Influence of HPMC on self leveling mortar


Influence of HPMC on self leveling mortar

Self leveling mortar relies on its own weight to form a flat, smooth and solid foundation on the base material, so that other materials can be laid or bonded, and large area and high efficiency construction can be realized at the same time. Therefore, high fluidity is a very important feature of self leveling mortar; in addition, it must have certain water retention and bonding strength, which will not produce the phenomenon of water segregation, and has the characteristics of heat insulation and low temperature.

General self leveling mortar requires good fluidity, but the actual flow of cement slurry is usually only 10-12cm; HPMC is the main premixed mortar additive, although the amount is very low, it can significantly improve the performance of mortar, and can improve the consistency, working performance, bonding performance and water retention performance of mortar. It plays a very important role in the field of ready mixed mortar.

1 liquidity
HPMC has significant influence on the water retention, consistency and construction performance of self leveling mortar. Especially as self leveling mortar, fluidity is one of the main indexes to evaluate self leveling performance. On the premise of ensuring the normal composition of mortar, the fluidity of mortar can be adjusted by changing the amount of cellulose ether. However, if the content is too high, the fluidity of mortar will be reduced. Therefore, the amount of cellulose ether should be controlled in a reasonable range.

2. Water retention
Water retaining mortar is an important index of the stability of the internal components of fresh cement mortar. In order to make the gel materials fully hydrated, a reasonable amount of HPMC can be maintained over a longer period of time to maintain moisture content in the mortar. Generally speaking, with the increase of HPMC dosage, the water retention rate of slurry also increases. The water retention function of cellulose ether can prevent the matrix from absorbing too much water quickly and hinder the evaporation of water, so as to ensure the slurry environment to provide enough water for cement hydration. In addition, the viscosity of HPMC has great influence on the water retention of mortar. The higher the viscosity is, the better the water retention is. 400 for self leveling mortar mpa.SHPCM The general viscosity of can improve the mortar and the leveling of mortar, in order to improve the density.

3 setting time
HPMC has retardation effect on mortar. With the increase of HPMC content, the setting time of mortar will be prolonged. The flame retardant effect of HPMC on cement paste mainly depends on the degree of substitution of alkyl, and has nothing to do with molecular weight. The smaller the degree of substitution of alkyl, the higher the content of hydroxyl, and the more obvious the retardation effect. Moreover, with high HPMC content, the lag effect of cement early composite hydration is more obvious, so the lag effect is more obvious.

4 flexural strength and compressive strength
Generally speaking, strength is one of the important evaluation criteria for cementitious materials. With the increase of HPMC content, the compressive strength and flexural strength of mortar will decrease.

5 binding force
HPMC has a great influence on the bond properties of mortar. HPMC can form a closed polymer film between the liquid system and the cement hydration particles, which promotes the polymer particles outside the cement film to produce more water, which is conducive to the complete hydration of the cement, thus increasing the bond strength of the hardened cement slurry. At the same time, 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 matrix, and reduces the slip between the interfaces. To a certain extent, the adhesion between mortar and matrix is enhanced. In addition, due to the existence of cellulose ether in cement slurry, a special interface transition zone and interface layer are formed between mortar particles and hydration products. The interface layer makes the interface transition zone more flexible and less rigid, so that the mortar has a strong bond strength.