A fiber automatic scattering device and method for preparing UHPC

Abstract

A kind of fiber automatic scattering device and method for preparing UHPC, it is related to concrete preparation technical field, above-mentioned fiber automatic scattering device includes: mixing kettle, it is equipped with stirring shaft in;Torque sensor, it is connected to above-mentioned stirring shaft, for obtaining the torque signal of above-mentioned stirring shaft;Fiber scattering mechanism, it is set to above-mentioned mixing kettle top, for scattering fiber to above-mentioned mixing kettle;Controller, it is for obtaining stirring shaft torque according to above-mentioned torque signal, and when judging above-mentioned stirring shaft torque drops from torque peak value to torque threshold value, delay preset time control fiber scattering mechanism work.The fiber automatic scattering device and method of the application, realize the accurate timing of fiber addition according to the torque of stirring shaft, so as to realize the accurate automatic scattering of fiber, solve the technical problem of reducing the performance of UHPC product in related art due to inappropriate fiber scattering time.

Description

Technical Field

[0001] This application relates to the field of concrete preparation technology, specifically to an automatic fiber spreading device and method for preparing UHPC. Background Technology

[0002] Ultra-High Performance Concrete (UHPC) is a novel cement-based composite material. It achieves high strength, high toughness, and high durability by incorporating active powders to achieve close packing of particles, minimizing internal defects such as pores and microcracks, and reinforcing the matrix with fibers. Compared to ordinary concrete or high-strength concrete, UHPC exhibits significantly improved overall performance. Its superior compressive and tensile strength, high toughness, and high impermeability perfectly meet the requirements of engineering structures developing towards greater height, larger spans, and heavier loads. It is a promising new cement-based composite material with far-reaching application prospects. The incorporation of fibers has a crucial impact on the performance of UHPC.

[0003] In related technologies, there are two main ways to add fibers to UHPC. The first method is to add the fibers together with the dry mix and dry mix them, then add water and additives and stir to form the UHPC. The second method is to prepare the matrix first, and then add the fibers after the UHPC matrix has fluidized and continue stirring to form the UHPC.

[0004] However, in the first method described above, the hard friction between the powder and aggregates and the copper-plated fibers during dry mixing can cause the plating on the fiber surface to peel off, making the fibers prone to corrosion and thus deteriorating the durability of UHPC. Simultaneously, dry mixing can cause the agglomeration of composite and inorganic fibers, reducing the workability and later-stage performance of the UHPC slurry. In practice, the second method often requires operators to manually add fibers to the mortar, increasing labor and time costs and posing certain safety hazards. Furthermore, the timing of fiber addition is highly subjective and random; fibers added too early will also be rubbed off by the high viscosity of the UHPC, while fibers added too late will affect the performance of the UHPC and its preparation efficiency. Summary of the Invention

[0005] This application provides an automatic fiber spreading device and method for preparing UHPC, which can solve the technical problem in the prior art that the performance of UHPC products is reduced due to inappropriate fiber spreading time.

[0006] In a first aspect, embodiments of this application provide an automatic fiber spreading device for preparing UHPC, the automatic fiber spreading device comprising: A mixing pot, which contains a stirring shaft; A torque sensor, which is connected to the stirring shaft, is used to acquire the torque signal of the stirring shaft. A fiber spreading mechanism is disposed above the mixing pot and is used to spread fibers into the mixing pot. The controller is used to obtain the torque of the stirring shaft based on the torque signal mentioned above, and when it is determined that the torque of the stirring shaft drops from the torque peak to the torque threshold, it delays the operation of the fiber spreading mechanism for a preset time.

[0007] In conjunction with the first aspect, in one embodiment, the controller is further configured to use the highest torque value as the torque peak value and a preset percentage value of the torque peak value as the torque threshold value when the stirring shaft torque no longer increases and begins to decrease.

[0008] In conjunction with the first aspect, in one implementation, the aforementioned preset percentage is 20-40%.

