基于钢-混凝土组合结构轻量化的粗骨料超高性能混凝土研究进展与应用

粗骨料超高性能混凝土(ultra high performance concrete, UHPC)是实现钢-混凝土组合结构轻量化的重要载体，分析了粗骨料UHPC的性能优势和技术瓶颈，综述了粗骨料UHPC力学性能、体积稳定性、韧性和施工性能的提升原理、技术措施和作用效果，得到诱导、加速胶凝材料水化调控水化产物和微结构，可发挥粗骨料刚性骨架作用，提升常温下力学性能，使其弹性模量可达近60GPa，徐变系数低于0.4；掺加内养护剂、功能性聚合物抑制内部相对湿度下降，采用膨胀剂补偿收缩变形，可降低自收缩超过60%，提高抗裂能力；基于聚合物基体增韧和骨料-纤维协同增韧，提升拉伸韧性，可使粗骨料UHPC拉伸强度达10MPa；采用微纳米材料和选择性吸附聚合物，调控流变性能，可实现施工的高流动与物相均匀分布的统一。介绍了粗骨料UHPC典型应用工程，通过提高钢-混凝土组合结构的刚度、抗裂性能和抗疲劳性能，大幅降低结构自重，有效提升了桥梁的跨越能力。

Research progress and application of coarse aggregate ultra high performance concrete used for lightweight steel-concrete composite structure

Coarse aggregate ultra high performance concrete (UHPC) is an important carrier for achieving lightweight of steel-concrete composite structures. The performance advantages and technical bottlenecks of coarse aggregate UHPC are analyzed, and the performance improvement principles, technical methods and effects are reviewed from four aspects, namely mechanical properties, volume stability, toughness and workability. It’s shown that inducing and accelerating the hydration of cementitious materials could regulate hydration products and microstructure, and the role of rigid skeleton induced by coarse aggregate is played to enhance the mechanical properties at room temperature, among which the elasticity modulus can reach nearly 60GPa and the creep coefficient is less than 0.4. The internal curing agent and functional polymer are added to inhibit the decrease of internal relative humidity, and the expansion agent is adopted to compensate the shrinkage deformation, which can reduce the autogenous shrinkage by more than 60% and improve the crack resistance. Based on the principles of polymer matrix toughening and aggregate-fiber synergistic toughening, the tensile toughness is enhanced, which can make the tensile strength of coarse aggregate UHPC break through 10 MPa. Bination of micro and Nano materials and selective adsorption polymers are used to regulate the rheological performance, which can realize the unification of high flowability and uniform distribution of material phases. Finally, typical application projects of coarse aggregate UHPC are introduced, which can significantly reduce the self-weight of the structure and effectively improve the span capacity of the bridge by improving the stiffness, crack resistance and fatigue resistance of the steel-concrete composite structure.