Compressive and Flexural Strength Behavior of Ultra-high Performance Mortar Reinforced with Cellulose Nano-fibers

Abstract

Cellulose fibers, because of their chemical and physical characteristics, are compatible with other materials to be used for the production of building components. This paper presents the influence of using cellulose nano fibers (CNFs) made from plant-derived cellulose as a reinforcement in ultra-high performance (UHP) mortar. In this study, the dispersion method of CNFs using manual and mechanical mixing was also observed. The effects of different dosage of CNFs, namely, 0.005%, 0.01% and 0.015% by wt. of binders (premixed low-heat cement and silica fume) with a constant waterto binder ratio of 0.15, were evaluated based on the compressive and flexural strengths at the seventh day after steam curing. Results show that the highest compressive strength value of 184MPa was reached by UHP mortar sample containing 0.005% CNFs by wt. of binders. However, addition of more CNFs content up to 0.015% did not result in further improvement. Based on load-CMOD curves, UHP mortar reinforced with 0.005% CNFs was found most effective in enhancing the energy absorption capacity and toughness index with flexural strength at peak load of 14.44MPa (36% higher than control UHP mortar). The results indicate the well-post crack behavior of CNFs mortars in comparison with control UHP low-heat cement mortar. Moreover, Scanning Electron Microscopy (SEM) analysis shows that the phenomenon of bridging effect of CNFs could not be significantly detected since the short fiber might be fractured under loading due to less bonding. Furthermore, this study concludes that even a low volume fraction, i.e 0.005%, of CNFs is very sufficient in increasing the ductility of ultra-high performance mortar.