An enhanced recycled aggregate, its preparation method and application in a solid waste stabilized macadam base course

Abstract

The present invention discloses a strengthened recycled aggregate, its preparation method and application in a solid waste stabilized macadam base course, belonging to the technical field of building materials. The recycled aggregate is ball-milled, heated and shaped to obtain shaped recycled aggregate and recycled fine powder; the recycled fine powder is mixed with nano-materials and fillers and then ball-milled to obtain activated recycled fine powder; an alkaline solid waste activator, a precursor material and the activated recycled fine powder are mixed and ball-milled to obtain a solid waste cementitious material; the solid waste cementitious material is mixed with water to obtain a solid waste cementitious material mixture slurry, and the shaped recycled aggregate is coated with the slurry to obtain a strengthened recycled aggregate that can be used to prepare a stabilized macadam base course. Through ball-milling shaping and coating treatment, the present invention effectively removes the old mortar attached to the surface of the recycled aggregate, reduces the number of edges and corners, decreases the porosity, solves the problems of high porosity, high water absorption rate and low apparent density of the recycled aggregate, improves its mechanical properties, and thus can be used to prepare a stabilized macadam base course.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to a strengthened recycled aggregate, a preparation method thereof, and an application in a solid waste stabilized macadam base course. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the overall understanding of the present invention, and is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] With the continuous advancement of industrialization and urbanization, the demand for building materials and the generation of construction waste and bulk industrial solid waste have increased significantly, resulting in increasingly serious resource consumption and ecological environment damage. Optimally treating bulk solid waste and using it as a road stabilized macadam base course material can not only solve the environmental pollution problems caused by the stacking and burying of bulk solid waste, but also reduce the overexploitation of natural resources, which is in line with the core concept of the green development of the comprehensive utilization of resources industry.

[0004] Recycled aggregate refers to the aggregate obtained by classifying, crushing, and screening construction waste such as waste concrete. The recycled coarse aggregate made of waste concrete has old mortar adhered to its surface, is rough, has many particle edges and corners, and is damaged during the crushing process, forming a large number of microcracks inside, resulting in prominent problems such as high porosity, high water absorption, low apparent density, high crushing index, and high Ca(OH)2 crystal content in the recycled aggregate. If only the recycled aggregate is simply used to replace natural aggregate to prepare a road stabilized macadam base course, there are often problems of low mechanical properties, severely restricting the popularization and application of recycled aggregate in road engineering construction. When strengthening recycled aggregate by physical strengthening, chemical strengthening, or biological strengthening methods, such as CN116143437 N, CN 115215572A, CN114716211A, etc., the strengthening effect is insufficient, the water absorption and crushing value index are still relatively large, and there is still a large difference from the performance of natural aggregate, making it impossible to be used in large quantities. In addition, most current solid waste cementitious materials use bulk solid waste materials with high "silicon-aluminum" content, and through physical activation, chemical activation, or composite activation forms, they have cementitious properties and are expected to become potential substitutes for cement, providing an effective solution to the problems of high carbon emissions in cement manufacturing and bulk solid waste stacking. However, currently, solid waste cementitious materials need to use externally added strong alkaline reagents for activity activation, and the hardened specimens have serious efflorescence, causing secondary pollution to the environment. In addition, the added strong alkaline reagents also increase the production cost of solid waste cementitious materials, restricting their large-scale use. Summary of the Invention

[0005] To solve the deficiencies of the prior art, the object of the present invention is to provide a strengthened recycled aggregate, its preparation method and application in the solid waste stabilized macadam base course. The present invention uses recycled aggregate and other solid waste cementitious materials to prepare the stabilized macadam base course, which has high mechanical strength to solve the problem that it is difficult to utilize solid wastes such as construction waste.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] In the first aspect of the present invention, a preparation method of a strengthened recycled aggregate is provided, which includes the following steps:

[0008] Ball-mill and shape the recycled aggregate, and heat during the ball-milling and shaping process; after the ball-milling and shaping are completed, shaped recycled aggregate and recycled fine powder are obtained;

[0009] Mix the recycled fine powder with nano-materials and fillers, and then ball-mill to obtain activated recycled fine powder; mix the alkaline solid waste activator, precursor material and the activated recycled fine powder, and then ball-mill to obtain a solid waste cementitious material; mix the solid waste cementitious material with water to obtain a solid waste cementitious material mixture slurry;

[0010] Immerse the shaped recycled aggregate in the solid waste cementitious material mixture slurry, take out the shaped recycled aggregate after soaking and perform standard curing to obtain the strengthened recycled aggregate.

[0011] In some embodiments of the present invention, the ball-milling and shaping time is 5 - 10 min, and the rotation speed is 20 - 40 r / min.

[0012] In some embodiments of the present invention, for the heating, the heating temperature is 450 - 550 °C.

[0013] In some embodiments of the present invention, the nano-materials include nano-silica and / or nano-calcium oxide, and the fillers include bayer red mud and / or desulfurized gypsum;

[0014] The mass ratio of the recycled fine powder, nano-materials and fillers is (90 - 95):(0.5 - 1):(4 - 9.5).

[0015] In some embodiments of the present invention, the alkaline solid waste activator includes bayer red mud, desulfurized gypsum and carbide slag, and the mass ratio of bayer red mud, desulfurized gypsum and carbide slag is (5 - 6):(2 - 4):(0.5 - 1);

[0016] The precursor material includes at least one of blast furnace slag, coal gangue powder, waste glass powder and fly ash;

[0017] The mass ratio of the alkaline solid waste activator, precursor material and activated recycled fine powder is: (1 - 3):(5 - 8):(0.5 - 2).

