Recycled aggregate concrete with carbon absorption and carbon sequestration capacity and preparation method thereof

Abstract

The application discloses a recycled aggregate concrete with carbon absorption and carbon fixation capacity and a preparation method thereof, and comprises the following components in mass percentage: pretreated recycled coarse aggregate 1031-1244 parts, fine aggregate 708-854 parts, cement 168-212 parts, mineral powder 89-125 parts, composite micro powder 198-264 parts, water 132-158 parts, water reducing agent 7.7-10.4 parts and carbon fixation material 42-64 parts. The application can fill and close micropores on the recycled aggregate, further enhance the mechanical properties of the recycled aggregate, reduce the influence of the large water absorption of the recycled aggregate on the concrete mix design, mixing and later performance, utilize the carbon dioxide absorption capacity of nonylphenol polyoxyethylene ether and the porous characteristics of the recycled aggregate, and further improve the carbon dioxide absorption capacity in structure.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of concrete, in particular to a recycled aggregate concrete with carbon absorption and carbon sequestration capability and a preparation method thereof. BACKGROUND

[0002] Cement plays a vital role in the construction industry. When producing traditional Portland cement, limestone (mainly containing calcium carbonate CaCO3) and clay are calcined at high temperature in a cement kiln, resulting in cement clinker mainly composed of calcium oxide CaO (content about 60% to 70%). This process releases a large amount of carbon dioxide. According to research, the cement industry contributes 5% to 8% of global carbon dioxide emissions. In addition, although recycled aggregate has been widely studied and considered as a sustainable material that can replace natural crushed stone commonly used in concrete, it consumes a large amount of energy in the process of crushing and screening waste concrete, so its positive impact on the environment, especially on global emission reduction targets, is still controversial.

[0003] Carbon sequestration and negative carbon concrete is a special concrete that is vigorously promoted and developed in the field of green building materials at the present stage, mainly using the mechanism of chemical reaction between CO2 and hydration products such as Ca(OH)2, CSH in the concrete matrix to sequester carbon. Specifically, CO2 reacts with Ca(OH)2, CSH and other hydration products to form CaCO3, which is stably stored in concrete. At the same time, due to the porous nature of recycled aggregate itself, it is often used as a carbonated aggregate carrier, which can effectively sequester carbon and improve the mechanical properties of recycled aggregate, further solving the problem of recycling recycled aggregate.

[0004] However, ordinary carbonated recycled aggregate cannot solve the problem of weak interface transition zone (ITZ) between new and old mortar when it is used, and the calcium carbonate deposited on the surface of recycled aggregate may hinder the complete carbonation of the internal cement paste. The standard carbonation method has limited effect on the quality modification of recycled aggregate. SUMMARY

[0005] The purpose of the present application is to provide a recycled aggregate concrete with carbon absorption and carbon sequestration capability and a preparation method thereof to solve the problems raised in the background.

[0006] To achieve the above purpose, the present application provides the following technical solution: a recycled aggregate concrete with carbon absorption and carbon sequestration capability and a preparation method thereof, comprising the following components by mass: pretreated recycled coarse aggregate 1031-1244 parts, fine aggregate 708-854 parts, cement 168-212 parts, mineral powder 89-125 parts, composite micro powder 198-264 parts, water 132-158 parts, water reducing agent 7.7-10.4 parts, carbon sequestration material 42-64 parts, and catalyst 0.4-3 parts.

[0007] The cement is P.O 42.5 ordinary portland cement; the particle size of the pretreated recycled coarse aggregate is 10-20 mm, single particle gradation, and the porosity is 45-60%; the fine aggregate is machine-made sand, and the fineness modulus is 2.5.

