Pre-curing time effect on carbon capacity and microscopic properties of paste backfill produced by alumina production solid wastes and its practical application

Abstract

To address the urgent need for CO2 sequestration amid global warming, this study proposes a novel strategy for storing CO2 in goaf areas using tailings-cemented paste backfill (TCPB) derived from alumina production wastes. The influence of pre-curing time (1d, 1.5d, 2d, 3d and 4d) on the CO2 storage capacity and microscopic properties of TCPB was systematically investigated across three curing stages: initial pre-curing (Stage I), CO2 curing for 1d (Stage II), and subsequent conventional curing up to 28d (Stage III). Results indicated that CO2 uptake first increased and then decreased with prolonged pre-curing time, reaching a maximum of 3.14% at 2d. Specimens pre-cured for 2d achieved a compressive strength of 5.18 MPa after Stage III, meeting engineering backfilling requirements. TG-DTG analysis revealed that the total CaCO3 content in these specimens reached 10.68% and 12.65% after Stages II and III, respectively. XRD and FTIR analyses further demonstrated enhanced crystallinity of CaCO3 and a higher degree of silicate polymerization in samples pre-cured for 1 similar to 2d. Microstructural observations confirmed the formation of acicular aragonite and well-crystallized calcite, along with a moderately developed pore structure that facilitated CO2 participation in strength development. This study presents an integrated "backfilling-mining-CO2 storage" strategy, demonstrating that pre-curing TCPB in goaf for 2d enables the sequestration of approximately 708.49 kg of CO2 in a single 6 x 60 x 3 m(3) goaf. The work provides a scientifically grounded and scalable dual solution for industrial solid-waste valorization and CO2 mineralization, offering a synergistic pathway towards systemic cleaner production that combines waste recycling, carbon management and safe mining practices.