An ultra-high performance concrete material with modified coarse aggregate, its preparation method and its application

Abstract

This invention relates to the field of concrete technology, specifically to an ultra-high performance concrete material with modified coarse aggregate, its preparation method, and its application. The raw materials, by weight, include the following components: 420-480 parts cement, 42-50 parts fly ash, 620-730 parts river sand, 1100-1250 parts modified coarse aggregate, 4-8 parts water-reducing agent, 40-80 parts steel fiber, and 150-220 parts deionized water. This invention involves coating the coarse aggregate with nanoporous carbon, followed by a hydrothermal reaction to facilitate cobalt particle doping, and finally growing carbon nanotubes on its surface. This effectively enhances the skeletal function of the prepared coarse aggregate in concrete, improves the inhibition of concrete shrinkage, and enhances the performance of the prepared concrete.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, specifically to an ultra-high performance concrete material with modified coarse aggregate, its preparation method, and its application. Background Technology

[0002] Ultra-high performance concrete (UHVPC) is a cement-based composite material with ultra-high strength, high durability, and high toughness. Due to its excellent physical and mechanical properties and broad application prospects, it is widely used in engineering fields such as bridges, tunnels, and high-rise buildings. However, because UHVPC has a very low water-cement ratio, it has large autogenous shrinkage and drying shrinkage, resulting in significant long-term stability issues, which poses a great challenge to its practical application.

[0003] Therefore, the research team's previous studies have shown that incorporating coarse aggregates into ultra-high performance concrete systems can reduce the amount of cementitious materials used and lower costs to some extent. Coarse aggregates primarily act as a skeleton in concrete; their interlocking and anchoring effects can reduce concrete shrinkage and improve concrete performance.

[0004] Existing coarse aggregates are generally added directly to concrete, offering limited support and anchoring functions. The surface of coarse aggregates lacks sites for mechanical interlocking with the concrete mix, hindering their ability to suppress shrinkage. Therefore, addressing the problems mentioned in the background, those skilled in the art propose a method of surface modification with coarse aggregates, which effectively enhances their skeletal and anchoring properties, thereby improving concrete performance. Summary of the Invention

[0005] The purpose of this invention is to provide an ultra-high performance concrete material with modified coarse aggregate, its preparation method, and its application, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An ultra-high performance concrete material doped with modified coarse aggregate, comprising the following raw materials by weight:

[0008] 420-480 parts cement, 42-50 parts fly ash, 620-730 parts river sand, 1100-1250 parts modified coarse aggregate, 4-8 parts water-reducing agent, 40-80 parts steel fiber, and 150-220 parts deionized water.

[0009] The preparation method of the doped modified coarse aggregate includes the following steps:

[0010] S101. Mix nanoporous carbon and carboxymethyl cellulose in a deionized aqueous solution until homogeneous to obtain a mixture. Mix the obtained mixture with coarse aggregate until homogeneous and then spray dry to obtain granules.

[0011] S102. The particulate matter obtained in step S101 is calcined at 450-600℃ in an argon atmosphere for 1-3 hours to obtain carbon-coated coarse aggregate.

[0012] S103. The carbon-coated coarse aggregate obtained in step S102 is added to a deionized aqueous solution containing urea, cobalt salt and sodium acetate, and hydrothermally reacted at 85-95℃ for 8-10 hours. After that, it is filtered to obtain the filtrate.

[0013] S104. The filter material obtained in step S103 is vacuum dried at 70-100℃ to constant weight, and then calcined at 550-750℃ for 3-5 hours in an argon atmosphere to obtain pre-reacted coarse aggregate.

[0014] S105. The pre-reacted coarse aggregate obtained in step S104 is mixed with melamine and calcined at 750-900℃ for 2-3 hours in an argon atmosphere to obtain doped modified coarse aggregate.

