Solid waste-based green high-performance concrete and preparation method thereof

Abstract

The application discloses a kind of solid waste-based green high-performance concrete and preparation method thereof, and relates to the technical field of concrete preparation.The solid waste-based green high-performance concrete provided by the application includes the following components by mass fraction: cement 260-300 parts, fly ash 60-80 parts, granulated blast furnace slag 50-70 parts, iron tailings sand 740-780 parts, recycled aggregate 1040-1080 parts, elastin-like polypeptide composite powder 8-12 parts, chitin nanocrystals 0.5-0.8 parts, non-ionic surfactant 0.5-0.8 parts, water reducing agent 5-8 parts, and water 155-165 parts.The application promotes the mutual synergy of recycled aggregate, elastin-like polypeptide composite powder and chitin nanocrystals, not only improves the density of recycled aggregate itself and the overall concrete, but also significantly inhibits the generation of harmful bubbles in concrete, greatly improves the density, mechanical strength and durability of solid waste-based green high-performance concrete.

Description

Technical Field

[0001] This invention relates to the field of concrete preparation technology, and in particular to a solid waste-based green high-performance concrete and its preparation method. Background Technology

[0002] With the deepening of urbanization in my country, the amount of construction and mining solid waste generated is increasing year by year. Its dumping and landfilling not only occupy a large amount of land resources but also put continuous pressure on the ecological environment. At the same time, concrete, as the most important building material, faces the severe challenge of over-exploitation and resource depletion of its traditional natural sand and gravel aggregates. Crushing and screening construction waste into recycled aggregates, and co-using mining solid waste such as iron tailings to replace natural sand and gravel, to prepare solid waste-based green concrete, is a key technological path to achieve high-value recycling of resources, reduce carbon emissions from the construction industry, and contribute to the construction of "zero-waste cities," with significant environmental, resource, and social benefits.

[0003] However, compared to natural aggregates, solid waste-based aggregates (such as recycled aggregates and iron tailings sand) generally have inherent defects due to their complex sources and varying processing methods. Recycled aggregates undergo crushing and hydration processes, resulting in numerous internal microcracks, high porosity, high water absorption, and low strength. Iron tailings sand, on the other hand, has poor particle size distribution, angular shapes, and contains a certain amount of heavy metals, which may affect its stability and durability. These defects directly lead to a series of technical challenges for solid waste-based concrete:

[0004] First, it has poor crack resistance; the aggregate itself has microcracks and a high porosity structure, and the interfacial transition zone (ITZ) between it and the new cement paste is weak, which makes it easy to become a channel for crack initiation and propagation under stress or environmental action.

[0005] Secondly, it is difficult to coordinate strength and workability; the high water absorption rate of aggregates leads to fluctuations in the effective water-cement ratio, and freshly mixed concrete is prone to problems such as rapid slump loss, introduction of many air bubbles, and poor homogeneity, which limits the development of strength after hardening.

[0006] Third, the durability is significantly insufficient; the internal pores and microcrack system provide a rapid migration path for moisture and corrosive media, which seriously deteriorates the concrete's resistance to impermeability, freeze-thaw cycles and carbonation, affecting the long-term service safety of the structure.

[0007] Existing technologies mainly focus on localized improvements to single solid waste components, such as pretreatment of recycled aggregates through mechanical grinding, acid washing, polymer impregnation, or slurry coating; or performance compensation through optimized mix proportions and the use of high-efficiency water-reducing agents. While these methods can improve aggregate performance to some extent, they are often inefficient, costly, and have limited strengthening effects. They struggle to systematically address deep-seated defects within solid waste aggregates, insufficient interfacial strengthening, and compatibility issues when utilizing multiple solid wastes in synergistic applications. Furthermore, their effects on crack propagation inhibition, bubble stability control, and long-term durability improvement remain insignificant.

[0008] Therefore, in order to realize the large-scale and high-value utilization of solid waste from construction and mining, and to promote substantial breakthroughs in green concrete technology, it is urgent to start from a systemic perspective of multi-solid waste synergistic modification, interface integration enhancement, and microstructure fine control, and focus on solving the core technical problems of easy crack propagation, weak interface transition zone, and low strength and poor durability caused by many air bubbles in recycled aggregate concrete. In this way, we can prepare green high-performance concrete with balanced performance and reliable service, and provide a material basis for improving the service life of engineering structures and promoting the green transformation of the construction industry. Summary of the Invention

[0009] This invention provides a solid waste-based green high-performance concrete and its preparation method. Through aggregate modification optimization and the synergistic effect of multiple components in the formulation system, comprehensive modification is achieved from three aspects: microcrack filling and inhibition of propagation, interfacial transition zone strengthening, and bubble microstructure regulation. This significantly improves the mechanical and durability properties of the solid waste-based concrete, overcomes the performance bottlenecks of traditional solid waste-based concrete, and realizes the efficient and high-value utilization of solid waste. Specifically, this is achieved through the following technologies.

[0010] This invention provides a solid waste-based green high-performance concrete, comprising the following components by mass fraction: 260-300 parts cement, 60-80 parts fly ash, 50-70 parts granulated blast furnace slag, 740-780 parts iron tailings sand, 1040-1080 parts recycled aggregate, 8-12 parts elastin-like polypeptide composite powder, 0.5-0.8 parts chitin nanocrystals, 0.5-0.8 parts nonionic surfactant, 5-8 parts water-reducing agent, and 155-165 parts water.

