Driving Change - Transport NSWs Integration of Circular Economy in Roadways Projects
PTA's Groundbreaking Study on Steel Furnace Slag Aggregate
Smart Concrete - Revolutionising the Future of Construction
16th Global Slag Conference Recap - Dubai, UAE 2024
Australian Government Tasks Productivity Commission to Explore Circular Economy Benefits
12th EUROSLAG Conference Recap - Bilbao, Spain 2024: The Future of Ferrous Slag
The Role of Slag in Reducing Corrosion in Geopolymer Concrete
106th NSA Annual Meeting Recap: A Global Gathering of Leaders in the Slag Industry
Suvo Develops Low-Carbon Cement from Nickel Slag Forging the Future: Strategic Collaboration to Decarbonise Steel
Chief Executive Director: Craig Heidrich
Editor: Kaspar Moore
Contributors: Alfie Lloyd-Perks, Katrina Jende, Robert McCaffrey, Christian Foia, Dept. of Climate Change, Energy, the Environment, and Water. Heino Schütten, Chani Tennakoon, Charles Ochola, Chris Page.
EDITORIAL
Welcome back to the second and final issue of ASA Connections for 2024!
As we close out the year, the Australasian (Iron & Steel) Slag Association are excited to share the latest innovations and updates in slag and sustainability in this issue of Connections. Dive into breakthrough research, impactful projects, and the dynamic events that shaped 2024.
In this issue of Connections, we are pleased to report that Transport for NSW is leading the way in sustainable infrastructure by embedding circular economy principles and low-carbon materials into its projects. In its Nowra Bridge project, they used a developed asphalt mix comprising of 66% steel furnace slag aggregate (SFS). An Excellent step towards their ambitious targets to address emissions from their operations, maintenance, construction, and road use.
In a ground-breaking move, Proficiency Testing Australia (PTA) has completed its first proficiency study using 14mm steel furnace slag aggregate—marking a shift from traditional natural quarry materials. The program highlighted slag's potential as a reliable, eco-friendly alternative for construction. Partnering with Australian Steel Mill Services and Colas NSW, PTA’s study showcased the versatility of steel furnace slag in heavy-duty asphalt applications, paving the way for safer, more sustainable roads.
News from UNSW, where their own Professor Wengui Li is pioneering “smart concrete” that self-heals, senses microscopic damage, and integrates recycled materials like slag and fly ash. This nextgen concrete cuts down on emissions, reduces repair needs, and supports sustainable construction. By enhancing durability and resilience, it’s laying the groundwork for smarter, greener cities of the future.
The 16th Global Slag Conference in Dubai brought together 175 delegates from 32 countries, offering cutting-edge insights on sustainable slag use in construction. Highlights included important presentations, field trips, discussions on global slag markets, and the prestigious Global Slag Awards amid a desert dinner. With high praise for its networking and technical sessions, the conference set the stage for the 2025 event in Vienna, Austria.
Australia is ramping up its circular economy efforts with a new Productivity Commission inquiry, which the Association has been invited to make a submission. Tasked by the Albanese government, this year-long inquiry will explore how Australia can reuse by-products, keep materials in use longer, improve resource productivity, and create a thriving, eco-friendly economy that benefits businesses, consumers, and the environment alike. With Australia’s material footprint lagging behind the OECD, this initiative could mark a significant shift towards a more sustainable future.
EUROSLAG's 12th conference in Bilbao, Spain, brought together 230 global participants to discuss the future of ferrous slags in a decarbonising steel industry. As the steel sector shifts toward low-CO2 processes, EUROSLAG's dedication to research,
standardisation, and international collaboration has never been more crucial. Looking to the future, the conference highlighted the potential to save millions of tonnes of natural resources and CO2 emissions—proving that slags are not just a by-product, but a key player in the future of sustainable industries.
Dr. Chani Tennakoon, Technical Manager at Independent Cement & Lime, has produced a valuable article on Geopolymer concrete with a high slag content which shows promising durability in chloriderich environments. It is understood that increased slag levels enhance the concrete's resistance to chloride ion penetration. With higher concentrations of calcium-based reaction products, these slag-rich mixes delay chloride-induced corrosion, suggesting an extended service life for structures in harsh conditions.
The 106th Annual Meeting of the National Slag Association (NSA) in Marco Island, Florida, was an exciting opportunity for over 200 industry professionals from around the world to come together and shape the future of the slag sector. The event sparked engaging discussions on innovations in artificial intelligence, tackling regulatory challenges, and the vital role of leadership and safety in the industry's growth.
