Iron tailing powder-slag powder co-doped concrete and preparation method thereof

Abstract

The invention discloses iron tailing powder-slag powder co-doped concrete and a preparation method thereof, and belongs to the technical field of concrete materials. The invention aims to solve the problem that concrete for an intertidal zone bank protection structure is difficult to adapt to composite working conditions of high-salt soaking, tidal scouring, wave impact and silt abrasion. The concrete is prepared from the following components in parts by mass: 30 to 40 parts of P.O 42.5 ordinary Portland cement, 35 to 50 parts of modified iron tailing powder, 15 to 28 parts of superfine slag powder, 2 to 6 parts of steel slag-based nano calcium-lignosulfonate grafted composite powder, 2.0 to 4.0 parts of desulfurized gypsum, 1.0 to 3.0 parts of lithium slag powder, 0.5 to 1.5 parts of hydrated calcium aluminate, 0.8 to 2 parts of modified hydroxyapatite nano powder and 105 to 130 parts of modified iron tailing aggregate, 0.4-1.2 parts of basalt fibers, 0.7-1.5 parts of a polycarboxylic acid type high-efficiency water reducing agent, 0.1-0.5 part of a modified konjac glucomannan-polyether amine copolymer and the like. Through the synergistic effect of multiple components, intertidal zone composite working condition erosion can be effectively resisted, the long-term service requirement of a revetment structure is met, and meanwhile the resource utilization rate of solid waste such as iron tailings is increased.

Description

Technical Field

[0001] This invention belongs to the field of concrete technology, specifically a composite concrete made from iron tailings powder and slag powder and its preparation method. Background Technology

[0002] The construction of long-term intertidal revetment structures in coastal land reclamation projects is a crucial scenario for expanding land resources and ensuring the extension of port hinterlands in southeastern coastal areas and the Bohai Rim region of my country. This scenario requires a large amount of concrete to construct load-bearing and impact-resistant structures such as gravity revetments and lattice retaining walls. These structures are exposed to the unique natural environment of the intertidal zone, characterized by high salinity, dynamic scouring, and abrasion. They must continuously withstand the combined effects of high-salinity seawater immersion, alternating tidal scouring, strong wave impacts from typhoons, and abrasion from bedload sediment. This complex environment places extremely high demands on the comprehensive performance of the revetment concrete, including durability, impact resistance, and abrasion resistance. If the concrete is not suitable, premature structural damage and shortened service life can easily occur, thus affecting the overall safety of the land reclamation project. At the same time, the large scale of land reclamation projects necessitates urgent requirements for material cost control and solid waste disposal. Iron tailings, as a major solid waste generated from mining, are abundant and widely sourced. They also have high particle hardness and moderate density, which makes them compatible with the physical properties of concrete aggregates. Therefore, using iron tailings to prepare concrete has become one of the technical directions that meet the needs of this scenario. However, in practical applications, the unique working conditions of intertidal revetments—high salinity, dynamic scouring, and the combined effects of impact and abrasion—make it difficult to directly adapt existing iron tailings-related concrete technologies. Specifically, the following technical challenges exist: Firstly, under high-salinity seawater immersion conditions, the high concentration of chloride ions in the seawater easily penetrates into the concrete pores, reacting chemically with the reinforcing steel to generate corrosion products, causing the steel to expand and the concrete to crack. Iron tailings themselves have low reactivity, which on the one hand results in relatively high porosity inside conventional iron tailings concrete, further accelerating the chloride ion penetration rate; on the other hand, insufficient reactivity also leads to slow concrete strength development, making it difficult to meet the early load-bearing capacity requirements of the revetment structure.

[0003] Secondly, under the alternating wet and dry conditions of tidal flow, the concrete surface will repeatedly undergo the process of "soaking and absorbing water - drying and losing water", which will cause micro-cracks to form on the surface material due to shrinkage between wet and dry conditions. At the same time, the scouring effect of tidal flow will continue to erode these micro-cracks, causing them to gradually expand and destroy the integrity of the concrete surface, providing more channels for chloride ion penetration. Third, under the impact of strong waves caused by typhoons, the instantaneous impact force of the waves on the concrete revetment can easily cause the concrete surface to peel off and the edges and corners to break. Fourth, under the continuous abrasive conditions of seabed sediment, the sediment particles will constantly rub against the concrete surface, gradually wearing down the surface material. Therefore, it is of great significance to develop a composite concrete made from iron tailings powder and slag powder that can adapt to the combined working conditions of high salinity seawater immersion, alternating wet and dry tidal scouring, strong wave impact from typhoons, and abrasion from seabed sediment. Summary of the Invention

[0004] The purpose of this invention is to provide a composite concrete made from iron tailings powder and slag powder and its preparation method, which can effectively solve the problem that concrete used in intertidal revetment structures is difficult to adapt to the combined working conditions of high salt immersion, tidal erosion, wave impact and silt abrasion.

