A heating-carbonization strengthening method to enhance the carbonization depth of recycled aggregates

Abstract

This invention belongs to the field of bulk solid waste resource utilization technology, and provides a heating-carbonization strengthening method to improve the carbonization depth of recycled aggregate. The method includes: using waste heat to vibrate and heat the recycled aggregate at 80℃~120℃ for 1~3 hours to obtain heat-treated aggregate; carbonizing the heat-treated aggregate under conditions of pressure 0.8~1.2MPa, exhaust gas concentration ≥95%, temperature 80~150℃, and humidity 20%RH~100%RH for 8~24 hours; and sieving to obtain strengthened recycled aggregate. This invention utilizes the thermal stress generated by thermal expansion to cause the fragile residual mortar on the surface of the recycled aggregate to detach, while simultaneously enlarging the microcracks and pores in the internal residual mortar, facilitating the entry of exhaust gas into the microcracks and pores, increasing the carbonization depth, and improving the aggregate strengthening effect.

Description

Technical Field

[0001] This invention belongs to the field of resource utilization technology of bulk solid waste, and specifically relates to a heating-carbonization enhancement method for improving the carbonization depth of recycled aggregates. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Recycled construction waste aggregate is aggregate with a nominal particle size of less than 40mm obtained from waste concrete blocks generated during building demolition, road resurfacing, concrete production, engineering construction, and other situations, after crushing and processing. The large quantities of waste concrete generated are difficult to dispose of and are often left in open-air dumps, occupying significant land resources and damaging the surrounding environment, failing to meet the needs of sustainable ecological development. At the same time, engineering construction consumes enormous amounts of natural resources such as sand and gravel aggregates; the amount of sand and gravel aggregate used per kilometer of highway is approximately 54,000-60,000 tons. The rational utilization of waste concrete can not only alleviate the increased cost of building materials caused by the shortage of natural resources but also promote the solution of environmental problems, thus having significance for the long-term development of resources.

[0004] Recycled aggregates are covered with a significant amount of old cement mortar, and the crushing process generates numerous microcracks. Compared to natural aggregates, they have disadvantages such as high water absorption and high crushing value, limiting their large-scale utilization. To improve the utilization rate of waste concrete, recycled aggregates prepared from waste concrete need to undergo strengthening treatment. Carbonation modification is a green and environmentally friendly method for strengthening recycled aggregates. Patents such as CN 116143437 N and CN 115215572A employ this method. However, the former only reduces water absorption and crushing value by 19.2% and 9.7%, respectively, while the latter only reduces water absorption by 23.0%. The strengthening effect is insufficient, and the water absorption and crushing value indicators remain too high, preventing the large-scale application of recycled aggregates. This is mainly because as the carbonation reaction proceeds, the carbonation products fill the pores and microcracks while accumulating on the aggregate surface, hindering CO2 penetration. This results in insufficient carbonization depth, preventing internal strengthening, and thus only a slight improvement in water absorption and crushing value. The performance remains significantly different from natural aggregates, hindering large-scale utilization. There is an urgent need for a composite strengthening method that can improve the carbonization depth of recycled aggregates. Summary of the Invention

[0005] To address the problems of high water absorption, high crushing value, insufficient carbonization depth, unsatisfactory strengthening effect, and significant differences in performance compared to natural aggregates, this invention provides a heating-carbonization strengthening method to improve the carbonization depth of recycled aggregates. First, the recycled aggregates are heated using waste heat and exhaust gas from power plant desulfurization and denitrification processes. The thermal stress generated by the thermal expansion effect causes the fragile residual mortar on the surface of the recycled aggregates to fall off. At the same time, the microcracks and pores in the residual mortar are enlarged, facilitating the exhaust gas to enter the microcracks and pores for a full reaction, thereby increasing the carbonization depth and improving the strengthening effect of the aggregates.

[0006] At the same time, using the residual heat before desulfurization and denitrification can reduce the moisture content of recycled aggregates and control the humidity of the carbonization environment, avoiding excessive moisture from blocking the interconnected pores. The temperature rise is conducive to the diffusion of exhaust gas into the microcracks and pores, making the carbonization reaction more complete. After a large number of CO2 molecules are heated, the molecular thermal motion accelerates, which increases the carbonization reaction rate and shortens the carbonization reaction time.

