Dynamic carbon injection recycled coarse aggregate concrete, and preparation method and application thereof

Abstract

The application belongs to the technical field of concrete, and particularly relates to a dynamic carbon injection recycled coarse aggregate concrete and a preparation method and application thereof. The preparation method of the concrete comprises the following steps: (1) uniformly stirring cement, mineral powder, recycled coarse aggregate, fine aggregate, fly ash, a carbon fixation agent, a retarder and a water reducing agent in water to obtain a mixture; (2) injecting carbon dioxide into the mixture to obtain carbon mixed concrete; and (3) curing the carbon mixed concrete. The application provides a method for preparing the dynamic carbon injection recycled coarse aggregate concrete by using the carbon fixation agent, the retarder, the cement, the mineral powder, the recycled coarse aggregate, the fine aggregate, the fly ash and the water reducing agent as raw materials. The method is simple in process and easy for large-scale production. The concrete prepared by the method has a high carbon fixation rate, excellent mechanical properties and can effectively avoid rapid hydration.

Description

Technical Field

[0001] This invention belongs to the field of concrete technology, specifically relating to a dynamic carbon-injected recycled coarse aggregate concrete, its preparation method, and its application. Background Technology

[0002] Concrete is a general term for engineering composite materials that bind aggregates together with cementing materials, and it is widely used in civil engineering. As one of the major sources of carbon emissions, the low-carbon transformation of the concrete industry is of great significance to the ecological environment.

[0003] There are two main ways for concrete to solidify carbon dioxide: one is to react pre-treated industrial waste with carbon dioxide to generate carbonate materials; the other is to place freshly mixed concrete in an environment with suitable temperature and humidity and introduce carbon dioxide for curing before it is fully hydrated. However, carbon dioxide accelerates the hydration rate of cementitious materials. As mixing continues, hydration products increase rapidly, causing a sharp decrease in the fluidity of the concrete in a short period of time, and the mixture loses its plasticity prematurely, thus affecting its workability. Currently, additives such as gluconate and lignin sulfonate are often added to concrete to improve its carbon fixation capacity. However, these additives have a weak complexing ability for calcium ions, and the precipitation rate of calcium carbonate is slow, resulting in a still low efficiency of carbon dioxide fixation in concrete.

[0004] Therefore, it is necessary to develop a new type of concrete that can effectively inhibit the early rapid hydration of cement-based materials, reduce the amount of hydration products generated, and reduce the attraction and key properties between anions and cations. This will ensure that the concrete maintains normal workability and hydration process while guaranteeing successful carbon dioxide injection, and ensure that the final product quality meets the requirements for use. Summary of the Invention

[0005] The primary objective of this invention is to provide a method for preparing dynamically carbon-injected recycled coarse aggregate concrete, which is simple and easy to implement.

[0006] The second objective of this invention is to provide a dynamically carbon-injected recycled coarse aggregate concrete with a high carbon fixation rate, excellent mechanical properties, and the ability to effectively prevent rapid hydration.

[0007] The third objective of this invention is to provide an application of dynamically carbon-injected recycled coarse aggregate concrete, which has broad prospects.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing dynamically carbon-injected recycled coarse aggregate concrete includes the following steps:

[0010] (1) Add cement, mineral powder, recycled coarse aggregate, fine aggregate, fly ash, carbon fixative, retarder, and water-reducing agent to water and stir evenly to obtain a mixture;

[0011] (2) Carbon dioxide is injected into the mixture to obtain carbon-mixed concrete;

[0012] (3) Curing the carbon-mixed concrete is then complete;

[0013] The preparation process of the carbon fixation agent in step (1) is as follows: take mullite whiskers and add them to water, then add spermidine and stir to react. After the reaction is completed, centrifuge, wash and dry to obtain the carbon fixation agent.

[0014] Furthermore, the ratio of water, mullite whiskers, and spermidine is 1 mL: (0.3-0.6) mg: (0.5-1) mg; the stirring reaction temperature is 50-60℃, and the time is 8-10 h.