An Australian organisation Suvo Strategic Minerals has produced a high-strength, low-carbon cement made from nickel slag. Their recent trials in Indonesia showed promising results, with the slagbased cement achieving impressive strength levels after just seven days— this has set to position Suvo as a leader in cement alternatives.
Finally, In a major collaboration, BHP, BlueScope, and Rio Tinto are advancing decarbonisation in the steel industry through the NeoSmelt pilot project. This initiative aims to develop near-zero emissions steelmaking technologies in Australia, combining worldclass expertise to overcome technological hurdles and pave the way for a sustainable future.
Kaspar Moore Editor Kaspar Moore
Driving Change: TRANSPORT NSW'S INTEGRATION OF CIRCULAR ECONOMY IN ROADWAY PROJECT Driving Change: TRANSPORT
NSW'S INTEGRATION OF CIRCULAR ECONOMY IN ROADWAY PROJECT
Transport NSW (TfNSW) are one of the largest procurers of projects in Australia, having significant demand for construction materials. With this, TfNSW have a responsibility to work with suppliers and delivery partners to encourage a shift towards low carbon alternatives, and the use of sustainable materials.
Their road and highway projects across the state are delivering on this by incorporating circular economy principles to reduce waste and pollution and to keep products and materials in use for longer.
TfNSW’s Net Zero and Climate Change Policy sets ambitious targets to address emissions from their operations, maintenance, construction, and road use. Having adjusted accordingly to focus on the areas of - Improving environmental outcomes, responding to climate change, align spending and impact, TfNSW aim to achieve net zero in Transport operational and fleet emissions by 2035.
THE NOWRA BRIDGE PROJECT
Rethinking traditional construction methodologies of hessian and plastics, the project team used reusable thermal curing blankets to maintain the optimum conditions for concrete curing, increasing the use of this resource by approximately two skip bins per bridge segment.
For an adjacent local road constructed as part of the project, their delivery partner developed an asphalt mix with 85 per cent recycled content, comprising of steel furnace slag aggregates (66 per cent), recycled asphalt pavement (15 per cent), recycled glass (2.5 per cent) and filler (1.5 per cent). The team also took an innovative approach by using varying slag particle sizes, resulting in the highest recycled content in asphalt across any of their infrastructure projects to date.
THE SYDNEY ROAD ASSET PERFORMANCE
In Greater Sydney, TfNSW’s maintenance contractors are continuously improving and introducing new ways of recycling and reusing materials. One of their delivery partners is reducing the need to replace pipes by relining the inside of the pipe, extending its life by 10 years. Relining can be undertaken without digging up the pipes or displacing vegetation, thus reducing environmental impacts and labour cost.
To manage mattresses that are illegally dumped, another delivery partner worked with social enterprise Soft Landing, which
repurposes timber bases into mulch, recycles mattress springs for metal roofing and reuses mattress foam for carpet underlay, achieving a 75 per cent recycling rate for all mattress components. A number of TfNSW’s delivery partners are implementing measures to improve asphalt sustainability including:
• Recovering almost all by-product asphalt within road maintenance for reprocessing into new asphalt.
• Incorporating recycled content into asphalt mixes including crushed glass and steel furnace slag aggregate.
• Using warm mix additives, which allows asphalt to be compacted at temperatures of up to 30°C below standard hot mix temperatures, reducing emissions from asphalt production by approximately 20 per cent.
Visit Transport’s Sustainability website for more examples of how we are working towards a NSW in where every journey is people and planet positive, and access their Transport Sustainability Report here.
PROFICIENCY TESTING AUSTRALIA’S GROUNDBREAKING STUDY ON
STEEL FURNACE SLAG AGGREGATE
Proficiency Testing Australia (PTA) has successfully completed the first large-scale proficiency study on 14mm Steel Furnace Slag Aggregate, in its 33rd round of the aggregate proficiency testing program (APT Program). The program’s aim was to assess the laboratories’ abilities to competently perform the prescribed analyses on a 14mm steel furnace slag aggregate sample.
It was the first proficiency testing program organised by PTA that did not use a natural quarry aggregate. Overall, 87 laboratories participated in the program, demonstrating an interest among construction materials testing laboratories in testing alternative materials.
"Proficiency Testing Australia (PTA), assesses laboratories' competence in performing tests and measurements while providing an external audit of their quality control procedures. PTA specifically serves the construction materials industry by offering testing programs for aggregates, soils, concrete, rocks, cement, asphalt, and bitumen, and comparing the results from different laboratories on identical samples."
