Ultrahigh-durability solid-waste-based low-carbon concrete and preparation method thereof

Abstract

The invention relates to the technical field of concrete, in particular to ultrahigh-durability solid-waste-based low-carbon concrete and a preparation method thereof. The concrete comprises the following main components: S95-grade granulated blast furnace slag micro powder, steel slag micro powder, I-grade fly ash, activated hydrotalcite, functionalized silicon dioxide powder, silica sand, a low-modulus water glass exciting agent and the like. The amphiphilic polymer brush-like layer is constructed on the surface of the nano silicon dioxide, so that the dispersion stability and the interface bonding are remarkably improved; activated hydrotalcite is prepared by adopting a calcining-re-intercalation process, so that the chloride ion fixing capability is enhanced; the water-absorbent resin particles pre-filled with sodium metaaluminate are used for realizing synchronous slow release of internal nutrient water and reaction active ions, so that the shrinkage is effectively controlled and the pore structure is optimized; and a short-time carbon dioxide curing process is combined, so that rapid improvement of early strength and densification of the microstructure are promoted.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and in particular to an ultra-high durability solid waste-based low-carbon concrete and its preparation method. Background Technology

[0002] With the deepening of global climate change and sustainable development concepts, the construction engineering sector is facing unprecedented pressure for green and low-carbon transformation. Traditional silicate cement concrete emits large amounts of carbon dioxide during its production process, approximately 0.8-0.9 tons of carbon dioxide per ton of silicate cement produced, making it a major source of carbon emissions in the construction industry. At the same time, marine engineering, coastal infrastructure, and concrete structures in highly corrosive environments face severe durability challenges. Problems such as chloride ion corrosion leading to steel reinforcement corrosion and concrete carbonation cracking are frequent, significantly shortening the design service life of these structures.

[0003] To address the aforementioned issues, alkali-activated cementitious materials technology has emerged. These materials primarily utilize industrial solid wastes such as slag, fly ash, and steel slag. An alkaline activator is used to activate their latent activity, forming an aluminosilicate gel product with cementing properties. Compared to traditional silicate cement, alkali-activated materials can reduce carbon dioxide emissions by 60%-80%, while effectively utilizing industrial solid waste and achieving resource recycling. However, existing alkali-activated concrete technology still faces numerous technical bottlenecks.

[0004] First, early shrinkage is a significant problem in alkali-activated materials. Due to the rapid chemical reaction and water loss during the activation process, the material is prone to significant self-shrinkage and drying shrinkage in the early stages of hardening, leading to microcracks that provide pathways for the penetration of harmful media. Second, the high continuity of pores restricts its impermeability. The pore structure of the alkali-activated reaction products often exhibits high connectivity, with a high proportion of macropores, allowing corrosive media such as chloride and sulfate ions to easily penetrate deeply, severely affecting the long-term durability of the structure.

[0005] Regarding material composition, the dispersibility problem of nanofillers in traditional alkaline-activated systems has long remained unresolved. Unmodified nano-silica is prone to agglomeration in strongly alkaline environments, failing to fully realize its filling density and interfacial reinforcement effects. Existing surface modification methods mostly employ simple silane coupling agent treatment or single functional group grafting, which are difficult to achieve stable dispersion and effective interfacial bonding in complex alkaline-activated environments.

[0006] The lack of a pore regulation mechanism is another key technical challenge. Although internal curing technology has been successfully applied in silicate cement concrete, its applicability and effectiveness in alkali-activated systems remain controversial. Traditional internal curing materials only provide moisture supply and cannot participate in the reaction process, thus having limited effect on promoting the formation of dense structures and inhibiting the development of harmful pores.

[0007] Furthermore, insufficient chloride ion fixation capacity severely restricts the application of alkali-activated concrete in marine environments. Traditional alkali-activated products lack an effective chloride ion binding mechanism and cannot chemically bind chloride ions like the AFm phase in silicate cement hydration products. Although existing studies have attempted to add functional materials such as layered double hydroxides, their activation level and ion exchange capacity are often insufficient, making it difficult to achieve efficient chloride ion fixation.

[0008] In summary, while existing alkali-activated concrete technologies achieve the goals of low carbon and environmental protection, how to effectively solve key technical problems such as large early shrinkage, strong pore continuity, and insufficient resistance to chloride ion erosion, and construct a new concrete material system that combines ultra-high durability and significant carbon emission reduction benefits, remains a technical challenge that urgently needs to be overcome. Summary of the Invention

[0009] In view of this, the purpose of this invention is to propose an ultra-durable solid waste-based low-carbon concrete and its preparation method, so as to solve the problems of large early shrinkage and strong pore connectivity in alkali-activated concrete, which lead to insufficient impermeability and chloride ion resistance.

