Cellulose ether is a modifier widely used in building materials, especially in concrete. Cellulose ethers mainly include hydroxypropyl methylcellulose (HPMC), methyl cellulose (MC), hydroxyethyl cellulose (HEC), etc. They can change the physical and chemical properties of cement-based materials in concrete, thereby improve its performance.

1. Water retention
Cellulose ethers have strong water retention capabilities. Adding cellulose ethers to concrete mixtures can significantly improve the water retention of concrete and reduce water loss. This is especially important for concrete constructed in high temperature or dry environments in summer, because it can effectively prevent dry cracking on the concrete surface. In addition, the water retention of cellulose ether can also reduce bleeding, thereby improving the uniformity of concrete.

2. Improve liquidity
The addition of cellulose ether can improve the fluidity of concrete. This is mainly because cellulose ether can increase the viscosity of the mixture and make the concrete slurry more uniform, thereby reducing the separation of mortar and coarse aggregate. At the same time, cellulose ether can increase the thixotropy of the concrete mixture, allowing it to maintain a high viscosity in a static state, while the viscosity decreases under the action of external forces, making construction and molding easier.

3. Delay the coagulation time
Cellulose ethers can delay the setting time of concrete. Its mechanism is mainly to slow down the hydration reaction of cement by forming a protective film around the cement particles. This feature is very useful in long-term transportation of concrete and large-volume concrete construction, because it can extend the construction time of concrete and avoid early setting.

4. Improve compressive strength
Within a certain range, the addition of cellulose ether can improve the compressive strength of concrete. This is because while cellulose ether improves the water retention of concrete, it can also improve the uniformity of cement paste, thereby reducing porosity and improving compactness. Research shows that the addition of cellulose ether has a more obvious effect on improving the early strength of concrete. However, it should be noted that too high a dosage of cellulose ether may have an adverse effect on the later strength.

5. Improve frost resistance
Cellulose ethers can also play a role in improving frost resistance in concrete. It reduces the bleeding rate of concrete and improves the density of concrete, making the pore structure inside the concrete more fine, thereby reducing the movement and freezing expansion of water in the pores, which helps to improve the freeze-thaw resistance of concrete.

6. Reduce the risk of cracking
The water retention and setting time retardation properties of cellulose ethers help reduce shrinkage cracks in concrete during the hardening process. Cellulose ether can effectively reduce the shrinkage stress of cement-based materials during early moisture loss, reduce the shrinkage rate of concrete, thereby reducing the risk of cracking.

The application of cellulose ethers in concrete has significant advantages, including increasing water retention, improving fluidity, delaying setting time, increasing compressive strength, enhancing frost resistance and reducing the risk of cracking. However, attention should be paid to the dosage and type selection of cellulose ethers in practical applications to avoid possible negative effects. The rational use of cellulose ether can significantly improve the overall performance of concrete and provide higher quality materials for construction projects.