[0007] Finally, the heated recycled aggregate is placed in a high-temperature, high-pressure, high-concentration carbonization reactor for carbonization enhancement. By increasing the pressure and exhaust gas concentration, the recycled aggregate is deeply carbonized, which ultimately significantly reduces the water absorption rate and crushing value of the recycled aggregate, thereby enabling the large-scale application of recycled aggregate.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A first aspect of the present invention provides a heating-carbonization strengthening method for increasing the carbonization depth of recycled aggregates, comprising:

[0010] The recycled aggregate is heated by vibration at 80℃~120℃ for 1~3 hours using waste heat to obtain heat-treated aggregate;

[0011] The heat-treated aggregate is carbonized for 8–24 hours under the conditions of pressure 0.8–1.2 MPa, exhaust gas concentration ≥95%, temperature 80–150℃, and humidity 20% RH–100% RH; then screened to obtain reinforced recycled aggregate.

[0012] In some embodiments, the particle size range of the recycled aggregate is 0-31.5 mm.

[0013] In some embodiments, the vibration frequency is 3-10 Hz and the amplitude is 5-10 cm.

[0014] In some embodiments, the waste heat and exhaust gas are the waste heat and exhaust gas from the power plant before desulfurization and denitrification.

[0015] In some embodiments, the waste concrete blocks are pretreated by crushing and screening.

[0016] In some embodiments, circulating air is supplied during the carbonization process.

[0017] In some embodiments, the particle size range of the reinforced recycled aggregate is 0-31.5 mm.

[0018] In some embodiments, the high-temperature, high-pressure, high-concentration carbonization reactor mainly consists of a touchscreen microcomputer control system, a reactor body, a refrigeration system, a heating system, and a humidification system. The microcomputer touchscreen controls temperature, humidity, and exhaust gas concentration, and allows for arbitrary setting of the test duration. It has excellent control, display, recording, and protection functions. The inner chamber of the test chamber is made of 304 stainless steel plate. The refrigeration system uses an imported fully enclosed compressor. Exhaust gas measurement uses an imported CO2 sensor with high accuracy. Temperature measurement uses a high-precision Pt100 sensor, humidity measurement uses an imported high-precision humidity sensor, and the circulating air system uses a high-quality, high-temperature resistant circulating fan to ensure the uniformity of temperature, humidity, and exhaust gas. The entire carbonization test process is fully automatic. In the event of a malfunction, an audible and visual alarm will be issued, and appropriate safety protection will be automatically activated.

[0019] This invention utilizes the waste heat and exhaust gas from power plant desulfurization and denitrification processes to heat-treat recycled aggregates. Heating causes the fragile residual mortar on the surface of the recycled aggregates to detach, while simultaneously expanding the micro-cracks and pores within the residual mortar. The waste heat temperature before desulfurization and denitrification is 150–200℃, and this temperature provides the best heating and strengthening effect for the recycled aggregates. Since cement mortar and old aggregates have different coefficients of thermal expansion, heating can embrittle the old cement mortar adhering to the surface of the recycled aggregates. If the temperature is too low, the thermal stress generated by the thermal expansion effect is insufficient, and the weakened mortar on the surface of the recycled aggregates cannot detach. If the temperature is too high, the micro-cracks will expand excessively, causing damage to the aggregates themselves and deteriorating their performance.

[0020] Compared to pure carbon dioxide, the exhaust gas from power plants before desulfurization and denitrification contains other acidic gases. This application has measured the composition of the exhaust gas and does not require the composition of the main components in the exhaust gas.

[0021] The waste heat in this application is the waste heat of flue gas. The heat sources for waste heat are wide-ranging and can be obtained from waste incineration plants, cement plants, steel plants, etc.

[0022] Specifically, the following steps are included:

[0023] Step 1: The waste concrete blocks are crushed and screened for pretreatment to select recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0024] Step 2: Industrial waste heat treatment. The recycled aggregate is placed in a waste heat heating system and heated for 1 to 3 hours using the waste heat before desulfurization and denitrification.

[0025] The crushing method described is secondary processing crushing using jaw crushers and impact crushers.

[0026] The waste heat and tail gas temperature before desulfurization and denitrification in the power plant can be controlled between 100℃ and 250℃. By using different heating temperatures, the size of microcracks and pores in the recycled aggregate can be controlled in a directional manner, reducing heat input and greatly reducing energy consumption.

