Optimization method of modified bamboo fiber partially replacing steel fiber in uhp

Abstract

The application provides an optimization method for partially replacing steel fibers with modified bamboo fibers in UHPC, and specifically comprises the following steps: selecting fresh bamboo, cutting the bamboo tube, and pretreating the bamboo tube to obtain bamboo strips; modifying the bamboo strips to produce modified bamboo fibers with a preset length; uniformly mixing 1.0% volume of end-hook type steel fibers, 1.0% volume of modified bamboo fibers with a preset length, and ultra-high performance concrete in a fiber mixer; filling the ultra-high performance concrete into a mold and vibrating to form; curing and hardening the formed concrete to obtain a hybrid fiber ultra-high performance concrete structure component. The hybrid fiber ultra-high performance concrete structure component prepared by the application has almost the same compressive strength as the steel fiber UHPC, and the flexural strength and splitting tensile strength are better than those of the steel fiber; and the hybrid incorporation of the modified bamboo fibers and the steel fibers can achieve the dual goals of green low carbon and reduced UHPC cost.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of ultra-high performance concrete, in particular to an optimization method for replacing steel fibers with modified bamboo fibers in UHPC. BACKGROUND

[0002] In the ever-changing building industry, material innovation has always been an important driving force for the development of the industry. Ultra-high performance concrete (UHPC) is a new type of building material leading the industry trend, which has high strength, high toughness, high durability, self-compacting, beauty and texture. With its outstanding performance and wide application prospect, it has become the darling of the construction industry.

[0003] Ultra-high performance concrete is usually added with steel fibers to improve its performance. Steel fibers play a locking role at micro-cracks to prevent crack expansion; enhance impact resistance by absorbing and buffering external force impact to improve the impact resistance of concrete; improve tensile strength and improve load-carrying capacity; prolong service life and make concrete more durable. However, the cost of steel fibers is relatively high, which is a major factor limiting its application scale.

[0004] Therefore, scholars have been committed to finding more economical and environmentally friendly steel fiber replacement materials. SUMMARY

[0005] The purpose of the present application is to improve and innovate in view of the shortcomings and problems in the background art, and to provide an optimization method for replacing steel fibers with modified bamboo fibers in UHPC.

[0006] An optimization method for replacing steel fibers with modified bamboo fibers in UHPC, specifically comprising the following steps:

[0007] Step S1, selecting fresh bamboo, cutting the bamboo tube, and pretreating the bamboo tube to obtain bamboo strips;

[0008] Step S2, modifying the bamboo strips to produce modified bamboo fibers of a predetermined length;

[0009] Step S3, stirring 1.0% volume of end-hook type steel fibers, 1.0% volume of modified bamboo fibers of a predetermined length, and ultra-high performance concrete in a fiber mixer;

[0010] Step S4, filling the ultra-high performance concrete into a mold and vibrating to form; curing and hardening the formed concrete to prepare a hybrid fiber ultra-high performance concrete structure component.

[0011] Further, the step S1 of pretreatment specifically includes:

[0012] Whole material process: remove the branches and sharp tips on the bamboo tube, and cut the bamboo tube into single stems;

[0013] Bamboo piece preparation: split bamboo into bamboo pieces of specific size;

[0014] Inner layer removal: remove the green and yellow parts of the bamboo pieces.

[0015] Further, the step S2 specifically includes:

[0016] Chemical modification of the bamboo strips;

[0017] Place the bamboo strips in an oven at 103°C for 6 hours to achieve complete dehydration of the bamboo fibers;

[0018] Prepare a 4% sodium chlorite solution, add glacial acetic acid to adjust the pH value of the solution, and place it in a constant temperature water bath at 80°C for heating. The dehydrated bamboo fibers are placed in a beaker, and the beaker opening is sealed with plastic wrap. The treatment time is 2-5 hours;

[0019] Wash the solution remaining on the surface of the bamboo pieces with deionized water;

[0020] Place the bamboo sample after delignification in an oven at 60°C for 15 minutes;

[0021] Dry at room temperature for 2 hours;

[0022] Obtain single bundle of modified bamboo fibers by defibrating with a bamboo decomposition machine.