The 33rd APT program is accredited by International Accreditation New Zealand and was organised in collaboration with Australian Steel Mill Services (ASMS) for sample supply and Luke Murphy of Colas NSW for sample preparation, pretesting and technical assistance.
The program was designed to cover the following methods:
• Bulk Density
• Particle Density and Water Absorption of Aggregate
• Particle Size Distribution
• Material Finer than 75 µm
• Particle Shape by Proportional Caliper (2:1 Ratio)
• Flakiness Index
It is evident that steel furnace slag exhibits a larger variability of results than natural quarry aggregate. Steel furnace slag is subject to a number of conditions that can affect its physical properties and, in turn, the results’ variability, including the production process, raw material chemical composition, and the rate at which it is cooled.
In comparison, natural quarry aggregate sourced from a single geological deposit is more likely to have a relatively uniform composition.
Despite its variability, steel furnace slag exhibits many physical and mechanical properties that are appropriate for its application in the asphalt industry, making it a versatile and financially viable alternative to natural quarry aggregate.
Acknowledgments:
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WHAT IS STEEL FURNACE SLAG AGGREGATE?
ASMS follows the Basic Oxygen Steelmaking process, which utilises the molten iron from a blast furnace with the addition of scrap steel and fluxes (burnt lime or dolomite), which promote fluidity and enable impurities to be removed in the form of slag. These fluxes are fed into a vessel, and a lance injects oxygen, enabling a reaction between constituents to produce steel and steel slag.
The steel is tapped from the vessel into a steel ladle, and the steel slag is poured into a slag pot. The slag pot is then handled by specialised equipment, and the slag is poured into pits for cooling. The steel slag is then removed from the pits and processed by ASMS into asphalt aggregates, road bases, fill materials and filter materials. The products produced are known as Steel Furnace Slag (SFS).
THE BENEFITS OF STEEL FURNACE SLAG
- TRANSPORT NSW
The application of SFS aggregates in road construction offers several notable benefits, particularly under the Transport for NSW Heavy Duty Asphalt specification in NSW.
Its high density and angularity make it an excellent alternative to natural quarry aggregate for creating durable and stable asphalt pavements. These properties enhance the strength and load-bearing capacity of the pavement, making it ideal for heavy-duty applications. SFS also has a high Polished Aggregate Friction Value, which can improve the resistance of the asphalt-wearing surface, increasing safety for road users. Using this by-product in road construction aids in conserving natural aggregate resources and minimises environmental impact.
The Colas NSW Tomago asphalt plant has incorporated steel furnace slag into its asphalt mixes for many years, to produce high-quality asphalt that meets stringent performance specifications. Using steel slag aggregate in heavy-duty asphalt under local specifications can deliver benefits to NSW’s road infrastructure.
For more information, visit pta.asn.au
article was authored by Christian Foia from Proficiency Testing Australia, Luke Murphy from Colas NSW, and Mark Micallef from Australian Steel Mill Services.
SMART CONCRETE
- REVOLUTIONISING THE FUTURE OF CONSTRUCTION
Concrete is the backbone of our modern world, but its production is a major contributor to global carbon emissions. At the university of NSW, Scientia Associate Professor Wengui Li, is leading efforts in pioneering new ‘smart concrete’ and sustainable construction materials. This concrete is self-sensing, self-healing and has electromagnetic shielding capabilities.
“It enables infrastructure to integrate these functionalities without the need for additional equipment such as sensors. This enhances structural coherence. These functionalities not only drive the development of smart concrete but also form the foundational basis for the development of smart cities,” says A/Prof Li.
THE SELF-HEALING CAPABILITIES OF SMART CONCRETE
Cracks in concrete have always been a problem because it loses water as it hardens and shrinks. Factors that cause cracking include excess water in the mix, the speed of drying, stresses exceeding strength, expansion and shrinkage.
Smart concrete can be designed to heal hairline cracks within a couple of weeks of them appearing. This is achieved by adding a crystalline mixture to the mix and working it throughout the concrete as a whole.
“When small cracks develop due to shrinkage, thermal expansion, or minor mechanical stress, the crystalline mixture will be exposed to air,” explains A/Prof Li. “Water is crucial for the healing process, whether it comes from moisture in the air or is intentionally added later. The water enters the cracks and reacts with the crystalline additives.
“This reaction forms new crystalline structures to fill the cracks, similar to compounds that make up hardened cement paste. The effectiveness of the self-healing depends on the crack width, ideally within 0.2 mm. In narrower cracks, the space is more conducive to the rapid formation and bridging of the crystalline structures.”
