Concrete Product and Methods of Preparing the Same

Abstract

A concrete product set by pouring a concrete slurry includes a) a concrete mixture; b) a graphene admixture; c) a colloidal silica admixture; and d) at least one reinforcing fiber selected from the group of fibers. As the poured concrete slurry cures, the poured slurry hardens into a composite material product, and the composite material defines capillary structures that at least in part fill with silica and lime, and the surrounding composite material is embedded with graphene. In another exemplary embodiment, the present invention is directed to a process for preparing a concrete product. The process comprises the steps of a) preparing a concrete slurry; b) pouring the concrete slurry; and c) allowing the concrete slurry to cure. In another exemplary embodiment, the present invention is directed to the product itself; namely, a concrete product with or without fibers, or to the admixture(s).

Claims

1. A concrete product set by pouring a concrete slurry, the poured concrete slurry comprising: a) a concrete mixture; b) a colloidal silica admixture; c) a graphene admixture; and d) at least one fiber selected from the group of fibers consisting of steel fibers, helix fibers, basalt fibers, polyvinyl alcohol (PVA) fibers, carbon fibers, and synthetic fibers; wherein, as the poured concrete slurry cures, the poured slurry hardens into a composite material, the composite material defining capillary structures that at least in part fill with silica and lime, and graphene; wherein the silica and lime react to produce a gel structure of calcium silicate hydrate that at least partially fill the capillary structures; and wherein the graphene embed along and partially fill the capillary structures; whereby the calcium silicate hydrate reduces internal tensile forces acting on the concrete product, and whereby the embedded graphene at least in part distribute the load of the composite material acting on the concrete product.

2. The concrete product of claim 1 wherein the silica has a size ranging from between about 3.0 nanometers (nm) to about 100.0 nm, and wherein the graphene are about 1.10±0.20 nm thick with lattice constant of about 0.27 nm×0.41 nm.

3. The concrete product of claim 1 wherein the concrete product is set by pouring the concrete slurry and then applying a curing technique to the poured concrete slurry, and wherein the curing technique comprises spray-applying a secondary colloidal silica and graphene onto the poured concrete slurry.

4. The concrete product of claim 3 wherein the secondary colloidal silica and graphene also is spray-applied onto the poured concrete slurry subsequent to removing a trowel machine.

5. The concrete product of claim 3 wherein the silica of the secondary colloidal silica and graphene application has a size ranging from about 3.0 nm to about 25.0 nm, and wherein the graphene of the secondary colloidal silica and graphene application are about 1.10±0.20 nm thick with lattice constant of about 0.27 nm×0.41 nm.

6. The concrete product of claim 3 wherein the secondary colloidal silica and graphene is spray-applied onto the poured concrete slurry subsequent to cement in the poured concrete slurry being set.

7. The concrete product of claim 1 wherein the concrete mixture comprises aggregate, cement, and water, and wherein the concrete mixture is defined by a water to cement ratio of between about 0.400 to about 0.450.

8. The concrete product of claim 1 wherein the at least one fiber selected from the group consisting of steel fibers, helix fibers, basalt fibers, PVA fibers, carbon fibers, and synthetic fibers represents between about 0.20% by volume to about 0.50% by volume of the poured concrete slurry.

9. A process for preparing a concrete product, the process comprising: a) preparing a concrete slurry, the concrete slurry comprising: i) a concrete mixture; ii) a colloidal silica admixture; iii) a graphene admixture; and iv) at least one fiber selected from the group of fibers consisting of steel fibers, helix fibers, basalt fibers, PVA fibers, carbon fibers, and synthetic fibers; b) pouring the concrete slurry; and c) allowing the concrete slurry to cure such that capillary structures develop as the concrete product sets from the poured concrete slurry, and such that the capillary structures of the product at least in part fill with silica and lime, and graphene, and such that the silica and lime react to produce a gel structure of calcium silicate hydrate that at least partially fill the capillary structures, and such that the graphene embed along and partially fill the capillary structures.

10. The process for preparing a concrete product of claim 9 wherein the preparing step comprises preparing the concrete slurry with colloidal silica having a size ranging from between about 3.0 nm to about 100.0 nm, and with graphene having a size of about 1.10±0.20 nm thick with lattice constant of about 0.27 nm×0.41 nm.

11. The process for preparing a concrete product of claim 10 wherein the preparing step additionally comprises adding the colloidal silica admixture to the concrete slurry in ranges of between about 0.50% to about 1.50% by weight of cement in the concrete mixture, and adding the graphene admixture to the concrete slurry in ranges of between about 0.01% to about 0.10% by weight of cement.

12. The process for preparing a concrete product of claim 10 wherein the preparing step additionally comprises adding the colloidal silica admixture to the concrete slurry in ranges of between about 0.50% to about 10.0% by weight of cement in the concrete mixture, and adding the graphene admixture to the concrete slurry in ranges of between about 0.01% to about 0.10% by weight of cement.

13. The process for preparing a concrete product of claim 9 additionally comprising the step of spray-applying a secondary colloidal silica and graphene onto the poured concrete slurry to facilitate curing thereof.

14. The process for preparing a concrete product of claim 13 wherein the spray-applying step comprises spray-applying the secondary colloidal silica and graphene onto the poured concrete slurry subsequent to removal of a trowel machine and prior to cement in the poured concrete slurry being completely set.

15. The process for preparing a concrete product of claim 13 wherein the spray-applying step comprises spray-applying the poured concrete slurry with a secondary colloidal silica and graphene application having silica with size ranging from about 3.0 nm to about 25.0 nm, and having graphene with size of about 1.10±0.20 nm thick with lattice constant of about 0.27 nm×0.41 nm.

16. The process for preparing a concrete product of claim 13 wherein the spray-applying step comprises spray-applying the secondary colloidal silica and graphene onto the poured concrete slurry subsequent to cement in the poured concrete slurry being set.

17. The process for preparing a concrete product of claim 9 wherein the preparing step comprises preparing the concrete slurry for pouring with dosages of steel fibers as the at least one fiber selected from the group of fibers of between about 33.0 pounds per cubic yard (lbs./cuyd) to about 66.0 lbs./cuyd.

