Low-carbon concrete cured by cement kiln tail flue gas and preparation method thereof

Abstract

The application discloses a low-carbon concrete for curing of cement kiln tail flue gas, and each component and weight percentage thereof are as follows: 10-50 parts of low-carbon cement, 5-25 parts of calcium-rich cementitious material, 1-3 parts of auxiliary material, 85-110 parts of coarse aggregate, 60-100 parts of fine aggregate, 0.5-1 part of additive, and 12-20 parts of water; the auxiliary material comprises Na2CO3 and Na2SiO3; wherein, all the water is firstly mixed with part of the calcium-rich cementitious material, CO2 is introduced to perform pre-carbonization, a pre-carbonated solution is obtained, and then the pre-carbonated solution is mixed with other raw materials. The application introduces in-situ generated nano calcium carbonate into the concrete by pre-carbonization technology, and then utilizes the cement kiln tail flue gas to perform step-by-step carbonization curing on the green body to obtain a low-carbon concrete product; the low-carbon concrete product can have good mechanical properties and durability, has significant economic and environmental benefits, and is suitable for large-scale popularization and application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a low-carbon concrete cured by cement kiln tail flue gas and a preparation method thereof. BACKGROUND

[0002] The utilization and storage technology of carbon dioxide is considered as an important technical approach to realize emission reduction and an important means to cope with climate change. In the field of building materials, low calcium carbonized products formed by carbonation curing have gradually become a research hotspot due to the advantages of strong carbon sequestration capacity and low carbon emission of low calcium silicate minerals such as CS, γ-C2S and C3S2.

[0003] Domestic and foreign scholars have developed a series of new carbon sequestration building material products based on the carbonation performance of low calcium silicate minerals. Patent CN109796169B discloses a preparation method of a composite reinforced carbonized product, which uses low calcium silicate minerals with low calcium-silicon ratio as the main raw material, and adds active magnesium oxide and alkali metal nitrate solution as a composite reinforcing phase to obtain a high composite reinforced carbonized product by accelerating carbonization. Patent CN114873979B discloses a low-carbon cement concrete and a preparation method thereof, which uses low calcium cement as the main carbonization component, introduces a hydrating active cementitious material to provide early form removal strength, and after adding the remaining components, it is quickly cast and formed, and after form removal, it is placed in a carbonation reaction kettle for accelerated carbonization to obtain a low-carbon cement concrete. However, in order to improve the mechanical properties and carbon sequestration performance of low calcium carbonized products, most of the accelerated carbonization is carried out in a high concentration carbon dioxide or even pure CO2 atmosphere, which undoubtedly increases the energy consumption and cost of carbon capture and enrichment, and puts forward higher requirements for the corresponding production equipment, which is contrary to the original intention of energy saving and emission reduction.

[0004] Cement kiln tail flue gas is waste gas in the cement production process, and its main components are CO2, NO x , water vapor and dust, etc. The concentration of carbon dioxide is generally 10-30%, and researchers use industrial flue gas to cure low calcium cement and develop a series of low-strength building products. However, when using cement kiln tail flue gas to cure high-strength building material products such as low calcium cement concrete products, due to the low carbon dioxide pressure and concentration, high temperature and high humidity of the cement kiln tail flue gas, it is not conducive to the full reaction of carbon dioxide with the active components in the building products, which limits the carbonation reaction degree and carbonation depth, and further leads to low product strength and other problems. Therefore, most of the existing cement kiln tail flue gas is used to cure products such as aerated blocks, solid bricks and boards that have low strength or size requirements. Further exploring the application of cement kiln tail flue gas in high-strength building materials has important research and application significance. SUMMARY

