Method of producing nanoconcrete with high-energy mixing

Abstract

In a method of producing nanoconcrete according the bottom-up approach of nano technology with the High-Energy Mixing of composition including cement, water, sand, additives and superplasticizers, the mixing is performed with flow of mixture characterized by Reynolds number and Power number in the range of 20-800 and 0.1-4.0 respectively with installation a disk horizontally into mixing assembly on the top layer of activated mixture coaxially with vertical axis of assembly and with the axis of impeller rotation on the adjustable level to avoid destroying created gel as a result of interruptions of process, to increase laminarity of the mixture flow, energy absorption by the mixture, and shear stress for creation additional quantity of the nanostructured Calcium Silicate Hydrate (C-S-H) gel necessary for making nanoconcrete.

Claims

1. A method of producing nanoconcrete comprising: providing a mixing container and an impeller; filling the container with cement and water; installing a disk horizontally with respect to a direction of gravity and coaxially with respect to an axis of rotation of the impeller into the mixing container above the impeller and/or above the cement and water; and rotating the impeller to perform High-Energy Mixing (HEM) with the cement and water such that a mixture flow is characterized by dimensionless Reynolds number and Power number in the range of 20-800 and 0.1-4.0 respectively, wherein the impeller forces a bottom of the mixture up to a top of the mixture during the High-Energy Mixing (HEM), wherein the High-Energy Mixing (HEM) creates nanostructured Calcium Silicate Hydrate (C-S-H) gel, and wherein the disk prevents the created gel from being destroyed from interruptions in the High-Energy Mixing (HEM) and increases an amount of the gel that is created by increasing laminarity of the mixture flow, said increase in laminarity causing an increase in the mixture's energy absorption and shear stress.

2. The method of claim 1, wherein the filling of the container also comprises filling the container with sand, superplasticiser, and shrinkage compensating additives.

3. The method of claim 1, wherein the disk has an opening at a center of the disk for a part of the mixture that goes near and/or onto a top of the disk during the High-Energy Mixing (HEM) to circulate back down, and wherein the disk is fabricated from flexible material or a metal lattice.

4. The method of claim 1, wherein a height of the disk inside of the container is adjustable.

5. The method of claim 1, further comprising: providing measuring devices to measure the temperature of the mixture and power consumption and the rotational speed of the impeller; measuring the power consumption and the rotational speed of the impeller when the container is empty; measuring the power consumption and the rotational speed of the impeller during the High-Energy Mixing (HEM); and calculating the dimensionless Reynolds number and Power number from the measured power consumptions and the rotational speeds of the impeller along with the mixture's density and geometrical parameters, wherein the container, impeller, and disk are part of a small scale working prototype, and wherein the calculated Reynolds number and Power number can be used to scale up to a production scale.

6. A method of producing multiple batches of nanoconcrete comprising: creating a first batch of nanoconcrete according to the method of claim 1; and creating a second batch of nanoconcrete, wherein a volume of the mixture used to create the first batch of nanoconcrete is different than a volume of the mixture used to create the second batch of nanoconcrete, wherein average values of gross and net specific power, Reynolds number, and Power number are the same during the creating of the first batch and the creating of the second batch, and wherein geometric parameters are proportionally changed between the creating of the first batch and the creating of the second batch.

7. The method of claim 6, wherein the same container is used in the creating of the first and second batch, wherein the changing of the geometric parameters include moving the disk and the impeller up or down according to a level of the mixture, and wherein the average values of the gross and net specific power, Reynolds number, and Power number are kept the same by adjusting a power provided to the impeller during the High-Energy Mixing (HEM).

Description

BRIEF DESCRIPTION OF DRAWINGS AND TABLE

(1) FIG. 1 High-Energy Mixing with and without movable disk.

(2) ACirculation of mixture in the High-Energy Mixer with cover and without movable disk,

(3) BHigh-Energy Mixer equipped with movable disk located horizontally and having the central hole. Disk made of flexible material or of metal lattice. The handles attached to disk for installing it at the top layer of activated mixture.

