Use of recycled CRT funnel glass as fine aggregate in dry-mixed concrete paving blocks

This paper investigates the feasibility of using recycled glass derived from discarded cathode ray tube (CRT) glass as an alternate fine aggregate for the production of dry-mixed concrete paving blocks. The recycled CRT funnel glass used had been acid treated and regarded as a non hazardous material based on the regulatory thresholds of the Toxicity Characteristic Leaching Procedure (TCLP). Two series of concrete paving blocks were prepared, one with and one without the use of coarse aggregate. Additionally, TiO2, a photo-catalyst was added to the surface layer of the blocks during the fabrication process to effect photo-catalytic reaction for the removal of an air pollutant, nitrogen oxide (NO). For each series, the CRT glass was used to replace the fine aggregate by volume at different ratios. Their physical, mechanical and durability properties, lead leachability, and photocatalytic air purifier performance were studied. The results show that the use of up to 100% CRT funnel glass as fine aggregate in concrete paving blocks not only have satisfactory levels in compressive strength (>45 MPa) and ASR expansion (<0.1%), but improved the resistance to water absorption, drying shrinkage and photocatalytic performance for reducing air pollutants. However, the TCLP results reveal that the casting method of producing dry-mixed concrete blocks had a significant influence on lead leaching, and the replacement ratio of the CRT glass should be limited to about 25%.