Surfactant-Assisted Processing of Carbon Nanotube Cement-Based Nanocomposites: Microstructural, Electrical, and Mechanical Properties

Five types of surfactants were employed, individually or in combination, as dispersants to introduce multi-wall carbon nanotubes (MCNTs) into cement matrix. The surfactants included beta-naphthalene sulfonate-based superplasticizer (FDN), methylcellulose (MC), polyacrylic acid (PAA), sodium dodecyl sulfonate (SDS), and cetyltrimethyl ammonium bromide (CTAB). The dispersion effects on MCNTs in 12 types of suspended solutions and cured cement matrix were evaluated visually by blackness uniformity and stability, and by microscale morphology of the suspensions. Mechanical strength, electrical conductivity, and SEM images of dispersed MCNTs-reinforced cement composites (MNTRCs) were also analyzed. The mechanism of the action of surfactants on assisted dispersing of MCNTs in aqueous suspension and cement hydration was verified. The accumulated results showed that CTAB (w(CTAB) w(MCNTs) = 1 similar to 3:1) yielded the best uniform and stable dispersion of MCNTs; the corresponding MNTRC had the 2nd highest mean values of flexural, compressive strength and the lowest deviation (f(t) = 3.12 +/- 0.103 MPa; f(c) = 35.7 +/- 1.16 MPa), and the highest mean conductivity and even deviation (sigma(c) = 3.28 x 10(-3) +/- 4.991 x 10(-4) S/m). MCNTs were well dispersed and compatible with cement hydration with micro-mechanical crack bridging effect. Four evaluation techniques of the MCNTs dispersion effect were well validated and consistent with each other.