[0015] Furthermore, the preparation process of the retarder in step (1) is as follows: take bentonite and add it to water, add hexadecylmethyldihydroxyethylammonium bromide and heat and stir to react. After the reaction is completed, filter and dry to obtain pretreated bentonite; add the pretreated bentonite to water, then add chlorogenic acid and phytic acid and heat to react. After the reaction is completed, filter, wash and dry to obtain the retarder.

[0016] Furthermore, the ratio of bentonite, water, and hexadecylmethyldihydroxyethylammonium bromide is 1g:(80-100)mL:(0.2-0.5)g; the heating and stirring reaction temperature is 50-60℃, and the time is 1-3h.

[0017] Furthermore, the ratio of the amount of bentonite, water, chlorogenic acid, and phytic acid used in the pretreatment is 1g:(30-40)mL:(0.3-0.5)g:(0.1-0.2)g; the heating reaction temperature is 80-90℃ and the time is 3-5h.

[0018] Furthermore, by weight, the amounts of each raw material used in concrete in step (1) are as follows: 150-200 parts cement, 50-100 parts mineral powder, 400-500 parts recycled coarse aggregate, 200-300 parts fine aggregate, 50-100 parts fly ash, 5-10 parts carbon fixative, 0.2-0.5 parts retarder, 3-5 parts water-reducing agent, and 80-120 parts water.

[0019] Furthermore, the mineral powder is S95 or S105 grade mineral powder; the recycled coarse aggregate is crushed stone material formed from concrete construction waste; the particle size of the recycled coarse aggregate is 4.5-9.5mm, and the apparent density is 2400-2500kg / m³. 3The mud content is less than 2%, and the water absorption rate is 4-5%; the fine aggregate is manufactured sand or natural sand; the fly ash is Grade I fly ash; and the water-reducing agent is polycarboxylate water-reducing agent.

[0020] Furthermore, the mineral powder is grade S95; the fine aggregate is natural sand; and the cement is PO42.5 cement.

[0021] Furthermore, the temperature for maintenance is 18-25℃, and the humidity is 80-95%.

[0022] A dynamic carbon-injected recycled coarse aggregate concrete was prepared using the above-mentioned preparation method.

[0023] An application of dynamically carbon-injected recycled coarse aggregate concrete, which is applied to building engineering or road engineering.

[0024] Compared with the prior art, the main advantages of the present invention are as follows:

[0025] 1. This invention provides a method for preparing dynamically carbon-injected recycled coarse aggregate concrete using carbon fixative, retarder, cement, mineral powder, recycled coarse aggregate, fine aggregate, fly ash, and water-reducing agent as raw materials. This method is simple and easy to mass-produce. The concrete prepared using this method has a high carbon fixation rate, excellent mechanical properties, and effectively avoids rapid hydration.

[0026] 2. The carbon-fixing agent added to concrete raw materials in this invention uses stable mullite whiskers as a carrier for spermidine, which improves the stability of spermidine and allows it to be fully dispersed in the concrete matrix, thereby improving its carbon fixation efficiency. Simultaneously, the polyamino structure on spermidine has a good adsorption effect on carbon dioxide, which can be converted into stable calcium carbonate, improving the mechanical properties of concrete.

[0027] 3. The retarder added to concrete raw materials in this invention is prepared from bentonite, hexadecylmethyldihydroxyethylammonium bromide, chlorogenic acid, and phytic acid. First, the bentonite is pretreated with hexadecylmethyldihydroxyethylammonium bromide to increase the interlayer spacing, which helps disperse cement particles and improves the fluidity of the concrete. Under heating conditions, chlorogenic acid and phytic acid molecules can partially insert into the expanded bentonite interlayers or be adsorbed onto the bentonite surface. For example, there is electrostatic attraction between positively charged quaternary ammonium salts and negatively charged phytic acid. Both chlorogenic acid and phytic acid possess a large number of negatively charged groups (such as phenolic hydroxyl groups, phosphate groups, and carboxyl groups), and they can also form hydrogen bond networks, preventing chlorogenic acid and phytic acid from becoming unstable and failing too quickly in concrete. Chlorogenic acid contains a large number of active groups such as phenolic hydroxyl and carboxyl groups, which, through complexation with calcium ions, slow down the initial hydration reaction rate of C3S in cement. Phytic acid contains six phosphate groups, exhibiting strong chelating ability. It can form a stable complex with calcium ions generated in the early stage of cement hydration, slowing down the hydration reaction rate of cement minerals (such as C3A and C3S) without affecting early strength. Through the synergistic effect of the above components, it can effectively avoid rapid hydration of concrete and fully meet the construction requirements of carbon-injected concrete. Attached Figure Description

