Method for preparing lightweight recycled aggregate from construction waste
By crushing, screening, and adding auxiliary materials to construction waste, lightweight porous recycled aggregates are prepared, solving the problem of difficult utilization of construction waste and realizing resource recycling and energy conservation and emission reduction of building materials.
Patent Information
- Application Number
- CN202511026573.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-24
- Publication Date
- 2025-12-12
AI Technical Summary
The large amount of fine aggregates from construction waste is difficult to utilize efficiently, leading to environmental pollution and resource waste. At the same time, traditional aggregates rely on natural sand and gravel or high-cost artificial aggregates, which pose ecological and economic problems.
Lightweight porous recycled aggregate is prepared by coarsely crushing and screening broken bricks and concrete blocks from construction waste, adding auxiliary materials such as fly ash, clay and cement, and then granulating and sintering or solidifying at room temperature.
The prepared lightweight recycled aggregate has low density and good thermal insulation performance, which can reduce the building load and improve the thermal insulation effect. It conforms to the concept of green environmental protection and is suitable for building insulation boards and roofing underlayment, etc., to achieve resource recycling.
Smart Images
Figure BDA0005516133550000071
Abstract
Description
Technical Field
[0001] This invention relates to the field of building materials technology, specifically to a method for preparing lightweight recycled aggregate from construction waste. Background Technology
[0002] With the rapid development of urban construction, the amount of construction waste generated has increased dramatically. A large portion of this fine construction waste, such as the fine particles and powdery components from crushed bricks, tiles, and concrete blocks, is difficult to utilize efficiently due to its low value. Currently, most of this fine construction waste is directly landfilled or used for simple road paving, which not only occupies a large amount of land resources but also causes serious damage to the ecological environment.
[0003] On the other hand, in the field of building materials such as insulation boards and roofing underlayment, traditional aggregates mostly rely on natural sand and gravel resources or use more expensive artificial aggregates. The over-exploitation of natural sand and gravel resources has triggered a series of ecological and environmental problems; while the use of high-cost artificial aggregates increases the production cost of building materials and limits their large-scale application. Therefore, how to transform low-value construction waste fines into high-performance aggregates suitable for building insulation boards, roofing underlayment, and other fields has become an urgent problem to be solved by the industry. Summary of the Invention
[0004] The purpose of this invention is to provide a method for preparing lightweight recycled aggregate from construction waste, in order to solve the problems mentioned in the background art.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0006] A method for preparing lightweight recycled aggregate from construction waste includes the following steps:
[0007] The broken bricks, tiles, and concrete blocks in the construction waste are first coarsely crushed, then crushed a second time, and then screened to obtain a mixture of fine aggregate and powder.
[0008] Add auxiliary materials, a binder and water to the above-mentioned fine aggregate and powder mixture. The auxiliary materials include fly ash and clay, and the binder is cement.
[0009] The mixture is placed in a granulation equipment for rolling granulation, and the diameter of the wet particles is kept in the range of 5-20 mm by adjusting the amount of water added.
[0010] Wet particles are fed into a sintering furnace for heating and expansion, or solidified at room temperature to obtain lightweight recycled aggregate.
[0011] Furthermore, the particle size of the material after coarse crushing is less than 50 mm, and the particle size of the material after secondary crushing is less than 10 mm.
[0012] Furthermore, in the auxiliary materials, fly ash and clay are added at a mass ratio of (2-3):1.
[0013] Furthermore, the amount of cement added is 3%-5% of the mass of the mixture, and the amount of water added is 20%-30% of the mass of the mixture.
[0014] Furthermore, the granulation equipment is a disc granulator, with a disc rotation speed of 150-250 rpm and a granulation time of 15-25 minutes.
[0015] Furthermore, when the wet particles are fed into the sintering furnace for heating and expansion, they are heated to 900-1100°C at a heating rate of 3-7°C / min, causing the gas inside the wet particles to expand and form a porous structure. After holding at this temperature for 2-3 hours, they are cooled.
[0016] Furthermore, the room temperature curing method includes CO2 curing or alkali activation, wherein:
[0017] When using CO2 curing, place the wet granules in an environment with a humidity of 60%-80% and a CO2 concentration of 15%-25% for 24-48 hours.
[0018] When using alkali activation, the alkali solution is mixed with wet particles and reacted at room temperature for 12-24 hours. The pH value of the alkali activator solution is 12-14.
