多因素耦合作用下高流动度水泥基材料拌合物的剪切增稠效应研究

The preparation of self-compacting concrete according to modern technology could enlarge the application range of high fluidity cementitious materials in modern transportation, ocean and hydraulic engineering. The rheological behavior of high fluidity cementitious materials with shear thickening effect is complex, and the workability are significant to the stability of construction equipment and security of field technicians where high shear rates are applied such as mixing and pumping. ConTec Viscometer would be used in this research to obtain rheological properties such as yield stress and plastic viscosity of fresh cement paste, mortar and concrete by means of rheological function in linear or power type. Empirical rheology test would be also performed in order to obtain the empirical rheology parameters such as slump flow and so on. The relationship between yield and slump flow would be proposed. The prediction model of rheological parameters based on empirical rheological properties would be constructed. The variation of shear thickening behavior under single factor would be firstly constructed according to the theory of cluster formation. Furthermore, the hydration process would be considered and the microstructure analysis results would be relied on, proposing the variation of shear thickening behavior under coupled effects of multi-factors such as length-diameter ratio, particle size and volume fraction and so on. The predicting model of parameters characterizing shear thickening behavior under composite effects would be constructed, providing technical support for design and construction of high fluidity concrete.

采用现代技术配制自密实混凝土，能有效拓展水泥基材料在现代交通、海洋以及水利等工程领域的应用范围。具备剪切增稠效应的高流动度水泥基材料流变行为复杂，其在泵送、喷射等高剪切速率条件下的工作性能关系到施工设备的稳定和现场人员的安全。项目使用同轴双筒流变仪，合理选择线性或幂律型流变学方程，获得新拌水泥浆、砂浆及混凝土拌合物的剪切应力和塑性粘度等流变参数。同时进行经验流变性能试验，获得坍落扩展度和T500等经验流变性能参数，借助屈服准则探寻屈服应力与坍落扩展度之间的关系，建立基于经验流变性能的流变参数预测模型。由团簇形成理论揭示单一因素下剪切增稠效应的变化规律，进而考虑胶凝材料的水化进程，依托矿物掺合料微观形貌的分析结果，揭示纤维长径比、颗粒粒径及体积分数等诸多因素耦合作用下拌合物流变参数及剪切增稠效应的变化规律，并构建剪切增稠效应表征参数的预测模型，为高流动度水泥基材料的设计和应用提供技术支持。

开展高流动度水泥基材料流变性能研究，为自密实混凝土设计施工提供技术支持，对于提高海洋资源的开发能力具有重要的理论意义和实用价值。申请项目使用ConTec Viscometer混凝土流变仪对新拌浆体的流变性能进行测试，分别应用线性的Bingham方程和非线性的Herschel-Bulkley方程，通过求解Couette反演问题获取Bingham屈服应力、Bingham塑性粘度、Herschel-Bulkley屈服应力、粘度系数、流动指数等若干流变参数，建立了高流动度水泥基材料的流变参数与经验流变性能的关系。借助团簇形成理论，探寻单一因素影响下拌合物的剪切增稠行为的发展规律，建立拌合物流动指数和粘度系数的预测模型。进而提出高流动度水泥基材料拌合物剪切增稠效应在多因素耦合作用下的预测方法，为拌合物在搅拌、泵送、喷射等高剪切速率环境下的工作性能提供参考依据。