High-performance green low-carbon concrete and preparation method thereof

Abstract

The invention relates to the technical field of building materials, in particular to high-performance green low-carbon concrete and a preparation method thereof.The preparation method comprises the steps that cement, recycled aggregate, fly ash, silica fume, a polycarboxylic acid water reducer and water are mixed according to a specific proportion, and the concrete is prepared through the steps of staged water adding, vibration table compaction, precise curing and the like. By optimizing the raw material ratio and introducing a specific technical means, the problems that traditional green low-carbon concrete is low in early strength, insufficient in durability and poor in construction performance are solved, meanwhile, carbon emission is remarkably reduced, and the green low-carbon concrete meets the requirements of green low-carbon buildings and has excellent mechanical properties, durability and construction adaptability.

Description

Technical Field

[0001] This application relates to the field of building materials technology, and in particular to a high-performance green low-carbon concrete and its preparation method. Background Technology

[0002] Concrete, as one of the most widely used building materials, is consumed in enormous quantities globally. Traditional concrete mainly consists of cement, aggregates, water, and some admixtures. The carbon emissions from cement production are becoming increasingly serious, and the extensive use of natural sand and gravel resources causes irreversible environmental damage. In recent years, to address this challenge, the concept of green, low-carbon concrete has gradually emerged. Its core lies in reducing cement usage, increasing the proportion of recycled materials and industrial waste, while ensuring that the mechanical properties of the concrete are not affected.

[0003] The main problems faced by existing technologies: Although some progress has been made in the research and development of green and low-carbon concrete, its strength and durability are still insufficient, especially in terms of performance stability under extreme climatic conditions and ease of construction.

[0004] Patent CN107285681A discloses a high-performance building material comprising cement, glass sand, polystyrene, coupling agent, straw fiber, quartz sand, bamboo charcoal granules, and titanium stearate. The beneficial effects of this invention are: using corn straw as the main raw material, it is environmentally friendly and safe; the addition of other raw materials ensures the stability of the building material, extends its service life, and is green and environmentally friendly; the added quartz sand increases wear resistance. However, in practical applications, although this technical solution improves the environmental friendliness and some physical properties of the material by adding multiple components, its effect on reducing carbon emissions is limited, and it fails to significantly improve early strength and long-term durability.

[0005] Patent CN108358518A discloses an eco-friendly anti-mildew building material, comprising an inorganic antibacterial agent, diatomaceous earth, quartz sand, cement, polystyrene, nano-silica, calcium oxide, corn stalks, and water. The beneficial effects of this invention are: the added inorganic antibacterial agent effectively prevents mold growth, extends the service life of the building material, is environmentally friendly, and ensures human health; the added corn stalks utilize waste materials, protecting the ecological environment. However, in practical applications, while this technical solution possesses certain environmental characteristics, its low-carbon performance still needs improvement, and its performance stability under complex construction environments is not ideal.

[0006] Neither of the two existing technical solutions mentioned above has fully addressed the carbon emission problem in achieving green and low-carbon goals. Furthermore, they are insufficient in improving early strength and long-term durability, making it difficult to fully meet the demands of modern buildings for high-performance green and low-carbon concrete. Summary of the Invention

[0007] This application provides a high-performance green low-carbon concrete and its preparation method, aiming to solve the problems of low early strength, insufficient long-term durability and poor construction performance of existing green low-carbon concrete by optimizing the raw material ratio and introducing specific technical means.

[0008] In one aspect, this application provides a method for preparing high-performance green low-carbon concrete, comprising the following steps: S10: mixing 5% to 20% cement, 60% to 75% recycled aggregate, 10% to 15% fly ash, 5% to 10% silica fume, and 0.2% to 0.5% polycarboxylate superplasticizer with an appropriate amount of water according to mass percentage to obtain an initial mixture; S20: stirring the initial mixture for 3 to 5 minutes at a stirring speed of 40 to 60 rpm to ensure sufficient dispersion of each component; S30: adding water in stages during the stirring process, first adding 60% to 70% of the total water volume. S40: Pour the mixture into a mold and compact it on a vibrating table at a frequency of 2800 to 3200 times per minute for 15 to 30 seconds; S50: Demold the compacted concrete after curing for 24 hours at a temperature of 20 to 25 degrees Celsius and a relative humidity of 90% to 95%; S60: Continue to cure the demolded concrete specimens under standard curing conditions for up to 28 days at a temperature of 20 to 25 degrees Celsius and a relative humidity of not less than 95%.