(4) CCirculation of mixture with disk made of flexible material.

(5) DCirculation of mixture with disk made of metal lattice.

(6) HTop of mixture before impeller rotation, L and D.sub.sheight and diameter of cylindrical surface formed when the impeller rotates, D.sub.cdiameter of container.

(7) FIG. 2 Re number change in High-Energy Mixing without movable disk (test 1, variant #23A*), *The number of variant in the laboratory journal and Excel file Working with Olson's effect is shown.

(8) Cement:Sand:Water=1:0.00:0.37.

(9) Characteristics of process: quantity of interruptions0, coefficient of power absorption by the mixture 0.516, Re average 826, Power number average 0.18, Rpm average 2889 (Rpm for empty activator 3066), absorption of the specific energy by the mixture E=50.6 K j/kg, average Shear stress 1709 N/m.sup.2, self heating of the mixture as a result of mechanical activation t=21 C. during 288 sec. of activation.

(10) FIG. 3 Re number change in High-Energy Mixing with movable disk of flexible material (test 1, variant 23),

(11) Cement:Sand:Water=1:0.00:0.37.

(12) Characteristics of process: quantity of interruptions0, coefficient of power absorption by the mixture 0.580, Re average 668, Power number average 0.137, Rpm average 2849 (Rpm for empty activator 3066), absorption of the specific energy by the mixture E=55.3 K j/kg, average Shear stress 2370 N/m.sup.2, self heating of the mixture as a result of mechanical activation t=20 C. during 243 sec. of activation.

(13) FIG. 4 Penetration resistance development at temperature 15 C. (test 1),

(14) Cement:Sand:Water=1:0.00:0.37.

(15) Activation: 1HEM with disk made of flexible material (K c-s-h=3.63), 2HEM without disk (K c-s-h=1.74). K c-s-h is relation between areas of graphs for activated variant and control variant, made with conventional mixing3.

(16) FIG. 5 Re number change in High-Energy Mixing without movable disk (test 2, variant #38A),

(17) Cement:Sand:Water=1:0.00:0.37.

(18) Characteristics of process: quantity of interruptions0, coefficient of power absorption by the mixture 0.561, Re average 424, Power number average 0.42, Rpm average 2730 (Rpm for empty activator 3060), absorption of the specific energy by the mixture E=82.9 K j/kg, average Shear stress 4119 N/m.sup.2, self heating of the mixture as a result of mechanical activation t=22 C. during 352 sec. of activation.

(19) FIG. 6 Re number change in High-Energy Mixing with movable disk of metal lattice (test 2, variant #38), Cement:Sand:Water=1:0.00:0.37.

(20) Characteristics of process: quantity of interruptions0, coefficient of power absorption by the mixture 0.605, Re average 276, Power number average 0.55, Rpm average 2654 (Rpm for empty activator 3060), absorption of the specific energy by the mixture E=86.7 K j/kg, average Shear stress 6395 N/m.sup.2, self heating of the mixture as a result of mechanical activation t=22 C. during 307 sec. of activation.

(21) FIG. 7 Penetration resistance development at temperature 15 C. (test 2),

(22) Cement:Sand:Water=1:0.00:0.37.

(23) Activation: 1HEM with disk made of metal lattice (K c-s-h=2.25), 2HEM without disk (K c-s-h=1.22). K c-s-h is relation between areas of graphs for activated variant and control variant, made with conventional mixing3.

(24) FIG. 8 Re number change in High Energy Mixing without flexible disk (test 3, variant #34DA), Cement:Sand:Water=1:0.64:0.37.

(25) Characteristics of process: quantity of interruptions 10, coefficient of power absorption by the mixture0.485, Re average 447, Power number average 0.39, Rpm average 2260 (Rpm for empty activator 2387), absorption of the specific energy by the mixture E=50.9 K j/kg, average Shear stress 3002 N/m.sup.2, self heating of the mixture as a result of energy absorption t=25 C. during 350 sec. of activation.