[0005] The objective of this invention is achieved through the following technical solution: A type of iron tailings powder-slag powder composite concrete comprises the following components by weight: 30-40 parts of P·O 42.5 ordinary Portland cement, 35-50 parts of modified iron tailings powder, 15-28 parts of ultrafine slag powder, 2-6 parts of steel slag-based nano-calcium-lignin sulfonate grafted composite powder, 2.0-4.0 parts of desulfurized gypsum, 1.0-3.0 parts of lithium slag powder, 0.5-1.5 parts of hydrated calcium aluminate, 0.8-2 parts of modified hydroxyapatite nanoparticles, 105-130 parts of modified iron tailings aggregate, 0.4-1.2 parts of basalt fiber, 0.7-1.5 parts of polycarboxylate-based high-efficiency water-reducing agent, 0.1-0.5 parts of modified konjac glucomannan-polyetheramine copolymer, and 30-45 parts of deionized water; The modified iron tailings powder is obtained by hybrid modification of iron tailings powder with γ-methacryloxypropyltrimethoxysilane (KH-570)-nano silica modifier. The preparation method of the steel slag-based nano-calcium-lignin sulfonate grafted composite powder is as follows: steel slag-based nano-calcium is modified by coating with polyethylene glycol, and lignin sulfonate is modified with methacrylic anhydride; then the modified steel slag-based nano-calcium and modified lignin sulfonate are mixed, reacted with an initiator, and then filtered and dried to obtain the powder. The modified konjac glucomannan-polyetheramine copolymer is obtained by first mixing konjac glucomannan and polyetheramine, and then grafting and copolymerizing it with graphene oxide nanosheets modified with sodium dodecylbenzenesulfonate. The modified hydroxyapatite nanopowder is obtained by modifying hydroxyapatite nanopowder with hexadecyltrimethylammonium bromide; The modified iron tailings aggregate is obtained by modifying iron tailings aggregate with a titanate-aluminate composite coupling agent.

[0006] As some possible implementations of this application, the specific surface area of ​​the ultrafine slag powder is ≥550m² / kg.

[0007] As some possible implementations of this application, in the KH-570-nano silica hybrid modifier, the mass ratio of KH-570 to nano silica is (7-8):(2-3).

[0008] As some possible implementations of this application, in the steel slag-based nano-calcium-lignin sulfonate grafted composite powder, the modified lignin sulfonate and the modified steel slag-based nano-calcium are in a mass ratio of (3-5):1.

[0009] As some possible embodiments of this application, the hydroxyapatite nanoparticles have a particle size of 40nm-100nm and a specific surface area of ​​≥900m² / kg. As some possible implementations of this application, the modified iron tailings aggregate has a particle size of 4mm-22mm; the mass ratio of titanate to aluminate is (3-4):(1-2).

[0010] As some possible embodiments of this application, the basalt fiber has a length of 10mm-20mm and a diameter of 12μm-16μm.

[0011] As one possible implementation of this application, in the modified konjac glucomannan-polyetheramine copolymer, the mass ratio of konjac glucomannan to polyetheramine is (3-5):1. In addition, to achieve the above objectives, this application also provides a method for preparing iron tailings powder-slag powder composite concrete. The method involves mixing P·O 42.5 ordinary silicate cement, modified iron tailings powder, ultrafine slag powder, steel slag-based nano-calcium-lignin sulfonate grafted composite powder, desulfurized gypsum, lithium slag powder, hydrated calcium aluminate, modified hydroxyapatite nanoparticles, modified iron tailings aggregate, basalt fiber, polycarboxylate-based high-efficiency water-reducing agent, modified konjac glucomannan-polyetheramine copolymer, and deionized water until homogeneous to obtain a concrete mixture. The concrete mixture is then poured into molds and cured according to standard conditions to obtain the finished product.

[0012] Compared with the prior art, the beneficial effects of the present invention are: The iron tailings powder-slag powder composite concrete prepared by this invention can adapt to the complex environment of high salt immersion in the intertidal zone, alternating wet and dry erosion by tides, strong wave impact from typhoons, and abrasion by seabed sediment. The specific beneficial effects are as follows: In the cementitious material system: iron tailings powder can fill the macroscopic pores inside concrete, realizing the resource utilization of solid waste; after modification with KH-570-nano silica hybrid modifier, active groups are introduced on the surface, which can form chemical bonds with the hydroxyl groups in the steel slag-based nano-calcium-lignin sulfonate grafted composite powder, helping to improve the interface transition zone defects between iron tailings and cement matrix. Steel slag-based nano-calcium itself has certain activity and can undergo a secondary pozzolanic reaction with Ca(OH)2 produced by cement hydration to generate stable hydrated calcium silicate gel, improving the strength of the cementitious system and filling micron-nano pores; after polyethylene glycol coating modification, the dispersibility is improved, which can reduce the local performance degradation caused by agglomeration and better play the role of filling and compacting. Ultrafine slag powder itself has good pozzolanic activity and can synergistically optimize the cementitious structure with cement hydration products; after synergistic with modified iron tailings powder, it helps to make up for the insufficient activity caused by high iron tailings content. The synergistic effect of these three factors can reduce the internal pore channels of concrete, lower the chloride ion penetration rate under high-salt immersion environment, improve the structural stability of the structure, enhance the load-bearing capacity against typhoon and strong wave impact, and help alleviate the defects of traditional iron tailings concrete such as slow strength development and poor impermeability.

