【作者】 姜从盛；

【导师】 胡曙光；

【作者基本信息】 武汉理工大学 ， 材料学， 2010， 博士

【摘要】 混凝土材料是人类最大宗的人造建筑材料,其固有缺点是自重大与脆性突出,改善混凝土的脆性、实现混凝土的轻质高强化是提高混凝土材料使用效能,减轻结构自重,节约建筑材料资源与能源的最有效技术途径之一,也是混凝土材料科学基础理论研究与应用技术开发的主要目标。论文依托国家自然科学基金项目“高强轻集料混凝土的脆性特征及其增韧技术(编号：50272045)”,运用细观力学原理与分析方法,对轻集料混凝土的断裂力学行为进行了数值模拟分析与试验验证,探明了轻集料混凝土中的脆性机、理。在此基础上,提出轻质高强混凝土韧化设计方法,系统研究了高韧性轻质高强混凝土的配比优化设计方法,掌握了高韧性轻质高强混凝土的配比关键技术参数及其系统增韧技术,并将研究成果成功应用于实际工程。论文开展的主要工作和取得的重要成果有：依据轻集料混凝土组成与结构特点,利用蒙特卡罗方法研究提出了轻集料混凝土随机集料分布物理模型,结合轻集料的几何形态和级配分析计算,构建出可供有限元计算与分析的轻集料混凝土数值模型,确定了混凝土细观单元体尺度与断裂性质的关系以及有限元单元体网格划分方法,分析设定了各种应力作用条件下的材料破坏准则,探讨了轻集料-水泥石界面层性能对混凝土断裂力学行为的影响,提出了轻集料混凝土断裂行为的细观非线性有限元分析方法,构建出轻集料混凝土断裂行为数值模拟分析模型。利用细观非线性有限元模型实现了轻集料混凝土的准静态断裂过程数值模拟,分别对单轴拉伸、单轴压缩、三点弯曲应力作用下轻集料混凝土的断裂行为进行了细观力学分析,得到了不同应力作用下轻集料混凝土的应力-应变曲线,获得了不同加载时刻轻集料混凝土内部应力分布状态,探明了轻集料混凝土中裂缝产生、扩展规律,并实时原位观测了轻集料混凝土从加载开始到最终破坏全过程的裂纹扩展和变形状态,探明了轻集料混凝土的脆性断裂破坏机理。基于轻集料混凝土脆性断裂行为的细观力学分析结果,提出了轻集料混凝土裂缝扩展路径曲化、界面韧化的轻质高强混凝土增韧设计原理、方法,提出了利用高强高韧性颗粒物质取代轻集料制备高韧性轻质高强混凝土的技术方法,系统研究了普通集料取代率、普通集料级配设计对混凝土力学性能、密度与韧性指数的影响,确定了最佳的材料制备参数,实验表明在普通集料取代轻集料30%以上的情况下,轻质混凝土的延性指数可提高40%以上,大大改善了轻质高强和混凝土的脆性。开发了轻集料聚合物浸渍与界面增韧剂复合增韧轻集料-水泥石界面改性技术,显著改善了轻集料混凝土的脆性。探讨了水胶比、轻集料的体积率、胶凝材料组成主要因素对轻质高强混凝土强度、密度与韧性的影响规律,掌握了协调强度、密度与脆性的混凝土配比优化设计方法,系统研究了纤维、聚合物增韧技术对于轻质高强混凝土韧性的影响规律,开发了适于轻质高强混凝土的纤维与聚合物增韧技术。综合应用以上集成技术,研制开发出高韧性轻质高强混凝土,总结提出了高韧性轻质高强混凝土应用成套关键技术,成功将其应用于钢箱梁桥面铺装工程与预应力混凝土桥梁工程,并取得显著的经济与社会效益。更多还原

【Abstract】 Concrete is the most widely used construction material and its intrinsic disadvantages are heavy dead weight and prominent brittleness. The improvement in brittleness of concrete with lightweight and high strength is of the most efficient routes to increase the use effectiveness, reduce the dead load of structures and conserve construction resource and energy, it is also the main target for theoretical research and application development of concrete materials.Under the support of NSFC (National Natural Science Foudation of China) grant "The brittleness characteristics and toughening technology of high strength light weight aggregate concrete (LWAC)" (50272045). The fractural mechanical behavior of LWAC is numerically modeled and experimentally verified by mesomechanics and the brittleness mechanism is explored. Based on this, the toughening method of LWAC is put forward and the mix design is systematically studied, from which, key parameters are obtained and the research outcome is applied to some projects.The primary research carried out and results obtained are as follows:Based on the composition and structure of LWAC, Monte Carlo Method is employed to put forward the random aggregate distribution model of LWAC; the model of finite element method (FEM) is constructed based on the geometry and grading of lightweight aggregate(LWA), from which, the relationship between meso unit dimension and fracture property of concrete, and the meshing of FEM elements; The failure criteria under various stress levels are analyzed, and the influence of LWA-cement interface on the fractural mechanical behavior; The meso non-linear FEM of the fractural mechanical behavior of LWAC is put forward and the model for numerical analysis is constructed.Quasi-static fracture process of LWAC is numerically modeled by meso non-linear finite element model; the fracture behavior of LWAC is investigated by uniaxial extension, compression, three-point flexural experiments and the corresponding stress-strain curves and the stress distribution within concrete are obtained. The crack generation, propagation within LWA is clarified and monitored in situ from the start of loading to total failure, from which, the brittle failure mechanism is demystified.Based on the above results, the toughening method by winding the crack propagation path and toughening the interface is put forward, and the replacement of LWA by high strength, high flexibility material to prepare high strength concrete is put forward. The effect of replacement ratio, conventional mix design method on mechanical property, density and toughening index of concrete is investigated and the optimized parameters are obtained. Results indicate that with a replacement ratio of above 30%, the ductility index of lightweight concrete is increased by 40%. The combination of polymer impregnation and interface toughening to improve the LWA-cement paste interface is put forward and the brittleness of concrete is greatly improved.The effect of w/b, LWA volume and the composition of cementitious materials on strength, density and toughening of concrete is studied and the mix design method by optimizing strength, density and brittleness is mastered; the effect of fibre, polymer toughening on the toughening of lightweight concrete.Concrete of high strength, toughness and light weight is developed by the integration of the above techniques and its application key technologies are summarized. It has been successfully applied to several projects of the paving of steel box bridge and prestressed concrete bridges with noticeable economic and social benefits.更多还原