Study On The Rheology And Pumping Process Of Fresh Concrete Based On DEM

Concrete pumping equipments are widely used because of their perfectperformance such as high construction efficiency, large construction scope, andreliable construction process. However, concrete pumping equipments have a series ofproblems, largely influencing the advanced development of their advantages. Theseproblems are mainly: blockages in concrete pumping process often appear; pumpingpipe, especially the bents, easily wear in pumping process and so on. The study on themechanical properties of fresh concrete is the key for the solution of the blockage andwear of pipe in pumping process. Recently numerical simulation has been a main wayfor the study of rheology of fresh concrete. Discrete element method (DEM) has anatural advantage due to discrete body characteristics of fresh concrete. This paperhas done a lot of work to study the feasibility and validity of studying flow behaviorof fresh concrete using discrete element method simulation.In this paper, the DEM models of fresh concrete were established based on PFC2Duser define model platform which can describe microstructure of fresh concrete byintroducing rolling friction mechanism and liquid bridge model. The design of therolling friction model was verified through the simulation of single particle motion.An experimental research on granule piling process was done to study the effect ofstorage height and opening width on soybean piling morphology, Soybean pilingprocess simulation was done based on the different discrete element models and theresults show that the introduction of rolling friction mechanism would help to makeDEM more accurate to simulate soybean a piling process. The simulation of rheologyof fresh concrete was done using DEM based on slump test, L box flow test, V boxflow test, U box flow test, break-dam test, rotating viscometer test and lifting sphereviscometer test etc. And the results of simulations were in a good agreement withreported results and experiment results done in this paper. Flow characteristic of freshconcrete in pipe was studied and pressure loss calculation method was built. Blockagemechanism of pipe in pumping process was studied and the main influence factorswere studied based on DEM simulation. Wear mechanism of bent when pumpingprocess was studied, and the effect of pumping velocity, pipe bend, shape ofaggregate on wear of bent was studied based on DEM simulation.The results of this study show: DEM introducing rolling friction contact model would be more correct to describe the interaction of aggregate in fresh concrete; DEMcan simulate the rheology characteristics of fresh concrete using Reasonableparameters; DEM can simulate the flow characteristic of fresh concrete in pipe andthe interaction of pipe and fresh concrete. As a new research method in the field ofrheology and pumping behavior of fresh concrete, the exploratory work in this paperwould offer a valuable research method.