Ultra-high performance concrete and preparation process thereof

Abstract

The present application relates to the field of concrete, specifically discloses ultra-high performance concrete and its preparation process, concrete includes the following raw materials: cement, glass beads, mineral powder, silica fume, fine aggregate, water, water-reducing agent, steel fiber, expansion agent, modified nanoporous carbon fiber, magnesium slag powder and casein water-absorbing composition;Modified nanoporous carbon fiber is modified by nanoporous carbon fiber after cesium sulfate solution immersion;Casein water-absorbing composition is obtained by mixing casein and chitosan-based water-absorbing polymer and genipin;Its preparation process includes the following steps:Cement, glass beads, mineral powder, silica fume and fine aggregate are mixed, expansion agent, magnesium slag powder and casein water-absorbing composition are added;Water-reducing agent is dissolved in water and added, steel fiber and modified nanoporous carbon fiber are added in batches, residual water is added, and ultra-high performance concrete is obtained. The present application has the characteristics of improving the autogenous shrinkage value of ultra-high performance concrete, while having higher mechanical strength.

Description

Technical Field

[0001] The present application relates to the field of concrete technology, and more specifically, to an ultra-high performance concrete and a preparation process thereof. Background Art

[0002] Concrete has been widely used in civil engineering structures. Compared with other building materials such as steel and wood, concrete products have many advantages, such as high cost-effectiveness, a wide range of raw materials, and easy preparation and processing. Therefore, it is widely used in municipal engineering, roads, bridges, and military engineering. With the advancement of the times, ordinary concrete is no longer sufficient for practical engineering applications. When loads act on concrete, its brittleness can cause large cracks in it, which also has a significant impact on the durability of building structures. Therefore, ultra-high performance concrete (UHPC) was developed, which has high tensile and compressive strength, strong durability, and good toughness. UHPC is made by fully mixing cement, mineral admixtures, metal fibers, water reducers, aggregates, and water. After curing, it forms a concrete with high toughness, high durability, and high strength. It is widely used in special fields such as nuclear power plants and dams, and has become a major direction for the future development of concrete.

[0003] For ultra-high performance concrete, due to its low water-binder ratio, lack of coarse aggregate, and the addition of active mineral admixtures, its mechanical properties and durability are greatly improved. However, at the same time, this also leads to the shrinkage of UHPC being greater than that of ordinary concrete. Although steel fiber can play a certain role in resisting cracking and reducing shrinkage due to its high elastic modulus, due to the low water-binder ratio of ultra-high performance concrete, the autogenous shrinkage of ultra-high performance concrete is serious, and it is urgently in need of alleviation and improvement.

[0004] At present, adding expansive agents to concrete to compensate for shrinkage is a better way to solve shrinkage cracking. Currently, there are mainly calcium oxide, calcium sulfoaluminate, magnesium oxide and calcium oxide-calcium sulfoaluminate composite expansive agents on the market. However, the addition of expansive agents requires water to play a role in offsetting shrinkage. Autogenous shrinkage is originally caused by the hydration reaction of internal cementitious materials and consumes water. Therefore, in order to achieve good autogenous shrinkage, water-absorbing materials are added to concrete. However, due to the low mechanical properties of porous water-absorbing materials, they will significantly weaken the strength of ultra-high performance concrete, limiting their application scenarios. Summary of the Invention

[0005] In order to improve the autogenous shrinkage value of ultra-high performance concrete and at the same time have higher mechanical strength, the present application provides an ultra-high performance concrete and a preparation process thereof.

[0006] In a first aspect, the present application provides an ultra-high performance concrete, which adopts the following technical solution:

[0007] An ultra-high performance concrete comprises the following raw materials in parts by weight: 790-855 parts of cement, 140-160 parts of glass microspheres, 105-125 parts of mineral powder, 85-105 parts of silica fume, 890-985 parts of fine aggregate, 195-207 parts of water, 8-12 parts of a water reducer, 150-160 parts of steel fibers, 10-15 parts of an expansion agent, 20-30 parts of modified nanoporous carbon fibers, 40-50 parts of magnesium slag powder, and 18-28 parts of a casein-water absorbing composition.

[0008] The modified nanoporous carbon fiber is obtained by modifying the nanoporous carbon fiber after soaking it in a cesium sulfate solution; and the casein-water-absorbing composition is obtained by mixing casein, a chitosan-based water-absorbing polymer and genipin.

