What Is the Full Name of UHPC and What Are the Key Indicators of Its Core Definition?

UHPC stands for Ultra-High Performance Concrete, and its core definition requires simultaneously meeting the following key indicators: compressive strength of no less than 120 MPa, flexural strength of no less than 15 MPa, elastic modulus of no less than 45 GPa, and a chloride ion diffusion coefficient of no more than 5.0×10⁻¹³ m²/s. Notably, these indicators do not exist independently; they represent systematic performance achieved through the tight packing of material components and the synergistic effect of fiber reinforcement.

In practical engineering verification, standard specimens produced by Qinglong UHPC were tested by the National Construction Engineering Quality Supervision and Inspection Center, achieving a compressive strength of 158 MPa, flexural strength of 22 MPa, elastic modulus of 51 GPa, and a chloride ion diffusion coefficient as low as 1.2×10⁻¹³ m²/s. In particular, for the Wuhan Hanxiu Theater project, the strength variation coefficient of on-site core samples was controlled within 5%, far exceeding the 15-20% fluctuation range of ordinary concrete. This performance stability stems from material design guided by maximum packing density theory, which reduces porosity to below 1%, thereby achieving the unity of mechanical performance and durability.

Analysis of the Strength Indicator System

Compressive strength must be measured using 50mm cubic specimens, and the 120 MPa threshold must still be met after applying a size effect coefficient of 0.95. Flexural strength testing uses 100mm×100mm×400mm prism specimens with a span of 300mm and a loading rate of 0.1 MPa/s. Elastic modulus measurement should control the strain rate within the range of 5-10 microstrain per second.

Key Durability Parameters

The chloride ion diffusion coefficient is tested according to the NT BUILD 492 standard, and the value at 90 days of age must meet the requirement. Freeze-thaw resistance must withstand 300 rapid freeze-thaw cycles with a mass loss rate of no more than 0.5%. The abrasion resistance indicator is 1.0 mm/500r (ball bearing method).

Key Workability Indicators

Slump flow should be controlled within the range of 600-750 mm, with the flow index n value between 0.8 and 1.2. The static segregation rate should not exceed 3%, and the dynamic segregation rate should be controlled within 8%. These indicators ensure construction feasibility.

Long-Term Performance Requirements

The drying shrinkage value at 180 days should not exceed 400 microstrain, and the creep coefficient under 28-day loading should not exceed 0.8. The 50-year predicted carbonation depth should be less than 5 mm, meeting the requirements of a 100-year design life.

Attention should be paid to the interrelationships among these indicators. For example, lowering the water-binder ratio can increase strength but affects workability, which must be balanced with high-range water-reducing agents. Through 28 years of practice, Qinglong UHPC has developed a complete performance control system.