Freeze–thaw-induced evolution of erosion mechanisms in cementitious materials under high-altitude environments

Abstract

Concrete hydraulic structures in cold, high-altitude regions are subjected to coupled freeze–thaw deterioration and sediment-laden flows, leading to progressive surface degradation. However, the influence of freeze–thaw damage on the governing erosion mechanism remains poorly understood, and existing erosion models generally assume constant material properties. This study investigates the evolution of erosion behavior in mortars cast under normal atmospheric pressure and simulated low-pressure conditions and develops a freeze–thaw-dependent Oka erosion model by incorporating the evolving material state into erosion prediction. Freeze–thaw testing, slurry-jet erosion experiments, microstructural characterization, three-dimensional surface analysis, and CFD-based simulations were conducted. Low-pressure casting reduced the initial air content from 2.10% to 0.83% and compressive strength by 7.1%, and microhardness decreased by 41% in the normal-pressure mortar and 69% in the low-pressure mortar after 100 freeze–thaw cycles. Under the reference erosion condition, freeze–thaw deterioration amplified erosion loss to 12.8 times the undamaged value for the normal-pressure mortar after 150 cycles and 14.1 times for the low-pressure mortar after 100 cycles. Progressive deterioration shifted erosion from matrix-controlled material removal to crack-controlled fracture and produced increasingly localized damage. For impact angles of 15°-75°, the proposed model predicted erosion loss with relative errors of -13.5% to 11.6% and maximum erosion depth with errors of -19.1% to 10.8%. The evolution of wall-material hardness, reference erosion rate, and velocity exponent further quantified the mechanistic transition. The proposed model provides a deterioration-dependent basis for assessing the erosion resistance of hydraulic cementitious materials exposed to cold, high-altitude environments.