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Utilizing alkaline solid waste for low-carbon construction material via in-situ calcium phase design
Bingyang He1,2, Xingyu Zhu3, Yuxin Lei4
1School of Energy and Environmental Engineering, University of Science and Technology Beijing, Beijing, China.
Nature Communications
|August 7, 2025
Summary
Steel slag pre-hydration creates a sustainable cement alternative. This low-carbon material enhances strength and significantly reduces greenhouse gas emissions compared to traditional cement.
Area of Science:
- Materials Science
- Sustainable Construction
- Waste Valorization
Background:
- Global cement production is a major source of greenhouse gases, necessitating low-carbon alternatives.
- Steel slag, an alkaline solid waste, presents potential as a sustainable construction material but faces challenges with free lime (f-CaO) and low hydration activity.
- Developing eco-friendly construction materials is crucial for achieving climate goals.
Purpose of the Study:
- To propose an in-situ calcium phase design strategy for steel slag.
- To develop a high-performance, low-carbon cementitious material using pre-hydrated steel slag.
- To assess the environmental impact and mechanical properties of the developed material.
Main Methods:
- Steel slag underwent an in-situ calcium phase design strategy and pre-hydration treatment.
- Fly ash and an alkaline activator were incorporated into the pre-hydrated steel slag mixture.
- Compressive strength, micro-crack formation, and global warming potential were analyzed.
- The effect of additional energy compensation (heat or microwave) on mechanical properties was investigated.
Main Results:
- Pre-hydration effectively mitigated free lime expansion and micro-crack formation.
- The addition of fly ash and alkaline activator resulted in a Na-rich gel, increasing compressive strength by 133.7%.
- The developed cementitious material exhibits a global-warming potential 60-66% lower than conventional cement.
- Energy compensation methods enhanced mechanical properties and shortened production cycles with minimal CO2 increase.
Conclusions:
- The proposed pre-hydration strategy enables the effective utilization of steel slag as a high-performance, sustainable cementitious material.
- This approach significantly reduces the carbon footprint of construction materials, contributing to climate change mitigation.
- The strategic use of alkaline solid waste offers a simple and effective pathway for sustainable industrial practices.
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