Solidification of shipyard solid waste using dolomite and rice husk ash as additives / Rosmawati Abdul Aziz

Industrial solid waste may pollute soil, air, surface water or underground water if it
contains toxic substances. This pollution if do not properly managed can cause
serious health risks and problem to the surrounding environment. In this study,
solidification was used to treat industrial solid waste from Malaysian Shipyard
Company. The physical and chemical stability of the waste was improved using
cement-based solidification. Similar to conventional concrete production, industrial
waste was used to replace sand with the proportions of 0% waste - 100% sand, 50%
waste - 50% sand, 70% waste - 30% sand, and 100% waste - 0% sand proportions. 5,
10, 15, and 20% rice husk ash (RHA) and dolomite were added as additives and the
effect of these materials on the strength and leaching of the concrete containing
waste were investigated. Solidification was evaluated by carrying out compressive
strength and leaching test. KH Method was also used in evaluating the effectiveness
of the encapsulation technology, which determines the strength and leaching
simultaneously. For compressive strength test, sample of 70% waste - 30% sand
proportion was found to be the optimum ratio that gives the highest strength for both
samples with and without additives. 100% waste - 0% sand also gives higher strength
compared to control (0% waste - 100% sand). The results show, presence of
dolomite, increased the concrete strength, with the optimum of 10% dolomite
addition. However, addition of 20% dolomite gives weaker concrete. Same results of
strength were obtained with the addition of RHA. Strength that gained with presence
of dolomite gives higher strength when compared to RHA. For leaching test, after
encapsulation, the leachability of contaminant were reduced for all samples of wastesand
proportions with and without additives. For oil and grease, sample of 50%
waste - 50% sand with 15% dolomite showed better result, which reduced at 83%.
KH Method shows that the results are compatible to the standard method for testing
strength and leaching. Through solidification, hazardous waste can be safely
disposed into landfill or used as by-product.