【作者】 张悦；

【导师】 覃源； 柴军瑞；

【作者基本信息】 西安理工大学 ， 水工结构工程， 2019， 硕士

【摘要】 聚丙烯纤维混凝土(Polypropylene fiber reinforced concrete,PPFRC)在我国水利工程、土木工程和岩土工程中使用广泛,在不同工程中,其配合比、纤维掺量、养护条件等均存在较大差异,对其性能也会有不同程度的影响。本文以聚丙烯纤维混凝土为对象,研究了不同养护龄期下不同掺量聚丙烯纤维混凝土的力学性能变化规律、纤维阻裂性能以及在不同应力条件下的破坏规律,以期为聚丙烯纤维混凝土的合理使用提供理论支撑。本文的研究内容包含以下几个方面:(1)统计分析了不同纤维掺量对混凝土强度、抗渗性能及抗干缩性能的影响规律。并结合工程应用情况,汇总了聚丙烯纤维混凝土应用于水利工程中的哪些部位,发现水利工程中常用的纤维掺量在0.6～1.5 kg/m3之间,其中0.9 kg/m3掺量使用最多。根据调研情况提出本文的研究问题。(2)讨论了不同纤维掺量对混凝土拌合物工作性能的影响,发现聚丙烯纤维(Polypropylene fiber,PPF)的添加降低了混凝土的可加工性。在水胶比为0.36的配合比中,掺量超过1.2 kg/m3时,混合料搅拌困难,需调整拌合用水与减水剂用量。聚丙烯纤维的添加有利于拌合物的粘聚性和保水性。(3)揭示了不同养护龄期、不同纤维掺量对混凝土抗压性能的影响程度。纤维的添加增强了混凝土抗压强度和轴压强度,提高了混凝土的抗压起裂能、破坏能和压缩韧性,减小了混凝土的压缩破坏程度,改善了混凝土的脆性并增加了其延展性。基于棱柱体轴心抗压试验,提出了不同养护龄期、不同纤维掺量混凝土的单轴受压应力一应变本构模型。(4)揭示了不同养护龄期、不同纤维掺量对混凝土抗拉性能的影响程度。纤维的添加增强了混凝土的劈拉强度和抗折强度,提高了混凝土的断裂能和韧性,提出了聚丙烯纤维混凝土劈拉强度与抗压强度关系曲线的方程。综上,讨论纤维掺量在不同养护龄期时对混凝土力学性能和损伤演化特性的影响,提出相关力学试验中的应力—应变本构模型,具有重要理论意义和实用价值。更多还原

【Abstract】 Polypropylene fiber reinforced concrete(PPFRC)is widely used in hydraulic engineering,civil engineering and geotechnical engineering in China.In different projects,the mix ratio,fiber content and curing conditions are quite different.Its performance will also have varying degrees of impact.In this paper,the mechanical properties,fiber cracking resistance and failure law under different stress conditions of polypropylene fiber reinforced concrete with different fiber content and different curing ages were studied to provide theoretical support for the rational use of polypropylene fiber reinforced concrete.The research content of this paper includes the following aspects:(1)the influence of different fiber content on concrete strength,impermeability and dry shrinkage resistance were analyzed statistically.Combined with engineering application,summarizes the parts of polypropylene fiber reinforced concrete used in hydraulic engineering,and found hydraulic engineering The commonly used fiber content is between 0.6～1.5 kg/m3,of which 0.9 kg/m3 is used most.According to the research situation,the research questions of this paper are proposed.(2)The influence of different fiber content on the workability of concrete mixture was discussed.It was found that the addition of polypropylene fiber reduced the workability of concrete.In the mixing ratio of water-binder ratio of 0.36,when the content exceeds 1.2 kg/m3,the mixing of the mixture is difficult,and the mixing water and the amount of the water reducing agent need to be adjusted.The addition of polypropylene fibers(PPF)facilitates the cohesiveness and water retention of the mixture.(3)The effect of different polypropylene fiber content on the compressive properties of concrete at different curing ages was revealed.The addition of fiber enhances the compressive strength and axial compressive strength of concrete,improves the compressive pre-crack energy absorption,compressive energy absorption and compressive toughness index of concrete,reduces the degree of compression damage of concrete,improves the brittleness of concrete and increases its ductility.Based on the axial compression test of prisms,the uniaxial compressive stress-strain constitutive model of concrete with different curing age and different fiber content was proposed.(4)The effect of different polypropylene fiber content on the splitting properties of concrete at different curing ages was revealed.The addition of fiber enhances the splitting strength and flexural strength of concrete,improves the fracture energy and toughness of concrete,and proposes an equation for the relationship between splitting strength and compressive strength of polypropylene fiber reinforced concrete.In summary,the influence of fiber content on the mechanical properties and damage evolution characteristics of concrete at different curing ages is discussed.The stress-strain constitutive model in the relevant mechanical tests is proposed,which has important theoretical significance and practical value.更多还原