(26) FIG. 9 Re number change in High-Energy Mixing with flexible disk (test 3, variant 34D), Cement:Sand:Water=1:0.64:0.37.

(27) Characteristics of the process: quantity of interruptions 0, coefficient of power absorption 0.60, Re average 178.7, Power number average 0.792, Rpm average 2151 (Rpm for empty activator 2387), absorption of the specific energy by the mixture 63.46 Kj/kg, average Shear stress 5389 N/m.sup.2, self heating of the mixture as a result of energy absorption t=25 C. during 275 sec. of activation.

(28) FIG. 10 Penetration resistance development at temperature 15 C. (test 3),

(29) Cement:Sand:Water=1:0.64:0.37.

(30) Activation: 1HEM with disk made of flexible material (K c-s-h=4.2), 2HEM without flexible disk (K c-s-h=2.80). K c-s-h is relation between areas of graphs for activated variant and control variant, made with conventional mixing3.

(31) FIG. 11 Re number change in High-Energy Mixing without metal lattice disk (test 4 variant #37A),

(32) Cement:Sand:Water=1:0.64:0.37.

(33) Characteristics of process: quantity of interruptions9, coefficient of power absorption by the mixture 0.460, Re average 433, Power number average 0.28, absorption of the specific energy by the mixture E=48 K j/kg., Rpm average 2262 (Rpm for empty activator 2385), average Shear stress 2643 N/m.sup.2, self heating of the mixture as a result of energy absorption t=25 C. during 379 sec. of activation.

(34) FIG. 12 Re number change in High-Energy Mixing with metal lattice disk (test 4, variant #37),

(35) Cement:Sand:Water=1:0.64:0.37.

(36) Characteristics of process: quantity of interruptions0, coefficient of power absorption by the mixture 0.577, Re average 197, Power number average 0.468, Rpm average 2211 (Rpm in empty activator 2387), absorption of the specific energy E=56.57 K j/kg, average Shear stress 4204 N/m.sup.2, self heating of the mixture as a result of energy absorption t=25 C. during 282 sec. of activation.

(37) FIG. 13 Penetration resistance development at temperature 15 C. (test 4)

(38) Cement:Sand:Water=1:0.64:0.37.

(39) Activation: 1HEM with disc made of grid bars (K c-s-h=8.5), 2HEM without disk, (K c-s-h=4.4). K c-s-h is relation between areas of graphs for activated variant and for the control variant made with conventional mixing3.

(40) TABLE-US-00001 TABLE 1 Improvement of technical parameters of the High-Energy mixing (HEM) process and C-S-H gel increase with introducing of the movable disk in mixing assembly. The main indexes of High-Energy Mixing Specific Average Test Cement/ Quantity Coefficient Energy Shear #, Sand/ Of Re of Power Absorption Stress, K FIG. Water ratio disk interruptions average absorption KJ/kg N/m.sup.2 c-s-h 1, 1:0.0:0.37 No 0 826 0.516 50.6 1709 1.74 FIG. 2 disk 1, 1:0.0:0.37 With 0 668 0.580 55.3 2370 3.63 FIG. 3 flexible disk 2, 1:0.0:0.37 No 0 424 0.561 82.9 4119 1.22 FIG. 5 disk 2, 1:0.0:0.37 Disk 0 276 0.605 86.7 6395 2.25 FIG. 6 Of Metal lattice 3, 1:0.64:0.37 No 10 447 0.485 50.9 3002 2.8 FIG. 8 disk 3, 1:0.64:0.37 With 0 178.7 0.60 63.46 5389 4.2 FIG. 9 Flexible disk 4, 1:0.64:0.37 No 9 433 0.46 48.0 2643 4.4 FIG. 11 disk 4, 1:0.64:0.37 Disk 0 197 0.577 56.57 4204 8.5 FIG. 12 Of Metal lattice

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(41) According to the present invention, a method for producing nanoconcrete in compliance with the bottom-up approach of nano technology, based on a high-energy mixing of a composition consisting of cement and water, mixing is performed with a mixture flow characterized by dimensionless criteria Reynolds number and Power number in the range of 20-800 and 0.1-4.0 respectively is proposed.

