Regenerated mortar durability improving process based on old matrix activation synergistic enhancement

Abstract

The invention discloses a recycled mortar durability improving process based on old matrix activation synergistic enhancement, and belongs to the technical field of mortar preparation. The problems that an existing recycled mortar treatment method is single, and the durability of the recycled mortar is insufficient due to inherent defects of the recycled aggregate are solved, the activity and interface bonding force of the recycled aggregate are improved through the synergistic effect of mechanical activation and chemical activation, and the durability of the recycled mortar is improved through the synergistic effect of interface modification, fiber reinforcement and a nanometer filling material. A multi-scale reinforcing system is formed, the uniformity and strength development of the regenerated mortar are ensured through a two-stage stirring process and staged maintenance, and the durability of the regenerated mortar is remarkably improved through old matrix activation, synergistic reinforcement and optimization of the preparation process.

Description

Technical Field

[0001] The present invention relates to the technical field of mortar preparation, and specifically to a process for improving the durability of recycled mortar based on the activation and synergistic enhancement of old substrates. Background Art

[0002] Traditional methods for treating recycled mortar are single, and due to the inherent defects of recycled aggregates (such as high porosity, many microcracks, and weak interfacial bonding), the durability of recycled mortar is insufficient; therefore, it does not meet the existing requirements, and for this reason, we propose a process for improving the durability of recycled mortar based on the activation and synergistic enhancement of old substrates. Summary of the Invention

[0003] The purpose of the present invention is to provide a process for improving the durability of recycled mortar based on the activation and synergistic enhancement of old substrates. Through the synergistic effect of mechanical activation and chemical activation, the activity and interfacial bonding force of recycled aggregates are improved. Through the synergistic effect of interfacial modification, fiber reinforcement, and nano-fillers, a multi-scale reinforcement system is formed. Then, through a two-stage mixing process and staged curing, the uniformity and strength development of recycled mortar are ensured, solving the problems raised in the above background art.

[0004] To achieve the above purpose, the present invention provides the following technical solution: A process for improving the durability of recycled mortar based on the activation and synergistic enhancement of old substrates, comprising the following steps: Pre-treatment of old substrates: Crushing and screening construction waste to obtain recycled aggregates with a particle size of 1 - 10 mm, and washing the recycled aggregates; Activation of old substrates: Sequentially performing mechanical activation and chemical activation on the recycled aggregates; The mechanical activation includes crushing the recycled aggregates to a particle size ≤ 5 mm, and monitoring and controlling the mechanical activation process; The chemical activation includes soaking in an alkaline activator solution with an activator concentration of 4% - 7% for 24 - 48 hours. After soaking, the recycled aggregates are dried by spray drying, and the drying efficiency of the recycled aggregates under different combinations is evaluated through an efficiency evaluation model; Synergistic enhancement treatment: Performing interfacial modification on the activated recycled aggregates, and adding fiber reinforcement materials and nano-fillers to form a multi-scale reinforcement system; Preparation of recycled mortar: Mixing the treated recycled aggregates with a cementitious material, water, and an admixture in a mass ratio of 1:2:0.4:0.01, stirring evenly, and obtaining recycled mortar with improved durability after standard curing.

[0005] Furthermore, in the pre-treatment step of the old substrates: The crushing and screening adopt multi-stage screening, and the construction waste is classified into recycled aggregates with particle sizes of 1 - 5 mm and 5 - 10 mm; The recycled aggregate is cleaned by ultrasonic cleaning technology for 10 - 20 minutes to remove the tiny impurities and microcracks on the surface of the recycled aggregate; The water content of the cleaned recycled aggregate is controlled within 1% - 3%.

[0006] Furthermore, the mechanical activation includes the following steps: The crushing of the recycled aggregate uses a multi - stage crushing device; The surface roughness of the crushed recycled aggregate is not less than Ra1.5μm; The fine powder of the crushed recycled aggregate is removed by air separation, and the fine powder content is controlled below 5%.

[0007] Furthermore, the mechanical activation process is monitored and controlled, specifically: Based on the laser scanner, the contour information of the recycled aggregate is obtained, and the initial surface roughness of the recycled aggregate is determined based on the contour information; Based on the initial surface roughness, the number of crushing target roughnesses less than the initial surface roughness is determined from the preset multi - stage crushing equipment as the number of crushing levels, and the crushing time for each crushing level is determined based on the volume of the recycled aggregate; The calculation formula for the crushing time is as follows: Where, represents the crushing time of the current crushing level, represents the number of crushing levels, represents the roughness of the recycled aggregate when entering the current crushing level, represents the crushing target roughness of the current crushing level, e represents the natural constant, with a value of 2.72, represents the volume of the recycled aggregate when entering the current crushing level, represents the efficiency coefficient of the current crushing level, represents the standard crushing time; The recycled aggregate is crushed according to the number of crushing levels and the crushing time, and the current surface roughness of the recycled aggregate is monitored in real - time; In the operation of the last crushing level, the crushing of the recycled aggregate is completed until the current surface roughness of the recycled aggregate meets the preset requirements and is not less than Ra1.5μm; Obtain the initial fine powder content of the crushed recycled aggregate, and determine the wind speed level for removing fine powder based on the initial fine powder content and the weight of the recycled aggregate; The calculation formula for the wind speed level is as follows: Where, represents the wind speed level, represents rounding up, represents the initial fine powder content, represents the weight of the recycled aggregate, represents the volume of the recycled aggregate after crushing is completed, represents the energy consumption coefficient of the wind power equipment; The fine powder removal of the recycled aggregate is carried out according to the described wind speed grade.

