1. A preparation method of modified layered double hydroxide for improving the anti-carbonization performance of concrete is characterized by comprising the following steps:

preparation of Mg-Fe-CO₃Type LDHs;

mixing the Mg-Fe-CO₃Calcining the LDHs for 4-6 h at the temperature rise rate of 5-10 ℃/min and the calcining temperature of 400-500 ℃ to obtain the modified Mg-Fe-CO₃And (3) type LDHs.

2. The method for preparing the modified layered double hydroxide for improving the anti-carbonization performance of the concrete according to claim 1, wherein the Mg-Fe-CO is prepared by taking ferric nitrate nonahydrate, magnesium nitrate hexahydrate, sodium hydroxide, sodium carbonate and deionized water as raw materials and adopting a hydrothermal synthesis method₃Type LDHs;

the composite material comprises the following raw materials in parts by mass:

3. the method for preparing the modified layered double hydroxide for improving the anti-carbonization performance of concrete according to claim 2, wherein the Mg-Fe-CO is added₃The preparation method of the LDHs specifically comprises the following steps:

weighing ferric nitrate nonahydrate, magnesium nitrate hexahydrate and deionized water according to the proportion to prepare 200-400 ml of mixed salt solution, performing ultrasonic dispersion for 4-6 min, weighing sodium hydroxide, sodium carbonate and deionized water according to the proportion to prepare 200-400 ml of mixed alkali solution, and performing ultrasonic dispersion for 4-6 min;

pouring the dispersed mixed salt solution and the dispersed mixed alkali solution into an autoclave at the same time for reaction, wherein the time of the autoclave is set to be 1-4 h, the temperature is set to be 150-200 ℃, the rotating speed is set to be 400-600 r/min, and the pressure is set to be 1-5 MPa;

after the reaction is finished, pouring out the mixed solution in the autoclave, repeatedly performing suction filtration and washing on the mixed solution for 4-6 times by using deionized water until the solution is neutral, placing the filter cake in a vacuum drying oven at 80-105 ℃ for drying to constant weight, and grinding to obtain Mg-Fe-CO₃And (3) type LDHs.

4. The preparation method of the modified layered double hydroxide for improving the anti-carbonization performance of concrete according to claim 3, wherein the ultrasonic dispersion is carried out by using an ultrasonic disperser, and the power of the ultrasonic disperser is 120W.

5. A modified layered double hydroxide for improving the anti-carbonation performance of concrete, characterized in that it is prepared by the method according to any one of claims 1 to 4.

6. Use of a modified layered double hydroxide according to claim 5 for anti-carbonisation of concrete.

7. Use according to claim 6, characterized in that the modified layered double hydroxide is mixed with concrete.

8. The use according to claim 7, wherein the modified layered double hydroxide is mixed with the concrete in a mass ratio of the modified layered double hydroxide to the concrete of 0.5 to 2%.

Background

In cities and industrial areas, the concentration of carbon dioxide is very high due to environmental pollution, and the problem of steel bar corrosion caused by carbonization is increasingly serious. The carbonization of concrete refers to the acidic gas CO in the air₂A neutralization reaction process for reducing the alkalinity of the concrete by reacting with alkaline substances in the liquid phase of the concrete. When the neutralization depth is larger than the thickness of the protective layer of the concrete, a passive film on the surface of the steel bar under the protective layer is damaged, and the steel bar is corroded along with the combined action of water and air. The volume expansion caused by corrosion causes longitudinal cracks in the length direction of the steel bar and leads to the peeling of the protective layer, thereby reducing the section of the member, reducing the bearing capacity and finally causing the structural member to be damaged or fail. Therefore, the damage of concrete carbonization to the structure is a not negligible problem, and the research on the carbonization of concrete has profound significance.

In recent years, the impact of anthropogenic carbon dioxide on climate change has been recognized, which has led to a global commitment to reduce carbon dioxide (CO)₂) And other greenhouse gases. Accordingly, research is currently being conducted by various organizations to develop new and improved building materials, repair and repair techniques, and to better understand the physical and chemical mechanisms that lead to deterioration.

