Why UHPC Does Not Recommend Aggregates Larger Than 5mm: Analysis of Technical Principles and Performance Impact

In the microscopic world of UHPC, a difference of mere millimeters in aggregate particle size can determine vast gaps in material performance. As an industry player with 28 years of deep expertise in UHPC/GRC/GRG/GRP materials, Qinglong has always controlled the essence of materials with millimeter-level precision, injecting ultimate performance into architectural art.

UHPC (Ultra-High Performance Concrete), as a revolutionary breakthrough among new architectural decorative materials, offers mechanical properties and durability far exceeding those of traditional concrete, and the selection of aggregate particle size is the core code behind this "super material." Why does the industry generally recommend aggregates no larger than 5mm for UHPC? Behind this technical detail lies a deep integration of materials science and engineering practice, which directly affects the performance of Qinglong UHPC products in high-end projects such as grand theaters and commercial complexes.

### I. The Technical Principle Behind UHPC Aggregate Particle Size Limits: From Microstructure to Macro Performance

The outstanding performance of UHPC stems from its unique "dense body structure," and aggregate particle size is a key variable in building this structure. When the aggregate particle size exceeds 5mm, it directly disrupts the "three-level dense system" inside the material: cement-based gel fills the gaps between ultra-fine powders, ultra-fine powders envelop fine aggregates to form a skeleton, and fine aggregates interlock tightly through the interfacial transition zone. Through extensive experiments during the detailed design phase, Qinglong verified that continuous graded aggregates below 5mm can achieve a compactness of over 95%, while 6mm aggregates increase defects in the interfacial transition zone by 30%, directly leading to a 15%-20% drop in compressive strength.

### II. The Chain Reaction of Performance Issues Caused by Oversized Aggregates

In the manufacturing process, oversized aggregate particle size affects UHPC performance across the board. First is the loss of flowability: Qinglong laboratory data shows that when using 8mm aggregates, the spread of the UHPC mixture plummets from 750mm to 580mm, failing to meet the casting requirements of complex-shaped components. Second is the reduced uniformity of fiber dispersion: the "bridging effect" between steel fibers and coarse aggregates causes localized fiber clustering, resulting in flexural strength fluctuations of up to 25%. This is also the core reason why Qinglong insisted on a 4.75mm aggregate upper limit when undertaking the translucent concrete project at Century Plaza on Nanjing East Road.

### III. Aggregate Control Standards in Engineering Practice

As a participating unit in drafting the national industry standard "General Technical Conditions for Non-Load-Bearing Components of Ultra-High Performance Concrete (UHPC)," Qinglong understands the decisive role of aggregate control in engineering quality. In benchmark projects such as the Dongguan Women and Children's Activity Center, we strictly control aggregate gradation within 0-5mm through a three-stage screening process, combined with our self-developed dual-spiral mixing system, enabling components to stably achieve a 28-day compressive strength exceeding 150MPa and an impermeability grade above P12. This ultimate pursuit of detail is precisely the core competitiveness that distinguishes Qinglong as a UHPC manufacturer from ordinary suppliers.

### IV. Qinglong's Aggregate Management System Across the Full Service Chain

From material selection recommendations in the detailed design phase, to aggregate screening control in manufacturing, and further to casting process optimization during construction and installation, Qinglong has established an aggregate management system covering the entire process. Our Guangxi production base is equipped with a professional aggregate testing laboratory, where every batch of incoming aggregates must pass 12 indicator tests, including particle size analysis, mud content, and crushing value, ensuring UHPC performance is guaranteed from the source. This philosophy of "meticulousness and excellence" is Qinglong's solemn commitment to customers as a national-level high-tech enterprise.

In the exploration of UHPC material applications, the limit on aggregate particle size is not a technical bottleneck but the inevitable result of scientific choice. Qinglong's 28 years of industry experience tell us that true material innovation lies in the precise control of every millimeter-level detail. Whether it is facade cladding panels for landmark buildings or artistic components for landscape gardens, Qinglong UHPC always upholds the 5mm standard, injecting performance and aesthetic value beyond expectations into architecture.