PSI - Issue 67

6

Hwan Lee et al. / Procedia Structural Integrity 67 (2025) 107–114 Author name / Structural Integrity Procedia 00 (2024) 000 – 000

112

12000

12000

7 day 28 day 90 day

7 day 28 day 90 day

10000

10000

8000

8000

6000

6000

4000

4000

Compressive strength (psi)

Compressive strength (psi)

2000

2000

0

0

Control

CNT_0.01 CNT_0.03 CNT_0.05

Control

NMK_5

NMK_7.5

NMK_10

(b)

(a)

Fig. 3 Compressive strength of mortar samples of (a) nano metakaolin and (b) CNT

2.3. Bulk resistivity

Fig. 4 shows the resistivity of mortar samples at 28 days and 90 days. 5 wt% of NMK did not improve the resistivity of samples compared to the control samples, while 7.5 wt% and 10 wt% of NMK increased the resistivity. At 28 days, 7.5 wt% and 10 wt% of NMK increased the resistivity by 192.9% and 360.7%, respectively. Also, at 90 days, 7.5 wt% and 10 wt% of NMK increased the resistivity by 101.7% and 281.2%. Because the higher resistivity value is an indicator of denser microstructure, the results suggest that NMK could act as pozzolanic material in cement composites by consuming more calcium hydroxide (CH) and forming more C-S-H (Abo-El-Enein et al. 2014). In contrast, samples with CNT did not show a significant increase in resistivity compared to samples with NMK.

10 15 20 25 30 35 40

10 15 20 25 30 35 40

28 day 90 day

28 day 90 day

Resistivity (k Ω∙ cm)

Resistivity (k Ω∙ cm)

0 5

0 5

C

NMK_5

NMK_7.5 NMK_10

C

CNT_0.01 CNT_0.03 CNT_0.05

(a) (b) Fig. 4 Resistivity of mortar samples of (a) nano metakaolin and (b) CNT