Study on edge effects in salt frost scaling tests: Implications for surface degradation assessment

Surface scaling and internal structural deterioration caused by cyclic freezing and thawing exposure are among the most common degradation mechanisms in concrete structures exposed to cold climates. Standard laboratory methods such as the CDF (Capillary suction of Deicing Chemicals and Freeze-thaw) test evaluate surface scaling across the entire exposed area. Severe deterioration can lead to increased edge-scaling, potentially underestimating material performance. To mitigate this, the authors previously proposed a 3D laser scanning method that excludes peripheral zones from surface scaling evaluation. However, due to differing reference areas, direct comparison to standard CDF results is not possible. This study introduces a modified CDF setup using a silicone tray to physically segment the exposed surface, enabling peripheral-free assessment and comparability with 3D scan results. This simple, yet effective approach allows, for the first time, a direct comparison between mass-loss-based and volumetric measurements. The modified test reveals substantial differences between inner and outer zones, depending on cement type and maximum aggregate size. Improved compaction can reduce outer zone scaling. Scaling values (g/m 2 ) from 3D scanning depend on the assumed material density used to convert volumetric loss (m 3 ). Whole-sample densities tend to overestimate scaling, while cement paste densities provide consistent agreement with the modified test. A linear correlation was found between 3D scan-based scaling mass and mean scaling depth, whereas the modified CDF test shows a non-linear trend. These findings highlight significant spatial inhomogeneities in scaling behavior, emphasizing the need to consider edge effects when evaluating freeze-thaw resistance of cementitious materials.