Abstract: An apparatus for the activation of cement comprises at least one electromagnetic particle size reducer having a common reducer hopper at the inlet ensuring a gravity feeding of cement to the reducer, and a series sequence including a receiving hopper having a crusher and a conveying screw in a casing having a classifier in the form of a screen arranged at the outlet of the screw and communicating with the reducer hopper having an inclined bottom wall, the screen of the classifier comprising a body of revolution which is rigidly secured to the shaft of the screw coaxially with the shaft and arranged together with a portion of the screw and casing inside the reducer hopper upstream the inlet of the electromagnetic reducer.

Abstract: A rapid-setting dry packing mix for eliminating bore hole troubles contains: 40 to 50 percent by weight of cement powder, 50 to 60 percent by weight of gypsum or alabaster, 0.01 to 3.0 percent by weight of barium hexaferrite powder in particles commensurate in size with those of the binder.A method for manufacturing the rapid-setting dry packing mix for eliminating bore hole troubles consists in a mechanical mixing in an alternating electromagnetic field powders of cement, gypsum or alabaster and barium hexaferrite taken in required proportions, the above barium hexaferrite powder being introduced through abrasion of working tools which are magnetized pellets prepared on the basis of barium hexaferrite.

Abstract: A plug for eliminating troublesome zones in wells, comprising a plugging agent in the form of a dry quick-setting mixture packed in an elastic water-proof cylindrical chamber having the same diameter as the well being treated and whose bottom end is stoppered, whereas the top end thereof is provided with retainers and is shaped as a double strip formed by the walls of the cylindrical chamber and defined by two peripheral longitudinal seams running to the boundary line of the plugging agent, said strip being bent along said boundary line over the plug body so as to be forced thereagainst by said elastic retainers.