The rapid depletion of natural aggregate resources has led to the exploration of recycled aggregates as sustainable alternatives. The steel industry annually generates 28 million tons of magnesia-based waste refractories (WMRs), making their incorporation into construction materials a potential strategy for resource conservation. However, WMR recycling poses a challenge because of its susceptibility to volume expansion during hydration. This study evaluated the feasibility of an environmentally friendly additive, lignosulfonate (LS), for stabilizing crushed waste magnesia refractory bricks (CWMR) to explore the potential application of WMR as construction aggregates. The swelling properties, including the free swell index (FSI) and the swell pressure (Ps), and mechanical properties including unconfined/uniaxial compressive strength (qU), shear wave velocity (VS), and thermal conductivity (lambda) of LS stabilized CWMR (CWMLS) were evaluated over different curing periods at varying LS contents (LSc). Hydration transformed CWMR from sandlike to highly plastic silt-like, resulting in a significant FSI of 250 % and Ps of 5.2 MPa. LS effectively stabilized CWMR, as indicated by decreased FSI and Ps, and enhanced qU and VS. Microscopic observation and mineralogy analyzes confirmed that LS stabilizes CWMR by adsorbing onto its surface. Stabilization of thermal conductivity at higher LSc over curing periods further supports these interactions. Macroscopic behavioral analyzes give stabilized effect of 94.3 % at LSc = 5 % with minimal improvement at higher LSc. These findings highlight LS as a promising stabilizer for mitigating hydration-induced expansion and improving the mechanical properties of CWMR, supporting its application as a recycled aggregate in construction.

Reducing the uncertainty in aerosol radiative forcing requires a comprehensive understanding of the factors affecting black carbon (BC) light absorption. In this study, the characteristics and influencing factors of light absorption enhancement (Eabs) of refractory BC (rBC) were investigated by conducting intensive measurements at an urban site in northwest China during the early summer of 2018. On average, the absorption of rBC was enhanced by 34% as a result of the internal mixing of rBC with other aerosol components. Secondary inorganic aerosols (SIAs) were found to have considerable effects on the Eabs of rBC. The Eabs showed a robust linear relationship with the bulk nitrate/rBC mass ratio in fine particles, with an increase of 3% per nitrate/rBC ratio unit. A notable increase in Eabs from dusk to the next morning was observed, in accordance with the diurnal variations in nitrate and sulfate, indicating the excellent contribution of non-photochemical formation of SIAs to Eabs. This fact was further supported by the positive correlation of the nitrate/rBC and sulfate/rBC ratios with relative humidity (RH) rather than photochemical indicators. This study indicates that the aqueous and/or heterogeneous formation of SIAs is likely the dominant aging pathway leading to the high Eabs of rBC.