Bridge high-performance high-anti-crack concrete and preparation method thereof

Abstract

The application relates to the technical field of concrete, in particular to a bridge high-performance high-anti-cracking concrete and a preparation method thereof. The concrete comprises sea sand, basalt gravel, marine portland cement, silica fume, kaolin, nano-aluminum oxide, grafted composite corrosion inhibitor carrier powder, polyvinyl alcohol short-cut fiber, light-burned / heavy-burned magnesium oxide, water reducing agent, shrinkage reducing agent and mixing water. The corrosion inhibitor carrier takes kaolin as a core, is sequentially subjected to amination, polyacrylic acid grafting, Ca 2+ The site is introduced and is ternary bridged with 1-hydroxyethylidene-1,1-bisphosphonic acid and calcium hydroxide, and then sequentially loaded with polyallylamine hydrochloride and sodium nitrite. The system can construct an anchorable and slow-releasing composite protective layer on the steel-slush interface, and can synergistically inhibit microcracks through pore structure refinement and time sequence expansion, thereby significantly improving the resistance to chloride ion penetration, delaying pitting corrosion, improving the shrinkage resistance and strength retention.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and in particular to a high-performance, high-crack-resistant concrete for bridges and its preparation method. Background Technology

[0002] Traditional bridge concrete faces multiple durability challenges in marine environments, including chloride ion corrosion, steel reinforcement corrosion, and shrinkage cracking, and existing technologies have significant limitations. Current corrosion inhibition technologies mainly rely on the direct incorporation of inorganic or organic corrosion inhibitors, but these generally suffer from the following technical defects: First, the corrosion inhibitors are unevenly dispersed in the concrete matrix and tend to agglomerate during mixing and pouring, leading to discontinuous protection of the steel reinforcement surface; second, the corrosion inhibitors have poor compatibility with cement-based materials and are prone to chemical degradation or deactivation in highly alkaline environments, resulting in a significant decline in long-term corrosion inhibition effectiveness; third, the corrosion inhibitors are easily lost through migration with the pore solution, especially in high-salinity seawater environments, where the loss rate driven by the diffusion gradient is significantly accelerated, leading to insufficient corrosion inhibitor concentration at the steel reinforcement interface.

[0003] Existing crack-resistant technologies mostly use a single expanding agent to compensate for shrinkage, which has obvious technical bottlenecks: the expansion sequence does not match the development of shrinkage, excessive expansion in the early stage may introduce new tensile stress, while insufficient expansion in the later stage cannot effectively compensate for drying shrinkage; the expansion agent and the matrix interface are poorly bonded, and the expansion products are prone to forming weak links in the interface area, which become the starting point for crack initiation; a single expansion mechanism is difficult to simultaneously counteract the combined effects of autogenous shrinkage, drying shrinkage and temperature shrinkage, and the compensation effect is limited under complex stress conditions.

[0004] While traditional pore structure optimization techniques can improve compactness, they often come at the cost of performance: ultrafine admixtures such as silica fume can refine pore size, but they can lead to a significant increase in water demand and deterioration of workability; fiber incorporation can improve toughness, but it is difficult to disperse and prone to clumping, affecting uniformity; when multiple materials are used in combination, the interaction mechanism is complex and it is difficult to optimize the ratio.

[0005] More importantly, existing technologies lack systematic integration, making it difficult to synergistically improve crack resistance and corrosion resistance: optimizing crack resistance alone may reduce density and affect impermeability; improving corrosion resistance alone may increase brittleness and exacerbate cracking risk; and there is a lack of effective technical means to construct a multifunctional protective layer at the steel-slurry interface.

[0006] Therefore, there is an urgent need to develop a technology that can both ensure long-term corrosion resistance and effectively suppress various types of shrinkage cracking. This is a major challenge currently facing concrete material technology. Summary of the Invention

[0007] In view of this, the purpose of this invention is to propose a high-performance, high-crack-resistant concrete for bridges and its preparation method, so as to achieve a synergistic improvement in the crack resistance and corrosion resistance of bridge concrete in marine environments.

