Study On Self-compacting Combined Aggregate Concrete Mechanical And Durability Properties

The coarse aggregate of combined aggregate concrete be composed of the naturalstone and ceramic composition in this pape, both the advantages of ordinary concrete andlightweight aggregate concrete.Combined aggregate concrete is widely used in high-rise,high prestress, ocean engineering and large span bridge engineering. Segregationphenomenon of combined aggregate concrete is one of the main problems existing atpresent, directly affect the mechanical properties and durability properties of combinedaggregate concrete. In this paper, according to the current technical specification forapplication of self-compacting concrete determine preliminary mix of self-compactingcombined aggregate concrete, through the mixture stratification test to study the mixtureheterogeneity, optimization of self-compacting combined aggregate concrete. On this basis,study on effect of water cement ratio, aggregate type and substitution rate of penetrationperformance on mechanical properties, shrinkage deformation, carbonation resistance andresistance to chloride ion penetration of self-compacting combined aggregate concrete, atthe same, study on performance differences of the same strength grade combined aggregateconcrete, lightweight aggregate concrete and ordinary concrete, the main conclusions areas follows:(1) In the experiment of the combined aggregate concrete mixture stratification, theproportion of three layer mixture ceramists and detritus within33%±3%, homogeneity ofmixture is good, from the33%deviation smaller, mixture heterogeneity is better. Theslump extension of L400ceramists prepared self-compacting combined aggregate concreteshould be controlled at550mm~590mm, and the slump extension of L700ceramistsprepared self-compacting combined aggregate concrete should be controlled at550mm~660mm.(2) Compressive strength, tensile strength, axial compressive strength and modulus ofelasticity the basic mechanical properties of self-compacting combined aggregate concretewith the increase in reducing water-binder ratio; at the same water-binder ratio,compressive strength and specific strength from big to small order: common concrete,L400ceramists prepared combined aggregate concrete，L700ceramists prepared combinedaggregate concrete and lightweight aggregate concrete; Tensile strength, axial compressive strength and modulus of elasticity and other mechanical properties of L700ceramistsprepared combined aggregate concrete is greater than L400ceramists prepared combinedaggregate concrete.(3) After7d age, the shrinkage ratio of self-compacting combined aggregate concreteincreased with the increasing water-binder ratio; at the same water-binder ratio, before90dshrinkage rate of lightweight aggregate concrete and ordinary concrete is nearly same, after90d shrinkage rate of ordinary concrete was lower than that of lightweight aggregateconcrete, the shrinkage rate were higher than that of combined aggregate concrete; in C35and C25, shrinkage of lightweight aggregate concrete and ordinary concrete is nearly same,both were significantly higher than that of combined aggregate concrete, in C20concrete,shrinkage rate of combined aggregate concrete and normal aggregate concrete shrinkage islittle difference; shrinkage gap of combined aggregate concrete and normal aggregateconcrete shrinkage is little difference, were significantly lower than that of lightweightaggregate concrete; with logarithm function d=a Ln(t)+b characterization of combinedaggregate concrete and lightweight aggregate concrete after28d shrinkage ratio (d) and age(T) relationship is more appropriate.(4)Carbonization depth, chloride ion diffusion coefficient and electric flux of theconcrete increase with increasing water-binder ratio; at the same water-binder ratio,carbonization depth, chloride ion diffusion coefficient and electric flux of lightweightaggregate concrete is maximum; Carbonation depth of L700ceramists prepared combinedaggregate concrete and ordinary concrete is the smallest, but its chloride ion diffusioncoefficient and the electric flux center; chloride ion diffusion coefficient and the electricflux of cylinder compressive strength (apparent density) lower light aggregate preparedcombined aggregate concrete is smallest, but its carbonation depth center. In the conditionof same strength grade, carbonization depth, chloride ion diffusion coefficient and theelectric flux of the concrete from big to small order: ordinary concrete, combinedaggregate concrete and lightweight aggregate concrete.