Can 1 % make all the difference? Researchers prove that a small dose of antifreeze agent dramatically boosts the frost resistance of recycled concrete, reshaping how we build sustainably in cold climates.
Study: Frost resistance improvement of recycled powder concrete by chemical admixtures. Image Credit: Prime Background/Shutterstock.com
In a study published in the journal Scientific Reports, researchers explored how chemical admixtures can boost the frost resistance of recycled powder concrete (RPC), a crucial step in making construction waste more viable for use in cold climates where durability is key.
Recycled Powder and its Role in Sustainable Construction
Concrete and masonry debris make up a major share of construction waste worldwide. One increasingly viable solution is to repurpose this waste into supplementary cementitious materials, such as recycled powder (RP), which can act as a filler and offer pozzolanic activity, boosting overall concrete performance.
Despite its environmental benefits, RP tends to increase water demand and reduce frost resistance, limiting its use in colder regions.
This study set out to tackle that challenge by testing how different chemical admixtures might counter these drawbacks, with a focus on improving RPC’s durability in freeze-thaw conditions.
How the Study Was Conducted
To understand the impact of admixtures on frost resistance, researchers ran a detailed series of lab tests. They first assessed how well RP interacted with different polycarboxylate superplasticizers (PCs) through adsorption analysis to identify the most compatible formulation.
Three types of admixtures were tested:
- Antifreeze water-reducing agent (AR)
- Air-entraining agent (AE)
- Antifreeze agent (AF)
RPC specimens were mixed with varying RP contents and admixture dosages, then subjected to freeze-thaw cycles to assess frost resistance. Key indicators included compressive strength, mass loss rate (MLR), and relative dynamic modulus of elasticity (RDM).
Microstructural changes were studied using super-depth-of-field (SDF) imaging, scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP), all in accordance with national testing standards in China.
What the Results Showed
The standout performer was the antifreeze agent (AF). After 200 freeze-thaw cycles, the ranking of admixture effectiveness was:
1 % AF > AR > 5 % AE
AF significantly refined the RPC’s pore structure, reducing harmful pores larger than 200 nm by 8.73 %. This led to more hydration products, a denser matrix, and lower susceptibility to frost heave, improving long-term durability.
- AR contributed to higher early compressive strength but fell short over time due to increased water demand and less complete hydration.
- AE helped buffer freeze-thaw stress by creating stable air voids, but when overused, the excess air content weakened compressive strength.
Although all three admixtures improved frost resistance to some degree, AF offered the best balance between structural performance and durability. The findings underscore the value of tailoring admixture selection and dosage to meet specific performance goals.
Implications for Cold-Weather Construction
This research offers timely insights for engineers and builders working in cold regions, where frost resistance is a critical factor in structural longevity.
By boosting RPC's frost resistance with carefully chosen admixtures, recycled materials become a more practical and environmentally sound option for concrete infrastructure.
These findings also support broader sustainability goals, helping reduce waste and promote circular use of materials without sacrificing performance. The study provides clear, actionable guidance for applying recycled materials in cold-weather construction projects.
Final Takeaways and Next Steps
This study confirms that frost resistance in recycled powder concrete can be significantly improved through targeted use of chemical admixtures, particularly antifreeze agents. It reinforces the idea that sustainable materials can meet high-performance demands when properly engineered.
Looking ahead, the researchers recommend:
- Evaluating long-term performance under diverse environmental conditions
- Analyzing the cost-effectiveness of admixture use at scale
- Conducting controlled studies on admixture combinations and optimal dosages
These next steps will help refine mix designs and unlock new possibilities for eco-conscious, durable construction.
Journal Reference
Yang, C., & et al. (2026). Frost resistance improvement of recycled powder concrete by chemical admixtures. Sci Rep. DOI: 10.1038/s41598-026-35840-8, https://www.nature.com/articles/s41598-026-35840-8
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