[0010] To achieve the above objectives, this invention provides an ultra-durable solid waste-based low-carbon concrete, comprising the following components by weight: 1550-1650 parts of S95 grade granulated blast furnace slag powder, 280-320 parts of steel slag powder, 180-220 parts of Grade I fly ash, 40-60 parts of activated hydrotalcite, 25-35 parts of functionalized silica powder, 15-25 parts of silica sand, 300-360 parts of low-modulus water glass activator, 50-70 parts of mixing water, 22-26 parts of pre-filled sodium aluminate water-absorbing resin particles, and 3-5 parts of polycarboxylate superplasticizer.

[0011] The functionalized silica powder is prepared by sequentially grafting 3-bromopropyltrimethoxysilane initiator, polystyrene intermediate layer and sulfobetaine methacrylate-octadecyl methacrylate amphiphilic polymer brush layer onto the surface of silica nanoparticles.

[0012] Preferably, the activated hydrotalcite is prepared by calcining synthetic hydrotalcite at 480-520°C for 3-5 hours, followed by anion exchange activation by impregnation with sodium bicarbonate aqueous solution for 45-90 minutes.

[0013] Preferably, the pre-filled sodium aluminate water-absorbing resin particles are prepared by allowing water-absorbing resin particles to stand and adsorb in an aqueous solution of sodium aluminate with a concentration of 8wt%-12wt% for 1.5-3 hours.

[0014] Preferably, the specific surface area of ​​the steel slag powder is higher than 390 m². 2 / kg, with SiO2 content of 17%-20% and CaO content of 40%-50%.

[0015] Preferably, the low-modulus water glass activator has a modulus of 1.3-1.5 and a solid content of 30%-35%.

[0016] Preferably, the specific surface area of ​​the silica nanoparticles is 350 m². 2 / g.

[0017] Preferably, the specific preparation steps of the functionalized silica powder are as follows: S1: Disperse silica nanopowder in a mixed solution of anhydrous ethanol and deionized water, add 3-bromopropyltrimethoxysilane, stir and react at 55-65°C for 1.5-3h under nitrogen protection, filter and wash, and then vacuum dry at 75-85°C for 2-3h to obtain silica powder with surface-grafted initiators. S2: Surface-grafted initiator silica powder is dispersed in toluene, and styrene, cuprous bromide and pentamethyldiethylenetriamine are added in sequence. The mixture is stirred at 65-75°C for 4-6 hours under nitrogen protection. After filtration, washing and vacuum drying, silica powder grafted with polystyrene is obtained. S3: Disperse the grafted polystyrene silica powder in a mixed solvent of water and methanol, add sulfobetaine methacrylate monomer and octadecyl methacrylate, then add cuprous bromide and pentamethyldiethylenetriamine, stir at room temperature for 3.5-5 h under nitrogen protection to carry out chain extension reaction, filter and wash, and then vacuum dry at 55-65°C for 2-3 h to obtain functionalized silica powder.

[0018] Preferably, in step S1, the weight ratio of silica nanopowder to 3-bromopropyltrimethoxysilane is 300:45-75.

[0019] Preferably, in step S2, the weight ratio of silica powder with surface grafting initiator to styrene is 300:120-180.

[0020] Preferably, in step S3, the weight ratio of the grafted polystyrene silica powder, sulfobetaine methacrylate, and octadecyl methacrylate is 310-340:120-200:6-10.

[0021] Preferably, the particle size of the water-absorbing resin particles is 150-300 μm.

[0022] Preferably, the concentration of the sodium aluminate aqueous solution is 8wt%-12wt%.

[0023] Furthermore, the present invention also provides a method for preparing ultra-high durability solid waste-based low-carbon concrete, comprising the following steps: (1) S95 grade granulated blast furnace slag powder, steel slag powder, grade I fly ash, activated hydrotalcite, functionalized silica powder and silica sand are dry-mixed in a forced mixer for 180s to obtain a cementitious composite powder; then low modulus water glass activator and mixing water are added and pre-mixed for 60s, followed by the addition of pre-filled sodium aluminate water-absorbing resin particles and polycarboxylate superplasticizer and continued mixing for 120s to obtain a mixture; (2) The mixture is poured and compacted, and after standing for 2 hours, it is demolded and placed in a carbon dioxide curing box. It is cured for 4-8 hours with carbon dioxide at a pressure of 0.08-0.12 MPa and a volume fraction of 3%-8%. Then it is transferred to a curing room at a temperature of 20°C and a relative humidity of 96% to cure until the desired age is reached, thus obtaining ultra-high durability solid waste-based low-carbon concrete.

[0024] This invention achieves a technological breakthrough in the ultra-high durability of solid waste-based low-carbon concrete through a multi-scale synergistic control strategy, and has the following significant beneficial effects: Nanoscale interface optimization effects: By constructing an amphiphilic polymer brush layer on the surface of silica nanoparticles, the dispersion stability of the nanofiller in a strongly alkaline environment was significantly improved. The surface-grafted sulfobetaine structure provides zwitterionic groups, forming strong interfacial bonds with calcium-aluminum silicate hydration products; long-chain alkyl groups enhance hydrophobicity and effectively prevent aggregation. This surface modification strategy enables nano-silica to be uniformly distributed in the matrix, fully utilizing its space-filling effect, significantly reducing the proportion of harmful pores, and fundamentally improving the material's density and impermeability.

