The role of RHA-blended cement in stabilizing metal-containing wastes

Time to final setting, strength development and leachability of heavy metals from the solidified wastes using reactive rice husk ash (rRHA)-blended cement as solidification binder were investigated. The rRHA was prepared by firing at 650 °C for 1 h. Synthetic metal hydroxides and plating sludge were solidified using cement blended with 0, 10, 20 and 30 wt.% rRHA. Experimental results showed that synthetic Zn(OH)2 and the plating sludge caused rapid setting for cement paste but prolong the final setting for rRHA-blended cements. The rate of strength development was also decreased during the first 14 days of curing. However, these interfering effects were reduced when cement was blended with 10 wt.% rRHA. In addition, the plating sludge could be loaded at 30 wt.% to the cement blended with 10 wt.% rRHA and gave both the 28-day strength and metal concentration in TCLP leachates that meet the regulatory limits for landfilling.