考虑钢筋锈蚀的纳米SiO2强化再生骨料混凝土梁受力性能研究

采用纳米强化再生骨料表面的措施来改善再生骨料性能,分别考虑强化液中纳米SiO₂掺量、再生粗骨料取代率的影响,设计制作了1根普通混凝土基准梁和8根再生骨料混凝土矩形截面梁,采用内置近距离小阴极的方法对梁内受力钢筋进行通电非均匀加速锈蚀,待受拉主筋锈蚀到一定程度后进行四点受弯加载,对加载过程中的裂缝开展情况、荷载-挠度曲线以及极限承载力进行了记录及分析。考虑钢筋锈蚀率及再生骨料取代率等因素的影响,对锈胀开裂之后的再生骨料混凝土梁的承载力计算公式进行了修正,得出了可用于设计的受弯承载力计算公式。结果表明:相同锈蚀程度下,强化再生骨料混凝土梁的抗弯承载力比天然骨料混凝土有所降低,其中25%再生骨料取代率时承载性能退化较多,抗弯承载力下降19.3%; 混凝土裂缝开展趋势较为一致,最大裂缝宽度随钢筋锈蚀程度增加而增大,随纳米SiO₂掺量增加先减小后增大; 近距离小阴极通电可实现混凝土内钢筋的加速非均匀锈蚀; 所提出的方法及获得的结论有助于推动再生骨料混凝土在沿海等不利环境中的应用。

Research on Mechanical Properties of Nano-SiO2 Strengthened Recycled Aggregate Concrete Beam with Corroded Reinforcements

Measurement of nano-reinforced recycled aggregate surface was adopted to improve the performance of recycled aggregate. Considering the influences of nano-SiO₂ content and replacement ratio of recycled aggregate, 1 ordinary performance concrete(OPC)beam and 8 recycled aggregate concrete(RAC)beams were designed and made. Non-uniform corrosion of steel was accelerated with electrification between the steel bar and a nearby fine stainless-steel wire embedded in concrete beams. The crack development, load-deflection curve and ultimate bearing capacity were recorded and analyzed during four-point bend loading process after the reinforcement achieved a desired corrosion condition. The calculation formula of bearing capacity of RAC beams after corrosion-induced cracking was revised by considering the effects of steel corrosion ratio and replacement ratio of recycled aggregate. The results show that the flexure capacity of RAC beam is lower than that of natural aggregate concrete beam with the same corrosion ratio. The bearing capacity of RAC beam with 25% replacement of recycled aggregate decreases 19.3%, which is larger than other RAC beams. The development of concrete crack is basically same for all beams. The maximum crack width increases with the increase of corrosion ratio of reinforcement and decreases firstly and then increases with the increase of nano-SiO₂ content. Non-uniform corrosion of steel in concrete can be accelerated with electrification between the steel bar and a nearby fine stainless-steel wire embedded in concrete beams. The proposed method and results are helpful to promote the application of RAC in coastal environment.