Why Aggregates Larger Than 5mm Are Not Recommended for UHPC: An Analysis from Material Properties and Performance Impact Perspectives

In the world of Ultra-High Performance Concrete (UHPC), a difference of mere millimeters in aggregate size determines a world of difference in material performance. As an industry leader with 28 years of deep expertise in UHPC/GRC/GRG/GRP materials, Qinglong Group will start from the underlying logic of materials science to reveal why 5mm is the golden point for UHPC aggregate selection.

As a revolutionary breakthrough in new architectural decoration materials, UHPC's core secret of "ultra-high performance" lies hidden in its microstructure. Unlike ordinary concrete, UHPC achieves ultra-high matrix density through optimized particle gradation, and as the skeletal material, the choice of aggregate size directly affects the material's mechanical properties and constructability. During its participation in developing the industry standard "General Technical Conditions for Non-Load-Bearing Components of Ultra-High Performance Concrete (UHPC)", Qinglong Group verified through hundreds of comparative experiments: when aggregate size exceeds 5mm, defects in the internal interfacial transition zone increase significantly, becoming a key cause of performance shortcomings.

I. 5mm Particle Size: The Mechanical Boundary of UHPC Density

UHPC's exceptional performance stems from its unique "close packing" principle. Through electron microscope scanning, Qinglong's technical team found that when continuous-graded aggregates below 5mm are used, the voids between particles can be fully filled by ultra-fine powders, forming a dense structure at a "molecular level". This structure allows UHPC to easily exceed 150MPa in compressive strength and surpass 30MPa in flexural strength. However, when aggregate size increases to 6mm, the interfacial transition zone thickness grows from 20μm to 45μm, directly causing a 30% drop in impermeability—which for UHPC products exposed to natural environments, such as curtain wall panels and landscape components, means a fatal weakening of durability.

II. Constructability: The Process Advantages of 5mm Aggregate

In detailed design and production manufacturing, aggregate size directly affects UHPC's rheological properties. Practical data from Qinglong Group's Nanning production base shows: with 5mm aggregate, the slump flow of the UHPC mixture can reach over 750mm, meeting the casting requirements of complex-shaped components, and is especially suitable for the precision machining common in GRG products, such as double-curved surfaces and openwork reliefs. In a landmark project, UHPC sunshades using 3-5mm aggregate achieved dimensional precision at the 0.1mm level, while the control group using 8mm aggregate saw mold filling rate drop by 15% and surface bubble defects increase twofold.

III. Full-Chain Perspective: Qinglong's 5mm Aggregate Application Philosophy

As a national high-tech enterprise integrating full-chain services of detailed design, manufacturing, construction and installation, and after-sales maintenance, Qinglong Group incorporates the 5mm aggregate standard into full product lifecycle management. In the Century Plaza renovation project on Nanjing East Road, light-transmitting UHPC components used 4.5mm special aggregates, ensuring both light transmittance and structural safety. The project won the Silver Award of the First UHPC Construction Engineering Innovation Award (AALBORG WHITE Cup). This confirms the key value of scientific material selection in fulfilling the mission of "creating beautiful architecture".

From material properties to engineering practice, choosing a 5mm aggregate size is the optimal balance point between UHPC performance and workmanship. With 28 years of industry experience and 58 patented technologies, Qinglong Group has always made scientific material selection the cornerstone of product innovation. Whether for real estate curtain walls, municipal landscapes, or overseas projects, we maintain millimeter-level precision control, providing designers and owners with UHPC/GRC/GRG/GRP solutions that combine aesthetic expressiveness with structural reliability, fulfilling our vision commitment to "become an outstanding manufacturing-leading enterprise in the world".