Ultrasonic Detection of Chloride Ions and Chloride Binding in Portland Cement Pastes

Arturo Emanuel Ramírez-Ortíz,Prisciliano F De J Cano-Barrita,Francisco Castellanos

doi:10.1186/s40069-018-0254-7

Arturo Emanuel Ramírez-Ortíz, Prisciliano F De J Cano-Barrita + Show 1 more

Open Access

https://doi.org/10.1186/s40069-018-0254-7

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Abstract

Chloride ions diffuse through the concrete cover and interact with the cement hydration products. As a result, some chloride ions become chemically and/or physically bound. Free chloride ions are the primary cause of steel corrosion in reinforced concrete structures. In this study, ultrasound was used to detect the presence and binding of chloride ions in cement pastes that contained supplementary cementing materials. Four cement pastes with w/c ratio of 0.55 were prepared and cast into cylindrical specimens that were moist cured for 254 days before being oven dried at 105 °C. The dried specimens were vacuum-saturated with NaCl solutions at various concentrations. Through-transmission ultrasonic measurements were performed as a function of time using 500 kHz longitudinal wave transducers. The results indicated exponential relationships between energy/amplitude weighted average frequency and the amount of chloride chemically bound by the cement pastes.

Highlights

One of the primary factors that influences the durability of concrete structures is penetration of aggressive species such as chloride ions
This paper proposes the basis for an experimental monitoring technique based on US that identifies the presence and binding of chloride ions in four hydrated cement pastes
When the ground cement pastes are immersed in a 3.0 mol/L NaCl solution, the external solution concentration stabilizes during the 3rd week

Summary

Introduction

One of the primary factors that influences the durability of concrete structures is penetration of aggressive species such as chloride ions. Chloride ions present in concrete mix constituents, deicing salts, or marine environments are the main cause of steel corrosion in reinforced concrete structures (Neville 1995). Some of the chloride ions that penetrate the concrete cover become physically and chemically bound to the hydration products (Hirao et al 2005; Marinescu and Brouwers 2012; Paul et al 2015; Suryavanshi et al 1996; Talero 2012; Thomas et al 2012), while others remain free. Free chlorides are present in the pore solution and cause corrosion of reinforcing steel upon reaching it at a certain threshold concentration (Ann and Song 2007; Glass and Buenfeld 1997; Grantham 2003; Saremi et al 2002)

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