A method for strengthening construction solid waste aggregates

Abstract

This invention discloses a method for strengthening construction solid waste aggregate, comprising the following steps: 1) uniformly mixing a polymer emulsion with inorganic nanomaterials, and curing at room temperature to obtain a composite polymer emulsion; 2) mixing the composite polymer emulsion with construction solid waste aggregate, and performing vibration composite under negative pressure; then curing under normal pressure, followed by heating and drying to obtain strengthened recycled aggregate. This invention employs a composite strengthening method using polymer emulsion and inorganic materials, further combined with negative pressure vibration and curing processes, which can effectively reduce the water absorption rate of recycled aggregate and improve its strength. Furthermore, the preparation method is simple, easy to operate, and uses widely available raw materials, resulting in significant economic and environmental benefits, making it suitable for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of road materials technology, specifically relating to a method for strengthening construction solid waste aggregates. Background Technology

[0002] With the rapid advancement of urbanization, the disposal of construction waste generated during urban redevelopment has become a major concern. Waste concrete constitutes the largest proportion of construction waste. Reusing waste concrete can not only reduce the over-exploitation and waste of natural resources but also prevent environmental pollution, truly achieving the goals of resource conservation and reducing harmful emissions.

[0003] The poor performance of recycled aggregates is mainly due to the large amount of old mortar adhering to their surface and the micro-cracks generated during the crushing process. This results in recycled aggregates typically having lower strength than traditional natural aggregates, and higher water absorption rates. Processing recycled aggregates through various methods can reduce their inherent defects and enable their effective reuse. If recycled aggregates can be better applied to road asphalt mixtures, it can not only reduce the consumption of natural aggregates but also significantly reduce the quantity of recycled aggregates, providing a better pathway for the resource utilization of recycled aggregates.

[0004] Currently, there are some solutions for strengthening recycled aggregates. For example, CN113800813A discloses a recycled aggregate strengthening slurry and its preparation method, which fully utilizes the performance characteristics of magnesium oxychloride cement to prepare high-performance granular recycled aggregates in a short time; CN112897918A discloses a recycled aggregate strengthening liquid and its preparation method, which prepares a recycled aggregate strengthening liquid by configuring sodium carbonate, sodium hydroxide and polyvinyl alcohol in weight percentages, solving the problems of rough surface, high porosity, high water absorption and high crushing index of recycled aggregates; CN114591016A discloses a recycled aggregate strengthening method using biodeposition, in which recycled aggregates are soaked in bacterial solution. This method can be applied to the areas of recycled aggregates that need repair, achieving better repair results. However, the above solutions usually use a single strengthening method, mainly targeting a certain defect, and may even lead to a decrease in other properties of the recycled aggregates after strengthening. In addition, the cement mortar on the surface of the recycled aggregates is usually not removed well. Summary of the Invention

[0005] The main objective of this invention is to address the problems and shortcomings of existing technologies by providing a method for strengthening construction solid waste aggregates. This method employs a composite strengthening approach using polymer emulsions and inorganic materials, further combined with processes such as negative pressure vibration and curing. The resulting strengthened recycled aggregates can effectively balance good mechanical properties and durability, making them suitable for widespread application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for strengthening construction solid waste aggregates includes the following steps:

[0008] 1) The polymer emulsion and inorganic nanomaterials are mixed evenly and allowed to stand at room temperature for curing to obtain a composite polymer emulsion;

[0009] 2) The composite polymer emulsion is mixed with construction solid waste aggregate, and then vibrated and compounded under negative pressure. After curing under normal pressure and heating and drying, the reinforced recycled aggregate is obtained.

[0010] In the above scheme, the room temperature static curing time is 6-18 hours.

[0011] In the above scheme, the polymer emulsion can be one or more of acrylic polymer emulsion, epoxy polymer emulsion, EVA copolymer emulsion, etc.; its solid content is 10-30%.

[0012] In the above scheme, the inorganic nanomaterial can be nano-silica; 200 mesh, with a purity of 99.5% or higher.

[0013] In the above scheme, the mass ratio of the polymer emulsion to the inorganic nanomaterial is 1:(0.1-0.2).

[0014] Preferably, the mixing step in step 1) employs a high-speed shearing process, wherein the shearing frequency is 2-4 kHz and the time is 30-40 min.

[0015] In the above scheme, the construction solid waste aggregate is obtained by crushing, screening and washing construction solid waste, and its particle size is greater than 2.36mm.

[0016] In the above scheme, the solid-liquid ratio of the construction solid waste aggregate to the composite polymer emulsion is 1g:1.33-2ml.

