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Title: Degradation processes of reinforced concretes by combined sulfate–phosphate attack

A novel form of alteration due to the interaction between hydrated cement phases and sulfate and phosphate-based pollutants is described, through the characterization of concrete samples from an industrial reinforced concrete building. Decalcification of the cement matrices was observed, with secondary sulfate and phosphate-based mineral formation, according to a marked mineralogical and textural zoning. Five alteration layers may be detected: the two outermost layers are characterized by the presence of gypsum–brushite solid solution phases associated with anhydrous calcium sulfates and phosphates, respectively, while a progressive increase in apatite and ammonium magnesium phosphates is observable in the three innermost layers, associated with specific apatite precursors (brushite, octacalcium phosphate and amorphous calcium phosphate, respectively). The heterogeneous microstructural development of secondary phases is related to the chemical, pH and thermal gradients in the attacked cementitious systems, caused by different sources of pollutants and the exposure to the sun's radiation.
Authors:
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [6]
  1. Inter-Departmental Research Center for the Study of Cement Materials and Hydraulic Binders (CIRCe), University of Padova, Via Gradenigo 6, 35131 Padova (Italy)
  2. (ICEA), University of Padova, Via Marzolo 9, 35131 Padova (Italy)
  3. Department of Earth Sciences, University of Cambridge, Downing Street, CB2 3EQ Cambridge (United Kingdom)
  4. BAM Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205 Berlin (Germany)
  5. (Germany)
  6. Department of Geosciences, University of Padova, Via Gradenigo 6, 35131 Padova (Italy)
Publication Date:
OSTI Identifier:
22475482
Resource Type:
Journal Article
Resource Relation:
Journal Name: Cement and Concrete Research; Journal Volume: 68; Other Information: Copyright (c) 2014 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; APATITES; CALCIUM PHOSPHATES; CALCIUM SULFATES; CEMENTS; GYPSUM; LAYERS; MAGNESIUM PHOSPHATES; MATRIX MATERIALS; MICROSTRUCTURE; POLLUTION; PRECURSOR; REINFORCED CONCRETE; SCANNING ELECTRON MICROSCOPY; SOLID SOLUTIONS; TEMPERATURE GRADIENTS; X-RAY DIFFRACTION