Issue 41

X. Wu et alii, Frattura ed Integrità Strutturale, 41 (2017) 388-395; DOI: 10.3221/IGF-ESIS.41.50 392 Figure 4 : The mechanical properties of cement-based composite materials test specimens which were mixed with different amount of carbon nano-tubes after 14 days of maintenance. The testing results of the mechanical properties of carbon nano-tubes cement-based composite materials after 14 days of maintenance are shown in Fig. 5. Fig. 5 shows that the compressive and bending strength of carbon nano-tubes cement- based composite materials was significantly improved (10% mostly) compared to the blank group after 28 days of maintenance. When the mixing amount of carbon nano-tubes was 0.10% that of cement, the bending strength reached the maximum value, 9.07 MPa, which was 12.56% higher than the blank controls. When the mixing amount of carbon nano- tubes was 0.05%, the compressive strength reached the maximum value, 72.44 MPa, suggesting an improvement of 13.01%. When the mixing amount of carbon nano-tubes was 0.10wt%, the variation of the compressive strength was not obvious but the variation of the bending strength was. The variation tendencies of the compressive and bending strength changed. The bending strength fluctuated significantly with the increase of carbon nano-tubes amount, increasing first and then decreasing. Regardless of No.0 blank sample, the curve showed unilateral slow drop. Figure 5 : The mechanical properties of cement-based composite materials test specimens which were mixed with different amount of carbon nano-tubes after 28 days of maintenance. The variation of the compressive and bending strength of the cement-based composite material test specimens which were mixed with different amount of carbon nano-tubes following the changes of age is shown in Fig. 6 and 7. The two figures demonstrated that the compressive and bending strength of the test specimens which was mixed with carbon nano-tubes tended to increase with the changes of age, and the increase amplitude decreased progressively. When the mixing amount of carbon nano-tubes was 0.10%, the improvement of the bending strength was optimal; the bending strength of the aforementioned test specimen was 9.07 MPa after 28 days of maintenance, which was 12.56% higher than that of the blank test specimen. As to the compressive strength, the cement-based composite material test specimen whose content of carbon