Accelerated carbonation of ferrous and non-ferrous slags to produce clinker-free carbonate-bonded blocks: Synergetic reduction in environmental leaching. (19th September 2022)

• Record Type: Journal Article
• Authors: Srivastava, Sumit; Snellings, Ruben; Nielsen, Peter; Cool, Pegie
• Is Part Of: Construction & building materials. Volume 348(2022)
• Publication Date: 2022-09-19
• Subjects: Waste utilization -- CO2-utilization -- CCUS -- Carbonate binder -- Environmental leaching -- Environmental remediation; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2022.128630
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Clinker-free blocks by accelerated carbonation of ferrous and/or non-ferrous slags. Decreased Cr-leaching in SSS used individually, disproportional decrease with NFMS. Pb-slag vs P(CO2 ): decreased Pb-leaching, Co/Zn/Mn leaching increase then decrease. Synergetic reduction in leaching from mixes of ferrous/non-ferrous slags. In addition to encapsulation, a chemical synergy between sulfide/Cr is discussed. Abstract: Clinker-free, carbonate-bonded monoliths are prepared by accelerated carbonation for immobilization of hazardous elements present in: a stainless-steel slag, two copper slags, and one lead slag. In addition to the studies on individual slags, mixes of copper slags and lead slags with 33 % and 66 % replacements of stainless-steel slag are also studied. Combinations of two temperatures (30 and 60 °C) and three CO2 -pressures (1, 5, and 10 barg) are studied. Among the non-ferrous slags carbonated individually, lead slag carbonated at 10 barg exhibited carbonate-cementation. The carbonate-bonded monoliths containing stainless-steel slag exhibited high compressive strengths, individually or as in its mixes with other slags. In stainless-steel slag, while its individual carbonation also showed a decrease in Cr-leaching, the Cr-leaching from its mixes with non-ferrous slags are disproportionately lower: possible chemical synergy of stainless-steel slag with sulfidic non-ferrous slags is discussed. For lead slag individually, carbonation significantly decreases Pb-leaching; while Co, Zn, and Mn leaching first increase and then decrease with an increase in CO2 -pressure. In mixes of lead slag with stainless-steel slag, Pb, Co, Zn, and Mn leaching are significantly decreased. Temperature does not have a significant influence on the product properties. Copper slag remained relatively insensitive towards carbonation. Comparisons are made with the Flemish legislative limits.