Dynamit Nobel Aktiengesellschaft

Klaus Deneke

Hansjurgen Hass

Gunter Vogel

Helmut Clasen

Kurt Allemann

Arnold Lenz

Disclosed is a spray concrete which, even at a water-cement ratio of 0.45 to 0.55, is still easy to work, can be sprayed well, and sets and hardens rapidly. It contains, in addition to the conventional additives, additions of naphthalinesulfonicacid-formaldehyde condensation products and highly concentrated alkaline aqueous solutions of potassium aluminate, potassium carbonate and caustic potash. The concrete according to the invention displays an especially rapid solidification when it contains up to 3% by weight alkali silicates or an adequate amount in highly dispersed silicic acid (SiO.sub.2). The additives are incorporated into the concrete preferably directly at the worksite prior to spraying.

Easy-working spray concrete

The present invention relates to liquid accelerators for the setting of concrete mixtures. These accelerators have a long shelf life even in higher concentrations than the liquid accelerators known heretofore and, within the defined concentrations, produce no precipitation. The new accelerators are characterized by containing only potassium aluminate, potassium carbonate and potassium hydroxide in a defined range. They can be used in any known hydraulic binding agents, they shorten the set time of these binding agents, and they improve the compressive strength of the products made with them.

Liquid accelerator for the setting of concrete mixtures

A process for separating radioactive impurities from baddeleyite to obtain zirconium dioxide containing only traces of radioactive impurities, comprising grinding the baddeleyite preferably to a particle size of a maximum of 2% greater than 0.06 mm and then treating it directly with a 10 to 60% by weight aqueous alkali hydroxide solution at elevated temperatures below the boiling point of said solution at temperatures of 80.degree. to 140.degree. C. for 2 to 15 hours or until the desired degree of purity of the zirconium dioxide is obtained. In a preferred embodiment, sodium hydroxide is utilized and the ground baddeleyite preliminarily has been purified to the content of greater than 98% (zirconium dioxide+hafnium dioxide) by known methods.

Process for the separation of radioactive impurities of baddeleyite

A thermally conductive refractory electrical insulating embedding composition comprising granular magnesium oxide and granular fused magnesium iron alumino silicate; and electrical heating assembly having an electrically conductive heating member and a jacket and disposed between said member and said jacket a thermally conductive refractory electrically insulating embedding composition comprising granular magnesium oxide and granular fused magnesium iron alumino silicate.

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Troisdorf, Germany

Klaus Deneke