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    • 专利摘要:
    Concrete mixture containing a cation exchange laminar clay, wherein said laminar clay comprises an organosilane anchored in its interlaminar space and at least one anionic compound bound to said organosilane. The clay thus modified is an intermediate compound to be able to insert anions in a matrix of positive charge with great exchange capacity that in principle would have admitted cations, such as for example the smectites. The result is that it has the ability to release in a controlled manner the corrosion-inhibiting anions intercalated between its sheets in response to an increase in the concentration of chloride anions or a decrease in pH in cement-based compositions such as reinforced concrete. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2680269A1
    申请号:ES201730266
    申请日:2017-02-28
    公开日:2018-09-05
    发明作者:Lisardo M. FORT ALARCÓN；Rafael ALFONSO LUCAS；Jose Manuel Lloris Cormano；Cristina SUESTA FALCÓ；Margarita E. LECHA TAITOT；Pilar CALERO RODRÍGUEZ
    申请人:I Box Create S L；I-Box Create SL；
    IPC主号:
    专利说明:

    FIELD OF THE INVENTION The present invention relates to an additive for concrete, for use in the construction sector.
    10 BACKGROUND OF THE INVENTION Although reinforced concrete structures are very durable, they also suffer visible damage attributable to the corrosion of steel. Therefore, there is currently a need for the development of effective corrosion inhibitors.
    15 Corrosion damage is caused by lowering the pH in the concrete. The entrance of atmospheric carbon dioxide through the pores decarbonates the concrete to form carbonic acid. This effect is also increased in areas of marine environments due to the presence of chloride ions.
    20 In this application "corrosion" means the electrochemical process that takes place on the surface of a metal when it comes into contact with water, oxygen or other corrosive elements that cause its deterioration.
    25 Corrosion protection methods for reinforced concrete distinguish those that act on concrete and those that act on steel.
    The methods that act on steel do so as a coating. Its main disadvantage is the loss of adhesion between the rebar and the die
    30 of concrete, which supposes a reduction of the mechanical properties of the structure. The durability of these coatings is also limited in a medium of pH> 13, such as concrete.
    The methods that act on the concrete use resins, waxes, paints and protective membranes applied as a coating, or additives that inhibit corrosion added to the mixture. The latter have the advantage of their easy use and the disadvantage that their effectiveness against the effects of ions
    5 chloride and carbon dioxide is debatable at the moment.
    There are coatings on the surface of the concrete that use an organosilicon compound with the possibility of migrating inwards to the reinforcement. This compound retards the migration of salts through the structure thanks to an effect of water repulsion. However, it cannot be eliminated in long periods of time.
    In this regard, US 6174461 81 discloses a silane-modified silicate or siloxane coating that acts as a sealing material applied to the concrete as an exterior coating. The inhibitor may be an amine salt, an amino alcohol, a glucoheptanoate or calcium nitrite or a mixture thereof. It is an effective product for application in repair and maintenance processes of structures that can migrate by leaching. But in addition to that it is a little durable solution, its great drawback is that leaching occurs in the same way towards the interior as well as the exterior of the structure polluting the environment. The
    The publication does not suggest that the inhibitor is released in a controlled manner nor does it describe that it may be supported on the structure of a laminar clay, as in the present invention.
    US 2010119851 A1 describes a formulation to prevent corrosion that
    25 comprises a water-soluble organic polymer and an organosilicon compound based on an oligomeric mixture of alkyl-alkoxy-siloxanes. The product is applied as a barrier coating on the exterior surface of the concrete to prevent the entry of salts, presenting the same problems as the previous case.
    In the art, alkali metal and alkaline earth metal nitrites are used in the concrete as chemical corrosion inhibitors. Specifically, sodium nitrite or calcium nitrite. The disadvantage of nitrites is that they worsen the initial performance of concrete, delay the curing process and reduce mechanical strength. As they are also soluble compounds, they undergo leaching processes, losing part of the product and freeing the environment.
    US 2003/0101898 A1 describes a composition based on organosilane and / or
    5 organosiloxane that is added directly to the concrete mix to reduceactive corrosion of reinforcement steel. Being a liquid compound again itYou can lose by leaching. On the other hand, it has been proven that the action ofwater soluble inhibitors on the surface of the steel present in the matrix ofConcrete does not always have a positive effect on corrosion currents. This
    This may be due to the fact that the inhibitor does not diffuse sufficiently well through the cement and a sufficient concentration of inhibitor is not reached on the metal surface. On the contrary, the modified clays of the present invention do remain homogeneously and efficiently dispersed within the mixture.
