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

The fiber orientation in double-curved UHPC shapes directly affects structural strength and crack resistance. Through four core approaches—mold design optimization, mixing process adjustment, grouting method improvement, and curing regime refinement—fibers can be distributed in an orderly manner along load-bearing directions, 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.

I. Mold Design Optimization: Guiding Directional 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 and distribute fibers along the tangent direction of the curved surface. The flow guide groove spacing of Qinglong's double-curved molds is ≤200mm, ensuring uniform fiber distribution. Built-in guiding components: A detachable guiding mesh is installed inside the mold to control fiber movement trajectories and prevent fiber agglomeration at curved surface corners. Qinglong's guiding mesh has an aperture of 5-8mm without affecting UHPC compactness. Mold material selection: Polyurethane soft molds or GRP molds are used, offering good flexibility and sealing performance to fit double-curved shapes. Qinglong's double-curved molds have a surface smoothness of ≤0.1mm/m, reducing fiber flow resistance.

II. 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 assist dispersion and prevent fiber agglomeration. Qinglong controls the aspect ratio of stainless steel fibers at 80-100 to enhance the reinforcement 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, then cementitious materials and water are added. Qinglong's mixing process achieves a fiber dispersion uniformity of 98%. Mix performance control: The UHPC mix spread is adjusted to 750-800mm to ensure moderate flowability, allowing fibers to flow with the mix while preventing fiber settlement. Qinglong's mix passes fluidity tests with a 100% pass rate.

III. Grouting Method Improvement: Controlling Fiber Orientation Direction

High-pressure grouting process: 0.2-0.3MPa high-pressure grouting is applied with simultaneous multi-point injection from the bottom or sides of the mold, controlling the grouting speed (1-2L/min) so that fibers align orderly along the grouting direction. Qinglong's high-pressure grouting achieves a fiber orientation rate of ≥85% along load-bearing directions. Vibration-assisted forming: High-frequency vibration (200-300Hz) is combined with the grouting process to eliminate air bubbles and promote directional fiber distribution. Vibration time is controlled at 30-60 seconds to prevent excessive vibration from causing fiber disorder. 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 area. The Guangxi New Media Center double-curved UHPC panel project achieved uniform fiber distribution through segmented grouting.

IV. Curing Regime Refinement: Safeguarding the Fiber Reinforcement Effect

Steam curing optimization: A four-stage steam curing process of "pre-curing – temperature rise – constant temperature – cooling" is adopted, with a constant temperature of 50-60°C held for 12-16 hours to promote UHPC strength development and ensure tight bonding between fibers and the matrix. Qinglong's steam curing enables UHPC to reach 80% of its design strength at 7 days. Subsequent 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%.

V. Qinglong's Optimization Results and Project Verification

Performance improvement data: After fiber orientation optimization, double-curved UHPC shapes achieve a flexural strength ≥35MPa and a crack resistance strength ≥5MPa, an increase of over 30% compared to non-optimized products; impact resistance ≥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), after fiber orientation optimization, have shown no cracking or deformation over years of use; the double-curved GRC/UHPC panels of Hainan Poly Peninsula No. 1, after fiber orientation optimization, achieved a wind load resistance of 0.9kN/㎡, far exceeding design standards. Technical innovation: Qinglong holds 3 patents related to fiber distribution in double-curved UHPC and participated in drafting the fiber distribution standard of the "General Technical Conditions for Ultra-High Performance Concrete (UHPC) Non-Load-Bearing Components".

Fiber orientation optimization for double-curved UHPC shapes must run through the entire process of design, production, and curing. Qinglong Group, with its precise process control and advanced technical means, achieves orderly fiber distribution and strength improvement. Selecting a manufacturer with fiber orientation optimization capability is the core guarantee of quality stability for double-curved UHPC shape projects.