Once again on thaumasite – a substance that does not have binding properties

Thaumasite exists as a rare mineral of the calcium carbonate silicate sulphate hydrate type that was first discovered by the Swedish geologist Nordenskiold in 1878. He named the mineral thaumasite after the Greek word thaumázein ‘to be surprised’. A simple empirical formulation for thaumasite is the following: CaCO3.CaSiO3.CaSO4.15H2O or Ca6[Si(OH)6]2(CO3)2(SO4)224H2O, a hexagonal prism type of phase like ettringite is. The non-binder thaumasite can have a positive application in oil exploration offshore through designing concrete with short-service lifetime and eco-friendliness. The first known appearance of the non-binder thaumasite in Europe arose in Stoke-on-Trent, UK, in February 1969. Thaumasite plus ettringite were found in a mortar with blistering on the surfaces. This had been applied to masonry cement under cold damp conditions with lack of proper rendering on some internal walls being constructed. Information about the calcium germanate equivalent of thaumasite (carraraite or germano-thaumasite) is given.

Author: J. Bensted

Section: Concrete

Keywords: thaumasite, ettringite, carraraite, concrete