[0009] In conjunction with the first aspect, in one implementation, the aforementioned preset time is 5-15 seconds.

[0010] In conjunction with the first aspect, in one embodiment, the fiber spreading mechanism includes a storage tank and an electric valve, wherein the lower end of the storage tank is provided with a discharge port and the discharge port is provided with the electric valve.

[0011] In conjunction with the first aspect, in one embodiment, the controller includes: The signal conversion module is used to receive the torque signal acquired by the torque sensor and convert the torque signal into a digital signal. The signal recognition module is used to identify the converted digital signal and transmit the identified stirring shaft torque to the judgment module. The aforementioned judgment module is used to determine whether the torque of the stirring shaft has decreased from the torque peak value to the torque threshold value; The control module is used to open the electric valve after a preset time when the judgment module determines that the torque of the stirring shaft has dropped from the torque peak to the torque threshold.

[0012] Secondly, embodiments of this application provide an automatic fiber spreading method using the aforementioned automatic fiber spreading device for preparing UHPC, the automatic fiber spreading method comprising: The predetermined volume of fiber is placed into the fiber spreading mechanism; The UHPC matrix material is added to the mixing pot according to the predetermined ratio and stirred, and the torque of the stirring shaft is obtained by the controller; When the controller determines that the torque of the stirring shaft has dropped from the peak torque to the threshold torque, it delays the operation of the fiber spreading mechanism for a preset time.

[0013] In conjunction with the second aspect, in one embodiment, the controller includes a signal conversion module and a signal recognition module; The above-mentioned acquisition of the stirring shaft torque via the controller specifically includes: The signal conversion module receives the torque signal acquired by the torque sensor and converts the torque signal into a digital signal. The torque of the stirring shaft is obtained by identifying the converted digital signal through a signal recognition module.

[0014] In conjunction with the second aspect, in one embodiment, the controller further includes a judgment module and a control module; After the controller obtains the torque of the stirring shaft, it also includes: The judgment module determines whether the torque of the stirring shaft has dropped from the torque peak to the torque threshold, and sends the judgment result to the control module.

[0015] In conjunction with the second aspect, in one embodiment, the proportions of the above-mentioned UHPC matrix material, based on parts by mass, are as follows: 750-950 parts cement, 100-200 parts silica fume, 50-150 parts microspheres, 850-1200 parts fine aggregate, 8-15 parts admixture, and 180-210 parts water; The aforementioned fibers are any one of copper-plated steel fibers, polypropylene fibers, polyoxymethylene fibers, polyvinyl alcohol fibers, glass fibers, and basalt fibers; The volumetric doping of the aforementioned fibers is 0.5% to 3% of the UHPC matrix material.

[0016] The beneficial effects of the technical solutions provided in this application include: By installing a stirring shaft inside the mixing tank and a fiber spreading mechanism above it, and by mounting a torque sensor on the stirring shaft, the torque sensor monitors and acquires the torque signal of the stirring shaft and sends it to the controller. The controller then determines the torque of the stirring shaft based on the torque signal and, when it determines that the torque of the stirring shaft has dropped from the peak torque to the torque threshold, delays the operation of the fiber spreading mechanism for a preset time to spread fibers into the mixing tank. This achieves accurate timing of fiber addition based on the torque of the stirring shaft, thus realizing accurate and automatic fiber spreading and solving the technical problem in related technologies where inappropriate fiber spreading time reduces the performance of UHPC products. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of the automatic fiber spreading device for preparing UHPC according to an embodiment of this application; Figure 2 This is a front view of an automatic fiber spreading device for preparing UHPC according to an embodiment of this application; Figure 3 This is a side view of an automatic fiber spreading device for preparing UHPC according to an embodiment of this application; Figure 4 This is a top view of an automatic fiber spreading device for preparing UHPC according to an embodiment of this application; Figure 5 This is a schematic diagram of the controller module in an embodiment of this application; Figure 6 This is a schematic flowchart of the automatic fiber spreading method according to an embodiment of this application; Figure 7 This is a photograph of the original copper-plated steel fiber before stirring in Example 1; Figure 8 This is a photograph of the copper-plated steel fiber taken out after stirring in Example 1. Figure 9 This is a diagram showing the spread of the UHPC slurry formed after stirring in Example 2. Figure 10 This is a photograph of the copper-plated steel fiber taken out after stirring in Comparative Example 1. Figure 11 This is a diagram showing the spread of the UHPC slurry formed after stirring in Comparative Example 2.