(42) The inventive method includes installation a disk horizontally into mixing assembly (FIG. 1-B) at the top layer of activated mixture coaxially with vertical axis of assembly and with the axis of impeller rotation on the adjustable level, to avoid destroying created gel as a result of interruptions of High-Energy mixing, to increase laminarity of the mixture flow, energy absorption by the mixture, and shear stress for creation additional quantity of the nanostructured Calcium Silicate Hydrate (C-S-H) gel necessary for making nanoconcrete.

(43) The inventive method comprise forming the activating assembly as a small scale working prototype of a production scale activating assembly, monitoring a temperature of the activated mixture, power consumption and impeller rotation parameters with and without mixture by a sensor and measuring devices, and inputting running values of said parameters as variables and geometrical parameters of the activating assembly as constants and outputting running and average values of measured and calculated parameters including the temperature of activated mixture, net power consumption, apparent dynamic viscosity, shear stress and the dimensionless criteria Reynolds and Power numbers, by a computer device.

(44) In activation with High-Energy Mixing according the present invention the main part of the activated mixture is located under disk. The volume of circulating mixture increases in comparing with original one when impeller doesn't rotate and excess of it is moving up around flexible disk (FIG. 1-C) or disk made of metal lattice (FIG. 1-D) on the top of it and further through the central opening down to rotating impeller. All of this happens because vortex sucks excess of mixture back to main volume. This reduces dispersion of the mixture inside the mixer.

(45) In the device of a disk suspension the opportunity of its displacement on vertical direction is provided. The viscosity of mixture changes during the process of activation as a result of C-S-H gel formation. In some cases especially if the mixture contains sand the interruptions of the mixture circulation occurs and the power consumption fells down. The shift of the disk down allows avoiding interruptions of the process and restores the power consumption.

(46) In the inventive method vertical adjustment of disk location is provided through hangers (FIG. 1-B,C,D) with separate mechanical device (here didn't shown).

(47) The results of tests presented in graphs FIG. 2-FIG. 13 and in Table 1 show that introducing of the disk into the mixer and installation of it at the top layers of the mixture during High-Energy Mixing improve conditions of activation, namely allows to avoid interruptions of the process, increases laminarity of flaw (or reduces Re number) of the activated mixture and as a result rises absorption of energy by the mixture and increases shear stress. All of this makes better conditions for creation additional quantity of nano structured C-S-H gel.

(48) In the present invention the average value of Reynolds number significantly reduced by using disc made of an elastic material or a metal lattice, i.e. turbulence decreases and laminar flow of the mixture increases during the process of High-Energy mixing. This corresponds to an increase in the absorption of energy by a mixture consisting only of cement and water, and also containing sand. As a result the shear stress between the particles of the mixture significantly increases (see Table 1). This indicates an improvement in activation efficiency because of greater localization of the circulating mixture in comparing with activation without a disk where the mixture is dispersed throughout the full volume of the mixer (FIG. 1-A). As a result, conditions are created for a significant increase in the index of extension the relative content of nano-structured C-S-H gel (Table. 1).

(49) In the inventive method it is possible to provide changing a volume of activated mixture by proportionally changing geometric parameters of the activating assembly while maintaining constant average values of net specific power and Reynolds and Power numbers for each particular task and mixture.

(50) In the inventive method it is possible also to provide occurring at production small changes in the volume of the mixture activated with HEM by moving up and down the disk made of flexible material or the metal lattice inside the same cylindrical container designed for required maximal volume.

(51) State of water in the volume of C-S-H gel increased as a result of High-Energy Mixing according the inventive method can be present within the interlayer structure as H.sub.2O or OH. The capillary pores 10-50 nanometers in diameter and larger than 3-5 micrometers between C-S-H clusters can contain free water solution.

