2025 Volume 81 Issue 6 Article ID: 24-00228
This paper reports the results of various experiments conducted to clarify the mechanism of pinholes and blistering in the waterproof layers of road bridge concrete decks. In the experiments, pinholes and blisters in the waterproofing layer were reproduced using concrete slabs with different concrete pore structure and moisture contents, and multiple experiments were conducted. As a result, it was clarified that pinholes occur when the air inside voids located at a very shallow position in the concrete surface expand due to the heat of the waterproofing material, causing the air to be released to the surface through the pores. Regarding blistering, it was clarified that it occurs when moisture inside the concrete moves to the surface during the process of evaporation to the exterior due to rising atmospheric temperature, where it turns into water vapor and expands in volume. Furthermore, it was shown that pinholes and blistering tend to occur more easily in concrete with many pores than in dense-surfaced concrete, and that these phenomena can be suppressed by constructing a denser surface layer.
