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本文采用拔出试验法研究了水灰比、丙烯酸共聚乳液、减水剂、纤维外形、纤维直径、纤维埋深及纤维走向等因素的变化对界面粘结强度的影响。实验表明:减小界面水膜层的厚度,加强界面过渡环都能提高界面粘结强度和钢纤维增强效果。聚合物水泥砂浆与双肢钢纤维的粘结强度最大。 本文还通过显微硬度试验测得界面过渡环的性状及范围。实验表明:在钢纤维与基体的界面过渡环中,最弱点不是在紧贴纤维表面处,而是在距纤维表面为25～35μm处,水灰比越低,过渡环最弱点的最微硬度值越高,最弱点与纤维表面的距离越小。通过能谱分析得知,在紧贴纤维表面的水泥石中,铁离子浓度最大,并随着与纤维表面的距离增加而逐渐减小。在距离为40μm处,铁离子浓度已很小,并逐渐趋于恒定。铁离子的存在可能会提高界面密实度。此外,还采用扫描电子显微镜,观察和研究了界面形貌。
In this paper, pull-out test method was used to study the effects of water-cement ratio, acrylic copolymer emulsion, water-reducing agent, fiber shape, fiber diameter, fiber depth and fiber orientation on interface bond strength. Experiments show that: reducing the thickness of the interface water film layer, strengthening the interface transition ring can improve the interface bond strength and steel fiber reinforcement effect. Polymer cement mortar and double-limb steel fiber have the highest bond strength. In this paper, the properties and the range of the interfacial transition rings were also measured by microhardness test. Experiments show that the weakest point in the interface transition between the steel fiber and the matrix is not close to the fiber surface but 25 to 35 μm away from the fiber surface. The lower the water-cement ratio, the lowest hardness of the weakest point of the transition ring. The higher the value, the lower the distance from the weakest point to the fiber surface. According to the energy spectrum analysis, the concentration of iron ions is the highest in the cement stone close to the fiber surface, and gradually decreases as the distance from the fiber surface increases. At a distance of 40 μm, the iron ion concentration is very small and gradually becomes constant. The presence of iron ions may increase the density of the interface. In addition, scanning electron microscopy was used to observe and study the interface morphology.