DESC:EARLIEST PRIORITY DATE:
This Application claims priority from a Provisional patent application filed in India having Patent Application No. 202121003644, filed on January 27, 2021 and titled “A COMPOSITION FOR A CORROSION INHIBITING ADMIXTURE”.
FIELD OF INVENTION
[0001] Embodiments of the present invention relates to a field of corrosion inhibition compositions. More particularly, it relates to a synergistic admixture for corrosion inhibition of reinforcement metals and acceleration of concrete setting time.

BACKGROUND OF THE INVENTION

[0002] A corrosion inhibiting admixture is a chemical compound that, when added to a liquid or gas, decreased the corrosion rate of a material, typically a metal or an alloy, that comes into contact with the fluid. The corrosion inhibiting admixture is an admixture that extends the time to corrosion initiation or significantly reduce the corrosion rate of embedded metal, or both, in concrete subjected to high humidity or chlorides or both.

[0003] EP0247773A1 discloses a method of treating a reinforced concrete structure to inhibit corrosion of the reinforcement which comprises the step of inserting within the concrete a vapour phase corrosion inhibitor, whereby the inhibitor migrates through the porous structure of the concrete, and more particularly along the concrete/reinforcement interface, to protect the reinforcement.

[0004] US5916483A discloses an additive for inhibiting the corrosion of metals in a construction material containing an inorganic binder, wherein said additive is in admixture with said inorganic binder and comprises a reaction product of an amine and an acid, wherein said reaction product is at least a partially neutralized salt, and said acid is selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, pyrophosphoric acid, phosphonic acid, benzoic acid, aminobenzoic acid, sulfanilic acid, salicylic acid, sebacic acid, oleic acid, linoleic acid, adipic acid, tetrahydroxy-adipic acid, lactic acid, tartaric acid, citric acid, gluconic acid, heptonic acid and ascorbic acid

[0005] The conventional composition used as the corrosion inhibiting admixture in reinforced cement concrete (RCC) only extends the time to corrosion initiation in steel reinforcing bar (rebars) embedded in the RCC. However, setting time taken by the concrete remains the same or in fact increases, thereby making the composition less efficient as the increased setting time increases the typical duration needed for a particular construction activity.

[0006] Hence, there is a need for an improved composition for a corrosion inhibiting admixture to address the aforementioned issues.

SUMMARY OF THE INVENTION
[0007] In accordance with an embodiment of the invention, a synergistic admixture for corrosion inhibition of reinforcement metals and acceleration of concrete setting time is disclosed. The synergistic admixture comprises of a first pre-defined amount of active compound and a second pre-defined amount of active compound, wherein the first pre-defined amount of active compound comprises of monocyclohexylamine (MCHA) carbamate salt and the second pre-defined amount of active compound comprises of monocyclohexylamine (MCHA) benzoate salt.

[0008] In accordance with an embodiment of the present invention, wherein the pre-defined amount of first active compound is in the range of 50% to 70%.

[0009] In accordance with an embodiment of the present invention, wherein the pre-defined amount of second active compound is in the range of 30% to 50%.

[0010] In accordance with an embodiment of the present invention, wherein the synergistic admixture exhibits corrosion inhibiting property in reinforcement metals.

[0011] In accordance with an embodiment of the present invention, wherein exhibits acceleration property in initial setting time of the concrete.

[0012] In accordance with an embodiment of the present invention, wherein the synergistic admixture gets absorbed on the reinforcement metals and forms a strong covalent bond, wherein the absorbed layer repels chloride ions and water molecules.

[0013] In accordance with an embodiment of the present invention, wherein the synergistic admixture exhibits 95% corrosion inhibition efficiency.

[0014] In accordance with an embodiment of the present invention, wherein the synergistic admixture reduces the initial concrete setting time by accelerating the reaction time between C3A and gypsum.

[0015] To further clarify the advantages and features of the present disclosure, a more particular description of the disclosure will follow by reference to specific embodiments thereof, which are illustrated in the appended figures. It is to be appreciated that these figures depict only typical embodiments of the disclosure and are therefore not to be considered limiting in scope. The disclosure will be described and explained with additional specificity and detail with the appended figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG.1 is a schematic representation of The XPS graph of binding energy for Fe-N in accordance with an embodiment of the present disclosure;

[0017] FIG. 2 is a schematic representation of XPS graph of Nitrogen binding energy for Sepocem TTCI Powder inhibitor in accordance with an embodiment of the present disclosure;

[0018] FIG. 3 is a schematic representation of XPS graph of Oxygen binding energy for Sepocem TTCI Powder inhibitor in accordance with an embodiment of the present disclosure; and

[0019] FIG. 4 is a schematic representation of XPS graph of Carbon binding energy for Sepocem TTCI Powder inhibitor in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION
[0020] For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as would normally occur to those skilled in the art are to be construed as being within the scope of the present disclosure.

