Reinforcement methods and environmental assessment of sustainable cold-bonded artificial aggregates prepared from...

Limestone calcined clay cement (LC3) and municipal solid waste incineration bottom ash (MSWIBA) were used to produce cold-bonded artificial aggregates, integrating the use of a low-clinker binder with solid-waste resource recovery. Three groups of LC3-MSWIBA artificial aggregates (LMAA) mixtures were prepared, and eleven curing regimes were adopted, including steam and water curing at 20-80 °C, water curing, sealed curing, carbonation curing and natural curing. Their physical properties, single-particle compressive strength, phase assemblage, microstructure, and heavy-metal leaching behavior were systematically characterized; the compressive strength of LMAA concrete and direct production costs were also evaluated. At the same curing temperature, water-cured LMAA generally outperformed steam-cured LMAA. Peak compressive strength were generally obtained at 40-60 °C, with a maximum 28 d value exceeding 3.5 MPa. Sealed curing produced performance comparable to the high-humidity 20 °C reference, whereas natural curing offered no clear advantage. X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) indicated that differences among curing regimes were mainly associated with the degree of hydration, carbonate-bearing phases, and pore structure. Under the TCLP extraction conditions used in this study, the measured heavy-metal concentrations in the leachates were below the applicable regulatory limits. At a 50% volume replacement of natural coarse aggregate, concrete containing L50M70 showed only a 0.4% reduction in 28 d compressive strength relative to the natural-aggregate control, whereas the reduction increased to 21.7% at 100% volume replacement. Among the conditions examined and under the baseline economic assumptions adopted in this study, L50M70 subjected to 40 °C water curing provided the most favorable balance among aggregate performance, MSWIBA utilization, concrete compatibility, and direct curing cost.