Composite prefabricated concrete duct piece and preparation method thereof

Abstract

The invention belongs to the technical field of pipe pieces, and particularly relates to a composite prefabricated concrete pipe piece and a preparation method thereof. The composite prefabricated concrete duct piece comprises a duct piece body and a reinforcement cage arranged in the duct piece body, the duct piece body is made of a concrete material, and the concrete material comprises cement, a mineral admixture, coarse aggregate, fine aggregate, an early-strength polycarboxylate superplasticizer, a functional admixture and water. The early strength type polycarboxylate superplasticizer is prepared by taking the isopentenol polyoxyethylene ether, the triallyl phosphate, the L-vinylglycine and the acrylic acid as monomers, so that the early strength of concrete is improved; modified polypropylene fiber, lithium silicate and methyl cellulose are adopted to jointly form a functional admixture, hydroxyethyl methylacrylate is grafted to the surface of the polypropylene fiber, and the anti-cracking performance, the anti-seepage performance and the mechanical performance of the concrete are improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of pipe segments, and particularly relates to a composite prefabricated concrete pipe segment and a preparation method thereof. BACKGROUND

[0002] With the acceleration of urbanization and the continuous advancement of infrastructure construction, prefabricated concrete pipe segments play an increasingly important role in various engineering fields. In urban rail transit construction, the shield method has become the mainstream, and prefabricated concrete pipe segments bear important structural support and protection functions. As a key component of the shield tunnel lining structure, the quality of the prefabricated concrete pipe segments directly affects the safety and durability of the tunnel structure, and further affects the stable operation of the entire urban rail transit system.

[0003] In the production process of existing prefabricated concrete pipe segments, quality defects such as air holes and cracks often occur. When applied to scenarios such as highway tunnels and subways, the water vapor barrier ability is poor. Water vapor permeating into the concrete pipe segments can cause corrosion of the steel bars in the concrete pipe segments, affecting the mechanical properties of the concrete pipe segments, and further affecting the load-bearing capacity and service life of the pipe segments. A common improvement method is to use new types of admixtures. For example, anti-cracking agents can effectively reduce shrinkage cracks generated during the hardening process of concrete, improving the anti-cracking performance of concrete. Rust inhibitors can delay the rusting of steel bars, protecting the steel bars from external erosion and prolonging the service life of the pipe segments. However, the use of new types of admixtures also has some problems. Some admixtures have poor compatibility with concrete, which can cause poor work performance of concrete, such as rapid loss of slump, segregation, and other phenomena. The dosage of admixtures also needs to be accurately controlled. Too little dosage may not achieve the desired effect, and too much dosage may cause other problems, such as reduced strength.

[0004] Chinese patent application file with publication number CN112608105A discloses a prefabricated pipe segment concrete, which includes cement 110-140 parts, mineral admixture 30-45 parts, sand 130-180 parts, stone 250-330 parts, water reducing agent 4-5 parts, water 35-45 parts, and modified hydrotalcite powder 15-20 parts. The preparation method of the modified hydrotalcite powder is as follows: calcium nitrate tetrahydrate, aluminum nitrate nonahydrate, and calcium nitrite are dissolved in deionized water, sodium hydroxide solution is added dropwise at 35-40℃, the pH value is adjusted to 11-12, and then stirring and heating to 70-80℃ for reaction. After vacuum filtration and washing, the modified hydrotalcite powder is obtained by drying. However, the amount of cement and mineral admixture in this formula is relatively small, resulting in insufficient cement density, which cannot meet the strength requirements of oxygen evaporation early demolding, affecting production efficiency. In addition, the use of sodium hydroxide to adjust the pH value and the use of calcium nitrite as raw material in the modified hydrotalcite powder result in high alkali content of the modified hydrotalcite, which can cause alkali-aggregate reaction when applied to pipe segment concrete, leading to pipe segment cracking and reduced durability. SUMMARY

[0005] In order to solve the technical problems of poor mechanical properties and impermeability of concrete in the prior art, the application provides a composite prefabricated concrete segment and a preparation method thereof.

