PSI - Issue 28

Angeliki-Eirini Dimou et al. / Procedia Structural Integrity 28 (2020) 1694–1701 A.-E. Dimou et al. / Structural Integrity Procedia 00 (2019) 000–000

1699

6

0 1 2 3 4 5 6 7 8 specimens' age: 28 days

+20 %

+2 %

Compressive strength (MPa) Blank paste

rGO reinforced paste

MWCNTsCOOH reinforced paste

Fig. 4. Compressive strength of the examined pastes at 28 d of age.

specimens' age: 28 days

3.0

+56 %

2.5

2.0

1.5

1.0

0.5

Flexural strength (MPa)

0.0

rGO reinforced paste

MWCNTsCOOH reinforced paste

Blank paste

Fig. 5. Flexural strength of the examined pastes at 28 d of age.

3.3 Electrical resistance tests The results of the electrical resistance tests are presented in Fig. 6, where it can be noticed that the electrical resistance of the blank paste is about 0.74 MOhm. The nano-reinforced pastes of MWCNTsCOOH and rGO exhibited resistance values of 0.65 MOhm and 0.61 MOhm, respectively. This means that in both reinforced cases the electrical resistance drops about 15 %. It is known that the CBNs possess advanced electrical properties. Therefore, a significant change in electrical resistance of the composite was expected, although the amount of nanomaterials is very low. All similar studies show that the addition of such materials lead to a significant decrease of the electrical resistance, e.g. Phrompet et al. (2019) and Lee et al. (2020). There are three mechanisms contributing to the increase of electrical flow; direct conduction due to physical contact among the nanoparticles, electron flow through ions in pore solution in the matrix and the tunnelling effect (Lee et al. 2019). The decrease in electrical resistance in both cases can be correlated either with the formation of electrical conductive paths either with direct contact of the nanoparticles or with the decrease of the distances among nanoparticles, thus transforming the binder to be more electrically conductive.