新型混杂纤维增强水泥基复合材料（HyFRCC）的流变特性及机理研究

Fibers can remarkably improve the toughness, static and dynamic mechanical properties of cementitious composites. Multi-scale hybrid fiber system (Macroscale fiber + Mesoscale fiber + Microscale fiber) is proposed on the basis of multi-level characteristic of cementitious composites. Excellent properties of fibers are concentrated to the hybrid fiber system to make it possess positive hybrid effect. And this multi-scale hybrid fiber system is the product of development in both theory and application. Meanwhile, the increment in fiber types leads to the complicated relationships in component-structure-property of hybrid fiber reinforced cementitious composites (HyFRCC). The deteriorated workability and severe fabrication of HyFRCC become the outstanding issues to solve. It is assumed that favorable workability of mixture is the key factor and precondition dominating the optimum properties of HyFRCC in hardened state. In this project, correlations between the rheology and component, micro-structure and properties of HyFRCC were discussed. Studies were focused on establishing quantitative relations of rheological and mechanical properties with fiber, matrix parameters and fiber distribution. Image analysis and numerical simulations were employed to build rheology models suitable for HyFRCC. Therefore, theoretical foundations are expected to provide for optimizing mix proportion, fabrication technology, improving hardened properties and thereby the application of HyFRCC in engineering.

纤维可对水泥基材料显著增韧，可明显提高材料的静、动态力学性能。基于水泥基材料多层次结构特征构建的多尺度混杂纤维体系（宏观+细观+微观纤维），由于其集成了各种纤维材料的优异性能而表现出优异的正混杂效应，是纤维水泥基材料的理论和实践发展到当前阶段的必然产物。然而纤维种类的增多使得该新型混杂纤维增强水泥基复合材料（HyFRCC）中组成-结构-性能的关系变得异常复杂，混杂纤维体系对工作性劣化及对制备工艺的苛求问题尤为突出，良好的拌合物工作性已成为实现HyFRCC优异性能的前提和关键。本研究从系统探讨混杂纤维水泥基材料的流变性与其组成、微观结构及性能的相关性入手，着眼于纤维体系参数、基体参数、纤维分散性与流变学参数及基本力学性能参数的量化关系研究，采用先进的图像分析及数值模拟技术，建立适用于新型HyFRCC的流变模型，为优化配合比设计及制备工艺、提高硬化物综合性能、实现大规模工程应用提供理论依据。

由碳酸钙晶须、钢纤维及聚乙烯醇纤维构建的新型混杂纤维体系可以在微观、细观与宏观尺度上发挥协同作用，对水泥基材料进行多层次多尺度的增强增韧，因此新型混杂纤维增强水泥基复合材料（HyFRCC）能够表现出优异的动、静态力学性能与耐久性能。然而，在对新型HyFRCC的进一步研究中发现，新型HyFRCC的拌合物性能优化不足，三种纤维在基体中分散不良，因此新型HyFRCC的硬化性能表现极不稳定。基于上述问题，本课题系统研究了碳酸钙晶须/钢纤维/聚乙烯醇纤维增强水泥基材料与新型HyFRCC的流动与流变性能，探索了因素变化下新型HyFRCC的流变响应机理；通过流变学参数量化了新型HyFRCC配合比优化效果，获得兼具优异流变性与硬化物性能的新型HyFRCC；确定了适用于表征新型HyFRCC流变性能的研究模型，提出基于柔性纤维的纤维分散参数，建立了纤维增强水泥基材料流变性能-分散性能-力学性能的定量联系；借助新型混杂纤维体系的纤维之间/纤维-基体之间相互作用及其微观结构演变，揭示新型HyFRCC拌合物的流变学机理。研究成果可为新型HyFRCC优良综合性能的获取提供理论依据，也为新型HyFRCC的大规模施工应用提供可行性建议。