(52) According R. A. Olson at al. (Interpretation of the impedance spectroscopy of cement paste via computer modeling, Part III Microstructural analysis of frozen cement paste, Journal of materials science 30, 1995, p. 5081 [9]) the calorimetric results of hardened cement paste show three well-defined peaks at approximately 8, 23, and 40 C. The peak at 8 C. is due to freezing bulk water in macro pores. The peak at 23 C. corresponds to the freezing of the smaller capillary pores of C-S-H gel, while the rather broad peak at 40 C. represents the low temperature transition of supersaturated solution in gel pores. Very little additional freezing occurs below this last peak.

(53) Taking into account the results of the Mr. Olson research shown here above in order to evaluate the main result obtained from the application of the present invention, in the inventive process an approximate quantitative method of comparing mixtures with different amounts of C-S-H gel was created and used. The method is based on the determination of Penetration Resistance development of the cement containing mixtures hardening at temperature 15 C. during several days. At these conditions the liquid phase in nano-sized pores of C-S-H gel doesn't freeze and able to interact with cement increasing the Penetration Resistance. The index of penetration resistance is determined every day after thawing when the mixture temperature increases from 15 C. to +5 C. This non standardized method was broadly used in this invention for approximate estimation of the quantity of C-S-H gel increase after the inventive method of High-Energy Mixing in comparison with already known method (Method of producing activated construction mixture, the application Ser. No. 13/476,003 published Nov. 21, 2013, as invention No: 2013/0395963A1 [8]) and conventionally mixed control variant. For this purpose the coefficient (K.sub.c-s-h) was created and used. K.sub.c-s-h is defined as the ratio of the areas of the graphs Penetration Resistance in psi-aging time at 15 C. in hours (see FIG. 4, 7, 10, 13 and Table 1).

(54) Water in nano pores of C-S-H gel has a greater density i.e. smaller specific volume than ordinary water, filling micro and macro pores and capillaries in hardening cement paste. This can cause chemical shrinkage, which in ordinary concrete is small and does not create large internal stresses (J. Thomas, H. Jennings The Science of Concrete 2108, 5.3.1.1., p. 50 [6A]). In the case of nanoconcrete, where the volume of gel can be increased several times the risk of chemical shrinkage increases, which may cause the necessity of adding shrinkage compensating additives. This is provided by this invention.

The Physical Basis of the High-Energy Mixing (HEM) Process

(55) The necessity to control the flow of the mixture developing in the mixer and effectiveness of energy usage requires considering additional parameters to calculate Reynolds and Power numbers. This also allows transferring the technological process fulfilled on the small scale activator to big production scale machine keeping the same levels of these criteria. It requires to consider some groups of parameters: geometrical parameters such as diameter of impeller rotationDs (m), height of bladeL (m), diameter of containerDc (m) and height of mixture in container before mixing-activationH (m); physical parameters such as net power of activationP (Watt) and total power inputP (Watt), net energy of activationE and total input of energy E (joules), as well as velocity of impellerN (Rpm and Rps).

(56) Physical parameters values of the turned on empty activator labeled here as X.sub.0, the current values of them taken in the process of activation are labeled as X.sub.t. The present invention is based on experiments with multiple variations of these parameters during the activation of construction mixtures prepared with different proportions of cement, sand and water as well as with variety of impellers and their rotational speed.

(57) Formulas for above mentioned dimensionless criteria to control their flow during the activation are formulas for stirred vessel (P. K. Biswas, K. M. Godiwalla, D. Sanyal, S. C. Dev A simple technique for measurement of apparent viscosity of slurries: sand-water system, Materials & Design, India Elsevier Science Ltd. Vol. 23, 2002, p. 511-519, see p. 512, right column, [10]):
Re=(ND.sub.s.sup.2)/(1)
Np=P/(N.sub.t.sup.3D.sub.s.sup.5)(2)
where is a density of the mixture in kg per cu. m, N.sub.t is a speed of impeller in Rps (revolutions per second), D.sub.sdiameter of impeller in m, apparent dynamic viscosity in Pas (Pascal-second), Pnet power in watt.