[0013] In the synergistic activation system: desulfurized gypsum can provide sulfate ions, which react with cement hydration products and Ca released from steel slag-based nano-calcium. 2+ The synergistic effect of activated alumina in slag powder and iron tailings powder provides a basis for the formation of ettringite; lithium slag powder itself is rich in Li. + This helps accelerate the hydration process of cementitious materials; hydrated calcium aluminate can regulate the formation rate and crystal morphology of ettringite, reducing disordered growth of ettringite. The synergistic effect of these three agents can reduce the uneven distribution of hydration products caused by a single activator, improving the utilization rate of iron tailings and slag powder. Hydroxyapatite nanoparticles possess ion exchange and surface adsorption capabilities, and can pass through OH groups in the crystal lattice... - With Cl in seawater - Ion exchange generates stable chlorapatite compounds; after modification with hexadecyltrimethylammonium bromide, the surface hydrophilicity and hydrophobicity are optimized, the dispersion in the concrete system is more uniform, the adsorption efficiency is improved, the formation of magnesium-calcium chloride salts and ettringite-type salts is reduced, the risk of salt expansion and cracking in high-salt environments is alleviated, and the surface integrity of concrete under tidal and alternating wet and dry conditions is improved, thus addressing the problem of insufficient adaptability of conventional activation systems in high-salt scenarios.

[0014] In the aggregate and reinforcement system: Iron tailings aggregate itself has high hardness and moderate density, providing a physical basis for use as coarse aggregate in concrete. It can bear loads and resist abrasion from seabed sediment. After modification with a titanate-aluminate composite coupling agent, the interfacial bonding strength between the surface and the cementitious matrix is ​​improved, which helps reduce the possibility of interfacial delamination under extreme conditions such as alternating tidal and wet erosion and strong wave impact from typhoons. Basalt fiber itself has inherent high strength and high toughness. When evenly distributed in the aggregate system, it can inhibit the propagation of microcracks caused by alternating tidal and wet erosion and strong wave impact from typhoons, improve the toughness of concrete, and when working synergistically with cementitious materials, it helps to enhance the bonding effect between aggregates, reduce crack formation from the source, and improve the stability of concrete under dynamic erosion and impact conditions.

[0015] Among other additives: Polycarboxylate-based high-efficiency water-reducing agents can reduce the agglomeration force between cementitious material particles and improve the fluidity of concrete. Konjac glucomannan-polyetheramine copolymer has both thickening and adsorption properties, which can improve the anti-segregation performance of concrete and initially adsorb chloride ions in high-salt environments; after graft copolymerization, the stability of the molecular chain structure is improved, the chloride ion encapsulation ability is enhanced, and the effect of reducing the chloride ion penetration rate is more lasting. Graphene oxide nanosheets have a two-dimensional sheet structure and physical barrier properties, which can reduce the penetration path of chloride ions in high-salt environments; after modification with sodium dodecylbenzenesulfonate, a negative charge is introduced on the surface, reducing its own agglomeration, and synergistically forming a coating-barrier protective layer with the copolymer, delaying the aging of organic modified components under tidal and dry alternating conditions and improving their aging resistance. In addition, after surface modification, the three types of nano-components (graphene oxide, hydroxyapatite, and steel slag-based nano-calcium) can reduce synergistic aggregation, which helps to achieve uniform distribution and play a filling and reinforcing role. Together with the ion adsorption effect of hydroxyapatite, they form a dual guarantee against salt erosion, further enhancing the concrete's ability to resist alternating tidal and wet erosion and seabed sediment abrasion.

