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Binder Composition
Unconfined Compressive Strength
indexed to Portland

Portland

Day 7
Day 28
Cement Only

Cement
Quicklime
Limestone
Pozzolan
MPa
St. dev
MPa
St. dev
Day 7
Day 28

50%
0.0%
25.0%
25.0%
10.3
1.8
12.8
3.0
0.78
1.01

50%
16.7%
16.7%
16.7%
9.8
0.3
13.6
0.7
0.74
1.07

50%
10.0%
20.0%
20.0%
10.8
0.5
14.7
1.4
0.81
1.16

50%
5.0%
25.0%
20.0%
8.6
1.0
14.6
2.2
0.65
1.15

50%
5.0%
20.0%
25.0%
9.1
1.5
17.1
2.2
0.68
1.35

50%
5.0%
22.5%
22.5%
10.8
0.5
11.8
1.1
0.82
0.93

50%
7.5%
21.3%
21.3%
10.7
0.6
15.2
1.2
0.80
1.20

50%
12.5%
18.8%
18.8%
10.5
0.3
16.7
1.0
0.79
1.31

50%
10.0%
20.0%
20.0%
9.8
1.7
15.7
1.9
0.74
1.24

50%
5.0%
22.5%
22.5%
8.7
0.4
15.5
0.7
0.65
1.22

50%
7.5%
21.3%
21.3%
10.3
0.4
15.0
1.7
0.77
1.18

50%
7.5%
22.5%
20.0%
8.5
0.8
13.7
1.3
0.64
1.08

50%
7.5%
20.0%
22.5%
11.3
0.3
17.7
2.4
0.85
1.40

100%
0.0%
0.0%
0.0%
13.3
2.2
12.7
1.9
1.00
1.00

50%
0.0%
0.0%
50.0%
10.8
2.0
14.0
1.2
0.81
1.10

50%
0.0%
50.0%
0.0%
7.2
0.1
8.1
0.9
0.54
0.64

50%
50.0%
0.0%
0.0%
4.2
0.6
3.8
0.2
0.32
0.30

As shown in Table 2, multiple Binder Compositions including Portland Cement and the product had a higher UCS than Portland Cement combined with just one of (i) quicklime, (ii) limestone, or (iii) pozzolan. That is, the improvement in UCS of the blends of the present technology disclosed herein are due in part to a combined effect of each of quicklime, limestone, and pozzolan. For example, without being bound by theory, (i) the quicklime can provide calcium and/or calcium hydroxide particles and an alkali environment for silicate and aluminate found in the pozzolan to complete cement reactions that form calcium silicate hydrates and/or aluminum silicate hydrates that increase strength of the blend, (ii) the limestone can provide nucleation sites to catalyze such cement reactions, thereby enabling the reactions to initiate faster and/or better, and (iii) the pozzolan acts as a source of silicate and aluminate, and react with the quicklime and/or calcium to enable strength-building pozzolanic reactions. Additionally or alternatively, the improvement in UCS for embodiments of the present technology may be due to the fines filler effect, which suggests that a specific particle size (e.g., fine limestone particles) or particle size distribution of the composition optimizes strength achieved when combined to make the mine backfill product. As disclosed herein, omitting one of the quicklime, limestone or pozzolan will result in a composition with a lower UCS over time. Each composition including cement, quicklime, limestone, and pozzolan will provide some amount of strength, but there will be some ideal blend that optimizes these beneficiation mechanisms, e.g., from the limestone fines versus adding more reactants for the cement reactions.

FIG. 2 is a flow diagram of a method 200 for producing lime-based cement extender compositions, in accordance with embodiments of the present technology. The method 200 includes milling feed components comprising lime particles (e.g., the lime source 105; FIG. 1), limestone particles (e.g., the limestone source 105; FIG. 1), and pozzolan particles (e.g., the pozzolan source 105; FIG. 1) (process portion 202) to produce a milled product. Each of the lime particles, limestone particles, and pozzolan particles can originate from respective lime, limestone, and pozzolan sources, and be weighed and conveyed via conveyor belts for milling. Milling the feed components can be done in a horizontal ball mill and can produce a milled product comprising (i) at least 10% by weight of the lime particles, (ii) 20%, 25%, 30%, 35%, 40%, 45%, 50%, or 25-50% by weight limestone particles, and (ii) 35%, 40%, 45%, 50%, 60%, 65%, 70% or 35-70% by weight pozzolan particles. Additionally or alternatively, the milled blend can comprise a calcium oxide concentration of 45-65%, a magnesium oxide concentration of 0.5-2%, an iron oxide concentration of 0.5-2.0%, an aluminum oxide concentration of 2-8%, a silicon dioxide concentration of 20-40%, a potassium oxide concentration of 20,000-30,000 ppm, and a sodium oxide concentration of 10,000-20,000 ppm, e.g., as determined by elemental analysis from inductively-coupled plasma methods. Milling (e.g., grinding) the feed components can also simultaneously blend the individual feed components to form a uniform blend, as well as dry the feed components to reduce their residual moisture content. Without being bound by theory, the heat for drying the feed components may originate from the heat of friction from the mechanical grinding action of the ball mill. Additionally or alternatively, the moisture content can also be reduced via the interaction of quicklime of the lime particles and residual moisture present within the ball mill, which react with one another (via Reaction 1) to form calcium hydroxide and heat.