[0019] Furthermore, the alkaline solution is a sodium hydroxide solution with a mass concentration of 8-12 mol / L.
[0020] Furthermore, before the crushing and screening step, the construction waste is subjected to iron removal treatment, which is carried out using an electromagnetic iron separator with a magnetic field strength of 800-1200 Gs.
[0021] Furthermore, the sieve used for sieving has a mesh size of 0.5 mm.
[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0023] 1. This invention uses broken bricks, tiles, concrete blocks, etc. from construction waste as the main raw materials. Through crushing, screening, adding auxiliary materials for granulation, and molding, lightweight recycled aggregate is prepared. This provides a new high-value-added utilization method for low-value construction waste fines, effectively reduces the environmental pressure caused by construction waste accumulation, and realizes the recycling of resources.
[0024] 2. The lightweight recycled aggregate prepared by this invention has a light and porous particle size, and its density is much lower than that of natural crushed stone. When applied to concrete, it can significantly reduce the self-weight of concrete, reduce the load on the building structure, and reduce the amount of building materials used. At the same time, the porous structure endows it with certain thermal insulation properties, which can effectively improve the thermal insulation effect of building insulation boards, roofing layers and other materials, and meet the requirements of building energy conservation.
[0025] 3. In the preparation method provided by the present invention, the sintering furnace heating expansion can be selected according to actual needs, or room temperature curing methods such as CO2 curing and alkali activation can be used. Among them, the room temperature curing method can significantly reduce energy consumption, which is in line with the concept of green environmental protection and sustainable development. Moreover, the method is simple in process, controllable in operation, and easy to realize industrial production. The lightweight aggregate prepared has broad application prospects in building insulation boards, roofing subfloors, etc., which helps to promote the development of the construction waste resource utilization industry. Detailed Implementation
[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0027] Example 1
[0028] A method for preparing lightweight recycled aggregate from construction waste includes the following steps:
[0029] The first step is to feed the broken bricks, tiles and concrete blocks from the construction waste into a jaw crusher for coarse crushing, so that the particle size of the material after coarse crushing is less than 50mm; then feed it into an impact crusher for secondary crushing, so that the particle size of the material after secondary crushing is less than 10mm; finally, it is screened by a vibrating screen with a screen aperture of 0.5mm to obtain a mixture of fine aggregate and powder.
[0030] The second step is to add fly ash and clay to the above fine aggregate and powder mixture in a mass ratio of 2:1, along with 3% cement as a binder and 20% water.
[0031] Step 3: Place the above mixture into a disc granulator, set the disc speed to 150 rpm, and the granulation time to 15 minutes. Adjust the amount of water added during the granulation process so that the diameter of the formed wet particles is in the range of 5-20 mm.
[0032] The fourth step is to feed the wet particles into a sintering furnace and heat them to 900°C at a heating rate of 3°C / min. This causes the gas inside the wet particles to expand and form a porous structure. After holding the temperature for 2 hours, the particles are cooled to obtain lightweight recycled aggregate.
[0033] Example 2
[0034] A method for preparing lightweight recycled aggregate from construction waste includes the following steps:
[0035] The first step is to coarsely crush and then secondary crush the broken bricks and concrete blocks in the construction waste, and then obtain a mixture of fine aggregate and powder by screening. The particle size of the material after coarse crushing is less than 45mm, the particle size of the material after secondary crushing is less than 8mm, and the screen mesh size is 0.5mm.
[0036] The second step is to add auxiliary materials, cementitious agents and water to the mixture of fine aggregates and powders. The mass ratio of fly ash to clay is 2.5:1, the amount of cement added is 4% of the mass of the mixture, and the amount of water added is 25% of the mass of the mixture.
[0037] The third step is to place the mixture in a disc granulator, set the disc speed to 200 rpm, granulate for 20 minutes, and adjust the amount of water added so that the diameter of the wet particles is 5-20 mm.
[0038] The fourth step involves CO2 curing in a room-temperature curing method. The wet particles are placed in an environment with 70% humidity and 20% CO2 concentration for 36 hours to obtain lightweight recycled aggregate.
[0039] Example 3
[0040] A method for preparing lightweight recycled aggregate from construction waste includes the following steps:
[0041] The first step is to perform coarse crushing and secondary crushing on the broken bricks, tiles and concrete blocks in the construction waste. After coarse crushing, the particle size of the material is less than 40mm, and after secondary crushing, the particle size of the material is less than 6mm. Then, the material is screened by a vibrating screen with a screen size of 0.5mm to obtain a mixture of fine aggregate and powder.
