A modified carbon mixed Co-Fe-LDH / LDO cement-based material, a preparation method thereof and a raw material ratio correction method

Abstract

The application provides a modified carbon mixing cement-based material doped with Co-Fe-LDH / LDO, a preparation method and a raw material ratio correction method; raw materials are cement, mixing water, Co-Fe-LDH, Co-Fe-LDO and carbon dioxide; the preparation method is as follows: Co-Fe-LDH and Co-Fe-LDO are added into part of the mixing water, ultrasonic dispersion is carried out, and a mixed solution with uniform dispersion is obtained; then cement is poured into a stirring device, the mixed solution and the remaining mixing water are added, and carbon dioxide is continuously introduced until a specified amount is reached; after uniform stirring, the LDH / LDO modified carbon mixing cement-based material is obtained; according to a calculation formula, the raw material ratio is regulated, and an optimal design ratio method of cement fluidity and carbon sequestration capacity is obtained, so that the working performance and carbon sequestration capacity of cement are effectively ensured; the material effectively utilizes and absorbs carbon dioxide, slows down the greenhouse effect, and has strong carbon sequestration capacity and good fluidity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of low-carbon concrete, in particular to a modified carbon-mixed cement-based material doped with Co-Fe-LDH / LDO, a preparation method thereof and a raw material ratio correction method. BACKGROUND

[0002] Layered double hydroxide (LDH) is a kind of composite metal hydroxide with host-guest structure, the host layer is composed of two or more metal cations, and the interlayer is anion and water molecule. It has excellent properties such as ion exchangeability, structure memory effect, thermal stability, acid-base bifunctionality, and is widely used in catalysts, lubricants, medical industry, etc.

[0003] The application of layered double hydroxide in cement-based materials is one of the hotspots of current research. Due to its excellent ion exchange and adsorption properties, it can be used to combine chloride ions and carbonate ions in cement-based materials, effectively reducing the carbonation effect and chloride ion erosion of mixed concrete. LDH can obtain calcined product LDO after calcination above 600℃, which retains the layered structure of LDH and greatly increases the specific surface area; therefore, its adsorption effect is significantly enhanced compared with LDH. In addition, LDO has adjustable surface acid-base properties and two-dimensional layered structure, so it can also be used as active heterogeneous catalyst and carrier. However, LDO has higher basicity than LDH, and due to calcination, part of its interlayer structure is destroyed, so its ion binding capacity will decrease to some extent compared with LDH.

[0004] Compared with conventional calcium-aluminum and magnesium-aluminum LDH, cobalt-iron-based LDH has higher current density and thermal stability, and its crystal interlayer spacing is larger, which helps to promote ion combination and adsorption, and has higher specific surface area, and its adsorption capacity can reach 2-3 times of that of conventional LDH. Therefore, cobalt-iron-based LDH has strong advantages as a modification material for carbon-mixed cement.

[0005] A Chinese invention patent with patent number CN112745084A discloses a NiFe-LDH cement-based composite wave-absorbing material and a preparation method thereof. By adding a uniformly dispersed NiFe-LDH mixing aqueous solution during cement mixing, a cement-based composite wave-absorbing material with low electromagnetic wave reflectivity is obtained, which can effectively absorb electromagnetic wave pollution. A Chinese invention patent with patent number CN115784647A discloses a preparation process of modified cement and early-strength super-high-performance concrete thereof. Li-Fe layered double metal hydroxide powder and acidic retarder are dispersed in ethanol liquid to form a mixed suspension. The atomized mixed suspension collides with the cement particles carried by the hot carrier gas, so that the mixed suspension is sprayed onto the surface of the cement particles, and the ethanol on the surface of the cement particles is evaporated under the action of the hot carrier gas to obtain modified cement. The prepared concrete has the characteristics of super-early strength, setting time, and more stable early performance.

[0006] Most of the existing invention patents are to mix LDH into cement for mixing, thereby effectively improving various properties thereof, but there are few applications of mixing LDH and LDO into carbon mixed cement, and the current carbon mixed cement faces problems such as poor fluidity and low carbon dioxide absorption capacity. By combining the advantages and disadvantages of LDH and LDO, the working performance of carbon mixed cement can be improved by composite mixing of LDH and LDO. Therefore, it is of great significance to develop a modified carbon mixed cement material with good fluidity, i.e. fluidity, and high carbon dioxide absorption capacity by double mixing of LDH / LDO. SUMMARY

[0007] The purpose of the present application is to provide a modified carbon mixed cement-based material with double mixing of Co-Fe-LDH / LDO and a preparation method and raw material ratio correction method thereof. The material is simple to prepare and easy to use, can effectively improve the fluidity and carbon sequestration capacity of carbon mixed cement, and has high application value in the field of low-carbon concrete. The raw material ratio correction formula mentioned in the present application can effectively combine the ratio research, and control the amount of absorbed carbon dioxide according to the required fluidity, has a wide application prospect and a certain research reference value.

