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The presence of pyrite in the aggregate used to make concrete can lead to severe deterioration as pyrite oxidizes. [51] In early 2009, problems with Chinese drywall imported into the United States after Hurricane Katrina were attributed to pyrite oxidation, followed by microbial sulfate reduction which released hydrogen sulfide gas (H 2 S).
Framboidal structure comprises roughly spherical aggregates of discrete equi-regular euhedral microcrystallites of around 0.5 μm in diameter, with the average aggregate size ranging from 5-20 μm. Framboid diameter tends to correlate positively with microcrystal size, and microcrystal packing is most commonly irregular and disordered.
In its turn, H 2 SO 4 reacts with portlandite (present in the hardened cement paste, HCP) and calcite (CaCO 3 (present in limestone aggregates or in carbonated HCP). The strong acidification of the medium caused by pyrite oxidation releases bicarbonate ions (HCO − 3) or carbon dioxide (CO 2) along with calcium (Ca 2+) and sulfate ions (SO 2 ...
Concretions in Torysh, Western Kazakhstan Concretions with lens shape from island in Vltava river, Prague, Czech Republic Marlstone aggregate concretion, Sault Ste. Marie, Michigan, United States A concretion is a hard and compact mass formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary ...
Mundic once [2] referred to pyrite, [3] but has now adopted the wider meaning of concrete deterioration caused by oxidisation of pyrites within the aggregate (usually originating from mine waste). The action of water and oxygen on pyrite forms sulphate (a salt of sulphuric acid ), thereby depleting the pyrite, causing loss of adhesion and ...
Crystal aggregate (lapis lazuli from Afghanistan) In geology, particularly in mineralogy and petrology, an aggregate is a mass of mineral crystals, mineraloid particles or rock particles. [1] [2] Examples are dolomite, which is an aggregate of crystals of the mineral dolomite, [3] and rock gypsum, an aggregate of crystals of the mineral gypsum. [4]
Within County Mayo the expert committee concluded that the defective blocks were caused by internal sulphate attack sourced from framboidal pyrite within the aggregate, as evidenced from both presence of framboidal pyrite and elevated sulphate content. [1]
The shape of a single crystal and/or aggregate of multiple crystals of the same mineral. Magnetism ... many iron minerals are nonmagnetic. (for example, pyrite). [4 ...