[0016] In summary, the finished concrete prepared by this invention has a good strength retention rate after high-salt solution wet-dry cycles, and can maintain stable performance under tidal wet-dry alternation, strong wave impact, seabed sediment abrasion and strong ultraviolet superposition environment. While improving the service stability of intertidal infrastructure, it also helps to utilize solid waste resources and helps to improve the technical bottleneck of intertidal revetment and other transportation infrastructure that is prone to corrosion and has a short service life. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to specific embodiments and comparative examples. Components for which preparation methods are not mentioned in the embodiments and comparative examples are all commercially available conventional products (such as P·O 42.5 ordinary silicate cement, methyl allyl polyoxyethylene ether (TPEG) type salt-resistant polycarboxylate high-efficiency water-reducing agent (solid content 40%, water reduction rate ≥30%), basalt fiber, etc.). All "parts" refer to parts by mass. In industrial production, "kg" can be used as the unit of mass.

[0018] Example 1 1. Preparation of some non-commercially available components.

[0019] (1) Preparation of modified iron tailings powder: ① Raw material pretreatment: Take commercially available iron tailings powder, crush it with a jaw crusher, ball mill it, pass it through a 200-mesh sieve, and dry it in an oven at 105℃ for 6 hours to remove moisture, and obtain pretreated iron tailings powder. ② Preparation of hybrid modifier: Take γ-methacryloyloxypropyltrimethoxysilane (KH-570) and nano silica (particle size 20-50nm) at a mass ratio of 7:3, add anhydrous ethanol (the amount is 3 times the total mass of KH-570 and nano silica), and ultrasonically disperse for 30min (power 300W, frequency 20kHz) to obtain KH-570-nano silica hybrid modifier solution; ③ Modification reaction: Take 100 parts of pretreated iron tailings powder, add 30 parts of the above hybrid modifier solution, and soak at 25℃ with constant temperature stirring at 400r / min for 2h; then place in an oven at 105℃ to dry for 4h, grind through a 200-mesh sieve to obtain modified iron tailings powder.

[0020] (2) Preparation of steel slag-based nano-calcium-lignin sulfonate grafted composite powder: ① Purchased steel slag was crushed and ball-milled to 200 mesh. The steel slag was then mixed with sodium carbonate at a mass ratio of 1:0.8 and calcined in a muffle furnace at 900℃ for 3 hours to activate the calcium phase, resulting in activated steel slag. 100 parts of activated steel slag were then added to 500 parts of deionized water and reacted in a hydrothermal reactor at 200℃ for 5 hours. After the reaction, the mixture was cooled to room temperature and centrifuged (8000 r / min, 10 min) to collect the precipitate. The precipitate was then added to a 0.4% (w / w) polyethylene glycol aqueous solution (polyethylene glycol molecular weight 2000; solid-liquid ratio 1:10, g:ml), stirred at 25℃ for 2 hours, filtered, and dried at 105℃ for 3 hours to obtain modified steel slag-based nano-calcium. ② Take 100 parts of commercially available lignin sulfonate, add 300 parts of deionized water to dissolve, add 15 parts of methacrylic anhydride, stir and react at 450 r / min for 3 h at 60℃, remove excess water by vacuum distillation (60℃, 0.07 MPa), dry and grind through a 200 mesh sieve to obtain modified lignin sulfonate. ③ Take modified lignin sulfonate and modified steel slag-based nano-calcium at a mass ratio of 4:1, add them to a mixing vessel, add ammonium persulfate initiator (the amount added is 1.5% of the total mass of modified lignin sulfonate and modified steel slag-based nano-calcium), add 200 parts of deionized water, and stir in a 70℃ water bath at 500r / min for 4h. After the reaction is completed, filter, dry at 105℃ for 5h, and ball mill until the specific surface area is ≥800m² / kg to obtain steel slag-based nano-calcium-lignin sulfonate grafted composite powder.

[0021] (3) Preparation of modified konjac glucomannan-polyetheramine copolymer: ① Take konjac glucomannan and polyetheramine at a mass ratio of 4:1, add 500 parts of deionized water, and stir at 400 r / min at 50℃ to dissolve; take 5 parts of commercially available graphene oxide, add 1000 parts of deionized water, and ultrasonically disperse for 30 min (power 300W, frequency 20kHz); add sodium dodecylbenzenesulfonate (addition amount is 0.5% of the mass of graphene oxide), continue ultrasonication for 30 min, centrifuge (speed 10000 r / min, time 15 min), collect the precipitate, wash with deionized water until the filtrate is free of foam, and obtain modified graphene oxide nanosheet wet material; ② The above-mentioned modified graphene oxide nanosheet wet material was added to the konjac glucomannan-polyetheramine solution and ultrasonically dispersed for 20 min (power 300W, frequency 20kHz); 0.3 parts of ammonium persulfate initiator were added, the temperature was raised to 65℃, and the reaction was stirred at 500 r / min for 5 h under nitrogen protection; after the reaction was completed, the mixture was cooled to room temperature, the product was collected by centrifugation, vacuum dried at 60℃ (0.08MPa) for 6 h, and ground through a 200 mesh sieve to obtain the modified konjac glucomannan-polyetheramine copolymer.

