Raghunath Sreenath, Hoque Mahfuzul, Foster E Johan
Department of Chemical and Biological Engineering, The University of British Columbia, 2385 East Mall, Vancouver, British Columbia, Canada V6T 1Z4.
Bioproducts Institute, 2385 East Mall, Vancouver, British Columbia, Canada V6T 1Z4.
ACS Sustain Chem Eng. 2023 Jul 12;11(29):10727-10736. doi: 10.1021/acssuschemeng.3c01392. eCollection 2023 Jul 24.
Fiber cement reinforced with pulp fibers is one of the key drivers for the decarbonization of nonstructural building materials, where the inclusion of sustainable pulp fibers at high proportions (i.e., > 8 wt %) renders poor workability of fiber-cement slurry with a concomitant loss 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 hydration and weaken the strength of the cured composite. Thus, it is crucial to explore renewable and bio-based superplasticizers devoid of any negative traits (if possible) of the conventional PCEs. In this study, we examined wood-derived cellulose nanocrystals (CNCs) as a multifunctional additive in fiber cement (bleached pulp fiber content: 8 wt %). In fiber cement, variation of the content (0.02-4 wt %) of CNCs resulted in improvement in the shear thinning behavior of the fiber-cement slurry and thereafter increased the hydration kinetics at high CNC contents (2-4 wt %). Notably, the flexural strength of the composite also exhibited improvement upon the addition of CNCs; the maximum strength was observed at 4 wt % of CNCs. Overall, the beneficial roles of CNCs afforded >10 wt % (in-total) bio-based content in fiber cement without compromising the mechanical strength and curing time (compared to PCEs); hence, the findings of this study could unravel new avenues in interface engineering of cement composites leveraging the multifunctional features of biomaterials, thus enhancing sustainability.
纸浆纤维增强的纤维水泥是非结构建筑材料脱碳的关键驱动因素之一，在这种材料中，高比例（即>8 wt%）加入可持续纸浆纤维会导致纤维水泥浆的工作性能变差，同时机械强度也会损失。石化衍生的高效减水剂，即聚羧酸盐（PCEs），主要用于纤维水泥（包括水泥砂浆）中，因为它们能显著改善（含量<0.5 wt%）浆料的流变学性能，但会降低水化速率并削弱固化复合材料的强度。因此，探索不含传统PCEs任何负面特性（如果可能的话）的可再生和生物基高效减水剂至关重要。在本研究中，我们研究了源自木材的纤维素纳米晶体（CNCs）作为纤维水泥（漂白纸浆纤维含量：8 wt%）中的多功能添加剂。在纤维水泥中，改变CNCs的含量（0.02 - 4 wt%）会改善纤维水泥浆的剪切变稀行为，进而在高CNC含量（2 - 4 wt%）时提高水化动力学。值得注意的是，添加CNCs后复合材料的抗弯强度也有所提高；在4 wt%的CNCs时观察到最大强度。总体而言，CNCs的有益作用使纤维水泥中的生物基含量总计超过10 wt%，而不会损害机械强度和固化时间（与PCEs相比）；因此，本研究的结果可以利用生物材料的多功能特性为水泥复合材料的界面工程开辟新途径，从而提高可持续性。