[0042] The second step is to add auxiliary materials, cementitious agents and water to the mixture of fine aggregates and powders. The mass ratio of fly ash to clay is 3:1, cement accounts for 5% of the mass of the mixture, and water accounts for 30% of the mass of the mixture.
[0043] The third step is to put the mixture into a disc granulator, rotate the disc at 250 rpm, and granulate for 25 minutes to form wet granules with a diameter of 5-20 mm.
[0044] The fourth step involves using an alkali-activated, room-temperature curing method. A 10 mol / L sodium hydroxide solution is mixed with the wet particles. The pH of the alkali activator solution is 13. The mixture is reacted at room temperature for 18 hours to obtain lightweight recycled aggregate.
[0045] Example 4
[0046] A method for preparing lightweight recycled aggregate from construction waste includes the following steps:
[0047] The first step is to coarsely crush the broken bricks, tiles, and concrete blocks in the construction waste so that the particle size of the material after coarse crushing is less than 48mm; after secondary crushing, the particle size of the material is less than 9mm; and then sieve it through a vibrating screen with a screen size of 0.5mm to obtain a mixture of fine aggregate and powder.
[0048] The second step is to add fly ash and clay to the fine aggregate and powder mixture by mass ratio of 2.2:1, and at the same time add cement as a binder accounting for 3.5% of the mass of the mixture, and water accounting for 22% of the mass of the mixture.
[0049] Step 3: Put the above mixture into a disc granulator, rotate the disc at 160 rpm, granulate for 16 minutes, and adjust the amount of water added so that the diameter of the wet particles is in the range of 5-20 mm.
[0050] The fourth step is to feed the wet particles into a sintering furnace and heat them to 950°C at a heating rate of 4°C / min. This causes the gas inside the wet particles to expand and form a porous structure. After holding the temperature for 2.5 hours, the particles are cooled to obtain lightweight recycled aggregate.
[0051] Example 5
[0052] A method for preparing lightweight recycled aggregate from construction waste includes the following steps:
[0053] The first step is to coarsely crush and then secondary crush the broken bricks, tiles and concrete blocks in the construction waste. After coarse crushing, the particle size of the material is less than 42mm, and after secondary crushing, the particle size of the material is less than 7mm. The mixture of fine aggregate and powder is obtained by screening through a vibrating screen with a screen size of 0.5mm.
[0054] The second step is to add auxiliary materials, cementitious agents and water to the mixture of fine aggregates and powders. The mass ratio of fly ash to clay is 2.8:1, the amount of cement added is 4.5% of the mass of the mixture, and the amount of water added is 28% of the mass of the mixture.
[0055] The third step is to place the mixture in a disc granulator, rotate the disc at 220 rpm, granulate for 22 minutes, and adjust the amount of water added so that the diameter of the wet particles is 5-20 mm.
[0056] The fourth step involves using a room-temperature curing method with CO2 curing. The wet particles are placed in an environment with 75% humidity and 22% CO2 concentration for 40 hours to obtain lightweight recycled aggregate.
[0057] Example 6
[0058] A method for preparing lightweight recycled aggregate from construction waste includes the following steps:
[0059] The first step is to coarsely crush and then secondary crush the broken bricks, tiles and concrete blocks in the construction waste. After coarse crushing, the particle size of the material is less than 38mm, and after secondary crushing, the particle size of the material is less than 5mm. The material is then screened through a vibrating screen with a screen size of 0.5mm to obtain a mixture of fine aggregate and powder.
[0060] The second step is to add auxiliary materials, cementitious agents and water to the mixture of fine aggregates and powders. The mass ratio of fly ash to clay is 3:1, cement accounts for 5% of the mass of the mixture, and water accounts for 30% of the mass of the mixture.
[0061] The third step is to put the mixture into a disc granulator, rotate the disc at 240 rpm, and granulate for 24 minutes to form wet granules with a diameter of 5-20 mm.
[0062] The fourth step involves using an alkali-activated, room-temperature curing method. A sodium hydroxide solution with a mass concentration of 11 mol / L is mixed with the wet particles. The pH value of the alkali activator solution is 13.5. The mixture is reacted at room temperature for 20 hours to obtain lightweight recycled aggregate.
