Compressive strength behavior of calcined gypsum sludge-sand specimens

A lead-acid storage battery industry in India produces lead contaminated acidic effluent. Lime neutralization of the acidic effluent produces lead contaminated gypsum sludge. The ability of calcined gypsum to harden and gain strength upon hydration is exploited for possible re-use of the gypsum sludge in civil engineering applications. Heating gypsum sludge (chemical formula — CaSO 4 .0.5H 2 O) at 140°C obtained the calcined gypsum sludge (chemical formula — CaSO 4 .0.5H 2 O). CGS-sand slurries containing CGS (calcined gypsum sludge) contents from 10 to 100% were air-dried and their unconfined compressive strengths were determined in the un-soaked state. Toxicity characteristics leaching procedure (TCLP) tests were conducted with CGS-sand specimens to examine if the amounts of lead released by the CGS-sand specimens were within the TCLP limit of 5mg/L. Experimental results demonstrated that the air-dried CGS-sand specimen containing 34% CGS content satisfied the...