| Due to the characteristic of coarse aggregate and construction technology and the development of C40 high performance concrete in Hei Longjiang Province,the investigation on the shrinkage of C40 HPC is getting imperative. In this paper, effects of species of mineral admixture and their dosage on the compressive strength and dry shrinkage of C40 HPC were discussed in detail. The main achievements can be summarized as follows:The design of orthogonal experiment was used to investigate the properties of fly ash concrete. By applying the range analysis and variance analysis, the optimal value of the content of binder, water cement ratio and dosage of fly ash as well as the optimal mix proportion of HPC were confirmed.The compressive strength of four groups C40 HPC with fly ash, fly ash + Calcium-added granulated cinders, fly ash + Calcium-added fly ash and fly ash + zeolite powder was investigated. By regression analysis, the relationship between the compressive strength of HPC and the content of mineral admixture was set up. The dry shrinkage of four groups C40 HPC with fly ash, fly ash + Calcium-added granulated cinders , fly ash + Calcium-added fly ash and fly ash + zeolite powder was studied. The dry shrinkage of all specimens was measured till 90 days. The basic laws of effects of species and content of mineral admixture on the shrinkage of HPC were deduced. The relationship between the species as well as the content of mineral admixture and the drying shrinkage of C40 HPC at 90 days was given.With the help of scanning electron microscopy (SEM), the microstructure of hardened cement paste with different mineral admixture, which were fly ash, fly ash + Calcium-added granulated cinders, fly ash + Calcium-added fly ash as well as fly ash + zeolite powder, was analysed. By using SEM analysis, the effects of curing ages on the microstructure of HPC were studied. The changes of microstructure can explain the difference in dry shrinkage of different mix proportion in C40 HPC. |
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