Metakaolin in White Cement Mortars

Here are presented the results of an experimental study conducted to investigate the physical- mechanical performance of white cement bound products. White cement is a key ingredient in buildings with unplastered concrete blockwork facades of special architectural value. A metakaolin pozzolan is used instead of the more commonly used dark grey silica fume. An acrylic product is used as superplasticizer, testing different concentrations in an effort to reduce the larger amount of water required by white cement pastes. The physical-mechanical properties of the examined mortars were found to depend decisively on the poor performance of the superplasticizer that proved to be unable to reduce the water-to-cement ratio significantly. On the other hand, the metakaolins tested, especially the products obtained by the calcination of Sardinian kaolinic clays, containing thermodynamically unstable silica phases, appeared to be more effective especially at short curing times.