1. Introduction
Polystyrene particle insulation mortar is a material commonly used for building exterior wall insulation. It combines the advantages of polystyrene particles (EPS) and traditional mortar, providing good insulation effect and mechanical properties. In order to further improve its comprehensive performance, especially to enhance its adhesion, crack resistance and construction performance, redispersible latex powder (RDP) is often added. RDP is a polymer emulsion in powder form that can be redispersed in water.
2. Overview of redispersible latex powder (RDP)
2.1 Definition and properties
Redispersible latex powder is a powder made by spray drying a polymer emulsion obtained by emulsion polymerization. It can be redispersed in water to form a stable emulsion with good film-forming and adhesion properties. Common RDPs include ethylene-vinyl acetate copolymer (EVA), acrylate copolymer and styrene-butadiene copolymer (SBR).
2.2 Main functions
RDP is widely used in building materials and has the following functions:
Enhance adhesion: Provide excellent adhesion performance, making the bond between mortar and substrate, mortar and polystyrene particles stronger.
Improve crack resistance: Improve the crack resistance of mortar by forming a flexible polymer film.
Improve construction performance: Increase the flexibility and construction fluidity of mortar, easy to spread and level.
Improve water resistance and freeze-thaw resistance: Enhance the water resistance and freeze-thaw cycle resistance of mortar.
3. Application of RDP in polystyrene particle insulation mortar
3.1 Improve bonding strength
In polystyrene particle insulation mortar, adhesion is a key performance. Since polystyrene particles themselves are hydrophobic materials, they are easy to fall off from the mortar matrix, resulting in failure of the insulation system. After adding RDP, the polymer film formed in the mortar can effectively cover the surface of polystyrene particles, increase the bonding area between them and the mortar matrix, and improve the interfacial bonding force.
3.2 Enhanced crack resistance
The polymer film formed by RDP has high flexibility and can form a mesh structure inside the mortar to prevent the expansion of cracks. The polymer film can also absorb the stress generated by external forces, thereby effectively preventing cracks caused by thermal expansion and contraction or shrinkage.
3.3 Improved construction performance
Polystyrene particle insulation mortar is prone to poor fluidity and difficulty in spreading during construction. The addition of RDP can significantly improve the fluidity and workability of the mortar, making the mortar easy to construct and improving construction efficiency. In addition, RDP can also reduce the segregation of the mortar and make the distribution of mortar components more uniform.
3.4 Improved water resistance and durability
Polystyrene particle insulation mortar needs to have good water resistance in long-term use to prevent rainwater from eroding the insulation layer. RDP can form a hydrophobic layer in the mortar through its film-forming properties, effectively preventing moisture from entering the mortar. In addition, the flexible film provided by RDP can also enhance the mortar’s anti-freeze and thaw properties and extend the service life of the insulation mortar.
4. Mechanism of action
4.1 Film-forming effect
After RDP is redispersed in water in the mortar, the polymer particles gradually merge into one to form a continuous polymer film. This film can effectively seal the tiny pores in the mortar, prevent the intrusion of moisture and harmful substances, and enhance the bonding force between the particles.
4.2 Enhanced interface effect
During the hardening process of the mortar, RDP can migrate to the interface between the mortar and the polystyrene particles to form an interface layer. This polymer film has strong adhesion, which can significantly improve the bonding force between the polystyrene particles and the mortar matrix and reduce the generation of interface cracks.
4.3 Improved flexibility
By forming a flexible network structure inside the mortar, RDP increases the overall flexibility of the mortar. This flexible network can disperse external stress and reduce stress concentration, thereby improving the crack resistance and durability of the mortar.
5. Effect of RDP addition
5.1 Appropriate addition amount
The amount of RDP added has a significant effect on the performance of polystyrene particle insulation mortar. Generally, the amount of RDP added is between 1-5% of the total cementitious material mass. When the amount added is moderate, it can significantly improve the bonding strength, crack resistance and construction performance of the mortar. However, excessive addition may increase costs and affect the hardness and compressive strength of the mortar.
5.2 Relationship between addition amount and performance
Bond strength: As the amount of RDP added increases, the bonding strength of the mortar gradually increases, but after reaching a certain proportion, the effect of further increasing the amount added on the improvement of the bonding strength is limited.
Crack resistance: An appropriate amount of RDP can significantly improve the crack resistance of the mortar, and too little or too much addition may affect its optimal effect.
Construction performance: RDP improves the fluidity and workability of the mortar, but excessive addition will cause the mortar to become too viscous, which is not conducive to construction operations.
6. Practical application and effect
6.1 Construction case
In actual projects, RDP is widely used in exterior insulation systems (EIFS), plaster mortars and bonding mortars. For example, in the external wall insulation construction of a large commercial complex, by adding 3% RDP to the polystyrene particle insulation mortar, the construction performance and insulation effect of the mortar were significantly improved, and the risk of cracking during the construction process was effectively reduced.
6.2 Experimental verification
The experimental study showed that the polystyrene particle insulation mortar with the addition of RDP had significant improvements in bonding strength, compressive strength and crack resistance at 28 days. Compared with the control samples without RDP, the bonding strength of the RDP-added samples increased by 30-50% and the crack resistance increased by 40-60%.
Redispersible latex powder (RDP) has important application value in polystyrene particle insulation mortar. It effectively improves the comprehensive performance of the insulation mortar by enhancing bonding strength, improving crack resistance, improving construction performance, and improving water resistance and durability. In practical applications, the appropriate addition of RDP can significantly improve the stability and durability of the insulation system, providing an important guarantee for building energy conservation and structural safety.
Post time: Jun-19-2024