[0008] To achieve the above objectives, this invention provides a high-performance, high-crack-resistant concrete for bridges, prepared from the following raw materials in parts by weight: 7200 parts sea sand, 3200 parts basalt crushed stone, 5300 parts marine silicate cement, 500 parts silica fume, 600 parts kaolin, 50-90 parts nano-alumina, 450-750 parts grafted composite corrosion inhibitor powder, 120-160 parts polyvinyl alcohol chopped fibers, 105-175 parts lightly calcined magnesia, 52.5-87.5 parts darkly calcined magnesia, 60-80 parts polycarboxylate-based high-efficiency water-reducing agent, 60-80 parts propylene glycol ether-type shrinkage reducer, and 2300-2700 parts mixing water.

[0009] The grafted composite corrosion inhibitor powder is prepared by sequentially aminated kaolin with 3-aminopropyltriethoxysilane to obtain kaolin powder with amino groups on the surface, then grafting polyacrylic acid in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride / N-hydroxysuccinimide to obtain polyacrylic acid grafted kaolin powder, then introducing calcium ion bridging sites with anhydrous calcium chloride to obtain polyacrylic acid grafted kaolin powder with calcium ion bridging sites, then reacting with 1-hydroxyethylidene-1,1-diphosphonic acid and calcium hydroxide to obtain a ternary bridged grafted powder, and finally loading polyallylamine hydrochloride and sodium nitrite sequentially and drying.

[0010] Preferably, based on 600 parts by weight of kaolin, there are 4-8 parts of 3-aminopropyltriethoxysilane.

[0011] Preferably, based on 600 parts by weight of kaolin powder with amino groups on its surface, there are 8-12 parts of polyacrylic acid.

[0012] Preferably, based on 600 parts by weight of polyacrylic acid-grafted kaolin powder, there are 8-14 parts of anhydrous calcium chloride.

[0013] Preferably, based on 600 parts by weight of polyacrylic acid-grafted kaolin powder with calcium ion bridging sites, there are 12-16 parts by mass of 50% aqueous solution of 1-hydroxyethylidene-1,1-diphosphonic acid and 2.5-3.5 parts by mass of calcium hydroxide.

[0014] Preferably, based on 600 parts by weight of grafted powder with a ternary bridging structure, there are 3.5-6.5 parts of polyallylamine hydrochloride and 15-27 parts of sodium nitrite.

[0015] Preferably, the average particle size of the nano-alumina is 50 nm.

[0016] Preferably, the average length of the polyvinyl alcohol chopped fibers is 12 mm and the average diameter is 40 μm.

[0017] Preferably, the lightly calcined magnesium oxide has an activity index of 45s and an average particle size of 15μm; the recalcined magnesium oxide has an activity index of 350s and an average particle size of 18μm.

[0018] Preferably, the fineness modulus of the sea sand is 2.6-2.9 and the mud content is ≤3%; the particle size of the basalt crushed stone is 5-10mm and the content of needle-like and flaky particles is ≤10%.

[0019] Preferably, the polyacrylic acid has a weight-average molecular weight of 100,000; and the polyallylamine hydrochloride has a weight-average molecular weight of 45,000.

[0020] Preferably, the polycarboxylate superplasticizer is of model SiKa ViscoCrete-540P.

[0021] Preferably, the propylene glycol ether shrinkage reducer is Sika Control-SRA 50.

[0022] Preferably, the marine silicate cement is of type DC-3511.

[0023] Preferably, the silica fume is metallurgical grade microsilica powder, grade C.

[0024] Preferably, the mixing water is added twice, the polycarboxylate-based high-efficiency water-reducing agent is added after being dissolved in the first stage of mixing water, and the propylene glycol ether-type shrinkage reducing agent is added after being dissolved in the second stage of mixing water, with the mixing water added in equal amounts twice.

[0025] Preferably, the average particle size of the kaolin raw material for the grafted composite corrosion inhibitor powder is 5 μm.

[0026] Furthermore, the present invention also provides a method for preparing high-performance, high-crack-resistant concrete for bridges, comprising the following steps: first, dry mixing sea sand, basalt gravel, marine silicate cement, silica fume, kaolin, and nano-alumina in a mixer for 120 seconds; then, dissolving a polycarboxylate-based high-efficiency water-reducing agent in the first stage of mixing water and adding it in, followed by wet mixing for 60 seconds; then, adding grafted composite corrosion inhibitor powder; then, dissolving a propylene glycol ether-type shrinkage reducer in the second stage of mixing water and adding it in, while simultaneously sprinkling in chopped polyvinyl alcohol fibers and wet mixing for 60 seconds; finally, adding lightly calcined magnesium oxide and heavily calcined magnesium oxide and mixing for 60 seconds to obtain high-performance, high-crack-resistant concrete for bridges.

