In the race toward sustainable infrastructure, the concrete industry stands at a crucial turning point. While concrete remains the most consumed construction material globally, its environmental footprint—largely stemming from the high carbon intensity of Portland cement—demands urgent innovation. Amid efforts to reduce CO₂ emissions and enhance concrete durability, cellulose nanomaterials have emerged as one of the most promising nanotechnology solutions.

Among these, Cellulose Nanocrystals (CNCs), derived from renewable biomass, are being increasingly investigated for their potential to improve concrete properties without compromising environmental goals. While most prior research has focused on laboratory-scale formulations, recent advancements have now begun testing CNCs under actual construction conditions—paving the way for broader real-world adoption.

This blog explores the field-scale application of CNCs in concrete pavement and evaluates their influence on fresh and hardened properties, shrinkage resistance, and long-term durability.

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What Are Cellulose Nanocrystals (CNCs)?

CNCs are rod-shaped nanomaterials produced primarily through acid hydrolysis of cellulose. With diameters as small as 5–20 nm and lengths ranging from 100–300 nm, CNCs are characterized by:

• High crystallinity (up to 90%)

• Exceptional stiffness (elastic modulus ~150 GPa)

• Large surface area and active hydroxyl groups

These properties not only make CNCs mechanically reinforcing fillers but also influence cement hydration kinetics, microstructure densification, and crack mitigation—particularly appealing for concrete exposed to long-term mechanical stress and shrinkage-induced cracking.

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Why Add CNCs to Concrete?

CNCs offer a host of benefits in concrete matrices:

• Hydrophilicity: Allows better dispersion in aqueous cement mixtures.

• Electrostatic repulsion: Promotes cement particle separation and reduces early agglomeration.

• Water retention: Aids internal curing and hydration continuation.

• Crack bridging: Strengthens interfacial transition zones.

These characteristics prompted researchers to test CNCs in Portland Limestone Cement (PLC) and Ordinary Portland Cement (OPC) systems during full-scale pavement construction.

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Field Study Overview: Bringing Nanotechnology to the Pavement

To evaluate the practicality of CNCs in real construction, a nine-slab test track was constructed at a California research facility using three distinct concrete mixes:

1. OPC mix (with Ground Granulated Blast Furnace Slag – GGBFS)

2. PLC mix (with GGBFS)

3. PLC + CNC mix (0.10% CNC by weight of cementitious material)

CNCs were dispersed using high-shear blending, ensuring uniform integration into the concrete mix at the construction site.

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Results and Insights

1. Workability and Fresh Properties

CNC integration caused a slight reduction in slump compared to PLC-only mixes—a likely outcome of water being absorbed by CNCs due to their hydroxyl-rich surfaces. However, air content and density remained unaffected, and overall constructability was smooth across all slabs.

Interestingly, initial and final setting times were delayed with CNC addition. This aligns with prior findings that CNC particles may adsorb onto cement grains and hinder hydration initiation—leading to longer dormant phases.

2. Hydration Behavior

Using isothermal calorimetry, researchers tracked the hydration kinetics over a seven-day period. Although CNCs slightly delayed the peak hydration rate (similar to the setting time results), the overall cumulative heat release was comparable to PLC-only mixes.

This balance between extended induction periods and sustained heat release suggests CNCs support more gradual and controlled hydration—beneficial in hot climates where rapid setting can lead to early-age cracking.

3. Mechanical Performance

Contrary to expectations, CNCs did not significantly improve compressive or flexural strength at the 28-day or 120-day mark. However, compared to OPC, both PLC and PLC+CNC mixes showed a 10–15% improvement in mechanical strength—likely due to the finer limestone particles and secondary hydration reactions forming calcium carboaluminates.

Key takeaway: While CNCs may not drastically alter strength under field conditions, they do not compromise it either, making them safe for performance-critical applications.

4. Drying Shrinkage: A Breakthrough Benefit

Among all measured properties, drying shrinkage showed the most notable improvement. At seven months, concrete with CNCs exhibited 9% lower shrinkage than the PLC mix, and nearly 20% lower than OPC. This is a critical finding, especially for arid regions where shrinkage-related cracking compromises pavement durability.

This reduction is believed to stem from CNCs acting as internal water reservoirs, enabling longer hydration and denser microstructure formation, including high-density calcium-silicate-hydrate (C-S-H) gels.

5. Durability and Moisture Resistance

Durability tests confirmed that both PLC and CNC-enhanced concrete had higher electrical resistivity than OPC, indicating a denser, less connected pore network that impedes ion transport—especially chlorides.

However, when it came to water absorption, the standalone PLC mix outperformed the CNC variant. Although still better than OPC, the CNC mix exhibited slightly higher water intake, possibly due to CNC’s own moisture affinity or field-related dispersion limitations.

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CNC Dispersion: Practical Considerations

One challenge in scaling CNC use lies in dispersion techniques. Laboratory ultrasonication isn’t feasible for large volumes, but this study showed that high-shear blending for several hours can match the dispersion quality of ultrasonication.

This approach offers a scalable method for real-world construction without requiring new or costly equipment.

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Cost and Commercial Viability

While technical feasibility is now evident, economic feasibility remains under scrutiny:

• Current CNC prices (~$146/kg from commercial sources) can add up to $50 per m³ of concrete.

• Lab-scale production costs are significantly lower (~$4.89/kg), suggesting cost reductions are possible as demand increases and industrial-scale production ramps up.

Nonetheless, even at current prices, targeted use in critical infrastructure or crack-sensitive applications (e.g., bridge decks, airport runways) could justify the investment due to reduced maintenance costs and improved service life.

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Future Outlook: What Needs More Research?

The study identified several areas for further exploration:

• Alternative dispersion techniques (e.g., high-pressure homogenization)

• Optimal CNC dosage and morphology

• Life Cycle Assessment (LCA) to compare environmental gains vs. production emissions

• Early-age performance testing (before day 7) to explore the hydration boost observed with lower CNC dosages

With these in mind, the future of CNCs in civil engineering looks bright—especially if supported by standardization and cost optimization.

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Conclusion

This groundbreaking pilot study proves that Cellulose Nanocrystals can be successfully implemented in large-scale concrete construction. While the mechanical benefits may vary based on context, the consistent improvements in shrinkage resistance and durability underscore CNCs’ potential as a next-generation concrete additive.

As the construction industry strives to meet environmental and performance targets simultaneously, bio-based nanomaterials like CNCs offer a powerful, scalable solution that bridges innovation with sustainability.