[0019] In the picture: 1. Mixing pot; 2. Mixing shaft; 3. Torque sensor; 4. Fiber spreading mechanism; 5. Control console; 51. Signal conversion module; 52. Signal recognition module; 53. Judgment module; 54. Control module. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present application.

[0021] In a first aspect, embodiments of this application provide an automatic fiber spreading device for preparing UHPC.

[0022] In one embodiment, reference is made to Figure 1 , Figure 1This is a schematic diagram of an embodiment of the automatic fiber spreading device used in the preparation of UHPC according to this application. Figure 1 As shown, the automatic fiber spreading device for preparing UHPC includes a mixing tank 1, a mixing shaft 2, a torque sensor 3, a fiber spreading mechanism 4, and a controller.

[0023] The aforementioned stirring vessel 1 is equipped with the aforementioned stirring shaft 2. The aforementioned torque sensor 3 is connected to the aforementioned stirring shaft 2 and is used to acquire the torque signal of the stirring shaft 2.

[0024] The fiber spreading mechanism 4 is disposed above the mixing pot 1 and is used to spread fibers into the mixing pot 1.

[0025] The controller is used to obtain the stirring shaft torque based on the torque signal, and when it is determined that the stirring shaft torque drops from the torque peak to the torque threshold, it delays the operation of the fiber spreading mechanism 4 for a preset time, that is, delays the operation of the fiber spreading mechanism 4 to spread fibers into the mixing pot 1 for a preset time.

[0026] In this embodiment, the controller is located inside the control console 5, which is located on one side of the mixing pot 1. The controller is electrically connected to the torque sensor 3 and the fiber spreading mechanism 4, respectively, so as to control the operation of the fiber spreading mechanism 4 according to the monitoring results of the torque sensor 3.

[0027] In this embodiment, a stirring shaft is installed inside the mixing tank, a fiber spreading mechanism is installed above the mixing tank, and a torque sensor is installed on the stirring shaft. The torque sensor monitors and acquires the torque signal of the stirring shaft and sends it to the controller. The controller can then acquire the torque of the stirring shaft based on the torque signal. When it is determined that the torque of the stirring shaft has dropped from the peak torque to the torque threshold, the fiber spreading mechanism is controlled to work after a preset time to spread the fiber into the mixing tank. This achieves accurate timing of fiber addition based on the torque of the stirring shaft, thereby realizing accurate and automatic fiber spreading. This solves the technical problem in related technologies where inappropriate fiber spreading time reduces the performance of UHPC products.

[0028] like Figure 2-4 As shown, in one embodiment, one end of the stirring shaft 2 extends out of the stirring pot 1, and the extended end of the stirring shaft 2 is connected to the torque sensor 3.

[0029] Furthermore, in one embodiment, the controller is also used to take the highest torque value as the torque peak value and a preset percentage value of the torque peak value as the torque threshold value when the stirring shaft torque no longer increases and begins to decrease.

[0030] Optionally, the controller is also configured to store the initial stirring shaft torque as the maximum value when it is acquired, and then continuously determine whether the stirring shaft torque at the current moment is greater than the stored maximum value each time a new stirring shaft torque is acquired; if the stirring shaft torque at the current moment is greater than the stored maximum value, then the current stirring shaft torque is used as the maximum value and the storage is updated; otherwise, that is, when the stirring shaft torque at the current moment is less than or equal to the stored maximum value, the stored maximum value is kept unchanged.