[0015] Furthermore, in step S101, the mass ratio between the deionized aqueous solution of nanoporous carbon and carboxymethyl cellulose and the coarse aggregate is 1:(5-7):(10-14).

[0016] Furthermore, in step S101, the mass fraction of carboxymethyl cellulose is 10-15%.

[0017] Furthermore, in step S103, the mass ratio of urea, sodium acetate, cobalt salt, carbon-coated coarse aggregate and deionized water is (3-5):1:(5-10):(100-150):(600-900).

[0018] Furthermore, the cobalt salt used in step S103 is cobalt nitrate hexahydrate.

[0019] Furthermore, in step S105, the mass ratio between melamine and pre-reacted coarse aggregate is 1:(15-30).

[0020] Furthermore, in step S101, the coarse aggregate is either limestone or basalt, and the particle size of the coarse aggregate is 10-20 mm; the particle size of the nanoporous carbon is 1000-2000 nm, and the pore size of the nanoporous carbon is 50-80 nm.

[0021] Furthermore, the water-reducing agent is a polycarboxylate-type water-reducing agent; the particle size of the river sand is 0.5-2 mm.

[0022] A method for preparing ultra-high performance concrete material with modified coarse aggregate includes the following steps:

[0023] S1. Add cement, fly ash, river sand and modified coarse aggregate to deionized water in the order of mass parts and stir until evenly mixed to obtain a mixture.

[0024] S2. Add steel fibers and water-reducing agent to the mixture obtained in step S1 according to the mass proportions, and stir evenly to obtain concrete slurry.

[0025] S3. Pour the concrete slurry obtained in step S2 into the mold, cure and demold to obtain ultra-high performance concrete material.

[0026] Application of ultra-high performance concrete with modified coarse aggregate as a building material.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. In this invention, nanoporous carbon is coated on the outside of coarse aggregate, and a composite material of nanoporous carbon and cobalt salt is formed by hydrothermal reaction of nanoporous carbon and cobalt. Then, it is calcined with melamine to form carbon nanotubes in situ on the surface. The coarse aggregate plays a skeleton role in concrete, improves its mechanical interlocking ability, and improves concrete performance.

[0029] 2. In this invention, carbon is first coated and then carbon nanotubes are synthesized. Porous carbon can better adsorb cobalt ions and carry out hydrothermal reactions. In addition, the resulting carbon nanotubes have a stronger interfacial bonding ability with carbon, which improves the locking ability. The coarse aggregate has a stronger ability to inhibit concrete shrinkage. The introduction of this carbon nanotube also reduces the problem of easy agglomeration of nanomaterials themselves, and better exerts their performance. Attached Figure Description

[0030] Figure 1 This is a process flow diagram for preparing ultra-high performance concrete materials in this invention;

[0031] Figure 2 This is a process flow diagram for preparing doped and modified coarse aggregates in this invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Please see Figures 1 to 2This invention provides an ultra-high performance concrete material with modified coarse aggregate, its preparation method, and its application.

[0034] Example 1

[0035] A method for preparing ultra-high performance concrete material with modified coarse aggregate includes the following steps:

[0036] S1. Add 440 parts of cement, 48 parts of fly ash, 660 parts of river sand and 1150 parts of modified coarse aggregate to 180 parts of deionized water and stir until uniform to obtain a mixture. The average particle size of the river sand is 1 mm.

[0037] S2. Add 65 parts of steel fiber and 6 parts of water-reducing agent to the mixture obtained in step S1, and stir evenly to obtain concrete slurry. The water-reducing agent used is polycarboxylate water-reducing agent.

[0038] S3. Pour the concrete slurry obtained in step S2 into the mold, cure and demold to obtain ultra-high performance concrete material.