[0027] This invention significantly improves the synergistic performance of crack resistance and corrosion resistance in bridge concrete through innovative surface chemical construction technology, and has the following technical advantages:

[0028] Significantly enhanced interfacial anchoring stability: Activation of the kaolin surface with aminosilane provides stable chemical bonding sites for polyacrylic acid grafting, forming a layer of covalently linked functional groups. This avoids the technical drawback of easy desorption of corrosion inhibitors under traditional physical adsorption methods. The multi-point bridging structure composed of calcium ions and hydroxyethylidene diphosphonic acid forms a three-dimensional coordination network on the carrier surface, providing multiple anchoring points for subsequent corrosion inhibitor components and significantly improving resistance to leaching in high-salt environments.

[0029] The controlled-release mechanism is precise and controllable: the stepwise loading of polyallylamine hydrochloride and nitrite constructs a two-component synergistic controlled-release system. Polyallylamine hydrochloride forms a polymer protective film on the steel reinforcement surface, providing a physical shielding effect; nitrite, as an anodic corrosion inhibitor, maintains the stability of the passivation film on the steel reinforcement surface. The gradient release of the two components through the carrier ensures that a sufficient concentration of corrosion inhibitor is maintained on the steel reinforcement surface over a long period of time, effectively inhibiting the initiation and spread of pitting corrosion.

[0030] Optimized time-sequential stress compensation mechanism: The activity difference between light-burned and reheated magnesia enables phased volume compensation in the early and middle-late stages. Light-burned magnesia undergoes rapid hydration in the early stage to offset autogenous shrinkage and early drying shrinkage; reheated magnesia undergoes continuous hydration in the middle and late stages to compensate for long-term drying shrinkage and carbonization shrinkage. This time-sequential expansion strategy avoids the technical problem of mismatch in the timing of a single expansion agent, ensuring stress balance at each age.

[0031] Refined pore structure control: The bridging effect of chopped polyvinyl alcohol fibers inhibits the initiation and connection of microcracks; the synergistic effect of nano-alumina and silica fume, through the filling effect and pozzolanic reaction, refines the pore size distribution and optimizes pore connectivity. This refined pore structure significantly extends the effective diffusion path of harmful ions, improving impermeability.

[0032] Multi-performance synergistic optimization: Crack resistance and corrosion resistance are truly synergistically improved, avoiding the side effects that may result from single-performance optimization in traditional technologies. Densification and toughness enhancement are achieved simultaneously, achieving a good balance between strength development and durability maintenance.

[0033] Its low-carbon and environmentally friendly characteristics are prominent: using natural mineral kaolin as the core carrier reduces the amount of polymer materials used, aligning with the concept of low-carbon construction. Surface chemical modification technology improves material utilization efficiency and reduces overall material consumption. The process avoids high-energy-consuming steps such as high-temperature calcination, significantly reducing the carbon footprint of the production process.

[0034] It has good prospects for large-scale application: the preparation process is relatively simple and easy to industrialize; it is well adapted to existing concrete production equipment and easy to promote and apply; the material cost is controllable and it has economic feasibility for commercial application. Detailed Implementation

[0035] 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.

[0036] In this specific embodiment of the invention, the kaolin was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., product number K100132, with an average particle size of 5 μm; the weight-average molecular weight of polyacrylic acid was 100,000, and the weight-average molecular weight of polyallylamine hydrochloride was 45,000; the marine silicate cement was model Dechang Weiye DC-3511, and the silica fume was metallurgical grade microsilica powder, grade C; the average particle size of nano-alumina was 50 nm; the fineness modulus of the sea sand was 2.6-2.9, and the mud content was ≤3%; the needle-like and flaky content of the basalt crushed stone was ≤10%, and the particle size was 5-10 mm; the polycarboxylate-based high-efficiency water-reducing agent was model SiKa ViscoCrete-540P; and the propylene glycol ether-type shrinkage reducing agent was model Sika Control-SRA. 50; the average length of polyvinyl alcohol chopped fibers is 12 mm, the average diameter is 40 μm, and the tensile strength is 1250 MPa; the activity index R of lightly calcined magnesium oxide is 45 s (citric acid method), the average particle size is 15 μm, and the activity index R of darkly calcined magnesium oxide is 350 s (citric acid method), the average particle size is 18 μm.