The method 200 further includes separating oversized particles from the milled blend to produce a product (e.g., the product or lime-based cement extender composition referred to elsewhere herein), such that at least 90%, 95%, 97%, or 99% of the particles of the product pass 200 mesh (process portion 204). Stated differently, at least 90% of the particles of the product have a particle size no greater than 75 microns. Separation of the oversized particles can occur via an air classifier (e.g., the classifier 125), in which oversized particles are directed back to the mill (e.g., via a chute or return line) for further grinding and size reduction, and the remaining particles are directed to an outlet of the classifier. Structures other than air classifiers, such as screen decks, can also be used to separate oversized particles. The oversized particles directed back to the mill are eventually returned to the classifier (e.g., via a plurality of conveyors and bucket loaders). The remaining particles (e.g., the particles passing 200 mesh) can be directed to a dust collector, and subsequently to storage (e.g., product silos) as product for distribution to customers.

In some embodiments, the product can be combined with cement, e.g., to be used in the mining industry as mine backfill. Doing so can effectively extend the use of cement, by maintaining or enhancing its utility while improving the economics associated with its use. The product can comprise 40%, 45%, 50%, or 55% of the blend, with cement comprising the balance. The cement blend can have a UCS that increases over time, e.g., from Days 7 to 28 after formulation. For example, the UCS of the product 7 days of being formed is at least 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, or 13 MPa, and the unconfined compressive strength of the product 28 days of being formed is at least 11 MPa, 12 MPa, 13 MPa, 14 MPa, 15 MPa, 16 MPa, or 17 MPa. Additionally or alternatively, the cement blend can over time have a higher UCS relative to cement alone. For example, the UCS of a cement blend comprising about 50% by weight of each of Portland Cement and product (i.e., quicklime, limestone, and pozzolan), at Day 28, can be higher than that of Portland Cement on its own. Additionally, the UCS of a cement blend comprising about 50% by weight of each of Portland Cement and product (i.e., quicklime, limestone, and pozzolan), at Day 28, can be higher than the UCS of Portland Cement and one of (i) quicklime, (ii) limestone, or (iii) pozzolan.

Embodiments of the present disclosure enable the production of products (e.g., mine backfill) by producing a lime-based cement extender composition that can effectively act as a substitute or alternative for fly ash when combined with cement. As such, embodiments of the present disclosure enable the production of improved compositions for mine backfill applications that do not include or rely on fly ash, and, additionally, are not affected by the diminishing supply and increased price of fly ash. Additionally, the lime-based cement extender compositions of the present technology can form an improved product that uses relatively less material, last longer, and has a higher unconfined compressive strength, relative to mine backfill products that include fly ash. Additionally, producing embodiments of the present technology can result in fewer greenhouse gas emissions and a smaller carbon footprint relative to that of fly ash, which is produced as a by-product of coal facilities.

III. Experimental Results

FIGS. 3A-3C are plots illustrating the relationship between UCS (MPa) and varying amounts of individual components of a composition, in accordance with embodiments of the present technology. FIG. 3A illustrates the relationship between UCS and varying amounts of quicklime, FIG. 3B illustrates the relationship between UCS and varying amounts of limestone, and FIG. 3C illustrates the relationship between UCS and varying amounts of pozzolan. The composition used for each of the plots of FIGS. 3A-3C includes 50% cement, and varying amounts of the individual components as shown in FIGS. 3A-3C. As such, the percentages shown for each of the individual components in FIGS. 3A-3C represents 50% of the composition. Moreover, for each of the plots, which shows varying amounts of one of the quicklime, limestone, or pozzolan, the amount of the other components also varies. For example, for the plot of FIG. 3A which shows the amount of quicklime varying from 0% to about 34%, the amount of limestone and/or pozzolan also varies as the amount of quicklime increases. With reference to FIGS. 3A-3C together, the UCS exhibits a peak at various amounts for each of the individual components. For example, the UCS peak for quicklime occurs at about 17% (FIG. 3A), the UCS peak for limestone occurs at about 25% (FIG. 3B), and the UCS peak for pozzolan occurs at about 65% (FIG. 3C). As such, in some embodiments an optimal strength for the overall composition can occur when the composition comprises about 45-55% cement, about 6-10% quicklime, about 10-15% limestone, and about 30-35% pozzolan.

