Super-early-strength steel slag-based ultra-high-performance fiber reinforced concrete under induced eddy current as well as preparation method and application thereof
By using electromagnetic induction coils for induction eddy current heating in ultra-high performance fiber reinforced concrete, the problems of extended set time and early strength reduction after steel slag powder are incorporated are solved, and early strength improvement and final strength are guaranteed.
Patent Information
- Application Number
- CN202411910741.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-24
- Publication Date
- 2025-05-13
Smart Images
Figure CN119977445A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of cement concrete, and specifically relates to an ultra-early-strength steel slag-based ultra-high performance fiber-reinforced concrete under induced eddy current, and a preparation method and application thereof. Background Art
[0002] Steel slag is an inevitable solid waste produced in the steelmaking process. Although the specific chemical composition of different steel slags may fluctuate, its main chemical composition is the same, which is CaO, SiO2, Al2O3, Fe2O3, MgO and a small amount of MnO, FeO, P2O5 and metal Fe. The main mineral components are dicalcium silicate, tricalcium silicate, RO phase, free calcium oxide, free magnesium oxide and tetracalcium aluminoferrate. At present, the main use of steel slag is in the field of building materials, most of which are used as cement concrete admixtures. The finely ground steel slag powder is evenly distributed in the cementitious material, the particle expansion rate is small, and there will be no poor stability problems at the appropriate dosage. As an underutilized industrial waste slag, steel slag should be used in concrete. Research should be strengthened to give full play to its greater application value in cement concrete and realize the high value of solid waste resources.
[0003] High performance and long life are one of the important ways to achieve low-carbon development of concrete. Ultra High Performance Fibre Reinforced Concrete (UHPFRC), as a new type of cement-based material with excellent mechanical properties and durability, has attracted great attention from scholars and engineers at home and abroad in the past decade, and has quickly become a hot spot in the field of scientific research and engineering application. Although the research and application of UHPFRC materials have developed rapidly, its material composition characteristics such as high cementitious materials and water reducer dosage and low water-cement ratio have caused a large amount of cement in the system to be unhydrated and only participate in physical filling, resulting in material waste. Using steel slag powder to replace part of cement to prepare UHPFRC, a high-value civil engineering material, is of great significance for realizing the high-value utilization of steel slag and the low-carbon green development of UHPFRC materials. However, since steel slag powder contains free calcium oxide, its large amount of use in UHPFRC materials will prolong the setting time of concrete, thereby causing a decrease in early strength, which is not conducive to the application of UHPFRC.
[0004] How to add a large amount of steel slag powder into UHPFRC materials without affecting the early strength and final strength is a difficulty in this field. Summary of the invention
[0005] In view of the deficiencies in the prior art, one of the objects of the present invention is to provide an improved method for preparing steel slag-based ultra-high performance fiber reinforced concrete, which can incorporate a large amount of steel slag into the ultra-high performance fiber reinforced concrete and ensure that the concrete has excellent early strength and final strength.
[0006] In order to achieve the above object, the technical solution adopted by the present invention is:
[0007] A method for preparing steel slag-based ultra-high performance fiber-reinforced concrete, wherein the steel slag-based ultra-high performance fiber-reinforced concrete comprises the following components in parts by weight: 400-600 parts of cement; 100-180 parts of silica fume; 150-200 parts of fly ash; 150-250 parts of steel slag; 980-1200 parts of quartz sand; 160-200 parts of water; 30-40 parts of water reducer; and 140-160 parts of steel fiber. The preparation method comprises the steps of molding the raw materials to obtain a molded body, performing eddy current induction heating on the molded body using an electromagnetic induction coil, and performing subsequent curing.
[0008] In the present invention, the electromagnetic induction coil generates heat inside the concrete forming body when an alternating current voltage is applied, so that the concrete is hydrated. This heating generated by electromagnetic induction is an induced eddy current form.