[0009] According to this application, by precisely controlling the raw material ratio and employing technical methods during mixing and curing, the problems of low early strength, poor workability, and insufficient long-term durability of traditional green low-carbon concrete are solved. Specifically, the high proportion of recycled aggregates and industrial waste such as fly ash and silica fume not only significantly reduces cement usage but also improves the density of concrete through the micro-filling effect of fly ash and silica fume. In addition, the staged water addition method effectively improves the workability of the mixture, while the vibration table compaction treatment further enhances the uniformity and density of the concrete.

[0010] Preferably, in step S10, the particle size of the recycled aggregate ranges from 5 mm to 20 mm, and the water absorption rate of the recycled aggregate is controlled between 5% and 8%.

[0011] By adopting the above technical solutions, the particle size distribution and water absorption rate of recycled aggregate directly affect the workability and mechanical properties of the mixture after hardening. Therefore, by screening and pre-treating recycled aggregate, it is ensured that it meets the above requirements.

[0012] Preferably, in step S10, the fly ash has a fineness of no more than 12% residue on a 45-micron sieve and a loss on ignition of no more than 5%.

[0013] By adopting the above technical solutions, the fineness and loss on ignition of fly ash as an admixture have a significant impact on the early strength and long-term durability of concrete. By selecting fly ash that meets these indicators, its pozzolanic activity can be fully utilized to promote cement hydration.

[0014] Preferably, in step S10, the specific surface area of ​​the silica fume is 15,000 square centimeters per gram to 20,000 square centimeters per gram, and the silica content is not less than 90%.

[0015] By adopting the above technical solution, the high specific surface area and high active silica content of silica fume enable it to fill the gaps between cement particles, thereby improving the density and impermeability of concrete.

[0016] Preferably, in step S10, the solid content of the polycarboxylate superplasticizer is 20% to 30%, and the water reduction rate is 25% to 35%.

[0017] By adopting the above technical solution, polycarboxylate superplasticizers adsorb onto the surface of cement particles, reducing the friction between particles, thereby significantly improving the fluidity and workability of the mixture.

[0018] Preferably, in step S30, the specific operation of adding water in stages is as follows: first, add 60% to 70% of the total water to the mixture, and then add the remaining 30% to 40% of the water after stirring for 2 minutes.

[0019] By adopting the above technical solution, this staged water addition method avoids the segregation of the mixture caused by adding water all at once, while ensuring that the fluidity of the mixture gradually improves to meet construction requirements.

[0020] Preferably, in step S40, the amplitude of the vibration table is 0.5 mm to 1 mm.

[0021] By adopting the above technical solution, the amplitude and frequency of the vibrating table together determine the compaction effect of concrete. A reasonable amplitude can expel air bubbles inside the concrete and avoid aggregate segregation.

[0022] Preferably, in step S50, the temperature fluctuation of the curing environment does not exceed 2 degrees Celsius, and the relative humidity fluctuation does not exceed 3%.

[0023] By adopting the above technical solutions, a stable curing environment helps the early strength development of concrete while reducing the risk of cracking caused by environmental changes.

[0024] Secondly, this application provides a high-performance green low-carbon concrete, which is prepared according to the method described in any of the ways described in the first aspect.

[0025] According to this application, the raw material ratio of this high-performance green low-carbon concrete has been optimized. The high proportion of recycled aggregate significantly reduces the consumption of natural sand and gravel resources, while the incorporation of fly ash and silica fume effectively reduces cement usage, thereby reducing carbon emissions. Furthermore, through staged water addition and vibration table compaction techniques, the problems of poor fluidity and insufficient density of the mixture are solved, resulting in concrete exhibiting excellent characteristics in terms of early strength, long-term durability, and workability.

[0026] Preferably, the high-performance green low-carbon concrete has a 28-day compressive strength of 40 MPa to 60 MPa and a flexural strength of 5 MPa to 8 MPa.

