Thickening effect of cellulose ether

Cellulose ether endows wet mortar with excellent viscosity, can significantly increase the bonding ability of wet mortar and grassroots, improve the anti-sag performance of mortar, widely used in plaster mortar, external insulation system and brick bonding mortar. The thickening effect of cellulose ether can also increase the uniformity and anti-dispersion ability of new cement based materials, to prevent the stratification, segregation and bleeding of mortar and concrete, can be used in fiber concrete, underwater concrete and self-compacting concrete.

Cellulose ether increases the viscosity of cement-based materials from the viscosity of cellulose ether solution. Usually use “viscosity” this metric to evaluate cellulose ether solution viscosity, the viscosity of cellulose ether generally refers to a certain concentration (2%) of cellulose ether solution, temperature (20 ℃) and shear rate (or rotate speed, such as 20 RPM) conditions, with provisions of the measuring instrument, such as rotating viscometer measured viscosity values. Viscosity is an important parameter of evaluating performance of cellulose ether and cellulose ether, the higher the viscosity of the solution, the better the viscosity of cement base material, the viscosity of base material can, sag resistance and resistance to the stronger the dispersion ability, but if the viscosity is too big, can affect cement base material mobility and maneuverability (such as the construction of plaster mortar adhesive plaster). Therefore, the viscosity of cellulose ether used in dry-mixed mortar is usually 15,000 ~ 60,000 Mpa. s-1, and the viscosity of cellulose ether is required to be lower for self-leveling mortar and self-compactconcrete with higher fluidity requirements. In addition, the thickening effect of cellulose ether will increase the water requirement of cement-based materials, thus increasing the output of mortar. The viscosity of a cellulose ether solution depends on the molecular weight (or degree of polymerization) and concentration of the cellulose ether, solution temperature, shear rate, and test method. The higher the polymerization degree of cellulose ether, the greater the molecular weight, the higher the viscosity of its aqueous solution; The higher the dosage (or concentration) of cellulose ether, the higher the viscosity of its aqueous solution, but in use should pay attention to the selection of appropriate dosage, so as not to mix too high, affect the performance of mortar and concrete; Like most liquids, the viscosity of cellulose ether solution will decrease with the increase of temperature, and the higher the concentration of cellulose ether, the greater the effect of temperature; Cellulose ether solution is usually a pseudoplastic body with the property of shear thinning. The higher the shear rate, the lower the viscosity.

Therefore, the cohesion of mortar will be reduced by external force, which is conducive to the scraping construction of mortar, making mortar can have good workability and cohesion. However, cellulose ether solution will show Newtonian fluid characteristics when the concentration is very low and the viscosity is very small. When the concentration increases, the solution gradually presents pseudoplastic fluid characteristics, and the higher the concentration, the more obvious the pseudoplastic.



Post time: Jun-14-2022