[0006] In order to achieve the above-mentioned purpose, the technical scheme of the application is as follows: A composite prefabricated concrete segment, comprising a segment body and a steel reinforcement cage arranged in the segment body, the segment body being a concrete material, and the concrete material comprising the following components in parts by weight: cement 100-150 parts, mineral admixture 40-50 parts, coarse aggregate 220-260 parts, fine aggregate 140-150 parts, early strength polycarboxylate superplasticizer 3-8 parts, functional admixture 20-30 parts, and water 80-100 parts; The preparation method of the early strength polycarboxylate superplasticizer is as follows: isoprenol polyoxyethylene ether, triallyl phosphate, L-ethyleneglycine and sodium bisulfite are added into an ethanol aqueous solution, stirred and dissolved, heated to 50-60 DEG C, and acrylic acid, mercaptopropionic acid and hydrogen peroxide are simultaneously added dropwise under stirring, and after the dropwise addition is completed, the reaction is kept for 2-3 h, and then 80-85 DEG C reduced pressure distillation is carried out, and then cooling is carried out to obtain the early strength polycarboxylate superplasticizer.

[0007] In the present application, by using isopentenyl alcohol polyoxyethylene ether, phosphoric acid triallyl ester, L-vinyl glycine and acrylic acid as reaction monomers, a free radical polymerization reaction is initiated under a redox initiator system to generate a side chain structure with different lengths. The shorter side chain can quickly play a role in the early hydration of cement to enhance the adsorption of water reducing agent molecules and cement particles and improve the dispersibility of cement particles, thereby promoting early hydration reaction. The longer side chain provides a sustained steric hindrance effect in the later stage to maintain the dispersion state of cement particles, which is beneficial to the development of the later strength of concrete. In addition, the introduction of polyoxyethylene ether group in the side chain of water reducing agent molecules through steric hindrance effect effectively disperses cement particles and promotes their hydration reaction; the introduction of phosphate group in the side chain of water reducing agent molecules through complexation reaction with calcium ions in cement to form a stable complex, thereby accelerating the hydration process of cement; L-vinyl glycine can introduce amino and carboxyl groups in the side chain of water reducing agent molecules, and acrylic acid can introduce carboxyl groups in the side chain of water reducing agent molecules. Amino has strong basicity and can react with acidic groups on the surface of cement particles to form chemical bonds, thereby enhancing the adsorption between water reducing agent molecules and cement particles. This strong adsorption effect enables the water reducing agent to more effectively disperse cement particles and promote early hydration of cement. Amino can also react with calcium hydroxide produced during the hydration process of cement to generate ettringite and other mineral phases with early strength effect, further improving the early strength of concrete; carboxyl groups can form complexes with calcium ions in cement hydration products to break the coating layer of petrified products on the surface of particles, promote the continuous dissolution and hydration of cement particles, shorten the hydration induction period and improve the early strength of concrete.

[0008] Further, the molar ratio of isopentenyl alcohol polyoxyethylene ether, phosphoric acid triallyl ester, L-vinyl glycine and acrylic acid in the preparation method of early strength polycarboxylate superplasticizer is 1:(0.35-0.52):(0.62-0.75):(4-6).

[0009] The application adjusts the molecular structure of the early-strength polycarboxylate superplasticizer by controlling the molar ratio of prenol polyoxyethylene ether, triallyl phosphate, L-vinylglycine and acrylic acid. The molar ratio of prenol polyoxyethylene ether and acrylic acid can determine the dispersibility and dispersion retention of the polycarboxylate superplasticizer. When the acid-ether ratio is reduced, the long side chain of the polyether provides a better steric hindrance effect, which can effectively prevent the agglomeration of cement particles, but the production rate of early hydration products of cement is slowed down. When the acid-ether ratio is increased, the density of the side chain is weakened, and the dispersibility of the cement particles is reduced. The amount of triallyl phosphate and L-vinylglycine determines the density of the early-strength functional groups in the superplasticizer molecules. When the amount is increased, the early strength of the concrete is increased, but the dispersibility of the cement is reduced. When the amount is reduced, the early strength of the concrete is improved.

[0010] Further, in the preparation method of the early-strength polycarboxylate superplasticizer, the molar ratio of sodium bisulfite and hydrogen peroxide is (0.5-0.8):1, and the amount of hydrogen peroxide is 0.9%-1.2% of the sum of the amounts of prenol polyoxyethylene ether, triallyl phosphate, L-vinylglycine and acrylic acid. The amount of mercaptopropionic acid is 0.1%-0.2% of the sum of the amounts of prenol polyoxyethylene ether, triallyl phosphate, L-vinylglycine and acrylic acid.

[0011] Further, in the preparation method of the early-strength polycarboxylate superplasticizer, the mass percentage of the ethanol aqueous solution is 70%-85%.

[0012] Further, the functional admixture is composed of modified polypropylene fibers, lithium silicate and methyl cellulose in a mass ratio of (10-15):(3-7):(1-2).