[0025] Precise micron-level pore size control: The use of pre-filled sodium aluminate-based water-absorbing resin particles enables the simultaneous slow release of internally stored water and reactive ions. This technology not only effectively suppresses the self-shrinkage and drying shrinkage of alkali-activated materials, eliminating the microcrack problem caused by rapid water loss in traditional techniques, but also promotes the formation of aluminum-rich hydration / gel products through the slow release of aluminate ions, further optimizing the pore structure distribution. Compared to traditional internal water-only solutions, this technology achieves synergistic optimization of volume stability and early densification.

[0026] Multiple chloride ion barrier effects: Activated hydrotalcite prepared via a calcination-reintercalation process provides numerous exchangeable anion sites, resulting in a strong ion exchange binding effect on chloride ions. This functional component continuously captures and immobilizes chloride ions during material service, effectively reducing the diffusion and migration of free chloride ions, thus constructing a multi-layered protection system combining chemical bonding and physical barrier effects. Compared to unactivated layered double hydroxides, the activation treatment significantly improves ion exchange capacity and binding stability.

[0027] Synergistic Improvement of Early Strength and Long-Term Performance: Short-term carbon dioxide curing promotes the rapid formation of carbonate mineral phases, resulting in a significant increase in early strength and further densification of the microstructure. While providing high early strength, this curing process consumes some pore volume through carbonation, reducing the connectivity of permeation channels. Compared to traditional steam curing, carbon dioxide curing consumes less energy and simultaneously achieves carbon capture and storage, demonstrating significant environmental benefits.

[0028] Multi-scale synergistic enhancement effect: This invention constructs a complete multi-scale control system through the systematic integration of nanoscale interface regulation, microscale pore optimization, ionic-scale chemical bonding, and macroscopic processes. Each functional component exerts a synergistic effect at different scales: surface-modified nano-silica optimizes interface bonding, activated hydrotalcite provides ion barrier, pre-filled water-absorbing resin regulates pore structure, and carbon dioxide curing promotes densification. This synergistic effect enables the material to maintain excellent mechanical properties while possessing ultra-high impermeability, resistance to chloride ion corrosion, and long-term durability.

[0029] Comprehensive Low-Carbon and Environmental Benefits: This invention uses industrial solid waste as the main cementing material, significantly reducing the amount of silicate cement used and achieving remarkable carbon emission reduction. Simultaneously, carbon capture and utilization are achieved through carbon dioxide curing, further enhancing environmental benefits. Compared with traditional concrete, this invention achieves ultra-high durability while demonstrating the dual advantages of resource recycling and green manufacturing, providing important technical support for the low-carbon transformation of construction engineering. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0031] Figure 1 The X-ray diffraction patterns of the concrete in Embodiment 2 and Comparative Examples 1-6 of the present invention are shown below. Figure 2 The infrared spectra of silica nanoparticles, polystyrene-grafted silica powder, and functionalized silica powder in Example 2 of this invention are shown. Detailed Implementation

[0032] 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.

[0033] Example 1:

[0034] (1) 300g of silica nanoparticles (specific surface area 350m²) 2 / g) was dispersed in a mixed solution of 1500g anhydrous ethanol and 150g deionized water, and 45g of 3-bromopropyltrimethoxysilane was added. The mixture was stirred at 55°C for 1.5h under nitrogen protection. After filtration, the mixture was washed twice with ethanol and twice with water, and then dried under vacuum at 75°C for 2h to obtain silica powder with surface-grafted initiators. (2) 300g of silica powder with surface grafted initiator groups was dispersed in 1500g of toluene, and 120g of styrene, 2g of cuprous bromide and 4g of pentamethyldiethylenetriamine were added in sequence. The mixture was stirred at 65°C for 4h under nitrogen protection. After filtration, the mixture was washed twice with toluene and twice with ethanol, and dried under vacuum at 55°C for 2h to obtain silica powder grafted with polystyrene. (3) 310g of grafted polystyrene silica powder was dispersed in a mixed solvent of 1550g water and methanol in a volume ratio of 4:1, 120g of sulfobetaine methacrylate monomer and 6g of octadecyl methacrylate were added, followed by 2g of cuprous bromide and 4g of pentamethyldiethylenetriamine. The chain extension reaction was carried out by stirring at room temperature for 3.5h under nitrogen protection. After filtration, the powder was washed 3 times each with methanol and water, and dried under vacuum at 55°C for 2h to obtain functionalized silica powder. (4) 1000g of synthetic hydrotalcite (DHT-4A) was placed in a muffle furnace and calcined at 480°C for 3h. After cooling to room temperature, it was then soaked in 400g of sodium bicarbonate aqueous solution with a concentration of 8wt% for 45min for anion exchange activation. After filtration, washing with water, and drying at 80°C, activated hydrotalcite was obtained. (5) Add 220g of water-absorbing resin particles (WANICE WHS 900, particle size 150-300μm) to 880g of sodium aluminate aqueous solution with a concentration of 8wt% and let it stand for 1.5h to adsorb. Filter and let it stand at room temperature for 1.5h to dry the surface to obtain water-absorbing resin particles pre-filled with sodium aluminate. (6) Mix 15500g of S95 grade granulated blast furnace slag powder and 2800g of steel slag powder (specific surface area 395m²). 2 The following ingredients were mixed in a forced mixer for 180 seconds: 1800g of Grade I fly ash, 400g of activated hydrotalcite, 250g of functionalized silica powder, and 150g of silica sand, with SiO2 content of 18.2% and CaO content of 43.1%. Then, 3000g of low-modulus water glass activator (modulus 1.4, solid content 32%) and 500g of mixing water were added and premixed for 60 seconds. Subsequently, 220g of pre-filled sodium aluminate water-absorbing resin particles and 30g of polycarboxylate superplasticizer (Sika ViscoCrete-530P) were added and the mixture was stirred for another 120 seconds to obtain the final product. (7) The mixture is poured and compacted, and after standing for 2 hours, it is demolded and placed in a carbon dioxide curing box. It is cured for 4 hours with 3% carbon dioxide at 0.08 MPa pressure, and then transferred to a curing room at 20°C and 96% relative humidity to be cured until the desired age, thus obtaining ultra-durable solid waste-based low-carbon concrete.

