Improving water retention of loess and promoting plant growth in arid mining areas using cement-bonded coal gangue porous material

• A coal gangue-based porous material can replace loess for land reclamation. • The porous material improves the water retention of loess. • The effect of the porous material on water retention is pore-dependent. Topsoil scarcity in mining areas necessitates suitable alternative materials for land reclamation. This study investigated a cement-bonded coal gangue porous material (CGPM) for enhancing the water retention of loess. CGPM was mixed with loess at volume ratios of 0%, 10%, 30%, 50%, and 100% (v/v). Soil water characteristic curves were determined via centrifugation, and pore size distribution was estimated from the soil water suction-equivalent pore diameter relationship. Column experiments quantified the effects of CGPM on water infiltration and evaporation, while pot experiments evaluated its influence on ryegrass ( Lolium perenne L.) growth under drought stress. Environmental safety was assessed through heavy metal leaching tests and total content analysis. Results indicated that CGPM reduced soil bulk density by 3.5-35.1%, increased field capacity by 6.6-30.4%, and effectively inhibited water infiltration and evaporation (cumulative evaporation reduced by 1.2-8.6%). Infiltration dynamics and wetting front movement were well described by the power function and the Kostiakov model. Heavy metal contents met Chinese standards (GB 5085.3-2007 and GB 15618-2018), confirming low ecological risk. An incorporation ratio of 30% (v/v) was identified as optimal, increasing saturated water content by 9.4%, reducing evaporation by 2.0%, and lowering the permanent wilting point by 70.5%. In conclusion, amending loess with 30% CGPM effectively improves its hydraulic properties while ensuring environmental safety, offering a promising topsoil substitute for ecological restoration in mining areas.