[0013] In the application, modified polypropylene fibers, lithium silicate and methyl cellulose are used together to form a functional admixture. Through the synergistic effect of crack resistance, densification and thickening, the anti-cracking performance, anti-permeability performance and mechanical properties of the concrete are improved. The modified polypropylene fibers in the concrete constrain the plastic shrinkage and dry shrinkage of the cement paste through the bridging effect, form a three-dimensional network structure, and prevent the expansion of micro-cracks during the hardening process of the concrete. The lithium silicate can react with the cement hydration products to generate dense calcium silicate hydrate gel, fill the defects in the interface transition zone between the cement paste and the aggregate, and improve the interface bonding strength. The methyl cellulose can delay the evaporation speed of water in the concrete, avoid dry shrinkage cracks on the surface due to rapid water loss, and improve the workability of the concrete, avoiding the formation of connected pores due to bleeding.

[0014] Further, the preparation method of the modified polypropylene fiber is as follows: the polypropylene fiber is put into anhydrous ethanol, ultrasonic cleaning, filtration, drying, then put into potassium permanganate solution, stirring at 60-65 DEG C for 30-40 min, filtration, then soaked in hydrochloric acid solution for 10-20 min, filtration, washing with deionized water until neutral, drying, then adding into a reaction kettle with toluene, nitrogen deoxidation, stirring and heating to 70-80 DEG C, stirring for 30 min, then adding benzoyl peroxide toluene solution dropwise, stirring and reacting for 1-1.5 h, adding hydroxyethyl methacrylate dropwise, heating to 90-95 DEG C after the completion of dropwise adding, reacting for 4-6 h, adding 30-45 mL of resorcinol ethanol solution, stirring for 30-40 min, cooling, filtration, washing, drying, to obtain the modified polypropylene fiber.

[0015] The polypropylene fiber is etched in potassium permanganate under the assistance of ultrasonic wave in the application, the number of active sites on the surface of the polypropylene fiber is increased, then hydroxyethyl methacrylate is grafted on the surface of the polypropylene fiber under the initiation of benzoyl peroxide, and hydroxyl and ester groups and other polar groups are introduced on the surface of the polypropylene fiber, the roughness of the surface of the polypropylene fiber and the increase of the polar groups improve the bonding force between the polypropylene fiber and the concrete, the polypropylene can effectively transfer stress, and a firm three-dimensional network is formed in the concrete, when a micro crack is generated, greater bridging resistance can be provided, the generation and expansion of cracks are effectively inhibited, and the crack resistance and mechanical properties of the concrete are effectively improved.

[0016] Further, the mass percentage of the potassium permanganate solution in the preparation method of the modified polypropylene fiber is 5%-8%, the mass percentage of the hydrochloric acid solution is 10%-15%, the mass percentage of the benzoyl peroxide toluene solution is 3%-5%, and the mass percentage of the resorcinol ethanol solution is 0.1%-0.3%; the mass ratio of the polypropylene fiber, hydroxyethyl methacrylate and benzoyl peroxide is 10:(3-5):(0.2-0.3).

[0017] Further, the mineral admixture is composed of silica fume, slag powder, fly ash and zeolite powder according to the mass ratio of (4-8):(27-31):(22-25):(8-13).

[0018] The mineral admixture is composed of silica ash, slag powder, fly ash and zeolite powder, the silica ash can react with calcium hydroxide generated by cement hydration to generate a large amount of dense calcium silicate hydrate gel, fill the capillary pores in the concrete, and significantly reduce the diffusion coefficient of aluminum ions; the slag powder has a microcrystalline core effect, which can not only accelerate the cement hydration process, but also improve the early and late strength development of concrete, reduce internal pores through filling effect, improve the interface defect and improve the impermeability; the spherical particles of fly ash can improve the workability of concrete, and the pozzolanic effect can promote the secondary hydration to generate gel material, optimize the internal structure and interface transition zone of concrete, and improve the mechanical properties of concrete; the zeolite powder contains active silicon dioxide and aluminum trioxide, which has both pozzolanic activity and adsorption properties, which can not only react with calcium hydroxide to generate cementitious material and improve the compressive strength, but also adsorb water and harmful ions through its own porous structure to reduce the water permeation channel and improve the impermeability of concrete.

[0019] Further, the coarse aggregate is 12-20mm continuous graded gravel, and the apparent density is 2700kg / m 3 ; the fine aggregate is coarse sand with a fineness modulus of 3.0-3.5.

