Study On Optimization Of Mix Proportion Design Method Of High Strength Manufactured Sand Self-Compacting Concrete

As infrastructure construction continues to advance,the demand for quality and production of concrete in engineering is on the rise.As a representative of high performance concrete,selfcompacting concrete(SCC)has the advantages of good workability,no need to vibrate,easy pumping and high construction efficiency.But with the decline of the natural sand resources.It is a general trend to use manufactured sand instead of natural sand as fine aggregate of concrete.However,there is no systematic summary of the mix design method for the formulation of highstrength manufactured sand self-compacting concrete(MSH-SCC).High-strength SCC is widely used in buildings and infrastructures that require higher strength,better durability,better protection and better impact resistance.In this paper,we combine the design method based on empirical parameters and aggregate compacting factors to optimize the gradation of the aggregate system in the design process,and integrate the excess paste theory and particle inclusion theory to design the baseline proportions for three strength classes of concrete,C40,C60 and C80.After that,the working and mechanical properties of SCC of three different strength classes were tested with the four parameters of mechanical sand replacement rate,supplementary cementitious material(SCM),sand rate and maximum nominal particle size as variables,and the mechanism of the above variables on the working and mechanical properties of concrete was investigated.After the workability and mechanical properties,this paper investigates the effect of supplementary cementitious materials on the morphology of the interfacial transition zone(ITZ)and hydration products of SCC.After that,the effects of the mechanism sand substitution rate and the maximum nominal particle size on the rheological parameters are investigated to further reveal the mechanism of the influence of the auxiliary cementing materials on the mechanical properties of SCC from the microscopic perspective,and the mechanism of the influence of the maximum nominal particle size and the mechanism sand substitution rate on the workability of MSH-SCC.On the basis of the results of the tests,the grey correlation degree method was used to analyze the influence of the replacement rate of manufactured sand,SCM,maximum nominal particle size and sand ratio on the workability and mechanical properties.The range of mix proportion parameters with good workability is proposed.In addition,two-dimensional and three-dimensional models of SCC workability and mix proportion parameters were established.This model is simplified into an empirical formula,and the SCC mix design method is improved to better guide the mix design of self-compacting concrete with manufactured sand.