Performance of limestone-calcined clay cement mortar incorporating high volume ferrochrome waste slag aggregate

Abstract

This study set out to investigate the mechanical performance and physical properties of Limestone Calcined Clay Cement (LC3) – based mortar incorporating high dosage of ferrochrome (FeCr) slag aggregates. Green, sustainable and economical alternative binder has been prepared by replacing 60 wt% of the Ordinary Portland Cement (OPC) by a blend of limestone (LS) powder and metakaolin (MK) with LS: MK of 1:2 (wt%). The mortar specimens were produced with FeCr slag aggregate as a substitute for natural sand with different replacement ratios ranging from 25 % to 100 % with a stride of 25 wt%. The mini-slump flow test was conducted to assess the mortars behavior in the fresh state. Compressive and tensile strengths, capillary water absorption, leaching behavior and microstructure were investigated for the hardened mortars at 28 days of hydration. With the increase of FeCr replacement ratio, the water-binder ratio (w/b), compressive strength and tensile strength increased. OPC and LC3 mortars incorporating 100 % FeCr attained enhancements by about 71 and 63 % for compressive strength and 22 and 17 % for tensile strength respectively. The total replacement of sand with FeCr aggregate has decreased the water absorption of LC3 mortars by 11 %. The chromium and heavy metals leaching from LC3 mortar made with 100 % FeCr slag showed very low levels as a result of the improved microstructure in terms of compactness and interfacial transition zone (ITZ) tightness. Recycling of FeCr waste with utilization of green alternative binder in the production of mortar with improved mechanical performance is helpful in reducing the carbon footprint in the construction industry.