Sandoz Gmbh

Mbt Holding Ag

Josef F Drs

Salvatore Valenti

Max Oppliger

Tom Arild Melbye

Odd M Tjugum

Bernhard Leikauf

A method for coating a substrate with a cementitious composition by spraying, comprising the addition to the initial cementitious mix one of a .beta.-naphthalene sulphonate-formaldehyde condensate and a water-soluble poly(alkylene oxide) of molecular weight from 100,000-8,000,000, the other being added at the spraying nozzle, there being additionally added at the nozzle (preferably as a single component with the other nozzle-added material) an accelerator selected from aluminium sulphate, aluminium hydroxide and aluminium hydroxysulphate. In a preferred embodiment, the material added at the nozzle also contains a superplasticiser.

Cement spraying admixture

Fluidity control of cementitious compositions

A process for modifying the slump of a concrete or mortar by the addition at different times of a water-soluble poly(alkylene oxide) and a .beta.-naphthalene sulphonate-formaldehyde condensate, a plasticizer or superplasticizer which is selected from lignosulphonates, melamine sulphonate formaldehyde condensates, carboxylates and selected styrene-maleic anhydride copolymers. The poly(alkylene oxide) is preferably partially replaced by a (hydroxy)alkyl cellulose. The process is advantageously used in shotcreting.

Workable cementitious compositions

The storage and processing times of sprayed concrete can be significantly extended by the addition of a retarder, a chemical compound which is capable of chelating with calcium ions. Preferred retarders are phosphonic acid derivatives which have at least one amino and/or hydroxyl group. The retarder can be used for both wet- and dry-sprayed concrete, the usual accelerators can be used for activation, and the strength is not adversely affected.

Shotcrete compositions

A process for improving the rebound properties of sprayed concrete comprises the inclusion therein of micro-silica which has been pretreated with from 2 to 25% by weight thereof of a liquid selected from water, an alkanolamine, a polyol and an aqueous solution of at least one concrete additive, an alkanolamine, a polyol and a water-soluble cellulosic compound. The process is especially effective when used in conjunction with the dry spraying process.

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Vienna, Austria

Josef F Drs