[0021] The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such a process or method. Appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but not necessarily do, all refer to the same embodiment.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting.

[0023] In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.

[0024] Embodiments of the present invention are related to a composition for a corrosion inhibiting admixture and accelerating initial concrete setting time.

[0025] According to an embodiment of the invention, a synergistic admixture for corrosion inhibition of reinforcement metals and acceleration of concrete setting time is disclosed. The synergistic admixture comprises of a first pre-defined amount of active compound and a second pre-defined amount of active compound, wherein the first pre-defined amount of active compound comprises of monocyclohexylamine (MCHA) carbamate salt and the second pre-defined amount of active compound comprises of a monocyclohexylamine (MCHA) benzoate salt.

[0026] In one exemplary embodiment, a structure of the MCHA carbamate salt is as follows:

[0027] In one exemplary embodiment, a structure of the MCHA carbamate salt is as follows:

[0028] According to an embodiment of the present invention, wherein the pre-defined amount of first active compound is in the range of 50% to 70%.

[0029] According to an embodiment of the present invention, wherein the pre-defined amount of second active compound is in the range of 30% to 50%.

[0030] According to an embodiment of the present invention, wherein the synergistic admixture exhibits corrosion inhibiting property in reinforcement metals.

[0031] According to an embodiment of the present invention, wherein exhibits acceleration property in initial setting time of the concrete.

[0032] According to an embodiment of the present invention, wherein the synergistic admixture gets absorbed on the reinforcement metals and forms a strong covalent bond, wherein the absorbed layer repels chloride ions and water molecules.

[0033] According to an embodiment of the present invention, wherein the synergistic admixture exhibits 95% corrosion inhibition efficiency.

[0034] According to an embodiment of the present invention, wherein the synergistic admixture reduces the initial concrete setting time by accelerating the reaction time between C3A and gypsum.

[0035] In one embodiment of the present invention, the synergistic admixture may be obtained by thoroughly blending in a high-intensity mixer. The corrosion inhibiting admixture may be used for reducing a rate of corrosion of steel reinforcing bars (rebars) embedded in reinforced cement concrete (RCC).

[0036] According to an embodiment of the present invention, the corrosion inhibiting synergistic admixture is added to the RCC in the green stage and mixed well. Later, when the steel rebars are embedded into the RCC, the corrosion inhibiting synergistic admixture may get adsorbed on a surface of the steel rebars by traversing/migrating through the media which is both green and hardened concrete. The adsorption is through the polar groups as well as the p – electrons of the double bond. This adsorbed layer repels the chloride ions and water molecules away from the surface of the steel rebars.

[0037] In one embodiment of the present invention, the MCHA carbamate salt accelerates the reaction of Tricalcium aluminate (C3A) with gypsum. Also, the formation of Monosulphate from ettringite is accelerated. This reduces the initial setting time of the RCC. In one exemplary embodiment, the corrosion inhibiting synergistic admixture reduced the initial setting time of the RCC by less than half for that of the control concrete mix.

[0038] Further, in one embodiment, the corrosion inhibiting synergistic admixture while getting adsorbed on the steel rebars, displaces any existing chloride ions and water molecules which may be already present on the surface of the steel rebars.

[0039] Further according to an embodiment of the present invention, when the rebars submerged in pore water solution (simulating the concrete) are subjected to passivation potential for 2 hours the corrosion inhibiting synergistic admixture of the present invention forms an adsorbed layer of 20 microns on the surface of the steel rebars. This results in a very high inhibition efficiency of more than 95% when measured by the Tafel Polarization method. The Tafel polarization also exhibited a shift in corrosion potential at both the anodic and cathodic sites which makes the corrosion inhibiting admixture a bipolar inhibitor.

