Abstract: A stack of parts, such as the stator disks of a turbomolecular pump, the parts being stacked alternately with spacers, includes a spacer having a knife-shaped deformable portion. When the stack is installed for the first time, the portion is compressed so as to take up the tolerances of the stack between abutment surfaces, e.g. delimited by a pump body and a corresponding casing. The invention applies in particular to turbomolecular pumps and aims to eliminate the operations of adjustment, re-machining, or matching that are usually required when installing a stator assembly.

Abstract: The processibility and initial mechanical strengths of hydraulic cement compositions, e.g., Portland cement, are improved by formulating therewith an adjuvant comprising (i) a water-soluble salt of the condensation product of an aromatic sulfonic acid with HCHO (formulated either alone or in admixture with a water-soluble salt of an aromatic sulfonic acid which has not been condensed with HCHO), (ii) lithium hydroxide, and (iii) a hydroxide of another alkali metal or of an alkaline earth metal.

Abstract: Mortars and concretes are formulated from hydraulic binders, and are adapted for more rapid setting and hardening in cold weather, such formulations including the admixture of hydraulic binder, aggregates and water, and such formulations being characterized in that they include:(a) a water-soluble dispersant/water-reducing agent;(b) an inorganic basic agent selected from the group comprising the hydroxides of alkali metals other than lithium, alkaline earth metal hydroxides and the mixtures of one of such hydroxides with lithium hydroxide; and(c) a water-soluble salt of an inorganic oxyacid or an aliphatic or aromatic carboxylic acid, said acid having an ionization constant pKa of less than 2.5 in water at 25.degree.C.

Abstract: The water solubility of certain heteropolysaccharide salts of calcium is enhanced by effecting the dissolution thereof conjointly with an organic acid or anhydride thereof having at least one pK value between 5 and 7, the calcium salt or salts of such organic acid or anhydride itself or themselves being soluble in water.

Abstract: Certain alumino-calcium compounds are added to hydraulic binders, as water reducing agents for enhancing the workability of such binders while at the same time reducing the requisite quantities of water needed therefor.