PSI - Issue 64

Sothyrak Rath et al. / Procedia Structural Integrity 64 (2024) 122–129 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

127

6

0.50

0.50

a

b

Air curing Water curing

0.40

0.40

0.30

0.30

0.20

0.20

0.10 Porosity (ml/ml)

0.10 Porosity (ml/ml)

0.00

0.00

0.000

0.002

0.006

0.3 0.4 0.5 0.6 0.7

w/c ratio

AEA content (wt%)

Fig. 4. Porosity of concrete cores: (a) S1; (b) S2 samples.

100

100

a

b

Air curing Water curing

80

80

60

60

40 DF (%)

40

DF (%)

20

20

0

0

0.000

0.002

0.006

0.3

0.4

0.5

0.6

0.7

w/c ratio

AEA content (wt%)

Fig. 5. Durability factors of concrete samples: (a) S1; (b) S2.

3.2. Durability factor of concrete Fig. 5 shows the durability factors of concrete. For the S1 series, only the sample with a w/c ratio ≥ 0.4 exhibit s a higher durability factor. This result supports the finding that an AEA is not necessary to improve the scaling resistance when the w/c ratio is ≤ 0.3 (Gagne and Pigeon (1990)). This tendency can be attributed to the lower bleeding capacity (Powers (1968)) and denser pore structure (Valenza and Scherer (2007)) of low-w/c concrete. Fig. 5(b) shows that the AEA has both effects on frost resistance. This result supports the finding that there is an optimum AEA dosage where the AEA below and above this optimum have different effects on frost resistance (González et al. (2021)). The concrete with AEA lower than optimum value exhibited more elongated voids, which improved its frost resistance, whereas concrete with AEA higher than optimum exhibited a more spherical shape, lower porosities, fewer small pores, and smaller pore sizes, which reduced the frost resistance. 4. Discussion To investigate the possibility of using the drilling powder method for estimating the frost resistance of concrete, we examined the correlation between powder porosity and durability factor, as shown in Fig. 6(a). Samples with high porosity exhibit a low durability factor; however, no regression equation can be derived from this relationship. For porosities greater than 0.06 ml/ml, despite the porosity varying about two times, the durability factor remains low and nearly constant. This may be because of the samples having a sufficient saturation level in the pores, thereby allowing the expanding frozen water during freezing to exert enough pressure to damage the cement matrix. These results indicate that in a certain higher range of porosity, changes in porosity do not affect the degree of frost damage. This tendency can be attributed to the presence of a high volume and number of large capillary pores in the high-porosity sample. When concrete has a large capillary pore volume (i.e. w/c > 0.5) the permeation coefficient considerably depends on the amount of moisture content, implying that the pore size in this range has minimal influence on the