Case Studies in Construction Materials 15 (2021) e00644 Available online 2 August 2021 2214-5095/© 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Case study Moisture and ion mobilization and stratifcation in post-tensioned (PT) grout during hydration Samanbar Permeh *, Kingsley Lau, Berrin Tansel Florida International University, 10555 W. Flagler St., Miami, FL 33174, United States A R T I C L E INFO Keywords: Grout hydration Ion mobility Corrosion Cementitious grout Post-tensioned tendons Compression ABSTRACT Mobilization and stratifcation of ions and moisture in post-tensioned tendons during grout hy- dration can create adverse conditions which can promote corrosion. The transport of sulfate and chloride ions associated with grout segregation in large-scale tendon mockups was assessed. The grout was mixed with 15 % excess water over the manufacturers recommended limit to promote segregation and with different sulfate and chloride concentrations. The moisture content and both sulfate and chloride ion concentrations in the grout from the top sections of the tendons were signifcantly higher than grout from lower elevations. An ion-concentration factor (ICF) was defned as the ratio of the ion concentration in the leachate produced from the hydrated grout and the initial concentration in the grout mix water. The ion mobility in relation to moisture was analyzed in terms of the sulfate and chloride ions and their interactions with the solid and liquid phases during grout hydration. 1. Introduction Prestressed concrete bridge construction in the United Stated became widely used in the twentieth century. It allows the con- struction of large bridges with longer spans and opens up the range of design possibilities. The term prestressing is used to describe the process of introducing internal forces in a concrete structural element during the construction process in order better to resist the external loads that will be applied when the structure is put into service [1]. When the steel is tensioned after concrete placement the process is called post-tensioning (PT). The prestressing strands, duct, and fller material are collectively referred to as a tendon. The tendon can be embedded in the concrete or placed within the open spaces of an enclosed concrete structural elements. There has been a concern over the inspection of tendons in post-tensioned concrete bridges because of the diffcultly of detection and quantifcation the extent of deterioration [2]. Corrosion damage to the prestressed steel of PT concrete components can occur by different mechanisms depending on the pre- stressing conditions and environmental exposure. PT tendons are differentiated as being bonded or unbounded. The unbonded PT tendons can use fexible fllers (i.e., grease and wax) to provide encapsulation of the steel and act as a barrier to environmental exposure. The prestress steel is set in a duct embedded in concrete and injected with cementitious grout in bonded PT systems. The systems used for bonded PT concrete typically consist of the concrete structural element, pre-stressing steel (in the form strand, wire, or bar), duct that houses the pre-stressing steel, cementitious grout, and the anchorage system [2]. Concrete is cast in forms and allowed to reach a predetermined strength before the prestressing steel is tensioned. The alkaline cementitious environment in the grout of * Corresponding author. E-mail address: samanbar.permeh1@fu.edu (S. Permeh). Contents lists available at ScienceDirect Case Studies in Construction Materials journal homepage: www.elsevier.com/locate/cscm https://doi.org/10.1016/j.cscm.2021.e00644 Received 10 May 2021; Received in revised form 14 July 2021; Accepted 27 July 2021