[0005] To address the shortcomings of the existing technologies, the main objective of this invention is to provide a low-carbon concrete cured by cement kiln tail flue gas. This invention utilizes pre-carbonation technology to uniformly introduce in-situ generated nano-calcium carbonate into the concrete, providing numerous nucleation sites for early hydration and later carbonation processes. Then, the concrete is cured in stages using cement kiln tail flue gas to produce the finished low-carbon concrete. The concrete preparation process can absorb a large amount of CO2, significantly reducing carbon emissions from cement plants. Furthermore, the preparation process is simple, has a short production cycle, and low production costs. The resulting low-carbon concrete products exhibit both good mechanical and durability properties, making them suitable for large-scale application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A low-carbon concrete for curing with cement kiln tail flue gas comprises the following components and their respective weight percentages: 10-50 parts low-carbon cement, 5-25 parts calcium-rich cementitious material, 1-3 parts additives, 85-110 parts coarse aggregate, 60-100 parts fine aggregate, 0.5-1 part admixture, and 12-20 parts water; the additives include Na2CO3 and Na2SiO3; wherein, all the water is first mixed with a portion of the calcium-rich cementitious material, and CO2 is introduced for pre-carbonation to obtain a pre-carbonated solution, which is then mixed with other raw materials.

[0008] In the above scheme, the mass ratio of calcium-rich cementitious material to water (all water in low-carbon concrete) used in the precarbonation solution is 0.01 to 0.09:1; preferably 0.02 to 0.06:1.

[0009] Furthermore, the specific preparation steps of the precarbonated solution include: uniformly mixing a portion of calcium-rich cementitious material with water, then continuously introducing CO2 and stirring to obtain the precarbonated solution.

[0010] In the above scheme, the CO2 introduction rate is 1 to 10 L / min; CO2 is introduced until the pH value of the resulting precarbonated solution is 6.0 to 9.0.

[0011] In the above scheme, the stirring rate is 1000-2000 rpm.

[0012] In the above scheme, the ratio of the precarbonation solution to the total mass of low-carbon cement and remaining calcium-rich cementitious materials is 0.1 to 0.8:1.

[0013] Furthermore, the ratio of the precarbonated solution to the total mass of low-carbon cement and remaining calcium-rich cementitious materials is 0.2 to 0.4:1.

[0014] In the above scheme, the Ca / Si ratio of the low-carbon cement is 1.0 to 1.5, and the specific surface area is 300 to 750 m². 2 / kg.

[0015] Furthermore, the chemical components and their mass percentages in the low-carbon cement include: CS 60-80%, C3S2 10-30%, β-C2S 0-10%, and f-CaO 0-5%.

[0016] In the above scheme, the calcium-rich cementitious material can be selected from one or more of the following: slag, high-calcium fly ash, fly ash, steel slag, electroplating slag, kiln ash, etc.; its chemical composition has an alkaline oxide CaO content > 35wt% and a specific surface area > 800m². 2 / kg.

[0017] Preferably, the calcium-rich cementitious material is one or both of high-calcium fly ash and slag.

[0018] In the above scheme, the mass ratio of Na2CO3 to Na2SiO3 in the auxiliary material is 10:1 to 5.

[0019] In the above scheme, the admixture is a polycarboxylate superplasticizer with a water reduction rate of 30-50%.

[0020] In the above scheme, the coarse aggregate is continuously aggregated crushed stone with a particle size of 5-25mm; the fine aggregate has a particle size of 0-5mm and a fineness modulus of 2.1-3.5.

[0021] The preparation method of the above-mentioned low-carbon concrete cured by cement kiln tail flue gas includes the following preparation steps:

[0022] 1) Take a portion of the calcium-rich cementitious material and mix it with all the water. Then, introduce CO2 into the resulting mixture and stir until the pH value is 6.0-9.0 to obtain a pre-carbonated solution.

[0023] 2) Weigh out the low-carbon cement, the remaining calcium-rich cementitious material, the pre-carbonation solution, the additives, the coarse aggregate, and the fine aggregate, mix them evenly, add the admixture and stir to obtain a concrete mixture; pour, vibrate and mold; after natural curing, remove the formwork to obtain the concrete product;

[0024] 3) The obtained concrete product is transferred into a reaction vessel equipped with an inlet valve and an outlet valve for vacuum treatment; then kiln tail gas is continuously introduced until the pressure inside the reaction vessel reaches atmospheric pressure; the outlet valve is opened and kiln tail gas is continued to be introduced, forming a circulating kiln tail gas in the reaction vessel for atmospheric pressure curing; the outlet valve is closed and kiln tail gas is continued to be introduced until the pressure inside the carbonization kettle is 0.3-0.6 MPa, and then pressure curing is carried out in a closed reaction environment (kiln tail gas is stopped) to obtain the low-carbon concrete product.

