Utilization of Dredged River Sediment in Preparing Autoclaved Aerated Concrete Blocks

Abstract

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.