[0018] In some embodiments of the present invention, the mass ratio of water to solid waste cementitious material is (1-5):1.

[0019] In some embodiments of the present invention, the shaped recycled aggregate is cleaned and dried, and then immersed in the solid waste cementitious material mixture slurry. Intermittent vibration soaking is adopted, with vibration soaking for 5-10 minutes, and then static soaking for 30-60 minutes. Vibration soaking and static soaking are alternated, and the total soaking time is 5-6 hours.

[0020] The second aspect of the present invention provides a strengthened recycled aggregate, which is prepared by the above preparation method.

[0021] In some embodiments of the present invention, the particle size composition of the strengthened recycled aggregate is as follows:

[0022] The proportion of 0.075-2.36 mm is 10-30 wt%;

[0023] The proportion of 2.36-4.75 mm is 15-25 wt%;

[0024] The proportion of 4.75-9.5 mm is 20-35 wt%;

[0025] The proportion of 9.5-19.0 mm is 25-40 wt%;

[0026] The proportion of 19.0-31.5 mm is 10-20 wt%.

[0027] The third aspect of the present invention provides an application of the above strengthened recycled aggregate in a solid waste stabilized macadam base course.

[0028] The fourth aspect of the present invention provides a solid waste stabilized macadam base course. By weight, the raw materials of the solid waste stabilized macadam base course include: 3-6 parts of solid waste cementitious material, 100-120 parts of the above strengthened recycled aggregate, and 8-10 parts of water;

[0029] In the solid waste cementitious material, by mass percentage, it includes 10-30% of alkaline solid waste activator, 60-80% of precursor material, and 10-20% of activated recycled fine powder.

[0030] The fifth aspect of the present invention provides a preparation method of the above solid waste stabilized macadam base course, including the following steps: mixing the solid waste cementitious material, strengthened recycled aggregate and water in proportion, and obtaining the solid waste stabilized macadam base course after paving, rolling and curing.

[0031] The beneficial effects of the present invention are:

[0032] The present invention processes recycled aggregates by means of mechanical enhanced ball milling - heating and shaping, which can effectively reduce the content of old mortar attached to the recycled aggregates, effectively reduce the number of edges and corners, remove impurities, and provide a relatively clean surface environment for further strengthening treatment. Then, the recycled aggregates are coated with a slurry prepared from a solid waste cementitious material made of activated recycled fine powder, alkaline solid waste activator, and precursor material, reducing the porosity of the recycled aggregates and the edges and corners on the surface of the recycled aggregates, obtaining strengthened recycled aggregates, solving problems such as high porosity, high water absorption, low apparent density, high crushing index, and high content of Ca(OH)₂ crystals in the recycled aggregates, and improving their mechanical properties, so that they can be popularized and applied in road engineering construction. Among them, the present invention uses a solid waste cementitious material to coat the recycled aggregates. On the one hand, the gel formed by the solid waste cementitious material through alkali activation can fill the pores or microcracks of the recycled aggregates and effectively wrap on the surface of the recycled aggregates, forming a slurry layer with a dense microstructure. On the other hand, the activator reacts with the silicon-aluminum substances attached to the pores or microcracks of the recycled aggregates to generate more C-A-S-H gels, further exerting the filling effect and reducing the porosity of the recycled aggregates. In addition, using the solid waste cementitious material as the strengthening liquid can fully consume large amounts of solid waste, which is beneficial to environmental protection.

[0033] The present invention conducts multi-stage strengthening treatment on recycled aggregates and prepares a stabilized macadam base with various other solid waste materials, abandoning the dependence on high-energy-consuming cement and natural sand and stone in the traditional preparation method. Using the solid waste cementitious material prepared from large amounts of solid waste as the binder, activated recycled fine powder as the auxiliary binder, and strengthened recycled aggregates as the aggregates, it promotes the full utilization of construction recycled aggregates and the large-scale application of large amounts of solid waste in road engineering construction, conforming to the concepts of green transportation and sustainable development. Specific embodiments

[0034] Term explanation:

[0035] The stabilized macadam base, namely the cement stabilized macadam base, is a road base prepared by using cement as the cementitious material and mixing it with aggregates, fly ash, etc. Compared with traditional rigid and flexible bases, the cement stabilized macadam base has the following characteristics:

[0036] 1. Higher bearing capacity: The cement stabilized macadam base has higher strength and stability, can bear larger loads, and is suitable for various types of roads.

[0037] 2. Better anti-seepage and anti-cracking performance: The cement in the cement stabilized macadam base can effectively prevent water penetration and avoid diseases such as cracks and potholes on the road.

[0038] 3. Environmental protection and sustainability: Compared with traditional rigid bases, the amount of cement used in the cement-stabilized macadam base is less, reducing the environmental impact. At the same time, the crushed stone can be recycled, showing good sustainability.

[0039] To further understand the present invention, the preferred embodiments of the present invention will be described below in conjunction with examples. However, it should be understood that these descriptions are only to further illustrate the features and advantages of the present invention, rather than a limitation on the claims of the present invention.

[0040] The present invention provides a kind of strengthened recycled aggregate obtained by mechanically strengthening, ball-milling and shaping waste solids, activating recycled fine powder and slurry-coating waste solid cementitious materials. The obtained strengthened recycled aggregate has low porosity, low water absorption, high apparent density and high mechanical properties, and can be used for the preparation of stabilized macadam base.

