高掺量粉煤灰对高延性水泥基材料力学性能影响

Influence of High-volume Fly Ash on Mechanical Properties of Engineered Cementitious Composite

为了改善高延性水泥基材料(ECC)的延性,降低其生产成本,同时保证其力学性能,研究提高粉煤灰掺量对ECC各项性能的影响。作为ECC的应用和材料设计的重要参考依据,高掺量粉煤灰对ECC的力学性能及其损伤特性的影响尚未明确。本研究设计三点弯曲试验、四点弯曲试验、单轴拉伸试验、抗压强度试验以及单根纤维拔出试验,用于研究不同粉煤灰掺量对ECC的断裂韧性、开裂强度、弹性模量、界面特性、延度、弯曲和拉伸强度以及抗压强度等力学性能的影响,为材料的设计提供参考依据。结果表明:ECC早期的断裂韧性、开裂强度随粉煤灰的含量升高而降低,受拉更易开裂;但随着粉煤灰掺量增加,ECC的弯曲与拉伸延性均增大,而弯曲与拉伸强度均减小;粉煤灰掺量的增加会使ECC的抗压强度显著降低;随着粉煤灰掺量增加,界面摩擦强度减小,集体与界面之间更易产生滑移而非断裂;在掺量较高时,粉煤灰掺量的增加虽然使得ECC早期力学性能降低,但仍能够达到改善ECC延性的工程目的;延性的改善能够显著提高ECC在桥面铺装、桥梁伸缩缝、联接梁等工程中的性能表现。在工程中可以将以上结论作为依据,结合工程自身需求,合理设计ECC的粉煤灰掺量。

In order to improve the ductility of engineered cementitious composite(ECC),reduce its production cost and ensure its mechanical properties,the effect of increasing fly ash content on the properties of ECC is studied.As an important reference for the application of ECC and material design,the effect of high content fly ash on the mechanical properties and damage characteristics of ECC is not clear.Three-point bending test,four-point bending test,uniaxial tensile test,compressive strength test and single fiber pull-out test are designed,it is used to study the effect of different fly ash content on ECC mechanical properties such as fracture toughness,cracking strength,elastic modulus,interface property,ductility,bending and tensile strength and compressive strength,provide the reference basis for the material design.The result shows that(1)the fracture toughness and cracking strength of ECC decrease with the increase of fly ash content,but with the increase of fly ash content,the bending and tensile ductility of ECC increase,while the bending and tensile strength decrease;(2)the increase of fly ash content will reduce the compressive strength of ECC significantly;(3)with the increase of fly ash content,the interfacial friction strength decreases,and the slip rather than fracture is more likely to occur between the mass and interface;(4)when the content of fly ash is high,the increase of the content of fly ash can reduce the early mechanical properties of ECC,but still improve the ductility of ECC;(5)the improvement of ductility can significantly improve the performance of ECC in bridge deck pavement,bridge expansion joints,joint beams and other projects.The conclusion can be used as a basis in the project,combined with the project’s own needs,reasonable design of ECC fly ash content.