[0020] The application further provides a preparation method of the composite prefabricated concrete segment, comprising the following steps: S1: fixing the reinforcement cage to complete the installation of the embedded part; S2: mixing cement, mineral admixture, coarse aggregate, fine aggregate and functional admixture, adding a mixed solution of early-strength polycarboxylate superplasticizer and water, and stirring uniformly to obtain a concrete material; S3: generating a 3D digital model according to the shape and size of the segment, pouring the 3D digital model into a 3D printing software, and performing 3D printing on the concrete material prepared in step S2, demolding after curing for 24h, steam curing for 7-14 days, and natural curing for 28 days to obtain a concrete segment.

[0021] The application adopts the 3D printing technology, the whole segment is continuously printed during the printing process, the gaps and weak interfaces generated by traditional mold splicing are avoided, and the impermeability, corrosion resistance and mechanical properties of the segment are improved.

[0022] Compared with the prior art, the composite prefabricated concrete segment and the preparation method thereof have the following technical advantages: (1) the early-strength polycarboxylate superplasticizer is prepared by using iso-pentenyl alcohol polyoxyethylene ether, phosphoric acid triallyl ester, L-ethyleneglycine and acrylic acid as monomers under the action of an oxidation-reduction system initiator, which effectively improves the early strength of concrete, shortens the demolding time of the concrete segment, and improves the production efficiency; (2) The functional admixture is prepared by using modified polypropylene fiber, lithium silicate and methyl cellulose, and the anti-cracking, densification and thickening synergistic effects can improve the anti-cracking performance, anti-permeability and mechanical properties of the concrete; (3) The hydroxyethyl methacrylate is grafted to the surface of the polypropylene fiber, so that the interface bonding strength between the polypropylene fiber and the concrete is improved, and the anti-cracking performance and the mechanical properties of the concrete are effectively improved. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The molecular structure of the early-strength polycarboxylate superplasticizer is shown in the figure. Figure 2 The nuclear magnetic resonance spectrum of the early-strength polycarboxylate superplasticizer prepared in Preparation Example 3 is shown in the figure. Figure 3 The infrared spectrum of the modified polypropylene fiber prepared in Preparation Example 6 is shown in the figure. DETAILED DESCRIPTION

[0024] The following will be further described in combination with specific embodiments, but the present application is not limited to the following embodiments. Those skilled in the art can make various modifications according to the basic idea of the present application, as long as they do not deviate from the basic idea of the present application, and they are within the scope of the present application.

[0025] The raw materials described in the specific embodiment are commercially available unless otherwise specified. The molecular structure of the early-strength polycarboxylate superplasticizer described in the specific embodiment is shown in the figure. Figure 1 The cement is P·O 42.5 Portland cement.

[0026] The composite prefabricated concrete segment in the specific embodiment includes a segment body and a steel reinforcement cage arranged in the segment body, the segment body is a concrete material, and the preparation method of the composite prefabricated concrete segment includes the following steps: S1: fixing the steel reinforcement cage to complete the installation of the embedded part; S2: mixing cement, mineral admixture, coarse aggregate, fine aggregate and functional admixture, adding a mixed solution of early-strength polycarboxylate superplasticizer and water, and stirring uniformly to obtain a concrete material; S3: generating a 3D digital model according to the shape and size of the segment, pouring the 3D digital model into a 3D printing software, and using the concrete material prepared in step S2 to perform 3D printing, demolding after curing for 24 hours, steam curing for 7-14 days, and natural curing for 28 days to obtain a concrete segment.

[0027] Preparation Example 1 The preparation method of the early-strength polycarboxylic water reducing agent is as follows: 10 mol of isoamylene polyoxyethylene ether, 3.5 mol of phosphorus acid triallyl ester, 6.2 mol of L-ethylene glycine and 0.27 mol of sodium bisulfite are added into 1 L of 70% mass fraction ethanol aqueous solution, stirred and dissolved, heated to 50°C, and 40 mol of acrylic acid, 0.06 mol of mercaptopropionic acid and 0.54 mol of hydrogen peroxide are added dropwise under stirring, and after the dropwise addition is completed, the reaction is preserved for 2 h, distilled at 80°C under reduced pressure, cooled, and the early-strength polycarboxylic water reducing agent is obtained.

