Research on the Distribution Law of Coarse Aggregate and Pore Structure in Shotcrete Based on X-Ray Ct Technology

Abstract

This paper aims to study the influence of the spraying process on the distribution law of concrete coarse aggregate and pore structure. In the paper, X-ray Computed Tomography scans are used to study the coarse aggregate distribution and pore structure of the preparation of shotcrete, high-temperature curing shotcrete and shotcrete with MWCNTs. The distribution pattern of coarse aggregate and pore of shotcrete is obtained. The results show that: the coarse aggregate loss of shotcrete is serious within 30 mm from the wall and the coarse aggregate increases significantly in 30 ~ 70 mm. The addition of 0.03% MWCNTs increased the coarse aggregate of shotcrete by 36.63%.within 30 mm from the wall, it can also effectively increase by 54.38% and the coarse aggregate of 5 ~ 7 mm increased the most. The number of shotcrete pores decreases with the increase of pore diameter. The proportion of small pores is up to 85%, the proportion of large pores is only 2%, but the volume of large pores reaches 87%. The addition of 0.03% MWCNTs can reduce the number of small pores in the shotcrete and reduce the mean pore diameter, resulting in a decrease in the porosity of the shotcrete. When the curing temperature is 80℃, the porosity of shotcrete increases, and the pores decrease due to interconnection. The pores around the coarse aggregate account for over 70% of the total porosity, with pores larger than 1mm accounting for 75%. This paper has a good reference value for the development of shotcrete and the selection of coarse aggregate in the actual working conditions.

Keywords: CT scan, shotcrete, coarse aggregate, Porosity, MWCNTs