[0037] Example 1, (1) 2400g of anhydrous ethanol, 120g of deionized water and 600g of kaolin were mixed and dispersed. 4g of 3-aminopropyltriethoxysilane was added, stirred for 45min and filtered. The mixture was washed twice with anhydrous ethanol and dried at 60°C to obtain kaolin powder with amino groups on the surface.

[0038] (2) Add 600g of kaolin powder with amino surface to 3000g of deionized water and disperse it fully. Add 8g of polyacrylic acid, 1.6g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.8g of N-hydroxysuccinimide. Adjust the pH of the solution to 5, stir for 100min, filter and wash with water and dry at 60℃ to obtain polyacrylic acid grafted kaolin powder.

[0039] (3) Disperse 600g of polyacrylic acid grafted kaolin powder in 3000g of deionized water, add 8g of anhydrous calcium chloride, stir for 25min, filter and dry at 60℃ to obtain polyacrylic acid grafted kaolin powder with calcium ion bridging sites.

[0040] (4) Add 12g of 50% aqueous solution of 1-hydroxyethylidene-1,1-diphosphonic acid and 2.5g of calcium hydroxide to 2000g of deionized water, stir for 10min, then add 600g of polyacrylic acid grafted kaolin powder with calcium ion bridging sites, soak for 50min, filter, wash with water and dry at 60℃ to obtain grafted powder with ternary bridging structure;

[0041] (5) Dissolve 3.5g of polyallylamine hydrochloride in 3000g of deionized water, then add 600g of grafted powder with ternary bridging structure, soak for 25min, filter, then dissolve 15g of sodium nitrite in 3000g of deionized water, soak for 25min, filter and dry at 60℃ to obtain grafted composite corrosion inhibitor powder.

[0042] (6) 7200g of sea sand, 3200g of basalt gravel, 5300g of marine silicate cement, 500g of silica fume, 600g of kaolin and 50g of nano alumina were put into a forced mixer and dry-mixed for 120s. 60g of polycarboxylate-based high-efficiency water-reducing agent was dissolved in 1150g of water and added to the mixer. The mixture was wet-mixed for 60s. 450g of grafted composite corrosion inhibitor powder was then added. 60g of propylene glycol ether shrinkage reducer was dissolved in 1150g of water and added to the mixer. 120g of polyvinyl alcohol chopped fiber was sprinkled in and wet-mixed for 60s. 105g of lightly calcined magnesium oxide and 52.5g of heavily calcined magnesium oxide were then added and mixed for 60s to obtain high-performance, high-crack-resistant concrete for bridges.

[0043] Example 2, (1) 2400g of anhydrous ethanol, 120g of deionized water and 600g of kaolin were mixed and dispersed. 6g of 3-aminopropyltriethoxysilane was added, stirred for 60min and filtered. The mixture was washed twice with anhydrous ethanol and dried at 60°C to obtain kaolin powder with amino groups on the surface.

[0044] (2) Add 600g of kaolin powder with amino surface to 3000g of deionized water and disperse it fully. Add 10g of polyacrylic acid, 2g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1g of N-hydroxysuccinimide. Adjust the pH of the solution to 5, stir for 120min, filter and wash with water and dry at 60℃ to obtain polyacrylic acid grafted kaolin powder.

[0045] (3) Disperse 600g of polyacrylic acid grafted kaolin powder in 3000g of deionized water, add 11g of anhydrous calcium chloride, stir for 30min, filter and dry at 60℃ to obtain polyacrylic acid grafted kaolin powder with calcium ion bridging sites.

[0046] (4) Add 14g of 50% aqueous solution of 1-hydroxyethylidene-1,1-diphosphonic acid and 3g of calcium hydroxide to 2000g of deionized water, stir for 10min, then add 600g of polyacrylic acid grafted kaolin powder with calcium ion bridging sites, soak for 60min, filter and wash with water and dry at 60℃ to obtain the grafted powder with ternary bridging structure.

[0047] (5) Dissolve 5g of polyallylamine hydrochloride in 3000g of deionized water, then add 600g of grafted powder with ternary bridging structure, soak for 30min, filter, then dissolve 21g of sodium nitrite in 3000g of deionized water, soak for 30min, filter and dry at 60℃ to obtain grafted composite corrosion inhibitor powder.

