酸碱腐蚀PVA纤维对砂浆强度的影响

Influence of acid and alkaline corroded PVA fiber on strength of mortar

为研究聚乙烯醇(PVA)纤维的耐酸碱性及其对砂浆强度的影响,将相同质量的纤维分别浸泡在HCl和NaOH溶液中,测试其质量损失率随时间的变化,并采用扫描电子显微镜(SEM)观测其微观形貌的变化。同时,采用原状纤维和受腐蚀纤维分别制备纤维增强水泥砂浆,测试其抗压和抗拉强度,并采用SEM对试件断裂面微观形貌进行观测。结果表明,随着PVA纤维浸泡时间的延长,前3 d质量损失率迅速增大,之后增长速率减小;经过酸碱腐蚀后,纤维表面微结构出现明显变化,在相同条件下经过HCl溶液处理过的纤维其表面破坏相对更严重;纤维的化学腐蚀对纤维砂浆的28 d抗压和抗拉强度几乎没有造成不良影响,说明尽管酸碱腐蚀作用能造成纤维的质量损失和表面层破损,但是其力学性能仍保持在较高水平,纤维表面层破损对提高其与基体的粘结有利。

The chemical stability of polyvinylalcohol （PVA） fibers and its influence on the strength of mortar were studied. Two samples of PVA fibers of the same amount were soaked in sodium hy- droxide and hydrochloric acid solutions respectively, after which the mass loss ratio was measured. Scanning electron microscope （SEM） observation was performed to detect the surface morphologies of the fibers. The original and corroded fibers were both adopted to prepare cement mortar respec- tively and the strengths of the two kinds of cement mortar were measured. The fracture surface of the specimens was also detected by SEM. It was revealed that with the prolonging of immersion time, the mass loss ratio was increased sharply in the first 3 days and then the increment speed slowed down. There appears to be obvious changes for the micro morphology of the fibers. The damage to acid corroded fibers was worse than that to alkali corroded fibers at the same conditions. The strength of cement mortar prepared with corroded fibers at day 28 shows almost no decrease indicat- ing that although chemical treatment causes mass losses and damages on the superficial layer, thetensile strength of the fiber still remains at a high level and the surface damage of fibers is beneficial to the bonding strength with the matrix.