[0011] The method for preparing the recycled aggregate is as follows:

[0012] Moisten the original recycled aggregate with water to a moisture content of 6%-8%, and let it stand.

[0013] Tannic acid was added to an aqueous dispersion of graphene oxide with a solid content of 1.0 wt%-2.0 wt%, stirred until homogeneous, and allowed to stand.

[0014] The moistened original recycled aggregate and the tannic acid-graphene oxide mixture were mixed and stirred evenly, dried at 60-70℃ for 80-120 min, cured while maintaining the moisture content of the recycled aggregate at 15%-20%, and allowed to stand to obtain recycled aggregate.

[0015] Furthermore, in the method for preparing the recycled aggregate, the original recycled aggregate comprises 150-200 parts by mass fraction, the graphene oxide dispersion comprises 40-60 parts, and the tannic acid comprises 12-16 parts.

[0016] Specifically, in the method for preparing the recycled aggregate, the original recycled aggregate comprises 180 parts by mass fraction, graphene oxide dispersion comprises 50 parts by mass fraction, and tannic acid comprises 14 parts by mass fraction.

[0017] When using recycled aggregate prepared by the above-mentioned special preparation method, the present invention wets the recycled aggregate with water to appropriately soften the hardened cement paste on its surface.

[0018] Tannic acid (TA) is readily soluble in water and dissolves rapidly in aqueous dispersions of graphene oxide. The tannic acid molecule contains numerous phenolic hydroxyl groups that can form strong hydrogen bonds with the surface functional groups of graphene oxide (GO), and it also interacts with the sp(s) groups of graphene oxide through its aromatic rings. 2 π-π stacking of carbon domains promotes the uniform adsorption of tannic acid on the surface of graphene oxide sheets, forming a "negative charge layer," which improves the stability of graphene oxide and prevents agglomeration. During heating and drying, the "concentration" effect of water evaporation amplifies the TA-GO bridging, forming a dense organic-inorganic network (tannic acid serves as the organic bridge, while the inorganic graphene oxide sheets are inorganic).

[0019] During the curing process, the multiple phenolic hydroxyl groups of tannic acid can complex with the calcium ions of the old mortar components on its surface to form nanoscale TA-Ca polymer precipitates, which fill the microcracks and pores of the recycled aggregate.

[0020] The graphene oxide sheets, bridged by tannic acid, are arranged in a more ordered manner, providing a template effect. When recycled aggregate is added to concrete, the abundant oxygen-containing functional groups (such as -COOH, -OH, etc.) on the surface of the graphene oxide nanosheets can strongly adsorb cement particles and hydration product ions (Ca). 2+ Graphene oxide nanosheets, with silicate ions as nucleation sites, accelerate the orderly growth of hydration products (such as CSH gel) on their surface, significantly improving density. When microcracks propagate in concrete, the graphene oxide nanosheets embedded in the matrix have a "stitching" effect, bridging the cracks by absorbing fracture energy through their own stretching and slippage, thus preventing further propagation.

[0021] Iron tailings sand contains high levels of iron oxides (Fe). 3+ (Abundant in content) and small amounts of heavy metal ions (Pb) 2+ Cu 2+ When mixed with recycled aggregate in concrete, the phenolic hydroxyl groups of tannic acid on the surface of the modified recycled aggregate can react with the Fe on the surface of iron tailings sand particles. 3+ Formation of stable octahedral coordination complexes (TA-Fe) 3+ The composite material generates a dense cross-linked network that fills pores and microcracks, strengthens the interfacial transition zone (ITZ), and further improves density. Simultaneously, the cross-linked network exhibits excellent barrier effects, significantly reducing chloride ion migration and enhancing the durability of green concrete.

[0022] The multiple phenolic hydroxyl groups of tannic acid can react with Pb in tailings sand. 2+ Cu 2+ Heavy metal ions can form stable five- or six-membered chelate rings, generating insoluble or low-migration complexes; TA-Fe 3+ The network provides a physical barrier to limit ion diffusion. In the highly alkaline environment of concrete, hydration products (such as CSH colloids) further adsorb / encapsulate these complexes, synergistically reducing the risk of heavy metal leaching from tailings sand.

[0023] Therefore, when selecting the aforementioned special recycled aggregate, this invention achieves the following: First, through the synergistic effect of tannic acid and graphene oxide on the original recycled aggregate, it can fill and repair the microcracks and voids in the recycled aggregate, thereby enhancing its own strength; Second, under the action of tannic acid, graphene oxide can more effectively act on cement particles and hydration product ions, accelerating the growth of hydration products and improving the overall density of concrete; Third, it can react with Fe in iron tailings sand. 3+ It complexes / chelates with other heavy metal ions to form a cross-linked network, inhibiting ion diffusion, improving concrete durability, and synergistically reducing the risk of heavy metal leaching from tailings sand with hydration products.

