Crushed aggregate production from centralized combined and individual waste sources in Hong Kong

Owing to the comprehensive building redevelopment programmes in Hong Kong, there is a huge volume of concrete waste generated that will soon exhaust all the available landfill areas. As such, recycled aggregate is advocated. However, the use of recycled aggregate has been confined to lower-grade applications until now, such as the lower layers of a pavement structures, e.g., capping and sub-base. The main reason is the variable behaviour of recycled aggregates collected from different sources to be crushed in a centralized recycling plant. This paper applies some international standards to classify recycled aggregates. Aggregates were collected from twelve sources, including 10 from demolition sites (Samples 1–10), one from Tuen Mun Area 38 centralized recycling plant (Sample 11) and one from ordinary virgin aggregate (Sample 12). From test results, Sample 6, akin to Sample 12 (virgin aggregate), was found to be suitable for all types of construction applications, while Samples 2 and 9 were completely unsuitable as recycled concrete aggregates for any application grade. Sample 11 (Tuen Mun Area 38 centralized recycling plant) was found only suitable for non-structural applications, such as base course and fill. It is concluded that the different sources of recycled aggregate should preferably be separately crushed and classified rather than processed in a combined form centrally which will lower its overall quality and limit its application.