[0009] By adopting the above technical solution, the magnesium slag powder is mainly composed of magnesium oxide, which reacts in the cement hydration stage to form an expansive substance, hydroxide enzyme, which compensates for the shrinkage effect while filling the residual holes in the system caused by the addition of the water-absorbing composition, thereby increasing the autogenous shrinkage value while also improving the mechanical strength of the concrete; the present application also adds modified nanoporous carbon fibers modified by soaking the nanoporous carbon fibers in a cesium sulfate solution. The addition of nanoporous carbon fibers further improves the strength of the concrete, and the cesium sulfate solution soaking causes the porous carbon fibers to be embedded with cesium ions, which have lower hydration energy. Therefore, the nanoporous carbon fibers play a reinforcing role while also hindering the hydration of the concrete to a certain extent. Ultimately, the concrete has a low autogenous shrinkage value while increasing its hardness.

[0010] In addition, the ultra-high performance concrete of the present application also contains a composition obtained by mixing casein, a chitosan-based water-absorbing polymer and genipin. Casein is hygroscopic and cooperates with the water-absorbing polymer to realize its water-releasing and hydrating process, thereby realizing internal maintenance of the ultra-high performance concrete and further alleviating the autogenous shrinkage of the ultra-high performance concrete. More importantly, casein hardens rapidly in a humid environment, thereby playing a significant reinforcing role and improving its mechanical strength. Moreover, casein, as a casein, can form a cross-linked macromolecular substance with chitosan under the action of genipin, thereby playing a better reinforcing role. The ultra-high performance concrete finally obtained significantly improves its autogenous shrinkage while also having excellent mechanical strength.

[0011] Optionally, the modified nanoporous carbon fiber is prepared by the following method:

[0012] Soak the nanoporous carbon fibers in a cesium sulfate solution and stir to obtain a mixture:

[0013] The mixture is filtered, and the precipitate is baked at high temperature. The specific baking operation is: baking at 400-420° C. for 1-2 hours, and then cooling naturally to obtain the modified nanoporous carbon fiber.

[0014] By adopting the above technical solution, the nanoporous carbon fiber is soaked, allowing cesium ions to be embedded into the pores of the porous carbon fiber. Then, after filtering, it is baked at high temperature to form nano-cesium oxide powder embedded in the porous structure of the carbon fiber. After adding concrete, the contact area is larger, which better plays the role of reducing the surface tension of capillary water.

[0015] Optionally, the casein-water absorbing composition is prepared by comprising the following raw materials in parts by weight: 8-15 parts of casein, 12-23 parts of chitosan, 20-30 parts of PAM-CaCl2 hydrogel, 1-3 parts of genipin, 5-12 parts of

[0016] Silane coupling agent.

[0017] By adopting the above technical solution, the PAM-CaCl2 hydrogel acts as a hygroscopic porous polymer to play an internal curing role, thereby delaying the decrease of the capillary pore concave liquid level. While the chitosan is being used for internal curing, it is also cross-linked with casein under the action of genipin to form a network macromolecule, so that the composition can not only play an internal curing role, but also increase the mechanical strength. In the present application, casein and PAM-CaCl2 hydrogel are first mixed and then added to further enhance the reinforcing effect of the composition. The addition of a silane coupling agent helps to improve the compatibility of the composition with other inorganic materials in the concrete raw materials.

[0018] Optionally, the casein-water absorbing composition is prepared by the following method:

[0019] The PAM-CaCl2 hydrogel and chitosan are mixed and added to a carbonate aqueous solution, and then genipin is added and mixed, and casein is added. After ultrasonic treatment for 20-40 minutes, a silane coupling agent is added and mixed, and then granulated and dried to obtain a casein-water-absorbing composition.

[0020] By adopting the above technical solution, PAM-CaCl2 hydrogel and chitosan are first mixed and added to a carbonate aqueous solution, and then casein is added after genipin is added. Ultrasonic treatment is performed to dissolve and disperse the casein in the solution system to produce cross-linking, while the system becomes hard. Then, a silane coupling agent is added, mixed, and dried to obtain a composition.

[0021] Optionally, the ultra-high performance concrete raw material further comprises 10-15 parts by weight of ethylenediamine;

[0022] Adipic acid is also added during the preparation of the casein-water absorbing composition, and the prepared casein-water absorbing composition mixed with adipic acid is added after the wall is coated. The specific operation is as follows:

[0023] When preparing the casein-water-absorbing composition, after ultrasonic treatment of casein, 8-12 parts by weight of adipic acid are added, and then ultrasonic treatment is continued for 10-20 minutes. Then, a silane coupling agent is added, and then granulation and drying are performed to obtain the casein-water-absorbing composition mixed with adipic acid.