Table 3 includes data corresponding to the amount of available CaO and pH for a type I/II cement (“Cement”), a lime-based cement extender product (“Product”), and a 1:1 mixture of the Cement and Product. The Product here can correspond to the product or lime-based cement extender composition described above with reference to FIGS. 1 and/or 2.

TABLE 3

Material
% Available CaO
pH

Type I/II Cement (“Cement”)
15.7
12.1

Lime Based Cement Extender (“Product”)
10.3
12.5

1:1 mixture of Cement and Product
16.4
12.5

The percent available CaO shown in Table 3 was determined based on ASTM C 25-19: “Standard Test Methods for Chemical Analysis of Limestone, Quicklime, and Hydrated Lime”. The pH was obtained by creating an about 5% slurry of the material in distilled water, and measuring the pH once the temperature stabilized at room temperature (about 22° C.) using a calibrated pH electrode.

As shown in Table 3, the lime supplies at least 10% available lime in the Product, which results in no reduction of available CaO in the blended mixtures. That is, the available lime of the Cement is about 15.7% and the available lime of the 1:1 mixture is about 16.4. Additionally, the lime maintains the pH above about 12.0, thereby enabling pozzolanic reactions to occur and/or continue, which develops UCS gains over time.

IV. Conclusion

It will be apparent to those having skill in the art that changes may be made to the details of the above-described embodiments without departing from the underlying principles of the present disclosure. In some cases, well known structures and functions have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments of the present technology. Although steps of methods may be presented herein in a particular order, alternative embodiments may perform the steps in a different order. Similarly, certain aspects of the present technology disclosed in the context of particular embodiments can be combined or eliminated in other embodiments. Furthermore, while advantages associated with certain embodiments of the present technology may have been disclosed in the context of those embodiments, other embodiments can also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages or other advantages disclosed herein to fall within the scope of the technology. Accordingly, the disclosure and associated technology can encompass other embodiments not expressly shown or described herein, and the invention is not limited except as by the appended claims.

Throughout this disclosure, the singular terms “a,” “an,” and “the” include plural referents unless the context clearly indicates otherwise.

Reference herein to “one embodiment,” “an embodiment,” “some embodiments” or similar formulations means that a particular feature, structure, operation, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present technology. Thus, the appearances of such phrases or formulations herein are not necessarily all referring to the same embodiment. Furthermore, various particular features, structures, operations, or characteristics may be combined in any suitable manner in one or more embodiments.

Unless otherwise indicated, all numbers expressing concentrations, strength, and other numerical values used in the specification and claims, are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the present technology. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Additionally, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein. For example, a range of “1 to 10” includes any and all subranges between (and including) the minimum value of 1 and the maximum value of 10, i.e., any and all subranges having a minimum value of equal to or greater than 1 and a maximum value of equal to or less than 10. As such, a range of “1-10” includes, for example, the values 2, 5.5, and 10.

The disclosure set forth above is not to be interpreted as reflecting an intention that any claim requires more features than those expressly recited in that claim. Rather, as the following claims reflect, inventive aspects lie in a combination of fewer than all features of any single foregoing disclosed embodiment. Thus, the claims following this Detailed Description are hereby expressly incorporated into this Detailed Description, with each claim standing on its own as a separate embodiment. This disclosure includes all permutations of the independent claims with their dependent claims.

The present technology is illustrated, for example, according to various aspects described below. Various examples of aspects of the present technology are described as numbered examples (1, 2, 3, etc.) for convenience. These are provided as examples and do not limit the present technology. It is noted that any of the dependent examples may be combined in any combination, and placed into a respective independent example. The other examples can be presented in a similar manner.

1. A lime-based cement extender composition, comprising:

- lime particles comprising calcium hydroxide and/or calcium oxide and at least 10% by weight of the composition;
- limestone particles comprising calcium carbonate and at least 20% by weight of the composition; and
- pozzolan particles comprising silicon dioxide and/or aluminum dioxide and at least 30% by weight of the composition,
- wherein at least 90% of the lime particles, limestone particles, and pozzolan particles are less than 75 microns.

2. The composition of any one of the clauses herein, wherein the lime particles comprise 10-20% by weight of the composition.

3. The composition of any one of the clauses herein, wherein the limestone particles comprise 40-50% by weight of the composition.

4. The composition of any one of the clauses herein, wherein the pozzolan particles comprise 40-50% by weight of the composition.

5. The composition of any one of the clauses herein, wherein: