Rafi Bin Shahadat^1,, Dr Khondoker Mahbub Hassan², Sayma Sultana Keya³

In response to the rapid urbanization of Bangladesh, the leather industry, as well as the production of leather waste, has increased significantly. Unfortunately, the methods for treating or disposing of dry tannery sludges remain poorly developed. Tannery sludge is inappropriate for direct disposal due to its high concentration of heavy metals and toxic metal salts. In this study, an exploratory investigation was carried out on the suitability of utilizing solid tannery waste as a partial substitute for fine aggregates in concrete to evaluate a sustainable management approach for the waste. A total of 63 concrete cylinders were cast with 0%, 2%, 4%, 6%, 8%, 10%, and 15% replacement of fine aggregates by dry sludge and evaluated for compressive strength and leaching of total chromium. The 28-day compressive strengths of the 2%, 4%, 6%, 8%, 10%, and 15% sludge-containing concrete cylinders were found to be 26.24 MPa, 22.02 MPa, 16.05 MPa, 9.79 MPa, 3.13 MPa, and 1.17 MPa, respectively. Thus, the optimum compressive strength, after replacement with tannery sludge, was 26.24 MPa at a 2% replacement.To determine leaching characteristics, a total of 18 cylinders from each batch were immersed in three different leachants of pH 4, pH 7, and pH 10 for 3, 7, 15, and 30 days. The sludge-concrete leached a maximum of 9.4 mg/kg, 1.37 mg/kg, and 3.21 mg/kg of chromium for acidic, neutral, and alkaline media, respectively. Results from the study indicate that, with increasing sludge percentage, compressive strength decreased while chromium leaching potential increased. Up to 4% sludge incorporation is considered suitable for both structural and environmental perspectives. This research presents a promising solution for the tannery waste pollution in Bangadesh by utilizing the waste in concrete.

Concrete, compressive strength, chromium leaching, tannery waste pollution, replacement of fine aggregate