[0008] Furthermore, the chemical activation includes the following steps: The alkaline activator is sodium hydroxide or sodium silicate; During the soaking process, ultrasonic wave-assisted treatment is adopted, the ultrasonic wave frequency is 20 - 40 kHz, and the treatment time is 10 - 30 minutes; After soaking, the recycled aggregate is dried by spray drying method, the drying temperature is 80 - 100 °C, and it is dried until the moisture content ≤ 1%.

[0009] Furthermore, in the co-enhancement treatment step: The interfacial modification treatment adopts coupling agent coating or impregnation treatment, the coupling agent is silane type or titanate type, and the coating amount is 0.1% - 0.5% of the mass of the recycled aggregate; The fiber reinforcement material is a mixture of polypropylene fiber and carbon fiber, the fiber length is 5 - 20 mm, the mass ratio is 2:1 - 3:1, and the addition amount is 1.0% - 2.0% of the mass of the recycled aggregate; The nano-filling material is a mixture of nano-silica and nano-alumina, the mass ratio is 1:1 - 2:1, and the addition amount is 0.2% - 1.0% of the mass of the recycled aggregate; Among them, before the addition of the nano-filling material, surface modification is carried out with a polycarboxylate modifier; The addition method of the nano-filling material is to add it in batches: For the first time, 50% - 60% of the nano-filling material is added when the recycled aggregate is mixed with the cementitious material; For the second time, the remaining 40% - 50% of the nano-filling material is added during the stirring process.

[0010] Furthermore, in the preparation step of the recycled mortar: The treated recycled aggregate, cementitious material, water and admixture are mixed and stirred according to the mass ratio of 1:2:0.4:0.01; The mixing and stirring adopt a two-stage stirring process, first stir at a low speed for 2 - 5 minutes, and then stir at a high speed for 1 - 3 minutes; The standard curing stage includes early steam curing and later natural curing. Among them, the temperature of the early steam curing is 40 - 60 °C, the time is 6 - 12 hours, and the temperature of the later natural curing is 20 ± 2 °C, and the humidity ≥ 90%; Cure for 7 days under the condition of natural curing in the later stage, and then continue to cure for 21 days in the natural environment, with the total curing time being 28 days.

[0011] Further, the cementitious material is a mixture of ordinary Portland cement, slag powder, and fly ash, and the mass ratio of the three is 60:10:5. Among them, the specific surface area of the slag powder ≥ 400 m² / kg, and the activity index ≥ 95%.

[0012] Further, the admixtures include a high-range water reducer and a retarder. The dosage of the high-range water reducer is 0.5%-1.0% of the mass of the cementitious material, and the dosage of the retarder is 0.1%-0.3% of the mass of the cementitious material.

[0013] Further, the recycled aggregate is dried by spray drying method, specifically: Set the inlet air temperature of the heating device to 80 - 100 °C, and determine the wind speed range, and determine the first energy consumption value corresponding to each wind speed within the wind speed range; Obtain the area of the feed inlet of the drying device, determine the feed rate range based on the feed inlet area, and determine the second energy consumption value corresponding to each feed rate within the feed rate range; Obtain the surface porosity of the recycled aggregate, and determine multiple combinations that meet the preset matching degree between the wind speed range and the feed rate range based on the surface porosity; Establish an efficiency evaluation model based on historical drying data, and determine the drying efficiency value of each combination based on the efficiency evaluation model; Based on the preset drying performance requirements, set an evaluation strategy. Based on the first energy consumption value, the second energy consumption value, and the drying efficiency value of each combination, and in combination with the evaluation strategy, determine the performance evaluation value of each combination; Select the combinations with performance evaluation values greater than the preset evaluation value from multiple combinations as the initial screening combinations, and sort the initial screening combinations in descending order based on the performance evaluation values to obtain a combination sequence; Set the drying parameters according to the order of the combination sequence to dry the recycled aggregate by spray drying method, and monitor the movement state of the recycled aggregate in the drying device in real time. When the sticking to the wall occurs, stop the drying operation and clean it; After the cleaning is completed, select the next combination in the combination sequence as the drying parameter to dry the recycled aggregate. If the sticking to the wall occurs, select the next combination in the combination sequence as the drying parameter to dry the recycled aggregate until the sticking to the wall does not occur, and keep the latest drying parameters unchanged.

[0014] Compared with the prior art, the beneficial effects of the present invention are: Through the synergistic effect of mechanical activation and chemical activation, the present invention can enhance the activity and interfacial bonding force of recycled aggregates. Through interfacial modification, the freeze-thaw resistance of mortar can be improved. The filling of nanomaterials and fiber reinforcement enhance the impermeability of mortar. The preparation of recycled mortar through a two-stage mixing process and staged curing ensures the uniformity and strength development of recycled mortar. Through the above processes of old matrix activation, synergistic enhancement, and optimized preparation process, the durability of recycled mortar is significantly improved. Description of the Drawings

[0015] Figure 1 It is a flowchart of the process for improving the durability of recycled mortar based on the synergistic enhancement of old matrix activation in the present invention. Detailed Embodiments