[0024] By adopting the above technical solution, the casein-water-absorbing composition is prepared in the present application with adipic acid, which is then added to concrete after being coated with the wall. After water is added, the wall is broken to release the adipic acid and the casein-water-absorbing composition. The adipic acid reacts with hexamethylenediamine in the raw material to form nylon and water. The nylon has good compressive strength, and the water can make up for the water consumption due to hydration, thereby alleviating the autogenous shrinkage. The casein-water-absorbing composition hardens after contacting water, which plays a role in internal curing and enhancing the mechanical properties.

[0025] Optionally, the specific operation of coating the casein-water-absorbing composition is as follows:

[0026] 3-8 parts of poly (N-vinyl caprolactam), 13-20 parts of poly (vinyl alcohol), 5-10 parts of urea, 8-15 parts of sodium bicarbonate and 20-25 parts of acetone are mixed by weight, and the mixture is sprayed onto a casein-water-absorbing composition mixed with adipic acid, and the mixture is dried to prepare adipic acid / casein-water-absorbing composition microcapsules.

[0027] By adopting the above technical solution, poly N-vinyl caprolactam and polyvinyl alcohol are used as the main components of the wall, poly N-vinyl caprolactam is used as the temperature-sensitive material for the wall, and sodium bicarbonate is added to the concrete to play a slow release role. The addition of urea can cool the internal temperature of the concrete during hydration, reduce water consumption due to hydration, and further volatilize water due to hydration heat, thereby further inhibiting the shrinkage phenomenon.

[0028] Optionally, the raw materials of the ultra-high performance concrete further include 8-16 parts by weight of polytetrafluoroethylene wax.

[0029] By adopting the above technical solution, polytetrafluoroethylene wax has a lower liquid surface tension coefficient, thereby reducing the surface water tension of the capillary pores in concrete, thereby having an excellent effect of inhibiting its own shrinkage.

[0030] Optionally, the mineral powder is S95 grade mineral powder;

[0031] The fine aggregate is quartz sand, and the fine aggregate includes 420-465 parts by weight of coarse sand, 170-190 parts by weight of medium sand and 300-330 parts by weight of fine sand;

[0032] The water reducing agent is a polycarboxylic acid water reducing agent with a water reducing rate of ≥40%.

[0033] In a second aspect, the present application provides a process for preparing ultra-high performance concrete, which adopts the following technical solution: A process for preparing ultra-high performance concrete, comprising the following steps:

[0034] Cement, glass beads, mineral powder, silica fume and fine aggregate are mixed and stirred, and then an expansion agent, magnesium slag powder and a casein-water absorbing composition are added, mixed and stirred to obtain a powder mixture;

[0035] The water reducer is dissolved in 75-85% water and then added to the powder mixture to obtain a solid-liquid mixture. The steel fiber and the modified nanoporous carbon fiber are then added in batches and stirred. Finally, the remaining water is added and stirred to obtain ultra-high performance concrete.

[0036] By adopting the above technical solution, the above preparation process is simple and convenient to operate and easy to industrialize.

[0037] Optionally, the raw materials of the ultra-high performance concrete further include 8-16 parts by weight of polytetrafluoroethylene wax, and the polytetrafluoroethylene wax is added together with the steel fiber.

[0038] In summary, this application has the following beneficial effects:

[0039] 1. Magnesium slag powder is added to the present application. Magnesium slag powder is mainly composed of magnesium oxide. It reacts to form an expansive substance, hydroxide, during the cement hydration stage. While compensating for shrinkage, it also fills the residual holes in the system caused by the addition of the water-absorbing composition, thereby increasing the autogenous shrinkage value while also improving the mechanical strength of the concrete.

[0040] 2. The present application also adds modified nanoporous carbon fibers obtained by soaking modified nanoporous carbon fibers in a cesium sulfate solution. The addition of the nanoporous carbon fibers further enhances the strength of the concrete. The soaking in the cesium sulfate solution embeds cesium ions in the porous carbon fibers, which have lower hydration energy. As a result, the nanoporous carbon fibers not only enhance the concrete but also hinder the hydration of the concrete. Ultimately, the concrete has a low autogenous shrinkage value while increasing its hardness.

[0041] 3. The present application adds a composition obtained by mixing casein, a chitosan-based water-absorbing polymer, and genipin. Casein is hygroscopic and cooperates with the water-absorbing polymer to achieve its water release and hydration process, thereby achieving internal curing of ultra-high performance concrete and further alleviating the autogenous shrinkage of ultra-high performance concrete. Casein quickly hardens in a humid environment, thereby playing a significant reinforcing role and improving its mechanical strength. Moreover, casein, as a casein, can form a cross-linked macromolecular substance with chitosan under the action of genipin, thereby playing a better reinforcing role. The ultra-high performance concrete finally obtained significantly improves its autogenous shrinkage while also having excellent mechanical strength.

