Carbon capture self-repairing light-weight concrete based on direct air capture and preparation method thereof

Abstract

The present application relates to a kind of carbon-absorbing self-repairing light concrete based on direct air capture and its preparation method, the concrete includes the following weight parts of raw material components: 400-500 parts of cementitious material, 400-600 parts of carbon-absorbing light aggregate, 20-25 parts of admixture, 200-250 parts of water.The present application uses light aggregate to prepare concrete, which helps to reduce the dead load of structure;Enhance its fireproof and heat insulation performance;At the same time, by the adsorption of concrete to the extremely low concentration of CO2 in air, it helps to alleviate the current climate change problem from the root;Finally, directly use the inexhaustible CO2 in air as the raw material of concrete self-repairing material CaCO3, which will greatly reduce the cost of concrete self-repairing material, and help to enhance the applicability of self-repairing concrete.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of self-repairing concrete, and relates to a carbon-absorbing self-repairing lightweight concrete based on direct air capture and a preparation method thereof. BACKGROUND

[0002] With the continuous development of material science, the performance of building materials in quality, energy consumption, fire prevention and the like is required to be higher in building engineering, and lightweight concrete as a solution has attracted widespread attention. One preparation method of lightweight concrete is to introduce a foaming agent into the concrete to generate stable bubbles in the concrete; another preparation method is to fill lightweight aggregates, such as natural aggregates such as pumice, volcanic slag and artificial aggregates such as ceramsite and expanded perlite, into the concrete. Compared with traditional concrete, lightweight concrete has smaller density and lighter quality, can reduce the self-weight of the building structure and improve the overall performance of the structure. At the same time, due to the low thermal conductivity, the lightweight concrete has excellent heat preservation, heat insulation and fireproof performance. At present, lightweight concrete has been widely used in building structures, bridge engineering, road engineering and the like. However, due to the large porosity of lightweight concrete, its ability to prevent external solution and gas from penetrating is weak, and its durability is poor. Especially under the influence of adverse environments such as cold climate, ion erosion and dry-wet cycle, lightweight concrete is prone to cracks, deterioration and even destruction.

[0003] At present, the methods for repairing cracks in concrete mainly include a filling method of slotting along the original crack and filling PMSC and epoxy resin mortar; a grouting method of injecting epoxy resin, urethane and the like into the crack; and a microbial method of inducing mineralization of CaCO3 by using microorganisms or biological enzymes. However, these traditional repair methods all need manual intervention, and the repair may delay the construction period due to the stoppage of work, which is time-consuming and laborious, and the repair effect is not stable enough. In this case, the self-repairing concrete technology is applied. The technology introduces a self-repairing agent into the concrete, and when the concrete produces cracks, the self-repairing agent releases or reacts with the concrete material to generate repair materials to automatically fill the cracks; or microorganisms are added to the concrete to metabolize and induce the generation of CaCO3 at the crack to repair the crack autonomously. However, the self-repairing concrete technology still faces great challenges, for example, some self-repairing agents have a limited service life, and after failure, they will remain in the concrete to reduce the strength thereof; and some bacteria used in certain self-repairing technologies will produce harmful gases during metabolism, which will adversely affect the environment.

[0004] The carbon emission of concrete accounts for about 5-8% of the total global carbon emission, especially the production of cement and the transportation of materials are accompanied by a large amount of CO2 emission. With the proposal of the "double carbon target", the concrete material also gradually develops in the direction of green environmental protection. The main way is to reduce the carbon emission at the production end by improving the concrete material formula, such as using industrial waste to replace cement and reducing the amount of cement; or using waste concrete or industrial waste as recycled aggregate to reduce the demand for primary resources. However, the physical and mechanical properties of the new concrete prepared by using these environmentally friendly materials are uneven, and the zero emission technology has a very limited contribution to the "double carbon target". At present, there is almost no research or application on the negative emission technology of directly capturing air based on the principle of directly capturing air to adsorb the extremely low concentration of CO2 in the air. On the other hand, the atmospheric environment is a huge carbon reservoir, and the CO2 in the air is inexhaustible. If the CO2 in the air can be directly captured and utilized and converted into CO3 2- , as the raw material of the self-repairing material CaCO3 commonly used in concrete, it will have great potential in the field of self-repairing concrete technology. SUMMARY

[0005] The purpose of the present application is to provide a kind of carbon absorption self-repairing lightweight concrete based on direct air capture and its preparation method, which uses lightweight aggregate to prepare concrete, which is conducive to reducing the self-weight of concrete material and enhancing its fireproof and heat insulation performance. By adsorbing the extremely low concentration of CO2 in the air in the concrete material, it is simultaneously converted into CO3 2- , as the raw material of the self-repairing material of concrete, it breaks through the technical bottleneck of carbon absorption negative emission technology of concrete and utilization of CO2 in the air for self-repairing concrete.

