PSI - Issue 64

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

126

5

a

b

0 5 10

F – T chamber

Specimen

-20 -15 -10 -5

Temperature (℃)

0 30 60 90 120 150 180 210 240

Duration (min)

Fig. 2. (a) F – T exposure setup; (b) Exposure conditions per F – T cycle.

3. Results 3.1. Porosities of the powder and concrete core sample

The porosities of the cement paste obtained from the concrete powders are presented in Fig. 3, showing a consistent trend of porosities according to the concrete properties. A similar result for the porosity of the paste portion from the chunk concrete sample, was observed, ranging from 0.025 ml/g for 0.3 w/c under water curing to 0.130 ml/g for 0.6 w/c under outdoor air curing (Tanaka (2021)). These tendencies imply the validity of the proposed method. In Fig. 3(a), the increasing porosity with an increasing w/c ratio is attributed to an increase in the capillary pore volume of higher-w/c concrete (Gao et al. (2014)). The effect of curing conditions on porosity is also observed, with the water-cured sample exhibiting lower porosity than the air-cured sample, which can be attributed to differences in hydration level due to the differences in moisture supply during hardening process. Fig. 3(b) shows the effect of AEA content on powder porosity. The porosity of the sample with AEA decreased compared to that without AEA content. This can be attributed to the lower pore range considered in this study (10 – 250 nm) as the addition of AEA can increase the pore volume in relatively larger pores and decrease in finer pores (Chung et al. (2020)). Fig. 4 shows the porosities of the concrete cores, where no common pattern of porosity with respect to the concrete properties can be observed. This tendency can be attributed to the variation in coarse aggregate content, as the presence of coarse aggregates significantly influences the total pore volume. Therefore, the porosity, which is the division of pore volume over sample volume, can fluctuate greatly. This supports a suggestion that concrete cores used for evaluating the compressive strength should be larger than 25 mm in diameter (NDIS 3439 (2022)).

0.00 0.02 0.04 0.06 0.08 0.10 0.12

0.00 0.02 0.04 0.06 0.08 0.10 0.12

a

b

Air curing Water curing

Φ p (Ø10−250 nm) (ml/ml)

Φ p (Ø10−250 nm) (ml/ml)

0.000

0.002

0.006

0.3 0.4 0.5 0.6 0.7

AEA content (wt%)

w/c ratio

Fig. 3. Porosity of cement paste of concrete powder: (a) S1; (b) S2 sample.