Research On Preparation Of Self-compacting Ultra-high Performance Concrete(UHPC) And Its Properties

Ultra-high Performance Concrete(Referred to as UHPC) is a kind of cement-based composite materials which component material particle gradation is the best, and contains a certain proportion of reinforced materials with tension toughness that are fine short steel fiber or organic fiber. What’s more, with traditional concrete and High Performance Concrete(Referred to as HPC) compared, its strength and durability can be improved greatly.In this paper, the main work is the optimization of raw materials of UHPC. The specific process includes: through the compatibility experiments of series of water-reducers with polycarboxylates and Jiangxi local cement, silica fume to determine the Jiangxi local cement and water-reducers, to choose the best performance of fiber(steel fiber, organic fiber or complex doped) in order to improve the toughness of concrete, to select the fine quartz sand and to use solid waste material(ground quartz powder) to replace cement or silica fume. And then we need to determine and optimize the mixture ratio, next use common formulation techniques to formulate the compacting Ultra-high Performance Concrete with its compressive strength of not less than 100 MPa, tensile strength of not less than 15 MPa.The results show:The first, using the preferred raw materials which contain the local ‘yangfang’ brand cement in Jiangxi, ‘Sanrui’ SP-600-02 models powder polycarboxylate type superplasticizer, Jiangxi river sand(particle size less than or equal 2.36 mm, clay content of 2.4%) and corresponding mixing ratio(water-cement ratio is 0.18, the cement: silica fume: river sand is 1: 0.25: 1.1), we can formulate out the UHPC which can meet 100 MPa compressive strength, 5 MPa tensile strength and self-compacting requirements.The second, ground quartz powder replacing silica fume can produce good results: ground quartz powder replace the amount of 10%, not only strength achieve objectives and requirements, but also to meet UHPC self-compacting effect.The third, fiber can cause a slight decrease compressive strength, and tensile strength will enable greatly enhanced to improve the toughness of UHPC, in which a single steel fiber(2% cement content by mass) is more effective than single-doped organic fibers. Complexing steel fiber and aramid chopped fiber(total content 2% by mass of cement, which accounted for 1.5% of steel fiber, aramid short cut fibers for 0.5%) can make the best toughening and the best tensile strength and flexural properties. Fiber can have some impact on the UHPC compressive strength and tensile strength, but the impact on the tensile strength larger, reinforced UHPC toughness.