Abstract: This study investigates the resistance and damage of ultra-high performance shotcrete (UHPSC) under sand-laden flows, focusing on the effect of different steel fiber contents. Underwater abrasion tests are conducted to measure mass loss over time, and surface morphology is examined using laser microscopy. Results show the UHPSC sample’s abrasion evolution features uniform wear without abrupt mass loss. After abrasion of 4 h long, the abrasion resistance of its front surface is 1.4 times that of the side surface, and 1.2 times and 2.0 times that of UHPC (with the same mix proportion) and ordinary concrete respectively. The steel fiber content significantly influences abrasion performance－the abrasion rate increases first and then decreases as fiber content increases from 0% to 1.5%; at 0.5% fiber content, it is 9.58% higher than that of the fiber-free group; at 1.00%, 1.25%, and 1.50%, it decreases by 5.45%, 14.5%, and 38.7% respectively. And, a hybrid combination of 1.0% steel fiber and 0.5% polypropylene fiber decreases the abrasion rate by 19.9%. This study demonstrates UHPSC has excellent anti-abrasion performance and a good prospect in hydraulic application involving sand-laden flow abrasion.

Key words: ultra-high performance shotcrete, abrasion resistance, steel fiber, underwater water-sand abrasion test, hydraulic repair materials