[0035] Example 2:

[0036] (1) 300g of silica nanoparticles (specific surface area 350m²) 2 / g) was dispersed in a mixed solution of 1500g anhydrous ethanol and 150g deionized water, and 60g 3-bromopropyltrimethoxysilane was added. The mixture was stirred at 60°C for 2h under nitrogen protection. After filtration, the mixture was washed three times each with ethanol and water, and then dried under vacuum at 80°C for 2h to obtain silica powder with surface-grafted initiators. (2) 300g of silica powder with surface grafted initiator groups was dispersed in 1500g of toluene, and 150g of styrene, 3g of cuprous bromide and 6g of pentamethyldiethylenetriamine were added in sequence. The mixture was stirred at 70°C for 5h under nitrogen protection. After filtration, the mixture was washed twice with toluene and twice with ethanol, and dried under vacuum at 60°C for 2h to obtain silica powder grafted with polystyrene. (3) 320g of grafted polystyrene silica powder was dispersed in a mixed solvent of 1600g water and methanol in a volume ratio of 4:1, 160g of sulfobetaine methacrylate monomer and 8g of octadecyl methacrylate were added, and then 3g of cuprous bromide and 6g of pentamethyldiethylenetriamine were added. The chain extension reaction was carried out by stirring at room temperature for 4h under nitrogen protection. After filtration, the powder was washed three times with methanol and three times with water and dried under vacuum at 60°C for 2h to obtain functionalized silica powder. (4) Place 1000g of synthetic hydrotalcite (DHT-4A) in a muffle furnace and calcine at 500°C for 4h. Cool it to room temperature and then soak it in 500g of 10wt% sodium bicarbonate aqueous solution for 60min for anion exchange activation. Filter, wash with water, and dry at 80°C to obtain activated hydrotalcite. (5) Add 240g of water-absorbing resin particles (WANICE WHS 900, particle size 150-300μm) to 960g of sodium aluminate aqueous solution with a concentration of 10wt% and let stand for 2h to adsorb, filter, and let stand at room temperature for 2h to dry the surface to obtain water-absorbing resin particles pre-filled with sodium aluminate. (6) Mix 16,000g of S95 grade granulated blast furnace slag powder and 3,000g of steel slag powder (specific surface area 395m²). 2 / kg, SiO2 content 18.2%, CaO content 43.1%), 2000g of Grade I fly ash, 500g of activated hydrotalcite, 300g of functionalized silica powder and 200g of silica sand were dry-mixed in a forced mixer for 180s to obtain a cementitious composite powder; then 3200g of low modulus water glass activator (modulus 1.4, solid content 32%) and 600g of mixing water were added and pre-mixed for 60s, followed by the addition of 240g of pre-filled sodium aluminate water-absorbing resin particles and 40g of polycarboxylate superplasticizer (Sika ViscoCrete-530P) and continued mixing for 120s to obtain a mixture; (7) The mixture is poured and compacted, and after standing for 2 hours, it is demolded and placed in a carbon dioxide curing box. It is cured for 6 hours with 5% carbon dioxide at 0.1 MPa pressure, and then transferred to a curing room at 20°C and 96% relative humidity to be cured until the desired age, thus obtaining ultra-durable solid waste-based low-carbon concrete.