[0028] Figure 1 SEM image of the carbon fixative prepared in Example 1;

[0029] Figure 2 SEM image of the retarder prepared in Example 4. Detailed Implementation

[0030] The technical solution of the present invention will be further described below with reference to specific embodiments. However, those skilled in the art should understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the reagents or instruments used are all conventional products obtained through commercial channels.

[0031] The cement used in this invention is PO42.5 cement, and the mineral powder is grade S95; the recycled coarse aggregate is crushed stone material formed from concrete construction waste; the particle size of the recycled coarse aggregate is 4.5-9.5mm, and the apparent density is 2400-2500kg / m³. 3 The mud content is less than 2%, and the water absorption rate is 4-5%; the fly ash is Grade I fly ash; the water-reducing agent is polycarboxylate water-reducing agent; the fine aggregate is natural sand with a modulus of 2.3-3.

[0032] I. Preparation Example

[0033] Preparation Example 1

[0034] This preparation example provides a carbon fixative, and the preparation process is as follows:

[0035] The mullite whiskers were added to water at a ratio of 1 mL:0.5 mg:0.7 mg, followed by spermidine. The mixture was stirred at 55°C for 9 hours. After the reaction was complete, the mixture was centrifuged, washed, and dried to obtain the carbon-fixing agent. The SEM image of the carbon-fixing agent is shown below. Figure 1 .

[0036] Preparation Example 2

[0037] This preparation example provides a carbon fixative, and the preparation process is as follows:

[0038] With water, mullite whiskers and spermidine in a ratio of 1 mL: 0.3 mg: 0.5 mg, mullite whiskers were added to water, followed by spermidine. The mixture was stirred at 50 °C for 10 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain the carbon fixative.

[0039] Preparation Example 3

[0040] This preparation example provides a carbon fixative, and the preparation process is as follows:

[0041] With water, mullite whiskers and spermidine in a ratio of 1 mL: 0.6 mg: 1 mg, mullite whiskers were added to water, followed by spermidine. The mixture was stirred at 60 °C for 8 h. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain the carbon fixative.

[0042] Preparation Example 4

[0043] This preparation example provides a retarder, and the preparation process is as follows:

[0044] Bentonite, water, and hexadecylmethyldihydroxyethylammonium bromide were mixed in a ratio of 1 g:90 mL:0.4 g. The mixture was ultrasonically dispersed in water, then hexadecylmethyldihydroxyethylammonium bromide was added, and the mixture was reacted at 55°C for 2 hours. After the reaction was complete, the mixture was filtered and dried to obtain pretreated bentonite. Pretreated bentonite, water, chlorogenic acid, and phytic acid were mixed in a ratio of 1 g:35 mL:0.4 g:0.15 g. The mixture was then added to water, followed by chlorogenic acid and phytic acid, and reacted at 80°C for 5 hours. After the reaction was complete, the mixture was filtered, washed, and dried to obtain a retarder. The SEM image of the retarder is shown below. Figure 2 .

[0045] Preparation Example 5

[0046] This preparation example provides a retarder, and the preparation process is as follows:

[0047] Bentonite, water, and hexadecylmethyldihydroxyethylammonium bromide were mixed in a ratio of 1g:80mL:0.2g. The bentonite was added to water and ultrasonically dispersed until uniform. Then, hexadecylmethyldihydroxyethylammonium bromide was added, and the mixture was reacted at 60℃ for 1 hour. After the reaction was completed, the mixture was filtered and dried to obtain pretreated bentonite. Pretreated bentonite, water, chlorogenic acid, and phytic acid were mixed in a ratio of 1g:30mL:0.5g:0.2g. The pretreated bentonite was added to water, followed by the addition of chlorogenic acid and phytic acid. The mixture was reacted at 90℃ for 3 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain a retarder.

