钢纤维增韧自密实微膨胀钢管混凝土

Investigation on toughness of steel fibre reinforced self-compacting micro-expansion concrete-filled steel tube

钢管混凝土（CFST）桁架连续梁桥因跨度大（大于50m）、同时承受纵向压应力和横向拉应力双重作用导致核心混凝土韧性不足.对此开展了钢纤维自密实微膨胀钢管混凝土的增韧、及工作性、力学性能等研究.通过微膨胀剂的合理掺入和系列配合比优化设计,成功试配了钢纤维增韧自密实微膨胀钢管混凝土.结果显示,所得自密实微膨胀钢管混凝土坍落度在220mm以上,扩展度在550mm以上,自密实性良好.波纹状钢纤维对改善混凝土抗压性能有明显作用,抗压强度提高了25%~35%,而多锚点状钢纤维对改善混凝土抗弯性能有明显作用,韧性提高约2~3倍,混凝土破坏呈现延性破坏而不是常见的脆性破坏.钢纤维最优体积掺量为0.75%.

Due to the long-span（over 50 m） and the dual role of the longitudinal and the horizontal tensile stress,the core concrete of the concrete-filled steel tube（CFST） truss beam bridge is lack of toughness.Investigations on toughness,workability,and mechanical properties of the steel fibre reinforced self-compacting micro-expansion CFST are carried out.By optimizations of micro-expansive agent and mix designs,series of the self-compacting micro-expansion CFST are successfully prepared.Experimental results show that the slump and expansion of the self-compacting micro-expansion CFST are above 220 and 550 mm,respectively.Compressive strength of the CFST increases by 25% to 35% when adding corrugated steel fibre and its bengding toughness index increases by 2 to 3 times by using multi-anchor steel fibre.The optimal dosage of steel fibre is 0.75% volume fraction.This concrete failure characterizes by obvious ductile fracture instead of brittle fracture as usual.