EXPERIMENTAL DETAILS

[0040] The binding energies of the Sepocem TTCI film analyzed by X-ray Photoelectron Spectroscopy (XPS) are as follows: From the XPS Binding energy plots of Sepocem TTCI Powder inhibitor the findings are as follows with corresponding reported references:

1. The Fe-C bond energy is 284.4 eV which indicates bond formation with C 2p orbital.
2. The bond energy of Fe-O is 531. 8 eV which attributes the formation of bond with O 1s orbital.
3. The bond energies 355.6 eV as well as 359 eV show the formation of bond with Ca 2p orbital i.e Fe-Ca.
4. The bond energies between 396.6 eV and 399.9 eV indicates the formation of Fe-N bond (formation of Fe-N bond with 1s orbital of nitrogen observed).
5. The reported bond energies and the binding energies observed support the formation of Fe-N, Fe-Ca, Fe-O and Fe-C bonds in the Sepocem TTCI Powder inhibitor.
[0041] The typical binding energies observed are: Fe-O: 528.0-536.0 eV, Fe-N: 396.0 to 412 eV and Fe-Ca: 342.0- 354 eV.
[0042] The XPS graph of binding energy for Fe-N is show in FIG. 1, the XPS graph of Nitrogen binding energy for Sepocem TTCI Powder inhibitor is shown in FIG. 2, the XPS graph of Oxygen binding energy for Sepocem TTCI Powder inhibitor is shown in FIG. 3 and the XPS graph of Carbon binding energy for Sepocem TTCI Powder inhibitor is show in FIG. 4.
[0043] The observations are as follows: the TTCI sample was tested to JIS Z 1535 test and showed no corrosion spots. This displays excellent inhibition as well as migrating properties of the vapour phase inhibitor. Specimen of nominal mix of M30 grade concrete were cast.
[0044] The TTCI sample was tested as per ASTM D 59. The media used was pore water solution. The inhibition efficiency of the inhibitor sample was found to be 91%.
[0045] The TTCI sample was tested for electrochemical impedance with instruments calibrated as per ASTM G 106. The following is the data:
At OCP
R, (ohm): 12.525
Rp (Ohm): 6060
Cdl. (mhO): 7.15 x 10-5
At 200mV
Rs (ohm): 12.610
Rp (ohm): 642
Cdl. (mhO): 0.9 x 10-4
[0046] The performance of powder inhibitor Sepcoem TTCI in concrete having a NaCI content of 5 kgs per m3 was evaluated. The evaluation is carried out based on ASTM C 876 and ASTM G 59. ASTM C 876 is a measure of the half-cell potential of the rebars. ASTM G 59 quantifies the rate of corrosion of the rebars. Both tests together would give an understanding about the behaviour of Sepocem TTCI in high chloride content environments.
[0047] Grade of concrete considered was M30 (30Mpa). Cement content was 380 kg per cum. Water cement ratio was 0.38 (Water: Cement, by weight). The water used in concrete was NaCI solution of 3.5% concentration. This results in a chloride content of 3 kg/cum of concrete. Test Specimen was cast using Sepocem TTCI at a proportion of 0.3 kg per cum of concrete.
Parameter Method Result Remark
Half cell potential ASTM C 876 -118 mV >125mV with SCE ref electrode, which indicates. 90% probability of no
corrosion
Rate of Corrosion ASTM G 59 0.0021mmpy Falls below
0.0025mmpy
Control ASTM C 876 -485mV Half Cell Potential
Control ASTM G 59 0.0402mmpy Rate of Corrosion

Observations and Remarks:
[0048] The test was discontinued after it was observed that the corrosion of rebars did not initiate at a NaCI concentration of 5 kg per cubic metre of concrete.
[0049] ASTM C 876 mentions that there is 90% probability of no corrosion if the half-cell potential is below -125 mV (ref electrode SCE). The reading of -118 mV indicates that the corrosion initiation is yet to happen.
[0050] The rate of corrosion when less than 0.0025mm per year indicates corrosion is yet to start. The reading of 0.0021 mm per year indicates no corrosion.
[0051] Both test results in conjunction prove that there is no onset of corrosion.
[0052] The test concludes that the chloride threshold value of the rebars (in concrete with Sepocem TTCI at a proportion of 0.3 kg per cum) is higher than the 5 kgs of NaCI per cubic meter of concrete.
[0053] The chloride threshold value of rebars in the control specimen is much lesser than 5 kg of NaCI per cubic meter of concrete. It can be inferred from the readings that corrosion has already started in the control specimen.
[0054] The samples of “Sepocem TTCI”, are analysed for its various parameters and observations. The tests are carried out with 0.2 kg per cum of Seposem TTCI in concrete for severe environments, as follows:
Sr. No. Test Parameter Test method/
code Observations
1
Corrosion reduction by Tafel
Polarization

