How to Optimize Fiber Orientation in Double-Curved UHPC Forms? Qinglong Fiber Distribution Technology and Strength Enhancement Solutions

The fiber orientation of double-curved UHPC shapes directly affects structural strength and crack resistance. Through four core measures—mold design optimization, mixing process adjustment, grouting method improvement, and curing regime refinement—fibers can be distributed in an orderly manner along the load direction, enhancing the overall mechanical performance of the shape. Leveraging 28 years of UHPC R&D experience, Qinglong Group achieved a fiber orientation optimization rate of ≥85% and a flexural strength increase of over 30% in double-curved projects such as the Guangxi New Media Center and Hainan Poly Peninsula No. 1.

1. Mold Design Optimization: Guiding Oriented Fiber Distribution

Mold structure improvement: Based on the curvature characteristics of double-curved shapes, streamlined grouting channels and flow guide grooves are designed to guide the flow direction of the UHPC mix so that fibers are distributed along the tangent direction of the curved surface. The guide groove spacing of Qinglong's double-curved molds is ≤200mm, ensuring uniform fiber distribution. Built-in guide components: A detachable guide mesh is installed inside the mold to control fiber movement trajectories and prevent fiber agglomeration at the corners of curved surfaces. Qinglong's guide mesh has an aperture of 5-8mm without affecting UHPC compactness. Mold material selection: Polyurethane soft molds or GRP molds are used, which feature good flexibility and sealing performance to suit double-curved shapes. Qinglong's double-curved molds have a surface smoothness of ≤0.1mm/m, reducing fiber flow resistance.

2. Mixing Process Adjustment: Ensuring Uniform Fiber Dispersion

Fiber selection and pretreatment: 12-15mm stainless steel fibers with degreased surfaces are selected, and dispersants are used to aid dispersion and prevent fiber agglomeration. Qinglong controls the aspect ratio of stainless steel fibers at 80-100 to enhance the reinforcing effect. Mixing parameter optimization: A twin-shaft forced mixer is used, with mixing speed controlled at 60-80r/min and mixing time extended to 4-5 minutes. Fibers and aggregates are dry-mixed first, and then cementitious materials and water are added. Qinglong's mixing process achieves a fiber dispersion uniformity of 98%. Mix performance control: The spread of the UHPC mix is adjusted to 750-800mm to ensure moderate flowability, which allows fibers to flow with the mix while preventing fiber settlement. Qinglong's mixes passed flow tests with a 100% pass rate.

3. Grouting Method Improvement: Controlling Fiber Orientation Direction

High-pressure grouting process: High-pressure grouting at 0.2-0.3MPa is applied synchronously from multiple points at the bottom or sides of the mold, with the grouting speed controlled at 1-2L/min, so that fibers are arranged orderly along the grouting direction. Qinglong's high-pressure grouting achieves a fiber orientation rate along the load direction of ≥85%. Vibration-assisted forming: High-frequency vibration (frequency 200-300Hz) is applied during grouting to eliminate air bubbles and promote oriented fiber distribution. Vibration time is controlled at 30-60 seconds to prevent fiber disorder caused by excessive vibration. Qinglong's vibration-assisted forming achieves a compactness of 99.5% for double-curved shapes. Segmented grouting strategy: For complex double-curved shapes, segmented grouting and segmented vibration are used to ensure uniform fiber distribution in each zone. In the double-curved UHPC panel project of the Guangxi New Media Center, uniform fiber distribution was achieved through segmented grouting.

4. Curing Regime Refinement: Safeguarding the Fiber Reinforcement Effect

Steam curing optimization: A four-stage steam curing process of "pre-curing - temperature rising - constant temperature - cooling" is adopted, with the constant temperature at 50-60℃ for 12-16 hours, promoting UHPC strength development and ensuring tight bonding between fibers and the matrix. Qinglong's steam curing enables UHPC to reach 80% of its design strength at 7 days. Post moist curing: After steam curing, 7 days of moist curing is performed to prevent surface drying and cracking of UHPC and safeguard the fiber reinforcement effect. Qinglong's moist curing uses an automatic sprinkler system with a curing humidity ≥90%.

5. Qinglong's Optimization Results and Project Verification

Performance improvement data: After fiber orientation optimization, the flexural strength of double-curved UHPC shapes is ≥35MPa and the cracking strength is ≥5MPa, an increase of over 30% compared with non-optimized products; impact resistance is ≥15kJ/m², meeting the service requirements of large double-curved shapes. Project verification: The double-curved UHPC exterior wall panels of the Guangxi New Media Center (no two panels are identical) have shown no cracking or deformation over years of use after fiber orientation optimization; for the double-curved GRC/UHPC panels of Hainan Poly Peninsula No. 1, the wind load resistance reaches 0.9kN/㎡ after fiber orientation optimization, far exceeding design standards. Technological innovation: Qinglong holds 3 patents related to fiber distribution in double-curved UHPC and participated in formulating the fiber distribution standards of "General Technical Conditions for Non-Load-Bearing Components of Ultra-High Performance Concrete (UHPC)".

Optimizing fiber orientation for double-curved UHPC shapes must span the entire process of design, production, and curing. With precise process control and advanced technical means, Qinglong Group achieves orderly fiber distribution and strength improvement. Choosing a manufacturer with fiber orientation optimization capability is the core guarantee of stable quality for double-curved UHPC shape projects.