Mineralogical Characterization of Dolomitic Aggregate Concrete: The Camarasa Dam (Catalonia, Spain)

• Main Authors: Encarnación Garcia, Pura Alfonso, Esperança Tauler
• Format: Article
• Language: English
• Published: MDPI AG 2020-01-01
• Series: Minerals
• Subjects: dolomite; sand-cement; concrete; dedolomitization reaction
• Online Access: https://www.mdpi.com/2075-163X/10/2/117

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.