[0031] When the stirring shaft torque decreases to 80% of the currently stored maximum value, it is determined that the stirring shaft torque will no longer increase and will continue to decrease. At this point, the currently stored maximum value is taken as the torque peak value, and a preset percentage of this torque peak value is taken as the torque threshold value.

[0032] Furthermore, in one embodiment, the aforementioned preset percentage is 20-40%.

[0033] Preferably, the preset percentage is 30%, that is, the torque threshold is 30% of the peak torque.

[0034] Furthermore, in one embodiment, the preset time is 5-15 seconds. That is, the preset spreading time is 5-15 seconds after the stirring shaft torque drops to the torque threshold.

[0035] Since the mortar mixing process of UHPC is accompanied by significant changes in rheological properties, fibers need to be added at the moment when the rheological properties of UHPC change abruptly from a high-viscosity state to a fluidized state.

[0036] Although the rheological properties of UHPCs with different compositions vary, their overall trends are similar: the torque value initially increases, then rapidly decreases after reaching its peak. When the torque value drops to 20%–40% of its peak value, the UHPC approaches a slurry state, and then remains completely slurry for 5–15 seconds. This is the optimal time to add fibers. Based on this, the preferred spreading time is 5–15 seconds after the torque value monitored by the torque sensor reaches the torque threshold.

[0037] In this embodiment, the controller is used to analyze and process the received torque signal. When the torque value is detected to start to decrease and no longer increase, the maximum torque value before the decrease is taken as the torque peak value, and 30% of the torque peak value is defined as the torque threshold value. When the measured torque value is detected to reach the torque threshold value, the timing starts. When the timing time reaches 5~15s, the electric valve is controlled to open for a predetermined time to allow the fiber to fall into the mixing pot. After that, the valve is controlled to close, and the judgment module stops working.

[0038] Furthermore, in one embodiment, the fiber spreading mechanism 4 includes a storage tank and an electric valve. The lower end of the storage tank is provided with a discharge port, and the discharge port is provided with the electric valve. The controller is used to control the opening of the electric valve to control the operation of the fiber spreading mechanism 4.

[0039] In this embodiment, the spreading rate and amount of fiber stored in the fiber storage tank can also be controlled by controlling the opening and closing degree and opening and closing time of the electric valve. The specific parameters can be set according to the actual situation.

[0040] like Figure 5 As shown, in one embodiment, the controller includes a signal conversion module 51, a signal recognition module 52, a judgment module 53, and a control module 54.

[0041] The signal conversion module 51 is connected to the torque sensor 3 and is used to receive the torque signal acquired by the torque sensor 3, convert the torque signal into a digital signal, and then send it to the signal recognition module 52.

[0042] The aforementioned signal recognition module 52 is used to recognize the converted digital signal and transmit the recognized stirring shaft torque to the judgment module 53.

[0043] The aforementioned judgment module 53 is used to determine whether the torque of the stirring shaft has decreased from the peak torque to the torque threshold. The aforementioned judgment module 53 is also used to send the judgment result to the control module 54.

[0044] The control module 54 is connected to the electric valve and controls its opening and closing. The control module 54 is also used to open the electric valve after a preset time when the judgment module 53 determines that the torque of the stirring shaft has decreased from its peak value to a torque threshold value.

[0045] Secondly, embodiments of this application provide an automatic fiber spreading method using the above-described automatic fiber spreading device for preparing UHPC.

[0046] In one embodiment, reference is made to Figure 6 , Figure 6 This is a schematic flowchart of an embodiment of the automated fiber spreading method for preparing UHPC according to this application. Figure 6 As shown, the above-mentioned automatic fiber spreading method includes: S1. Place the fiber with a predetermined volume of mixed fiber into the fiber spreading mechanism 4.

