Superfluid UHPC (Ultra High Performance Polycarbonate) based on ultra-dispersed silica mortar and preparation method of superfluid UHPC

Abstract

The invention relates to the technical field of concrete, and particularly discloses a superfluid UHPC based on ultra-dispersed silica mortar and a preparation method thereof, the superfluid UHPC comprises the following components by weight: 400-600 parts of cement, 50-150 parts of silica fume, 500-800 parts of a composite mineral admixture, 400-600 parts of quartz sand, 150-300 parts of steel fiber, 20-50 parts of a water reducer, and 100-200 parts of water; wherein the addition mode of the silica fume is as follows: the silica fume is firstly prepared into silica fume slurry by adopting a dispersing agent, alkali and water, and then the silica fume slurry is added into a dry mixture formed by mixing the other components. According to the preparation method disclosed by the invention, the ultra-dispersed silica mortar is firstly prepared, so that the silica fume is uniformly dispersed in the mortar, the problem of agglomeration of the silica fume in the UHPC is effectively avoided, and the utilization rate of the silica fume is improved, so that the strength and durability of the UHPC are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and in particular to a superfluid UHPC based on ultra-dispersed silica mortar and a preparation method thereof. Background Art

[0002] Ultra-high-performance concrete (UHPC) boasts exceptional properties such as ultra-high strength, high toughness, and high durability, and holds broad application prospects in areas such as construction, bridges, and marine engineering. However, conventional UHPC, due to its high cement content and low water-cement ratio, suffers from poor workability and significant shrinkage, limiting its widespread adoption. Silica fume, a key component of UHPC, significantly enhances concrete's strength and durability. However, its fine particles and large specific surface area make it prone to agglomeration in concrete, making it difficult to disperse evenly, hindering its full performance.

[0003] Therefore, it is of great significance to develop a preparation method that can evenly disperse silica fume and effectively improve the workability of UHPC. Summary of the Invention

[0004] The purpose of the present invention is to provide a superfluid UHPC based on ultra-dispersed silica fume slurry and a preparation method thereof, so as to solve the problem that silica fume is easy to agglomerate in concrete, thereby improving the strength and durability of UHPC.

[0005] The present invention is achieved through the following technical solutions: A superfluid UHPC based on super-dispersed silica slurry comprises the following components in parts by weight: Cement 400-600 parts, silica fume 50-150 parts, composite mineral admixture 500-800 parts, quartz sand 400-600 parts, steel fiber 150-300 parts, water reducer 20-50 parts, water 100-200 parts; Among them, the addition method of silica fume is: Silica fume is first prepared into silica fume slurry using a dispersant, alkali and water, and then the silica fume slurry is added to the dry mix obtained by mixing other components.

[0006] The main differences between the present invention and the prior art are: The present invention does not directly add silica fume when mixing concrete. Instead, the silica fume is first prepared into silica fume slurry, so that the silica fume is evenly dispersed in the slurry. This can avoid the problem of silica fume agglomeration in UHPC, thereby improving the utilization rate of silica fume and significantly improving the strength and durability of UHPC.

[0007] The principle of uniform dispersion of silica fume in slurry is: In an alkaline environment, the surface of the silica fume particles in the silica fume slurry carries a negative charge. The electrostatic repulsion between the silica fume particles is used to reduce the agglomeration of the silica fume and maintain dispersion. Combined with the dispersing effect of the dispersant, the silica fume is evenly dispersed in the slurry.

[0008] In a preferred embodiment, the dispersant includes at least one of carboxyl-containing acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymers and their salts, carboxylic acid-sulfonate copolymers and their salts, hydrolyzed polymaleic anhydride and their salts, maleic acid-acrylic acid copolymers / mixtures and their salts, polyacrylic acid and their salts, polymaleic acid and their salts, and polybutene acid and their salts.

[0009] Specifically, the dispersants selected in this invention all contain carboxylic acid groups, allowing them to adsorb onto the surfaces of silica fume particles via these groups. This imparts a more negative charge to the surfaces, enhancing the electrostatic repulsion between the particles. Simultaneously, the dispersants form a thick steric hindrance layer on the surfaces of the silica fume particles. When two silica fume particles approach each other, the molecular chains of the dispersant adsorbed on their surfaces squeeze each other, generating a repulsive force. This steric hindrance effect further prevents direct contact and agglomeration between the silica fume particles, ensuring their stable dispersion within the system.

