The effect of hydroxypropyl methylcellulose on self-leveling mortar

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The effect of  on self-leveling mortar

Relying on its own weight, self-leveling mortar forms a flat, smooth and firm foundation on the substrate, allowing other materials to be laid or bonded, while achieving large-area, high-efficiency construction. Therefore, high fluidity is a very important feature of mortar self-leveling mortar; in addition, it must have a certain water retention and bonding strength, will not cause water segregation, and have the characteristics of thermal insulation and low temperature.

Generally, self-leveling mortar requires good fluidity, but the actual flow of cement slurry is usually only 10-12cm; cellulose ether is the main additive for ready-mixed mortar. Consistency, workability, adhesion and water retention. It plays a very important role in the field of ready-mixed mortar.

1. Liquidity

Cellulose ether has a significant effect on the water retention, consistency and construction performance of self-leveling mortar. Especially as self-leveling mortar, fluidity is one of the main indicators for evaluating self-leveling performance. On the premise of ensuring the normal composition of the mortar, the fluidity of the mortar is adjusted by changing the amount of cellulose ether. However, high content will reduce the fluidity of the mortar, so the control amount of cellulose ether should be within a reasonable range.

2. Water retention

Water-retaining mortar is an important indicator of the stability of the internal components of fresh cement mortar. In order to make the gel material fully hydrated, a reasonable amount of cellulose ether can be used to maintain the moisture in the mortar for a long period of time. Generally speaking, as the amount of cellulose ether increases, the water retention rate of the slurry also increases. The water retention effect of cellulose ether can prevent the matrix from quickly absorbing too much water and hinder the evaporation of water, thereby ensuring that the slurry environment provides enough water for cement hydration. In addition, the viscosity of cellulose ether has a great influence on the water retention of mortar. The higher the viscosity, the better the water retention. The general viscosity of 400 viscosity cellulose ether for self-leveling mortar can improve the leveling of mortar and mortar to increase density.

3. Set time

Cellulose ethers have a blocking effect on mortar. With the increase of cellulose ether content, the setting time of mortar will be prolonged. The flame retardant effect of cellulose ether on cement paste mainly depends on the degree of substitution of the alkyl group and has nothing to do with the molecular weight. The smaller the degree of alkyl substitution, the larger the hydroxyl content, and the more obvious the retardation effect. However, with high cellulose ether content, the early complex film delaying moisture effect is more obvious, so the delay effect is more obvious.

4. Bending strength and compressive strength

In general, strength is one of the important evaluation criteria for cementitious cementitious materials. With the increase of cellulose ether content, the compressive strength and flexural strength of mortar will decrease.

Bond strength

Cellulose ether has a great influence on the bonding properties of mortar. Cellulose ether forms the sealing effect of the hydration polymer film between the liquid phase system and the cement particles, which promotes the polymer particles outside the cement film to have more water, which is conducive to the complete hydration of the cement, thereby increasing the strength of the cement hardened glue. At the same time, an 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 matrix, and reduces the slippage between the interfaces. To a certain extent, the bonding force between the mortar and the substrate is enhanced. In addition, due to the presence of cellulose ethers in the cement slurry, a special interfacial transition zone and interfacial layer are formed between the mortar particles and the hydration products. The interface layer makes the interface transition zone more flexible and less rigid, so that the mortar has a strong bond strength.