Issue 41

X. Wu et alii, Frattura ed Integrità Strutturale, 41 (2017) 388-395; DOI: 10.3221/IGF-ESIS.41.50 390 Figure 1 : The schematic diagram of carbon nano-tubes structure. Specimen moulding and testing Carbon nano-tubes were added into the solution of CTAB. The mass ratio of CTAB to carbon nano-tubes was 10:1. Ultrasonic dispersion processing was performed using a ultrasonic apparatus, for 60 min, to ensure carbon nano-tubes evenly distributing in the water solution to form carbon nano-tubes suspension. Then the carbon nano-tubes suspenion was poured into a cement mixer along with the cement; the water cement ratio was 0.30. The stirring lasted for 6 min; the ratio of duration of stirring at the low speed to duration of stirring at the high speed was 2:1. The mixture of carbon nano-tubes and cement paste in the mixing pot was rapidly poured into a standard test mould in a specification of 40mm×40 mm×160 mm and another one in a specification of 40 mm×40 mm×40 mm at the end of stirring. It was vibrated to be dense mechanically. The moulds were removed after 24-h standard maintenance. Each test specimen was numbered and then put into water at the temperature of (20 ± 1) amount are shown in Tab. 3. The microstructures of some specimens are shown in Fig. 2. Sample Water to cement ratio (W/C) Mix proportion/wt% MWCNTs CTAB Water reducer No.0 0.30 0 0 0.1 No.1 0.30 0.05 0.5 0.1 No.2 0.30 0.10 1.0 0.1 No.3 0.30 0.15 1.5 0.1 No.4 0.30 0.20 2.0 0.1 No.5 0.30 0.25 2.5 0.1 Table 3 : The mix proportion of carbon nano-tubes cement-based composite materials Figure 2 : The microstructures of some specimens (the mixing amount of multiple-wall carbon nano-tubes in (a) - (d) is 0.05%, 0.1%, 0.2% and 0.25% respectively).