Lifting, transferring and mixing device for coarse aggregate ultra-high performance concrete premix

Abstract

The coarse aggregate ultra-high performance concrete premix lifting, transferring and mixing device comprises a control system, an aggregate batching system, an aggregate lifting system, a dry mixing main machine system, a feeding vehicle, a steel fiber feeding system and a stirring system, the whole stirring process is automatically controlled and comprises key steps of automatic metering, automatic raw material feeding, mixing and the like, so that manual operation is remarkably reduced, errors and inconsistency caused by manual metering are avoided, and the accuracy and repeatability of stirring each time are ensured; step-by-step feeding of each part is coordinated through a control system, so that the stirring efficiency and the uniformity of concrete are improved; by establishing a relational expression between a concrete mixture stirring uniformity index and parameters such as the stirring time, the stirring speed, the number of stirring blades, the vibration frequency of the two-stage vibrating screen and the like, key parameters in the stirring process are more accurately controlled, and it is ensured that the stirring uniformity of each batch of concrete reaches a preset standard.

Description

Technical Field

[0001] The invention relates to the technical field of concrete preparation, and in particular to a coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device. Background Art

[0002] Coarse aggregate ultra-high performance concrete (CA-RPC) has significant advantages in structural engineering such as bridges due to its excellent physical properties, such as high compressive strength and high elastic modulus. The use of this material can not only improve the bearing capacity of the structure, but also effectively control the deformation of the structure. Through the composite steel fiber, the toughness is significantly enhanced, and its fracture resistance is 250 times that of ordinary concrete, close to the level of steel. Its "strain hardening" property means that even if the matrix cracks, the steel fibers can continue to play a role, enhancing the overall toughness of the material and effectively restraining the expansion of cracks.

[0003] However, despite the many advantages of CA-RPC materials themselves, their production process faces some challenges. At present, the mixing equipment of CA-RPC has not yet achieved a high degree of automation and mainly relies on manual feeding, which limits production efficiency and prolongs the production cycle, which is not conducive to large-scale production and construction needs. In the process of manual feeding, dust is easily generated due to material handling and mixing operations, which not only poses a threat to the respiratory health of workers, but also seriously affects the air quality of the surrounding environment. In addition, the addition of steel fibers puts higher requirements on mixing equipment. Existing mixing equipment has deficiencies in mixing uniformity, and it is difficult to ensure that the steel fibers are evenly dispersed in the CA-RPC matrix. Uneven mixing will affect the mechanical properties and durability of CA-RPC, reducing its performance in practical applications. Summary of the invention

[0004] The purpose of the present invention is to provide a coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device to solve the technical problems raised in the above-mentioned background technology, to carry out technical innovation and improvement on the mixing equipment of CA-RPC, to achieve a higher degree of automation, reduce manual operation, and improve production efficiency and mixing quality.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device, comprising a control system, an aggregate batching system, an aggregate lifting system, a dry mixing main system, a feeding vehicle, a steel fiber delivery system and a mixing system; the output end of the aggregate batching system cooperates with the lower end of the aggregate lifting system, the upper end of the aggregate lifting system cooperates with the feed port of the dry mixing main system, the delivery port of the feeding vehicle cooperates with the discharge port of the dry mixing main system, and is used to receive the dry powder mixture mixed in the dry mixing main system, the feeding vehicle unloads the dry powder mixture to the mixing system, the mixing system is provided with an automatic weighing water tank for weighing and delivering the required amount of water in the concrete premix to form the concrete premix, the steel fiber delivery system delivers a preset amount of steel fiber to the mixing system for mixing to form a concrete mixture, the control system controls the mixing time and mixing speed of the mixing system, the water adding time and water adding amount of the automatic weighing water tank, and the feeding time of the steel fiber delivery system;

[0007] The mixing system includes a plurality of vertical-shaft planetary mixers, each of which is equipped with a motor and a mixing chamber. A mixing shaft is arranged in each mixing chamber. The motor is connected to the mixing shaft via a transmission device. The mixing shaft is provided with a plurality of mixing blades. The mixing shaft drives the mixing blades to rotate under the drive of the motor to mix the concrete mixture.

