Pumping Performance Analysis Of High Strength Machine-made Sand Concrete Based On Discrete Element Simulation

With the fast development of economy,our country building structure gradually towards the top,the complication such as direction,at the same time also faces a more stringent engineering condition and the construction of more complicated environment,a number of such new changes and new requirements that common concrete have been unable to meet the demand of construction,to farther improve the performance of concrete.In addition,the traditional river sand is increasingly exhausted,and machine-made sand has gradually become a reliable substitute for it.Different from ordinary concrete,machine-made sand concrete also has high fluidity and abundant raw materials.However,the test method of rheological parameters of ordinary concrete can not accurately reflect the working performance of high strength machine-made sand concrete.At the same time,pumping concrete construction technology has been widely used,the mechanism of sand concrete pump is also faced with high pressure,long distance and bifurcation is more complex and severe engineering conditions,then also brought a lot of engineering problems,such as segregation,tube plugging,unclear,shall not apply to the calculation theory and the pressure loss in the process of pumping more severe problems.The calculation formula of pumping pressure loss in the current code has doubts about the applicability of machine-made sand concrete,and it is difficult to test the pumping pressure loss of machine-made sand concrete in the actual construction process.Therefore,it is of great significance to use the discrete element numerical simulation method to analyze the rheological properties and pumping pressure loss of machine-made sand concrete.Based on the high end of town Hector highway zhai river bridge piers high strength pumped concrete mechanism sand as the research object,the mechanism of a large number of sand concrete mixture ratio test,on the basis of using the discrete element software PFC3D experiment of mechanism sand concrete slump and the pumping process is simulated,and the main research contents and research results are as follows:(1)a large number of concrete mixture ratio test,research and analysis of sand ratio,water cement ratio,sand mechanism and the influence factors,such as dosage of fly ash concrete slump,the relationship between degree of extension performance,the study found that when the water cement ratio of 0.3 ～ 0.32,sand ratio around 0.4,the dosage of fly ash 60 kg/m after high strength mechanism of sand concrete working performance is best.(2)The PFC3D discrete element software was used to simulate the slump test process of mechanized sand concrete.The relationship between the variable parameters of concrete mixing flow and slump and dilatancy was analyzed,and the rheological parameters of the concrete mixture used in the field were obtained through fitting analysis,which provided a parameter basis for the subsequent research on the pumping pressure loss of concrete.(3)using discrete element software PFC3D simulation mechanism of sand concrete in different pumping pipe conveying process,the different mixing proportion of concrete with different mixture speed in various pumping pressure loss in the pipeline,analyzes the pumping pressure loss and concrete mixing,pumping speed,pump pipe type changed parameters of logistics,as well as the relations between the mix proportion;It provides a reference for field pumping process design and equipment selection.