[0048] (6) 7200g of sea sand, 3200g of basalt gravel, 5300g of marine silicate cement, 500g of silica fume, 600g of kaolin and 70g of nano alumina were put into a forced mixer and dry-mixed for 120s. 70g of polycarboxylate-based high-efficiency water-reducing agent was dissolved in 1225g of water and added to the mixer. The mixture was wet-mixed for 60s. 600g of grafted composite corrosion inhibitor powder was added. 70g of propylene glycol ether shrinkage reducer was dissolved in 1225g of water and added to the mixer. 140g of polyvinyl alcohol chopped fiber was sprinkled in and wet-mixed for 60s. 140g of lightly calcined magnesium oxide and 70g of heavily calcined magnesium oxide were added and mixed for 60s to obtain high-performance, high-crack-resistant concrete for bridges.

[0049] Example 3, (1) 2400g of anhydrous ethanol, 120g of deionized water and 600g of kaolin were mixed and dispersed. 8g of 3-aminopropyltriethoxysilane was added, stirred for 75min and filtered. The mixture was washed twice with anhydrous ethanol and dried at 60°C to obtain kaolin powder with amino groups on the surface.

[0050] (2) Add 600g of amino-containing kaolin powder to 3000g of deionized water and disperse it fully. Add 12g of polyacrylic acid, 2.4g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and 1.2g of N-hydroxysuccinimide. Adjust the pH of the solution to 5, stir for 150min, filter and wash with water and dry at 60℃ to obtain polyacrylic acid grafted kaolin powder.

[0051] (3) Disperse 600g of polyacrylic acid grafted kaolin powder in 3000g of deionized water, add 14g of anhydrous calcium chloride, stir for 40min, filter and dry at 60℃ to obtain polyacrylic acid grafted kaolin powder with calcium ion bridging sites.

[0052] (4) Add 16g of 50% aqueous solution of 1-hydroxyethylidene-1,1-diphosphonic acid and 3.5g of calcium hydroxide to 2000g of deionized water, stir for 10min, then add 600g of polyacrylic acid grafted kaolin powder with calcium ion bridging sites, impregnate for 80min, filter, wash with water and dry at 60℃ to obtain grafted powder with ternary bridging structure;

[0053] (5) Dissolve 6.5g of polyallylamine hydrochloride in 3000g of deionized water, then add 600g of grafted powder with ternary bridging structure, soak for 45min, filter, then dissolve 27g of sodium nitrite in 3000g of deionized water, soak for 45min, filter and dry at 60℃ to obtain grafted composite corrosion inhibitor powder.

[0054] (6) 7200g of sea sand, 3200g of basalt gravel, 5300g of marine silicate cement, 500g of silica fume, 600g of kaolin and 90g of nano alumina were put into a forced mixer and dry-mixed for 120s. 80g of polycarboxylate-based high-efficiency water-reducing agent was dissolved in 1350g of water and added to the mixer. The mixture was wet-mixed for 60s. 750g of grafted composite corrosion inhibitor powder was then added. 80g of propylene glycol ether-type shrinkage reducer was dissolved in 1350g of water and added to the mixer. 160g of polyvinyl alcohol chopped fiber was sprinkled in and wet-mixed for 60s. 175g of lightly calcined magnesium oxide and 87.5g of heavily calcined magnesium oxide were then added and mixed for 60s to obtain high-performance, high-crack-resistant concrete for bridges.

[0055] Comparative Example 1:

[0056] The difference between Comparative Example 1 and Example 2 is that the 3-aminopropyltriethoxysilane amination modification in step (1) is omitted, and kaolin is directly used to replace the subsequent modification carrier. The other conditions are the same as in Example 2.

[0057] Comparative Example 2:

[0058] The difference between Comparative Example 2 and Example 2 is that the polyacrylic acid grafting process in step (2) is omitted, and kaolin that has only been aminated is used in subsequent steps. The other conditions are the same as in Example 2.

[0059] Comparative Example 3:

[0060] The difference between Comparative Example 3 and Example 2 is that the ternary bridging structure in steps (3) and (4) is cancelled, and only polyacrylic acid grafted kaolin powder is used as a carrier and enters the subsequent loading step. The other conditions are the same as those in Example 2.

[0061] Comparative Example 4:

[0062] The difference between Comparative Example 4 and Example 2 is that the addition of polyallylamine hydrochloride in step (5) was omitted, and the grafted powder of the ternary bridged structure was directly immersed in sodium nitrite solution for treatment. The other conditions were the same as in Example 2.