[0041] The first typical embodiment of the present invention provides a preparation method of strengthened recycled aggregate, comprising the following steps:

[0042] Ball-mill and shape the recycled aggregate, and heat during the ball-milling and shaping process; after the ball-milling and shaping are completed, obtain shaped recycled aggregate and recycled fine powder;

[0043] Mix the recycled fine powder with nano-materials and fillers and then ball-mill to obtain activated recycled fine powder; mix an alkaline waste solid activator, a precursor material and the activated recycled fine powder and then ball-mill to obtain waste solid cementitious materials; mix the waste solid cementitious materials with water to obtain a waste solid cementitious material mixture slurry;

[0044] Immerse the shaped recycled aggregate in the waste solid cementitious material mixture slurry, take out the shaped recycled aggregate after soaking and perform standard curing to obtain strengthened recycled aggregate.

[0045] The present invention proposes a "three-step method" for strengthening recycled aggregates, namely mechanical strengthening ball milling - heating and shaping treatment, activation of recycled fine powder, and slurry coating treatment of solid waste cementitious materials. The mechanical strengthening ball milling - heating and shaping treatment can reduce the content of old mortar attached to the recycled aggregates, effectively reduce the number of edges and corners, remove impurities, and provide a relatively clean surface environment for further strengthening treatment. Moreover, during the ball milling process, the filling material will also fill the cracks and pores of the recycled aggregates through physical adsorption. The activation of recycled fine powder is to fully mix nano materials and filling materials with the recycled fine powder (obtained during the mechanical strengthening ball milling - heating and shaping treatment) by physical ball milling method, improve the specific surface area and silicon-aluminum content of the recycled fine powder, and firmly attach the filling material with excitation effect to the surface of the recycled fine powder. In the present invention, slurry coating treatment is carried out on the solid waste cementitious materials. On the one hand, the gel formed by the solid waste cementitious materials through alkali activation can fill the pores or micro-cracks of the recycled aggregates and effectively wrap the surface of the recycled aggregates, forming a slurry layer with a dense microstructure. On the other hand, the activator reacts with the silicon-aluminum substances attached to the pores or micro-cracks of the recycled aggregates to generate more C-A-S-H gels, further exerting the filling effect and reducing the porosity of the recycled aggregates. In addition, using the solid waste cementitious materials as the strengthening liquid can fully consume large amounts of solid waste, which is beneficial to environmental protection. This method has the characteristics of simplicity, convenience, and strong operability for strengthening recycled aggregates.

[0046] In some embodiments of the present invention, for the heating, the heating temperature is 450 - 550 °C, and specifically, it can be selected as 450 °C, 451 °C, 460 °C, 470 °C, 480 °C, 490 °C, 500 °C, 510 °C, 520 °C, 530 °C, 540 °C, 549 °C or 550 °C, etc.

[0047] In some embodiments of the present invention, the ball milling and shaping time is 5 - 10 min, and specifically, it can be selected as 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, etc. The ball milling and shaping can be carried out in a wear tester, and the rotation speed of the wear tester can be 20 - 40 r / min, and specifically, it can be selected as 20 r / min, 21 r / min, 23 r / min, 25 r / min, 27 r / min, 29 r / min, 30 r / min, 31 r / min, 33 r / min, 35 r / min, 37 r / min, 39 r / min or 40 r / min, etc.

[0048] In some embodiments of the present invention, after mixing the recycled fine powder with nano materials and filling materials, ball milling is carried out for 5 - 10 min, and specifically, it can be selected as 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, etc.

[0049] In some embodiments of the present invention, the nanomaterials include nano-silica and / or nano-calcium oxide, and the fillers include Bayer red mud and / or desulfurized gypsum;

[0050] The mass ratio of the recycled fine powder, nanomaterials and fillers is (90 - 95):(0.5 - 1):(4 - 9.5).

[0051] In some embodiments of the present invention, the alkaline solid waste activator includes Bayer red mud, desulfurized gypsum and carbide slag, and the mass ratio of Bayer red mud, desulfurized gypsum and carbide slag is (5 - 6):(2 - 4):(0.5 - 1);

[0052] The precursor material includes at least one of blast furnace slag, coal gangue powder, waste glass powder and fly ash;

[0053] The mass ratio of the alkaline solid waste activator, precursor material and activated recycled fine powder is: (1 - 3):(5 - 8):(0.5 - 2).

[0054] In some embodiments of the present invention, the mass ratio of water to the solid waste cementitious material is (1 - 5):1.

[0055] In some embodiments of the present invention, the alkaline solid waste activator, precursor material and the activated recycled fine powder are mixed and then ball milled for 3 - 5 min, specifically selectable as 3 min, 3.5 min, 4 min, 4.5 min or 5 min, etc.; A ball mill can be used for ball milling, and the rotation speed during ball milling is 400 - 500 r / min, specifically selectable as 400 r / min, 410 r / min, 420 r / min, 430 r / min, 440 r / min, 450 r / min, 460 r / min, 470 r / min, 480 r / min, 490 r / min or 500 r / min, etc.

