Curing conditions effect on pore structure, compressive strength and elastic modulus of cementitious tailings backfills

As a widespread application in underground metal mines, cementitious tailings backfill (CTB) has a significant implication for recycling dangerous process tailings and enhancing the safety of mining voids. The pore structure of CTB that is liable on the features and proportions of tailings and binders is correlated to its mechanical characteristics (i.e., elastic modulus, uniaxial compressive strength). This study deals with the influence of curing conditions such as temperature (20–50 °C), stress (0–540 kPa), and time (3–28 days) on mechanical and pore structure characteristics of CTB. Fill samples were prepared in a stable solid dosage and cement/water ratio of 76% and 1/6, respectively, and put into cylindrical molds (D × H: 50 × 100 mm). A new lab instrument with adjustable curing conditions was adopted for fills. A PC-controlled mechanical press and Hg intrusion porosimetry were applied to assess CTB's strength and pore structure properties. Results suggest that, with advancing curing temperature/stress, the strength and elastic modulus of CTB show a rising trend, while its growth rates show a falling trend. CTB's porosity shows a declining trend, and it exists a good linear correlation between fill's strength and apparent porosity. CTB's strength essentially depends on the volume of medium (1–10 μm) and micro (0.01–1 μm) pores. As a result, several practical equations for CTB specimens are established, which consider types of tailings and admixtures.