A novel nutrient-rich biochar modified eco-concrete with simultaneously enhanced mechanical and planting performance

Eco-concrete is an environmentally friendly construction material integrating structural performance with ecological functions. To promote solid waste valorization and enhance multifunctionality, we developed a novel nutrient-rich biochar-modified eco-concrete (NB-EC) using animal manure-derived biochar. NB possessed irregular porous micromorphology, high mineral contents, abundant surface functional groups, and a mesoporous structure with large specific surface area, endowing it with strong interfacial reactivity and nutrient retention capacity. These properties contributed to the improved microstructure of NB-EC, which showed a denser matrix, stronger interfacial bonding, increased calcium silicate hydrate (C–S–H) formation, and reduced calcium hydroxide (CH) and calcium carbonate (CaCO 3 ) contents. Correspondingly, NB-EC achieved superior mechanical performance, with compressive and flexural strengths of 10.5 MPa and 3.6 MPa at 28 days. Furthermore, CH consumption was enhanced and hydration was prolonged, likely driven by the pozzolanic-like and nucleation-promoting effects of NB. Beyond mechanical benefits, NB-EC exhibited excellent planting performance, with the highest plant height, biomass, vegetation coverage, and chlorophyll, protein, and starch contents, which were supported by favorable physicochemical properties including increased porosity (~27%), water permeability (5.51 mm/s), water absorption (13.1%), moderated alkalinity (pH 9.7), and sustained nutrient release (N: ~60 mg/L; K: ~100 mg/L). This work offers new insights into the design of sustainable eco-concrete with dual structural and ecological benefits, while advancing the high-value utilization of agricultural waste in green construction.