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Title: Observations on dedolomitization of carbonate concrete aggregates, implications for ACR and expansion

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. -- Highlights: •The dedolomitization caused no expansion. •It occurs in the dolostone aggregate without reactive silica involvement. •It has taken place already with the presence of the cement binder. •A significant alteration occurred: formation of rims, new pores and phases.
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [2]
  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)
Publication Date:
OSTI Identifier:
22220830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Cement and Concrete Research; Journal Volume: 54; Other Information: Copyright (c) 2013 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CARBONATES; CEMENTS; CONCRETES; LIMESTONE; RESONANCE IONIZATION MASS SPECTROSCOPY; SCANNING ELECTRON MICROSCOPY; SILICA; SOLUTIONS; X-RAY DIFFRACTION; X-RAY FLUORESCENCE ANALYSIS