[0056] In some embodiments of the present invention, the shaped recycled aggregate is cleaned and dried (fully removing free water) and then immersed in the solid waste cementitious material mixture slurry, and intermittent vibration immersion is adopted for 5 - 10 min, specifically selectable as 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, etc.; Then soak statically for 30 - 60 min, specifically selectable as 30 min, 31 min, 35 min, 39 min, 40 min, 41 min, 45 min, 49 min, 50 min, 51 min, 55 min, 59 min or 60 min, etc.; Vibration immersion and static immersion are carried out alternately, and the total soaking time is 5 - 6 h, specifically selectable as 5 h, 5.1 h, 5.2 h, 5.3 h, 5.4 h, 5.5 h, 5.6 h, 5.7 h, 5.8 h, 5.9 h or 6 h, etc.

[0057] In the second aspect of the present invention, there is provided a strengthened recycled aggregate, which is prepared by the above-mentioned preparation method.

[0058] In some embodiments of the present invention, the particle size composition of the strengthened recycled aggregate is as follows:

[0059] The proportion of 0.075 - 2.36 mm is 10 - 30 wt%, and specifically, it can be selected from 10 wt%, 11 wt%, 13 wt%, 15 wt%, 17 wt%, 19 wt%, 20 wt%, 21 wt%, 23 wt%, 25 wt%, 27 wt%, 29 wt% or 30 wt%, etc.;

[0060] The proportion of 2.36 - 4.75 mm is 15 - 25 wt%, and specifically, it can be selected from 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt% or 25 wt%, etc.;

[0061] The proportion of 4.75 - 9.5 mm is 20 - 35 wt%, and specifically, it can be selected from 20 wt%, 21 wt%, 23 wt%, 25 wt%, 27 wt%, 29 wt%, 30 wt%, 31 wt%, 33 wt%, 34 wt% or 35 wt%, etc.;

[0062] The proportion of 9.5 - 19.0 mm is 25 - 40 wt%, and specifically, it can be selected from 25 wt%, 26 wt%, 27 wt%, 29 wt%, 30 wt%, 31 wt%, 33 wt%, 35 wt%, 37 wt%, 39 wt% or 40 wt%, etc.;

[0063] The proportion of 19.0 - 31.5 mm is 10 - 20 wt%, and specifically, it can be selected from 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt% or 20 wt%, etc.

[0064] In the third aspect of the present invention, there is provided an application of the above-mentioned strengthened recycled aggregate in a solid waste stabilized crushed stone base layer.

[0065] In the fourth aspect of the present invention, there is provided a solid waste stabilized crushed stone base layer. By weight, the raw materials of the solid waste stabilized crushed stone base layer include:

[0066] 3 - 6 parts of solid waste cementitious material, and specifically, it can be selected from 3 parts, 3.1 parts, 3.5 parts, 3.9 parts, 4 parts, 4.1 parts, 4.5 parts, 4.9 parts, 5 parts, 5.1 parts, 5.5 parts, 5.6 parts or 6 parts;

[0067] 100 to 120 parts of the above-mentioned strengthened recycled aggregate, specifically selectable as 100 parts, 101 parts, 103 parts, 105 parts, 107 parts, 109 parts, 110 parts, 111 parts, 113 parts, 115 parts, 117 parts, 119 parts or 120 parts;

[0068] 8 to 10 parts of water, specifically selectable as 8 parts, 8.1 parts, 8.3 parts, 8.5 parts, 8.7 parts, 8.9 parts, 9 parts, 9.1 parts, 9.3 parts, 9.5 parts, 9.7 parts, 9.9 parts or 10 parts;

[0069] In the solid waste cementitious material, by mass percentage, it includes 10 to 30% (such as 10%, 11%, 13%, 15%, 17%, 19%, 20%, 21%, 23%, 25%, 27%, 29% or 30%, etc.) of alkaline solid waste activator, 60 to 80% (such as 60%, 61%, 63%, 65%, 67%, 69%, 70%, 71%, 73%, 75%, 77%, 79% or 80%, etc.) of precursor material and 10 to 20% (such as 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, etc.) of activated recycled fine powder.

[0070] In the fifth aspect of the present invention, a method for preparing the above-mentioned solid waste stabilized crushed stone base layer is provided, including the following steps: mixing the solid waste cementitious material, strengthened recycled aggregate and water in proportion, and after paving, rolling and curing, the solid waste stabilized crushed stone base layer is obtained.

[0071] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with specific embodiments.

[0072] Unless otherwise specified, the raw materials used in the following examples are all conventional commercially available products and can be obtained by purchase. For example, nano-silica with a purity of 99.5% is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; nano-calcium oxide with a particle size <160nm and a particle proportion of 98% is purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0073] Example 1

[0074] This example provides a strengthened recycled aggregate, and its preparation method is as follows:

[0075] S1. Initially crush and screen the construction waste to obtain recycled aggregate, then place it in an abrasion tester for ball milling and shaping. The shaping time is 5 minutes, the rotation rate of the abrasion tester is 40 r / min, heating is carried out during ball milling, the heating temperature is 450 °C, and after ball milling, recycled fine powder and shaped recycled aggregate are obtained.

[0076] S2. Mix the recycled fine powder obtained in step S1 with the nanomaterials and fillers at a mass ratio of 90:0.5:9.5, and then perform ball milling for 5 min to obtain activated recycled fine powder. Among them, by mass percentage, the nanomaterials contain 30% nano-silica and 70% nano-calcium oxide; the fillers contain 60% Bayer red mud and 40% desulfurized gypsum.

