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Development of an Accurate Methodology for Measuring the Pore Fluid pH of Low-pH Cementitious Materials

AutorAlonso, M.; García Calvo, José Luis
Palabras clavepH measurement methodology
Low-pH cements
Statistical analysis
Fecha de publicación2011
Citación13th International Congress on the Chemistry of Cement;
ResumenLow pH cementitious (LopHC) materials are expected to be used in the construction of an underground repository for the geological disposal of high level radioactive waste (HLW). A fundamental aspect of the development of LopHC is the accurate and reliable measurement of the pore fluid pH in order to qualify and help quantify mix designs to achieve specific pH targets. The main objective of the current research is the development of an agreed protocol for measuring the pH value of LopHC. There are four different methods described in the literature for characterizing the pore solution of cementitious materials: 1) Pore fluid expression; 2) Leaching methods, including both in-situ and ex-situ techniques); 3) Percolation methods; and 4) Embedded pH sensors. The first three methods are used for extracting the pore solution of the concrete before pH determination, while the fourth, using embedded pH sensors, takes direct measurement of the pore fluid pH value. Of these methods, pore fluid expression (PFE) was chosen to represent the Reference Method because it is considered to be the most reliable and ex-situ leaching (ESL) with and without filtering were chosen as candidates for the Routine Method because they are fast, cheap and simple. In a first step, different parameters that may affect the measured pH values were evaluated, including the solid/liquid ratio, fineness, carbonation, time, and the results obtained from a pH meter in comparison with an OH– titration. Based on the results obtained from the first step, selected protocols were proposed and tested for reproducibility and repeatability in 8 laboratories of 7 countries using the same LopHC sample. The proposed methodologies showed very promising results with low deviation and high reproducibility and have allowed the development of an agreed set of simple protocols for the determination of pH in LopHC.
Aparece en las colecciones: (CISDEM) Comunicaciones congresos
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