Selection Methods and Functions of Cellulose Ethers in Dry Mortar-HPMC

HPMC, a building chemical, is one of our best-selling products, offering low price and high quality. It can be used as a thickener and water-retaining agent in building mortar, plaster, and putty. Shijiazhuang Cellulose Co., Ltd., a cellulose manufacturer from China, can provide you with ample supply.

One of the biggest differences between dry-mixed mortar and traditional mortar is the use of a small amount of chemical additives to modify dry-mixed mortar. Adding one additive to dry-mixed mortar is called primary modification, while adding two or more additives is called secondary modification. The quality of dry-mixed mortar depends on the correct selection of components and the harmonious matching of these components. Because chemical additives are relatively expensive and have a significant impact on the performance of dry-mixed mortar, the dosage of the additive should be the primary consideration when selecting it. The following is a brief introduction to the selection method of the chemical additive cellulose ether.

Cellulose ethers, also known as rheology modifiers, are admixtures used to adjust the rheological properties of fresh mortar and are used in almost every type of mortar. When selecting the type and dosage, the following properties should be considered:

(1) Water retention at different temperatures;

(2) Thickening effect, viscosity;

(3) Consistency versus temperature, and its effect on consistency in the presence of electrolyte;

(4) Form and degree of etherification;

(5) Improvement of mortar thixotropy and positioning ability (essential for mortars applied to vertical surfaces);

(6) Dissolution rate, conditions, and completeness of dissolution.

In addition to cellulose ethers (such asmethylcellulose ether), vinyl polyvinyl acetate (PVC) can also be added to dry-mix mortar, i.e., secondary modification. The inorganic binders (cement, gypsum) in the mortar ensure high compressive strength, while having minimal effect on tensile and flexural strength. PVC forms an elastic membrane within the pores of the cement paste, allowing the mortar to withstand high deformation loads and improving wear resistance. Practice has shown that adding different amounts of methylcellulose ether and PVC to dry-mix mortar can prepare thin-layer adhesive mortar, plastering mortar, decorative plastering mortar, aerated concrete block masonry mortar, and self-leveling mortar for cast-in-place floors. Using them in combination not only improves the quality of the mortar but also significantly increases construction efficiency.

In practical applications, to improve overall performance, multiple admixtures need to be used in combination. There are optimal mixing ratios for different additives. As long as the dosage range and ratio are appropriate, they can all improve mortar performance from different aspects. However, when used alone, their modifying effect on mortar is limited, and sometimes they may even have negative effects. For example, adding cellulose alone, while increasing mortar cohesion and reducing segregation, significantly increases the water consumption of the mortar, which is retained inside the mortar, leading to a substantial decrease in compressive strength. Similarly, adding air-entraining agents alone can significantly reduce mortar segregation and water consumption, but the increased number of air bubbles can cause a downward trend in mortar compressive strength. To maximize the improvement of masonry mortar performance while avoiding harm to other mortar properties, ensuring that the consistency, segregation, and strength of the masonry mortar meet engineering requirements and relevant technical specifications, and avoiding the use of lime paste to save cement and protect the environment, it is essential to take comprehensive measures and develop and use composite admixtures from the perspectives of water reduction, viscosity enhancement, water retention and thickening, and air entrainment and plasticization.