[0010] That is, the above-mentioned dispersant screened out by the present invention can achieve ultra-dispersion performance of silica fume in silica fume slurry, so that the prepared silica fume slurry has a lower particle size and a higher activity index, and the prepared silica fume slurry has a higher ZETA absolute value, which is more conducive to improving the performance of UHPC.

[0011] The super-dispersion of the present invention refers to the deagglomeration of the originally agglomerated particle system in the densified silica fume through a specific modification process, so that the silica fume particles are dispersed to a state of single silica fume particle size, forming a uniform and stable dispersion system (uniform and stable generally means a suspension rate greater than 90%), thus achieving super-dispersion; when the activity index is greater than 130%, the prepared silica fume slurry has high activity.

[0012] In a preferred embodiment, the molecular weight of the dispersant is 1000 to 10000.

[0013] A molecular weight that is too low results in weak adsorption, insufficient steric hindrance, and poor dispersion stability; a molecular weight that is too high leads to difficulty in dissolution, excessive viscosity, and bridging flocculation and coagulation. Limiting the molecular weight to 1,000 to 10,000 achieves an optimal balance between electrostatic repulsion, steric hindrance, solution fluidity, and process feasibility, ensuring excellent dispersibility, workability, and long-term stability of the silica ash slurry.

[0014] In a preferred embodiment, the pH value of the silica slurry is 8-13.

[0015] The alkaline environment ionizes the silanol (Si-OH) on the surface of the silica fume particles into SiO- , so that the surface of the silica fume particles is negatively charged, and the electrostatic repulsion between the silica fume particles is used to reduce the agglomeration of silica fume.

[0016] In a preferred embodiment, the solid content of the silica slurry is 40% to 70%.

[0017] A method for preparing superfluid UHPC based on super-dispersed silica slurry comprises the following steps: S1. Preparation of silica ash slurry: silica ash is first prepared into silica ash slurry using a dispersant, alkali and water, wherein the pH value of the prepared silica ash slurry is 8-13; S2. Preparation of UHPC dry mix: Cement, composite mineral admixture, and quartz sand are mixed in proportion and stirred evenly to obtain UHPC dry mix; the stirring speed is 200-500 r / min and the stirring time is 3-5 min; S3. Preparation of Superfluid UHPC: The silica ash slurry prepared in step S1 is slowly added to the UHPC dry mix prepared in step S2 while stirring, and the mixture is uniformly mixed. A water reducer and water are then added and stirred, and finally, steel fiber is added and stirred uniformly to obtain superfluid UHPC. The stirring speed is 300-600 rpm. After the silica ash is added, the stirring speed is maintained and stirring is continued for 5-10 minutes. In other words, part of the water in the UHPC formula of this invention is used to prepare the silica ash slurry, and the remaining part is added together with the water reducer when mixing concrete.

[0018] Step S1 specifically includes the following steps: S11, dissolving the base in water to form an alkaline solution, and then adding a dispersant to the alkaline solution to form a uniform solution; S12, gradually adding silica fume to the solution prepared in step S11 to obtain a mixed system; S13. Perform high-speed dispersion treatment on the mixed system, and then let it stand and filter to obtain silica ash slurry; the equipment for high-speed dispersion treatment includes high-speed dispersion equipment, homogenizer, sand mill, colloid mill or ball mill.

[0019] In a preferred embodiment, in step S11, the base is a monovalent ion base, and the monovalent ion base includes at least one of sodium hydroxide, potassium hydroxide, ammonia water, triethylamine and tetramethylammonium hydroxide.

[0020] In a preferred embodiment, in step S12, the silica fume is added at a rate of 0.5-5 kg / min.

[0021] In a preferred embodiment, in step S12, the silica fume is added at a rate of 1 to 3 kg / min.