[0006] The purpose of the present application can be realized by the following technical scheme:

[0007] One of the technical schemes of the present application provides a kind of carbon absorption self-repairing lightweight concrete based on direct air capture, which comprises the following raw material components by weight: 400-500 parts of cementitious material, 400-600 parts of carbon absorption lightweight aggregate, 20-25 parts of additive, 200-250 parts of water.

[0008] Further, the cementitious material is a mixture of ordinary portland cement and bentonite. Further, the mass ratio of ordinary portland cement and bentonite is 16:1-20:1. Bentonite is a natural clay mineral, and the main mineral component is montmorillonite. In an alkaline environment, SiO2 and Al2O3 in bentonite are dissolved, and Si-O and Al-O bonds are broken to form free unsaturated active bonds, which react with Ca 2+ and OH -The volcanic ash reaction occurs to generate CSH, CAH and Aft and other cementitious hydration products, which fill in the adjuvants, the particle bonding effect is enhanced, and the overall strength of the concrete is increased. On the other hand, the bentonite colloid will adhere to the surface of the steel bar and gather to form a protective layer to inhibit the diffusion of dissolved oxygen, prevent the steel bar from being oxidized, and at the same time increase the time of chloride ion penetration into the concrete, slow down the damage of the passivation layer on the surface of the steel bar caused by the increase of chloride ion, thereby preventing the steel bar from being corroded and enhancing the durability thereof.

[0009] Further, the carbon-absorbing lightweight aggregate is a hybrid ion exchange resin.

[0010] Still further, the hybrid ion exchange resin is prepared by the following method:

[0011] (a) The ion exchange resin is weighed and immersed in a CuCl2 solution, and filtration is performed to obtain the ion exchange resin loaded with Cu 2+ ;

[0012] (b) The ion exchange resin loaded with Cu 2+ is immersed in a NaOH solution, and filtration is performed to obtain the hybrid ion exchange resin.

[0013] More preferably, in step (a), the concentration of the CuCl2 solution is 10 g / L-20 g / L, the volume of the solution is 20-30 times that of the ion exchange resin, and the immersion time is 72 h-84 h.

[0014] More preferably, in step (b), the mass fraction of the NaOH solution is 1%-5%, the volume of the NaOH solution is 15-20 times that of the ion exchange resin, and the immersion time is 36 h-48 h.

[0015] More preferably, the ion exchange resin is a macroporous weakly basic styrene anion exchange resin.

[0016] The hybrid ion exchange resin of the present application has a density of 1100 kg / m 3 -1200 kg / m 3 , and is lighter in mass, so that when used as a concrete aggregate, the density of the concrete can be reduced, the self-weight of the structure can be reduced, and the fireproof and heat insulation performance of the concrete can be enhanced. The working schematic diagram is as shown in Figure 1 Based on the Lewis acid-base reaction, Cu 2+ is connected to three N atoms by a covalent bond, and since Cu 2+ still has two positive charges that are not neutralized, it can serve as an ion exchange site of the entire material system. OH - is loaded as a counterion, and due to the principle of acid-base neutralization reaction, it will perform irreversible directional adsorption on low-concentration CO2 in the air; when contacting CO2 in the air, due to the synergistic effect of acid-base neutralization and electrostatic attraction, the weakly acidic CO2 will be reacted into HCO3- After the combination on the coordination site; after the adsorption, when there is Cl-, the weakly basic anion exchange resin will combine with Cl - The priority of HCO3 - is higher than that of HCO3 - will be combined on the coordination site, replacing the HCO3 - which has been combined. - The unstable HCO3 2- will enter the strong alkaline solution phase, and react to generate CO3 2+ , which will react with Ca - to generate CaCO3. When cracks occur in the concrete, CaCO3 can be used as a repair material to repair the cracks, thereby realizing the self-repairing process of the concrete.

[0017] Further, the additive is a mixture of calcium chloride and quicklime, and preferably, the mass ratio of the two is 9:1 to 12:1. The calcium chloride can provide the Cl - needed for the desorption of the hybrid ion exchange resin, and also can provide Ca 2+ as a calcium source for the generation of CaCO3 repair material. In addition, the calcium chloride, as an early strength agent, can promote the hydration reaction of the cement, and react with 3CaO·Al2O3 in the hydration product to generate cement stone structure, thereby improving the early strength of the concrete. The quicklime, as an additive, can maintain the pH of the material between 12 and 13 together with the cement. The strong alkaline environment can promote the release of active ions of the bentonite to generate pozzolanic reaction, thereby improving the strength of the concrete, and also can convert the unstable HCO3 - released by the desorption of the hybrid ion exchange resin into CO3 2- , which will react with Ca 2+ to generate CaCO3 repair material. At the same time, the quicklime can also provide Ca 2+ as a calcium source for the generation of CaCO3 repair material.

