Chloride Diffusivity and Resistivity of Cured and Mature Binary/Ternary Concrete [Final Report]

US Transportation Collection2019PDFTech ReportPresuel-Moreno, Francisco JKazemi, AmirkhosroBarman, SanjoyRaof, FarhadFlorida Atlantic University. Center for Marine MaterialsFlorida. Department of TransportationFlorida. Department of TransportationFloridaUnited StatesAbsorptionAdmixturesChloridesConcreteCorrosionDiffusivityDurabilityService lifeReinforced concreteResistivity methodApparent diffusion coefficientnon-steady state diffusionnon-steady state migrationresistivitysorptivitybinary and ternary mixesBDV27-977-09Final report, December 21, 2015 \u2013 February 15, 2019This investigation was performed to gain additional insight into the long-term durability of reinforced concrete structures. The chloride diffusion of concrete with supplementary cementitious materials is known to decrease with time, eventually reaching a stable value. This study aims to better understand when the chloride diffusion rate transitions from decreasing values to a stable minimum. The bulk diffusion tests and the rapid migration tests were carried out on concrete specimens that have been curing for several years (and that were characterized also at an earlier age). There are several reasons why the apparent diffusion (Dapp) values do not match with Dnssd, including the fact that Dnssd specimens are immersed all the time and exposed indoors to lab room temperature, whereas the field structures are exposed to temperature and humidity changes depending on time of the day, seasonal changes, and the elevation within the structure, which results in moisture variations within the concrete. The chloride diffusion coefficients (Dnssm and Dnssd) of mature concrete were obtained. For some concrete compositions, Dapp values were calculated from chloride profiles obtained on cored specimens exposed to simulated field conditions for approximately 4 years. The Dapp values were obtained only on a subset of the concrete mixtures investigated. Matured high performance concrete cylinders were available that were prepared as part of earlier projects. Most of these concrete cylinders have been curing for more than 4 years. The Dnssd were obtained after exposure for 10 to 12 months in 16.5% NaCl solution (i.e., bulk diffusion test). The Dnssm values were obtained from rapid migration tests per the Nordtest NT Build 492 method. The Dnssd and Dnssm values were correlated to the resistivity values measured on companion cylinders (if available) or to the resistivity values measured on the cylinders before starting the diffusion tests. Four concrete compositions were prepared in 2016 as part of this project. The sorptivity, resistivity, porosity, Dnssd, and Dnssm were characterized several times over the duration of the project.120