Dynamic strength evolution and multiscale deterioration mechanism of sulfur-bearing cemented tailings backfill under impact loading

Abstract

Sulfur-bearing tailings are increasingly used in cemented tailings backfill (CTB), yet their dynamic response under impact loading remains poorly understood because previous studies have focused primarily on static behavior. To address this gap, this study systematically investigates the dynamic compressive strength (DCS) evolution and microstructural response of sulfur-bearing CTB under impact loading. The effects of elemental sulfur content (0–15 wt% of total solids), curing age (7–56 d), and impact energy (8–16 J) were evaluated through drop-weight impact tests, X-ray diffraction (XRD), scanning electron microscopy (SEM), and image-based porosity analysis. During 7–28 d of curing, DCS initially increased and then decreased with sulfur content, reaching an optimum at 6%. At 7 d and 8 J, 6% sulfur increased DCS by 32.0%. In contrast, after 56 d of curing, increasing sulfur content from 0% to 15% reduced DCS from 4.12 to 0.50 MPa, corresponding to an 87.9% decrease. At 28 d and 16 J, porosity decreased from 27.53% at 0% sulfur to 24.29% at 6%, but increased to 44.44% at 15%. Moderate sulfur content promoted hydration-product formation and pore refinement, whereas excess sulfur and prolonged curing induced gypsum and expansive ettringite accumulation, crystallization pressure, and microcracking. These findings reveal the microstructure-controlled mechanism governing the non-monotonic DCS evolution of sulfur-bearing CTB and provide guidance for its design and long-term stability assessment under dynamic loading.