[0024] Furthermore, the preparation method of the elastin-like polypeptide complex powder is as follows:

[0025] The elastin-like peptide solution was added dropwise to the sodium alginate solution, and calcium chloride was added at the same time. The mixture was stirred and stirred until homogeneous.

[0026] The resulting mixture was freeze-dried to obtain an elastin-like polypeptide composite powder.

[0027] The concentration of the elastin-like polypeptide solution is 1wt%-3wt%, the concentration of the sodium alginate solution is 0.2wt%-0.5wt%, the mass of the calcium chloride is 1-2% of the sodium alginate solution, and the mass ratio of the elastin-like polypeptide solution to the sodium alginate solution is 2:1.

[0028] Furthermore, the elastin-like polypeptide powder has a particle size of 120 mesh, an effective ingredient content of ≥98%, a moisture content of ≤3%, and a molecular weight of 552; the sodium alginate has a molecular weight of 50-200 kDa and a purity of ≥98%.

[0029] Optionally, the selected elastin-like polypeptide solution is prepared by dissolving elastin-like polypeptide powder in deionized water or a buffer solution at a predetermined concentration.

[0030] When preparing elastin-like peptide solutions, the dissolution temperature can be controlled between 4-10℃, and stirring should be continued until complete dissolution. If necessary, a 0.22 μm filter membrane can be used to remove bacteria and other microorganisms, as well as other insoluble substances.

[0031] Air bubbles in concrete are mainly classified into three categories: harmful large air bubbles (>100 μm), moderately harmful air bubbles (50-100 μm), and low-harm air bubbles (20-50 μm). Elastin-like peptides (ELPs) possess thermosensitive and fibrous self-assembling molecular properties; they are soluble and interfacially active at low temperatures, and phase separation occurs when the temperature rises above a threshold, forming aggregates or micelles. When ELPs are added to concrete, the initial hydration level and temperature are relatively low, allowing the ELPs to dissolve and widely distribute, playing a lubricating role, improving concrete fluidity, reducing the water-cement ratio, and preventing excessive water from introducing air bubbles. The amphiphilic structure of ELPs can also adsorb harmful large air bubbles in concrete, reducing the surface tension of the bubbles, making them easier to break down into smaller bubbles under external stirring or vibration disturbance.

[0032] As the internal temperature of the concrete rises during vibration, elastin-like peptides gradually self-assemble into nanofibers with good colloidal stability, forming a three-dimensional network structure. These nanofibers, with their high aspect ratio geometry, induce large air bubbles to rupture and redistribute into smaller bubbles through localized stress. Combined with the vibration process, this maximizes the dissipation of air bubbles. Once the bubbles disappear, the colloidal nanofibers fill the porous cementitious interface transition zone, improving the smoothness and density of the concrete surface. The colloidal elastin-like peptides also possess good moisture retention properties, providing effective internal curing and enhancing the concrete's strength and crack resistance.

[0033] During concrete mixing, the highly alkaline environment can lead to the degradation or weakening of elastin-like peptides. Combining sodium alginate with elastin-like peptides, utilizing the properties of sodium alginate polysaccharides and the presence of carboxylic acid groups (-COOH), can help them interact with the calcium in concrete. 2+ The reaction forms an insoluble gel, encapsulating ELPs and building a physical barrier. The carboxylic acid groups can also react with OH groups in the concrete. - Combine, release H + This lowers the local pH of elastin-like peptides, protecting their structure from initial damage by high alkalinity. Adding calcium chloride to a solution containing sodium alginate and ELPs introduces Ca2+. 2+ It can also form an ionic cross-linking network of sodium alginate, enhancing the stability of the solution and the freeze-dried powder. The final freeze-drying process also helps maintain the activity of elastin-like peptides.

[0034] Furthermore, the chitin nanocrystals have a diameter of 10-20 nm, a length of 500-800 nm, and a specific surface area of ​​50-80 m². 2 / g, crystallinity ≥85%.

[0035] The chitin nanocrystals selected in this invention exhibit strong hydrophilicity, high specific surface area, and a rod-like morphology (10-20 nm in diameter and 500-800 nm in length). Their surface is rich in hydroxyl (-OH), amide (-NHCOCH3), and a small amount of amino / carboxyl groups. Utilizing their rod-like, high aspect ratio structure, they can form tiny "bridges" when uniformly dispersed in concrete. These bridges tightly bind with cement hydration products (CSH gel) through hydrogen bonds and van der Waals forces, effectively transferring and dispersing stress, thereby increasing the strength and toughness of the concrete.

[0036] Specifically, on the one hand, the hydroxyl / amide groups on the surface of chitin nanocrystals can form a hydrogen-bonded interpenetrating network with the functional groups (carboxyl / hydroxyl groups) of graphene oxide in recycled aggregates, simultaneously acting as a "bridging" agent with tannic acid. The three form a ternary composite synergistic structure, filling nanopores and inhibiting crack initiation from weak ITZs. On the other hand, the high-modulus rigidity of chitin nanocrystals complements the flexible chains of elastin-like peptides, forming a polyelectrolyte composite (cationic properties combined with electrostatic interaction of carboxyl / amino groups and hydrogen bonding in the protein peptides), stabilizing and strengthening the nanofiber structure formed by the self-assembly of elastin-like peptides. Concrete is rich in polyvalent calcium ions, and the elastin-like peptide molecular chains contain negatively charged carboxyl groups -COO. - Calcium ions form cross-linking points between chains through electrostatic interactions, making the self-assembled elastin-like polypeptide nanofiber network structure more compact. Through the combined effect of these two aspects, the nanofibers formed by the self-assembly of elastin-like polypeptides are denser and more robust, effectively enhancing the rigidity and strength of the nanofibers.

