Preparation of a low-carbon plant-compatible ecological concrete with fertilizer self-release characteristics based on multi-solid waste co-recycling and its environmental impact

Abstract

Plant-compatible ecological concrete is a new functional slope protection material that perfectly combines engineering protection and ecological restoration, and has significant superiority in ecological benefits. In this study, a high greenness low-carbon plant-compatible eco-concrete (LCPEC) with fertilizer self-release properties was developed via using multi-solid waste-based low-alkalinity cementitious materials (LACM) and self-ignited coal gangue aggregates (SCGAs). The physicochemical properties, hydration products and leaching characteristics of heavy metals and phosphorus of LACM under multi-components system were systematically investigated and reveal that phosphogypsum can be used as an excellent alkalic-reducing material but bring about a sharp reduction in strength, whereas the synergistic effect PG with the multi-components system is more conducive to the balanced development of alkalinity and strength. In addition, the optimal LACM component with the performance at pH 8.75 and 28-day compressive strength of 99.7 MPa was obtained based on the response surface analysis. Moreover, the fact that the continuous leaching of phosphorus and heavy metal leaching concentrations were lower than the standard limits suggested that LCPEC possess environmental friendliness and fertilizer self-release properties. Furthermore, the sustainable self-release of fertilizer in LCPEC is related to the long-term self-formation of CaHPO4·2H2O and Ca(H2PO4)2 in LACM matrix and the accumulation and micropore precipitation of nutrient elements due to the water absorption characteristics of porous structure on SCGAs surface. Finally, life cycle assessment and economic analysis indicated that LCPEC is more environmental-friendly, cost-saving and energy-efficient than traditional eco-concrete.