PSI - Issue 64

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

128

7

100

100

a

b

S1 S2

S1 S2

80

80

0.0481 ml/ml (threshold porosity)

60

60

− 10%

+10%

No clear trend

40

40

20

20

Durability factor (%)

Durability factor (%)

0

0

0.00 0.03 0.06 0.09 0.12 0.15

0.0

0.1

0.2

0.3

0.4

0.5

Porosity (Ø10−250 nm) (ml/ml)

Porosity (ml/ml)

Fig. 6. Correlation between the durability factors and porosities of: (a) powder samples; (b) concrete cores.

permeation rate (Korhonen (2002)). Consequently, the water absorption rate in this large porosity range would be similar, leading to similar frost damage initiation. Because a large porosity range significantly increases the degree of frost damage, a low porosity range can decrease the degree of frost damage as the excess pressures from frozen water on the pore walls can be lower than the strength of the cement matrix. This implies the existence of a threshold porosity where frost damage can be categorized as high or low. In evaluating the safety of structures subjected to frost damage, concrete with a durability factor below 60% is considered unsafe or to have reached the end of its service life (Xuan et al. (2020)). Therefore, we adopted this criterion to investigate the possibility of using powder porosity to assess the safety of structure. At a powder porosity of 0.0481 ml/ml, the durability factor below or above 60% can be distinguished, as shown in Fig. 6(a). This indicates that the threshold porosity capable of differentiating high and low durability factors is retained in the powder sample. From Fig. 6(a), a threshold line, including ±10% error margins, delineating the powder porosity was drawn. Thus, the threshold powder porosity of 0.0481 ± 0.00481 ml/ml can be used to categorize the safety of the structure under frost damage. The method for evaluating the safety of structures under frost damage in this study incorporates the advantages of the existing drilling powder method, which has been proposed for assessing concrete compressive strength (Rath et al. (2023)). The ability to use the porosity of concrete core to estimate frost resistance was investigated by examining their degree of correlation, as shown in Fig. 6(b). From this figure, no specific correlation is observed, which is attributed to the inconsistent porosity of core samples, as shown in Fig. 4. This result indicates that the core sample cannot be used for estimating concrete frost resistance, although it induced larger damage than the drilling powder. 5. Conclusion This study examined the possibility of using powder porosity to estimate the frost resistance of concrete with different properties. The feasibility of using a powder sample for evaluating frost resistance was investigated by comparing it with a 5-mm core sample. The 5-mm core sample cannot be used to evaluate the frost resistance of concrete, although it caused more significant damage than the proposed method. The results showed that the safety of concrete under frost damage can be evaluated using the threshold powder porosity. These results demonstrate the potential of using the drilling powder method to evaluate the frost resistance of concrete. However, more studies are necessary to gather more data for determining the threshold porosity for a more accurate evaluation. Future studies should include concrete with different properties, including the amount of AEA and aggregate content. Additionally, as in-situ concrete (to be assessed) can experience frost damage at the time of testing, future studies should investigate the condition of partial frost damage on the applicability of the drilling powder method. In this regard, the drilling powder method can accurately evaluate the frost resistance of concrete with minimal damage.