[0008] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0009] A modified carbon mixed cement-based material with double mixing of Co-Fe-LDH / LDO, comprising the following components in parts by mass: cement 350-400 parts, mixing water 200-250 parts, cobalt-iron layered double metal hydroxide Co-Fe-LDH 3-4 parts, calcined cobalt-iron layered double metal hydroxide Co-Fe-LDO 2-3 parts, and carbon dioxide 2-8 parts.

[0010] The calcined cobalt-iron layered double metal hydroxide Co-Fe-LDO is prepared by the following steps:

[0011] Step a1: Take several Co-Fe-LDH in a muffle furnace calcination at 600℃, the heating rate is 3℃ / min, after keeping warm, natural cooling to obtain calcined cobalt-iron layered double hydroxide Co-Fe-LDO.

[0012] Further, the cement is ordinary Portland cement, model P·O 42.5.

[0013] Further, the cobalt-iron layered double hydroxide Co-Fe-LDH particle size is 0.5-2.0 microns, and the specific surface density is 0.2-0.4 g / mol.

[0014] A preparation method of a modified carbon-mixed cement-based material doped with Co-Fe-LDH / LDO, for preparing any of the modified carbon-mixed cement-based materials doped with Co-Fe-LDH / LDO, comprising the following steps:

[0015] Step one, according to the mass fraction, 100-120 parts of mixed water are taken from the 200-250 parts of mixed water, the Co-Fe-LDH and the Co-Fe-LDO are added to the mixed water, and ultrasonic dispersion is carried out until uniform dispersion, to obtain a LDH / LDO suspension with a milky white color;

[0016] Step two, the cement is added to the stirring device for dry mixing, then the remaining mixed water and the LDH / LDO suspension are added, and the stirring is continued until uniform stirring, to obtain a cement slurry;

[0017] Step three, the carbon dioxide is introduced into the cement slurry at a rate of 8-10 L / min, and the stirring is continued, so that the cement slurry continuously absorbs carbon dioxide during the mixing process, and finally a carbon-mixed cement slurry is obtained;

[0018] Step four, the carbon-mixed cement slurry is poured into a mold, the excess slurry is scraped off, and after 7 days of curing in a curing room, the mold is demolded, to obtain a modified carbon-mixed cement-based material doped with Co-Fe-LDH / LDO.

[0019] Further, in step one, the ultrasonic dispersion time is 60s-180s, and in step two, the dry mixing time is 30s, and the continued stirring time of the remaining mixed water and the LDH / LDO suspension is 60s-120s.

[0020] Further, during the curing process, the temperature is maintained at 20±2℃, and the relative humidity is above 95%.

[0021] Further, the stirring device comprises: a stirring tank, a stirring motor, a stirring part, a flow meter, a barometer, a buffer tank, a pressure steel bottle, an A gas pipe and a B gas pipe; the stirring tank comprises a stirring barrel and a stirring cover, the stirring barrel is open at the top end and is used for containing materials; the stirring cover is arranged at the top end opening of the stirring barrel and is locked and sealed with the stirring barrel through a plurality of buckles on the side of the stirring barrel; the stirring cover is provided with a central opening in the middle part; the stirring part is arranged in the stirring tank and is fixedly connected with the output end of the stirring motor arranged on the upper end surface of the stirring cover through one end penetrating the central opening in the middle part of the stirring cover; the barometer is used for detecting the air pressure in the stirring tank; the pressure steel bottle is connected with the buffer tank through the A gas pipe; the buffer tank is used for normalizing the carbon dioxide released from the pressure steel bottle at normal temperature and normal pressure, and the carbon dioxide is introduced into the stirring tank through the B gas pipe; and the flow meter is used for counting the amount of carbon dioxide introduced into the stirring tank.

[0022] Further, one-way valves are arranged on the A gas pipe and the B gas pipe, which are used for avoiding reverse flow of carbon dioxide gas due to air pressure change; and rubber pads are arranged on the contact surface between the stirring cover and the stirring barrel, which are used for improving the sealing effect.

[0023] A raw material ratio correction method of a modified carbon mixed cement-based material with Co-Fe-LDH / LDO double-doping, used for correcting the raw material ratio of the modified carbon mixed cement-based material with Co-Fe-LDH / LDO double-doping, characterized in that it comprises the following steps:

[0024] Step one, according to the required carbon dioxide content, preliminarily design the water-cement ratio and the mass ratio m(LDH) / m(LDO) of Co-Fe-LDH and Co-Fe-LDO;

[0025] Step two, according to the Levenberg-Marquardt algorithm and the Spearman correlation coefficient algorithm, record the carbon dioxide content as M1, the mass ratio m(LDH) / m(LDO) as M2, and the water-cement ratio as M3, and perform function fitting on M1, M2 and M3 with respect to the cement fluidity Y to obtain the following calculation formula:

[0026]

[0027] Step three, according to the required cement fluidity Y, according to the calculation formula obtained in step two, by changing the values of M2 and M3 in the formula to control the maximum amount of carbon dioxide that can be adsorbed, according to the values of M2 and M3, the mix ratio in step one is corrected to obtain the final raw material mix ratio of the modified carbon mixed cement-based material.