[0028] Preparation Example 2 The preparation method of the early-strength polycarboxylic water reducing agent is as follows: 10 mol of isoamylene polyoxyethylene ether, 5.2 mol of phosphorus acid triallyl ester, 7.5 mol of L-ethylene glycine and 0.79 mol of sodium bisulfite are added into 1 L of 85% mass fraction ethanol aqueous solution, stirred and dissolved, heated to 60°C, and 60 mol of acrylic acid, 0.17 mol of mercaptopropionic acid and 0.99 mol of hydrogen peroxide are added dropwise under stirring, and after the dropwise addition is completed, the reaction is preserved for 3 h, distilled at 85°C under reduced pressure, cooled, and the early-strength polycarboxylic water reducing agent is obtained.

[0029] Preparation Example 3 The preparation method of the early-strength polycarboxylic water reducing agent is as follows: 10 mol of isoamylene polyoxyethylene ether, 4.6 mol of phosphorus acid triallyl ester, 6.9 mol of L-ethylene glycine and 0.44 mol of sodium bisulfite are added into 1 L of 80% mass fraction ethanol aqueous solution, stirred and dissolved, heated to 55°C, and 52 mol of acrylic acid, 0.11 mol of mercaptopropionic acid and 0.74 mol of hydrogen peroxide are added dropwise under stirring, and after the dropwise addition is completed, the reaction is preserved for 2.5 h, distilled at 83°C under reduced pressure, cooled, and the early-strength polycarboxylic water reducing agent is obtained.

[0030] Preparation Example 4 The preparation method of the modified polypropylene fiber is as follows: 100 g of polypropylene fiber is placed in anhydrous ethanol (solid-liquid ratio of 1:50), ultrasonic cleaning for 30 min, filtration, drying, then placed in a 5% potassium permanganate solution, stirring at 60°C for 30 min, filtration, then soaked in a 10% hydrochloric acid solution for 10 min, filtration, washed with deionized water until neutral, dried at 80°C for 2 h, then added to a reaction kettle together with toluene (solid-liquid ratio of 1:15), deoxygenated by nitrogen, stirred and heated to 70°C, then 3% benzoyl peroxide toluene solution was added dropwise after stirring for 30 min, the amount of benzoyl peroxide was 2 g, stirring reaction for 1 h, then 30 g of hydroxyethyl methacrylate was added at a constant speed, after the addition was completed, the temperature was raised to 90°C, and the reaction was kept for 4 h, then 30 mL of 0.1% hydroquinone ethanol solution was added, stirred for 30 min, cooled, filtered, washed with toluene, anhydrous ethanol and deionized water respectively for 3 times, and dried at 60°C for 8 h to obtain the modified polypropylene fiber.

[0031] Preparation Example 5 The preparation method of the modified polypropylene fiber is as follows: 100 g of polypropylene fiber is placed in anhydrous ethanol (solid-liquid ratio of 1:50), ultrasonic cleaning for 30 min, filtration, drying, then placed in a 5% potassium permanganate solution, stirring at 60°C for 30 min, filtration, then soaked in a 10% hydrochloric acid solution for 10 min, filtration, washed with deionized water until neutral, dried at 80°C for 2 h, then added to a reaction kettle together with toluene (solid-liquid ratio of 1:15), deoxygenated by nitrogen, stirred and heated to 70°C, then 3% benzoyl peroxide toluene solution was added dropwise after stirring for 30 min, the amount of benzoyl peroxide was 2 g, stirring reaction for 1 h, then 30 g of hydroxyethyl methacrylate was added at a constant speed, after the addition was completed, the temperature was raised to 90°C, and the reaction was kept for 4 h, then 30 mL of 0.1% hydroquinone ethanol solution was added, stirred for 30 min, cooled, filtered, washed with toluene, anhydrous ethanol and deionized water respectively for 3 times, and dried at 60°C for 8 h to obtain the modified polypropylene fiber.

[0032] Preparation Example 6 The preparation method of the modified polypropylene fiber is as follows: 100 g of polypropylene fiber is placed in anhydrous ethanol (solid-liquid ratio of 1:50), ultrasonic cleaning for 30 min, filtration, drying, then placed in a 5%-8% potassium permanganate solution, stirring at 63℃ for 35 min, after filtration, soaked in a 13% hydrochloric acid solution for 15 min, filtration, washed with deionized water until neutral, dried at 80℃ for 2 h, then added to a reaction kettle with toluene (solid-liquid ratio of 1:15), nitrogen deoxygenation, stirring to 75℃, after stirring for 30 min, 4% benzoyl peroxide toluene solution is added dropwise, the amount of benzoyl peroxide is 2.5 g, stirring for 1.2 h, 40 g of hydroxyethyl methacrylate is added at a constant speed, after the addition is completed, the temperature is raised to 93℃, and the reaction is kept for 5 h, 39 mL of 0.2% hydroquinone ethanol solution is added, stirring for 35 min, cooling, filtration, washing with toluene, anhydrous ethanol and deionized water respectively for 3 times, drying at 60℃ for 8 h, and obtaining the modified polypropylene fiber.