[0048] Preparation Example 6

[0049] This preparation example provides a retarder, and the preparation process is as follows:

[0050] Bentonite, water, and hexadecylmethyldihydroxyethylammonium bromide were mixed in a ratio of 1g:100mL:0.5g. The bentonite was added to water and ultrasonically dispersed evenly. Then, hexadecylmethyldihydroxyethylammonium bromide was added, and the mixture was reacted at 50℃ for 3 hours. After the reaction was completed, the mixture was filtered and dried to obtain pretreated bentonite. Pretreated bentonite, water, chlorogenic acid, and phytic acid were mixed in a ratio of 1g:40mL:0.3g:0.1g. The pretreated bentonite was added to water, followed by chlorogenic acid and phytic acid. The mixture was reacted at 80℃ for 5 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain a retarder.

[0051] Preparation Example 7

[0052] The difference between this preparation example and preparation example 4 is that phytic acid was not added, and the amount of chlorogenic acid was adjusted to be the same as the total amount of phytic acid and chlorogenic acid in preparation example 4.

[0053] II. Implementation Examples

[0054] Example 1

[0055] This embodiment provides a method for preparing dynamically carbon-injected recycled coarse aggregate concrete, including the following steps:

[0056] (1) By weight, 174 parts of cement, 63 parts of mineral powder, 456 parts of recycled coarse aggregate, 233 parts of fine aggregate, 74 parts of fly ash, 6 parts of carbon fixative of Preparation Example 1, 0.3 parts of retarder of Preparation Example 4, 4 parts of water-reducing agent, and 90 parts of water were weighed and added to water and stirred evenly to obtain a mixture.

[0057] (2) Carbon dioxide is injected into the mixture (flow rate of 2L / min, injection time of 30min) to obtain carbon-mixed concrete;

[0058] (3) The carbon-mixed concrete is cured in an environment with a temperature of 22°C and a humidity of 85%.

[0059] This embodiment also provides a dynamic carbon-injected recycled coarse aggregate concrete, which is prepared using the above-described preparation method.

[0060] Example 2

[0061] This embodiment provides a method for preparing dynamically carbon-injected recycled coarse aggregate concrete, including the following steps:

[0062] (1) By weight, 200 parts of cement, 100 parts of mineral powder, 500 parts of recycled coarse aggregate, 300 parts of fine aggregate, 100 parts of fly ash, 10 parts of carbon fixative of Preparation Example 2, 0.5 parts of retarder of Preparation Example 5, 5 parts of water-reducing agent, and 120 parts of water are weighed and added to water and stirred evenly to obtain a mixture.

[0063] (2) Carbon dioxide is injected into the mixture (flow rate of 2L / min, injection time of 30min) to obtain carbon-mixed concrete;

[0064] (3) Curing the carbon-mixed concrete in an environment with a temperature of 25°C and a humidity of 95% is sufficient.

[0065] This embodiment also provides a dynamic carbon-injected recycled coarse aggregate concrete, which is prepared using the above-described preparation method.

[0066] Example 3

[0067] This embodiment provides a method for preparing dynamically carbon-injected recycled coarse aggregate concrete, including the following steps:

[0068] (1) By weight, 150 parts of cement, 50 parts of mineral powder, 400 parts of recycled coarse aggregate, 200 parts of fine aggregate, 50 parts of fly ash, 5 parts of carbon fixative of Preparation Example 3, 0.2 parts of retarder of Preparation Example 6, 3 parts of water-reducing agent, and 80 parts of water were weighed and added to water and stirred evenly to obtain a mixture.

