Leaching of cement: Study of the surface layer

Leaching of cement pastes shows that the properties of the surface layer are similar whether or not the cement paste contains slag. Substantial amounts of calcium, and smaller amounts of silicon, are leached out. Iron and magnesium are not released, but their content in the surface layer increases, with respect to an internal reference. Magnesium precipitates in the form of hydrotalcite, whereas the calcium of calcium silicate hydrates (CSH) is replaced by iron and dissolves out. Hydrogarnets undergo little, or no, leaching.