[0018] The second technical solution of the present application provides a preparation method of carbon-absorbing self-repairing lightweight concrete based on direct air capture: comprising the following steps:

[0019] The cementitious material, carbon-absorbing lightweight aggregate, additive, and water are weighed, and the components are sequentially added to a concrete mixer according to the proportioning, the rotating speed can be set to 285 r / min, and the stirring is performed for 3 min until the uniformity is achieved. After the stirring is completed, the concrete mixture is filled in a steel plate mold, and a vibrating method is used to ensure the compactness of the concrete mixture. The plastic film is used for sealing to maintain the surface humidity of the test piece, and the test piece is placed in a room temperature environment for standing (preferably for 1 day). The mold is removed, and the test piece is placed in a standard curing room (the curing conditions are preferably a temperature of 20±2℃ and a relative humidity of greater than 95%) for curing (the time is preferably 28 days), and the carbon-absorbing self-repairing lightweight concrete is obtained.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] (1) The light aggregate is used to prepare the concrete, which can reduce the density of the concrete, help to reduce the dead load of the structure, and reduce the thermal conductivity of the concrete, and help to enhance the fireproof and heat insulation performance.

[0022] (2) The concrete can adsorb CO2 with extremely low concentration in the air, and the negative emission technology can greatly promote the development of the green and environmentally friendly building materials, eliminate the greenhouse gas, and help to alleviate the current climate change problem from the root.

[0023] (3) The inexhaustible CO2 in the air is directly used as the raw material of the self-repairing material CaCO3 of the concrete, which can achieve the carbon emission reduction target, greatly reduce the cost of the self-repairing material of the concrete, and help to enhance the applicability of the self-repairing concrete. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a working schematic diagram of the hybrid ion exchange resin.

[0025] Figure 2 is a mutual interaction mechanism diagram among the components of the carbon-absorbing self-repairing light concrete material. DETAILED DESCRIPTION

[0026] The present application will be described in detail below in combination with the drawings and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0027] In the following examples, the ordinary Portland cement type is P.O. 42.5, which is purchased from Anhui Conch Cement Co., Ltd.; the bentonite is RY-C calcium-based bentonite purchased from Jianping County Runying Mining Industry Co., Ltd. in Liaoning Province; and the ion exchange resin is a weak alkaline styrene anion exchange resin, which is purchased from Lanxess AG Company and the type is Lewait MonoPlus TP 109.

[0028] The preparation scheme of the hybrid ion exchange resin includes the following steps: (a) 10 g of the ion exchange resin is weighed and immersed in 300 mL of CuCl2 solution with a mass concentration of 15 g / L, the immersion time is 72 h, and the Cu 2+ loaded ion exchange resin is obtained by filtering through a filtration device; (b) the Cu 2+ loaded ion exchange resin is immersed in 200 mL of NaOH solution with a mass fraction of 3% for 36 h, and the hybrid ion exchange resin is obtained by filtering.

[0029] In the embodiments, the preparation, curing and testing of the concrete test piece are performed in accordance with GB / T50081-2019 “Standard for Testing Methods of Physical and Mechanical Properties of Concrete”.

[0030] All raw materials of the concrete are placed in a concrete mixer, and the rotating speed is set to 285 r / min, and the concrete is stirred for 3 min until it is uniform.

[0031] After the stirring is completed, the concrete mixture is filled in a 150 mm x 150 mm x 150 mm steel plate mold, and a vibrating method is used to ensure that the concrete mixture is compacted.

[0032] The test piece is sealed with a plastic film to maintain the surface humidity, and is placed in a room temperature environment for 1 d.

[0033] The mold is removed, and the test piece is placed in a standard curing room (temperature 20±2℃, relative humidity greater than 95%) for curing for 28 d, thereby obtaining a carbon-absorbing self-repairing lightweight concrete based on direct air capture.

