Sürdürülebilir Kalkınma Amaçları
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- MakaleYalnız künye2022Scopus SJRQ1Performance of fly ash-blended Portland cement concrete developed by using fine or coarse recycled concrete aggregate
Şimşek, O.; Pourghadri Sefidehkhan, H.; Gökçe, H.S.
The recycling of concrete and industrial wastes in the production of new concrete structures has increased its share due to the growing environmental concerns of the world. In this study, the use of recycled concrete aggregate at various replacement amounts (0–100 %) was investigated to be fine or coarse aggregate sources instead of crushed natural aggregate to understand better its effects on the dimensional stability and durability aspects of fly ash-blended Portland cement concrete. In the presence of recycled concrete aggregate, fly ash was very important for eliminating possible mechanical losses of concrete at 90 days. The use of coarse recycled concrete aggregate resulted in better compressive strength values of concrete exposed to with and without wetting–drying and freezing-thawing cycles when compared to fine ones. While the free drying shrinkage of concrete increased at significant amounts (68 and 79 %) for fine and coarse recycled concrete aggregate, the restrained drying shrinkage crack widths were reduced up to by 13.5 %. In conclusion, it should be noted that the amount and size of recycled concrete aggregate need to be designed by considering the residual quality and dimensional stability of concrete, which exposes weathering actions in place.
AtıfScopus57WoS50OpenAlex54
İncele - MakaleAçık Erişim2020Scopus SJRQ1Gamma ray and neutron shielding characteristics of polypropylene fiber-reinforced heavyweight concrete exposed to high temperatures
Demir, İ.; Gümüş, M.; Gökçe, H.S.
The residual properties of shielding structures need to be redefined after exposure to elevated temperatures due to their probable radiological hazards on biodiversity. In this study, the effect of high temperatures on mechanical, gamma ray and neutron attenuation characteristics was determined for limestone, barite and siderite concrete shields reinforced with polypropylene fiber. The increase in temperature up to 600 °C reduced the ultrasonic pulse velocity and compressive strength values of these shields by 59% and 62%, respectively. A good linear correlation (R2 ≥ 0.97) was found between these values. While the gamma ray linear attenuation coefficients increased by 9% for barite concrete, and reduced by 15% for normal concrete and by 17% for siderite concrete at 600 °C, trivial fluctuations (from −1% to +7%) were observed at 300 °C. The neutron attenuation factors of these shields gradually reduced up to 31% with the increase of temperature. The performance of siderite concrete was found to be slightly better than that of barite concrete in terms of strength and neutron shielding characteristics. With the satisfactory linear attenuation coefficients at all energy levels of gamma rays, barite concrete seems to be the most suitable concrete type under high temperature risks.
AtıfScopus142WoS132OpenAlex150İncele