摘要
通过将再生微粉以10%、20%、30%的取代率替代水泥后制备再生微粉混凝土试块,将其底面以上1 cm的部分浸泡于3%的MgSO_(4)溶液中,进行单边冻融循环实验,研究MgSO_(4)溶液与冻融循环的耦合作用对再生微粉混凝土性能的影响。结果表明:当再生微粉取代率为10%时,再生微粉混凝土表现出较好的抗盐侵蚀和抗冻性能,试块的最大冻融循环次数可达60次,优于基准混凝土。取代率为20%及30%的混凝土则表现出较为严重的物理剥蚀和化学膨胀破坏,其抗冻能力显著下降。通过SEM(扫描电子显微镜)、XRD(X射线衍射)和NMR(核磁共振)等手段分析混凝土内部的微观结构变化规律,发现MgSO_(4)溶液盐侵蚀与冻融循环共同作用下,再生微粉混凝土内部结构遭到破坏,有石膏、钙矾石、碳酸钙等膨胀性物质生成,混凝土内部有害孔及多害孔的数量增加,从而导致再生微粉混凝土发生破坏。
The recycled fine powder was taken as cementitious material to prepare concrete specimens with 10%,20%and 30%replacement rates.The lower 1 cm of each specimen was immersed in a 3%MgSO_(4) solu⁃tion,then the freeze-thaw cycle experiment was carried out to investigate the coupling effect of MgSO_(4) solution and freeze-thaw cycles on the properties of recycled micro-powder concrete.The findings revealed that concrete with a 10%replacement rate exhibited superior resistance to these environmental stresses,enduring up to 60 cy⁃cles—significantly outperforming the reference concrete.In contrast,specimens with 20%and 30%replacement rates exhibited relatively severe physical erosion and chemical expansion damage,resulting in a marked decline in frost resistance.Microstructural analyses using Scanning Electron Microscopy(SEM),X-ray Diffraction(XRD),and Nuclear Magnetic Resonance(NMR)techniques indicated that the combined effects of MgSO_(4) ero⁃sion and freeze-thaw cycles led to the internal structure of recycled micro-powder concrete was damaged.The formation of swelling compounds such as gypsum,ettringite,and calcium carbonate contributed to an increase in harmful pore structures,ultimately compromising the integrity of recycled fine powder concrete.
作者
华永田
李滢
HUA Yongtian;LI Ying(School of Civil and Water Resources,Qinghai University,Xining 810016,China;Key Laboratory of Material and Engineering Safety for Building Energy Conservation in Qinghai Province,Xining 810016,China)
出处
《青海交通科技》
2024年第6期149-156,共8页
Qinghai Transportation Science and Technology
基金
国家自然科学基金项目(51668052)
青海省科技厅基础研究计划项目(2023-ZJ-725)资助。
关键词
盐侵蚀
冻融循环
再生微粉
耦合作用
salt attack
freeze-thaw cycle
recycled fine powder
coupling effect
