Degradable green high-performance concrete and preparation method thereof

Abstract

The invention belongs to the technical field of building materials, particularly discloses degradable green high-performance concrete and a preparation method thereof, and aims to solve the problems that existing degradable concrete is insufficient in strength and durability, uncontrollable in degradation rate and poor in working performance. The concrete is prepared from Portland cement, blast furnace slag micro powder, fly ash, modified bio-based polymer particles, natural and recycled aggregate, nano silicon dioxide, cellulose ether, a polycarboxylic acid type water reducing agent and a pH response type degradation accelerant. The preparation method comprises the following steps: mechanical activation and pickling of the recycled aggregate, surface coating of polymer particles, premixing of dry powder, introduction of the polymer by wet stirring, doping and mixing of the aggregate, and carbonization curing. By the adoption of the technical scheme, the high performance that the 28-day compressive strength exceeds 50 MPa and the chloride ion diffusion coefficient is as low as 3 * 10 square meters per second can be achieved, the 180-day mass loss rate in the acid environment is larger than 50%, degradation is controllable, and environment friendliness is achieved.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a biodegradable green high-performance concrete and its preparation method. Background Technology

[0002] With the deepening of global sustainable development strategies, the research and development of green building materials has become an important direction in the field of civil engineering. Concrete, as the most widely used engineering material, relies on energy-intensive cement and non-renewable aggregates in its traditional formulations. This not only results in high carbon emissions but also makes it difficult to degrade naturally after disposal, causing a serious environmental burden over time. Against this backdrop, developing new concrete materials that combine mechanical properties with environmental friendliness has become a key breakthrough for achieving a low-carbon transformation in the construction industry. Among these, biodegradable concrete, by introducing bio-based or environmentally responsive components, aims to achieve controlled decomposition after its service life, thereby reducing the lasting impact of construction waste on the ecosystem.

[0003] However, existing biodegradable concrete generally suffers from significantly lower strength and durability compared to traditional concrete, making it difficult to meet the basic requirements of structural engineering for load-bearing capacity and long-term stability. Furthermore, most degradation mechanisms rely on specific environmental conditions (such as high humidity or microbial enrichment), and the degradation rate is uncontrollable in normal use environments, easily leading to premature material deterioration or prolonged retention. In addition, existing preparation processes often sacrifice workability for degradation characteristics, increasing construction difficulty, insufficient density, and consequently leading to increased crack sensitivity and further reduction in durability.

[0004] Therefore, there is an urgent need for a green high-performance concrete and its preparation method that can achieve stable and reliable performance during service life and efficient and controllable degradation after service life, while ensuring high strength and good construction performance. Summary of the Invention

[0005] The purpose of this invention is to provide a biodegradable green high-performance concrete and its preparation method, which can effectively solve the problems mentioned in the background art, such as insufficient strength and durability of existing biodegradable concrete, uncontrollable degradation rate, and decreased workability due to preparation process.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A biodegradable green high-performance concrete and its preparation method, comprising the following specific steps: Step 1: Raw material preparation and pretreatment, by weight, prepare 30 to 50 parts of silicate cement, 15 to 25 parts of blast furnace slag powder, 10 to 20 parts of fly ash, 5 to 15 parts of modified bio-based polymer particles, 40 to 60 parts of natural aggregate, 20 to 30 parts of recycled aggregate, 2 to 5 parts of nano-silica, 0.1 to 0.5 parts of cellulose ether, 0.5 to 1.5 parts of polycarboxylate superplasticizer, and 1 to 3 parts of pH-responsive degradation promoter; mechanically activate and acid-wash the recycled aggregate to remove surface deposits and improve its surface roughness and activity; perform surface coating treatment on the modified bio-based polymer particles to form a slow-release layer with a thickness of 1 to 5 micrometers; Step 2: Dry powder premixing. The silicate cement, blast furnace slag powder, fly ash, nano-silica, and cellulose ether are added to a forced mixer and dry-mixed at 30-50 rpm for 3-5 minutes to ensure uniform dispersion of each component. Step 3: Wet mixing and polymer introduction. 70-80% of the total water volume is slowly added to the dry powder mixture obtained in Step 2, along with the polycarboxylate superplasticizer. The mixer is started and stirred at 60-80 rpm for 2-4 minutes. Subsequently, the modified bio-based polymer particles and pH-responsive degradation accelerator are added in batches, and stirring continues for 3-5 minutes to form a uniform slurry. Step 4: Aggregate incorporation and final mixing. The pretreated natural and recycled aggregates are added to the slurry obtained in Step 3, along with the remaining water. The mixer speed is increased to 80-100 rpm, and stirring continues for 5-8 minutes until a concrete mixture with good workability and no segregation or bleeding is obtained. Step 5: Molding and Curing. The concrete mixture is poured into a mold and vibrated for 30 to 60 seconds using a vibrating table with a frequency of 50 Hz and an amplitude of 0.5 mm. The molded specimen is then placed in a standard curing room with a temperature of 20 ± 2 degrees Celsius and a relative humidity of ≥ 95% for 24 to 48 hours. After demolding, the specimen is transferred to a carbonation curing chamber with a temperature of 60 degrees Celsius and a carbon dioxide concentration of 20% for accelerated carbonation curing for 7 to 14 days, finally obtaining the biodegradable green high-performance concrete.

