The role of cellulose in cement

The role of cellulose in cement

1. Water retention function

The hydration reaction of cement requires sufficient moisture, especially in high temperature or dry environments, where moisture is prone to rapid evaporation, leading to incomplete hydration and mortar cracking. Cellulose ether improves water retention through the following mechanisms:

• Water absorption: Cellulose ether molecule is hydrophilic, which can absorb water and form gel structure to lock free water in mortar.

Humidity compensation: Studies have shown that the water absorption rate of flax cellulose fibers can reach 3.45-6.03 times their own weight, effectively compensating for internal humidity and reducing early water loss.

Application effect: The water retention rate can be increased from 80% to over 95%, extending the operable time of mortar and improving construction and workability.

Practical significance: Enhanced water retention makes mortar easier to apply, reduces wall cracking, and is particularly suitable for thin plastering and dry climates.

2. Thickening and improving construction performance

The thickening effect of cellulose ether is achieved by increasing the viscosity of mortar:

• Viscosity improvement: The viscosity of HPMC aqueous solution is related to its molecular weight and concentration, and high viscosity HPMC can significantly increase the viscosity of mortar.

Construction smoothness: Thickened mortar is easier to scrape, reducing sliding or flowing, and improving construction efficiency.

• Anti segregation: Cellulose ether prevents aggregate settling and maintains the uniformity of mortar.

Practical significance: The thickening effect makes mortar more suitable for vertical surface construction, such as wall plastering, and improves construction quality.

3. Delaying effect

Cellulose ether delays the hydration rate of cement by adsorbing on the surface of cement particles

• Extended setting time: Studies have shown that cellulose ether can extend the initial setting time of mortar by 1-2 hours, making it convenient for construction adjustments.

• Improve early strength: The retarding effect ensures more complete hydration reaction and reduces early strength loss.

Practical significance: The retarding effect is suitable for large-scale construction or high-temperature environments, extending the operating window.

4. Crack resistance and shrinkage resistance

Cellulose ether reduces shrinkage and cracking of mortar through water retention and internal curing effects:

Shrinkage inhibition: Flax cellulose fibers can significantly inhibit self shrinkage, and short fibers (0.5mm) have better effects than long fibers (5mm).

Crack blocking: The mesh structure of cellulose fibers enhances the toughness of mortar and reduces the propagation of microcracks.

Practical significance: Improved crack resistance and extended mortar life, suitable for exterior wall plastering and insulation mortar.

5. Other functions

• Air entraining effect: Cellulose ether introduces tiny bubbles during the mixing process, improving the frost resistance and durability of mortar.

• Improved bonding strength: The water retention and thickening effects enhance the bonding strength between mortar and substrate, making it suitable for scenarios such as tile pasting.

• Environmental friendliness: Cellulose ether is a renewable material that meets the requirements of green buildings.