[0022] In a preferred embodiment, during the preparation of silica fume slurry, the mass ratio of silica fume to water is (40-70): (30-60), and the amount of dispersant used is 0.1%-2% based on the mass of silica fume.

[0023] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. The present invention prepares ultra-dispersed silica fume slurry first, so that the silica fume is evenly dispersed in the slurry, effectively avoiding the problem of silica fume agglomeration in UHPC, improving the utilization rate of silica fume, and thus significantly improving the strength and durability of UHPC.

[0024] 2. The superfluid UHPC obtained by the preparation method of the present invention has good workability, its expansion can reach 600-700mm, T500 is less than 6.5s, has the advantages of good fluidity, is easy to construct and operate, and can meet the casting requirements of complex structures. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with the examples. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention. The embodiments described below are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0026] In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one of ordinary skill in the art that these specific details are not necessarily required to practice the present invention. In other examples, well-known structures, materials, or methods are not specifically described to avoid obscuring the present invention. The materials, instruments, and reagents used in the following examples, unless otherwise specified, are commercially available. The techniques used in the examples, unless otherwise specified, are conventional techniques well known to those skilled in the art.

[0027] Example: In order to solve the problem of silica fume agglomeration affecting the performance of concrete caused by adding silica fume directly to concrete mixing in the existing UHPC preparation process, this embodiment provides a superfluid UHPC based on ultra-dispersed silica fume slurry, comprising the following components in parts by weight: 400-600 parts of cement, 50-150 parts of silica fume, 500-800 parts of composite mineral admixture, 400-600 parts of quartz sand, 150-300 parts of steel fiber, 20-50 parts of water reducer, and 100-200 parts of water. The water reducer may be a polycarboxylate water reducer. The cement, composite mineral admixture, quartz sand, and steel fiber are mixed in a conventional manner. The method of adding silica fume is different from the prior art. The specific method of adding silica fume is as follows: Silica fume is first prepared into a silica fume slurry using a dispersant, alkali, and water. The slurry is then added to the dry mix of the other components. Because the silica fume in this slurry is evenly dispersed throughout the slurry and the electrostatic repulsion between silica fume particles effectively reduces the likelihood of agglomeration, adding silica fume to concrete as a slurry reduces the likelihood of agglomeration and improves its dispersion in the concrete. This maximizes the effectiveness of the silica fume and increases its utilization, significantly enhancing the strength and durability of UHPC.

[0028] When preparing concrete, appropriate amount of silica ash slurry is added based on the solid content of the prepared silica ash slurry. That is, the content of silica ash in the embodiment formula is calculated based on the solid content of the silica ash slurry and the amount of silica ash slurry added.

[0029] Among them, the dispersant includes at least one of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer and its salt, carboxylic acid-sulfonate copolymer and its salt, hydrolyzed polymaleic anhydride and its salt, maleic acid-acrylic acid copolymer / mixture and its salt, polyacrylic acid and its salt, polymaleic acid and its salt and polybutene acid and its salt.

[0030] The specific salt may be a sodium salt or a potassium salt. For example, polyacrylate includes at least one of sodium polyacrylate and potassium polyacrylate; and polymaleate includes at least one of sodium polymaleate and potassium polymaleate.

[0031] The molecular weight of the dispersant is preferably 1,000 to 10,000.

[0032] In order to further improve the dispersibility of silica fume in silica fume slurry, additional alkali is added to adjust the pH value of silica fume slurry to 8~13.

[0033] Among them, the solid content of silica ash slurry is 40%~70%.

[0034] The above-mentioned method for preparing superfluid UHPC based on ultra-dispersed silica slurry comprises the following steps: S1. Preparation of silica ash slurry: silica ash is first prepared into silica ash slurry using a dispersant, alkali and water, wherein the pH value of the prepared silica ash slurry is 8-13; specifically comprising the following steps: S11. First dissolve the alkali in water to form an alkaline solution, and then add a dispersant to the alkaline solution to make the pH value of the prepared silica ash slurry 8-13; dissolve the dispersant in the alkaline solution at 0.1%-2% of the mass of the silica ash, and stir with a high-speed stirrer for 2 minutes to ensure that the dispersant is completely dissolved to form a uniform solution.