[0007] Preferably, the modified bio-based polymer particles in step 1 are a blend of polylactic acid and polyhydroxyalkanoates, wherein the mass percentage of polylactic acid is 60% to 80% and the mass percentage of polyhydroxyalkanoates is 20% to 40%; the particle size distribution is 0.1 mm to 1.0 mm, and the slow-release layer coated on its surface is composed of biodegradable polycaprolactone and calcium stearate in a mass ratio of 8:2. Preferably, the pH-responsive degradation promoter in step 1 is a solid particle composed of citric acid and sodium bicarbonate in a mass ratio of 1:1.5, with a particle size range of 0.05 mm to 0.2 mm. This promoter begins to slowly release carbon dioxide gas and generate organic acid ions when the ambient pH value is below 6.5. Preferably, the mechanical activation treatment of the recycled aggregate in step 1 uses a vertical impact crusher, with a processing time of 5 to 10 minutes and an impact speed of 40 meters per second; the acid washing treatment uses a 5% hydrochloric acid solution, soaking time of 30 minutes, followed by rinsing with water until neutral and drying. Preferably, in step 2, the forced mixer has a capacity of 0.5 cubic meters, and the gap between the mixing blades and the liner is 3 mm to ensure no dead zones in the mixing process; during dry mixing, the material temperature is controlled between 15°C and 35°C. Preferably, in step 3, during wet mixing, water is added using atomized spraying, with water droplet diameter less than 100 micrometers; the polycarboxylate superplasticizer has a solid content of 40% and a water reduction rate greater than or equal to 30%. Preferably, in step 4, the natural aggregate is continuously graded crushed stone with a maximum particle size not exceeding 20 mm and a crushing index less than or equal to 10%; the recycled aggregate is obtained from construction waste concrete through crushing and screening, with a particle size of 5 mm to 15 mm and a water absorption rate controlled within 5%. Preferably, the carbonation curing chamber in step 5 is equipped with a gas circulation system to ensure uniform carbon dioxide concentration distribution with fluctuations not exceeding ±2%. During the curing process, the compressive strength gain of the specimen is monitored every 24 hours. Carbonation curing can be terminated early when the 7-day strength reaches 80% of the design strength. Preferably, the slump of the concrete mixture is controlled between 180 mm and 220 mm, the spread is greater than or equal to 500 mm, and the slump loss in 2 hours is less than 30 mm to meet the requirements of pumping construction. Preferably, the biodegradable green high-performance concrete achieves a compressive strength of over 50 MPa and a flexural strength of over 5 MPa under standard curing conditions after 28 days, with a chloride ion diffusion coefficient of less than 3 x 10^-12 square meters per second. When it reaches the end of its service life and is placed in an acidic water environment with a pH value less than 6.0, the mass loss rate within 180 days is greater than 50%, and the degradation products are non-toxic to the environment.Preferably, the preparation method further includes monitoring the degradation process. A pH sensor and strain gauge pre-embedded inside the concrete are used to monitor changes in pH and volumetric strain within the concrete in real time. When the pH value remains below 6.5 and the volume expansion rate exceeds 0.1%, the degradation process is considered to have started. Before pre-embedding, the pH sensor and strain gauge undergo multi-layer encapsulation: first, the sensor chip is encapsulated in a special ceramic or glass shell resistant to strong alkalis (pH>13); second, the leads are made of corrosion-resistant platinum or titanium alloy wires and are led out using glass-metal sealing technology; finally, the entire sensor unit is wrapped with a flexible epoxy resin buffer layer that is compatible with concrete. The sensor's power supply and data transmission utilize energy harvesting technology and a low-power Bluetooth module to ensure long-term operation without an external power source. Preferably, the method is suitable for precast component production lines, employing automated batching systems and robotic arms for material distribution and vibration. A single production cycle does not exceed 45 minutes, and the product qualification rate is greater than or equal to 98%.