[0009] In the prior art, UHPFRC materials usually have high cementitious materials and water reducing agent dosage, and low water-cement ratio, which will lead to a large amount of cement in the system that has not been fully hydrated. The added cement only participates in the physical filling effect, which wastes the addition of cement and fails to achieve sufficient strength. When adding steel slag powder, because it contains free calcium oxide, when its addition amount is large, it will cause the setting time of concrete to be prolonged, resulting in a decrease in the early strength of concrete products, limiting its application scenarios, especially application scenarios with high requirements for early strength. The inventors of this application have found through research that after the steel slag-based ultra-high performance fiber reinforced concrete is formed, it is subjected to induced eddy current heating by an external electromagnetic induction coil to generate heat inside it, so that the concrete is fully hydrated, which can significantly improve the early strength of this type of concrete and ensure the final strength at the same time. In addition, when the amount of steel slag added is high, excellent early strength and final strength can still be guaranteed, so that the performance can still be guaranteed when the cost of concrete is reduced. The principle of induction heating is that, firstly, steel slag, as an iron-containing material, together with steel fibers, constructs a very uniform micro-mesoscopic iron phase network inside the ultra-high performance fiber reinforced concrete. Secondly, by applying an induction coil on the surface of the concrete, through the two steps of electromagnetism and magnetic heating, the iron phase inside the concrete generates eddy currents, thereby evenly generating heat inside the concrete, accelerating the hydration of the concrete and improving the early strength of the concrete.
[0010] In addition, the present application designs the dosage of raw materials for concrete based on the principle of maximum density of the system, further ensuring that the steel slag-based ultra-high performance fiber-reinforced concrete has significantly improved early strength and excellent final strength.
[0011] In some specific embodiments, the electromagnetic induction coil is arranged outside the molded body and is 10 to 15 cm away from the molded body. In the present invention, the shape of the molded body is not particularly limited, for example, it can be square, etc. When the surface of the molded body is flat, the aforementioned distance is the vertical distance from the surface of the molded body to the coil. In the present invention, the electromagnetic induction coil can be a coil made of ordinary wire.
[0012] In some specific embodiments, the voltage of the electromagnetic induction coil is 500-700V, the frequency is 100-150KHz, and the output power is 7-8KW.
[0013] In some specific embodiments, the electromagnetic induction coil is arranged outside the molded body and is 10-15 cm away from the molded body. The voltage of the electromagnetic induction coil is 580-620V, the frequency is 120-130KHz, and the output power is 7.5-8KW.
[0014] At a specific voltage, the distance between the electromagnetic induction coil and the concrete body will affect the speed and degree of the induction eddy current heating inside the concrete body, thereby affecting the speed of the internal cement hydration, and ultimately affecting the early strength of the concrete product. The above distance and voltage of the present invention can further ensure that the steel slag-based ultra-high performance fiber-reinforced concrete has excellent early strength and final strength.
[0015] In some specific embodiments, the induction eddy current heating time is 4 to 6 hours.
[0016] In some specific embodiments, the subsequent curing is performed at a temperature of 18-22° C. and a humidity of 95%-100%.
[0017] In some specific embodiments, the molding is casting molding.
[0018] In some specific embodiments, the induction eddy current heating is performed 20-30 hours after the molding is completed.
[0019] In some specific embodiments, the cement is a silicate cement having a strength of not less than 52.5 MPa, such as ordinary silicate cement with a strength grade of 52.5.
[0020] In some specific embodiments, the SiO2 content of the silica fume is above 90%, for example, ordinary silica fume available on the market that meets the above content.
[0021] In some specific embodiments, the fly ash is grade I fly ash.
[0022] In some specific embodiments, the basicity coefficient of the steel slag is greater than 2.5.
[0023] In some specific embodiments, the particle size of the quartz sand is 0.01-1.25 mm.
[0024] In some specific embodiments, the steel fiber is a straight copper-coated steel fiber.
[0025] In some specific embodiments, the steel fiber has a length of 10-20 mm and a diameter of 0.10-0.30 mm.
[0026] In some specific embodiments, the tensile strength of the steel fiber is above 2000 MPa.
[0027] In some specific embodiments, the water reducer is a polycarboxylate water reducer, and the solid content is 10%-30%.
[0028] In some specific embodiments, the water reducing agent has a water reducing rate of 30% or more.