[0039] The preparation method of the above-mentioned doped and modified coarse aggregate includes the following steps:

[0040] S101. Mix 100 parts of nanoporous carbon and 600 parts of 12wt% deionized water of carboxymethyl cellulose evenly to obtain a mixture. Mix the obtained mixture evenly with 1300 parts of coarse aggregate and then spray dry to obtain granules. The coarse aggregate is limestone with an average particle size of 15 mm, the average particle size of nanoporous carbon is 1200 nm, and the average pore size of nanoporous carbon is 60 nm.

[0041] S102. The particulate matter obtained in step S101 is calcined at 500°C for 2 hours in an argon atmosphere to obtain carbon-coated coarse aggregate.

[0042] S103. Add 1300 parts of carbon-coated coarse aggregate obtained in step S102 to a deionized aqueous solution containing urea, cobalt salt and sodium acetate. The amounts of urea, sodium acetate, cobalt salt and deionized water are 40 parts, 10 parts, 80 parts and 7000 parts, respectively. The mixture is subjected to hydrothermal reaction at 90°C for 9 hours. After filtration, the filtrate is obtained. The cobalt salt is cobalt nitrate hexahydrate.

[0043] S104. The filter material obtained in step S103 is vacuum dried at 80°C to constant weight, and then calcined at 700°C for 4.5 h in an argon atmosphere to obtain pre-reacted coarse aggregate.

[0044] S105. Mix 1250 parts of pre-reacted coarse aggregate obtained in step S104 with 50 parts of melamine, and calcine at 800℃ for 2.5h in an argon atmosphere to obtain doped modified coarse aggregate.

[0045] Example 2

[0046] A method for preparing ultra-high performance concrete material with modified coarse aggregate includes the following steps:

[0047] S1. Add 420 parts of cement, 42 parts of fly ash, 620 parts of river sand and 1100 parts of modified coarse aggregate to 150 parts of deionized water and stir until evenly mixed to obtain a mixture. The average particle size of the river sand is 0.5 mm.

[0048] S2. Add 40 parts of steel fiber and 4 parts of water-reducing agent to the mixture obtained in step S1, and stir evenly to obtain concrete slurry. The water-reducing agent used is polycarboxylate water-reducing agent.

[0049] S3. Pour the concrete slurry obtained in step S2 into the mold, cure and demold to obtain ultra-high performance concrete material.

[0050] The preparation method of the above-mentioned doped and modified coarse aggregate includes the following steps:

[0051] S101. Mix 130 parts of nanoporous carbon and 650 parts of 10wt% deionized water of carboxymethyl cellulose evenly to obtain a mixture. Mix the obtained mixture evenly with 1300 parts of coarse aggregate and then spray dry to obtain granules. The coarse aggregate is limestone with an average particle size of 10 mm, the average particle size of nanoporous carbon is 1000 nm, and the average pore size of nanoporous carbon is 50 nm.

[0052] S102. The particulate matter obtained in step S101 is calcined at 450°C for 1 hour in an argon atmosphere to obtain carbon-coated coarse aggregate.

[0053] S103. Add 1300 parts of carbon-coated coarse aggregate obtained in step S102 to a deionized aqueous solution containing urea, cobalt salt and sodium acetate. The amounts of urea, sodium acetate, cobalt salt and deionized aqueous solution are 39 parts, 13 parts, 65 parts and 7800 parts, respectively. The mixture is subjected to hydrothermal reaction at 85°C for 8 hours. After filtration, the filtrate is obtained. The cobalt salt is cobalt nitrate hexahydrate.

[0054] S104. The filter material obtained in step S103 is vacuum dried at 70°C to constant weight, and then calcined at 550°C for 3 hours in an argon atmosphere to obtain pre-reacted coarse aggregate.

[0055] S105. Mix 1250 parts of pre-reacted coarse aggregate obtained in step S104 with 83 parts of melamine, and calcine at 750°C for 2 hours in an argon atmosphere to obtain doped modified coarse aggregate.