[0028] Compared with the prior art, the present application has the following beneficial effects:

[0029] (1) The early and late strength of the modified carbon mixed cement of the double-doped LDH / LDO is significantly improved, and the fluidity is significantly enhanced; the early 3d strength is up to 17.32Mpa, the late 28d strength is up to 36.77Mpa, and the fluidity is up to 30.04cm.

[0030] (2) The calcined product LDO of cobalt-iron layered double metal hydroxide is used as a composite modified material in the application, the preparation is simple, the property is stable, the cost is low, and the fluidity and carbon sequestration capacity of the carbon mixed cement can be effectively changed by controlling the mixing ratio of Co-Fe-LDH and Co-Fe-LDO.

[0031] (3) The stirring device can effectively control the amount of carbon dioxide in the mixing process, the stirring speed is 2-4 times of that of an ordinary cement stirring barrel, can effectively promote the absorption of carbon dioxide by cement, and the system is in a fully sealed state, so that the effective absorption of carbon dioxide by cement during mixing can be ensured.

[0032] (4) The modified carbon mixed cement material of the double-doped LDH / LDO has the advantages of simple preparation method, easy production, convenient use, convenient transportation, high fluidity and high strength, and has great use value in the field of low-carbon concrete.(5) The application provides a correlation formula of the fluidity of carbon mixed cement and the carbon dioxide content, which quantitatively corrects the ratio design of carbon mixed cement, and has certain research value for the ratio design of carbon mixed cement. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The figure is a schematic diagram of the stirring device of an embodiment of the application;

[0034] Figure 2 The figure is a physical diagram of the stirring device of an embodiment of the application;

[0035] In the figure: 1, pressure steel bottle; 2, buffer tank; 3, A gas pipe; 4, B gas pipe; 5, one-way valve; 6, flowmeter; 7, stirring motor; 8, pressure gauge; 9, stirring cover; 10, lock; 11, stirring barrel; 12, stirring part. DETAILED DESCRIPTION

[0036] The technical solutions in the application will be described below in conjunction with the embodiments in the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0037] The inventive principle of the application is:

[0038] Layered double hydroxides (LDHs) have excellent ion exchange and adsorption capacity, which can effectively remove the ions such as chloride and carbonate that have adverse effects on concrete. However, due to the limitation of specific surface area of LDHs, the total amount of ions that can be adsorbed is limited, and the synergistic effect of LDHs with carbon dioxide in carbon mixing cement is not clear. LDO is a product obtained by calcining LDH at high temperature. Compared with LDH, LDO has a higher specific surface area, and thus has a stronger adsorption capacity for ions. However, compared with LDH, LDO has stronger alkalinity, which may lead to a decrease in the strength of the final cement in the cement hydration process.

[0039] Cobalt-iron-based LDH has more excellent properties than other LDHs, has better thermal stability, larger interlayer spacing of crystal, helps to promote the combination and adsorption of ions, and has a higher specific surface area, and the adsorption capacity can reach 2-3 times of that of conventional LDHs, which plays an efficient role in the absorption of harmful anions in cement and concrete.

[0040] Carbon mixing cement is a new technology. Compared with the traditional carbon curing method, it has the advantages of low cost and short carbonation time. Moreover, due to the in-situ formation of calcium carbonate, the carbonation products can be uniformly distributed in the matrix, effectively filling the microstructure, thereby improving the performance of cement-based materials. However, the introduction of carbon dioxide will lead to rapid hardening of cement-based materials, and the fluidity will decrease sharply with the increase of carbon dioxide content. This is mainly related to the flocculation structure of the hydration products and carbonation products formed on the surface of cement clinker.

[0041] In the specific embodiment, the calcined cobalt-iron layered double hydroxide Co-Fe-LDO is prepared by the following steps:

[0042] Step a1: several Co-Fe-LDHs are calcined in a muffle furnace at 600 DEG C for 4h, the heating rate is 3 DEG C / min, and the temperature is kept for 8h natural cooling to obtain the calcined cobalt-iron layered double hydroxide Co-Fe-LDO.