[0069] (2) Carbon dioxide is injected into the mixture (flow rate of 2L / min, injection time of 30min) to obtain carbon-mixed concrete;

[0070] (3) Curing the carbon-mixed concrete in an environment with a temperature of 18°C ​​and a humidity of 80% is sufficient.

[0071] This embodiment also provides a dynamic carbon-injected recycled coarse aggregate concrete, which is prepared using the above-described preparation method.

[0072] IV. Comparative Examples

[0073] Comparative Example 1

[0074] This comparative example provides a method for preparing concrete, which differs from Example 1 in that the carbon-fixing agent in Example 1 is replaced with spermidine, while the remaining process conditions are kept the same as in Example 1.

[0075] This comparative example also provides a type of concrete prepared using the above-described preparation method.

[0076] Comparative Example 2

[0077] This comparative example provides a method for preparing concrete, which differs from Example 1 in that the carbon-fixing agent in Example 1 is replaced with a mixture of spermidine and mullite whiskers, with the same dosage and ratio as in Example 1, and the remaining process conditions are kept consistent with those in Example 1.

[0078] This comparative example also provides a type of concrete prepared using the above-described preparation method.

[0079] Comparative Example 3

[0080] This comparative example provides a method for preparing concrete, which differs from Example 1 in that the retarder in Preparation Example 4 is replaced with a mixture of bentonite, chlorogenic acid and phytic acid, with the same dosage and ratio as in Preparation Example 4, and the remaining process conditions are kept consistent with those in Example 1.

[0081] This comparative example also provides a type of concrete prepared using the above-described preparation method.

[0082] Comparative Example 4

[0083] This comparative example provides a method for preparing concrete, which differs from Example 1 in that the retarder in Preparation Example 4 is replaced with the retarder in Preparation Example 7, while the remaining process conditions are kept the same as in Example 1.

[0084] This comparative example also provides a type of concrete prepared using the above-described preparation method.

[0085] V. Experimental Examples

[0086] The concrete obtained in Examples 1-3 and Comparative Examples 1-4 were prepared into 100mm×100mm×100mm test blocks, and the performance of each test block was tested as follows:

[0087] Compressive strength: Tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", and the results are shown in Table 1;

[0088] Carbon fixation rate: Using test blocks aged 28 days, the original mass of each test block and the mass of the test block after 90 days of storage at room temperature and pressure were recorded, and the carbon fixation rate was calculated. The results are shown in Table 1.

[0089] Slump: The test was conducted in accordance with GB / T50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", and the results are shown in Table 1.

[0090] Table 1

[0091] ;

[0092] As shown in Table 1, compared with Comparative Examples 1-2, the carbon fixation rate of the concrete obtained by this invention is significantly increased. These results indicate that the carbon fixative prepared by this invention can improve carbon fixation efficiency. Further analysis reveals that this invention uses stable mullite whiskers as a carrier for spermidine, improving the stability of spermidine and allowing it to be fully dispersed in the concrete matrix, thereby increasing its carbon fixation efficiency. Simultaneously, the polyamino structure on spermidine has a good adsorption effect on carbon dioxide, which can convert carbon dioxide into stable calcium carbonate, improving the mechanical properties of the concrete.

