钢纤维—水泥石基体界面特征及对混凝土宏观性能影响的研究

发布时间：2018-04-18 18:42

本文选题：钢纤维混凝土 + 硅灰　；参考：《重庆交通大学》2015年硕士论文

【摘要】：钢纤维混凝土因其优良的工作性能而开始在工程中大量应用,然而钢纤维与混凝土基体间薄弱的界面粘结导致钢纤维的增强增韧效果难以有效完全发挥。本论文采用目前常用的添加有机聚合物和无机矿物掺和料硅灰来对混凝土进行改性处理,以期提高钢纤维与混凝土基体间的界面粘结性能,进而增强钢纤维混凝土的宏观力学性能。为此,本论文测试了不同硅灰和聚合物掺量时钢纤维混凝土的抗压、劈裂抗拉、抗折强度等宏观力学指标;自行设计模具及夹具进行钢纤维拉拔试验,研究硅灰和聚合物对钢纤维—水泥石基体界面粘结性能的影响;研究了钢纤维埋置角度、钢纤维表面形貌以及混凝土基体强度等级和龄期对界面粘结性能的影响;对界面区以及水泥石基体进行显微硬度、SEM试验、XRD试验以及低温氮吸附微观孔隙测定等试验,从微观上对硅灰和聚合物对钢纤维与水泥石基体界面粘结性能的影响和作用机理进行解释。通过上述这些试验获得以下结论:○1硅灰能较好的提高混凝土抗折、抗压以及劈裂抗拉强度,而聚合物则降低了混凝土的这些力学性能;单掺钢纤维时,能一定程度提高混凝土的这些宏观力学性能,但存在一个介于0.6%~0.9%的最优掺量;○2硅灰极大地提高了钢纤维与水泥石基体间的界面粘结强度,但硅灰掺量超过9%后容易导致钢纤维被拔断而瞬间失效,并且硅灰还会因抑制了钢纤维自身的弹塑性变形而降低钢纤维混凝土适应变形的能力。而聚合物能提高钢纤维的极限位移,并能通过对界面粘结的弱化而使钢纤维被拉拔时不易断裂而消耗更多的能量,同时还能提高钢纤维混凝土适应变形的能力;○3在钢纤维埋置角度为45°时,界面粘结强度达到最大,但掺硅灰后倾斜的钢纤维更容易被拔断,钢纤维埋置角度越大该现象越明显;凸肋形钢纤维与基体间的界面粘结强度明显高于表面光圆的钢纤维,且界面粘结强度随混凝土基体强度的提高而增大,两者之间存在一定的函数关系;○4硅灰能够增大界面区显微硬度值并缩小界面区与水泥石基体间力学性能的差距,并有利于水泥的水化反应,促进C-S-H凝胶的生成,抑制Ca(OH)2晶体的产生,降低了界面区和基体的微观孔隙体积而改善了界面区结构,有利于提高界面粘结性能。聚合物虽也能缩小界面区显微硬度最小值并一定程度降低了大孔径的有害孔隙总体积,但其也导致Ca(OH)2晶体含量和尺寸增加,基体显微硬度的降低,从而界面粘结性能还是随聚合物掺量的增加而呈下降趋势;○5将界面区的力学参数和微观结构参数与混凝土结构的宏观力学性能联系起来,得出界面粘结强度、钢纤维拉拔韧度、显微硬度、比表面积以及微观总孔体积与混凝土抗压强度和抗折强度间的函数关系式,既揭示了界面区特征参数对混凝土抗压、抗折强度的影响趋势,又为预测实际工程中混凝土结构的力学性能提供了理论基础。
[Abstract]:Steel fiber reinforced concrete and used widely in engineering because of its excellent performance, however, between the steel fiber and concrete matrix interfacial bonding leads to weak reinforcing and toughening effect of steel fiber is difficult to effectively play completely. This paper uses the present commonly used to add organic polymer and inorganic mineral admixture for modification of silica fume concrete, to improve the interfacial bond strength between the steel fiber and concrete matrix, thus enhancing the macro mechanical properties of steel fiber reinforced concrete. The compressive steel fiber concrete this paper tested different silica fume and polymer dosage, splitting tensile strength, flexural strength and other mechanical parameters; design of tooling and fixture of steel fiber pullout test, effects of silica fume and polymer on the steel fiber cement matrix interfacial bonding properties; steel fiber on buried angle steel fiber surface shape Effect of appearance and the grade of concrete strength and age on interfacial properties; microhardness of interfacial zone, and the cement matrix SEM test, XRD test and low temperature nitrogen adsorption test determination of micro pore, explain and effect of silicon fume and polymer effect on steel fiber and cement matrix bonding mechanism from the microscopic. The following conclusions are obtained through the experiment: 1, silica fume can improve the concrete good bending, compressive and splitting tensile strength, and decreased the mechanical properties of polymer concrete; single doped fiber, can to some extent improve the macro mechanical properties of concrete, but there is an optimal dosage is 0.6%~0.9%; 2, silica fume has greatly improved the interfacial bond strength between steel fiber and cement matrix, but the silica fume quantity more than 9% easily lead to steel fiber were pulled off and Instantaneous failure, and also because of inhibition of steel fiber and silica fume the elastic-plastic deformation of steel fiber reinforced concrete and reduce the ability to adapt to the deformation. And the polymer can improve the ultimate displacement of steel fiber, and by the weakening of the interfacial bond and the steel fiber drawing is not easy to break and consume more energy, but also improve the the deformation capacity of steel fiber reinforced concrete; 3, buried in the steel fiber angle is 45 degrees, the interfacial bond strength reached the maximum, but the steel fiber tilt after silica fume is more likely to be pulled off, steel fiber embedded angle increases, the phenomenon is more obvious; the interfacial bond strength of rib shaped steel fiber and matrix the surface is obviously higher than that of steel fiber light round, and the interfacial bond strength with concrete strength increases, there is a certain relation between them; 4, silica fume can increase the interfacial microhardness value and narrow circle The mechanical properties of the surface area and the gap between the cement matrix, and is conducive to the hydration of cement, promote the formation of C-S-H gel, inhibition of Ca (OH) 2 crystal, reduces the micro pore volume of interfacial zone and matrix and improve the interface structure, can improve the interface bonding performance of polymer is. Can also reduce the interfacial microhardness and the minimum degree reduces the total harmful pore volume of large aperture, but also lead to Ca (OH) 2 crystal content and size increase, decrease the hardness of matrix, thus the bonding performance of the interface or with the polymer dosage increased and decreased 5, the mechanical parameters; the interface and microstructure parameters and macro mechanical properties of concrete structure together, that the interfacial bond strength, steel fiber pull-out toughness, microhardness, surface area and total pore volume of the micro and concrete compressive strength and bending The functional relationship between strength reveals the trend of influence of interface area characteristic parameters on compressive strength and flexural strength of concrete, and provides a theoretical basis for predicting the mechanical properties of concrete structures in actual engineering.

【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528.572

【参考文献】