Delayed ettringite formation (DEF) can damage concrete that has experienced a temperature above about 70°C. Claims that slow release of sulfate from the clinker can have a similar effect in concrete not thus heated are unsupported.
Ettringite definition is - a mineral Ca6Al2(SO4)3(OH)12.26H2O consisting of hydrous basic sulfate of calcium and aluminum. a mineral Ca6Al2(SO4)3(OH)12.26H2O consisting of hydrous basic sulfate of calcium and aluminum…
Ettringite is also known as c ement bacillus, which is the name of a naturally occurring mineral of the same composition and structure. The formation of ettringite or cement bacillus has been recognized as the cause of excessive expansion, cracking and even complete disintegration of concrete subjected to intensive sulfate attack.
The ettringite was identified by EDS-analyses which revealed also trace amounts of Cu, Si and As. At very high magnifications the hexagonal cross-section and the basal pinacoid can be recognised. This material was found in 2015. Collection Heinz Förch, photo Harald Schillhammer.
Ettringite crystals have a P31c with a=11.224 Å, c= 21,108 Å, while thaumasite crystals fall into space group P6 3 with a= 11.04 Å, c= 10.39 Å. While these two minerals form a solid solution, the difference in space groups lead to discontinuities in unit cell parameters. Differences between structures of ettringite and thaumasite arise from the columns of cations and anions: Ettringite ...
Ettringite Group. Although it is generally assumed that a solid solution series between ettringite and thaumasite exists, both species have different space groups and a possible discontinuity was identified, characterised by a gap in the a-dimension of the solid-solution phases (Barnett et al., 2000).
Ettringite is a hydrous calcium aluminium sulfate mineral with formula: Ca 6 Al 2 (SO 4) 3 (OH) 12 ·26H 2 O. It is a colorless to yellow mineral crystallizing in the trigonal system . The prismatic crystals are typically colorless, turning white on partial dehydration.