[0056] Example 3

[0057] A method for preparing ultra-high performance concrete material with modified coarse aggregate includes the following steps:

[0058] S1. Add 480 parts of cement, 50 parts of fly ash, 730 parts of river sand and 1250 parts of modified coarse aggregate to 220 parts of deionized water and stir until evenly mixed to obtain a mixture. The average particle size of the river sand is 2 mm.

[0059] S2. Add 80 parts of steel fiber and 8 parts of water-reducing agent to the mixture obtained in step S1, and stir evenly to obtain concrete slurry. The water-reducing agent is a polycarboxylate water-reducing agent.

[0060] S3. Pour the concrete slurry obtained in step S2 into the mold, cure and demold to obtain ultra-high performance concrete material.

[0061] The preparation method of the above-mentioned doped and modified coarse aggregate includes the following steps:

[0062] S101. Mix 93 parts of nanoporous carbon and 651 parts of 15 wt% carboxymethyl cellulose in a deionized aqueous solution to obtain a mixture. Mix the obtained mixture with 1300 parts of coarse aggregate and then spray dry to obtain granules. The coarse aggregate is limestone with an average particle size of 20 mm, the average particle size of nanoporous carbon is 2000 nm, and the average pore size of nanoporous carbon is 80 nm.

[0063] S102. The particulate matter obtained in step S101 is calcined at 600°C for 3 hours in an argon atmosphere to obtain carbon-coated coarse aggregate.

[0064] S103. Add 1300 parts of carbon-coated coarse aggregate obtained in step S102 to a deionized aqueous solution containing urea, cobalt salt and sodium acetate. The amounts of urea, sodium acetate, cobalt salt and deionized water are 43.5 parts, 8.7 parts, 87 parts and 7830 parts, respectively. The mixture is subjected to hydrothermal reaction at 95°C for 10 hours. After filtration, the filtrate is obtained. The cobalt salt is cobalt nitrate hexahydrate.

[0065] S104. The filter material obtained in step S103 is vacuum dried at 100°C to constant weight, and then calcined at 750°C for 5 hours in an argon atmosphere to obtain pre-reacted coarse aggregate.

[0066] S105. Mix 1250 parts of pre-reacted coarse aggregate obtained in step S104 with 42 parts of melamine, and calcine at 900°C for 3 hours in an argon atmosphere to obtain doped modified coarse aggregate.

[0067] Example 4

[0068] A method for preparing ultra-high performance concrete material with modified coarse aggregate includes the following steps:

[0069] S1. Add 450 parts of cement, 48 parts of fly ash, 710 parts of river sand and 1200 parts of modified coarse aggregate to 210 parts of deionized water and stir until evenly mixed to obtain a mixture. The average particle size of the river sand is 1 mm.

[0070] S2. Add 65 parts of steel fiber and 7 parts of water-reducing agent to the mixture obtained in step S1, and stir evenly to obtain concrete slurry. The water-reducing agent is a polycarboxylate water-reducing agent.

[0071] S3. Pour the concrete slurry obtained in step S2 into the mold, cure and demold to obtain ultra-high performance concrete material.

[0072] The preparation method of the above-mentioned doped and modified coarse aggregate includes the following steps:

[0073] S101. Mix 100 parts of nanoporous carbon and 650 parts of 12wt% deionized water solution of carboxymethyl cellulose evenly to obtain a mixture. Mix the obtained mixture evenly with 1300 parts of coarse aggregate and then spray dry to obtain granules. The coarse aggregate is basalt with a particle size of 15 mm. The average particle size of the nanoporous carbon is 1400 nm and the average pore size of the nanoporous carbon is 60 nm.

[0074] S102. The particulate matter obtained in step S101 is calcined at 550°C for 2 hours in an argon atmosphere to obtain carbon-coated coarse aggregate.

