Effect of fly ash cenospheres on properties of multi-walled carbon nanotubes and polyvinyl alcohol fibers reinforced geopolymer composites

Abstract

This article proposes a lightweight engineered geopolymer composite (LW-EGC) that combines functionalized multi-walled carbon nanotubes (MWCNTs) and polyvinyl alcohol (PVA) fibers, with fly ash cenospheres (FAC) used as lightweight filling materials. The tensile and bending properties of LW-EGC were studied using a uniaxial tensile test and four-point bending test. The relationship between ultimate tensile strain and mid-span displacement was discussed. The crystal composition and chemical bond of raw materials and LW-EGC were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR), and the micromorphology was analyzed via field emission scanning electron microscopy (FESEM). The test results showed the following: (1) When 10% mass fraction of FAC was added, LW-EGC-10% had a compressive strength of 33.7 MPa, a density of 1522 kg/m3, a flowability of 255 mm, and a tensile strain capacity of 6.03%. (2) The crack width of LW-EGC was generally less than 90 μm, and the crack spacing was generally less than 2 mm with the introduction of FAC, which indicates excellent crack control ability. (3) The XRD spectra indicated that the production of new crystal images was not significant in the geopolymerization, and the FT-IR spectra showed that the reaction products were mainly new aluminosilicate phases. (4) During the extraction of MWCNT and PVA fibers, large extrusion deformation occurred, leaving a large number of broken matrix and FAC fragments on the fiber surface, which made the LW-EGC have excellent tensile strain capacity. The results show that FAC is a promising material for the production of ductility and lightweight structural components with potential for correct processing and efficient recovery of FAC.