动态疲劳荷载下玄武岩纤维混凝土抗渗性衰减及机理研究

Impermeability Attenuation and Mechanism of Basalt Fiber Reinforced Concrete under Dynamic Fatigue Load

为了探究动态疲劳荷载作用下玄武岩纤维混凝土抗渗性衰减规律及机理,基于抗渗性优选了玄武岩纤维最佳参数;利用自主研发的加载装置设计了疲劳试验,分析疲劳荷载下电通量的变化规律;研究了荷载作用下微观结构的演化以揭示玄武岩纤维混凝土抗渗性衰减机理。结果表明:混凝土抗渗性随玄武岩纤维长度和掺量增加呈现先增强后减弱的变化规律,基于抗渗性推荐玄武岩纤维的最佳长度为12 mm,掺量为0.08%(质量分数);随疲劳作用次数和应力比增加,玄武岩纤维混凝土电通量增加幅度低于基准混凝土,其更适合在重载、重交通地区应用;玄武岩纤维细化了混凝土孔结构,无害孔比例增加18.51%,疲劳荷载下混凝土孔径呈扩张趋势,孔分布呈粗化状态;疲劳加载前期混凝土微裂缝主要沿长度方向延伸,而加载后期以宽度扩展为主;玄武岩纤维延缓了混凝土孔结构劣化和微裂缝扩展,从而降低了抗渗性衰减幅度。

To explore the attenuation rules and mechanism of impermeability of basalt fiber reinforced concrete under dynamic fatigue load,the best parameters of basalt fiber were optimized based on impermeability.The fatigue tests were designed with the self-developed loading device,and the variation rules of electric flux under fatigue load were analyzed.The evolution of microstructure was studied to reveal the attenuation mechanism of impermeability.The results show that the impermeability of concrete increases first and then decreases with the rise of basalt fiber length and content.Based on impermeability,the optimal length and content of basalt fiber are 12 mm and 0.08%(mass fraction).With the rise of fatigue times and stress ratio,the increase of electric flux of basalt fiber reinforced concrete is lower than that of reference concrete,which is more suitable for heavy load and heavy traffic areas.Basalt fiber refines the pore structure of concrete,and the proportion of harmless pore increases by 18.51%.The pore size of concrete shows an expansion trend and the pore distribution is coarser under fatigue load.The microcracks mainly extend in the length direction at the early stage of fatigue loading,while the microcracks mainly extend in the width direction at the later stage.Basalt fiber delays the deterioration of pore structure and the propagation of microcracks,so as to reduce the attenuation range of impermeability.