【作者】 李益进；

【导师】 周士琼；

【作者基本信息】 中南大学 ， 道路与铁道工程， 2005， 博士

【摘要】 在桥梁结构向大跨、重载、轻质、高强、耐久方向发展的今天，高性能混凝土成为混凝土桥梁的首选材料。超细粉煤灰(UFA)采用电收尘气流分选工艺收集，细度达到500m~2／kg以上，是一种可用于配制高性能混凝土的优质矿物掺合料。但由于我国相关规范的规定，粉煤灰在预应力梁尤其是铁路预应力桥梁中的应用受到限制，一般在预应力混凝土梁中拒掺粉煤灰。本文针对工程技术人员的疑虑开展研究。突破现行国家标准的规定，以25％的UFA等量取代水泥，成功配制出了铁路预应力梁用高性能混凝土，并首次应用于我国铁路预应力混凝土桥梁。 论文的主要工作及成果如下： 1、系统研究了超细粉煤灰的物理性能、形貌、Zeta电位等粉体性能，探讨了其水化硬化行为。发现超细粉煤灰高性能混凝土(UFA-HPC)的早期强度取决于W／C而后期强度决定于W／B。利用超细粉煤灰的粉体效应，特别是减水增强效应，可补偿由于掺UFA引起的混凝土早期强度降低。优化配制的C50～C80超细粉煤灰高性能混凝土工作性能好，应力—应变全曲线形状与同强度等级普通高强混凝土接近，弹性模量较高，徐变收缩较小，耐久性能优异。满足铁路预应力混凝土桥梁的要求。 2、开展了C50～C80超细粉煤灰高性能混凝土模型梁疲劳性能试验研究。在国内首次证明以20～40％的UFA等量取代水泥，生产的超细粉煤灰高性能混凝土预应力梁疲劳性能满足规范要求。经过200万次疲劳试验梁体未开裂，处于弹性阶段，位移和应变随荷载的增加呈良好的线性关系。基频测试结果也表明梁体的刚度基本不变，梁体受力性能稳定。从结构动力学性能方面为超细粉煤灰在铁路预应力梁中的应用提供了技术支持。 3、综合考虑混凝土的工作性能、力学性能、耐久性能和桥梁结构的疲劳性能，确定超细粉煤灰掺量以等量取代25％的水泥为宜。该成果首次应用于我国铁路预应力混凝土桥梁，粉煤灰掺量突破了现行国家标准的规定，为有关规范的修改、制定提供了科学依据。 4、研究了矿物掺合料、外加剂及反应温度对复合水泥基材料水化历程的影响，建立了复合水泥基材料的水化动力学方程及超细粉煤灰水泥浆体水化程度和宏观性能之间的关系式。矿物掺合料自身的水更多还原

【Abstract】 With the development of bridge structure towards long-span, heavy load, light-weight, high strength and good durability, High Performance Concrete (HPC) has been becoming the first choice material of concrete bridge today. Ultra-fine Fly Ash (UFA) has been collected by electro-static precipitators and airflow classifying technology, the specific surface area of UFA ≥500m~2/kg, it is a good kind of mineral admixture for preparing HPC. Because of specifications of relevant standards, the application of fly ash in prestressed bridge girder is limited, especially for railway prestressed bridge girder. In general, fly ash is refused for railway prestressed girder. In this paper, a series of research is done against engineers’ anxiety. The specification of current national standards is broken through, UFA replaces equally 25% of cement by mass, HPC for railway prestressed girder was prepared successfully and applied to LuoYang-ZhanJiang railway prestressed concrete girders for the first in China.The main work and achievements in this paper are as follows: 1 、 Physico-chemical characteristics, morphologies and Zeta potential et al. were investigated systematically, the action effects of UFA was analyzed. Early strength of HPC with UFA (UFA-HPC) depends on W/C, and its long-term strength depends on W/B. The acting effects of UFA, especially the effect of water reducing and enhancement, can compensate concrete early strength decreasing due to incorporating UFA. UFA-HPC preparing by optimization meet the requirements of railway prestressed concrete bridge girder. The workability of UFA-HPC is good, the shape of stress-strain curves is approach to that of ordinary high strength concrete with same strength grade, its Young’s modulus is larger, creep and dry shrinkage is smaller, and its durability is excellent.2、 The fatigue properties of C50-C80 UFA-HPC model beam was tested and studied. It was proved that the fatigue properties of UFA-HPC prestressed girder meet the requirements of railway code when 20-40% of cement was replaced equally by UFA. Those concrete beams which have undergone 2,000,000 fatigue tests did not crack, still being in elastic更多还原