Multi-technique investigation regarding the impact of cellulose nanofibers on ultra-high-performance concrete at the macroscopic and microscopic levels

초록

Cellulose nanofibers (CNFs) are renewable building materials with excellent potential for development. In this paper, we present a multi-technique study of the properties of samples with CNF addition at the macroscopic and microscopic levels. The hydration kinetics, autogenous shrinkage, microstructure, mechanical properties, and durability of the samples were investigated. The results are as follows: (1) CNFs suppress early hydration and accelerate later hydration. (2) The autogenous shrinkage decreased considerably with an increase in added CNFs. (3) Thermogravimetric analysis revealed that as the CNFs content increased, the combined water and calcium hydroxide content increased. X-ray diffraction and attenuated total reflection-Fourier transform infrared experiments revealed the calcium hydroxide content in the hydration products was low. (4) SEM tests revealed fiber pull-out, hydration product attachment on the CNFs surface, and fiber pocket formation in specimens with 0.3% CNF. (5) A two-aspect effect of CNFs on compressive strength was observed, namely an increase followed by a decrease. The final strength change depends on the amount of CNFs added and the high strength of the CNFs. (6) The addition of 0.1% CNFs refined the pore structure and improved the electrical resistivity. When CNFs were added in excess, the porosity increased and the resistivity decreased.

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