Nanocellulose for improved concrete performance: A macro-to-micro investigation for disclosing the effects of cellulose filaments on strength of cement systems

To fulfill further eco-efficiency requirements, concrete technology practitioners are currently challenged to provide concretes with tailored properties to meet sustainability and resilience requirements for infrastructural systems. As such, nano-engineering concrete by incorporating nanocellulose materials (NCM) can disclose new research directions for tailoring properties necessary for sustainable cement composites. The current study investigates the performance of cement systems incorporating cellulose filaments (CF) and aims at fostering new understanding of the macroscale mechanical performance with a top-down multiscale approach. The study investigates the mechanical performance (i.e., compressive strength, flexural capacity, and elastic modulus) at macroscale of cement pastes incorporating CF at dosages of 0.0%, 0.05%, 0.10%, 0.20% and 0.30 wt%. The findings are supplemented by microstructure investigations, namely, degree of hydration and micromechanical properties (hardness, indentation modulus, and contact creep modulus) of microstructure phases using nanoindentation coupled with quantitative energy-dispersive spectroscopy (NI-QEDS). Results showed that CF incorporation resulted into 15–25% enhancements in macro-mechanical properties with up to 74% enhancement in flexural toughness. These enhancements are driven by a twofold microstructure change, i.e.: increased degree of hydration (15%) and higher micromechanical properties of C-S-H matrix (∼12–25%). CF is a promising nano-reinforcement for engineering cement composites with superior mechanical performance, while promoting the development of ecological construction materials.