In this study, an expansive ultra-high performance concrete (UHPC) was prepared by combining use of lightweight aggregate (LWA) and CaO-expansive agent (EA) for concrete-filled steel tube applications. The coupled effects of LWA and EA on the volume stability, mechanical properties and microstructure of UHPC were systematically evaluated. The expansive stress of the outer wall of UHPC-filled steel tube was also determined. The test results showed that the EA and LWA could be effectively combined to produce a high expansive UHPC, and the internal curing effect of LWA mitigated the self-desiccation and promoted the hydration of EA, refining the pore structure of matrix. As a result, the expansive UHPC exhibited high levels of expansion and high mechanical properties. A maximum circumferential expansion of 308 μϵ and triaxial compressive stress of 3.65 MPa at 24 h could be obtained, which compacted the core UHPC and improved the interfacial bond between the steel tube and the UHPC.

在这项研究中，通过结合使用轻骨料（LWA）和CaO膨胀剂（EA）来制备膨胀超高性能混凝土（UHPC），用于钢管混凝土。系统评价了LWA和EA对UHPC的体积稳定性，力学性能和微观结构的耦合作用。还确定了UHPC填充钢管外壁的膨胀应力。试验结果表明，EA和LWA可以有效地结合形成高膨胀的UHPC，LWA的内部固化作用减轻了自干性并促进了EA的水合作用，改善了基质的孔结构。结果，膨胀的UHPC表现出高水平的膨胀和高机械性能。最大圆周膨胀为308μl，三轴压缩应力为3。