18. The process for preparing a concrete product of claim 9 wherein the preparing step comprises preparing the concrete slurry for pouring with dosages of helix fibers, basalt fibers, PVA fibers, or carbon fibers, as the at least one fiber selected from the group of fibers, of between about 3.0 lbs./cuyd to about 7.5 lbs./cuyd, or about 3.0 lbs./cuyd to about 35.0 lbs./cuyd if helix fibers.

19. A concrete product set from a poured concrete slurry, the poured concrete slurry comprising a concrete mixture, a colloidal silica admixture, a graphene admixture, and at least one fiber selected from the group of fibers consisting of steel fibers, helix fibers, basalt fibers, PVA fibers, carbon fibers, and synthetic fibers, the concrete product comprising capillary structures that are at least in part filled with a reaction product of silica and lime, and at least in part embedded with and filled with graphene, the reaction product of silica and lime being a gel structure of calcium silicate hydrate, the embedded graphene being graphene monolayers or overlapping graphene, whereby the calcium silicate hydrate reduces internal tensile forces acting on the concrete product, and whereby the embedded graphene monolayers or overlapping graphene at least in part distribute the load acting on the concrete product.

20. The concrete product of claim 19 wherein the silica has a size ranging from between about 3.0 nm to about 100.0 nm, and wherein the graphene are about 1.10±0.20 nm thick with lattice constant of about 0.27 nm×0.41 nm.

21. The concrete product of claim 19 wherein the concrete product is cured by application of a spray-applied secondary colloidal silica and graphene oxide.

22. The concrete product of claim 21 wherein the silica of the secondary colloidal silica and graphene application have a size ranging from about 3.0 nm to about 25.0 nm, and wherein the graphene have a size of about 1.10±0.20 nm thick with lattice constant of about 0.27 nm×0.41 nm.

23. The concrete product of claim 19 wherein the concrete mixture comprises aggregate, cement, and water, and wherein the concrete mixture is defined by a water to cement ratio of between about 0.400 to about 0.450.

24. The concrete product of claim 19 wherein the at least one fiber selected from the group consisting of steel fibers, helix fibers, basalt fibers, PVA fibers, carbon fibers, and synthetic fibers represents between about 0.20% by volume to about 0.50% by volume of the poured concrete slurry.

25. A fiberless concrete product set by pouring a concrete slurry onto a substrate, the poured concrete slurry comprising: a) a concrete mixture; b) a colloidal silica admixture; and c) a graphene admixture; wherein, as the poured concrete slurry cures, the poured slurry hardens into a composite material, the composite material defining capillary structures that at least in part fill with silica and lime, and graphene; wherein the silica and lime react to produce a gel structure of calcium silicate hydrate that at least partially fill the capillary structures; and wherein the graphene embed along and partially fill the capillary structures; whereby the calcium silicate hydrate reduces internal tensile forces acting on the concrete product, and whereby the embedded graphene at least in part distribute the load of the composite material acting on the concrete product.

26. The fiberless concrete product of claim 25 wherein the silica has a size ranging from between about 3.0 nm to about 100.0 nm, and wherein the graphene are about 1.10±0.20 nm thick with lattice constant of about 0.27 nm×0.41 nm.

27. The fiberless concrete product of claim 25 wherein the concrete product is set by pouring the concrete slurry and then applying a curing technique to the poured concrete slurry, and wherein the curing technique comprises spray-applying a secondary colloidal silica and graphene onto the poured concrete slurry.

28. The fiberless concrete product of claim 27 wherein the secondary colloidal silica and graphene also is spray-applied onto the poured concrete slurry subsequent to removing a trowel machine.

29. The fiberless concrete product of claim 27 wherein the silica of the secondary colloidal silica and graphene application has a size ranging from about 3.0 nm to about 25.5 nm, and wherein the graphene of the secondary colloidal silica and graphene application are about 1.10±0.20 nm thick with lattice constant of about 0.27 nm×0.41 nm.

30. A process for preparing a fiberless concrete product, the process comprising: a) preparing a concrete slurry, the concrete slurry comprising: i) a concrete mixture; ii) a colloidal silica admixture; and iii) a graphene admixture; b) pouring the concrete slurry; and c) allowing the concrete slurry to cure such that capillary structures develop as the concrete product sets from the poured concrete slurry, and such that the capillary structures of the product at least in part fill with silica and lime, and graphene, and such that the silica and lime react to produce a gel structure of calcium silicate hydrate that at least partially fill the capillary structures, and such that the graphene embed along and partially fill the capillary structures.

31. The process for preparing a fiberless concrete product of claim 30 wherein the preparing step comprises preparing the concrete slurry with colloidal silica having a size ranging from between about 3.0 nm to about 100.0 nm, and with graphene having a size of about 1.10±0.20 nm thick with lattice constant of about 0.27 nm×0.41 nm.

32. The process for preparing a fiberless concrete product of claim 31 wherein the preparing step additionally comprises adding the colloidal silica admixture to the concrete slurry in ranges of between about 0.50% to about 1.5% by weight of cement in the concrete mixture, and adding the graphene admixture to the concrete slurry in ranges of between about 0.01% to about 0.10% by weight of cement and the preparing step additionally comprises adding the colloidal silica admixture to the concrete slurry in ranges of between about 0.50% to about 10.0% by weight of cement in the concrete mixture, and adding the graphene admixture to the concrete slurry in ranges of between about 0.01% to about 0.10% by weight of cement.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG. 1 is a perspective view of an exemplary concrete slab.

[0025] FIG. 2 is a magnified perspective view of a cut-away portion of the concrete slab of FIG. 1.

[0026] FIG. 3 is a flow diagram showing the steps of a first illustrative embodiment of a method for placing a concrete slab on a substrate.

[0027] FIG. 4 is a flow diagram showing the steps of a second illustrative embodiment of a method for placing a concrete slab on a substrate.

[0028] FIG. 5 is a flow diagram showing the steps of a third illustrative embodiment of a method for placing a concrete slab on a substrate.