    15 Various patents related to inhibitors have been published that include layered clays taking advantage of their ability to house active compounds in the interlaminar space.
    The surface charge of clays is the result of isomorphic substitution along
    20 of the crystalline structure. There are two large groups of clays depending on their load. Anionics with a laminar structure of the hydroxide type have a positive charge, are capable of exchanging anions and are also known as hydrotalcites or double laminar hydroxides; they are the ~ anion exchange clays. "The cationic ones
    or "cation exchange clays" are formed by aluminosilicate sheets and
    25 have a negative charge with the capacity to house small cations in the interlaminar space.
    Within the cationic group, smectites are known for their great exchange capacity. In smectites, isomorphic substitution results in loading
    30 negative in the sheets that is generally compensated by the intercalation of cations such as Na ·, Ca2 or Mg2., Easily interchangeable. '¡¡
    Cation exchange layered clays are capable of inhibiting corrosion in galvanized steel when delamination occurs. For example, bentonite
    It provides a release system for rare earth and alkaline earth cations that are only released when an electrolyte appears on the surface of a corroded metal.
    5 Anionic clays or hydrotalcites are rare in nature. Is it soformed by double laminar metal hydroxides with sheet structure whoseinterlaminar space has a positive charge and is able to retain anions and molecules,presenting anion exchange properties. However, they present alimited ion exchange capacity, much lower than cationic smectites. The
    The ability to inhibit a corrosion inhibitor linked to hydrotalcites is by necessity reduced.
    Compounds from modified hydrotalcites solve the corrosion problem used as additives in coating products or paints that are
    15 apply on metal surfaces. In this regard, US Pat. No. 7481877 82 describes modified hydrotalcites with a corrosion inhibitor to additive a coating paint. The product achieves a synergistic effect. However, its application on reinforced concrete reinforcing bars immersed in a medium at pH> 13 is not contemplated.
    The patent US 7879146 82 describes a method for the controlled release of a series of organic additives that act as superplasticizers and accelerators or retarders of curing and are intercalated in hydrotalcites for cement-based compositions. It takes advantage of the ability to exchange organic anions and
    25 inorganic for the modification of the consistency and setting time of fresh concrete. The additive in this case is directly linked in the interlaminar space. However, as mentioned above, the exchange capacity of these hydrotalcites is limited.
    WO 2011065825 A1 describes a corrosion inhibitor system of reinforced concrete with hydrotalcites modified with specific inhibitors, which include carboxylic groups and amine groups. However, another disadvantage of hydrotalcites lies in their instability at pH <9, which is the pH value that is reached locally at the points where corrosion has started, so the hydrotalcite itself would be unstable once the process.
    US 5435846 A describes the combination of a cation exchange compound and
    5 another anion exchange as additives in cement, for example, a calcium-substituted zeolite and a hydrocalumite (calcium and aluminum hydrotalcite). This additive prevents corrosion of reinforcing steel in reinforced concrete and the arid alkali reaction caused by the alkali metal ions contained in the concrete by eliminating attack ions by an ion exchange with the zeolite or hydrocalumite. He
    The deterioration inhibitory effect is a direct consequence of the cationic exchange processes of zeolite (arid-alkali pathology) or anionic hydrocalumite (corrosion). Corrosion inhibition is produced by an exchange effect between the hydrocalumite that releases nitrite or nitrate ions with inhibitory effect and traps chloride ions from the medium. In this case there is no modification with organic compounds
    15 of the hydrocalumite for anchoring the inhibitor anion to the structure of the inorganic compound.
    Application WO 2009072888 A 1 is considered the closest publication of the technique. It describes a laminar inorganic clay that incorporates an ionic organic component 20 and a biocidal compound for the construction sector. The biocide partially resists microbial growth. The document describes the substitution of the counterion present between the clay sheets with functional organic molecules that modify hydrophobicity and improve affinity for the biocide. One of the preferable embodiments is an inorganic laminar material with positive or negative charge, which could be a clay of the smectite type or a double laminar hydroxide with an organic compound modifying the family of quaternary ammonium salts, phosphonates, sulphonates or carboxylic acids and derived salts, which bind to the biocidal agent. However, both the biocide and the organic modifier can be released to the medium by an ion exchange process with some of the
    30 cations present in solution in the pores of the building material, which reduces its effectiveness. In the present invention, however, the anchoring of the organosilane makes the modified clay more stable for the sense of the inhibitor anion; It is not simply an ion exchange process.
