Use of CRT Funnel Glass as a Fine Aggregate in Self-Compacting Mortar: The Effect of Limestone on Pb Immobilization

Abstract

End-of-life CRTs are classified as hazardous waste since the funnel glass component has a high Pb content. Alternative management of the glass is required due to the cessation of closed-loop recycling of CRT glass. This study aims to compare the feasibility of using CRT funnel glass as fine aggregates in a self-compacting mortar by addition of limestone to enhance the Pb immobilization. Sample mixtures of self-compacting mortar were prepared from Ordinary Portland cement Type 1 (OPC) with water/cementitious (W/C) ratio of 0.38 by weight, which contained 0, 20 and 40 wt% of Samsung CRT funnel glass ground to sizes smaller than 595 µm as a sand replacement. The sample with glass mixtures contained additions of 5, 10 and 15 wt% of limestone, ground to sizes smaller than 297 µm as a viscosity modifying agent (VMA). The samples’ flow ability was tested by V-funnel and Marsh cone. Pb-fixation in the samples was analysed by TCLP at 7 days and 14 days. The addition of limestone as a viscosity modifying agent improved flow ability in mixtures with CRT funnel glass, with the addition of 10 wt% limestone showing the highest flow improvement in V-funnel tests for both glass mixtures. CRT funnel glass utilized as sand replacement at 20 and 40 wt% showed Pb leaching results within the US EPA allowable limits. However, the addition of limestone reduced the Pb immobilization ability in mortars. A silica based VMA such as fly ash and rice husk ash should be used for these applications.