[0035] S12. Gradually add silica fume to the solution prepared in step S11 to obtain a mixed system. The amount of silica fume added is determined based on the desired silica fume slurry concentration, generally accounting for 40% to 70% of the total silica fume slurry mass. The silica fume addition rate should be moderate, ranging from 0.5 to 5 kg / min. Preferably, the silica fume addition rate is 1 to 3 kg / min to avoid agglomeration caused by excessive addition.

[0036] S13. The mixed system is subjected to a high-speed dispersion process for 10 minutes. During this process, the strong shear force generated by the high-speed rotation fully disperses the silica fume particles in the mixed solution. Equipment for high-speed dispersion can include a high-speed dispersing device, a homogenizer, a sand mill, a colloid mill, or a ball mill. The slurry is then allowed to stand for 10 minutes and filtered through a 200-mesh screen to obtain a silica fume slurry.

[0037] S2. Preparation of UHPC dry mix: Cement, composite mineral admixture, and quartz sand are mixed in a low-speed mixer according to the proportions and stirred evenly at a mixer speed of 200-500 r / min for 3-5 minutes to obtain a UHPC dry mix; S3. Preparation of superfluid UHPC: The silica ash slurry prepared in step S1 is slowly added to the UHPC dry mix prepared in step S2 while stirring; stirring is carried out at a speed of 300-600 r / min, and the addition rate of the silica ash slurry is controlled at 1-3 kg / min. After the addition is completed, stirring is continued for 5-10 minutes to mix evenly, and then a water reducer and water are added and stirred. Finally, steel fiber is added and stirred evenly to obtain superfluid UHPC.

[0038] S4. Molding and Curing: Pour the superfluid UHPC mixture into a mold and vibrate it to form a mold. The vibration time is 1-3 minutes and the vibration frequency is 50-100Hz. The molded specimens are cured under standard curing conditions for 24-48 hours, then demolded. They are then cured in a steam curing oven at a temperature of 80-95°C and a relative humidity greater than 90% for 48-72 hours before subsequent testing.

[0039] In order to better illustrate the technical effects of this embodiment, the following specific cases are used for illustration.

[0040] Example 1: A superfluid UHPC based on ultra-dispersed silica slurry, consisting of the following components: 550 parts cement, 60 parts silica fume, 600 parts composite mineral admixture, 550 parts quartz sand, 180 parts steel fiber, 30 parts polycarboxylate superplasticizer, and 140 parts water. The composite mineral admixture is obtained by uniformly mixing mineral powder, fly ash, and microspheres in a mass ratio of 2:1:2.

[0041] The preparation process of superfluid UHPC based on super-dispersed silica slurry in this embodiment is as follows: S1. Preparation of silica slurry: S11. Add weighed 0.15% sodium hydroxide to a certain amount of water. The specific amount of water is determined based on the solid content of 50% and the amount of silica fume. At the same time, stir with a high-speed stirrer for 2 minutes to ensure that the sodium hydroxide is completely dissolved to form a uniform alkaline solution. Add 0.1% sodium polyacrylate (molecular weight 3000) to the alkaline solution to obtain a mixed solution. Keep stirring during the addition of sodium polyacrylate for 1 minute to ensure that the sodium polyacrylate is fully dispersed in the alkaline solution to form a stable mixed solution. The added amounts of sodium hydroxide and sodium polyacrylate are both calculated based on the mass of silica fume.

[0042] S12. Under stirring, gradually add silica fume to the mixed solution to obtain ultra-dispersed and highly active silica fume slurry; the addition rate of silica fume is 3 kg / min to avoid agglomeration caused by too fast addition.

[0043] S13. After the addition of silica fume, the mixed system was subjected to high-speed dispersion treatment (1500r / min) for 10 minutes, and then allowed to stand for 10 minutes and filtered through 200 mesh to obtain ultra-dispersed silica fume slurry. The pH value of the ultra-dispersed silica fume slurry was measured to be 8.9.