[0043] The present application combines the advantages and disadvantages of LDH and LDO, controls the mixing ratio of LDH and LDO, and develops a Co-Fe-LDH / LDO composite modified carbon mixing cement-based material. In the specific embodiment, the following stirring device is used for cement stirring and carbon dioxide mixing:

[0044] The stirring device comprises a stirring tank, a stirring motor 7, a stirring part 12, a flowmeter 6, a pressure gauge 8, a buffer tank 2, a pressure steel cylinder 1, an A gas pipe 3 and a B gas pipe 4; the stirring tank comprises a stirring barrel 11 and a stirring cover 9, the top end of the stirring barrel 11 is open, and is used for containing materials;

[0045] The stirring cover 9 is arranged at the top opening of the stirring barrel 11, and the stirring barrel 11 is locked and sealed through a plurality of buckles 10 arranged at the side of the stirring barrel 11; the stirring cover 9 is provided with a middle opening; the stirring part 12 is arranged in the stirring barrel and is fixedly connected with the output end of the stirring motor 7 arranged at the upper end surface of the stirring cover 9 through one end penetrating the middle opening of the stirring cover 9;

[0046] The barometer 8 is used for detecting the air pressure in the stirring barrel; the pressure cylinder 1 is connected with the buffer tank 2 through the A gas pipe 3; the buffer tank 2 is used for converting the carbon dioxide released in the pressure cylinder 1 into normal temperature and pressure, and the carbon dioxide is introduced into the stirring barrel through the B gas pipe 4; and the flowmeter 6 is used for counting the amount of carbon dioxide introduced into the stirring barrel.

[0047] The A gas pipe 3 and the B gas pipe 4 are provided with one-way valves, which are used for avoiding the reverse flow of carbon dioxide gas due to the change of air pressure; and the contact surface between the stirring cover 9 and the stirring barrel 11 is provided with a rubber pad, which is used for improving the sealing effect.

[0048] Embodiment 1

[0049] Co-Fe-LDH / LDO composite modified carbon-mixed cementitious material

[0050] Prepare the required mixing water 30%, cobalt-iron layered double hydroxide LDH 3.33%, calcined cobalt-iron layered double hydroxide LDO 1.67%, and cement 65% by weight percentage, and the water-cement ratio is 0.46 at this time. Weigh 10% of the mixing water by weight percentage, add the required cobalt-iron layered double hydroxide Co-Fe-LDH and calcined cobalt-iron layered double hydroxide Co-Fe-LDO to the mixing water, and ultrasonic dispersion for 60s-180s until uniform dispersion, to obtain a milky white LDH / LDO suspension; add the cement into the stirring barrel and dry mix for 30s, then add the remaining mixing water and LDH / LDO suspension, and continue to stir for 60s-120s until uniform stirring; seal the stirring barrel with the stirring cover, then pass carbon dioxide into the stirring barrel at a rate of 10L / min through the pressure cylinder, and the total amount of carbon dioxide passed into the above-mentioned material is 1% of the total mass of the material, and at the same time, the stirring motor is turned on, so that the cement paste continuously absorbs carbon dioxide during the mixing process, that is, the carbon-mixed cement paste is formed; place the conical mold in the center of the test plate, fill the cement paste, smooth it with a scraper, and then quickly lift the mold, record the diameters of the cement in two perpendicular directions, calculate the average value, and measure the fluidity of the cement to be 26.3cm, the 3d strength to be 17.32Mpa, and the 28d strength to be 29.24Mpa, according to the formula:

[0051]

[0052] In the formula, M1=0.01, M2=2, M3=0.46, the fluidity Y of the cement can be calculated as 26.12 cm, which is close to the test result.

[0053] Example 2

[0054] A Co-Fe-LDH / LDO composite modified carbon-mixed cement-based material

[0055] Prepare the required mixing water 23.57%, cobalt-iron layered double hydroxide LDH 4%, calcined cobalt-iron layered double hydroxide LDO 1%, cement 71.43% by weight percentage, and the water-cement ratio is 0.33 at this time. Weigh 10% of the mixing water by weight percentage, add the required cobalt-iron layered double hydroxide Co-Fe-LDH and calcined cobalt-iron layered double hydroxide Co-Fe-LDO to the mixing water, and perform ultrasonic dispersion for 60-180 s until uniform dispersion, obtaining a milky white LDH / LDO suspension; add cement to the stirring barrel and dry mix for 30 s, then add the remaining mixing water and LDH / LDO suspension, continue stirring for 60-120 s until uniform stirring; seal the stirring barrel with a stirring cover, then pass carbon dioxide into the stirring device at a rate of 10 L / min through a pressure cylinder, a total of 2% of the total mass of the above-mentioned materials carbon dioxide, and at the same time open the stirring motor, so that the cement paste continuously absorbs carbon dioxide during the mixing process, i.e. to form a carbon-mixed cement paste; place the conical mold in the center of the test plate, fill the cement paste, smooth it with a scraper, and quickly lift the mold, record the diameters of the cement in two perpendicular directions, and calculate the average value. The fluidity of the cement is measured to be 22.4 cm, the 3d strength is 11.64 Mpa, and the 28d strength is 29.65 Mpa, according to the formula:

[0056]

[0057] In the formula, M1=0.02, M2=4, M3=0.33, the fluidity Y of the cement can be calculated as 22.25 cm, which is close to the test result.