Layered Double Hydroxides (LDHs) are a general term for hydrotalcite and hydrotalcite-like compounds, and a series of supramolecular materials intercalated and assembled from these compounds are called hydrotalcite-like intercalation materials (LDHs). LDHs have larger specific surface area and higher anion exchange capacity, flexible interlayer domain can accommodate various types of anions and polar molecules, and the LDHs have the characteristics of adjustable chemical composition of a host layer plate, variety and quantity of interlayer guest anions and adjustable particle size and distribution of an intercalation assembly, show selectivity to anions and have the sequence of CO₃ ^2->SO₄ ^2->HPO₄ ^2->F^->Cl^->B(OH)^4->NO^3-The material can be used for improving the anti-carbonization performance of concrete.

Disclosure of Invention

In view of the defects of the prior art, the invention aims to provide a modified layered double hydroxide for improving the carbonization resistance of concrete and a preparation method and application thereof.

The technical scheme of the invention is as follows:

a preparation method of modified layered double hydroxide for improving the carbonization resistance of concrete comprises the following steps:

preparation of Mg-Fe-CO₃Type LDHs;

mixing the Mg-Fe-CO₃Calcining the LDHs for 4-6 h at the temperature rise rate of 5-10 ℃/min and the calcining temperature of 400-500 ℃ to obtain the modified Mg-Fe-CO₃And (3) type LDHs.

Optionally, the Mg-Fe-CO is prepared by taking ferric nitrate nonahydrate, magnesium nitrate hexahydrate, sodium hydroxide, sodium carbonate and deionized water as raw materials and adopting a hydrothermal synthesis method₃Type LDHs;

the composite material comprises the following raw materials in parts by mass:

alternatively, the Mg-Fe-CO₃The preparation method of the LDHs specifically comprises the following steps:

weighing ferric nitrate nonahydrate, magnesium nitrate hexahydrate and deionized water according to the proportion to prepare 200-400 ml of mixed salt solution, performing ultrasonic dispersion for 4-6 min, weighing sodium hydroxide, sodium carbonate and deionized water according to the proportion to prepare 200-400 ml of mixed alkali solution, and performing ultrasonic dispersion for 4-6 min;

pouring the dispersed mixed salt solution and the dispersed mixed alkali solution into an autoclave at the same time for reaction, wherein the time of the autoclave is set to be 1-4 h, the temperature is set to be 150-200 ℃, the rotating speed is set to be 400-600 r/min, and the pressure is set to be 1-5 MPa;

after the reaction is finished, pouring out the mixed solution in the autoclave, repeatedly performing suction filtration and washing on the mixed solution for 4-6 times by using deionized water until the solution is neutral, placing the filter cake in a vacuum drying oven at 80-105 ℃ for drying to constant weight, and grinding to obtain Mg-Fe-CO₃And (3) type LDHs.

Optionally, ultrasonic dispersion is performed by using an ultrasonic disperser, and the power of the ultrasonic disperser is 120W.

The invention relates to a modified layered double hydroxide for improving the anti-carbonization performance of concrete, wherein the modified layered double hydroxide is prepared by the method.

The invention relates to an application of a modified layered double hydroxide in concrete carbonization resistance.

Optionally, the modified layered double hydroxide is mixed with the concrete according to the mass ratio of the modified layered double hydroxide to the concrete of 0.5-2%.

