Mix Proportion Optimization Design And Durability Research Of C55High Performance Concrete

By the example of Heiyagou2#extra-large bridge of the highway from Hebei Baodingto Fuping City, the feasibility of coarse aggregate technical indexes preparing for C55concrete is systematically analyzed, and the mix proportion design is given, the mechanicalproperties, durability and dry shrinkage performance of C55high performance concretehave been tested and studied in this paper, specific work and achievements are as follows:(1) The technical indexes of coarse aggregate are studied systematically in the variousindustry standards and national standard, the standard test is also compared. Combining thegranite coarse aggregate technology index and testing results in engineering, its applicationfeasibility in the C55concrete is analyzed, and the demand of concrete aggregate limit isachieved of which the granite aggregate in the aspect of rock strength, robustness andalkali-aggregate activity. The requirements of preparation of the C55high performanceconcrete technology is also satisfied in the grading, mud content and clay lump content,sulfide and sulfate content, crushing value, etc. The existing technology and testing resultsshow that the granite aggregate can be used in the preparation of C55concrete strengthgrade.(2) Through theoretical analysis and test methods, the main factors, such as the amountof cement, gelation system, aggregate system and varieties of water reducing agent of themix proportion of concrete are studied, for the influence of the C55high performanceconcrete workability and mechanical properties. On this basis, the mix proportion ofconcrete is put forward, and the optimization of the mix proportioning of the recommendbenchmark C55strength grade concrete is put forward.(3)The influence of electric permeability of concrete is researched by the electricpermeability test.The result is proved that mixing fly ash and silica fume can improve theelectric permeability of concrete.Concrete freeze-thaw cycle test results show that thegranite satisfies the requirement of frost resistance of concrete.(4) The effect such as the gelling material and different kinds of coarse aggregate onthe dry shrinkage deformation is analized.With the same proportions for different lithology ofgranite and limestone, the concrete drying shrinkage rate after3days is basically the same. In the early stage, the single doped silica fume concrete shrinkage rate is bigger, in the otherhand, when mixing fly ash and silica fume it is much bigger after7days.