[0075] S103. Add 1300 parts of carbon-coated coarse aggregate obtained in step S102 to a deionized aqueous solution containing urea, cobalt salt and sodium acetate. The amounts of urea, sodium acetate, cobalt salt and deionized water are 50 parts, 10 parts, 90 parts and 8000 parts, respectively. The mixture is subjected to hydrothermal reaction at 85°C for 10 hours. After filtration, the filtrate is obtained. The cobalt salt is cobalt nitrate hexahydrate.

[0076] S104. The filter material obtained in step S103 is vacuum dried at 85°C to constant weight, and then calcined at 700°C for 4 hours in an argon atmosphere to obtain pre-reacted coarse aggregate.

[0077] S105. Mix 1250 parts of pre-reacted coarse aggregate obtained in step S104 with 60 parts of melamine, and calcine at 880°C for 2 hours in an argon atmosphere to obtain doped modified coarse aggregate.

[0078] Comparative Example 1

[0079] The difference between the comparative example and Example 1 is that step S105 was completely eliminated in the preparation of the doped modified coarse aggregate, while the remaining steps are exactly the same as in Example 1.

[0080] Comparative Example 2

[0081] The difference between Comparative Example 2 and Example 1 is that steps S101 and S102 were completely eliminated in the preparation of the doped modified coarse aggregate. The coarse aggregate was directly added to a deionized aqueous solution containing urea, cobalt salt and sodium acetate for hydrothermal reaction. The remaining steps were exactly the same as in Example 1.

[0082] Comparative Example 3

[0083] The difference between Comparative Example 3 and Example 1 is that the 1150 parts of doped modified coarse aggregate added were replaced with 1150 parts of coarse aggregate that had not undergone the treatment of steps S101-105. The remaining steps were exactly the same as those in Example 1.

[0084] Comparative Example 4

[0085] The difference between Comparative Example 4 and Comparative Example 1 is that 10 parts of carbon nanotubes are added in step S1, while the rest of the steps are exactly the same as those in Comparative Example 1.

[0086] Comparative Example 5

[0087] The difference between Comparative Example 5 and Comparative Example 1 is that 15 parts of carbon nanotubes were added in step S1, while the rest of the steps were exactly the same as those in Comparative Example 1.

[0088] Comparative Example 6

[0089] The difference between Comparative Example 6 and Comparative Example 1 is that 20 parts of carbon nanotubes are added in step S1, while the rest of the steps are exactly the same as those in Comparative Example 1.

[0090] In the above embodiment, the curing time during demolding is 28 days, the curing temperature is 20°C, and the curing humidity is 95%.

[0091] The elastic modulus, flexural strength, and splitting tensile strength of the concrete prepared in Examples 1-4 and Comparative Examples 1-6 were tested according to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The test results are shown in Table 1 below:

[0092] Table 1: Performance test results of concrete prepared in Examples 1-4 and Comparative Examples 1-6

[0093]

[0094] By comparing the data of Example 1 and Comparative Example 1 in Table 1 above, it can be found that after omitting step S105, the elastic modulus, flexural strength, and splitting tensile strength of the prepared concrete all decreased. In step S105, melamine and pre-reacted coarse aggregate were calcined together, and carbon nanotubes were formed on the surface of the pre-reacted coarse aggregate through the catalysis of the cobalt particles, thereby improving its performance. The data of Example 1 and Comparative Example 2 show that after omitting the coating of nanoporous carbon on the surface of the coarse aggregate, the concrete performance decreased. Due to the lack of porous carbon, the interfacial bonding ability between the formed carbon nanotubes and the coarse aggregate was reduced, which reduced the locking ability of the coarse aggregate in the concrete gel material and decreased the shrinkage inhibition effect. By comparing the data of Example 1, Comparative Example 1, and Comparative Examples 4-6, it can be found that adding carbon nanotubes alone can improve the strength of concrete. However, in this invention, the method of in-situ growth of carbon nanotubes on the surface of coarse aggregate facilitates the uniform dispersion of carbon nanotubes in the concrete, and its promoting effect on concrete performance is more excellent.

