PSI - Issue 67

Shohana Iffat et al. / Procedia Structural Integrity 67 (2025) 1–7 Iffat et al. / Structural Integrity Procedia 00 (2024) 000–000

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GONR suspensions, for use as benchmark specimens. All specimens were cast in plastic molds, covered with plastic lids, and then kept at room temperature and removed from the molds after 7 and 28 days of curing. 2.3. Test protocols The dispersibility of the GONRs in DI water solutions was assessed quantitatively through dynamic light scattering (DLS) testing using a particle and molecular size analyzer (model Zetasizer Nano ZS, Malvern Panalytical Ltd.). For each GONR concentration and oxygen content, a suspension sample of 1 mL was utilized to measure the zeta potential. Each measurement was performed 10 times to characterize variability.

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Fig. 1– Photographs of GONR aqueous suspensions used to manufacture prototype cement concrete: (a) 0.0125 g/L (~0.0005 wt% in concrete); and (b) 1.25 g/L (~0.05 wt% in concrete).

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Fig. 2 – Uniaxial compression testing of concrete specimens: (a) specimen during test; and (b) summary of results (histogram bins and error bars indicate mean and standard deviation).

Uniaxial compression tests were performed on the 7-day and 28-day cured cylindrical specimens using a servo hydraulic loading frame. The load was applied in displacement-control mode at a rate of 0.3 mm/minute. A representative test setup is shown in Fig. 2a. Four specimens were tested for each GONR concentration (0, 0.0005 and 0.05 wt%), and each oxygen content (32.3 O%, 41.3 O%) for each test date (after 7 days and 28 days of curing).