Comparison Between Leeb and Knoop Hardness on Metakaolin-Based Geopolymers

Geopolymers represents a relatively new material, for sustainable building and Cultural Heritage restoration, that are of greatest interest in the field of Earth Sciences, not only because they are made starting from natural inorganic materials, but also for their peculiar mechanical features and for a low CO2 emission. In the present work, it was experimented the use of a portable Leeb D instrument to determine the microhardness of some metakaolin-based geopolymer specimens by comparing its results with those obtained by the Knoop microdurometer. The Knoop test is indicated by the ASTM standards for determining the hardness of advanced ceramic materials. In our idea, the method can be used for a fast in situ measurement of the hardness properties of the materials, to be subsequently verified after sampling with laboratory measurements