Abstract
This paper describes two visual approaches, namely an area ratio method and a grayscale variation method, to evaluate the effective diffusion depth inside cement-based systems when subjected to external sulfate attack. The former is based on the calculation of the amount of pixels within two areas, namely the area of cross section and the undiffused area, while the latter is per the normalized color variation. Three types of binder, all conforming to the Canadian Standards Association (CSA), were employed to produce three batches of cylindrical specimens, which were immersed in a sulfate-rich environment for up to 12 wk. The effective diffusion depths, obtained by the two visual approaches described here, were compared with the sulfate content found experimentally through chemical titration. The results show that the proposed visual methods can capture the effective diffusion depths inside cement-based systems after exposure to sulfate attack. The maximum value ranged from 7.0 to 11.0 mm over 12 wk of exposure. The proposed visual techniques enable a quick assessment to decide whether further repair is warranted.