The separation problem between core concrete and steel tube is one of the main bottlenecks restricting the construction of super large-span concrete-filled steel tubular arch bridges. One of the main measures to solve this problem is to prepare micro expansive core concrete by using the shrinkage compensation property of expansive agent. This study investigated the deformation and mechanical properties of core concrete containing CaO-based and MgO-based expansive agent under both the constant temperature and the varying temperature. The results showed that concrete containing CaO-based and MgO-based expansive agents can produce remarkable expansion which increases with the increase of CaO-MgO ratios under the constant temperature of 20 °C, but decreases with the increase of CaO-MgO ratios under the varying temperature. Through the restraint from the steel tube can reduce the expansion value, proper selection of CaO-MgO ratio can still produce enough expansion in core concrete to compensate autogenous and thermal shrinkage, with the concrete still in expansion state when the temperature finally stabilizes. Thus it is beneficial to maintain the integrity between the core concrete and the steel tube. The results obtained will provide guidance for the application of this kind of expansive agent in concrete-filled steel tube structure.

核心混凝土与钢管之间的分离问题是制约超大跨度钢管混凝土拱桥施工的主要瓶颈之一。解决该问题的主要措施之一是利用膨胀剂的收缩补偿性能来制备微膨胀性芯混凝土。本文研究了在恒定温度和变化温度下，含CaO基和MgO基膨胀剂的核心混凝土的变形和力学性能。结果表明，含有CaO基和MgO基膨胀剂的混凝土在20°C恒温下可产生显着的膨胀，随CaO-MgO比的增加而增加，而随CaO-MgO比的增加而降低。温度变化。通过从钢管上的约束可以减少膨胀值，的氧化钙 - 氧化镁比率适当选择仍然可以产生在芯混凝土足够的扩展在扩展状态仍然补偿自生和热收缩，与混凝土当温度最后稳定。因此，保持芯混凝土与钢管之间的完整性是有利的。获得的结果将为这种膨胀剂在钢管混凝土结构中的应用提供指导。因此，保持芯混凝土与钢管之间的完整性是有利的。获得的结果将为这种膨胀剂在钢管混凝土结构中的应用提供指导。因此，保持芯混凝土与钢管之间的完整性是有利的。获得的结果将为这种膨胀剂在钢管混凝土结构中的应用提供指导。