ASTM G59
Inhibition efficiency
89.4%
2
pH

Standard pH
meter, pH paj er
11
3
Accelerated corrosion test
JIS Z 1535
No corrosion spots I.e.
Passes the test.
4
Nature of Inhibitor-traversing
type corrosion inhibitor(TTCI)

JIS Z 1535
Passes
5
Immersion Test for 720 hours
(rebar weight loss method)

ASTM G1
1.12 mpy
6
Polarization test by Tafel
polarization, with 3.5% NaCI for 20 days

ASTM G3
2.40mpy
7
Effect on embedded steel
rebars exposed to chloride environment after 9 cycles

ASTM G109
Nil Coulombs
8
Vapour Inhibiting ability test
NACE TMO208
Grade 4 (excellent
corrosion protection effect)
9 Impedance Data for Sepocem

TTCI

ASTM G 106

A. At OCP

Rs
Ohm) 12.505

R, (Ohm) C065

Cyb mhO 7.15x 10-*

B. At 200mV

Rs
Ohm) 12.610

R,
Ohm) 641

C dl MhO 0.9 x 10*
10
Chloride Mitigation Profile properties of
concrete with and without Sepocem TTCI
a.
Chloride % in concrete at 30mm depth
after 90 days. (For all types of cement eg. OPC, PPC, PSC, SRC)
AASHTO T-259
Without Sepocem TTCI:
0.023% .
With Sepocem TTCI: Negligible
b.
Ability to resist chloride ion penetration
ASTM C-1202
(RCPT)(for all types of cement eg. OPC,PPC, PSC, SRC)
1. Concrete grade M30, water cement ratio-0.45 Without Sepocem TTCI: 1650 coulombs
With Sepocem TTC I
:778 coulombs.
2. Concrete grade M40 water cement ratio- 0.40 Without Sepocem TTCI: 1556 coulombs.
With Sepocem TTCI
683 coulombs.
12
Compressive strength of M25 grade
concrete, Nominal mix with water cement ratio 0.40
Increase of around 4% in
compressive strength was observed at 28 days.

[0055] Various embodiments of the present disclosure enable reducing the rate of corrosion of the steel rebars in the RCC even when exposure conditions include high chloride ion concentrations. The corrosion inhibiting synergistic admixture of the present invention gets adsorbed on the steel rebar surface and forms a strong covalent bond with the steel rebars and also accelerates the initial setting time of the concrete mix. This is especially desirable in cold weather concreting or underwater concreting and applications like shotcrete in case of tunnels.
[0056] The synergistic admixture of the present invention is an organic corrosion inhibitor which reduces the rate of corrosion of the steel rebars as well as accelerates the initial setting time of the RCC. This makes the corrosion inhibiting synergistic admixture of the present invention as unique, as it is a combination of being both organic corrosion inhibitor as well as an accelerator.
[0057] While specific language has been used to describe the disclosure, any limitations arising on account of the same are not intended. As would be apparent to a person skilled in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein.
[0058] The figures and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts need to be necessarily performed. Also, those acts that are not dependant on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples.

,CLAIMS:1. A synergistic admixture for corrosion inhibition of reinforcement metals and acceleration of concrete setting time, wherein the synergistic admixture comprises of:
a first pre-defined amount of active compound; and
a second pre-defined amount of active compound,
wherein the first pre-defined amount of active compound comprises of monocyclohexylamine (MCHA) carbamate salt and the second pre-defined amount of active compound comprises of a monocyclohexylamine (MCHA) benzoate.
2. The synergistic admixture as claimed in claim 1, wherein the pre-defined amount of first active compound is in the range of 50% to 70%.
3. The synergistic admixture as claimed in claim 1, wherein the pre-defined amount of second active compound is in the range of 30% to 50% .
4. The synergistic admixture as claimed in claim 1, wherein the synergistic admixture exhibits corrosion inhibiting property in reinforcement metals.
5. The synergistic admixture as claimed in claim 1, wherein exhibits acceleration property in initial setting time of the concrete.
6. The synergistic admixture as claimed in claim 1, wherein the synergistic admixture gets absorbed on the reinforcement metals and forms a strong covalent bond, wherein the absorbed layer repels chloride ions and water molecules.
7. The synergistic admixture as claimed in claim 1, wherein the synergistic admixture exhibits 95% corrosion inhibition efficiency.
8. The synergistic admixture as claimed in claim 1, wherein the synergistic admixture reduces the initial concrete setting time by accelerating the reaction time between C3A and gypsum.

Dated this 25th day of January 2022

Signature

Jinsu Abraham
Patent Agent (IN/PA-3267)
Agent for the Applicant