[0037] This invention also provides a method for preparing solid waste-based green high-performance concrete, comprising the following steps:

[0038] The chitin nanocrystals and 10-15 parts of water are mixed evenly to form a first mixture; the elastin-like polypeptide composite powder, 20-25 parts of warm water, and half a part of nonionic surfactant are stirred evenly to form a second mixture; the first mixture and the second mixture are mixed evenly to obtain a standby solution.

[0039] Cement, fly ash, and granulated blast furnace slag are mixed evenly, then water-reducing agent and 80-100 parts of water are added and mixed evenly; the prepared liquid is added and mixed evenly to obtain the mixture.

[0040] Iron tailings sand, recycled aggregate, remaining nonionic surfactant, and remaining water are added to the mixture and mixed evenly to obtain solid waste-based green high-performance concrete slurry.

[0041] The preparation process of the above-mentioned solid waste-based green high-performance concrete follows the principle of "liquid-liquid premixing, solid-liquid encapsulation, and orderly feeding" to ensure that the nano- and active components are uniformly dispersed and fully integrated with the modified aggregate and cementitious system.

[0042] Compared with the prior art, the advantages of the present invention are:

[0043] 1. By selecting recycled aggregates synergistically modified with tannic acid and graphene oxide, multi-solid-waste synergy is achieved between recycled aggregates and iron tailings sand. Firstly, tannic acid enhances the stability and dispersibility of graphene oxide, and the two construct a dense organic-inorganic network on the aggregate surface. Tannic acid and recycled aggregate old mortar form nanoscale TA-Ca precipitates, filling microcracks and pores; in concrete, graphene oxide plays a nucleation and bridging role, promoting the orderly growth of hydration products and inhibiting crack propagation, thus strengthening density. Secondly, the tannic acid on the surface of the recycled aggregates reacts with the Fe in the iron tailings sand... 3+ It forms stable coordination complexes, strengthens the interfacial transition zone, and improves density. At the same time, tannic acid forms stable chelates with heavy metal ions in tailings sand. Combined with the physical barrier of the TA-Fe network and the adsorption of CSH, it synergistically reduces the risk of heavy metal leaching, thus achieving high performance and environmental safety of green concrete.

[0044] 2. This invention utilizes elastin-like peptides to regulate the air bubble structure and properties of concrete. In the initial mixing stage, the elastin-like peptides act as a lubricant, reducing the water-cement ratio and preventing excessive water from introducing air bubbles. During vibration, as the temperature rises, the elastin-like peptides self-assemble into nanofibers. Through localized stress induction, harmful air bubbles are largely dissipated, transforming into low-harm small air bubbles that are further dissipated by vibration. Simultaneously, the nanofiber colloids fill pores and interfacial transition zones, enhancing the internal curing effect and further improving the concrete's density, surface smoothness, and strength. The introduction of sodium alginate and calcium chloride composite stabilizes the peptide activity, buffering the alkaline environment's damage to the peptide structure and ensuring the long-term stable function of the elastin-like peptides in the concrete.

[0045] 3. This invention introduces chitin nanocrystals for synergistic optimization of concrete, recycled aggregates, and elastin-like peptides. Utilizing the properties of chitin nanocrystals, they not only effectively improve the overall strength and toughness of concrete but also form a ternary synergistic structure with graphene and tannic acid in modified recycled aggregates, filling pores and inhibiting the propagation of interfacial cracks. The chitin nanocrystals and the flexible chains of elastin-like peptides complement each other, forming a rigid-flexible composite structure that stabilizes and strengthens the nanofiber network formed by the self-assembly of elastin-like peptides, further optimizing the internal structure of concrete.

[0046] In summary, this invention achieves multi-scale optimization and control of the microstructure of recycled aggregate concrete through the synergistic effect of multiple components, including recycled aggregates and solid waste-based materials such as iron tailings sand, elastin-like polypeptide composite powder, and chitin nanocrystals. Simultaneously, it effectively inhibits the generation and expansion of harmful air bubbles in the concrete, comprehensively improving the workability, mechanical properties, and durability of solid waste-based green high-performance concrete. This provides an innovative technical solution for constructing a high-performance, low-carbon footprint solid waste resource-based concrete system. Detailed Implementation

[0047] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0048] Some embodiments of the present invention provide a solid waste-based green high-performance concrete, comprising the following components by mass fraction: 260-300 parts cement, 60-80 parts fly ash, 50-70 parts granulated blast furnace slag, 740-780 parts iron tailings sand, 1040-1080 parts recycled aggregate, 8-12 parts elastin-like polypeptide composite powder, 0.5-0.8 parts chitin nanocrystals, 0.5-0.8 parts nonionic surfactant, 5-8 parts water-reducing agent, and 155-165 parts water.