[0037] Example 3:

[0038] (1) 300g of silica nanoparticles (specific surface area 350m²) 2 / g) was dispersed in a mixed solution of 1500g anhydrous ethanol and 150g deionized water, and 75g of 3-bromopropyltrimethoxysilane was added. The mixture was stirred at 65°C for 3h under nitrogen protection. After filtration, the mixture was washed 4 times each with ethanol and water, and then dried under vacuum at 85°C for 3h to obtain silica powder with surface-grafted initiators. (2) 300g of silica powder with surface grafted initiator groups was dispersed in 1500g of toluene, and 180g of styrene, 4g of cuprous bromide and 8g of pentamethyldiethylenetriamine were added in sequence. The mixture was stirred at 75°C for 6h under nitrogen protection. After filtration, the mixture was washed twice with toluene and twice with ethanol, and dried under vacuum at 60°C for 3h to obtain silica powder grafted with polystyrene. (3) 340g of grafted polystyrene silica powder was dispersed in a mixed solvent of 1700g water and methanol in a volume ratio of 4:1, 200g of sulfobetaine methacrylate monomer and 10g of octadecyl methacrylate were added, and then 4g of cuprous bromide and 8g of pentamethyldiethylenetriamine were added. The chain extension reaction was carried out by stirring at room temperature for 5h under nitrogen protection. After filtration, the powder was washed 4 times each with methanol and water, and dried under vacuum at 65°C for 3h to obtain functionalized silica powder. (4) 1000g of synthetic hydrotalcite (DHT-4A) was placed in a muffle furnace and calcined at 520°C for 5h. After cooling to room temperature, it was then soaked in 600g of sodium bicarbonate aqueous solution with a concentration of 12wt% for 90min for anion exchange activation. After filtration, washing with water, and drying at 80°C, activated hydrotalcite was obtained. (5) Add 260g of water-absorbing resin particles (WANICE WHS 900, particle size 150-300μm) to 1040g of sodium aluminate aqueous solution with a concentration of 12wt% and let stand for 3h to adsorb, filter, and let stand at room temperature for 3h to dry the surface to obtain water-absorbing resin particles pre-filled with sodium aluminate. (6) Mix 16500g of S95 grade granulated blast furnace slag powder and 3200g of steel slag powder (specific surface area 395m²) 2 The following ingredients were mixed in a forced mixer for 180 seconds: 2200g of Grade I fly ash, 600g of activated hydrotalcite, 350g of functionalized silica powder, and 250g of silica sand, with SiO2 content of 18.2% and CaO content of 43.1%. Then, 3600g of low-modulus water glass activator (modulus 1.4, solid content 32%) and 700g of mixing water were added and premixed for 60 seconds. Subsequently, 260g of pre-filled sodium aluminate water-absorbing resin particles and 50g of polycarboxylate superplasticizer (Sika ViscoCrete-530P) were added and the mixture was stirred for another 120 seconds to obtain the final product. (7) The mixture is poured and compacted, and after standing for 2 hours, it is demolded and placed in a carbon dioxide curing box. It is cured for 8 hours with 8% carbon dioxide at 0.12 MPa pressure, and then transferred to a curing room at 20°C and 96% relative humidity to be cured until the desired age, thus obtaining ultra-durable solid waste-based low-carbon concrete.

[0039] Comparative Example 1: The difference between Comparative Example 1 and Example 2 is that 300g of ordinary silica nanoparticles without surface modification were directly added, without silanization, polystyrene grafting, or surface functionalization treatment of amphiphilic polymer brush layer construction. The other conditions were the same as in Example 2.

[0040] Comparative Example 2: The difference between Comparative Example 2 and Example 2 is that only polystyrene grafting was used, and amphiphilic polymer brush layer grafting was not performed. All other conditions were the same as in Example 2.

[0041] Comparative Example 3: The difference between Comparative Example 3 and Example 2 is that only amphiphilic polymer brush grafting was used, and polystyrene grafting was not performed. All other conditions were the same as in Example 2.

[0042] Comparative Example 4: The difference between Comparative Example 4 and Example 2 is that 500g of raw hydrotalcite without calcination-reintercalation activation treatment was used directly as a component of the gelled composite powder without undergoing calcination at 500°C for 4 hours and sodium bicarbonate solution impregnation anion exchange activation process. The other conditions were the same as in Example 2.

[0043] Comparative Example 5: The difference between Comparative Example 5 and Example 2 is that 240g of water-absorbing resin particles containing only deionized water were used, without pre-storing sodium aluminate solution. The water-absorbing resin particles were placed in 960g of deionized water for 2 hours for adsorption before use. The other conditions were the same as in Example 2.

[0044] Comparative Example 6: The difference between Comparative Example 6 and Example 2 is that Comparative Example 6 adopts only the standard wet curing system. After molding, the product is directly sent to a curing room with a temperature of 20°C and a relative humidity of 96% for curing until the desired age. No carbon dioxide curing treatment is performed. All other conditions are the same as in Example 2.

