Cellulose ether(CE) is a water-soluble polymer derived from natural cellulose. In construction, the most common cellulose ethers are Hydroxypropyl MethylCellulose(HPMC), HEMC(Hydroxyethyl Methyl Cellulose), Hydroxyethyl Cellulose(HEC), and CMC(Carboxymethyl Cellulose). This article will discuss the role of cellulose ethers and how to match the right one to the unique requirements of different mortar systems.
The Role and Properties of Cellulose Ether in Cement Mortar
- Moisture Control
The most critical property of cellulose ethers in mortar applications is to maintain sufficient moisture in the mortar for proper cement hydration. This prevents premature drying, reduces cracking, and increases the strength and durability of the cured mortar. In general, water retention in cellulose ethers depends on viscosity, dosage, and particle size. Higher viscosity grades and a good particle size distribution usually improve water retention.
- Thickening
As a thickening agent, cellulose ether increases the viscosity of mortar, stabilizing the mix and preventing segregation or sedimentation of particles during application. The thickening effect of cellulose ether in cement mortar is influenced by its degree of etherification, viscosity, and particle size, and these factors are generally proportional to its performance. It is therefore possible to achieve the desired anti-sag performance and optimum consistency in mortar formulations. This ensures better workability, stability, and application efficiency in construction projects.
- Air Entraining
Alkyl groups in cellulose ether lower the surface tension of its aqueous solution. This gives it an air-entraining effect in cement mortars. The incorporation of suitable air bubbles into the mortar improves its workability due to the “ball bearing” effect of the bubbles, which reduces friction between the particles, improving flowability and workability. However, the amount of air entrainment must be carefully controlled. Excessive air bubbles can negatively affect the strength of the mortar by introducing harmful voids that weaken its structural integrity.
- Extended Opening Time
Cellulose ether slows down the hydration process of cement, thereby delaying its setting and hardening. This effect extends the open time of the mortar, which can be beneficial in applications where longer workability is required. However, in colder regions, this retardation can negatively affect the performance of the mortar due to slower setting. The retarding effect of cellulose ethers increases with higher degrees of etherification, modification, and viscosity.
- Adhesion Enhancement
In addition, as a high molecular weight, long-chain polymer, cellulose ether improves the bond between the mortar and the substrate when added to cementitious systems. By effectively retaining moisture in the mix, it ensures proper hydration and curing while improving adhesion to various surfaces. This dual functionality makes cellulose ether a critical additive for achieving durable and reliable construction results.
Principles for Selecting Cellulose Ether for Different Mortar Products
Thin Plaster System
Take the render mortar in thin plastering systems as an example. Since the render is directly exposed to the external environment and loses moisture quickly, it requires a high water retention rate. This is especially critical during summer construction, where the mortar must retain moisture under high temperatures. To meet these requirements, a higher-viscosity Cellulose ether is preferred. However, to maintain good workability, the viscosity should not be excessively high. Therefore, the ideal CE for this application should have a high water retention rate while maintaining moderate viscosity to balance performance and ease of application.
Cement-based Plaster
Plastering mortar requires excellent uniformity to ensure smooth and even application during plastering. It also demands good sag resistance, high pumpability, and superior flowability and workability. Thus, it is recommended to select a cellulose ether with relatively low viscosity but with a fine particle size, which allows for rapid dispersion and quick consistency development in cement mortar. This ensures ideal performance in terms of application ease, stability, and overall efficiency.
Tile Adhesive
In tile adhesive applications, ensuring safety and efficiency is critical. This requires the mortar to have an extended open time, excellent anti-slip performance, and strong adhesion between the substrate and tiles. As a result, tile adhesives place high demands on the quality of cellulose ether, which is typically used in relatively high dosages.
To achieve a longer open time, the Cellulose Ether must have a high water retention capacity. For superior anti-slip performance, the CE needs to provide effective thickening to enhance the sag resistance of the mortar.
Therefore, while selecting CE for tile adhesives, it is essential to choose a product that balances sufficient viscosity, appropriate etherification level, and optimal particle size. For anti-slip tile adhesives, highly modified CE is recommended.
Self Leveling Mortar
Self-leveling mortar requires excellent leveling performance, making low-viscosity cellulose ether the ideal choice for this application. Since self-leveling mortar needs to flow and spread evenly across the floor after mixing, it demands high fluidity and pumpability, which are achieved with a higher water-to-material ratio. To prevent bleeding, the selected cellulose ether must effectively control surface water retention while also providing sufficient viscosity to prevent sedimentation.
Masonry Mortar
Masonry mortar, which is applied in thick layers and comes into direct contact with masonry surfaces, requires excellent workability and water retention. Additionally, it must ensure strong bonding with the masonry surface to improve application efficiency and overall construction performance. Therefore, the viscosity of the CE should not be excessive, but sufficient to maintain proper water retention and workability for optimal results.
Insulation Plaster
Primarily hand-applied, insulating plasters require the selected cellulose ether to provide excellent workability, superior consistency, and exceptional water retention. In addition, the CE should have high viscosity and strong air-entraining properties to ensure optimal performance.
LANDU Recommendations and Specifications
Products |
Viscosity(mPa.s, 2%sol.) |
Application |
|---|---|---|
|
CMC-C301 |
4000-6000 |
Bonding mortar, self-leveling mortar, Plastering mortar |
|
HPMC-K100 |
45000~60,000 |
Tile adhesive, Wall putty, Cement plaster, EIFS |
|
HPMC-K200H |
35,000~45,000 |
Tile adhesive, Wall putty, EIFS |
|
HEMC-EM80 |
78,000 - 85,000 |
Tile adhesive, Render, Gypsum based mortar |
Final thoughts
The role of cellulose ether includes moisture control, thickening, air-entraining, retardation, and enhancing tensile bond strength. These functions correspond to several key factors that must be considered when evaluating and selecting cellulose ether, such as viscosity, degree of etherification, level of modification, product stability, active ingredient content, and particle size. When choosing CE for different mortar products, it is essential to define the specific performance requirements based on the application and usage conditions of the mortar.
As a leading manufacturer of Cellulose Ether in China, LANDU ensures consistent quality and innovation in every batch. Our dedicated R&D team develops customized solutions to address specific project requirements. Contact us today to learn more about our products or request a free sample to experience the performance of LANDU cellulose ether firsthand!