[0063] Comparative Example 5:

[0064] The difference between Comparative Example 5 and Example 2 is that polyallylamine hydrochloride, ternary bridged grafted powder and sodium nitrite are directly mixed in a weight ratio of 5:600:21 to replace the grafted composite corrosion inhibitor powder in step (6), with a total addition amount of 600g. The other conditions are the same as in Example 2.

[0065] Comparative Example 6:

[0066] The difference between Comparative Example 6 and Example 2 is that the double doping of light-burned magnesium oxide and heavy-burned magnesium oxide was cancelled, and only light-burned magnesium oxide was added, with an addition amount of 210g. The other conditions were the same as in Example 2.

[0067] Performance testing:

[0068] Specimen preparation: After all concrete is mixed, it is immediately poured into molds of the corresponding specifications, compacted on a vibrating table, and the surface is smoothed; after standing at room temperature for 24 hours, it is demolded and placed in a standard curing room (temperature 20±2℃, relative humidity above 95%) for curing until the test age. For the specifications and quantities of specimens required for different test items, please refer to the description of each test item.

[0069] Chloride ion permeability test: Specimen specifications: φ100×50mm circular discs, 3 parallel specimens per group, standard curing for 28 days. The specimens were cut from the center of φ100×200mm cylindrical specimens, the cut surfaces were polished smooth, and vacuum-saturated with water for 24 hours before use. The test followed the rapid determination method for chloride ion migration coefficient in GB / T 50082-2009. The saturated specimens were installed in a permeation tank, with one side containing 0.3mol / L NaOH solution (cathode) and the other side containing 3.0% NaCl solution (anode). A 60V DC voltage was applied, and the current passing through was recorded over 6 hours. The cumulative current flux was calculated, and the average value was calculated. The results are shown in Table 1.

[0070] Electrochemical testing of steel reinforcement corrosion: Specimen specifications: φ100×200mm cylinder, with an internal φ12mm HRB400 steel reinforcement (centered, exposed end epoxy-encapsulated), 5 specimens per group. After 28 days of standard curing, immersion tests were started. The immersion medium was 3.5% NaCl solution, and the specimens were completely submerged. The solution was changed every 2 weeks. Open circuit potential (OCP) monitoring was performed using a saturated calomel electrode as a reference, measured daily for 90 consecutive days. The time of initial pitting corrosion (the time when OCP drops to -350mV) was recorded. Linear polarization resistance (LPR) testing was performed at 90 days, with a scan range of ±20mV vs OCP and a scan rate of 0.125mV / s. Polarization resistance and corrosion rate were calculated. The results are shown in Table 1.

[0071] Limiting shrinkage crack resistance: Specimen specifications: a steel ring (inner diameter φ330mm, wall thickness 25mm) encased in a concrete ring (outer diameter φ430mm), 2 specimens per group. Strain gauges were attached to the inner surface of the steel ring. After pouring concrete for 24 hours, the outer mold was removed, and the specimens were placed in a constant temperature and humidity chamber (20±2℃, RH 60±5%). The strain changes of the steel ring were continuously monitored, and the time of the first crack appearance and the corresponding steel ring strain value were recorded. The results are shown in Table 2.

[0072] Compressive strength: Specimen specifications: 100mm cube, 3 specimens per group at each age, in accordance with GB / T 50081-2019. The compressive strength was measured at 7, 28, and 56 days. The cube compressive strength of each group of concrete was calculated, and the results are shown in Table 2.

[0073] Table 1. Electrochemical test results of chloride ion penetration resistance and steel corrosion resistance

[0074]

[0075] Table 2. Tests on restricted shrinkage resistance, crack resistance, and compressive strength.

[0076]

[0077] Data Analysis:

[0078] As can be seen from the data of Examples 1-3 in Tables 1 and 2, the concrete prepared by this invention exhibits a synergistic relationship between chloride ion migration, steel corrosion resistance, limited shrinkage and crack resistance, and mechanical integrity. This indicates that the material configuration is not a single shielding or expansion effect, but rather is jointly regulated by multi-level interfaces and pore structures. It is speculated that the grafting of polyacrylic acid onto kaolin provides stable carboxyl sites, forming a multi-point bridging framework with the participation of calcium ions and hydroxyethylidene diphosphonic acid ligands. Combined with the orderly adsorption and slow release of nitrite and polyallylamine hydrochloride, the staged micro-expansion of lightly calcined and heavily calcined magnesium oxide, the bridging of polyvinyl alcohol short-cut fibers, and the densification of silica fume and alumina, the effective diffusion channels are shortened, microcracks are suppressed, thereby delaying pitting corrosion initiation and maintaining the continuity of strength growth.