[0008] Preferably, the pretreatment step of the pretreated recycled coarse aggregate is:

[0009] S1: soaking the recycled coarse aggregate in a non-corrosive ion solution rich in Ca 2+ / Mg 2+ , such as one or more of Mg(OH)2, MgO, MgCl2, Ca(OH)2, CaCl2, C4H6CaO4, etc., for 1.5-2 h with sufficient stirring;

[0010] S2: adding 15-20 parts of nonylphenol polyoxyethylene ether and 4-6 parts of hydroxypropyl methyl cellulose to the solid carrier suspension obtained in S1, stirring thoroughly, and soaking for 0.5-1 h;

[0011] S3: performing low-frequency microwave drying treatment on the recycled coarse aggregate treated in S1 and S2, at a temperature of 40℃ for 4-6 h;

[0012] S4: pre-wetting the recycled coarse aggregate treated in S1, S2, and S3, and placing it in a closed environment with a humidity of 50-70%, a temperature of 24±2℃, and a CO2 concentration of 60-100% for carbonation treatment. After the carbonation is completed, the aggregate is dried again, at a drying temperature of 50-60℃ for 22-24 h, to obtain the pretreated recycled coarse aggregate.

[0013] Preferably, the viscosity of the non-corrosive ion solution is 0.03-0.12 Pa·s, and the solid-liquid ratio is 0.2 g / ml-0.8 g / ml.

[0014] Preferably, the mineral powder is S105 grade mineral powder.

[0015] Preferably, the water reducing agent is SPC-100 polycarboxylic acid high-performance water reducing agent.

[0016] Preferably, the composite micro-powder is a hydraulic cementing material prepared by grinding and mixing certain proportions of solid waste such as granulated blast furnace slag, steel slag, industrial by-product gypsum, fly ash, and iron tailings.

[0017] Preferably, the composite micro-powder comprises, by mass fraction: 40.3% gypsum, 25.3% raw gypsum, 6.8% dicalcium silicate, 23.5% tetracalcium aluminoferrite, 1.9% tricalcium aluminate, 0.2% quartz, and 2.0% mica.

[0018] Preferably, the density of the composite micro powder is 2.8 g / cm³. 3 Specific surface area is 512 m² 2 / kg, with a flowability ratio of 95%, an activity index of 83% at 7 days, and an activity index of 108% at 28 days.

[0019] Preferably, the carbon-fixing material is a mixture of sepiolite powder and melamine-phenolic resin, with a mixing ratio of sepiolite powder: ammonium carbamate = 4-6: 5-7.

[0020] This application provides a method for preparing recycled aggregate negative carbon permeable concrete as described in any of the preceding claims, comprising the following steps:

[0021] SS1. First, mix the pretreated recycled coarse aggregate, fine aggregate and 10% water in a mixer for 30 seconds to fully pre-wet the aggregate. Then add cement, mineral powder, composite micro powder and carbon fixation material and mix for 60 seconds to make the aggregate and powder evenly mixed.

[0022] SS2. Add the remaining 90% water and water-reducing agent and stir. After stirring, observe the mixing condition to obtain recycled aggregate carbon-fixing concrete.

[0023] The technical effects and advantages of this invention are as follows:

[0024] (1) This application utilizes Ca-rich 2+ / Mg 2+ Regenerated coarse aggregate was soaked in a non-corrosive ionic solution, and nonylphenol polyoxyethylene ether and hydroxypropyl methylcellulose were added to a fully stirred solid carrier suspension to form a dense gel coating on the surface of the recycled coarse aggregate. Subsequently, the aggregate was dried and pre-moistened with carbon. Through these operations, CO2 and Ca... 2+ / Mg 2+ In an aqueous solution environment, a chemical reaction involves storing CO2 gas as stable hydration products, such as CaCO3 or hydrated basic magnesium carbonate, within porous recycled coarse aggregate. This process not only fixes carbon but also improves the mechanical properties of the recycled coarse aggregate itself, and solves the problem of corrosion of reinforcing steel caused by a decrease in pH value within the concrete matrix under conventional carbonation treatment. Nonylphenol polyoxyethylene ether and hydroxypropyl methylcellulose are added to a solid carrier suspension, and after thorough wetting and stirring, the gel is solidified by low-frequency microwave drying, uniformly coating the surface of the recycled coarse aggregate. This process fills and seals the micropores on the recycled aggregate, further enhancing its mechanical properties and reducing the impact of the high water absorption of recycled aggregate on concrete mix design, mixing, and subsequent performance. Furthermore, by utilizing the carbon dioxide affinity of nonylphenol polyoxyethylene ether and the porous nature of the recycled aggregate, the structure can further enhance the adsorption capacity for carbon dioxide.

