Applicability of rheometers to characterizing earth mortar behavior. Part I: experimental device and validation

The workability of earth mortars made with natural soils composed of clay and sand, also called soil mortars, such as sand-cement mortars, is in general studied using simple methods that are very useful in situ but are often incapable of describing the rheology in the fresh state. A more precise understanding of earth mortar behavior in the fresh state would enable more accurate prescription for building. The experimental devices used today, e. g., the slump test or flow table, indicate only one measurement which could possibly yield one rheological parameter, whereas at least two parameters are necessary to define the constitutive law of fresh sand-cement mortars in the case of a Bingham fluid behavior. A rheometer procedure is studied here in order to determine an earth mortar behavior law. Since this was the first time that this device was used with this material, we had to develop our experimental procedure using a rheometer, such as the blades required to shear the earth mortar and also the range of the applied rotation speed. The calibration of two blades is discussed and an interval of speed and time adequate for the test is given to define the earth mortar's rheology.