[0058] Example 3

[0059] A Co-Fe-LDH / LDO composite modified carbon-mixed cement-based material

[0060] The required mixing water 26.86%, cobalt-iron layered double hydroxide LDH 4.5%, calcined cobalt-iron layered double hydroxide LDO 1.5%, and cement 67.14% by weight percentage were prepared, and the water-cement ratio was 0.40 at this time. The mixing water with a weight percentage of 10% was weighed, the required cobalt-iron layered double hydroxide Co-Fe-LDH and calcined cobalt-iron layered double hydroxide Co-Fe-LDO were added to the mixing water, and ultrasonic dispersion was performed for 60-180 s until uniform dispersion, to obtain a LDH / LDO suspension with a milky white color; the cement was added to the stirring barrel and dry-mixed for 30 s, then the remaining mixing water and the LDH / LDO suspension were added, and stirring was continued for 60-120 s until uniform stirring; the stirring barrel was sealed with a stirring cover, then carbon dioxide was introduced into the stirring tank at a rate of 10 L / min through a pressure steel cylinder, and a total of 1.5% of the total mass of the above-mentioned materials of carbon dioxide was introduced, while the stirring motor was turned on, so that the cement paste continuously absorbed carbon dioxide during the mixing process, i.e., a carbon-mixed cement paste was formed; the conical mold was placed in the center of the test plate, the cement paste was filled, and the mold was quickly lifted after being flattened with a scraper, and the diameters of the cement in two perpendicular directions were recorded, and the average value was calculated. The measured fluidity of the cement was 20.1 cm, the 3d strength was 10.99 Mpa, and the 28d strength was 36.77 Mpa, and according to the formula:

[0061]

[0062] In the formula, M1=0.015, M2=3, M3=0.40, the fluidity Y of the cement can be calculated as 20.17 cm, which is close to the test result.

[0063] Example 4

[0064] A Co-Fe-LDH / LDO composite modified carbon-mixed cement-based material

[0065] The required mixing water 23.57%, cobalt-iron layered double hydroxide LDH 3.33%, calcined cobalt-iron layered double hydroxide LDO 1.67%, and cement 71.43% by weight percentage were prepared, and the water-cement ratio was 0.33 at this time. The mixing water with a weight percentage of 10% was weighed, the required cobalt-iron layered double hydroxide Co-Fe-LDH and calcined cobalt-iron layered double hydroxide Co-Fe-LDO were added to the mixing water, and ultrasonic dispersion was performed for 60-180 s until uniform dispersion, to obtain a LDH / LDO suspension with a milky white color; the cement was added to the stirring barrel and dry-mixed for 30 s, then the remaining mixing water and the LDH / LDO suspension were added, and stirring was continued for 60-120 s until uniform stirring; the stirring barrel was sealed with a stirring cover, then carbon dioxide was introduced into the stirring tank at a rate of 10 L / min through a pressure steel cylinder, and a total of 1% of the total mass of the above-mentioned materials of carbon dioxide was introduced, and at the same time the stirring motor was turned on, so that the cement paste continuously absorbed carbon dioxide during the mixing process, i.e., a carbon-mixed cement paste was formed; the conical mold was placed in the center of the test plate, the cement paste was filled, and the mold was quickly lifted after being flattened with a scraper, and the diameters of the cement in two perpendicular directions were recorded, and the average value was calculated. The measured fluidity of the cement was 30.04 cm, the 3d strength was 12.17 Mpa, and the 28d strength was 33.87 Mpa, and according to the formula:

[0066]

[0067] In the formula, M1=0.01, M2=2, and M3=0.33, the fluidity Y of the cement can be calculated as 30.27 cm, which is close to the test result.

