It has been unexpected found that the machinability and corrosion resistance of powder metal parts can be greatly improved by incorporating calcium aluminoferrite powder, such as naturally occurring brownmillerite powder (Ca.sub.2(Al,Fe).sub.2O.sub.5), into the part. Improved machinability is of enormous value in manufacturing countless parts where it is necessary or desirable to machine the part after it has been sintered, such as is frequently the case with gears, rotors and sprockets. In the practice of this invention, calcium aluminoferrite powder can also be incorporated into parts which will not necessarily be machined for the sole purpose of attaining better corrosion resistance. Surprisingly, the incorporation of the calcium aluminoferrite powder into such parts does not significantly compromise the strength, durability, or wear characteristics of the part and generally improves the service life of the part by providing better corrosion resistance.

A cement manufacturing plant can include at least one emission abatement mechanism. In some embodiments, the emission abatement mechanism can utilize a plurality of pulsed gases passed through a reactor to treat a solid particulate material passed through the reactor. The pulsed reactant gas can be pulsed through the reactor so that the pulsed gas passes from a middle portion of the reactor to a first end of the reactor at which the solid particulates can be fed into the reactor. In some embodiments, the reactant gas can be output from the first end to a down corner or other reactant gas conduit for transport to a treatment device.

Methods for preparing a carbonated supplementary cementitious materials, including semi-wet carbonation, cyclic carbonation, non-slurry carbonation, high temperature carbonation and/or granular carbonation of a carbonatable material.

Generating methane by adding hydrogen to CO.sub.2 in exhaust gas discharged a from cement production facility or CO.sub.2 that is separated and recovered from the exhaust gas, and using the methane as an alternative fuel to fossil fuel such as coal, petroleum, natural gas and the like, by methanation of CO.sub.2 in the exhaust gas from the cement production facility that includes exhaust gas originated from lime stone not from the fossil oil and effectively utilizing it, it is possible to reduce usage of the fossil fuel, suppress CO.sub.2 originated from energy, and improve an effect of reducing greenhouse gas.

Methods of preparing engineered cementitious composite precursors include carbonating a fly ash comprising >about 25% by weight of calcium oxide (CaO) and having a water content of >about 12% to <about 18% by weight of water by exposing the fly ash to a first gas stream comprising carbon dioxide to form a carbonated fly ash. A steel slag is also carbonated that comprises >about 40% by weight of calcium oxide (CaO) and having a water content of >about 12% to <about 18% by weight of water by exposing the steel slag to a second gas stream comprising carbon dioxide to form a carbonated steel slag. The carbonated fly ash and the carbonated steel slag are suitable for use as engineered cementitious composite precursors in a bendable engineered cementitious composite composition that further comprises Portland cement, a polymeric fiber, and a superplasticizer.

Methods, systems, and apparatus for generating a recipe for a concrete mixture, comprising: obtaining an optical characterization of a set of particles; determining, based on the optical characterization, physical characteristics of the set of particles; generating a multispherical approximation of the set of particles; selecting, based on the physical characteristics of the set of particles and from a database of performance rules, performance rules applicable to the set of particles; predicting performance of a proposed recipe for a concrete mixture formed from the set of particles by: determining a wet flowability rating of the proposed recipe based on the selected performance rules; and determining a dry packing rating of the proposed recipe based on the multispherical approximation; iteratively altering the proposed recipe and predicting performance of the altered proposed recipe until the predicted performance satisfies performance criteria to obtain a final recipe; and outputting the final recipe.

A method of processing exhaust gas containing CO.sub.2, such as exhaust gas from a cement production plant, includes burning fuel in the combustion reactor with the O.sub.2 content of the exhaust gas being used as an oxidizing agent, controlling the combustion in the combustion reactor so that the exhaust gas from the combustion reactor contains less than 10 vol.-% of oxygen and at least 80 vol.-% of a mixture of CO and CO.sub.2, and feeding the exhaust gas from the combustion reactor into a conversion reactor, in which the CO.sub.2 and optionally the CO contained in the exhaust gas is converted into a hydrocarbon fuel.

A method of making a cement composite can include contacting an aqueous solution comprising calcium ions with a carbon dioxide source producing a carbonated aqueous solution. Fine particles can be submerged in the carbonated aqueous solution to produce microaggregate particles comprising the fine particles coated with calcium carbonate. The microaggregate particles can be combined with cement particles to produce the cement composite. The cement composite can be used in cementing applications for hydrocarbon wells including for casing liners and well plugs.

Described are cementitious reagent materials produced from globally abundant inorganic feedstocks. Also described are methods for the manufacture of such cementitious reagent materials and forming the reagent materials as microspheroidal glassy particles. Also described are apparatuses, systems and methods for the thermochemical production of glassy cementitious reagents with spheroidal morphology. The apparatuses, systems and methods make use of an in-flight melting/quenching technology such that solid particles are flown in suspension, melted in suspension, and then quenched in suspension. The cementitious reagents can be used in concrete to substantially reduce the CO.sub.2 emission associated with cement production.

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for simulating a concrete mixture. One of the methods includes obtaining an optical characterization of physical particles, generating a multispherical approximation of the physical particles, the multispherical approximation having reduced dimensionality compared to the optical characterization, simulating an aggregate mixture by applying the multispherical approximation of the particles to a physics simulator to obtain a predicted performance of the proposed aggregate mixture, selectively altering the aggregate mixture based on a comparison with performance metrics and simulating the altered aggregate mixture until the predicted performance satisfies the performance metrics to obtain a final aggregate mixture, and outputting the final aggregate mixture