[0023] Further, the step S3 specifically includes:

[0024] Mix cement, silica fume, micro-fine mineral powder, quartz powder, fly ash, and quartz sand into the fiber mixer, dry mix for 5 minutes, add mixing water, and stir for 5 minutes.

[0025] Add 1.0% volume fraction of end-hook type steel fibers and 1.0% volume fraction of modified bamboo fibers, and stir for 10 minutes.

[0026] Further, the step S4 specifically includes:

[0027] Pour the uniformly stirred ultra-high performance concrete into the mold coated with release agent, set the vibration time to 3 minutes using a vibration table, and vibrate to form, and then tamp the test block into shape;

[0028] After the test piece is formed, it is placed in a standard curing room for 2 days;

[0029] After the test block is demolded, it is placed in a cement rapid curing box, the heating rate is set to , and the temperature is raised to 72°C for 3 days, and finally the test block is cured in a standard curing room for 28 days. The rate of cooling is adjusted back to room temperature.

[0030] Further, the fiber mixer comprises a box body, a feeding pipe is arranged on the top wall of the box body, a guide hopper is arranged below the feeding pipe, a feeding hopper is fixedly connected to the bottom end of the guide hopper, a conical block is arranged at the bottom center of the feeding hopper, the outlet of the guide hopper is located directly above the conical block, at least the guide hopper is in the shape of a circular truncated cone, the cross-sectional diameter of the top end of the guide hopper is greater than the diameter of the outlet of the bottom end of the feeding pipe, the outer wall of the feeding hopper is connected with a first sliding block through a connecting structure, the first sliding block is slidingly arranged on a first sliding rod, and the first sliding block reciprocates along the central axis of the first sliding rod under the action of a driving mechanism.

[0031] Further, the cross-sectional diameter of the top end of the guide hopper is 2.0-5.0 times the diameter of the outlet of the bottom end of the feeding pipe.

[0032] Further, the driving mechanism comprises a first motor, a residual conical gear is fixedly connected to the output end of the first motor, the residual conical gear is in meshing connection with a first conical gear and a second conical gear in sequence, the first conical gear and the second conical gear are installed on the same gear shaft, the gear shaft drives a threaded rod to rotate through a transmission mechanism, and the middle part of the threaded rod penetrates through the first sliding block and is in threaded connection with the first sliding block.

[0033] Further, a worm is rotatably connected inside the first sliding block, the central axis of the worm is perpendicular to the central axis of the first sliding rod, the worm is in meshing connection with a worm wheel, a residual gear is interference-fitted on the shaft of the worm wheel, the teeth on the residual gear are used for meshing connection with a second rack, the second rack is installed on a second sliding block, the second sliding block is slidingly arranged on a second sliding rod, a spring is sleeved on the second sliding rod, one end of the connecting structure away from the feeding hopper is connected with the second sliding block, and an interference-fitted third gear is arranged on at least one end of the outer surface of the worm, the third gear is in meshing connection with a first rack installed on the lower surface of the top wall of the box body.

[0034] Further, a stirring structure is further arranged inside the box body, and a discharging structure is arranged on the bottom wall of the box body.

[0035] Compared with the prior art, the present application has the following advantages: (1) The natural bamboo fiber is modified in the present application, so that it has high strength and high elastic modulus. The performance of the modified bamboo fiber is greatly improved, the tensile strength of the bamboo fiber can reach 1500MPa~1800MPa, and the elastic modulus can reach 70GPa. The modified bamboo fiber can better pass through the crack to form an effective fiber bridge, thereby improving the compressive strength of the UHPC. Under the premise of the same volume content of 2%, the UHPC with a hybrid fiber combination of 1.0% end-hook type steel fiber + 1.0% 12mm length modified bamboo fiber has almost the same compressive strength as the steel fiber UHPC, and the flexural strength and splitting tensile strength are better than the steel fiber. Moreover, the hybrid incorporation of modified bamboo fiber and steel fiber can achieve the dual goals of green low carbon and reducing the cost of UHPC;

[0036] (2) Bamboo resources are very abundant, and once planted, they can grow forever and have strong renewability. Using modified bamboo fiber to partially replace part of the steel fiber in the ultra-high performance concrete component has great economic benefits. The growth process of bamboo resources is a carbon fixation process, which fully meets the development concept of green low carbon;

[0037] (3) The fiber mixer of the present application can make the discharge of the feeding pipe fall exactly on the conical block even if the guide hopper and the feeding hopper move relative to the box. The conical block makes the fibers disperse into the box. If the guide hopper and the feeding hopper move relative to the box, the fibers are further dispersed in different positions of the box, thereby avoiding uneven dispersion of the fibers in the ultra-high performance concrete due to clumping. In addition, during the movement of the first sliding block relative to the box in the width direction, the guide hopper and the feeding hopper are automatically driven to reciprocate in the front and back directions relative to the box. After the circular table-shaped guide hopper moves forward and backward and left and right relative to the feeding pipe, it does not interfere with the feeding pipe. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described in the following only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0039] Figure 1 The structural schematic diagram of the ultra-high performance concrete provided by the embodiments of the present application;

[0040] Figure 2 The structural schematic diagram of the fiber mixer provided by the embodiments of the present application;

[0041] Figure 3 For the purpose of the present application Figure 2 A local enlarged structure schematic view at the place of B in the present application is shown in the figure;

[0042] Figure 4 A cross-sectional structure schematic view of the first sliding block provided by the embodiment of the present application and located at the left side of the feeding hopper is shown in the figure;

[0043] Figure 5 A cross-sectional structure schematic view of the first sliding block provided by the embodiment of the present application and located at the right side of the feeding hopper is shown in the figure;

[0044] Figure 6 A cross-sectional structure schematic view of the mounting frame provided by the embodiment of the present application is shown in the figure.

[0045] The figure shows the following: a box 1, a feeding pipe 2, a guide hopper 3, a feeding hopper 4, a conical block 5, a connecting structure 6, a first sliding block 7, a threaded rod 8, a first sliding rod 9, a mounting frame 10, a first motor 11, a residual conical gear 12, a first conical gear 13, a second conical gear 14, a first gear 15, a second gear 16, a first rack 17, a third gear 18, a worm 19, a worm wheel 20, a residual gear 21, a second rack 22, a second sliding block 23, a second sliding rod 24, a spring 25, a stirring structure 26, a discharging structure 27, modified bamboo fiber 28, steel bamboo fiber 29, ultra-high performance concrete 30. DETAILED DESCRIPTION

[0046] In order to make the purpose, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0047] It should be noted that when an element is referred to as being "fixed" to another element, it can be directly on the other element or there can be an intervening element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there can be an intervening element.

[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0049] Example 1

[0050] The present application provides an optimization method for replacing steel fibers with modified bamboo fibers in UHPC, which specifically comprises the following steps:

[0051] Step S1, fresh bamboo is selected, and a bamboo cylinder is cut off, and the bamboo cylinder is pretreated to obtain a bamboo strip;

[0052] Specifically, first, fresh bamboo of 1 year old is selected, and bamboo tubes of the same height are cut off, with a diameter of 80-92 mm and a thickness of 6.1-7.2 mm. The bamboo tube is a bamboo tube segment 1.5 m away from the ground, with a length of about 2.0 m. After the bamboo tube is cut off, the bamboo tube is pretreated. The main process of pretreatment mainly includes the material sorting process. The material sorting process first removes the branches and sharp tips on the bamboo tube to ensure uniformity in subsequent processing. Then, the bamboo is cut into single stems with a length of 33 cm to meet the needs of preparing bamboo chips.

[0053] After the material sorting process, the bamboo chip preparation process is carried out. In the bamboo chip preparation process, the bamboo tube is split into bamboo chips of a specific size using machine or manual technology. These bamboo chips usually have a length of 33 cm, a width of 8-10 mm, and a thickness of 2-4 mm. The size of the bamboo chips can be adjusted according to the needs of the product. After the bamboo chip preparation process, the inner layer removal process is carried out. In the inner layer removal process, the bamboo green and bamboo yellow parts in the bamboo chips are removed by machine or manual method to ensure the quality and stability of the bamboo and prepare for subsequent use. The accurate execution of the above pretreatment steps ensures smooth conversion from bamboo to bamboo chips, providing a solid bamboo foundation for experimental projects.