[0027] By adopting the above technical solutions, compressive strength and flexural strength are important indicators for evaluating the mechanical properties of concrete. The above strength range indicates that this concrete has broad application prospects in structural engineering.

[0028] Preferably, the chloride ion diffusion coefficient of the high-performance green low-carbon concrete is 1.5 × 10⁻⁶. -12 Square meters per second to 3.0 × 10 -12 Square meters per second.

[0029] By adopting the above technical solution, the chloride ion diffusion coefficient reflects the impermeability of concrete. A lower diffusion coefficient means that the concrete has good durability and can effectively resist the intrusion of external corrosive media.

[0030] Preferably, the carbon emissions of the high-performance green low-carbon concrete are between 200 kg / m³ and 300 kg / m³.

[0031] By adopting the above technical solutions, reducing cement usage and increasing the proportion of industrial waste incorporated, the carbon emissions of this concrete are significantly lower than those of traditional concrete, meeting the requirements of green and low-carbon buildings.

[0032] Preferably, the slump of the high-performance green low-carbon concrete is 180 mm to 220 mm.

[0033] By adopting the above technical solution, slump is an important indicator for measuring the workability of concrete. The above slump range indicates that the concrete has good fluidity and can meet the operational requirements in complex construction environments.

[0034] In summary, the high-performance green low-carbon concrete and its preparation method provided in this application solve the problems of low early strength, insufficient long-term durability, and poor workability of existing green low-carbon concrete by optimizing the raw material ratio and introducing specific technical means. This concrete not only possesses excellent mechanical properties and durability but also significantly reduces carbon emissions, meeting the demands of modern construction for green and low-carbon materials. Detailed Implementation

[0035] This application provides a method for preparing high-performance green low-carbon concrete, comprising the following steps: S10: mixing 5% to 20% cement, 60% to 75% recycled aggregate, 10% to 15% fly ash, 5% to 10% silica fume, and 0.2% to 0.5% polycarboxylate superplasticizer with an appropriate amount of water according to mass percentage to obtain an initial mixture; S20: stirring the initial mixture for 3 to 5 minutes at a stirring speed of 40 to 60 rpm to ensure sufficient dispersion of each component; S30: adding water in stages during the stirring process, first adding 60% to 70% of the total water volume, and then... Add the remaining 30% to 40% water after stirring for 2 minutes to adjust the workability of the mixture; S40: Pour the mixture into a mold and compact it on a vibrating table at a frequency of 2800 to 3200 times per minute for 15 to 30 seconds; S50: After compaction, demold the concrete after curing for 24 hours at a temperature of 20 to 25 degrees Celsius and a relative humidity of 90% to 95%; S60: Continue to cure the demolded concrete specimens under standard curing conditions for up to 28 days, with standard curing conditions being a temperature of 20 to 25 degrees Celsius and a relative humidity of not less than 95%.

[0036] In step S10, cement, as a binder, is used at a rate controlled between 5% and 20%, effectively reducing carbon emissions while ensuring the basic mechanical properties of the concrete. Recycled aggregate accounts for 60% to 75%, with a particle size range of 5 mm to 20 mm and a water absorption rate controlled between 5% and 8%. The high proportion of recycled aggregate not only reduces the consumption of natural sand and gravel resources but also improves the workability of the mixture through its water absorption characteristics. Fly ash accounts for 10% to 15%, with a fineness of no more than 12% residue on a 45-micron sieve and a loss on ignition of no more than 5%. The incorporation of fly ash promotes the cement hydration reaction, thereby increasing the density of the concrete. Silica fume accounts for 5% to 10%, with a specific surface area of ​​15,000 square centimeters per gram to 20,000 square centimeters per gram and a silica content of no less than 90%. The high specific surface area and high silica content of silica fume enable it to fill the voids between cement particles, thereby improving the density and impermeability of concrete. The dosage of polycarboxylate superplasticizer is 0.2% to 0.5%, with a solid content of 20% to 30% and a water reduction rate of 25% to 35%. Polycarboxylate superplasticizers significantly improve the fluidity and workability of the mixture by adsorbing onto the surface of cement particles, reducing interparticle friction.