[0049] Optionally, the method for preparing the recycled aggregate is as follows:

[0050] Moisten the original recycled aggregate with water to a moisture content of 6%-8%, and let it stand.

[0051] Tannic acid was added to an aqueous dispersion of graphene oxide with a solid content of 1.0 wt%-2.0 wt%, stirred until homogeneous, and allowed to stand.

[0052] The moistened original recycled aggregate and the tannic acid-graphene oxide mixture were mixed and stirred evenly, dried at 60-70℃ for 80-120 min, cured while maintaining the moisture content of the recycled aggregate at 15%-20%, and allowed to stand to obtain recycled aggregate.

[0053] In the method for preparing the recycled aggregate, the original recycled aggregate comprises 150-200 parts by mass fraction, the graphene oxide dispersion comprises 40-60 parts by mass fraction, and the tannic acid comprises 12-16 parts by mass fraction.

[0054] Specifically, the original recycled aggregate consisted of 180 parts, graphene oxide dispersion of 50 parts, and tannic acid of 14 parts.

[0055] Optionally, the preparation method of the elastin-like polypeptide complex powder is as follows:

[0056] The elastin-like peptide solution was added dropwise to the sodium alginate solution, and calcium chloride was added at the same time. The mixture was stirred and stirred until homogeneous.

[0057] The resulting mixture was freeze-dried to obtain an elastin-like polypeptide composite powder.

[0058] The concentration of the elastin-like polypeptide solution is 1wt%-3wt%, the concentration of the sodium alginate solution is 0.2wt%-0.5wt%, the mass of the calcium chloride is 1-2% of the sodium alginate solution, and the mass ratio of the elastin-like polypeptide solution to the sodium alginate solution is 2:1.

[0059] Among them, the elastin-like polypeptide has a particle size of 120 mesh, an effective ingredient content of ≥98%, a moisture content of ≤3%, and a molecular weight of 552; the sodium alginate has a molecular weight of 50-200 kDa and a purity of ≥98%.

[0060] Optionally, the selected elastin-like polypeptide solution is prepared by dissolving elastin-like polypeptide powder in deionized water or a buffer solution at a predetermined concentration.

[0061] When preparing elastin-like peptide solutions, the dissolution temperature can be controlled between 4-10℃, and stirring should be continued until complete dissolution. If necessary, a 0.22 μm filter membrane can be used to remove bacteria and other microorganisms, as well as other insoluble substances.

[0062] Optionally, the chitin nanocrystals have a diameter of 10-20 nm, a length of 500-800 nm, and a specific surface area of ​​50-80 m². 2 / g, crystallinity ≥85%.

[0063] This invention also provides a method for preparing the above-mentioned solid waste-based green high-performance concrete, comprising the following steps:

[0064] The chitin nanocrystals and 10-15 parts of water are mixed evenly to form a first mixture; the elastin-like polypeptide composite powder, 20-25 parts of warm water, and half a part of nonionic surfactant are stirred evenly to form a second mixture; the first mixture and the second mixture are mixed evenly to obtain a standby solution.

[0065] Cement, fly ash, and granulated blast furnace slag are mixed evenly, then water-reducing agent and 80-100 parts of water are added and mixed evenly; the prepared liquid is added and mixed evenly to obtain the mixture.

[0066] Iron tailings sand, recycled aggregate, remaining nonionic surfactant, and remaining water are added to the mixture and mixed evenly to obtain solid waste-based green high-performance concrete slurry.

[0067] In the above preparation method, chitin nanocrystals and water can be mixed using ultrasound with an ultrasound power of 600-800W and an ultrasound time of 15-20 min, until a uniform, stable, and non-particulate semi-transparent colloidal suspension is formed.

[0068] In the above preparation method, cement, fly ash, and granulated blast furnace slag powder can be dry-mixed for 1-2 minutes, and then all the water-reducing agent and most of the remaining mixing water (about 100-115 parts) can be added.

[0069] Optionally, the raw materials, such as cement, fly ash, granulated blast furnace slag, iron tailings sand, nonionic surfactants, and water-reducing agents, can all be commercially available raw materials according to the actual requirements of the performance parameters of solid waste-based green high-performance concrete. Among them, ordinary Portland cement is preferred, and different grades of cement, fly ash, and granulated blast furnace slag can be selected according to actual needs.

[0070] Specifically, ordinary Portland cement PO 42.5 or PO 52.5 can be selected for cement; Class I or Class II fly ash can be selected; for example, nonionic surfactants such as fatty alcohol polyoxyethylene ether and alkylphenol polyoxyethylene ether can be selected; and water-reducing agents such as polycarboxylate water-reducing agents can be selected.

[0071] For ease of comparison, the sources and specifications of the raw materials used in the following specific implementation cases are shown in Table 1 below.

[0072] Table 1. Raw material sources and specifications of concrete

[0073]

[0074] Example 1

[0075] The solid waste-based green high-performance concrete provided in this embodiment includes the following components by mass fraction: 280 parts cement, 70 parts fly ash, 60 parts granulated blast furnace slag, 70 parts iron tailings sand, 1060 parts recycled aggregate, 10 parts elastin-like polypeptide composite powder, 0.6 parts chitin nanocrystals, 0.6 parts nonionic surfactant, 7 parts water-reducing agent, and 160 parts water.

