Application of HPMC in Gypsum-Based Self-Leveling Mortar

Hydroxypropyl methylcellulose (HPMC), a cellulose ether widely used in building materials, plays a key modifying role in high-performance gypsum-based self-leveling mortars. By retaining water, adjusting rheological properties, and enhancing stability, it significantly improves workability and the mechanical durability of the final material.

1. Overview of Gypsum-Based Self-Leveling Mortar

Gypsum-based self-leveling mortar is a flooring material made with building gypsum as the primary binder, supplemented with aggregates, fillers, and various admixtures. It boasts excellent fluidity, efficient construction, high smoothness, and environmental friendliness, making it widely used in various types of interior flooring. To meet the modern engineering requirements for high strength, high wear resistance, and rapid construction, this material is continuously evolving towards higher performance. However, issues such as rapid setting, large shrinkage, and short workability of gypsum require admixtures such as HPMC to address these issues.

2. HPMC Mechanism of Action

Water Retention: HPMC forms a polymer membrane structure within the mortar, effectively retaining water, ensuring full hydration of the gypsum and promoting crystal growth, thereby improving structural density and strength, and preventing cracking and flow loss caused by rapid water loss.

Rheological Property Modification: HPMC's thickening effect helps optimize the flow and spreadability of the mortar, allowing it to self-level under its own weight while preventing segregation and bleeding, ensuring a uniform and smooth surface.

Improving Workability: HPMC delays the setting of gypsum and extends its open time, providing an ample working window for construction. Its excellent thixotropy ensures optimal mortar flowability during mixing and spreading, while remaining stable upon standing.

Enhancing Stability: By promoting full hydration and improving the microstructure, HPMC effectively reduces shrinkage, minimizes the risk of cracking, and enhances the mechanical strength and durability of the hardened structure.

3. Advantages in High-Performance Systems

Ensuring High Material Performance: By maintaining the required moisture for hydration, HPMC promotes full gypsum reaction, forming a high-strength, low-porosity structure.

Improves construction adaptability: Particularly suitable for large-scale construction, it provides excellent workability and paving results.

Optimizes surface quality: Suppresses pinholes, cracks, and bleeding, resulting in a smooth and fine surface.

Environmental compatibility: HPMC is non-toxic and biodegradable, consistent with the environmentally friendly properties of gypsum-based materials and in line with green building requirements.

4. Application Considerations

When using HPMC in high-performance gypsum-based self-leveling mortars, it is important to carefully select the appropriate type and dosage:

It is recommended to use medium- to low-viscosity grades to balance rheological and water retention requirements;

The typical dosage range is 0.1%–0.3%. Excessive dosage may result in decreased fluidity;

It must be used in conjunction with admixtures such as water reducers and retarders to optimize overall performance.

5. Conclusion

HPMC plays an irreplaceable role in high-performance gypsum-based self-leveling mortars. By comprehensively improving water retention, rheological properties, workability, and stability, it ensures the successful application of the material in high-standard projects. With the continued growth in demand for green building materials and high-quality flooring systems, the application of HPMC will be further deepened and expanded.