    In the present invention the organosilane offers the silane group to react with the hydroxyl groups (-OH) of the clay surface. The interlaminar zone is thus modified with said organosilane bound thereto stably by Si-O siloxane groups, while the free end of the molecule has a positive charge for
    5 interact with the inhibitor anion. This allows the incorporation of molecular anionic inhibitors instead of cationic agents and more effectively when they are bound to the structure, so that their release is controlled in the medium, taking advantage of the exchange capacity of the cationic clays.
    10 The problem of the technique is to find a stable system capable of inhibiting the corrosion of reinforced concrete effectively in the long term. The solution proposed by the present invention is the inclusion in the concrete matrix of a cation exchange clay of great exchange capacity modified with an organosilane capable of housing an anionic inhibitor.
    DESCRIPTION OF THE INVENTION The present invention is a concrete mixture containing a cation exchange laminar clay, wherein said cation exchange laminar clay comprises an organosilane anchored in an interlaminar space and at least one anionic compound.
    20 attached to said organosilane.
    In a preferable aspect, said laminar clay is present in a proportion of 0.01% to 1% by weight with respect to the weight of cement. In a more preferable aspect, said organosilane is an alkoxysilane.
    In another preferable aspect, said concrete mixture also contains cement in a proportion of 9% to 16% by weight with respect to the total weight of the mixture; aggregates from 70% to 85% by weight with respect to the total weight of the mixture; a polycarboxylate as plasticizer additive of 0.5% to 1.5% with respect to the weight of cement; and a compound with base
    Modified phosphate, preferably sodium phosphate, or a sugar, preferably sucrose, as a retarding additive of 0.5% to 2.5% by weight relative to the weight of cement, for a total percentage of 100%.
    That is, one aspect of the present invention is the inclusion in the concrete matrix of expanded layered clays with an organosilane combined with organic or inorganic anions, so that these modified clays are capable of retaining said inhibitor anions until they occur in the half changes that
    5 indicate the occurrence of corrosion reactions.
    Said modified clay is an intermediate compound to be able to insert anions into a positively charged matrix that in principle would have been accepted from cations but with great exchange capacity, such as smectites. The result is
    10 a clay that has the ability to release in a controlled manner the corrosion inhibitory anions interspersed between its sheets in response to an increase in the concentration of chloride anions or a decrease in pH in cement-based compositions such as reinforced concrete.
    15 Anionic inhibitors are more effective against corrosion than cationic ones, as well as more bulky. The great technical advantage of the present invention is that it achieves an intermediate compound to be able to insert anions that until now did not fit in a cation exchange matrix.
    The smectites in the present invention are the most common phyllosilicates, and within them, the most common is montmorillonite. The scope of the present invention is extended to bentonite, which is the natural material of clay extracted directly from the quarry. Bentonite comprises different types of clay and as a major component montmorillonite. The content of Montmorillonite determines the degree of
    25 purity of the bentonite extracted.
    A very preferable aspect of the invention is cation exchange laminar clay, preferably a smectite and most preferably montmorillonite, which comprises an organosilane anchored in an interlaminar space and at least one
    An anionic compound bound to said organosilane, preferably a nitrite anion, an amino anion, a carboxyl or dicarboxyl anion, more preferably 11-aminoundecanoate, 4-aminobenzoate, sebacate or nitrite anion. Preferably also, the organosilane has at least one free cationic group.
    In a further preferable aspect, said anionic compound is present in a proportion of 3% to 6.5%, preferably 3% to 5%, by weight with respect to the weight of the clay.
    5 These inhibitors have the ability to delay up to three times the time it takes for corrosion to appear in the absence of inhibitors. They do not lose effectiveness over time, since the inhibitory anion is retained in the interlaminar zone and is not leached by moisture as is the case with traditional liquid inhibitors. An additional advantage over liquid inhibitors of the
    The technique is that they do not delay the setting time of fresh concrete or worsen the mechanical strength of cured concrete.
    A more preferable aspect is the use of the ion exchange laminar clay of the invention as an additive in a cement mixture.
    The invention relates to chemically modified lamellar clays by the laminar intercalation of an organosilane organic compound with corrosion-inhibiting anions that are attached to the chemical structure of the modified clay by means of ionic bonds for cement, mortar and concrete compositions.
    The anion bound to an organosilane or an alkoxysilane is capable of reacting with the ferrous ion that is produced in the anodic reaction resulting in stable and protective compounds such as Fe20 3, so as to reduce the rate of corrosion. Inhibitory anions compete with the CI-attack ion to capture the ferrous ion Fe2 +
    25 which is the product of the anodic reaction in which the Fe of the reinforcement bar is oxidized.
    The present invention can be presented as a family of corrosion inhibiting additives for reinforced concrete. These additives consist of a solid powder
    30 whose composition comprises chemically modified lamellar clays in the interlaminar space by means of organosilanes attached to an inhibitory anion.
