The invention comprises a method of sequestering carbon dioxide. The method comprises delivering hyaloclastite, a volcanic glass or pumice to a mill capable of reducing the particle size of the hyaloclastite, a volcanic glass or pumice; processing the hyaloclastite, a volcanic glass or pumice in the mill so that the processed hyaloclastite, a volcanic glass or pumice has a volume-based mean particle size of less than or equal to 40 m; and exposing the hyaloclastite, a volcanic glass or pumice to carbon dioxide in gaseous, liquid or solid form during or after the particle reduction process.

The present disclosure relates to shaped cementitious compositions that comprise a substrate for aquatic flora and/or fauna attachment; methods for providing a substrate for aquatic flora and/or fauna attachment comprising depositing a shaped cementitious composition into a body of water; and methods for making a shaped cementitious composition. The shaped cementitious composition is formed from a pourable cementitious mixture comprising: (a) a pozzolan comprising a natural pozzolan and/or a manmade pozzolan; (b) MgO and/or Mg(OH).sub.2; (c) an aqueous solution comprising one or more accelerants; and (d) at least one aggregate. In some cases, the MgO and/or Mg(OH).sub.2 of (b) is included in the aqueous solution of (c). And, in various cases, the manmade pozzolan comprises a slag.

The present disclosure pertains to a cement mixture that includes calcium sulfoaluminate (CSA) and an additive. The additive may include, without limitation, magnesium oxide (MgO), ground granulated blast-furnace slag (GGBFS), wollastonite, and combinations thereof. The present disclosure also pertains to a cementitious material that includes a cement mixture of the present disclosure. Further embodiments of the present disclosure pertain to methods of forming a cementitious material by (1) mixing CSA with an additive of the present disclosure to form a mixture; and (2) curing the mixture.

Methods of making settable compositions that include uncured carbonate aggregates are provided. Aspects of the methods include: preparing a carbonate slurry, subjecting the carbonate slurry to rotational action (optionally with an aggregate substrate), to produce an uncured carbonate aggregate, and then combining the uncured carbonate aggregate with a cement component and a liquid to produce the settable composition. Also provided are settable compositions produced by the methods and uses thereof.

Methods of making a hydraulic cement are provided. Aspects of the methods include employing precipitated calcium carbonate (PCC), such as a CO.sub.2 sequestering PCC, as a feedstock for lime (CaO) production. Also provided are hydraulic cements and concretes produced by methods of embodiments of the invention, as well as products produced therefrom. In addition, systems for practicing methods of embodiments of the invention are provided.