Study On Rheological Properties Of Lignin Based Surfactants In Cement Paste Contained Clay

The dispersion ability of conventional polycarboxylic acids(PCE)in concrete is much impeded by clay impurities.It has made people focus on how to improve the dispersion of polycarboxylic acids(PCE)in cement paste contained clay.Lignin is the second largest biomass resource in the world,which is easily obtained and inexpensive,and it is also searved as the first generation of water-reducing agent.And it has a good compatibility with PCE.All of the bove,a class of modified lignin is surgent to researched and developed to synergies with PCE in cement paste contained clay.In this paper,a lignin-based surfactant(PGL),lignin quaternary ammonium salt(NLS)was used for clay tolerance in cement paste,prepared by modification of alkali lignin(AL)and sodium lignosulfonate(LS).The main research methods and conclusions are as follows:The lignin polyether was prepared by two-step method.The dispersibility of PGL was characterized by the test of paste flow,fluidity loss and rheological properties.The basic physical and chemical properties of PGL were characterized by the foaming performance,surface tension and ZETA potential.The kinetics and thermodynamic adsorption of PGL on montmorillonite and X-ray diffraction(XRD)of adsorbed montmorillonite were studied to research the adsorption and dispersion mechanism.The results showed that PGL has good antimud performance.The fluidity of the cement paste increased from 200 mm to 240 mm.after the incorporation of 0.012% PGL.The rheological behavior of the cement paste contained montmorillonite,PCE and PGL is consistent with the Herschel-Bulkley model.The adsorption kinetics of PGL on montmorillonite was conformed to the Quasi-secondary adsorption kinetics model,and the adsorption thermodynamics was conformed to the Freundlich adsorption model.The XRD results revealed that PGL had inserted into the layer structure of alumosilicates,so that the spacing of the montmorillonite layer was widened from 1.23 nm to 1.52 nm.There is a much greater spatial effect of PGL than PCE.Once the montmorillonite was adsorbed by PEGgrafted-lignin,the montmorillonite surface would be occupied by PGL so that reducing the adsorption of PCE.So,the effective adsorption capacity of PCE on cement surface would be increased and the dispersion effect would be enhanced.In this paper,the lignin quaternary ammonium salt(NLS)was prepared,and its dispersibility in cement paste contained clay was studied.The results showed that the compatibility of NLS with polycarboxylic acid was great,and NLS could play a synergies with PCE in a certain dosage range.The rheological behavior of the cement paste contained montmorillonite,PCE and NLS was consistent with the Herschel-Bulkley model,and the NLS could improve the thixotropic properties of the cement paste.The adsorption kinetics of NLS was in accordance with the Freundlich adsorption model,and its adsorption amount on montmorillonite was 9 times than the amount of lignosulfonate.The hydrodynamic radius of the mixture of PCE and NLS was about 56.1 nm in cement pore solution.It is that NLS acted as a release agent,it can not only adsorb polycarboxylic acid,but also be adsorbed on montmorillonite adsorption.The adsorbption effect of montmorillonite and NLS is stronger than the adsorbption effect of NLS and PCE.On the one hand,once NLS was absorbed on montmorillonite and it would be no longer released.On the other hand,PCE would be released from NLS because of the weak force of PCE and NLS.Which also makes the NLS has good anti-mud performance.