Steel slags are industrial by-products of steel manufacturing, characterized as highly calcareous, siliceous and ferrous. They can be categorized into basic oxygen furnace (BOF) slag, electric arc furnace (EAF) slag, and ladle furnace (LF) slag. They are found to be useful in many fields, such as road construction, asphalt concrete, agricultural fertilizer, and soil improvement. However, better utilization for value-added purposes in cement and concrete products can be achieved. In this paper, an overview of the recent achievements and challenges of using steel slags (BOF, EAF and LF slag) as cement replacement (usually ground into powder form with the size of 400–500 m2/kg) and aggregate in cement concrete is presented. The results suggest that the cementitious ability of all steel slags in concrete is low and requires activation. For the incorporation of steel slags as aggregate in concrete, special attention needs to be paid due to the potential volumetric instability associated with the hydration of free CaO and/or MgO in the slags. Studies have indicated that adequate aging/weathering and treatments can enhance the hydrolyses of free-CaO and -MgO to mitigate the instability. Considering the environmental and economic aspects, steel slags are also considered to have a potential use as the raw meal in cement clinker production.

Characteristics of steel slags and their use in cement and concrete—A review

Supplementary cementitious materials: New sources, characterization, and performance insights

Steel slag is a by-product discharged from the steelmaking process, which is characterized by abundant free calcium/magnesium oxide, low cementitious properties, and high contents of heavy metals. The disposal of steel slag at landfills not only wastes valuable resources but also causes serious pollutions to the environment. However, the direct use of untreated steel slag poses a great risk to the mechanical properties and durability of the steel slag-derived composites. In recent years, research on the use of steel slag as eco-friendly construction materials has experienced an unprecedented advance, particularly with the discovery that accelerated carbonation is conducive to improving the inferior properties. This review summarizes the various types of steel slags based on chemical/mineral compositions and the related physic-chemical properties. It also highlights recent progress on the use of accelerated carbonation to improve the quality of steel slag in the context of a wide range of influencing factors, such as temperature, reaction time, CO2 concentration and pressure, moisture, particle size and gradation of steel slag, and additives. A major challenge is to dissect the interconnectedness between the influencing factors and their relative contributions to the property improvement of steel slag. After that, we introduce the practical applications of carbonated steel slag with improved properties. Finally, we provide new insights into the mechanisms and challenges of using accelerated carbonation as a treatment of steel slag for future research and industrial applications.

Use of steel slag as sustainable construction materials: A review of accelerated carbonation treatment

Accelerated carbonation curing of cement mortars containing cement kiln dust: An effective way of CO2 sequestration and carbon footprint reduction

Influence of mineral admixtures on carbonation curing of cement paste

Effects of temperature and carbonation curing on the mechanical properties of steel slag-cement binding materials

In this study, we replaced 30% of the cement with steel slag to prepare binding material; additionally, small amounts of CaCO3 and CaSO4·2H2O were added. This was done to study the compound effect of CaCO3 and CaSO4·2H2O on the strength of steel slag-cement binding materials. The hydration degree of the steel slag cementitious material was analyzed by XRD, TG and SEM. The results showed that the optimum proportions of CaCO3 and CaSO4·2H2O were 3% and 2%, respectively. Compared with the steel slag-cement binders without adding CaCO3 and CaSO4·2H2O, the compressive strength increased by 59.9% at 3 days and by 17.8% at 28 days. Acting as the nucleation matrix, CaCO3 could accelerate the hydration of C3S. In addition, CaCO3 was involved in the hydration reaction, generating a new hydration product, which could stably exist in a slurry. Meanwhile, CaSO4·2H2O could increase the number of AFt. The compound effect of CaCO3 and CaSO4·2H2O enhanced the intensity of steel slag-cement binding materials and improved the whole hydration behavior.

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Qian Liu

Papers

Effects of temperature and carbonation curing on the mechanical properties of steel slag-cement binding materials

Compound Effect of CaCO3 and CaSO4·2H2O on the Strength of Steel Slag - Cement Binding Materials