BACKGROUND

The field of the present disclosure is related to cementitious reagents, and more particularly, to the creation of relatively homogeneous cementitious reagent materials and cementitious materials from abundant heterogeneous feedstocks.

Concrete has played an important role in civilization for thousands of years and is still the most commonly used building material. Concrete may be formed by mixing water, aggregate (e.g., sand, gravel, and/or rock), and cement. Through a hydration process, hydraulic cements bind the aggregate into a solid composite. Concrete may be characterized by the type of aggregate or cement used, the properties it exhibits, or by the methods used in its production.

Cement is the essential binding component of concrete that allows flowable concrete slurries to harden into a useful composite material at ambient temperatures. Many binder chemistries have been successfully used to make concrete, but Portland cement and its variations have been the dominant concrete binder for almost 200 years. Despite advances in production efficiency and material performance, there are significant and intrinsic problems with Portland cement chemistry that cannot be solved at any reasonable cost by current methods.

Portland cement production is a CO2intensive process that causes about 8% of global anthropogenic CO2emissions. Some estimates project that cement demand will increase by 12-23% by 2050. However, the growing absolute demand for cement is at odds with the need for complete decarbonization of the economy that is also required by 2050 to avoid catastrophic effects of climate change, according to the UN IPCC Climate Report 2018. There is therefore an urgent need for drastically lowering the specific CO2emissions of cement, especially because absolute production volume is increasing.

One way that the industry has tried to reduce the CO2emission of cement is by developing geopolymer cements, which are generally aluminosilicate inorganic polymers that cure through a geo-polymerization process. Commercially relevant geopolymer cements in use today include several specific solid reagents (commonly: metakaolin (MK-750), ground granulated blast furnace slag (GGBFS), and coal fly ash). However, these reagents cannot satisfy the global transition to low-CO2cements because supply is relatively limited in geography and volume compared to the enormous demand for cement. Also, the cost of shipping these products from production locations is significant compared to their market value.

Cementitious reagents are useful in both hydraulic and geopolymer cements. Geopolymer reagents, and supplementary cementitious materials (SCMs), are typically selected from several common cementitious materials: byproduct ashes from combustion (e.g., coal fly ash), slag byproducts (e.g., ground granulated blast furnace slag), calcined clays (e.g., metakaolin), and natural pozzolans (e.g., volcanic ash). These materials are generally substantially non-crystalline and sometimes reactive in cementitious systems such as in geopolymeric systems.

Since the majority of SCMs that are used in blended hydraulic cements are industrial by-products (e.g., coal combustion, or quality iron production), their material properties are a result of the industrial by-product and are not specifically tailored as a quality cementitious reagent. Accordingly, these materials lack any guarantee of ideal or even consistent composition and quality, and their suitability as cementitious reagents varies from plant to plant, and over time. There is also no control over production location, and the concrete industry lacks control over future availability of these critically important cementitious materials. It would be much more advantageous if the production location could be chosen based on market needs, particularly because shipping of cementitious materials is very expensive.

Fly ash is a partially glassy aluminosilicate by-product of coal combustion. It is frequently used as an admixture in hydraulic cement mixes to improve flowability and create a pozzolanic reaction to improve properties of concrete including strength, resistance to alkali-silica reaction and others. Unfortunately, only certain coal and combustion processes create a consistent supply of fly ash of a quality acceptable for use in concrete (e.g., ASTM Type C and Type F ash, or CSA Type C, CI, and F ashes). Ash is not produced as an optimal SCM; rather, combustion is optimized for power generation and pollution prevention: there is no guaranteed consistency of by-product ash. Further challenges for the future of fly ash in concrete include a significant decrease in regional availability due to transition from coal energy to natural gas in many markets, carbon introduced post-combustion can negatively affect air entrainment in concrete, recovery of ash from impoundments will increase cost, and quality must be verified through testing in each case.