    The modified clays of the present invention maintain the characteristic of a controlled release of the inhibitor anions against certain changes in the environment that imply an appearance of corrosion, such as a decrease in pH.
    or an increase in the concentration of chloride ions triggering the corrosion processes in reinforced concrete exposed to marine environments.
    5 BRIEF DESCRIPTION OF THE FIGURESFigure 1. Schematic of the structure of a clay sheet modified withtrimetaaminopropylsilane (left), imidazole salt (center), trietaaminopropylsilane(right)Figure 2. Infrared spectrum of the modified laminar clay with the group
    10 imidazolpropylsilane and nitrite anion
    Figure 3. Infrared spectrum of the modified laminar clay with the imidazolpropylsilane group and the 11-aminoundecanoic anion.
    Figure 4. Infrared spectrum of the modified laminar clay with the imidazolpropylsilane group and the sebacate anion.
    Figure 5. Infrared spectrum of the modified laminar clay with the imidazolpropylsilane group and the 4-aminobenzoic anion.
    Figure 6. Thermogravimetric Analysis (ATG) and its curve derived from clay modified with imidazolpropylsilane groups. Broken line is weight in grams. Continuous line is the derivative.
    Figure 7. ATG Y derived from clay modified with the imidazolpropylsilane group and the 11-aminoundecanoic anion. Broken line is weight in grams. Continuous line is the derivative.
    Figure 8. ATG Y derived from modified clay with the imidazolpropylsilane group and the sebacate anion. Broken line is weight in grams. Continuous line is the derivative.
    Figure 9. ATG Y derived from the modified clay with the imidazolpropylsilane group and the 4-aminobenzoate anion. Broken line is weight in grams. Continuous line is the derivative.
    Figure 10. Representation of absorption intensity at 265 nm, versus time for dispersions of laminar clay modified with inhibitor anion 4
    30 aminobenzoic acid at pH 7 and pH 11. Broken line is Abs.Max PC432 sCI pH = 7. Continuous line is the Abs.Max PC432 sCI pH = 11.
    Figure 11. Representation of the absorption intensity at 265 nm, versus time for laminar clay dispersions modified with 4-aminobenzoic inhibitor anion at pH 11 and at the same pH, but with an excess of chloride anions. Broken line is Abs.Max PC432 pH = 11, 1: 5CI. Continuous line is Abs.Max PC432
    5 Sci pH = 11.
    Figure 12. Representation of the absorption intensity at 265 nm, versus time for the dispersions of laminar clay modified with 4-aminobenzoic inhibitor anion at pH 7 and at the same pH, but with an excess of chloride anions. Broken line is Abs.Max PC432 sCI pH = 7. Continuous line is Abs.Max PC432 pH = 7,
    10 1: 5CI.
    Figure 13. Representation of the compressive strength at different ages of curing (2, 7 and 28 days) for normalized mortar specimens with different corrosion inhibitors.
    • Cbntrol
    - + -11-aminoundeca1oioo
    - ~ 4-aminoben20ioo
    _ • S3bádco
    ...) (.. Nitrite
    15 Figure 14. Representation of the compressive strength of concrete with low cement content at different curing ages (2, 7 and 28 days) with different inhibitors.
    ··· x ·· Nitrite
    - .... ~ sandwich
    Figure 15. Values of compressive strengths at different ages of cure (2,
    20 7, and 28 days), for concrete specimens with a high cement content with additions based on modified lamellar clays with inhibitory anions incorporated between the sheets. Concrete with cement content> 350 kg / m3.
    • Control•••: 1 (•• Nitrite
    Figure 16. Open circuit potential according to ASTM C 876 Standard (in mV) versus time, of mortar specimens cured 7 days and placed in the 5% NaCl solution. Control is the reference sample and Nitrite 1 and Nitrite 2 samples with clay
    5 laminar modified with imidazolpropylsilane group and with nitrite inhibitor anion.
    -..... CDntrol..... Nitrite 1-4-Nitrite 2
    Figure 17. Open circuit potential according to ASTM C 876 Standard (in mV) versus time, of mortar specimens cured 2 days and placed in the solution at 5% of
    10 born Control is the reference sample and Nitrite is a sample with laminar clay modified with imidazolpropylsilane group and with nitrite inhibitor anion.
    ...... Cbntrol
    ~ Nitrite
    Figure 18. Corrosion potentials for concrete specimens (with high cement content) submerged in 5% NaCI solution. Reference sample (Control),
    15 shows with an inhibitor additive based on clay modified with imidazolpropylsilane groups and with Nitrite anion, and shows with inhibitor additive based on clay modified with imidazolpropylsilane groups and with 11aminoundecanoic organic anion.