[0029] FIG. 6 is a flow diagram showing the steps of a fourth illustrative embodiment of a method for placing a concrete slab on a substrate.

[0030] FIG. 7 is a perspective view of an exemplary fiberless concrete slab.

DETAILED DESCRIPTION

[0031] For a further understanding of the nature, function, and objects of the present invention, reference should now be made to the following detailed description. While detailed descriptions of the preferred embodiments are provided herein, as well as the best mode of carrying out and employing the present invention, it is to be understood that the present invention may be embodied in various forms. Specific details disclosed herein are not to be interpreted as limiting but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in virtually any appropriately detailed system, structure, or manner.

[0032] For purposes of this disclosure, a “jointless” concrete slab refers to a slab that does not have cut joints and that is capable of managing the cracks and fractures without the cut joints. Percent (%) by weight refers to the aggregate weight of the silica in comparison to the final weight of cement in a final concrete product. A “fiberless” concrete slab refers to a slab that does not have steel fibers, synthetic fibers, or other like internal reinforcements, and that still remains capable of managing the cracks and fractures without the fibers.

[0033] For purposes of this disclosure, graphene refers to the broad category of single-layer allotropes of carbon, which are arranged in a two-dimensional hexagonal, or honeycomb lattice. As is well known in the art, carbon is capable of forming many allotropes—structurally different forms of the same element—due to valency, for example. Well-known forms of carbon include diamond and graphite.

[0034] Graphene—in the broadest sense—is a portmanteau of “graphite” and the suffix “-ene”, reflecting the fact that the graphite allotrope of carbon essentially consists of stacked graphene layers. The IUPAC (International Union for Pure and Applied Chemistry) recommends use of the term “graphite” for the three-dimensional material, and “graphene” only when the reactions, structural relations, or other properties of the graphite's individual layers are being referred to. Another definition—of “isolated or free-standing graphene”—teaches that the layer(s) (up to 10 layers together, for example) be sufficiently isolated from its environment, but would include layer(s) suspended or transferred to silicon dioxide or silicon carbide via exfoliation, sonication, or chemical vapor deposition, etc., for example.

[0035] In any sense, the individual layers or stacks of layers of graphite of any type—graphite, graphite oxide, or graphite with other functional groups—may be known simply as graphene in the art. In each layer, the carbon atoms are arranged in a hexagonal, or honeycomb lattice with a bond length of about 0.142 nm, and a distance between planes of about 0.335 nm; however, these variables may slightly vary depending on the specific chemical structure of the graphene. Atoms in the plane are bonded covalently, with only three of the four potential bonding sites satisfied. Bonding between layers is via weak van der Waals bonds, which allow layers of graphite to be easily separated, or to slip past each other.

[0036] Graphite oxide, formerly called graphitic oxide or graphitic acid, is a compound of carbon, oxygen, and hydrogen in variable ratios, obtained by treating graphite with strong oxidizers and acids for the resolving of extra metals, for example. The maximally oxidized bulk product is a yellow solid with C:O ratio between 2.1 and 2.9, that retains the layer structure of graphite, but with a much larger and irregular spacing. The bulk material spontaneously disperses in basic solutions or can be dispersed by sonication in polar solvents to yield monomolecular sheets known as graphene oxide, for example. The “graphene” obtained by reduction of graphene oxide (GO)—reduced graphene oxide or r-GO herein—still has many chemical and side-structural groups that distinguish them from pure graphene. Strictly speaking “oxide” is an incorrect but historically established name. Besides oxygen epoxide groups (bridging oxygen atoms), other functional side groups for graphene include: carbonyl (C═O); hydroxyl (—OH); phenol, for graphite oxides prepared using sulphuric acid (e.g., Hummer's method), to name a few.

[0037] With regard to GO reduction, monolayers of r-GO with few functional or side groups, or defects, are readily available for commercial use. The rapid heating of GO along with exfoliation or sonication, for example, is known to yield highly dispersed carbon powder with a few percent of graphene in composition. Similarly, dispersed r-GO suspensions can be synthesized in water via hydrothermal dehydration methods, without the use of any surfactants.

[0038] As such, graphene as used herein refers to the broad category of single-layer allotropes of carbon as described above and herein. Embodiments and aspects of the present disclosure provide a system for, and method of, preparing and pouring a concrete slurry for the formation of concrete products, which are not susceptible to the limitations and deficiencies of the prior art. The inventive concepts described herein allow for the formation, in certain non-limiting embodiments, of concrete slabs and rafts, based on the synergistic combination of a prepared concrete slurry with a curing technique.

[0039] Further, the inventive concepts described herein also allow for the formation, in certain non-limiting embodiments, of concrete products that are less susceptible to cracking or fracturing, and that are less susceptible to the complications derived therefrom.

[0040] The inventive concepts described herein also allow for a decreased need for and a decreased use of traditional reinforcements such as rebar and/or mattings. This allows for efficiencies in time, labor, and resources, and allows for a streamlining and simplifying of the process for forming and maintaining a concrete product.

[0041] As further background and context: throughout the United States of America, the large majority of concrete slabs are installed with a pattern of saw-cuts configured as joints. The joints control the inherent drying, shrinking, and cracking that occurs in the concrete. The American Concrete Institute™ (ACI) standards for a 1,000,000 square foot industrial warehouse with a 6″ slab will define approximately 25 miles of control joints. If concrete slabs-on-ground are designed per ACI Guide ACI 360R-10, typical concrete mixtures, such as 4,000 pounds per square inch (psi) 28-day compressive strength mixtures, are expected to shrink about ⅜″ to ½″ per 100 feet while drying/curing.

[0042] A person having ordinary skill in the art understands that such solutions are complex, complicated, and resource intensive. In one example, ACI 360R-10 calls for the installation of doweled joints to provide adequate load transfer between adjacent slabs, especially, if load transfer, due to frequent “rolling traffic”, is expected. In another instance, guidelines for joint spacing are given in ACI 360R-10 Chapter 6, Figure 6.6, wherein the graph shows joints for a typical concrete slab at about 14.0′ distances for 6″ thick floors and about 17.0′ joint distances for 8″ thick floor.

