Fiber cement reinforced with pulp fibers is one of thekey driversfor the decarbonization of nonstructural building materials, wherethe inclusion of sustainable pulp fibers at high proportions (i.e.,> 8 wt %) renders poor workability of fiber-cement slurry witha concomitantloss in mechanical strength. Petrochemical-derived superplasticizers,i.e., polycarboxylates (PCEs), are predominantly used in fiber cement(including cement mortars) because they dramatically improve (content<0.5 wt %) the slurry rheology but reduce the rate of hydrationand weaken the strength of the cured composite. Thus, it is crucialto explore renewable and bio-based superplasticizers devoid of anynegative traits (if possible) of the conventional PCEs. In this study,we examined wood-derived cellulose nanocrystals (CNCs) as a multifunctionaladditive in fiber cement (bleached pulp fiber content: 8 wt %). Infiber cement, variation of the content (0.02-4 wt %) of CNCsresulted in improvement in the shear thinning behavior of the fiber-cementslurry and thereafter increased the hydration kinetics at high CNCcontents (2-4 wt %). Notably, the flexural strength of thecomposite also exhibited improvement upon the addition of CNCs; themaximum strength was observed at 4 wt % of CNCs. Overall, the beneficialroles of CNCs afforded >10 wt % (in-total) bio-based content infibercement without compromising the mechanical strength and curing time(compared to PCEs); hence, the findings of this study could unravelnew avenues in interface engineering of cement composites leveragingthe multifunctional features of biomaterials, thus enhancing sustainability. Cellulose nanocrystals as a green andsustainable additivefor cement composites modify rheology, accelerate hydration kinetics,and improve mechanical properties.