[0047] S2. Add the UHPC matrix material to the mixing pot 1 according to the predetermined ratio and stir, and obtain the stirring shaft torque through the controller.

[0048] The controller processes the signal transmitted by the torque sensor and determines whether the preset dispensing timing has been reached.

[0049] S3. When the controller determines that the torque of the stirring shaft drops from the peak torque to the threshold torque, it delays the operation of the fiber spreading mechanism 4 for a preset time. That is, when the preset spreading time is reached, the controller controls the fiber spreading mechanism to open, so that the fiber spreading mechanism adds a predetermined amount of fiber to the mixing pot, thus completing the automatic spreading of the fiber.

[0050] The order of steps S1 and S2 can be reversed.

[0051] Furthermore, in one embodiment, the controller includes a signal conversion module and a signal recognition module.

[0052] The above-mentioned acquisition of the stirring shaft torque via the controller specifically includes: First, the torque signal acquired by the torque sensor 3 is received through the signal conversion module, and the torque signal is converted into a digital signal.

[0053] Then, the converted digital signal is identified by the signal recognition module to obtain the stirring shaft torque.

[0054] Furthermore, in one embodiment, the controller further includes a judgment module and a control module.

[0055] After obtaining the stirring shaft torque, the controller also includes: The judgment module determines whether the torque of the stirring shaft has dropped from the torque peak to the torque threshold, and sends the judgment result to the control module.

[0056] Furthermore, in one embodiment, the proportions of the above-mentioned UHPC matrix material, based on parts by mass, are as follows: 750-950 parts cement, 100-200 parts silica fume, 50-150 parts microspheres, 850-1200 parts fine aggregate, 8-15 parts admixture, and 180-210 parts water.

[0057] In this embodiment, step S2 above involves adding the UHPC matrix material to the mixing pot 1 according to a predetermined ratio and stirring it, and obtaining the stirring shaft torque through a controller. Specifically, this includes: First, cement, silica fume, microspheres, fine aggregate, admixtures and water are added to the mixing pot according to the predetermined ratio.

[0058] Then, the aforementioned automatic fiber spreading device is activated, causing the stirring shaft 2 to stir the UHPC matrix material in the mixing pot 1. The torque sensor monitors the torque signal of the stirring shaft in real time and transmits it to the controller. At this time, the controller acquires the torque of the stirring shaft and makes a real-time judgment.

[0059] Furthermore, in one embodiment, the aforementioned fiber is any one of copper-plated steel fiber, polypropylene fiber, polyoxymethylene fiber, polyvinyl alcohol fiber, glass fiber, and basalt fiber.

[0060] In this embodiment, the fibers in the storage tank are copper-plated steel fibers. The surface of the copper-plated steel fibers is coated with a copper layer to prevent the steel fibers from being corroded.

[0061] Furthermore, in one embodiment, the volumetric doping of the aforementioned fibers is 0.5% to 3% of the UHPC matrix material.

[0062] The automatic fiber spreading device and method provided by the present invention will be described below with reference to specific embodiments.

[0063] Example 1 This embodiment provides an automatic fiber spreading device for UHPC mixing. The device includes a mixing tank 1 with an internal mixing shaft 2, a fiber spreading mechanism 4 positioned above the mixing tank 1, and a control console 5 with a controller located on one side of the mixing tank 1. The mixing shaft 2 is connected to a torque sensor 3. The fiber spreading mechanism 4 includes a storage tank and an electric valve located at the discharge port of the storage tank. The fibers stored in the storage tank are copper-plated steel fibers.

[0064] In this embodiment, the preset application timing is set to 10 seconds after the torque value monitored by the torque sensor decreases to 30% of the peak torque.

