Disclosed is a composite gypsum board comprising a set gypsum core disposed between face (e.g., Manila) and back (e.g., Newsline) cover sheets. The set gypsum core is formed from a core slurry comprising stucco, water, and optional additives, such as foaming agent, migrating starch, accelerator, retarder, dispersant, etc. A dense layer formed from a dense layer slurry comprising stucco, water, fiber (e.g., paper fiber), and optionally, strength-enhancing starch, is disposed between the core and the face paper. The dense layer slurry contains a greater concentration of fiber, and optionally, strength-enhancing starch, than the core slurry, but the concentration of one or more other additives (e.g., accelerator, retarder, dispersant, or combinations thereof) is lower or the same in the dense slurry as compared with the core slurry. Also disclosed is a method of making board using one board mixer. In embodiments, paper fiber is added to water to form a suspension. The suspension is introduced, while in a non-laminar state, into the dense slurry. Further disclosed is apparatus, such as an extractor and an additive injection system, which can be a part of a cementitious slurry mixing and dispensing assembly.

According to the present invention, there is provided a wet accelerator for use in the manufacture of a gypsum product, said wet accelerator comprising water, particles of calcium sulphate dihydrate and a stabiliser. Additionally, a method of preparing a wet accelerator and a method of producing a gypsum product are described.

An additive injection system can be a part of a cementitious slurry mixing and dispensing assembly. The additive injection system can be used to inject an additive into an auxiliary slurry discharge conduit carrying a secondary flow of cementitious slurry produced in the assembly such that the secondary slurry stream is different from a main slurry stream discharged from a main slurry discharge conduit.

A method for continuously forming gypsum-based panels of high fixing strength comprises the steps of: •forming a mixture comprising stucco, non-pregelatinized migratory starch, glass fibre, fluidizer and water; •casting the mixture in a continuous band; •maintaining the band under conditions sufficient for the stucco to form an interlocking matrix of set gypsum; •cutting the band to form one or more wet panel precursors; and •drying the wet panel precursor to form one or more gypsum-based panels. •The weight ratio of water to stucco in the mixture is less than 0.7; •the stucco is present in the mixture in an amount of over 60 wt % relative to the total solids content of the mixture; •the starch is present in the mixture in an amount of over 3 wt % relative to the stucco; •the glass fibre is present in the mixture in an amount of over 1 wt % relative to the stucco; •the fluidizer is present in the mixture in an amount of at least 0.1 wt % relative to the stucco; and the density of the gypsum-based panel is greater than 700 kg/m.

Provided are a gypsum set accelerator wherein the gypsum set accelerator is a dry-milled mixture comprising calcium sulfate dihydrate co-ground with one or more of the following: a polycarboxylic ether (PCE) and/or a sulfonated melamine polycondensate (SMP), gypsum slurries formulated with the gypsum set accelerator and methods for producing the gypsum set accelerator and manufacturing gypsum products with the gypsum set accelerator.

In accordance with the present invention, provided is a method for producing a solidifying material for radioactive waste disposal, the method including a first step (S100) of pulverizing radioactive concrete waste and separating aggregates and paste and a second step (S200) of using the paste to produce a solidifying raw material, wherein the second step (S200) includes a calcination treatment step (S210) of calcining a mixture obtained by mixing an additional material with the paste; a sintering treatment step (S220) of sintering the mixture in a sintering furnace after the calcination treatment step (S210); and a rapid-cooling treatment step (S230) of rapid-cooling the mixture after the sintering treatment step (S220) to produce a clinker.

Provided are a granulated blast-furnace slag activator and a method of manufacturing the same. The granulated blast-furnace slag activator includes, in percent by weight, the following raw materials: 62% to 95% of gypsum and 5% to 38% of high belite sulfoaluminate cement clinker. Also provided is a method of manufacturing cement by mixing the granulated blast-furnace slag activator with granulated blast-furnace slag at a certain ratio.

Mineral fines are used to reduce clinker content in concrete, mortar and other cementitious compositions, typically in combination with one or more pozzolanically active SCMs. Mineral fines can replace and/or augment a portion of hydraulic cement binder and/or fine aggregate. Mineral fines can advantageously replace a portion of cement binder and fine aggregate, acting as an intermediate that fills a particle size void between the largest cement particles and smallest fine aggregate particles. Supplemental lime can advantageously maintain or enhance balance of calcium ions in the mix water and/or pore solution. Supplemental sulfate can advantageously address sulfate deficiencies caused by high clinker reduction, use of water reducers and/or superplasticizers, and SCMs containing aluminates. Such systematic approach to beneficially using mineral fines, SCMs, lime, and sulfate addresses many issues and permits high clinker reduction with similar or increased strength.

Provided are a granulated blast-furnace slag activator and a method of manufacturing the same. The granulated blast-furnace slag activator includes, in percent by weight, the following raw materials: 62% to 95% of gypsum and 5% to 38% of high belite sulfoaluminate cement clinker. Also provided is a method of manufacturing cement by mixing the granulated blast-furnace slag activator with granulated blast-furnace slag at a certain ratio.

A method for continuously forming gypsum-based panels of high fixing strength comprises the steps of: forming a mixture comprising stucco, non-pregelatinized migratory starch, glass fibre, fluidizer and water; casting the mixture in a continuous band; maintaining the band under conditions sufficient for the stucco to form an interlocking matrix of set gypsum; cutting the band to form one or more wet panel precursors; and drying the wet panel precursor to form one or more gypsum-based panels. The weight ratio of water to stucco in the mixture is less than 0.7; the stucco is present in the mixture in an amount of over 60 wt % relative to the total solids content of the mixture; the starch is present in the mixture in an amount of over 3 wt % relative to the the stucco; the glass fibre is present in the mixture in an amount of over 1 wt % relative to the stucco; the fluidizer is is present in the mixture in an amount of at least 0.1 wt % relative to the stucco; and the density of the gypsum-based panel is greater than 700 kg/m.