[0017] In the above scheme, the negative pressure condition is 3.4-4 kPa.

[0018] In the above scheme, the vibration frequency used in the vibration composite is 20-40Hz, the amplitude is 1-4mm, and the time is 30-40min.

[0019] In the above scheme, the health preservation temperature is 20-30℃ and the time is 12-24h.

[0020] In the above scheme, the drying temperature is 100-120℃ and the time is 8-12h.

[0021] The recycled aggregate prepared according to the above scheme has a crushing value of 15-22%, an apparent relative density of 2.6-2.8, and a water absorption rate of 0.5-1.85%.

[0022] The principle of this invention is as follows:

[0023] This invention first mixes a polymer emulsion with inorganic materials at room temperature and allows them to stand for curing, which promotes more uniform suspension of the inorganic materials in the polymer emulsion. Then, recycled aggregate is immersed in the composite polymer emulsion and compounded under negative pressure and vibration conditions, followed by curing. This process fills and repairs large pores in the recycled aggregate. The polymer emulsion immersion method improves the pore structure of the recycled aggregate, increases its density, and enhances its strength. Furthermore, the polymer emulsion used in this invention has gelling properties and can solidify quickly, effectively improving the water absorption problem of the recycled aggregate. In addition, the composite polymer emulsion described in this invention can also reduce the cement mortar content on the aggregate surface to a certain extent during the compounding process with construction solid waste aggregate, further improving the overall performance and durability of the aggregate.

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

[0025] 1) This invention employs a composite strengthening method of polymer emulsion and inorganic materials, and further combines negative pressure vibration and heat curing processes to effectively improve the pore structure of recycled aggregates and reduce the thickness of mortar on the aggregate surface to a certain extent. This effectively reduces the water absorption rate of recycled aggregates and enhances their strength, providing a new approach for the efficient application of recycled aggregates in asphalt mixtures.

[0026] 2) The polymer emulsions and inorganic materials used are widely available, the polymer emulsions have good strengthening effect, have little environmental impact, and are highly economical;

[0027] 3) The strengthening method used in this invention is relatively simple, easy to operate, consumes less resources, and is suitable for widespread application. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the strengthening process of the recycled aggregate described in this invention. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to embodiments, so as to facilitate a clearer understanding of the present invention, but these embodiments do not constitute a limitation on the present invention.

[0030] In the following embodiments, the construction solid waste aggregate used is obtained through preliminary treatment by jaw crushing, screening and washing, and its particle size is 2.36-4.75mm, 4.75-9.5mm or 9.5-16mm.

[0031] The acrylic polymer emulsion used was DETO waterborne acrylic polymer emulsion, supplied by Dongguan DETO New Material Technology Co., Ltd., with a solid content of 44.6%. The copolymer EVA emulsion used was supplied by Guangzhou Zhonggao Chemical Co., Ltd., with a solid content of 54.3%. The epoxy polymer emulsion used was supplied by Foshan Juntu New Material Co., Ltd., with a solid content of 33.2%.

[0032] The nano-silica used was provided by Nanjing Baoket New Materials Co., Ltd., with a mesh size of 200 and a purity of 99.5%.

[0033] Example 1

[0034] A method for strengthening construction solid waste aggregates includes the following steps:

[0035] 1) 538g of acrylic polymer emulsion and 262g of water were placed in a high-speed shearing machine with a shearing frequency of 2kHZ and mixed evenly for 20min to obtain 800g of acrylic polymer emulsion with a solid content of 30%.

[0036] 2) 72g of nano silica was added to 800g of acrylic polymer emulsion with a solid content of 30% and mixed evenly at a frequency of 2kHz using a high-speed shearing machine for 30min. After standing at room temperature for 12h, 872g of compound polymer emulsion was obtained.

[0037] 3) Place 872g of compound polymer emulsion and 600g of construction solid waste aggregate (4.75-9.5mm) in a negative pressure container, and simultaneously turn on the vibration device and evacuate. The negative pressure in the negative pressure container reaches 3.7kPa±0.3kPa within 2 minutes. At the same time, it is continuously vibrated at 25Hz and 2mm amplitude for 30 minutes. Then it is taken out and kept at 30℃ for 12 hours. Finally, it is placed in an oven at 110℃ for 8 hours to allow the recycled aggregate to dry fully, thus obtaining the reinforced recycled aggregate.

[0038] Example 2

[0039] A method for strengthening construction solid waste aggregates includes the following steps:

[0040] 1) 404g of acrylic polymer emulsion and 396g of water were placed in a high-speed shearing machine with a shearing frequency of 2kHZ and mixed evenly for 20min to obtain 800g of acrylic polymer emulsion with a solid content of 20%.