[0065] This embodiment also provides an automatic fiber spreading method using the above-mentioned automatic fiber spreading device, comprising the following steps: First, cement, silica fume, microspheres, fine aggregate, admixtures, and water are weighed according to a mass ratio of 850:150:100:1000:12:190 and added to the mixing pot. Copper-plated steel fibers are then added to the fiber spreading mechanism at a volume ratio of 2%. The automatic fiber spreading device is turned on by switching on the switch, causing the stirring shaft to stir the UHPC matrix material in the mixing pot. The torque sensor monitors the torque signal of the stirring shaft in real time and transmits it to the control console.

[0066] Then, the controller of the aforementioned console processes the signal transmitted by the aforementioned torque sensor to determine whether the torque of the stirring shaft has decreased to the torque threshold (i.e., the torque has decreased to 30% of the peak torque). When the torque threshold is detected, the timer is set for another 10 seconds, at which point the spreading time is reached. At this time, the controller transmits the control signal to the electric valve, and then the controller stops working. The electric valve that receives the controller signal opens, allowing the aforementioned fiber spreading mechanism to add the copper-plated steel fiber into the aforementioned mixing pot, thus completing the automatic spreading of the fiber.

[0067] In this embodiment, copper-plated steel fibers were added to the mixing pot after 3 minutes and 42 seconds of stirring. After another 90 seconds of stirring, the automatic fiber spreading device was turned off, and the stirred UHPC was removed. The spread of this UHPC was measured to be 605 mm. A portion of the UHPC slurry was taken, washed, and the copper-plated steel fibers were removed and compared with the original copper-plated steel fibers. Figure 7 and Figure 8 As shown, the coating on the steel fiber surface remains intact without peeling. After pouring some UHPC slurry into the mold and allowing it to stand for 24 hours, the mold was removed and the mechanical properties were tested after curing for 28 days. The test results showed a flexural strength of 26.5 MPa and a compressive strength of 138.4 MPa.

[0068] Example 2 The automatic fiber spreading device and method provided in this embodiment differ from that in Embodiment 1 only in the type of fiber in the storage tank. The rest of the structure and method are the same as in Embodiment 1 and will not be described again here.

[0069] In this embodiment, the fibers in the storage tank are polypropylene fibers.

[0070] like Figure 9 As shown, the UHPC obtained after stirring in this embodiment has an expansion of 405 mm, uniform fiber distribution, and good slurry fluidity. The stirred UHPC was then molded, cured, and tested for mechanical properties in accordance with the method in Example 1. The results showed that the flexural strength was 19.6 MPa and the compressive strength was 127.5 MPa.

[0071] Example 3 The automatic fiber spreading device and method provided in this embodiment are the same as those in Embodiment 1, except that the setting method of spreading timing is changed. The rest are the same as those in Embodiment 1 and will not be described again here.

[0072] In this embodiment, the fiber is spread 5 seconds after the torque value monitored by the torque sensor reaches the torque threshold. The torque threshold is 20% of the peak torque. The UHPC extension obtained in this embodiment is 595 mm. The stirred UHPC from this embodiment is then molded, cured, and its mechanical properties are tested according to the method described in Example 1. The results show a flexural strength of 25.6 MPa and a compressive strength of 137.5 MPa.

[0073] Example 4 The automatic fiber spreading device and method provided in this embodiment are the same as those in Embodiment 1, except that the setting method of spreading timing is changed. The rest are the same as those in Embodiment 1 and will not be described again here.

[0074] In this embodiment, the fiber is spread 15 seconds after the torque value monitored by the torque sensor reaches the torque threshold. The torque threshold is 40% of the peak torque. The UHPC extension obtained in this embodiment is 600 mm. The stirred UHPC from this embodiment is then molded, cured, and its mechanical properties are tested according to the method described in Example 1. The results show a flexural strength of 25.2 MPa and a compressive strength of 134.7 MPa.

[0075] Compared with the results measured in Example 1, it can be seen that the torque threshold can vary from 20% to 40%, and the interval between reaching the threshold and fiber feeding can vary from 5 to 15 seconds. The performance of UHPC does not change significantly, indicating that UHPC is thoroughly stirred and the slurry is relatively uniform in this method.