[0025] In the above scheme, the CO2 concentration of the kiln tail flue gas is 10-30 vol%, the temperature is 70-100℃, the humidity is 40-80%, the inlet flow rate and the exhaust flow rate are the same, and the gas flow rate per minute is 1 / 20 to 1 / 5 of the volume of the reaction vessel.

[0026] In the above scheme, the natural maintenance time mentioned in step 2) is 12 to 24 hours.

[0027] In the above scheme, the normal pressure curing time in step 3) is 2 to 12 hours; the pressure curing time is 12 to 30 hours.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1) The additive materials used in this invention are mainly composed of Na2CO3 and Na2SiO3, which can provide a highly alkaline environment, enabling low-carbon cement and calcium-rich cementitious materials to undergo mineral bonding reactions, dissolving Si, Al, and Ca ions from the mineral surface. After polymerization, dehydration, and hardening, NCS-(A)-H gel and micro calcite crystals are formed, providing certain early strength to the obtained specimens, shortening the specimen demolding cycle, and significantly improving the production efficiency of the products.

[0030] 2) This invention employs pre-carbonation technology. First, carbon dioxide is introduced into a low-concentration mixture formed by a portion of the calcium-rich cementitious material and all water, reacting with the calcium in the slurry. 2+ The reaction forms an appropriate amount of nano-calcium carbonate microcrystals (the pH value of the precarbonation solution is 6.0-9.0), which are uniformly distributed inside the resulting mixture under high-speed stirring. The resulting precarbonation slurry is then incorporated into concrete, which can provide heterogeneous nucleation sites for the early hydration of concrete and improve the early strength of the specimen. At the same time, some nano-calcium carbonate microcrystals can provide growth nucleation sites for the carbonation products of concrete, which can accelerate the subsequent carbonation reaction process and significantly improve the degree of carbonation of the green body.

[0031] 3) This invention employs a stepwise carbonization technology. In the first step, circulating flue gas is introduced into a vacuum reaction vessel for carbonization. Low-concentration carbon dioxide at normal pressure continuously penetrates into the center of the concrete blank, reacting with calcium ions and water to generate carbonization products. Simultaneously, the circulating flue gas flow from the kiln tail regulates the internal humidity of the concrete, providing a favorable humidity environment for the carbonization reaction and facilitating the diffusion of carbon dioxide within the blank. In the second step, under pressurized conditions, high-pressure flue gas rapidly penetrates and diffuses into the internal pores of the concrete, reacting quickly with the carbonization components to generate CaCO3 and high-polymerization silica gel, significantly improving the mechanical properties of the concrete. At the same time, a large amount of solidified flue gas is absorbed from the kiln tail, reducing carbon emissions.

[0032] 4) The low-carbon concrete described in this invention directly uses industrial flue gas for carbonization curing, eliminating the need for CO2 purification and enrichment of industrial flue gas. This turns industrial flue gas from waste into treasure, effectively reducing the cost and energy consumption of carbon capture and enrichment. At the same time, it fully utilizes the temperature and humidity characteristics of industrial flue gas to accelerate the carbonization curing of the green body, significantly reducing production energy consumption and effectively reducing equipment requirements and production costs.

[0033] 5) The low-carbon concrete prepared by this invention has a low carbon footprint, and the preparation process is simple, the production cycle is short, and the production cost is low. The low-carbon concrete products prepared have excellent comprehensive performance, can meet various practical engineering needs, and are suitable for large-scale promotion and application. Detailed Implementation

[0034] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

[0035] In the following examples, the low-carbon cement has a Ca / Si ratio of 1.15 and a specific surface area of ​​550 m². 2 / kg; the calcium-rich cementitious material is high-calcium fly ash, containing 35.6% CaO, 38.2% SiO2, and 18.2% Al2O3, with a specific surface area of ​​900 m². 2 / kg; the additives consist of 5 parts industrial-grade sodium carbonate and 1 part sodium silicate; the coarse aggregate is continuously aggregated dolomite crushed stone with a particle size of 5-25mm; the fine aggregate is manufactured sand with a particle size of 0-5mm and a fineness modulus of 3.1; the water-reducing agent is polycarboxylate water-reducing agent provided by Subote, with a water reduction rate of 45%.