[0008] As a preferred technical solution of the present invention, the aggregate batching system includes a coarse aggregate storage bin and a fine aggregate storage bin. The output ends of the coarse aggregate storage bin and the fine aggregate storage bin are both provided with a three-level metering system. The three-level metering system prepares the aggregate mixture according to the concrete design mix ratio requirements.

[0009] Furthermore, the coarse aggregate stored in the coarse aggregate storage bin is crushed stone or pebble, and the fine aggregate stored in the fine aggregate storage bin is one or a combination of natural sand, machine-made sand, corundum, and silicon carbide.

[0010] As a preferred technical solution of the present invention, the dry mixing host system includes a powder storage bin, a powder conveying system, a powder weighing system and a dry mixing system. The powder conveying system is located between the powder storage bin and the dry mixing system. The output end of the powder storage bin cooperates with the rear end of the powder conveying system, and the front end of the powder conveying system cooperates with the powder weighing system. The output end of the powder weighing system is provided with a valve, and the input end of the powder weighing system receives and weighs the powder, and the powder is put into the dry mixing system through the valve for uniform mixing.

[0011] Furthermore, the powder conveying system adopts a screw conveyor, a pneumatic conveyor or a belt conveyor.

[0012] Furthermore, the powder storage bin stores a mixture of cement and additives.

[0013] As a preferred technical solution of the present invention, an ultrasonic detection device is also included to detect the uniformity of the concrete mixture. The uniformity detection result satisfies the following formula:

[0014]

[0015] Where K is the uniformity, m is the number of layers of the ultrasonically tested concrete mixture, ρ0 is the theoretical density of the concrete mixture, is the average density of each layer of the concrete mixture, ρ i is the surface density of the concrete mixture layer i.

[0016] As a preferred technical solution of the present invention, the steel fiber delivery system includes a steel fiber storage bin, a two-stage vibrating screen, a steel fiber conveying system and a steel fiber weighing system. The feed port of the two-stage vibrating screen cooperates with the output end of the steel fiber storage bin, the two-stage vibrating screen performs two-stage vibration uniformity on the steel fibers in the steel fiber storage bin, the discharge port of the two-stage vibrating screen cooperates with the rear end of the steel fiber conveying system, the front end of the steel fiber conveying system cooperates with the steel fiber weighing system, and the steel fiber weighing system adopts subtraction weighing method for weighing.

[0017] Furthermore, the uniformity index of the concrete mixture stirred by the mixing system is determined by the mixing time and mixing speed of the vertical axis planetary mixer, the number of the mixing blades, the feeding time of the steel fiber feeding system and the vibration frequency of the two-stage vibrating screen, and satisfies the following formula:

[0018]

[0019] Wherein, η1, η2, η3 are adjustment coefficients, t1 is the dry mixing time of the dry powder mixture, t2 is the wet mixing time after the mixing system is added with water, t3 is the steel fiber feeding time, t4 is the mixing time of the concrete mixture, v is the mixing speed of the vertical axis planetary mixer, n is the number of the mixing blades, and p is the vibration frequency of the two-stage vibrating screen;

[0020] The sum of the wet mixing time after adding water to the mixing system, the steel fiber feeding time and the mixing time of the concrete mixture should be controlled within the design range and satisfy the following formula:

[0021] T min ≤t2+t3+t4≤T max

[0022] Where, T max is the maximum limit of the design range, Tmin is the minimum limit of the design range.

[0023] The mixing speed of the vertical axis planetary mixer is a key factor affecting the uniformity of the concrete mixture. Increasing the mixing speed of the vertical axis planetary mixer can enhance the relative movement between materials and promote the mixing of different components, thereby improving the uniformity of the concrete. When the mixing speed is too slow, the various components in the concrete cannot be fully mixed. In particular, for concrete containing steel fibers, too low a mixing speed may cause the steel fibers to be not evenly dispersed. When the mixing speed is too fast, some components in the concrete, especially heavier aggregates, may segregate, which in turn reduces the uniformity of the concrete.

[0024] In the initial stage of dry mixing, various dry powder components, such as cement, fly ash, mineral powder, aggregate, etc., begin to be mixed. The longer the dry mixing time of the dry powder mixture, the more it helps to break up the original lump structure, reduce the segregation caused by the gravity of the material, and ensure that the various components of the concrete are evenly distributed.