[0076] Comparative Example 1 Comparative Example 1 provides an automatic fiber spreading method during the mixing process of UHPC. The composition and proportion of the UHPC used in Comparative Example 1 are the same as those in Example 1. The difference is that an automatic fiber spreading device is not used. Instead, copper-plated steel fibers are added manually and mixed together with cement, silica fume, microspheres, fine aggregates, admixtures, and water. The overall mixing time is the same as in Example 1.

[0077] The UHPC expansion obtained after stirring in Comparative Example 1 was 605 mm. The copper-plated steel fibers were then removed as described in Example 1. Figure 10 As shown, the copper-plated steel fiber surface exhibits coating peeling. Following the method described in Example 1, the stirred UHPC was molded, cured, and its mechanical properties were tested. The results showed a flexural strength of 24.6 MPa and a compressive strength of 133.5 MPa.

[0078] Compared with Example 1, it can be seen that although the properties of the UHPC slurry stirred by this method do not change much, the copper-plated steel fiber surface shows coating peeling, which will inevitably lead to easy corrosion of the fiber and thus deteriorate the durability of UHPC.

[0079] Comparative Example 2 Comparative Example 2 provides an automatic fiber spreading method during the mixing process of UHPC. The composition and proportion of the UHPC used in Comparative Example 2 are the same as those in Example 2. The difference is that an automatic fiber spreading device is not used. Instead, polypropylene fibers are added manually, and the polypropylene fibers are added together with cement, silica fume, microspheres, fine aggregates, admixtures, and water for mixing. The overall mixing time is the same as in Example 2.

[0080] like Figure 11As shown, the UHPC obtained after stirring in Comparative Example 2 had an expansion of 375 mm. The stirred UHPC was then molded, cured, and subjected to mechanical property tests in accordance with the method described in Example 1. The results showed that the flexural strength was 14.3 MPa and the compressive strength was 114.5 MPa.

[0081] Compared with Example 2, adding polypropylene fibers during the stirring time resulted in a significant reduction in the spread and mechanical properties of the UHPC slurry. This was mainly due to fiber agglomeration, which led to uneven fiber dispersion.

[0082] Comparative Example 3 Comparative Example 3 provides an automatic fiber spreading method during the mixing process of UHPC. The composition and ratio of the UHPC used in Comparative Example 3 are the same as those in Example 1. The difference is that an automatic fiber spreading device is not used. Instead, copper-plated steel fibers are added manually. The copper-plated steel fibers are added after cement, silica fume, microspheres, fine aggregate, admixtures and water are mixed and stirred for 10 minutes. The mixture is then stirred for another 90 seconds before stopping.

[0083] The UHPC obtained after stirring in Comparative Example 3 had an expansion of 595 mm. The stirred UHPC was then molded, cured, and subjected to mechanical property tests according to the method described in Example 1. The results showed a flexural strength of 23.1 MPa and a compressive strength of 129.5 MPa. Compared to Example 1, the mechanical properties of the UHPC were somewhat reduced. This was mainly due to the excessive stirring time, which introduced excessive air bubbles into the UHPC, reducing its internal density and further decreasing its strength.

[0084] It can be seen that the timing of fiber application has a significant impact on the mechanical properties of UHPC during the preparation process. The apparatus and method in this embodiment can effectively improve the mechanical properties of UHPC by automatically determining the accurate application time, thereby increasing the degree of automation.

[0085] The automatic fiber spreading method of this embodiment is applicable to the above-mentioned automatic fiber spreading devices. It monitors the torque of the stirring shaft in real time through a torque sensor, and then uses a controller to compare the measured torque of the stirring shaft with a preset threshold parameter to determine whether the spreading time has been reached. When the spreading time is reached, the fiber spreading mechanism is controlled to start, thereby accurately and efficiently spreading the fiber automatically at the appropriate time. This achieves accurate and automatic fiber spreading during the UHPC stirring process and avoids the impact of inappropriate fiber spreading time on the performance of UHPC products.