[0044] S2. Preparation of UHPC dry mix: Cement, composite mineral admixture, and quartz sand were mixed in a low-speed mixer according to the proportions and stirred evenly at a mixer speed of 450 r / min for 4 min to obtain a UHPC dry mix; S3. Preparation of superfluid UHPC: Slowly add the silica ash slurry prepared in step S1 to the UHPC dry mix prepared in step S2 while stirring; stir at a speed of 500 r / min, and control the addition rate of silica ash slurry at 2 kg / min. Continue stirring for 10 minutes after addition to mix evenly, then add water reducer and water and stir, and finally add steel fiber and stir evenly to obtain superfluid UHPC.

[0045] S4. Molding and Curing: The superfluid UHPC mixture was poured into a mold and vibrated for 3 minutes at a frequency of 80 Hz. The molded specimens were cured under standard curing conditions for 36 hours before demolding. The specimens were then cured in a steam curing chamber at 90°C and relative humidity greater than 90% for 60 hours before subsequent testing.

[0046] Example 2: This embodiment is based on embodiment 1, and differs from embodiment 1 in that: The dispersants used in the preparation of silica ash slurry were different, and an equal amount of sodium polymaleate (3000 molecular weight) was used to replace sodium polyacrylate.

[0047] Example 3: This embodiment is based on embodiment 1, and differs from embodiment 1 in that: The dispersants used in the preparation of silica ash slurry were different, and an equal amount of hydrolyzed polymaleic anhydride (3000 molecular weight) was used to replace sodium polyacrylate.

[0048] Example 4: This embodiment is based on embodiment 1, and differs from embodiment 1 in that: The dispersants used in the preparation of silica ash slurry were different, and an equal amount of polyacrylic acid (3000 molecular weight) was used to replace sodium polyacrylate.

[0049] Example 5: This embodiment is based on embodiment 1, and differs from embodiment 1 in that: The dispersants used in the preparation of silica mortar were different, and an equal amount of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer (3000 molecular weight) was used to replace sodium polyacrylate.

[0050] Example 6: This embodiment is based on embodiment 1, and differs from embodiment 1 in that: The dispersants used in the preparation of silica ash slurry were different, and an equal amount of maleic acid-acrylic acid copolymer sodium salt (3000 molecular weight) was used to replace sodium polyacrylate.

[0051] Example 7: This embodiment is based on embodiment 1, and differs from embodiment 1 in that: The amount of sodium hydroxide used in the preparation process of silica slurry is different. In this embodiment, the amount of sodium hydroxide used is 0.22%. The pH value of the ultra-dispersed silica slurry of this embodiment is measured to be 10.0. At the same time, the amount of sodium polyacrylate is increased to 0.5%.

[0052] Example 8: This embodiment is based on embodiment 1, and differs from embodiment 1 in that: The amount of sodium hydroxide used in the preparation process of silica slurry is different. In this embodiment, the amount of sodium hydroxide used is 0.35%. The pH value of the ultra-dispersed silica slurry of this embodiment is measured to be 11.2. At the same time, the amount of sodium polyacrylate is increased to 1.0%.

[0053] Example 9: This embodiment is based on embodiment 1, and differs from embodiment 1 in that: The alkali and its dosage in the process of preparing silica slurry are different. The alkali used in this embodiment is triethylammonium, and the dosage of triethylammonium is 0.4%. The pH value of the super-dispersed silica slurry in this embodiment is measured to be 8.9.

[0054] Example 10: This embodiment is based on embodiment 1, and differs from embodiment 1 in that: The alkali and its dosage in the process of preparing silica ash slurry are different. The alkali used in this embodiment is ammonia water, and the dosage of ammonia water is 0.5%. The pH value of the super-dispersed silica ash slurry in this embodiment is measured to be 9.0.

[0055] Example 11: This embodiment is based on Example 1, and differs from Example 1 in that the amounts of the various components in UHPC are different: A superfluid UHPC based on ultra-dispersed silica slurry, consisting of the following components: 500 parts of cement, 100 parts of silica fume, 800 parts of composite mineral admixture, 500 parts of quartz sand, 240 parts of steel fiber, 25 parts of polycarboxylate water reducer, and 160 parts of water.

