Ⅰ.Core Function

The "multiple thin layers" application method involves controlling the thickness of each individual coat (typically 0.3~0.5mm per layer) through layered construction. This ensures the coating fully penetrates the substrate and forms a uniform film, ultimately resulting in a continuous, defect-free waterproofing membrane.

Ⅱ.Analysis of Technical Mechanism

1.Stress Release and Crack Resistance Improvement

Hazard of Thick Single Coats: When a single layer is applied too thickly (>1mm), internal stresses generated during curing - due to solvent evaporation or water emission - can easily lead to shrinkage cracking.

·Thick coat:Concentrated shrinkage stress → Crazing

·Thin coat:Dispersed stress → Uniform film formation

Layered Stress Dissipation: When each layer is kept below ~0.5mm, the curing shrinkage forces are released progressively with each layer, enhancing the overall tensile strength.

2.Optimization of Film Density

·Enhanced Penetration:Thin layers allow the coating to fully saturate the pores of the substrate (e.g., concrete capillaries), improving mechanical anchorage.

·Elimination of Pinholes:In solvent-based coatings (e.g., polyurethane), a thick coat can cause rapid skin formation on the surface, trapping escaping solvents and forming pinholes. Layered application allows micro-pores to be sealed progressively.

3.Controlled Drying Process

Coordination of Surface Dry and Through Dry:

·When a single layer is ≤0.5mm, water-based coatings (e.g., acrylic) achieve surface dry in approximately 1 hour and through dry in about 4 hours (at standard conditions), enabling effective intercoat adhesion.

·Excessively thick coats are prone to being "surface dry but wet inside," leading to blistering or delamination during subsequent application.

Ⅲ.Key Parameter Control

Ⅳ.Key Construction Techniques

1.Tool Selection:

·Notched Trowel:Controls thickness (e.g., a 1.5mm notch depth levels to ~0.5mm).

·Short Nap Roller:Ensures even distribution of coating, avoiding local buildup.

2.Application Direction:

Apply each subsequent coat perpendicular to the previous one to eliminate weak areas caused by unidirectional application patterns.

3.Treatment of Critical Details:

·Internal Corners/Pipe Penetrations:First, apply a thin coat to embed geotextile/fabric, then build up with layered coats.

·Cracks: Use a "one fabric, three coats" process (coat → mesh fabric → coat → coat) to enhance crack resistance.

Ⅴ.Consequences of Non-Compliant Application

Conclusion：
The "multiple thin layers" method is the optimal solution for balancing material performance with construction controllability. It achieves this through gradual stress release, optimized penetration depth, and a controlled drying process. Construction must strictly adhere to the principles of "each layer ≤0.5mm, interval ≥4 hours, and perpendicular application direction between layers.