of 200mm, the secretion of water only 30% of normal concrete. Of course, bleeding and bleeding rate of water and superplasticizer type. Such as amino acid-based superplasticizer dosage is more sensitive, a slight excess can lead to concrete bleeding, segregation. This could be applied to other complex system with a retarding effect, it can also be chemically modified to improve its performance.