MONITORING MICRO-DAMAGE
Smart concrete can also be used to measure and monitor early damage at a microscopic level. Piezoresistivity is the changes in electrical resistance in response to mechanical stress or strain. Using this quality in smart concrete allows for data to be collected when pressure or weight is applied, changing its electrical resistance of the concrete.
“When pressure or weight is applied to the concrete, the internal structure undergoes slight deformations which changes the electrical resistance,” says A/Prof Li. “Instead of embedding sensors, we developed a novel concrete with excellent piezoresistivity. When cracks begin to form within the concrete, even if they are microscopic, they alter the pathways of electrical current flow. This results in a measurable change in the electrical resistance, and we can collect the signal as an indicator. As the electrical resistance of a concrete-based sensor is repeatable in an elastic regime, it also makes it a stress sensor.”
ADVANCING SUSTAINABILITY
Smart concrete is sustainable as it uses alternative binders to the current fossil fuel heavy standard. These alternatives include industrial byproducts like fly ash, slag and silica fume. This not only reduces the reliance on energy-consuming cement but also helps in recycling byproduct materials.
“Using nanomaterials improves the mechanical properties and durability of concrete,” says A/Prof Li. “This means less cement is required to achieve the same performance. Smart concrete can self-monitor and self-heal which increases its lifespan and reduces the frequency of repairs and replacements.”
There is also a form called geopolymer concrete, that uses industrial byproducts, such as fly ash from coal combustion and slag from iron production. This is combined with alkaline activators to generate the binder, with outstanding benefits.
“Geopolymer concrete generates lower carbon emissions because it does not rely on Portland cement, which is highly energy-consuming to produce and a major source of CO2 emissions,” says A/Prof Li. “Geopolymer concrete has superior durability and resistance to chemical attacks, making it suitable for harsh environments. It’s fireresistant without significant loss of strength after higher temperature treatment. It achieves a high early strength, which is beneficial for projects requiring short construction time."
REVOLUTIONISING THE FUTURE OF CONSTRUCTION
The construction industry is beginning to embrace the profound benefits of smart concrete. Smart concrete requires less volume, self-heals and gives early warning of any issues.
“Smart concrete allows for efficient resource management,” says A/ Prof Li. “There is reduced need for frequent repairs and it contributes to sustainability goals by lowering overall environmental impact. The future opportunities of this product in the construction industry are very exciting.”
CONFERENCERECAP DUBAI, UAE 2024
The 16th Global Slag Conference has successfully taken place in Dubai, UAE, in April with 175 registered delegates from 32 countries, two field trips to slag grinding plants and the Global Slag Awards dinner at a spectacular camp on the edge of the Arabian Desert.
CONFERENCERECAP DUBAI, UAE 2024 CONTINUED
FIRST DAY
On the first day there were excellent deliveries from Joe Harder, Charles Zeynel, Charles Ochola, Sharon Morgan, Lisa Bhadsavle, Youssef Tawfik, Kalevi Kostiainen, Jagabandhu Kole, Nie Wenhai, and Bipin Sharma.
With key speakers presenting on the following: Joe Harder of OneStone Consulting started the event with an overview of trends in the global slag industry. Only 40 countries produce iron. The traditional means of producing pig iron, using blast furnace (BF) technology, is slowly changing, partly due to the intensity of CO2 production.
Charles Zeynel of ZAG International, the next speaker, has been proclaiming the value of supplementary cementitious materials (SCMs) for several decades, but demand has finally caught up with supply due to decarbonisation and simple economics. Charlie pointed out that many more different types of slags are now being valorised, alongside other SCMs, due to the carbon intensity - and production expense - of OPC. Arusha Ahmed Khan of Cemcoa, part of the Shun Shing Group (owners of Green Cement slag grinding plant in Dubai, location of the event’s first field trip), who gave an overview of Asian slag markets. Crude steel production in Japan has been slowly falling, but the country is still a major exporter, primarily to Asian markets but also to the US. EAF steel production is increasing throughout Asia.
DESSERT IN THE DESERT AND AWARDS
After the first day of the conference, delegates enjoyed a dinner on the edge of the sandy Arabian desert, including some delicious, sweet desserts and a spectacular fire-show. The Global Slag Awards were presented, including the ‘slag personality of the year’ awards, which went to Arusha Ahmed Khan of Cemcoa, to Anil Bhadsavle of WALAN Specialty Construction Products, to Niklas Törnkvist of Magsort and to Charles Ochola of the US National Slag Association. JSW Steel and JSW Cement won ‘slag product producer of the year,’ Magsort won for equipment supplier of the year, the ArcellorMittal-Nippon Steel India JV won plant of the year for the Hazira plant in Gujarat, Ecocem won product of the year for ACT, and Saudi Ready-Mix Concrete won for slag user of the year. CarbiCrete won the ‘technical innovation’ award (see also below).