[0016] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0017] To solve the technical problem that the existing treatment methods for recycled mortar are single, and the durability of recycled mortar is insufficient due to the inherent defects of recycled aggregates (such as high porosity, many microcracks, and weak interfacial bonding), please refer to Figure 1 The following technical solutions are provided in this embodiment: The process for improving the durability of recycled mortar based on the synergistic enhancement of old matrix activation includes the following steps: Old matrix pretreatment: Crushing and screening construction waste to obtain recycled aggregates with a particle size of 1 - 10 mm, and cleaning the recycled aggregates; Old matrix activation: Sequentially performing mechanical activation and chemical activation on the recycled aggregates; The mechanical activation includes crushing the recycled aggregates to a particle size ≤ 5 mm, and monitoring and controlling the mechanical activation process; The chemical activation includes soaking in an alkaline activator solution with an activator concentration of 4% - 7% for 24 - 48 hours. After soaking, the recycled aggregates are dried by spray drying, and the drying efficiency of the recycled aggregates under different combinations is evaluated through an efficiency evaluation model; Synergistic enhancement treatment: Performing interfacial modification on the activated recycled aggregates, and adding fiber reinforcement materials and nano-filling materials to form a multi-scale reinforcement system; Recycled mortar preparation: Mixing the treated recycled aggregates with a cementitious material, water, and admixture in a mass ratio of 1:2:0.4:0.01, stirring evenly, and obtaining recycled mortar with improved durability after standard curing; Among them, in the mass ratio formula of recycled aggregate, cementitious material, water and admixture, the mass of the recycled aggregate is 1, the mass range of the cementitious material can be 1.5 - 2.5, the mass range of water can be 0.3 - 0.5, and the mass range of the admixture can be 0.01 - 0.1.

[0018] The technical effects of the above technical solution are as follows: Through the pretreatment of the old substrate by crushing and screening construction waste, recycled aggregate can be obtained. Through the resource utilization of construction waste, low-carbon environmental protection and sustainable development are achieved. The obtained recycled aggregate is treated by combining mechanical activation and chemical activation, which improves the activity and interfacial bonding performance of the recycled aggregate. At the same time, through interface modification treatment and the construction of a multi-scale reinforcement system, the durability and mechanical properties of the recycled mortar are further improved. Finally, through the two-stage mixing process and staged curing, the recycled mortar with improved durability is obtained, which can effectively extend the service life of the building structure.

[0019] In the pretreatment step of the old substrate: Multi-stage screening is adopted for crushing and screening, and the construction waste is classified into recycled aggregates with particle sizes of 1 - 5 mm and 5 - 10 mm. The recycled aggregate is cleaned by ultrasonic cleaning technology for 10 - 20 minutes to remove the tiny impurities and microcracks on the surface of the recycled aggregate. The moisture content of the cleaned recycled aggregate is controlled within 1% - 3%.

[0020] The technical effects of the above technical solution are as follows: By multi-stage screening, the construction waste is classified into recycled aggregates with particle sizes of 1 - 5 mm and 5 - 10 mm, optimizing the particle size distribution of the recycled aggregate, thereby improving the grading performance of the recycled aggregate. By cleaning the recycled aggregate by ultrasonic cleaning technology, the tiny impurities and microcracks on the surface of the recycled aggregate can be effectively removed, significantly improving the cleanliness and interfacial bonding performance of the recycled aggregate. Controlling the moisture content of the cleaned recycled aggregate within 1% - 3% ensures the uniformity and stability of the recycled aggregate in the subsequent preparation process. The pretreatment of the old substrate not only improves the quality and performance of the recycled aggregate, but also reduces the dependence on natural aggregate, reduces resource consumption and carbon emissions, and provides important technical support for the development of low-carbon buildings and new wall materials.

[0021] Mechanical activation includes the following steps: Multi-stage crushing equipment is used for crushing the recycled aggregate. The surface roughness of the crushed recycled aggregate is not less than Ra1.5 μm. The crushed recycled aggregate is removed of fine powder by air separation, and the fine powder content is controlled below 5%.

[0022] In one embodiment, it further includes: monitoring and controlling the mechanical activation process, specifically: Based on the laser scanner to obtain the contour information of recycled aggregates, and determine the initial surface roughness of recycled aggregates based on the contour information; Determine the number of crushing target roughness levels less than the initial surface roughness from the preset multi-stage crushing equipment, use the numerical value of the number as the number of crushing levels, and determine the crushing time for each crushing level based on the volume of recycled aggregates; The calculation formula for the crushing time is as follows: Wherein, represents the crushing time of the current crushing level, represents the number of crushing levels, represents the roughness when the recycled aggregates enter the current crushing level, represents the crushing target roughness of the current crushing level, e represents the natural constant, with a value of 2.72, represents the volume of recycled aggregates when entering the current crushing level, represents the efficiency coefficient of the current crushing level, represents the standard crushing time; Crush the recycled aggregates according to the number of crushing levels and the crushing time, and monitor the surface roughness of the current recycled aggregates in real time; Complete the crushing of the recycled aggregates until the surface roughness of the current recycled aggregates meets the preset requirements and is not lower than Ra1.5μm during the operation of the last crushing level; Obtain the initial fine powder content of the crushed recycled aggregates, and determine the wind speed level for removing fine powder based on the initial fine powder content and the weight of the recycled aggregates; The calculation formula for the wind speed level is as follows: Wherein, represents the wind speed level, represents rounding up, represents the initial fine powder content, represents the weight of the recycled aggregates, represents the volume of the recycled aggregates after completion of crushing, represents the energy consumption coefficient of the wind power equipment; Remove the fine powder from the recycled aggregates according to the wind speed level.

[0023] In this embodiment, the greater the efficiency coefficient of the current crushing level, the smaller the corresponding crushing time, and the value range of the efficiency coefficient is 0.4 - 0.6.

[0024] In this embodiment, the larger the volume of the recycled aggregates, the larger the corresponding crushing time.

[0025] In this embodiment, the more the number of crushing levels, the finer the corresponding crushing grade, and the relatively longer the crushing operation time. Therefore, the setting of the crushing time for each level can be relatively small.

[0026] In this embodiment, It is set according to historical experience.

