基于多层次结构特征的新型混杂纤维增强水泥基复合材料(HyFRCC)的性能及机理研究

High brittleness and low toughness of cementitious composite can be improved by the interactions of different fibers in hybrid fiber reinforced cementitious composites. However, the traditional hybrid manner and hybrid system can not well conside the multi-level characteristic and the multi-scale fracture process of cementitious composites, especially lacking the improvement of cement hydration products level and cement paste level. Therefore, the positive hybrid effect of traditional HyFRCC isn't very pronounced. Meanwhile, the high production cost also limits the widespread application of HyFRCC. Based on the effective reinforcing effect of calcium carbonate whisker (CW) on the microscopic level of cementitious composite, a new kind of fiber hybridization containing CW, polyvinyl alcohol fiber and steel fiber was designed in this project to prepare a new kind of HyFRCC. The mix proportion design and optimization, rheology, static and dynamic mechanical properties, and durability of this new HyFRCC will be studied systematically. It aims at setting up a design framework of this new HyFRCC based on the multi-level characteristic of cementitious composite, building the micro-mechanical model and static mechanical constitutive model, revealing the hybrid effect of the new fiber hybridization system and the internal connection between micro-mechanisms and overall performance of this new HyFRCC. This project will provide theoretical basis for improving the performance, reducing the production cost and promoting the large scale application of fiber reinforced cementitious composite.

混杂纤维增强水泥基复合材料(HyFRCC)借助不同纤维的协同作用以改善水泥基材料固有的高脆、低韧特性。但是，由于未能很好地契合水泥基材料自身的多层次组成结构特征和多尺度破坏过程，特别是缺乏对水泥水化产物及水泥净浆层次的结构改善，因而传统的纤维混杂方式和混杂体系难以表现出显著的正混杂效应。同时，纤维的高成本也是限制其广泛应用的瓶颈。本课题基于性优价廉的碳酸钙晶须对水泥基材料微观层次的高效增强作用，设计由碳酸钙晶须/聚乙烯醇纤维/钢纤维构成的新型混杂纤维体系，制备新型HyFRCC。系统研究其配合比设计与优化、流变学特性、静态、动态力学性能及耐久性；建立基于水泥基材料多层次结构特征的新型HyFRCC设计方法；构建其微观力学模型及静态力学本构关系；探索新型混杂纤维体系协同作用机制，以及微观机理与宏观性能的内在联系。研究成果可为提高纤维增强水泥基材料性能，降低成本，推进其大规模工程应用提供理论依据。

本项目在项目负责人前期主持的国家自然科学基金青年基金项目《碳酸钙晶须增强水泥基复合材料（CWRC）的基础研究》（51102035, 2012-2014）的基础上，基于性优价廉的碳酸钙晶须在微观尺度上对水泥基材料有高效的增强增韧作用，契合水泥基材料自身的多层次组成结构特征和多尺度破坏过程，构建碳酸钙晶须/聚乙烯醇纤维（PVA）/钢纤维（SF）新型混杂纤维体系，制备新型混杂纤维增强水泥基复合材料（HyFRCC），同时解决了传统HyFRCC的材料设计缺陷和高成本问题。 通过系统研究其配合比设计与优化、拌合物的流变性、流动性、硬化物的静态、动态力学性能及耐久性，建立了基于水泥基材料多层次结构特征的新型 HyFRCC 设计方法，得到各项性能最优的混杂体系配合比方案；同时，通过构建其微观力学模型及静态力学本构关系，探明了新型混杂纤维体系协同作用机制，以及其微观机理与宏观性能的内在联系。.本项目取得的研究成果实现了项目研究目标，达到了成果预期，为该新型高性能水泥基复合材料在近年内实现可观的工程应用做好了理论和技术指导准备。