SECOND DAY
Into the second day, we were presented with insightful deliveries by Arunachala Sadangi, Kelly Cook, David Algermissen, Volkert Feldrappe, Andreas Neumann, Pithchai Sivakumar, Ryan Bourns, Kenneth Lerner, John Reddy, Ali Abdelhaq, and Balasubramaniam.
Featured key speakers presented on the following: Arunachala Sadangi of Nuvoco Vistas Corporation gave the first presentation on the second day, giving a ‘deep dive’ into beneficiation technology for the improvement of reactivity of LD slags, through reducing its iron content, increasing its glass content, and improving its basicity factor.
Kelly Cook of Edw. C. Levy Co. gave a two-part presentation, with the first part giving details of a seven-year case study of the use of steel slag in a heavily used concrete pad. In the second part, Kelly asked whether hexavalent chromium is really present in slags, or if it is present only as an experimental relict.
Volkert Feldrappe of the FEhS next spoke about the use of steel slag in concrete, concluding that if it is to be used, then its free lime content must be low: EAF and DRI-EAF slags (and copper slag) will normally have sufficient soundness, while BOF slag will need to be treated to minimise free lime content.
CONCLUSIONS
Delegates subsequently gathered for a farewell party, during which the prizes for best presentation were awarded (as voted by the delegates).
David Algermissen of the FEhS was third for his paper on DRI slags; Arusha Ahmed Khan was second for her paper on slag markets in Asia; and Kelly Cook of Edw. C. Levy Co. was first for her paper on use of steel slags and on slag characterisation.
After the success of the first post-Covid Global Slag Conference, in Düsseldorf in 2023, delegates voiced their preference to take place in Dubai in 2024. Their intuition that the event would bring great interest and participation from Asia-based delegates was amply bourne-out by the very large number of delegates attending the event in the Middle East.
The event was strongly praised for its technical content, for its smooth organisation and for its excellent networking opportunities. This year’s conference has really set the tone, with high anticipation for next year’s instalment. The 17th Global Slag Conference 2025 will be held in Vienna, Austria from 25th to 26th of June 2025.
Learn more about the conferecne and the speaker’s presentation here.
Find out more about the 2025 17th Global Slag Conference here.
NOMINATIONS ARE NOW OPEN!
AUSTRALIAN GOVERNMENT TASKS PRODUCTIVITY COMMISSION TO EXPLORE CIRCULAR ECONOMY BENEFITS
The Federal Government run by Anthony Albanese has tasked the Productivity Commission to lead an inquiry into opportunities to boost circularity across the Australian economy. In a circular economy, materials and products are kept in use longer, by designing longer lasting and recyclable products, and by boosting by-product repurposing and recycling infrastructure.
This inquiry is about exploring sustainable solutions that are good for the environment and good for business – helping to reduce material going to landfill while also encouraging more efficient use of raw materials. Better quality and longer lasting products and better labelling of these products are also good for consumers, reducing the need to throw away and replace poorly made goods.
FOCUS OF THE INQUIRY
Over the next 12 months, the inquiry will:
• Explore the potential for Australia to improve resource productivity in ways that benefit the economy and the environment – including by providing more choices for consumers.
• Identify priority areas for Australia, including considering where other countries have made the greatest progress.
• Identify barriers that limit the efficient use of raw materials and prospective approaches to address them.
The Productivity Commission inquiry was a key recommendation of the Circular Economy Ministerial Advisory Group, which advises the Australian Government on ways to realise opportunities associated with the circular economy.
“This is all about looking into new ways to add value to our material resources to create more jobs and more opportunities for more people,” said Treasurer, Jim Chalmers.
“By re-using and recycling and repairing more of our by-products, we can create more opportunities right through the supply chain for Australian companies and Australian workers… Australia’s economic output per kilogram of materials consumed is less than half the OECD benchmark, and this inquiry will look at how we can lift that performance.”
Tanya Plibersek, the Minister for the Environment and Water, said the government is focused on building a circular economy where we waste less and reuse more. Continuing to explain that “Australia currently has the third highest material footprint per capita in the OECD, and the fourth lowest rate of materials productivity. According to the most recent National Waste Report, Australian households and businesses generate the equivalent of almost three tonnes of waste per person, per year,” she said.
