Zeng Wei, Wang Weiqi, Wang Qiannan, Li Mengya, Zhang Lining, Tong Yunyun
School of Civil Engineering and Architecture, Zhejiang University of Science and Technology, Hangzhou 310023, China.
Zhejiang International Science and Technology Cooperation Base for Waste Resource Recycling and Low-Carbon Building Materials Technology, Zhejiang University of Science and Technology, Hangzhou 310023, China.
Materials (Basel). 2024 Apr 16;17(8):1819. doi: 10.3390/ma17081819.
This paper describes hybrid fiber's influence on the crack permeability of cracked concrete exposed to freeze-thaw cycles. A permeability setup and a laser-scanning setup have been designed to measure the crack permeability and the fractured surface roughness of cracked hybrid fiber-reinforced concrete, containing polypropylene fiber and steel fiber, under a splitting tensile load. The results show that, when the effective crack width of the specimens is less than 25 μm, the rough crack surface significantly reduces the concrete's crack permeability. As the crack width increases, the effect of the concrete crack surface on crack permeability gradually decreases, and the crack permeability of the concrete is closer to the Poiseuille flow model. The permeability parameter derived from the Poiseuille flow model is effective for assessing the crack permeability of concrete. Compared to the modified factor ξ of crack permeability, the permeability parameter α can effectively evaluate and quantify the development trend of crack permeability within a certain range of crack widths. The permeability parameter α of SF20PP2.3, subjected to the same freeze-thaw cycles, decreases by 16.3-94.8% compared to PP4.6 and SF40, and SF20PP2.3 demonstrates a positive synergistic effect on the crack impermeability of cracked concrete. The crack impermeability of SF40PP2.3, subjected to the same freeze-thaw cycles, lies between that of PP6.9 and SF60. The roughness of crack surface (X) and the crack permeability (Y) are highly correlated and follow an exponential curve (Y = 1.0415 × 10·e) in concrete. This demonstrates that hybrid fibers enhance crack impermeability by increasing the crack surface roughness. Furthermore, the combination of polypropylene fiber and steel fiber effectively promotes the formation of micro-cracks and facilitates the propagation of multiple cracks in the concrete matrix. This combination increases the head loss of water flow through the concrete and decreases the crack permeability.
本文描述了混杂纤维对经历冻融循环的开裂混凝土裂缝渗透性的影响。设计了一种渗透装置和一种激光扫描装置，用于测量含聚丙烯纤维和钢纤维的混杂纤维增强开裂混凝土在劈裂拉伸荷载作用下的裂缝渗透性和断裂表面粗糙度。结果表明，当试件的有效裂缝宽度小于25μm时，粗糙的裂缝表面显著降低了混凝土的裂缝渗透性。随着裂缝宽度的增加，混凝土裂缝表面对裂缝渗透性的影响逐渐减小，混凝土的裂缝渗透性更接近泊肃叶流动模型。由泊肃叶流动模型导出的渗透参数对于评估混凝土的裂缝渗透性是有效的。与裂缝渗透性修正因子ξ相比，渗透参数α能在一定裂缝宽度范围内有效评估和量化裂缝渗透性的发展趋势。在相同冻融循环作用下，SF20PP2.3的渗透参数α相比PP4.6和SF40降低了16.3 - 94.8%，且SF20PP2.3对开裂混凝土的抗渗性表现出正协同效应。在相同冻融循环作用下，SF40PP2.3的抗渗性介于PP6.9和SF60之间。在混凝土中，裂缝表面粗糙度(X)与裂缝渗透性(Y)高度相关，且呈指数曲线关系(Y = 1.0415×10·e)。这表明混杂纤维通过增加裂缝表面粗糙度来提高抗渗性。此外，聚丙烯纤维和钢纤维的组合有效地促进了微裂缝的形成，并有利于混凝土基体中多条裂缝的扩展。这种组合增加了水流过混凝土的水头损失，降低了裂缝渗透性。
