Utilization of Dredged River Sediment in Preparing Autoclaved Aerated Concrete Blocks

Refereed/Peer-reviewed In this study, the dredged river sediment, soft texture and fine particles, is mixed with other materials and transformed into eco-friendly autoclaved aerated concrete (hereinafter referred to as AAC) blocks. The results indicated the bricks produced under the conditions of 30%–34% dredged river sediment, 24% cement, 10% quick lime, 30% fly ash, 2% gypsum and 0.09% aluminum powder with 0.5 water to material ratio, 2.2 MPa autoclave pressure and 6 h autoclave time, the average compressive strength of 4.5 MPa and average dry density of 716.56 kg/m³ were obtained, the two parameters (strength & density) both met the requirement of national industry standard. At the same time, the contents of dredged river sediment, cement, lime, fly ash, gypsum and aluminum powder were 15%, 48%, 20%, 15%, 2% and 0.09%, respectively, and the non-AAC block made of 0.5 water to material ratio, the average compressive strength of 3.1 MPa and average dry density of 924.19 kg/m³ were obtained, the two parameters (strength & density) also met the requirement of national industry standard. In addition, the AAC block’s phase composition and morphology were micro-analyzed by SEM and XRD, the main substances in AAC block were found to be tobermorite and CSH, Among them, the chemical bond between Si-O-Si and Al-O-Al is broken, Al-O-Si is regenerated, Al substituted tobermorite with better strength is formed, and the compressive strength of AAC is further improved.