A recent study has explored how nanocellulose fibers (CFs) derived from wood pulp affect the mechanical, hydration, shrinkage, and pore structure characteristics of ordinary Portland cement (OPC) mortar. The fibers were added to mortar mixes in varying amounts to assess their impact on physical, mechanical, and microstructural properties.
Study: Hydration Products and Properties of Nanocellulose Fibre-Reinforced Mortar. Image Credit: Marco Lazzarini/Shutterstock.com
Why Cellulose Fibers?
Fiber-reinforced cementitious composites are widely used to enhance strength and durability in concrete. Among the various fiber options, cellulose fibers—especially those sourced from agricultural or forestry byproducts—are gaining attention for their lower cost, renewable origin, and environmental benefits.
Unlike synthetic fibers like carbon or steel, which can be expensive and energy-intensive to produce, cellulose fibers are biodegradable and more sustainable. They also help reduce autogenous shrinkage by retaining internal moisture, which is particularly important in high-performance concrete that tends to crack early in its life cycle.
Given their potential to reduce shrinkage, limit cracking, and support internal curing, CFs are being explored as a practical additive for cement-based materials. This study focused on nanocellulose fibers derived from wood pulp to evaluate their performance across multiple key properties.
How the Study Was Set Up
The CFs used in this research came from sustainably managed forests in the Netherlands. A control mix (M0) made of OPC and fine sand served as the baseline. Six additional mixes (M1–M6) were created by adding CFs in increasing dosages, from 0.15 % to 1.5 % by weight of cement.
For testing, each mix was cast into 42 prism samples (160 × 40 × 40 mm3). Half were used to assess mechanical properties—flexural and compressive strength—while the other half were used to measure drying shrinkage. Flexural strength was tested using a three-point bending setup, and compressive strength was measured on the broken halves of those samples.
After 28 days, selected samples from mixes M1, M2, and M3 were analyzed using mercury intrusion porosimetry (MIP) to evaluate pore structure. X-ray diffraction (XRD) and X-ray fluorescence (XRF) were performed on compressive test remnants to investigate chemical composition. Additional tools like Fourier-transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM) were used to characterize the fibers and cement matrix. A flow test was also conducted to examine workability.
What the Results Showed
As more CF was added, workability and flexural strength generally declined. However, mixes with up to 0.51 % fiber content (M1–M4) retained flexural strength within 10 % of the control, indicating that small to moderate additions had minimal impact on mechanical performance. Beyond that range, particularly in M5 and M6, the drop in strength became statistically significant.
Compressive strength followed a similar pattern. Mixes M1, M3, and M4 showed slight improvements of 1.6 %, 6.8 %, and 1.9 % over the control, but those gains weren’t statistically significant due to overlapping error margins. Higher dosages in M5 and M6 led to more noticeable strength reductions.
Shrinkage performance told a different story. Mixes with 0.15 % and 0.45 % CF experienced lower drying shrinkage compared to the control. The 0.45 % mix (M3) stood out for its reduced surface shrinkage cracking, suggesting that this dosage may hit the right balance between performance and durability. As always with fiber-reinforced materials, proper dispersion played a key role in these results.
Porosity also changed with fiber content. MIP and FESEM analysis revealed that adding CFs—especially at the 0.45 % level—altered pore structure by increasing both pore size and total porosity. These effects were clearly dosage-dependent, with more fibers leading to more pronounced changes.
Final Thoughts
This study highlights how wood-derived nanocellulose fibers can serve as effective additives in cement mortars, supporting both sustainability and performance. At optimal dosages—around 0.45 %—CFs helped reduce shrinkage and crack formation without sacrificing strength. They also influenced the hydration process, affecting the development of key phases like calcium silicate hydrate, portlandite, and carbonates.
While higher fiber contents introduced challenges like reduced workability and increased porosity, lower dosages showed clear benefits. As the construction industry continues to look for greener materials, cellulose fibers offer a promising path forward—especially when carefully dosed and well-dispersed in cement mixes.
Journal Reference
Agunbiade, T. & Mangat, P. S. (2025). Hydration Products and Properties of Nanocellulose Fibre-Reinforced Mortar. Sustainability, 17(6), 2719. DOI: 10.3390/su17062719, https://www.mdpi.com/2071-1050/17/6/2719
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