[0042] 4. In the present application, adipic acid is mixed when preparing the casein-water-absorbing composition, and then the composition is added to concrete after the wall is coated. After water is added, the wall is broken to release the adipic acid and the casein-water-absorbing composition. The adipic acid reacts with the hexamethylenediamine in the raw material to form nylon and water. Nylon has good compressive strength, and water can make up for the water consumption due to hydration, thereby alleviating the autogenous shrinkage. The casein-water-absorbing composition hardens after contacting water, which plays a role in internal curing and enhancing mechanical properties. DETAILED DESCRIPTION

[0043] The present application is further described in detail below with reference to the examples. It is particularly noted that if no specific conditions are specified in the following examples, the reactions are carried out according to conventional conditions or the conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following examples can be obtained from common commercial sources.

[0044] In the following examples, P.0 52.5 grade ordinary Portland cement was used as cement;

[0045] The mineral powder is S95 grade;

[0046] The fine aggregate is quartz sand, and the fine aggregate includes 420-465 kg of coarse sand, 170-190 kg of medium sand and 300-330 kg of fine sand. The particle size of the fine sand is 0.063 mm-0.2 mm, the particle size of the medium sand is 0.2 mm-0.63 mm, and the particle size of the coarse sand is 0.63 mm-2 mm.

[0047] The water reducing agent is a polycarboxylic acid water reducing agent with a water reducing rate of 40% and a model of TS-J;

[0048] The expansion agent is calcium sulphoaluminate expansion agent;

[0049] Nanoporous carbon fibers can be purchased from Heshi New Materials, with a carbon fiber diameter of 3-4.5 μm;

[0050] The model of PTFE wax powder is KTL-8N;

[0051] The following preparation examples 1-4 are preparation examples of modified nanoporous carbon fibers:

[0052] Preparation Example 1

[0053] A preparation process for modified nanoporous carbon fibers comprises the following steps:

[0054] The nanoporous carbon fibers were immersed in a 40 wt% cesium sulfate solution and stirred to obtain a mixture:

[0055] The mixture was filtered, and the precipitate was baked at high temperature. The specific baking operation was: baking at 410° C. for 1.5 hours, and then naturally cooling to obtain the modified nanoporous carbon fiber.

[0056] Preparation Example 2

[0057] A preparation process for modified nanoporous carbon fibers comprises the following steps:

[0058] The nanoporous carbon fibers were immersed in a 40 wt% cesium sulfate solution and stirred to obtain a mixture:

[0059] The mixture was filtered, and the precipitate was baked at high temperature. The specific baking operation was: baking at 400° C. for 2 hours, and then naturally cooling to obtain modified nanoporous carbon fibers.

[0060] Preparation Example 3

[0061] A preparation process for modified nanoporous carbon fibers comprises the following steps:

[0062] The nanoporous carbon fibers were immersed in a 40 wt% cesium sulfate solution and stirred to obtain a mixture:

[0063] The mixture was filtered, and the precipitate was baked at high temperature. The specific baking operation was: baking at 420° C. for 1 hour, and then naturally cooling to obtain the modified nanoporous carbon fiber.

[0064] Preparation Example 4

[0065] A preparation process of modified nanoporous carbon fiber is carried out according to the method in Preparation Example 1, except that after the mixture is filtered, the precipitate is dried at 65° C. for 1.5 hours to obtain the modified nanoporous carbon fiber.

[0066] Preparation Example 5

[0067] A preparation process of a casein-water absorbing composition comprises the following steps:

[0068] 25 kg of PAM-CaCl2 hydrogel and 18 kg of chitosan were mixed and added to 28 kg of 12 wt% sodium bicarbonate aqueous solution, and then 2 kg of genipin was added and mixed. 10 kg of casein was added and ultrasonically treated for 30 minutes. Then, 8 kg of silane coupling agent KH-550 was added and mixed. Then, the mixture was granulated and dried to obtain a casein-water-absorbing composition.

[0069] Preparation Example 6

[0070] A preparation process of a casein-water absorbing composition comprises the following steps:

[0071] 20 kg of PAM-CaCl2 hydrogel and 12 kg of chitosan were mixed and added to 25 kg of 12 wt% sodium bicarbonate aqueous solution, and then 1 kg of genipin was added and mixed. 8 kg of casein was added and ultrasonically treated for 20 minutes. Then, 5 kg of silane coupling agent KH-550 was added and mixed. Then, the mixture was granulated and dried to obtain a casein-water-absorbing composition.

