Julson Tchio: The grant was awarded in 2025 through the Tutkijatmaailmalle grant system. Application 20250042: Advanced surface modification and characterisation of low-CO2 steel slag cement

FROM INDUSTRIAL WASTE TO TOMORROW’S BUILDINGS 

Transforming Steel Slag into Sustainable Construction Materials 

Written Content for Walter Åström Foundation 

THE OPPORTUNITY & THE SCIENCE 

A Paradox Worth Solving 

Every day, massive steel plants across Finland—SSAB, Outokumpu, and others produce the steel that becomes our cars, buildings, and bridges. But they also create mountains of slag, a rocky by-product that looks almost volcanic after it cools. For decades, we’ve paid to dispose of this material. Meanwhile, Finland imports thousands of tons of cement annually, shipping in both the product and its embedded emissions. 

Here’s the paradox I’m working to solve: That ”waste” slag could replace what we’re importing. Why This Matters: The Cement Crisis 

Cement production is responsible for 8% of all global CO₂ emissions more than all trucks worldwide. The process hasn’t changed fundamentally in 200 years: heat limestone to 1,450°C (hotter than lava) in massive kilns burning fossil fuels, then release even more CO₂ through the chemical reaction itself. As the world builds more infrastructure, this problem accelerates. The construction industry must transform and we have the materials to do it. 

My Research: Finding the Switch 

Steel slag contains the same chemical elements as cement such as calcium, silicon, aluminum. The energy-intensive work already happened during steel production. Think of slag like a fully charged battery that’s been turned off. My research is finding the right switch to activate it so it can bind materials together, create strength, and last decades, just like cement does, but without the massive environmental cost. 

I work between the University of Oulu’s Fibre and Particle Engineering research unit and the University of Sheffield’s SMASH group, investigating how to transform industrial by-products into high-performance construction materials. 

The circular economy vision: Old way—Mine limestone → Massive energy → Cement | Meanwhile: Make steel → Slag waste → Disposal costs. New way—Make steel (already doing) → Capture slag → Minimal activation → Use as cement. It’s elegant, efficient, and perfectly timed for Finland: steel industry booming, construction expanding, climate commitments demanding action.

The Scientific Challenge 

Hardened cement’s hidden complexity makes this challenging. Under powerful X-ray tomography, you discover an intricate network of crystals, gels, pores, and interfaces evolving over time. When you replace Portland cement with steel slag, everything changes: different chemistry, different crystal structures, different reaction rates, different long-term performance. My job: Understand, map, measure, predict, and optimize all of this. 

Inside the research: Using X-ray tomography at Sheffield, I create 3D models of cement internal structure, investigating pore networks, crack initiation sites, and how structure evolves over years. I test different slag types Blast Furnace Slag versus Electric Arc Furnace slag with various ”activation” methods, comparing performance to Portland cement across dozens of metrics: strength, durability, environmental resistance, sustainability benefits. 

Some days feel more like being a detective gathering clues, testing hypotheses, until patterns emerge. Equipment breaks. Results contradict expectations. But then comes that moment when months of confusing data suddenly make sense. That’s why we do this. 

Real-World Impact: Decarbonization at Scale 

My research focuses on alkali-activated materials, supplementary cementitious materials (SCM), and geopolymers alternative binders that can dramatically reduce construction’s carbon footprint. 

Key findings: Certain slag formulations achieve comparable or superior strength to Portland cement; long-term durability shows promise in accelerated tests; carbon footprint reductions of 50-80% depending on formulation; applications ranging from structural concrete to specialized infrastructure. 

The broader significance: Every ton of Portland cement replaced eliminates roughly 0.9 tons of CO₂ emissions. If 30% of global cement were replaced, we’d eliminate 2-3% of total global emissions equivalent to grounding every commercial aircraft worldwide. This is transformation at the scale needed to address climate change. 

COLLABORATION, SUPPORT & THE PATH FORWARD 

Research Requires Resources 

Research is expensive: X-ray tomography costs thousands of euros per day; chemical analyses run hundreds of euros each; international collaboration demands travel, time, coordination. Without funding, research simply doesn’t happen. 

