High-strength, high-early hardening ultra-high performance concrete and its preparation method

Abstract

The present invention provides a rapid hardening ultra-high performance concrete and its preparation method and application. The components of the provided ultra-high performance concrete include red mud, silica fume, cement, quartz sand, water reducing agent, water and steel fiber. The red mud is added to the ultra-high performance concrete, and can be used to replace some commercial accelerators or gel materials for rapid hardening without the need for firing activation or dealkalization treatment for the red mud. It can effectively reduce the deposition of solid waste red mud in landfills, reduce the amount of gel materials such as cement used in the ultra-high performance concrete, reduce the CO2 emissions and costs during the preparation process of the ultra-high performance concrete, and promote the safe recycling and reuse of red mud. The provided rapid hardening ultra-high performance concrete has fast early strength evolution, high later strength, dense system, rapid structure formation, and can effectively inhibit the alkaline liquid leaching and radioactive radiation of red mud.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to a Chinese patent application filed with the China Patent Office on December 22, 2021, with application number CN202111580483.3 and title "High-Earth, High-Speed ​​Hardening Ultra-High-Performance Concrete and Its Preparation Method and Application," the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to the technical field of concrete, and more particularly to a high-early hardening, ultra-high performance concrete and its preparation method and application. [Background technology]

[0003] Red mud is an alkaline solid waste product generated during the alumina production process. Depending on the grade of bauxite, 1 to 1.5 tons of red mud is generated for every ton of alumina produced. Currently, red mud is mainly disposed of by landfilling, which not only takes up a large amount of land, but also causes a series of environmental problems, such as land salinization and groundwater pollution, due to the alkaline leaching caused by the high alkalinity of red mud (pH value 10 to 12.5).

[0004] Currently, the main means of recycling red mud include the preparation of adsorbents, the extraction of valuable metals, and the production of cement. However, red mud (especially Bayer process red mud) exhibits strong alkalinity (pH > 10), so in the above recycling cases, the red mud must be dealkalized or neutralized using an acidic neutralizer, which increases the cost and difficulty of red mud recycling. From the perspective of cement hydration, the high alkalinity of red mud accelerates the hydration of cement, promoting the setting and hardening of concrete and the achievement of early strength. However, when the amount of red mud mixed is low (mixing amount < 150 kg / m), 3 ), the supply of alkali is insufficient, and the early strength effect brought about is limited. A high amount of red mud mixed in, while exerting a rapid hardening effect, causes a significant deterioration in concrete performance. In addition, the large amount of red mud mixed in increases the radioactive risk of the product.

[0005] In summary, existing red mud recycling and reuse technologies have problems such as complicated processes (requiring a dealkalization pretreatment process) and questionable alkali resistance and radioactivity performance of the products. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to provide a rapid-hardening, high-performance concrete, and its preparation method and application. In this invention, red mud is added to the ultra-high-performance concrete in a high amount as an early-hardening agent, and under the premise of ensuring the product's excellent mechanical properties and durability, the concrete's solidification time is significantly shortened, the early strength development is promoted, and at the same time, the accumulation of red mud and the resulting environmental pollution problems are alleviated, and the alkaline leaching of red mud and the radioactive risks are significantly reduced. [Means for solving the problem]

[0007] To achieve the above objectives, the present invention provides the following technical solutions: The present invention provides an ultra-high performance concrete of high-early hardening type, which, when calculated by mass fraction, has the following properties: It contains the following ingredients: 110-180 parts red mud, 70-80 parts silica fume, 130-290 parts cement, 400-500 parts quartz sand, 10-15 parts water reducer, 80-100 parts water and 50-75 parts steel fiber.

[0008] Preferably, the particle size of the quartz sand is 0.075 to 0.6 mm, The particle size of the red mud is 0.01 to 0.075 mm, The average particle size of the silica fume is 300 nm, and the activity index is ≧100%.

[0009] Preferably, the water-reducing agent is a polycarboxylic acid-based high-performance water-reducing agent, the fixed content of the polycarboxylic acid-based high-performance water-reducing agent is 20%, and the water-reducing rate is ≧35%.

[0010] Preferably, the cement is ordinary Portland cement having a strength level of 52.5.

