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Title (Primary) Effects of dielectric heating of fresh concrete on its microstructure and strength in the hardened state
Author Höhlig, B.; Schmidt, D.; Mechtcherine, V.; Hempel, S.; Schröfl, C.; Trommler, U.; Roland, U.;
Journal Construction and Building Materials
Year 2015
Department TUCHEM;
Volume 81
Language englisch;
POF III (all) T15;
Keywords Concrete; Radio-wave technology; Dielectric heating; Heat treatment; Hydration; Early-age strength; Microstructure investigation
UFZ wide themes RU4;
Abstract By means of radio-wave technology it is possible to allow the uniform, rapid and accurate, temperature-controlled heating of fresh concrete. This results in the significantly accelerated release of hydration heat. The heat release from this second source can be easily compensated by the temperature-controlled reduction of RF energy input. The consequences are accelerated hydration and higher early-age compressive strength. Early-age concrete, heat-treated by radio waves, have a denser microstructure with a higher gel-pore content and more C-S-H phases than untreated concrete. When cured at the maximum temperature of 80 °C, secondary ettringite can be formed in concrete, whereas this is not the case for the treatment temperatures of 40 °C and 60 °C. At the age of 28 d, heat-treated concretes exhibit a looser microstructure than does untreated concrete. Larger portlandite crystals and secondary ettringite are its characteristic features as a consequence of the much faster reaction rates in the early-age concrete. This results in lower values of the compressive strength of the heat-treated concrete.
ID 15900
Persistent UFZ Identifier https://www.ufz.de/index.php?en=20939&ufzPublicationIdentifier=15900
Höhlig, B., Schmidt, D., Mechtcherine, V., Hempel, S., Schröfl, C., Trommler, U., Roland, U. (2015):
Effects of dielectric heating of fresh concrete on its microstructure and strength in the hardened state
Constr. Build. Mater. 81 , 24 - 34