[0008] Compared with existing technologies, this invention has the following beneficial effects: By optimizing the raw material ratio and introducing modified bio-based polymer particles and pH-responsive degradation promoters, while ensuring the high strength and high durability of concrete, it achieves stable performance during the service life and controllable and efficient degradation after the service life ends; by adopting specific pretreatment processes and multi-stage curing systems, it significantly improves the utilization rate of recycled aggregates and the early strength development of concrete, improves the workability of the mixture, and reduces crack sensitivity; the entire preparation process is green and environmentally friendly, effectively reducing cement consumption and carbon emissions, providing a feasible technical path for solving the construction waste problem. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the overall technical solution architecture of the biodegradable green high-performance concrete and its preparation method proposed in this invention. Figure 2 This is a schematic diagram illustrating the core principle framework of the synergistic effect between modified bio-based polymer particles and pH-responsive degradation promoters in this invention. Figure 3 This is a multi-stage process flow diagram of the concrete preparation process in this invention; Figure 4 This is a schematic diagram of the multi-level interaction relationship and data flow between the stable performance of concrete during its service life and its controllable degradation after service life in this invention. Detailed Implementation Example 1

[0010] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0011] Currently, against the backdrop of the deepening global sustainable development strategy, the research and development of green building materials has become an important direction in the field of civil engineering. Concrete, as the most widely used engineering material, relies on energy-intensive cement and non-renewable aggregates in its traditional formulations. This not only results in high carbon emissions but also makes it difficult to degrade naturally after disposal, causing a serious environmental burden due to long-term accumulation. In this context, developing new concrete materials that combine mechanical properties with environmental friendliness has become a key breakthrough for achieving a low-carbon transformation in the construction industry. Biodegradable concrete, by introducing bio-based or environmentally responsive components, aims to achieve controlled decomposition after its service life, thereby reducing the lasting impact of construction waste on the ecosystem. However, existing biodegradable concrete generally suffers from significantly lower strength and durability than traditional concrete, making it difficult to meet the basic requirements of structural engineering for load-bearing capacity and long-term stability. Furthermore, most degradation mechanisms depend on specific environmental conditions (such as high humidity or microbial enrichment), and the degradation rate is uncontrollable in normal use environments, easily leading to premature material deterioration or long-term retention. In addition, existing preparation processes often sacrifice workability for degradation characteristics, increasing construction difficulty, insufficient density, and consequently leading to increased crack sensitivity and further decline in durability. To address the aforementioned technical problems, this invention proposes optimizing the raw material ratio and introducing modified bio-based polymer particles and pH-responsive degradation promoters. This ensures high strength and durability of concrete while achieving stable performance during its service life and controllable, efficient degradation after service. Specific pretreatment processes and multi-stage curing regimes significantly improve the utilization rate of recycled aggregates and the early strength development of concrete, enhance the workability of the mixture, and reduce crack sensitivity. The entire preparation process is green and environmentally friendly, effectively reducing cement usage and carbon emissions. This provides a feasible technical path for solving the construction waste problem and is applied to a biodegradable, green, high-performance concrete and its preparation method.

[0012] Reference Appendix Figure 1 The schematic diagram of the overall technical solution architecture for the biodegradable green high-performance concrete and its preparation method proposed in this invention illustrates the complete process chain from raw material preparation, pretreatment, multi-stage mixing, molding to multi-stage curing. The various functional modules work synergistically to ensure that the final product possesses both high performance and controllable degradation characteristics. (See attached reference.) Figure 2 A schematic diagram illustrating the core principle framework of the synergistic effect between modified bio-based polymer particles and pH-responsive degradation promoters reveals the physicochemical interaction mechanism between the two within the concrete matrix. This mechanism is key to achieving service-life stability and efficient post-service degradation. (See attached reference) Figure 3 The multi-stage process flow diagram for concrete preparation details the precise control process from dry powder premixing, wet mixing, aggregate addition to final mixing, ensuring uniform dispersion of each component and achieving the required workability. (See attached reference.) Figure 4The diagram illustrating the multi-level interaction and data flow between the stable performance of concrete during its service life and its controllable degradation after service life clarifies the data flow and control logic throughout the entire process, from degradation triggered by changes in environmental pH to monitoring by internal sensors, volumetric strain response, and final material decomposition.

