Investigation of the performance of superfine tailings wet shotcrete doped with nano-TiO2: From macro performance to hydration mechanism

The recycling of superfine tailings has become an important research direction in the mining field toward low-carbon and clean production. In this study, superfine tailings were used as aggregate, and nano-TiO₂ (NT) was introduced as a reinforcing material to prepare NT-doped superfine tailings wet shotcrete (TWSC). Macro-scale experiments showed that as the NT dosage increased, the strength of TWSC exhibited a trend of first increasing and then decreasing, with the optimal dosage being 2 %. Microscopic characterization reveals that at an NT dosage of 2 % and different curing ages, TWSC exhibits abundant and stable hydration products, the lowest porosity, and a relatively complete three-dimensional bonding structure at the microscopic level. The polymerization degree of the gel phase, a key hydration product, is highest, consistent with the strength changes. Density functional theory (DFT) calculations indicate that during the early hydration stage, the presence of NT forms Si-O-Ti, providing heterogeneous nucleation sites for the formation of the calcium silicate hydrate(C-S-H) gel phase. This synergizes with Si-O-Si and Si-O-Al to serve as the key steps in the dimerization reaction prior to gel phase nucleation, thereby promoting the early hydration reaction of TWSC. This study provides new insights into the potential utilization and improved utilization rate of superfine tailings in wet shotcrete.