A New Type of Clay Resistant Polycarboxylate Superplasticizers with a Snowflake-shaped Molecular Structure

The polycarboxylate superplasticizers (PCA) with comb structure is easily adsorbed by clay minerals in aggregates, esp. as its easy adsorption by montmorillonite, which will seriously affects the performance of concrete. For minimizing this detrimental effect, a new type polycarboxylate superplasticizer is synthesized by esterification and polymerization based on the molecular structure optimal design. The new type polycarboxylate superplasticizer consists a snowflakeshaped side chain (PCA-SF), of which the molecular structure is confirmed by infrared spectrum analysis. After testing the dispersing capacity of PCA-SF with and without montmorillonite, we found this new PCA has better compatibility with montmorillonite. Compared with normal polycarboxylate superplasticizer (PCA-1), the compatibility with montmorillonite of this new type PCA-SF is 40% higher. The experimental results of IR and XRD on the mechanism of the action of montmorillonite and PCA is basically coincide with the test results from other scholar's research, the conclusion is that PCA intercalated montmorillonite layers, and enlarge the size of montmorillonite crystal layer about one molecule side chain of PCA agent. SEM observed the microscopic appearance of montmorillonite in cement stone, and compared the effects of PCA-SF and PCA-1 played on the interfacial transition of montmorillonite and cement stone, the result showed that when PCA-SF exist, the interface between montmorillonite and cement stone is much smaller.