[0068] Example 5

[0069] A Co-Fe-LDH / LDO composite modified carbon-mixed cement-based material

[0070] The required mixing water 30%, cobalt-iron layered double hydroxide LDH 4%, calcined cobalt-iron layered double hydroxide LDO 1%, cement 65% by weight percentage were prepared, and the water-cement ratio was 0.46 at this time. The mixing water with a weight percentage of 10% was weighed, the required cobalt-iron layered double hydroxide Co-Fe-LDH and calcined cobalt-iron layered double hydroxide Co-Fe-LDO were added to the mixing water, and ultrasonic dispersion was performed for 60s-180s until uniform dispersion, to obtain a LDH / LDO suspension with a milky white color; the cement was added to the stirring barrel and dry-mixed for 30s, then the remaining mixing water and the LDH / LDO suspension were added, and stirring was continued for 60s-120s until uniform stirring; the stirring barrel was sealed with a stirring cover, then carbon dioxide was introduced into the stirring tank at a rate of 10L / min through a pressure steel cylinder, and a total of 1% of the total mass of the above-mentioned materials of carbon dioxide was introduced, and at the same time the stirring motor was turned on, so that the cement paste continuously absorbed carbon dioxide during the mixing process, i.e. carbon mixed cement paste was formed; the conical mold was placed in the center of the test plate, the cement paste was filled, and the mold was quickly lifted after the scraper was leveled, and the diameters of the cement in two perpendicular directions were recorded, and the average value was calculated. The measured fluidity of the cement was 29.53cm, the 3d strength was 9.47Mpa, and the 28d strength was 28.63Mpa, according to the formula:

[0071]

[0072] In the formula, M1=0.01, M2=4, M3=0.46, the fluidity Y of the cement can be calculated as 29.62cm, which is close to the test result.

[0073] Example 6

[0074] A Co-Fe-LDH / LDO composite modified carbon mixed cement-based material

[0075] Prepare the required mixing water 23.57%, cobalt-iron layered double hydroxide LDH 3.33%, calcined cobalt-iron layered double hydroxide LDO 1.67%, cement 71.43% by weight percentage, at this time the water-cement ratio is 0.33. Take 10% of the mixing water by weight percentage, add the required cobalt-iron layered double hydroxide Co-Fe-LDH and calcined cobalt-iron layered double hydroxide Co-Fe-LDO to the mixing water, and perform ultrasonic dispersion for 60s-180s until uniform dispersion, obtaining a milky white LDH / LDO suspension; add cement to the stirring barrel and dry mix for 30s, then add the remaining mixing water and LDH / LDO suspension, continue to stir for 60s-120s until uniform stirring; seal the stirring barrel with a stirring cover, then pass carbon dioxide into the stirring tank at a rate of 10L / min through a pressure cylinder, a total of 2% of the total mass of the above materials carbon dioxide, while turning on the stirring motor, so that the cement paste continuously absorbs carbon dioxide during the mixing process, i.e. forming a carbon mixed cement paste; place the conical mold in the center of the test plate, fill it with cement paste, smooth it with a scraper, then quickly lift the mold, record the diameters of the cement in two perpendicular directions, and calculate the average value. The measured fluidity of the cement is 16.1cm, the 3d strength is 13.29Mpa, and the 28d strength is 31.57Mpa, according to the formula:

[0076]

[0077] wherein M1=0.02, M2=2, M3=0.33, the fluidity of the cement Y=15.25cm can be calculated, which is relatively close to the test result.

[0078] Example 7

[0079] A Co-Fe-LDH / LDO composite modified carbon mixed cement-based material

[0080] Prepare the required mixing water 30%, cobalt-iron layered double hydroxide LDH 4%, calcined cobalt-iron layered double hydroxide LDO 1%, cement 65% by weight percentage, at this time the water-cement ratio is 0.46. Take 10% of the mixing water by weight percentage, add the required cobalt-iron layered double hydroxide Co-Fe-LDH and calcined cobalt-iron layered double hydroxide Co-Fe-LDO to the mixing water, and perform ultrasonic dispersion for 60s-180s until uniform dispersion, obtaining a milky white LDH / LDO suspension; add cement to the stirring barrel and dry mix for 30s, then add the remaining mixing water and LDH / LDO suspension, continue stirring for 60s-120s until uniform mixing; seal the stirring barrel with a stirring cover, then pass carbon dioxide into the stirring tank at a rate of 10L / min through a pressure cylinder, a total of 2% of the total mass of the above materials carbon dioxide, while turning on the stirring motor, so that the cement paste continuously absorbs carbon dioxide during mixing, i.e. carbon mixing cement paste is formed; place the conical mold in the center of the test plate, fill it with cement paste, smooth it with a scraper, then quickly lift the mold, record the diameters of the cement in two perpendicular directions, and calculate the average value. The measured fluidity of the cement is 19.5cm, the 3d strength is 11.53Mpa, and the 28d strength is 31.21Mpa, according to the formula:

[0081]

[0082] wherein M1=0.02, M2=4, M3=0.46, the fluidity of the cement Y=19.32cm can be calculated, which is close to the test result.