[0072] Preparation Example 7

[0073] A preparation process of a casein-water absorbing composition comprises the following steps:

[0074] 30 kg of PAM-CaCl2 hydrogel and 23 kg of chitosan were mixed and added to 30 kg of 12 wt% sodium bicarbonate aqueous solution, and then 3 kg of genipin was added and mixed. 15 kg of casein was added and ultrasonically treated for 40 minutes. Then, 12 kg of silane coupling agent KH-550 was added and mixed. Then, the mixture was granulated and dried to obtain a casein-water-absorbing composition.

[0075] Preparation Example 8

[0076] A process for preparing adipic acid / casein-water-absorbing composition microcapsules comprises the following steps:

[0077] 25 kg of PAM-CaCl2 hydrogel and 18 kg of chitosan were mixed and added to 28 kg of 12 wt% sodium bicarbonate aqueous solution, followed by adding 2 kg of genipin and mixing, and then adding 10 kg of casein. After ultrasonic treatment for 30 minutes, 10 kg of adipic acid was added, and ultrasonic treatment was continued for 15 minutes. Then, 8 kg of silane coupling agent KH-550 was added and mixed, and then granulated and dried to obtain a casein-water-absorbing composition mixed with adipic acid as core particles;

[0078] 5 kg of poly (N-vinyl caprolactam), 16 kg of poly (vinyl alcohol), 8 kg of urea, 12 kg of sodium bicarbonate and 22 kg of acetone were mixed and sprayed onto a casein-water-absorbing composition mixed with adipic acid as a wall material, and then dried to prepare adipic acid / casein-water-absorbing composition microcapsules.

[0079] The mass ratio of the core material particles to the wall material is 1:1.

[0080] Preparation Example 9

[0081] A process for preparing adipic acid / casein-water-absorbing composition microcapsules comprises the following steps:

[0082] 25 kg of PAM-CaCl2 hydrogel and 18 kg of chitosan were mixed and added to 28 kg of 12 wt% sodium bicarbonate aqueous solution, followed by the addition of 2 kg of genipin and mixing. 10 kg of casein was added and ultrasonicated for 30 minutes. 8 kg of adipic acid was also added and ultrasonicated for 10 minutes. 8 kg of silane coupling agent KH-550 was then added and mixed. Granulation and drying were then performed to obtain a casein-water-absorbing composition mixed with adipic acid as core particles.

[0083] 3 kg of poly (N-vinyl caprolactam), 13 kg of poly (vinyl alcohol), 5 kg of urea, 8 kg of sodium bicarbonate and 20 kg of acetone were mixed and sprayed onto a casein-water-absorbing composition mixed with adipic acid as a wall material, and then dried to prepare adipic acid / casein-water-absorbing composition microcapsules.

[0084] The mass ratio of the core material particles to the wall material is 1:0.8.

[0085] Preparation Example 10

[0086] A process for preparing adipic acid / casein-water-absorbing composition microcapsules comprises the following steps:

[0087] 25 kg of PAM-CaCl2 hydrogel and 18 kg of chitosan were mixed and added to 28 kg of 12 wt% sodium bicarbonate aqueous solution, followed by adding 2 kg of genipin and mixing, and then adding 10 kg of casein. After ultrasonic treatment for 30 minutes, 12 kg of adipic acid was added, and ultrasonic treatment was continued for 20 minutes. Then, 8 kg of silane coupling agent KH-550 was added and mixed, and then granulated and dried to obtain a casein-water-absorbing composition mixed with adipic acid as core particles;

[0088] 8 kg of poly (N-vinyl caprolactam), 20 kg of poly (vinyl alcohol), 10 kg of urea, 15 kg of sodium bicarbonate and 25 kg of acetone were mixed and sprayed onto a casein-water-absorbing composition mixed with adipic acid as a wall material, and dried to prepare adipic acid / casein-water-absorbing composition microcapsules.

[0089] The mass ratio of the core material particles to the wall material is 1:1.2.

[0090] Example 1

[0091] A process for preparing ultra-high performance concrete comprises the following steps:

[0092] 830 kg of cement, 150 kg of glass beads, 115 kg of mineral powder, 90 kg of silica fume and 950 kg of fine aggregate were added to a stirring pot and mixed for 2 minutes, and then 12 kg of calcium sulfoaluminate expansion agent, 45 kg of magnesium slag powder and 22 kg of the casein-water-absorbing composition prepared in Preparation Example 5 were added and mixed to obtain a powder mixture;

[0093] 10 kg of water reducer was dissolved in 160 kg of water, and then added to the powder mixture and stirred for 10 minutes to obtain a solid-liquid mixture. Then, 155 kg of steel fiber and 25 kg of modified nanoporous carbon fiber prepared in Preparation Example 1 were added and stirred in three portions. Finally, the remaining 40 kg of water was added in two portions and stirred for 6 minutes to obtain ultra-high performance concrete.