[0043] While these may appear to be adequate solutions to the shrinking/cracking problem, the current state of the art indicates the opposite. The practice of saw-cutting modern concrete, and cutting the control joints, causes other issues such as curling, spalling, joint/joint filing maintenance, limited rack post layout options for warehouses, increased wear/tear on surface equipment (e.g. automobiles, forklifts, robotic equipment), and increased injury to workers, to name a few. These are examples of how current prior art solutions give rise to unpredictable results, and how the common teachings in the art—steering concrete-product producing entities to employ one or more solutions—adds unnecessary complexity and unforeseen consequences.

[0044] Due to the latest safety and health regulations in the United States of America for silica exposure, there is a significant cost to concrete-product producing businesses stemming from risk-mitigation practices (e.g., vacuuming, containment, collection, disposal) during the saw-cutting process, in order to contain the hazardous pozzolan dust and other additive-dust produced therefrom.

[0045] Concern for these risk-mitigation practices, and other possible future unpredictable results, is not unwarranted. Type F Fly Ash is the most common artificial pozzolan and is derived from coal combustion. The amorphous glassy spherical morphology of the particle provides the pozzolanic activity and is a respiratory hazard, not accounting for any other contaminants in the fly ash.

[0046] Silica fume is a waste product of the silicon metal industry, usually retrieved from the stack gases of electric arc furnaces, and is a microparticulate of almost pure amorphous silica. Silica fume is notoriously difficult and expensive to handle, transport and mix, as it is a light, fluffy, possibly air-born material (almost as fine as cigarette ash, with a bulk density of about between 200.0 kilograms per meter cubed (kg/m{circumflex over ( )}3) to about 300.0 kg/m{circumflex over ( )}3, and a relative density of between about 2.20 to about 2.50). Despite its drawbacks, it has become a standard additive in the art for high-strength concretes, and is often used in combination with both cement and fly ash.

[0047] Contributing to this potential hazard, silica fume usually is a by-product resulting from the production of silicon or ferrosilicon metal alloys or other silicon alloys, or derived from the pyrolysis of rice hulls, metakaolin, etc. Silica fume typically contains about 90% of amorphous silicon dioxide depending on the source. Undensified silica fume consists of very fine vitreous spherical particles with an average diameter of about 150.0 nm, whereas the average cement particle has a diameter of about 10.0 um. Because of its extreme fineness and high silicon content, silica fume also is generally a very effective pozzolan but also is known as a respiratory hazard, not accounting for any contaminants in the fume.

[0048] Although seamless concrete slabs are prevalent in Europe, with little to no production of dusts, etc. to mitigate against, the vast majority of the slabs are steel-fiber reinforced and without shrinkage reducing admixtures (SRAs) and without complicated cement formulations. Under these circumstances, the common teachings in the art steer concrete-product producing businesses to keep the concrete formulations simple; however, they rely on already-deficient techniques from the past to compensate. The deficiencies of these solutions are described in greater detail as background and context information; however, a person having ordinary skill in the art understands that slabs using these prior art composite-concrete compositions possess the following deficiencies: (1) size restrictions based on the internal reinforcement; (2) need for maintenance and inspection of reinforcements; (3) more complicated engineering and higher material costs and demands; and (4) a higher minimum thickness of the slab due to the added internal reinforcements, etc.

[0049] In the United States of America, there are few industrial slab installations without joints. Most of these industrial slab installations without joints use a shrinkage-compensating concrete comprising a Type K cement incorporating a calcium sulfoaluminate additive. This Type K cement, which is one example of the broader field of expansive cements, is used in combination with rebar or steel fibers to help restrain the cement as it expands. These expansive cements also require at least a 7-day wet cure to ensure that the designed expansion occurs. In short, this technique results in a concrete product with high internal expansion, which puts the concrete under intense internal compression. This is done to combat the inherent shrinkage of traditional concrete and yet still has many inherent deficiencies understood by a person having ordinary skill in the art.

[0050] With the above context in mind, a first exemplary embodiment of the inventive concepts provides a system for, and method of, preparing and pouring a concrete slurry for the formation of concrete products, wherein micro- and/or nano-particles, particulates, carbon-chains, and/or fibers are paired with a durable and flexible blend of aggregates, pastes, and admixtures, to provide an impermeable jointless and/or fiberless mass of concrete exhibiting exceptional tensile strength and durability for the heaviest loads and equipment.

[0051] A second exemplary embodiment provides a system for, and method of, forming of a concrete product via a concrete slurry and curing technique, wherein the concrete slurry leverages colloidal silica and graphene in combination with fibers (steel ASTM 820 fibers, helix fibers, basalt fibers, polyvinyl alcohol fibers, carbon fibers, and/or other macro synthetic ASTM C1116 fibers, for example, wherein ASTM is defined as American Society for Testing and Materials and its consensus standards, grades, and certifications, as of 6 Aug. 2020) to create a jointless mass. The colloidal silica and graphene composite is used as an admixture and/or sprayed onto the surface as a “cure” soon after or right after the trowel machine is removed.

[0052] The colloidal silica or graphene work to fill the capillary structure to reduce internal tensile forces or to provide stiffness and strength, which drastically reduces the likelihood of shrinking and cracking of the concrete. Spraying the surface of the poured concrete slurry with the colloidal silica and graphene composite at the appropriate time and dosage as described herein has been found by the inventor to be similar to a 28-day wet cure. With regard to the colloidal silica, open capillaries are filled with reactive nanometer-sized silica that react with the free lime to produce a stable gel structure of calcium silicate hydrate, which eliminates moisture loss by plugging the pores of the capillary structures. With regard to the graphene, the concrete structure defining the capillaries is embedded with nanometer-sized graphene, which are defined by stiffness and strength due to the presence of a two-dimensional graphene backbone. It is possible that the graphene may overlap to create an interwoven layer structure that distributes load. The inventor has also found that this process is not temporary, and is instead a permanent solution.