[0025] (2) The application uses a special composite powder as the main cementitious material, which is a hydraulic cementitious material prepared by mixing granulated blast furnace slag, steel slag, industrial by-product gypsum, fly ash, iron tailings and other solid waste as raw materials and grinding them to a certain proportion. The unit price of the composite powder solid waste-based cementitious material is only 200-210 yuan / ton, which is more than 100 yuan / ton cheaper than ordinary Portland cement. At the same time, it has early and 28d activity comparable to S105 mineral powder. According to the test preparation verification, the 7d strength of C50 concrete prepared by replacing cement with 40% of the composite powder can reach 53.6Mpa, and the 28d strength can reach 72.5Mpa. Using the composite powder can not only greatly reduce the production cost, but also meet the requirements of concrete strength.

[0026] (3) The application uses a carbon sequestration material prepared by mixing sepiolite powder and melamine phenolic resin in a ratio of 4-6:5-7, which has water channels and pores as well as a large specific surface area, giving it good adsorption capacity and improving the air permeability of the formed concrete, providing a channel for carbon dioxide to enter the concrete matrix, and at the same time adsorbing and releasing CO2, regulating the reaction rate of CO2 and the hydration products in the concrete matrix, and making the carbonation reaction more complete. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, not all. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0028] The application provides a recycled aggregate concrete with carbon absorption and sequestration capacity and a preparation method thereof. The recycled aggregate carbon sequestration concrete provided in the following examples and comparative examples uses P·O42.5 ordinary Portland cement as the selected cement; the particle size of the selected recycled coarse aggregate is 10-20mm single-grain grading; the selected recycled fine aggregate is machine-made sand with a fineness modulus of 2.5; the selected mineral powder is S105 grade mineral powder; the selected water reducing agent is SPC-100 polycarboxylic high-performance water reducing agent; the selected purity of nonylphenol polyoxyethylene ether is 99%; and the selected composite powder includes, by mass fraction, 40.3% gypsum, 25.3% raw gypsum, 6.8% dicalcium silicate, 23.5% tetracalcium aluminate, 1.9% tricalcium aluminate, 0.2% quartz and 2.0% mica.

[0029] The preparation method of the recycled aggregate carbon sequestration concrete used in the following examples and comparative examples is as follows:

[0030] SS1. First, the pretreated recycled coarse aggregate, fine aggregate and 10% water are stirred in a mixer for 30s to fully pre-wet the aggregate, and then cement, mineral powder, composite powder, carbon sequestration material are added and stirred for 60s to mix the aggregate and powder evenly.

[0031] SS2. The remaining 90% water and water reducing agent are added and stirred, and after stirring is completed, the mixing condition is observed to finally obtain the recycled aggregate carbon sequestration concrete.

[0032] Example 1

[0033] The recycled aggregate carbon sequestration concrete provided in this embodiment has raw materials including: pretreated recycled coarse aggregate 1031 parts, fine aggregate 734 parts, cement 168 parts, mineral powder 101 parts, composite powder 198 parts, water 142 parts, water reducing agent 7.7 parts, and carbon sequestration material 51 parts.

[0034] The treatment method of the pretreated recycled coarse aggregate is:

[0035] S1: Soak the recycled coarse aggregate in a Ca(OH)2 suspension with a solid-liquid ratio of 0.2g / ml and a viscosity of 0.0294 Pa·s for 2h and stir thoroughly;

[0036] S2: Add 17 parts of nonylphenol polyoxyethylene ether and 4 parts of hydroxypropyl methyl cellulose to the solid carrier suspension obtained in S1, stir thoroughly, and soak for 1h;

[0037] S3: Perform low-frequency microwave drying treatment on the recycled coarse aggregate treated in S1 and S2, at a temperature of 40℃ for 5h;

[0038] S4: Pre-wet the recycled coarse aggregate treated in S1, S2 and S3, and place it in a closed environment with a humidity of 50-70%, a temperature of 24±2℃, and a CO2 concentration of 100% for carbonation treatment. After carbonation is completed, the aggregate is dried again, with a drying temperature of 50℃ and a drying time of 24h, to finally obtain the pretreated recycled coarse aggregate.

[0039] The mixing ratio of the carbon sequestration material is sepiolite powder: melamine phenolic resin = 5:5.

