Steel Slag Utilization in Cement and Concrete Systems
Summary
Steel slag, the principal by-product of blast-furnace and basic oxygen furnace steelmaking, holds significant promise as a supplementary cementitious material and aggregate in concrete systems. Its complex mineralogy—dominated by dicalcium silicate (belite) and brownmillerite phases—affords latent hydraulic properties that can be activated through alkali treatment, chemical admixture, thermal quenching and mechanical grinding. Incorporation of steel slag into ordinary Portland cement or alternative binders reduces clinker demand, lowers CO₂ emissions and valorises industrial waste within the built environment. Challenges to widespread adoption include variable composition, volume instability due to free lime and periclase expansion, and potential heavy-metal leaching. Recent advances focus on optimising slag fineness, accelerating reactivity with oxalate or citrate activators, and integrating slag into belite calcium sulfoaluminate or alkali-activated systems to achieve robust early strength, enhanced durability and minimal environmental risk. Such developments underpin circular economy objectives and support decarbonisation imperatives across global cement and concrete industries.
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Steel Slag Utilization in Cement and Concrete Systems publication trend
The graph below shows the total number of articles in steel slag utilization in cement and concrete systems across all publications each year (not limited to Nature Index journals).
Technical terms
Steel slag: A heterogeneous by-product of steelmaking, rich in calcium silicate, ferrite and oxide phases, used as a supplementary cementitious material or aggregate.
Alkali activation: A process employing alkaline solutions (for example sodium silicate or hydroxide) to dissolve slag constituents and trigger cementitious gel formation.
Calcium–Silicate–Hydrate (C-S-H) gel: The primary binder phase in cementitious systems, responsible for mechanical strength and durability through its amorphous, layered structure.
Hydrogarnet: A calcium-aluminium-silicate hydrate phase formed during slag hydration that contributes to strength development and heavy-metal immobilisation.
Brownmillerite: A calcium ferrite-aluminate phase in steel slag that hydrates under alkaline activation, influencing early strength kinetics.
Belite calcium sulfoaluminate cement: A low-carbon cement blend in which belite and calcium sulfoaluminate phases replace clinker, offering rapid strength gain and reduced CO₂ footprint.
References
- Characterisation of alkali-activated stainless steel slag and blast-furnace slag cements. Cement and Concrete Composites (2023).
- Sodium oxalate activation of basic oxygen furnace slag for building materials. Resources Conservation and Recycling (2023).
- Utilization of air granulated basic oxygen furnace slag as a binder in belite calcium sulfoaluminate cement: A sustainable alternative. Journal of Cleaner Production (2024).
- Improving the early reactivity of activated basic oxygen furnace slag – The influence of particle fineness and grinding aids. Journal of CO2 Utilization (2024).
- Hydration of potassium citrate-activated BOF slag. Cement and Concrete Research (2021).
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