Engineers have turned industrial waste into concrete that’s tougher and blocks radiation. It could change how we build hospitals, reactors - even space facilities.
Study: Mechanical, microstructural, and radiation shielding characteristics of sustainable high-strength concrete incorporating recycled wastes blended powders. Image Credit: ashok india/Shutterstock.com
Researchers investigated the mechanical, microstructural, and radiation-shielding properties of sustainable high-strength concrete (HSC) made with recycled industrial waste-blended powders.
The study, published in the journal Scientific Reports, highlights the potential of using industrial by-products such as silica fume (SF), limestone powder (LS), and dealuminated kaolin (DK) to improve concrete performance while reducing the environmental impact of traditional cement production.
Tackling Carbon Emissions in Construction
Ordinary Portland cement (OPC), a staple of modern construction, is responsible for about 7–8 % of global carbon dioxide (CO2) emissions. As the demand for infrastructure continues to grow, so does the urgency to find cleaner alternatives. This has led to growing interest in supplementary cementitious materials (SCMs) like SF, LS, and DK, which possess pozzolanic properties, chemical traits that help reinforce the cement matrix.
High-strength concrete (HSC), which offers a compressive strength of 40 MPa or more, is especially well-suited for incorporating SCMs. These materials not only strengthen the mix but also help reduce the environmental toll of cement production, making them a promising path toward more sustainable construction.
A Closer Look at the Testing Process
To evaluate the full potential of these industrial by-products, the researchers designed nine different concrete mixes using various combinations of SF, LS, and DK. The study aimed to assess how these blends affected fresh and hardened properties such as workability, compressive strength, and microstructure.
Workability was measured using slump tests, while mechanical strength was assessed through compressive and tensile strength testing. To understand microstructural changes, the team used scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDX).
Notable Gains in Strength and Microstructure
The study revealed that incorporating SF, LS, and DK led to significant improvements in the mechanical performance of high-strength concrete. For instance, the mix containing 10 % DK showed a 37.3 % increase in compressive strength and a 43.35 % increase in tensile strength compared to the control.
Similarly, adding 15 % SF resulted in a 17.7 % boost in compressive strength. When combined, a ternary blend of 15 % SF and 10 % DK achieved a 23.4 % increase, while the quaternary mix - 15 % SF, 10 % LS, and 10% DK - delivered 23.4% and 22.3% improvements in compressive and tensile strength, respectively.
These gains were strongly linked to the pozzolanic reactivity of SF and DK, which encouraged the formation of additional calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H) gels. This chemical activity contributed to a denser, more robust concrete matrix. Supporting this, EDX analysis showed lower Ca/Si and Ca/Al ratios, indicating a higher degree of hydration. Microstructural imaging further confirmed the densification, revealing fewer cracks, reduced porosity, and more efficient hydration throughout the matrix.
However, these improvements came with a trade-off in workability. The addition of fine SCMs reduced slump values across all mixes, signaling lower flowability. This effect was especially pronounced in ternary and quaternary combinations, likely due to the increased surface area and internal friction that raised water demand during mixing.
Effective Radiation Shielding Capabilities
In addition to mechanical improvements, the study found that several of the concrete mixes also offered massive improvements in terms of radiation shielding, an important advantage for structures exposed to ionizing radiation. This was especially evident in blends containing DK, either alone or in combination with SF and LS.
Mixes such as DK10 and SF15LS10DK10 recorded the highest linear attenuation coefficients (LAC) for gamma rays, thanks to their higher density and favorable elemental composition. These properties improve the material’s ability to absorb and scatter radiation, reducing its penetration depth.
When it came to shielding fast neutrons, the results were even more pronounced. DK10, SF15LS10, and SF15LS10DK10 achieved the highest neutron removal cross-sections, along with the lowest half-value and relaxation lengths, all of which are indicators of superior neutron attenuation.
Taken together, the findings suggest that SF, LS, and DK not only contribute to strength and durability but also enhance the material’s capacity to block harmful radiation. This dual functionality makes these mixes particularly suitable for high-performance applications where both structural integrity and radiation protection are critical.
Applications for Sustainable Construction Practices
The results of this study have implications for advancing sustainable construction. By partially replacing traditional cement with SF, LS, and DK, engineers can both improve the mechanical performance of high-strength concrete and also reduce its environmental footprint.
The enhanced strength and durability of these mixes make them well-suited for structural applications, such as load-bearing elements and pavements. Just as importantly, the added benefit of radiation shielding broadens their potential use in environments where protection from ionizing radiation is essential, such as hospitals, nuclear power plants, and research facilities.
Conclusion and Future Directions
This research points to a promising shift in how we think about building materials. Using industrial by-products like SF, LS, and DK isn’t just about improving concrete strength - it’s about reimagining what concrete can do, and what it can replace. The fact that these materials also contribute to radiation shielding makes their potential even more compelling, especially in places where safety and durability can’t be compromised.
That said, there’s still work to do before these mixes are ready for widespread use.
One of the big unknowns is how they’ll perform over time. Will they hold up under extreme temperatures? What happens when they’re exposed to chemicals or moisture for years on end? These are questions that need answering before engineers can confidently apply them in real-world projects.
There’s also the question of consistency. Because these materials come from industrial waste streams, their properties can vary; something that needs to be accounted for if they’re going to be used at scale. And from a practical standpoint, getting the balance right between strength, workability, and sustainability will be key.
Still, the opportunity here is clear. With further research, smarter mix designs, and support from the construction industry, these materials could help push concrete into a more sustainable era where performance and environmental responsibility go hand in hand.
Journal Reference
Elbauomy, A.K., & et al. (2025). Mechanical, microstructural, and radiation shielding characteristics of sustainable high-strength concrete incorporating recycled wastes blended powders. Sci Rep 15, 40398. DOI: 10.1038/s41598-025-23824-z. https://www.nature.com/articles/s41598-025-23824-z
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