Ding Xinxin, Zhao Mingshuang, Li Hang, Zhang Yuying, Liu Yuanyuan, Zhao Shunbo
International Joint Research Lab for Eco-Building Materials and Engineering of Henan, North China University of Water Resources and Electric Power, Zhengzhou 450045, China.
Collaborative Innovation Center for Efficient Utilization of Water Resources, North China University of Water Resources and Electric Power, Zhengzhou 450045, China.
Materials (Basel). 2022 Aug 31;15(17):6024. doi: 10.3390/ma15176024.
Considering the random orientation and distribution of steel fibers in concrete, the synergistic reinforcement of steel fibers on concrete is much complex than the bond of single fiber. It is meaningful to study the bond behavior of steel fiber during many actions. With the inclination angle of steel fiber to pullout direction and the fiber spacing as main factors, this paper carried out fifteen groups of pullout tests for hook-end steel fiber embedded in manufactured sand mortar. The inclination angle ranged from 0 to 60°, and the fiber spacing ranged from 3.5 mm to 21.2 mm. The characteristic pullout load-slip () curve of steel fibers are given out after treating the original complete curves of each group test. The values of key points featured the debonding, peak and residual pullout loads and slips are determined from the characteristic curves. Based on a multi-index synthetical evaluation method, the nominal debonding strength, bond strength, residual bond strength and the debonding work, slipping work, and pullout work, as well as the debonding energy ratio, slipping energy ratio, and pullout energy ratio are analyzed. Results indicate that the bond performance represented by above indexes changes with the inclination angle and spacing of steel fibers. Except for the bond mechanism performing the same as aligned steel fibers by pullout test, the bond is dominated by the resistance of mortar to peeling off near pullout surface and scraping along pullout direction. When the inclination angle is over 15° or 30°, the bond performance is generally decreased, due to the peeling off of mortar on surface of transversal section with a certain depth. When the fiber spacing is over than 5 mm, the bond performance becomes worst due to the scraping out of mortar along with the slip of steel fibers.
考虑到钢纤维在混凝土中的随机取向和分布，钢纤维对混凝土的协同增强作用比单根纤维的粘结复杂得多。研究钢纤维在多种作用下的粘结性能具有重要意义。以钢纤维与拔出方向的倾斜角和纤维间距为主要因素，对埋入机制砂砂浆中的端钩型钢纤维进行了15组拔出试验。倾斜角范围为0至60°，纤维间距范围为3.5毫米至21.2毫米。对每组试验的原始完整曲线进行处理后，给出了钢纤维的特征拔出荷载-滑移（）曲线。从特征曲线确定了脱粘、峰值和残余拔出荷载及滑移等关键点的值。基于多指标综合评价方法，分析了名义脱粘强度、粘结强度、残余粘结强度以及脱粘功、滑移功和拔出功，以及脱粘能量比、滑移能量比和拔出能量比。结果表明，上述指标所代表的粘结性能随钢纤维的倾斜角和间距而变化。除了拔出试验中粘结机理与排列整齐的钢纤维相同外，粘结主要由砂浆在拔出表面附近的剥离阻力和沿拔出方向的刮擦阻力控制。当倾斜角超过15°或30°时，由于横截面上一定深度处砂浆的剥离，粘结性能通常会降低。当纤维间距超过5毫米时，由于砂浆随着钢纤维的滑移而被刮出，粘结性能变得最差。
