Because the polycarboxylate superplasticizer is not sensitive to the type and concentration of ions in the cement slurry solution, and the longer side chain is not easy to be covered by cement hydrate, it can exert long-term dispersibility and is suitable for various cements. Superior to high-efficiency water reducers such as naphthalene. However, this is only relative.
Compatibility test of polycarboxylate superplasticizer and naphthalene superplasticizer. The test results show that naphthalene is not suitable for cement, accounting for 20%, and polycarboxylate water reducer also has 13%, which is not suitable for cement. It can be seen that the polycarboxylate superplasticizer also has the problem of cement adaptability. As some have analyzed, it doesn’t work with any cement.
The influence of cement on the adaptability of commonly used superplasticizers is mainly the mineral composition and content ratio of cement, the specific surface area of cement, the alkali content in cement, the type, amount and solubility of cement, etc. Cement accelerators and types of cement. The higher the C3A content in the mixture, the higher the specific surface area, the higher the alkali content, and the poorer the fluidity of the concrete.
The above-mentioned influencing factors also exist in the use of polycarboxylate superplasticizer. The more important issue is that the sulfate ion content in cement will affect the application effect of polycarboxylate superplasticizer. big. This is mainly because a large number of sulfate ions and polycarboxylate superplasticizer molecules compete with cement particles, thereby reducing the adsorption capacity of polycarboxylate superplasticizers. Therefore, when the sulphate content in cement is high, it will set.
The water-reducing function of the carboxylic acid-based high-performance water-reducing agent will drop sharply, and a large amount of leakage will appear after a certain period of time. It has also been suggested that when a large amount of sulfate ions are present in the water, the EO chains in the polycarboxylate superplasticizer will shrink, thereby reducing the volume repulsion of the EO chains. When the above-mentioned cement with high sulfate content is mixed with naphthalene-based high-efficiency water reducer, sulfur trioxide can inhibit the hydration of C3A and improve the retention of concrete.