Suitability of waste slags from Industries as Construction Material: a case study of Imperial Smelting Furnace (ISF) slag from Hindustan Zinc Limited (HZL)

摘要

ISF slag from Zinc industries is produced in huge quantity as a waste byproduct. It is a metal bearing waste, the primary production of Zinc, which is covered under the hazardous category Schedule-1, category 7.3 of hazardous waste (management and handling) rules 1989, MOEF, India as amended in May 2003. This waste has a potential for contamination of groundwater by leaching of metals. Preliminary screening tests were conducted to replace sand by ISF slag from HZL with binder as Portland pozzolana cement (PPC) in concrete mixes in an attempt to solidify and stabilize this waste within environmentally acceptable norms. Toxicity characteristics leaching procedure (TCLP) was adapted to check leaching of metals using the procedures given in Indian standards. Sand was replaced by slag in a proportion of 50 and 80% by weight for two mixes M20 and M25 grade concrete. M25 grade concrete with 50% replacement of sand satisfied both the strength criteria and leaching limits in the TCLP test, whereas, 80% replacement of sand by slag in M25 mix did not satisfy both leaching limits and strength criteria. Mix M20 satisfied strength criteria but leaching of Lead (Pb) was more than the allowable limits for the TCLP test. An attempt was also made to use this slag replacing sand partly in the concrete of grade M20 and M25 with Ordinary Portland cement (OPC) as binder. It was observed that 45% replacement of sand by slag satisfied the strength criteria for both the mixes. TCLP results indicated that the leaching of metals was within the allowable limit for both concrete mixes M20 and M25. Detailed studies are underway based on above results to arrive at an optimum utilization strategy for this hazardous category waste, which may relieve the industry of providing vast spaces for its temporary storage.