[0011] Preferably, the steel fibers have a length of 13 mm, a diameter of 0.65 mm, and a tensile strength of ≥ 2000 MPa, and the steel fibers are long, straight, copper-plated steel fibers.

[0012] Preferably, the red mud is Bayer process red mud.

[0013] Preferably, the specific gravity of the quartz sand is 2560 kg / m 3 is.

[0014] The present invention also provides a method for preparing the high-strength, high-hardness, ultra-high performance concrete described in the above technical solution, performing a first mixing of silica fume, cement, quartz sand and red mud to obtain a first premixture; performing second mixing on the first premix, water, and a water-reducing agent to obtain a second premix; and performing a third mixing of the second premix and the steel fibers to obtain the high-early-strength, high-speed-hardening ultra-high performance concrete.

[0015] Preferably, the mixing time of the first mixing is 120 to 180 seconds, the mixing time of the second mixing is 240 to 360 seconds, and the mixing time of the third mixing is 60 seconds.

[0016] The present invention also provides the application of the high-strength, high-early hardening ultra-high performance concrete according to the above technical solution or the high-strength, high-early hardening ultra-high performance concrete obtained by the preparation method according to the above technical solution in building materials or decorative materials.

[0017] Preferably, the application comprises: A step of pouring high-early hardening ultra-high performance concrete into a mold, and then vibrating, leaving it to stand, and demolding it to obtain a prefabricated member; maintaining the prefabricated element under steam maintenance conditions; or Or, and sequentially pouring and laminating maintenance for the high-early hardening ultra-high performance concrete.

[0018] Preferably, the vibration time is 60 to 180 seconds.

[0019] Preferably, the standing time is 3 hours.

[0020] Preferably, the steam maintenance conditions include increasing the temperature to 45°C at a rate of 5°C / min, performing preventive maintenance for 12 hours, then increasing the temperature to 100°C at a rate of 11°C / min, performing steam maintenance for 6 hours, and finally cooling to room temperature at a rate of 6.7°C / h.

[0021] The present invention provides an ultra-high performance concrete of the high-early hardening type, which contains, calculated by mass fraction, 110 to 180 parts of red mud, 70 to 80 parts of silica fume, 130 to 290 parts of cement, 400 to 500 parts of quartz sand, 10 to 15 parts of a water-reducing agent, 80 to 100 parts of water, and 50 to 75 parts of steel fiber. [Effects of the Invention]

[0022] In this invention, the high alkalinity of red mud significantly improves the alkalinity of ultra-high performance concrete (UHPC) slurry, promoting cement hydration, shortening the induction period, accelerating solidification, and improving early strength. Furthermore, the small particle size of red mud (between silica fume and cement) provides nucleation sites for hydration products, accelerating hydration, shortening solidification time, and improving early strength. Based on this, by optimizing the composition of cement-based materials and minerals, the volcanic ash effect and filling effect of red mud are fully restored, resulting in the preparation of ultra-high strength, highly durable cement-based materials. The present invention adds red mud to UHPC to replace some gel materials, alleviating the problem of red mud accumulation and the resulting environmental pollution, reducing the amount of gel materials such as cement and silica fume used, reducing CO2 emissions, reducing the cost of UHPC, and promoting the safe recycling and utilization of red mud. Furthermore, the high-strength, fast-hardening UHPC concrete structure provided by this invention is dense, providing better protection against alkaline leaching from red mud. Finally, the high-early hardening ultra-high performance concrete provided by the present invention can shield the radioactivity of red mud and significantly reduce radioactive risks, which is beneficial to the safety and long-term operation and maintenance of red mud-based ultra-high performance concrete components, and realizes safe, efficient and high-allocation recycling of red mud.

[0023] The test results of the example show that the amount of alkaline leaching of the high-early hardening ultra-high performance concrete provided by the present invention is low, meets the standard of "Method for Determining Leachable Harmful Substances in Wall Materials", and the radionuclide value is significantly reduced compared to red mud, and at the same time, the internal irradiation index I Ra and external irradiation index I r The values ​​are all smaller than that of red mud and smaller than 1, meeting the internal and external irradiation index indices required by Chinese standards.