[0077] S3. Mix the solid waste cementitious materials composed of alkaline solid waste activator, precursor materials, and activated recycled fine powder and then perform ball milling. The ball milling duration is 3 min and the rotation speed is 500 r / min to obtain solid waste cementitious materials; mix the solid waste cementitious materials with water to prepare a solid waste cementitious material mixture slurry. By mass percentage, the solid waste cementitious materials include 30% slag, 35% fly ash, 14.3% Bayer red mud, 9.5% desulfurized gypsum, 1.2% carbide slag, and 10% activated recycled fine powder. The mass ratio of solid waste cementitious materials to water is 1:1.

[0078] S4. Dry the free water in the shaped recycled aggregate prepared in step S1, and place it in the solid waste cementitious material mixture slurry obtained in S3 for soaking. Intermittent vibration is carried out during soaking. After vibrating for 5 min each time, it is static for 60 min. The total soaking duration is 6 h. After the soaking is completed, take out the soaked shaped recycled aggregate and perform standard curing (curing for 28 days at a temperature of 20 ± 2°C and a humidity greater than 95%) to obtain strengthened recycled aggregate.

[0079] Example 2

[0080] This example provides a strengthened recycled aggregate, and its preparation method is as follows:

[0081] S1. Initially crush and screen the construction waste to obtain recycled aggregate, and then place it in an abrasion tester for ball milling and shaping. The shaping duration is adjusted to 10 min, the rotation rate of the abrasion tester is adjusted to 20 r / min, and heating is carried out during ball milling. The heating temperature is adjusted to 500°C. After ball milling, recycled fine powder and shaped recycled aggregate are obtained.

[0082] S2. Mix the recycled fine powder obtained in step S1 with the nanomaterials and fillers at a mass ratio of 95:1:4, and then perform ball milling for 5 min to obtain activated recycled fine powder. Among them, by mass percentage, the nanomaterials contain 50% nano-silica and 50% nano-calcium oxide; the fillers contain 70% Bayer red mud and 30% desulfurized gypsum.

[0083] S3. Mix the solid waste cementitious material composed of the alkaline solid waste activator, precursor material, and activated recycled fine powder, and then ball mill it for 4 minutes at a rotation speed of 400 r / min to obtain the solid waste cementitious material; mix the solid waste cementitious material with water to prepare a solid waste cementitious material mixture slurry. Among them, by mass percentage, the solid waste cementitious material includes 30% slag, 20% fly ash, 20% Bayer red mud, 8% desulfurized gypsum, 2% carbide slag, and 20% activated recycled fine powder. The mass ratio of the solid waste cementitious material to water is 1:3.

[0084] S4. Dry the free water in the shaped recycled aggregate prepared in step S1, and soak it in the solid waste cementitious material mixture slurry obtained in S3. During soaking, intermittent vibration is carried out, vibrating for 10 minutes and then standing still for 30 minutes each time. The total soaking time is 5 hours. After the soaking is completed, take out the soaked shaped recycled aggregate and conduct standard curing (curing for 28 days at a temperature of 20 ± 2°C and a humidity greater than 95%) to obtain the strengthened recycled aggregate.

[0085] Example 3

[0086] This example provides a strengthened recycled aggregate, and its preparation method is as follows:

[0087] S1. Initially crush and screen the construction waste to obtain recycled aggregate, and then place it in an abrasion tester for ball milling and shaping. Adjust the shaping time to 8 minutes, adjust the rotation rate of the abrasion tester to 30 r / min, and heat during ball milling. Adjust the heating temperature to 480°C. After ball milling, obtain recycled fine powder and shaped recycled aggregate.

[0088] S2. Mix the recycled fine powder obtained in step S1 with the nanomaterial and filler according to a mass ratio of 93:1:6, and then conduct ball milling for 5 minutes to obtain activated recycled fine powder. Among them, by mass percentage, the nanomaterial contains 40% nano-silica and 60% nano-calcium oxide; the filler contains 50% Bayer red mud and 50% desulfurized gypsum.

[0089] S3. Mix the solid waste cementitious material composed of the alkaline solid waste activator, precursor material, and activated recycled fine powder, and then ball mill it for 3.5 minutes at a rotation speed of 450 r / min to obtain the solid waste cementitious material; mix the solid waste cementitious material with water to prepare a solid waste cementitious material mixture slurry. By mass percentage, the solid waste cementitious material includes 35% slag, 35% fly ash, 12.5% Bayer red mud, 5% desulfurized gypsum, 2.5% carbide slag, and 10% activated recycled fine powder. The mass ratio of the solid waste cementitious material to water is 1:5.

[0090] S4. Dry the free water in the shaped recycled aggregate prepared in step S1, and soak it in the solid waste cementitious material mixed slurry obtained in S3. During soaking, intermittent vibration is carried out. After vibrating for 8 minutes each time, it is static for 40 minutes. The total soaking time is 5.5 hours. After the soaking is completed, take out the soaked shaped recycled aggregate and carry out standard curing (curing for 28 days at a temperature of 20±2°C and a humidity greater than 95%) to obtain the strengthened recycled aggregate.

[0091] Example 4

[0092] This example provides a strengthened recycled aggregate, and its preparation method is as follows:

[0093] S1. Initially crush and screen construction waste to obtain recycled aggregate, and then place it in an abrasion tester for ball milling and shaping. The shaping time is adjusted to 7 minutes, the rotation speed of the abrasion tester is adjusted to 35 r / min, and heating is carried out during ball milling. The heating temperature is adjusted to 500°C. After the ball milling is completed, recycled fine powder and shaped recycled aggregate are obtained.