[0034] First, the compressive strength of each embodiment is tested to obtain the 28 d compressive strength f cu After the loading is completed, the test piece is removed from the pressure testing machine, and is placed in a laboratory environment for carbon capture and self-repairing, and the compressive strength test is performed again after 28 d to obtain the compressive strength f cr after self-repairing. The self-repairing rate can be calculated by the following formula:

[0035]

[0036] Example 1

[0037] A carbon-absorbing self-repairing lightweight concrete based on direct air capture comprises the following raw materials: ordinary Portland cement 8.0 kg, bentonite 0.4 kg, hybrid ion exchange resin 10 kg, calcium chloride 0.45 kg, quicklime 0.05 kg, and ordinary tap water 4.2 kg.

[0038] Example 2

[0039] A carbon-absorbing self-repairing lightweight concrete based on direct air capture comprises the following raw materials: ordinary Portland cement 8.0 kg, bentonite 0.4 kg, hybrid ion exchange resin 10 kg, calcium chloride 0.50 kg, quicklime 0.06 kg, and ordinary tap water 4.2 kg.

[0040] Example 3

[0041] A carbon-absorbing self-repairing lightweight concrete based on direct air capture comprises the following raw materials: ordinary Portland cement 8.0 kg, bentonite 0.4 kg, hybrid ion exchange resin 10 kg, calcium chloride 0.55 kg, quicklime 0.07 kg, and ordinary tap water 4.2 kg.

[0042] Comparative Example 1

[0043] Most of them are the same as Example 1, except that the process of preparing the hybrid ion exchange resin omits the step of configuring CuCl2 solution and adding ion exchange resin impregnation.

[0044] Comparative Example 2

[0045] Most of them are the same as Example 1, except that the mass concentration of CuCl2 solution configured in the process of preparing the hybrid ion exchange resin is 5g / L.

[0046] Comparative Example 3

[0047] Most of them are the same as Example 1, except that the mass concentration of CuCl2 solution configured in the process of preparing the hybrid ion exchange resin is 25g / L.

[0048] Comparative Example 4

[0049] Most of them are the same as Example 1, except that the process of preparing the hybrid ion exchange resin omits the step of configuring NaOH solution and impregnating the Cu 2+ loaded ion exchange resin in it.

[0050] Comparative Example 5

[0051] Most of them are the same as Example 1, except that the mass fraction of NaOH solution configured in the process of preparing the hybrid ion exchange resin is 0.5%.

[0052] Comparative Example 6

[0053] Most of them are the same as Example 1, except that the mass fraction of NaOH solution configured in the process of preparing the hybrid ion exchange resin is 10%.

[0054] Comparative Example 7

[0055] Most of them are the same as Example 1, except that the cementing material is ordinary Portland cement of equal mass.

[0056] Comparative Example 8

[0057] Most of them are the same as Example 1, except that the admixture is replaced by single quicklime of equal mass.

[0058] Comparative Example 9

[0059] Most of them are the same as Example 1, except that the admixture is replaced by single calcium chloride of equal mass.

[0060] Table 1 Test results of each example and comparative example

[0061]

[0062]

[0063] From the above table, the density of the concrete specimens prepared in Example 1, Example 2 and Example 3 are all around 840 kg / m 3 , which is lighter than the traditional concrete. After obtaining the ultimate compressive strength f cu through the compressive strength test, the specimens are placed in the laboratory environment for 28 days. Without introducing other repair agents and admixtures, the self-repairing rate can reach more than 60%. This is because the hybrid ion exchange resin adsorbs CO2 in the air, and Cl - provided by calcium chloride is desorbed to release HCO3 - . In a strong alkaline environment, the reaction becomes CO3 2- , which reacts with Ca 2+ provided by calcium chloride and quicklime to form CaCO3, which fills between the cracks of the concrete, achieving self-repairing of the concrete and restoring part of its strength. At the same time, the 28d compressive strength and self-repairing rate of Example 3 are slightly higher than those of Example 1 and Example 2. This is because with the increase of the amount of quicklime and calcium chloride admixture, the calcium source is increased and the alkalinity of the whole system is enhanced, which makes the bentonite release more active silicon and aluminum ions during the curing stage, promotes the progress of the pozzolanic reaction, and helps to improve the strength. In the self-repairing stage, it is more conducive to the mineralization reaction of CaCO3, and the self-repairing effect is good.

[0064] From the test results of Comparative Example 1, Comparative Example 2 and Comparative Example 3, when the process of configuring CuCl2 solution and adding ion exchange resin impregnation is omitted during the preparation of the hybrid ion exchange resin, the ion exchange resin lacks Cu 2 + This ion exchange site cannot capture CO2 in the air, nor can it release HCO3 - participate in mineralization reaction, and the concrete does not have self-repairing ability; with the increase of the mass concentration of the configured CuCl2 solution, the concrete in Comparative Example 2 partially restores its self-repairing ability; with the further increase of the mass concentration of the configured CuCl2 solution, the concrete in Comparative Example 3 has the same self-repairing ability as Example 1. It needs to be clear that although the Cu 2+ concentration in Comparative Example 3 is much higher than that in Comparative Example 1, because the ion exchange resin has reached a saturated state of loading Cu 2+ , therefore, the excess Cu 2+ does not significantly increase the self-repairing ability of the concrete.