[0024] The present invention also provides a method for preparing the high-strength, high-early hardening, ultra-high performance concrete described in the above solution, in which the high-strength, high-early hardening, ultra-high performance concrete is obtained by mixing and preparing each component, and sedimentation and accumulation of components are avoided while ensuring sufficient dispersion of particles and hydration of gel material.

[0025] The present invention also provides applications for the rapid-hardening ultra-high performance concrete described in the above solution, which can be used in building materials and decorative materials. The rapid-hardening ultra-high performance concrete provided by the present invention is reddish-brown in color and has a certain aesthetic effect. This material meets the requirements of national standards GB6566-2010 "Controlled Amounts of Radionuclides in Building Materials" and GB / T39804-2021 "Determination Method for Leachable Harmful Substances in Wall Materials," reducing building material costs and meeting safety, economic, environmental protection, and other requirements. It can be used in roads, bridge panel paving, and prefabricated components, ensuring safe and stable operation and maintenance of the components while reducing costs and shortening construction periods. DETAILED DESCRIPTION OF THE INVENTION

[0026] The present invention provides an ultra-high performance concrete of high-early hardening type, which, when calculated by mass fraction, has the following properties: It contains the following ingredients: 110-180 parts red mud, 70-80 parts silica fume, 130-290 parts cement, 400-500 parts quartz sand, 10-15 parts water reducer, 80-100 parts water and 50-75 parts steel fiber.

[0027] Unless otherwise specified, there are no special requirements for the source of each component in the high-early hardening, high-performance concrete described in the present invention, and any source known to those skilled in the art may be used.

[0028] When calculated by mass fraction, the high-early-strength, fast-hardening ultra-high performance concrete provided by the present invention contains 110 to 180 parts of red mud, preferably 115 to 179 parts, and more preferably 119 to 178 parts. In the present invention, the particle size of the red mud is preferably 0.01 to 0.075 mm, more preferably 0.02 to 0.06 mm, and even more preferably 0.03 to 0.05 mm. In the present invention, the red mud is preferably red mud produced by the Bayer process.

[0029] Based on the mass fraction of the red mud, the high-early hardening ultra-high performance concrete provided by the present invention contains 70-80 parts, preferably 71-78 parts, more preferably 72-76 parts of silica fume. In the present invention, the average particle size of the silica fume is preferably 300 nm. In the present invention, the activity index of the silica fume is preferably ≧100%. In one embodiment of the present invention, the silica fume is preferably purchased from EK Corporation.

[0030] Based on the mass fraction of the red mud, the high-early hardening, rapid-setting ultra-high performance concrete provided by the present invention contains 130 to 290 parts, preferably 140 to 280 parts, more preferably 150 to 270 parts of cement. In the present invention, the cement is preferably ordinary Portland cement having a strength level of 52.5.

[0031] The high-early hardening, rapid-setting ultra-high performance concrete provided by the present invention contains 400 to 500 parts, preferably 410 to 490 parts, and more preferably 420 to 480 parts, of quartz sand based on the mass fraction of the red mud. In the present invention, the particle size of the quartz sand is preferably 0.075 to 0.6 mm, more preferably 0.1 to 0.5 mm, and even more preferably 0.2 to 0.4 mm. In the present invention, the quartz sand preferably has a continuous particle size distribution and a specific gravity of preferably 2560 kg / m 3 In the embodiment of the present invention, the quartz sand is preferably purchased from Hunan Yangmao Quartz Sand Filter Material Co., Ltd.

[0032] Based on the mass fraction of the red mud, the high-early hardening ultra-high performance concrete provided by the present invention contains 10 to 15 parts, preferably 11 to 14 parts, and more preferably 12 to 13 parts of a water-reducing agent. In the present invention, the water-reducing agent is preferably a polycarboxylic acid-based superplasticizer. In the present invention, the fixed content of the polycarboxylic acid-based superplasticizer is preferably 20%. In the present invention, the water-reducing ratio of the water-reducing agent is preferably ≧35%. In a specific embodiment of the present invention, the polycarboxylic acid-based superplasticizer is preferably a polycarboxylic acid-based superplasticizer produced by Jiangsu Subote Advanced Materials Co., Ltd.