[0022] (4) Preparation of modified hydroxyapatite nanopowder: ① Dissolve 10 parts of ammonium dihydrogen phosphate in 50 parts of deionized water; slowly add an aqueous solution containing 24 parts of calcium nitrate (mass fraction of 8%) while stirring at 300 r / min; adjust the pH to 7.5 with ammonia; heat to 80℃ and stir at a constant temperature for 4 h; filter and collect the precipitate, wash with deionized water until the filtrate is free of chloride ions, and vacuum dry at 60℃ (0.08 MPa) for 5 h to obtain hydroxyapatite nanopowder; ② Take 10 parts of the above hydroxyapatite nanopowder (particle size 40-100nm), add 40 parts of a 0.3% hexadecyltrimethylammonium bromide solution, stir and soak at 350r / min for 2h at 25℃; filter and collect the product, wash 3 times with deionized water, vacuum dry at 60℃ (0.08MPa) for 4h, grind and pass through a 200-mesh sieve to obtain modified hydroxyapatite nanopowder.

[0023] (5) Preparation of modified iron tailings aggregate: ① Purchased iron tailings were crushed and screened to obtain aggregates of 4mm-22mm. The aggregates were washed with deionized water to remove surface impurities and dried in an oven at 105℃ for 4 hours to obtain pretreated iron tailings aggregates. Separately, titanate coupling agent (NDZ-311) and aluminate coupling agent (DL-411) were prepared by mixing them in a mass ratio of 3:2 with anhydrous ethanol to prepare a 1.0% mass fraction solution. The solution was stirred evenly to obtain a composite coupling agent solution. ② Take 100 parts of pretreated iron tailings aggregate and 30 parts of composite coupling agent solution, stir at 200 r / min for 1 h at 25℃; dry in an oven at 105℃ for 3 h to obtain modified iron tailings aggregate.

[0024] 2. Preparation process of iron tailings powder-slag powder composite concrete.

[0025] (1) Ultrasonic dispersion of nano-components: Take 19 parts of deionized water, add 1.4 parts of modified hydroxyapatite nanopowder, and disperse for 40 min using an ultrasonic device at 20 kHz and 300 W to obtain a nano-component dispersion.

[0026] (2) Pre-hydration treatment: 35 parts of P·O 42.5 ordinary Portland cement, 42 parts of modified iron tailings powder, 22 parts of ultrafine slag powder (specific surface area ≥550m² / kg), and 4 parts of steel slag-based nano-calcium-lignin sulfonate grafted composite powder were added to a mixing tank, and the above-mentioned nano-component dispersion was poured in. After stirring evenly, the mixture was placed in an environment of 10-15℃ and 90% relative humidity for 12 hours for pre-hydration, and then placed in an environment of 25℃ and 90% relative humidity for 12 hours to obtain a pre-hydrated cementitious mixture. The interfacial bonding force of the cementitious material was improved by segmented pre-hydration, which reduced the later cracks.

[0027] (3) Mixing and stirring: Add 3.0 parts of desulfurized gypsum, 2.0 parts of lithium slag powder, 1.0 parts of hydrated calcium aluminate, 118 parts of modified iron tailings aggregate, 0.8 parts of basalt fiber (15 mm in length and 14 μm in diameter), 1.1 parts of methyl allyl polyoxyethylene ether (TPEG) type salt-resistant polycarboxylic acid high-efficiency water-reducing agent (solid content 40%, water reduction rate ≥30%), 0.3 parts of modified konjac glucomannan-polyetheramine copolymer and the remaining 19 parts of deionized water to the prehydrated cementitious mixture. First, stir at a low speed of 300 r / min for 2 min, and then stir at a high speed of 600 r / min for 5 min to obtain a uniform concrete mixture.

[0028] (4) Casting and molding: Pour the concrete mixture into a 100mm×100mm×100mm mold, place it on a vibrating table and vibrate for 3 minutes to remove air bubbles, and scrape the surface smooth. (5) Standard curing: After curing the test mold in a standard curing box at 20±2℃ and relative humidity ≥95% for 24 hours, the mold is removed and the curing continues for 28 days to obtain finished concrete.

[0029] Example 2 Compared to Example 1, the following adjustments are made (unless otherwise mentioned, they are considered the same as in Example 1): 1. Adjustment of preparation parameters for some non-commercially available components: (1) In the preparation of modified iron tailings powder, the mass ratio of KH-570 to nano silica was adjusted to 8:2, the mass fraction of the hybrid modifier solution was adjusted to 1.2%, and the soaking and stirring time was adjusted to 1.5h; (2) In the preparation of modified hydroxyapatite nanopowder, the mass fraction of hexadecyltrimethylammonium bromide solution was adjusted to 0.4%, and the soaking temperature was adjusted to 30℃.

