Method For Making Concrete Admixtures Containing Carbon Nanoparticles

Abstract

A method for making an admixture for concrete includes the steps of providing a carbon nanomaterial comprised of carbon nanoparticles and wetting and dispersing the carbon nanomaterial in a liquid organic solvent/compound mixture comprised of amine based compounds configured to de-agglomerate and uniformly disperse the carbon nanoparticles. The method also includes the step of selecting the organic/solvent compound mixture to perform the wetting and dispersing step and to also perform at least one additional function in a particular type of concrete. An admixture for making concrete comprises a suspension of uniformly dispersed carbon nanoparticles having a predetermined percentage range by mass of the admixture in an organic solvent/compound mixture comprising an amine based compound having a predetermined percentage range by mass of the organic solvent/compound mixture.

Claims

1. A method for making an admixture for concrete comprising: providing a carbon nanomaterial comprised of carbon nanoparticles having a predetermined percentage range by mass of the admixture; wetting and dispersing the carbon nanomaterial in a liquid organic solvent/compound mixture comprised of amine based compounds configured to de-agglomerate and uniformly disperse the carbon nanoparticles; and selecting the organic/solvent compound mixture to perform the wetting and dispersing step and to perform at least one additional function in a particular type of concrete.

2. The method of claim 1 wherein the wetting and dispersing step is performed without liquid water.

3. The method of claim 1 further comprising adding water to the organic/solvent compounds mixture after the wetting and dispersing step.

4. The method of claim 1 wherein the organic solvent/compound mixture comprises alkanolamines.

5. The method of claim 1 wherein the organic solvent/compound mixture comprises compounds selected from the group consisting of mono-ethanolamine, di-ethanolamine, tri-ethanolamine, tri-isopropanolamine, N-methyldiethanolamine, diethanolisopropanolamine (DEIPA), ethyldiisopropylamine (EDIPA), N,N,N,N-tetrakis-(2-hydroxyethyl)-ethylenediamine (THEED) and N,N,N,N-tetrakis-(2-hydroxypropyl)-ethylenediamine (THPE/EDTP).

6. The method of claim 1 further comprising mixing the admixture with a cementitious material.

7. The method of claim 6 wherein the at least a portion of the cementitious material comprises a pozzolan material

8. The method of claim 7 wherein the pozzolan material comprises a material selected from the group consisting of slag, fly ash and micro silica.

9. The method of claim 1 wherein the carbon nanoparticles comprise particles selected from the group consisting of carbon nanotube particles, carbon nanofiber particles, graphene particles, graphite particles, carbon black, polycrystalline carbon particles, nanodiamonds, and single-layer or multi-layer fullerene particles.

10. An admixture for making concrete comprising: a suspension of uniformly dispersed carbon nanoparticles having a predetermined percentage range by mass of the admixture in an organic solvent/compound mixture comprising an amine based compound having a predetermined percentage range by mass of the organic solvent/compound mixture, the amine based compound selected to uniformly disperse the carbon nanoparticles and to perform at least one additional function in a particular type of concrete.

11. The admixture of claim 10 wherein the amine based compound comprises an alkanolamine.

12. The admixture of claim 10 wherein the amine based compound comprises a compound selected from the group consisting of mono-ethanolamine, di-ethanolamine, tri-ethanolamine, tri-isopropanolamine, N-methyldiethanolamine, diethanolisopropanolamine (DEIPA), ethyldiisopropylamine (EDIPA), N,N,N,N-tetrakis-(2-hydroxyethyl)-ethylenediamine (THEED) and N,N,N,N-tetrakis-(2-hydroxypropyl)-ethylenediamine (THPE/EDTP).

13. The admixture of claim 10 wherein the particular type of concrete comprises a pozzolan material.

14. The admixture of claim 10 further comprising a concrete accelerator mixed with the organic solvent/compound mixture.

15. The admixture of claim 14 wherein the concrete accelerator comprises a metallic salt.

16. The admixture of claim 15 wherein the metallic salt comprise a compound selected from the group consisting of NaSCN, NaNO2, Ca(NO2)2, NaNO3, Ca(NO3)2 and combinations thereof.

17. The admixture of claim 10 further comprising a concrete hydration stabilizer mixed with the organic solvent/compound mixture.

18. The admixture of claim 17 wherein the concrete hydration stabilizer comprises a mono-di- and/or tri-phosphonate or mono- di- and/or tri phosphonic acid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Exemplary embodiments are illustrated in the referenced figures of the drawings. It is intended that the embodiments and the figures disclosed herein be considered illustrative rather than limiting.

