Abstract: A laboratory abrasion experiment is conducted to determine the wear resistance of a patched concrete pier under the action of sediment-laden flows in a tributary of the upper Yellow, namely the Taohe River. We use a self-developed rotation device to test four types of concrete specimens－intact, damaged-unrepaired, epoxy mortar-repaired, and polyurethane mortar-repaired model piers－and use 3D surface topography scanning to examine the evolution of abrasion damage. These results suggest that the repair material can improve the abrasion resistance of damaged concrete, and that polyurethane mortar is better in performance than epoxy mortar. In particular, at a sand-to-stone ratio of 1:3 and rotational speed of 2100 r/min, the concrete pier－repaired with polyurethane mortar and then abrased 72 hours in the flow－exhibits a 51.4% reduction in mass loss rate in comparison with the unrepaired one. The repaired surface layer of the pier inhibits surface micro-cracks extending deeper; At 1600 r/min, the maximum valley depth is reduced by 46.0% compared with the unrepaired specimen. The generalized grey relational degree, combined with the entropy weight method, identifies the priority of factors influencing mass loss as: sand-to-stone ratio > flow velocity > abrasion duration. The findings lay a theoretical basis useful for performance evaluation and maintenance of the bridge piers in sediment-laden flows.

Key words: concrete, epoxy mortar, polyurethane mortar, abrasion resistance, generalized grey relational analysis, sediment-laden flow