Ground Granulated Blast Furnace Slag (GGBFS) is a glassy CaO—SiO2by-product of iron production in blast furnaces. Concretes incorporating GGBFS have many advantageous properties including improved chemical durability, whiteness, reduced heat of hydration, mitigation of CO2footprint, and other beneficial properties. Unfortunately, the supply of blast furnace slag is quite limited due to the small number of blast furnaces operating in most markets. As such, GGBFS is in high demand as a quality SCM and prices for this by-product are now similar to the price of cement itself. Additionally, the limited geographic supply leads to shortages or at least high shipping costs for many local concrete markets. Finally, iron production and resulting blast furnace slag supply are not coupled directly to concrete demand, leaving supply volume, local availability, and market price of these important admixtures largely up to chance.

Natural pozzolans are siliceous or aluminosiliceous materials that are able to participate in the pozzolanic reaction with Ca(OH)2. These include as-mined or calcined volcanic ash, diatomaceous earth, kaolinite and other clays, MK-750 and other natural minerals and rocks that react with lime to produce a hydrated calcium silicate compound. Natural pozzolans can be very effective SCMs in concrete, however they require mining of non-renewable resources and pozzolans often require significant shipping distances since deposits are not extremely common. Also, natural materials often require significant processing such as calcining to enhance reactivity.

Fly ash (usually with low CaO content, as in type F), GGBFS, and certain natural and processed “pozzolans” (e.g., volcanic ashes, zeolites, and MK-750) are also common geopolymer reagents, and the same unfortunate limitations on supply, geographic availability, price, quality, and consistency apply for their application in geopolymer binders and cements.

To overcome certain limitations of these existing SCM and geopolymer reagent supplies, several attempts have been made to improve on aspects of traditional methods. Despite some improvements, these man-made products or compositions still possess numerous deficiencies, for instance with respect to reactivity and chemistry of reagents for use in geopolymer chemistry (e.g., optimizing reagents to later produce high coordination, branched, and three-dimensional alkali/alkaline earth aluminosilicate polymers). They also require expensive lab-grade reagents and cannot simply use globally abundant feedstocks.

Also, previously manufactured glassy cementitious reagents have angular or fibrous particle morphology. Thus, cement pastes made from such reagents require a lot of water and have relatively poor workability (e.g., with excessive yield stress or higher than optimal plastic viscosity) which is a barrier to use in practical concrete applications.

Combustion ashes and silica fume typically do not have angular particle morphology. However, these are not available in sufficient quantities, do not have appropriate chemistry, and/or are too expensive to support a large-scale transition to high SCM blend hydraulic or geopolymer cements.

There is thus a need for cementitious reagents that solve existing workability issues with a similar degree of effectiveness as super plasticizers and water reducers in equivalent Portland cement mix designs. There is also a need for a method of reducing CO2emissions in production of Portland cement, and particularly, a need for an engineered cementitious reagent with low or zero process CO2emissions that can be used as a supplementary cementitious material in hydraulic cements, and/or as a solid geopolymer reagent.

There is also need for a cementitious reagent that can be produced ubiquitously from globally abundant feedstocks, is reactive in cementitious systems, and delivers workable low-yield stress cement mixes.

Furthermore, there is a need for production of cementitious reagents wherein the production location could be chosen based on market needs. There is particularly a need for non-angular particle or microspheroidal glassy particles useful in cementitious reagents, geopolymer reagents, supplementary cementitious materials (SCM), cement mixes and concrete.

There is also a need for the economical production of such microspheroidal glassy particles, e.g., by using globally abundant feedstocks. There is also a need for apparatuses, systems and methods using in-flight melting/quenching such wherein solid particles are flown in suspension, melted in suspension, and then quenched in suspension.

The dominant cement used in concrete today is a hydration-curing calcium silicate product known as Portland cement. Unfortunately, manufacture of Portland cement clinker causes CO2process emissions (from heating limestone) that are globally impactful (about 3-5%, not counting fuel-derived GHG emissions). The process is carried out in a rotary kiln with raw meal flowing countercurrent to the kiln burner. The process is very energy intensive, consuming ˜3-5 GJ/ton, of which about 1.5 GJ/ton is spent simply calcining limestone. Of the few viable strategies to decrease environmental impact of cement, geopolymer chemistry provides a globally viable alternative cement with improved environmental and material performance. The inconsistent supply and limited geographic availability of traditional geopolymer reagents such as fly ash and slags have limited standardization and adoption of geopolymer concretes. On the other hand, an increasing demand for supplementary cementitious materials (SCM) in hydraulic cements (to enhance material and environmental performance) has further squeezed demand for these materials.