[0013] In the aforementioned biodegradable green high-performance concrete and its preparation method, step 1, raw material preparation and pretreatment, involves preparing 30 to 50 parts by weight of silicate cement, 15 to 25 parts by weight of blast furnace slag powder, 10 to 20 parts by weight of fly ash, 5 to 15 parts by weight of modified bio-based polymer particles, 40 to 60 parts by weight of natural aggregate, 20 to 30 parts by weight of recycled aggregate, 2 to 5 parts by weight of nano-silica, 0.1 to 0.5 parts by weight of cellulose ether, 0.5 to 1.5 parts by weight of polycarboxylate superplasticizer, and 1 to 3 parts by weight of pH-responsive degradation promoter; mechanically activating and acid washing the recycled aggregate to remove surface deposits and improve its surface roughness and activity; and surface coating the modified bio-based polymer particles to form a slow-release layer with a thickness of 1 to 5 micrometers. Specifically, in step 1, ordinary Portland cement with a strength grade of 42.5 or 52.5 is selected, with a specific surface area of ​​not less than 350 square meters per kilogram and a sulfur trioxide content of not more than 3.5%, to ensure sufficient hydration reaction and early strength development. Blast furnace slag powder has a specific surface area of ​​not less than 400 square meters per kilogram, an activity index of not less than 75% at 7 days and not less than 95% at 28 days, and serves as an auxiliary cementitious material, effectively reducing heat of hydration and improving later strength and durability. Fly ash conforming to GB / T 1596 standard, Grade I or II fly ash, with a fineness (45-micron sieve residue) not exceeding 12% and a loss on ignition not exceeding 5%, its spherical particle shape helps improve the fluidity of the mixture. Natural aggregate is continuously graded crushed stone with a maximum particle size not exceeding 20 mm, a crushing index less than or equal to 10%, an apparent density not less than 2600 kg / m³, and a needle-like / flaky particle content not exceeding 5%, to ensure the skeleton strength and density of the concrete. The recycled aggregate is obtained from construction waste concrete through two-stage crushing by a jaw crusher and a cone crusher, followed by vibrating screening. The particle size is strictly controlled within the range of 5 mm to 15 mm, and the water absorption rate is controlled within 5%. Its mechanical activation treatment adopts a vertical impact crusher with a processing time of 5 to 10 minutes and an impact speed of 40 meters per second. This process uses high-speed impact force to generate micro-cracks on the surface of the recycled aggregate and peel off the weakened layer, significantly improving its specific surface area and surface activity. The acid washing treatment uses a 5% hydrochloric acid solution and soaks for 30 minutes to dissolve inert substances such as residual calcium hydroxide and calcium carbonate on the surface. Then, it is rinsed with clean water until neutral (pH value of 7) and placed in a 105-degree Celsius oven to dry to constant weight, ensuring that its internal pore structure is clean and the active sites are exposed. Nano-silica is an amorphous gas-phase product with an average particle size of 15 nanometers, a specific surface area of ​​200 square meters per gram, and a purity of over 99.8%. Its ultra-high activity can fill the micropores between cement particles, accelerate the hydration reaction, and refine the pore structure, thereby significantly improving the density and impermeability of concrete.The cellulose ether is hydroxypropyl methylcellulose (HPMC) with a viscosity of 40,000 mPa·s (2% aqueous solution, 20°C). Its main functions are water retention, thickening, and improving the cohesiveness of the mixture, preventing segregation and bleeding. The polycarboxylate superplasticizer has a solid content of 40% and a water reduction rate of ≥30%. The polyoxyethylene side chains in its molecular structure provide excellent steric hindrance, achieving high water reduction and good slump retention. The modified bio-based polymer particles are a blend of polylactic acid (PLA) and polyhydroxyalkanoates (PHA), with PLA accounting for 60% to 80% by mass and PHA accounting for 20% to 40% by mass. The particles are produced by melt blending and underwater pelletizing using a twin-screw extruder, with the particle size distribution strictly controlled between 0.1 mm and 1.0 mm. This particle size range ensures uniform dispersion in the concrete matrix and allows for the formation of effective interconnected channels during degradation. The surface-coated slow-release layer is composed of biodegradable polycaprolactone (PCL) and calcium stearate in a mass ratio of 8:2. This composite layer is formed by a fluidized bed coating process, with a thickness precisely controlled between 1 and 5 micrometers. Its function is to isolate the internal polymer from moisture and alkaline environments during the service life of the concrete, maintaining material stability. After the service life ends, when the environmental pH value decreases, the slow-release layer degrades preferentially, thereby triggering the rapid decomposition of the internal polymer. The pH-responsive degradation accelerator is a solid granule composed of citric acid and sodium bicarbonate in a mass ratio of 1:1.5. It is produced through high-speed mixing, tableting, crushing, and sieving processes, with a particle size range of 0.05 mm to 0.2 mm. When the ambient pH value is below 6.5, the accelerator begins to undergo an acid-base neutralization reaction, slowly releasing carbon dioxide gas and generating citrate ions. The carbon dioxide gas forms microbubbles inside the concrete, increasing pore connectivity, while the citrate ions chelate calcium ions, disrupting the stability of cement hydration products. The synergistic effect of these two factors accelerates the disintegration of the concrete matrix.