[0056] Comparative Example 1: This comparative example is based on Example 1, and differs from Example 1 in that: No sodium hydroxide was used in the preparation of the silica ash slurry, and the pH value of the super-dispersed silica ash slurry of this comparative example was measured to be 1.75.

[0057] Comparative Example 2: This comparative example is based on Example 1, and differs from Example 1 in that: The dispersants used in the preparation of silica ash slurry are different, and an equal amount of polynaphthalene formaldehyde sulfonic acid sodium salt (3000 molecular weight) is used to replace sodium polyacrylate.

[0058] Comparative Example 3: This comparative example is based on Example 1, and differs from Example 1 in that: The dispersants used in the preparation of silica mortar are different, and an equal amount of melamine is used to replace sodium polyacrylate.

[0059] Comparative Example 4: This comparative example is based on Example 1, and differs from Example 1 in that: The dispersants used in the preparation of silica ash slurry were different, and an equal amount of polycarboxylic acid (3000 molecular weight) was used to replace sodium polyacrylate.

[0060] Comparative Example 5: This comparative example is based on Example 1, and differs from Example 1 in that: No dispersant is used in the preparation of silica mortar.

[0061] Comparative Example 6: This comparative example is based on Example 1, and differs from Example 1 in that: The alkali and its dosage in the process of preparing silica mortar are different. The alkali used in this embodiment is aluminum hydroxide, and the dosage of aluminum hydroxide is 0.35%. At the same time, the dosage of sodium polyacrylate is increased to 1.0%. The pH value of the ultra-dispersed silica mortar of this embodiment is measured to be 9.0.

[0062] Comparative Example 7: This comparative example is a blank control. The concrete formula of this comparative example is the same as that of Example 1, except that the silica fume is not prepared into silica fume slurry, but is directly added to the concrete. The preparation process of the concrete of this comparative example is as follows: S1. Preparation of UHPC dry mix: Cement, composite mineral admixture, quartz sand, and silica fume were mixed in a low-speed mixer according to the proportions and stirred uniformly at a mixer speed of 450 r / min for 4 min to obtain a UHPC dry mix; S2. Preparation of superfluid UHPC: Then add water reducer and water and stir, and finally add steel fiber and stir evenly to obtain superfluid UHPC.

[0063] The properties of the silica mortars prepared in Examples 1 to 10 and Comparative Examples 1 to 6 are shown in Table 1: Table 1 The superfluid UHPC prepared from Examples 1 to 7 and cured in the following manner was tested for strength, expansion, and T500; the test results are shown in Table 2.

[0064] Table 2 From the data in Table 2, we can see that: 1) The expansion of the UHPC concrete of the present invention is between 600-700 mm, while the expansion of the blank group and the prepared UHPC concrete obtained by different preparation processes of the silica ash slurry will be reduced.

[0065] 2) The 28d compressive strength of the UHPC concrete of the present invention is all above 170 MPa, the 28d flexural first crack strength is all above 15.0 MPa, and the 28d ultimate flexural strength is all above 28 MPa. The higher 28d flexural first crack strength and 28d ultimate flexural strength indicate that the UHPC concrete prepared by the present invention has good durability. However, the blank group and the different preparation processes of the silica ash mortar will result in lower 28d compressive strength, 28d flexural first crack strength, and 28d ultimate flexural strength of the prepared UHPC concrete.

[0066] Among them, the expansion and T500 test: Wet the slump cone and smooth flat plate with a damp cloth, load the UHPC mixture into the slump cone in two layers, compact it by tamping, and level it. Lift the slump cone vertically and steadily while starting a stopwatch. After the mixture stops flowing, measure the expansion diameters in the two vertical directions and take the average value as the expansion. When the expansion diameter reaches 500mm, record the time taken as T500. The test must be carried out within 2 minutes of mixing completion.

[0067] Among them, compressive strength test: The UHPC mixture was placed into a 100mm×100mm×100mm cubic mold and vibrated to compaction. After 24 hours, the mold was removed and the mixture was cured in a curing chamber at a temperature of 20±2°C and a humidity of ≥95% to the specified age. During testing, the specimen was placed at the center of the lower platen of a pressure testing machine and loaded at a rate of 1.0-1.5MPa / s until failure. The maximum failure load was recorded, and the compressive strength was calculated by dividing the load by the compressive area.

