Long-term use of modern Portland cement concrete: The impact of Al-tobermorite formation

• Published in: Materials & design Vol. 198; p. 109297
• Main Authors: Maruyama, Ippei, Rymeš, Jiří, Aili, Abudushalamu, Sawada, Shohei, Kontani, Osamu, Ueda, Shinya, Shimamoto, Ryu
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.01.2021; Elsevier
• Subjects: Aggregate; Calcium-silicate-hydrate; Compressive strength; Reaction; Calcium-silicate-hydrate; Compressive strength; Reaction; Aggregate
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2020.109297

The distribution of compressive strength in thick concrete members exposed to various environments in a nuclear power plant undergoing decommissioning is investigated. X-ray diffraction data, scanning electron microscopy analysis, and chemical analysis data reveal that rock-forming minerals in the aggregate had reacted and portlandite had been consumed to form calcium alumino silicate hydrates (C-A-S-H) when evaporable water content was sufficient. In addition, the study confirms Al-tobermorite formation in modern concrete after 16.5 years of elevated temperature conditions ranging from 40 to 55 °C. It is concluded that an appropriate aggregate and binder combination for the concrete enhances the compressive strength of thick concrete members thanks to the reaction of rock-forming minerals with portlandite, and also strengthens the chemical stability through the formation of Al-tobermorite under elevated temperature conditions and sufficient evaporable water content. [Display omitted] •The first detailed investigation results of concrete from a commercial NPP 47 years after construction are presented.•Al-tobermorite formation in modern Portland cement concrete in service was confirmed.•Reaction between aggregate and cement hydrates produced C-A-S-H and Al-tobermorite.•The reaction developed the strength of concrete dramatically.