[0025] The longer the concrete mix is ​​mixed, the more time the various materials have to mix, allowing the cement particles to come into more complete contact with the water, which in turn promotes the hydration reaction and achieves a more even distribution.

[0026] The greater the number of mixing blades, the larger the contact area between the concrete mixture and the mixing blades, which more frequently lifts the material from the bottom to the top and then disperses it to various areas of the mixer, improves the mixing efficiency, promotes the convection and exchange of materials inside the mixer, reduces local concentration differences, and reduces the unevenness of local areas.

[0027] The higher vibration frequency of the two-stage vibrating screen can more effectively separate and disperse the aggregated steel fibers, improve the fluidity of the steel fibers, make them easier to mix with other concrete components, ensure that the steel fibers are added to the concrete in a timely and even manner, and reduce agglomeration.

[0028] Based on long-term practical experience and theoretical research, the three-blade vertical planetary mixer is considered to be an ideal choice for balancing the mixing effect and economic benefits. The three-blade vertical planetary mixer can effectively cover the entire mixing area of ​​the mixer, achieve continuous material lifting, throwing and mixing, and reduce manufacturing and maintenance costs. Therefore, the number of mixing blades n of the vertical planetary mixer is usually kept relatively constant. When the specifications of the steel fiber are determined, in order to ensure the moving speed and separation effect of the steel fiber on the screen, the vibration frequency of the two-stage vibrating screen is usually kept relatively constant.

[0029] Therefore, the uniformity K is mainly related to the dry mixing time t1 of the dry powder mixture, the mixing speed v of the vertical shaft planetary mixer, and the ratio of the mixing time t4 of the concrete mixture to the mixing time from adding water to the time when the concrete mixture is discharged from the machine. In actual production management, due to the physical and chemical reaction characteristics, material properties and mixing process requirements in the concrete preparation process, the dry mixing time of the dry powder mixture and the ratio of the mixing time of the concrete mixture to the mixing time from adding water to the time when the concrete mixture is discharged from the machine are relatively constant. Therefore, the uniformity K is mainly directly related to the mixing speed v of the vertical shaft planetary mixer.

[0030] Furthermore, the design range of the sum of the wet mixing time after adding water to the mixing system, the steel fiber feeding time and the mixing time of the concrete mixture is 4 to 8 minutes, that is, the time from adding water to the concrete mixture leaving the machine is not less than 4 minutes and not more than 8 minutes, that is, 4min≤t2+t3+t4≤8min.

[0031] In summary, the beneficial effects of the present invention are:

[0032] 1. The coarse aggregate ultra-high performance concrete premix lifting, transportation and mixing device is managed by the control system, which integrates the aggregate batching system, aggregate lifting system, dry mixing host system, feeding car, steel fiber delivery system and mixing system, and realizes the automatic control of the entire mixing process, including key steps such as automatic metering, automatic delivery of raw materials and mixing, which significantly reduces manual operation, thus avoiding errors and inconsistencies that may be caused by manual metering. The automation system ensures the accuracy and repeatability of each mixing, improves the quality control level of concrete production, and enhances the stability and reliability of the production process. In addition, it also improves production efficiency, shortens the production cycle, helps to meet the needs of large-scale production, reduces the dust problem that may be generated during the manual feeding process, improves the working environment, protects the health of workers, and also reduces the impact on the surrounding environment.

[0033] 2. The feed port of the two-stage vibrating screen in the present invention cooperates with the output end of the steel fiber storage bin and performs two-stage vibration on the steel fiber storage bin to achieve homogenization. The steel fiber is transmitted from the steel fiber conveying system to the steel fiber weighing system for measurement according to the ratio by subtraction weighing method, and the steel fiber is evenly sprinkled on the dry powder mixture for mixing. This not only improves the uniformity of the dispersion of the steel fiber in the concrete mixture, avoids the agglomeration of high-strength fine steel fibers due to concentration, but also significantly improves the mixing effect. It makes the mixing process more efficient, can shorten the mixing cycle, and thus improves the overall mixing efficiency.

