PSI - Issue 28

N.A. Kosheleva et al. / Procedia Structural Integrity 28 (2020) 1883–1891 Author name / Structural Integrity Procedia 00 (2019) 000–000

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It should be noted that the data presented in Fig. 6 is shown without temperature compensation, and therefore include a change in the Bragg wavelength associated with a change in temperature. Since the samples were made from the same material, were located in the same environmental conditions, and the observed temperature changes inside the samples differ slightly from each other, the analysis and comparison of the data obtained from the FBG sensors is assumed reasonable.

a b Fig. 6. Strain change over time measured by embedded FBG sensors for sample 1 (a) and sample 2 (b).

Figure 7 shows the change in temperature inside the studied samples during the first 72 hours. The temperature of the cement mixture increases rapidly in the early hours and reaches its maximum values approximately 11.5 hours after casting. It is known that the higher the curing temperature, the faster the reactions between cement and water takes place and, therefore, the shorter the setting time (Kara and Korjakins, 2013).

Fig. 7. Samples temperature change over time.

Shrinkage plots for cylindrical and prismatic samples during the first three days, obtained using an external laser position sensor are shown in Fig. 8. The maximum shrinkage of the samples occurred during the first hours after casting (sample 1 – 1.5 hours, sample 2 -2.5 hours). It should be noted that the shrinkage profile on the free surface