Zou, Fubing, et al. Journal of Industrial and Engineering Chemistry 55 (2017): 91-100.
Challenge: Polycarboxylate superplasticizers (PCEs) are essential for modern concrete workability, but their performance when combined with common retarder sodium gluconate (SG) is inconsistent. This uncertainty stems from an incomplete understanding of the molecular-level interaction between SG and PCEs, particularly those with varying polymer architectures.
Solution: A series of experiments were conducted to understand the effect of SG on the dispersing efficiency of two typical PCEs with different side-chain grafting density (PCE2: low density, PCE6: high density) in terms of adsorption behavior, dispersion performance, and the underlying interactions at the molecular level.
Key Findings:
· Positive Effect (Grafting & Chain Extension): SG complexes with Ca2+, potentially grafting onto PCE side chains. This straightens the PCE structure, increasing effective PEO chain length and enhancing steric hindrance/dispersion.
· Negative Effect (Competitive Adsorption): SG competes with PCE for adsorption sites on cement particles, reducing dispersion efficiency.
· The net effect of SG depends heavily on the PCE's molecular structure, specifically the carboxyl group grafting density in its side chains. Grafting/straightening effect is significantly hindered in PCEs with high PEO chain density (e.g., PCE6).
· The severity of negative competitive adsorption depends on the relative adsorption strength between the specific PCE and SG. PCEs with stronger adsorption affinity suffer less dispersion loss.
Ma, Xiaobing, et al. Journal of Cleaner Production 419 (2023): 138317.