[0037] In step S20, the control of stirring time and speed is to ensure that the components are fully dispersed and to avoid uneven mixture due to insufficient stirring. The stirring time is controlled between 3 and 5 minutes, and the stirring speed is controlled between 40 and 60 revolutions per minute.

[0038] In step S30, the specific operation of adding water in stages is as follows: First, add 60% to 70% of the total water to the mixture, stir for 2 minutes, and then add the remaining 30% to 40% of the water. This staged water addition method avoids the segregation of the mixture caused by adding water all at once, while ensuring that the fluidity of the mixture gradually improves to meet construction requirements.

[0039] In step S40, the amplitude of the vibrating table is 0.5 mm to 1 mm, the vibration frequency is 2800 to 3200 times per minute, and the vibration time is 15 to 30 seconds. The amplitude and frequency of the vibrating table together determine the compaction effect of the concrete. A reasonable amplitude can expel air bubbles inside the concrete and prevent aggregate segregation.

[0040] In step S50, the temperature fluctuation of the curing environment shall not exceed 2 degrees Celsius, and the relative humidity fluctuation shall not exceed 3%. A stable curing environment helps the early strength development of concrete while reducing the risk of cracking caused by environmental changes.

[0041] In step S60, the standard curing conditions are a temperature of 20 to 25 degrees Celsius and a relative humidity of not less than 95%. Strict control of the standard curing conditions ensures that the concrete reaches the design strength requirements within 28 days.

[0042] This application also provides a high-performance green low-carbon concrete, prepared according to any of the methods described in this application. The raw material ratio of this concrete is optimized, wherein the high proportion of recycled aggregate significantly reduces the consumption of natural sand and gravel resources, while the incorporation of fly ash and silica fume effectively reduces cement usage, thereby reducing carbon emissions.

[0043] The 28-day compressive strength of this high-performance green low-carbon concrete ranges from 40 MPa to 60 MPa, and its flexural strength ranges from 5 MPa to 8 MPa. The test results for compressive and flexural strength indicate that this concrete has broad application prospects in structural engineering.

[0044] The chloride ion diffusion coefficient of this high-performance green low-carbon concrete is 1.5 × 10⁻⁶. -12 Square meters per second to 3.0 × 10 -12 The test results for the chloride ion diffusion coefficient indicate that the concrete has good durability and can effectively resist the intrusion of external corrosive media.

[0045] This high-performance, green, low-carbon concrete has a carbon emission of 200 kg / m³ to 300 kg / m³. By reducing cement usage and increasing the proportion of industrial waste incorporated, the carbon emission of this concrete is significantly lower than that of traditional concrete, meeting the requirements for green and low-carbon buildings.

[0046] The slump of this high-performance, green, low-carbon concrete ranges from 180 mm to 220 mm. Slump test results indicate that this concrete exhibits good fluidity, meeting the operational requirements of complex construction environments.

[0047] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0048] Example 1, S10: 10% cement, 70% recycled aggregate, 12% fly ash, 8% silica fume, 0.3% polycarboxylate superplasticizer, and an appropriate amount of water were mixed according to mass percentage to obtain an initial mixture. The recycled aggregate had a particle size range of 5 mm to 20 mm and a water absorption rate of 6%; the fly ash had a fineness of 10% residue on a 45-micron sieve and a loss on ignition of 4%; the silica fume had a specific surface area of ​​18,000 square centimeters per gram and a silica content of 92%; and the polycarboxylate superplasticizer had a solid content of 25% and a water reduction rate of 30%. S20: The initial mixture was stirred for 4 minutes at a speed of 50 rpm. S30: During stirring, 65% of the total water was added first, and the remaining 35% was added after stirring for 2 minutes. S40: Pour the mixture into the mold and compact it on a vibrating table at a frequency of 3000 times per minute, an amplitude of 0.8 mm, and a compaction time of 20 seconds. S50: After compaction, cure the concrete at 22 degrees Celsius and 92% relative humidity for 24 hours before demolding. S60: Continue curing the demolded concrete specimens under standard curing conditions for up to 28 days: 23 degrees Celsius and 96% relative humidity.