“The transition to a circular economy clearly requires economy-wide changes, with innovative thinking and reforms from governments and businesses. This is the opportunity that the Productivity Commission will explore, and I look forward to its report.”
12TH EUROSLAG CONFERENCE RECAP - BILBAO, SPAIN 2024: THE FUTURE OF FERROUS SLAG
EUROSLAG brings together 26 organisations and companies from 17 countries, including the FEhS Institute and the German Ferrous Slag Association. As a European network for the production, use and development of ferrous slags and slag-based products, EUROSLAG focuses on research and technology, European standardisation, and internal and external communication.
The transformation of the steel industry's focus to lowering CO2 during manufacturing processes has had a massive impact on the by-product ferrous slag. The 12th EUROSLAG conference that took place on the 23rd to 25th this October in Bilbao, Spain, voiced the challenges the industry currently face and the solutions available.
Under the motto ‘Slags for the Future, the Future of the Slags’, 230 participants from 34 countries exchanged ideas in the sessions that included: ‘Legislation and Standardisation’, ‘Applications and Best Practices’, ‘Future Trends in the Steel Sector and Implications on Slag’, and ‘Tendencies in Slag Utilisation and Research Projects’. The European Association of Producers and Processors of Ferrous Slag - EUROSLAG, is an organisation based in Duisburg, who puts together this trade event every two years. This year in Bilbao, EUROSLAG had the major support of the Basque Steel Cluster Association Siderex, the Spanish Steel Industry Association Unesid and the Spanish Steel Technology Platform Platea.
In addition to the influence of the decarbonisation process on the properties and availability of slags, this year's EUROSLAG focused on the impact of legislation and standardisation, including technical and ecological issues, innovative production and processing, characterisation and use of slags, new areas of application and the recovery of metallic raw materials from ferrous slags.
One of the core tasks was the necessary changes to the regulations for the use of slag products for the modern steel industry.
The organisers also emphasised the industry's strong commitment to innovation, modernisation, and sustainability as well as the importance of research and international networking.
Thomas Reiche, Chairman of EUROSLAG and Managing Director of FEhS Building Materials Institute from Duisburg shared that ‘We would like to thank the Spanish organisers for this very successful event. The large number of participants this year, not only from Europe', emphasising the economic and ecological importance of by-products for the steel industry.
In 2023, 35.8 million tonnes of iron and steel slag were produced in the European Union and Great Britain. Over 90 per cent of this was used in building materials, fertilisers, and metallurgy.
This avoided the extraction of 44 million tonnes of natural rock and the emission of around 12 million tonnes of CO2 through the use of granulated blast furnace slag.
In the period from 2000 to 2023, a total of 1.17 billion tonnes of natural rock and 416 million tonnes of the climate-damaging gas were saved. This track record must be confirmed and expanded in the future.’
Every two years, EUROSLAG organises the Slag Conference together with national partners. The 13th edition will take place in Sweden in 2026 and is organised by Jernkontoret, Swerim and the University of Lulea.
Photo: Round table discussion at EUROSLAG 2024 (c) FEhS-Institut
THE ROLE OF SLAG IN REDUCING CORROSION IN GEOPOLYMER CONCRETE
Geopolymer concrete with a high slag content produces the following primary reaction products: calcium silicate hydrate (C-S-H), calcium aluminate silicate hydrate (C-A-S-H), sodium aluminate silicate hydrate (N-A-S-H), and hydrotalcite phases [1,2,3] .
As the slag content in geopolymer blends increases, the binder contains more C-S-H and C-A-S-H than N-A-S-H, along with a higher amount of hydrotalcite phases [1,4]. C-A-S-H products are known to have a greater binding capacity for chloride ions (and accompanying sodium ions) than N-AS-H, which can help limit the ingress of these ions. Figure 1 shows the chloride diffusion rate of slag-containing geopolymer concrete. As the slag percentage increases, the chloride diffusion rate decreases.
This indicates that geopolymer concrete containing slag takes longer to initiate corrosion, especially in mixes with higher slag content (>50%). As the slag content in geopolymer concrete increases, the initiation time for chloride-induced corrosion also increases. These findings suggest that slagblended geopolymer concrete structures would have a longer service life in chloride-rich environments compared to those without slag.
References
1. Ismail I, Bernal S.A.,Provis J.L.,San Nicolas R.,Brice d.g.,Kilculle A.R.,Hamdan S, Van Denventer J.S.J, Influence of fly ash on the water and chloride permeability of alkali-activated mortar and concretes, construction and building materials, Volume 48 pp 1187-1201, 2013.
