开裂后延性材料与钢纤维混凝土抗氯离子侵蚀对比

通过施加弯曲荷载预先在混凝土梁中产生宽度不等的裂缝或不同的拉应变损伤,然后以3%(质量分数)NaCl溶液连续浸泡或干湿循环方法对混凝土梁进行氯离子侵蚀.测定混凝土裂缝处氯离子含量,研究比较钢纤维混凝土和高延性低收缩材料(LSECC)中裂缝对氯离子侵蚀性能的影响.结果表明:混凝土中裂缝对氯离子渗透影响显著,裂缝大大加快了氯离子的侵蚀.钢纤维混凝土裂缝处氯离子含量(质量分数)最高可达相同浸泡龄期无裂缝处的3～4倍.连续浸泡30d时,钢纤维混凝土裂缝处氯离子含量随裂缝宽度的增大而增加,连续浸泡60d时氯离子含量基本达到饱和.干湿循环条件下,钢纤维混凝土所受的氯离子侵蚀更为严重,经10次干湿循环后其裂缝处氯离子含量可达连续浸泡后的3倍左右.在连续浸泡和干湿循环环境中,LSECC抗氯离子侵蚀性能均优于钢纤维混凝土,尤其在干湿循环环境中,LSECC抗氯离子侵蚀能力更为突出.

Comparative Study on Cl- Penetration in Cracked High Ductility and Low Shrinkage Material and Steel Fiber Concrete

The effect of cracks in steel fiber concrete(SFRC) and high ductility and low shrinkage material(LSECC) on Cl- penetration was investigated by pre induced flexural cracks in concrete beams. The cracked beams with different crack width or tensile strains were then continuously soaked with 3%(by mass) NaCl solution or undergone drying and wetting cycles. The content(by mass) of Cl- in concrete at the locations of cracks was determined by drilling powder sample with electric hammer. The experimental results show that the influence of cracks on the Cl- penetration is very significant. The content of Cl- at the location of cracks in SFRC is 34 times compared to the place without cracks. The Cl- content in SFRC is increased with increase of the crack width for the specimens soaked for 30 d. At 60 d after soaked, the content of Cl- becomes almost constant irrespective of the penetration depth. Under drying and wetting conditions, the content of Cl- in SFRC greatly increases compared to those of continuously soaked. By contrast, LSECC can apparently reduce the content of Cl-, especially under drying and wetting conditions. The resistance to Cl- penetration for LSECC is obviously significant.