(58) In the present invention the mixer-activator considered as a kind of rotational viscometer. It creates a possibility to use equations (1), (2) and (5) from (E. Freire et al. Process ability of PVDF/PMMA blends studied by torque rheometry, Materials Science and Engineering C 29, pp. 657-661, Elsevier 2009 [11]), to calculate the apparent dynamic viscosity () values in Pas through shear stress and shear rate herein used formulas (see p.p. 658,659) transformed for conditions of High-Energy mixing:
=/,(3)
Where, is shear stress in N/m2, is shear rate in sec.sup.1.
=torque/(2R.sub.s.sup.2L),(4)
=(2(2N.sub.t)R.sub.c.sup.2)/(R.sub.c.sup.2R.sub.s.sup.2)(5)

(59) Thus all these values may be calculated having the geometrical parameters of activator (R.sub.c, R.sub.s and L) mentioned above (see FIG. 1) as well as the data of rotation velocity (N.sub.t), net torque: T=P/(2N.sub.t)P.sub.0/(2N.sub.0) and net Power: P=P.sub.tP.sub.0 measured during the process of activation with HEM.

(60) The equation for dynamic viscosity is valid for rotational viscometers with the rotated cylinder or blades immersed into liquid. In the present invention the main apparatus consists of the cylindrical container and impeller with straight or skewed blades (FIG. 1-B). The calculated dynamic viscosity (l) named as apparent dynamic viscosity of the mixture in the process of activation is a result of inertial forces action, developing into mixture, and consequently may be used as a denominator in the formula of Reynolds number. By adjusting the position of the flexible disk or disk made of metal lattice, it is possible to influence internal inertial forces. This changes the apparent dynamic viscosity and, consequently, the Reynolds number, Power number, specific absorbed energy and shear stress (see the sample of calculation of these parameters in Method of producing activated construction mixture, U.S. patent application Ser. No. 13/476,003 publication No US 2013/0305963.2013, Table 2, page 5-6 [8].

(61) In the inventive method further comprising forming the activating assembly as a small scale working prototype and/or a production scale activating assembly, monitoring a temperature of the activated mixture, power consumption and paddle rotation parameters with and without a mixture by a sensor and measuring devices; and inputting running values of said parameters as variables and geometrical parameters of the activating assembly and density of mixture as constants and outputting running and average values of measured and calculated parameters including gross and net power consumption, shear stress, apparent dynamic viscosity, and the dimensionless criteria Reynolds and Power numbers as well as interruptions of process and temperature of the mixture by a computer device.

(62) The expected rotational velocity of the production scale mixer loaded with mixture, N (Rps) calculated as average from the conditions:
Re.sub.small scale mixer=Re.sub.production scale mixer;1-st,
N.sub.small scale mixer=N.sub.production scale mixer.2-nd,
The expected velocity of impeller for the empty production scale mixer should be increased by multiplying this calculated value on the ratio N.sub.empty/N.sub.loaded known for the small scale mixer.

(63) In the inventive method calculation of production scale High-Energy mixer comprising proportionally changing a volume of small scale working prototype and other geometric parameters named here above while maintaining equals for small and production scale of mixing assembly maximal and average values of gross and net specific power and average values of Reynolds and Power numbers in order to correctly choose drive and geometry of the production scale mixer for each particular task and mixture. See the example of the results of calculation of the production scale the High-Energy mixer in Method of producing activated construction mixture, U.S. patent application Ser. No. 13/476,003 publication No US 2013/0305963, 2013, Table 3, page 6 [8].

(64) It will be clear that changes in the details, materials, steps and arrangement of parts which have been described and illustrated to explain the nature of the present invention as well as eliminating some of claimed parameters of invented process may be made by those skilled in the art upon reading of this disclosure with attaining considerable increase of C-S-H gel and other shown above changes of properties of the High-Energy Mixed mixture and in spite of it continue to stay within the principles and scope of present invention.

(65) It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of method differing from the type described above.

(66) While the invention has been illustrated and described as embodied in a method for producing nanoconcrete with the High-Energy Mixing, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

(67) Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the stand point of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

(68) What is claimed as new and desired to be protected by Letters Patent is set forth in appended claims.