J. Giro-Paloma, A. Maldonado-Alameda, A. Alfocea-Roig, J. Mañosa, J. M. Chimenos, J. Formosa
https://doi.org/10.3390/app11083528
Applied Sciences, 2021, Vol 2, Pages 3528
Quartile Q2 (2019), Impact (2019) 2.474
During the glass selection process by optical sorting equipment, a rejection material called CSP (Ceramic, Stone, and Porcelain) is generated. The CSP residue contains approximately 80 wt % of glass, around 4 wt % of ceramic, and 4 wt % of porcelain; the remaining components are small pieces of metals, polymers, papers, and organic materials. According to the Catalan recycling glass companies, around 4–5 wt % of the recycled glass is CSP, which is more than 30.000 t of CSP per year in Catalonia.
The CSP characterization reveals that CSP is mainly compound by SiO2, Al2O3, alkali metals, and CaO, which are key components for the Alkali-Activated Cement (AAC) development. Consequently, this study is focused on the potential of CSP as a precursor to synthesize AAC. AAC consists of the reaction of an aluminosilicate powder precursor with a highly alkaline activator solution to form sodium aluminosilicate hydrate or calcium aluminosilicate hydrate gels. The concentration of the alkali activator (NaOH: 1 M, 4 M, and 8 M) and the Liquid-to-Solid (L/S, 0.5 and 0.6) ratio were tested in the formulation of the AAC (Fig. 1). The AAC specimens at 28 days cured were evaluated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FIR), scanning electron microscopy (SEM), apparent density (ρapp), and compressive strength (σs). These were determined at the age of 28 days for a better understanding of mechanical properties.
The results obtained showed that the L/S of 0.5 and 4.0 M for NaOH concentration are the best conditions, due to the mechanical properties (ρapp= 1.75 g·cm−3; σs= 52.8 MPa), cohesion (SEM), and formed phases (XRD and FT-IR). This research sheds light on the potential use of the CSP as a precursor for AAC. It should be emphasized that CSP is a residue in Spain and is disposed of in landfills because it is not useful for the recycling glass cullet industry. Therefore, the present research is a relevant solution for enhancing sustainable and environmental criteria, as well as following a circular economy strategy.
Funding
This research was partially funded by the Spanish Government (BIA201783912-C2-1-R). Mr. Alex Maldonado-Alameda and Mr. Jofre Mañosa are grateful to the Catalan Government for their research Grants, FI-DGR 2017 and FI 2020, respectively.
Research category: Construction Materials