Heat treatment of fresh concrete by radio waves – Avoiding delayed ettringite formation. (15th July 2017)

• Record Type: Journal Article
• Authors: Höhlig, Björn; Schröfl, Christof; Hempel, Simone; Noack, Ina; Mechtcherine, Viktor; Schmidt, Detlef; Trommler, Ulf; Roland, Ulf
• Is Part Of: Construction & building materials. Volume 143(2017)
• Page Start: 580
• Page End: 588
• Publication Date: 2017-07-15
• Subjects: Concrete -- Heat treatment -- Radio waves -- Temperature control -- Durability -- Delayed ettringite formation; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2017.03.111
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Precisely tunable heat treatment of concrete with radio waves. Avoiding the exceeding of temperature limitations. Minimising the risk of long-term damage caused by delayed ettringite formation. Abstract: Heat treatment of concrete during the early stages of hydration using the new radio wave technology enables a uniform energy supply at distinct rates under steady, closed-loop temperature control. This precise control of temperature makes it possible to implement accurately and uniformly any heat treatment regime based on existing or future guidelines over the entire volume of a concrete element. The article at hand presents this new technology briefly and focuses on the issue of possible delayed ettringite formation which might compromise concrete durability. By means of ESEM- and XRD-analysis the influence of the different heat treatment temperatures on the concrete microstructure could be comprehensively investigated. It was found that a maximum temperature of 60 °C should not be exceeded because higher temperatures cause severe delayed ettringite formation. Dielectric heating as such had no additional influence on microstructural damage, especially on the extent of the formation of delayed ettringite.