[0034] 3. The construction sequence of the present invention is that the aggregate batching system outputs the coarse aggregate and fine aggregate mixture to the aggregate lifting system for transmission, the dry mixing host system mixes the coarse aggregate and fine aggregate mixture into dry powder according to the proportion to form a dry powder mixture, the feeding vehicle carries the dry powder mixture to the mixing system for dry mixing, then adds water for wet mixing, and finally puts in steel fiber. Dry mixing first and then wet mixing helps to distribute dry powder and water more evenly, reduce the uneven phenomenon caused by local wetting or drying, reduce the wear of high-hardness materials such as steel fibers on equipment in the early stage of mixing, and improve mixing efficiency and uniformity of concrete.

[0035] 4. By establishing a quantitative relationship between the mixing uniformity index of the concrete mixture and parameters such as mixing time, mixing speed, number of mixing blades, vibration frequency of the two-stage vibrating screen, etc., the key parameters in the mixing process can be controlled more accurately, thereby optimizing the production process, improving the quality and consistency of concrete, ensuring that the mixing uniformity of each batch of concrete meets the predetermined standards, ensuring the mechanical properties and durability of concrete, and reducing quality fluctuations. Accurate calculation helps to quickly determine the minimum time and resources required to achieve the required mixing uniformity, reduce over-mixing or under-mixing, improve production efficiency, reduce production costs, and promote technological innovation. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device of the present invention;

[0037] Figure 2 is a schematic diagram of the aggregate batching system of the present invention;

[0038] Figure 3 is a fitting curve diagram of the uniformity K and the mixing speed v of the vertical axis planetary mixer in this embodiment;

[0039] Among them: 1-feeding car, 2-aggregate batching system, 21-coarse aggregate storage bin, 22-fine aggregate storage bin, 23-three-level metering system, 3-aggregate lifting system, 4-dry mixing host system, 41-powder storage bin, 42-powder conveying system, 43-dry mixing system, 6-steel fiber delivery system, 61-steel fiber storage bin, 62-steel fiber conveying system, 7-mixing system, 71-vertical planetary mixer. DETAILED DESCRIPTION

[0040] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments given here are only used to illustrate and explain the present invention, and cannot be used to limit the present invention.

[0041] It should be noted that many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention may also have other implementations and variations thereof. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0042] like Figure 1 to Figure 2 As shown, the coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device includes a control system, an aggregate batching system 2, an aggregate lifting system 3, a dry mixing main system 4, a feeding vehicle 1, a steel fiber delivery system 6 and a mixing system 7; the output end of the aggregate batching system 2 cooperates with the lower end of the aggregate lifting system 3, the upper end of the aggregate lifting system 3 cooperates with the feed port of the dry mixing main system 4, the delivery port of the feeding vehicle 1 cooperates with the discharge port of the dry mixing main system 4, and is used to receive the dry powder mixture mixed in the dry mixing main system 4, the feeding vehicle 1 unloads the dry powder mixture to the mixing system 7, the mixing system 7 is provided with an automatic weighing water tank for weighing and delivering the required amount of water in the concrete premix to form the concrete premix, the steel fiber delivery system 6 delivers a preset amount of steel fiber to the mixing system 7 for mixing to form a concrete mixture, and the control system controls the mixing time and mixing speed of the mixing system 7, the water adding time and water adding amount of the automatic weighing water tank, and the feeding time of the steel fiber delivery system 6;

[0043] The mixing system 7 includes a plurality of vertical planetary mixers 71, each of which is equipped with a motor and a mixing chamber. A mixing shaft is provided in each mixing chamber. The motor is connected to the mixing shaft through a transmission device. The mixing shaft is provided with a plurality of mixing blades. The mixing shaft drives the mixing blades to rotate under the drive of the motor to mix the concrete mixture.

[0044] The output end of the aggregate batching system 2 cooperates with the aggregate lifting system 3, the dry mixing host system 4, the stirring system 7 and the steel fiber delivery system 6 to form a continuous production process, reducing production interruptions and material waste. Key steps such as automatic metering, automatic raw material delivery and mixing significantly reduce manual operations and avoid errors and inconsistencies that may be caused by manual metering, which helps to meet the needs of large-scale production. The automated and closed production line reduces the generation of dust and noise and reduces the impact on the environment.

