混凝土用高强轻集料的复合结构设计与矿物组成调控

High strength lightweight aggregate concrete shows typical brittle failure characteristics, the fundamental reason is that the strength and elastic modulus of lightweight aggregate are far lower than that of ordinary aggregate. It is very difficult to improve the "specific strength" (a ratio of strength/quality) of the lightweight aggregate according to the existing design method and production technology. In this project, a new type of the high strength lightweight aggregate that has a nuclear-shell structure, which take the cordierite as main crystal phase for nuclear and belite clinker for shell will be developed by using once calcination process. The preparation process, the mineral composition and proportion in nuclear and hydration process of the mineral on shell on the performance of the lightweight aggregate will be studied, and the relationship between its composition and structure and macro performance will also be explained. Furthermore, the characteristic of the high strength lightweight aggregate, the sintering combined district on nuclear-shell and the interfacial transition zone（ITZ） on the failure process of the lightweight aggregate concrete will be obtained, and the corresponding mechanism will be explored. The new designing theory and key preparation technique of the high strength lightweight aggregate that based on the coordinated development of strengthening and toughening will be established. This is very helpful to enrich and improve existing design and preparation method for the high strength lightweight aggregate.

高强轻集料混凝土呈典型脆性破坏特征，根本原因在于轻集料的自身强度和弹性模量均远低于普通集料。现有高强轻集料的设计理念和生产工艺致使其“比强度”（强度与质量之比）的提升非常困难。本项目从高强轻集料混凝土的损伤破坏特点出发，提出以堇青石为内核主晶相、高贝利特熟料为外壳，一次烧成，具有核-壳复合结构的高强轻集料设计思路，全面研究制备工艺参数、内核矿物组成及其比例，以及外壳表层矿物水化过程对高强轻集料性能的影响规律，并阐明其组成和结构变化与宏观性能的内在联系；进一步，考察该高强轻集料、核-壳烧结结合区，以及外壳-水泥石界面过渡区特性对所得轻集料混凝土受荷破坏过程的影响规律与作用机制；实现基于强化和韧化协调发展的高强轻集料精细化设计目标，获得关键制备技术，丰富和完善现有高强轻集料设计与制备方法。

高强轻集料混凝土的发展与应用为装配式构件、超高层建筑、超大跨度桥梁等大型工程建设提供了关键新材料，其轻质和高强的特点不仅有利于减轻结构自重、缩小结构断面、降低工程造价，也有利于结构工程抗震防灾能力的提升和服役寿命的延长，具有显著的技术、经济和社会价值。但是，高强轻集料的自身强度和弹性模量均远低于普通集料，致使高强轻集料混凝土初裂强度高，脆性破坏特征显著。现有高强轻集料的设计理念和生产工艺致使其“比强度”的提升非常困难。.本课题基于高性能轻集料混凝土内部裂纹开展与破坏机制，从轻集料自身的组成-结构-性能及其与水泥石界面过渡区性能两方面出发，提出了堇青石/贝利特核壳结构高强轻集料设计方法。研究了制备工艺参数、核内矿物组成及其比例，以及外壳表层矿物水化过程对高强轻集料性能的影响规律，并阐明其组成和结构变化与宏观性能的内在联系。进一步，采用有限元方法对核壳结构轻集料混凝土的微区应力分布进行了模拟，考察了高强轻集料、核壳结合区，以及外壳与水泥石界面过渡区特性对核壳高强轻集料混凝土受荷破坏过程的影响规律与作用机制，研究结果表明，降低内核中高弹性模量的矿物含量、减小核壳厚度比以及形成核壳界面结合区有利于均匀化轻集料混凝土的微区应力分布，减少应力集中现象。本课题提出了增强增韧协调发展的高强轻集料新设计理论和关键制备技术，这对于丰富和改进现有的高强轻集料设计和制备方法有很大的帮助，也为高性能轻集料混凝土的设计、制备和应用提供了重要参考依据。