[0010] FIG. 1 is a flow diagram illustrating steps in a method for making an admixture for concrete; and

[0011] FIG. 2 is a graph showing depth of abrasion vs. time for Holcim I/II straight cement in reference and mixes with admixture #3 or #9 at dosages of 0.1 w/w % and 0.3 w/w %.

DETAILED DESCRIPTION

[0012] As used herein, the term admixture means ingredients added to concrete before or during mixing. U.S. Pat. No. 10,584,072, which is incorporated herein by reference, discloses admixtures containing carbon nanoparticles for making concrete. These admixtures are sometimes referred to in this disclosure as EDENCRETE. The term amine means a class of organic compounds of nitrogen that may be considered as derived from ammonia (NH3) by replacing one or more of the hydrogen atoms with alkyl groups or functionalized alkyl groups, for example hydroxyalkyl groups.

[0013] The term concrete means a material in either a cured or an uncured state that includes cement (with or without supplementary cementing materials, such as blast furnace slag, fly ash, limestone fines, and silica fume), mineral aggregate sand and stones, and water. The term cement means hydratable cement such as Portland cement produced from clinker containing hydraulic calcium silicates. The term cementitious means materials that form a plastic paste when mixed with a liquid, which harden and function as a glue or binder for holding the composite concrete material together. Cementitious materials form a hard matrix to bind aggregates and contribute to the properties of hardened concrete through hydraulic or pozzolanic activity. While Portland cement is a common concrete matrix material, alternative examples include, but not limited to, various limes and mortars, fly ashes, ground blast-furnace slag, and silica fume. The term plasticizer means a surfactant used to uniformly disperse particles in uncured concrete.

[0014] The term carbon nanoparticle means a particle comprising an allotrope of carbon with one or more particle dimensions on the order of 1000 nanometers (nm) or less. The term carbon nanomaterial means a mixture containing carbon nanoparticle. Nanotubes mean cylindrical nanostructures comprising one or more cylindrical tubes of atoms having a high length to diameter ratio. Nanotubes can be categorized as single-walled nanotubes (SWNTs) or multi-walled nanotubes (MWNTs). Nanotube particles comprise individual molecules, particles, or agglomerates of particles comprised of nanotubes. Nanofibers means cylindrical nanostructures with a high length to diameter ratio, with atomic layers in a stacked plate, cup, or cone configuration. Nanofiber particles comprise individual molecules, particles, or agglomerates of particles comprised of nanofibers. Graphene means small particles of a two-dimensional hexagonal lattice of sp.sup.2 hybridized carbon atoms. Graphene is the basic structure of many other allotropes of carbon, including carbon nanotubes, carbon nanofibers, graphite, and other fullerenes. Graphite means a carbon crystalline atomic structure comprised of layers of graphene. Carbon black means a fine powder comprised of nanometer scale particles and agglomerates with an amorphous paracrystalline or polycrystalline atomic structure, usually made from decomposition and incomplete combustion of hydrocarbon feedstocks, but for the purposes of this disclosure, carbon black also includes finely-ground charcoal, coal, or activated carbon materials. Nanodiamonds means nanometer scale particles of a carbon allotrope with diamond crystal atomic structure. Fullerene means molecules or particles comprised of graphitic crystalline structures with defects in the hexagonal atomic lattice that bend or curve the layer(s) into spheres (onions), buds, cones, horns, tubes, or other composite shapes built from sub-structures with these simpler forms. Nano-silica means silica material with one or more particle dimensions on the order of 500 nanometers (nm) or less.

[0015] Providing A Carbon Nanomaterial Comprised Of Carbon Nanoparticles. The carbon nanomaterial can be produced using a heated reactor and catalytic decomposition of a hydrocarbon feed gas. For performing the production process, a catalyst and reaction conditions in the reactor are selected to provide different types of carbon nanoparticles in selected mass percentage ranges. For example, the reaction conditions and the catalyst can be selected and controlled such that the carbon nanomaterial includes at least two different types of carbon nanoparticles as described above.

[0016] Rather than being produced in a heated reactor, the carbon nanomaterial can be provided as a desired composition of carbon nanoparticles. For example, certain carbon nanomaterials are mass produced and commercially available in industrial commodity markets from a producer. With either production or commercial purchase of the carbon nanomaterial, different types of carbon nanoparticles produced from different processes can be blended or mixed together to provide a particular carbon nanomaterial having desired characteristics, such as desired mass percentage ranges of the different carbon nanoparticles. The step of providing the carbon nanomaterial can also include the step of crushing or grinding the carbon nanomaterial into a powder configured for uniform dispersion in a liquid. This process can be performed using a suitable mechanical crushing or grinding apparatus.

