The Research On Test For Pressure Bleeding And Properties Of High Flowing Pump Concrete Of C60

High flowing pump concrete of C60 has been widely used in railway, road, bridge and high building, for its desired properties including high strength, long durability and good workability. When high flowing pump concrete of C60 is produced, more water and water reducing agent is used. So it often appears segregation and bleeding. During the construction, people concern about the strength of concrete and the cracking, but doesn't concern about bleeding. In fact, the bleeding of fresh concrete is harmful to surface, inner structures and performance of concrete.In this paper, the indexes of bleeding used in the rate of pressure bleeding, as well the other indexes of workability, such as slump and L fluidity were tested. By using 42.5MPa ordinary Portland cement and water reducing agent, high flowing pump concrete with strength class of C60 and slump of 180mm is produced. Studies are carried out on the influence of the raw materials and the made parameters upon the rate of pressure bleeding of high flowing pump concrete of C60. And the measures to prevent bleeding were provided. According the result of the experiments, It can be concluded as following:1)The rate of pressure bleeding of concrete using river gravel with larger maximum size and bad gradation is larger than it using crushed stone with smaller maximum size and good gradation. When high flowing pump concrete of C60 is produced, it is better to adopt coarse aggregate which maximum size of is not more than 25mm, to adopt optimum gradation that is recommended in the specification and closed to the middle of gradation curve as possible. 2)The larger the amount of fine aggregate is and the smaller fineness modulus is, the smaller the rate of pressure bleeding becomes. As fine aggregate, it's better to adopt hard and good gradation II Region river sand and artificial sand, of which fineness modulus shouldn't be less than 2.6 and percent of mud shouldn't be more than 1.5%. 3) With the increasing using of the water reducing agent, the rate of pressure bleeding will be great. When the amount of the water reducing agent reaches 1.4%, there will be bleeding on the surface of the concrete.4) As fly ash and silicon fume can effectively reduce the rate of pressure bleeding, it's better to adopt high quality or Class I fly ash, and the amount of fly ash shouldn't be more than 25%, and the optimum amount of silicon fume should be 5~10%. 5) With other conditions unchanged, the rate of pressure bleeding...