[0027] The industrial waste heat heating system contains an intelligent high-vibration device with a vibration frequency of 3-10Hz and an amplitude of 5-10cm, which is beneficial for removing some of the weakened mortar on the surface of the heated recycled aggregate and expanding microcracks and pores.

[0028] A second aspect of this invention provides reinforced recycled aggregate prepared by the above-described method. This invention utilizes reinforced recycled aggregate to replace natural crushed stone to prepare cement-stabilized fully recycled aggregate, which is used in road base courses under extremely heavy traffic loads, and its mechanical and frost-resistant properties are studied.

[0029] Furthermore, the mechanical properties are the 7-day unconfined compressive strength, and the freeze-thaw resistance is the mass change and unconfined compressive strength of the sample after 30 freeze-thaw cycles.

[0030] A third aspect of the present invention provides an inorganic binder stabilized material, comprising: cement, the above-mentioned reinforced recycled aggregate, and water.

[0031] A fourth aspect of the present invention provides the application of the above-described reinforced recycled aggregate in the fields of road construction and building.

[0032] Beneficial effects of the present invention

[0033] (1) In view of the problem that the traditional carbonization method forms a deposit on the surface, which hinders the entry of CO2 and only strengthens the surface, resulting in insufficient carbonization depth, the present invention proposes to use the waste heat and tail gas before the desulfurization and denitrification of power plants to heat the recycled aggregate. The thermal stress generated by the thermal expansion effect causes the fragile residual mortar on the surface of the recycled aggregate to fall off. At the same time, it expands the microcracks and pores of the residual mortar inside, which is conducive to the tail gas entering the microcracks and pores, increasing the carbonization depth and improving the aggregate strengthening effect.

[0034] (2) The present invention uses a high-temperature, high-pressure, high-concentration carbonization reactor to carry out the gas-solid reaction of tail gas and recycled aggregate. The tail gas concentration, pressure, temperature and humidity are easy to control and the operation is simple. While strengthening carbonization, it effectively treats the sulfur-containing (sulfur dioxide) and nitrate-containing (nitrogen oxide) flue gas in industrial tail gas, which can accelerate the carbonization of recycled aggregate and reduce the time by 50% compared with the traditional carbonization method. The carbonization depth is improved by increasing the tail gas concentration and pressure.

[0035] (3) Compared with the traditional carbonization method, the heating-carbonization strengthening method proposed in this invention significantly improves the performance of recycled aggregates. The water absorption rate can be reduced by 68.9%, the crushing value can be reduced by 57.0%, and all of them can meet the Class II aggregate standard, and some can meet the Class I aggregate standard. It has a wide range of applications and can be used for concrete with strength grades of C30-C60 and other requirements such as frost resistance, impermeability and so on, as well as road base courses under extremely heavy traffic loads. It can also be used for concrete with strength grades greater than C60. The mechanical properties and frost resistance of inorganic binder stabilized materials prepared by using recycled aggregates strengthened by this invention are significantly enhanced.

[0036] (4) The preparation method of the present invention is simple, practical and easy to promote. Detailed Implementation

[0037] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0038] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are explanations of the present invention and not limitations thereof.

[0039] In this embodiment, the crushing value and water absorption rate of natural and recycled aggregates were tested according to the relevant test methods in the "Specifications for Testing Aggregates in Highway Engineering" JTGE42-2005. The main physical properties of untreated recycled aggregates were: water absorption rate 6.82% and crushing value 22.3%. The main physical properties of natural aggregates were: water absorption rate 1.56% and crushing value 9.45%. It can be seen that the main physical properties of recycled aggregates differ significantly from those of natural aggregates. The method of this invention and existing technologies were used for processing:

[0040] Example 1:

[0041] (1) The waste concrete at the construction waste disposal site is screened and impurities are removed. It is then crushed by a jaw crusher and an impact crusher, and finally screened to obtain recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0042] (2) Place the recycled aggregate obtained in step (1) into a waste heat heating device and vibrate it at a high temperature of about 100°C for 2 hours.

[0043] (3) The heat-treated recycled aggregate is placed in a high-temperature, high-pressure, high-concentration carbonization reactor and carbonized for 10 hours under the conditions of tail gas concentration of 99%, pressure of 1.0 MPa, temperature of 100℃ and humidity of 40% RH.

