Using recycled construction waste as aggregates for paving blocks

The use of paving blocks made from recycled materials, in particular recycled concrete aggregate derived from demolition waste streams, has gained a wider acceptance in Hong Kong. However, the use of wastes generated from building activities is generally considered unsuitable for this application. This paper describes a study on the use of construction waste in the production of paving blocks for residential applications. Construction waste (concrete rubble, clay brick, low-quality and high-quality ceramic tiles, lightweight blocks, concrete masonry blocks, timber and bamboo) was crushed into fine aggregate prior to production of the paving blocks. The density, compressive strength, breaking load, modulus of rupture and water absorption were measured for these laboratory-prepared paving blocks. The results were compared with those from control paving blocks fabricated using river sand. The influence of iron oxide pigment on the properties of the paving blocks was determined. The weathering properties of the paving blocks prepared with recycled materials were also assessed. The results indicate that it is feasible to recycle building site waste for use in paving block production, but the inclusion of lightweight materials should be avoided or limited. Based on the findings, limits of different waste materials allowed in paving block production are recommended.