Has the advantages that: the modified layered double hydroxide of the invention can obviously improve the anti-carbonization performance of the concrete when being added into the concrete as the admixture, because the carbonization process of the concrete is actually CO in the air₂The gas penetrates into the concrete and reacts with its basic substances Ca (OH)₂After chemical reaction, carbonate CaCO is generated₃And water, the process of making the concrete alkaline-reduced is called concrete carbonization, and Mg-Fe-CO₃After the LDHs is calcined at high temperature, interlayer water is completely lost, a large number of hydroxyl groups are separated, a three-dimensional network-shaped mixed oxide is formed, a higher surface area is provided, a large number of alkaline sites appear at interlayer positions, and CO adsorption is greatly improved₂The ability of the cell to perform. When CO in the air₂When gas permeates into concrete, the gas is modified to Mg-Fe-CO₃The anion adsorption capacity of the LDHs is CO₃ ^2->OH^-This makes CO₃ ^2-Will be adsorbed on the modified Mg-Fe-CO₃In the interlayer structure of the LDHs, the carbonization depth of concrete can be effectively reduced, the loss of alkaline substances is avoided, and the LDHs has a good application prospect in the aspect of improving the carbonization resistance of concrete; in addition, the preparation method is mature and stableSimple reaction process, convenient operation, low energy consumption, easy treatment and no secondary pollution. The method has good application prospect in the aspect of improving the anti-carbonization performance of the concrete, and provides a new way for the method for improving the anti-carbonization performance of the concrete.

Drawings

FIG. 1 shows modified Mg-Fe-CO of the present invention₃Structural schematic diagram of type LDHs; wherein 1 is modified Mg-Fe-CO₃Type LDHs, 2 is carbonate ion.

FIG. 2 shows modified Mg-Fe-CO with different doping amounts₃The compressive strength of the type LDHs is compared with that of the mortar test block carbonized to different ages.

Detailed Description

The invention provides a modified layered double hydroxide for improving the anti-carbonization performance of concrete and a preparation method and application thereof, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and more clear. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The embodiment of the invention provides a preparation method of modified layered double hydroxide for improving the anti-carbonization performance of concrete, which comprises the following steps:

s10 preparation of Mg-Fe-CO₃Type LDHs;

s20, mixing the Mg-Fe-CO₃Calcining the LDHs for 4-6 h (total calcining time), wherein the heating rate is 5-10 ℃/min, the calcining temperature is 400-500 ℃, and modified Mg-Fe-CO is prepared₃The structure of the type LDHs is shown in figure 1.

The concrete carbonization process is actually CO in the air₂The gas penetrates into the concrete and reacts with its basic substances Ca (OH)₂After chemical reaction, carbonate CaCO is generated₃And water, the process of making the concrete less basic is called concrete carbonation.

The embodiment of the invention can obviously improve the anti-carbonization performance of the concrete by adding the modified layered double hydroxide as the admixture into the concrete, because the Mg-Fe-CO₃After the type LDHs are calcined at high temperature, interlayer water is completely lost, and hydroxyl is largeThe amount is separated, the ordered layered structure is destroyed, a three-dimensional network-shaped mixed oxide is formed, a higher surface area is provided, the pore volume is increased, a large number of alkaline sites appear at the interlayer positions, and the adsorption of CO is greatly improved₂The ability of the cell to perform. When CO in the air₂When gas permeates into concrete, the gas is modified to Mg-Fe-CO₃The anion adsorption capacity of the LDHs is CO₃ ^2->OH^-This makes CO₃ ^2-Will be adsorbed on the modified Mg-Fe-CO₃In the interlayer structure of the LDHs, the carbonization depth of concrete can be effectively reduced, the loss of alkaline substances is avoided, and the LDHs has a good application prospect in the aspect of improving the carbonization resistance of concrete.

The preparation method provided by the embodiment of the invention is mature and stable, simple in reaction process, convenient to operate, low in energy consumption, easy to treat and free of secondary pollution. The method has good application prospect in the aspect of improving the anti-carbonization performance of the concrete, and provides a new way for the method for improving the anti-carbonization performance of the concrete.

In step 10, in one embodiment, the Mg-Fe-CO is prepared by a hydrothermal synthesis method using ferric nitrate nonahydrate, magnesium nitrate hexahydrate, sodium hydroxide, sodium carbonate, and deionized water as raw materials₃And (3) type LDHs.