The Walter Åström Foundation: Catalytic Impact 

The Walter Åström Foundation’s travel grant transformed my research trajectory. It enabled hands-on collaboration with world-leading experts at Sheffield, access to equipment existing in only a handful of locations globally, international conference presentations where ideas get challenged and refined, and relationship building that accelerates progress for everyone involved. 

This wasn’t just logistical support it was strategic investment in building collaborative networks where breakthroughs happen. Every euro created multiplier effects: new techniques learned, unexpected connections made, future collaborations seeded. The foundation demonstrated that Finland values innovation and sustainability, creating pathways for future researchers. 

The I4WORLD Program & Mentorship

The EU Marie Skłodowska-Curie Action I4WORLD program provided comprehensive, sustained support for PhD researchers not one experiment, but an entire program. Most experiments fail. That’s how science works. Short-term funding creates pressure for safe results. Long-term funding enables bold, transformative research. 

I’m profoundly grateful for my supervisors: Prof. Juho Yliniemi (University of Oulu) brings expertise in alternative cementitious materials and Finnish industrial context; Prof. Brant Walkley (University of Sheffield) is a world-leading expert in Alternative cement chemistry; Dr. Elijah Adesanya (University of Oulu), with research planning, data collection, device training, etc. Together, they provide technical guidance, strategic advice, reality checks, and encouragement. Young researchers often face imposter syndrome. Having mentors who believe in you, who’ve navigated these paths that’s invaluable. 

International Collaboration & Young Researcher Perspective 

My work exemplifies modern research transcending borders: lab in Oulu, equipment in Sheffield, research questions affecting the world. Different research cultures reveal blind spots; relationships last careers; knowledge transfers across contexts. 

Challenges, Opportunities & Commitment 

Real obstacles exist: Technical variable industrial by-products require consistent formulations; 200 years of cement data must be compressed. Economic new infrastructure needed; cement is cheap; construction is conservative. Regulatory building codes require extensive testing; liability frameworks aren’t established. 

Why I’m optimistic: Every transformative innovation faced similar obstacles. Electric vehicles, renewable energy, LEDs all seemed impossible until they weren’t. Climate urgency is creating policy support, research funding, industry interest, public demand. We don’t have luxury of slow adoption. That urgency creates opportunities. 

Finland’s Opportunity 

Finland has unique advantages: booming steel industry, strong research infrastructure, political commitment to sustainability, circular economy values. The opportunity: Become to sustainable construction what Finland became to mobile technology a global leader and knowledge exporter. What it requires: Continued research investment, industry-academia partnerships, policy support, willingness to lead. The timeline is now. First movers gain competitive advantages. 

My Commitment: Hope Made Tangible 

Research frustrates regularly experiments fail, equipment breaks, progress feels slow. But every time I see slag mountains unused or read climate warnings, I remember why this matters. 

I’m committed to: Rigorous science with no overpromising; practical application at scale; knowledge sharing through open collaboration; honest communication explaining both potential and limitations. 

The Walter Åström Foundation’s support made my contribution possible. I’m deeply grateful. The Vision 

Steel slag sits in piles across Finland. The knowledge to transform it exists and is improving. The infrastructure can be built. The economic case makes sense. The environmental imperative is clear. What’s needed: Commitment. Investment. Collaboration. Willingness to change. 

We can do this. We’re figuring out how. With continued support from organizations like the Walter Åström Foundation, from programs like I4WORLD, from supervisors who mentor and challenge we will do this.

The concrete of tomorrow will be built from yesterday’s waste, will last decades, and will help create a sustainable world. If 30% of global cement were replaced with slag alternatives, we’d eliminate 2-3% of total global emissions. 

That’s not just research. That’s hope made tangible. 

Research supported by the Walter Åström Foundation and the EU Marie Skłodowska-Curie Action I4WORLD program 

Supervised by Prof. Juho Yliniemi (University of Oulu), Prof. Brant Walkley (University of Sheffield), and Dr. Elijah Adesanya (University of Oulu)