Properties of cement- based solidified waste containing lead and chromium hydroxides

الملخص EN

Experiments were completed to investigate the effects of synthetic lead and chromium hydroxides on the properties of cement-based solidified wastes.

Synthetic lead and chromium hydroxides have been mixed with Ordinary Portland Cement at 10, 20 and 30 wt.

% and water to- solid ratio of 0.45 was used throughout the experiments.

The final setting, strength development and metal leach ability of the solidified wastes were determined using Vicar Needle, unconfined compressive strength and a modified American Nuclear Standards Committee (ANSI/ ANS -16.1) respectively.

It was found that the addition of lead and chromium hydroxides interferes with the normal hydration reaction of OPC by prolonging the final setting time from 4 hours to 78 and 100 hours at 10 and 20 wt.

% of lead hydroxide and setting was not observed up to 150 hours at a 30 wt.

%.

Chromium hydroxide also causes similar interference but the effect is significantly less than that of lead hydroxide.

The hydration retardation caused by the addition of lead and chromium hydroxide results in the microstructures development of the solidified wastes to be different from that of normal cement hydration and therefore the compressive strength of the solidified wastes has been reduced.

Leaching of lead and chromium from the solidified wastes is determined by leachate pH.

The ingression of acidic leach ant through connected primarily porosity of the solidified wastes causes desorption and resolubilization of lead and chromium.