[0083] Example 8

[0084] A Co-Fe-LDH / LDO composite modified carbon mixing cement-based material

[0085] The required mixing water 30%, cobalt-iron layered double hydroxide LDH 3.33%, calcined cobalt-iron layered double hydroxide LDO 1.67%, and cement 65% by weight percentage were prepared, and the water-cement ratio was 0.46 at this time. The mixing water with a weight percentage of 10% was weighed, the required cobalt-iron layered double hydroxide Co-Fe-LDH and calcined cobalt-iron layered double hydroxide Co-Fe-LDO were added to the mixing water, and ultrasonic dispersion was performed for 60-180 s until the solution was uniformly dispersed in the form of a milky white suspension; the cement was added to the stirring barrel and dry mixed for 30 s, and then the mixing water and the LDH / LDO suspension were added, and stirring was continued for 60-120 s until the stirring was uniform; the stirring barrel was sealed with a stirring cover, and then carbon dioxide was introduced into the stirring tank at a rate of 10 L / min through a pressure cylinder, and a total of 2% of the total mass of the above-mentioned materials was introduced, and at the same time, the stirring motor was turned on, so that the cement paste continuously absorbed carbon dioxide during the mixing process, that is, the carbon-mixed cement paste was formed; the conical mold was placed in the center of the test plate, the cement paste was filled, and the mold was quickly lifted after being leveled with a scraper, and the diameters of the cement in two perpendicular directions were recorded, and the average value was calculated. The fluidity of the cement was measured to be 14.21 cm, the 3d strength was 14.17 Mpa, and the 28d strength was 35.41 Mpa, and according to the formula:

[0086]

[0087] In the formula, M1=0.02, M2=2, and M3=0.46, the fluidity Y of the cement can be calculated to be 12.32 cm, which is close to the test result.

[0088] Comparative Example:

[0089] The same amount of mixing water and cement as in Example 8 was weighed, but no cobalt-iron layered double hydroxide LDH and calcined cobalt-iron layered double hydroxide LDO was added, and the water-cement ratio was 0.46 at this time. The cement was added to the stirring barrel and dry mixed for 30 s, and then the mixing water was added, and stirring was continued for 60-120 s until the stirring was uniform; the stirring barrel was sealed with a stirring cover, and then carbon dioxide was introduced into the stirring tank at a rate of 10 L / min through a pressure cylinder, and a total of 2% of the total mass of the above-mentioned materials was introduced, and at the same time, the stirring motor was turned on, so that the cement paste continuously absorbed carbon dioxide during the mixing process, that is, the carbon-mixed cement paste was formed; the conical mold was placed in the center of the test plate, the cement paste was filled, and the mold was quickly lifted after being leveled with a scraper, and the diameters of the cement in two perpendicular directions were recorded, and the average value was calculated. The fluidity of the cement was measured to be 10.25 cm, the 3d strength was 11.28 Mpa, and the 28d strength was 30.66 Mpa. It can be seen that the cement without the addition of LDH / LDO has a decrease in fluidity and strength.

[0090] The modified carbon-mixed cement-based material with double-doped Co-Fe-LDH / LDO of the application can effectively improve the poor fluidity and low strength of carbon-mixed cement. The early and late strength of the modified carbon-mixed cement with double-doped LDH / LDO prepared by the application is significantly improved, and the fluidity is significantly strengthened. The early 3d strength is up to 17.32 Mpa (Example 1), the late 28d strength is up to 36.77 Mpa (Example 3), and the fluidity is up to 30.04 cm (Example 4). By double-doping cobalt-iron layered double hydroxide Co-Fe-LDH and calcined cobalt-iron layered double hydroxide Co-Fe-LDO, the shortcomings of low specific surface area and low adsorption capacity of conventional LDH are overcome, and the performance of cement is further improved. The carbon dioxide adsorption effect is effectively controlled through three parameters of water-cement ratio, LDH / LDO ratio and CO2 content, an optimal design ratio method of cement fluidity and carbon dioxide adsorption capacity is formed, and the relationship between cement fluidity and water-cement ratio, carbon dioxide adsorption capacity and LDH / LDO ratio is fitted by using formula, which is helpful to realize the dual optimization of carbon sequestration capacity and working performance of carbon-mixed cement.

Claims

1. A modified carbon-based cementitious material with dual Co-Fe-LDH / LDO admixture, characterized in that, By weight, it contains the following components: 350-400 parts cement, 200-250 parts mixing water, 3-4 parts cobalt-iron layered bimetallic hydroxide Co-Fe-LDH, 2-3 parts calcined cobalt-iron layered bimetallic hydroxide Co-Fe-LDO, and 2-8 parts carbon dioxide. The calcined cobalt-iron layered bimetallic hydroxide Co-Fe-LDO is prepared by the following steps: Step a1: Take a certain amount of Co-Fe-LDH and calcine it in a muffle furnace at 600℃ with a heating rate of 3℃ / min. After holding at the temperature, it is naturally cooled to obtain calcined cobalt-iron layered bimetallic hydroxide Co-Fe-LDO.

2. The modified carbon-based cementitious material with dual Co-Fe-LDH / LDO admixture according to claim 1, characterized in that, The cement is ordinary Portland cement, with the grade being P·O 42.