[0049] Example 2 S10: According to mass percentage, 15% cement, 65% recycled aggregate, 10% fly ash, 10% silica fume, 0.4% polycarboxylate superplasticizer, and an appropriate amount of water are mixed to obtain an initial mixture. The recycled aggregate has a particle size range of 5 mm to 20 mm and a water absorption rate of 7%; the fly ash has a fineness of 11% residue on a 45-micron sieve and a loss on ignition of 5%; the silica fume has a specific surface area of ​​16,000 square centimeters per gram and a silica content of 91%; the polycarboxylate superplasticizer has a solid content of 28% and a water reduction rate of 32%. S20: The initial mixture is stirred for 5 minutes at a speed of 60 rpm. S30: During stirring, 70% of the total water is added first, and the remaining 30% is added after stirring for 2 minutes. S40: Pour the mixture into the mold and compact it on a vibrating table at a frequency of 3200 times per minute, an amplitude of 1 mm, and a compaction time of 30 seconds. S50: After compaction, cure the concrete at 24 degrees Celsius and 94% relative humidity for 24 hours before demolding. S60: Continue curing the demolded concrete specimens under standard curing conditions for up to 28 days: 25 degrees Celsius and 97% relative humidity.

[0050] Example 3S10: 20% cement, 60% recycled aggregate, 15% fly ash, 5% silica fume, 0.5% polycarboxylate superplasticizer, and an appropriate amount of water were mixed according to mass percentage to obtain an initial mixture. The recycled aggregate had a particle size range of 5 mm to 20 mm and a water absorption rate of 8%; the fly ash had a fineness of 12% residue on a 45-micron sieve and a loss on ignition of 5%; the silica fume had a specific surface area of ​​20,000 square centimeters per gram and a silica content of 93%; and the polycarboxylate superplasticizer had a solid content of 30% and a water reduction rate of 35%. S20: The initial mixture was stirred for 3 minutes at a speed of 40 rpm. S30: During stirring, 60% of the total water was added first, and the remaining 40% was added after stirring for 2 minutes. S40: Pour the mixture into the mold and compact it on a vibrating table at a frequency of 2800 times per minute, an amplitude of 0.5 mm, and a compaction time of 15 seconds. S50: After compaction, cure the concrete at 20 degrees Celsius and 90% relative humidity for 24 hours before demolding. S60: Continue curing the demolded concrete specimens under standard curing conditions for up to 28 days: 21 degrees Celsius and 95% relative humidity.

[0051] Comparative Example 1 (S10): 30% cement, 70% natural aggregate, 0% fly ash, 0% silica fume, and 0% polycarboxylate superplasticizer were mixed with an appropriate amount of water according to mass percentage to obtain an initial mixture. (S20): The initial mixture was stirred for 5 minutes at a speed of 60 rpm. (S30): All water was added at once. (S40): The mixture was poured into a mold and compacted on a vibrating table at a frequency of 3000 times per minute, an amplitude of 0.8 mm, and a compaction time of 20 seconds. (S50): The compacted concrete was cured at 22°C and 92% relative humidity for 24 hours before demolding. (S60): The demolded concrete specimens were cured under standard curing conditions for 28 days: 23°C and 96% relative humidity.

[0052] Comparative Example 2S10: 10% cement, 70% recycled aggregate, 12% fly ash, 8% silica fume, and 0.3% polycarboxylate superplasticizer were mixed with an appropriate amount of water according to mass percentages to obtain an initial mixture. The recycled aggregate had a particle size range of 5 mm to 20 mm and a water absorption rate of 6%; the fly ash had a fineness of 10% residue on a 45-micron sieve and a loss on ignition of 4%; the silica fume had a specific surface area of ​​18,000 square centimeters per gram and a silica content of 92%; and the polycarboxylate superplasticizer had a solid content of 25% and a water reduction rate of 30%. S20: The initial mixture was stirred for 2 minutes at a speed of 30 rpm. S30: All water was added at once. S40: The mixture was poured into a mold and compacted on a vibrating table at a frequency of 3000 times per minute, an amplitude of 0.8 mm, and a compaction time of 20 seconds. S50: After vibrating and compacting, the concrete is cured at 22 degrees Celsius and 92% relative humidity for 24 hours before demolding. S60: The demolded concrete specimens are then cured for another 28 days under standard curing conditions: 23 degrees Celsius and 96% relative humidity.