[0036] In the following embodiments, the concrete strength specimens were 150×150×150mm in size, and the strength tests were conducted in accordance with the "Test Methods for Physical and Mechanical Properties of Concrete" (GBT 50081-2019); the concrete durability performance was conducted in accordance with the relevant provisions of the "Standard for Test Methods for Long-Term Performance and Durability of Ordinary Concrete" (GBT 50082-2009); and the carbon emission estimation was based on the "Standard for Calculation of Carbon Emissions from Buildings" (GB / T 51366-2019) and "Green and Low-Carbon Manufacturing Technology for Cement and Concrete".

[0037] Example 1

[0038] A low-carbon concrete for curing with cement kiln tail flue gas comprises the following raw materials by weight: 12 parts low-carbon cement, 12.32 parts calcium-rich cementitious material, 1.5 parts additives, 90 parts coarse aggregate, 70 parts fine aggregate, 0.6 parts water-reducing agent, and 15.68 parts water; the preparation steps are as follows:

[0039] 1) Preparation of precarbonated solution

[0040] a. Mix 15.68 parts of water with 0.32 parts of calcium-rich cementitious material until homogeneous to obtain a mixture;

[0041] b. Under stirring at 1500 rpm, CO2 was continuously introduced into the resulting mixture at a flow rate of 3 L / min to allow for full reaction until the pH of the slurry was 8, resulting in a precarbonated solution (16 parts).

[0042] 2) Concrete preparation

[0043] a. Mix 12 parts low-carbon cement, 12 parts calcium-rich cementitious material, 16 parts pre-carbonation solution, 1.5 parts additive material, 90 parts coarse aggregate, and 70 parts fine aggregate evenly, and add 0.6 parts water-reducing agent to obtain concrete mixture.

[0044] b. Pour the concrete mixture into the mold and vibrate it to shape;

[0045] c. After natural curing for 15 hours, the formwork is removed to obtain the concrete product;

[0046] 3) Concrete carbonation curing

[0047] a. Transfer the product into a carbonization autoclave equipped with an inlet valve and an outlet valve for vacuum treatment;

[0048] b. Continuously introduce kiln tail gas into a sealed carbonization kettle until the pressure inside the kettle reaches atmospheric pressure;

[0049] c. Open the exhaust valve to allow the kiln tail flue gas to be discharged into the circulating gas storage tank to form circulating kiln tail flue gas. Under the condition of circulating kiln tail flue gas, maintain normal pressure for 6 hours.

[0050] d. Immediately close the exhaust valve, introduce kiln tail flue gas into the carbonization kettle at a pressure of 0.4 MPa, and cure for 20 hours to obtain low-carbon concrete finished product.

[0051] In this embodiment, the industrial flue gas used has a CO2 concentration of 15 vol%, a temperature of 80°C, a humidity of 70%, and a gas flow rate of 1 / 15 of the carbonization reactor volume per minute.

[0052] Example 2

[0053] A low-carbon concrete for curing with cement kiln tail flue gas comprises the following raw materials by weight: 25 parts low-carbon cement, 18.48 parts calcium-rich cementitious material, 2 parts additives, 100 parts coarse aggregate, 75 parts fine aggregate, 0.9 parts water-reducing agent, and 15.52 parts water; the preparation steps are as follows:

[0054] 1) Preparation of precarbonated solution:

[0055] a. Mix 15.52 parts of water with 0.48 parts of calcium-rich cementitious material until homogeneous to obtain a mixture;

[0056] b. Under stirring at 1500 rpm, CO2 was continuously introduced into the resulting mixture at a flow rate of 3 L / min to allow for full reaction until the pH of the slurry reached 7.5, resulting in a precarbonated solution (16 parts).