[0054] Step S2, modifying the bamboo strips to make modified bamboo fibers of a preset length;

[0055] In this embodiment, the bamboo strips are modified by traditional chemical methods. Specifically, the bamboo strips are placed in an oven at 103°C for 6 hours to achieve complete dehydration of the bamboo fibers. Second, a 4% sodium chlorite solution is prepared, and glacial acetic acid is added to adjust the pH value of the solution. The solution is heated in a constant temperature water bath at 80°C, and the beaker opening is sealed with plastic wrap. The treatment time is 2-5 hours. The bamboo chips are washed with deionized water to remove the solution remaining on the surface of the bamboo chips. Then, the bamboo sample after delignification is placed in an oven at 60°C for 15 minutes, and dried at room temperature for 2 hours before storage. Finally, single modified bamboo fibers are prepared by defibrillation of the bamboo using a bamboo decomposition machine.

[0056] In this embodiment, the modified bamboo fibers of a preset length can be 6 mm, 9 mm, and 12 mm.

[0057] It should be noted that the method for making modified bamboo fibers of a preset length also includes a physical method, which directly processes the cut-off bamboo cylinder. Specifically, first, the bamboo cylinder is subjected to a softening process, the bamboo cylinder specimen is soaked in water for 12 hours, and then the bamboo cylinder is placed in a solution of 8% by mass fraction of NAOH for high-temperature normal-pressure cooking softening for 90 minutes to achieve the softening effect of the bamboo cylinder. Second, the softened bamboo cylinder is subjected to a pressure fiberizing test using a bamboo cutting machine. After the fiberizing is completed, the specimen is cleaned and arranged, and then dried in a vacuum drying oven to obtain the modified bamboo fibers.

[0058] It should be further noted that the natural bamboo fibers are modified to have high strength and high elastic modulus, and the performance of the modified bamboo fibers is greatly improved, with a tensile strength of 1500MPa~1800MPa and an elastic modulus of 70GPa.

[0059] Step S3, stirring 1.0% by volume of end-hook type steel fibers, 1.0% by volume of modified bamboo fibers of a preset length, and ultra-high performance concrete in a fiber mixer;

[0060] Specifically, first, the raw materials of ultra-high performance concrete (UHPC) are added to the fiber mixer, and the raw materials of ultra-high performance concrete (UHPC) are stirred in the fiber mixer. After uniform stirring, 1.0% by volume of end-hook type steel fibers and 1.0% by volume of modified bamboo fibers of a preset length are added to the fiber mixer; continue to stir to uniformly disperse the fiber raw materials in the concrete.

[0061] Specifically, the mass of each material is accurately measured, and the cement, silica fume, micro-fine powder, quartz powder, fly ash, and quartz sand are mixed and poured into the fiber mixer, and dry mixing is performed for 5 Slowly add the mixing water (high-efficiency water reducing agent and water), and stir for 5 Finally, slowly and uniformly add the fibers, and stir for 10 .

[0062] It should be noted that the preparation principles of ultra-high performance concrete and ordinary concrete are different. The main manifestations are as follows: the maximum packing density theory is adopted for ultra-high performance concrete, and the most compact packing is formed by configuring different particle size particles; ultra-high performance concrete does not use coarse aggregate, and the particle size of fine aggregate is also required to be not greater than 1 mm; materials such as silica fume, fly ash, cement, ultra-active slag powder, quartz powder, super-efficient water reducing agent (polycarboxylic acid water reducing agent), quartz, and water are used.

[0063] In this embodiment, 1.0% by volume of end hook type steel fiber and 1.0% by volume of modified bamboo fiber of preset length are mixed in the cement base. Compared with the performance of 2% by volume of steel fiber UHPC under the premise of the same volume of fiber, the UHPC of the present application 1.0% by volume of end hook type steel fiber + 1.0% by volume of modified bamboo fiber of preset length is superior to the steel fiber in the bending strength and the splitting tensile strength under the condition that the compressive strength is almost unchanged. Moreover, the mixed incorporation of modified bamboo fiber and steel fiber can achieve the double goals of green low carbon and reducing the cost of UHPC.

[0064] It should be noted that the end hook type steel fiber referred to in this embodiment refers to the finished steel fiber with a fiber diameter of 2.0 mm and a hook at the end.

