Study On Mix Proportion Optimization Design Of High Performance Concrete Based On The Resistance To Chloride Ion Permeability

The calculation of mix proportion of high-performance concrete has big differences incomparison with common concrete, so it is necessary to find a suitable method for the mixproportion of high-performance concrete. Taking the resistance to chloride ion permeability asthe durability index, a better mix design method should be studied out for the strength grade ofC30、C40、C50、C60high-performance concrete, when they are in the environment of marineand de-icing salt. Chloride salt can cause reinforced concrete structure degradation or evenpremature failure. With the existing research results of our team, adopte the high-performanceconcrete durable mix proportion design method, which based on the overall calculation method,to prepare the different strength grades from C30to C60high-performance concrete. Then aftera series of experimental analysis, optimize the mix proportion design method. The maincontents and results are as follows:1. Adopte the high-performance concrete durable mix proportion design method, whichbased on the overall calculation method, to prepare the different strength grades from C30toC60high-performance concrete. Then test its compressive strength and the resistance tochloride ion permeability. The results show that the electric flux through concrete is greater thanthe standard requirements, which needs to be improved; Its compressive strength was alsolarger, and the surplus value of the compressive strength decreased with the increment ofconcrete strength grade. Study states that the problem of this mix proportion design method arethe large dosage of binding material,water consumption and sand ratio.2. Introducing correction coefficient γ to correct water use formula of the overallcalculation method, preliminary optimize the mix proportion, prepare different strength gradesfrom C30to C60high-performance concrete. Test results show that the compressive strength ofdifferent strength grades of concrete compared with the compressive strength before thepreliminary optimization has declined, and decline fairly.According to the law of the surplusvalue of compressive strength before optimized and compressive strength after preliminaryoptimized, it can be infer that, in view of the C30to C60high-performance concrete, the lowerthe strength grade, the correction coefficient can be reduced. Resistance to chloride ionpenetration test shows that the high-performance concrete of different strength grades, thehigher strength grade, the more electric flux obvious decline. That is, in view of the C30to C60high-performance concrete, the lower the strength grade, the values of correction coefficient γcan be reduced.3. When determine the water correction coefficient: γ_C30=0.83⁰.86， γ_C40=0.86⁰.89， γ_C50=0.89⁰.93， γ_C60=0.91⁰.95, use compound admixture of ground steel slag powder∶flyash∶silica fume=4∶5∶1to verify this optimization of mixture ratio. It can obtaine a goodoptimization effect. The results show that the compressive strength meet the design standards, the resistance to chloride ion permeability reaches the standard quality requirements.4. The results of mercury injection method test indicate that the microstructure of concreteimproves when the mix proportion is optimized, the average aperture is a bit lower; The higherstrength grade of high-performance concrete, the more compact its pore structure.