[0045] Performance testing: X-ray diffraction analysis: Concrete samples aged 28 days were ground to 325 mesh and tested using an X-ray diffractometer with a scanning range of 5°-80°.

[0046] Fourier transform infrared spectroscopy: Tested using a Fourier transform infrared spectrometer, scanning range 4000-400 cm⁻¹ -1 .

[0047] Compressive strength test: The test was conducted according to GB / T 50081-2019. 150mm×150mm×150mm cubic specimens were prepared and cured under standard curing conditions for 7 days, 28 days, and 90 days. A compression testing machine was used with a loading rate of 0.8MPa / s to determine the maximum load at which the specimen failed. The compressive strength was calculated. Six specimens were prepared for each group, and the average value was taken as the test result. The results are shown in Table 1.

[0048] Pore ​​structure analysis: The pore structure parameters of concrete were determined using mercury intrusion porosimetry. 28-day-old hardened concrete samples were crushed into 5-10 mm particles and dried at 60°C for 24 hours to constant weight. An automatic mercury intrusion porosimeter was used, with a test pressure range of 0.1-400 MPa, corresponding to a pore size range of 3 nm-100 μm. The proportion of harmful pores (>100 nm) was analyzed, and the results are shown in Table 1.

[0049] Water permeability test: The test was conducted according to the water permeability test method in GB / T 50082-2009. A frustum-shaped specimen with an upper diameter of 175 mm, a lower diameter of 185 mm, and a height of 150 mm was prepared and tested after 28 days of curing. A stepwise pressurization method was used, with an initial water pressure of 0.1 MPa, increasing by 0.1 MPa every 8 hours until water seepage appeared on the bottom surface of the specimen. The maximum water pressure value at the point of seepage was recorded, and the seepage height and water permeability grade were calculated. Six specimens were prepared for each group, and the water permeability grade was determined based on the maximum water pressure of four specimens without seepage. The results are shown in Table 1.

[0050] Chloride ion penetration resistance test: The test was conducted according to the RCM method in GB / T 50082-2009. Circular specimens with a diameter of 100 mm and a thickness of 50 mm were prepared and vacuum-saturated with water for 24 hours after a 28-day curing period. The specimens were placed in the RCM test apparatus, with the cathode chamber filled with 0.3 mol / L NaOH solution and the anode chamber filled with 10% NaCl solution. A 30V DC voltage was applied for 24 hours. After the test, the specimens were cleaved axially, sprayed with 0.1 mol / L AgNO3 solution for color development, and the chloride ion penetration depth was measured. The chloride ion migration coefficient was calculated. Three specimens were prepared for each group, and the average value was taken as the test result. The results are shown in Table 1.

[0051] Artificial seawater erosion resistance test: The seawater erosion test was conducted according to JTS / T 236-2019 "Technical Specification for Testing and Inspection of Concrete in Waterway Engineering". An artificial seawater solution (containing 3.5% NaCl, 0.11% MgCl2, 0.04% MgSO4, 0.04% CaSO4, and 0.02% KCl) was prepared, and 100mm×100mm×100mm cubic specimens cured for 28 days were completely immersed. The erosion solution was replaced every 60 days, and the test period lasted until 540 days. The seawater erosion strength retention rate after 540 days was calculated to evaluate the design service life of the marine structure.

[0052] Table 1 Performance Test Results

[0053] Data Analysis: As shown in Table 1, the performance test results of Examples 1-3 demonstrate that the solid waste-based low-carbon concrete prepared by this invention exhibits excellent properties in terms of compressive strength, pore structure, impermeability, resistance to chloride ion penetration, and durability against seawater erosion. Overall, the material compatibility and process pathway significantly improve the material density and interfacial compatibility through multi-scale control. For example, surface-functionalized nano-silica enhances its dispersibility and adhesion to the matrix through molecular brushes and hydroxyl / zwitterionic structures, significantly reducing the proportion of harmful pores and enhancing the formation of a dense structure. The introduction of activated hydrotalcite endows the material with good anion exchange and fixation capabilities, effectively inhibiting the migration of corrosive substances such as chloride ions. Layer-by-layer protection from pores, structure to interface ensures a synergistic improvement in overall permeability barrier and mechanical properties. Simultaneously, the slow-release system within the water-absorbing resin not only provides internal water retention but also supplies active ions such as aluminate ions for early reactions, promoting the formation of a dense hydration / gel phase while maintaining both volume stability and early strength. In terms of process, the combination of carbon dioxide curing and wet curing effectively promotes the formation of carbonates and further densification of the microstructure, achieving rapid improvement in early strength. The synergistic effect of these three factors provides the invention with comprehensive performance advantages, including good adaptability to room temperature construction, ultra-high durability, and significant carbon emission reduction.