[0063] Comparative Example 1
[0064] A method for treating construction waste, comprising the following steps:
[0065] The first step involves simply crushing the broken bricks, tiles, and concrete blocks in the construction waste without further crushing or screening.
[0066] The second step involves adding only cement and water to the crushed material, without adding fly ash or clay auxiliary materials. The amount of cement added is 3% of the material mass, and the amount of water added is 20% of the material mass.
[0067] The third step is to manually knead the above mixture into blocks without granulating it using a granulation device.
[0068] Step 4: Allow the block to air dry naturally, without undergoing sintering furnace heating or room temperature curing treatment;
[0069] Comparative Example 2
[0070] A method for preparing aggregate from construction waste includes the following steps:
[0071] The first step is to coarsely crush the broken bricks, tiles, and concrete blocks in the construction waste, then crush them a second time, and finally screen them to obtain a mixture of fine aggregate and powder.
[0072] The second step is to add auxiliary materials, a binder and water to the above-mentioned fine aggregate and powder mixture. The auxiliary materials only contain fly ash and no clay is added. The binder is cement. The amount of cement added is 3% of the mass of the mixture, and the amount of water added is 20% of the mass of the mixture.
[0073] The third step is to place the mixture in a granulation equipment for rolling granulation, and adjust the amount of water added so that the diameter of the wet particles formed is in the range of 5-20 mm.
[0074] The fourth step involves feeding the wet particles into a sintering furnace, but the heating rate is too fast, reaching 1200°C at a rate of 15°C / min, and without heat preservation, directly cooling to obtain aggregate.
[0075] Comparative Example 3
[0076] A method for preparing aggregate from construction waste includes the following steps:
[0077] The first step is to coarsely crush the broken bricks, tiles, and concrete blocks in the construction waste, then crush them a second time, and finally screen them to obtain a mixture of fine aggregate and powder.
[0078] The second step is to add auxiliary materials, cementitious agents and water to the above fine aggregate and powder mixture. The mass ratio of fly ash to clay is 1:1, the amount of cement added is 2% of the mass of the mixture, and the amount of water added is 15% of the mass of the mixture.
[0079] The third step is to place the mixture in a granulation equipment for rolling granulation, and adjust the amount of water added so that the diameter of the wet particles formed is in the range of 5-20 mm.
[0080] The fourth step is to feed the wet granules into a sintering furnace, heat them to 850°C at a heating rate of 2°C / min, hold them at that temperature for 1 hour, and then cool them to obtain aggregate.
[0081] Experimental Example 1
[0082] Basic performance tests were performed on the products prepared in Examples 1-6 and Comparative Examples 1-3:
[0083] Bulk density test: Refer to GB / T17431.1-2010 "Lightweight aggregates and their test methods Part 1: Lightweight aggregates" to determine the bulk density of each product;
[0084] Compressive strength test: Each product is made into a standard specimen, and the compressive strength is tested according to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete".
[0085] Water absorption test: The water absorption rate was determined according to GB / T17431.2-2010 "Lightweight aggregates and their test methods Part 2: Lightweight aggregates test methods";
[0086] The test results are shown in Table 1:
[0087] Table 1
[0088] project <![CDATA[Bulk density (kg / m 3 )]]> Compressive strength (MPa) Water absorption rate (%) Example 1 580 8.2 12.5 Example 2 550 7.8 11.8 Example 3 530 8.0 12.2 Example 4 570 8.3 12.3 Example 5 540 7.9 11.5 Example 6 520 8.1 12.0 Comparative Example 1 1200 3.5 25.6 Comparative Example 2 850 5.2 18.3 Comparative Example 3 780 4.8 20.1
[0089] As shown in Table 1, the bulk density of the lightweight recycled aggregates prepared in Examples 1-6 is significantly lower than that of the comparative examples, indicating their superior lightweight properties; their compressive strength is significantly higher than that of the comparative examples, indicating good structural strength; and their water absorption rate is relatively low, demonstrating good impermeability. In contrast, the product performance of Comparative Example 1 is poor due to its rough processing technology; the product performance of Comparative Example 2 is inferior to that of the examples due to unreasonable raw material ratio and process parameters; and the product performance of Comparative Example 3 is also insufficient due to poor raw material ratio and process control. This verifies the advantages of the method of the present invention.