[0065] From the test results of Comparative Example 4, Comparative Example 5 and Comparative Example 6, when the process of preparing the hybrid ion exchange resin is omitted, the process of configuring NaOH solution and immersing the ion exchange resin loaded with Cu 2+ in the solution, the ion exchange resin lacks OH - , the equilibrium ion, and thus cannot capture CO2 in the air, and thus cannot release HCO3 - to participate in the mineralization reaction, and the concrete does not exhibit obvious self-repairing performance; as the mass fraction of the configured NaOH solution increases, the concrete in Comparative Example 5 partially restores the self-repairing performance; as the mass fraction of the configured NaOH solution further increases, the concrete in Comparative Example 6 almost restores the same self-repairing performance as that in Example 1. However, since the combination of Cu 2+ and OH - has reached a saturated state, the excess OH - does not significantly improve the self-repairing performance of the concrete.

[0066] From the test results of Comparative Example 7 and Comparative Example 8, when the admixture is single quicklime, the density and compressive strength of the concrete in Comparative Example 7 are improved, but since there is no Cl - in the concrete material, HCO3 - combined with the ion exchange resin cannot be desorbed, and the concrete does not generate a mineralization reaction after being damaged under pressure, and thus the concrete does not have self-repairing performance; when the admixture is single calcium chloride, the density and compressive strength of the concrete in Comparative Example 8 are decreased, and it is considered that since there is no quicklime, the pH value in the concrete is low, the number of active ions released by the bentonite is small, and the amount of cementitious products generated by the pozzolanic reaction is limited, and thus the compressive strength of the concrete is lower than that in Example 1. In the self-repairing stage, Cl - can release HCO3 - and react with OH - to generate CO3 2- , and thus participate in the mineralization reaction, but since there is no quicklime admixture in the material, the amount of OH - is limited, and thus HCO3 - cannot be completely converted into CO3 2- , and the self-repairing performance of the concrete is limited. Therefore, in the implementation, the roles of the two components of the admixture in the material system and the ratio thereof should be fully considered.

[0067] The foregoing description of the embodiments has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Modifications and variations are possible in light of the above teachings or can be acquired from practice of the application. As well, the description is presented in the context of the preferred embodiments as a number of alternatives. It is not intended to limit the application to the precise form described.

Claims

1. A carbon-absorbing self-healing lightweight concrete based on direct air capture, characterized in that, The raw material components include the following parts by weight: 400-500 parts cementitious material, 400-600 parts carbon-absorbing lightweight aggregate, 20-25 parts admixture, and 200-250 parts water; The cementing material is a mixture of ordinary silicate cement and bentonite; The mass ratio of ordinary silicate cement to bentonite is 16:1 to 20:1; The carbon-absorbing lightweight aggregate is a hybrid ion exchange resin, which is prepared by the following method: Step (a): Weigh out the ion exchange resin impregnated in CuCl2 solution, filter to obtain the loaded Cu 2+ Ion exchange resin; Step (b): Load Cu 2+ The ion exchange resin was impregnated with NaOH solution and filtered to obtain a hybrid ion exchange resin; The ion exchange resin is a macroporous, weakly basic styrene-based anion exchange resin. In step (a), the concentration of CuCl2 solution is 10 g / L to 20 g / L, the solution volume is 20 to 30 times the volume of ion exchange resin, and the impregnation time is 72 h to 84 h. In step (b), the mass fraction of the NaOH solution is 1%-5%, the volume of the NaOH solution is 15-20 times the volume of the ion exchange resin, and the soaking time is 36h-48h. The additive is a mixture of calcium chloride and quicklime, with a mass ratio of 9:1 to 12:

1.

2. The method for preparing carbon-absorbing self-healing lightweight concrete based on direct air capture as described in claim 1, characterized in that, Includes the following steps: (1) Weigh out the cementitious material, carbon-absorbing lightweight aggregate, admixture and water; (2) Add each component to the concrete mixer in the order of proportions and mix until uniform; (3) After mixing, the resulting concrete mixture is filled into a steel plate mold and compacted by vibration. (4) Seal with plastic film to maintain the surface humidity of the specimen and place it in a room temperature environment to stand; (5) Remove the formwork and place it in a standard curing room for curing to obtain carbon-absorbing self-healing lightweight concrete.

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