5.

3. The modified carbon-based cementitious material with dual Co-Fe-LDH / LDO admixture according to claim 1, characterized in that, The cobalt-iron layered bimetallic hydroxide Co-Fe-LDH has a particle size of 0.5-2.0 micrometers and a specific surface density of 0.2-0.4 g / mol.

4. A method for preparing a modified carbon-based cementitious material with dual Co-Fe-LDH / LDO admixture, used to prepare the modified carbon-based cementitious material with dual Co-Fe-LDH / LDO admixture as described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Weigh 100-120 parts of the mixing water from 200-250 parts by weight, add the Co-Fe-LDH and Co-Fe-LDO to the weighed mixing water, and perform ultrasonic dispersion until uniform dispersion to obtain a milky white LDH / LDO suspension. Step 2: Add the cement to the mixing device and dry mix, then add the remaining mixing water and LDH / LDO suspension, and continue mixing until the mixture is uniform to obtain cement paste; Step 3: The carbon dioxide is introduced into the cement paste at a rate of 8-10 L / min, and stirring is continued so that the cement paste continuously absorbs carbon dioxide during the mixing process, and finally carbon-mixed cement paste is obtained. Step four: Pour the carbon-mixed cement paste into a mold, scrape off the excess paste, and cure in a curing room for 7 days before demolding to obtain the modified carbon-mixed cement-based material with double adsorption of Co-Fe-LDH / LDO.

5. The method for preparing a modified carbon-based cementitious material with dual Co-Fe-LDH / LDO admixture according to claim 4, characterized in that, In step one, the ultrasonic dispersion time is 60s-180s. In step two, the dry mixing time is 30s. The remaining mixing water and LDH / LDO suspension are stirred for 60s-120s.

6. The method for preparing a modified carbon-based cementitious material with dual Co-Fe-LDH / LDO admixture according to claim 4, characterized in that, During the maintenance process, the temperature should be maintained at 20±2℃ and the relative humidity at 95% or higher.

7. The method for preparing a modified carbon-based cementitious material with dual Co-Fe-LDH / LDO admixture according to claim 4, characterized in that, The stirring device includes: a stirring tank, a stirring motor (7), a stirring component (12), a flow meter (6), a pressure gauge (8), a buffer tank (2), a pressure cylinder (1), an A-pipe (3) and a B-pipe (4); the stirring tank includes a stirring bucket (11) and a stirring cover (9), the stirring bucket (11) has an opening at the top for holding materials; The stirring cover (9) is located at the top opening of the stirring tank (11) and is locked and sealed by several latches (10) on the side of the stirring tank (11); the stirring cover (9) has a hole in the middle; the stirring component (12) is located in the stirring tank and one end protrudes through the hole in the middle of the stirring cover (9) and is fixedly connected to the output end of the stirring motor (7) located on the upper surface of the stirring cover (9); The pressure gauge (8) is used to detect the pressure inside the mixing tank; the pressure cylinder (1) is connected to the buffer tank (2) through the A gas pipe (3); the buffer tank (2) is used to bring the carbon dioxide released from the pressure cylinder (1) to room temperature and pressure, and to introduce the carbon dioxide into the mixing tank through the B gas pipe (4); the flow meter (6) is used to count the amount of carbon dioxide introduced into the mixing tank.

8. The method for preparing a modified carbon-based cementitious material with dual Co-Fe-LDH / LDO admixture according to claim 7, characterized in that, One-way valves are installed on the A pipe (3) and B pipe (4) to prevent carbon dioxide gas from flowing backward due to pressure changes; rubber pads are installed on the contact surfaces of the stirring cover (9) and the stirring tank (11) to improve the sealing effect.

9. A method for correcting the raw material proportions of a modified carbon-based cementitious material with dual Co-Fe-LDH / LDO admixture, used to correct the raw material proportions of the modified carbon-based cementitious material with dual Co-Fe-LDH / LDO admixture as described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Based on the required carbon dioxide dosage, conduct preliminary mix design for the water-cement ratio and the mass ratio of Co-Fe-LDH to Co-Fe-LDO, m(LDH) / m(LDO); Step two: Based on the Levenberg-Marquardt algorithm and the Spearman correlation coefficient algorithm, the carbon dioxide content is denoted as M1, m(LDH) / m(LDO) as M2, and the water-cement ratio as M3. M1, M2, and M3 are fitted with a function of cement fluidity Y to obtain the following calculation formula: Step 3: Based on the required cement fluidity Y, and using the calculation formula obtained in Step 2, the values ​​of M2 and M3 in the formula are changed to regulate the maximum amount of carbon dioxide that can be adsorbed. Based on the values ​​of M2 and M3, the mix proportion in Step 1 is corrected to obtain the final mix proportion of modified carbon-mixed cementitious materials.

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