Experiment on C40 Machine-made Sand Concrete with Combined Admixture of Limestone Powder and Substandard Fly Ash

摘要

The combined admixture of limestone powder and substandard fly ash for the preparation of C40 machine-made sand concrete were studied. The results show that the C40 machine-made sand concrete prepared with the combined admixture of limestone powder and substandard fly ash has very good workability, with a 60min slump loss of less than 15mm. The combined admixture of limestone powder and substandard fly ash has very good filling effect and crystal nucleus effect, which makes hardened cement paste structure and interface structure more compact. The chloride ion permeability coefficient of machine-made sand concrete at 28d are less than 182×10~(-14)m~2/s, showing that the C40 machine-made sand concrete has good resistance to chloride ion permeation. It can be seen from SEM and energy spectrum technique that the structure of machine-made sand concrete is compact, and the C-S-H gel in the concrete has low calcium-silicate ratio.