[0094] S2. Mix the recycled fine powder obtained in step S1 with nano materials and fillers according to a mass ratio of 92:1:7, and then carry out ball milling for 7 minutes to obtain activated recycled fine powder. Among them, by mass percentage, the nano material contains 8% nano silicon dioxide and 20% nano calcium oxide; the filler contains 90% Bayer red mud and 10% desulfurized gypsum.

[0095] S3. Mix the solid waste cementitious materials composed of alkaline solid waste activator, precursor material, and activated recycled fine powder and then carry out ball milling. The ball milling time is 5 minutes and the rotation speed is 400 r / min to obtain the solid waste cementitious material; mix the solid waste cementitious material with water to prepare a solid waste cementitious material mixture slurry. Among them, by mass percentage, the solid waste cementitious material includes 40% slag, 30% fly ash, 6.25% Bayer red mud, 2.5% desulfurized gypsum, 1.25% carbide slag, and 20% activated recycled fine powder. The mass ratio of solid waste cementitious material to water is 1:4.

[0096] S4. Dry the free water in the shaped recycled aggregate prepared in step S1, and soak it in the solid waste cementitious material mixed slurry. During soaking, intermittent vibration is carried out. After vibrating for 8 minutes each time, it is static for 50 minutes. The total soaking time is 5 hours. After the soaking is completed, take out the soaked shaped recycled aggregate and carry out standard curing (curing for 28 days at a temperature of 20±2°C and a humidity greater than 95%) to obtain the strengthened recycled aggregate.

[0097] Example 5

[0098] This example provides a strengthened recycled aggregate, and its preparation method is as follows:

[0099] S1. Initially crush and screen construction waste to obtain recycled aggregates, then place them in a abrasion tester for ball milling and shaping. Adjust the shaping time to 8 min, the rotation speed of the abrasion tester to 40 r / min, heat during ball milling, and adjust the heating temperature to 490 °C. After ball milling, recycled fine powder and shaped recycled aggregates are obtained.

[0100] S2. Mix the recycled fine powder obtained in step S1 with nano materials and fillers in a mass ratio of 91:0.8:8.2, and then perform ball milling for 7 min to obtain activated recycled fine powder. Among them, by mass percentage, the nano materials contain 70% nano silica and 30% nano calcium oxide; the fillers contain 80% Bayer red mud and 20% desulfurized gypsum.

[0101] S3. Mix the solid waste cementitious materials composed of alkaline solid waste activator, precursor materials, and activated recycled fine powder, and then perform ball milling for 4 min at a rotation speed of 480 r / min to obtain solid waste cementitious materials; mix the solid waste cementitious materials with water to prepare a solid waste cementitious material mixture slurry. By mass percentage, the solid waste cementitious materials include 40% slag, 40% fly ash, 10% Bayer red mud, 4% desulfurized gypsum, 1% carbide slag, and 5% activated recycled fine powder. The mass ratio of solid waste cementitious materials to water is 1:2.

[0102] S4. Dry the free water in the shaped recycled aggregates prepared in step S1, and soak them in the solid waste cementitious material mixture slurry obtained in S3. Perform intermittent vibration during soaking, stop for 40 min after vibrating for 10 min each time, and the total soaking time is 6 h. After soaking, take out the soaked shaped recycled aggregates and perform standard curing (cure for 28 days at a temperature of 20 ± 2 °C and a humidity greater than 95%) to obtain strengthened recycled aggregates.

[0103] Example 6

[0104] This example provides a stabilized macadam base course, which, by weight, includes 100 parts of strengthened recycled aggregates, 3 parts of solid waste cementitious materials, and 8 parts of water. Among them, the strengthened recycled aggregates and solid waste cementitious materials are the same as those in Example 1. The gradation of the strengthened recycled aggregates is shown in Table 1 below:

[0105] Table 1 Gradation of Strengthened Recycled Aggregates in Example 6

[0106]

[0107] Using the raw materials of the above stabilized macadam base course, make specimens in the laboratory for testing mechanical properties. The specific steps are as follows:

[0108] Pour the solid waste cementitious materials, strengthened recycled aggregates, and water into a mixer and mix evenly to obtain a mixture;

[0109] Put the well - stirred mixture into a molding machine for pressing to obtain specimens;

[0110] Put the pressed specimens into a curing chamber with a temperature of 20 ± 2 °C and a humidity greater than 75% for curing.

[0111] Example 7

[0112] This example provides a stabilized macadam base course, by weight, including 100 parts of strengthened recycled aggregate, 6 parts of solid waste cementitious material, and 8 parts of water. Among them, the strengthened recycled aggregate and the solid waste cementitious material are the same as those in Example 2. The gradation of the strengthened recycled aggregate is shown in Table 2 below:

[0113] Table 2 Gradation of Strengthened Recycled Aggregate in Example 7

[0114]

[0115] Use the raw materials of the above - mentioned stabilized macadam base course to make specimens in the laboratory for testing mechanical properties. The specific steps refer to Example 6.

[0116] Example 8

[0117] This example provides a stabilized macadam base course, by weight, including 120 parts of strengthened recycled aggregate, 5 parts of solid waste cementitious material, and 10 parts of water. Among them, the strengthened recycled aggregate and the solid waste cementitious material are the same as those in Example 3. The gradation of the strengthened recycled aggregate is shown in Table 3 below:

[0118] Table 3 Gradation of Strengthened Recycled Aggregate in Example 8

[0119]

[0120] Use the raw materials of the above - mentioned stabilized macadam base course to make specimens in the laboratory for testing mechanical properties. The specific steps refer to Example 6.

