Hydration–pore architecture regulation and multifunctional performance of a quaternary solid-waste-based lightweight porous cementitious material

Abstract

This study investigates the hydration behavior and pore structure regulation of a quaternary solid-waste-based lightweight cementitious system composed of steel slag (SS), blast furnace slag (BFS), phosphogypsum (PG), and copper slag (Cu-slag). Three functional admixtures—lithium carbonate (Li₂CO₃), hydroxypropyl methylcellulose (HPMC), and calcium stearate (CS)—were incorporated to elucidate their effects on rheological properties, hydration kinetics, pore structure evolution, and the resulting hardened performance of the lightweight matrix. Multi-scale characterization techniques, including X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetry–differential thermogravimetry (TG–DTG), were employed to clarify the underlying mechanisms governing phase assemblage development and microstructural evolution. The results indicate that Li₂CO₃ significantly accelerates early hydration and enhances strength development by promoting the rapid formation of hydration products, whereas excessive dosages induce abnormal expansion and pore coarsening. HPMC improves viscosity stability and water retention, facilitating uniform bubble dispersion and refined pore architecture, which contributes to reduced thermal conductivity. CS promotes the formation of hydrophobic interfacial films and reduces connected porosity, thereby improving matrix integrity and durability-related properties. The admixture-induced regulation of hydration kinetics and pore architecture collectively leads to coordinated improvements in mechanical performance, thermal insulation, and electromagnetic attenuation behavior, with the absorption mechanism predominantly governed by dielectric loss assisted by magnetic loss. A minimum reflection loss of −67.02 dB at 10.20 GHz with a thickness of 2.78 mm was achieved. In addition, life cycle assessment results demonstrate that the developed material exhibits substantial reductions in embodied carbon, energy consumption, and cost compared with ordinary Portland cement–based foamed concrete. These findings provide mechanistic insights into admixture-regulated hydration and pore structure evolution in solid-waste-based lightweight cementitious materials and demonstrate their potential for resource-efficient construction applications.