A new study published in Scientific Reports has found that treating recycled concrete with magnetized water and nano-silica can increase compressive strength by up to 14 % while significantly reducing damage from acid rain. After evaluating 80 engineered concrete mixes under simulated sulfuric acid exposure, researchers identified an optimal blend that enhances durability without compromising sustainability.
Study: Sulfuric acid corrosion resistance of recycled aggregate concrete containing magnetized water. Image Credit: Love Employee/Shutterstock.com
Rethinking Concrete for a More Sustainable Future
Sustainability has become a central priority in the construction industry, particularly in concrete production. Among the most promising solutions is recycled aggregate concrete (RAC), which incorporates construction and demolition waste to reduce environmental impact.
By limiting reliance on virgin aggregates and diverting waste from landfills, RAC supports more responsible resource use. However, its environmental advantages come with technical challenges. Compared to conventional concrete, RAC often exhibits lower mechanical strength and reduced durability, especially in aggressive environments such as those exposed to sulfuric acid or acid rain. These conditions accelerate material degradation and can significantly compromise structural integrity.
Addressing this performance gap calls for targeted material refinement.
Targeted Modifications to Strengthen RAC
To improve RAC performance under acidic exposure, the researchers introduced two complementary modifications: magnetized water (MW) and nano-silica (NS).
Magnetized water, produced by passing water through a magnetic field, has been shown to enhance cement hydration and promote more uniform microstructural development. Nano-silica, a highly reactive supplementary material, contributes through pozzolanic reactions that refine pore structure and strengthen the cement matrix.
Individually, both materials offer measurable benefits. The central question of the study, however, was whether their combined use could meaningfully improve RAC’s resistance to sulfuric acid attack while maintaining its sustainability advantages.
To answer that question, the team designed a comprehensive experimental program.
Research Methodology: Investigating MW and NS Synergy
The study examined 80 concrete mixtures with systematic variations in:
- RAC replacement levels (0 % to 100 %)
- Nano-silica dosage (0 % to 6 %)
- Magnetized water exposure time (0 to 30 minutes)
To simulate real-world conditions, specimens were exposed to acid rain solutions with pH levels of 2.5, 4.0, 5.5, and 7.0 over curing periods of 28, 56, and 90 days.
Rather than immersing samples continuously, researchers used a controlled spray system that applied an acidic solution for one hour per day, followed by laboratory conditioning. This approach more closely replicated natural rainfall cycles and allowed for realistic durability assessment.
Each mixture was evaluated using compressive strength testing, electrical resistivity measurements, sorptivity analysis, and mass loss tracking. Together, these metrics provided a detailed picture of both mechanical performance and resistance to acid penetration.
From Testing to Results: Clear Performance Trends
The results confirmed a predictable baseline trend. Increasing acidity reduced compressive strength in all mixtures. When pH declined from 7 to 2.5, reference concrete experienced strength losses ranging from 16.2 % to 25.4 %, with greater reductions over longer exposure durations.
Replacing natural aggregates with recycled content further decreased strength. Average reductions were:
- 3.2 % at 25 % replacement
- 6.4 % at 50 % replacement
- 15.9 % at 75 % replacement
- 25.4 % at 100 % replacement
Yet this downward trend shifted once nano-silica and magnetized water were introduced.
Nano-silica improved compressive strength by 2.4 % to 6.8 %, while magnetized water contributed gains of 2.2 % to 6.8 %. When combined (specifically 6 % NS with 30 minutes of MW exposure), the mixture resulted in a 14.1 % increase in strength compared to control specimens.
Durability indicators reflected similar improvements. Electrical resistivity rose by 12 % to 38 %, signaling reduced permeability and a denser internal structure. Mass loss decreased by approximately 33 %, and sorptivity dropped by 32 %, indicating stronger resistance to acid ingress.
Even so, under highly acidic conditions (pH 2.5), resistivity declined over time across all mixes. This finding reinforces an important point, that while material optimization improves performance, extreme acidity remains a dominant deterioration mechanism.
Among all formulations, the combination of 25 % RAC, 6 % NS, and 30 minutes of MW exposure delivered the most balanced mechanical and durability performance.
Practical Implications for Harsh Environments
Taken together, the findings suggest a clear pathway for strengthening recycled aggregate concrete in corrosive environments. By enhancing hydration, refining pore structure, and improving the interfacial transition zone (ITZ), the combined use of MW and NS helps offset RAC’s traditional weaknesses.
For regions affected by acid rain and industrial pollution, these improvements translate into longer service life and reduced maintenance demands. Importantly, they do so while preserving RAC’s sustainability benefits.
The study also points to potential secondary advantages. Previous research cited by the authors suggests magnetized water may improve workability and hydration efficiency, potentially reducing overall water demand. Although water reduction was not directly measured in this program, it represents an area worth further exploration.
Conclusion and Future Directions
This research demonstrates that carefully engineered material modifications can significantly enhance the performance of recycled aggregate concrete under sulfuric acid exposure. Improvements in compressive strength, electrical resistivity, and durability metrics show that sustainability and structural reliability do not have to be competing priorities.
At the same time, the gradual decline in performance under prolonged low-pH exposure highlights the need for continued optimization, particularly for infrastructure subjected to severe environmental conditions.
Future studies should investigate long-term field performance under mixed acid exposure and variable climate cycles. Deeper microstructural analysis would also help clarify the mechanisms driving hydration enhancement and pore refinement when magnetized water and nano-silica are used together.
Journal Reference
Bamshad, O., &. et al. (2026). Sulfuric acid corrosion resistance of recycled aggregate concrete containing magnetized water. Sci Rep. DOI: 10.1038/s41598-026-38607-3, https://www.nature.com/articles/s41598-026-38607-3
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