    ~ CDntrol ..... Nitrite - "Il-11-aminoundecanoioo
    Figure 19. Corrosion potentials over time for concrete specimens (with low cement content) submerged in 5% NaCl. Reference sample without inhibitor additive (CONTROL), sample with inhibitor additive based on laminar clay modified with imidazolpropylsilane groups and with Nitrite anion and sample with inhibitor additive based on clay modified with imidazolpropylsilane groups and with organic anion Sebacato.
    ~ cx :: NTR: l ... •••• Nitrito ~ .8: IDa: ato
    Figure 20. Corrosion potentials over time for concrete specimens
    5 (with low cement content) submerged in 10% NaCI. Reference sampleno inhibitor additive (CONTROL), sample with clay-based inhibitor additivemodified with imidazolpropylsilane groups and with nitrite anion and sample with additiveclay-based inhibitor modified with imidazolpropylsilane and anion groupsOrganic Sebacato.
    ~ c: o-.rTR: l .... Nitrito ~ · :: ebacato 10
    DETAILED DESCRIPTION OF THE INVENTION With the intention of showing the present invention in an illustrative way but in no way limiting, the following examples are provided.
    Example 1: Procedure for obtaining the silane modifying compound 1- (tri-ethoxysilyl-propyl) -N-methylimidazole chloride (IMIDAZOL SALT). In a round bottom flask equipped with a reflux condenser and a nitrogen atmosphere 20, 53 g of 1-methyl-imidazole (0.25 mol) and 60.20 are introduced
    20 g of 3-chloropropyl-triethoxy-silane (0.25 mol). This mixture is maintained at 95 oC for 24 hours. The resulting product is extracted with diethyl ether and the product obtained is dried under reduced pressure by rotary evaporator at 40 ° C.
    Example 2: Modification of Montmorillonite laminar clay with salt
    25 imidazole with propylsilane groups. In a round bottom flask equipped with a reflux condenser and a nitrogen atmosphere, 20 grams of montmorillonite clay are introduced, dispersed in 400 mL of distilled H20, left under stirring for 3 hours at a temperature of 30 ° C. Then 75 mL of EtOH and 100 mL of Acetic Acid are added. This
    30 dispersion is added 40 g of the Imidazole salt. This mixture is left under stirring at a temperature of BODC for 24 hours. Finally, it is washed with distilled water, separated by centrifugation at 3000 rpm. and freeze dried at -50DC.
    Example 3: Incorporation of the inhibitor anion (11-amiundecanoic acid, acid 4
    5 aminobenzoic acid, sebacic acid, nitrite anion) to laminar clay modified withthe imidazolpropylsilane group.In a round bottom flask a dispersion with 50 gr Laminar Clay is preparedModified with imizadolpropylsilane groups and dissolved in 300 mL of H20, leftunder stirring for 3 hours and at a temperature of 30De. Then they are added
    10 50 g of inhibitor anion precursor acid (4-aminobenzoic acid or sebacic acid or 11-aminoundecanoic acid) or 25 g of sodium nitrite, in case the inhibitory anion is nitrite, in 200 mL of basic HzO (pH = 1 O) at 25% by weight and left under stirring for 24 hours. Finally, it is washed with a mixture of distilled water and Ethanol (50:50) by filtration and lyophilized. Four types of clays are thus obtained
    15 modified.
    Example 4: Characterization of synthesized products. The characterization of the synthesized products has been performed by Fourier transform infrared spectroscopy analysis (FTIR) and by analysis
    20 thermogravimetric (TGA).
    FTlR spectra of clay modified with imidazolpropylsilane and various inhibitory anions.
    The spectrum corresponding to the modified laminar clay is shown in Figure 2
    25 with the imidazolpropylsilane group to which the nitrite anion has been incorporated. The characteristic vibration frequency of the NO bonds in the nitrite anion around 1250 cm-1 is masked between the vibration frequencies of the modified lamellar clay with the imidazolepropylsilane group, although greater widening can be seen in the BOO area a 1400 cm · l, with respect to the spectrum of
    30 product without nitrite anion_
    The spectrum of Figure 3 corresponds to the incorporation of the 11-aminoinodecanoate anion into the modified laminar clay with the imidazolpropylsilane group. The signals corresponding to the organic anion are clearly observed, at 2992 and 2850 cm-1 the signals corresponding to the vibration frequencies of the C-H bonds of the anion appear. At 1642, 1505 and 1393 cm-1, the signals of the links appear
    C-C and C-O.