[0044] (4) Screen the recycled aggregate obtained in step (3), retain the recycled aggregate of 0-31.5mm, clean it and dry it naturally to constant weight for later use.

[0045] Example 2:

[0046] (1) The waste concrete at the construction waste disposal site is screened and impurities are removed. It is then crushed by a jaw crusher and an impact crusher, and finally screened to obtain recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0047] (2) Place the recycled aggregate obtained in step (1) into a waste heat heating device and vibrate it at a high temperature of about 200°C for 2 hours.

[0048] (3) The heat-treated recycled aggregate is placed in a high-temperature, high-pressure, high-concentration carbonization reactor and carbonized for 10 hours under the conditions of tail gas concentration of 99%, pressure of 1.0 MPa, temperature of 100℃ and humidity of 40% RH.

[0049] (4) Screen the recycled aggregate obtained in step (3), retain the recycled aggregate of 0-31.5mm, clean it and dry it naturally to constant weight for later use.

[0050] Example 3:

[0051] (1) The waste concrete at the construction waste disposal site is screened and impurities are removed. It is then crushed by a jaw crusher and an impact crusher, and finally screened to obtain recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0052] (2) Place the recycled aggregate obtained in step (1) into a waste heat heating device and vibrate it at a high temperature of about 250°C for 2 hours.

[0053] (3) The heat-treated recycled aggregate is placed in a high-temperature, high-pressure, high-concentration carbonization reactor and carbonized for 10 hours under the conditions of tail gas concentration of 99%, pressure of 1.0 MPa, temperature of 100℃ and humidity of 40% RH.

[0054] (4) Screen the recycled aggregate obtained in step (3), retain the recycled aggregate of 0-31.5mm, clean it and dry it naturally to constant weight for later use.

[0055] Example 4:

[0056] (1) The waste concrete at the construction waste disposal site is screened and impurities are removed. It is then crushed by a jaw crusher and an impact crusher, and finally screened to obtain recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0057] (2) Place the recycled aggregate obtained in step (1) into a waste heat heating device and vibrate it at a high temperature of about 200°C for 2 hours.

[0058] (3) The heat-treated recycled aggregate is placed in a high-temperature, high-pressure, high-concentration carbonization reactor and carbonized for 10 hours under the conditions of tail gas concentration of 97%, pressure of 1.0 MPa, temperature of 100℃ and humidity of 40% RH.

[0059] (4) Screen the recycled aggregate obtained in step (3), retain the recycled aggregate of 0-31.5mm, clean it and dry it naturally to constant weight for later use.

[0060] Example 5:

[0061] (1) The waste concrete at the construction waste disposal site is screened and impurities are removed. It is then crushed by a jaw crusher and an impact crusher, and finally screened to obtain recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0062] (2) Place the recycled aggregate obtained in step (1) into a waste heat heating device and vibrate it at a high temperature of about 200°C for 2 hours.

[0063] (3) The heat-treated recycled aggregate is placed in a high-temperature, high-pressure, high-concentration carbonization reactor and carbonized for 10 hours under the conditions of tail gas concentration of 95%, pressure of 1.0 MPa, temperature of 100℃ and humidity of 40% RH.

[0064] (4) Screen the recycled aggregate obtained in step (3), retain the recycled aggregate of 0-31.5mm, clean it and dry it naturally to constant weight for later use.

[0065] Example 6:

[0066] (1) The waste concrete at the construction waste disposal site is screened and impurities are removed. It is then crushed by a jaw crusher and an impact crusher, and finally screened to obtain recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0067] (2) Place the recycled aggregate obtained in step (1) into a waste heat heating device and vibrate it at a high temperature of about 200°C for 2 hours.

[0068] (3) The heated recycled aggregate is placed in a high-temperature, high-pressure, high-concentration carbonization reactor and carbonized for 10 hours under the conditions of tail gas concentration of 99%, pressure of 1.2 MPa, temperature of 100℃ and humidity of 40% RH.

[0069] (4) Screen the recycled aggregate obtained in step (3), retain the recycled aggregate of 0-31.5mm, clean it and dry it naturally to constant weight for later use.

[0070] Example 7:

[0071] (1) The waste concrete at the construction waste disposal site is screened and impurities are removed. It is then crushed by a jaw crusher and an impact crusher, and finally screened to obtain recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0072] (2) Place the recycled aggregate obtained in step (1) into a waste heat heating device and vibrate it at a high temperature of about 200°C for 2 hours.

