In dry-mixed mortar products, two cementitious material systems, cement and redispersible polymer powder are an ideal match. Combining the two in dry-mixed mortar products achieves significant synergistic effects. Any cementing material used alone can have unattainable properties that allow polymer-modified mortar to be used on various special occasions and have obvious advantages in quality control, construction operations, storage, and environmental protection.
1. Tile bonding mortar
Ceramic tiles are durable, waterproof, easy to clean, and have good decorative and functional properties. They are now widely used in indoor and outdoor places such as walls, floors, ceilings, kitchens, bathrooms, and swimming pools.
The thick-layer construction method is the traditional way of applying ceramic tiles; that is, ordinary mortar is first applied to the back of the ceramic tiles, and then pressed onto the base layer. The thickness of the mortar layer is about 10mm to 30mm. Although this construction technology is very suitable for construction on uneven bases, it has obvious disadvantages:
- The efficiency of pasting ceramic tiles could be low.
- The technical requirements for construction personnel are high.
- The flexibility of the bonding mortar increases the risk of falling off.
- It is difficult to strictly control the quality of the mortar at the construction site.
Due to the existing shortcomings, this construction technology is only suitable for high water absorption ceramic tiles. The ceramic tiles, The ceramic tiles need to be soaked in water to achieve sufficient bonding strength before pasting.
Due to the modification of redispersible polymer powder and cellulose ether, this type of tile bonding mortar has good adhesion to different base layers (including fully vitrified tiles with deficient water absorption) surface layers. It has good joint performance and flexibility to absorb stress caused by temperature differences and other factors from the surface, as well as excellent resistance to sag. It can carry out thin-layer construction within a long enough opening time, and there is no need to pre-wet the tiles in water. The construction speed is accelerated, this construction method is easy to operate, and it is also easy to control on-site construction quality.
The functions of fresh tile bonding mortar prepared with redispersible polymer powder are extending the working time and adjustable time, improving its water retention performance to ensure hydration of cement; specially modified redispersible polymer powder can enhance the resistance to drapeability; easy to apply to the substrate and easy to press the tiles into the adhesive to improve workability. Ceramic tile bonding mortar formulated with redispersible polymer powder has good adhesion to various base materials (including mortar, wood, old tiles, and PVC) and has good deformation ability under different climatic conditions.
2. External wall insulation system
Exterior Insulation and Finishing Systems (EIFS) are multi-layer external wall systems that prevent moisture from penetrating interior walls while providing excellent energy efficiency and architectural design flexibility and creativity. This system is increasingly used in composite insulation systems for building exterior walls. The system combines thermal insulation panels such as extruded polystyrene (XPS). Molded polystyrene boards (EPS) are pasted on the base layer, then covered with a protective mortar layer embedded with fiberglass mesh, and finally, the decorative surface layer is made.
The bonding mortar, modified with re-dispersible polymer powder in the external wall insulation system is bonding mortar, protective mortar, and decorative mortar, used as an adhesive mortar to adhere the polystyrene board to the wall while protecting the polystyrene board and preventing aging due to climatic conditions. The layer should be about 3mm thick. It is made of alkali-resistant fiberglass mesh as a reinforcing material. The protective mortar modified by re-dispersible polymer powder is covered on the surface layer of the polystyrene board and finally covered with a 2mm to 3mm thick decorative mortar modified by re-dispersible polymer powder as a decorative and protective surface layer.
For the redispersible polymer powder modified in the external wall insulation system, the most important performance is the bonding strength with the base material or polystyrene board; for the plastering mortar, the most important performance is the bonding strength with the polystyrene board, excellent impact strength, and low water absorption after compounding with the alkali-resistant glass fiber mesh cloth. The weakest link in the external wall insulation system is the bonding interface between the polystyrene board and the mortar. In actual projects, the most likely problem is the cracking of the surface layer. The mortar modified with re-dispersible polymer powder with the polystyrene board, water-resistant bonding strength, impact resistance closely related to the system’s anti-cracking performance, and system water absorption can all meet relevant requirements. Ethylene-vinyl acetate copolymers with high ethylene content and, thus, low Tg (glass transition temperature) values have always dominated the formulation of bonding and plastering mortars for exterior wall insulation finishing systems. EVA polymer with high ethylene content has excellent flexibility, a fundamental property for plastering mortars to achieve high-impact strength. This re-dispersible polymer powder provides excellent bonding properties in mortars for expanded polystyrene panels (extruded polystyrene panels) under dry, moist, and freeze-thaw conditions. EVA polymer powders with high ethylene content are economically the most efficient choice because they can exhibit good performance at relatively low dosages.
In the external wall insulation system, the effect of redispersible polymer powder on hardened mortar is: good adhesion to polystyrene boards and other substrates, excellent flexibility and impact resistance, excellent water vapor permeability, good hydrophobicity, and weather resistance; the effect on fresh mortar is to extend the working time and improve the water retention performance to ensure the hydration of the cement and improve the workability.
3. Self-leveling mortar
The ground structures of self-leveling mortar mainly include floating ground structure systems and composite ground structure systems. The floating floor is laid on top of the sound insulation layer without any contact with the load-bearing floor or walls of the building. A thin layer of self-leveling floor material is often used for leveling under the final floor surface (such as carpet, PVC floor, or wooden floor). Composite floor construction generally does not use a sound insulation layer. Instead, a thicker pumpable self-leveling floor layer is laid on the load-bearing floor which is applied directly to the leveling layer.
Self-leveling mortar has high-performance requirements. It should have excellent flow characteristics when freshly mixed and use as little mixing water as possible. There should be no bleeding or settling, excellent self-healing properties, and extended opening and work times. The strength should increase rapidly after sufficient opening time, and it should have good adhesion and cohesion to the base layer, high flexural strength, high wear resistance, and low shrinkage or expansion in the hardened state. In addition to casein or synthetic water-reducing agents that are often used in self-leveling mortars to achieve the required fluidity, redispersible polymer powder also needs to be added for modification to meet the fluidity, cohesion, and adhesion properties of self-leveling mortars, and strict requirements on flexural strength.