[0029] In some specific embodiments, the preparation method comprises the following steps: 1) weighing cement, silica fume, fly ash, steel slag powder, quartz sand, steel fiber, water reducer, and water respectively according to weight parts; 2) mixing the weighed cement, silica fume, fly ash, and steel slag powder for 20-200 seconds, then pouring quartz sand into the powder, stirring for 20-200 seconds, then pouring water and water reducer into the mixture, stirring until the raw materials become slurry, and then automatically stirring for 2-6 minutes according to the standard mortar stirring procedure, then slowly and evenly pouring steel fiber in the manual slow stirring mode of the standard mortar machine, slowly stirring for 2-6 minutes, and finally pouring The concrete sample is cast into a mold; 3) after 20-30 hours of molding, the sample is subjected to eddy current heating by an external electromagnetic induction coil, wherein the distance between the induction coil and the upper surface of the sample is 10-15 cm, the output voltage of the induction heating coil is 580-620 V, the frequency is 120-130 KHz, and the output power is 7.5-8 KW. Heat is generated from the inside of the concrete sample by eddy current heating to accelerate the hydration of the concrete. The heating time is 4-6 hours, and then the concrete sample is placed in a standard curing room for curing to obtain the steel slag-based ultra-high performance fiber reinforced concrete.
[0030] The present invention also provides steel slag-based ultra-high performance fiber-reinforced concrete prepared by the preparation method of the aforementioned steel slag-based ultra-high performance fiber-reinforced concrete.
[0031] Furthermore, the 2-day compressive strength of the steel slag-based ultra-high performance fiber-reinforced concrete is 80-100 MPa, and the 28-day compressive strength is 150-170 MPa.
[0032] In the present invention, 2-day compressive strength refers to the compressive strength after a subsequent curing time of 2 days, and 2-day compressive strength refers to the compressive strength after a subsequent curing time of 28 days. The curing environment is the aforementioned temperature of 18-22°C and humidity of 95%-100%, such as standard curing.
[0033] The present invention also provides application of the aforementioned steel slag-based ultra-high performance fiber-reinforced concrete in the field of construction.
[0034] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:
[0035] The ultra-early-strength steel slag-based ultra-high performance fiber-reinforced concrete of the present invention has a strength of more than 89MPa in 2 days and a compressive strength of more than 158MPa in 28 days. The present invention realizes the resource utilization of large amounts of steel slag and the later strength increase of ultra-high performance fiber-reinforced concrete on the basis of ensuring the early strength of steel slag-based ultra-high performance fiber-reinforced concrete, and the steel slag content in the cementitious material is more than 15%. BRIEF DESCRIPTION OF THE DRAWINGS
[0036] Figure 1 It is a schematic diagram of the induction eddy current heating of steel slag-based ultra-high performance fiber reinforced concrete according to the present invention. DETAILED DESCRIPTION
[0037] The technical solution of the present invention is described in detail below in conjunction with specific embodiments so that those skilled in the art can better understand and implement the technical solution of the present invention, but the present invention is not limited to the scope of the examples.
[0038] Some of the raw materials used in the following examples and comparative examples are from the following sources:
[0039] Cement, ordinary Portland cement with strength grade 52.5 and 28d compressive strength of 58.2MPa;
[0040] Silica fume, common commercial silica fume, SiO2 content 93%;
[0041] Fly ash, ordinary commercial fly ash, grade Ⅰ;
[0042] Steel slag powder, high basicity ordinary steel slag powder with qualified stability, basicity is 2.54;
[0043] Quartz sand, commercially available quartz sand, particle size range 0-1.25 mm;
[0044] Steel fiber, length 13mm, diameter 0.2mm, tensile strength 2000MPa;
[0045] Water reducing agent, solid content 20%, water reduction rate 30%;
[0046] Water, ordinary tap water.
