Municipal waste utilization as a substitute for natural aggregate in the light of the circular economy

The presented study investigated the possible utilization of municipal solid waste (MSW) < 10 mm as a recycled aggregate for the production of new lightweight ceramic products. The percentage of municipal waste <10 mm was in the order of 15 %, 20 %, 25 %, and 30 % to produce M-15, M-20, M-25, and M-30 compositions, respectively. Clay, tailings, and glass were also added to the waste part in different proportions. Qualitative tests of the waste samples were performed using XRF (WDX) spectroscopy, which showed the possible uses and binding in the proposed process. The obtained lightweight aggregate was subjected to tests such as bulk density in the loose, water absorption, and compressive strength. Furthermore, we evaluated the environmental impacts of the various compositions of individual materials based on the life cycle assessment. The results showed that the average water absorption of the materials was in the range of 12.34 %-14.07 %, while the average compressive strength ranged from 9.69 MPa to 17.16 MPa. XRD analysis showed that the samples mainly consist of two different polymorph of SiO2 cristobalite, SiO2 quartz and rhomboidal hematite Fe2O3 iron oxide. The lightweight ceramics specimen of M-25 with 50 % clay, 15 % tailings, and 10 % glass as aggregates displayed the best properties. Electron microscopy images show that the number of "macropores" increases as the amount of street cleaning waste in the material increases. Based on the life cycle assessment results for environmental impact categories, emissions, and material and energy use, M-25 exhibited the most optimal composition with the least environmental impact as new material.