[0014] In the aforementioned biodegradable green high-performance concrete and its preparation method, step 2 involves premixing dry powder materials. The silicate cement, blast furnace slag powder, fly ash, nano-silica, and cellulose ether are added to a forced mixer and dry-mixed at a speed of 30 to 50 revolutions per minute for 3 to 5 minutes to ensure uniform dispersion of each component. Specifically, in step 2, the forced mixer has a capacity of 0.5 cubic meters, and the gap between the mixing blades and the liner is 3 millimeters. This gap size has been optimized through fluid dynamics simulation to ensure that the materials are mixed without dead zones or accumulation, achieving uniform mixing at the microscale. During dry mixing, the material temperature is controlled between 15 and 35 degrees Celsius by the mixer jacket cooling system to prevent premature dissolution of cellulose ether or agglomeration of nano-silica due to frictional heat generation. The combination of dry mixing time and speed (3 to 5 minutes, 30 to 50 revolutions per minute) was determined through orthogonal experiments to ensure uniform dispersion of ultrafine powders such as nano-silica in the cementitious material system without excessive mixing leading to powder loss. At the end of dry mixing, the uniformity coefficient of the mixture (calculated by sampling and measuring the standard deviation of the content of each component) should be less than 5% to ensure the stability of subsequent wet mixing.

[0015] In the aforementioned biodegradable green high-performance concrete and its preparation method, step 3, wet mixing and polymer introduction, involves slowly adding 70% to 80% of the total water volume to the dry powder mixture obtained in step 2, along with the polycarboxylate superplasticizer. The mixer is then started and stirred at 60 to 80 revolutions per minute for 2 to 4 minutes. Subsequently, the modified bio-based polymer particles and pH-responsive degradation promoter are added in batches, and stirring continues for 3 to 5 minutes to form a uniform slurry. Specifically, in step 3, water is added via atomized spraying, where a high-pressure nozzle atomizes the water into tiny droplets with a particle size of less than 100 micrometers, which are then uniformly sprayed onto the surface of the dry powder mixture. This method greatly increases the contact area between water and powder, accelerates the wetting process, and prevents localized overwetting and clumping. The polycarboxylate superplasticizer is injected simultaneously with the atomized water using a metering pump, ensuring its dispersing effect is fully utilized in the initial hydration stage. The initial stage of wet mixing (2 to 4 minutes, 60 to 80 revolutions per minute) aims to form a uniform, viscous slurry. The cement paste provides a good foundation for the subsequent encapsulation of aggregates. Subsequently, modified bio-based polymer particles and pH-responsive degradation accelerators are added in 3 to 5 batches, with each batch spaced 30 seconds apart, to prevent particle agglomeration or sedimentation caused by adding all at once. Stirring continues for 3 to 5 minutes to ensure that the polymer particles and accelerator particles are uniformly suspended in the paste, forming a stable suspension system. At this time, the viscosity of the paste should be controlled at 800 to 1200 mPa·s (Brookfield viscometer, 20 degrees Celsius) to ensure good encapsulation when subsequent aggregates are incorporated.

[0016] In the above-mentioned biodegradable green high-performance concrete and its preparation method, in step 4, aggregate incorporation and final mixing, pretreated natural aggregate and recycled aggregate are added to the slurry obtained in step 3, and the remaining water is added. The speed of the mixer is increased to 80 to 100 revolutions per minute, and the mixing is continued for 5 to 8 minutes until a concrete mixture with good workability and no segregation or bleeding is obtained. Specifically, in step 4, natural aggregates and recycled aggregates are pre-mixed evenly in aggregate bins according to a certain ratio, and then fed into the mixer in one go via a belt conveyor; the remaining water (accounting for 20% to 30% of the total water consumption) is used to adjust the final workability of the mixture; the mixer speed is increased to 80 to 100 revolutions per minute to provide sufficient shear force to ensure that the slurry fully coats each aggregate particle, especially the rough-surfaced recycled aggregates; the mixing time of 5 to 8 minutes has been verified by experiments to be sufficient to make the mixture macroscopically uniform, with no visible separation of slurry and aggregates; the slump of the final concrete mixture is strictly controlled between 180 mm and 220 mm, the spread is greater than or equal to 500 mm, and the slump loss after 2 hours is less than 30 mm, which fully meets the requirements of modern pumping construction for high fluidity and high plasticity retention; at the same time, by controlling the water absorption rate of recycled aggregates and pre-wetting treatment, the loss of workability of the mixture caused by secondary water absorption of recycled aggregates is effectively avoided.