[0047] Example 1
[0048] This embodiment provides a steel slag-based ultra-high performance fiber-reinforced concrete, the raw material formula (weight parts) is shown in Table 1, and the preparation method is as follows:
[0049] Weigh each raw material according to the weight portion in Table 1; mix and stir the weighed cement, silica fume, fly ash, and steel slag powder for 45 seconds, then pour quartz sand into the powder and stir for 45 seconds, then pour water and water reducer into the mixture, stir until the raw materials become slurry, and then stir automatically for 240 seconds according to the standard mortar mixing procedure, then slowly and evenly pour the steel fiber into the standard mortar machine in the manual slow stirring mode, stir slowly for 240 seconds, and finally pour into the mold to cast the concrete sample; after forming for 24 hours, use an external electromagnetic induction coil to perform Induction eddy current heating is carried out, wherein the distance between the induction coil and the upper surface of the sample is 10 cm, the output voltage of the induction coil is 600 V, the frequency is 123 kHz, the output power is 7.8 kW, and heat is generated from the inside of the concrete sample in the form of induced eddy current to accelerate the hydration of the concrete. The heating time is 4 hours, and then the concrete sample is placed in a standard curing room (temperature is 18-22°C, humidity is 95%-100%) for curing, so as to obtain ultra-early strength steel slag-based ultra-high performance fiber reinforced concrete under induced eddy current.
[0050] Example 2
[0051] This embodiment provides a steel slag-based ultra-high performance fiber reinforced concrete, which is basically the same as Embodiment 1, except that the distance between the induction coil and the upper surface of the sample is adjusted from 10 cm to 15 cm.
[0052] Embodiment 3-5
[0053] This embodiment provides a steel slag-based ultra-high performance fiber reinforced concrete, which is basically the same as Embodiment 1, except that the raw material formula is different, see Table 1 for details.
[0054] Comparative Example 1
[0055] This comparative example provides a steel slag-based ultra-high performance fiber reinforced concrete, which is basically the same as Example 1, except that the distance between the induction coil and the upper surface of the sample is adjusted from 10 cm to 20 cm.
[0056] Comparative Example 2
[0057] This comparative example provides a steel slag-based ultra-high performance fiber reinforced concrete, which is basically the same as Example 1, except that the distance between the induction coil and the upper surface of the sample is adjusted from 10 cm to 5 cm.
[0058] Comparative Examples 3-5
[0059] This comparative example provides a steel slag-based ultra-high performance fiber-reinforced concrete, which is basically the same as Example 1, except that the raw material formula is different, see Table 1 for details.
[0060] Comparative Example 6
[0061] This comparative example provides a steel slag-based ultra-high performance fiber reinforced concrete, which is basically the same as Example 1, except that the preparation method is different (no induction heating by induction coil), as follows:
[0062] Weigh each raw material according to the weight portion in Table 1; mix the weighed cement, silica fume, fly ash and steel slag powder for 45 seconds, then pour quartz sand into the powder and stir for 45 seconds, then pour water and water reducer into the mixture, stir until the raw materials become a slurry, and then automatically stir for 240 seconds according to the standard mortar mixing procedure, then slowly and evenly pour the steel fiber in the manual slow stirring mode of the standard mortar machine, slowly stir for 240 seconds, and finally pour into the mold to cast and form a concrete sample; after forming for 24 hours, the concrete sample is placed in a standard curing room (temperature of 18-22°C, humidity of 95%-100%) for curing, thereby obtaining steel slag-based ultra-high performance fiber reinforced concrete.
[0063] Table 1 Raw material formula of each embodiment and comparative example (by weight)
[0064]
[0065] Performance Testing
[0066] For the concrete prepared in the above embodiments and comparative examples, the 2-day compressive strength and 28-day compressive strength were tested according to GB 50728-2011 standard, and the results are shown in Table 2.
