Cellulose ethers give excellent viscosity to wet mortar, significantly increase the bonding ability of wet mortar to the substrate and improve the sagging resistance of mortar, and are widely used in plastering mortar, brick bonding mortar and exterior insulation systems. The thickening effect of cellulose ether can also increase the anti-dispersing ability and homogeneity of freshly mixed materials, prevent material delamination, segregation and water secretion, and can be used in fiber concrete, underwater concrete and self-compacting concrete.
The thickening effect of cellulose ethers on cementitious materials results from the viscosity of the cellulose ether solution. Under the same conditions, the higher the viscosity of the cellulose ether, the better the viscosity of the modified cementitious material, but if the viscosity is too high, it will affect the fluidity and workability of the material (e.g. sticky plaster knives). Self-levelling mortars and self-compacting concrete, which require high fluidity, require low viscosity of cellulose ethers. In addition, the thickening effect of cellulose ethers increases the water requirement of cementitious materials and increases the yield of mortar.
The viscosity of cellulose ether solutions depends on the following factors: molecular weight of cellulose ether, concentration, temperature, shear rate and test method. Under the same conditions, the greater the molecular weight of cellulose ether, the higher the viscosity of the solution; the higher the concentration, the higher the viscosity of the solution, in the use of attention should be paid to avoid excessive dosing and affect the working properties of mortar and concrete; cellulose ether solution viscosity will decrease with the increase in temperature, and the higher the concentration, the greater the influence of temperature; cellulose ether solution is usually a pseudoplastic fluid, with the nature of shear thinning, the greater the test The greater the shear rate of the test, the smaller the viscosity, so the cohesion of the mortar will be reduced under the action of external forces, which is conducive to the scraping construction of mortar, so that the mortar can have good workability and cohesion at the same time; because the cellulose ether solution is a non-Newtonian fluid, the test viscosity test methods, instrumentation or testing environment, the same cellulose ether solution test results may vary greatly.
Post time: Apr-01-2022