Dry Cement-PVA Blend Reduces Shrinkage and Enhances Ductility
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Solution Overview
Problem
Existing concrete compositions face challenges in achieving high tensile strength, ductility, thermal stability, and low shrinkage without using reinforcing materials or elastomeric phases, while maintaining low viscosity and permeability during hardening.
Innovation Solution
A cement powder blend comprising 45-90 wt.% Portland cement, 0-25 wt.% siliceous fly ash, 0-25 wt.% limestone, and 5-30 wt.% polyvinylalcohol (PVA) with specific size distribution and ester values, which forms hybrid particles with the calcium phase upon hydration, reducing shrinkage and enhancing ductility and thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If reinforcing materials such as steel or fibrous reinforcement materials are included in concrete, then tensile strength and ductility are improved, but elasticity deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the cement slurry by incorporating PVA and controlling the water-to-cement ratio, enabling the material to achieve both high tensile strength and high elasticity without traditional reinforcement
Solution Approach 2:
The patent creates a composite material system by combining Portland cement, PVA, and water to form a unified concrete composition that integrates reinforcement and elasticity functions within the cement matrix itself
2Ease of operation
If viscosity increasing agents such as PVA are added to cement composition, then handling properties are improved, but shrinkage degree upon hardening increases
Solution Approach 1:
The patent optimizes the PVA concentration parameter within a specific range (5-30 wt.%) and controls the water-to-cement ratio to achieve the dual benefit of improved handling properties and reduced shrinkage, transforming the trade-off into a synergistic relationship
3Stability of the object's composition
If elastomeric phases are included in concrete, then flexibility is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts the flexibility function from separate elastomeric phases and integrates it directly into the cement slurry through PVA incorporation, eliminating the need for complex multi-phase manufacturing processes while maintaining flexibility
Solution Approach 2:
The patent makes the cement slurry itself multi-functional by incorporating PVA to simultaneously provide flexibility, improved handling, and controlled shrinkage, replacing the need for separate elastomeric phases
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 cement composition achieves reduced shrinkage, high ductility, and improved thermal stability, allowing for concrete with enhanced flexibility and fatigue resistance, suitable for use without reinforcing materials and compatible with other construction materials like asphalt.
Implementation Method 1
polyvinylalcohol (PVA) with specific size distribution and ester values, which forms hybrid particles with the calcium phase upon hydration
Implementation Method 2
Concrete is typically made by curing an aqueous slurry of cement
Data Source
AI summary
The invention relates to a cementitious powder blend comprising, based on total weight—45-90 wt % Portland cement; pref. 50-80 wt %—0-25 wt % siliceous fly ash; pref. 5-20 wt %—0-25 wt % limestone; pref. 5-20 wt %—5-30 wt % polyvinylalcohol, pref. 5-15 wt %. The PVA preferably has—a size distribution with D10=170-270 μm, D50=370-450 μm. D90=690-850 μm and D100=1000-1300 μm; and—an ester value in the range of 1-250 mg KOH/g, as determinable by EN-ISO 3681:1998 and/or wherein the polyvinyl alcohol has a viscosity of a 4% aqueous solution at 20° C. in the range of 1-40 mPa·s, as determinable by EN-ISO 12058-1:2002. A substantial part of the PVA may be present in the form of hybrid particles composed of Portland cement and the polyvinylalcohol. Further, the invention relates to concrete composed of the cementitious powder blend, water and aggregate as well as flexible concrete products made therefrom. The cementitious powder blend is used for—for the preparation of a paving of a road or other infrastructural element; for the preparation of a base course for a road or other infrastructural element; for the manufacture of a floor of a building; for the repair of a concrete structure; for grouting; or—as an injection into a concrete structure.