Properties of coarse and lightweight aggregates from unburned dredged soil

Taihu lake dredged sediment was selected as raw material to produce smallsize (＜12 mm) wrapshell lightweight aggregates (WSLAs) from unburned process.The unburned coarse and lightweight aggregates (UCLAs) was obtained by bonding and shell wrapping process from WSLAs.The effects of WSLAs gradation on UCLAs density,particle size distribution and particle strength were then investigated with 20~25 mm UCLAs in this study.The characteristics,such as size distribution,packing density,water adsorption,cylinder compressive strength,crushing value and freezingthawing resistance of UCLAs,were examined and compared with natural coarse aggregates (NCAs) in accordance with the Chinese National Standards (GB/T 14685-2011).The results showed that the best performance UCLAs were WSLAs1~3 mm accounting for 10%,3~5 mm for 25%,5~8 mm for 50%,and 8~12 mm for 15%.The density and particle strength of this best performance UCLAs obtained from this WSLAs combination were 1.644 g/cm3 and 2.75 MPa,respectively.At the same time, the internal structure of UCLAs was stable and the shell structure was dense.The water absorption rate was only 189%,which showed a durability being comparable to that of NCAs.There was not mass loss in 25 days of salt solution erosion and 25 cycles of freezethaw resistance.The crushing value of UCLAs was 18.6%,which was higher than that of NCAs (9.5%),but meets the requirement of GB/T 14685-2011 for class Ⅱ coarse aggregate.Therefore, it can be used as skeleton support in building concrete.

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