[0057] 2) Concrete preparation

[0058] a. Mix 25 parts low-carbon cement, 18 parts calcium-rich cementitious material, 16 parts pre-carbonation solution, 2 parts additive material, 100 parts coarse aggregate, and 75 parts fine aggregate evenly, and add 0.9 parts water-reducing agent to obtain concrete mixture.

[0059] b. Pour the concrete mixture into the mold and vibrate it to shape;

[0060] c. After natural curing for 15 hours, the formwork is removed to obtain the concrete product;

[0061] 3) Concrete carbonation curing

[0062] a. Transfer the product into a carbonization autoclave equipped with an inlet valve and an outlet valve for vacuum treatment;

[0063] b. Continuously introduce kiln tail gas into a sealed carbonization kettle until the pressure inside the kettle reaches atmospheric pressure;

[0064] c. Open the exhaust valve to allow the kiln tail flue gas to be discharged into the circulating gas storage tank to form circulating kiln tail flue gas. Under the condition of circulating kiln tail flue gas, maintain normal pressure for 8 hours.

[0065] d. Immediately close the exhaust valve, introduce kiln tail flue gas into the carbonization kettle at a pressure of 0.4 MPa, and cure for 24 hours to obtain low-carbon concrete finished product.

[0066] In the above scheme, the CO2 concentration of the industrial flue gas is 20 vol%, the temperature is 80℃, the humidity is 60%, and the gas flow rate per minute is 1 / 15 of the carbonization kettle volume.

[0067] Example 3

[0068] A low-carbon concrete cured by cement kiln tail flue gas comprises the following raw materials in parts by weight: 40 parts low-carbon cement, 22.8 parts calcium-rich cementitious material, 3 parts additives, 95 parts coarse aggregate, 90 parts fine aggregate, 1 part water-reducing agent, and 15.2 parts water; the preparation steps are as follows:

[0069] 1) Preparation of precarbonated solution:

[0070] a. Mix 15.2 parts of water with 0.8 parts of calcium-rich cementitious material until homogeneous to obtain a mixture;

[0071] b. Under stirring at 1500 rpm, CO2 was continuously introduced into the resulting mixture at a flow rate of 3 L / min to allow for full reaction until the pH of the slurry was 7.5, resulting in a precarbonated solution (16 parts).

[0072] 2) Concrete preparation

[0073] a. Mix 40 parts low-carbon cement, 22 parts calcium-rich cementitious material, 16 parts pre-carbonation solution, 3 parts additives, 95 parts coarse aggregate, and 90 parts fine aggregate evenly, and add 1 part water-reducing agent to obtain concrete mixture.

[0074] b. Pour the concrete mixture into the mold and vibrate it to shape;

[0075] c. After natural curing for 15 hours, the formwork is removed to obtain the concrete product;

[0076] 3) Concrete carbonation curing

[0077] a. Transfer the product into a carbonization autoclave equipped with an inlet valve and an outlet valve for vacuum treatment;

[0078] b. Continuously introduce kiln tail gas into a sealed carbonization kettle until the pressure inside the kettle reaches atmospheric pressure;

[0079] c. Open the exhaust valve to allow the kiln tail flue gas to be discharged into the circulating air storage tank to form circulating kiln tail flue gas. Under the condition of circulating kiln tail flue gas, maintain at normal pressure for 10 hours.

[0080] d. Immediately close the exhaust valve, introduce kiln tail flue gas into the carbonization kettle at a pressure of 0.5 MPa, and cure for 24 hours to obtain low-carbon concrete finished product.

[0081] In the above scheme, the CO2 concentration of the industrial flue gas is 20 vol%, the temperature is 90℃, the humidity is 60%, and the gas flow rate per minute is 1 / 10 of the carbonization kettle volume.

[0082] Comparative Example 1

[0083] A low-carbon concrete for curing with flue gas from a cement kiln tail, comprising the following raw materials by mass: 25 parts low-carbon cement, 18.48 parts calcium-rich cementitious material, 100 parts coarse aggregate, 75 parts fine aggregate, 0.9 parts water-reducing agent, and 15.52 parts water.

