Green alkali-activated mortar: Sustainable use of discarded cathode-ray tube glass powder as precursor

Abstract

With technological development, the cathode-ray tubes (CRTs) are being phased out and discarded. However, the discarded CRT is non-degradable, and the presence of lead in it may cause serious contamination to soil and water resources. As a sustainable method to recycle discarded CRT glass, we tested the discarded CRT glass powder (CGP) at up to 70% substitution by mass in alkali-activated slag (AAS) mortar. The Frattini test results show that discarded CGP exhibits high pozzonlanic activity. Moreover, strength tests suggest that discarded CGP can be used as a precursor in AAS mortar without leading to severe strength reduction, and alkali-silica reaction (ASR) expansion results also demonstrate the positive mitigation effect of CGP in AAS mortar. Thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscope (SEM) results show that the substitution of discarded CGP did not produce new geopolymerization products, nor did it change the structure of the products. According to the toxicity characteristic leaching procedure (TCLP), when the discarded CGP substitution is below 50%, lead leaching from the AAS mortars satisfies the regulatory limit. Thus, the proposed strategy in this study has a potential to develop a new eco-friendly AAS mortar by using large-volume, hazardous, discarded CRT glass powder.