[0017] In the aforementioned biodegradable green high-performance concrete and its preparation method, step 5, molding and curing, involves injecting the concrete mixture into a mold and vibrating it for 30 to 60 seconds using a vibrating table with a frequency of 50 Hz and an amplitude of 0.5 mm; subsequently, the molded specimen is placed in a standard curing room with a temperature of 20 ± 2 degrees Celsius and a relative humidity of ≥ 95% for curing for 24 to 48 hours; after demolding, the specimen is transferred to a carbonation curing chamber with a temperature of 60 degrees Celsius and a carbon dioxide concentration of 20% for accelerated carbonation curing for 7 to 14 days, ultimately obtaining the biodegradable green high-performance concrete. Specifically, in step 5, the parameters of the vibration table (50 Hz, 0.5 mm) are optimized to effectively eliminate air bubbles in the mixture, improve density, and prevent aggregate segregation or polymer particle floating due to excessive vibration. The standard curing stage (20 ± 2 degrees Celsius, relative humidity greater than or equal to 95%) aims to ensure the normal progress of cement hydration reaction and obtain sufficient early strength to meet demolding requirements. The carbonation curing chamber is equipped with a gas circulation system, which forces the gas in the chamber to circulate through a centrifugal fan, ensuring uniform carbon dioxide concentration distribution with fluctuations not exceeding ± 2%. The mechanism of carbonation curing is that high-concentration carbon dioxide reacts with cement hydration products calcium hydroxide and hydrated calcium silicate to generate dense calcium carbonate crystals. The process not only significantly improved the early strength of concrete (7-day strength can reach more than 80% of the design strength), but also significantly reduced porosity and chloride ion diffusion coefficient, enhancing durability. During the curing process, the compressive strength growth of the specimens was monitored every 24 hours using a non-contact ultrasonic strength meter. When the 7-day strength reached 80% of the design strength, carbonation curing could be ended early and natural curing could be initiated to save energy. The resulting biodegradable green high-performance concrete achieved a 28-day compressive strength of more than 50 MPa and a flexural strength of more than 5 MPa under standard curing conditions, with a chloride ion diffusion coefficient of less than 3 x 10^-12 square meters per second, fully meeting the technical requirements for structural concrete of strength grade C50 and above.

[0018] Furthermore, the preparation method also includes monitoring the degradation process. A pH sensor and strain gauge embedded within the concrete are used to monitor changes in pH and volumetric strain in real time. When the pH value remains below 6.5 and the volume expansion rate exceeds 0.1%, the degradation process is considered to have begun. Specifically, the pH sensor uses a miniature solid-state electrode encapsulated in alkali-resistant epoxy resin, with a range of 0 to 14 and an accuracy of ±0.1%. The strain gauge is a vibrating wire or fiber optic grating type, with a range of ±1000 micro-strain and an accuracy of 0.1% of full scale. Before concrete pouring, both are fixed to key monitoring positions on the component using a dedicated bracket, and signal lines are led out through a waterproof junction box. Monitoring data is uploaded to a cloud management platform in real time via a wireless transmission module. The platform's built-in algorithm continuously analyzes the data. Once the dual criteria of "pH value remaining below 6.5 (lasting longer than 24 hours) and volume expansion rate exceeding 0.1%" are met, an automatic warning is triggered, notifying relevant parties that the component has entered the degradation stage and requires disposal or recycling. This monitoring system provides data support for the full life cycle management of concrete, enabling visualization and controllability of the degradation process.

[0019] Furthermore, the method is applicable to precast component production lines, employing an automated batching system and robotic arms for material distribution and vibration. A single production cycle does not exceed 45 minutes, and the product qualification rate is greater than or equal to 98%. Specifically, the automated batching system consists of a central control computer, a high-precision electronic scale (accuracy 0.1%), a pneumatic butterfly valve, and a screw conveyor. It can automatically weigh and feed all powders, aggregates, and admixtures, with errors controlled within ±0.5%. The robotic arm is equipped with a flexible material hopper at its end, which can automatically plan the path according to the mold shape to achieve uniform material distribution. The vibration process is completed by a high-frequency internal vibrator installed at the end of the robotic arm, with vibration parameters (frequency, amplitude, insertion depth, and time) precisely controlled by a program. The entire production process, from batching to demolding and warehousing, achieves a high degree of automation and informatization, significantly improving production efficiency and product quality stability.