[0053] At this high-level non-limiting example, the use of colloidal silica as an admixture and/or spray works with the internal cement molecule. Colloidal silica, which is included within the category of pozzolans, is a suspension of fine amorphous, nonporous, and typically spherical silica in a liquid phase. During curing and thereafter, the colloidal silica will react with free lime, increasing the density and structural strength of the solid structures formed. The increased density and long-term pozzolanic action ties up free lime, which limits the creation of channels and decreases the permeability in the concrete structure. Moreover, the resultant chemical and structural effect also helps keep contaminants on the surface of the concrete.

[0054] The use of the dispersed graphene as an admixture and/or spray in an exemplary embodiment works to prevent shrink cracking and moisture loss. Graphite oxide may be hydrophilic and easily hydrated when exposed to water in liquid or gas phase, resulting in a distinct increase of the inter-planar distance (up to about 1.2 nm in its saturated state). Additional water may be incorporated into the interlayer space between graphene due to high-pressure induced effects. The hydration state of graphene in liquid water corresponds to insertion of about 2-3 water monolayers, for example. Complete removal of water from graphene is known to be difficult as direct heating at 60-80° C. commonly results in partial decomposition and degradation of the chemical structure. Conversely, graphite and the derived graphene may have negligible solubility in water.

[0055] A third exemplary embodiment provides a process for placing a jointless concrete slab on a substrate for industrial and commercial applications. The applications on the surface of the slab may involve automated facilities with laser-guided equipment moving on the slab, where even the slightest imperfection in the slab can bring the whole facility to a stand-still. The slab is characterized by being virtually free of curling and cracking, and having superior abrasion-resistance. The slab also is characterized by having higher than normal resistance to the effects of aggressive water and chemical attack, such as salt, when compared to traditional concrete composite materials. The slab also provides a highly dense, highly accurate, and planar concrete surface with limited internal macro-reinforcements and a thinner cross section than a conventional concrete slab of the same strength.

[0056] For this particular embodiment, the process comprises: (1) preparing a concrete slurry with a water to cement ratio of between about 0.400 to about 0.450, with steel fibers or macro synthetic fibers (helix, basalt, PVA, carbon or other macro synthetic fibers, for example), or a combination of these fibers, (2) preparing the concrete slurry with a colloidal silica and graphene, integral thereto, (3) performing a “spray-apply” step using colloidal silica, and (4) providing reaction and performance enhancing chemicals to the slurry or to the curing/to-be finished product. The overall process comprises establishing a highly accurate, and well compacted subbase preparation as a foundation in preparation for placement of the concrete.

[0057] A fourth exemplary embodiment provides a method comprising the step of using steel fibers to mitigate shrinkage cracks in the concrete. Fibers help mitigate plastic and drying shrinkage by arresting the movement of the concrete slab and distributing any shrinkage across the entire slab and fiber network area by means of micro cracking, i.e., when shrinkage occurs the fibers engage and redistribute the shrinkage. This holds true for both steel and macro-synthetic fibers, as described in greater detail herein.

[0058] This step may be one step in a series of steps making up an exemplary embodiment. As is described in greater detail herein, shrinkage cracks occur either as early plastic shrinkage, nucleating in the first 24 hours while the concrete has low strength, or nucleating as late cracks, due to the external restraint of the volume change during the drying shrinkage. As water is lost in the cement paste, shrinking places the aggregates in compression. Fine and discrete cracks nucleate and extend from the perimeter of the aggregates, and the numerous fine cracks continue to extend, while shrinkage increases over time and the cracks coalesce. As the concrete slab shrinks, the concrete slab shortens in all directions. The microcracks then combine at the location of the greatest strain and stress, where subsequently a crack will form.

[0059] For this particular embodiment, the step of using steel fibers to mitigate shrinkage cracks in the concrete allows for fibers to be randomly distributed throughout the concrete slab and can, with close spacing and good bonding, intercept the formation of cracks. Different types of steel fibers may be used for different applications. Some Type 2 steel fibers are sized to number about 9000.0 fibers per pound (lb.) and are used typically in dosages of about 33.0 lbs./cuyd (representing about 0.250% by volume of concrete) to about 66.0 lbs./cuyd (representing about 0.50% by volume of concrete). Some Type 1 steel fibers are sized and number about 2500.0 fibers per pound and may also be used. Helix fibers also may be added to the concrete slurry in dosage rates of about 3.0 lbs./cuyd to about 35.0 lbs./cuyd.

[0060] A fifth exemplary embodiment provides a method comprising the step of using macro synthetic fibers to mitigate shrinkage cracks in concrete. This step may be one step in a series of steps making up an exemplary method of the present invention. The effect of the macro synthetic fibers is similar to the step of using steel fibers to mitigate shrinkage cracks in the concrete. However, the step of using macro synthetic fibers to mitigate shrinkage cracks in concrete also improves water retention and, therefore, assures a more complete hydration of the cement, and may also reduce plastic shrinkage more effectively than steel fibers in some circumstances. Further, the high fiber count associated with the step of using macro synthetic fibers intercepts the formation of microcracks and, therefore, reduces the formation of larger cracks. The macro synthetic fibers also may be added to the concrete in dosage rates of about 3.0 lbs./cuyd representing about 0.20% by volume of concrete to about 7.50 lbs./cuyd, representing about 0.50% by volume of concrete.

[0061] A sixth exemplary embodiment provides a method comprising the step of using or adding colloidal silica and graphene to the slurry. This step may be one step in a series of steps making up an exemplary method of the present invention.

[0062] With regard to the graphene oxide or graphene, an oxidation product of the compound carbon with or without oxygen, and hydrogen in variable CO ratios of between 2.1 and 2.9 may come made available in an aqueous solution. In its dry form, it essentially presents as a black powder or soot. The bulk oxidation-product—dispersed in solution or not—is defined as having graphene nanoplatelets—single layer and multi-layer graphene—in its composition with or without trace minerals like biochar and/or granular non-activated carbon.

