Pozzolana from Burnt Gaize and Moler

Gaize is soft, porous, highly siliceous, sedimentary rock containing a proportion of clay, which is found distributed over a considerable area in Ardennes and Meuse valley in France. Often fossiliferous, it may contain a fraction of carbonate and clay. Sometimes, silicified beaches are found in diffused form. Silicification results of impregnating the porosity of the silica colloidal type called opal [silica hydrated compound, SiO2.nH2O] with traces of Mg, Ca, Al, Fe, As, Na, K etc. It contains silica in a gelatinous condition and has a density of only 1.4 after drying. The rock has been used in the raw state as a pozzolana, but usually it is burnt at a temperature of about 900°C.

Moler earth, a typical type of diatomaceous material is naturally occurring, soft, siliceous sedimentary rock that is easily crumbled into fine white to off-white powder. It has a particle size ranging from less than 3 micrometer to more than 1 millimeter but typically 10 to 200 micrometers. The powder has an abrasive feel and is very light due to its high porosity. The typical chemical composition of oven dried diatomaceous earth is, silica 80-90%, alumina 2-4% and iron oxide 0.5-2%. It has shown pozzolanic properties and is used for concrete work in sea water in Denmark. Initially the raw moler was used, but the burnt moler was found to be superior and used instead of the raw product.