[0095] In summary, the ultra-high performance concrete prepared in this invention has superior overall performance and is suitable for application in the construction field as a building material.

[0096] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-performance concrete material doped with modified coarse aggregate, characterized in that, Raw materials comprising the following components by weight: 420-480 parts cement, 42-50 parts fly ash, 620-730 parts river sand, 1100-1250 parts modified coarse aggregate, 4-8 parts water-reducing agent, 40-80 parts steel fiber, and 150-220 parts deionized water. The preparation method of the doped modified coarse aggregate includes the following steps: S101. Mix nanoporous carbon and carboxymethyl cellulose in a deionized aqueous solution until homogeneous to obtain a mixture. Mix the obtained mixture with coarse aggregate until homogeneous and then spray dry to obtain granules. S102. The particulate matter obtained in step S101 is calcined at 450-600℃ in an argon atmosphere for 1-3 hours to obtain carbon-coated coarse aggregate. S103. The carbon-coated coarse aggregate obtained in step S102 is added to a deionized aqueous solution containing urea, cobalt salt and sodium acetate, and hydrothermally reacted at 85-95℃ for 8-10 hours. After that, it is filtered to obtain the filtrate. S104. The filter material obtained in step S103 is vacuum dried at 70-100℃ to constant weight, and then calcined at 550-750℃ for 3-5 hours in an argon atmosphere to obtain pre-reacted coarse aggregate. S105. The pre-reacted coarse aggregate obtained in step S104 is mixed with melamine and calcined at 750-900℃ for 2-3 hours in an argon atmosphere to obtain doped modified coarse aggregate.

2. The ultra-high performance concrete material with modified coarse aggregate according to claim 1, characterized in that, In step S101, the mass ratio between the deionized aqueous solution of nanoporous carbon and carboxymethyl cellulose and the coarse aggregate is 1:(5-7):(10-14).

3. The ultra-high performance concrete material with modified coarse aggregate according to claim 2, characterized in that, In step S101, the mass fraction of carboxymethyl cellulose is 10-15%.

4. The ultra-high performance concrete material with modified coarse aggregate according to claim 1, characterized in that, In step S103, the mass ratio of urea, sodium acetate, cobalt salt, carbon-coated coarse aggregate and deionized water is (3-5):1:(5-10):(100-150):(600-900).

5. The ultra-high performance concrete material with modified coarse aggregate according to claim 3, characterized in that, The cobalt salt used in step S103 is cobalt nitrate hexahydrate.

6. The ultra-high performance concrete material with modified coarse aggregate according to claim 1, characterized in that, In step S105, the mass ratio of melamine to pre-reacted coarse aggregate is 1:(15-30).

7. The ultra-high performance concrete material with modified coarse aggregate according to claim 1, characterized in that, In step S101, the coarse aggregate is either limestone or basalt, and the particle size of the coarse aggregate is 10-20 mm; the particle size of the nanoporous carbon is 1000-2000 nm, and the pore size of the nanoporous carbon is 50-80 nm.

8. The ultra-high performance concrete material with modified coarse aggregate according to claim 1, characterized in that, The water-reducing agent is a polycarboxylate-type water-reducing agent; the particle size of the river sand is 0.5-2 mm.

9. A method for preparing ultra-high performance concrete material with doped and modified coarse aggregate as described in any one of claims 1-8, characterized in that, Includes the following steps: S1. Add cement, fly ash, river sand and modified coarse aggregate to deionized water in the order of mass parts and stir until evenly mixed to obtain a mixture. S2. Add steel fibers and water-reducing agent to the mixture obtained in step S1 according to the mass proportions, and stir evenly to obtain concrete slurry. S3. Pour the concrete slurry obtained in step S2 into the mold, cure and demold to obtain ultra-high performance concrete material.

10. The application of ultra-high performance concrete with doped modified coarse aggregate as described in any one of claims 1-8 as a building material.

Images