EVA Waterproof Sheet Silica Surface Layer Concrete Adhesion
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Solution Overview
Problem
Conventional waterproof sheets for tunnels exhibit poor adhesion properties with concrete structures, leading to water leakage due to gaps and adhesion failures, and require enhanced tensile strength and elongation to withstand construction stresses and environmental changes.
Innovation Solution
A waterproof sheet with a silica-containing surface layer having a silicon dioxide content of 90% or more, applied over a specific depth, reacts with cement to form a strong bond, providing a tensile breaking strength of 10 MPa or more and a mortar adhesion strength of 15 N/cm or more, ensuring firm integration with concrete.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional waterproof sheets are used, then the basic waterproofing function is provided, but the adhesion property to concrete structure is poor leading to water leakage
Solution Approach 1:
The patent applies local quality by creating a surface layer with different composition and properties from the bulk material. The waterproof sheet has a surface layer enriched with vinyl acetate units (30-90% by mass) that specifically enhances adhesion to concrete, while the interior maintains the base polymer structure. This localized modification at the surface directly addresses the adhesion problem without compromising the overall waterproofing function.
Solution Approach 2:
The patent utilizes parameter changes by controlling the vinyl acetate content in the surface layer within a specific range (30-90% by mass) and the thickness of this layer (1-50 μm). By optimizing these parameters, the sheet achieves maximum adhesion strength to concrete while maintaining flexibility and waterproofing performance. The specific parameter ranges are determined to balance adhesion enhancement with material integrity.
2Strength
If the waterproof sheet needs to withstand construction stresses and environmental changes, then higher tensile strength and elongation are required, but this may compromise adhesion properties
Solution Approach 1:
The patent segments the waterproof sheet into distinct functional zones: a surface layer (1-50 μm thick) optimized for adhesion with high vinyl acetate content, and an interior bulk material providing mechanical strength and flexibility. This segmentation allows each layer to be optimized for its specific function - the surface for bonding to concrete and the interior for withstanding tensile stresses during construction and service.
Solution Approach 2:
The patent creates a composite structure within the waterproof sheet by forming a surface layer with different polymer composition (higher vinyl acetate content) than the interior. This composite approach combines the adhesion benefits of vinyl acetate-rich surface with the mechanical properties of the base polymer in the interior, achieving both strong concrete bonding and adequate tensile performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The waterproof sheet effectively prevents water infiltration by maintaining a strong, gap-free bond with concrete structures, even under stress and environmental changes, ensuring prolonged watertightness and mechanical integrity.
Implementation Method 1
a silica-containing surface layer containing silica having a silicon dioxide content of 90% by mass or more in a ratio of from 30 to 200 mg/cm³ on a surface of the base sheet... reacts with cement to form a strong bond
Data Source
Figure 1~2
Figure 3(a)~3(b)
Figure 4~5(b)
AI summary
Method of producing a waterproof sheet for a tunnel which is to be built by a cut and cover tunneling method comprising a base sheet containing a synthetic resin which is an ethylene-vinyl acetate copolymer having a content of a structural unit derived from vinyl acetate of 30% by mass or more, and having on a surface thereof a silica-containing surface layer containing silica having a silicon dioxide content of 90% by mass or more, the method comprising a step of coating the base sheet with a silica dispersion liquid and drying under heating to form the silica-containing surface layer, the silica dispersion liquid comprising (i) to (iii): (i) silica having a silicon dioxide content of 90% by mass or more, dispersed in (ii) an organic solvent exhibiting dissolution action on said ethylene-vinyl acetate copolymer of the base sheet, and (iii) a thickener having affinity with the synthetic resin of the base sheet, the thickener being an ethylene-vinyl acetate copolymer having a content of structural unit derived from vinyl acetate of 30 to 90% by mass, the silica in the silica-containing surface layer being present in a content of from 30 to 200 mg/cm3, the silica-containing surface layer being formed over a depth of from 5 to 30 µm from the surface of the waterproof sheet, the waterproof sheet having a tensile breaking strength of 20 MPa or more, a tensile breaking elongation of from 10 to 50%, a tear strength of 50 N or more and a watertightness on deterioration in evenness or levelness of 10 mL/day or less, and a mortar adhesion strength of 15 N/cm or more.