[0030] 2. Adjustment of concrete preparation parameters: (1) The ultrasonic dispersion process was adjusted to use 19.8 parts deionized water and 1.0 parts modified hydroxyapatite nanopowder, with the dispersion power adjusted to 240W and the time adjusted to 35min; (2) The prehydration process is adjusted to 35 parts of P·O 42.5 ordinary Portland cement, 38 parts of modified iron tailings powder, 20 parts of ultrafine slag powder, and 4 parts of steel slag-based nano-calcium-lignin sulfonate grafted composite powder. The temperature of the first step is adjusted to 12-15℃ and the time remains unchanged. The standing time of the second step is adjusted to 10h. (3) The mixing and stirring process was adjusted to include 3.0 parts desulfurized gypsum, 2.0 parts lithium slag powder, 1.0 parts hydrated calcium aluminate, 118 parts modified iron tailings aggregate, 0.8 parts basalt fiber, 1.1 parts TPEG type salt-resistant polycarboxylic acid high-efficiency water-reducing agent, 0.3 parts modified konjac glucomannan-polyetheramine copolymer and 16.2 parts deionized water. The stirring process was low speed 250r / min for 3min and high speed 550r / min for 6min.

[0031] Example 3 Compared to Example 1, the following adjustments are made (unless otherwise mentioned, they are considered the same as in Example 1): 1. Adjustment of preparation parameters for some non-commercially available components: (1) In the preparation of steel slag-based nano-calcium-lignin sulfonate grafted composite powder, the mass ratio of modified lignin sulfonate to modified steel slag-based nano-calcium was adjusted to 5:1, and the amount of initiator added was adjusted to 1.8%; (2) In the preparation of modified iron tailings aggregate, the mass ratio of titanate to aluminate was adjusted to 4:1, and the mass fraction of the composite coupling agent solution was adjusted to 1.2%.

[0032] 2. Adjustment of concrete preparation parameters: (1) The ultrasonic dispersion process was adjusted to use 18.45 parts deionized water and 1.4 parts modified hydroxyapatite nanopowder, with the dispersion frequency adjusted to 24 kHz and the time adjusted to 45 min. (2) The prehydration process was adjusted to use 35 parts of P·O 42.5 ordinary Portland cement, 48 parts of modified iron tailings powder, 26 parts of ultrafine slag powder, and 4 parts of steel slag-based nano-calcium-lignin sulfonate grafted composite powder. The temperature of the first step was adjusted to 10℃ and the time was adjusted to 10h. The standing time of the second step was adjusted to 14h. (3) The mixing and stirring process is adjusted to 3.0 parts desulfurized gypsum, 2.0 parts lithium slag powder, 1.0 parts hydrated calcium aluminate, 118 parts modified iron tailings aggregate, 1.0 parts basalt fiber, 1.1 parts TPEG type salt-resistant polycarboxylic acid high-efficiency water-reducing agent, 0.4 parts modified konjac glucomannan-polyetheramine copolymer and 22.55 parts deionized water. The stirring process is low speed 350r / min stirring for 2min and high speed 650r / min stirring for 4min.

[0033] Comparative Example 1 Compared to Example 1, the modified hydroxyapatite nanoparticles in the raw materials were removed, while the remaining raw materials and their amounts, the preparation process of non-commercially available components, and the concrete preparation process steps were all the same as in Example 1.

[0034] Comparative Example 2 Compared to Example 1, the modified iron tailings powder was replaced with an equal mass of unmodified iron tailings powder (which was only crushed, ball-milled, and dried, without KH-570-nano silica hybrid modification). The remaining raw materials and dosages, preparation processes of non-commercially available components, and concrete preparation process steps were all the same as in Example 1.

[0035] Comparative Example 3 Compared to Example 1, the steel slag-based nano-calcium-lignin sulfonate grafted composite powder was replaced with an equal mass of 'ungrafted mixture' (directly mixed with modified lignin sulfonate and modified steel slag-based nano-calcium at a mass ratio of 4:1 as in Example 1, without grafting reaction; mixing conditions: stirring at 500 r / min for 30 min at 25°C). All other raw materials and dosages, preparation processes for non-commercially available components, and concrete preparation processes were consistent with Example 1.

[0036] Comparative Example 4 Compared to Example 1, the modified konjac glucomannan-polyetheramine copolymer in the raw materials was removed, while the remaining raw materials and dosages, the preparation process of non-commercially available components, and the concrete preparation process steps were all the same as in Example 1.

[0037] Comparative Example 5 Compared to Example 1, the "KH-570 - nano silica hybrid modifier" was replaced with an equal mass and concentration of "single KH-570 modifier" (without silica), while the other conditions remained unchanged. The other raw materials and dosages, the preparation process of non-commercially available components, and the concrete preparation process steps were all the same as in Example 1.