    5 The spectrum of Figure 4 corresponds to the incorporation of the sebacate anion into the modified laminar clay with the imidazolpropylsilane group. They are clearly observed
    the signals corresponding to the organic anion, at 2935 and 2850 cm-appear the signals corresponding to the vibration frequencies of the C-H bonds of the anion. At 1701 cm-1 the characteristic signal of the carboxylic group appears.
    10 Finally, the spectrum of Figure 5 corresponds to the incorporation of the 4-aminobenzoate anion into the modified laminar clay with the imidazolpropylsilane group. The signals corresponding to the organic anion are clearly observed, at the different frequencies that appear in the figure.
    15 Thermogravimetric analysis of clay modified with imidazolpropylsilane and various inhibitory anions. Analyzing the mass loss curves of the modified clay with the imidazolpropylsilane group, a first decrease is observed in Figure 6 until
    20 100 ° C due to moisture removal. From that temperature to 500 ° C the decomposition of organic matter (representing 12% weight loss), due to the imidazolpropylsilane group occurs. From that temperature and up to 750 ° C, dehydroxylation of the -OH groups of the clay sheets occurs.
    25 Figure 7 shows the thermogravimetric analysis and its curve derived from the clay sample modified with imidazolpropylsilane groups and the 11-aminoinodedecanoate anion. Analyzing the mass loss curve, a decrease in weight is observed from a temperature of 100 ° C to a temperature of 500 ° C.
    Decomposition of organic matter due to the imidazolpropylsilane group and the 11-aminoundecanoate anion, which represents a 60% weight loss. From that temperature the dehydroxylation of the -OH groups of the clay sheets occurs.
    The thermogravimetric analysis and the curve derived from the clay modified with imidazolpropylsilane groups and the sebacate anion are presented in Figure 8. Analyzing the mass loss curve a decrease from 100 ° C temperature to 500 ° C is observed by the decomposition of organic matter due to the group
    5 imidazolpropylsilane and sebacate anion, which represents a 55% weight loss. From that temperature the dehydroxylation of the -OH groups of the clay sheets occurs.
    Figure 9 shows the thermogravimetric analysis and the curve derived from the
    10 clay modified with imidazolpropylsilane groups and the 4-aminobenzoate anion. Analyzing the mass loss curve, a decrease in weight from 100 ° C to 500 ° C is observed due to the loss of organic matter due to the imidazolpropylsilane group and the 4-aminobenzoate anion, which represents a 60% weight loss . From that temperature the dehydroxylation of the
    15 -OH groups of clay sheets.
    Example 5: Controlled release assays of the 4-amino-benzoic organic inhibitor anion (ref. Product PC432) from inside the modified clay sheets.
    20 The modified laminar clay was tested with the inhibitory anion by visible ultraviolet spectroscopy in basic medium and in the presence of chloride anions, which it absorbs in the UV-vis region with a maximum absorption at a wavelength ().,) 265 nm Release tests were carried out by measuring the maximum absorption as a function of time over an aqueous solution in which the particles are dispersed
    25 of modified clay with inhibitor anion. In Figure 10 Results are available to assess the release process under four different conditions: pH = 11, pH = 7, pH = 11 with an excess of chloride anions (5 equivalents) and pH = 7 with excess anions chloride (5 equivalents). Absorption intensity at the wavelength of 265 nm has been represented separately as a function of time for pH 11 and pH 7 and
    30 to 400 min in Figure 11. It is observed that the initial release at pH 11 occurs at a faster rate, although after approx. 100 min., The release process for pH 7 occurs more rapidly and at pH 11 more smoothly and progressively. In the first 200 minutes at pH 7 the maximum release is already reached, while at pH 11 this maximum is not reached until 1250 hours.
    In Figures 12 and 13 the curves for pH 7 and 11 have been shown separately up to 400 min. In both figures it can be seen that the release curves when the chloride anions are present are much more pronounced. This indicates that
    5 The release of the inhibitor, when there are chlorides in the medium, is practically immediate without even affecting the pH.
    Example 6: Effect of the new inhibitors in mortars.Cement mortar specimens were prepared in accordance with the UN E-EN standard
    10 196-1. The cement used was a 42.5 RlSR resistant to sulfates and seawater. The water / cement ratio is 0.5 and the aggregate cement ratio was 3 (normalized proportions). Kneading is carried out systematically, in accordance with what is defined in the UNE-EN 196-1 standard. Once the kneading process is finished, the mixture is poured into the appropriate molds for each of the tests,
    15 4x4x16 for compression tests and cylindrical molds with a diameter of 7 cm and a length of 10 cm for the rest of the tests. These specimens will have inside a steel bar for the tests in which the potential or the corrosion rate is to be determined.
