纤维与水泥基体黏结性能及影响因素研究北大核心CSCD

纤维混凝土的韧性来源于纤维的桥接作用,而桥接作用的核心问题是纤维与水泥基体的黏结性能。为了探究纤维对混凝土的增韧机理,本文开展了不同养护龄期(0~28 d)、拔出速率(1~30 mm/min)、纤维锚固长度(10~60 mm)以及粉煤灰掺量(0~30%)下聚丙烯纤维水泥基砂浆的单根纤维拔出试验(single fiber pull-out test,SFPT),基于能量耗散原理和试验数据,建立了聚丙烯纤维水泥基砂浆韧性指数与纤维拔出过程中吸能指数的数学关系,提出了基于广义灰色关联理论的界面黏结强度影响因素计算分析方法。研究结果表明:随着养护龄期、拔出速率和纤维锚固长度的增加,聚丙烯纤维水泥基体界面黏结强度均逐渐增大,但纤维的韧性指数在养护18 h时较佳,拔出速率6 mm/min、锚固长度20 mm时最佳。当粉煤灰掺量为20%左右,纤维-水泥基体界面黏结性能最佳。并基于广义灰色关联分析法,阐明了四种因素与界面黏结强度的数学关联,研究成果可以为纤维水泥基砂浆的设计与应用提供理论支撑。

Study on bonding properties and influencing factors of fiber and cement matrix

The toughness of fiber reinforced concrete comes from the bridging effect of fibers, and the core of this effect depends on the bonding performance of fibers and cement matrix. To explore the concrete toughening mechanism of fibers, we conduct single fiber pull-out tests (SFPT) for polypropylene fiber-reinforced concrete under different conditions of curing ages (0 - 28 d), pull-out rates (1 - 30 mm/min), fiber anchorage lengths (10 - 60 mm), and fly ash contents (0 - 30%). Based on the principle of energy dissipation and the experimental data, we work out a mathematical relationship of the concrete toughness index versus the energy absorption index for fiber pull-out, and develop a calculation and analysis method for the influencing factors of interfacial bond strength based on the generalized grey relational theory. The results show that with the increase in curing age, pull-out rate or fiber anchorage length, the bond strength of the polypropylene fiber-cement matrix interface increases gradually, but the toughness index is better at the curing age of 18 h, and peaks at a pull-out rate of 6 mm/min and an anchorage length of 20 mm. And the interface bonding performance is the best at the fly ash content of about 20%. Based on the general grey correlation analysis method, mathematical correlation is clarified between the interfacial bond strength and the four factors. This study deepens our understanding of fiber-cement bonding and promotes the design and application of fiber-reinforced concrete.