[0076] The method for preparing recycled aggregate used in this embodiment is as follows:

[0077] (1) First, heat 180 parts of original recycled aggregate to 60°C, stir at low speed and continuously spray water to moisten it, so that the moisture content reaches 8%, and let it stand for 30-40 minutes.

[0078] 50 parts of graphene oxide aqueous dispersion and 14 parts of tannic acid were stirred at 50℃ for 10 min and then allowed to stand for 30 min.

[0079] (2) After mixing the pretreated recycled aggregate and graphene oxide-tannic acid mixture for 30 minutes, stop stirring and then dry at 70°C for 80 minutes. Then enter the curing stage. During the curing period, spray water evenly multiple times to make the aggregate moisture content reach 20%. Let it stand at room temperature for 7 days to obtain the final recycled aggregate.

[0080] The preparation method of the elastin-like polypeptide composite powder selected for the above-mentioned solid waste-based green high-performance concrete is as follows:

[0081] (1) Slowly add 1.5 wt% ELPs solution to 0.35 wt% sodium alginate solution, with a solution mass ratio of 2:1. At the same time, add 2% calcium chloride by mass of sodium alginate solution. Stir magnetically while adding the solution (200-300 rpm) for 10-20 minutes.

[0082] (2) The obtained mixed solution was frozen at -80℃ for 12 h and then dried in a freeze dryer for 30 h to obtain elastin-like polypeptide complex powder.

[0083] The preparation method of the above-mentioned solid waste-based green high-performance concrete includes the following steps:

[0084] (1) 0.6 parts of chitin nanocrystals and 13 parts of water were ultrasonically mixed with an ultrasonic power of 800 W and an ultrasonic time of 15 min to form a uniform, stable, and non-particulate semi-transparent colloidal suspension (first mixture).

[0085] Mix elastin-like polypeptide complex powder, 20 parts of warm water (approximately 40°C), and 1 / 2 mass (i.e., 0.3 parts) of nonionic surfactant until completely dissolved to form a clear or slightly turbid solution (second mixture).

[0086] Mix the two aqueous solutions together and stir for 10 minutes to obtain the prepared solution.

[0087] (2) Add the cement, fly ash, and granulated blast furnace slag powder of the formula into a forced mixer and dry mix for 2 minutes. Add 90 parts of mixing water and all the water-reducing agent and mix to form a uniform slurry. Then add the prepared liquid obtained in step (1) and continue to mix for 3 minutes to ensure uniform mixing.

[0088] Then add iron tailings sand, recycled aggregate, remaining nonionic surfactant, and remaining water, and continue stirring and mixing for 5 minutes. The surface of the aggregate particles is uniformly coated with the slurry, and the mixture has no bleeding or segregation, thus obtaining concrete slurry.

[0089] Example 2

[0090] The solid waste-based green high-performance concrete provided in this embodiment, the recycled aggregate, the elastin-like polypeptide composite powder and the concrete preparation method are the same as in Example 1, the difference being that: by mass fraction, it includes 260 parts of cement, 60 parts of fly ash, 70 parts of granulated blast furnace slag, 780 parts of iron tailings sand, 1080 parts of recycled aggregate, 12 parts of elastin-like polypeptide composite powder, 0.8 parts of chitin nanocrystals, 0.8 parts of nonionic surfactant, 8 parts of water-reducing agent and 155 parts of water.

[0091] Example 3

[0092] The solid waste-based green high-performance concrete provided in this embodiment, the recycled aggregate, the elastin-like polypeptide composite powder and the concrete preparation method are the same as in Example 1, the difference being that: by mass fraction, it includes 300 parts cement, 80 parts fly ash, 50 parts granulated blast furnace slag, 740 parts iron tailings sand, 1040 parts recycled aggregate, 8 parts elastin-like polypeptide composite powder, 0.5 parts chitin nanocrystals, 0.5 parts nonionic surfactant, 5 parts water-reducing agent and 165 parts water.

[0093] Example 4

[0094] The solid waste-based green high-performance concrete, elastin-like polypeptide composite powder, and concrete preparation method provided in this embodiment are the same as those in Example 1, as are the concrete raw material composition and dosage. The difference lies in the following: in the preparation method of recycled aggregate, the original recycled aggregate is 200 parts, the graphene oxide dispersion is 60 parts, and the tannic acid is 16 parts.

[0095] Example 5

[0096] The solid waste-based green high-performance concrete, elastin-like polypeptide composite powder, and concrete preparation method provided in this embodiment are the same as those in Example 1, as are the concrete raw material composition and dosage. The difference lies in the following: in the preparation method of recycled aggregate, the original recycled aggregate is 150 parts, graphene oxide dispersion is 40 parts, and tannic acid is 12 parts.

[0097] Example 6

[0098] The solid waste-based green high-performance concrete, recycled aggregate, and concrete preparation method provided in this embodiment are the same as those in Example 1, as are the concrete raw material composition and dosage. The difference lies in the preparation method of the elastin-like polypeptide composite powder, where the concentration of the elastin-like polypeptide solution is 3 wt% and the concentration of the sodium alginate solution is 0.5 wt%.