[0040] Example 2

[0041] The recycled aggregate carbon sequestration concrete provided in this embodiment has raw materials including: pretreated recycled coarse aggregate 1031 parts, fine aggregate 734 parts, cement 168 parts, mineral powder 101 parts, composite powder 198 parts, water 142 parts, water reducing agent 7.7 parts, and carbon sequestration material 51 parts.

[0042] The treatment method of the pretreated recycled coarse aggregate is:

[0043] S1: the recycled coarse aggregate is soaked in a Ca(OH)2 suspension with a solid-liquid ratio of 0.6 g / ml and a viscosity of 0.0793 Pa·s for 2 h with sufficient stirring;

[0044] S2: 20 parts of nonylphenol polyoxyethylene ether and 5 parts of hydroxypropyl methyl cellulose are added to the solid carrier suspension obtained in S1, and the mixture is stirred thoroughly and soaked for 1 h;

[0045] S3: the recycled coarse aggregate treated in S1 and S2 is subjected to low-frequency microwave drying treatment at a temperature of 40℃ for 5 h;

[0046] S4: the recycled coarse aggregate treated in S1, S2 and S3 is pre-wetted and placed in a closed environment with a humidity of 50-70%, a temperature of 24±2℃ and a CO2 concentration of 100% for carbonization treatment, and after the carbonization is completed, the aggregate is dried again at a temperature of 50℃ for 24 h, to obtain the pretreated recycled coarse aggregate.

[0047] The mixing ratio of the carbon sequestration material is sepiolite powder: melamine phenolic resin = 5:7.

[0048] Example 3

[0049] The recycled aggregate carbon sequestration concrete provided in this example comprises: 1244 parts of pretreated recycled coarse aggregate, 708 parts of fine aggregate, 212 parts of cement, 89 parts of mineral powder, 264 parts of composite micro powder, 132 parts of water, 10.4 parts of water reducing agent and 42 parts of carbon sequestration material.

[0050] The treatment method of the pretreated recycled coarse aggregate is as follows:

[0051] S1: the recycled coarse aggregate is soaked in a Ca(OH)2 suspension with a solid-liquid ratio of 0.8 g / ml and a viscosity of 0.1046 Pa·s for 2 h with sufficient stirring;

[0052] S2: 15 parts of nonylphenol polyoxyethylene ether and 6 parts of hydroxypropyl methyl cellulose are added to the solid carrier suspension obtained in S1, and the mixture is stirred thoroughly and soaked for 1 h;

[0053] S3: the recycled coarse aggregate treated in S1 and S2 is subjected to low-frequency microwave drying treatment at a temperature of 40℃ for 5 h;

[0054] S4: the recycled coarse aggregate treated in S1, S2 and S3 is pre-wetted and placed in a closed environment with a humidity of 50-70%, a temperature of 24±2℃ and a CO2 concentration of 60% for carbonization treatment, and after the carbonization is completed, the aggregate is dried again at a temperature of 50℃ for 24 h, to obtain the pretreated recycled coarse aggregate.

[0055] The mixing ratio of the carbon sequestration material is sepiolite powder: melamine phenolic resin = 6:5.

[0056] Embodiment 4

[0057] The raw materials of the recycled aggregate carbon sequestration concrete provided in this embodiment include: pretreated recycled coarse aggregate 1031 parts, fine aggregate 854 parts, cement 168 parts, mineral powder 125 parts, composite micro powder 198 parts, water 158 parts, water reducing agent 7.7 parts, and carbon sequestration material 64 parts.

[0058] The treatment method of the pretreated recycled coarse aggregate is as follows:

[0059] S1: soaking the recycled coarse aggregate in a Ca(OH)2 suspension with a solid-liquid ratio of 0.2 g / ml and a viscosity of 0.0294 Pa·s for 1.5 h and fully stirring;

[0060] S2: adding 20 parts of nonylphenol polyoxyethylene ether and 4 parts of hydroxypropyl methyl cellulose to the solid carrier suspension obtained in S1, fully stirring, and soaking for 0.5 h;

[0061] S3: performing low-frequency microwave drying treatment on the recycled coarse aggregate treated in S1 and S2, at a temperature of 40℃ for 6 h;

[0062] S4: pre-wetting the recycled coarse aggregate treated in S1, S2, and S3, and placing it in a closed environment with a humidity of 50-70%, a temperature of 24±2℃, and a CO2 concentration of 80% for carbonation treatment, and then drying the aggregate again after carbonation is completed, at a drying temperature of 50℃ for 24 h, to obtain the pretreated recycled coarse aggregate.

