PSI - Issue 37

João Custódio et al. / Procedia Structural Integrity 37 (2022) 644–651 João Custódio et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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– the semi-adiabatic method (also known as Langavant method) covered by the NP EN 196-9:2010, and the isothermal conduction calorimetry method described in the NP EN 196-11:2020. The best correlation between the cement heat of hydration obtained with the two methods, for the analysed samples, was obtained when using the heat of hydration measured at 41 hours with the semi-adiabatic method (Q 41h,EN 196-9 ) and the heat of hydration measured at 168 hours with the isothermal conduction calorimetry method (Q 168h,EN 196-11 ). It was found that the isothermal conduction calorimetry method tends to give slightly lower values of heat of hydration than the semi-adiabatic method (on average, -11 % when compared to the value obtained at 41 h with the semi-adiabatic method, Q 41h,EN196-9 , and -14 % when compared to the value obtained at 120 h with the semi-adiabatic method, Q 120h,EN196-9 ). The temperature estimates made with the cement heat of hydration values determined with the semi-adiabatic method (70.7 ºC), as well as with cement heat of hydration values estimated from the isothermal conduction method (70.8 ºC), were very close to the temperature attained in a real structural element (68.9 ºC). Despite the interesting results, more assessments will be performed both at the laboratory, with more cements, and in-situ, with more real cases, to validate the aforementioned approach for different structural element geometries/dimensions, cements, aggregates, admixtures, and environmental conditions. The results obtained so far in the L PC Test Method no. 66 “Reactivity of a concrete mix ture design with respect to the delayed ettringite formation – Performance testing”, show that the assessed concrete mix ture is likely to be susceptible to the deleterious development of ISR when used in a structure, as long as the remaining conditions for its development are met, namely the presence of a sufficient amount of moisture in the concrete. Thus, to avoid deleterious expansion of the deck’s concrete, that might have repercussions in the structure’s performance, mitigation measures will have to be adopted onsite to maintain the temperatures at an acceptable level. Acknowledgements João Custódio carried out the work in the scope of the FCT Investigator Project IF/00595/2015/CP1326/CT0001, financed by the Fundação para a Ciência e a Tecnologia, FCT (Portugal); the author wishes to acknowledge this financial support. References ACI 2013. ACI CT-13 Concrete Terminology. Farmington Hills, MI: American Concrete Institute (ACI). Custódio, J. 2017. Projeto FCT de Investigação Exploratória “Enhancing Diagnosis, Prognosis and Mitigation of Internal Expans ive Reactions in Concrete Structures (IF/00595/2015)”. Fundação para a Ciência e a Tecnologia (FCT). Custódio, J. 2020. ENHANCE – Enhancing diagnosis, prognosis and mitigation of internal expansive reactions in concrete structures (2017 2021). Project Interim report. LNEC - Proc. 0202/111/21202. Relatório 463/2019 – DM/NBPC. Custódio, J. & Ribeiro, A. B. 2015a. Internal expansive reactions in concrete structures – Deterioration of the mechanical properties. Ciência & Tecnologia dos Materiais, 27 , 108-114. Custódio, J. & Ribeiro, A. B. 2015b. Projeto LNEC de Investigação, Desenvolvimento e Inovação “Deterioração do betão por reaç ões expansivas internas: Diagnóstico e Prognóstico. LNEC - Laboratório Nacional de Engenharia Civil, I.P. Custódio, J. & Ribeiro, A. B. 2019. 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