Study On Optimization Method For Mix Proportion And Performance Of Concrete Based On Maximum Density

The green and high-performance concrete is a trend for the development of concrete.Fly ash,slag and other mineral admixtures,recycled coarse and fine aggregate materials more and more widely used,as a result the traditional concrete with 4 components turn into multi components hybrid materials.So,the adaptation of traditional mix proportion design method is worse and worse.This is due to some parameters in it are determined by the empirical table with intense subjectivity,trial-mix and adjustment need to be done continuously by experience,therefore the performance of concrete can’t be ensure.For the mixed material,it is the immediate and fundamental way for rising its performance that improve the compactness and realize a mixture with homogeneous and void less.Currently,methods for mix proportion design of concrete base on maximum density had been proposed,but there still been some problems include considering single,completing maximum density of aggregate merely,and applying in practice hardly.In order to realize the design of the biggest compactness for concrete from three views of cementing materials,aggregate and paste-aggregate ratio.Testing on relation of the density for cementing materials with the amount of admixture,modifying the compaction-interaction coefficient in compressible interaction packing model(CIPM),and presenting coefficient of rich for paste volume based on the density of aggregate are studied in this paper,on the basis,the mix proportion design method based on the coefficient is proposed.The main content of this paper include:(1)On the base of reviewing the theories and optimization method on account of maximum density of mix design,the coefficient of rich for paste volume has been proposed combine with the absolute volume method and definition of density.It can describe the balance between the aggregate volume and paste volume,reduce the scale of value by experience and realize the design of mix theoretically.(2)In order to achieve the maximum compactness of cementing materials,by testing and calculation analyzed with TOUFAR model,the transformation law between proportion of admixture and density of cementing materials,therefore,studied the relationship between void volume and water requirement of cementing materials at normal consistency during the binary system(fly ash or slag with cement)and ternary system(fly ash,slag and cement).The result shows that the density of system reduce as the rising of admixture proportion in binary system,but the density is significantly better than binary system in the ternary system.And the density is stable when the admixture proportion for fly ash and slag are 20% and 25% respectively.(3)For calculating the aggregate density of the system,and find the maximum density as the percentage of coarse and fine aggregate is different,studied and analyzed the CIPM particle model have be done.Experiment found there are significantly difference between the model value and measured value of mixture density,and the former is less than the latter without exception.Using error analysis between them and controlling by least square error obtain the amended compaction-interaction coefficient(28)6.1LeC 、(28)8.0W eC with the help of inverse analysis.And experimental verification of the value shows that it can use for calculating the density of aggregate and it is reliable.(4)On the basis of cementing materials and aggregate density are solved,it is time to optimize the paste volume in concrete using coefficient of rich for paste volume.First of all,experiment that analyze the influence of the coefficient for workability and strength of concrete for concrete contain the different water-binder ratio,shows that slump and compressive strength present the phenomenon which rise gradually and reach the highest point following fall slowly,and the change range of slump is bigger.Further,according to slump and compressive strength determine the optimal value of coefficient,and experimental data indicate the value for C30 and C40 concrete are 1.251 and 1.624 respectively.(5)Employing the optimal value and combine the absolute volume method and BOLOMEY formula which use for calculating the compressive strength of concrete,a new mix proportion optimization method proposed,and explain its calculation process in detail.