[0027] In this embodiment, the energy consumption coefficient of the wind power equipment takes a value of 0.6 - 0.8. The larger the energy consumption coefficient, the higher the corresponding wind speed grade.

[0028] In this embodiment, the standard crushing time is determined based on the average value of the historical crushing time of the recycled aggregate, and on this basis, the crushing time is further refined.

[0029] In this embodiment, the larger the initial surface roughness, the more the number of corresponding crushing levels.

[0030] The beneficial effects of the above design scheme are as follows: By obtaining the contour information of the recycled aggregate based on a laser scanner, the initial surface roughness of the recycled aggregate is determined based on the contour information; Based on the initial surface roughness, the number of crushing target roughnesses smaller than the initial surface roughness is determined from a preset multi-level crushing device as the number of crushing levels, and the crushing time for each crushing level is determined based on the volume of the recycled aggregate. When calculating the crushing time, parameters such as the efficiency coefficient and historical time setting are considered to ensure that while the obtained crushing time meets the requirements, the energy consumption requirement is reduced. Then, in the operation of the last crushing level until the current surface roughness of the recycled aggregate meets the preset requirements and is not lower than Ra1.5μm, the crushing of the recycled aggregate is completed, and the initial fine powder content of the crushed recycled aggregate is obtained. Based on the initial fine powder content and the weight of the recycled aggregate, the wind speed grade for removing fine powder is determined. When determining the wind speed grade, the ratio of weight to volume and the energy consumption coefficient are considered to ensure that while the obtained wind speed grade completes the task, the energy consumption requirement is reduced, and finally, the reasonable mechanical activation of the recycled aggregate is realized, providing a basis for further chemical activation and process improvement.

[0031] Chemical activation includes the following steps: The alkaline activator is sodium hydroxide or sodium silicate; During the soaking process, ultrasonic wave-assisted treatment is adopted. The ultrasonic wave frequency is 20 - 40 kHz, and the treatment time is 10 - 30 minutes; After soaking, the recycled aggregate is dried by spray drying. The drying temperature is 80 - 100°C, and it is dried until the moisture content ≤ 1%.

[0032] The technical effects of the above technical solution are as follows: In mechanical activation, the recycled aggregate is crushed to a particle size of ≤5 mm by a multi-stage crushing device, significantly improving the activity and interfacial bonding performance of the recycled aggregate. And by removing fine powder through air separation, the cleanliness and uniformity of the aggregate are further optimized. In chemical activation, sodium hydroxide or sodium silicate is used as an alkaline activator, and ultrasonic-assisted treatment is adopted, which can significantly enhance the chemical activity of the recycled aggregate. After soaking, spray drying is used to ensure the drying uniformity and low moisture content of the recycled aggregate, providing excellent physical and chemical conditions for subsequent preparation.

[0033] In the co-enhancement treatment step: For the interfacial modification treatment, coupling agent coating or impregnation treatment is adopted. The coupling agent is a silane-based or titanate-based coupling agent, and the coating amount is 0.1%-0.5% of the mass of the recycled aggregate; The fiber reinforcement material is a mixture of polypropylene fiber and carbon fiber. The fiber length is 5-20 mm, the mass ratio is 2:1-3:1, and the addition amount is 1.0%-2.0% of the mass of the recycled aggregate; The nano-filler material is a mixture of nano-silica and nano-alumina. The mass ratio is 1:1-2:1, and the addition amount is 0.2%-1.0% of the mass of the recycled aggregate Among them, before the addition of the nano-filler material, surface modification is carried out using a polycarboxylate modifier; The addition method of the nano-filler material is to add it in batches: For the first time, 50%-60% of the nano-filler material is added when the recycled aggregate is mixed with the cementitious material; For the second time, the remaining 40%-50% of the nano-filler material is added during the stirring process.

[0034] The technical effects of the above technical solution are as follows: The interfacial modification treatment uses a silane-based or titanate-based coupling agent to coat or impregnate the recycled aggregate, significantly improving the interfacial bonding performance between the aggregate and the cementitious material, reducing interfacial defects, and improving the overall strength and durability of the recycled mortar. The addition of the fiber reinforcement material effectively inhibits the propagation of microcracks in the recycled mortar, significantly improving the crack resistance and impact resistance. The addition of the nano-filler material significantly improves the compactness and impermeability of the mortar. At the same time, surface modification of the nano-filler material with a polycarboxylate modifier enhances its dispersibility and reactivity.

[0035] In summary, the co-enhancement treatment significantly improves the compressive strength, crack resistance and durability of the recycled mortar, enabling it to meet the requirements of high-performance building structures. Through resource recycling and multi-scale reinforcement technology, this process not only reduces the environmental burden of construction waste, but also reduces the dependence on natural resources.

[0036] In the preparation step of the recycled mortar: Mix the processed recycled aggregate with the cementitious material, water and admixture according to the mass ratio of 1:2:0.4:0.01 and stir; The mixing and stirring adopt a two-stage stirring process, first stir at a low speed for 2 - 5 minutes, and then stir at a high speed for 1 - 3 minutes; The standard curing stage includes early steam curing and later natural curing, specifically: The temperature of the early steam curing is 40 - 60 °C, and the time is 6 - 12 hours, which accelerates the cement hydration reaction and significantly improves the early strength; The temperature of the later natural curing is 20 ± 2 °C, and the humidity ≥ 90%, ensuring the long-term stability and durability of the recycled mortar; Cure for 7 days under the conditions of the later natural curing, and then continue to cure in the natural environment for 21 days, and the total curing time is 28 days; Among them, the cementitious material is a mixture of ordinary Portland cement, slag powder and fly ash, and the mass ratio of the three is 60:10:5. Among them, the mass range of the ordinary Portland cement can be 60 - 80, the mass range of the slag powder can be 10 - 30, and the mass range of the fly ash can be 5 - 15. The specific surface area of the slag powder ≥ 400 m² / kg, and the activity index ≥ 95%. It not only improves the strength and durability of the recycled mortar, but also reduces the cement consumption and carbon emissions; The admixtures include a high-range water reducer and a retarder. The dosage of the high-range water reducer is 0.5% - 1.0% of the mass of the cementitious material, and the dosage of the retarder is 0.1% - 0.3% of the mass of the cementitious material, further optimizing the workability and strength development of the recycled mortar and ensuring the balance of the construction performance and the final performance.