[0073] (3) The heat-treated recycled aggregate is placed in a high-temperature, high-pressure, high-concentration carbonization reactor and carbonized for 10 hours under the conditions of tail gas concentration of 99%, pressure of 0.8 MPa, temperature of 100℃ and humidity of 40% RH.

[0074] (4) Screen the recycled aggregate obtained in step (3), retain the recycled aggregate of 0-31.5mm, clean it and dry it naturally to constant weight for later use.

[0075] Example 8:

[0076] (1) The waste concrete at the construction waste disposal site is screened and impurities are removed. It is then crushed by a jaw crusher and an impact crusher, and finally screened to obtain recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0077] (2) Place the recycled aggregate obtained in step (1) into a waste heat heating device and vibrate it at a high temperature of about 200°C for 2 hours.

[0078] (3) The heat-treated recycled aggregate is placed in a high-temperature, high-pressure, high-concentration carbonization reactor and carbonized for 10 hours under the conditions of tail gas concentration of 99%, pressure of 1.0 MPa, temperature of 80℃ and humidity of 40% RH.

[0079] (4) Screen the recycled aggregate obtained in step (3), retain the recycled aggregate of 0-31.5mm, clean it and dry it naturally to constant weight for later use.

[0080] Example 9:

[0081] (1) The waste concrete at the construction waste disposal site is screened and impurities are removed. It is then crushed by a jaw crusher and an impact crusher, and finally screened to obtain recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0082] (2) Place the recycled aggregate obtained in step (1) into a waste heat heating device and vibrate it at a high temperature of about 200°C for 2 hours.

[0083] (3) The heat-treated recycled aggregate is placed in a high-temperature, high-pressure, high-concentration carbonization reactor and carbonized for 10 hours under the conditions of tail gas concentration of 99%, pressure of 1.0 MPa, temperature of 120℃ and humidity of 40% RH.

[0084] (4) Screen the recycled aggregate obtained in step (3), retain the recycled aggregate of 0-31.5mm, clean it and dry it naturally to constant weight for later use.

[0085] Example 10:

[0086] (1) The waste concrete at the construction waste disposal site is screened and impurities are removed. It is then crushed by a jaw crusher and an impact crusher, and finally screened to obtain recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0087] (2) Place the recycled aggregate obtained in step (1) into a waste heat heating device and vibrate it at a high temperature of about 200°C for 2 hours.

[0088] (3) The heated recycled aggregate is placed in a high-temperature, high-pressure, high-concentration carbonization reactor and carbonized for 10 hours under the conditions of tail gas concentration of 99%, pressure of 1.0 MPa, temperature of 150℃ and humidity of 40% RH.

[0089] (4) Screen the recycled aggregate obtained in step (3), retain the recycled aggregate of 0-31.5mm, clean it and dry it naturally to constant weight for later use.

[0090] Example 11:

[0091] (1) The waste concrete at the construction waste disposal site is screened and impurities are removed. It is then crushed by a jaw crusher and an impact crusher, and finally screened to obtain recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0092] (2) Place the recycled aggregate obtained in step (1) into a waste heat heating device and vibrate it at a high temperature of about 200°C for 2 hours.

[0093] (3) The heated recycled aggregate is placed in a high-temperature, high-pressure, high-concentration carbonization reactor and carbonized for 10 hours under the conditions of tail gas concentration of 99%, pressure of 1.0 MPa, temperature of 100℃ and humidity of 60% RH.

[0094] (4) Screen the recycled aggregate obtained in step (3), retain the recycled aggregate of 0-31.5mm, clean it and dry it naturally to constant weight for later use.

[0095] Example 12:

[0096] (1) The waste concrete at the construction waste disposal site is screened and impurities are removed. It is then crushed by a jaw crusher and an impact crusher, and finally screened to obtain recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0097] (2) Place the recycled aggregate obtained in step (1) into a waste heat heating device and vibrate it at a high temperature of about 200°C for 2 hours.

[0098] (3) The heated recycled aggregate is placed in a high-temperature, high-pressure, high-concentration carbonization reactor and carbonized for 10 hours under the conditions of tail gas concentration of 99%, pressure of 1.0 MPa, temperature of 100℃ and humidity of 80% RH.

