Mix Proportion Optimization Design Of High Performance Concrete With Compound Mineral Admixtures

In the field of high-performance manufacturing, compound mineral admixtures are becoming more and more important. However, there is no standard mix proportion design method for high-performance concrete which contains more than two kinds of mineral admixtures. To find out the better mix proportion design method, A admixture (SS:FA:SF=3:5:2) and B admixture (SS:GGBS:FA=1:2:1) are used to make C40 and C50 high-performance concrete, when the overall calculation method is optimized for the mix proportion design. The main contents in this paper are as follows:(1) Optimize the mix proportion of high-performance concrete with compound mineral admixturesThe total amount of cementitious material and the sand ratio are relatively high when the overall calculation method is used for mix design, and they are solved by correcting the formulas of water content and sand ratio withγ1 andγ2, respectively. In order to ascertainγ1 andγ2, the cementitious material consumption and the sand ratio are adjusted according to the concrete compresstive strength. The results shows that, when A admixture is used as cement replacement, coefficientγ1 ranges between 0.83 and 0.87, coefficientγ2 ranges between 0.90 and 0.92; when B admixture is used as cement replacement, coefficientγ1 ranges between 0.90 and 0.92, coefficientγ2 ranges between 0.90 and 0.92.(2) The compressive strength testThe compressive strength of concrete, which is made according to the optimized mix proportion, meets the design requirement; And with the amount of mineral admixtures increases, the compressive strength decreases; Compared with the benchmark concrete, the compressive strength of concrete with A admixture is higher, the compressive strength of concrete with B admixture is higher only when the admixture amount is less than 20%.(3) The durability testWhen the concrete is made according to the optimized mix proportion, its anti-chloride ion penetration increases obviously; But the carbonation resistance of concrete with A admixture reduces, the carbonation resistance of concrete with B admixture improves.(4) Analysis of the concrete pore structureThe mercury injection method test results show that the microstructure of concrete improves when the mix proportion is optimized, the average aperture are a bit lower; The pore structure of A admixture concrete is more dense.