Preparation of non-sintered lightweight aggregates from dredged sediments and modification of their properties

A novel preparation technique of non-sintered lightweight aggregates (LWAs) from dredged sediments was conducted in this study. In order to deal with the problem of hydration and low strength of the ceramsites without calcination, waterproofing lightweight aggregates (WLAs) and wrap-shell lightweight aggregates (WSLAs) are manufactured through the process of waterproofing and wrap-shell, respectively, and untreated lightweight aggregates (ULAs) were utilized as core layer. The performance characteristics, such as basic physical properties, mechanical strengths, water resistance, harsh environment resistance, and microstructure, of ULAs, WLAs and WSLAs were investigated. Results show that ULAs have a uniform particle size distribution, but their compressive strength is rather low (0.27 MPa), and the value of water absorption was as high as 24.18%. WSLAs were equipped with a hard and stable concrete shell, which raised their compressive strength to 2.46 MPa, and the salt, frost and shearing resistance were improved. These results reveal that, if dredged sediment would be used as raw material for producing non-sintered LWAs in concrete pouring, a stable shell layer was extremely essential to avoid their obtained specimen from crushing or being hydrated.