CFD Simulation Of Aggregates Segregation In Fresh Self-compacting Concrete

Segregation resistance is an important index for evaluating the working behavior of fresh concrete.Self-compacting concrete is easier to segregate because of its high fluidity.Because of the invisibility of slurry,the aggregates distribution of concrete is usually studied by experiment or cutting test blocks to obtain two-dimensional images.It is not only time-consuming and laborious,but also the two-dimensional data can not fully represent the overall distribution of three-dimensional.With the development of computer science,numerical simulation can accurately observe the aggregates movement and distribution of concrete from three-dimensional space.Based on the principle of GMO(General Moving Object)in computational fluid mechanics,this paper regards fresh concrete as a two-phase medium of coarse aggregates and mortar,and the mortar is simulated by Bingham fluid model.The main research work is as follows:(1)Considering the real shape of aggregates in self compacting concrete,threedimensional aggregate stochastic modeling is realized.By simulating the movement of aggregate in visualized fluid carbomer gel,the feasibility of GMO method in studying the movement of aggregates in mortar is verified.(2)The factors affecting the movement of single coarse aggregate in mortar are studied from the aspects of rheological parameters,size and shape of coarse aggregates.The results show that the yield stress of mortar,the particle size and shape of coarse aggregate have significant influence on the settlement and velocity of coarse aggregate,the change of mortar viscosity does not cause the obvious change of settlement,but has a significant effect on the settlement velocity.(3)The movement behavior of coarse aggregates in mortar of three groups of self compacting concrete with different gradations is studied.The results show that the segregation behavior of different coarse aggregate gradations is different under the same conditions,but it still shows certain regularity,among which the gradations with less large size aggregate and more small size aggregate are relatively stable.