Polycarboxylate Based Water Reducer Concrete Admixture
Polycarboxylate Water Reducer Concrete Admixture Polycarboxylic acid water reducers have developed rapidly abroad in recent years due to their superior performance and pollution-free production, especially in Japan, where the ratio of polycarboxylic acid to naphthalene has exceeded 7:3. Polycarboxylate Superplasticizer Polycarboxylic acid water reducers are very different from traditional water reducers in terms of molecular structure, action principle and performance in concrete.
Therefore, correct understanding and rational use are important links in promoting the application of polycarboxylic acid water reducers. Polycarboxylate Water Reducer Concrete Admixture Polycarboxylic acid water reducers have the characteristics of small dosage, high water reduction rate, good plasticity retention, strong adaptability to cement and small concrete shrinkage. However, in the process of engineering application of Polycarboxylate Water Reducer Concrete Admixture polycarboxylic acid water reducers, it was found that this water reducer, like other water reducers, also has certain limitations, and its advantages are only relative. Therefore, it still needs to be tested and tested before it can be used in the production and use process. In the process of engineering application, the following problems often occur, and analytical solutions are proposed based on actual conditions.
The composition of cement and cementitious materials is complex and varied. From the perspective of adsorption-dispersion mechanism,
it is impossible to find a water reducer that is suitable for everything. Although polycarboxylic acid water reducer has a wider adaptability than naphthalene, it may still have poor adaptability to some cements. This adaptability is mostly reflected in: reduced water reduction rate and increased slump loss. Even for the same cement, the effect of the water reducer will be different when ball-milled to different finenesses.
Phenomenon: A mixing station uses a certain P-042.5R cement in the area to supply C50 concrete to a construction site. It uses a polycarboxylic acid-based high-efficiency water reducer. When making the concrete mix ratio, it is found that the amount of water reducer used in this cement is slightly more than that of other cements. However, during actual mixing, the slump of the concrete mixture delivered from the factory is visually 210mm. When unloading the concrete into the concrete pump truck at the construction site, it is found that the concrete in the truck cannot be unloaded. After notifying the factory to send a bucket of water reducer to add to the mixing, the visual slump is 160mm, which can basically meet the pumping requirements. However, during the unloading process, the concrete cannot be unloaded again. The concrete in the truck is immediately returned to the factory, and a large amount of water and a small amount of water reducer are added before it can be unloaded. It almost solidifies in the mixer truck.
Cause analysis: Failure to insist on doing a compatibility test with admixtures for each batch of cement before opening.
Prevention: A compounding test is done for each batch of cement with the construction mix ratio before opening. Choose appropriate admixtures. Cement with "coal gangue" as admixture has poor compatibility with polycarboxylic acid water reducer, so avoid using it.