Effect of multi-walled carbon nanotubes on mechanical and durability of fly ash concrete
Polyvinylpyrrolidone(PVP)was used as a dispersant and combined with ultrasonic technology to dis-perse multi walled carbon nanotubes(MWCNTs).A water-based dispersion of MWCNTs was prepared,and it was used as a doping phase to prepare fly ash concrete.The influence of multi walled carbon nanotube content on the mechanical and durability properties of fly ash concrete was studied through TEM,XRD,SEM,FT-IR,mechanical performance testing and rapid freeze-thaw experiments.The results indicated that PVP combined with ultrasonic technology could effectively disperse MWCNTs,and the addition of MWCNTs to fly ash con-crete could accelerate the cement hydration reaction and increase the generation of hydration products such as C-S-H and Ca(OH)2.Moderate doping of MWCNTs could refine the internal pore structure of cement,reduce the number of cracks and large-sized pores,and transform the failure mode of fly ash concrete from brittle fracture to ductile fracture.The peak load and deformation of the MWCNTs-0.3％specimen reached their maximum val-ues,which were 41.6 kN and 2.92 mm,respectively.The compressive strength and flexural strength reached their maximum values,which were 60.5 and 11.2 MPa,respectively.After 100 rapid freeze-thaw cycles,the mass loss rate of the MWCNTs-0.3％sample was the lowest value of 0.271％,and the maximum relative dy-namic elastic modulus was 84.34％,indicating a significant improvement in frost resistance.
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