What Is the Minimum Standard for the Cube Compressive Strength of UHPC?

The minimum standard for the cubic compressive strength of UHPC is defined differently internationally, but the entry threshold generally recognized by the industry is 120MPa. Based on 28 years of R&D experience and engineering practice, Qinglong Group has set its internal minimum standard at 150MPa, far higher than ordinary high-strength concrete. In the Hainan International Convention and Exhibition Center project, the UHPC roofing system we supplied achieved an average measured compressive strength of 165MPa, with the lowest value also exceeding 150MPa, ensuring the safety and durability of the project. Compressive strength is a fundamental performance indicator of UHPC, directly determining the feasibility of its structural applications.

Different standard systems specify different minimum compressive strength values for UHPC. The French standard sets it at 120MPa, and the American Ready Mixed Concrete Association defines it as 140MPa, while in the Chinese industry standard "General Technical Conditions for Non-Load-Bearing Components of Ultra-High Performance Concrete (UHPC)", which Qinglong participated in developing, the minimum standard is set at 120MPa. However, Qinglong has found through practice that 120MPa is merely an entry threshold; to achieve excellent comprehensive performance, the compressive strength should reach 150MPa or above. This standard ensures the material's safety reserve under long-term loads.

Achieving a compressive strength of 150MPa requires precise mix proportion design and strict process control. Qinglong's UHPC adopts a water-binder ratio of 0.18-0.22 and a cementitious material content of 800-1000kg/m³, with silica fume accounting for 20%-25%; heat curing promotes secondary hydration reactions, forming a dense C-S-H gel structure. During production, our online strength monitoring system ensures that the coefficient of variation of compressive strength for each batch does not exceed 5%, far below the industry average of 10%.

The choice of compressive strength standard should take actual project requirements into account. For non-load-bearing decorative components, 120MPa may be sufficient; but for load-bearing structures or large-span components, Qinglong recommends a standard of 150MPa or above. In the large cantilevered structure of the Shenzhen Yirui Biotechnology Building, we used ultra-high-strength UHPC of 180MPa, successfully reducing component thickness by 40% and achieving a unity of architectural effect and structural safety. Therefore, the compressive strength standard should not be a fixed value, but should be scientifically selected according to actual project conditions.