[0041] 2) Add 48g of nano-silica to 800g of acrylic polymer emulsion with a solid content of 20% and use a high-speed shearing machine to shear and mix evenly at a frequency of 2kHz for 30min. Let it stand at room temperature for 12h to obtain 848g of compound polymer emulsion.

[0042] 3) Place 848g of compound polymer emulsion and 600g of construction solid waste aggregate (4.75-9.5mm) in a negative pressure container, simultaneously turn on the vibration device and evacuate the vacuum. The negative pressure in the negative pressure container reaches 3.7kPa±0.3kPa within 2 minutes. At the same time, continue to vibrate at 25Hz and 2mm amplitude for 30 minutes. Then take it out and cure it at 30℃ for 12 hours. Finally, place it in an oven at 110℃ for 8 hours to allow the recycled aggregate to dry fully, thus obtaining the reinforced recycled aggregate.

[0043] Example 3

[0044] A method for strengthening construction solid waste aggregates includes the following steps:

[0045] 1) 173g of acrylic polymer emulsion and 627g of water were placed in a high-speed shearing machine with a shearing frequency of 2kHZ and mixed evenly for 20min to obtain 800g of acrylic polymer emulsion with a solid content of 10%.

[0046] 2) Add 24g of nano-silica to 800g of acrylic polymer emulsion with a solid content of 10% and use a high-speed shearing machine to shear and mix evenly at a frequency of 2kHz for 30min. Let it stand at room temperature for 12h to obtain 824g of compound polymer emulsion.

[0047] 3) Place 824g of compound polymer emulsion and 600g of construction solid waste aggregate (4.75-9.5mm) in a negative pressure container, and simultaneously turn on the vibration device and evacuate. The negative pressure in the negative pressure container reaches 3.7kPa±0.3kPa within 2 minutes. At the same time, continue to vibrate at 25Hz and 2mm amplitude for 30 minutes. Then take it out and cure it at 30℃ for 12 hours. Finally, place it in an oven at 110℃ for 8 hours to allow the recycled aggregate to dry fully, thus obtaining the reinforced recycled aggregate.

[0048] Example 4

[0049] A method for strengthening construction solid waste aggregates includes the following steps:

[0050] 1) 296g of copolymer EVA emulsion and 604g of water were placed in a high-speed shearing machine with a shearing frequency of 2kHZ and mixed evenly for 20min to obtain 800g of copolymer EVA emulsion with a solid content of 20%;

[0051] 2) Add 48g of nano-silica to 800g of copolymer EVA emulsion with a solid content of 20% and use a high-speed shearing machine to shear and mix evenly at a frequency of 2kHZ for 30min. Let it stand at room temperature for 12h to obtain 848g of compound polymer emulsion.

[0052] 3) Place 848g of compound polymer emulsion and 600g of construction solid waste aggregate (4.75-9.5mm) in a negative pressure container, and simultaneously turn on the vibration device and evacuate. The negative pressure in the negative pressure container reaches 3.7kPa±0.3kPa within 2 minutes. At the same time, continue to vibrate at 25Hz and 2mm amplitude for 30 minutes. Then take it out and heat it at 30℃ for 12 hours. Finally, place it in an oven at 110℃ for 8 hours to dry the recycled aggregate thoroughly, thus obtaining the reinforced recycled aggregate.

[0053] Comparative Example 1

[0054] A method for strengthening construction solid waste aggregates includes the following steps:

[0055] 1) 538g of acrylic polymer emulsion and 262g of water were placed in a high-speed shear machine with a shearing frequency of 2kHz and mixed evenly for 20min. The mixture was then allowed to stand at room temperature for 12h to obtain 800g of acrylic polymer emulsion with a solid content of 30%.

[0056] 2) Place 800g of acrylic polymer emulsion and 600g of construction solid waste aggregate (4.75-9.5mm) in a negative pressure container, and simultaneously turn on the vibration device and evacuate. The negative pressure in the negative pressure container reaches 3.7kPa±0.3kPa within 2 minutes. At the same time, vibrate continuously for 30 minutes at 25Hz and an amplitude of 2mm. Then take it out and cure it at 30℃ for 12 hours. Finally, place it in an oven at 110℃ for 8 hours to allow the recycled aggregate to dry fully, thus obtaining the reinforced recycled aggregate.

[0057] Comparative Example 2

[0058] A method for strengthening construction solid waste aggregates includes the following steps:

[0059] 1) Mix 404g of acrylic polymer emulsion with 396g of water using a glass rod for 20 minutes to obtain 800g of acrylic polymer emulsion with a solid content of 20%.