[0063] The mixing ratio of the carbon sequestration material is sepiolite powder: melamine phenolic resin = 4:7.

[0064] Embodiment 5

[0065] The raw materials of the recycled aggregate carbon sequestration concrete provided in this embodiment include: pretreated recycled coarse aggregate 1198 parts, fine aggregate 805 parts, cement 196 parts, mineral powder 102 parts, composite micro powder 243 parts, water 147 parts, water reducing agent 9.1 parts, and carbon sequestration material 56 parts.

[0066] The treatment method of the pretreated recycled coarse aggregate is as follows:

[0067] S1: soaking the recycled coarse aggregate in a Ca(OH)2 suspension with a solid-liquid ratio of 0.6 g / ml and a viscosity of 0.0793 Pa·s for 1.5 h and fully stirring;

[0068] S2: 18 parts of nonylphenol polyoxyethylene ether and 5 parts of hydroxypropyl methylcellulose were added to the solid carrier suspension obtained in S1, and stirred thoroughly, and soaked for 1 h;

[0069] S3: The recycled coarse aggregate treated in S1, S2 was subjected to low-frequency microwave drying treatment, the temperature was 40 DEG C, and the time was 5 h;

[0070] S4: The recycled coarse aggregate treated in S1, S2, S3 was pre-wetted, and was placed in a closed environment with a humidity of 50-70%, a temperature of 24±2 DEG C, and a CO2 concentration of 100% for carbonation treatment. After carbonation, the aggregate was dried again, the drying temperature was 50 DEG C, and the drying time was 24 h, and finally the pretreated recycled coarse aggregate was obtained.

[0071] The mixing ratio of the carbon sequestration material is sepiolite powder: melamine phenolic resin = 5:6.

[0072] Example 6

[0073] The difference from Example 5 is that the mixing ratio of the carbon sequestration material is sepiolite powder: melamine phenolic resin = 7:4.

[0074] Comparative Example 1

[0075] The difference from Example 5 is that the composite micro powder is completely replaced by S95 grade mineral powder.

[0076] Comparative Example 2

[0077] The difference from Example 5 is that the recycled coarse aggregate is not pretreated.

[0078] Comparative Example 3

[0079] The difference from Example 5 is that the recycled coarse aggregate pretreatment step S1 is omitted.

[0080] Comparative Example 4

[0081] The difference from Example 5 is that the nonylphenol polyoxyethylene ether in the recycled coarse aggregate pretreatment step S2 is replaced by lauryl alcohol polyoxyethylene ether.

[0082] Comparative Example 5

[0083] The difference from Example 5 is that the recycled coarse aggregate is not pre-wetted and carbonated.

[0084] Performance test

[0085] 1. Concrete mechanical property test: the 28d cubic compressive strength and splitting tensile strength of the concrete were tested according to the mechanical property test method in GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".

[0086] 2. Concrete permeability test: The permeability coefficient of the concrete at 28d was determined according to the permeability coefficient determination method in CJJ / T135-2009 “Technical Specification for Permeable Cement Concrete Pavement”.

[0087] 3. Carbon absorption and fixation capacity test of concrete: The recycled aggregate permeable concrete mixed by each example and the comparative example was made into a cube of 150mmx150mmx150mm, and the mass of the test block at 28d was recorded as the original mass, the mass at 90d under normal temperature and pressure was recorded as the carbonated mass, and the mass loss rate (%) was calculated. After the concrete absorbs carbon dioxide, calcium carbonate is generated in the matrix, which causes the mass of the concrete to increase. The carbon absorption and fixation capacity of the concrete is evaluated by the mass loss rate. When the mass loss rate is less than 5%, it is determined that the concrete has carbon absorption and fixation performance. When the mass loss rate is negative, it means that the mass increases, and the carbon absorption and fixation capacity is stronger.