[0084] The preparation method is the same as in Example 2, and will not be repeated here:

[0085] Comparative Example 2

[0086] A low-carbon concrete for curing with cement kiln tail flue gas has the following composition by mass parts: 25 parts low-carbon cement, 18.48 parts calcium-rich cementitious material, 15.52 parts water, 2 parts additives, 100 parts coarse aggregate, 75 parts fine aggregate, and 0.9 parts water-reducing agent; its preparation method is roughly the same as that in Example 2, except that the pre-carbonation solution described in step 1) is not prepared in advance.

[0087] Comparative Example 3

[0088] A low-carbon concrete for curing with cement kiln tail flue gas has the following composition by mass parts: 25 parts low-carbon cement, 19.6 parts calcium-rich cementitious material, 2 parts additives, 100 parts coarse aggregate, 75 parts fine aggregate, 0.9 parts water-reducing agent, and 4.4 parts water. Its preparation method is roughly the same as in Example 1, except that the pre-carbonation solution preparation steps are as follows: a. Mix 14.4 parts water with 1.6 parts calcium-rich cementitious material to obtain a slurry; b. Continuously introduce CO2 into the above-mentioned slurry stirred at 1500 r / s to allow for sufficient reaction until the slurry pH reaches 7.5, thus obtaining the pre-carbonation solution.

[0089] Comparative Example 4

[0090] A low-carbon concrete cured by cement kiln tail flue gas, comprising the following raw materials by mass: 25 parts low-carbon cement, 18.48 parts calcium-rich cementitious material, 2 parts additives, 100 parts coarse aggregate, 75 parts fine aggregate, 0.9 parts water-reducing agent, and 15.52 parts water. The preparation method is roughly the same as in the example, except that after curing the concrete product, circulating kiln tail flue gas is directly introduced for carbonation curing for 32 hours to obtain the finished concrete product.

[0091] Comparative Example 5

[0092] A method for preparing low-carbon concrete using kiln tail flue gas curing: 25 parts of low-carbon cement, with the following raw materials by mass: 18.48 parts of calcium-rich cementitious material, 2 parts of additives, 100 parts of coarse aggregate, 75 parts of fine aggregate, 0.9 parts of water-reducing agent, and 15.52 parts of water. The preparation method is roughly the same as in the previous example, except that after curing the concrete product, 0.4 MPa kiln tail flue gas is directly introduced for carbonation curing for 32 hours to obtain the finished concrete product.

[0093] Comparative Example 6

[0094] A low-carbon concrete cured by cement kiln tail flue gas has the following composition by mass parts: 25 parts low-carbon cement, 18.48 parts calcium-rich cementitious material, 2 parts additives, 100 parts coarse aggregate, 75 parts fine aggregate, 0.9 parts water-reducing agent, and 15.52 parts water. Its preparation method is largely the same as the example, except that after curing the concrete product, it is directly introduced into a pure CO2 atmosphere for carbonation curing. The carbonation regime is: pressure 0.4 MPa, temperature 80℃, carbonation curing for 32 hours; thus, the finished concrete product is obtained.

[0095] Comparative Example 7

[0096] A type of ordinary concrete is composed of the following components by mass fraction: 28 parts of PO42.5 cement, 5 parts of fly ash, 6 parts of mineral powder, 100 parts of coarse aggregate, 90 parts of fine aggregate, 16.5 parts of water, and 0.6 parts of water-reducing agent. The above materials are mixed evenly and then molded. After natural curing for 24 hours, the formwork is removed and the concrete is moved into a curing room for standard curing for 28 days.

[0097] The concrete obtained in Examples 1-3 and Comparative Examples 1-7 were subjected to mechanical property and durability tests, and carbon emission estimates were made. The results are shown in Table 1, and the carbon emission of different materials in the concrete is shown in Table 2.