[0067] Table 2 Performance test results
[0068]
[0069]
[0070] As can be seen from Table 2, by comparing the results of Examples 1 and 2 with Comparative Examples 1 and 2, it can be seen that although the preparation methods of the two are the same, the distance between the coils of the induction eddy current heating is different. The appropriate induction heating distance can produce the most suitable heating rate. When the distance is close, it will cause the heating speed to be too fast, thereby causing the internal structure of the UHPC to deteriorate, thereby affecting the early and final strengths; but when the distance is far, the heating effect will not be obvious, thereby affecting the early strength. By comparing the results of Example 1 with Comparative Examples 3-5, it can be seen that although the preparation methods of the two are the same, the early strength of concrete can also be improved by induction eddy current heating, but the material compatibility composition in the embodiment is designed based on the maximum density of the system, resulting in the mechanical properties of the concrete to be more excellent, especially the final compressive strength at 28 days. By comparing the results of Example 1 with Comparative Example 6, it can be seen that the induction eddy current heating method can significantly improve the early strength of steel slag-based ultra-high performance fiber reinforced concrete while not deteriorating its final strength.
[0071] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.
[0072] The endpoints and any values of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, the endpoint values of each range and the individual point values, and the individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.
Claims
1. A method for preparing steel slag-based ultra-high performance fiber-reinforced concrete, characterized in that: The steel slag-based ultra-high performance fiber-reinforced concrete comprises the following components in parts by weight: 400-600 parts of cement; Silica fume 100-180 parts; 150-200 parts of fly ash; 150-250 parts of steel slag; 980-1200 parts of quartz sand; 160-200 parts of water; 30-40 parts of water reducing agent; 140-160 parts of steel fiber; the preparation method comprises the steps of forming the raw materials to obtain a formed body, performing induction eddy current heating on the formed body by using an electromagnetic induction coil, and a subsequent curing step.
2. The method for preparing steel slag-based ultra-high performance fiber reinforced concrete according to claim 1, characterized in that: The electromagnetic induction coil is arranged outside the molded body and is 10 to 15 cm away from the molded body.
3. The method for preparing steel slag-based ultra-high performance fiber reinforced concrete according to claim 1, characterized in that: The voltage of the electromagnetic induction coil is 500-700V, the frequency is 100-150KHz, and the output power is 7-8KW.
4. The method for preparing steel slag-based ultra-high performance fiber reinforced concrete according to claim 1, characterized in that: The electromagnetic induction coil is arranged outside the formed body and is 10-15 cm away from the formed body. The voltage of the electromagnetic induction coil is 580-620V, the frequency is 120-130KHz, and the output power is 7.5-8KW.
5. The method for preparing steel slag-based ultra-high performance fiber reinforced concrete according to claim 1, characterized in that: The time of the induction eddy current heating is 4 to 6 hours.
6. The method for preparing steel slag-based ultra-high performance fiber reinforced concrete according to claim 1, characterized in that: The subsequent curing is carried out in an environment with a temperature of 18-22° C. and a humidity of 95%-100%; and / or, the molding is cast molding; and / or, the induction eddy current heating is carried out 20-30 hours after the molding is completed.
7. The method for preparing steel slag-based ultra-high performance fiber reinforced concrete according to claim 1, characterized in that: The cement is silicate cement with a strength of not less than 52.5 MPa; and / or the SiO2 content of the silica ash is above 90%; and / or the fly ash is grade I fly ash; and / or the basicity coefficient of the steel slag is above 2.5; and / or the particle size of the quartz sand is 0.01 to 1.25 mm.
8. The method for preparing steel slag-based ultra-high performance fiber reinforced concrete according to claim 1, characterized in that: The steel fiber is a straight copper-plated steel fiber; and / or the length of the steel fiber is 10-20 mm and the diameter is 0.10-0.30 mm; and / or the tensile strength of the steel fiber is above 2000 MPa; and / or the water reducer is a polycarboxylic acid water reducer with a solid content of 10%-30%; and / or the water reduction rate of the water reducer is above 30%.
9. A steel slag based ultra-high performance fiber reinforced concrete prepared by the method for preparing steel slag based ultra-high performance fiber reinforced concrete according to any one of claims 1 to 8.
10. The steel slag based ultra-high performance fiber reinforced concrete according to claim 9, characterized in that: Its 2-day compressive strength is 80-100MPa, and its 28-day compressive strength is 150-170MPa.
11. Application of the steel slag based ultra-high performance fiber reinforced concrete according to claim 9 or 10 in the field of construction.