influence of cellulose ether content on desulfurized gypsum-based self-leveling mortar

The influence of cellulose ether content on the basic properties of mortar:

The incorporation of cellulose ether has a significant impact on the properties of the mortar. With the increase of the content, the workability and cohesiveness of the mortar are significantly improved, the fluidity loss over time is significantly reduced, the construction performance is more excellent, and the hardened mortar has no delamination, and the surface smoothness, smoothness and smoothness The aesthetics have been greatly improved. At the same time, the water consumption for the mortar to reach the same fluidity increased significantly. At 5‰, the water consumption increased by 102%, and the final setting time was extended by 100 min, which was 2.5 times that of the blank sample. The early mechanical properties of the mortar decreased significantly with the increase of the cellulose ether content. When the content was 5‰, the 24 h flexural strength and compressive strength decreased to 18.75% and 11.29% of the blank sample, respectively. The compressive strength was 39.47% and 23.45% of the blank sample, respectively. It is worth noting that with the increase in the amount of water-retaining agent, the bulk density of the mortar also decreased significantly, from 2 069 kg/m3 at 0 to 1 747 kg/m3 at 5‰, a decrease of 15.56%. The compactness of the mortar decreases and the porosity increases, which is one of the reasons why the mechanical properties of the mortar decrease significantly.

Cellulose ether is a non-ionic polymer. Both the hydroxyl group on the cellulose ether chain and the oxygen atom on the ether bond can combine with water molecules to form hydrogen bonds, turning free water into bound water, thus playing a role in water retention. It is manifested as an increase in the cohesiveness of the slurry. The increase in the viscosity of the slurry will not only increase the water consumption, the dissolved cellulose ether will be adsorbed on the surface of the gypsum particles, which will hinder the progress of the hydration reaction and prolong the setting time; during the stirring process, a large number of bubbles will be introduced. Holes will be formed after the mortar is hardened, which will eventually reduce the strength of the mortar. Considering the unilateral water consumption, construction performance, setting time and mechanical properties, and durability of the mortar mixture, the content of cellulose ether in the desulfurized gypsum-based self-leveling mortar should not exceed 1%.

Under normal circumstances, the higher the viscosity and fineness of cellulose ether, the better the water retention and the increase in bonding strength. At the same time, the viscosity or molecular weight of cellulose ether is too high, which will affect the fluidity, construction performance and mechanics of the mortar. Performance will have a negative impact.