The invention relates to a method for producing a calcium silicate hydrate-comprising hardening accelerator in powder form, which comprises the steps of (a) providing an aqueous suspension comprising calcium silicate hydrate; (b) mixing at least one calcium compound, selected from calcium acetate, calcium formate, calcium hydroxide, calcium oxide, and mixtures of two or more of said compounds, with the aqueous suspension comprising calcium silicate hydrate; and (c) drying the resulting mixture. The invention also relates to the hardening accelerator obtainable by this method, to the use thereof, and to building material mixtures which comprise the hardening accelerator.

Portland cement clinker LCMs that include Portland cement clinker to mitigate or prevent lost circulation in a well are provided. A Portland cement clinker LCM may include Portland cement clinker, Portland cement, a carrier fluid, and an inorganic consolidation activator. Another Portland cement clinker LCM may include Portland cement clinker and a crosslinked fluid, such as a polyuronide crosslinked via calcium ions or a polysaccharide crosslinked via divinyl sulfone. Yet another Portland cement clinker LCM may include Portland cement clinker and polymer fibers or particulate glass. Methods of lost circulation control using a Portland cement clinker LCM are also provided.

A cement composition for use in a well that penetrates a subterranean formation comprising: cement; water; and an additive comprising zirconium dioxide, wherein at least a portion of the zirconium dioxide is in a metastable tetragonal phase, and wherein some or all of the zirconium dioxide that is in the metastable tetragonal phase transforms to a stable monoclinic phase after a stress is applied to the cement composition. The additive also reduces the dimensions of a crack located within the set cement composition. A method of cementing in a subterranean formation comprising: introducing a cement composition into the subterranean formation.

A shrinkage compensating concrete does not require restraint. The expansive forces developed during hydration compensate for concrete shrinkage, obviating the need for any added internal or external restraint element. Using this new shrinkage compensating concrete, substantially crack-free slabs may be built without using restraining steel bars, fibers, or other separate restraining element. The shrinkage compensating concrete includes a cement that develops internal expansive forces that never exceed the tensile strength of the concrete, such that the internal expansion compensates for the concrete shrinkage. The expansive cement may be an ASTMS, M or S cement, or other expansive cements may also be used.

A long-term stabilized aqueous initiator composition, which includes components for curing of a two-component mortar system composition. The long-term stabilized aqueous initiator composition includes an activator component that has an alkali and/or alkaline earth metal salt, an accelerator component that has a water-soluble alkali and/or alkaline earth metal salt, a retarder selected from citric acid, tartaric acid, lactic acid, salicylic, gluconic acid, and a mixture of these components, a mineral filler selected from a limestone filler, corundum, dolomite, alkaline-resistant glass, crushed stone, gravel, pebble, and a mixture of these components, a thickening agent, and water.

A method of controlling the setting time of a geopolymer by coating aluminosilicate particles with nanoparticles to slow the geopolymerization reaction. The coating effectiveness of the nanoparticles may be enhanced by pretreating the aluminosilicate particles with a layer-by-layer assembly of polyelectrolytes. A geopolymer is formed by mixing about 39% to about 66% by weight aluminosilicate source, about 0% to about 40% by weight sand, about 19% to about 33% by weight of alkali activator solution, and about 1% to about 4% nanoparticles.

A downhole treatment composition comprises a rare earth-containing compound comprising one or more of the following: scandium; yttrium; lanthanum; cerium; praseodymium; neodymium; promethium; samarium; lutetium; europium; gadolinium; terbium; dysprosium; holmium; erbium; thulium; or ytterbium, wherein the downhole treatment composition is a cement slurry, a drilling fluid, or a spacer fluid. Also disclosed are methods of cementing a wellbore, methods of displacing a first fluid, and methods of drilling a wellbore in a subterranean formation using the cement slurry, the spacer fluid, or the drilling fluid.

A soluble alkali metal compound for adjusting, in particular reducing, the viscosity of an aluminum sulfate suspension, the alkali metal being selected from among sodium, potassium and/or lithium.

A calcium-containing composition with fixed CO.sub.2 is produced by contacting a mixture of a calcium-containing composition before CO.sub.2 fixation and water with a CO.sub.2-containing gas. The calcium-containing composition, liquid water, and the CO.sub.2-containing gas having a temperature between 20 degree Celsius and 300 degree Celsius and a CO.sub.2 concentration between 1 volume % and 100 volume % are supplied to a reactor. By the supplied CO.sub.2-containing gas, the calcium-containing composition and water are made to flow in the reactor. Alternatively, the calcium-containing composition and water are in the reactor. Thus, CO.sub.2 is fixed in the calcium-containing composition and simultaneously the calcium-containing composition is dried to a water content of 5 mass % or less.

A mixture for covering joints between building boards in drywall constructions, which can be applied by spraying, wherein the mixture contains 0.01 to 10 wt.-% of a fibrous material, 1 to 20 wt.-% of a binder, 1 to 10 wt.-% of a thickener and 50 to 97.99 wt.-% of a solvent, and in which the fibrous material and the binder are present in a predetermined ratio in the range from 1:1 to 1:5. The present invention also relates to a method for filling joints in drywall constructions using such mixture, drywall constructions produced accordingly and the use of the sprayable mixtures described for reinforcing a drywall construction in the contact area between construction panels.