[0065] Step S4, filling the ultra-high performance concrete into the mold and vibrating to form; curing and hardening the formed concrete to prepare the hybrid fiber ultra-high performance concrete structural member;

[0066] Specifically, the uniformly stirred ultra-high performance concrete is poured into the mold coated with release agent, the vibration table is set to a vibration time of 3 min, and the concrete is vibrated to form. Finally, the test block is smoothed to form.

[0067] After the test piece is formed, it is placed in a standard curing room for 2 days before demolding. After the test block is demolded, it is placed in a cement rapid curing box, the temperature rising rate is set to , and the temperature is raised to 72 h for 3 days. Finally, the temperature is adjusted back to room temperature at a rate of . The test block is taken out to prepare the hybrid fiber ultra-high performance concrete structural member, and the ultra-high performance concrete structural member is shown in Figure 1 .

[0068] Performance test of the ultra-high performance concrete structural member:

[0069] In this embodiment, the effects of different shape types of steel fiber, three different volume contents (1%, 1.5%, and 2%) and hybrid hook type steel fiber and modified bamboo fiber on the fluidity and mechanical properties of ultra-high performance concrete (UHPC) are studied when the steel fiber is mixed alone.

[0070] Table 1 Test results of the fluidity of UHPC mixed with steel fiber alone

[0071] No. Fiber shape category Fiber length (mm) Dosage (%) Flowability (mm) A-0 No fiber / / 252 A-1 SF 12 1% 242 A-2 SF 12 1.5% 235 A-3 SF 12 2% 230 B-1 HF 12 1% 236 B-2 HF 12 1.5% 224 B-3 HF 12 2% 215

[0072] Note: SF: straight steel fiber; HF: end hook type steel fiber.

[0073] Table 2 Effect of steel fiber on the compressive strength of UHPC ​

[0074] No. Fiber type Volume dosage (%) Fiber length (mm) Compressive strength (MPa) A-0 No fiber / / 80 A-1 SF 1% 12 101 A-2 SF 1.5% 12 106 A-3 SF 2% 12 112 B-1 HF 1% 12 108 B-2 HF 1.5% 12 117 B-3 HF 2% 12 124

[0075] Table 3 Influence of steel fiber on flexural strength of UHPC

[0076] No. Fiber type Dosage (%) Fiber length (mm) Folding strength (MPa) A-0 No fiber / / 16 A-1 Flat type SF 1% 12 17.9 A-2 Flat type SF 1.5% 12 18.7 A-3 Flat type SF 2% 12 19.5 B-1 End hook type HF 1% 12 18.9 B-2 End hook type HF 1.5% 12 20.2 B-3 End hook type HF 2% 12 21.5

[0077] Table 4 Influence of hybrid fiber on flowability of UHPC

[0078] Fiber combination type Flowability Fiber combination type Flowability 1.5% HF + 0.5% BF 6 mm 215 1.5% SF + 0.5% BF 6 mm 220 1% HF + 1% BF 6 mm 187 1% SF + 1% BF 6 mm 202 0.5% HF + 1.5% BF 6 mm 175 0.5% SF + 1.5% BF 6 mm 176 1.5% HF + 0.5% BF 9 mm 202 1.5% SF + 0.5% BF 9 mm 214 1% HF + 1% BF 9 mm 172 1% SF + 1% BF 9 mm 196 0.5% HF + 1.5% BF 9 mm 157 0.5% SF + 1.5% BF 9 mm 169 1.5% HF + 0.5% BF 12 mm 185 1.5% SF + 0.5% BF 12 mm 210 1% HF + 1% BF 12 mm 165 1% SF + 1% BF 12 mm 185 0.5% HF + 1.5% BF 12 mm 147 0.5% SF + 1.5% BF 12 mm 163

[0079] Note: HF end-hook type steel fiber; SF flat type steel fiber; BF represents modified bamboo fiber.