[0063] The graphene, in comparison to graphite, have layers/stacked layers that are buckled, and the interlayer spacing is about two times larger (˜0.7 nm) than that of graphite. The graphene are about 1.10±0.20 nm thick and the graphene are spontaneously dispersed in a basic solution or mechanically dispersed by sonication in a polar solvent, as needed. Scanning tunneling microscopy shows the presence of local regions where oxygen atoms are arranged in a rectangular pattern with lattice constant of about 0.27 nm×0.41 nm. Graphene has unique surface properties, which make it a very good surfactant material stabilizing various colloidal systems.

[0064] For this particular embodiment, the dispersed graphene admixture is added to the concrete during the preparation phase in ranges of between about 0.01% to about 0.10% by weight of cement, depending on the concrete slurry design and the application.

[0065] With regard to colloidal silica, amorphous nanometer-sized silica (SiO.sub.2) in a size ranging from between about 3.0 nm to about 100.0 nm, or from between about 5.0 nm to about 100.0 nm, is in aqueous solution and is added to the concrete slurry along with the graphene admixture and the reaction enhancing and workability enhancing (rheology enhancing) admixtures, such as polycarboxylate. The silica will react with the free lime or calcium hydroxide (Ca(OH).sub.2) from the cement hydration to form a solid gel product called CSH, or calcium silicate hydrate (CaSiO.sub.3+H.sub.2O).

[0066] For this particular embodiment, as is shown in the following Formula 1: Ca(OH).sub.2+SiO.sub.2 ó CaSiO.sub.3+H.sub.2O (1), the colloidal silica aqueous solution is added to the concrete during the preparation phase in ranges of between about 0.50% to about 1.50% by weight of cement, depending on the concrete slurry design and the application. The above described chemical reaction will consume some of the capillary water and will fill the pores with the hydration products CSH and, therefore, greatly reduce drying shrinkage.

[0067] A seventh exemplary embodiment provides a method comprising the step of using a spray-applied colloidal silica and/or graphene as a curing technique. This step may be one step in a series of steps making up an exemplary method of the present invention. Amorphous colloidal silica with sizes of between about 3.0 nm to about 50.0 nm in an aqueous solution and/or graphene with sizes of about 0.5 nm is/are sprayed on a surface of the finished concrete slab after final set of the cement, or as described in greater detail herein.

[0068] The nanometer-sized silica penetrates up to about 3.0″ deep into the hardened concrete after between about 3.0 to about 6.0 hours after the final set of cement and react with the capillary pore water and available calcium hydroxide to form CSH, calcium silicate hydrate, as described herein. This also will seal the top of the concrete and prevent water from evaporating from the concrete mixture and thus enhance the cement hydration process. The spray-applied colloidal silica can be applied using a pump sprayer, a walk-behind electric-powered “turf” sprayer, and the like, as well as custom-made automated spraying machines. The entire surface of the slab is sprayed such that the silica and graphene penetrate and complete the filling of the capillary structures. This process step of spray-applying colloidal silica may occur after the concrete has been trowel finished and can be walked on without imprinting the surface.

[0069] An eighth exemplary embodiment provides a system for, and a method of, preparing and pouring a concrete slurry with colloidal silica, as described herein, for the formation of concrete products, wherein a polycarboxylate ether-based superplasticizer admixture is paired with the cement mixture, colloidal silica admixture, and/or the secondary spray-applied silica, to provide an impermeable jointless and/or fiberless mass of concrete. With a relatively low dosage (0.15-0.30% by weight of cement, for example), a polycarboxylate ether-based superplasticizer allows water reduction due to its chemical structure, which enables good particle dispersion. Polycarboxylate ether-based superplasticizers are composed of a methoxy-polyethylene glycol copolymer (side-chain) grafted with methacrylic acid copolymer (main-chain). The carboxylate group —COO—Na+ dissociates in water, providing a negative charge along the polycarboxylate ether-based superplasticizer backbone. The polycarboxylate ether-based superplasticizer backbone, which is negatively charged, permits the adsorption of the positively charged colloidal particles. As a consequence of PCE adsorption, the zeta potential of the suspended particles changes, due to the adsorption of the COO— groups on the colloid surface. This displacement of the polymer on the particle surface provides the side chains the opportunity to exert repulsion forces, which disperse the particles of the suspension and helps avoid friction.

[0070] A ninth exemplary embodiment provides a method of preparing a graphene and colloidal silica admixture comprising the step of adding graphite powder to a colloidal silica admixture, and either mechanically shearing the composite with a high-shear mixing device, and/or mechanically shearing the composite via probe sonication with an ultrasonic cavitation device, such that the resulting graphene are dispersed into the colloidal silica admixture. The resulting composite admixture may then be mixed into a concrete mixture as described herein.

[0071] FIG. 1 shows a perspective view of an exemplary jointless slab 1. The jointless slab 1 of FIG. 1 is shown placed in warehouse-type setting according to an exemplary embodiment. The jointless slab 1 is placed on top of a leveled and compacted substrate 3 and is for industrial and commercial applications in this exemplary embodiment. As a non-limiting example, applications that will be placed on or occur on top of the jointless slab 1 may involve automated facilities with laser-guided equipment moving on the jointless slab 1, where even the slightest imperfection can bring the whole facility to a stand-still. The jointless slab 1 is characterized by being virtually free of curling and cracking, and having superior abrasion-resistance.

[0072] The jointless slab 1 is illustrated in partial cut-away form to show layers of internal composition and structure of the composite material. The first cut-away section 10 illustrates the sub-surface, below the curing/to-be finished exterior 2. The sub-surface of the first cut-away section 10 is porous, unfinished and rough. The second cut-away section 20 illustrates the jointless slab 1 having a crack 22 to expose the internal composition of the composite material of the jointless slab 1. In particular, the jointless slab 1 comprises hardened aggregate and cement as well as one or more of steel fibers and macro synthetic fibers 24. However, in other exemplary embodiments, the jointless slab 1 may be made without such steel fibers and/or macro synthetic fibers. The hardened aggregate and cement, as well as steel fibers and macro synthetic fibers 24 if such fibers are included, at least in part define capillary structures 26 (best seen in FIG. 2) throughout the jointless slab 1. In an exemplary embodiment, capillary structures 26 (FIG. 2) are filled with reactive nanometer-sized silica that react with free lime to produce a stable gel structure of calcium silicate hydrate within the capillary structures 26. The concrete structure defining the capillary structures 26 is embedded with nanometer-sized graphene monolayers or overlapping graphene.