[0020] To illustrate the technical effects of this invention more specifically, an application example is constructed: the production of prefabricated segments for an underground integrated pipe gallery in a certain city. Using the method of this invention, the following components are selected by weight: 40 parts silicate cement, 20 parts blast furnace slag powder, 15 parts fly ash, 10 parts modified bio-based polymer particles (PLA:PHA=70:30, particle size 0.5 mm, PCL / calcium stearate slow-release layer thickness 3 micrometers), 50 parts natural aggregate (5 to 20 mm continuously graded crushed stone), 25 parts recycled aggregate (mechanically activated and acid-washed, particle size 5 to 15 mm, water absorption rate 4.2%), 3 parts nano-silica, 0.3 parts cellulose ether, 1.0 part polycarboxylate superplasticizer (solid content 40%), and 2 parts pH-responsive degradation promoter (citric acid:sodium bicarbonate=1:1.5, particle size 0.1 mm). Prepared according to steps 1 to 5, the final concrete mixture had a slump of 200 mm, a spread of 520 mm, and a slump loss of 25 mm after 2 hours. After curing, the 28-day compressive strength was 55 MPa, the flexural strength was 5.8 MPa, and the chloride ion diffusion coefficient was 2.5 x 10^-12 square meters per second. After 30 years of service, this precast segment needed to be demolished due to urban planning adjustments and was placed in a simulated acid rain environment with a pH of 5.5. After 180 days, the mass loss rate reached 58%, and the degradation products were tested and found to have no acute toxicity to aquatic organisms (LC50 greater than 100 mg / L), proving its environmental friendliness. Simultaneously, the pre-embedded sensors monitored an internal pH value dropping to 6.3 on day 30 and continuing to decrease, with a volume expansion rate reaching 0.12%, accurately indicating the start of degradation. Example 2

[0021] Based on Example 1, to meet the differentiated requirements of degradation triggering conditions in different engineering environments, this invention provides an alternative technical solution, the core of which lies in changing the chemical composition and response threshold of the pH-responsive degradation promoter. Specifically, the pH-responsive degradation promoter in step 1 is replaced with solid particles composed of tartaric acid and calcium carbonate in a mass ratio of 1:2, with a particle size ranging from 0.08 mm to 0.25 mm. The response mechanism of this promoter is that tartaric acid has a pKa1 of 2.98 and a pKa2 of 4.34, therefore it only begins to significantly ionize when the ambient pH is below 5.0, releasing hydrogen ions and reacting with calcium carbonate to generate carbon dioxide. This solution is suitable for scenarios where the expected service environment has large pH fluctuations (such as pH between 5.0 and 7.0), effectively avoiding accidental degradation triggered by a weakly acidic environment (such as pH 6.0), and improving the reliability of the material during its service life. The remaining raw material ratios, pretreatment processes, stirring, and curing parameters are the same as in Example 1. Tests showed that the concrete prepared by this method had a compressive strength of 52 MPa after 28 days under standard curing conditions, and a mass loss rate of 52% after 180 days when placed in an environment with a pH of 4.5, thus meeting the requirements of high performance and controllable degradation.

[0022] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A biodegradable green high-performance concrete and its preparation method, characterized in that: The specific steps include the following: Step 1: Raw material preparation and pretreatment. According to the mass parts, prepare 30 to 50 parts of silicate cement, 15 to 25 parts of blast furnace slag powder, 10 to 20 parts of fly ash, 5 to 15 parts of modified bio-based polymer particles, 40 to 60 parts of natural aggregate, 20 to 30 parts of recycled aggregate, 2 to 5 parts of nano silica, 0.1 to 0.5 parts of cellulose ether, 0.5 to 1.5 parts of polycarboxylate superplasticizer, and 1 to 3 parts of pH-responsive degradation accelerator. The recycled aggregate is mechanically activated and acid-washed to remove surface deposits and improve its surface roughness and activity; the modified bio-based polymer particles are surface-coated to form a slow-release layer with a thickness of 1 to 5 micrometers; Step 2: Dry powder premixing, the silicate cement, blast furnace slag powder, fly ash, nano silica and cellulose ether are put into a forced mixer and dry-mixed at a speed of 30 to 50 revolutions per minute for 3 to 5 minutes to ensure that each component is evenly dispersed; Step 3: Wet mixing and polymer introduction. Slowly add 70% to 80% of the total water volume to the dry powder mixture obtained in Step 2, and simultaneously add the polycarboxylate superplasticizer. Start the mixer and stir at a speed of 60 to 80 revolutions per minute for 2 to 4 minutes. Subsequently, add the modified bio-based polymer particles and pH-responsive degradation accelerator in batches, and continue stirring for 3 to 5 minutes to form a uniform slurry. Step 4: Aggregate incorporation and final mixing. Add the pretreated natural aggregate and recycled aggregate to the slurry obtained in Step 3, and add the remaining water. Increase the mixer speed to 80 to 100 revolutions per minute and continue stirring for 5 to 8 minutes until a concrete mixture with good workability and no segregation or bleeding is obtained. Step 5: Molding and Curing. The concrete mixture is poured into a mold and vibrated for 30 to 60 seconds using a vibrating table with a frequency of 50 Hz and an amplitude of 0.5 mm. The molded specimen is then placed in a standard curing room with a temperature of 20 ± 2 degrees Celsius and a relative humidity of ≥ 95% for 24 to 48 hours. After demolding, the specimen is transferred to a carbonation curing chamber with a temperature of 60 degrees Celsius and a carbon dioxide concentration of 20% for accelerated carbonation curing for 7 to 14 days. The biodegradable green high-performance concrete is finally obtained. Under standard curing conditions, the concrete has a compressive strength of over 50 MPa and a flexural strength of over 5 MPa after 28 days, and a chloride ion diffusion coefficient of less than 3 × 10⁻¹² square meters per second.