[0033] Based on the mass fraction of the red mud, the high-early hardening, ultra-high performance concrete provided by the present invention contains 80 to 100 parts, preferably 83 to 95 parts, more preferably 85 to 93 parts of water.

[0034] The high-early hardening, rapid-setting ultra-high performance concrete provided by the present invention contains 50 to 75 parts, preferably 55 to 70 parts, more preferably 60 to 65 parts, of steel fibers based on the mass fraction of the red mud. In the present invention, the length of the steel fibers is preferably 13 mm, the diameter is preferably 0.65 mm, and the tensile strength is preferably ≥ 2000 MPa. In the present invention, the steel fibers are preferably long, straight, copper-plated steel fibers.

[0035] The present invention also provides a method for preparing the high-strength, high-hardness, ultra-high performance concrete described in the above technical solution, performing a first mixing of silica fume, cement, quartz sand and red mud to obtain a first premixture; performing second mixing on the first premix, water, and a water-reducing agent to obtain a second premix; and performing a third mixing of the second premix and the steel fibers to obtain the high-early-strength, high-speed-hardening ultra-high performance concrete.

[0036] In the present invention, silica fume, cement, quartz sand, and red mud are subjected to first mixing to obtain a first premixture. In the present invention, the mixing time of the first mixing is preferably 120 to 180 seconds, more preferably 130 to 170 seconds. In the present invention, the equipment for the first mixing is preferably a mortar stirring pot. In the present invention, the first mixing is preferably stirring, and the rotation speed of the stirring is preferably 135 to 145 rpm, more preferably 138 to 143 rpm, and the time is preferably 90 seconds.

[0037] After obtaining the first premix, the present invention performs a second mixing of the first premix, water, and a water-reducing agent to obtain a second premix.

[0038] In the present invention, the mixing time of the second mixing is preferably 240 to 360 seconds, more preferably 250 to 350 seconds. In the present invention, the second mixing is preferably carried out under stirring conditions, and the rotation speed of the stirring is preferably 135 to 145 rpm, more preferably 138 to 143 rpm.

[0039] After obtaining the second premix, the present invention performs a third mixing on the second premix and steel fibers to obtain the high-early-strength, high-hardening, ultra-high performance concrete.

[0040] In the present invention, the mixing time of the third mixing is preferably 60 seconds. In the present invention, the third mixing is preferably carried out under stirring conditions, and the rotation speed of the stirring is preferably 135 to 145 rpm, more preferably 138 to 143 rpm.

[0041] The present invention also provides the application of the high-strength, high-hardening, ultra-high performance concrete described in the above solution in building materials or decorative materials.

[0042] In the present invention, the application of the high-strength, high-hardening ultra-high performance concrete preferably includes the steps of pouring the high-strength, high-hardening ultra-high performance concrete into a mold, and then vibrating, leaving and demolding the mold to obtain a prefabricated component; and maintaining the prefabricated component under steam maintenance conditions; Or, and sequentially pouring and laminating maintenance for the high-early hardening ultra-high performance concrete.

[0043] In the present invention, the vibration time is preferably 60 to 180 seconds, more preferably 70 to 170 seconds. In the present invention, the standing time is preferably 3 hours, and the standing is preferably carried out under conditions where a thin plastic film is covered. In the present invention, the steam maintenance conditions preferably include heating to 45°C at a rate of 5°C / min and performing preventive maintenance for 12 hours, then heating to 100°C at a rate of 11°C / min and performing steam maintenance for 6 hours, and finally cooling to room temperature at a rate of 6.7°C / h.

[0044] In order to further explain the present invention, the high-early hardening, high-performance concrete provided by the present invention will be described in detail below with reference to the drawings and examples, which should not be construed as limiting the scope of protection of the present invention.

[0045] Example 1 Calculated by mass fraction, 72 parts of silica fume, 288 parts of cement, 119 parts of red mud, and 425 parts of quartz sand were mixed and added to a mortar mixing pot and stirred for 90 seconds at a rotation speed of 140±5 rpm to obtain a first premix. 84 parts of water and 12 parts of a water-reducing agent were added to the obtained first premix and stirred for 240 seconds at a rotation speed of 140±5 rpm. After the mortar was formed, 50 parts of steel fiber were added and stirred for 60 seconds at a rotation speed of 140±5 rpm to obtain an early-hardening, high-performance concrete.