    20 The determination of the mechanical compressive strength of the cement mortar obtained was carried out according to UNE-EN 196-1. The dimensions of the prismatic specimens according to the regulations are 160x40x40 mm and the ages of curing at which the mechanical strengths are determined are 2, 7 and 28 days. The results of the compressive strength values are presented below.
    25 as a resistant index considering 100% for the control sample. The samples have been named according to the inhibitory anion with which they have been prepared. The additive has been added in a proportion of 0.5%.
    In Figure 14 it is observed that there is no great variation in the resistance values to
    30 compression, although it is observed that the values of the specimens with inhibitory anions are, in general, slightly lower than those of the control mortar, a trend that is clear after 28 days of curing for all inhibitory anions. The conclusion is that the presence of inhibitors does not adversely affect resistance in the proportions studied.
    Example 7: Effect of the new concrete inhibitors. Concrete specimens were prepared according to UNE-EN 206-1. The cement used was 42.5 R / SR, resistant to sulfates and seawater. Two different dosages have been prepared, to have a Dosage of a Concrete with a low
    5 Cement content (275 Kg / m3), 1128 kg / m3 of sand and 819 kg / m3 of gravel, with a water / cement ratio of 0.6 (Concrete Ila), and another dosage of a Concrete with a high Cement content (350 Kg / m3), 1140 kg / m3 of sand and 830 kg / m3 of gravel, with a water / cement ratio of 0.45 (concrete type lile). The additive has been added in a proportion of 0.5%. For resistance determination have been prepared
    10 cylindrical specimens 150 mm in diameter and 300 mm high, in accordance with EN 12390-1. The determination of the compressive strength has been carried out in accordance with the UNE-EN 12390-3 standard.
    • Concrete characterization with low Cement content (275 Kg / m3)
    15 According to the results of Figure 15, there is no great variation in the values of compressive strength in concrete specimens, with a faster increase in resistance observed in the samples with inhibitor during the first 48 hours. After 7 days, the rate of resistance increase is similar in all samples.
    • Concrete characterization with a high cement content (350 Kg / m3). For the characterization of concrete with a high cement content, an adjustment of the proportions of superplasticizer and setting retardant additive was previously made in the formulations with inhibitory additives and subsequently
    25 determined the mechanical strengths, with the same methodology as for low-cement concrete. The results in Figure 16 also indicate that inhibitors do not exert negative influences on resistance.
    Example 8: Corrosion tests in mortar.
    30 The methodology described in ASTM e 876 was followed. "Standard Test Method for Half-Cell Potentials". Thus, the open circuit potential was measured on a specimen that contains the corrugated steel bar inside, and that is immersed in a solution with a high concentration of NaCI to cause the migration of chlorides to the bar generating corrosion. This method described in the standard is used to estimate the half-cell electrical potential (or Open Circuit Potential, OCP) of a reinforcing steel of a concrete, both in the laboratory and in its commissioning, in order to determine the corrosion activity of steel. The measurements were made with a potentiostat-galvanostat, an electrode of calomelanos
    5 saturated (as reference electrode), and a connection between the potentiostat and the reinforced steel bar of the concrete specimen.
    According to ASTM C 876, more negative potentials of -270 mV with respect to a saturated calomelan electrode (SCE) indicate a probability
    10 greater than 90% active corrosion of steel. Less negative values of -120 mV SCE indicate a probability of corrosion below 5%. Finally, those values between -270 and -120 mV SCE provide enough uncertainty regarding the development of corrosion processes.
    15 Figure 17 shows the results of corrosion tests of cement mortar specimens cured 7 days with 0.5% inhibitor addition. As you can see, the sample identified as Control (standard mortar), initially presents very negative values, which indicates that corrosion processes occur at the beginning. Subsequently, the potential values increase due,
    20 probably, to the progress in the process of curing the samples. After 80 days of exposure to the attack solutions, the potential values are again below the value of -270 mV, indicating that generalized corrosion processes are occurring on the reinforcement bar. The other two samples tested (Nitrit01 and Nitrite 2) contain the clay-based additive developed
    25 laminar modified with imidazolpropylsilane groups and nitrite inhibitory anions. These specimens maintain the potential for corrosion in values where the possibility of corrosion processes is less than 5% after more than 250 days of attack, indicating the effectiveness towards the prevention of corrosion of synthesized products. In this case it is possible to triple the life of the specimen in the
    30 medium studied.