[0053] The high-performance green low-carbon concrete obtained in the above embodiments and comparative examples was subjected to performance tests, and the test results are shown in the table below: The test results in the table show that the high-performance green low-carbon concrete obtained in this application embodiment has a higher 28-day compressive strength, a lower chloride ion diffusion coefficient, lower carbon emissions, and a higher slump compared to the comparative example, indicating that this concrete exhibits excellent characteristics in terms of mechanical properties, durability, environmental friendliness, and workability. Comparative Example 1 did not use fly ash and silica fume, and did not employ a staged water addition method, resulting in a significant decrease in concrete performance. Comparative Example 2 also suffered from insufficient mixing time and speed, and did not employ a staged water addition method, similarly leading to a decrease in concrete performance.

[0054] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made to the structure, shape, and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for preparing high-performance green low-carbon concrete, characterized in that, The process includes the following steps: S10: Mix 5% to 20% cement, 60% to 75% recycled aggregate, 10% to 15% fly ash, 5% to 10% silica fume, and 0.2% to 0.5% polycarboxylate superplasticizer with an appropriate amount of water according to the mass percentage to obtain an initial mixture; S20: Stir the initial mixture for 3 to 5 minutes at a speed of 40 to 60 revolutions per minute; S30: During the stirring process, add water in stages, first adding 60% to 70% of the total water, and then adding the remaining water after stirring for 2 minutes. The remaining 30% to 40% water; S40: Pour the mixture into the mold and compact it on a vibrating table at a frequency of 2800 to 3200 times per minute for 15 to 30 seconds; S50: After compaction, demold the concrete after curing it for 24 hours at a temperature of 20 to 25 degrees Celsius and a relative humidity of 90% to 95%; S60: Continue to cure the demolded concrete specimens under standard curing conditions for 28 days, with the standard curing conditions being a temperature of 20 to 25 degrees Celsius and a relative humidity of not less than 95%.

2. The method for preparing high-performance green low-carbon concrete according to claim 1, characterized in that: In step S10, the particle size of the recycled aggregate ranges from 5 mm to 20 mm, and the water absorption rate of the recycled aggregate is from 5% to 8%.

3. The method for preparing high-performance green low-carbon concrete according to claim 1, characterized in that: In step S10, the fly ash has a fineness of 45 micrometers, a sieve residue of no more than 12%, and a loss on ignition of no more than 5%.

4. The method for preparing high-performance green low-carbon concrete according to claim 1, characterized in that... In step S10, the specific surface area of ​​the silica fume is 15,000 square centimeters per gram to 20,000 square centimeters per gram, and the silica content is not less than 90%.

5. The method for preparing high-performance green low-carbon concrete according to claim 1, characterized in that: In step S10, the solid content of the polycarboxylate superplasticizer is 20% to 30%, and the water reduction rate is 25% to 35%.

6. The method for preparing high-performance green low-carbon concrete according to claim 1, characterized in that: In step S40, the amplitude of the vibration table is 0.5 mm to 1 mm.

7. The method for preparing high-performance green low-carbon concrete according to claim 1, characterized in that: In step S50, the temperature fluctuation of the curing environment shall not exceed 2 degrees Celsius, and the relative humidity fluctuation shall not exceed 3%.

8. A high-performance, green, low-carbon concrete, characterized in that: Prepared according to the method according to any one of claims 1 to 7.

9. The high-performance green low-carbon concrete according to claim 8, characterized in that: Its 28-day compressive strength is 40 MPa to 60 MPa, its flexural strength is 5 MPa to 8 MPa, and its chloride ion diffusion coefficient is 1.5 × 10⁻⁶. -12 Square meters per second to 3.0 × 10 -12 Square meters per second.

10. The high-performance green low-carbon concrete according to claim 8, characterized in that: Its carbon emissions are between 200 kg / m³ and 300 kg / m³, and its slump is between 180 mm and 220 mm.

Images