[0037] The technical effects of the above technical solutions are as follows: Adopt a two-stage stirring process, mix and stir the processed recycled aggregate with the cementitious material, water and admixture according to the mass ratio, ensuring the uniform mixing and full reaction of the materials, improving the compactness and strength of the recycled mortar. In the curing stage, adopt staged curing. The early steam curing accelerates the cement hydration reaction, enabling the recycled mortar to obtain high early strength in a short time, meeting the requirements of rapid construction and early load-bearing. The later natural curing provides a suitable environment for the later hydration reaction of the cement, ensuring the continuous and stable growth of the strength of the recycled mortar.

[0038] In one embodiment, the recycled aggregate is dried by spray drying method, specifically: Set the inlet air temperature of the heating device to 80 - 100 °C, and determine the wind speed range, and determine the first energy consumption value corresponding to each wind speed in the wind speed range; Obtain the feeding port area of the drying device, determine the feeding speed range based on the feeding port area, and determine the second energy consumption value corresponding to each feeding speed in the feeding speed range; Obtain the surface porosity of the recycled aggregate, and determine multiple combinations that meet a preset matching degree between the wind speed range and the feeding speed range based on the surface porosity; Establish an efficiency evaluation model based on historical drying data, and determine the drying efficiency value of each combination based on the efficiency evaluation model; Based on the preset drying performance requirements, set an evaluation strategy. Based on the first energy consumption value, the second energy consumption value, and the drying efficiency value of each combination, and in combination with the evaluation strategy, determine the performance evaluation value of each combination; Select the combinations with performance evaluation values greater than the preset evaluation value from the multiple combinations as the initial screening combinations, and sort the initial screening combinations in descending order of the performance evaluation values to obtain a combination sequence; Set the drying parameters according to the order of the combination sequence, and use the spray drying method to dry the recycled aggregate. Real-time monitor the movement state of the recycled aggregate in the drying device. When the sticking to the wall occurs, stop the drying operation and perform cleaning; After the cleaning is completed, select the next combination in the combination sequence as the drying parameter to dry the recycled aggregate. If the sticking to the wall occurs, select the next combination in the combination sequence as the drying parameter to dry the recycled aggregate until the sticking to the wall does not occur, and keep the latest drying parameter unchanged.

[0039] In this embodiment, each wind speed in the wind speed range corresponds to a first energy consumption value, and the first energy consumption value is the consumption value of the heating device.

[0040] In this embodiment, each feeding speed in the feeding speed range corresponds to a second energy consumption value, and the second energy consumption value is the consumption value of the drying device.

[0041] In this embodiment, different surface porosities result in different matching degrees of the flow rate brought by the feeding speed and the wind speed. The standard of the matching degree is determined according to the contact situation between the flow rate and the fed recycled aggregate.

[0042] In this embodiment, the efficiency evaluation model is used to evaluate the drying efficiency of the recycled aggregate under different combinations.

[0043] In this embodiment, based on the preset drying performance requirements, set an evaluation strategy. Different preset drying performance requirements correspond to different evaluation strategies. The evaluation strategy is mainly to set the weights of the first energy consumption value, the second energy consumption value, and the drying efficiency value to determine the final evaluation value.

[0044] The beneficial effects of the above design are as follows: By determining the combination of feeding speed and wind speed that meets the requirements based on the contact situation between the flow rate and the feeding recycled aggregate with respect to the feeding speed and wind speed, and screening the combination of feeding speed and wind speed from the aspects of energy consumption and drying efficiency to obtain the candidate screening combinations, ensuring that the obtained drying parameters meet the performance requirements of the drying process. Then, based on the wall sticking situation, analyze the effect of each combination in the candidate screening combinations on the drying quality, and select the drying parameter combination with the best performance without wall sticking as the final drying parameter, ensuring the performance and quality requirements for the drying of recycled aggregate, and providing a basis for improving the activity and interfacial bonding strength.