[0121] Example 9

[0122] This example provides a stabilized macadam base course, by weight, including 110 parts of strengthened recycled aggregate, 6 parts of solid waste cementitious material, and 9 parts of water. Among them, the strengthened recycled aggregate and the solid waste cementitious material are the same as those in Example 4. The gradation of the strengthened recycled aggregate is shown in Table 3 below:

[0123] Table 4 Gradation of Strengthened Recycled Aggregate in Example 9

[0124]

[0125] Use the raw materials of the above - mentioned stabilized macadam base course to make specimens in the laboratory for testing mechanical properties. The specific steps refer to Example 6.

[0126] Example 10

[0127] This embodiment provides a stabilized macadam base course, which, by weight parts, comprises 100 parts of strengthened recycled aggregate, 5 parts of solid waste cementitious material, and 8 parts of water, wherein the strengthened recycled aggregate and the solid waste cementitious material are the same as those in Embodiment 5.

[0128] Table 5 Aggregate gradation of the strengthened recycled aggregate in Embodiment 10

[0129]

[0130] Using the raw materials of the above-mentioned stabilized macadam base course, specimens are made in the laboratory for testing mechanical properties, and the specific steps refer to Embodiment 6.

[0131] Comparative Example 1

[0132] This comparative example provides a stabilized macadam base course, which is different from Embodiment 6 in that the mixed slurry of the strengthened recycled aggregate uses commercially available P·O 42.5 ordinary Portland cement, and the other methods and steps are the same as those in Embodiment 6, and will not be elaborated here.

[0133] Comparative Example 2

[0134] This comparative example provides a stabilized macadam base course, which is different from Embodiment 6 in that the strengthened recycled aggregate used is not subjected to mechanical strengthening ball milling - heat shaping treatment, and the other methods and steps are the same as those in Embodiment 6, and will not be elaborated here.

[0135] Comparative Example 3

[0136] This comparative example provides a stabilized macadam base course, which is different from Embodiment 6 in that the strengthened recycled aggregate used only undergoes mechanical strengthening ball milling shaping treatment and does not undergo heat treatment, and the other methods and steps are the same as those in Embodiment 6, and will not be elaborated here.

[0137] Comparative Example 4

[0138] This comparative example provides a stabilized macadam base course, which is different from Embodiment 6 in that the recycled fine powder used is not subjected to recycled fine powder activation treatment, and the other methods and steps are the same as those in Embodiment 6, and will not be elaborated here.

[0139] Comparative Example 5

[0140] This comparative example provides a stabilized macadam base course, which is different from Embodiment 6 in that the strengthened recycled aggregate used is not subjected to solid waste cementitious material slurry coating treatment, and the other methods and steps are the same as those in Embodiment 6, and will not be elaborated here.

[0141] Comparative Example 6

[0142] This comparative example provides a stabilized macadam base course, which is different from Example 6 in that when the enhanced recycled aggregate used is treated with a solid waste cementitious material slurry wrapping, intermittent vibration soaking is not adopted. Other methods and steps are the same as those in Example 6 and will not be elaborated here.

[0143] Comparative Example 7

[0144] This comparative example provides a stabilized macadam base course, which is different from Example 6 in that standard curing is not adopted after the enhanced recycled aggregate used is treated with a solid waste cementitious material slurry wrapping. Other methods and steps are the same as those in Example 6 and will not be elaborated here.

[0145] Comparative Example 8

[0146] This comparative example provides a stabilized macadam base course, which is different from Example 6 in that the enhanced recycled aggregate used is not subjected to mechanical strengthening ball milling and shaping treatment, the recycled fine powder in the solid waste cementitious material is not activated, and the solid waste cementitious material slurry wrapping treatment is not carried out. Other methods and steps are the same as those in Example 6 and will not be elaborated here.

[0147] Performance test:

[0148] The stabilized macadam base courses obtained from Example 6 to Example 10 and Comparative Example 1 to Comparative Example 8 are tested. The performance indexes of the enhanced recycled aggregates used and the prepared stabilized macadam base courses in Example 6 to Example 10 and Comparative Example 1 to Comparative Example 8 are shown in Table 6 below:

[0149] Table 6 Performance test results of the stabilized macadam base courses obtained from Example 6 - 10 and Comparative Example 1 - 8

[0150]

[0151]

[0152] As shown in Table 6, the strengthening combination methods of recycled aggregates significantly improve the various properties of the strengthened recycled aggregates. The strengthened recycled aggregates used in Examples 6 to 10, that is, the strengthened recycled aggregates prepared in Examples 1 to 5, are significantly superior to Comparative Examples 1 to 8 in terms of water absorption rate, crushing index, and flake and elongated particle content. Moreover, the recycled aggregates in Comparative Example 8 that were not subjected to mechanical strengthening ball milling and shaping, recycled fine powder activation, and solid waste cementitious material slurry coating treatment are further deteriorated compared to other comparative examples in terms of water absorption rate, crushing index, and flake and elongated particle content, indicating that mechanical strengthening ball milling and shaping, recycled fine powder activation, and solid waste cementitious materials play a significant role in reducing the water absorption rate, crushing index, and flake and elongated particle content of recycled aggregates. On the one hand, the solid waste cementitious material is subjected to alkali activation treatment to form a cementitious material, which not only has excellent filling performance but also can precisely fill the pores and microcracks in the recycled aggregates. Moreover, it can tightly wrap around the surface of the recycled aggregates to construct a dense slurry layer. This slurry layer not only improves the microstructure of the recycled aggregates, enhances its overall density, but also improves its mechanical properties and durability. At the same time, during the reaction process, the alkali activator chemically reacts with the silicon-aluminum substances in the pores or microcracks of the recycled aggregates to generate more C-A-S-H gels. The generation of C-A-S-H gels further strengthens the filling effect. It is like a microscopic "adhesive" that tightly connects the particles inside the recycled aggregates, further reducing the porosity of the recycled aggregates and enhancing the density and strength of the recycled aggregates.

