海水拌和对纤维增强超高性能混凝土中钢纤维的影响

Effect of seawater mixing on steel fibers in ultra-high performance fiber reinforced concrete

通过采用不同水泥含量制备海水拌和纤维增强超高性能混凝土(UHPFRC),研究了海水拌和对UHPFRC中钢纤维的影响机理及其对宏观性能的作用机制。参照相关测试标准对其工作性能与力学性能进行了测试,同时设计单丝拉拔测试和水泥含量等效电路试验。通过场发射扫描电子显微镜和X射线能谱仪对钢纤维表面的元素分布进行了面扫描,进而形貌分析及锈蚀情况分析。首先,海水拌和会引起UHPFRC中钢纤维轻微锈蚀,导致钢纤维与基体之间脱黏拉应力增大,会略有降低钢纤维拉拔过程中的最大拉应力、平均黏结强度和等效黏结强度;其次,海水拌和UHPFRC后期抗压强度可以达到基准组的90%以上,可以满足它的力学性能使用要求;最后,海水拌和会引起UHPFRC体积电阻的增大,而水泥含量的增加会降低它的体积电阻,使钢纤维锈蚀程度减少。

The effect and mechanism of seawater mixing on steel fiber in ultra-high performance fiber reinforced concrete(UHPFRC)and the driving mechanism on macro properties were studied by preparing seawater mixing UHPFRC with different cement content.According to the relevant test standards,the working performance and mechanical properties were tested.The concrete pull-out test and the cement content equivalent circuit experiment were designed.At the same time,the element distribution of the steel fiber surface was scanned by the field emission scanning electron microscope and the X-ray energy spectrometer and then the study analyzed the morphology and rust situation.Firstly,the seawater mixing will cause slight corrosion of steel fiber in UHPFRC,resulting in the increase of debonding tensile stress between steel fiber and matrix,which slightly reduce the maximum tensile stress,average bonding strength and equivalent bonding strength during steel fiber pulling.Secondly,the late compressive strength of seawater mixing UHPFRC can reach more than 90%of the reference group,which can meet its mechanical properties.Finally,seawater mixing can increase the volume resistance of UHPFRC,while the increase of cement content can reduce the volume resistance,which would also lead to the reduction of steel fiber corrosion degree.