Abstract:
This research work investigated the compressive strength and leaching of heavy metal from the
solidified wastes using ordinary portland cement (OPC) and black husk ash (BHA) as binders. OPC
was replaced by BHA at 0, 10, 20 and 30% by wt. and metal sludge was loaded at 0, 10, 20, 30 and
50% by wt.. Results showed that the blended cement with 10% by wt. of BHA substitution gave the
highest strength after 28 days of curing. Compressive strength of cement blended with 10% by wt.
of BHA was 8.5, 8.2 and 9.1% higher than that of the plain hardened cement at the age of 28, 56
and 91 days, respectively. In addition, strength of the solidified wastes decreased when the amounts
of waste increased. It was found that the solidified waste containing 50% by wt. of metal sludge
gave a 28 - day strength of 94 kg/cm2, which was 77.7% lower than that of the control. Leachability
of heavy metals was tested using Multiple Extraction Procedure (MEP). It is observed that the
amounts of waste loading and leachate pHs affected leachability of heavy metals from the solidified
wastes. The cumulative concentration of Cu, Fe, Cr, Cd and Zn released from the solidified waste
containing 50% by wt. of metal sludge was 0.247, 2.348, 0.346, 0.006 and 0.389 mg/L, respectively.
However, concentration of these heavy metals in the leachates was not exceeded the standard
criteria of the Ministry of Industry.