Leaching-abrasion behaviour of canal lining concrete under alternating effect of freeze-thaw and low-velocity flowing water

Abstract

Under long-term alternating effect of freeze-thaw and low-velocity flowing water, characterising the leaching-abrasion behaviour of canal lining concrete has become a technical bottleneck in evaluating its durability in cold regions. To investigate this behaviour and elucidate the mechanisms and effects of these processes, this study conducted experiments under alternating freeze-thaw and flowing water conditions, with a maximum flow velocity of 5 m/s. The evolution of macro- and micro-scale properties, as well as phase composition, was analysed, and boundary movement criteria were established for concrete surface. The experimental results show that the abrasion depth of concrete increases linearly with service time. Compared to warm regions and static water environments, the combined effect of freeze-thaw cycles and flowing water in cold regions accelerates the leaching-abrasion rate by approximately 8 times. The rate is further amplified by factors of 1.18, 1.37, 1.22, 1.29, and 1.37 at flow velocities of 1, 2, 3, 4, and 5 m/s, respectively. This enhancement is primarily attributed to the deterioration of interfacial transition zone. Freeze-thaw are the dominant factor, inducing numerous microcracks, while flowing water significantly accelerates calcium leaching. Boundary movement on the concrete surface occurs when the residual solid calcium content and aggregate protrusion height reach critical values. The critical calcium content is 25 %, while the protrusion height decreases linearly with increasing aggregate diameter, reaching 60 % and 30 % for diameters of 4.75 and 9.5 mm, respectively. Under the action of leaching-abrasion alone, flowing water at velocities up to 5 m/s significantly accelerates leaching but causes negligible abrasion.