2. Kumar S.,Kumar R.,Mehrotra S.P., Influence of granulated blast furnace slag on the reaction,structure and properties of fly ash ased geopolymer, Journal of material science Volume 45,pp 607-615, 2009.
3. Puertas F., Fernandez-Jimenez A., Minerological and microstructural characterisation of alkali-activated fly ash/ slag pastes, Cement and concrete composities, Volume 25, pp 287-292, 2003.
4. Kayali O., Khan M.S.H, Sharfuddin Ahmed M., The role of hydrotalcite in chloride binding and corrosion protection in concretes with ground granulated blast furnace slag, cement and concrete composites, Volume 34, pp 936-945, 2012.
5. Tennakoon C, Shayan A, Sanjayan J, Xu A. Chloride ingress and steel corrosion in geopolymer concrete based on long term tests. Materials and designs, Volume 116 pp 287-299,2015.
Figure 1: Chloride profiles of concrete after 5 weeks of immersion test [5]
106 TH NSA ANNUAL MEETING RECAP: A GLOBAL GATHERING OF LEADERS IN THE SLAG INDUSTRY
The National Slag Association (NSA) recently held its 106th annual meeting at the picturesque JW Marriott Marco Island Beach Resort located in Marco Island, Florida. Delegates from North America, Europe, and Asia, united to discuss the future of the slag industry, comprising of over 200 attendees who represented mill service providers, steel mills, equipment manufacturers, researchers as well as students.
The event was officially kicked off by a golf outing followed by a lively reception cocktail that set the energy for the discussion ahead. A highlight of the opening was a compelling keynote from Eric Stuart Vice President, Sustainability & Environment for the Steel Manufacturers Association (SMA). Eric provided an assessment of the steel industry and its future, offering valuable insights into its evolving landscape both locally and globally.
Throughout the meeting, allied members shared cutting-edge innovations shaping the slag industry’s future. A key topic was the potential of artificial intelligence to drive significant improvements across the sector. These presentations demonstrated how AI can be harnessed not only to enhance productivity and operational efficiency, but also to create a safer, more sustainable working environment.
Several presentations also focused on the pressing regulatory and manufacturing challenges currently facing the slag industry. Deb Proctor led a detailed discussion on the findings from the latest human health risk assessment of Electric Arc Furnace (EAF) slag products, offering strategies to mitigate regulatory hurdles that are becoming increasingly complex. NSA Board Chairman Russ Burke followed with an insightful session on leadership, accountability, and partnership, stressing how the industry can learn from past manufacturing challenges and build a stronger, more resilient future.
The meeting also featured contributions from key government figures. Representatives from the Department of Labor’s Occupational Safety and Health Administration (OSHA) shared updates on evolving safety regulations, while Elizabeth Sangine, Chief of Mineral Commodities at the U.S. Geological Survey’s National Minerals Information Center, reminded attendees of the historical significance of slag as a mineral commodity — a classification that has existed since the early 1900s.
The event concluded with a safety awards banquet, where attendees celebrated the industry's commitment to safety excellence. The evenings keynote speaker, Jessica Gendron, delivered an inspiring talk on the importance of building a thriving workforce through strong relationships. Her emphasised themes of fostering trust and collaboration can provide a guide to companies through an evolving industry.
As the 106th NSA Annual Meeting drew to a close, it was clear that the slag industry is poised for a future with an understanding of the importance of strong leadership, safety, sustainability, and constant evolution. We look forward to seeing you at the next iteration of the NSA Annual Meeting next year.
SUVO DEVELOPS LOW-CARBON CEMENT FROM NICKEL SLAG
Suvo Strategic Minerals (ASX:SUV) is Australia’s only hydrous kaolin producer who wholly owned Pittong operation in Victoria, Australia. Suvo is on the way to developing a potential type of low-carbon cement from nickel slag during recently completed laboratory trials at the Makassar State University (UNM) in
The company is aiming to reduce the carbon footprint of cement production — which is currently the world’s single largest industrial emitter of greenhouse gasses.
According to the Cement Industry Federation, the total emissions from the integrated production of clinker and cement were 4.7 million tonnes of carbon dioxide in 2020-21.