[0073] The jointless slab 1 is illustrated with an optional and exemplary spray-apply system 28. The system 28 may also be used for spray-applying a secondary colloidal silica 30 as described herein (see FIG. 4 and FIG. 6). The system 28 comprises an optional human operator 32 using an exemplary embodiment of a spraying machine 34. The system 28 optionally is used after a concrete slurry of the present invention is poured, trowel finished, and can be walked on by the human operator 32, without imprinting the surface of the hardening jointless slab 1. The system 28 optionally sprays the entire surface of the jointless slab 1 to saturation such that the nanometer-sized colloidal silica and the graphene in the secondary silica spray 30 can penetrate the capillary structures 26 and the surrounding concrete structure defining the capillary structures 26.

[0074] FIG. 2 is a magnified perspective view of the crack 22 along the second cut-away section 20 of the jointless slab 1 of FIG. 1. The magnified section of FIG. 1 illustrated in FIG. 2 shows a view of the intersection of the hardened aggregate and cement as well as steel fibers and macro synthetic fibers 24, if included, that at least in part define the capillary structures 26 of the jointless slab 1.

[0075] FIG. 3 is a flow diagram of a first illustrative method 100 according to an exemplary embodiment. The method 100 discloses steps, not all of which are necessarily employed in each and every situation, but which may have similarities to other exemplary embodiments provided herein. The steps in the method 100 may be performed in or out of the order shown. The method 100 comprises the steps of: (1) preparing a concrete slurry comprising i) a concrete mixture; ii) a graphene admixture; iii) a colloidal silica admixture; and iv) at least one fiber selected from a group consisting of fibers selected from steel fibers and synthetic fibers (102); (2) pouring the concrete slurry onto the substrate (104); and (3) allowing the concrete slurry to cure (106). This method 100 allows the capillary structures to develop as the concrete slab sets from the poured concrete slurry, allows the capillary structures of the slab to at least in part fill with silica and lime, allows the silica and lime to react to produce a gel structure of calcium silicate hydrate that at least partially fill, respectively, the capillary structures, and allows the concrete structure defining the capillary structures to be embedded with nanometer-sized graphene monolayers or overlapping graphene.

[0076] In some exemplary embodiments, the preparing step 102 of method 100 comprises: (1) preparing a graphene and colloidal silica composite admixture comprising the steps of (i) adding graphite powder to a prepared colloidal silica admixture, and (ii) mechanically shearing the combination with a high-shear mixing device such that the sheared graphite powder yields dispersed graphene into the colloidal silica admixture; and (2) preparing the concrete slurry with the colloidal silica and graphene composite admixture, which comprises silica having a size ranging from between about 10.0 nm to about 100.0 nm, or from between about 5.0 nm to about 100.0 nm, or from between about 3.0 nm to about 100.0 nm, and graphene having a size ranging from between about 1.10±0.20 nm of thickness with particle size of about 0.5 nm. In another exemplary embodiment, the preparing step 102 comprises providing a prepared colloidal silica admixture, and preparing a graphene admixture that is independent from the prepared colloidal silica admixture. The admixtures may then be independently, but not necessarily separately, used to prepare the concrete slurry. In another exemplary embodiment, the preparing step 102 comprises preparing the graphene and colloidal silica admixture(s) comprising the steps of adding graphite powder to an aqueous solution and mechanically shearing the graphite powder via probe sonication with an ultrasonic cavitation device such that graphene are dispersed into solution.

[0077] In another embodiment, the preparing step 102 additionally comprises adding the colloidal silica admixture to the concrete slurry in ranges of between about 0.50% to about 1.50% by weight of cement in the concrete mixture, wherein % by weight refers to the aggregate weight of the silica in comparison to the final weight of cement in the final concrete product. In another exemplary embodiment, the preparing step 102 comprises adding the graphene, via a composite admixture or an independent graphene admixture, to the concrete slurry in ranges of between about 0.01% to about 0.10% by weight of cement, wherein % by weight in this instance refers to the aggregate weight of the graphene in comparison to the final weight of cement in the final concrete product. In another embodiment, the preparing step 102 additionally comprises preparing the concrete slurry for pouring with dosages of steel fibers as the at least one fiber selected from a group of fibers of between about 33.0 lbs./cuyd to about 66.0 lbs./cuyd. In another embodiment, the preparing step 102 additionally comprises preparing the concrete admixture for pouring with dosages of macro synthetic fibers as the at least one fiber selected from a group of fibers of between about 3.0 lbs./cuyd to about 7.5 lbs./cuyd.

[0078] FIG. 4 is a flow diagram of a second illustrative method 200 according to an exemplary embodiment. Some of the steps of the method 200 are identical to the steps in the method 100 of FIG. 3; therefore, only the differences in the method 200 are detailed herein. The method 200 additionally comprises the step 108 of spray-applying a secondary colloidal silica onto the poured concrete slurry to facilitate curing thereof. The spray-applying step 108 comprises spray-applying the secondary colloidal silica onto the poured concrete slurry subsequent to removal of a trowel machine and prior to cement in the poured concrete slurry being completely set. The spray-applying step 108 may comprise in other embodiments spray-applying the poured concrete slurry with an amorphous secondary colloidal silica in an aqueous solution having silica with size ranging from about 10.0 nm to about 50.0 nm, or from about 3.0 nm to about 50.0 nm, wherein the colloidal solution has a particle weight that ranges from about 5.0 to 20.0%, and wherein the coverage rate is about 250 gallons of colloidal solution per square foot, or from about 100.0 to about 500.0 gallons per square foot. The spray-applying step 108 also may comprise spray-applying the secondary colloidal silica onto the poured concrete slurry subsequent to cement in the poured concrete slurry being completely set, and spray-applying to the point of saturation or “flooding state” as is known in the art.