[0046] The red mud in the fast hardening ultra high performance concrete replaced 40% of the original volume of cement and was recorded as VC40.

[0047] Example 2 Calculated by mass fraction, 72 parts of silica fume, 180 parts of cement, 148 parts of red mud, and 425 parts of quartz sand were mixed and added to a mortar mixing pot and stirred for 90 seconds at a rotation speed of 140±5 rpm to obtain a first premix. 84 parts of water and 12 parts of a water-reducing agent were added to the obtained first premix and stirred for 240 seconds at a rotation speed of 140±5 rpm. After the mortar was formed, 50 parts of steel fiber were added and stirred for 60 seconds at a rotation speed of 140±5 rpm to obtain an early-hardening, high-performance concrete.

[0048] The red mud in the fast hardening ultra high performance concrete replaced 50% of the original volume of cement and was recorded as VC50.

[0049] Example 3 Calculated by mass fraction, 72 parts of silica fume, 144 parts of cement, 178 parts of red mud, and 425 parts of quartz sand were mixed and added to a mortar mixing pot and stirred for 90 seconds at a rotation speed of 140±5 rpm to obtain a first premix. 84 parts of water and 12 parts of a water-reducing agent were added to the obtained first premix and stirred for 240 seconds at a rotation speed of 140±5 rpm. After the mortar was formed, 50 parts of steel fiber were added and stirred for 60 seconds at a rotation speed of 140±5 rpm to obtain an early-strength, fast-hardening, ultra-high-performance concrete.

[0050] The red mud in the fast hardening ultra high performance concrete replaced 60% of the original volume of cement and was recorded as VC60.

[0051] (Comparative Example 1) Calculated by mass fraction, 72 parts of silica fume, 360 parts of cement, and 425 parts of quartz sand were mixed and added to a mortar mixing pot and stirred for 90 seconds at a rotation speed of 140±5 rpm to obtain a premix. 84 parts of water and 12 parts of water reducer were added to the premix and stirred for 240 seconds at a rotation speed of 140±5 rpm. After the mortar was formed, 50 parts of steel fiber were added and stirred for 60 seconds at a rotation speed of 140±5 rpm to obtain an ultra-high performance concrete without using red mud, which was recorded as Ref. 1.

[0052] (Comparative Example 2) Calculated by mass fraction, 69 parts of cement, 103 parts of red mud, and 517 parts of quartz sand were mixed and added to a mortar mixing pot and stirred for 90 seconds at a rotation speed of 140±5 rpm to obtain a premix, to which 86 parts of water were added and stirred for 240 seconds at a rotation speed of 140±5 rpm to obtain an ultra-high performance concrete that did not use silica fume, water reducer, or steel fiber, and this was recorded as Ref.2.

[0053] (Test example 1) The ultra-high performance concretes of Examples 1 to 3 and Comparative Examples 1 and 2 were subjected to tests on the material solidification time, 3-hour strength, 28-day strength and durability, and the test methods were as follows.

[0054] Condensation time: Test the condensation time of UHPC mortar according to JGJ / T70-2009《Standard for basic performance test method of construction mortar》 Compressive strength and bending strength determination: The ultra-high-speed hardening concretes obtained in Examples 1-3 and Comparative Examples 1-2 were poured into molds. The molds were placed on a vibrating table and vibrated for 180 seconds to achieve a high degree of vibration. The molded surfaces were then covered with a thin plastic film. After 1 day, the molds were demolded to obtain prefabricated components. The prefabricated components were maintained under standard maintenance conditions (temperature: 18-22°C, relative humidity: greater than 95%). After maintenance, the prefabricated components were dried. Testing was performed in accordance with GB17671-1999 "Testing Methods for Strength of Cement Mortar." Compressive strength and bending strength were measured using a universal pressure tester using molded components measuring 40mm x 40mm x 40mm and 40mm x 40mm x 160mm. The durability was evaluated by an electric flux test and a quick chloride ion migration test (RCM) using a cylindrical molded member with a diameter of 100 mm and a height of 50±2 mm.

