Characterization of permeability of seawater iron tailings mortar based on inter-pore connection

Abstract

Permeability is an important factor affecting the durability as the connection between pores provides a channel for water and ion permeation. However, the mechanism governing the influence of inter-pore connection is still unclear. This paper quantitatively calculates the connectivity and complexity of inter-pore connections based on pore structure scan images, and investigates the effect of different aggregates on the resistance of mortar to chloride-ion migration. Seawater ordinary mortar (SOM) and seawater iron tailings mortar (STM) were prepared. Pore scans and tests for chloride migration coefficient and chloride-ion content were conducted. Based on the maximum Feret diameter of the pores, the complexity index, Kci, was defined to characterize the complexity of inter-pore connections, and this extends existing calculation methods from one-dimensional to two-dimensional in nature. However,the complexity index correlates with the chloride migration coefficient and chloride-ion content well for seawater ordinary mortar only but not for seawater iron tailings mortar. Therefore, the critical image diameter, dic, was defined to characterize the connectivity of pores. This also overcomes the shortcomings of the MIP method, which does not give the spatial pore distribution. Last, the modified complexity index, Kmci, which modifies the complexity index using the critical image diameter, was presented. It is shown to correlate with test results well for both seawater ordinary and iron tailings mortars. Replacing Kci with Kmci greatly improves the linear correlation of complexity of inter-pore connection with chloride penetration resistance for seawater iron tailings mortar, with the correlation coefficient R increasing from 0.45 to 0.88.