Influence of condensed silica fume on the properties of cement-based solidified wastes

Influence of condensed silica fume (CSF) addition as cement replacement mat erial on the properties of cement-based solidification products was investi gated. Final setting, unconfined compressive strength, and leachability of the synthetic lead and chromium hydroxides were determined. CSF was used at 0, 5, 10, and 20 wt.%. substitution for Portland cement. A water-to-solid ratio (w/s) of 0.45 was used for all mixes. Experimental results showed tha t the severe retardation effect on ordinary Portland cement (OPC) hydration caused by lead hydroxide has been minimized due to the pozzolanic effect a nd, as a result, the time to final setting has been significantly reduced. In addition, compressive strength of the solidified wastes was increased to the highest with 10% cement replacement but decreased to lower than the on e without CSF at 20% replacement. Leaching of the amphoteric lead and chrom ium hydroxides is primarily determined by leachate pH and therefore lead wa s found in the leachates at higher concentration than chromium. (C) 2001 El sevier Science Ltd. All rights reserved.