Study On Rheological Property And Pumping Pressure Loss Of High-performance Concrete

In recent years, buildings have advanced toward to higher, more complicate and larger structures. Besides, the service conditions and construction environment of buildings have also become more special and tougher. These new challenges put forward severe trial to performance of concrete. Against this background, high performance concrete(HPC) was developed, and has become development direction of concrete in the future. Possessing high fluidity and viscidity, HPC is different from common concrete. So the traditional test measurements for common concrete cannot accurately reflect HPC’s workability. Meanwhile, with the development of automated construction, pumping concrete construction technology has been widely used. HPC’s pumping work is conducted under more complicate and tougher condition, such as high pressure, high height, long distance, bifurcation. So some pumping construction problems have come out, such as segregation, casing cap, fuzzy calculation theory, and serious pumping pressure loss. At present, the applicability of code formula for calculating pumping pressure loss to HPC is controversial. While test of HPC’s pumping pressure loss in a real pumping condition is expensive, the discrete element simulation studies on HPC’s rheological property and pumping pressure loss have significance.The paper takes fresh HPC as research object and use PFC2 D software to simulate. The major research contents and corresponding results are as follows:① Summarize the influence factors on pumping pressure loss. Through the practice project research on HPC’s pumping pressure loss, a comparison is carried out between formula of code and in-situ measurement. The result show that, the pumping pressure loss of HPC’s per unit length in horizon pipe by in-situ measuring is almost three times bigger than the calculation value, the total pumping pressure loss by in-situ measuring is almost one times bigger than calculated value of code formula.② According to HPC’s constitutive relation and algorithm of element’s contact parameters, the discrete element model was built to simulate HPC’s flow property. On this basis, the method to determine HPC’s rheological parameters was put forward. And through simulating flow text, the reliability of this program was verified. Researches show that: relative extension area(Γc) is mainly influenced by shear strength(fs), the relative flow time(Rc) is influenced by shear strength(fs) and damping factor(h); Through the HPC’s performance test, the mathematic relations between shear strength(fs) and damping factor(h), relative extension area(Γc) and relative flow time(Rc) were determined.③ The pressure loss of high-performance concretes in horizontal pipe, tapered pipe and elbow pipe were respectively simulated by using discrete element program. Through the studies of pressures and velocities’ of high-performance concretes with different flow property, aggregates’ characteristics of motion and mechanics in horizontal pipe were obtained. And through the study which was carried about the factors’ influences on concrete mixtures’ flow regime and pressure loss, then compare the results with criterion and practical engineering experience, conclusions are drawn. As for horizontal pipe’s pressure losses, there are differences between simulation results and specification evaluations, while the influence regularities are similar. The simulation results are consistent with in-situ measurements. Taper pipe’s pressure loss of the simulation results are about 2~3 times bigger than the corresponding simulation results of the horizontal pipe. Simulation values of pressure loss corresponding to different flow speeds in the elbow pipe are less than the calculated values of specification. Compared with codes of other countries, formula of Chinese code are conservative, but they can’t adapt to various rheological properties and strength of HPC’s pumping pressure loss calculation.