[0045] The technical solutions of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0046] Example 1 S1: Pretreatment of the old matrix Crush and screen construction waste (such as waste concrete blocks) at multiple levels, and classify to obtain recycled aggregates with particle sizes of 1 - 5 mm and 5 - 10 mm; Use ultrasonic cleaning technology to clean the recycled aggregates for 15 minutes to remove the tiny impurities and microcracks on the surface of the recycled aggregates. After cleaning, the moisture content of the recycled aggregates is controlled at 2%; S2: Activation of the old matrix Mechanical activation: Crush the recycled aggregates through a multi-level crushing device to a particle size ≤5 mm; The surface roughness of the crushed recycled aggregates reaches Ra1.5 μm; Remove fine powder by air separation, and control the fine powder content below 5%; Chemical activation: Immerse the mechanically activated recycled aggregates in a sodium hydroxide solution with a concentration of 5% for 36 hours; During the immersion process, use ultrasonic wave-assisted treatment with an ultrasonic frequency of 30 kHz and a treatment time of 20 minutes; After immersion, use spray drying method for drying at a drying temperature of 90°C until the moisture content ≤1%; S3: Synergistic enhancement treatment Interface modification treatment: Impregnate the activated recycled aggregates with a silane coupling agent, and the coating amount of the coupling agent is 0.3% of the mass of the recycled aggregates; Fiber reinforcing material: Add a mixture of polypropylene fibers and carbon fibers with a fiber length of 10 mm, a mass ratio of 2:1, and an addition amount of 1.5% of the mass of the recycled aggregates; Nanofiller: The nanofiller is a mixture of nano-silica and nano-alumina with a mass ratio of 1:1, and the addition amount is 0.5% of the mass of the recycled aggregate; Before addition, the nanofiller is surface-modified with a polycarboxylate modifier; The nanofiller is added in two times: 55% of the nanofiller is added when the recycled aggregate is mixed with the cementitious material for the first time; the remaining 45% of the nanofiller is added during the mixing process for the second time; S4: Preparation of recycled mortar Material ratio: Treated recycled aggregate: 100 kg; Cementitious material (ordinary Portland cement, slag powder, fly ash are mixed according to a mass ratio of 70:20:10): 200 kg; Water: 40 kg; Admixtures (the dosage of the high-range water reducer is 0.8% of the mass of the cementitious material, and the dosage of the retarder is 0.2% of the mass of the cementitious material): 0.8 kg (high-range water reducer) + 0.2 kg (retarder); Mixing process: A two-stage mixing process is adopted: first, mix at a low speed for 3 minutes, and then mix at a high speed for 2 minutes; Curing: Early steam curing: Temperature 50°C, time 8 hours; Late natural curing: Temperature 20±2°C, humidity ≥90%, after curing for 7 days, continue to cure in the natural environment for 21 days, and the total curing time is 28 days.

[0047] After testing, the 28-day compressive strength reaches 35 MPa, which is 25% higher than that of the untreated recycled mortar, and the impermeability grade reaches P12, which is 3 grades higher than that of the untreated recycled mortar.

[0048] Example 2 S1: Pretreatment of the old substrate The construction waste (such as waste concrete blocks) is subjected to multi-stage crushing and screening, and recycled aggregates with particle sizes of 1-5 mm and 5-10 mm are obtained by classification; The recycled aggregates are cleaned by ultrasonic cleaning technology for 20 minutes to remove the tiny impurities and microcracks on the surface of the recycled aggregates. The moisture content of the recycled aggregates after cleaning is controlled at 1.5%; S2: Activation of the old substrate Mechanical activation: The recycled aggregates are crushed by a multi-stage crushing equipment to a particle size ≤5 mm; The surface roughness of the crushed aggregates reaches Ra1.5 μm; The fine powder is removed by air separation, and the fine powder content is controlled below 5%; Chemical activation: Soak the mechanically activated recycled aggregate in a sodium silicate solution with a concentration of 6% for 48 hours; During the soaking process, ultrasonic assistance is used, with an ultrasonic frequency of 40 kHz and a treatment time of 30 minutes; After soaking, spray drying is used for drying, with a drying temperature of 80 °C until the moisture content ≤ 1%; S3: Synergistic enhancement treatment Interface modification treatment: Coat the activated recycled aggregate with a titanate coupling agent, and the coating amount of the coupling agent is 0.5% of the mass of the recycled aggregate; Fiber reinforcing material: Add a mixture of polypropylene fibers and carbon fibers, with a fiber length of 15 mm, a mass ratio of 3:1, and an addition amount of 2.0% of the mass of the recycled aggregate; Nanoparticle filler material: The nanoparticle filler material is a mixture of nano-silica and nano-alumina, with a mass ratio of 2:1, and an addition amount of 1.0% of the mass of the recycled aggregate; Before addition, surface modification of the nanoparticle filler material is carried out using a polycarboxylate modifier; The nanoparticle filler material is added in two times: 60% of the nanoparticle filler material is added when the recycled aggregate is mixed with the cementitious material for the first time; the remaining 40% of the nanoparticle filler material is added during the mixing process for the second time; S4: Preparation of recycled mortar Material ratio: Treated recycled aggregate: 100 kg; Cementitious material (ordinary Portland cement, granulated blast-furnace slag powder, fly ash are mixed in a mass ratio of 60:30:10): 250 kg; Water: 50 kg; Admixtures (the dosage of the high-range water reducer is 1.0% of the mass of the cementitious material, and the dosage of the retarder is 0.3% of the mass of the cementitious material): 1.0 kg (high-range water reducer) + 0.3 kg (retarder); Mixing process: Adopt a two-stage mixing process: First, mix at a low speed for 5 minutes, and then mix at a high speed for 3 minutes; Curing: Early steam curing: Temperature 60 °C, time 12 hours; Late natural curing: Temperature 20 ± 2 °C, humidity ≥ 90%, after curing for 7 days, continue to cure in the natural environment for 21 days, and the total curing time is 28 days.

[0049] After testing, the 28-day compressive strength reaches 40 MPa, which is 30% higher than that of the untreated recycled mortar, and the impermeability grade reaches P14, which is 4 grades higher than that of the untreated recycled mortar.