[0153] Comparing the 7-day unconfined compressive strength of the cement stabilized macadam base course in Table 6, it can be seen that the 7-day unconfined compressive strength of the cement stabilized macadam base course provided in Examples 6 to 10 is close to or higher than 5.0 MPa, while the cement stabilized macadam base courses provided in Comparative Examples 2 to 8 are all lower than the specification requirement of 4.0 MPa, mostly around 3.0 MPa. Only the strength provided in Comparative Example 1 just reaches 4.0 MPa, and the 7-day unconfined compressive strength of the cement stabilized macadam base course prepared with the recycled aggregates without any strengthening measures in Comparative Example 8 is only 1.9 MPa, far lower than the specification requirement.

[0154] In summary, the present invention strengthens the recycled aggregates by adopting treatment means such as mechanical strengthening ball milling and shaping, recycled fine powder activation, and solid waste cementitious material slurry coating, and then uses the strengthened recycled aggregates, activated recycled fine powder, and solid waste cementitious material to prepare a cement stabilized macadam base course. The 7-day unconfined compressive strength of this cement stabilized macadam base course is around 5.0 MPa, with high mechanical properties and can meet the construction requirements.

[0155] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing reinforced recycled aggregate, characterized in that: The steps include: The recycled aggregate is ball-milled and shaped, and heated during the ball-milling process; after the ball-milling process is completed, shaped recycled aggregate and recycled micro-powder are obtained; The regenerated micropowder is mixed with nanomaterials and fillers and then ball-milled to obtain activated regenerated micropowder; an alkaline solid waste activator, a precursor material and the activated regenerated micropowder are mixed and then ball-milled to obtain a solid waste gelling material; the solid waste gelling material is mixed with water to obtain a solid waste gelling material mixed slurry; The shaped recycled aggregate is immersed in the mixed slurry of the solid waste cementitious material, and intermittent vibration soaking is adopted, the vibration soaking is 5 to 10 minutes, and the static soaking is 30 to 60 minutes, and the vibration soaking and static soaking are carried out alternately, and the total soaking time is 5 to 6 hours. After the soaking is completed, the shaped recycled aggregate is taken out and standard curing is carried out to obtain the reinforced recycled aggregate; The ball milling shaping time is 5-10 min, and the rotation speed is 20-40 r / min; The heating temperature is 450-550°C; The mass ratio of recycled micro powder, nano material and filler is (90-95):(0.5-1):(4-9.5); The nano material includes nano silicon dioxide and / or nano calcium oxide, and the filler includes Bayer red mud and / or desulfurized gypsum; The alkaline solid waste activator comprises Bayer red mud, desulfurized gypsum and carbide slag, and the mass ratio of Bayer red mud, desulfurized gypsum and carbide slag is (5-6):(2-4):(0.5-1); The precursor material includes at least one of blast furnace slag, coal gangue powder, waste glass powder and fly ash; The mass ratio of the alkaline solid waste activator, the precursor material and the activated regenerated micropowder is (1-3):(5-8):(0.5-2).

2. The method for preparing a reinforced recycled aggregate according to claim 1, characterized in that: The mass ratio of water to solid waste cementitious material is (1-5):

1.

3. A reinforced recycled aggregate, characterized in that: The reinforced recycled aggregate is prepared by the preparation method according to any one of claims 1 to 2.

4. The reinforced recycled aggregate according to claim 3, characterized in that: The particle size composition of the reinforced recycled aggregate is as follows: 0.075~2.36 mm accounts for 10~30 wt%; 2.36~4.75 mm accounts for 15~25 wt%; 4.75~9.5 mm accounts for 20~35 wt%; 9.5~19.0 mm accounts for 25~40 wt%; 19.0~31.5 mm accounts for 10~20 wt%.

5. Use of the reinforced recycled aggregate according to claim 3 or 4 in a solid waste stabilized crushed stone base.

6. A solid waste stabilized gravel base, characterized in that: The raw materials of the solid waste stabilized crushed stone base layer include, by weight: 3 to 6 parts of solid waste cementitious materials, 100 to 120 parts of the reinforced recycled aggregate according to claim 3 or 4, and 8 to 10 parts of water; The solid waste gelling material comprises, by mass percentage, 10-30% of alkaline solid waste activator, 60-80% of precursor material and 10-20% of activated regenerated micro powder.

7. A method for preparing a solid waste stabilized gravel base layer according to claim 6, characterized in that: The method comprises the following steps: mixing solid waste cementitious materials, reinforced recycled aggregate and water in proportion, and obtaining a solid waste stabilized crushed stone base after spreading, rolling and curing.

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