[0055] The test results are shown in Table 1.

[0056] Table 1 Performance tests of ultra-high performance concretes of Examples 1 to 3 and Comparative Examples 1 and 2 JPEG0007776903000001.jpg38123

[0057] Table 1 shows that the early-strength, rapid-hardening ultra-high-performance concretes obtained in Examples 1-3 had a short initial set time, achieving initial set in 20-40 minutes and final set within 60 minutes. The 3-hour strengths of the early-strength, rapid-hardening ultra-high-performance concretes obtained in Examples 1-3 were 15.1-22.7 MPa. The early-strength, rapid-hardening ultra-high-performance concretes obtained in Examples 1-3 had excellent 28-day strength and durability, achieving 28-day strengths of >100 MPa, achieving ultra-high strength, and electric flux <100°C, falling within the negligible range of chloride ion penetration. Comparative Example 1 was an ultra-high-performance concrete that did not incorporate red mud early-strengthening agents. Its set time was 369-479 minutes, did not set in 3 hours, and did not meet the requirements for early-strength, rapid-hardening concrete. Comparative Example 2 is a concrete system that only contains red mud early-strengthening agent, and its early strength is low, only 1.1 MPa at 3 hours and only 19.3 MPa at 28 days. This shows that in order to achieve the rapid hardening effect of a conventional concrete system, the amount of red mud added needs to be significantly increased. However, the high amount of red mud added significantly reduced the early strength of the conventional concrete and also limited the subsequent strength development.

[0058] The electric flux of the high-strength, high-early hardening ultra-high performance concretes obtained in Examples 1 to 3 of the present invention was all lower than that of the ultra-high performance concretes in Comparative Examples 1 and 2, indicating that the durability performance of the high-strength, high-early hardening ultra-high performance concretes provided by Examples 1 to 3 of the present invention is higher than that of the conventional ultra-high performance concrete in Comparative Example 1 and the ordinary concrete in Comparative Example 2.

[0059] (Test example 2) The ultra-high performance concrete obtained in Examples 1 to 3 was subjected to radioactivity and alkalinity tests. The test samples were polished to granules smaller than 0.16 mm, sealed, and left for 7 days. The radioactivity of each nuclide was tested using a low-energy multi-channel gamma energy spectrometer, and the internal irradiation index (I Ra ), external radiation index (I r ) was calculated and the statistical results are shown in Table 2.

[0060] Table 2: Radioactivity test and alkalinity test results for Examples 1 to 3 JPEG0007776903000002.jpg43123

[0061] From Table 2, it can be seen that the ultra-high performance concretes of the high-early hardening type obtained in Examples 1 to 3 have low specific radioactivity, 226 The Ra specific radioactivity is 40-95 Bq / kg. 232 The specific radioactivity of Th is 95-150 Bq / kg. 40 The Ka specific radioactivity is 320-365Bq / kg, and the internal and external irradiation index is I Ra and I r The values ​​of are all smaller than 1, and satisfy the internal and external irradiation indexes required by GB6566-2010 "Limited Amounts of Radioactive Nuclides in Building Materials." + It has low ion content and meets the safety standard for building materials GBT39804-2021 "Determination of leachable hazardous substances in wall materials."

[0062] According to a simplified life cycle assessment (Damineli BL, Kemeid FM, Aguiar PS, et al. Measuring the eco-efficiency of cement use[J]. Cement and Concrete Composites, 2010, 32(8):555-562) and Aitcin's research (Aitcin PC. Cements of yesterday and today: concrete of tomorrow[J]. Cement and Concrete Research, 2000, 30(9):1349-1359), the carbon emissions and costs under the unit performance index (1 MPa) were used as indicators to evaluate the environmental effects and benefits of concrete and the economic benefits. The energy consumption (carbon dioxide emissions) and costs of the high-early hardening ultra-high-strength concrete obtained in Examples 1 and 2 and the ultra-high-performance concrete obtained in Comparative Example 1 were compared, and the results are shown in Table 3.

