*2.1. Dataset*

The dataset constructed in this paper consisted of 6952 RGB images with a 200 × 200 px resolution of concrete cracks (1304), concrete spalling (1100), concrete efflorescence (1029), and non-defective background (3519). Cracks and background images were extracted from the dataset established by the authors of [52].

More than 1200 images of Moroccan bridges representing decks and piers with concrete spalling and efflorescence were collected and processed according to the same experimental setup and procedure in [52]. The images were captured using two 20-MP consumer digital cameras with 5 mm of focal length, a sensitivity of 100 ISO, and a maximum resolution of 5152 × 3864. They were gathered at varying distances from bridges and a maximum 8× optical zoom was applied. Moreover, the images were taken under different weather and lighting conditions, and a flash was used to illuminate the dark bridge areas containing defects. It is noteworthy that the original images have not undergone any processing operations other than the manual cropping using the inbac tool [53].

The dataset in [52] was expanded with the concrete spalling and efflorescence classes, and the resulting dataset is publicly available at [54] for academic purposes.

Various colors, textures, surface conditions of concrete and defect representations were included in the constructed dataset to cover the variation of defect appearance, extent, and severity level in the real world of bridge inspection. Figure 2 presents sample images of the proposed dataset.

**Figure 2.** Sample images of the constructed dataset (row 1: concrete cracks, row 2: concrete spalling with exposed reinforcement, row 3: concrete efflorescence, row 4: different representations of the non-defective background class).