Various approaches have been used to manufacture cementitious reagents. However, these methods suffer from crucial deficiencies that have prevented an economic manufacturing process for glassy cementitious reagents. For instance, high-temperature refractory-lined furnaces and crucibles have been used to directly contain glass melts in existing academic research on cementitious reagents (a natural extension of traditional glassmaking techniques). However, solid refractory materials in crucibles and surrounding conventional furnaces require low heating and cooling rates (order of about 10-50° C./min) to avoid thermal shock breakage. Conventional melting furnaces have high thermal mass which makes maintenance difficult and costly as a result of long startup and shutdown cycles. It is preferable to avoid the need for refractories that directly contact the melt, so as to avoid, complexity, wear, and also considerable start up and shut down times.

Quenching of molten glass for cementitious reagents (blast furnace slag, for example) has previously required water, which is costly, inhibits heat recovery, could have negative environmental consequences, and may require added complication of solid/liquid separation. Melt quenching methods were thus either wasteful or slow, diminishing reactivity. Air-quenching methods of cooling melts are either too slow or require very specific chemistry to ensure low melt viscosities of about 1 Pa-s or less, which is not feasible for most desired feedstock materials.

Previous glass manufacturing methods have required costly particle size reduction (milling) of glassy product (typically before and after thermal processing).

Accordingly, there is still a need for a convenient and economic method of manufacturing a glassy cementitious reagent from globally abundant feedstocks.

There is also a need to minimize energy consumption and cope with very high and variable melt viscosity without requiring fluxes.

There is also a need for methods of producing microspheroidal glassy particles and for apparatuses and systems useful for producing such microspheroidal glassy particles.

SUMMARY

Embodiments relate to an alternative cement material (ACM), which in some embodiments includes solid microspheroidal glassy particles having one or more of the following properties: mean roundness (R)>0.8 and less than about 40% particles having angular morphology (R<0.7).

In some embodiments, the particles have a mean roundness (R) of at least 0.9. In embodiments, less than about 30% of the particles, or less than about 25% of the particles, or less than about 20% of the particles, or less than about 15% of the particles, or less than about 10% of the particles have an angular morphology (R<0.7).

In some embodiments, the particles include the mean oxide Formula 1: (CaO,MgO)a.(Na2O,K2O)b.(Al2O3,Fe2O3)c.(SiO2)d [Formula 1]; wherein a is about 0 to about 4, b is about 0.1 to about 1, c is 1, and d is about 1 to about 20.

In some embodiments, the particles further includes one or more of the following properties: (i) a content of 45%-100%, and preferably 90-100%, X-ray amorphous solid; and (ii) molar composition ratios of (Ca,Mg)0-12.(Na,K)0.05-1.(Al, Fe3+)1.Si1-20.

According to another aspect, some embodiments relate to a cementitious reagent including a mixture of microspheroidal glassy particles as defined herein.

According to another particular aspect, some embodiments relate to a cementitious reagent including a mixture of microspheroidal glassy particles, these particles exhibiting one or more of the following properties: (i) mean roundness (R)>0.8; (ii) less than about 20% particles having angular morphology (R<0.7); (iii) the oxide Formula 1 as defined hereinbefore; (iv) a content of 45%-100%, and preferably 90-100%, X-ray amorphous solid; (v) a molar composition ratio of (Ca,Mg)0-12.(Na,K)0.05-1.(Al, Fe3+)1.Si1-20; and (vi) a low calcium content of about <10 wt. % CaO, or an intermediate calcium content of about 10 wt. % to about 20 wt. % CaO, or a high calcium content of >30 wt. % CaO.