[0079] As can be seen from the data in Tables 1 and 2 for Example 2 and Comparative Example 1, Comparative Example 1 is generally weaker than Example 2 in terms of chloride ion intrusion, corrosion resistance, and limited shrinkage crack resistance, showing a trend of decreased interfacial protection sustainability and earlier crack appearance. This may be due to the lack of aminosilane activation, resulting in insufficient density and stability of the subsequent polyacrylic acid graft layer, leading to a decrease in the density and stability of bridging sites between calcium ions and 1-hydroxyethylidene-1,1-diphosphonic acid. This restricts the anchoring and orderly distribution of the inhibitor at the interface, thereby weakening the maintenance of long-term sustained release and electrochemical passivation.

[0080] As can be seen from the data in Tables 1 and 2 for Example 2 and Comparative Example 2, Comparative Example 2 showed a deteriorating trend in chlorine resistance, pitting delay, and shrinkage crack control. This indicates that the surface chemical basis of the support has a decisive influence on the overall performance. This may be because the support lacks sufficient carboxyl sites when ungrafted, making it difficult to form a stable multi-point coordination framework with 1-hydroxyethylidene-1,1-bisphosphonic acid through calcium ions. Consequently, the subsequent adsorption and sustained release of inhibitors exhibit characteristics of easy loss and discontinuity, and the interfacial film layer is not easily maintained intact.

[0081] As can be seen from the data in Tables 1 and 2 for Example 2 and Comparative Example 3, Comparative Example 3 showed a consistent decrease in corrosion resistance, impermeability, and crack resistance compared to Example 2, indicating that ternary bridging plays a crucial role in improving overall performance. This may be due to the lack of bridging between calcium ions and 1-hydroxyethylidene-1,1-diphosphonic acid with only polyacrylic acid grafting, resulting in insufficient multi-point coordination and spatial anchoring at the interface. The inhibitor distribution is more dominated by convection-diffusion, making it difficult to maintain a continuous adsorption layer at the steel-slurry interface, thus shortening the passivation duration.

[0082] As can be seen from the data in Tables 1 and 2 for Example 2 and Comparative Example 4, Comparative Example 4 is weaker than Example 2 in both corrosion resistance stability and shrinkage crack control, indicating that the system using nitrite alone is difficult to obtain the same continuous protection. This may be due to the lack of molecular chain coverage and electrostatic adsorption of polyallylamine hydrochloride, resulting in insufficient continuity and adhesion strength of the interfacial film. Even with the presence of bridging carriers and nitrite, it is difficult to form a tough and regenerable composite adsorption layer.

[0083] As can be seen from the data of Example 2 and Comparative Example 5 in Tables 1 and 2, Comparative Example 5 exhibits a discrete and unstable performance response, which is reflected in the difficulty in simultaneously improving impermeability, corrosion resistance, and crack resistance, indicating that the process path has a significant impact on the results. This may be because direct mixing makes it difficult to form an ordered interface of layer-by-layer self-assembly, and the inhibitor is more easily lost with seepage migration; while stepwise grafting-bridging-loading can construct gradient adsorption and chemical anchoring in the pore structure and interface region, maintaining the spatiotemporal synergy of the slow release and densification processes.

[0084] As can be seen from the data of Example 2 and Comparative Example 6 in Tables 1 and 2, Comparative Example 6 is inferior to Example 2 in terms of long-term impermeability, corrosion resistance, and crack delay, suggesting that single stress compensation is insufficient to cover the critical age. This may be because Example 2 uses a combination of lightly calcined and heavily calcined magnesia, allowing micro-expansion to occur sequentially over time; single-doped lightly calcined magnesia only provides early compensation, and the pores are easily reconnected during later stress redistribution. In synergy with fibers, silica fume, and nano-alumina, a more stable pore size distribution and crack suppression can be formed in Example 2.

