What Are the Raw Materials of UHPC? A Comprehensive Analysis of the Components of Ultra-High Performance Concrete

Ultra-high performance concrete (UHPC) is a cutting-edge building material whose exceptional performance is rooted in precisely proportioned raw materials. Compared with ordinary concrete, UHPC has a more complex raw material system with stricter requirements. Understanding the composition of UHPC raw materials is the foundation for understanding its exceptional performance and a key aspect of quality control. With 28 years of material R&D experience, Qinglong Group provides an in-depth analysis of the UHPC raw material system to offer customers professional insights.

Cementitious material is the core binder of UHPC, typically using high-strength Portland cement with a grade of no less than 52.5. Compared with ordinary concrete, UHPC uses a higher amount of cement but reduces porosity through optimized particle gradation. Through long-term practice, Qinglong Group has found that low-heat cement is better suited for large-scale UHPC component production, effectively reducing microcracks caused by thermal stress. It is worth noting that GRC materials typically use a sulphoaluminate cement system, while UHPC favors an optimized Portland cement system—a significant difference between the two in terms of raw materials.

Active mineral admixtures are key components for enhancing UHPC performance. Silica fume is the most critical among them, with a particle size only 1/100 that of cement particles, effectively filling microscopic pores. Industrial by-products such as ground slag powder and fly ash are also commonly used to optimize particle gradation and reduce hydration heat. According to Qinglong Group's experimental data, high-quality silica fume should have a silica content exceeding 90% and a specific surface area of 15-30m²/g, which is the fundamental guarantee for achieving UHPC's ultra-high strength. The application principles of these admixtures share similarities with GRC materials, but the specific requirements are more stringent.

Optimization of the aggregate system guarantees UHPC's high density. Traditional concrete uses continuously graded aggregates, while UHPC uses refined quartz sand with a maximum particle size of no more than 0.6mm, ensuring tight packing between particles. Through years of R&D, Qinglong Group has found that controlling the aggregate particle size within the 0.15-0.6mm range and adopting a three-level gradation achieves the densest packing state, enabling compressive strength to exceed 150MPa. This fine-grained requirement for aggregate size is similar in concept to the use of aggregates in GRC products but more stringent.

Fiber reinforcement is the source of UHPC's high toughness. Copper-plated micro steel fibers are the most commonly used reinforcement fibers, generally 6-20mm in length and 0.15-0.25mm in diameter. Unlike the glass fibers used in GRC, steel fibers provide stronger bridging action, significantly improving the material's toughness and impact resistance. Qinglong Group's research shows that with a fiber volume fraction of 2-3%, UHPC's flexural toughness can be increased by 30-50 times—something ordinary concrete cannot achieve.

Chemical admixtures are key to adjusting UHPC's workability. Polycarboxylate superplasticizers are the preferred choice, with a water reduction rate of up to 30-40%, ensuring the water-binder ratio drops below 0.2. Meanwhile, auxiliary admixtures such as retarders and thickeners are also proportioned according to construction conditions. The specialized admixture system developed by Qinglong Group keeps UHPC free from segregation and bleeding while maintaining high fluidity—a technology that leads the industry. It is worth noting that some admixture principles used in GRC production are similar to those of UHPC, but the specific formulations differ greatly.

Raw material quality control is the prerequisite for ensuring stable UHPC performance. Qinglong Group has established a strict supplier audit system and incoming inspection procedures, with every batch of raw materials undergoing chemical composition analysis and physical performance testing. In particular, the anti-rust treatment of steel fibers and the moisture content control of silica fume are key aspects of quality management. This comprehensive quality control system ensures that the UHPC products we produce deliver consistent and reliable performance.