[0088] 4. Carbon dioxide release amount test during curing process: The concrete mixed by each example and the comparative example was made into a cube test block of 150mmx150mmx150mm, and after demolding, it was cured for 28d. A portable infrared carbon dioxide monitor was used to monitor the carbon dioxide concentration in the curing room during the curing process. The initial carbon dioxide concentration in the curing room was 550ppm. The carbon dioxide concentration in the curing room was recorded when the test block was cured for 3d, 14d and 28d, respectively. When the carbon dioxide concentration is less than 650ppm, it means that it has carbon absorption capacity. When it is greater than 875ppm, it means that the concrete releases more carbon dioxide.

[0089] Table 1: Test table of mechanical properties of concrete

[0090] Test item Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 28d compressive strength / MPa 61.6 64.9 65.8 63.1 66.7 62.2 51.2 39.6 46.7 49.3 42.5 28d tensile splitting strength / MPa 6.92 7.26 7.35 7.08 7.49 6.86 5.79 4.19 4.75 4.89 4.31

[0091] Table 2: Test table of permeability of concrete

[0092] Test item Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Mass loss rate / % -0.168 -0.196 -0.174 -0.182 -0.191 -0.193 -0.189 -0.064 -0.094 [3d co2 concentration] 663 PPM 642 PPM 657 PPM 651 PPM 648 PPM 639 PPM 655 PPM 761 PPM 736 PPM 14d CO2 concentration 629 PPM 613 PPM 624 PPM 630 PPM 617 PPM 614 PPM 619 PPM 752 PPM 713 PPM 28d CO2 concentration 601 PPM 585 PPM 598 PPM 609 PPM 583 PPM 583 PPM 599 PPM 745 PPM 699 PPM Test item Comparative Example 4 Comparative Example 5 Mass loss rate / % -0.143 -0.177 [3d CO2 concentration] 684 PPM 654 PPM 14d CO2 concentration 649 PPM 620 PPM 28d CO2 concentration 625 PPM 595 PPM

[0093] The performance indicators of Comparative Example 3 and Example 6 can lead to the following conclusions: when the mixing ratio of carbon fixation material is sepiolite powder: melamine phenolic resin = 4-6:5-7, the mechanical properties and carbon absorption and fixation performance of the recycled aggregate carbon fixation concrete can be better balanced, which shows that sepiolite powder and melamine phenolic resin can play a better adsorption and slow-release capacity at this compounding ratio, improve the air permeability of the formed concrete, effectively control the reaction rate of CO2 and the internal hydration products of the concrete matrix, and make the carbonation reaction more complete.

[0094] The performance indicators of Comparative Example 5 and Comparative Example 1 can draw the following conclusions: when the composite micro powder is completely replaced by S95 grade mineral powder, the 28d mechanical properties of the recycled aggregate carbon fixation concrete decrease by 23.2%, the carbon fixation capacity changes little, and the rate and total amount of CO2 absorption of the matrix do not change significantly. The main reason is that the main components of the composite micro powder are steel slag, water slag and industrial gypsum. When the specific surface area of steel slag and water slag is 500m 2 / kg, the actual active ingredients in steel slag and water slag can be excited earlier, hydrated, and the microstructure of the concrete can be improved. At the same time, when CO2 enters the concrete matrix and reacts with the hydration products, the activity of steel slag and water slag can be further excited, and the mechanical properties of the recycled aggregate carbon fixation concrete can be continuously improved.

[0095] The performance indicators of Comparative Example 5 and Comparative Example 2 can draw the following conclusions: when the recycled aggregate is directly used without pretreatment, firstly, the recycled aggregate without ion solution immersion can only rely on the attached old mortar to absorb CO2, and the problem of high water absorption rate cannot be solved by the wrapping of nonylphenol polyoxyethylene ether and hydroxypropyl methyl cellulose and the microwave drying technology, which will expose the micropores of the recycled aggregate, and the mechanical strength will decrease. The lack of CO2 affinity of nonylphenol polyoxyethylene ether further reduces the CO2 fixation efficiency. The mechanical properties and carbon absorption and fixation capacity of the recycled aggregate carbon fixation concrete decrease significantly, and the compressive strength and splitting tensile strength decrease by 40.6% and 44.1% respectively, and the carbon fixation capacity decreases by 66.5%.