[0050] Example 3 S1: Pretreatment of the old matrix Crush and screen construction waste (such as waste concrete blocks) at multiple levels, and classify to obtain recycled aggregates with particle sizes of 1 - 5 mm and 5 - 10 mm; Use ultrasonic cleaning technology to clean the recycled aggregates for 10 minutes to remove tiny impurities and microcracks on the surface of the recycled aggregates. Control the moisture content of the recycled aggregates after cleaning at 1%; S2: Activation of the old matrix Crush the recycled aggregates through a multi-level crushing device to a particle size ≤ 5 mm; The surface roughness of the crushed recycled aggregates reaches Ra1.5 μm; Remove fine powder by air separation, and control the fine powder content below 5%; Chemical activation: Immerse the mechanically activated recycled aggregates in a 4% concentration sodium hydroxide solution for 24 hours; During the immersion process, use ultrasonic assisted treatment with an ultrasonic frequency of 20 kHz and a treatment time of 10 minutes; After immersion, use spray drying method for drying at a drying temperature of 100 °C until the moisture content ≤ 1%; S3: Synergistic enhancement treatment Interface modification treatment: Use silane coupling agent to impregnate the activated recycled aggregates, and the coating amount of the coupling agent is 0.1% of the mass of the recycled aggregates; Fiber reinforced material: Add a mixture of polypropylene fiber and carbon fiber with a fiber length of 5 mm and a mass ratio of 2:1, and the addition amount is 1.0% of the mass of the recycled aggregates; Nanoparticle filling material: The nanoparticle filling material is a mixture of nano-silica and nano-alumina with a mass ratio of 1:1, and the addition amount is 0.2% of the mass of the recycled aggregates; Before adding, use a polycarboxylate modifier to modify the surface of the nanoparticle filling material; Add the nanoparticle filling material in two times: Add 50% of the nanoparticle filling material when mixing the recycled aggregates and the cementitious material for the first time; Add the remaining 50% of the nanoparticle filling material during the stirring process for the second time; S4: Preparation of recycled mortar Material ratio: Treated recycled aggregates: 100 kg; Cementitious material (ordinary Portland cement, slag powder, fly ash are mixed according to a mass ratio of 80:10:10): 150 kg; Water: 30 kg; Admixtures (the dosage of high-range water reducer is 0.5% of the mass of the cementitious material, and the dosage of retarder is 0.1% of the mass of the cementitious material): 0.5 kg (high-range water reducer) + 0.1 kg (retarder); Mixing process: Adopt a two-stage mixing process: first mix at low speed for 2 minutes, and then mix at high speed for 1 minute Curing: Early steam curing: temperature 40°C, time 6 hours; Late natural curing: temperature 20 ± 2°C, humidity ≥ 90%. After curing for 7 days, continue to cure in the natural environment for 21 days, and the total curing time is 28 days.

[0051] After testing, the 28-day compressive strength reaches 30 MPa, which is 20% higher than that of the untreated recycled mortar, and the impermeability grade reaches P10, which is 2 grades higher than that of the untreated recycled mortar.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions for improving the durability of recycled mortar of the present invention, rather than limiting it. By adjusting the process parameters of the pretreatment, activation, synergistic enhancement treatment of the old matrix and the preparation of recycled mortar, it is also possible to improve the recycled mortar of any other strength grade. The technical solutions of the present invention have wide applicability and flexibility, and the parameters can be adjusted according to actual needs to meet the performance requirements of different application scenarios.

[0053] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0054] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. Process for improving the durability of recycled mortar based on the synergistic enhancement of activation of an old matrix, characterized in that, It includes the following steps: Pre-treatment of the old substrate: Crushing and screening construction waste to obtain recycled aggregates with a particle size of 1 - 10 mm, and cleaning the recycled aggregates; Activation of the old substrate: Sequentially performing mechanical activation and chemical activation on the recycled aggregates; The mechanical activation includes crushing the recycled aggregates to a particle size ≤ 5 mm, and monitoring and controlling the mechanical activation process; The chemical activation includes soaking in an alkaline activator solution with an activator concentration of 4% - 7% for 24 - 48 hours. After soaking, the recycled aggregates are dried by spray drying, and the drying efficiency of the recycled aggregates under different combinations is evaluated through an efficiency evaluation model; Synergistic enhancement treatment: Performing interfacial modification on the activated recycled aggregates, and adding fiber reinforcement materials and nano-filler materials to form a multi-scale reinforcement system; Preparation of recycled mortar: Mixing the treated recycled aggregates with a cementitious material, water, and admixture in a mass ratio of 1:2:0.4:0.01, stirring evenly, and obtaining recycled mortar with improved durability after standard curing.

2. The durability improvement process of recycled mortar based on the synergistic enhancement of old matrix activation according to claim 1, characterized in that: In the pre-treatment step of the old substrate: The crushing and screening adopt multi-stage screening to classify the construction waste into recycled aggregates with particle sizes of 1 - 5 mm and 5 - 10 mm; The ultrasonic cleaning technology is used to clean the recycled aggregates for 10 - 20 minutes to remove the tiny impurities and micro-cracks on the surface of the recycled aggregates; The water content of the cleaned recycled aggregates is controlled at 1% - 3%.

3. The durability improvement process of recycled mortar based on the synergistic enhancement of old matrix activation according to claim 1, characterized in that: The mechanical activation includes the following steps: The crushing of the recycled aggregates adopts multi-stage crushing equipment; The surface roughness of the crushed recycled aggregates is not lower than Ra1.5 μm; The fine powder in the crushed recycled aggregates is removed by air separation, and the fine powder content is controlled below 5%.

