PSI - Issue 30

A.A. Kychkin et al. / Procedia Structural Integrity 30 (2020) 64–70 A.A.Kychkin et al / Structural Integrity Procedia 00 (2019) 000 – 000

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During exposure, the mean annual air temperature in Yakutsk ranged from – 6.6° С to 7.7° С , the mean minimum temperature was recorded as – 47.9° С , the average maximum temperature was 35.0° С . The mean annual monthly relative air humidity ranged from 18 to 98%. The total precipitation was 225mm per year on average. The total annual solar radiation was 3680 MJ/m 2 . In Gelendzhik the mean annual air t emperature was 14.8° С , the mean minimum recorded temperature was 5° С , the mean maximum temperature was 24.8° С . The mean annual monthly air humidity ranged from 68 to 85%. The total precipitation was 665 mm per year in average. The total solar radiation was 5073 MJ/m 2 in average. The tension and three point bending tests were carried out on a Z600 Zwick/Roell universal testing machine based on State Standard 32492- 2015 “Composite polymer reinforcement for concrete structures” “Methods for physic al mechanical characterization”, State Standard 25.604 - 82 “Calculation and strength tests. Methods of mechanical tests for polymer matrix composites. The bending test at normal, higher and lower temperatures”. Linear thermal expansion (LTE) was measured on a ТМА 202 thermal mechanical analyzer (NETZSCH-Geratebau GmbH) at 5K/min heating rate in helium stream of 70ml/min. The measurements were carried out according to State Standard Р 57754- 2017 “Polymer composites. Estimation of linear thermal expansion usin g thermal mechanical analysis” at temperatures ranging from - 60 to 100° С . The glass transition temperature was measured at temperatures ranging from 25 to 250° С on DMA 242, NETZSCH Geratebau GmbH, at heating rate 1K/min, 5 Hz frequency and 10 μm amplitude in argon environment (gas flow rate 50ml/min) using dynamic mechanical analysis. 3. Results and discussion The comparison of the samples after 4 year exposure at different climate sites showed that the appearance of the samples exposed to moderate warm climate (Geledzhik) was subject to more changes than those in a very cold climate (Yakutsk). The samples exposed in Gelendzhik demonstrated more intense lightening, loss of shine, and breakage of the light braiding thread. The study suggests that failure starts from deterioration of the surface layer of composite rebars, thus, the larger the diameter of the samples, the more defects they show in the surface layer on the side exposed to the sun. Figure 1 presents changes in maximum force of the 6 and 8 mm Ø rebars for three point bending depending on exposure time before and after exposure in extremely cold and moderate warm marine climate. The figure demonstrates a significant increase in maximum force for bending with exposure time. In average, the maximum force for three point bending increased 22 % for Ø6mm and 58% for Ø8mm rebars. The test results suggest that the dependence of change in maximum force o n climate is ambiguous. The maximum force for bending is greater for Ø6 rebars exposed to moderate warm marine climate than extremely cold climate. It is opposite for Ø8 rebars.

Fig.1. Time dependent maximum force for bending of BFRP rebars 6 (1 and 2) and 8 (3 and 4) mm in diameter in climatic conditions of Yakutsk (1 and 3) and Gelendzhik (2 and 4)