[0098] Table 1. Performance tests and carbon emissions of the concrete obtained in Examples 1-3 and Comparative Examples 1-7

[0099]

[0100]

[0101] Table 2 Carbon emissions of different materials in concrete

[0102]

[0103] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A low-carbon concrete cured by cement kiln tail flue gas, characterized in that, The components and their respective weight percentages include: 10-50 parts low-carbon cement, 5-25 parts calcium-rich cementitious material, 1-3 parts additives, 85-110 parts coarse aggregate, 60-100 parts fine aggregate, 0.5-1 part water-reducing agent, and 12-20 parts water; the additives include Na2CO3 and Na2SiO3; wherein, all the water is first mixed with a portion of the calcium-rich cementitious material, and CO2 is introduced for pre-carbonation to obtain a pre-carbonized solution, which is then mixed with other raw materials; The mass ratio of calcium-rich cementitious material to water used in the precarbonated solution is 0.01~0.09:1; The Ca / Si ratio of the low-carbon cement is 1.0~1.5; The calcium-rich cementitious material has an alkaline oxide (CaO) content > 35% in its chemical composition. The cement kiln tail gas curing steps include: transferring the obtained concrete product into a reaction vessel equipped with an inlet valve and an outlet valve for vacuum treatment; then continuously introducing kiln tail gas until the pressure inside the reaction vessel reaches atmospheric pressure; opening the outlet valve and continuing to introduce kiln tail gas to form circulating kiln tail gas in the reaction vessel for atmospheric pressure curing; closing the outlet valve and continuing to introduce kiln tail gas until the pressure inside the carbonization kettle is 0.3~0.6MPa, and then performing pressure curing in a closed reaction environment to obtain the low-carbon concrete finished product; The CO2 concentration of the kiln tail flue gas is 10~30 vol%, the temperature is 70~100℃, and the humidity is 40~80%; the gas flow rate per minute is 1 / 20~1 / 5 of the volume of the reaction vessel.

2. The low-carbon concrete according to claim 1, characterized in that, The CO2 introduction rate is 1~10 L / min; the pH value of the resulting precarbonated solution after CO2 introduction is 6.0~9.

0.

3. The low-carbon concrete according to claim 1, characterized in that, The ratio of the precarbonated solution to the total mass of low-carbon cement and remaining calcium-rich cementitious materials is 0.1~0.8:

1.

4. The low-carbon concrete according to claim 1, characterized in that, The specific surface area of ​​the low-carbon cement is 300~750m². 2 / kg.

5. The low-carbon concrete according to claim 1, characterized in that, The calcium-rich cementitious material is one or more of the following: slag, high-calcium fly ash, fly ash, steel slag, electroplating slag, and kiln ash; its specific surface area is >800 m². 2 / kg.

6. The low-carbon concrete according to claim 1, characterized in that, The mass ratio of Na2CO3 to Na2SiO3 in the additive material is 10:1~5.

7. The low-carbon concrete according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate water-reducing agent with a water reduction rate of 30-50%.

8. The method for preparing low-carbon concrete cured by cement kiln tail flue gas according to any one of claims 1 to 7, characterized in that, The preparation steps are as follows: 1) Take a portion of the calcium-rich cementitious material and mix it with all the water. Then, introduce CO2 into the resulting mixture and stir until the pH value reaches 6.0~9.0 to obtain a pre-carbonated solution. 2) Weigh out the low-carbon cement, the remaining calcium-rich cementitious material, the pre-carbonation solution, the additives, the coarse aggregate, and the fine aggregate, mix them evenly, add the water-reducing agent and stir to obtain a concrete mixture; pour it, vibrate it to form it; after natural curing, remove the formwork to obtain the concrete product. 3) The obtained concrete product is transferred into a reaction vessel equipped with an inlet valve and an outlet valve for vacuum treatment; then kiln tail gas is continuously introduced until the pressure inside the reaction vessel reaches atmospheric pressure; the outlet valve is opened and kiln tail gas is continued to be introduced, forming a circulating kiln tail gas in the reaction vessel for atmospheric pressure curing; the outlet valve is closed and kiln tail gas is continued to be introduced until the pressure inside the carbonization kettle is 0.3~0.6MPa, and then pressure curing is carried out in a closed reaction environment to obtain the low-carbon concrete product.

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