Hoe werkt zelfnivellerende mortel het beste met behulp van cellulose-ethers?

Self-leveling mortar can rely on its weight to form a flat, smooth, and strong foundation on the substrate for laying or bonding other materials, and at the same time, it can carry out large-area and efficient construction. Therefore, high fluidity is a very significant feature of self-leveling mortar. Besides, it must have a certain degree of water retention and bonding strength, no segregation of water, and have the characteristics of insulation and low-temperature rise. Generally, self-leveling mortar requires good fluidity, but the fluidity of actual cement paste is usually only 10-12cm. Cellulose ether is an essential additive of ready-mixed mortar, which can significantly improve the performance of self-leveling mortar and plays a significant role in mortar.

1. Fluidity

As a self-leveling mortar, fluidity is one of the leading indicators for evaluating self-leveling performance. Under the premise of ensuring the regular composition of the mortar, the fluidity of the mortar can be adjusted by changing the content of fiber HPMC. However, too high a content will reduce the fluidity of the mortar, so the amount of cellulose ether should be controlled within a reasonable range.

2. Water retention

Mortar water retention is an important indicator to measure the stability of the internal components of fresh cement mortar. To fully carry out the hydration reaction of the gel material, a reasonable amount of cellulose ether can maintain the moisture in the mortar for a long time. Generally speaking, the water retention rate of the slurry increases with the increase of the cellulose ether content. The water-retaining effect of cellulose ether can prevent the substrate from absorbing too much water too quickly and hinder water evaporation, thus ensuring that the slurry environment provides sufficient water for cement hydration.

Besides, the viscosity of cellulose ether also has a more significant impact on the water retention of mortar. The higher the viscosity, the better the water retention. Generally, cellulose ethers with a viscosity of 400mpa.s are mostly used in self-leveling mortars, which can improve the leveling performance of the mortar and increase the density of the mortar.

3. Coagulation time

Cellulose ether has a retarding effect on mortar. As the content of cellulose ether increases, the setting time of the mortar is prolonged. The retardation effect of cellulose ether on cement paste mainly depends on the degree of substitution of alkyl groups, which has little to do with its molecular weight. The lower the degree of alkyl substitution, the greater the hydroxyl content, and the more pronounced the retarding effect. And the higher the content of cellulose ether, the more pronounced the retardation effect of the complex film on the early hydration of cement. Therefore, the more pronounced the retardation effect.

4. Flexural strength and compressive strength

Strength is one of the essential evaluation indexes for cement-based cementitious materials to cure the mixture. As the content of cellulose ether increases, the compressive strength and flexural strength of the mortar will decrease.

5. Bond strength

Cellulose ether has a significant influence on the bonding properties of mortar. Cellulose ether forms a polymer film with a sealing effect between the liquid phase system and the cement hydration particles, which promotes more water in the polymer film outside the cement particles, which is conducive to the complete hydration of the cement, so the bonding strength after hardening of the slurry is improved. Simultaneously, the appropriate amount of cellulose ether enhances the plasticity and flexibility of the mortar, reduces the rigidity of the transition zone between the mortar and the substrate, and reduces the slippage between the interface. To a certain extent, the bonding effect between the mortar and the substrate is enhanced.

In addition, due to cellulose ether in the cement paste, a unique interface transition zone and interface layer are formed between the mortar particles and the hydration product, which makes the interface transition zone more flexible and less rigid. Therefore, the mortar has a strong bonding strength.

From what we have discussed above, we can come to the conclusion that cellulose ether plays a great important role in self-leveling mortars. Therefore, the key factor to ensure a good final result is to choose appropriate cellulose ether products.