Selection of suitable cellulose nanofibers derived from eco-friendly sources for the production of lightweight cementitious composites with tuned rheological, mechanical, and microstructure properties

Abstract

Different cellulose nanofibers (CNF) and ordinary Portland cement (OPC) were combined to prepare CNF-OPC composite pastes at different water to cement ratios (W/C) to optimize density, thermal conductivity, and mechanical strength. The rheological data of CNF-OPC composites showed that the viscosity and yield stress of the mixtures were abruptly increased in comparison to those of OPC pastes at equal W/C. Rheological and morphological data showed that the uniformity of the CNF and degree of fiber entanglement plays a significant role in tuning the composite properties. CNF suspensions with short fibers were observed to improve the mechanical properties of the composite while suspensions with entangled fiber networks were found to decrease density and thermal conductivity. Loss of flexural strength of CNF-OPC compared to OPC was found to be to a lesser extent than loss of compressive strength. The dry density and thermal conductivity of the CNF-OPC composites were substantially reduced to the range of 750 (kg/m3) and 0.1 (W/m-1K-1) at W/C = 2. CNF caused a reduction in peak temperature and postponed the hydration peak by more than 2 hours compared to OPC.