The composite material comprises the following raw materials in parts by mass:

in one embodiment, the Mg-Fe-CO₃The preparation method of the LDHs specifically comprises the following steps:

s11, weighing ferric nitrate nonahydrate, magnesium nitrate hexahydrate and deionized water according to the proportion to prepare 200-400 ml of mixed salt solution, carrying out ultrasonic dispersion for 4-6 min, weighing sodium hydroxide, sodium carbonate and deionized water according to the proportion to prepare 200-400 ml of mixed alkali solution, and carrying out ultrasonic dispersion for 4-6 min;

s12, pouring the dispersed mixed salt solution and the dispersed mixed alkali solution into an autoclave at the same time for reaction, wherein the time of the autoclave is set to be 1-4 h, the temperature is set to be 150-200 ℃, the rotating speed is set to be 400-600 r/min (a rotor for rotation is placed in the autoclave), and the pressure is set to be 1-5 MPa;

s13, after the reaction is finished, pouring out the mixed liquid in the autoclave, repeatedly carrying out suction filtration and washing on the mixed liquid for 4-6 times by using deionized water until the solution is neutral, placing the filter cake in a vacuum drying oven at 80-105 ℃ for drying to constant weight, and grinding to obtain Mg-Fe-CO₃And (3) type LDHs.

It should be noted that the purity of the reagents used in the above steps is analytical grade.

In one embodiment, in the above step, ultrasonic dispersion is performed by using an ultrasonic disperser with a power of 120W.

In one embodiment, the vacuum used during vacuum drying is-0.1 mpa.

The embodiment of the invention provides a modified layered double hydroxide for improving the anti-carbonization performance of concrete, wherein the modified layered double hydroxide is prepared by the method provided by the embodiment of the invention.

The embodiment of the invention provides application of the modified layered double hydroxide in concrete carbonization resistance. The embodiment of the invention modifies Mg-Fe-CO₃The LDHs is added into concrete as an admixture, and the admixture is utilized to react with CO₃ ^2-The adsorption effect of (2) can effectively reduce the carbonization depth of concrete, avoids the loss of alkaline substances, and has good application prospect in the aspect of improving the carbonization resistance of concrete.

In one embodiment, the method of applying comprises: taking the modified layered double hydroxide as an additional admixture, and mixing the materials according to the weight ratio of (0.5-2): 100 mass ratio is added into the concrete. Further, the modified layered double hydroxide is used as an additional admixture, and the weight ratio of the modified layered double hydroxide to the added admixture is 1: 100 mass ratio is added into the concrete.

The invention is further illustrated by the following specific examples.

Firstly preparing modified Mg-Fe-CO₃Type LDHs:

s1, weighing 71.5g of ferric nitrate nonahydrate, 45.3g of magnesium nitrate hexahydrate and 400ml of deionized water according to the proportion to prepare 400ml of mixed salt solution, ultrasonically dispersing for 4min, weighing 16.8g of sodium hydroxide, 25.4g of sodium carbonate and 400ml of deionized water according to the proportion to prepare 400ml of mixed alkali solution, and ultrasonically dispersing for 4 min;

s2, pouring the dispersed mixed salt solution and the dispersed mixed alkali solution into a high-pressure kettle simultaneously for reaction, wherein the time of the high-pressure kettle is set to be 2 hours, the temperature is set to be 180 ℃, the rotating speed is set to be 450r/min, and the pressure is set to be 2.5 MPa;

s3, after the reaction is finished, pouring out the mixed liquor in the high-pressure kettle, repeatedly carrying out suction filtration and washing on the mixed liquor for 4 times by using deionized water until the solution is neutral, placing the filter cake in a vacuum drying box at the temperature of 95 ℃ for drying to constant weight, and grinding to obtain modified Mg-Fe-CO₃And (3) type LDHs.