[0045] As a preferred embodiment of the present invention, the aggregate batching system 2 includes a coarse aggregate storage bin 21 and a fine aggregate storage bin 22. The output ends of the coarse aggregate storage bin 21 and the fine aggregate storage bin 22 are both provided with a three-level metering system 23. The three-level metering system 23 prepares the aggregate mixture according to the concrete design mix ratio requirements.

[0046] The three-level metering system 23 is provided with a weighing sensor for graded detection of the weight of the material. The first-level metering bucket receives the material output from the coarse aggregate storage bin 21 and the fine aggregate storage bin 22 for preliminary metering. When the first-level metering bucket reaches the preset value, the control system will close the valve of the first-level metering bucket and open the valve of the second-level metering bucket to allow the material to continue to flow into the second-level metering bucket for further metering. Similarly, when the second-level metering reaches the preset value, the control system will close the valve of the second-level metering bucket and open the valve of the third-level metering bucket to complete the final precise metering. The control system will compare the actual metering result with the preset value, and adjust the material flow rate by adjusting the opening time and opening of the valve to ensure that the final aggregate ratio meets the design requirements. This is achieved through an automated control system, which reduces manual intervention and improves metering accuracy and production efficiency.

[0047] Furthermore, the coarse aggregate stored in the coarse aggregate storage bin 21 is crushed stone or pebble, and the fine aggregate stored in the fine aggregate storage bin 22 is one or a combination of natural sand, machine-made sand, corundum, and silicon carbide.

[0048] As a preferred embodiment of the present invention, the dry mixing host system 4 includes a powder storage bin 41, a powder conveying system 42, a powder weighing system and a dry mixing system 43. The powder conveying system 42 is located between the powder storage bin 41 and the dry mixing system 43. The output end of the powder storage bin 41 cooperates with the rear end of the powder conveying system 42, and the front end of the powder conveying system 42 cooperates with the powder weighing system. A valve is provided at the output end of the powder weighing system, and the input end of the powder weighing system receives and weighs the powder, and the powder is put into the dry mixing system 43 through the valve for uniform mixing.

[0049] Furthermore, the powder conveying system 42 adopts a screw conveyor, a pneumatic conveyor or a belt conveyor.

[0050] Screw conveyors are suitable for continuous or intermittent material transportation, and can be transported horizontally, inclined or vertically. When materials need to be transported on a relatively fixed path, the material has a small particle size, and it is not desired that the material be dispersed during transportation, screw conveyors are more suitable; pneumatic conveyors can transport materials through airflow in pipelines, reducing mechanical wear and making it easy to achieve automatic control. When the material transportation distance is long and the material particle size is small and easy to fly, pneumatic conveyors are more suitable, effectively avoiding the compression or crushing of materials during transportation and maintaining a hygienic working environment; belt conveyors can carry larger material loads and adapt to different production layouts. When the material particle size is large or the shape is irregular, and there are certain requirements for the conveying speed and acceleration, belt conveyors are more suitable. Therefore, in actual production operations, the appropriate conveyor can be selected based on the material's particle size, fluidity, fragility and other properties, as well as the distance to be transported, production space and layout, and operating costs.

[0051] Furthermore, the powder storage bin 41 stores a mixture of cement and additives.

[0052] As a preferred embodiment of the present invention, an ultrasonic detection device is also included to detect the uniformity of the concrete mixture, and the uniformity detection result satisfies the following formula:

[0053]

[0054] Where K is the uniformity, m is the number of layers of the ultrasonically tested concrete mixture, ρ0 is the theoretical density of the concrete mixture, is the average density of each layer of the concrete mixture, ρ i is the surface density of the concrete mixture layer i.

[0055] Ultrasonic testing technology is a fast and efficient non-destructive testing method that can perform non-destructive testing on concrete and predict indicators such as the mixing uniformity, strength, and durability of concrete products. To a certain extent, it can guide on-site construction of concrete pouring.