[0085] 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 high performance high crack resistance concrete for bridges, characterized by, The following raw materials are prepared by weight parts: sea sand 7200 parts, basalt gravel 3200 parts, marine portland cement 5300 parts, silica fume 500 parts, kaolin 600 parts, nano-alumina 50-90 parts, grafted composite corrosion inhibitor carrier powder 450-750 parts, polyvinyl alcohol chopped fiber 120-160 parts, light-burned magnesium oxide 105-175 parts, heavy-burned magnesium oxide 52.5-87.5 parts, polycarboxylate superplasticizer 60-80 parts, propylene glycol ether type shrinkage reducing agent 60-80 parts, mixing water 2300-2700 parts; The grafted composite corrosion inhibitor carrier powder is prepared by sequentially subjecting kaolin to 3-aminopropyl triethoxysilane amination to obtain kaolin powder with amino groups on the surface, grafting polyacrylic acid in the presence of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride / N-hydroxysuccinimide to obtain polyacrylic acid grafted kaolin powder, introducing calcium ion bridging sites by anhydrous calcium chloride to obtain polyacrylic acid grafted kaolin powder with calcium ion bridging sites, reacting with 1-hydroxyethylidene-1,1-biphosphonic acid and calcium hydroxide to obtain a ternary bridging structure grafted powder, and finally loading polyallylamine hydrochloride and sodium nitrite and drying; 3-aminopropyl triethoxysilane is 4-8 parts based on 600 parts by weight of kaolin; polyacrylic acid is 8-12 parts based on 600 parts by weight of kaolin powder with amino groups on the surface; Anhydrous calcium chloride is 8-14 parts based on 600 parts by weight of polyacrylic acid grafted kaolin powder; 1-hydroxyethylidene-1,1-biphosphonic acid aqueous solution with a mass fraction of 50% is 12-16 parts, and calcium hydroxide is 2.5-3.5 parts based on 600 parts by weight of polyacrylic acid grafted kaolin powder with calcium ion bridging sites; polyallylamine hydrochloride is 3.5-6.5 parts, and sodium nitrite is 15-27 parts based on 600 parts by weight of the ternary bridging structure grafted powder.

2. The high performance high crack resistance concrete for bridge according to claim 1, wherein The average particle size of the nano-alumina is 50 nm; the average length of the polyvinyl alcohol chopped fiber is 12 mm, and the average diameter is 40 μm.

3. The high performance high crack resistance concrete for bridge according to claim 1, wherein The light-burned magnesium oxide has an activity index of 45 s and an average particle size of 15 μm; the heavy-burned magnesium oxide has an activity index of 350 s and an average particle size of 18 μm.

4. The high performance high crack resistance concrete for bridge according to claim 1, wherein The sea sand has a fineness modulus of 2.6-2.9 and a clay content of ≤3%; the basalt gravel has a particle size of 5-10 mm and a needle flake content of ≤10%.

5. The high performance high crack resistance concrete for bridge according to claim 1, wherein The weight average molecular weight of the polyacrylic acid is 100000, and the weight average molecular weight of the polyallylamine hydrochloride is 45000.

6. The high performance high crack resistance concrete for bridge according to claim 1, wherein The mixing water is added in two times; the polycarboxylate superplasticizer is dissolved in the first stage of mixing water and then added, and the propylene glycol ether type shrinkage reducing agent is dissolved in the second stage of mixing water and then added.

7. The high performance high crack resistance concrete for bridge according to claim 6, wherein The mixing water is added in two equal amounts.

8. The high performance high crack resistance concrete for bridge according to claim 1, wherein The average particle size of the kaolin, which is the raw material of the grafted composite corrosion inhibitor carrier powder, is 5 μm.

9. A method of producing the high-performance high- crack-resistant concrete for bridges according to any one of claims 1 to 8, characterized by, The method comprises the following steps: firstly, put sea sand, basalt gravel, marine portland cement, silica fume, kaolin and nano alumina into a stirring machine for dry mixing for 120s; secondly, dissolve polycarboxylate superplasticizer in the first mixing water, add and wet mix for 60s; thirdly, add grafted composite corrosion inhibitor carrier powder; fourthly, dissolve propylene glycol ether type shrinkage reducing agent in the second mixing water, add and simultaneously sprinkle polyvinyl alcohol short fiber, and wet mix for 60s; finally, add light-burned magnesium oxide and heavy-burned magnesium oxide for 60s of whole mixing, to obtain bridge high-performance high-anti-cracking concrete.

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