[0038] Experimental Example The 28-day standard-cured finished concrete (size: 100mm×100mm×100mm) prepared in Examples 1-3 and Comparative Examples 1-5 were used as test samples for relevant performance tests. Three parallel samples were used in each group. The test results are shown in Table 1. The test methods are as follows: 1. Tidal Wet and Dry Erosion Performance Test: A simulated cycle test was adopted: one cycle was set to 12 hours. The specific procedure was "simulated seawater immersion for 6 hours [immersion conditions: constant temperature at 25℃, simulated seawater (NaCl concentration 3.5wt%, MgCl2 concentration 0.5wt%) completely submerging the sample] + hot air drying at 60℃ for 6 hours (drying conditions: wind speed 2m / s, simulating the strong wind drying environment of the intertidal zone)", and a total of 50 cycles were completed. After the cycle, the following were tested: ① Surface peeling amount: Δm = initial mass - mass after cycle; ② Compressive strength retention rate: retention rate = (compressive strength after cycle / initial compressive strength) × 100%; ③ Internal crack development: sound velocity reduction rate η = (initial sound velocity - sound velocity after cycle) / initial sound velocity × 100%, where η≤5% is qualified (indicating that no obvious through cracks have been generated inside, and the structural integrity is good). The velocity of sound was measured using an ultrasonic detector in accordance with GB / T 50082-2009.

[0039] 2. Typhoon strong wave impact performance test: According to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete", the drop hammer impact method is adopted: the sample is fixed on the impact test table and continuously impacted with an impact energy of 0.5kN·m. The number of impacts when the first visible crack appears in the sample is recorded (the number of impacts ≥30 is qualified).

[0040] 3. Test of seabed sediment abrasion performance: The rotary abrasion method was adopted. The 28-day standard cured finished product was used as the test sample. The sample was fixed in the abrasion test machine. The contact pressure between the abrasion wheel and the sample surface was 0.3 MPa. The abrasion medium was simulated seawater (NaCl concentration 3.5 wt%, MgCl2 concentration 0.5 wt%) + dried seabed sediment (particle size 0.1-2 mm) (mass ratio of the two 1:1). Abrasion was performed continuously for 24 hours. The mass loss rate of the sample after abrasion was measured (abrasion mass loss / initial mass × 100%). The mass loss rate ≤ 3% was considered qualified.

[0041] 4. High-salt immersion-ultraviolet irradiation superimposed test (suitable for intertidal high-salt + strong ultraviolet composite conditions): The sample is completely immersed in simulated seawater (NaCl concentration 3.5wt%, MgCl2 concentration 0.5wt%), and simultaneously placed in a xenon arc lamp aging test chamber with an irradiation intensity of 60W / m² (wavelength 300-400nm), a blackboard temperature of 60±3℃, and a relative humidity of 50±5%, for continuous synchronous treatment for 1000h. After treatment, the strength retention rate (compressive strength after cycle / initial compressive strength) × 100% and the chloride ion migration coefficient change rate (migration rate after test - migration rate before test) / migration rate before test × 100% are calculated under superimposed conditions, while the aging and cracking of the sample surface are observed.

[0042] Table 1: Note: '-' in Table 1 indicates that the corresponding project test was not carried out for this sample, and only the core performance verification was focused on.

[0043] As can be seen from Table 1: Examples 1-3 maintained good performance stability under simulated intertidal composite conditions. Specifically, after wet-dry cycles, surface spalling was ≤2.8g, strength retention was ≥90.3%, and sound velocity reduction was ≤2.5%, indicating excellent resistance to alternating wet-dry erosion and effectively preventing surface damage and internal structural deterioration caused by repeated soaking and drying. The impact resistance was ≥40 cycles, far exceeding the qualified standard (≥30 cycles), demonstrating outstanding resistance to strong typhoon wave impacts and the ability to withstand dynamic impact loads in the intertidal zone. The sediment abrasion mass loss rate was ≤1.5%, meeting the qualified requirement (≤3%), demonstrating good wear resistance and adaptability to long-term seabed sediment abrasion conditions. Under high-salt immersion-UV irradiation superimposed conditions, the strength retention was ≥85.9%, and the chloride ion migration coefficient change rate was ≤17.2%. Furthermore, none of the three samples showed surface cracking, only slight discoloration, indicating strong resistance to aging under high-salt + strong UV composite conditions in the intertidal zone, effectively ensuring structural integrity. The above excellent data demonstrate that the concrete prepared by this invention can meet the actual service requirements of intertidal revetment.