4. The durability improvement process of recycled mortar based on the synergistic enhancement of old matrix activation according to claim 3, wherein: It also includes: Monitoring and controlling the mechanical activation process, specifically: Obtaining the contour information of the recycled aggregates based on a laser scanner, and determining the initial surface roughness of the recycled aggregates based on the contour information; Determining the number of crushing target roughness levels smaller than the initial surface roughness from the preset multi-stage crushing equipment, taking the value of the number as the number of crushing levels, and determining the crushing time for each crushing level based on the volume of the recycled aggregates; Crushing the recycled aggregates according to the number of crushing levels and the crushing time, and real-time monitoring the current surface roughness of the recycled aggregates; Completing the crushing of the recycled aggregates until the current surface roughness of the recycled aggregates meets the preset requirements and is not lower than Ra1.5 μm during the operation of the last crushing level; Obtaining the initial fine powder content of the crushed recycled aggregates, and determining the wind speed level for removing fine powder based on the initial fine powder content and the weight of the recycled aggregates; Removing the fine powder from the recycled aggregates according to the wind speed level.

5. The durability improvement process of recycled mortar based on the synergistic enhancement of old matrix activation as claimed in claim 1, characterized in that: The chemical activation includes the following steps: The alkaline activator is sodium hydroxide or sodium silicate; Ultrasonic-assisted treatment is adopted during the soaking process, with an ultrasonic frequency of 20 - 40 kHz and a treatment time of 10 - 30 minutes; After soaking, the recycled aggregates are dried by spray drying at a drying temperature of 80 - 100 °C until the water content ≤ 1%.

6. The durability improvement process of recycled mortar based on the synergistic enhancement of old matrix activation according to claim 1, characterized in that: In the collaborative enhancement treatment step: for the interface modification treatment, coupling agent coating or impregnation treatment is adopted. The coupling agent is of the silane type or titanate type, and the coating amount is 0.1% - 0.5% of the mass of the recycled aggregate; The fiber reinforcing material is a mixture of polypropylene fiber and carbon fiber. The fiber length is 5 - 20 mm, the mass ratio is 2:1 - 3:1, and the addition amount is 1.0% - 2.0% of the mass of the recycled aggregate; The nano - filling material is a mixture of nano - silica and nano - alumina. The mass ratio is 1:1 - 2:1, and the addition amount is 0.2% - 1.0% of the mass of the recycled aggregate; Among them, before the addition of the nano - filling material, surface modification is carried out using a polycarboxylate modifier; The addition method of the nano - filling material is to add it in batches: For the first time, 50% - 60% of the nano - filling material is added when the recycled aggregate is mixed with the cementitious material; For the second time, the remaining 40% - 50% of the nano - filling material is added during the stirring process.

7. The durability improvement process of recycled mortar based on the synergistic enhancement of old matrix activation as claimed in claim 1, wherein: In the step of preparing the recycled mortar: The treated recycled aggregate, cementitious material, water and admixture are mixed and stirred according to the mass ratio of 1:2:0.4:0.01; The mixing and stirring adopt a two - stage stirring process. First, stir at a low speed for 2 - 5 minutes, and then stir at a high speed for 1 - 3 minutes; The standard curing stage includes early steam curing and later natural curing. Among them, the temperature of the early steam curing is 40 - 60 °C, the time is 6 - 12 hours, and the temperature of the later natural curing is 20 ± 2 °C, and the humidity ≥ 90%; Cure for 7 days under the conditions of later natural curing, and then continue to cure for 21 days in the natural environment. The total curing time is 28 days.

8. The durability improvement process of recycled mortar based on the synergistic enhancement of old matrix activation according to claim 7, characterized in that: The cementitious material is a mixture of ordinary Portland cement, slag micro - powder and fly ash. The mass ratio of the three is 60:10:

5. Among them, the specific surface area of the slag micro - powder ≥ 400 m² / kg, and the activity index ≥ 95%.

9. The durability improvement process of recycled mortar based on the synergistic enhancement of old matrix activation as claimed in claim 7, wherein: The admixture includes a water - reducing agent and a retarder. The dosage of the water - reducing agent is 0.5% - 1.0% of the mass of the cementitious material, and the dosage of the retarder is 0.1% - 0.3% of the mass of the cementitious material.

10. The durability improvement process of recycled mortar based on the synergistic enhancement of old matrix activation as claimed in claim 5, wherein: The recycled aggregate is dried by spray drying method. Specifically: Set the inlet air temperature of the heating device to 80 - 100 °C, and determine the wind speed range, and determine the first energy consumption value corresponding to each wind speed in the wind speed range; Obtain the feed inlet area of the drying device, determine the feed speed range based on the feed inlet area, and determine the second energy consumption value corresponding to each feed speed in the feed speed range; Obtain the surface porosity of the recycled aggregate, and determine multiple combinations that meet the preset matching degree between the wind speed range and the feed speed range based on the surface porosity; Establish an efficiency evaluation model based on historical drying data, and determine the drying efficiency value of each combination based on the efficiency evaluation model; Based on the preset drying performance requirements, set an evaluation strategy. Based on the first energy consumption value, the second energy consumption value and the drying efficiency value of each combination, and combined with the evaluation strategy, determine the performance evaluation value of each combination; Select the combination with the performance evaluation value greater than the preset evaluation value from multiple combinations as the initial screening combination, and sort the initial screening combination in descending order of the performance evaluation value to obtain a combination sequence; Set the drying parameters according to the order of the described combination sequence, and use spray drying method to dry the recycled aggregate. Monitor the movement state of the recycled aggregate in the drying device in real time. When the situation of sticking to the wall occurs, stop the drying operation and carry out cleaning; After the cleaning is completed, select the next combination in the combination sequence as the drying parameter to dry the recycled aggregate. If the situation of sticking to the wall occurs, select the next combination in the combination sequence as the drying parameter to dry the recycled aggregate in turn until the situation of sticking to the wall does not occur, and keep the latest drying parameter unchanged.

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