hydroxypropyl methylcellulose in dry-mixed mortar

Overview of HPMC

Hydroxypropyl methylcellulose (HPMC) is a non-ionic cellulose ether derived from natural polymer cellulose, which is modified by methylation and hydroxypropylation. HPMC has excellent thickening, water retention, film-forming, bonding and stability properties. Because it can form a transparent and stable colloidal solution in water, it is widely used in building materials, especially in dry-mixed mortar products. It plays an irreplaceable role.

Characteristics of dry-mixed mortar and applicability of HPMC

Dry-mixed mortar is a dry powder material uniformly mixed with cementitious materials (such as cement, gypsum, etc.), fine aggregates, fillers and various additives. When used, only a certain proportion of water needs to be added and stirred. It is convenient to construct, stable in performance, and controllable in quality, and has high performance requirements for additives. HPMC mainly improves the overall performance of the mortar by improving the construction, adhesion, water retention and anti-slip properties of the mortar.

The main role of HPMC in dry-mixed mortar

3.1. Water retention and thickening effect

HPMC has extremely strong water absorption, expansion and water retention capabilities. In dry-mixed mortar, HPMC can significantly reduce water loss, delay the cement hydration process, and ensure that the mortar has enough time to bond and harden on the base surface and brick surface. This water retention performance is particularly suitable for substrates with strong water absorption (such as aerated concrete, brick walls, etc.), effectively preventing water seepage, hollowing and cracking during construction. At the same time, the thickening effect of HPMC improves the rheology of the mortar, so that the mortar has good fluidity and stability during construction.

3.2. Improve construction and workability

Mortar with HPMC added has better lubricity and thixotropy, reduces resistance during construction, and makes plastering and scraping smoother. Especially in mechanical spray mortar, HPMC can optimize the pumping performance of the mortar, prevent nozzle clogging, and ensure that the mortar is not easy to sag after spraying. In addition, HPMC gives the mortar a better opening time, which is convenient for workers to adjust the construction progress and repair defects, and improve construction efficiency.

3.3. Enhanced adhesion and anti-slip properties

The polymer film formed by HPMC in the mortar can play a "bridge" role between the mortar and the substrate, improving the adhesion of the mortar to various substrates, and is especially suitable for use in tile adhesives and exterior wall insulation systems. At the same time, HPMC can effectively improve the anti-slip properties of the mortar, ensuring that tiles or stones do not fall after construction, meeting the requirements of vertical surface construction.

3.4. Delaying the setting time and improving the crack resistance

HPMC can delay the hydration rate of cement in the mortar, appropriately extend the setting time, help improve the working time of the mortar during the construction process, and avoid early shrinkage and cracking. At the same time, good water retention ensures that the mortar is more completely hydrated, forming a denser hydration product, and improving the strength and crack resistance of the hardened mortar.

3.5. Improve anti-sagging and anti-stratification performance

In the dry-mixed mortar system, the thickening and water-retaining effect of HPMC can prevent the separation of coarse and fine aggregates in the mortar, reduce bleeding and segregation, and improve the uniformity of the mortar. When applied on a vertical surface, it is not easy to fall or sag, ensuring the flatness and aesthetics of the coating.

3.6. Improve the weather resistance and durability of the mortar

The polymer protective film formed by HPMC can provide a certain flexibility in the hardened mortar, buffer the changes in external temperature and humidity, and reduce the internal stress concentration of the mortar, thereby improving the weather resistance and long-term service life of the dry-mixed mortar.

Specific applications in different types of dry-mixed mortars

Tile adhesive: improve water retention, prevent slippage, enhance adhesion and construction performance.

Plastering mortar: improve workability and water retention, reduce hollowing and cracking.

Self-leveling mortar: impart appropriate fluidity and thixotropy to ensure a smooth surface after construction.

Insulation system mortar: improve adhesion, extend construction time, and enhance durability.

Masonry mortar: reduce mortar stratification and water seepage, and ensure masonry stability and structural strength.

As the core additive in dry-mixed mortar, HPMC can improve the workability, water retention, adhesion and crack resistance of mortar in many aspects, ensuring the stability of mortar performance during construction and hardening. Reasonable selection of HPMC model (viscosity, degree of substitution, gel temperature, etc.) and dosage can achieve performance optimization for different dry-mixed mortar products and meet the needs of modern construction projects for high performance, convenient construction and durability.