Application of RDP in construction

Redispersible polymer powder (RDP) is one of the important functional additives indispensable in modern building dry-mix mortar systems. It is widely used in bonding mortar, plastering mortar, self-leveling mortar, insulation system, tile adhesive, caulking agent and other fields. Its main function is to improve the flexibility, bonding strength, crack resistance and water resistance of mortar, thereby improving the comprehensive performance and construction effect of building materials.

Definition and composition of RDP

Redispersible polymer powder is a free-flowing powder product obtained by spray drying a high molecular polymer obtained by emulsion polymerization. Its main components are ethylene-vinyl acetate copolymer (EVA), ethylene-acrylate copolymer (EBA), styrene-acrylate copolymer (St/BA), etc., and also contain auxiliary components such as protective colloids (such as polyvinyl alcohol PVA) and anti-caking agents (such as silica).

RDP can be redispersed into the original emulsion state after adding water and stirring, forming a uniform polymer film, thereby giving the dry-mixed mortar excellent flexibility, adhesion and durability.

Performance characteristics of RDP

2.1. Good redispersibility

RDP can be quickly dispersed in water to form a stable emulsion, so that the polymer is evenly distributed in the mortar.

2.2. Enhanced bonding strength

The polymer film can effectively penetrate into the pores of the substrate, enhance the mechanical bite and chemical bonding with the base surface, and significantly improve the bonding performance of the mortar.

2.3. Improved flexibility and crack resistance

RDP gives the mortar a certain elasticity, which can resist cracking caused by shrinkage, temperature changes and slight structural displacement.

2.4. Improved water resistance and weather resistance

The polymer film has good hydrophobicity and alkali resistance, which improves the water erosion resistance and durability of the mortar.

2.5. Excellent construction performance

RDP improves the water retention, construction fluidity, lubricity and smearability of the mortar, which is convenient for construction operation.

Mechanism of action of RDP

After RDP is dispersed in water to form an emulsion, the polymer particles are filled between the cement particles to form a continuous organic phase network. When the mortar hardens, the polymer forms a continuous flexible film in the matrix, interweaving with the inorganic phase (cement hydration product), enhancing the adhesion, flexibility and density of the overall structure.

Typical applications of RDP in construction

4.1. Tile Adhesive

RDP is the core additive in tile adhesive to improve the bonding strength, especially when pasting low water absorption tiles, vitrified tiles or on non-absorbent substrates. It can significantly enhance the initial adhesion and final adhesion, and improve water resistance, freeze-thaw resistance and aging resistance.

4.2. External wall insulation system (EIFS/ETICS)

In the external wall insulation system, RDP is used in insulation board bonding mortar and anti-cracking plastering mortar. Its main function is to enhance adhesion and flexibility, prevent the insulation layer from cracking due to stress deformation, and improve the durability and construction adaptability of the system.

4.3. Self-leveling mortar

Self-leveling mortar requires high fluidity and high adhesion. RDP improves the flexibility and crack resistance of self-leveling mortar, so that it can be laid evenly on the surface of the base, and it is not easy to crack or hollow after long-term use.

4.4. Repair mortar and interface agent

When repairing concrete structures or treating different substrates, RDP can improve the adhesion of mortar to the old concrete surface and prevent delamination at the interface between new and old materials.

4.5. Waterproof mortar and caulking agent

RDP gives waterproof mortar excellent impermeability and elongation properties, while improving crack resistance and pollution resistance in caulking agents, extending the service life of the product.

Selection suggestions

Different types of RDP have different performance focuses, such as EVA type focuses on adhesion and flexibility, and St/BA type emphasizes water resistance and weather resistance. In practical applications, the appropriate product model should be selected according to the specific mortar use, construction environment and cost control.

As a key functional material in modern building mortar systems, redispersible polymer powder plays a vital role in improving the performance of building materials, construction efficiency and engineering quality. With the development of green building materials and high-performance mortar, the application field of RDP will continue to expand and its technical level will continue to improve.