Sustainable micro-cellulosic additives for high-density fiber cement: emphasis on rheo-mechanical properties and cost–performance analysis†

To combat climate change (i.e., global warming), reducing the CO₂ footprint of cement-based building materials can be substantiated by incorporating cellulosic fibers into the cement matrix (fiber cement). However, such materials design imposes tremendous technical challenges towards the fabrication process, interlinked to its rheo-mechanical properties. Thus, polycarboxylate-based (petrochemical-derived) rheology modifiers and silica-based (carcinogenic) additives are usually added to the fiber-cement slurry. Micro-cellulosic biomaterials are technically a viable eco-friendly alternative, capable of modifying the rheo-mechanical properties, yet to be explored for high-density (>8 wt% fiber) fiber cement. Herein, we have employed morphologically distinctive alpha-cellulose (AC) and microcrystalline cellulose (MCC) as rheo-mechanical additives. The total content of biomaterials in the fiber cement was up to 12 wt%, where the ratio between the micro-cellulosic additive (AC/MCC) and the cellulosic fibers varied proportionally. As a result, various composites were fabricated based on combinations 1 (AC and fibers) and 2 (MCC and fibers), and their rheo-mechanical properties were characterized to understand the effect of this morphologically distinctive micro-cellulose. Firstly, the rheological analysis revealed that combination 1 reduced the yield stress (improving the workability) at any content – with 4 wt% AC content indicating a maximum reduction in yield stress of 30%. Secondly, flexural strength analysis revealed that combinations 1 and 2 improve the modulus of rupture (MOR), and combination 2 (at 6 wt% MCC content) resulted in a 42% increase in MOR. Finally, we presented the cost-to-performance ratio analysis (economic perspective), highlighting the positive ramifications of this sustainable rheology modifier and additives for the cement-based composite – an avenue for low-embodied carbon building materials without compromising the strength-to-weight ratio.