粉煤灰对PVA纤维/水泥基体界面作用及复合材料拉伸性能的影响

本文研究了粉煤灰掺量对基体强度、聚乙烯醇(PVA)纤维/水泥基体间界面作用以及无表面修饰PVA纤维应变硬化水泥基复合材料(SHCC)拉伸性能的影响。结果表明,随着粉煤灰掺量的增加,基体的28 d抗压强度在18~93 MPa内呈下降趋势。单轴拉伸试验结果表明,掺入20%(质量分数,下同)和50%粉煤灰对SHCC的影响不明显,随着粉煤灰掺量增至67%和80%,SHCC的多微缝开裂和应变硬化特征呈增强趋势,极限应变值也相应增大,最高达7.2%,并且具有轻质特性。单纤维拔出试验结果显示,高掺量粉煤灰不仅可以降低PVA纤维与基体间的化学黏结作用,还能减弱界面摩擦作用,从而有效抑制了PVA纤维在拔出过程中出现过早断裂,显著提高了无表面修饰PVA纤维SHCC的延展性。

Effect of Fly Ash on PVA Fiber/Cementitious Matrix Interfacial Interactions and Tensile Properties of Composites

The effects of fly ash content on matrix strength, the interfacial interactions between polyvinyl alcohol (PVA) fiber and cementitious matrix, and the tensile properties of strain-hardening cementitious composites (SHCC) with non-surface-modified PVA fibers were investigated. The results show that with the increase of fly ash content, the 28 d compressive strength of the matrix declines within the range of 18~93 MPa. The uniaxial tensile test results show that the effect of fly ash on SHCC at 20% (mass fraction, the same below) and 50% dosages is insignificant. With the fly ash dosage increasing to 67% and 80%, the multiple-microcracks and strain-hardening characteristics of SHCC tend to be enhanced, and the corresponding ultimate strain increases, up to 7.2%, and SHCC has a characteristic of light weight. The results of fiber pullout test display that the high content of fly ash not only reduces the chemical bond between PVA fibers and the matrix, but also weakens the interfacial friction, which effectively inhibits the premature rupture of PVA fibers during the pullout process, and enhances the ductility of SHCC with non-surface-modified PVA fibers.