Impact of Grout Strength on Performance of Rehabilitation Corroded Steel Pipes under Parallel-Plate Loading Tests

Aging culverts and steel pipes under roadways pose significant challenges as they reach the end of their service life. Traditional excavation and replacement methods are costly and disruptive, making trenchless rehabilitation techniques like sliplining a preferred alternative. Sliplining involves inserting a liner within a deteriorated pipe and filling the annular space with grout, which plays a crucial role in the structural performance of the rehabilitated system. This study is divided into two parts: first, a research review on sliplining, including past studies on grout performance and pipe rehabilitation; and second, an evaluation of grout strength on the mechanical behavior of sliplined corrugated steel pipes using parallel-plate loading tests. Two types of grouts were compared: a high-strength (HS) grout with a compressive strength of 2,700 kPa and a low-strength (LS) grout with a compressive strength of 250 kPa. Tests were conducted on pipes with varying degrees of corrosion (0%, 50%, and 90%) to assess load-carrying capacity, stiffness, and deformation. Parallel-plate loading tests revealed that grout strength significantly influences the mechanical performance of sliplined pipes. The low-viscosity grout provided moderate improvements, enhancing pipe stiffness, and reducing deformation under load, but showed limitations at higher loads, particularly in severely corroded pipes. In contrast, high-strength grout significantly increased stiffness and load-carrying capacity, reducing vertical diameter changes by over 90% compared to unlined pipes. These findings emphasize the importance of grout selection in optimizing sliplining rehabilitation outcomes. While both grouts improved pipe performance, the high-strength grout provided superior structural benefits, especially for pipes with extensive corrosion.