[0093] Table 1 also shows that, compared with Comparative Examples 3-4, the retarder obtained in this invention can slow down the initial hydration reaction rate of cement C3S, thereby effectively preventing rapid hydration of concrete. Further analysis reveals that this invention first pretreats bentonite with hexadecylmethyldihydroxyethylammonium bromide, increasing the interlayer spacing of the bentonite, which helps disperse cement particles and improves the fluidity of concrete. Under heating conditions, chlorogenic acid and phytic acid molecules can partially insert into the expanded bentonite interlayers or be adsorbed onto the bentonite surface. For example, there is electrostatic attraction between positively charged quaternary ammonium salts and negatively charged phytic acid. Both chlorogenic acid and phytic acid possess a large number of negatively charged groups (such as phenolic hydroxyl groups, phosphate groups, and carboxyl groups), and they can also form hydrogen bond networks, preventing chlorogenic acid and phytic acid from becoming unstable and failing too quickly in concrete. Chlorogenic acid contains a large number of active groups such as phenolic hydroxyl and carboxyl groups, whose complexation effect on calcium ions slows down the initial hydration reaction rate of cement C3S. Phytic acid contains six phosphate groups, which have a strong chelating ability. It can form a stable complex with calcium ions generated in the early stage of cement hydration, slowing down the hydration reaction rate of cement minerals (such as C3A and C3S) without affecting early strength. Through the synergistic effect of the above components, it can effectively avoid rapid hydration of concrete and fully meet the construction requirements of carbon-injected concrete.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A method for preparing dynamically carbon-injected recycled coarse aggregate concrete, characterized in that, Includes the following steps: (1) Add cement, mineral powder, recycled coarse aggregate, fine aggregate, fly ash, carbon fixative, retarder, and water-reducing agent to water and stir evenly to obtain a mixture; (2) Carbon dioxide is injected into the mixture to obtain carbon-mixed concrete; (3) Curing the carbon-mixed concrete is then complete; The preparation process of the carbon fixation agent in step (1) is as follows: take mullite whiskers and add them to water, then add spermidine and stir to react. After the reaction is completed, centrifuge, wash and dry to obtain the carbon fixation agent.

2. The method for preparing dynamically carbon-injected recycled coarse aggregate concrete according to claim 1, characterized in that, The ratio of water, mullite whiskers, and spermidine used is 1 mL: (0.3-0.6) mg: (0.5-1) mg; the stirring reaction temperature is 50-60℃ and the time is 8-10 h.

3. The method for preparing dynamically carbon-injected recycled coarse aggregate concrete according to claim 1, characterized in that, The preparation process of the retarder in step (1) is as follows: take bentonite and add it to water, add hexadecylmethyldihydroxyethylammonium bromide and heat and stir to react. After the reaction is completed, filter and dry to obtain pretreated bentonite; add the pretreated bentonite to water, then add chlorogenic acid and phytic acid and heat to react. After the reaction is completed, filter, wash and dry to obtain the retarder.

4. The method for preparing dynamically carbon-injected recycled coarse aggregate concrete according to claim 3, characterized in that, The ratio of bentonite, water, and hexadecylmethyldihydroxyethylammonium bromide is 1g:(80-100)mL:(0.2-0.5)g; the heating and stirring reaction temperature is 50-60℃, and the time is 1-3h.

5. The method for preparing dynamically carbon-injected recycled coarse aggregate concrete according to claim 3, characterized in that, The ratio of bentonite, water, chlorogenic acid, and phytic acid used in the pretreatment is 1g:(30-40)mL:(0.3-0.5)g:(0.1-0.2)g; the heating reaction temperature is 80-90℃ and the time is 3-5h.

6. The method for preparing dynamically carbon-injected recycled coarse aggregate concrete according to claim 1, characterized in that, By weight, the amounts of each raw material used in step (1) are: 150-200 parts cement, 50-100 parts mineral powder, 400-500 parts recycled coarse aggregate, 200-300 parts fine aggregate, 50-100 parts fly ash, 5-10 parts carbon fixative, 0.2-0.5 parts retarder, 3-5 parts water-reducing agent, and 80-120 parts water.

7. The method for preparing dynamically carbon-injected recycled coarse aggregate concrete according to claim 6, characterized in that, The mineral powder is S95 or S105 grade mineral powder; the particle size of the recycled coarse aggregate is 4.5-9.5mm; the fine aggregate is manufactured sand or natural sand; the fly ash is Grade I fly ash; and the water-reducing agent is polycarboxylate water-reducing agent.

8. The method for preparing dynamically carbon-injected recycled coarse aggregate concrete according to claim 1, characterized in that, The temperature for curing in step (3) is 18-25℃ and the humidity is 80-95%.

9. A dynamically carbon-injected recycled coarse aggregate concrete, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. An application of dynamically carbon-injected recycled coarse aggregate concrete, characterized in that, The dynamic carbon-injected recycled coarse aggregate concrete of claim 9 is applied to building construction or road construction.

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