2. The biodegradable green high-performance concrete and its preparation method according to claim 1, characterized in that: The modified bio-based polymer particles are a blend of polylactic acid and polyhydroxyalkanoates, wherein the mass percentage of polylactic acid is 60% to 80% and the mass percentage of polyhydroxyalkanoates is 20% to 40%; the particle size distribution of the particles is 0.1 mm to 1.0 mm, and the sustained-release layer coated on the surface is composed of polycaprolactone and calcium stearate in a mass ratio of 8:

2.

3. The biodegradable green high-performance concrete and its preparation method according to claim 1, characterized in that: The pH-responsive degradation promoter is a solid particle composed of citric acid and sodium bicarbonate in a mass ratio of 1:1.5, with a particle size ranging from 0.05 mm to 0.2 mm. The promoter begins to release carbon dioxide gas and generate organic acid anions when the ambient pH value is below 6.

5.

4. The biodegradable green high-performance concrete and its preparation method according to claim 1, characterized in that: The mechanical activation treatment of the recycled aggregate is carried out using a vertical impact crusher, with a processing time of 5 to 10 minutes and an impact speed of 40 meters per second; the acid washing treatment is carried out using a 5% hydrochloric acid solution, with a soaking time of 30 minutes, followed by rinsing with clean water until neutral and drying.

5. The biodegradable green high-performance concrete and its preparation method according to claim 1, characterized in that: In step 2, the gap between the mixing blades and the liner of the forced mixer is 3 mm; during the dry mixing process, the material temperature is controlled between 15 degrees Celsius and 35 degrees Celsius.

6. The biodegradable green high-performance concrete and its preparation method according to claim 1, characterized in that: In step 3, water is added by atomized spraying, with water droplet diameter less than 100 micrometers; the polycarboxylate superplasticizer has a solid content of 40% and a water reduction rate of greater than or equal to 30%.

7. The biodegradable green high-performance concrete and its preparation method according to claim 1, characterized in that: The natural aggregate is continuously graded crushed stone with a maximum particle size of no more than 20 mm and a crushing index of less than or equal to 10%; the recycled aggregate is obtained by crushing and screening construction waste concrete with a particle size of 5 mm to 15 mm and a water absorption rate controlled within 5%.

8. The biodegradable green high-performance concrete and its preparation method according to claim 1, characterized in that: The carbonization curing chamber is equipped with a gas circulation system to ensure that the carbon dioxide concentration is evenly distributed and the fluctuation range does not exceed ±2%. During the curing process, the compressive strength growth of the specimen is monitored every 24 hours. When the strength reaches 80% of the design strength after 7 days, the carbonization curing is ended in advance.

9. The biodegradable green high-performance concrete and its preparation method according to claim 1, characterized in that: The slump of the concrete mixture is controlled between 180 mm and 220 mm, the spread is greater than or equal to 500 mm, and the slump loss after 2 hours is less than 30 mm.

10. The biodegradable green high-performance concrete and its preparation method according to claim 1, characterized in that: The preparation method also includes monitoring the degradation process. By using pH sensors and strain gauges embedded in the concrete, the changes in pH value and volumetric strain inside the concrete are monitored in real time. When the pH value is consistently below 6.5 and the volume expansion rate exceeds 0.1%, the degradation process is determined to have started.

Images