Development and tests of lightweight aggregate using sewage sludge for nonstructural concrete

The purpose of this study is to efficiently treat sewage sludge discharged from sewage treatment plants and to evaluate the feasibility of lightweight aggregate made from a large quantity of sewage sludge. Sintered lightweight aggregate from sewage sludge is experimentally manufactured with various mass ratios of clay to sewage sludge by a rotary kiln, and is tested for density, water absorption, abrasion loss, crushing value, impact value and heavy metal leaching. Their physical properties are compared to those of a commercial sintered lightweight aggregate for nonstructural concrete. As a result, an experimentally manufactured lightweight aggregate with a recommendable sewage sludge content is similar or superior in physical properties to the commercial sintered lightweight aggregate. In particular, the water absorption of the lightweight aggregate recommended is about half or less than that of the commercial sintered lightweight aggregate. Because no toxic heavy metals are detected from the tested aggregate, it could be used as an environment-conscious artificial lightweight aggregate.