Nanofibrillated cellulose and cellulosic pulp for reinforcement of the extruded cement based materials

[Display omitted] •The high specific surface area of NC improves the fiber-matrix bonding.•The NC improves the stress transfer when the composite is subjected to load.•At 28 days the hybrid composite presents a higher modulus of rupture.•In the hybrid composite, the NC acts as nanoreinforcement after accelerated ageing. The use of cellulose nanofibers as reinforcement may contribute for improving particle packing and decrease the crack growth rate of composites at nanoscale. Additionally, the high specific surface area of cellulose nanofibers contributes to improve the adhesion between the cement particles. Thus, the aim of this work was the study the performance of hybrid composites reinforced with 8% pulp and 1% nanofibrillated cellulose compared to composites reinforced with only 9% of pulp produced by the extrusion process. The accelerated aging process by means of 200 wet and dry cycles was carried out to assess composite degradation. In the hybrid composites the nanofibrillated cellulose improved the mechanical behavior compared to the composite without nanofiber. This improvement may be associated with greater adherence between the nanofibrils and the cement matrix. After accelerated ageing, the composites with and without nanofibers showed no reduction in mechanical performance, which is attributed to the lower alkalinity provided by the accelerated carbonation. Therefore, the nanofibrillated cellulose showed to be a promising material for use as nanoreinforcement of the extruded hybrid cement-based composites.