[0099] Example 7

[0100] The solid waste-based green high-performance concrete, recycled aggregate, and concrete preparation method provided in this embodiment are the same as those in Example 1, as are the concrete raw material composition and dosage. The difference lies in the preparation method of the elastin-like polypeptide composite powder, where the concentration of the elastin-like polypeptide solution is 1 wt% and the concentration of the sodium alginate solution is 0.2 wt%.

[0101] Comparative Example 1

[0102] The solid waste-based green high-performance concrete provided in this comparative example has essentially the same composition, mass fraction, and concrete preparation method as Example 1. The difference is that this comparative example directly uses virgin recycled aggregate to replace the recycled aggregate in Example 1.

[0103] Comparative Example 2

[0104] The solid waste-based green high-performance concrete provided in this comparative example differs from Example 1 in that it does not use any elastin-like polypeptide composite powder. The amounts of other concrete raw materials and phases used are the same as in Example 1.

[0105] Comparative Example 3

[0106] The solid waste-based green high-performance concrete provided in this comparative example differs from that in Example 1 in that chitin nanocrystals were not added. The amounts of other concrete raw materials and phases used are the same as in Example 1.

[0107] Comparative Example 4

[0108] The solid waste-based green high-performance concrete provided in this comparative example differs from that in Example 1 in that it uses the same mass of ordinary manufactured sand from Zone II to replace iron tailings sand.

[0109] Comparative Example 5

[0110] The solid waste-based green high-performance concrete provided in this comparative example differs from that in Example 1 in that the same mass fractions of elastin-like polypeptide powder, sodium alginate powder, and calcium chloride powder are used to replace the elastin-like polypeptide composite powder; and in the corresponding concrete preparation steps, the elastin-like polypeptide powder, sodium alginate powder, and calcium chloride powder are directly added to the concrete.

[0111] Comparative Example 6

[0112] The solid waste-based green high-performance concrete provided in this comparative example differs from that in Example 1 in that the same mass fraction of original recycled aggregate, graphene oxide, and tannic acid are used to replace the recycled aggregate; and in the corresponding concrete preparation steps, the original recycled aggregate, graphene oxide, and tannic acid are directly added to the concrete.

[0113] Experimental Example: Performance Testing of Concrete

[0114] The workability, mechanical properties, crack resistance, and impermeability of the concrete prepared in the above embodiments and comparative examples were tested.

[0115] Specifically, the workability of freshly mixed concrete in the examples and comparative examples was tested according to the provisions of GB / T50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures". The mechanical properties of the concrete were tested according to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Ordinary Concrete". The early crack resistance and impermeability of the concrete were tested according to GB / T50082-2009 "Standard for Test Methods of Long-Term Performance and Durability of Ordinary Concrete". The early crack resistance of concrete was determined using the "crack plate test", and the test results were expressed as the calculated total crack area per unit area; the smaller the value, the better the crack resistance. The average water penetration height of the concrete under constant water pressure was determined using the "water penetration height method", which represents the concrete's water penetration resistance; the larger the average water penetration height value, the worse the water penetration resistance. The percentage of harmful pores (>100nm, %) in the concrete was determined with reference to GB / T 21650.1-2008 (Metal Intrusion Pore Size Distribution Determination).

[0116] The performance test results of each type of concrete are shown in Table 2.

[0117] Table 2 Test Results of Concrete Performance

[0118]

[0119] As shown in Table 2, the test results of Examples 1-7 exhibit excellent overall performance: slump ≥ 200 mm, 28-day compressive strength stable at 50.1-53.4 MPa, >100 nm harmful pores < 20%, water seepage height 26-31 mm, and total crack area per unit area 78-90 mm². 2 / m 2 All samples were rated as Class V in terms of crack resistance. Although the compressive strength and density of Examples 1-3 differed slightly due to variations in cement content and admixture ratio, they all maintained superior performance.

[0120] In contrast, Comparative Example 1, using unmodified virgin recycled aggregate, exhibited a concrete compressive strength of only 44 MPa at 28 days due to its numerous internal microcracks, high porosity, and high water absorption. The water penetration height reached 40 mm, and the proportion of harmful pores (>100 nm) was as high as 34.8%. This indicates that recycled aggregate synergistically modified with graphene oxide dispersion and tannic acid can significantly improve interfacial bonding and pore structure, thereby greatly enhancing the overall performance of recycled aggregate concrete.

[0121] Compared with Example 1, Comparative Example 2, which did not incorporate elastin-like polypeptide composite powder, showed a 20.8 percentage point increase in the proportion of harmful pores >100 nm, and a significant decrease in density and crack resistance. This indicates that the component plays an important role in regulating bubble structure, reducing harmful macropores, achieving internal curing, and improving overall density.

[0122] Comparative Example 3, without the addition of chitin nanocrystals, resulted in a 4.3 MPa decrease in 28-day compressive strength and a 27 mm increase in total crack area per unit area. 2 / m 2 This demonstrates that chitin nanocrystals have a synergistic effect on the formulation materials of the concrete of this invention. Utilizing their properties, they can not only effectively improve the overall strength and toughness of concrete, but also fill pores and inhibit the propagation of interfacial cracks, stabilize and strengthen the nanofiber network formed by the self-assembly of elastin-like peptides, and optimize the internal structure of concrete.

