Abstract: A method for monitoring structural changes in a binder in contact with a solid object, while the binder is curing. Conductivity measuring pick-ups are placed in the binder mass and at the boundary between the binder and the solid object. A low amplitude AC voltage is applied to each pick-up at a low frequency, and the pick-up output signals are compared by a differential inductive bridge. The difference between the output signals is indicative of the extent of adhesion of the binder to the solid object. Preferably, only those components of the pick-up signals which are in phase with the applied AC voltage are employed for the comparison.