[0054] Comparative Example 1 used unmodified silica nanoparticles without silanization, polystyrene grafting, or amphiphilic brush layer modification. This resulted in poor dispersibility and interfacial compatibility of the nanoparticles in an alkaline environment, leading to easy aggregation and a significant decrease in uniformity. This resulted in insufficient system densification, an increased proportion of macropores, decreased permeability barrier capacity, and an increased chloride ion migration coefficient, thus reducing the retention rate of seawater erosion resistance. This demonstrates the importance of surface functionalization of nano-silica for optimizing pore structure and improving impermeability and corrosion resistance.

[0055] Comparative Example 2 only used polystyrene grafting, without grafting with amphiphilic brush-like polymers. Although it partially improved the dispersibility of nano-silica and reduced agglomeration, its interface control ability was limited due to the lack of further compatibility with polarity matching and hydration products. While the proportion of harmful pores decreased somewhat, it remained relatively high, resulting in limited improvement in barrier properties and durability. The chloride ion migration coefficient and seawater erosion resistance were not as improved as in Example 2, indicating that the amphiphilic functional brush structure is key to further achieving synergistic performance enhancement.

[0056] Comparative Example 3 only grafted with amphiphilic polymers and lacked a polystyrene interlayer, resulting in poor adhesion and stability of the functional layer on the particle surface, with potential partial detachment or uneven distribution. Although it improved compatibility with the matrix to some extent and reduced the proportion of harmful pores, the insufficient structural integrity of the brush layer made it susceptible to environmental influences. Some nanoparticles failed to fully exert their space-filling and functional barrier functions, thus limiting the improvement of permeability and corrosion resistance.

[0057] Comparative Example 4 did not use calcined-re-intercalated activated hydrotalcite; instead, it directly added the original layered double hydroxide. Due to its lack of numerous exchangeable anion-active sites, it was difficult to effectively trap chloride ions, resulting in increased harmful pores in the system, decreased impermeability, a further increase in the chloride ion migration coefficient, and a deterioration in the material's resistance to seawater erosion. This verified the principle by which activated hydrotalcite improves multi-level anion blocking and durability.

[0058] Comparative Example 5 stored only deionized water inside the absorbent resin, instead of a sodium aluminate solution. While this resulted in some slow release of moisture and reduced shrinkage, it failed to provide aluminate ions that could react with the hydration products of the system, affecting early hydration and structural densification. Therefore, the reduction in the proportion of harmful pores was limited, and the long-term impermeability and resistance to chloride ion corrosion were inferior to Example 2. The synergistic effect of active ions in the internal conditioning system is particularly crucial for improving crack resistance and durability.

[0059] Comparative Example 6 completely eliminated carbon dioxide curing, employing only standard wet curing. Because it failed to promote the formation of microstructural phases such as carbonates and optimize pore size during the early curing stages, the overall porosity of the system remained high, resulting in weakened permeability barrier capacity, easier chloride ion migration, and decreased resistance to seawater erosion. Carbon dioxide curing plays an indispensable role in regulating the initial microstructure and achieving multiple densification and barrier effects, and is a key guarantee for achieving high performance in the early stages and long-term durability.

[0060] from Figure 1 It can be seen that Example 2 exhibits a distinct C-(A)-SH gel peak at 27°-35°. Simultaneously, carbon dioxide curing enhances the characteristic carbonate peaks at 29.4° (calcite 104), while the weakest peaks are observed in Comparative Example 6 (without carbon dioxide). The layered hydrotalcite-like phase peaks at 11.3° and 22.6° are clearer in the examples, but significantly weaker in Comparative Example 4 (unactivated LDH). The residual β-C2S peak at 32°-33° is stronger in Comparative Examples 4 and 6, but weakest in Example 2. The differences in phase composition and crystallinity are consistent with the pore structure and durability indices shown in Table 1. Example 2 exhibits the lowest proportion of harmful pores, the smallest RCM ion migration coefficient, and the highest impermeability rating, thus demonstrating superior overall performance.

[0061] from Figure 2 It can be seen that, compared with unmodified silica, the 3400 cm⁻¹ of the polystyrene-grafted silica powder sample... -1 Nearby -OH broadband with ~960 cm -1 (Si-OH) was significantly weakened, and 3060 / 3026, 2950 / 2920 / 2850, 1601 / 1492 and 758 / 698 cm⁻¹ were observed. -1 The presence of characteristic peaks of polystyrene indicates that styrene segments have been grafted onto the silica surface; after further functionalization, the sample showed peaks at 1728 cm⁻¹. -1 (C=O) and 1182 / 1035cm -1 (SO3) - A significant new peak appears at 1090-1200 cm⁻¹, and it coincides with the peak at 1090-1200 cm⁻¹. -1 The Si-O-Si envelope superposition forms a fuller absorption region, while 2918 / 2850, 1465 / 1377 and 720 cm⁻¹ are also observed. -1 Enhanced characteristics of equal-length chain hydrocarbons comprehensively indicate the successful construction of amphiphilic brush layers.