Suvo’s trials, which were completed by Professor Subaer Junaedi using nickel slag, comprised three samples which returned an average strength test of 29.9 megapascals (MPa) after seven days, with the highest strength reaching 37.5MPa. This is a significant discovery when considering that Normal Class concrete is defined as products ranging from 20 to 50 MPa compressive strength at 28 days
Nickel slag is a co-product of nickel production that is solidified under ambient atmospheric conditions. It is commonly stockpiled or sent to landfill. Executive Chairman Aaron Banks says if the cement industry were a country, it would only be behind China and the US in CO2 emissions.
Aaron Banks - Executive Chairman
“The world use of cement is equivalent to building New York City every 40 days,” he says. " "
“We are excited to have commenced this workstream in Indonesia testing the by-product of one of the country’s largest miners, with our ultimate goal being to manufacture an environmentally friendly and low carbon alternative to Portland cement.
“Achieving up to 37.5Mpa after only seven days is an outstanding first round trial result for the company and could provide an entry into a large industry.”
Banks adds that the opportunity to play a part in reducing emissions in the cement industry is comparable to the role of Electric vehicles (EVs) in replacing internal combustion engines in the global passenger car fleet.
The nickel slag used by UNM was provided by PT Huadi Nickel-Alloy Indonesia, which is a nickel pig iron operation. Suvo says it is considered one of Indonesia’s largest nickel producers and stockpiles significant quantities of nickel slag.
“We will now commence the next round of testing with UNM and will provide the results of both trials to PT Huadi which will allow us to advance negotiations with respect to a potential partnership and or the ongoing offtake of the nickel slag and commercialisation of a low carbon cement by the company,” he says.
FORGING THE FUTURE: STRATEGIC COLLABORATION TO DECARBONISE STEEL
In February 2024, BHP, BlueScope and Rio Tinto announced a collaboration to help tackle one of the most pressing issues in the global iron and steel sector: decarbonising steel production. Achieving this will take years and without major investment in innovation now, Australia risks being left behind. The collaboration provides an unprecedented combination of industry-leading expertise. This includes BlueScope’s expertise in steelmaking and industrial plant design, operation, and maintenance. BlueScope also brings unique experience of operating for over 40 years the only electric smelting furnace processing DRI in the world in New Zealand. BHP and Rio Tinto have a deep understanding of Pilbara iron ores and in-house iron and steelmaking expertise.
ABOUT THE TECHNOLOGY
A number of technologies are currently under development globally with the potential to produce near-zero emissions [1] steel. Longer term, a combination of Direct Reduced Iron (DRI) using blue or green hydrogen and electric smelting furnaces (ESF) using renewable energy shows promise for Pilbara iron ores. The focus of the NeoSmelt pilot however is to build, test and develop the technology in Australia, which is likely to require natural gas in the short to medium term.
The NeoSmelt pilot aims to prove that DRI produced from Pilbara ores can be processed into iron suitable for steelmaking in an ESF. If proven, this could provide a pathway for future emissions intensity reduction at iron and steelmaking operations, including at BlueScope’s facilities.
PILOT PROGRESS
The project is in pre-feasibility stage, which means that since February 2024 we have formed a project team, established a Framework Agreement to define the terms of the project and commenced assessment of suitable locations for the pilot. The factors involved in site selection include supporting infrastructure, available workforce, access to target industry and supply chain partners, and suitability for operational trials. The pre-feasibility study work program is expected to conclude by April 2025 and would then move to a feasibility study and costing estimates for the pilot.
SIGNIFICANCE OF THE COLLABORATION
This collaborative effort underscores the power of industry partnerships to harness research and innovation to overcome substantial technological obstacles. The project aligns with BHP, BlueScope and Rio Tinto’s strategies to help reduce industrial greenhouse gas emissions; contribute to Australia’s decarbonisation; encourage collaboration to solve industry challenges; drive innovation and upskill Australian industrial workforces for the future near zero emission steel economy. The NeoSmelt pilot represents an essential first step in a long road toward commercialisation, paving the way for the innovation required to strengthen Australia’s global competitiveness and future in the near-zero emission steel economy.
WHAT HAPPENS NEXT?
Depending on the outcome of the pre-feasibility and feasibility stages and the companies’ final investment decision, a pilot plant could be commissioned as early as 2027. This is one step in many of our investments in decarbonisation technologies and playing our part in Australia’s energy transition.
This is a collaborative pilot to solve a technological hurdle to decarbonisation of steelmaking to the benefit of all three companies and beyond.
Image: Tim Day (BHP Western Australia Iron Ore Asset President), Tania Archibald (BlueScope CEO Australian Steel Products), and Simon Trott (Rio Tinto Chief Executive Iron Ore), leaders of the companies within the partnership.
Image:
A conceptual render for the NeoSmelt pilot facility.
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