In some embodiments, the cementitious reagent is in the form of a non-crystalline solid. In some embodiments, the cementitious reagent is in the form of a powder. In some embodiments, the particle size distribution with D[3,2] (i.e., surface area mean, or Sauter Mean Diameter) is about 20 μm or less, more preferably 10 μm or less, or most preferably 5 μm or less. In one embodiment, the mixture of microspheroidal glassy particles of the cementitious reagent has the oxide Formula 1 as defined hereinabove. In some embodiments, the cementitious reagent includes less than about 10 wt. % CaO. In some embodiments, the cementitious reagent includes more than about 30 wt. % CaO. In some embodiments the cementitious reagent is about 40-100% and preferably about 80% X-ray amorphous, 90% X-ray amorphous, and up to about 100% X-ray amorphous, and in some embodiments, is 100% non-crystalline.

According to some embodiments, a geopolymer binder includes a cementitious reagent as defined herein. According to another particular aspect, some embodiments relate to a supplementary cementitious material (SCM) including a cementitious reagent as defined herein, for instance a SCM having at least 20 wt. % of the cementitious reagent.

According to another particular aspect, some embodiments relate to a solid concrete including a cementitious reagent as defined herein.

According to another particular aspect, some embodiments relate to the use of microspheroidal glassy particles as defined herein, and to the use of a cementitious reagent as defined, to manufacture a geopolymer binder or cement, a hydraulic cement, a supplementary cementitious material (SCM) and/or solid concrete.

According to another particular aspect some embodiments relate to a method for producing a cementitious reagent from aluminosilicate materials, including the steps of: (i) providing a solid aluminosilicate material; (ii) in-flight melting said solid aluminosilicate material to melt said material into a liquid and thereafter in-flight quenching said liquid to obtain a powder including solid microspheroidal glassy particles, thereby obtaining a cementitious reagent with said powder of microspheroidal glassy particles.

In some embodiments, the method further including: (iii) of grinding said powder of microspheroidal glassy particles into a finer powder. In one embodiment, the powder has a particle size distribution with D[3,2] of about 20 μm or less, more preferably 10 μm or less, or most preferably 5 μm or less.

In some embodiments, the cementitious reagent obtained by the method includes one or more of the following properties: reactivity in cementitious systems and/or in geopolymeric systems; delivers workable low yield stress geopolymer cement mixes below 25 Pa when a cement paste has an oxide mole ratio of H2O/(Na2O,K2O)<20; has a water content in a cement paste such that the oxide mole ratio H2O/(Na2O,K2O)<20; and forms a cement paste with higher workability than an equivalent paste with substantially angular morphology, given the same water content.

Throughout the instant specification, the term “substantially” in reference to a given parameter, property, or condition may mean and include to a degree that one of ordinary skill in the art would understand that the given parameter, property, or condition is met with a small degree of variance, such as within acceptable manufacturing tolerances. By way of example, depending on the particular parameter, property, or condition that is substantially met, the parameter, property, or condition may be at least approximately 90% met, at least approximately 95% met, or even at least approximately 99% met.

In some embodiments, the method further includes the step of adjusting composition of a non-ideal solid aluminosilicate material to a desired content of the elements Ca, Na, K, Al, Fe, and Si. In one embodiment the adjusting includes blending a non-ideal aluminosilicate material with a composition adjustment material in order to reach desired ratio(s) with respect to one or several of the elements Ca, Na, K, Al, Fe, and Si.

In some embodiments, the method further includes the step of sorting the solid aluminosilicate material to obtain a powder of aluminosilicate particles of a desired size. In some embodiments, the method further includes the step of discarding undesirable waste material from said solid aluminosilicate material.

In some embodiments, the in-flight melting includes heating at a temperature above a liquid phase temperature to obtain a liquid. In some embodiments, the temperature is between about 1000° C. to about 1600° C., or between about 1300° C. to about 1550° C.

In some embodiments, the method further includes the step of adding a fluxing material to the solid aluminosilicate material to lower its melting point and/or to induce greater enthalpy, volume, or depolymerization of the liquid. In some embodiments, the fluxing material is mixed with the solid aluminosilicate material prior to, or during the melting.

