The Effect On The Properties Of The Cement Paste By Adding Microbial Polysaccharides

Viscosity modifying admixtures are one of the important components in the underwater pouring concrete and the self-compacting concrete, which can reduce the bleeding of cement-based materials and improve its cohesive propert y. Some microbial polysaccharides as a viscosity modifying admixture in cement-based materials have been applied very widely. Microbial polysaccharides are biopolymers produced by a number of microorganisms in the growing and metabolic process, being provided with excellent physical and chemical properties. In recent years, with the gradual deepening to study microbial polysaccharides by investigators, new microbial polysaccharides and new uses of various microbial polysaccharides begin to been researched and developed. Therefore, the researches of fully exploring new uses of new microbial polysaccharide and using their excellent properties to improve the performance of cement-based materials are very necessary.With three microbial polysaccharides, Pullulan, Welan gum and Diutan gum for the study, this paper was taken to study the effect of microbial polysaccharides on standard consistency water, setting time, mini-slump, Zeta potential, mechanical properties, etc. of cement paste and the effect of fluidity, mechanical properties and anti-carbonation properties of mortar, in addition to explore the use of the film-forming ability of Pullulan in cement-based materials.The results show that, the incorporation of microbial polysaccharide increases the standard consistency water, while the presence of water reducer, standard consistency water content is more sensitive to microbial polysaccharides; Microbial polysaccharides have retarding effect on cement, in which the retarding effect of pullulan is most obvious; The incorporation of microbial polysaccharides will reduce the mini-slump of the cement paste, and prevent bleeding. Over time, the fluidity of cement paste mixed with Pullulan will not fall; Microbial polysaccharides and Polycarboxylate superplasticizer will reduce the Zeta potential values of cement paste; When the content of microbial polysaccharide is 0.08% or less of cement, its incorporation has no significant adverse effects on the hardened cement paste and Mortar, and has significant improvement to the late strength of mortar; Evaporation loss rate of cement paste with Pullulan is less than the blank cement paste; The incorporation of microbial polysaccharides can reduce the depth of carbonation of cement mortar, improving the anti-carbonation properties of mortar, But with the content of microbial polysaccharide increasing, the depth of carbonation of mortar will start to increase. In all mortar, the carbonation resistance of mortar mixed with 0.02% Pullulan is best.