[0017] Wetting And Dispersing The Carbon Nanomaterial In A Liquid Organic Solvent/Compound Mixture Comprised Of An Amine Based Compound. For example, the amine based compound can comprise an alkanolamine, such as a compound selected from the group consisting of mono-ethanolamine, di-ethanolamine, tri-ethanolamine, tri-isopropanolamine, N-methyldiethanolamine, diethanolisopropanolamine (DEIPA), ethyldiisopropylamine (EDIPA), N,N,N,N-tetrakis-(2-hydroxyethyl)-ethylenediamine (THEED) and N,N,N,N-tetrakis-(2-hydroxypropyl)-ethylenediamine (THPE/EDTP).

[0018] Selecting The Organic/Solvent Compound Mixture To Perform The Wetting And Dispersing Step And To Also Perform At Least One Additional Function In A Particular Type Of Concrete. One feature of the present method is that the organic compounds are selected such that they have beneficial effects for the concrete making process or end product. Characteristics that can be controlled by selection of the organic/solvent compound include wet properties, curing time and process and/or properties of the resulting concrete.

[0019] As an example, the inventors have been working with a group of compounds, which by themselves give increased compressive strength, this group of compounds are amine based and have been used for a number of applications in concrete chemistry; for example as cement clinker grinding aids, accelerators, retarders etc. By combining these functionalities with the possibility of dispersing a large amount of carbon nanomaterial in a low volume of an organic compound, allows us to achieve huge benefits to the concrete mix at very low dosages.

[0020] Exemplary amine based compounds can be from the group of alkanolamines and can include; mono-ethanolamine, di-ethanolamine, tri-ethanolamine, tri-isopropanolamine, N-methyldiethanolamine, Diethanolisopropanolamine (DEIPA), ethyldiisopropylamine (EDIPA), N,N,N,N-tetrakis-(2-hydroxyethyl)-ethylenediamine (THEED) and N,N,N,N-tetrakis-(2-hydroxypropyl)-ethylenediamine (THPE/EDTP) etc.

[0021] Using the method unexpected results in the form of large benefits from the combination of carbon nanomaterial with the alkanolamines, much larger than what could be expected based on the effect from each of the components on their own. Also, using the method some of the restrictions and drawbacks from using alkanolamines are reduced or eliminated by the presence of carbon nanomaterial. The inventor theorizes that this is due to all of the components being in a more activated state as they support each other in the admixture.

[0022] The efficiency of an organic solvent/compound to disperse carbon nanomaterial allows a significant increase in the loading of carbon in the admixtures and hence drastically reduces the dosage volume needed for concrete applications. For admixtures produced using the method, we are typically working in a dosage range of 2 to 64 oz per yard of concrete, equal to 1/64 to gallon per yard.

[0023] The admixture can also include a concrete accelerator mixed with the organic solvent/compound mixture. For example, the concrete accelerator can be selected from the group of known inorganic concrete accelerators such as; NaSCN, NaNO.sub.2, Ca(NO.sub.2).sub.2, NaNO.sub.3, Ca(NO.sub.3).sub.2, CaCl.sub.2), and combinations thereof.

[0024] In addition, the admixtures can also include or be based on a plasticizer. For example, polycarboxylate based plasticizers will assist in the dispersion of carbon nanomaterial and can assist in adjusting the wet properties of the concrete if desired, or if the carbon nanomaterial and alkanolamines changes these properties significantly.

[0025] Also with respect to the selecting step, the components of the admixture can be tailored for a particular type of concrete. For example, an amine can be chosen to specifically add reactively to a specific portion of the cementitious material of a mix design, this could for example specifically be the pozzolanic material included in a mix design. Typically, the pozzolans are a part of a concrete mix design, where they constitute a certain percentage of the cementitious material with the rest typically being a cement, typically an OPC (ordinary Portland cement),

[0026] Example. An object of the present method is to enrich a cement composition with high levels of carbon nanomaterial to give superior mechanical properties, specifically compressive, flexural and split tensile strengths relative to the prior art, but also enhancing secondary effects such as abrasion resistance, shrinkage reduction and reduced permeability. This is done by firstly producing high concentration carbon nanomaterial enriched amine-based cement admixtures and secondly adding these to mortar or concrete mixes during batching to enhance the properties of the resulting hardened mortar or concrete material.

