【作者】 曹继锋；

【导师】 丁一宁；

【作者基本信息】 大连理工大学 ， 结构工程， 2006， 硕士

【摘要】 合成纤维因材质不同、使用性能不同、类别不同,在混凝土中的用途也不同,传统的聚丙烯短纤维是一种单丝纤维,属于外掺料型短纤维,在混凝土中的主要作用是阻止基体中原有的微裂缝扩展并延缓新裂缝的出现,提高基体的变形能力,但对于混凝土的韧性并没有明显的改善。 高性能混凝土不仅要有良好的强度与工作性能,还应有优异的耐久性能和较好的韧性,以满足不同的工程需要。传统高强素混凝土材料的脆性大、抗冲击性差是影响其实际应用的一个重要因素。钢纤维可以显著提高混凝土的抗裂、抗折、抗冲击、抗疲劳等性能,其理论研究正不断走向成熟,工程应用领域也在不断扩大,但在特殊环境下容易锈蚀进而影响其耐久性且价格较高。聚丙烯纤维混凝土具有纤维掺量少、耐化学腐蚀性好、成本低等优点,其应用领域和应用工程量不断扩大。随着聚丙烯纤维混凝土技术的发展,纤维品种的多样化以及聚丙烯纤维质量的提高,国外已尝试使用部分聚丙烯长纤维或者将其和钢纤维混杂应用于混凝土中来增强增韧混凝土材料,这在国内研究的还比较少。 本文按照国际标准对新型仿钢丝聚丙烯合成长纤维增强高性能混凝土的工作度、含气量、强度、弯曲韧性、断裂能、截面纤维分布、梁的破坏形态等进行了试验研究。其中对纤维混凝土的弯曲韧性按照国际材料与结构联合会(RILEM)标准进行了深入的研究,应用RILEM标准来评价合成纤维混凝土的弯曲韧性有其优势,可以客观全面的反映合成纤维的增韧性能。 同时还研究了钢纤维混凝土及新型聚丙烯长纤维与钢纤维混杂时对纤维混凝土性能的影响。在弯曲韧性试验中,将滤波后的数据按照RILEM标准给出的公式计算得出了不同纤维混凝土的能量吸收值和等效抗弯强度,深入研究了新型聚丙烯长纤维部分取代钢纤维的可能性。试验表明:聚丙烯长纤维高性能混凝土可以得到较好的工作度、较强的能量吸收能力,可以明显的改善高性能混凝土的抗弯强度和弯曲韧性;在保证较好工作性能及较高抗压强度的前提下,将聚丙烯长纤维和钢纤维混杂应用于混凝土中可以充分发挥两种纤维各自的优势,可以取代部分钢纤维而达到相同或者更好的增韧效果,达到既可提高韧性又能降低成本的目的。更多还原

【Abstract】 Synthetic fiber has different uses according to different qualities and purposes when it is mixed in concrete. Classic polypropylene fiber is a monofilament belonging to micro-fiber which can be used to reduce shrinkage cracks of concrete at early age. Mostly, it is used to prevent extension of old crack in the concrete matrix and delay the appearance of new crack. It can also enhance the deformability of concrete matrix. But it hasn’t obviously contribution to improve the toughness of concrete.High performance concrete (HPC) should show various properties, such as relative high strength and workability, good toughness and excellent durability and to meet different engineering requirements. Plain concrete has high brittleness and low shock resistance, so it has difficulty in widespread availability. Steel fiber can obviously enhance cracking resistance, bending behaviour, impact resistance, fatigue resistance of concrete, the theory of steel fiber is nearly becoming mature and the application fields of steel fiber are expanding. But the price of steel fiber is high which limit its application. Polypropylene fiber reinforced concrete has merits such as low fiber content, low cost excellent resistance to chemical erosion and it has extensive application. As the development of the technique of polypropylene fiber reinforced concrete and the advance of the quality of polypropylene fiber, some scholars have attempted to mix macro-polypropylene fiber into concrete for the purpose of enhancing the toughness of concrete abroad. We also could mix steel fiber and macro-polypropylene fiber together into concrete to research the performance of steel-polypropylene hybrid fiber-reinforced concrete and use polypropylene fiber to partly replace steel fiber to reinforce concrete. There is little research on it inland presently.This article presents the experimental results of modified macro-polypropylene fiber reinforced high performance concrete such as workability, air content, compressive strength, fiexural toughness, fracture energy, the distribution of fiber on section, the failure form of the beam. The experiments have been carried out according to different international guidelines. The fiexural toughness has been deeply analyzed according to RILEM guideline. RILEM guideline has advantages in researching fiexural toughness of synthetic fiber reinforced concrete and could reflect true performance of synthetic fiber.The toughness of beams with steel fiber reinforcement and with hybrid fiber reinforcement has been compared. The energy absorption capacity and equivalent fiexural strength have beencalculated. The results show that modified macro-polypropylene fiber has better workability and energy absorption capability. We can use the modified macro-polypropylene fiber to obviously enhance the flexural toughness of concrete and can partly replace steel fiber, in order to increase the flexural toughness and reduce the cost.更多还原