[0033] Example 1 A composite type precast concrete segment, comprising a segment body and a steel cage arranged in the segment body, the segment body is a concrete material, the concrete material comprises the following components in parts by weight: cement 100 g, mineral admixture 40 g, coarse aggregate 220 g, fine aggregate 140 g, early strength polycarboxylate superplasticizer 3 g, functional admixture 20 g, water 100 g.

[0034] The functional admixture is composed of modified polypropylene fiber, lithium silicate and methyl cellulose in a mass ratio of 10:3:1; the mineral admixture is composed of silica fume, slag powder, fly ash and zeolite powder in a mass ratio of 4:27:22:8; the coarse aggregate is continuous graded gravel with a size of 12-20 mm, and the apparent density is 2700 kg / m 3 ; the fine aggregate is coarse sand with a fineness modulus of 3.0; the early strength polycarboxylate superplasticizer is prepared by preparation example 1; the modified polypropylene fiber is prepared by preparation example 4.

[0035] Example 2 A composite type precast concrete segment, comprising a segment body and a steel cage arranged in the segment body, the segment body is a concrete material, the concrete material comprises the following components in parts by weight: cement 150 g, mineral admixture 50 g, coarse aggregate 260 g, fine aggregate 150 g, early strength polycarboxylate superplasticizer 8 g, functional admixture 30 g, water 80 g.

[0036] The functional admixture is composed of modified polypropylene fiber, lithium silicate and methyl cellulose in a mass ratio of 15:7:2; the mineral admixture is composed of silica fume, slag powder, fly ash and zeolite powder in a mass ratio of 8:31:25:13; the coarse aggregate is continuous gradation gravel with a size of 12-20 mm and an apparent density of 2700 kg / m 3 ; the fine aggregate is coarse sand with a fineness modulus of 3.5; the early strength polycarboxylate superplasticizer is prepared according to Preparation Example 2; the modified polypropylene fiber is prepared according to Preparation Example 5.

[0037] Example 3 A composite type precast concrete segment includes a segment body and a steel cage arranged in the segment body, the segment body is a concrete material, the concrete material includes the following components in parts by weight: cement 135 g, mineral admixture 48 g, coarse aggregate 240 g, fine aggregate 145 g, early strength polycarboxylate superplasticizer 5 g, functional admixture 26 g, water 92 g.

[0038] The functional admixture is composed of modified polypropylene fiber, lithium silicate and methyl cellulose in a mass ratio of 13:5:1; the mineral admixture is composed of silica fume, slag powder, fly ash and zeolite powder in a mass ratio of 6:29:24:11; the coarse aggregate is continuous gradation gravel with a size of 12-20 mm and an apparent density of 2700 kg / m 3 ; the fine aggregate is coarse sand with a fineness modulus of 3.3; the early strength polycarboxylate superplasticizer is prepared according to Preparation Example 3; the modified polypropylene fiber is prepared according to Preparation Example 6.

[0039] Comparative Example 1 The concrete material in the comparative example is similar to that in Example 3, and the difference between the comparative example and Example 3 is that the comparative example uses a common commercially available polycarboxylate superplasticizer instead of the early strength polycarboxylate superplasticizer.

[0040] Comparative Example 2 The concrete material in the comparative example is similar to that in Example 3, and the difference between the comparative example and Example 3 is that the preparation method of the early strength polycarboxylate superplasticizer in the comparative example is as follows: 20 mol of isoamylene alcohol polyoxyethylene ether, 4.6 mol of triallyl phosphate, 6.9 mol of L-ethyleneglycine and 0.44 mol of sodium bisulfite are added into 1 L of 80% mass fraction ethanol aqueous solution, stirred and dissolved, heated to 55℃, and 42 mol of acrylic acid, 0.11 mol of mercaptopropionic acid and 0.74 mol of hydrogen peroxide are added dropwise under stirring, and after the dropwise addition is completed, the reaction is maintained for 2.5 h, and then distilled at 83℃ under reduced pressure, and cooled to obtain the early strength polycarboxylate superplasticizer.

[0041] Comparative Example 3 The concrete material in the present comparative example is similar to that in Example 3, and the difference between the present comparative example and Example 3 is that an equal amount of lithium silicate is used instead of methyl cellulose in the functional admixture of the present comparative example.

