The present disclosure relates to a cement or concrete composition comprising a hydraulic binder, a water reducing plasticiser, a rheological additive, and composite spheres for lowering the density of the composition, wherein the composite spheres comprise a core having one or more coating layers thereon.

A curing accelerator composition for building chemical mixtures comprises a mineral constituent and a polymeric water-soluble dispersant. The mineral constituent comprises a semi-ordered calcium silicate hydrate having an apparent crystallite size of 15 nm or less and less than 35% by weight of crystalline phases other than the semi-ordered calcium silicate hydrate. The composition displays a more pronounced accelerating effect than comparative compositions in which the mineral component comprises a calcium silicate hydrate having a higher degree of crystallinity.

A variety of systems, methods and compositions are disclosed for cementing in subterranean formations. Embodiments may include the use of slag co-grind in well cementing operations.

A variety of systems, methods and compositions are disclosed for cementing in subterranean formations. Embodiments may include the use of slag co-grind in well cementing operations.

Included are cement compositions and methods and systems for locating the cement compositions in a wellbore. An example method comprises deploying a sensing system in the wellbore and introducing the cement composition into the wellbore. The cement composition comprises a cement and hollow beads having a crush pressure and configured to emit an acoustic signal when imploded. The method further comprises pumping the cement composition through the wellbore to a depth with a wellbore pressure exceeding the crush pressure of the hollow beads to induce implosion of the hollow beads and the emission of the acoustic signal. The method further comprises sensing the emitted acoustic signal and determining the location of the cement composition in the wellbore from the sensed emitted acoustic signal.

Included are cement compositions and methods and systems for locating the cement compositions in a wellbore. An example method comprises deploying a sensing system in the wellbore and introducing the cement composition into the wellbore. The cement composition comprises a cement and hollow beads having a crush pressure and configured to emit an acoustic signal when imploded. The method further comprises pumping the cement composition through the wellbore to a depth with a wellbore pressure exceeding the crush pressure of the hollow beads to induce implosion of the hollow beads and the emission of the acoustic signal. The method further comprises sensing the emitted acoustic signal and determining the location of the cement composition in the wellbore from the sensed emitted acoustic signal.

A repaired reinforced concrete structure is provided which includes one or more reinforcing steel bars of cross-sectional area A.sub.x, the one or more reinforcing steel bars having one or more corroded sections of cross-sectional area A.sub.y, wherein A.sub.y is greater than or equal to approximately 0.6 A.sub.x. A reinforced ordinary Portland cement-based repair mortar is positioned directly on the one or more corroded sections of the one or more reinforcing steel bars without the addition of a lapped reinforcing steel bar. The reinforced repair mortar includes at least approximately 1 percent by volume of reinforcing steel fibers such that the reinforced repair mortar restores a strength of a repaired region to greater than approximately 100% of an original strength of the concrete structure in an uncorroded state. The repaired reinforced concrete structure is highly durable, as the repair mortar exhibits an air permeability resistance of greater than 1000 seconds.

A repaired reinforced concrete structure is provided which includes one or more reinforcing steel bars of cross-sectional area A.sub.x, the one or more reinforcing steel bars having one or more corroded sections of cross-sectional area A.sub.y, wherein A.sub.y is greater than or equal to approximately 0.6 A.sub.x. A reinforced ordinary Portland cement-based repair mortar is positioned directly on the one or more corroded sections of the one or more reinforcing steel bars without the addition of a lapped reinforcing steel bar. The reinforced repair mortar includes at least approximately 1 percent by volume of reinforcing steel fibers such that the reinforced repair mortar restores a strength of a repaired region to greater than approximately 100% of an original strength of the concrete structure in an uncorroded state. The repaired reinforced concrete structure is highly durable, as the repair mortar exhibits an air permeability resistance of greater than 1000 seconds.

Engineering bead slurries may be useful in producing lightweight cement slurries for use in subterranean cementing operations. For example, a method may include engineering a bead slurry to have a shelf-life of about 1 month or greater by performing at least one of (1) calculating the shelf-life for the bead slurry and (2) calculating a minimum yield point required to prevent a lightweight bead of the bead slurry from floating or settling in the bead slurry; wherein the bead slurry comprises a gelled base fluid and a plurality of lightweight beads having a specific gravity of about 0.8 or less; producing the bead slurry; mixing the bead slurry and a cement slurry to yield a lightweight cement slurry; introducing the lightweight cement slurry into a wellbore penetrating a subterranean formation; and allowing the lightweight cement slurry to set therein.

Engineering bead slurries may be useful in producing lightweight cement slurries for use in subterranean cementing operations. For example, a method may include engineering a bead slurry to have a shelf-life of about 1 month or greater by performing at least one of (1) calculating the shelf-life for the bead slurry and (2) calculating a minimum yield point required to prevent a lightweight bead of the bead slurry from floating or settling in the bead slurry; wherein the bead slurry comprises a gelled base fluid and a plurality of lightweight beads having a specific gravity of about 0.8 or less; producing the bead slurry; mixing the bead slurry and a cement slurry to yield a lightweight cement slurry; introducing the lightweight cement slurry into a wellbore penetrating a subterranean formation; and allowing the lightweight cement slurry to set therein.