[0056] The ultrasonic detection device in this embodiment includes three parts: an ultrasonic transducer, a computer and a sample container. The ultrasonic transducer is an acoustic-to-electric conversion device, including two probes for ultrasonic transmission and reception, and the probe frequency is 88kHz. The computer has a built-in control program, which can set test parameters, such as ultrasonic frequency, test spacing, etc., and display and record ultrasonic signals through an oscilloscope. The sample container is used to hold the sample to be tested and to place the probe. The concrete material is mixed and stirred by a vertical planetary mixer 71, and the stirred concrete sample is loaded into the ultrasonic detection device. The probe emits ultrasonic waves on one side of the sample and receives ultrasonic waves on the other side through a signal acquisition module, thereby performing density detection on the concrete mixture. The uniformity K of the present invention is measured by the actual average density. By comparing with the theoretical density ρ0, if If it is close to ρ0, it indicates that the uniformity of the concrete mixture is high.

[0057] As a preferred embodiment of the present invention, the steel fiber delivery system 6 includes a steel fiber storage bin 61, a two-stage vibrating screen, a steel fiber conveying system 62 and a steel fiber weighing system. The feed port of the two-stage vibrating screen cooperates with the output end of the steel fiber storage bin 61, the two-stage vibrating screen performs two-stage vibration uniformity on the steel fibers in the steel fiber storage bin 61, the discharge port of the two-stage vibrating screen cooperates with the rear end of the steel fiber conveying system 62, the front end of the steel fiber conveying system 62 cooperates with the steel fiber weighing system, and the steel fiber weighing system adopts subtraction weighing method for weighing.

[0058] The two-stage vibrating screen equipment is connected to the output end of the storage bin and is responsible for vibrating the steel fibers in two stages. The first stage of vibration is used to initially separate and homogenize the steel fibers, and the second stage of vibration further ensures the uniform distribution of the steel fibers to avoid agglomeration and unevenness. The subtraction weighing method ensures the accuracy of the weighing by measuring the initial weight of the container, the weight after adding the steel fibers, and then calculating the actual weight of the steel fibers.

[0059] Furthermore, the uniformity index of the concrete mixture mixed by the mixing system 7 is determined by the mixing time and mixing speed of the vertical axis planetary mixer 71, the number of mixing blades, the feeding time of the steel fiber feeding system 6 and the vibration frequency of the two-stage vibrating screen, and satisfies the following formula:

[0060]

[0061] Wherein, η1, η2, η3 are adjustment coefficients, t1 is the dry mixing time of the dry powder mixture, t2 is the wet mixing time after adding water to the mixing system 7, t3 is the steel fiber feeding time, t4 is the mixing time of the concrete mixture, v is the mixing speed of the vertical axis planetary mixer 71, n is the number of mixing blades, and p is the vibration frequency of the two-stage vibrating screen;

[0062] Among them, the sum of the wet mixing time after adding water to the mixing system 7, the steel fiber feeding time and the mixing time of the concrete mixture should be controlled within the design range and satisfy the following formula:

[0063] T min ≤t2+t3+t4≤T max

[0064] Where, T max is the maximum limit of the design range, T min is the minimum limit of the design range.

[0065] Furthermore, the design range of the sum of the wet mixing time after adding water to the mixing system 7, the steel fiber feeding time and the mixing time of the concrete mixture is 4 to 8 minutes, that is, the time from adding water to the concrete mixture leaving the machine is not less than 4 minutes and not more than 8 minutes, that is, 4min≤t2+t3+t4≤8min.

[0066] like Figure 3 As shown in the figure, in this embodiment, the concrete mix design parameters are 175 kg of water, 461 kg of cement, 512 kg of sand, 1252 kg of crushed stone, 0.8% of water reducer, and a water-cement ratio of 0.38. The cement is ordinary Portland cement with a density of 302 g·cm -3 The sand used is river sand with a fineness modulus of 2.6 and a bulk density of 1485 kg·m -3The crushed stone particle size is 5-10 mm, the water absorption rate is 23%, and the apparent density is 1660 kg·m -3 According to the physical and chemical reaction characteristics, material properties and mixing process requirements in the concrete preparation process, the dry mixing time t1 of the dry powder mixture is set to 3 min, the wet mixing time t2 of the mixing system 7 after adding water is set to 3 min, the steel fiber feeding time t3 is set to 1 min, and the mixing time t4 of the concrete mixture is set to 3 min, that is, t2+t3+t4=7 min, where the number of mixing blades n of the vertical axis planetary mixer 71 is 3, and the vibration frequency p of the two-stage vibrating screen is 50 Hz. The corresponding relationship between the uniformity K and the mixing speed v of the vertical axis planetary mixer 71 is sorted out, and the adjustment coefficients η1, η2, and η3 are 0.017, -2.28×10 -4 , 587.4, so the uniformity K formula is as follows:

