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Wednesday, 21 August 2019
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Raw materials & technologies, Technologies

Studying the corrosion kinetics of hardened Portland cement under acid attack

Thursday, 29 September 2016

Whereas the chemical reactions occurring during the acid corrosion of cementitious materials are now well known, their reaction rates have still not been measured.

Local study of the corrosion kinetics of hardened Portland cement under acid attack. Source: CFalk/pixelio.de

Local study of the corrosion kinetics of hardened Portland cement under acid attack. Source: CFalk/pixelio.de

Researchers from Institut Lumière Matière, Université de Lyon, have proposed a methodology using digital holographic interferometry to access to these pure surface reaction rates.

Differentiation between dissolution and precipitation steps

This method makes possible the differentiation between the dissolution and precipitation steps. The scientists have used it to measure the reaction rate constant of the dissolution of hardened Portland cement in aqueous solutions of nitric, sulfuric and hydrochloric acids at pH 2. This quantity is seen to be unexpectedly similar for the three acids, with a value of the order of 1 mg/m2/s. The researchers have measured the evolution of this reaction rate constant with the pH in nitric acid and the real pH of the solution at the material surface, which is always alkaline (pH  > 11), even for attacks by solution with pH as low as 1.

The study is published in: Cement and Concrete Research, Volume 90, December 2016, Pages 36–42

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