[0123] In Comparative Example 4, replacing iron tailings sand with the same mass of ordinary manufactured sand from Zone II resulted in a decrease in concrete compressive strength and an increase in water permeability. This indicates that the tannins on the surface of the recycled aggregate react with the Fe in the iron tailings sand. 3+ The stable coordination complexes formed have a significant strengthening effect on the interfacial transition zone, which is an important mechanism for improving density and impermeability.

[0124] Comparative Examples 5 and 6 show that recycled aggregate and elastin-like peptide composite powder were directly added to concrete in equal mass proportions, respectively. Compared with Example 1, the proportion of harmful pores was significantly increased, and the density and crack resistance were significantly deteriorated. This indicates that the elastin-like peptide composite powder and recycled aggregate must be pre-mixed into a composite material according to the technical method described in this invention to ensure that the elastin-like peptides and modified recycled aggregate produce the best synergistic effect with other components during concrete mixing and hardening, thereby achieving optimal overall performance improvement.

[0125] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A solid waste-based green high-performance concrete, characterized in that, The composition by mass fraction includes the following components: 260-300 parts cement, 60-80 parts fly ash, 50-70 parts granulated blast furnace slag, 740-780 parts iron tailings sand, 1040-1080 parts recycled aggregate, 8-12 parts elastin-like polypeptide composite powder, 0.5-0.8 parts chitin nanocrystals, 0.5-0.8 parts nonionic surfactant, 5-8 parts water-reducing agent, and 155-165 parts water. The method for preparing the recycled aggregate is as follows: Moisten the original recycled aggregate with water to a moisture content of 6%-8%, and let it stand. Tannic acid was added to an aqueous dispersion of graphene oxide with a solid content of 1.0 wt%-2.0 wt%, stirred until homogeneous, and allowed to stand. The moistened original recycled aggregate and the tannic acid-graphene oxide mixture were mixed and stirred evenly, dried at 60-70℃ for 80-120 min, cured while maintaining the moisture content of the recycled aggregate at 15%-20%, and allowed to stand to obtain recycled aggregate.

2. The solid waste-based green high-performance concrete according to claim 1, characterized in that, In the method for preparing the recycled aggregate, the original recycled aggregate comprises 150-200 parts by mass fraction, the graphene oxide dispersion comprises 40-60 parts by mass fraction, and the tannic acid comprises 12-16 parts by mass fraction.

3. The solid waste-based green high-performance concrete according to claim 2, characterized in that, In the method for preparing the recycled aggregate, the original recycled aggregate comprises 180 parts by mass fraction, graphene oxide dispersion comprises 50 parts by mass fraction, and tannic acid comprises 14 parts by mass fraction.

4. The solid waste-based green high-performance concrete according to claim 1, characterized in that, The preparation method of the elastin-like polypeptide complex powder is as follows: The elastin-like peptide solution was added dropwise to the sodium alginate solution, and calcium chloride was added at the same time. The mixture was stirred and stirred until homogeneous. The resulting mixture was freeze-dried to obtain an elastin-like polypeptide composite powder. The concentration of the elastin-like polypeptide solution is 1 wt%-3 wt%, the concentration of the sodium alginate solution is 0.2 wt%-0.5 wt%, the mass of the calcium chloride is 1-2% of the sodium alginate solution, and the mass ratio of the elastin-like polypeptide solution to the sodium alginate solution is 2:

1.

5. The solid waste-based green high-performance concrete according to claim 4, characterized in that, The elastin-like polypeptide powder has a particle size of 120 mesh, an effective ingredient content of ≥98%, a moisture content of ≤3%, and a molecular weight of 552; the sodium alginate has a molecular weight of 50-200 kDa and a purity of ≥98%.

6. The solid waste-based green high-performance concrete according to claim 4, characterized in that, The elastin-like polypeptide solution is prepared by dissolving elastin-like polypeptide powder in deionized water or buffer solution at a predetermined concentration. Furthermore, membrane filtration was used to remove microorganisms and insoluble matter.

7. The solid waste-based green high-performance concrete according to claim 1, characterized in that, The chitin nanocrystals have a diameter of 10-20 nm, a length of 500-800 nm, and a specific surface area of ​​50-80 m². 2 / g, crystallinity ≥85%.

8. A method for preparing solid waste-based green high-performance concrete according to any one of claims 1-7, characterized in that, Includes the following steps: The chitin nanocrystals and 10-15 parts of water are mixed evenly to form a first mixture; the elastin-like polypeptide composite powder, 20-25 parts of warm water, and half a part of nonionic surfactant are stirred evenly to form a second mixture; the first mixture and the second mixture are mixed evenly to obtain a standby solution. Cement, fly ash, and granulated blast furnace slag are mixed evenly, then water-reducing agent and 80-100 parts of water are added and mixed evenly; the prepared liquid is added and mixed evenly to obtain the mixture. Iron tailings sand, recycled aggregate, remaining nonionic surfactant, and remaining water are added to the mixture and mixed evenly to obtain solid waste-based green high-performance concrete slurry.

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