Application of high viscosity HPMC in dry-mixed mortar

Introduction

Hydroxypropyl Methylcellulose (HPMC) is a non-ionic water-soluble polymer widely used in construction, medicine, food, daily chemicals and other fields. High viscosity HPMC has important application value in dry-mixed mortar due to its unique physical and chemical properties. This article will discuss in detail the applicability, mechanism of action, performance advantages and influence of high viscosity HPMC in dry-mixed mortar on mortar quality.

**Basic properties of HPMC**

HPMC is a cellulose ether obtained by chemical modification of natural cellulose, with the following main properties:

1. **High solubility**: HPMC can dissolve in cold water and hot water to form a uniform and transparent solution.

2. **Excellent thickening**: HPMC has a significant thickening effect, especially high viscosity HPMC, which can provide high viscosity at low concentrations.

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

4. **Strong stability**: HPMC has stable chemical properties, is not affected by pH and electrolytes, and is suitable for various formulations.

5. **Good film-forming property**: HPMC can form a uniform film on the surface with good adhesion and flexibility.

**Mechanism of action of high viscosity HPMC in dry-mixed mortar**

1. **Thickening and rheological regulation**

High viscosity HPMC can significantly increase the viscosity of mortar as a thickener in dry-mixed mortar. It forms a three-dimensional network structure in the water phase, increases the viscosity of the system, and makes the mortar have good fluidity and thixotropy during construction. The thickening effect of high viscosity HPMC can also prevent the sedimentation of aggregates and fillers in the mortar, maintain the uniformity of the mixture, and improve the construction performance.

2. **Water retention and delayed drying**

High viscosity HPMC has excellent water retention performance, can form a stable hydration layer in the mortar, reduce the evaporation of water, and delay the drying speed of the mortar. Its water retention effect allows the mortar to have enough water for hydration reaction during the hardening process, improves the early strength and final strength, prevents shrinkage and cracking, and improves the durability and stability of the mortar.

3. **Improves bonding strength**

High-viscosity HPMC can improve the bonding strength between the mortar and the substrate in dry-mixed mortar. Its film-forming property allows the mortar to form a uniform bonding layer during the hardening process, enhances the bonding force between the mortar and the substrate, avoids hollowing and falling off, and improves the construction quality and durability.

4. **Improves construction performance**

The use of high-viscosity HPMC can significantly improve the construction performance of dry-mixed mortar. Its thickening effect allows the mortar to have good fluidity and thixotropy during the construction process, making it easy to apply and shape, reducing the sagging and dripping of the mortar, and improving the construction efficiency and quality. At the same time, the water retention effect of high-viscosity HPMC extends the operation time of the mortar, giving construction personnel more time to adjust and modify, and improving the construction effect.

**Specific application of high viscosity HPMC in dry-mixed mortar**

1. **Masonry mortar**

In masonry mortar, the thickening and water retention effects of high viscosity HPMC give the mortar good adhesion and water retention, ensuring that the masonry is not easy to crack and fall off during the hardening process. Its thickening effect can also improve the fluidity and thixotropy of the mortar, making it easier to construct and shape.

2. **Plastering mortar**

In plastering mortar, the use of high viscosity HPMC can significantly improve the water retention and construction performance of the mortar. Its thickening effect makes the mortar easy to apply and shape during construction, reduces sagging and dripping, and improves the plastering effect and surface quality. The water retention effect ensures that the plaster layer dries evenly during the hardening process to prevent cracking and falling off.

3. **Self-leveling mortar**

In self-leveling mortar, the thickening and rheological adjustment effects of high viscosity HPMC give the mortar good fluidity and self-leveling properties. Its water retention slows down the drying speed of the mortar, ensuring that the mortar has enough water for hydration reaction during the hardening process, improving the early strength and final strength, and avoiding shrinkage and cracking.

4. **Repair mortar**

In the repair mortar, the thickening and water retention of high-viscosity HPMC give the mortar good adhesion and water retention, ensuring that the repair layer is not easy to crack and fall off during the hardening process. Its thickening effect can also improve the fluidity and thixotropy of the mortar, facilitate construction and molding, and improve the repair effect and surface quality.

**How to use and precautions for high-viscosity HPMC**

1. **Dissolution and preparation**

High-viscosity HPMC usually exists in powder form and needs to be fully dissolved before use. It is recommended to gradually add HPMC 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 HPMC degradation. The dissolved HPMC solution should be filtered before use to remove undissolved particles and impurities.

2. **Dosage control**

The dosage of high-viscosity HPMC depends on the specific application needs and performance requirements. Generally, the dosage of high-viscosity HPMC in dry-mixed mortar ranges from 0.2% to 1.0%. The optimal dosage is determined by experiments to achieve ideal thickening, water retention and rheological adjustment effects.

3. **Combination with other additives**

High-viscosity HPMC 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 to avoid adverse reactions and performance degradation.

**Summary**

As a high-performance and multifunctional additive, high-viscosity HPMC is widely used in dry-mixed mortar. Its excellent thickening, water retention, rheological adjustment and bonding enhancement effects make dry-mixed mortar have good performance and effects during construction and use. Through scientific and reasonable formula design and usage methods, high-viscosity HPMC can significantly improve the overall quality of dry-mixed mortar, providing strong support for the performance improvement and application promotion of building materials. In the future development of dry-mix mortar products, the application prospects of high-viscosity HPMC will be broader, and its multifunctional properties will continue to promote innovation and progress in the dry-mix mortar industry.