Research On Mix Ratio Parameter Optimization Of Concrete Based On The Impact Of Manufactured Sand On Rheology

In recent years,the amount of sand and gravel used in construction in China has increased rapidly,and natural sand resources are increasingly shortage,so the replacement of natural sand by manufactured sand is the trend of sustainable development of the future construction industry,However,due to the different lithology of the mother rock and sand-making process,the characteristics of the sand in different parts are obviously different,it is necessary to study the concrete mix ratio method that adapts to the characteristics of the manufactured sand itself.As one of the properties of fresh concrete,rheology have an important influence on the comprehensive properties of hardening concrete materials,but the presence of coarse aggregate makes the rheology of fresh concrete difficult to measure,however,a large number of studies have shown that there is a certain relationship between the rheology of fresh concrete and the rheology of fresh mortar.Therefore,on the basis of rheology of mortar and other parameters of fresh concrete,it is of great theoretical and practical significance to comprehensively ratio the mix of high strength manufactured sand concrete.This paper uses two representative lithologic manufactured sands of granite and limestone in Fujian Province.By calculating the two manufactured sand particle morphology by microscope test,systematic testing manufactured sand characteristic index and calculating mortar water film thickness index,then we came to the following conclusion: The larger the angularity of the manufactured sand,the larger the void ratio,the smaller the bulk density,and the larger the specific surface area,the smaller the mortar water film thickness.Afterwards,this paper studied the effects of manufactured sand characteristics(gradation and stone powder content)and mix ratio parameters(water-cement ratio and polycarboxylate water reducing agent)on the workability of cement paste and rheology,then we came to the following conclusion:The increase of mortar rheological parameters(plastic viscosity and yield stress)reduces the mortar workability parameters(liquidity and consistency).Then,this paper refer to JGJ/T283-2012 "Technical Specification for Applicanti-on of Self-compacting Concrete" and CECS02-2004 "Guide to Design and Construction of Self-Compacting Concrete",and introduces the method of mix ratio parameters of self-compacting concrete,and studies the influence of the manufactured sand mixing ratio parameters(water-cement ratio and polycarboxylate water reducing agent)-stone powder content on the workability of the manufactured sand concrete and the workability and rheology of the sieve mortar,then we came to the following conclusion:The increase of concrete workability parameters(slump and flow)increases the mortar workability parameters(liquidity and consistency)and reduces the mortar rheological parameters(plastic viscosity and yield stress).Finally,this paper uses DOE software to simulate the test results of the manufactured sand concrete mix parameters,and realized the optimization of the mix ratio parameters of high strength manufactured sand concrete.The optimal mix ratio parameters of granite manufactured sand concrete are: water-cement ratio = 0.34,stone powder content = 10.39%,polycarboxylate water reducing agent dosage =1.43%,and the optimal mix ratio parameters of limestone manufactured sand concrette are: water-cement ratio = 0.34,stone powder content = 12.53%,polycarboxylate water reducing agent dosage = 1.55%.