Engineered novel multifunctional hybrid nanofiber reinforcement for improving the flexural strength and fracture of cementitious composites for sustainable concrete

Hasan, Hasan (2019) Engineered novel multifunctional hybrid nanofiber reinforcement for improving the flexural strength and fracture of cementitious composites for sustainable concrete. PhD thesis, UNSPECIFIED.

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Abstract

The carbonaceous nanomaterials (Multi wall carbon nanotubes (MWCNT), functionalised MWCNT and Carbon nanofibers (CNFs)) have outstanding properties (mechanical, electrical, etc., which can make them effectual nonoreinforcements for enhancing the properties of cementitious composites. unfortunately, these nanomaterials have a high tendency to agglomerate due to their strong Van der Waals self-attraction and hydrophobic surfaces. To date, ensuring a uniform dispersion in water and in the cementitious composite is the main challenge that hinders their effective use as a nano reinforcing agent. To address the issue of agglomeration of carbonaceous nanomaterials in cementitious composites, for the first time, a green process was developed to synthesise highly dispersible multifunctional hybrid nanoparticles using bio-derived nanoplatelets (BNPs) and MWCNT. Multifunctional hybrid nanoparticles BNP/MWCNT suspensions were analysed using Optical microscopy, Ultraviolet–visible spectroscopy (Uv-vis), Scanning Election microscopy (SEM), elemental analysis (energy dispersive X-ray diffraction (EDX) and thermal characterization (TG-DTG). In this work, extensive experimental studies have been conducted to investigate the hydration mechanism and microstructure characteristics of cementitious composites with BNP. The SEM, EDX, TG-DTG, Transmission Electron Microscopy (TEM), and X-ray diffraction (XRD) were used in this investigation. The mechanical properties of the resulting composites were characterised through compressive, flexural strength. More specially, the effect of BNP on fracture properties of cementitious composites has been investigated. The work has also focused on evaluating the effect of BNP/MWCNT on the hydration mechanism, microstructure characteristics and mechanical properties (compressive, flexural strength). As well as, the experiments were performed to examine the effects of BNP/MWNCT on fracture properties of cementitious composites. The obtained results on dispersion showed that, BNP, can be used to disperse MWCNT in aqueous solution and well dispersed MWCNT in aqueous solution were achieved. Addition of BNP resulted in cementitious composites to improve flexural strength, fracture properties and the microstructure of cementitious composites. The addition of multifunctional hybrid BNP/MWCNT to cementitious composites resulted in a significant improvement in the performance of cementitious composites and this gain could be attributed to uniform distribution of MWCNT, effective reinforcement effects, crack bridging and chemical bonding between BNP/MWCNT and cement hydrated products.