[0094] Example 2

[0095] A process for preparing ultra-high performance concrete comprises the following steps:

[0096] 790 kg of cement, 140 kg of glass beads, 105 kg of mineral powder, 85 kg of silica fume and 890 kg of fine aggregate were added to a stirring pot and mixed for 2 minutes, and then 10 kg of calcium sulfoaluminate expansion agent, 40 kg of magnesium slag powder and 18 kg of the casein-water-absorbing composition prepared in Preparation Example 6 were added and mixed to obtain a powder mixture;

[0097] 8 kg of water reducer was dissolved in 147 kg of water, and then added to the powder mixture and stirred for 8 minutes to obtain a solid-liquid mixture. Then, 150 kg of steel fiber and 20 kg of modified nanoporous carbon fiber prepared in Preparation Example 2 were added in two portions and stirred. Finally, the remaining 48 kg of water was added in two portions and stirred for 5 minutes to obtain ultra-high performance concrete.

[0098] Example 3

[0099] A process for preparing ultra-high performance concrete comprises the following steps:

[0100] 855 kg of cement, 160 kg of glass beads, 125 kg of mineral powder, 105 kg of silica fume and 985 kg of fine aggregate were added to a stirring pot and mixed for 3 minutes, and then 15 kg of calcium sulfoaluminate expansion agent, 50 kg of magnesium slag powder and 28 kg of the casein-water-absorbing composition prepared in Preparation Example 6 were added and mixed to obtain a powder mixture;

[0101] 12 kg of water reducer was dissolved in 175 kg of water, and then added to the powder mixture and stirred for 10 minutes to obtain a solid-liquid mixture. Then, 160 kg of steel fiber and 30 kg of modified nanoporous carbon fiber prepared in Preparation Example 3 were added and stirred in three portions. Finally, the remaining 32 kg of water was added in three portions and stirred for 7 minutes to obtain ultra-high performance concrete.

[0102] Example 4

[0103] A preparation process for ultra-high performance concrete is carried out according to the method in Example 1, except that the modified nanoporous carbon fibers are the modified nanoporous carbon fibers prepared in Preparation Example 4.

[0104] Example 5

[0105] A preparation process for ultra-high performance concrete is carried out according to the method in Example 1, except that an equal amount of the casein-water-absorbing composition prepared in Preparation Example 5 is replaced by an equal amount of the adipic acid / casein-water-absorbing composition microcapsules prepared in Preparation Example 9.

[0106] Example 6

[0107] A process for preparing ultra-high performance concrete is carried out according to the method of Example 1, except that an equal amount of the casein-water-absorbing composition prepared in Preparation Example 5 is replaced by an adipic acid / casein-water-absorbing composition microcapsule prepared in Preparation Example 8;

[0108] At the same time, 12 kg of ethylenediamine was added when the concrete was prepared while adding steel fibers.

[0109] Example 7

[0110] A process for preparing ultra-high performance concrete is carried out according to the method of Example 1, except that an equal amount of the casein-water-absorbing composition prepared in Preparation Example 5 is replaced by the adipic acid / casein-water-absorbing composition microcapsules prepared in Preparation Example 9;

[0111] At the same time, 10 kg of ethylenediamine was added when the concrete was prepared while adding steel fibers.

[0112] Example 8

[0113] A process for preparing ultra-high performance concrete is carried out according to the method of Example 1, except that an equal amount of the casein-water-absorbing composition prepared in Preparation Example 5 is replaced by the adipic acid / casein-water-absorbing composition microcapsules prepared in Preparation Example 10;

[0114] At the same time, 15 kg of ethylenediamine was added when the concrete was prepared while adding steel fibers.

[0115] Example 9

[0116] A process for preparing ultra-high performance concrete is carried out according to the method in Example 1, except that 12 kg of polytetrafluoroethylene wax is added at the same time as the steel fiber.

[0117] Example 10

[0118] A process for preparing ultra-high performance concrete is carried out according to the method in Example 1, except that 8 kg of polytetrafluoroethylene wax is added at the same time as the steel fiber.

[0119] Example 11

[0120] A process for preparing ultra-high performance concrete is carried out according to the method in Example 1, except that 16 kg of polytetrafluoroethylene wax is added at the same time as the steel fiber.

[0121] Comparative Example 1

[0122] A process for preparing ultra-high performance concrete is carried out according to the method in Example 1, except that an equal amount of the modified nanoporous carbon fibers is replaced by unmodified nanoporous carbon fibers.

[0123] Comparative Example 2

[0124] A process for preparing ultra-high performance concrete is carried out according to the method in Example 1, except that an equal amount of modified nanoporous carbon fibers is replaced by carbon fibers.