[0044] Comparative Example 1, due to the removal of modified hydroxyapatite nanoparticles, showed a significant decrease in strength retention under superimposed conditions, with fine microcracks appearing on the surface, insufficient resistance to salt erosion, and difficulty in adapting to the long-term service environment of the intertidal zone. Comparative Example 2, using unmodified iron tailings powder, had poor interfacial bonding performance, significant surface spalling after wet-dry cycles, and the appearance of penetrating microcracks, resulting in significant deterioration in overall performance. Comparative Example 3, using ungrafted composite powder, had insufficient internal density of the concrete, with scattered microcracks on the surface, and only average performance under superimposed conditions. Comparative Example 4, by removing modified konjac glucomannan-polyetheramine copolymer, had weakened resistance to chlorine encapsulation, with microcracks appearing on the surface under superimposed conditions, limiting its long-term protective effect. Comparative Example 5, using a single KH-570 modifier, had poor aging resistance and interfacial performance, with multiple microcracks appearing under superimposed conditions, indicating a relatively high risk of performance degradation.

Claims

1. A type of iron tailings powder-slag powder composite concrete, characterized in that, The product comprises the following components by weight: 30-40 parts of P·O42.5 ordinary silicate cement, 35-50 parts of modified iron tailings powder, 15-28 parts of ultrafine slag powder, 2-6 parts of steel slag-based nano-calcium-lignin sulfonate grafted composite powder, 2.0-4.0 parts of desulfurized gypsum, 1.0-3.0 parts of lithium slag powder, 0.5-1.5 parts of hydrated calcium aluminate, 0.8-2 parts of modified hydroxyapatite nanoparticles, 105-130 parts of modified iron tailings aggregate, 0.4-1.2 parts of basalt fiber, 0.7-1.5 parts of polycarboxylate-based high-efficiency water-reducing agent, 0.1-0.5 parts of modified konjac glucomannan-polyetheramine copolymer, and 30-45 parts of deionized water. The modified iron tailings powder is obtained by hybridizing iron tailings powder with KH-570 nano silica modifier. The preparation method of the steel slag-based nano-calcium-lignin sulfonate grafted composite powder is as follows: steel slag-based nano-calcium is modified by coating with polyethylene glycol, and lignin sulfonate is modified with methacrylic anhydride; then the modified steel slag-based nano-calcium and modified lignin sulfonate are mixed, reacted with an initiator, and then filtered and dried to obtain the powder. The modified konjac glucomannan-polyetheramine copolymer is obtained by first mixing konjac glucomannan and polyetheramine, and then grafting and copolymerizing it with graphene oxide nanosheets modified with sodium dodecylbenzenesulfonate. The modified hydroxyapatite nanopowder is obtained by modifying hydroxyapatite nanopowder with hexadecyltrimethylammonium bromide; The modified iron tailings aggregate is obtained by modifying iron tailings aggregate with a titanate-aluminate composite coupling agent.

2. The iron tailings powder-slag powder composite concrete according to claim 1, characterized in that, The specific surface area of ​​the ultrafine slag powder is ≥550m² / kg.

3. The iron tailings powder-slag powder composite concrete according to claim 1, characterized in that, In the KH-570-nano silica hybrid modifier, the mass ratio of KH-570 to nano silica is (7-8):(2-3).

4. The iron tailings powder-slag powder composite concrete according to claim 1, characterized in that, In the steel slag-based nano-calcium-lignin sulfonate grafted composite powder, the modified lignin sulfonate and the modified steel slag-based nano-calcium are in a mass ratio of (3-5):

1.

5. The iron tailings powder-slag powder composite concrete according to claim 1, characterized in that, The hydroxyapatite nanoparticles have a particle size of 40nm-100nm and a specific surface area of ​​≥900m² / kg.

6. The iron tailings powder-slag powder composite concrete according to claim 1, characterized in that, The modified iron tailings aggregate has a particle size of 4mm-22mm and a mass ratio of titanate to aluminate of (3-4):(1-2).

7. The iron tailings powder-slag powder composite concrete according to claim 1, characterized in that, The basalt fibers are 10mm-20mm in length and 12μm-16μm in diameter.

8. The iron tailings powder-slag powder composite concrete according to claim 1, characterized in that, In the modified konjac glucomannan-polyetheramine copolymer, the mass ratio of konjac glucomannan to polyetheramine is (3-5):

1.

9. The method for preparing iron tailings powder-slag powder composite concrete according to any one of claims 1-8, characterized in that, P·O 42.5 ordinary silicate cement, modified iron tailings powder, ultrafine slag powder, steel slag-based nano-calcium-lignin sulfonate grafted composite powder, desulfurized gypsum, lithium slag powder, hydrated calcium aluminate, modified hydroxyapatite nanoparticles, modified iron tailings aggregate, basalt fiber, polycarboxylate-based high-efficiency water-reducing agent, modified konjac glucomannan-polyetheramine copolymer, and deionized water are mixed evenly to obtain a concrete mixture. The concrete mixture is then poured into molds and cured according to standard to obtain the finished product.

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