Design and performance evaluation of a novel waterproof adhesive layer for concrete bridge decks

As a key interface in concrete bridge deck systems, the waterproof adhesive layer (WAL) must ensure both water resistance and reliable bonding. In this study, a polymer composite WAL (PCWAL) was developed via hydrophobic modification and fiber reinforcement, guided by central composite design (CCD). FTIR analysis confirmed no chemical reactions among components, while TGA-DSC revealed strong thermal stability with <2% mass loss at 200 °C. SiO₂ and PF modification significantly improved hydrophobicity (contact angle θ = 125.3°), enhancing anti-seepage properties. PCWAL maintained bonding strength at −25 °C without cracking, demonstrating excellent frost resistance. Under 10-day water immersion, bond strength declined by less than 5%, indicating strong water resistance. Surface contamination negatively affected adhesion: at 40 g/m², shear and pull-out strengths declined by 12.6% and 13.9%, respectively. Surface treatments—particularly milling—effectively restored bonding strength, increasing it by up to 16.0% (shear) and 11.5% (pull-out). These findings demonstrate that PCWAL possesses outstanding durability and bonding performance under complex environmental conditions, supporting its application in long-span concrete bridge decks.