The key behind dry mixed mortar: How does HEMC(Hydroxyethyl methyl cellulose) quality affect the quality of mortar

In the field of dry-mixed mortar, the amount of HEMC added is very low, but it can significantly improve the performance of mortar and is a major additive that affects the construction performance of mortar. HEMC plays an important role in mortar in three aspects: first, excellent water retention capacity, second, the effect on mortar viscosity and thixotropy, and third, interaction with cement.

In the field of dry-mixed mortar, the amount of HEMC added is very low, but it can significantly improve the performance of mortar and is a major additive that affects the construction performance of mortar. HEMC plays an important role in mortar in three aspects: first, excellent water retention capacity; second, the effect on mortar viscosity and thixotropy, and third, interaction with cement.

1. Water retention is an important property of HEMC

Many mortars have poor water retention and will separate water and slurry after standing for a few minutes. The water retention effect of cellulose ether depends on the water absorption of the base layer, the composition of the mortar, the layer thickness of the mortar, the water demand of the mortar, and the setting time of the setting material. Factors affecting the water retention effect of dry mortar include the amount of HEMC added, the viscosity of HEMC, the fineness of the particles, and the temperature of the use environment. The water retention of HEMC itself comes from the solubility and dehydration of cellulose ether itself. Kundu Chemical uses the weight method to test the water retention effect of HEMC. Under certain temperature and humidity conditions, the sample is weighed on the scale, and then the sample is soaked in water. After the soaking time is over, the sample is taken out, gently wiped dry on a paper towel, and then weighed.

2. The second effect of cellulose ether-thickening

It depends on: the degree of polymerization of cellulose ether, solution concentration, shear rate, temperature and other conditions.

The gelation property of the solution is a unique property of alkyl cellulose and its modified derivatives. There is also a good linear relationship between the consistency of cement paste and the amount of cellulose ether added. Cellulose ether can greatly increase the viscosity of mortar. The greater the amount added, the more obvious the effect. On the other hand, the higher the viscosity of cellulose, the better the thickening effect. For example, our KDOCEL HEMC 200M has a viscosity of 80,000 mPas (Brookfield viscosity), which is suitable for customers who pursue high viscosity.

3. The third function of cellulose ether is to delay the hydration process of cement

With the increase of cellulose ether addition, the setting time of mortar increases significantly. We can control the operable time of mortar by changing the amount of cellulose ether added. Cellulose ether gives mortar various beneficial properties, and also reduces the early hydration heat release of cement and delays the hydration dynamic process of cement. Of course, for special cases, we have special modified HEMC that can accelerate or decelerate the operable time of mortar, such as KDOCEL HEMC100EA, whose modification item increases the operable time and delays the aging of mortar. The higher the concentration of cellulose ether in mineral gel material, the more obvious the effect of hydration delay. HEMC not only delays coagulation, but also postpones the hardening process of cement mortar system.

In summary, in dry-mixed mortar, HEMC plays the role of water retention, thickening, delaying cement hydration dynamics, and improving construction performance. Good water retention makes cement hydration more complete, which can improve the viscosity of mortar, increase the bonding strength of mortar, and adjust the time. Our standard KDOCEL HEMC products have stable quality, strong water retention and thickening ability, and have a variety of models for different applications and needs, which have been tested for a long time by market. Welcome to discuss.