Crack Control Techniques for Surface Concrete of Seaport High-Piled Wharfs Using Thermoplastic GFRP Rebars

Addressing the cracking issue caused by concrete drying shrinkage stress in the cast-in-place surface layer of high-piled wharfs in seaports， technical measures were studied through theoretical analysis， laboratory tests， and numerical simulations. These measures involve adding thermoplastic Glassfiber-Reinforced Polymer （GFRP） rebars to the design based on the conventional single-layer steel reinforcement to disperse concentrated stress， thereby transforming harmful cracks into harmless ones. These measures were applied in the concrete construction of the berth surface layer in Kemen， Fujian Province. The results showed that after soaking in a simulated saline-alkali solution （pH≈13.4） at 60 ℃ for 90 days， the strength retention rate of the reinforcement material could still reach 76.3%. Using thermoplastic GFRP rebars with a diameter of 12 mm and a spacing of 10 cm， placed 2 cm away from the concrete protective layer， effectively reduced the maximum tensile stress on the concrete surface. Combined with construction quality control measures for thermoplastic GFRP rebars and concrete， the maximum shrinkage strain on the concrete surface could be controlled within 120×10⁻⁶ under strong wind and intense sunlight conditions. After six months of continuous monitoring， the appearance quality remained good， the cracking area was effectively reduced， and no harmful cracks were observed.