[0042] Comparative Example 4 The concrete material in the present comparative example is similar to that in Example 3, and the difference between the present comparative example and Example 3 is that an equal amount of modified polypropylene fiber is used instead of lithium silicate in the functional admixture of the present comparative example.

[0043] Comparative Example 5 The concrete material in the present comparative example is similar to that in Example 3, and the difference between the present comparative example and Example 3 is that an equal amount of polypropylene fiber is used instead of modified polypropylene fiber in the functional admixture of the present comparative example.

[0044] Comparative Example 6 The concrete material in the present comparative example is similar to that in Example 3, and the difference between the present comparative example and Example 3 is that the mineral admixture in the present comparative example is composed of silica fume, slag powder, fly ash and zeolite powder in a mass ratio of 13:5:11:20.

[0045] Test Example The concrete materials prepared in Example 1-Example 3, Comparative Example 1-Comparative Example 6 were subjected to mechanical property tests according to GB / T 50081-2019; and the concrete materials prepared in Example 1-Example 3, Comparative Example 1-Comparative Example 6 were subjected to impermeability and anti-cracking performance tests according to GB / T 50082-2024 “Standard for Test Methods for Long-term Performance and Durability of Concrete”. The test results are shown in Table 1.

[0046] Table 1: Performance test results

[0047] As can be seen from Table 1, the concrete material provided by the present application has good mechanical properties, impermeability and anti-cracking performance. According to the test results of Example 1-Example 3, Comparative Example 1-Comparative Example 6, the early strength type polycarboxylate superplasticizer prepared by the present application can effectively promote early hydration reaction, improve the early strength of concrete and the compactness of concrete; methyl cellulose can play a water-retaining role, avoiding rapid drying shrinkage of concrete to form cracks, thereby improving the mechanical properties, anti-cracking and impermeability of concrete; lithium silicate can improve the interfacial adhesion between concrete and aggregate, improving the compactness of concrete; modified polypropylene fiber can improve the anti-cracking performance and mechanical properties of concrete; and the amount ratio of mineral admixture will affect the mechanical properties and impermeability of concrete.

[0048] In addition, the early strength type polycarboxylate superplasticizer prepared in Preparation Example 3 was subjected to nuclear magnetic resonance tests, and the test results are shown in Figure 2; The infrared spectrum of the polypropylene fiber and the modified polypropylene fiber prepared in Preparation Example 6 was tested, and the test results are shown in Figure 3 .

[0049] It can be seen from Figure 2 that the peak at δ of 0.89 ppm is the characteristic peak of -CH3, the peaks at δ of 0.89 ppm and 1.07-1.42 ppm are the characteristic peaks of -CH2, the peaks at δ of 1.57 ppm and 2.37 ppm are the characteristic peaks of -CH, the peaks at δ of 3.35 ppm-3.55 ppm are the characteristic peaks of -CH2 in the polyoxyethylene ether, the peak at δ of 4.55 ppm is the characteristic peak of -CH2 in the phosphate group, the peak at δ of 8.93 ppm is the characteristic peak of -NH2, the peak at δ of 12.39 ppm is the characteristic peak of the carboxyl group in L-vinylglycine, and the peak at δ of 10.63 ppm is the characteristic peak of the carboxyl group in acrylic acid.

[0050] It can be seen from Figure 3 that the modified polypropylene fiber has a characteristic peak of a hydroxyl group at 3400 cm -1 and a characteristic peak of an ester group at 1730 cm -1 , which indicates that the hydroxyethyl methacrylate has been successfully grafted onto the surface of the polypropylene fiber.

[0051] The above examples are merely illustrative of the present application and are not intended to limit the present application. Those skilled in the art can modify the above examples without departing from the spirit and scope of the present application. All equivalent modifications or changes made by those skilled in the art without departing from the technical idea of the present application shall fall within the scope of the present application.

Claims

1. A composite precast concrete segment, characterized in that, It includes a tunnel segment body and a reinforcing cage disposed within the tunnel segment body. The tunnel segment body is made of concrete, and the concrete material comprises the following components in parts by weight: 100-150 parts cement, 40-50 parts mineral admixtures, 220-260 parts coarse aggregate, 140-150 parts fine aggregate, 3-8 parts early-strength polycarboxylate superplasticizer, 20-30 parts functional admixtures, and 80-100 parts water. The preparation method of the early-strength polycarboxylate superplasticizer is as follows: isopentenyl alcohol polyoxyethylene ether, triallyl phosphate, L-ethyleneglycine and sodium bisulfite are added to an ethanol aqueous solution, stirred and dissolved, heated to 50-60℃, and acrylic acid, mercaptopropionic acid and hydrogen peroxide are added dropwise while stirring. After the addition is completed, the reaction is kept at the temperature for 2-3 hours, and then distilled under reduced pressure at 80-85℃ and cooled to obtain the early-strength polycarboxylate superplasticizer.

