This bachelor thesis describes improvement of soils to subgrade pavement. It defines basic expressions, which we are taking in consideration by. Next we are talking about each parameter, which has to be included in final subsoil and which tests are suitable for these parameters. We are decribing California Bearing Ratio in detail and its test. This thesis study context between pH and CBR. Change between these two subjects is caused by addition of a binder. We are practically proving this causes in practical part of bachelor thesis.