[0067]

[0068] According to the curve trend of the relationship fitting, it can be seen that with the increase of the stirring speed v, the uniformity K value of the concrete mixture shows a trend of rising at the beginning, then stabilizing, and finally decreasing. This is because when the stirring speed is too slow, the various aggregates inside the concrete mixture cannot be fully mixed and evenly mixed. With the increase of the stirring speed, the relative movement between the materials is enhanced to make the various aggregates mixed evenly. When the stirring speed is further increased, some components in the concrete, especially the heavier aggregates, will cause segregation, which will reduce the uniformity of the concrete, that is, the uniformity K value will show a downward trend in the end. Based on the curve, it can be determined that in order to ensure that the uniformity K is controlled at more than 98%, the mixing speed v of the vertical axis planetary mixer 71 should be in the range of 24.56r / min to 33.68r / min.

[0069] The uniformity K of the concrete mixture was tested by an ultrasonic testing device. The density of three different layers in the concrete mixture was randomly selected as references, namely ρ1, ρ2, and ρ3, that is, m=3. When the mixing speed v of the vertical axis planetary mixer 71 was set to 26.36 r / min, based on the above parameter settings, ρ1, ρ2, and ρ3 were measured to be 2416.8 kg·m -3 、2456.5kg·m -3 、2370.5kg·m -3 , so the average density of each layer of the concrete mixture is calculated 2414.6 kg·m -3 According to the standard CB / T50080-2016 "Standard for Test Methods of Ordinary Concrete Mixtures", the theoretical density ρ0 is determined to be 2402.6 kg·m by calculating the mass volume formula of the concrete mixture. -3, then the detection result of uniformity K satisfies the following formula:

[0070]

[0071] In summary, when the mixing speed v of the vertical-shaft planetary mixer 71 is set to 26.36 r / min, the uniformity K detected by the ultrasonic detection means is 98.5%, and this result is consistent with the relationship between the uniformity K and the mixing speed v of the vertical-shaft planetary mixer 71, indicating that the ultrasonic detection means can accurately evaluate the uniformity of the concrete mixture and can be used as a scientific, reliable and effective tool for evaluating the mixing effect. At the same time, the relationship between the uniformity K and the mixing speed v can accurately predict the mixing effect, indicating that the relationship has a high reference value in practical applications and can be used to guide the operation and optimization of the mixer.

[0072] It should be understood that the above-mentioned embodiments are one or more embodiments of the present invention, and there are many other embodiments and variations thereof based on the present invention; the variations and modifications made by ordinary technicians in this industry through the present invention without making pioneering innovations all fall within the scope of protection of the present invention.

Claims

1. Coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device, characterized by: It comprises a control system, an aggregate batching system, an aggregate lifting system, a dry mixing main system, a feeding vehicle, a steel fiber delivery system and a mixing system; the output end of the aggregate batching system cooperates with the lower end of the aggregate lifting system, the upper end of the aggregate lifting system cooperates with the feed port of the dry mixing main system, the delivery port of the feeding vehicle cooperates with the discharge port of the dry mixing main system, and is used to receive the dry powder mixture mixed in the dry mixing main system, the feeding vehicle unloads the dry powder mixture to the mixing system, the mixing system is provided with an automatic weighing water tank for weighing and delivering the required amount of water in the concrete, thereby forming a concrete premix, the steel fiber delivery system delivers a preset amount of steel fiber to the mixing system for mixing to form a concrete mixture, the control system controls the mixing time and mixing speed of the mixing system, the water adding time and water adding amount of the automatic weighing water tank, and the feeding time of the steel fiber delivery system; The mixing system includes a plurality of vertical-shaft planetary mixers, each of which is equipped with a motor and a mixing chamber. A mixing shaft is arranged in each mixing chamber. The motor is connected to the mixing shaft via a transmission device. The mixing shaft is provided with a plurality of mixing blades. The mixing shaft drives the mixing blades to rotate under the drive of the motor to mix the concrete mixture.

