Cellulose ethers delay the drying process of cement

Introduction

Cellulose ethers are a class of polymer materials obtained by chemical modification of natural cellulose, which are widely used in construction, medicine, food, daily chemicals and other fields. In building materials, cellulose ethers have become important additives for dry-mixed mortar, putty powder, tile adhesive and other products due to their excellent water solubility, thickening, water retention and film-forming properties. This article will discuss in detail the mechanism of action, application advantages and impact of cellulose ethers on the performance of cement-based materials in delaying drying in cement-based materials.

**Basic properties of cellulose ethers**

The main types of cellulose ethers include hydroxypropyl methylcellulose (HPMC), methyl cellulose (MC), hydroxyethyl cellulose (HEC), etc. Its main properties are as follows:

1. **Water solubility**: Cellulose ethers can dissolve in cold and hot water to form a uniform colloidal solution.

2. **Thickening**: Cellulose ethers have a significant thickening effect and can provide high viscosity at low concentrations.

3. **Water retention**: Cellulose ethers can form a stable hydration layer in water, significantly improving the water retention capacity of the material.

4. **Film-forming property**: Cellulose ether can form a uniform film on the surface with good adhesion and flexibility.

**Delaying effect of cellulose ether on cement drying process**

1. **Water retention and delayed drying**

One of the important roles of cellulose ether in cement-based materials is to improve its water retention. Cement needs sufficient water during the hydration process to ensure the smooth progress of the hydration reaction and the integrity of the hardening process. However, during the construction process, especially in high temperature or high wind speed environment, the water evaporates quickly, causing the cement to dry too quickly, affecting the final strength and durability.

Cellulose ether can form a uniform three-dimensional network structure in the cement paste, wrap and retain water, reduce the rapid evaporation of water, and thus delay the drying process of cement. This water retention effect allows the cement paste to have more time for sufficient hydration reaction, improving the early strength and later performance of cement-based materials.

2. **Adjusting rheology and construction properties**

Cellulose ether has a significant thickening effect and can adjust the rheological properties of cement paste, so that it has better fluidity and operability during construction. An appropriate amount of cellulose ether can make cement paste smoother during construction, easier to apply and shape, and maintain a high viscosity when standing to prevent the material from sagging and segregation.

By slowing down the drying speed of cement, cellulose ether can extend the construction operation time, give construction workers more time to adjust and modify, and improve construction quality and efficiency.

3. **Improve the uniformity of cement-based materials**

Cement-based materials are prone to cracks during the drying process, especially when water loss is rapid in the early stage. Cellulose ether slows down the drying speed, so that the water in the cement paste can be evenly distributed and gradually evaporated, reducing shrinkage cracks caused by local water loss, and improving the overall uniformity and durability of the material.

**Specific application of cellulose ether in cement-based materials**

1. **Dry-mixed mortar**

In dry-mixed mortar, cellulose ether, as an important additive, can significantly improve the water retention and construction performance of mortar. Delaying the drying speed of mortar ensures that cement is fully hydrated and improves the strength and bonding properties of mortar. Especially in thin-layer construction and high-temperature dry environments, the role of cellulose ether is particularly important.

2. **Putty powder**

Cellulose ether plays a major role in thickening and water retention in putty powder, slowing down the drying speed of putty, improving construction operation time and surface flatness. Putty drying too quickly can easily lead to surface blistering and cracking. The addition of cellulose ether can effectively avoid these problems and ensure the quality and decorative effect of the putty layer.

3. **Tile adhesive**

In tile adhesive, cellulose ether not only improves the water retention and bonding properties of the adhesive, but also prolongs the construction open time, facilitating the adjustment and positioning of tiles. The addition of cellulose ether can prevent the tile adhesive from losing water too quickly during construction, ensuring bonding strength and construction quality.

**Usage and precautions of cellulose ether**

1. **Dissolution and preparation**: Cellulose ether usually exists in powder form and needs to be fully dissolved before use. It is recommended to gradually add cellulose ether to water under stirring conditions to avoid agglomeration. Warm water can be used to accelerate the dissolution process, but excessive temperatures should be avoided to prevent cellulose ether from degrading.

2. **Dosage control**: The amount of cellulose ether depends on the specific application needs and performance requirements. Normally, the dosage of cellulose ether in cement-based materials ranges from 0.1% to 1.0%. The optimal dosage is determined through experiments to achieve ideal water retention and thickening effects.

3. **Combination with other additives**: Cellulose ether can be used in combination with other functional additives such as water reducers, retarders, plasticizers, etc. to achieve better comprehensive performance. When used in combination, attention should be paid to the compatibility and mutual influence between the components.

**Summary**

As a high-performance and multifunctional additive, cellulose ether has a significant effect of delaying drying in cement-based materials. It effectively improves the construction performance and final quality of cement-based materials by improving the water retention of materials, adjusting rheological properties, extending the construction operation time and improving uniformity. Cellulose ether has become an indispensable and important component in a variety of cement-based materials such as dry-mixed mortar, putty powder, and tile adhesive. Through scientific and reasonable formula design and usage methods, the excellent performance of cellulose ether will provide strong support for the performance improvement and application promotion of building materials.