[0125] Comparative Example 3

[0126] A process for preparing ultra-high performance concrete is carried out according to the method in Example 1, except that no magnesium slag powder is added to the raw materials.

[0127] Comparative Example 4

[0128] A process for preparing ultra-high performance concrete is carried out according to the method in Example 1, except that no casein-water-absorbing composition is added to the raw materials.

[0129] Comparative Example 5

[0130] A preparation process for ultra-high performance concrete is carried out according to the method in Example 1, except that an equal amount of the casein-water-absorbing composition is replaced by a water-absorbing composition, wherein the water-absorbing composition is a composition obtained by mixing PAM-CaCl2 hydrogel and chitosan in a mass ratio of 1.4:1.

[0131] Comparative Example 6

[0132] A preparation process for ultra-high performance concrete is carried out according to the method in Example 1, except that the casein-water-absorbing composition is replaced with an equal amount of a mixture of casein and the water-absorbing composition. Specifically:

[0133] When preparing concrete, 4 kg of casein, 7.5 kg of chitosan and 10.5 kg of PAM-CaCl2 hydrogel were added when magnesium slag powder was added.

[0134] Comparative Example 7

[0135] A preparation process for ultra-high performance concrete is carried out according to the method in Example 1, except that the casein-water-absorbing composition is replaced with an equal amount of a mixture of casein and the water-absorbing composition. Specifically:

[0136] When preparing concrete, 6.3 kg of casein and 15.7 kg of PAM-CaCl2 hydrogel were added when magnesium slag powder was added.

[0137] Comparative Example 8

[0138] A process for preparing ultra-high performance concrete is carried out according to the method in Example 1, except that no genipin is added during the preparation of the casein-water-absorbing composition.

[0139] Performance testing

[0140] The 28-day compressive strength and autogenous shrinkage performance of the ultra-high performance concrete prepared in the examples and comparative examples of the present application were tested. The 28-day compressive strength was tested in accordance with the provisions of GB / T 50080-2016 "Test methods for properties of ordinary concrete mixtures", and the autogenous shrinkage performance was tested in accordance with GB / T 50082-2009 "Standard for test methods for long-term properties and durability of ordinary concrete". The performance test results are shown in Table 1 below.

[0141]

[0142]

[0143] With reference to upper table 1, it is known that the concrete obtained in the present application has excellent compressive strength and low autogenous shrinkage performance, in conjunction with the tested result of embodiment 1 and embodiment 4, when modified nano porous carbon fiber is prepared in concrete, after carbon fiber is loaded with cesium sulfate, it is not baked at high temperature, just when common oven dry, its compressive performance is reduced, and autogenous shrinkage performance also increases; In conjunction with the tested result of embodiment 5 and embodiment 7, when casein-water absorbing composition is prepared, it is also added with oxalic acid, and wall operation is carried out simultaneously, when coagulation and raw material are also added with ethylenediamine, its compressive strength significantly improves, and autogenous shrinkage performance is also significantly improved simultaneously, and in embodiment 5, only ethylenediamine is added, in concrete raw material, its performance is suitable with not adding ethylenediamine and ethylenediamine, and when adding ethylenediamine and ethylenediamine simultaneously, it helps to improve compressive strength and improve autogenous shrinkage performance. In conjunction with the tested result of embodiment 1 and embodiment 9-11, when concrete raw material is added with polytetrafluoroethylene wax, its compressive strength changes less, but its autogenous shrinkage performance is further improved.

[0144] Referring to the test results of Example 1 and Comparative Example 1, it can be seen that when the modified nanoporous carbon fiber is replaced by an equal amount of unmodified nanoporous carbon fiber, its compressive strength is reduced and the autogenous shrinkage value is also large. The treatment of porous carbon fiber with cesium sulfate helps to improve the compressive strength and improve the autogenous shrinkage phenomenon; combined with the test results of Comparative Example 2, when the modified nanoporous carbon fiber is replaced by carbon fiber in equal amounts, its compressive strength is good, but the autogenous shrinkage value is large; referring to the test results of Comparative Examples 3 and 4, when magnesium slag powder or casein-water-absorbing composition is not added to the raw material, its compressive strength decreases and the autogenous shrinkage value increases; combined with the test results of Comparative Examples 5 and 6, casein is not added in Comparative Example 5, but only PAM-CaCl2 hydrogel is added. and chitosan, it is obvious that its compressive strength is significantly reduced, and its autogenous shrinkage value is also large; while in Comparative Example 6, casein, chitosan and 10.5kg PAM-CaCl2 hydrogel are directly added without cross-linking to obtain a macromolecular composition, its compressive strength is also weaker than that of Example 1, and its autogenous shrinkage value is increased compared with Example 1; combined with Comparative Example 7 when only casein and PAM-CaCl2 hydrogel are added without chitosan and cross-linking agent, its performance is equivalent to that of Comparative Example 6, or even slightly weaker, and when the cross-linking agent genipin is not added in Comparative Example 8, its performance is also reduced. Casein, chitosan and PAM-CaCl2 hydrogel are made into cross-linked macromolecules under the action of a cross-linking agent and then added. Compared with direct addition, its performance improvement effect on compressive strength and autogenous shrinkage is more obvious.

