Impact of pyrolytic carbonaceous nano inerts addition on fracture and electromagnetic interference shielding characteristics of cementitious composites

• Published in: Theoretical and applied fracture mechanics 2019-10, Vol.103, p.102320, Article 102320
• Main Authors: Khalid, Anum, Khushnood, Rao Arsalan, Mahmood, Ayesha
• Format: Article
• Language: English
• Subjects: Agricultural wastes; Carbonaceous nano-inerts; Carbonized cotton stalk; Carbonized wheat straw; Cement reinforcements; Composite materials; Cotton; Crack branching and contouring; Crack bridging; Dispersion; Electromagnetic interference shielding effectiveness; Electromagnetic shielding; Electron micrographs; Fourier transforms; Fracture characteristics; Fracture toughness; Frequency ranges; Industrial applications; Infrared analysis; Intrusion; Mortars (material); Prisms; Pyrolysis; Raman spectroscopy; Spectroscopic analysis; Spectrum analysis; Strain rate; Straw; Superhigh frequencies; Synthesis; Thermogravimetric analysis; Wheat
• ISSN: 0167-8442; 1872-7638
• DOI: 10.1016/j.tafmec.2019.102320

•Novel cost-effective carbonaceous nano-inerts were successfully synthesized.•Fracture resilience enhanced to 59.8% in flexure and 44.5% in compression.•Electromagnetic shielding effectiveness was increased uptill 23.5db. The fragile behavior of traditional cementitious composites can be tweaked by reinforcing the matrices at nano scale via intrusions of carbonaceous inerts. However, high fabrication cost of these inerts barred their extensive industrial application. In the present study, cost-effective carbonaceous nano-inerts were synthesized via pyrolysis of agricultural wastes in the form of wheat straw and cotton stalk at a temperature of 500 °C in an inert environment. Carbon rich solid residue obtained from pyrolysis was milled to nano size and characterized through energy dispersive X-ray spectroscopy, X-ray diffraction analysis, thermogravimetric analysis, Fourier transform infrared spectroscopy and Raman spectroscopy. Synthesized carbonaceous nano-inerts from wheat straw and cotton stalk have been intruded in to cementitious matrix for the first time in the best knowledge of author, to enhance its fracture characteristics and electromagnetic interference shielding effectiveness. Cement mortar specimens were prepared with the intrusions of carbonaceous nano-inerts by 0.025, 0.05, 0.08, 0.2, 0.5 and 1 wt% of cement in addition mode, after being effectively dispersed in water. Three point bending tests were performed on notched prisms at a very sensitive strain rate of 0.003/min in strain controlled mode with the broken halves analyzed for resistance in compression. Substantial increase of 59.8% in fracture toughness and 44.5% in compression was attained with the addition of 1% carbonized cotton stalk and 0.5% carbonized wheat straw respectively. Moreover, scanning electron micrographs have verified the involved strengthening mechanisms encompassing crack branching, pinning and crack bridging via intruded nano-inerts. Furthermore, shielding against electromagnetic interference was tested in X-band frequency range of 8–12 GHz and maximum improvement of 23.5db and 22.9db was attained with intrusion of carbonized wheat straw and carbonized cotton stalk nano particles respectively.