[0027] Method of Preparing Cement Admixture

[0028] Cement Admixture According to the Present Method (1). 226 g of commercial grade 99% Triethanolamine was charged into a 500 ml glass beaker. 0.05 to 10 grams of dry Carbon Nanomaterial powder was charged into said glass beaker and mechanically agitated such that all the powder has been wetted by the Triethanolamine (TEA). While under mechanical mixing 0 to 40 grams of water is added to the TEA/CNT mixture until a homogenous black liquid is obtained.

[0029] Cement Admixture According to the Present Method (2). A cement admixture was prepared using the same method as cement Admixture According to the Present Method (1), except that 99% N-Methyldiethanolamine (MDEA) was used in place of Triethanolamine.

[0030] Cement Admixture According to the Present Method (3). A cement admixture was prepared using the same method as cement Admixture According to the Present Method (1), except that technical grade N,N,N,N-Tetrakis(2-hydroxyethyl)ethylenediamine (THEED) was used in place of Triethanolamine.

[0031] Cement Admixture According to the Present Method (4). A cement admixture was prepared using the same method as cement Admixture According to the Present Method (1), except that commercially available N,N,N,N-Tetrakis(2-hydroxyethyl)ethylenediamine (THEED) was used in place of 50% of the Triethanolamine, effectively producing a 1:1 mixture of the two amines. Carbon Nanomaterial was added to this mixture and stirred. Water can be added during the final mechanical mixing step to adjust viscosity.

[0032] Cement Admixture According to the Present Method (5). 226 g of commercial grade 99% diisopropanolamine was heated to 70 C in a 1 L glass beaker until a liquid was obtained. 5 to 35 g of water and mixed in said 1 L glass beaker order to obtain a liquid that is stable at standard temperatures and pressures. 0.01 to 10 g of dry Carbon Nanomaterial powder was charged into the glass beaker and mechanically agitated such that all the CNT powder has been wetted by the DIPA solution and mixed further until a homogenous black liquid is obtained.

[0033] Cement Admixture According to the Present Method (6). A cement admixture was prepared using the same method as cement Admixture According to the Present Method (5), except that 99% Triisopropanolamine (TIPA) was used in place of DIPA.

[0034] Cement Admixture According to the Present Method (7). A cement admixture was prepared using the same method as cement Admixture According to the Present Method (1), but with a metallic salt dissolved in the water fraction added during the final part of the mix sequence. The metallic salt can for example be a thiocyanate salt, such as NaSCN, a nitrit salt, such as NaNO.sub.2 or Ca(NO.sub.2).sub.2, or a nitrate salt, such as NaNO.sub.3 or Ca(NO.sub.3).sub.2 or combinations of these.

[0035] Cement Admixture According to the Present Method (8). A cement admixture was prepared using the same method as cement Admixture According to the Present Method (1), but with Aminotris(methylenephosphonic acid) (ATMP) dissolved in the water fraction added during the final part of the mix sequence. Other mono- di- and/or tri-phosphonate or mono- di- and/or tri phosphonic acid can also be used.

[0036] Cement Admixture According to the Present Method (9). A cement admixture was prepared using the same method as cement Admixture According to the Present Method (6), except that triethanolamine (TEA) was added to the liquid in the final steps of the process at a concentration of of 0.5% to 10% of the Triisopropanolamine (TIPA).

[0037] Examples of Effect of Admixtures in Hardened Concrete

[0038] Example 1: Strength enhancement in a 650 lb/cy 60% slag mix with Admixture #1 at dosages of 16, 24, 36 and 48 oz/cy.

TABLE-US-00001 Pz Compressive Breaks EdenCrete Dose 1-day vs ref 7-day vs ref 28-day vs ref 56-day vs ref Trial Name oz/cy ave % ave % ave % ave % 650 C 60% Reference 0 5767 0.0% 9817 0.0% 10710 0.0% Slag Pz 650 C 60% EC Pz #1 16 oz 6240 7.6% 10510 7.1% 11623 8.5% Slag Pz 650 C 60% EC Pz #1 24 oz 6513 12.4% 10513 7.1% 12183 13.8% Slag Pz 650 C 60% EC Pz #1 36 oz 6723 16.0% 11460 16.7% 12670 18.3% Slag Pz 650 C 60% EC Pz #1 48 oz 6547 12.9% 11617 18.3% 12677 18.4% Slag Pz

[0039] Example 2: Strength enhancement in a 650 lb/cy straight cement mix with Admixture #1 at dosages of 8, 16, 24 and 32 oz/cy.