[0099] (4) Screen the recycled aggregate obtained in step (3), retain the recycled aggregate of 0-31.5mm, clean it and dry it naturally to constant weight for later use.

[0100] Comparative Example 1:

[0101] (1) The waste concrete at the construction waste disposal site is screened and impurities are removed. It is then crushed by a jaw crusher and an impact crusher, and finally screened to obtain recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0102] (2) Place the recycled aggregate obtained in step (1) into a waste heat heating device and vibrate it at a high temperature of about 200°C for 2 hours.

[0103] (3) Screen the recycled aggregate obtained in step (2), retain the recycled aggregate of 0-31.5mm, clean it and dry it naturally to constant weight for later use.

[0104] Comparative Example 2:

[0105] (1) The waste concrete at the construction waste disposal site is screened and impurities are removed. It is then crushed by a jaw crusher and an impact crusher, and finally screened to obtain recycled aggregate with a particle size of 0-31.5mm. The aggregate is then washed clean and air-dried to constant weight.

[0106] (2) The recycled aggregate from step (1) is placed in a high-temperature, high-pressure, high-concentration carbonization reactor and carbonized for 10 hours under the conditions of 99% tail gas concentration, 1.0 MPa pressure, 100℃ temperature and 40% RH humidity.

[0107] (3) Screen the recycled aggregate obtained in step (2), retain the recycled aggregate of 0-31.5mm, clean it and dry it naturally to constant weight for later use.

[0108] According to the relevant test methods in the "Test Procedures for Aggregates in Highway Engineering" JTG E42-2005, the water absorption rate and crushing value of the recycled aggregates in Examples 1-12 and Comparative Examples 1-2 were tested, and the test results are shown in Table 1. The carbonation depth was measured by using a dropper to draw a small amount of 1.5% phenolphthalein alcohol solution and dripping it onto the reinforced recycled aggregates. Phenolphthalein turns red when it comes into contact with alkali, while the carbonized parts remain colorless. The specific carbonation depth was then measured using a carbonation depth measuring instrument. Three measurements were taken, and the average value was calculated to an accuracy of 0.1 mm.

[0109] Table 1. Basic physical properties of recycled aggregates under different carbonization conditions

[0110] Untreated recycled aggregate - 6.82 - 22.3 - Example 1 8.8 2.35 65.5 9.8 56.1 Example 2 9.5 2.12 68.9 9.6 57.0 Example 3 9.2 2.58 62.2 10.1 54.7 Example 4 8.5 2.86 58.1 10.9 51.1 Example 5 8.2 3.17 53.5 12.3 44.8 Example 6 8.1 3.20 53.1 12.8 42.6 Example 7 7.8 3.51 48.5 13.4 39.9 Example 8 7.6 3.60 47.2 13.5 39.5 Example 9 8.0 3.33 51.2 12.6 40.8 Example 10 7.2 3.72 45.5 14.0 37.2 Example 11 6.8 3.88 43.1 15.2 31.8 Example 12 6.5 4.05 40.6 15.5 30.5 Comparative Example 1 - 5.53 18.9 19.5 12.6 Comparative Example 2 3.5 4.89 28.3 17.6 21.1

[0111] As shown in Table 1, compared with traditional carbonization methods, the heating-carbonization synergistic strengthening method provided by this invention increases the aggregate carbonization depth by 171.4%, significantly reduces water absorption and crushing value. Compared with unstrengthened aggregate, the water absorption is reduced by a maximum of 68.9%, and the crushing value is reduced by a maximum of 57.0%. The water absorption and crushing value of recycled aggregate directly carbonized without heat treatment are reduced by 28.3% and 16.6%, respectively. This indicates that the heating-carbonization synergistic strengthening of recycled aggregate, by increasing the carbonization depth, reduces both water absorption and crushing value by more than 50%, significantly improving the quality of recycled aggregate and enabling its large-scale application.

[0112] The above-mentioned untreated and reinforced recycled aggregates and natural crushed stone were used to prepare inorganic binder stabilized materials for highway base courses, as shown in Examples 13-15 and Comparative Examples 3-5.

[0113] Example 13

[0114] The inorganic binder stabilized material described in this embodiment mainly includes P·O 42.5 cement, recycled aggregate treated in Example 2, and water, wherein the cement content is 5%.