[0068] Among them, the bending initial crack strength and ultimate bending strength test: A 100mm×100mm×400mm prism specimen was prepared and cured according to standard conditions. A three-point bending test was performed, with the specimen placed on supports (300mm apart) and a displacement meter installed mid-span. Loading was performed at a displacement rate of 0.05–0.1mm / min. The tensile surface was observed with a magnifying glass. The initial crack load was recorded when a crack ≥0.05mm appeared. Loading was continued until fracture, and the ultimate failure load was recorded. These values ​​were then substituted into the formula to calculate the initial crack strength and ultimate flexural strength.

[0069] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A superfluid UHPC based on super-dispersed silica slurry, characterized in that: It comprises the following components in parts by weight: Cement 400-600 parts, silica fume 50-150 parts, composite mineral admixture 500-800 parts, quartz sand 400-600 parts, steel fiber 150-300 parts, water reducer 20-50 parts, water 100-200 parts; Wherein, the silica fume is added in the following manner: The silica fume is first prepared into silica fume slurry by using a dispersant, alkali and water, and then the silica fume slurry is added into the dry mixture obtained by mixing other components.

2. The superfluid UHPC based on super-dispersed silica slurry according to claim 1, characterized in that: The dispersant comprises at least one of carboxyl-containing acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer and its salt, carboxylic acid-sulfonate copolymer and its salt, hydrolyzed polymaleic anhydride and its salt, maleic acid-acrylic acid copolymer / mixture and its salt, polyacrylic acid and its salt, polymaleic acid and its salt, and polybutene acid and its salt.

3. The superfluid UHPC based on super-dispersed silica slurry according to claim 2, characterized in that: The molecular weight of the dispersant is 1000-10000.

4. A superfluid UHPC based on super-dispersed silica slurry according to any one of claims 1 to 3, characterized in that: The pH value of the silica slurry is 8-13.

5. The superfluid UHPC based on super-dispersed silica slurry according to any one of claims 1 to 3, characterized in that: The solid content of the silica ash slurry is 40% to 70%.

6. The method for preparing superfluid UHPC based on ultra-dispersed silica slurry according to any one of claims 1 to 5, characterized in that: The steps include: S1. Preparation of silica ash slurry: The silica ash is first prepared into silica ash slurry using a dispersant, alkali and water, wherein the pH value of the prepared silica ash slurry is 8-13; S2. Preparation of UHPC dry mix: mixing the cement, the composite mineral admixture, and the quartz sand in proportion, stirring evenly, to obtain the UHPC dry mix; S3. Preparation of superfluid UHPC: slowly adding the silica ash slurry prepared in step S1 to the UHPC dry mix prepared in step S2 under stirring, mixing evenly, then adding a water reducer and water and stirring, and finally adding steel fiber and stirring evenly to obtain the superfluid UHPC.

7. The preparation method according to claim 6, characterized in that Step S1 specifically includes the following steps: S11, dissolving the alkali in water to form an alkaline solution, and then adding the dispersant to the alkaline solution to form a uniform solution; S12, gradually adding the silica fume to the solution prepared in step S11 to obtain a mixed system; S13, performing high-speed dispersion treatment on the mixed system, and then allowing it to stand and filter to obtain the silica ash slurry.

8. The preparation method according to claim 6, characterized in that In step S11, the base is a monovalent ion base.

9. The preparation method according to claim 6, characterized in that In step S12, the silica fume is added at a rate of 0.5-5 kg / min.

10. The preparation method according to claim 9, characterized in that The silica fume is added at a rate of 1-3 kg / min.

11. The preparation method according to claim 6, characterized in that In step S13, the equipment for performing the high-speed dispersion treatment includes a high-speed dispersion device, a homogenizer, a sand mill, a colloid mill or a ball mill.

12. The preparation method according to claim 6 or 7, characterized in that: In the process of preparing the silica ash slurry, the mass ratio of the silica ash to the water is (40-70): (30-60), and the amount of the dispersant used is 0.1%-2% based on the mass of the silica ash.

Images