TABLE-US-00002 Pz Compressive Breaks EdenCrete Dose 1-day vs ref 7-day vs ref 28-day vs ref Trial Name oz/cy ave % ave % ave % 650 C NY cem Reference 0 6843 0.0% 8103 0.0% 650 C NY cem EC Pz #1 8 oz 7127 4.2% 8587 6.0% 650 C NY cem EC Pz #1 16 oz 7153 4.5% 8640 6.6% 650 C NY cem EC Pz #1 24 oz 7563 10.5% 9220 13.8% 650 C NY cem EC Pz #1 32 oz 7453 8.9% 9093 12.2%

[0040] Example 3: Strength enhancement in a 750 lb/cy ternary mix (OPC+slag+fly ash) with Admixture #1 and #8 at dosages of 20, 24, 30 and 32 oz/cy.

TABLE-US-00003 Pz Compressive Breaks EdenCrete Dose 1-day vs ref 7-day vs ref 28-day vs ref 56-day vs ref Trial Name oz/cy ave % ave % ave % ave % Tri-Mix Ref 0 7363 0.0% 9133 0.0% 10143 0.0% 750 C Tri-Mix EC Pz #1 20 oz 7807 6.0% 10603 16.1% 11383 12.2% 750 C Tri-Mix EC Pz #1 24 oz 7900 7.3% 10503 15.0% 11667 15.0% 750 C Tri-Mix EC Pz #1 30 oz 8520 15.7% 11623 27.3% 12450 22.7% 750 C Tri-Mix EC Pz #8 32 oz 8090 9.9% 11120 21.8% 11923 17.5% 750 C

[0041] Example 4: Strength enhancement in a 850 lb/cy 20% class C fly ash mix with Admixture #1, #3 and #4 all at a dosage of 23 oz/cy.

TABLE-US-00004 Pz Compressive Breaks EdenCrete Dose 4-day vs ref 7-day vs ref Trial Name oz/cy ave % ave % CO 850C 20% Reference 0 6329 0.0% 6731 0.0% dass C FA CO 850C 20% EC Pz #3 23 7596 20.0% 7878 17.0% class C FA CO 850C 20% EC Pz #4 23 5915 6.5% 6310 6.3% Class C FA CO 850C 20% EC Pz #1 23 6707 6.0% 7291 8.3% class C FA

[0042] Example 5: Abrasion resistance in a straight Portland, Holcim I/II, Colorado mix design with Admixture #3 and #9 at low dosage, 0.1 w/w %, and high dosage, 0.3 w/w %. FIG. 2 illustrates the results.

[0043] Example 6: Results of abrasion resistance studies for six concrete mix designs of different Portland types with and without fly ash (including Example 5 from above). Presented in table I and II are abrasion resistance quantified using two metrics, wear rate and depth of abrasion at 20 minutes. Both methods tended to yield similar trending results. Table I and II summarize both the wear rate and depth of abrasion at 20 minutes (the elective termination of the test).

TABLE-US-00005 TABLE I Wear Rate Improvement EC Pz #3 EC Pz #3 EC Pz #9 EC Pz #9 0.1 w/w % 0.3 w/w % 0.1 w/w % 0.3 w/w % Devil's Slide Bridger 40% 60% 44% 50% F-ash Laramie PS F-Ash 25% 17% 19% 46% Sugar Creek PS F-Ash 35% 40% 37% 34% Holcim I/II PS F-Ash 47% 44% 54% 60% Holcim I/II 32% 42% 41% 48% Holcim I/II NE Plaines 35% 37% 45% 34% C-Ash

TABLE-US-00006 TABLE II Depth of Wear Improvement EC Pz #3 EC Pz #3 EC Pz #9 EC Pz #9 0.1 w/w % 0.3 w/w % 0.1 w/w % 0.3 w/w % Devil's Slide Bridger 31% 48% 28% 36% F-ash Laramie PS F-Ash 25% 22% 28% 39% Sugar Creek PS F-Ash 26% 33% 29% 24% Holcim I/II PS F-Ash 41% 43% 46% 55% Holcim I/II 21% 23% 32% 31% Holcim I/II NE Plaines 33% 32% 45% 26% C-Ash

[0044] While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and subcombinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.