Sustainable Utilization of Paper-Industry Lime Sludge through Development of Metakaolinite-Based Cementitious Binder

Abstract

The emphasis of the current study was on the calcination of lime sludge, performed at different temperatures from 650°C to 750°C, which consumes less energy as compared to the industrial process of calcination. Different proportions of calcined lime sludge and raw lime sludge were used with cement to form cementitious binders. M25 grade concrete was prepared with the application of the prepared binders and tested for strength properties at 7 and 28 days of curing. The binder consisted of 10% substitution of cement with as-received lime sludge and 30% substitution with calcined lime sludge and produced a compressive strength of concrete approximately similar to the control concrete. Reactive lime and metakaolinite performed an active role after the calcination of lime sludge at 650°C, which worked as pozzolana. This effect is also confirmed with isothermal calorimetry of the prepared binder. The prepared binder was sustainable with approximately 20% less production cost and 55% less emission of greenhouse gases as compared to ordinary portland cement.