Innovative application of silicon nanoparticles (SN): Improvement of the barrier effect in hardened Portland cement-based materials

• Amorphous silicon nanoparticles synthesized by sol–gel promotes the ionic transport of Si4+.
• The electric field forced the SN to move toward the cement matrix.
• Pores blocking, caused by the ingress of SN, was supported by N2–Physisorption results.
• The resistance to carbonation was improved by the block pore effect.
• SN treatment is a promising method since improves the durability on concrete’s hardened state.

The present study investigates the introduction SN prepared using the sol–gel method into a hardened Portland cement matrix by means of an electric field. The SNs were prepared from Si(OC2H5)4 and C2H6O with a mole fraction of 0.1051 in an alkaline medium. The XRD and TEM analyses confirmed that an irregular, nanometric (20–30 nm) amorphous material was obtained. FTIR analysis showed the characteristic bands of amorphous silicon. For SN migration, a suspension of 0.1% weight was prepared and placed in a cell in contact with a mortar specimen (50 mm diameter, 50 mm length). A voltage was applied (10–20 V, DC) for 4 h followed by a 54 days period of immersion in tap water. During this period, resistivity measurements were carried out until a significant change was observed in the specimens. Subsequently, the specimens were exposed to an atmosphere with CO2 for 7 days. The tests performed showed both an increase in the electrical resistivity and a significant decrease in the carbonation depth for all mortars treated with SN. The latter conclusion is confirmed by SEM images, which show the evolution of the microstructure of the matrix, due to the presence of the silicon ions.

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