[0096] The performance indicators of Comparative Example 5 and Comparative Example 3 can draw the following conclusions: if the recycled coarse aggregate pretreatment step S1 is omitted, that is, the recycled aggregate is not immersed in Ca 2+ / Mg 2+ solution, the mechanical properties and carbon fixation performance of the recycled aggregate carbon fixation concrete decrease significantly, and the compressive strength and splitting tensile strength decrease by 29.9% and 36.5% respectively, and the carbon fixation capacity decreases by 50.7%.

[0097] The performance indicators of Comparative Example 5 and Comparative Example 4 can draw the following conclusions: when the nonylphenol polyoxyethylene ether in the recycled coarse aggregate pretreatment step S2 is replaced by lauryl alcohol polyoxyethylene ether, the carbon capture capacity decreases, the rate and total amount of CO2 absorption of the matrix decrease, and the mechanical properties and carbon absorption and fixation performance of the recycled aggregate carbon fixation concrete decrease to different degrees.

[0098] The performance indicators of Comparative Example 5 and Comparative Example 5 can draw the following conclusions: when the recycled coarse aggregate is not pre-wetted and carbonized, the mechanical strength of the recycled aggregate without carbonization is low, which leads to a large decrease in the mechanical properties of the recycled aggregate carbon fixation concrete, and the compressive strength and splitting tensile strength decrease by 36.3% and 42.4% respectively.

[0099] It should be pointed out that the above-mentioned is only the preferred embodiment of the present application, and is not used to limit the present application, although the present application is described in detail with reference to the foregoing embodiments, for those skilled in the art, the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced equivalently, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A recycled aggregate concrete having a carbon absorption and carbon fixation ability, characterized by, The mass comprises the following components: 1031-1244 parts of pretreated recycled coarse aggregate, 708-854 parts of fine aggregate, 168-212 parts of cement, 89-125 parts of mineral powder, 198-264 parts of composite micro powder, 132-158 parts of water, 7.7-10.4 parts of water reducing agent, and 42-64 parts of carbon fixation material; The pretreatment step of the pretreated recycled coarse aggregate is: S1: soaking the recycled coarse aggregate in one or more non-corrosive ion solutions of Mg(OH)2, MgO, MgCl2, Ca(OH)2, CaCl2, and C4H6CaO4 for 1.5-2 hours with sufficient stirring; S2: adding 15-20 parts of nonylphenol polyoxyethylene ether and 4-6 parts of hydroxypropyl methyl cellulose to the suspension obtained in S1, stirring thoroughly, and soaking for 0.5-1 hour; S3: drying the recycled coarse aggregate treated in S1 and S2, with a temperature of 40℃ and a time of 4-6 hours; S4: placing the recycled coarse aggregate treated in S1, S2, and S3 in a closed environment with a humidity of 50-70%, a temperature of 24±2℃, and a CO2 concentration of 60-100% for carbonation treatment, and then drying the aggregate again after carbonation, with a drying temperature of 50-60℃ and a drying time of 22-24 hours, to obtain the pretreated recycled coarse aggregate; The composite micro powder is a hydraulic cementing material prepared by mixing and grinding granulated blast furnace slag, steel slag, industrial byproduct gypsum, fly ash, and iron tailings solid waste in a certain proportion; The carbon fixation material is a mixture of sepiolite powder and melamine phenolic resin.

2. The recycled aggregate concrete having carbon absorption and carbon fixation capacity according to claim 1, characterized in that, The particle size of the pretreated recycled coarse aggregate is 10-20 mm, with single-grain gradation and a porosity of 45-60%.

3. The recycled aggregate concrete having carbon absorption and carbon fixation capacity according to claim 1, characterized in that, The viscosity of the non-corrosive ion solution is 0.03-0.12 Pa·s, and the solid-liquid ratio is 0.2 g / ml-0.8 g / ml.

4. The recycled aggregate concrete having carbon absorption and carbon fixation capacity according to claim 1, characterized in that, The mineral powder is S105 grade mineral powder.

5. The recycled aggregate concrete having carbon absorption and carbon fixation capacity according to claim 1, characterized in that, The composite micropowder has a density of 2.8 g / cm 3 a specific surface area of 512 m 2 2 / g, a flow ratio of 95%, a 7d activity index of 83%, and a 28d activity index of 108%.