Manufacturing and application of artificial lightweight aggregate from water treatment sludge

The purpose of this study is to manufacture lightweight aggregates for the recycling of water treatment sludge (WTS), to identify the physical properties of the aggregates, and to present a means by which to utilize the manufactured lightweight aggregates. The chemical composition and thermal properties were examined via a raw materials analysis. The aggregate examined here was fired by the rapid sintering method and the single-particle density and water absorption rate were measured. WTS has a high LOI and the calcined inorganic material has high refractoriness. When 30 wt% of purified sludge was added, the single-particle density of the aggregates was in the range of 0.8–1.2g/㎤ at temperatures of 1150–1200 °C. At temperatures of 1200 °C or higher, ultra-lightweight aggregates having a single-particle density of 0.8 or less could be produced. When applied to concrete by replacing the general aggregate in the concrete, a specimen with strength values of 20–45 ㎫ at 28 days was obtained, and when applied as a filter material, the performance was equal to or exceeded that of ordinary sand.