2. The coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device according to claim 1 is characterized in that: The aggregate batching system comprises a coarse aggregate storage bin and a fine aggregate storage bin. Output ends of the coarse aggregate storage bin and the fine aggregate storage bin are both provided with a three-level metering system. The three-level metering system prepares aggregate mixture according to the concrete design ratio requirements.

3. The coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device according to claim 2 is characterized in that: The coarse aggregate stored in the coarse aggregate storage bin is crushed stone or pebble, and the fine aggregate stored in the fine aggregate storage bin is one or a combination of natural sand, machine-made sand, corundum and silicon carbide.

4. The coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device according to claim 1, characterized in that: The dry mixing host system includes a powder storage bin, a powder conveying system, a powder weighing system and a dry mixing system. The powder conveying system is located between the powder storage bin and the dry mixing system. The output end of the powder storage bin cooperates with the rear end of the powder conveying system, and the front end of the powder conveying system cooperates with the powder weighing system. The output end of the powder weighing system is provided with a valve, and the input end of the powder weighing system receives and weighs the powder, and the powder is put into the dry mixing system through the valve for uniform mixing.

5. The coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device according to claim 4, characterized in that: The powder conveying system adopts a screw conveyor, a pneumatic conveyor or a belt conveyor.

6. The coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device according to claim 4, characterized in that: The powder storage bin stores a mixture of cement and additives.

7. The coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device according to claim 1, characterized in that: It also includes an ultrasonic detection device for detecting the uniformity of the concrete mixture. The detection result of the uniformity K satisfies the following formula: Where K is the uniformity, m is the number of layers of the ultrasonically tested concrete mixture, ρ0 is the theoretical density of the concrete mixture, is the average density of each layer of the concrete mixture, ρ i is the surface density of the concrete mixture layer i.

8. The coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device according to claim 1, characterized in that: The steel fiber delivery system includes a steel fiber storage bin, a two-stage vibrating screen, a steel fiber conveying system and a steel fiber weighing system. The feed port of the two-stage vibrating screen cooperates with the output end of the steel fiber storage bin. The two-stage vibrating screen performs two-stage vibration uniformity on the steel fibers in the steel fiber storage bin. The discharge port of the two-stage vibrating screen cooperates with the rear end of the steel fiber conveying system. The front end of the steel fiber conveying system cooperates with the steel fiber weighing system. The steel fiber weighing system adopts subtraction weighing method for weighing.

9. The coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device according to claim 8, characterized in that: The uniformity index of the concrete mixture stirred by the mixing system is determined by the mixing time and mixing speed of the vertical axis planetary mixer, the number of the mixing blades, the feeding time of the steel fiber feeding system and the vibration frequency of the two-stage vibrating screen, and satisfies the following formula: Wherein, η1, η2, η3 are adjustment coefficients, t1 is the dry mixing time of the dry powder mixture, t2 is the wet mixing time after the mixing system is added with water, t3 is the steel fiber feeding time, t4 is the mixing time of the concrete mixture, v is the mixing speed of the vertical axis planetary mixer, n is the number of the mixing blades, and p is the vibration frequency of the two-stage vibrating screen; The sum of the wet mixing time after adding water to the mixing system, the steel fiber feeding time and the mixing time of the concrete mixture should be controlled within the design range and satisfy the following formula: T min ≤t2+t3+t4≤T max Where, T max is the maximum limit of the design range, T min is the minimum limit of the design range.

10. The coarse aggregate ultra-high performance concrete premix lifting, transporting and mixing device according to claim 9, characterized in that: The design range of the sum of the wet mixing time after adding water to the mixing system, the steel fiber feeding time and the mixing time of the concrete mixture is 4 to 8 minutes, that is, the time from adding water to the concrete mixture leaving the machine is not less than 4 minutes and not more than 8 minutes, that is, 4min≤t2+t3+t4≤8min.

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