Functional application research of VAE/RDP in building mortar system

In the field of advanced building materials engineering, ethylene-vinyl acetate copolymer-based redispersible latex powder (VAE/RDP) as the core material of polymer modification technology has achieved a leapfrog development of building mortar from traditional brittle cement-based materials to high-performance composite systems through its unique film-forming properties and interface regulation capabilities. This paper combines rheology, fracture mechanics and interface chemistry theory to systematically explain the key mechanism of VAE/RDP in three typical mortar systems.

1. Optimization of interfacial bonding mortar system

1. Molecular bonding enhancement mechanism

Polymer bridging effect: VAE latex particles (particle size 80-150μm) form a continuous phase polymer film (thickness 150-300nm, confirmed by SEM observation) during the hydration process, connecting the cement hydration product and the substrate interface through the dual effects of mechanical anchoring and chemical bonding.

Stress buffer model: elastic modulus gradient transition design (polymer film 2-5GPa vs ceramic tile 6-8GPa), reducing the interface stress concentration factor to 1.2-1.5 (finite element analysis data).

2. Key performance improvement verification

| Performance indicators | Blank mortar | VAE/RDP modified mortar (addition amount 2.5%) | Test standard |

|------------------|-------------------|------------------------------|-----------------|

| Wet-based bond strength | 0.6 MPa | 1.4 MPa (+133%) | EN 1348 |

| Anti-slip load | 0.3 kN | 0.8 kN (+167%) | ISO 13007-2 |

| Strength retention rate after thermal cycling | 62% | 92% | GB/T 29756 |

| Open time | 15 min | 45 min | EN 12004 |

3. Engineering adaptation plan

Vitrified tile bonding: Use VAE/RDP (solid content 98%) with Tg=+10℃, and match it with methyl cellulose ether (0.1% MC)

Stone curtain wall system: Compound epoxy modified RDP (addition amount 3.5%), achieve tensile bonding strength > 2.0MPa

II. Construction of functional wall putty system

1. Membrane strengthening mechanism

Three-dimensional network construction: VAE/RDP reacts with Ca(OH)₂ to generate organic-inorganic hybrid structure (XRD detection 2θ=29.4° characteristic peak enhancement), which optimizes the elastic modulus of putty film to 1.8-2.2GPa (nanoindentation test).

Deformation coordination ability: fracture energy is increased to 380 J/m² (three-point bending method), which is significantly higher than the 120 J/m² of traditional putty.

2. Key performance parameters

| Parameter name | Conventional putty | VAE/RDP modified putty (addition amount 1.8%) |

|-------------------|-------------------|------------------------------|

| Sandability (60-grit sandpaper) | 45s/0.1m² | 28s/0.1m² |

| Linear shrinkage | 0.15% | 0.06% |

| Scrub resistance | 800 times | 4500 times |

| Moisture permeability | 15 g/(m²·h) | 9 g/(m²·h) |

3. Design of new formula system

- Anti-cracking formula: VAE/RDP (2.0%) + polypropylene fiber (0.05%)

- Ecological system: bio-based VAE/RDP (carbon footprint reduced by 35%) + nano-montmorillonite (0.3%)

- High-precision leveling system: ultrafine RDP (D50=50μm) combined with thixotropic agent (Bentone EW 0.2%)

III. Performance upgrade path of plaster mortar

1. Rheological property regulation

- Plastic viscosity optimization: VAE/RDP (1.2%) reduces the Bingham model parameter τ0 of mortar from 58 Pa to 32 Pa, and μp is adjusted from 0.8 Pa·s to 1.2 Pa·s (measured by rotational rheometer).

- Structural recovery rate: The area of thixotropic ring is reduced by 40% (0.1-100s⁻¹ shear rate scanning), which significantly improves the anti-sagging property of construction.

2. Durability improvement verification

| Test items | Benchmark mortar | VAE/RDP modified mortar (1.5%) |

|-------------------|-------------------|------------------------------|

| Freeze-thaw cycles (50 times) | Mass loss 2.8% | Mass loss 0.7% |

| Carbonation depth (90d) | 6.5 mm | 3.2 mm |

| Chloride ion diffusion coefficient | 8.7×10⁻¹² m²/s | 2.3×10⁻¹² m²/s |

| Strength after wet heat aging | Strength retention rate 68% | Strength retention rate 92% |

3. Special mortar development

- Lightweight thermal insulation plaster: VAE/RDP (1.8%) + glass beads (40% vol) Thermal conductivity 0.085 W/(m·K)

- Self-cleaning surface system: TiO2@RDP core-shell structure material (photocatalytic efficiency increased by 3 times)

- Electromagnetic shielding mortar: VAE/RDP+carbon nanotubes (0.6%) Shielding effectiveness ＞25dB (1-3GHz)

IV. Technology development trends and challenges

1. Intelligent response system: Develop temperature-sensitive VAE/RDP (LCST=35℃) to achieve self-repair function of plaster layer

2. Digital design: Establish RDP dosage-performance prediction model based on machine learning algorithm (R²＞0.95)

3. Circular economy application: Use recycled aggregate interface modification technology to restore the bonding strength of waste concrete to 90% of the original aggregate

Conclusion

VAE/RDP has achieved the transformation of building mortar from simple bonding material to multifunctional intelligent system through its unique polymer phase change characteristics and interface engineering capabilities. It is recommended to use the life cycle cost analysis method (LCCA) in engineering applications, combined with the durability improvement effect of RDP (maintenance cost can be reduced by 40% based on a 60-year cycle) to optimize the material selection scheme. The latest research shows that the development of graphene-modified VAE/RDP will enable the mortar system to have structural health monitoring functions.