Observations on dedolomitization of carbonate concrete aggregates,implications for ACR and expansion |
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| Affiliation: | 1. University of Ljubljana, Faculty of Chemistry and Chemical Technology, Aškerčeva 5, 1000 Ljubljana, Slovenia;2. University of Ljubljana, Faculty of Civil and Geodetic Engineering, Jamova 2, 1000 Ljubljana, Slovenia;3. Magnel Laboratory for Concrete Research, Department of Structural Engineering, Ghent University, B9052 Ghent, Belgium;1. Institute of Theoretical and Applied Mechanics of the Czech Academy of Sciences, Prosecká 76, Prague 9, Czech Republic;2. Institute of Geonics of the Czech Academy of Sciences, Studentska 1768, 708 00 Ostrava-Poruba, Czech Republic;1. Department of Earth and Environmental Sciences, University of Michigan, 1100 N. University Ave.; Ann Arbor, MI 48109, USA;2. College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, 104 CEOAS Administration Building, Corvallis, OR 97331, USA;3. School of Earth and Ocean Sciences, University of Victoria, Bob Wright Centre, 3800 Finnerty Rd. (Ring Rd.), Victoria, British Columbia V8P 5C2, Canada;1. CONSTRUCT-LABEST, Faculty of Engineering (FEUP), University of Porto, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal;2. Faculty of Exact Sciences and Engineering, University of Madeira, Campus Universitário da Penteada, 9020-105 Funchal, Portugal |
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| Abstract: | Some carbonate aggregates used in concrete are unstable in a high alkaline solution, which is present also in pore solution of cement binder. This paper investigates the process of dedolomitization of carbonate aggregate rocks and mortar bars. Selected aggregates, limestone and dolostone are of high purity without reactive silica involvement confirmed by the XRD and the XRF. For the process of dedolomitization the effect of various temperatures, solutions and time was examined. In this investigation, measurements of expansion, optical and scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction were used. Te results indicate that the process of dedolomitization occurred not only in the NaOH solution but also in the water on the mortar bar with virgin dolostone aggregate. Elevated temperature, 60 °C, increased the rate of reaction. Furthermore, the rate of reaction significantly correlates with time, which has also been confirmed through the Rietveld analysis. |
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