[0145] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. An ultra-high performance concrete, characterized in that: It includes the following raw materials in parts by weight: 790-855 parts of cement, 140-160 parts of glass beads, 105-125 parts of mineral powder, 85-105 parts of silica fume, 890-985 parts of fine aggregate, 195-207 parts of water, 8-12 parts of water reducer, 150-160 parts of steel fiber, 10-15 parts of expansion agent, 20-30 parts of modified nanoporous carbon fiber, 40-50 parts of magnesium slag powder, and 18-28 parts of casein-water absorbing composition; Wherein, the modified nanoporous carbon fiber is prepared by the following method: Soak the nanoporous carbon fibers in a cesium sulfate solution and stir to obtain a mixture: The mixture was filtered, and the precipitate was baked at high temperature. The specific baking operation was: baking at 400-420° C. for 1-2 hours, and then naturally cooling to obtain modified nanoporous carbon fibers. The casein-water-absorbing composition was prepared from the following raw materials in parts by weight: 8-15 parts of casein, 12-23 parts of chitosan, 20-30 parts of PAM-CaCl2 hydrogel, 1-3 parts of genipin, and 5-12 parts of a silane coupling agent; the casein-water-absorbing composition is prepared by the following method: The PAM-CaCl2 hydrogel and chitosan are mixed and added to a carbonate aqueous solution, and then genipin is added and mixed, and casein is added. After ultrasonic treatment for 20-40 minutes, a silane coupling agent is added and mixed, and then granulated and dried to obtain a casein-water-absorbing composition.

2. The ultra-high performance concrete according to claim 1, characterized in that: The ultra-high performance concrete raw materials also include 10-15 parts by weight of ethylenediamine; Adipic acid is also added during the preparation of the casein-water absorbing composition, and the prepared casein-water absorbing composition mixed with adipic acid is added after the wall is coated. The specific operation is as follows: When preparing the casein-water-absorbing composition, after ultrasonic treatment of casein, 8-12 parts by weight of adipic acid are added, and then ultrasonic treatment is continued for 10-20 minutes. Then, a silane coupling agent is added, and then granulation and drying are performed to obtain the casein-water-absorbing composition mixed with adipic acid.

3. The ultra-high performance concrete according to claim 2, characterized in that: The specific operation of casein-water-absorbing composition wall coating is: 3-8 parts of poly (N-vinyl caprolactam), 13-20 parts of poly (vinyl alcohol), 5-10 parts of urea, 8-15 parts of sodium bicarbonate and 20-25 parts of acetone are mixed by weight, and the mixture is sprayed onto a casein-water-absorbing composition mixed with adipic acid, and the mixture is dried to prepare adipic acid / casein-water-absorbing composition microcapsules.

4. The ultra-high performance concrete according to claim 1, characterized in that: The raw materials of ultra-high performance concrete also include 8-16 parts by weight of polytetrafluoroethylene wax.

5. The ultra-high performance concrete according to claim 1, characterized in that: The mineral powder is S95 grade mineral powder; The fine aggregate is quartz sand, and the fine aggregate includes 420-465 parts by weight of coarse sand, 170-190 parts by weight of medium sand and 300-330 parts by weight of fine sand; The water reducing agent is a polycarboxylic acid water reducing agent with a water reducing rate of ≥40%.

6. The process for preparing ultra-high performance concrete according to claim 1, wherein: The following steps are involved: Cement, glass beads, mineral powder, silica fume and fine aggregate are mixed and stirred, and then an expansion agent, magnesium slag powder and casein-water absorbing composition are added, mixed and stirred to obtain a powder mixture; The water reducer is dissolved in 75-85% water and then added to the powder mixture to obtain a solid-liquid mixture. The steel fiber and the modified nanoporous carbon fiber are then added in batches and stirred. Finally, the remaining water is added and stirred to obtain ultra-high performance concrete.

7. The process for preparing ultra-high performance concrete according to claim 6, characterized in that: The raw materials of ultra-high performance concrete also include 8-16 parts by weight of polytetrafluoroethylene wax, and the polytetrafluoroethylene wax is added together with the steel fiber.

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