Influence of cracking on chloride diffusivity and moisture influential depth in concrete subjected to simulated environmental conditions

Abstract

Although Fick’s second law is always applied to predict chloride profiles in concrete due to its simple mathematical expression, it takes no consideration of cracking affects. However, concrete structures are not always crack-free, therefore clarifying the internal environment and relevant chloride diffusivity in cracked concrete is essential to predict chloride ingress since cracking always has a negative impact on concrete durability. In present work, series of experimental investigations on two coefficients (i.e., chloride diffusion coefficients and moisture influential depth) affecting chloride profiles at cracked concrete were carried out. For the investigation of chloride diffusivity, Electron Probe Micro Analysis (EPMA) was used to extract the accurate chloride concentration via area scanning, line scanning, and point scanning. In addition, specimens with two different types of mix (i.e., ordinary concrete and blast furnace slag concrete) and with two different exposed times (i.e., 30days and 60days) were tested for different surface crack patterns. Crack width investigated in present work ranges from 0.05mm to 0.20mm. Furthermore, the effective chloride diffusion coefficient for cracked concrete was calculated under the law of flux conservation by taking consideration of both crack patterns and concrete mixtures. On the other hand, for the investigation of moisture influential depth, a series of laboratory experiments with different cracking specimens were conducted to clarify the influence of external artificial weather on the relative humidity distribution in concrete crack, including periodic changing of external relative humidity and temperature, fog and rainfall simulation environments, the drying phase after precipitation.