Biochar-enhanced solid waste-derived aggregates with phase change materials for thermal energy storage and negative carbon emissions

Heat-stored functional artificial aggregates, combining solid waste cementitious skeleton with phase change materials (PCMs), exhibit promising application potential in improving thermal energy efficiency and emission reduction in building. In this study, a novel form-stable heat-stored aggregate was developed by integrating n-octadecane (ODE) into biochar-modified solid waste cementitious skeleton. The mechanical strengths, phase assemblage, microstructure and heat storage capacity of heat-stored aggregates were analyzed. The prepared heat-stored aggregate exhibited the cylinder compressive strength of over 5.0 MPa, the phase transition temperature of 28.0℃ and the latent heat of 31.7 J/g, along with superior mechanical properties and form-stable ability. In addition, economic, energy and environmental analysis indicated that the resulting heat-stored aggregate had a short cost payback period in building, exhibiting superior performances in terms of energy saving and negative carbon emissions for service life. In overall, this work provided novel insights into the optimized design of heat-stored functional aggregate with PCM for energy conservation and emission reduction in building.