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Title: Carbonation of 100-Year Bridges as a Guide to Preventing Modern Concrete from Degrading

Author(s): Ivan Janotka, Michal Bačuvčík, Peter Paulík, and Lukáš Húlek

Publication: Symposium Paper

Volume: 349


Appears on pages(s): 256-273

Keywords: carbonation, concrete, 100-year bridge, protective render coat, resistance

DOI: 10.14359/51732751

Date: 4/22/2021

A layer of 2-4 mm (0.08-0.16 in) protective render coat (PRC) has proven to be an effective anticarbonation barrier at two bridges protecting the underlying concrete against carbonation for 100 years. The carbonation of concrete under the PRC with low permeability was found to be less than 2 mm (0.08 in). It is assumed that the PRC was placed for aesthetic purposes. Taking into account the considered XC3 exposure class according to EN 206, to which concrete structures were subjected and compressive strengths of the underlying concrete between 20 - 25 MPa (2900 - 3625 psi), low carbonation depth can be explained by the presence of the PRC applied on concrete surface. The main scientific goal of this article is to explain the cause of extremely low carbonation depth of concrete under the PRC. Its composition has been unknown until now but the present research reveals the secret of this substance. Investigations of the aspects of low carbonation depth thoroughly focused on the PRC role covering concrete beneath as well as material development of new current PRC based on the present cement and sand, without the use of chemical admixtures, are also the subject of ongoing research.