[0090] Experiment Example 2
[0091] Durability tests were performed on the products prepared in Examples 1-6 and Comparative Examples 1-3:
[0092] Freeze-thaw cycle test: Each product was made into a standard sample and subjected to 200 freeze-thaw cycles in accordance with GB / T50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete". The mass loss rate and strength loss rate after freeze-thaw cycles were tested.
[0093] Sulfate resistance test: The sample was immersed in a 5% sodium sulfate solution, and the strength change after different immersion times was tested according to GB / T50082-2009.
[0094] The test results are shown in Table 2:
[0095] Table 2
[0096]
[0097] As shown in Table 2, the lightweight recycled aggregates prepared in Examples 1-6 showed lower mass loss rate and strength loss rate than the comparative examples in freeze-thaw cycle and sulfate attack resistance tests, while the strength retention rate was higher than that of the comparative examples. This further proves that the lightweight recycled aggregates prepared by the method of the present invention have better durability and are suitable for various building fields such as building insulation boards and roofing layers.
[0098] The present invention provides a detailed description of a method for preparing lightweight recycled aggregate from construction waste. Specific examples have been used to illustrate the principles and implementation methods of the invention. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including manufacturing and using any device or system, and implementing any combination method. It should be noted that those skilled in the art can make various improvements and modifications to the invention without departing from its principles. In particular, as long as there is no structural conflict, the features in the embodiments disclosed in this invention can be combined with each other in any way. The lack of an exhaustive description of these combinations in this specification is merely for the sake of brevity and resource conservation. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.
Claims
1. A method for preparing lightweight recycled aggregate from construction waste, characterized in that, Includes the following steps: The broken bricks, tiles, and concrete blocks in the construction waste are first coarsely crushed, then crushed a second time, and then screened to obtain a mixture of fine aggregate and powder. Add auxiliary materials, a binder and water to the above-mentioned fine aggregate and powder mixture. The auxiliary materials include fly ash and clay, and the binder is cement. The mixture is placed in a granulation equipment for rolling granulation, and the diameter of the wet particles is kept in the range of 5-20 mm by adjusting the amount of water added. Wet particles are fed into a sintering furnace for heating and expansion, or solidified at room temperature to obtain lightweight recycled aggregate.
2. The method for preparing lightweight recycled aggregate from construction waste according to claim 1, characterized in that, The particle size of the material after coarse crushing is less than 50 mm, and the particle size of the material after secondary crushing is less than 10 mm.
3. The method for preparing lightweight recycled aggregate from construction waste according to claim 1, characterized in that, The auxiliary materials are added in a mass ratio of (2-3):
1.
4. The method for preparing lightweight recycled aggregate from construction waste according to claim 1, characterized in that, The amount of cement added is 3%-5% of the mass of the mixture, and the amount of water added is 20%-30% of the mass of the mixture.
5. The method for preparing lightweight recycled aggregate from construction waste according to claim 1, characterized in that, The granulation equipment is a disc granulator, with a disc rotation speed of 150-250 rpm and a granulation time of 15-25 minutes.
6. The method for preparing lightweight recycled aggregate from construction waste according to claim 1, characterized in that, When the wet particles are fed into the sintering furnace for heating and expansion, they are heated to 900-1100℃ at a heating rate of 3-7℃ / min, so that the gas inside the wet particles expands to form a porous structure. After holding at this temperature for 2-3 hours, they are cooled.
7. The method for preparing lightweight recycled aggregate from construction waste according to claim 1, characterized in that, The room temperature curing method includes CO2 curing or alkali activation, wherein: When using CO2 curing, place the wet granules in an environment with a humidity of 60%-80% and a CO2 concentration of 15%-25% for 24-48 hours. When using alkali activation, the alkali solution is mixed with wet particles and reacted at room temperature for 12-24 hours. The pH value of the alkali activator solution is 12-14.
8. A method for preparing lightweight recycled aggregate from construction waste according to claim 7, characterized in that, The alkaline solution is a sodium hydroxide solution with a mass concentration of 8-12 mol / L.
9. A method for preparing lightweight recycled aggregate from construction waste according to claim 1, characterized in that, Before the crushing and screening step, the construction waste is subjected to iron removal treatment, which is carried out by an electromagnetic iron separator with a magnetic field strength of 800-1200 Gs.
10. A method for preparing lightweight recycled aggregate from construction waste according to claim 1, characterized in that, The sieve used for sieving has a mesh size of 0.5 mm.