Abstract

The Camarasa Dam was built in 1920 using dolomitic aggregate and Portland cement with two different compositions: type A (dolomite and Portland cement) and type B (dolomite and sand-cement). The sand cement was a finely powdered mixture of dolomite particles and clinker of Portland cement. The mineralogy of concrete was studied by optical microscopy, scanning electron microscopy, and x-ray powder diffraction. Reaction of dedolomitization occurred in the two types of concrete of the Camarasa Dam, as demonstrated by the occurrence of calcite, brucite, and/or absence of portlandite. In the type A concrete, calcite, brucite, and a serpentine-group mineral precipitated as a rim around the dolomite grains and in the paste. The rims, a product of the dedolomitization reaction, protected the surface of dolomite from the dissolution process. In type B concrete, in addition to dolomite and calcite, quartz and K-feldspar were present. Brucite occurred in lower amounts than in the type A concrete as fibrous crystals randomly distributed in the sand-cement paste. Although brucite content was higher in the type A concrete, type B showed more signs of loss of durability. This can be attributed to the further development of the alkali-silica reaction in this concrete type.

Highlights

  • Concrete made of dolomite aggregate, has been the source of problems such as expansion and cracking [1,2,3,4,5,6,7]

  • These deterioration problems were associated with the alkali-carbonate reaction (ACR) [8,9], which is produced when dolomitic rocks with clay minerals are used as aggregates or as a result of the reaction of dolomite with cryptocrystalline quartz [10]

  • The concrete of the Camarasa Dam is made of aggregates mainly composed of dolomite

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Summary

Introduction

Concrete made of dolomite aggregate, has been the source of problems such as expansion and cracking [1,2,3,4,5,6,7] These deterioration problems were associated with the alkali-carbonate reaction (ACR) [8,9], which is produced when dolomitic rocks with clay minerals are used as aggregates or as a result of the reaction of dolomite with cryptocrystalline quartz [10]. Dolomite reacts with the portlandite of the cement paste to produce calcite and brucite The kinetics of this reaction have been studied in different alkaline media, temperatures, and silica content [13,14,15,16].

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