[0079] In some exemplary embodiments, the step 108 of method 200 comprises spray-applying a graphene and colloidal silica composite admixture similar to the composite admixture defined herein for certain embodiments of step 102. In another exemplary embodiment, the step 108 of method 200 comprises spray-applying a prepared colloidal silica admixture and a graphene admixture prepared at the point-of-use and that is independent from the prepared colloidal silica admixture, those admixtures as defined herein for certain embodiments of step 102.

[0080] FIG. 5 is a flow diagram of a third illustrative method 300 according to an exemplary embodiment. In an exemplary embodiment the method 300 comprises the steps of: preparing a concrete slurry comprising i) a concrete mixture; ii) a graphene admixture; and iii) a colloidal silica admixture (202); pouring the concrete slurry onto the substrate (204); and allowing the concrete slurry to cure (206), such that capillary structures develop as the concrete slab sets from the poured concrete slurry, such that the capillary structures of the slab at least in part fill with silica and lime, such that the silica and lime react to produce a gel structure of calcium silicate hydrate that at least partially fill, respectively, the capillary structures, and such that the concrete structure defining the capillary structures is embedded with nanometer-sized graphene.

[0081] In some exemplary embodiments, similar to those described for FIG. 3 and FIG. 4, the preparing step 202 of method 200 comprises: (1) preparing a graphene and colloidal silica composite admixture comprising the steps of (i) adding graphite powder to a prepared colloidal silica admixture, and (ii) either mechanically shearing the combination with a high-shear mixing device, such that the dispersed graphene from the sheared graphite powder are dispersed into the colloidal silica admixture, and/or mechanically shearing the graphite powder via probe sonication with an ultrasonic cavitation device, such that dispersed graphene are dispersed into solution; and (2) preparing the concrete slurry with the colloidal silica and graphene composite admixture, which comprises silica having a size ranging from between about 10.0 nm to about 100.0 nm, or from between about 5.0 nm to about 100.0 nm, or from between about 3.0 nm to about 100.0 nm, and graphene having a size ranging from between about 1.10+/−0.20 nm of thickness with particle size of about 0.5 nm. In another exemplary embodiment, the preparing step 202 comprises providing a prepared colloidal silica admixture, and preparing a graphene admixture that is independent from the prepared colloidal silica admixture. The admixtures may then be independently, but not necessarily separately, used to prepare the concrete slurry.

[0082] In another embodiment, the preparing step 202 additionally comprises adding the colloidal silica admixture to the concrete slurry in ranges of between about 0.50% to about 10.0% by weight of cement in the concrete mixture. In another exemplary embodiment, the preparing step 202 comprises adding the graphene, via a composite admixture or an independent graphene admixture, to the concrete slurry in ranges of between about 0.01% to about 0.10% by weight of cement.

[0083] FIG. 6 is a flow diagram of a fourth illustrative method 400 according to an exemplary embodiment. Some of the steps of the method 400 are identical to steps in the method 300 of FIG. 5; therefore, only the differences in the method 400 are detailed herein. The method 400 additionally comprises the step 208 of spray-applying a secondary colloidal silica onto the poured concrete slurry to facilitate curing thereof. The spray-applying step 208 comprises spray-applying the secondary colloidal silica onto the poured concrete slurry subsequent to removal of a trowel machine and prior to cement in the poured concrete slurry being completely set. The spray-applying step 208 comprises spray-applying the poured concrete slurry with an amorphous secondary colloidal silica in an aqueous solution having silica with size ranging from about 10.0 nm to about 50.0 nm, or from about 3.0 nm to about 50.0 nm, or from about 3.0 nm to about 25.0 nm, or from about 3.0 nm to about 100.0 nm. The spray-applying step 208 comprises spray-applying the secondary colloidal silica onto the poured concrete slurry subsequent to cement in the poured concrete slurry being completely set.

[0084] In some exemplary embodiments, the step 208 of method 400 comprises spray-applying a graphene and colloidal silica composite admixture similar to the composite admixture defined herein for certain embodiments of step 202. In another exemplary embodiment, the step 208 of method 200 comprises spray-applying a prepared colloidal silica admixture and a graphene admixture prepared at the point-of-use and that is independent from the prepared colloidal silica admixture, those admixtures as defined herein for certain embodiments of step 202.

[0085] FIG. 7 shows a perspective view of an exemplary jointless and fiberless slab 500. The jointless and fiberless slab 500 is similar to the jointless slab 1 of FIG. 1; therefore, only the differences in the jointless and fiberless slab 500 are detailed herein.

[0086] The jointless and fiberless slab 500 is illustrated in partial cut-away form to show layers of internal composition and structure of the composite material. The second cut-away section 20 illustrates the jointless and fiberless slab 500 having a crack 22 to expose the internal composition of the composite material of the jointless and fiberless slab 500. In particular, the jointless and fiberless slab 500 comprises hardened aggregate and cement 524 without steel fibers and/or macro synthetic fibers. The hardened aggregate and cement 524 at least in part define capillary structures 26 (FIG. 2) throughout the jointless and fiberless slab 500, and the capillary structures 26 (FIG. 2) are filled with reactive nanometer-sized silica that react with free lime to produce a stable gel structure of calcium silicate hydrate within the capillary structures 26 (FIG. 2). The hardened aggregate and cement 524 defining the capillary structures 26 is embedded with nanometer-sized graphene. An optional spray-apply system 28 may be used for spray-applying a secondary colloidal silica and dispersed graphene composite 30 on the entire surface of the jointless and fiberless slab 500, and/or spray-applying a first application of a graphene variety not otherwise already used in the concrete, to saturation such that the nanometer-sized colloidal silica in the secondary spray 30 can penetrate and complete the fill of the capillary structures 26, and such that the graphene can be dispersed to embed along and partially fill the capillary structures 26 throughout the hardened aggregate and cement 524.

[0087] A wide variety of materials are available for the various parts discussed and illustrated herein. Although the device has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.