[0063] Table 3: Energy consumption and cost comparison table for concrete JPEG0007776903000003.jpg81121

[0064] From Table 3, it can be seen that the energy consumption and cost of preparing ultra-high performance concrete is high, and the carbon dioxide emissions are 462.9 kg / m 3 The cost is 4274 yuan / m 3 It was found that the high-early hardening ultra-high performance concrete provided by the present invention has low energy consumption and low cost, and the carbon dioxide emission of VC60 is 138.5 kg / m 3 The cost of VC60 is 2,309 yuan / m 3 It can be seen that the preparation cost and energy consumption of the high-early hardening ultra-high performance concrete provided by the present invention are both lower than those of ordinary ultra-high performance concrete.

[0065] Taking VC60 as an example, VC60 can reduce the preparation cost per cubic meter of ultra-high performance concrete, reduce CO2 emissions by 70.7%, and solidify and recover 371 kg of red mud. Taking an actual bridge construction as an example, a 15 cm thick steel-ultra-high performance concrete composite bridge deck was laid, of which the total amount of ultra-high performance concrete used was 6618.8 m 3 The statistics of concrete usage for bridge decks are shown in Table 4.

[0066] Table 4: Statistical table of the amount of ultra-high performance concrete used in bridge decks JPEG0007776903000004.jpg6898

[0067] From Table 4, it can be seen that by selecting the ultra-high performance concrete prepared by the present invention, the direct cost can be reduced by about 12.98 million yuan, the carbon dioxide emission treatment cost can be reduced by 470,000 yuan (the treatment cost is calculated according to 0.22 yuan / kg), and the red mud can be solidified by about 1,200 tons.

[0068] From the above examples, it can be seen that the high-early-strength, fast-hardening ultra-high performance concrete provided by the present invention not only has higher early strength and shorter solidification time, but also has ultra-high later strength, meeting the strength and construction time requirements of bridge construction and ultra-high performance concrete decorative elements, while also having relatively high durability, low preparation cost, and low energy consumption, and also achieving safe and efficient recycling and reuse of red mud.

[0069] The above description of the examples only contributes to understanding the method of the present invention and its core idea. It should be noted that those skilled in the art can make some improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications are also included in the scope of protection of the claims of the present invention. A person skilled in the art will recognize that several modifications to these examples are obvious, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to these examples shown herein, but belongs to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. It is an ultra-high performance concrete of the high-early hardening type, and when calculated by mass parts, A rapid hardening, ultra-high performance concrete consisting of 119 to 178 parts red mud, 72 parts silica fume, 144 to 288 parts cement, 425 parts quartz sand, 12 parts water reducer, 84 parts water and 50 parts steel fiber.

2. The particle size of the quartz sand is 0.075 to 0.6 mm, The particle size of the red mud is 0.01 to 0.075 mm, 2. The ultra-high performance concrete of claim 1, wherein the silica fume has an average particle size of 300 nm and an activity index of 100% or more.

3. 2. The ultra-high performance concrete of claim 1, wherein the water-reducing agent is a polycarboxylic acid-based high-performance water-reducing agent, the fixed content of the polycarboxylic acid-based high-performance water-reducing agent is 20%, and the water-reduction rate is 35% or more.

4. 2. The ultra-high performance concrete of claim 1, wherein the steel fibers have a length of 13 mm, a diameter of 0.65 mm, and a tensile strength of ≥ 2000 MPa, and the steel fibers are straight copper-plated steel fibers.

5. 3. The ultra-high performance concrete of claim 1, wherein the red mud is red mud produced by the Bayer process.

6. The specific gravity of the quartz sand is 2560 kg / m ３ 3. The ultra-high performance concrete of claim 1, wherein the high-strength, high-hardening type is

7. performing a first mixing of silica fume, cement, quartz sand and red mud to obtain a first premixture; performing a second mixing of the first premix, water, and a water-reducing agent to obtain a second premix; and performing a third mixing of the second premix and the steel fibers to obtain the rapid-hardening ultra-high performance concrete.

8. 8. The method according to claim 7, wherein the mixing time of the first mixing is 120-180 s, the mixing time of the second mixing is 240-360 s, and the mixing time of the third mixing is 60 s.

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