[0060] 2) Add 48g of nano-silica to 800g of acrylic polymer emulsion with a solid content of 20% and mix evenly with a glass rod for 30min. Let it stand at room temperature for 12h to obtain 848g of compound polymer emulsion.

[0061] 3) Place 848g of compound polymer emulsion and 600g of construction solid waste aggregate (4.75-9.5mm) in a negative pressure container, and simultaneously start vacuuming. The negative pressure in the container reaches 3.7kPa±0.3kPa within 2 minutes. After processing for 30 minutes, remove the container and cure it at 30℃ for 12 hours. Then, dry it in an oven at 110℃ for 4 hours to ensure that the recycled aggregate is fully dried, thus obtaining the reinforced recycled aggregate.

[0062] Comparative Example 3

[0063] A method for strengthening construction solid waste aggregates includes the following steps:

[0064] 1) 80g of nano silica powder and 720g of water were placed in a high-speed shearing machine with a shearing frequency of 2kHz and mixed evenly for 20min. The mixture was then allowed to stand at room temperature for 12h to obtain 800g of nano silica emulsion with a mass fraction of 10%.

[0065] 2) Place 800g of nano-silica emulsion and 600g of construction solid waste aggregate (4.75-9.5mm) in a negative pressure container, and simultaneously turn on the vibration device and evacuate. The negative pressure in the negative pressure container reaches 3.7kPa±0.3kPa within 2 minutes. At the same time, continue to vibrate at 25Hz and 2mm amplitude for 30 minutes. Then take it out and heat it at 30℃ for 12 hours. Finally, place it in an oven at 110℃ for 8 hours to dry the recycled aggregate thoroughly, thus obtaining the reinforced recycled aggregate.

[0066] The recycled aggregates obtained in Examples 1-3 and Comparative Examples 1-4 were subjected to crushing value and other aggregate properties tests, and the surface cement mortar interface thickness of the recycled aggregates in the same batch was tested (50 recycled aggregates from the same batch were selected for each experiment, and the surface cement mortar interface thickness of the aggregates before and after reinforcement was tested, and the average value of the measured thickness was calculated). The original recycled aggregates were used as a blank group. The specific test results are shown in Table 1.

[0067] Table 1. Performance test results of the reinforced recycled aggregates in Examples 1-3 and Comparative Examples 1-3

[0068]

[0069] The above results show that the mechanical properties of the recycled aggregate obtained by using the composite strengthening process described in this invention are significantly improved, the water absorption rate is significantly reduced, the cement mortar interface thickness is significantly reduced, and the technical indicators meet the requirements of the road surface specifications.

[0070] This invention is not limited to the embodiments described above. Those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention. Contents not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A method for strengthening construction solid waste aggregate, characterized in that, Includes the following steps: 1) The polymer emulsion and inorganic nanomaterials are mixed evenly and allowed to stand at room temperature for curing to obtain a composite polymer emulsion; the mixing step adopts a high-speed shearing process, wherein the shearing frequency is 2-4 kHz and the time is 30-40 min; 2) The composite polymer emulsion is mixed with construction solid waste aggregate and vibrated under negative pressure; then cured under normal pressure and dried by heating to obtain reinforced recycled aggregate; the curing temperature is 20-30℃ and the time is 12-24h. The polymer emulsion is one or more of acrylic polymer emulsion, epoxy polymer emulsion, and EVA copolymer emulsion; the inorganic nanomaterial is nano-silica.

2. The strengthening method according to claim 1, characterized in that, The polymer emulsion has a solid content of 10-30%.

3. The strengthening method according to claim 1, characterized in that, The mass ratio of the polymer emulsion to the inorganic nanomaterial is 1:(0.1-0.2).

4. The strengthening method according to claim 1, characterized in that, The room temperature settling time is 6-18 hours.

5. The strengthening method according to claim 1, characterized in that, The construction solid waste aggregate is obtained by crushing, screening and washing construction solid waste, and its particle size is greater than 2.36 mm.

6. The strengthening method according to claim 1, characterized in that, The solid-liquid ratio of the construction solid waste aggregate to the composite polymer emulsion is 1g:1.33-2ml.

7. The strengthening method according to claim 1, characterized in that, The negative pressure condition is 3.4-4 kPa; the vibration frequency used in the vibration composite is 20-40 Hz, the amplitude is 1-4 mm, and the time is 30-40 min.

8. The recycled aggregate obtained by the strengthening method according to any one of claims 1 to 7, characterized in that, Its crushing value is 15-22%, its apparent relative density is 2.6-2.8, and its water absorption rate is 0.5-1.85%.

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