In some embodiments, the in-flight melting/quenching includes reducing a temperature of the liquid below a glass transition temperature to achieve a solid. In some embodiments, the in-flight melting/quenching includes reducing a temperature of the liquid below about 500° C., or preferably below about 200° C., or lower. In some embodiments, reducing a temperature of the liquid includes quenching at a rate of about 102Ks−1to about 106Ks−1, preferably at a rate of >103.5Ks−1. In some embodiments, quenching includes a stream of cool air, steam, or water. In one embodiment, the method further includes separating quenched solid particles from hot gases in a cyclone separator.

In some embodiments, the method for producing a cementitious reagent from aluminosilicate materials may additionally include reducing particle size of the powder of solid microspheroidal glassy particles. In some embodiments reducing particle size may include crushing and/or pulverizing the powder in a ball mill, a roller mill, a vertical roller mill or the like.

According to another aspect, some embodiments relate to an apparatus for producing microspheroidal glassy particles, the apparatus including a burner, a melting chamber and a quenching chamber. The melting chamber and the quenching chamber may be completely separate or may be first and second sections of the same chamber, respectively. The apparatus may be configured such that solid particles are flown in suspension, melted in suspension, and then quenched in suspension in the apparatus.

In some embodiments, the burner provides a flame heating solid particles in suspension to a heating temperature sufficient to substantially melt said solid particles into a liquid. In some embodiments, the burner generates a flame that is fueled with a gas that entrains aluminosilicate feedstock particles towards the melt/quench chamber. The gas may include an oxidant gas and a combustible fuel. In some embodiments the burner may include at least one of a plasma torch, an oxy-fuel burner, an air-fuel burner, a biomass burner, and a solar concentrating furnace.

In some embodiments, the quenching chamber of the apparatus includes a cooling system for providing cool air inside the quenching chamber, the cool air quenching molten particles to solid microspheroidal glassy particles. In some embodiments, the cooling system includes a fluid (e.g., gas- or liquid-containing) cooling loop positioned around the quenching chamber.

In some embodiments, the apparatus may include one or more of a cyclone separator, a baghouse chamber, and an electrostatic precipitator (ESP) for collecting the microspheroidal glassy particles. A cyclone separator (or cyclone) is a centrifugal device in which microspheroidal glassy particles, due to their mass, may be directed by centrifugal force to the periphery of a cyclone chamber and may exit the chamber via a collection device fitted to the separator. A baghouse chamber, which may be operated in conjunction with a cyclone separator, includes an inlet for receiving a gas stream containing microspheroidal glassy particles, an outlet for exiting the gas stream after filtering, and a main chamber located between the inlet and the outlet. At least one filter bag may be housed within the main chamber for filtering the gas stream, i.e., for separating the microspheroidal glassy particles from the conveying gas stream. The filter bag may include a fabric filter bag, for example. An electrostatic precipitator may remove microspheroidal glassy particles from a conveying gas stream by using electrical energy to apply an electric charge to the particles. The charged particles may then be attracted to collector plates carrying an opposite charge.

According to some embodiments, a method for producing microspheroidal glassy particles includes: providing an in-flight melting/quenching apparatus including a burner, a melting chamber and a quenching chamber; providing solid particles; flowing said solid particles in suspension in a gas to be heated by said burner; heating said solid particles into said melting chamber to a heating temperature above liquid phase to obtain liquid particles in suspension; and quenching said liquid particles in suspension to a cooling temperature below a liquid phase temperature to obtain a powder including solid microspheroidal glassy particles.

In some embodiments of these methods, the solid particles include aluminosilicate materials. In some embodiments of these methods, the heating temperature is between about 1000° C. to about 1600° C., or between about 1300° C. to about 1550° C. In some embodiments of these methods, the cooling (quench) temperature is below about 500° C., or below about 200° C. In some embodiments of these methods, the quenching includes providing cool air inside the quenching chamber. In some embodiments, these methods further include collecting the powder with a collection system.

Additional aspects of some embodiments relate to the use of an apparatus as defined herein, particularly an apparatus including at least one of a plasma torch, an oxy-fuel burner, an air-fuel burner, a biomass burner, and a solar concentrating furnace, for producing a cementitious reagent from aluminosilicate materials using in-flight melting/quenching.

