The present disclosure relates to a medical cement composition containing calcium silicate in an amount of less than 20 wt % of a total weight of the composition, with a lithium salt being added thereto. The medical cement composition of the present disclosure has a low compressive strength of 12 MPa or less, after being hardened, for easy removal, excellent stability in storage, and high bioactivity.

A manufacturing method includes: (1) incorporating at least one soluble, calcium, magnesium, or other divalent cation-containing additive into a concrete mixture including aggregates prone to alkali-silica reaction; and (2) curing the concrete mixture to form a concrete product.

A manufacturing method includes: (1) incorporating at least one soluble, calcium, magnesium, or other divalent cation-containing additive into a concrete mixture including aggregates prone to alkali-silica reaction; and (2) curing the concrete mixture to form a concrete product.

Methods and systems of reducing lost circulation in a wellbore are provided. An example method includes providing a pozzolan slurry comprising a pozzolanic material and water; and providing a calcium slurry comprising a calcium source, a high pH activator, and water. The method further comprises allowing the pozzolan slurry and the calcium slurry to remain separate; wherein at least one of the pozzolan slurry and the calcium slurry comprise a thixotropic material; wherein at least one of the pozzolan slurry and the calcium slurry comprise a dispersant; wherein at least one of the pozzolan slurry and the calcium slurry comprise a weighting agent. The method additionally comprises mixing the pozzolan slurry and the calcium slurry to form a two-part thixotropic lost circulation slurry after the allowing the pozzolan slurry and the calcium slurry to remain separate. The method also includes introducing the two-part thixotropic lost circulation slurry to a lost circulation zone within the wellbore; and allowing or causing to allow the two-part thixotropic lost circulation slurry to set into a hardened mass within the lost circulation zone.

Methods and systems of reducing lost circulation in a wellbore are provided. An example method includes providing a pozzolan slurry comprising a pozzolanic material and water; and providing a calcium slurry comprising a calcium source, a high pH activator, and water. The method further comprises allowing the pozzolan slurry and the calcium slurry to remain separate; wherein at least one of the pozzolan slurry and the calcium slurry comprise a thixotropic material; wherein at least one of the pozzolan slurry and the calcium slurry comprise a dispersant; wherein at least one of the pozzolan slurry and the calcium slurry comprise a weighting agent. The method additionally comprises mixing the pozzolan slurry and the calcium slurry to form a two-part thixotropic lost circulation slurry after the allowing the pozzolan slurry and the calcium slurry to remain separate. The method also includes introducing the two-part thixotropic lost circulation slurry to a lost circulation zone within the wellbore; and allowing or causing to allow the two-part thixotropic lost circulation slurry to set into a hardened mass within the lost circulation zone.

The present invention provides a calcium sulphate-based product (e.g. a wall board) comprising gypsum, a pozzolan source such as a clay additive, rice husk ash or diatomaceous earth and a metal salt additive. The product may be produced by drying an aqueous slurry comprising calcined gypsum, the pozzolan source and the metal salt additive. The clay additive may be a kaolinitic clay. The metal salt additive may be a magnesium salt e.g. magnesium nitrate, magnesium chloride or magnesium hydroxide.

The present invention provides a calcium sulphate-based product (e.g. a wall board) comprising gypsum, a pozzolan source such as a clay additive, rice husk ash or diatomaceous earth and a metal salt additive. The product may be produced by drying an aqueous slurry comprising calcined gypsum, the pozzolan source and the metal salt additive. The clay additive may be a kaolinitic clay. The metal salt additive may be a magnesium salt e.g. magnesium nitrate, magnesium chloride or magnesium hydroxide.

A calcium sulphate-based product including gypsum and a shrinkage resistance additive. The shrinkage resistance additive is a metal nitrate, hydroxide, acetate or sulphate and is preferably provided in an amount greater than 4 wt % (based on the amount of additive and gypsum). The additive may be a nitrate of an alkali metal (e.g. potassium), an alkaline earth metal (e.g. magnesium or calcium), a transition metal (e.g. iron or zinc) or aluminium.

A calcium sulphate-based product including gypsum and a shrinkage resistance additive. The shrinkage resistance additive is a metal nitrate, hydroxide, acetate or sulphate and is preferably provided in an amount greater than 4 wt % (based on the amount of additive and gypsum). The additive may be a nitrate of an alkali metal (e.g. potassium), an alkaline earth metal (e.g. magnesium or calcium), a transition metal (e.g. iron or zinc) or aluminium.

This rapid-hardening mortar composition includes: a rapid-hardening admixture; cement; and a fine aggregate, wherein the cement is contained in an amount of 100 parts by mass to 2,000 parts by mass with respect to 100 parts by mass of the rapid-hardening admixture, the rapid-hardening admixture is a composition that contains: calcium aluminate; inorganic sulfate in an amount of 50 parts by mass to 200 parts by mass with respect to 100 parts by mass of the calcium aluminate; and a setting modifier in an amount of 0.1 parts by mass to 10 parts by mass with respect to 100 parts by mass of the calcium aluminate, and an average particle diameter of the calcium aluminate is in a range of 8 μm to 100 μm, and an average particle diameter of the setting modifier is in a range of 5 μm or less.