Study On The Influence Of Thixotropy Of Fresh Concrete On Transportation Process

As the main load-bearing structural material,concrete has the advantages of good durability,convenient construction and low cost,so it is widely used in various fields of the construction industry.The fluidity of fresh concrete affects the construction quality,and even the mechanical properties of hardened concrete.During the long-distance transportation of fresh concrete,with the increase of transportation time,the cement hydration will affect its flow performance and cause slump loss.Therefore,it is of great significance to study the impact of the thixotropic of fresh concrete on the transportation process.Based on the discrete element method,this paper studies the influence of thixotropic of fresh concrete on the transportation process.The main research contents and results are as follows:(1)The physical parameters of manufactured sand and stone used in the test were measured.Based on the discrete element numerical simulation EDEM,the Hertz Mindlin with JKR model is used as the contact model of fresh concrete particles,and the discrete element method of fresh concrete is established;It is verified by slump test that the discrete element numerical simulation EDEM can be used to study the flow performance of fresh concrete;(2)The relationship of hydration particles,flocculation particles and discrete particles with transport time was established;The relationship between particle contact surface energy en and transport time is established,and a thixotropic discrete element method for fresh concrete is proposed.The slump test of fresh concrete mixed at different times is carried out,and the numerical simulation and test results are compared to verify the effectiveness of the thixotropic discrete element method;(3)Based on the thixotropic discrete element method,the influence of thixotropic on the concrete transportation process is studied.Through the real-time monitoring of the movement trajectory of fresh concrete particles in the mixing drum,it is found that with the increase of transportation time,the fluidity and discharge uniformity of fresh concrete gradually decrease;Taking the fresh concrete transported for 20 min as an example,the uniformity of discharge can be improved by accelerating the rotation of the mixing drum at 5rpm for 50 s before discharge.