Carbonation Curing on Magnetically Separated Steel Slag for the Preparation of Artificial Reefs

Abstract

Magnetic separation is an effective method to recover iron from steel slag. However, the ultra-fine tailings generated from steel slag become a new issue for utilization. The dry separation processes generates steel slag powder, which has hydration activity and can be used as cement filler. However, wet separation processes produce steel slag mud, which has lost its hydration activity and is no longer suitable to be used as a cement filler. This study investigates the potential of magnetically separated steel slag for carbonation curing and the potential use of the carbonated products as an artificial reef. Steel slag powder and steel slag mud were moulded, carbonation-cured and seawater-cured. Various testing methods were used to characterize the macro and micro properties of the materials. The results obtained show that carbonation and hydration collaborated during the carbonation curing process of steel slag powder, while only carbonation happened during the carbonation curing process of steel slag mud. The seawater-curing process of carbonated steel slag powder compact had three stages: C-S-H gel formation, C-S-H gel decomposition and equilibrium, which were in correspondence to the compressive strength of compact increasing, decreasing and unchanged. However, the seawater-curing process of carbonated steel slag mud compact suffered three stages: C-S-H gel decomposition, calcite transfer to vaterite and equilibrium, which made the compressive strength of compact decreased, increased and unchanged. Carbonated steel slags tailings after magnetic separation underwent their lowest compressive strength when seawater-cured for 7 days. The amount of CaO in the carbonation active minerals in the steel slag determined the carbonation consolidation ability of steel slag and durability of the carbonated steel slag compacts. This paper provides a reference for preparation of artificial reefs and marine coagulation materials by the carbonation curing of steel slag.

Study on the Performance of Steel Slag and Its Asphalt Mixture with Oxalic Acid and Water Erosion

“…Moreover, some properties of different steel slags and natural aggregates are compared. The main components of steel slag are calcium oxide, iron oxide, and silica, accounting for more than 10%, while mechanical properties such as Los Angeles abrasion have quite different values, which is mainly a result of the different processes employed in different steel mills [ 22 , 23 ]: SSD is pristine steel slag, which was provided by Shandong Iron and Steel Co., Ltd., while EOF steel slag is energy-optimized furnace slag. The basic physical properties of limestone and the experimental results of SBS-modified asphalt are shown in Table 3 and Table 4 .…”

A Review on the Carbonation of Steel Slag: Properties, Mechanism, and Application

“…In addition, carbonated steel slag has also been applied in wastewater treatment [92][93][94], producing high value-added CaCO 3 [95,96], improving the hydration reactivity as a supplementary cementitious material [97], thermal insulation material [98], soft soil foundation consolidation [99], and artificial stone [100], showing great potential in the realistic application.…”

Evaluation of Potential Factors Affecting Steel Slag Carbonation

“…In addition to occupying valuable land resources, this phenomenon poses an important ecological threat [37,38]. Smelting slag storage in China is now subject to an environmental protection tax adopted in 2018 as part of a revision of the country's Environmental Protection Law [24].…”

“…Findings show the tetrahedral framework of clinoptilolite-type zeolite robust after low-temp calcination but degrades at 400 • C and collapses at 800 • C. Quartz peak intensity is consistent across the calcination temperature range. Li et al [24] examined the mechanism by which slag tailings from iron recycling are treated to induce carbonation, as well as the potential benefits of doing so to create artificial reefs; the results show that steel slag powder undergoes carbonation and hydration during curing while steel slag mud only undergoes carbonation. Moreover, Li et al [103] found that the strengths of steel slag-pressed blocks increased with higher temperatures (up to 400 • C) due to hydration.…”

“…They all agreed that CaCO 3 and silicate hydraulic solutions are the most important for improving cement's mechanical characteristics and durability following carbonation curing. Li et al [24] indicated that the CaO concentration of carbonation active minerals influenced the carbonation consolidation capability of steel slag tailings. Carbonated materials have a higher compressive strength than uncarbonated materials.…”