[0115] The recycled aggregate has particle sizes of 20-30mm, 10-20mm, 5-10mm and 0-5mm, with a corresponding gradation ratio of 28:22:20:30.

[0116] Example 14

[0117] The inorganic binder stabilized material described in this embodiment mainly includes P·O 42.5 cement, recycled aggregate treated in Example 7, and water, wherein the cement content is 5%.

[0118] The recycled aggregate has particle sizes of 20-30mm, 10-20mm, 5-10mm and 0-5mm, with a corresponding gradation ratio of 28:22:20:30.

[0119] Example 15

[0120] The inorganic binder stabilized material described in this embodiment mainly includes P·O 42.5 cement, recycled aggregate treated in Example 8, and water, wherein the cement content is 5%.

[0121] The recycled aggregate has particle sizes of 20-30mm, 10-20mm, 5-10mm and 0-5mm, with a corresponding gradation ratio of 28:22:20:30.

[0122] Comparative Example 3

[0123] The inorganic binder stabilized material described in this embodiment mainly includes P·O 42.5 cement, recycled aggregate treated according to Comparative Example 1, and water, wherein the cement content is 5%.

[0124] The recycled aggregate has particle sizes of 20-30mm, 10-20mm, 5-10mm and 0-5mm, with a corresponding gradation ratio of 28:22:20:30.

[0125] Comparative Example 4

[0126] The inorganic binder stabilized material described in this embodiment mainly includes P·O 42.5 cement, recycled aggregate treated according to Comparative Example 2, and water, wherein the cement content is 5%.

[0127] The recycled aggregate has particle sizes of 20-30mm, 10-20mm, 5-10mm and 0-5mm, with a corresponding gradation ratio of 28:22:20:30.

[0128] Comparative Example 5

[0129] The inorganic binder stabilized material described in this embodiment mainly includes P·O 42.5 cement and natural aggregate, wherein the cement content is 5%.

[0130] The natural aggregate has particle sizes of 20-30mm, 10-20mm, 5-10mm and 0-5mm, with a corresponding gradation ratio of 28:22:20:30.

[0131] Table 2. Test results of the inorganic binder stabilized materials described in Examples 13-15 and Comparative Examples 3-5.

[0132]

[0133]

[0134] As shown in Table 2, using the heating-carbonation strengthening method provided by this invention, the 7-day unconfined compressive strength of cement-stabilized fully recycled aggregate pavement base course can reach 6.6 MPa, meeting the strength requirements of 5.0–7.0 MPa under extremely heavy and extra-heavy traffic conditions on highways and first-class roads. Using the aggregate strengthening methods of Comparative Examples 3 and 4, the 7-day unconfined compressive strength is only 4.6 and 4.8 MPa, respectively.

[0135] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A heating-carbonization strengthening method for improving the carbonization depth of recycled aggregate, characterized in that, include: The recycled aggregate is heated by vibration at 80℃~120℃ for 1~3 h using waste heat to obtain heat-treated aggregate; The heat-treated aggregate is carbonized for 8-24 hours under the conditions of pressure 0.8-1.2 MPa, exhaust gas concentration ≥95%, temperature 80-150℃, and humidity 40%RH-100%RH; then screened to obtain reinforced recycled aggregate. The vibration frequency is 3-10Hz, and the amplitude is 5-10cm; The waste heat and exhaust gas mentioned are the waste heat and exhaust gas from the power plant before desulfurization and denitrification. The particle size range of the recycled aggregate is 0-31.5 mm.

2. The heating-carbonization strengthening method for improving the carbonization depth of recycled aggregate as described in claim 1, characterized in that, Waste concrete blocks are pre-treated by crushing and screening.

3. The heating-carbonization strengthening method for improving the carbonization depth of recycled aggregate as described in claim 1, characterized in that, During the carbonization process, air is circulated.

4. The heating-carbonization strengthening method for improving the carbonization depth of recycled aggregate as described in claim 1, characterized in that, The particle size range of the reinforced recycled aggregate is 0-31.5 mm.

5. The reinforced recycled aggregate prepared by the method according to any one of claims 1-4.

6. An inorganic binder stabilized material, characterized in that, include: Cement, the recycled aggregate reinforced according to claim 5, and water.

7. The application of the reinforced recycled aggregate as described in claim 5 in the fields of road construction and building.

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