混凝土施工过程流变行为及其微结构形成机制

Fresh concrete rheological property affects the construction performance seemingly, essentially it determines the mechanical properties and durability of the structure. The present foreign and domestic research on the durability and the rheology of concrete do not take account into the disturbance effect of construction process on the final structure performance. Based on the above research achievements and the existing problems, take the pumping concrete used widely and self-compacting concrete with special work performance as the research objects, introduced the dynamic behavior during the construction process including transportation, pumping, vibrating, horizontal flow, etc, the rheological behavior and the microstructure formation mechanism of concrete will be carried out. After quantify the key acting forces during the concrete construction process, the rheological properties evolution law of the concrete during the construction process will be disclosed. Considering the construction process of concrete the rheological properties prediction model will be set up. Adopting 3D discrete element simulation and the neutron tracking technology for dyeing aggregate, a new prediction method to predict concrete casting performance will be studied. Use the optical fiber sensor, the CT and low temperature scanning technology to obtain concrete microstructure characteristics during the construction process, considering the hydration contribution rate of the cementitious materials and the reinforcement constraints, take example by the colloid chemistry ,the electric double layer theory, the order-disorder transformation theory and the cluster formation theory, the microstructure formation mechanism of the concrete during the construction process will be disclosed in order to establish the original concrete structure durability evaluation method based on the rheological properties of the fresh concrete. The breakthrough will be attained in the field of the concrete structure durability evaluation quickly.

新拌混凝土流变性能表面上影响其施工性能，实质上决定了结构的力学性能及耐久性能。针对混凝土流变性能和耐久性能研究忽略了施工过程扰动的影响，拟以规模使用泵送混凝土和潜在应用前景自密实混凝土为对象，引入运输、泵送、振捣、水平流动等施工过程动态行为，研究混凝土施工过程流变行为及微结构形成机制。量化表征混凝土施工过程关键环节的作用力，揭示施工过程混凝土流变性能演变规律，建立考虑施工过程的混凝土流变性能预测模型；利用3D离散元模拟与染色骨料中子跟踪技术，提出混凝土可浇注性能预测新方法；采用光纤传感器、CT、低温扫描等，获得施工期混凝土微结构信息，综合胶凝材料水化贡献率和钢筋约束，借鉴胶体化学、双电层理论、簇形成理论、有序-无序转变理论等，揭示混凝土施工期微结构形成机制，建立混凝土施工期微结构与硬化体耐久性的相关性，提出基于流变性能的混凝土实体结构耐久性评价方法，实现对混凝土结构耐久性快速评价的新突破。

课题围绕施工过程关键参数对混凝土流变性能的影响，基于流变参数的混凝土浇筑性能模拟、早龄期混凝土微结构与耐久性相关性等关键技术开展了系列研究，探讨了不同流变模型和流变仪表征与测试混凝土流变性能的适用性，通过关键参数对混凝土流变性能和剪切变形行为的影响研究获得了基于单一变量的混凝土流变性能预测模型，揭示了混凝土剪切变形行为形成机制，提出了混凝土触变性能表征的新方法，模拟了混凝土在自身重力作用下可浇筑性能及缺陷行为，提出采用硬化混凝土3天气泡特征参数来快速、简便评价混凝土抗冻性能的技术指标。