Structural Characterization And Adsorption Characteristics Of Superplasticizer Prepared By Modification Of Bamboo Pulp Black Liquor

The lignin-type superplasticizer (GCL1-JB), which was modified by graft sulfonation ofalkali lignin from bamboo pulp black liquor, was used as an excellent concrete water-reducer.And the dispersion performance of GCL1-JB is significantly superior to that oflignosulphonate (SL). In order to explain why the dispersion performance between GCL1-JBand SL is so different, it’s necessary to characterize the structure of GCL1-JB and study theadsorption characteristics of GCL1-JB. In this study, the structure of GCL1-JB wascharacterized, the effect of the solution condition on the GCL1-JB with differentmicrostructures was discussed, and the adsorption characteristics of the GCL1-JBself-assembled films at the flat substrate were investigated. The main conclusions were asfollows.The GCL1-JB fraction with narrow molecular weight distribution was purified byultrafiltration and gel column chromatography separation, and was selected to study itsabsolute molecular weight and structure. After the GCL1-JB dissolved in the0.10mol/L NaClaqueous solutions and filtered, the absolute molecular weight of GCL1-JB was determined bystatic light scattering, which was considered to be the real molecular weight of GCL1-JBsingle molecules. The results showed that the GCL1-JB had a higher molecular weight andhigher content of sulfonic groups than lignosulphonate. Unlike the lignosulphonate with aspherical microgel structure, the GCL1-JB was a lignin-based formaldehyde condensationproduct with the long carbonyl aliphatic chains, which had the similar structural features withthe linear polyelectrolyte. The structural features described above were the reason why theGCL1-JB was of better dispersion performance than lignosulphonate.The solution condition had a significantly effect on the microstructure of GCL1-JB. TheGCL1-JB molecules were presented as stretch linear-like microstructure in water, andpresented as coiled sphere in the co-mixture of water and dioxane. The GCL1-JB with alinear-like microstructure did not obviously change with a temperature increase. However, theGCL1-JB with a spherical microstructure was further aggregated with increasing temperature.The multilayer adsorption of GCL1-JB was prepared through a layer-by-layer assembled technology, and the adsorption characteristics of GCL1-JB were further investigated. Theresults showed that the GCL1-JB with different molecular weight could adsorb on the solidsurface and form smooth and flat self-assembled films. And the GCL1-JB with highermolecular weight had a larger adsorbed amount. The GCL1-JB self-assembled film whichcould be built up based on hydrogen bonding, had a higher adsorbed amount, a fasteradsorption rate and a more rough surface than that formed by electrostatic interaction.Compared to the adsorption characteristics of lignosulphonate, the GCL1-JB film had acompact adsorption layer, a thick adsorption film, and a smooth surface. The zeta potential ofGCL1-JB was greater than that of SL when adsorbed on the cement surface. Thus, theGCL1-JB formed a greater space steric hindrance and electrostatic repulsion than thelignosulphonate. Therefore, the dispersion performance of GCL1-JB was better than that oflignosulphonate.