Microcracking monitoring and damage detection of graphene nanoplatelets-cement composites based on acoustic emission technology

This study aims to identify the micro-cracking pattern and structural applications of cement composites replaced with 0 wt%, 0.04 wt%, and 0.08 wt% contents of graphene nanoplatelets (GNPs) over cement weight through acoustic emission (AE) monitoring under mechanical degradation. The ultraviolet-visible spectroscopy (UV–vis) results showed that at 60 min sonication period, GNP-4 showed maximum absorbance rate of 16.15% compared to the GNP-8. The microstructural characteristics revealed that during hydration of cement there was no apparent cracks appeared in GNPs-cement composites compared to the reference specimen (GNP-0) which was 1.44 mm. The cracking mode and damaged detection of the tested specimens resulted in three distinct stages i.e., (I) pre-peak, (II) peak, and (III) post-peak under mechanical degradation. GNP-4 achieved 780 N flexural capacity which was increased by 30% and 21.87% compared to the GNP-0 and GNP-8. Similarly, a compressive strength of 63.12 MPa, 57.5 MPa, and 56 MPa at 28 days was obtained by GNP-4, GNP-8, and GNP-0, respectively. Based on AE hits and amplitude analysis, the resistance to fracture, damping capacity, and ductility of GNP-4 was improved by 25.30%, 25.1%, and 22.47% respectively, to that of GNP-0. Shear failure (>35 kHz) was observed in GNP-0, while GNPs cement composites recorded tensile failure (<35 kHz) through RA-AF parameters. The cracking pattern through Ib value with a warning sign of 1.5 between micro and macro-cracks and severity of damages through historical index (HI) and severity index (Sr) of GNPs cement composites was determined. Lastly, it was concluded that GNPs contents can significantly improve bending strength and delay the cracks initiation in cement composites.