Multi-Layer Coating for Concrete Formwork Boards
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Solution Overview
Problem
Concrete formwork panels face issues with crack formation due to thermal, humidity, and mechanical stresses, which affect the surface quality and structural integrity of concrete structures.
Innovation Solution
A multi-layer fiber-reinforced coating system is developed, where the resin in the inner layer has less shrinkage than the outer layer, and the coating is applied as a semi-finished product to absorb internal stresses, using a combination of resins like urea-melamine and melamine with acrylic plasticization, and incorporating fibers such as glass, basalt, and cellulose, with a controlled thickness and finish film for improved bonding and chemical resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a fiber-reinforced resin coating is applied to the formwork panel surface, then the surface strength and crack resistance are improved, but internal stresses from resin shrinkage during curing cause crack formation
Solution Approach 1:
The coating is divided into multiple layers with different resin types and shrinkage characteristics. The inner layer uses resin with lower shrinkage to bond to the substrate, while outer layers use resin with higher shrinkage resistance to face the concrete, creating a gradient structure that manages internal stresses across layers
Solution Approach 2:
Different regions of the coating have different resin compositions and properties. The inner layer near the wood substrate has resin with lower shrinkage, while outer layers have resin with progressively higher shrinkage resistance, matching the local stress conditions at each interface
2Reliability
If temperature changes occur below room temperature or freezing point, then thermal stresses are generated in the resin coating, but these stresses lead to crack formation
Solution Approach 1:
The coating uses composite resin systems combining different resin types (e.g., polyurethane, polyester, epoxy) with complementary thermal and mechanical properties. This composite structure distributes thermal stresses more evenly and prevents crack propagation that would occur in single-resin systems
Solution Approach 2:
The resin composition is specifically selected and adjusted to match the thermal expansion coefficients of the wood substrate and concrete. By controlling the chemical composition and crosslinking density of the resins, the thermal stress parameters are optimized to minimize differential expansion and contraction across temperature ranges
3Strength
If the resin coating is pressed with the base material during manufacturing, then bonding is achieved, but shrinkage stresses are locked in that cause later cracking
Solution Approach 1:
The coating layers are applied and allowed to cure partially or fully before final pressing with the substrate. This preliminary curing allows the resin to achieve its final shrinkage dimensions before bonding, so that subsequent pressing creates strong adhesion without locking in additional shrinkage stresses
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 solution effectively reduces crack formation across various temperature and humidity conditions, ensuring a stress-free surface and enhanced durability of the concrete formwork panels.
Implementation Method 1
the inherent and shrinkage stresses that are unavoidable, for example due to the polycondensation of the resin
Implementation Method 2
This prevents a resin, which shrinks comparatively extensively, from tending to crack when it comes into direct contact with the base material of the board
Data Source
AI summary
The invention relates to a concrete formwork board comprising a multilayer fiber-reinforced coating comprising a resin in the layer contacting the base material of the board, said resin comprising low shrinkage when initially cured and being pressed in an outer layer or pressed, in particular glued, onto the base material of the board as a previously cured, resinous coating material. The invention relates to a method for producing a concrete formwork board having a coating on the base material of the board, wherein a resin is used in order to implement a coating in a layer contacting the base material of the board, said resin having lower shrinkage when initially cured than a resin used in a layer that lies further outwards, or a semi-finished good comprising resin, said resin is cured and then pressed, in particular glued, onto the concrete formwork board.