Example 1

Mixing cement (portland cement) and standard sand at a mass ratio of 0.45 to water-cement (mortar ratio) of 1: 3, no incorporation of modified Mg-Fe-CO₃Preparing cement mortar by using the LDHs type, wherein the ingredients are shown in Table 1; taking the concrete as a control group, and carrying out accelerated carbonization test according to the test method standard of GB/T50082-2009 ordinary concrete long-term performance and durability, wherein the carbonization test conditions are as follows: CO 2₂The mass fraction is 20%, the temperature is 20 +/-2 ℃, the humidity is 70 +/-5%, and the test results are shown in table 2; using this as a control, the test pieces carbonized to 3d, 7d, and 28d were subjected to the compressive strength test, and the test results are shown in FIG. 2.

Example 2

Mixing cement (portland cement) and standard sand at a mass ratio of 0.45 to water-cement (mortar ratio) of 1: 3, doping modified Mg-Fe-CO accounting for 0.5 percent of the mass percentage of the cement₃The LDHs type is dry-mixed with cement in a grading way to prepare cement mortar, and the ingredients are shown in Table 1; carrying out accelerated carbonization test according to the test method standard of the long-term performance and the durability of GB/T50082-2009 ordinary concrete, wherein the carbonization test conditions are as follows: CO 2₂The mass fraction is 20%, the temperature is 20 +/-2 ℃, the humidity is 70 +/-5%, and the test results are shown in table 2; the test pieces carbonized to 3d, 7d and 28d were subjected to the compressive strength test, and the test results are shown in FIG. 2.

Example 3

Mixing cement (portland cement) and standard sand at a mass ratio of 0.45 to water-cement (mortar ratio) of 1: 3, doping modified Mg-Fe-CO accounting for 1 percent of the mass percentage of the cement₃The LDHs type is dry-mixed with cement in a grading way to prepare cement mortar, and the ingredients are shown in Table 1; carrying out accelerated carbonization test according to the test method standard of the long-term performance and the durability of GB/T50082-2009 ordinary concrete, wherein the carbonization test conditions are as follows: CO 2₂The mass fraction is 20%, the temperature is 20 +/-2 ℃, the humidity is 70 +/-5%, and the test results are shown in table 2; the test pieces carbonized to 3d, 7d and 28d were subjected to the compressive strength test, and the test results are shown in FIG. 2.

Example 4

Mixing cement (portland cement) and standard sand at a mass ratio of 0.45 to water-cement (mortar ratio) of 1: 3, doping modified Mg-Fe-CO accounting for 2 percent of the mass of the cement₃The LDHs type is dry-mixed with cement in a grading way to prepare cement mortar, and the ingredients are shown in Table 1; carrying out accelerated carbonization test according to the test method standard of the long-term performance and the durability of GB/T50082-2009 ordinary concrete, wherein the carbonization test conditions are as follows: CO 2₂The mass fraction is 20%, the temperature is 20 +/-2 ℃, the humidity is 70 +/-5%, and the test results are shown in table 2; the test pieces carbonized to 3d, 7d and 28d were subjected to the compressive strength test, and the test results are shown in FIG. 2.

Combining table 2 and fig. 2, it can be concluded that: adding modified Mg-Fe-CO₃The type LDHs can obviously enhance the anti-carbonization performance of silicate cement mortar, the improvement of the anti-carbonization performance is improved along with the increase of the doping amount, and the strength of the carbonized silicate cement mortar is kept highest when the doping amount is 1 percent in combination with the strength result of the carbonized silicate cement mortar.

TABLE 1 Cement mortar compounding table

TABLE 2 modified Mg-Fe-CO at different loadings₃Carbonization depth of mortar test block to different ages by type LDHs

In conclusion, the invention provides a modified layered double hydroxide for improving the anti-carbonization performance of concrete and a preparation method and application thereof. The invention modifies Mg-Fe-CO₃The LDHs is added into concrete as an admixture, and the admixture is utilized to react with CO₃ ^2-The adsorption effect of (2) can effectively reduce the carbonization depth of concrete, avoids the loss of alkaline substances, and has good application prospect in the aspect of improving the carbonization resistance of concrete.

It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.