An additive for producing a hardenable building material, especially a mineral composition comprising clays, comprising or consisting of: a) a dispersing agent, selected from aluminates, aluminate precursors, phosphates, silicates and/or polyacrylates, which is capable of dispersing clay particles in an aqueous slurry, and b) a coagulating agent, selected from salts of divalent metal cations, preferably salts of alkaline earth metals and/or iron, especially magnesium, calcium and/or iron salts, capable of causing clay particles to agglomerate in a aqueous slurry.

The invention discloses an environment-friendly cement self-repairing system, and its preparation method and application. The preparation method comprises the following steps: adding a shell curing agent into deionized water to prepare solution 1, adding an inorganic nano emulsifier into deionized water, ultrasonically dispersing, then adding polysaccharide-shell, and uniformly stirring to obtain emulsion polymerization aqueous phase; adding epoxy diluent into epoxy resin, and uniformly stirring; obtaining an emulsion polymerization oil phase; mixing the emulsion polymerization aqueous phase and emulsion polymerization oil phase, and stirring to obtain uniform emulsion; dropping the uniform emulsion into solution drop by drop by using pendant drop method, stirring until the droplets are shaped, then filtering, washing with deionized water, and drying to obtain self-repairing capsules; next, mixing with an environment-friendly curing agent to obtain an environment-friendly cement self-repairing system. The environment-friendly cement self-repairing system is green, nontoxic and harmless, has strong water absorption, can block tiny cracks by volume expansion when contacts with water, thus further enhances the cement self-repairing effect.

Methods of preparing a cementitious structure for carbon dioxide (CO.sub.2) sequestration are provided. The cementitious structure may be a cast in a mold. First, a cementitious composite material comprising binder and water is conditioned, for example, in a mold by exposing the cementitious composite material to ≥about 50% to ≤about 80% relative humidity for ≥about 3 hours to ≤about 24 hours. The cementitious composite material is then dried to remove ≥about 10% by weight of initial water in the cementitious composite material. The cementitious structure formed is capable of a carbon dioxide uptake level of greater than or equal to about 6% by weight binder. The cementitious structure has a tensile strain capacity of ≥about 1% and a uniaxial tensile strength of ≥about 1 MPa. The method may also include carbonating the cementitious structure, following by an optional further hydration process.

A green concrete and mortar compositions free of Portland cement are disclosed. The compositions comprise Natural pozzolan, nanosilica particles, and alkaline activator. The green concrete produced from the composition of the invention is cured at ambient temperature and has higher compressive strength than that of concrete made with Portland cement.

A cement composition for use in a well that penetrates a subterranean formation comprising: hydrated lime; a silicate; and water, wherein the composition is substantially free of a hydraulic cement. A method of treating a subterranean formation comprising: introducing the cement composition into the subterranean formation; and allowing the cement composition to set.

The disclosure relates to embodiments of a thixotropic, non-cementitious, thermal grout and applications or methods of use of the grout related to horizontal directional drilling, trenchless technology, trenching, and installation of pipe, conduits, ducts, utility lines, and other product lines which may, e.g., be in trenches, underground, or under obstacles, such as a body of water or roadways.

The present invention relates to a dry refractory particulate composition comprising a zeolithic microstructure, to a green body and to a refractory lining formed therefrom, and to uses thereof.

Disclosed herein are methods, compositions, and systems for cementing. A method of cementing may comprise: providing a composite cement composition comprising a pozzolan, an accelerator, and water, wherein the accelerator comprises a chloride salt and a sulfate salt, wherein the composite cement composition is free of Portland cement or comprises Portland cement in an amount of about 50% by weight of cementitious components or less; and allowing the composite cement composition to set.

A variety of systems, methods and compositions are disclosed, including, in one method, a method of cementing may comprise: providing a cement composition comprising: a hydraulic cement comprising Portland cement in an amount of about 50% by weight of hydraulic cement or less, water, and a phosphorylated amino polycarboxylic acid cement retarder; placing the cement composition in a wellbore; and allowing the cement composition to set. A cement composition, the composition comprising: a hydraulic cement comprising Portland cement in an amount of about 50% by weight of hydraulic cement or less; water; and a phosphorylated amino polycarboxylic acid cement retarder.

A nanozeolite modified green concrete contains alkali-activated natural pozzolan. Natural pozzolan is a green and sustainable material, potentially useful in green concrete, e.g., to curb greenhouse gas emissions associated with ordinary Portland cement production. Nanozeolite (NZ) is present as an additive to the green concrete, e.g., at 3 to 5 wt. %, of natural pozzolan to improve strength development and microstructural properties, resulting in superior strength and denser microstructure compared to a green concrete without nanozeolite.