[0086] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0087] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0088] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An automatic fiber spreading device for preparing UHPC, characterized in that, The automatic fiber spreading device includes: A mixing pot (1) is provided with a stirring shaft (2); A torque sensor (3) is connected to the stirring shaft (2) to acquire the torque signal of the stirring shaft (2); A fiber spreading mechanism (4) is disposed above the mixing pot (1) and is used to spread fibers into the mixing pot (1); The controller is used to obtain the stirring shaft torque according to the torque signal, and when it is determined that the stirring shaft torque drops from the torque peak to the torque threshold, it delays the operation of the fiber spreading mechanism (4) for a preset time.

2. The automatic fiber spreading device for preparing UHPC as described in claim 1, characterized in that: The controller is also used to take the highest torque value as the torque peak value and a preset percentage value of the torque peak value as the torque threshold value when the stirring shaft torque no longer increases and begins to decrease.

3. The automatic fiber spreading device for preparing UHPC as described in claim 2, characterized in that: The preset percentage is 20-40%.

4. The automatic fiber spreading device for preparing UHPC as described in claim 1, characterized in that: The preset time is 5-15 seconds.

5. The automatic fiber spreading device for preparing UHPC as described in claim 1, characterized in that: The fiber spreading mechanism (4) includes a storage tank and an electric valve. The lower end of the storage tank is provided with a discharge port, and the discharge port is provided with the electric valve.

6. The automatic fiber spreading device for preparing UHPC as described in claim 5, characterized in that, The controller includes: A signal conversion module is used to receive the torque signal acquired by the torque sensor (3) and convert the torque signal into a digital signal; The signal recognition module is used to identify the converted digital signal and transmit the identified stirring shaft torque to the judgment module. The judgment module is used to determine whether the torque of the stirring shaft has decreased from the torque peak to the torque threshold. The control module is used to open the electric valve after a preset time when the judgment module determines that the torque of the stirring shaft has dropped from the torque peak to the torque threshold.

7. A method for automatically spreading fibers using the automatic fiber spreading device for preparing UHPC as described in claim 1, characterized in that, The automatic fiber dispensing method includes: The predetermined volume of fiber is placed into the fiber spreading mechanism (4). The UHPC matrix material is added to the mixing pot (1) according to the predetermined ratio and stirred, and the stirring shaft torque is obtained by the controller; When the controller determines that the torque of the stirring shaft has dropped from the torque peak to the torque threshold, it delays the operation of the fiber spreading mechanism (4) for a preset time.

8. The automatic fiber spreading method as described in claim 7, characterized in that, The controller includes a signal conversion module and a signal recognition module; The process of obtaining the stirring shaft torque via the controller specifically includes: The torque signal obtained by the torque sensor (3) is received by the signal conversion module and converted into a digital signal. The torque of the stirring shaft is obtained by identifying the converted digital signal through a signal recognition module.

9. The automatic fiber spreading method as described in claim 8, characterized in that, The controller also includes a judgment module and a control module; After the controller obtains the torque of the stirring shaft, it also includes: The judgment module determines whether the torque of the stirring shaft has dropped from the torque peak to the torque threshold, and sends the judgment result to the control module.

10. The automatic fiber spreading method as described in claim 7, characterized in that, The proportions of the UHPC matrix material, by weight, are as follows: 750-950 parts cement, 100-200 parts silica fume, 50-150 parts microspheres, 850-1200 parts fine aggregate, 8-15 parts admixture, and 180-210 parts water; The fiber is any one of copper-plated steel fiber, polypropylene fiber, polyoxymethylene fiber, polyvinyl alcohol fiber, glass fiber, and basalt fiber. The volumetric doping of the fiber is 0.5% to 3% of the UHPC matrix material.

Images