2. The composite precast concrete segment according to claim 1, characterized in that, In the preparation method of the early-strength polycarboxylate superplasticizer, the molar ratio of isopentenyl alcohol polyoxyethylene ether, triallyl phosphate, L-ethyleneglycine and acrylic acid is 1:(0.35-0.52):(0.62-0.75):(4-6).

3. The composite precast concrete segment according to claim 1, characterized in that, In the preparation method of the early-strength polycarboxylate superplasticizer, the molar ratio of sodium bisulfite to hydrogen peroxide is (0.5-0.8):1, the amount of hydrogen peroxide used is 0.9%-1.2% of the sum of the amounts of isopentenyl polyoxyethylene ether, triallyl phosphate, L-ethyleneglycine, and acrylic acid; and the amount of mercaptopropionic acid used is 0.1%-0.2% of the sum of the amounts of isopentenyl polyoxyethylene ether, triallyl phosphate, L-ethyleneglycine, and acrylic acid.

4. The composite precast concrete segment according to claim 1, characterized in that, The mass percentage of the ethanol aqueous solution in the preparation method of the early-strength polycarboxylate superplasticizer is 70%-85%.

5. The composite precast concrete segment according to claim 1, characterized in that, The functional admixture is composed of modified polypropylene fiber, lithium silicate and methylcellulose in a mass ratio of (10-15):(3-7):(1-2).

6. The composite precast concrete segment according to claim 5, characterized in that, The modified polypropylene fiber is prepared as follows: Polypropylene fiber is placed in anhydrous ethanol, ultrasonically cleaned, filtered, and dried. Then, it is placed in a potassium permanganate solution and ultrasonically stirred at 60-65℃ for 30-40 minutes. After filtration, it is soaked in hydrochloric acid solution for 10-20 minutes, filtered again, washed with deionized water until neutral, and dried. Then, it is added together with toluene into a reaction vessel, nitrogen is purged to remove oxygen, and the temperature is raised to 70-80℃. After stirring for 30 minutes, a toluene solution of benzoyl peroxide is added dropwise, and the reaction is stirred for 1-1.5 hours. Hydroxyethyl methacrylate is added dropwise, and after the addition is complete, the temperature is raised to 90-95℃ and the reaction is maintained for 4-6 hours. 30-45 mL of hydroquinone ethanol solution is added, and the reaction is stirred for 30-40 minutes. After cooling, the fiber is filtered, washed, and dried to obtain the modified polypropylene fiber.

7. The composite precast concrete segment according to claim 6, characterized in that, In the preparation method of modified polypropylene fiber, the mass percentage of potassium permanganate solution is 5%-8%, the mass percentage of hydrochloric acid solution is 10%-15%, the mass percentage of benzoyl peroxide in toluene solution is 3%-5%, and the mass percentage of hydroquinone in ethanol solution is 0.1%-0.3%; the mass ratio of polypropylene fiber, hydroxyethyl methacrylate and benzoyl peroxide is 10:(3-5):(0.2-0.3).

8. The composite precast concrete segment according to claim 1, characterized in that, The mineral admixture is composed of silica fume, slag powder, fly ash and zeolite powder in a mass ratio of (4-8):(27-31):(22-25):(8-13).

9. The composite precast concrete segment according to claim 1, characterized in that, The coarse aggregate is 12-20mm continuously graded crushed stone with an apparent density of 2700 kg / m³. 3 The fine aggregate is coarse sand with a fineness modulus of 3.0-3.

5.

10. The method for preparing composite precast concrete segments according to any one of claims 1-9, characterized in that, Includes the following steps: S1: Fix the steel cage and complete the installation of the embedded parts; S2 mixes cement, mineral admixtures, coarse aggregates, fine aggregates and functional admixtures, adds a mixed solution of early-strength polycarboxylate superplasticizer and water, and stirs evenly to obtain concrete material; S3: Generate a 3D digital model based on the shape and size of the segment, import the 3D digital model into the 3D printing software, use the concrete material obtained in step S2 for 3D printing, demold after curing for 24 hours, steam curing for 7-14 days, and natural curing for 28 days to obtain the concrete segment.

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