Experimental research was carried out to investigate the infl uence of
aggregate hardness on Windsor probe test results. A series of concrete specimens
prepared from aggregates having a variety of Mohs ’ hardness values and also
specimens using an aggregate with a consistent class of Mohs ’ hardness were
prepared. The models once prepared were subjected to penetration tests. After
conducting the penetration tests, cores were extracted from the specimens.
A comparison between penetration tests and the core strength was carried out.
These show that the Windsor method is more reliable when only one class of Mohs ’
hardness is contained in the specimens. In this case the results can be considered
acceptable. The uncertainties grow as the number of classes of Mohs ’ hardness
increase. When testing during the presence of aggregates with different classes of
hardness, it is necessary to construct suitable curves of calibration.

• In situ concrete strength assessment: Infl uence of the aggregate hardness on the Windsor probe test results