流变学参数表征湿喷混凝土工作性研究进展

Research Progress of Rheology Parameters Characterizing Workability of Wet-mix Shotcrete

为提高工作性对湿喷混凝土施工性能(可输送性、可喷性)的指导作用,归纳了现有各种技术规范的工作性要求,回顾了流变特性与可喷性相关性研究进展,探讨了流变性能时变机制,总结了时变模型发展现状。结果表明,坍落度无法协调可输送性与可喷性工作性需求矛盾,流变学参数应用效果优于坍落度;屈服剪切应力增加,一次喷射厚度变大,回弹率减小;塑性黏度降低,管道输送压力减小,可输送性变好,但屈服剪切应力、塑性黏度与密实度的相关性尚需深入研究;主流的流变性能时变模型为指数、对数、线性、幂函数等经验公式,应加强有物理意义的模型推导;时变预测模型缺乏有效验证手段,应重点研发速凝体系下湿喷混凝土流变性能的原位评估方法。

In order to increase the role of workability to guide the construction performance(transportability and shootability)of wet-mix shotcrete,the requirements for workability in national technical specifications were summarized.The research progress on the correlation between rheological properties and shootability was reviewed.The time-varying mechanism of rheological properties was discussed.The current prediction models of time-depended variable rheological properties were summarized.The results show that slump could not solve the technical contradiction between transporta-bility and shootability,and rheological parameters were more useful than slump.The yield shear stress increased,the build-up thickness increased,and the rebound rate decreased.The plastic viscosity decreased,the pipeline transportation pressure decreased,which resulted in that the transportability improved.However,the correlation between yield shear stress and compactness,or plastic viscosity and compactness,still needed further research.The time-varying models of rheological properties were mostly empirical formulas such as exponential,logarithmic,linear,and power function.Therefore,the prediction models should be deduced considering more physical significance.The time-varying prediction models lacked effective verification methods,and the focus should be on developing in-situ evaluation methods for the rheological properties of wet-mix shotcrete under rapid setting systems.