玄武岩纤维混凝土孔隙结构及在围压下渗透性能研究

Study on pore structure and permeability of basalt fiber reinforced concrete under confining pressure

基于试验研究不同玄武岩纤维掺量混凝土的孔隙结构、力学性能及在围压作用下的抗渗性能。采用单轴压力机对纤维掺量为0%、0.05%、0.1%、0.2%、0.3%的玄武岩纤维混凝土开展单轴压缩、劈裂试验,利用TAW-2000伺服三轴试验机进行不同围压(4 MPa、5 MPa、6 MPa、7 MPa、8 MPa、9 MPa、10 MPa)作用下三轴压缩渗透试验,并结合全自动快速比表面积及孔隙度分析仪与扫描电子显微镜(SEM)获取试件内部孔隙变化及微观结构,分析玄武岩纤维对混凝土试件强度、韧性、孔隙结构及抗渗性能的影响规律。结果表明:玄武岩纤维的掺入能够极大改善混凝土试件的力学性能及延展性,纤维掺量为0.05%时试件抗压、抗拉强度最大,掺量为0.1%时试件韧性最佳,过量的纤维掺入反而会降低试件抵抗外荷载的能力;纤维的掺入能够减小试件孔隙直径,降低孔隙率,纤维与胶凝材料间形成良好的粘接效果,并在试件内部形成空间网状结构,增强试件整体性,减少裂隙的产生与扩展;不同围压下玄武岩纤维混凝土渗透率能始终小于素混凝土,纤维的掺入使得混凝土材料自身孔隙率降低,提高混凝土材料的抗渗能力,围压的增加使得两种混凝土试件的渗透率均不断降低直至趋于稳定,玄武岩纤维混凝土试件渗透率降幅较为平缓。

The pore structure, mechanical properties and impermeability of concrete with different basalt fiber contents under confining pressure were studied based on experiments. The uniaxial compression and splitting tests of basalt fiber concrete with 0 %, 0.05 %, 0.1 %, 0.2 % and 0.3 % fiber content were carried out by uniaxial compression machine. The triaxial compression and permeability tests under different confining pressures(4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa and 10 MPa) were carried out by TAW-2000 servo triaxial testing machine. Combined with automatic rapid specific surface area and porosity analyzer and scanning electron microscope(SEM), the internal pore changes and micro-structure of the specimens were obtained. The influence of basalt fiber on the strength, toughness, pore structure and impermeability of concrete specimens was analyzed. The results show that the incorporation of basalt fiber can greatly improve the mechanical properties and ductility of concrete specimens, and the compressive and tensile strengths of specimens are the highest at 0.05% of fiber incorporation, and the toughness of specimens is the best at 0.1% of fiber incorporation, but excessive fiber incorporation will reduce the ability of specimens to resist external load. Besides, the incorporation of fiber can reduce the pore diameter and porosity of the specimen, forming a good bonding effect between fiber and concrete material and eventually form a spatial mesh structure inside the specimen to enhance the integrity and reduce the generation and expansion of cracks. Under different confining pressures, the permeability of basalt fiber concrete is always smaller than that of plain concrete, the incorporation of fibers reduces the porosity of concrete materials and improves the permeability resistance, and the increase of the confining pressure makes the permeability of both kind of concrete specimens decrease continuously until it is in a stable state while the permeability of basalt fiber concrete specimens decreases more gently.