    Figure 18 shows the results of the corrosion tests of the cement mortar specimens cured 2 days. In this case, given the short time that has elapsed for the curing of the samples, they present very negative corrosion potentials even before immersing them in the attack solutions, indicating the beginning of the corrosion process on the reinforcing bar. This behavior remains widespread until 60 days, at which the potential of the sample with additive based on modified laminar clay with groups
    Imidazolpropylsilane and nitrite inhibitor anion (Nitrite 3) evolves to greater potentials, indicating that corrosion inhibitors begin to take effect once the curing of the specimens has occurred. This behavior is maintained for more than 200 days.
    10 Example 9: Corrosion tests on concrete. Figure 19 shows a representation of the corrosion potentials of three concrete samples with a high cement content (more than 350 Kg / m3) prepared and submerged in a 5% by weight NaCI. The concrete in the sample with additive with 11-aminateddecanoic inhibitor anion is not damaged by corrosion for up to 800 days.
    15 In the case of the sample with nitrite inhibitor anion it is clearly seen that it suffers corrosion damage around 300 days with potentials below -275 mV, subsequently recovering with potentials above -200 mV. The Control concrete sample begins to show potentials in the range of high probability of corrosion from 600 days. Therefore, the improvement that is achieved
    20 with inhibitor additives is greater than 200 days.
    Figures 20 and 21 show the corrosion behavior of concrete specimens with low cement content deposited in NaCl solution one with a concentration of 5% by weight and another of 10% by weight.
    25 When the attack is carried out with a 5% solution (Figure 20), it is observed that the specimens containing the inhibitor anions based on laminar clay modified with imidazolpropylsilane groups and with nitrite inhibitor anion and sebacate anion have corrosion potentials in the corresponding range at a probability of
    30 very low corrosion. On the contrary, the control sample without additive has potential for high probability of occurrence of corrosion processes after 200 days of testing. Therefore, products with inhibitory additives improve behavior in more than 200 days, doubling the durability of concrete.
    On the other hand, in concrete specimens with low cement content, submerged in the solution containing 10% by weight of NaCl (Figure 21), the specimen containing the product based on modified laminar clay with imdazolpropylsilane groups and inhibitor anion Nitrite initially shows negative potential values that are recovered after 120 days, keeping them in a non-corrosion condition for up to 400 days. On the contrary, the control specimen after 120 days begins to present very negative corrosion potentials, which indicate a very high probability of undergoing a corrosion process. In this case the improvement over the control specimen can be quantified in more than 300 days,
    10 tripling its durability.
    权利要求:
    Claims (8)
    [1]
    1. Cation exchange laminar clay, characterized in that it comprises an organosilane anchored in an interlaminar space and at least one anionic compound bound to said organosilane.
    2. A cation exchange laminar clay according to claim 1, characterized in that it is a smectite.
    [3]
    3. A catholic exchange laminar clay according to claim 2, characterized in that said smectite is montmorillonite.
    [4]
    Four. A cation exchange laminar clay according to any of the
    10 claims 1 to 3, characterized in that said organosilane has at least one free cathonic group.
    [5]
    5. A cation exchange laminar clay according to any one of claims 1 to 4, characterized in that said organosilane is an alkoxysilane.
    A cation exchange layered clay according to any one of claims 1 to 5, characterized in that said anionic compound is a nitrite anion, an amine, a carboxyl or a dicarboxyl.
    [7]
    7. A cation exchange laminar clay according to claim 6,
    characterized in that said anionic compound is 11-aminoundecanoate, 4-aminobenzoate, sebacate anion nitrite.
    [8]
    8. A cation exchange laminar clay according to any one of claims 1 to 7, characterized in that said anionic compound is present in a proportion of 3% to 6.5% by weight with respect to the weight of the clay.
    Use of the ion exchange laminar clay according to any one of claims 1 to 8, as an additive in a cement mixture.
    [10]
    10. Concrete mixture characterized in that it contains cement and the cation exchange laminar clay of any one of claims 1 to 8.
    [11]
    eleven. A concrete mixture according to claim 10, characterized in that said
    Cation exchange laminar clay is present in a proportion of between 0.01% and 1% by weight with respect to the weight of cement.
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    引用文献:
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    CN101215454A|2008-01-16|2008-07-09|武汉理工大学|Montmorillonite modified silicone seal gum and preparation method thereof|
    CN101654584A|2009-09-23|2010-02-24|江苏工业学院|Low-solvent ocean nanometer anticorrosion coating and preparation method thereof|
    CN103739231A|2014-01-07|2014-04-23|江苏苏博特新材料股份有限公司|Concrete steel fiber antirust agent with self-antirust function and preparation method of concrete steel fiber antirust agent|
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