[0062] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A type of ultra-high durability solid waste-based low-carbon concrete, characterized in that, The product comprises the following components by weight: 1550-1650 parts of S95 grade granulated blast furnace slag powder, 280-320 parts of steel slag powder, 180-220 parts of Grade I fly ash, 40-60 parts of activated hydrotalcite, 25-35 parts of functionalized silica powder, 15-25 parts of silica sand, 300-360 parts of low modulus water glass activator, 50-70 parts of mixing water, 22-26 parts of pre-filled sodium aluminate water-absorbing resin particles, and 3-5 parts of polycarboxylate superplasticizer. The functionalized silica powder is prepared by sequentially grafting 3-bromopropyltrimethoxysilane initiator, polystyrene intermediate layer and sulfobetaine methacrylate-octadecyl methacrylate amphiphilic polymer brush layer onto the surface of silica nanoparticles. The activated hydrotalcite is prepared by calcining synthetic hydrotalcite at 480-520°C for 3-5 hours and then immersing it in sodium bicarbonate aqueous solution for 45-90 minutes for anion exchange activation. The pre-filled sodium aluminate water-absorbing resin particles are prepared by allowing water-absorbing resin particles to stand and adsorb in an aqueous solution of sodium aluminate with a concentration of 8wt%-12wt% for 1.5-3 hours.

2. The ultra-high durability solid waste-based low-carbon concrete according to claim 1, characterized in that, The specific surface area of ​​the steel slag powder is higher than 390 m². 2 / kg, with SiO2 content of 17%-20% and CaO content of 40%-50%.

3. The ultra-high durability solid waste-based low-carbon concrete according to claim 1, characterized in that, The low-modulus water glass activator has a modulus of 1.3-1.5 and a solid content of 30%-35%.

4. The ultra-high durability solid waste-based low-carbon concrete according to claim 1, characterized in that, The specific surface area of ​​the silica nanopowder is 350 m². 2 / g.

5. The ultra-high durability solid waste-based low-carbon concrete according to claim 1, characterized in that, The specific preparation steps of the functionalized silica powder are as follows: S1: Disperse silica nanopowder in a mixed solution of anhydrous ethanol and deionized water, add 3-bromopropyltrimethoxysilane, stir and react at 55-65°C for 1.5-3h under nitrogen protection, filter and wash, and then vacuum dry at 75-85°C for 2-3h to obtain silica powder with surface-grafted initiators. S2: Surface-grafted initiator silica powder is dispersed in toluene, and styrene, cuprous bromide and pentamethyldiethylenetriamine are added in sequence. The mixture is stirred at 65-75°C for 4-6 hours under nitrogen protection. After filtration, washing and vacuum drying, silica powder grafted with polystyrene is obtained. S3: Disperse the grafted polystyrene silica powder in a mixed solvent of water and methanol, add sulfobetaine methacrylate monomer and octadecyl methacrylate, then add cuprous bromide and pentamethyldiethylenetriamine, stir at room temperature for 3.5-5 h under nitrogen protection to carry out chain extension reaction, filter and wash, and then vacuum dry at 55-65°C for 2-3 h to obtain functionalized silica powder.

6. The ultra-high durability solid waste-based low-carbon concrete according to claim 5, characterized in that, In step S1, the weight ratio of silica nanopowder to 3-bromopropyltrimethoxysilane is 300:45-75.

7. The ultra-high durability solid waste-based low-carbon concrete according to claim 5, characterized in that, In step S2, the weight ratio of silica powder with surface grafting initiator to styrene is 300:120-180.

8. The ultra-high durability solid waste-based low-carbon concrete according to claim 5, characterized in that, In step S3, the weight ratio of the grafted polystyrene silica powder, sulfobetaine methacrylate, and octadecyl methacrylate is 310-340:120-200:6-10.

9. The ultra-high durability solid waste-based low-carbon concrete according to claim 1, characterized in that, The particle size of the water-absorbing resin particles is 150-300μm; the concentration of the sodium aluminate aqueous solution is 8wt%-12wt%.

10. A method for preparing ultra-high durability solid waste-based low-carbon concrete according to any one of claims 1-9, characterized in that, Includes the following steps: (1) S95 grade granulated blast furnace slag powder, steel slag powder, grade I fly ash, activated hydrotalcite, functionalized silica powder and silica sand are dry-mixed in a forced mixer for 180s to obtain a cementitious composite powder; then low modulus water glass activator and mixing water are added and pre-mixed for 60s, followed by the addition of pre-filled sodium aluminate water-absorbing resin particles and polycarboxylate superplasticizer and continued mixing for 120s to obtain a mixture; (2) The mixture is poured and compacted, and after standing for 2 hours, it is demolded and placed in a carbon dioxide curing box. It is cured for 4-8 hours with carbon dioxide at a pressure of 0.08-0.12 MPa and a volume fraction of 3%-8%. Then it is transferred to a curing room at a temperature of 20°C and a relative humidity of 96% to cure until the desired age is reached, thus obtaining ultra-high durability solid waste-based low-carbon concrete.

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