Study On Workability Of Low Intensity Manufactured-Sand High Performance Concrete

Manufactured-sand is crushed and screened mechanically, the size of which is less than4.75mm.Unlike natural sand, manufactured-sand has characteristics of rougher surface, more edges and poorer particle gradation, so that when it used for preparating concrete of low strength grade, water consumption is relatively large, and concrete mixing is of poor workability and easily to segregate.With the changing of technical indicators of manufactured-sand, the requirements of high performance concrete obtained are met by II changing mixture ratio.In order to facilitate the construction,to explore which features of manufactured-sand have great influence on the workability of concrete, as well as to the manufactured-sand with different characteristics how to adjust the mixing proportion of concrete in order to achieve the purpose of good workability, has great practical value for engineering applications. The main goal of this article is to formulate high performance concrete of low strength grade with good workability. The main content of research is as follows:(1) Analysis of influencing factor of workability of high performance concrete of low strength grade. Combining with requirements of high performance concrete of low strength grade, preliminary analysis of the factors affecting concrete workability, provides theoretical basis for the mix proportion design and experimental analysis.(2) Design and optimization of mixture ratio of high performance concrete of low strength grade.According to the characteristics of workability, mechanical properties and durability characteristics, combining with knowledge of workability, on the basis of a large number of reference literature, and summarizing the existing mix proportion method, mix proportion method of manufactured-sand concrete of low strength grade are designed and optimizationed.On the basis of "regulations of the mix proportion design of ordinary concrete (JGJ55-2011) and the calculation method of mix proportion design of high performance concrete, this paper proposes a new method for mix proportion design---method of powder equivalent volume.In this method, determining water demand per unit volume of various powder, and the ratio which in to the cement water consumption per unit volume, is the equivalent coefficient of powder. In the process of calculating powder equivalent volume, powder volume is multiplied by the coefficient of equivalent size.On the basis of the above mix proportion design method, experiments and analysis were made,which is on the influence of different factors such as the water/cement ratio, powder equivalent volume, water, sand ratio, on workability of high performance manufactured-sand concrete of low strength grade, and determined that when the water/cement ratio0.6,water consumption170L,the powder equivalent volume170L, the sand ratio45%, the workability of concrete mixture is the best.(3) The influence of mineral admixtures and admixture on workability of manufactured-sand concrete of low strength grade.On the basis of the above mix proportion design method, we added mineral powder, HPMC, bentonite, polypropylene fiber, metakaolin, etc.,tested workability of concrete mixing and compressive strength of molding block,and also made experiment test and theory analysis on the conclusion of mix proportion design method based above. And ensure determine the optimum content of admixture, to meet the conditions of good workability and compressive strength of concrete.