The Research On Preparation Of Environmentally Friendly Ultra High Performance Concrete With Low Cost

At present stage, the popularization and application of UHPC manufactured all over the world had been greatly limited, because the quantity of cement per meter cube concrete was very large and the cost was greatly increased due to coarse aggregate, moreover, its working performance, especially its fluidity was poor because of its extremely small water binder ratio.So a systematic experimental research on the issue that the application of UHPC (Ultra High Performance Concrete) in practical projects had been restricted by the obstacles of UHPC in terms of its economical efficiency and working performance at present, was conducted.Firstly, the influence of such factors as river sand, silica fume, water binder ratio and curing system on the compressive strength and fluidity of UHPC was deeply discussed. It optimized the component proportion ratio of the materials of UHPC, so as to get the best mixing proportion.Then, the impact of aggregate on various specifications of UHPC was systematically analyzed, thus concluding that the categories of aggregate, impurities in river sand, the largest particle diameter, and the grading of river sand exert influence on various specifications of UHPC. By the use of Grey Linkage theory, this paper maked a detailed analysis of the influence of the grading of river sand on the compressive strength and fluidity of UHPC, with the conclusion that sands with particle diameter within 0.16 ~ 0.315mm exert the most influence on working performance of UHPC under the conditions of standard curing, heat water curing and high temperature curing.Last, the impact of adding fly ash on the working performance of UHPC had studied. With the prerequisite of the best mixing proportion, adding appropriate amount of fly ash had significantly improved the fluidity and long-term strength of UHPC; meanwhile,"cement functional factor"was proposed that the influence of fly ash on the utilization rate of cement in UHPC could be analyzed by, and this parameter would serve as a quantitative basis for the environmental performance of UHPC.To reduce the cost, cement had been replaced by fly ash, quartz sand by river sand and commonly used copper plated steel fiber in laboratory by ordinary steel fiber; to improve fluidity, by using superplasticizer and adding fly ash to establish ternary gelation system, the low-cost and environmental friendly UHPC with good fluidity and compressive strength of above 120MPa had been successed by using natural grading river sand whose particle diameter was below 2.5mm and equivalent fly ash which had taken the place of 20% cement.