[0080] Table 5 Influence of hybrid fiber on compressive strength of UHPC

[0081] Fiber combination type Compressive strength (MPa) Fiber combination type Compressive strength (MPa) 1.5% HF + 0.5% BF 6 mm 119.4 1.5% SF + 0.5% BF 6 mm 114.7 1% HF + 1% BF 6 mm 105.4 1% SF + 1% BF 6 mm 100.8 0.5% HF + 1.5% BF 6 mm 97.2 0.5% SF + 1.5% BF 6 mm 92.5 1.5% HF + 0.5% BF 9 mm 130.6 1.5% SF + 0.5% BF 9 mm 124.6 1% HF + 1% BF 9 mm 119.2 1% SF + 1% BF 9 mm 113.8 0.5% HF + 1.5% BF 9 mm 98.6 0.5% SF + 1.5% BF 9 mm 94.6 1.5% HF + 0.5% BF 12 mm 133.2 1.5% SF + 0.5% BF 12 mm 126.3 1% HF + 1% BF 12 mm 122.5 1% SF + 1% BF 12 mm 118.4 0.5% HF + 1.5% BF 12 mm 101.8 0.5% SF + 1.5% BF 12 mm 96.8

[0082] Note: HF end-hook type steel fiber; SF flat type steel fiber; BF represents modified bamboo fiber.

[0083] Table 6 Influence of hybrid fiber on flexural strength of UHPC

[0084] Fiber combination type Folding strength (MPa) Fiber combination type Folding strength (MPa) 1.5% HF + 0.5% BF 6 mm 16.8 1.5% SF + 0.5% BF 6 mm 15.7 1% HF + 1% BF 6 mm 19.9 1% SF + 1% BF 6 mm 18.7 0.5% HF + 1.5% BF 6 mm 15.1 0.5% SF + 1.5% BF 6 mm 14.1 1.5% HF + 0.5% BF 9 mm 19.4 1.5% SF + 0.5% BF 9 mm 18.8 1% HF + 1% BF 9 mm 22.5 1% SF + 1% BF 9 mm 21.4 0.5% HF + 1.5% BF 9 mm 0.5% SF + 1.5% BF 9 mm 1.5% HF + 0.5% BF 12 mm 1.5% SF + 0.5% BF 12 mm 1% HF + 1% BF 12 mm 1% SF + 1% BF 12 mm 0.5% HF + 1.5% BF 12 mm 0.5% SF + 1.5% BF 12 mm 18 0.5% SF + 1.5% BF 9 mm 15.8 1.5% HF + 0.5% BF 12 mm 20.9 1.5% SF + 0.5% BF 12 mm 18.7 1% HF + 1% BF 12 mm 23.3 1% SF + 1% BF 12 mm 22.2 0.5% HF + 1.5% BF 12 mm 18.2 0.5% SF + 1.5% BF 12 mm 17.3

[0085] Note: HF end-hook type steel fiber; SF flat type steel fiber; BF represents modified bamboo fiber.

[0086] Table 7 Influence of hybrid fiber on splitting tensile strength of UHPC

[0087] Fiber combination type Split tensile strength (MPa) Fiber combination type Split tensile strength (MPa) 1.5% HF + 0.5% BF 6 mm 9.2 1.5% SF + 0.5% BF 6 mm 7.6 1% HF + 1% BF 6 mm 11.8 1% SF + 1% BF 6 mm 10.2 0.5% HF + 1.5% BF 6 mm 7.6 0.5% SF + 1.5% BF 6 mm 6.4 1.5% HF + 0.5% BF 9 mm 10.8 1.5% SF + 0.5% BF 9 mm 8.8 1% HF + 1% BF 9 mm 13.0 1% SF + 1% BF 9 mm 10.8 0.5% HF + 1.5% BF 9 mm 9.0 0.5% SF + 1.5% BF 9 mm 7.8 1.5% HF + 0.5% BF 12 mm 13.1 1.5% SF + 0.5% BF 12 mm 11.2 1% HF + 1% BF 12 mm 14.8 1% SF + 1% BF 12 mm 13.5 0.5% HF + 1.5% BF 12 mm 10.4 0.5% SF + 1.5% BF 12 mm 8.9

[0088] Note: HF end-hook type steel fiber; SF flat type steel fiber; BF represents modified bamboo fiber.

[0089] Example 2

[0090] In the preparation process of hybrid fiber concrete, the raw materials and fibers of concrete are weighed according to the proportion, the raw materials of concrete are first put into the fiber mixer for stirring, the modified bamboo fiber and the end-hook type steel fiber are slowly added after stirring for a period of time, and the ultra-high performance concrete is obtained after uniform stirring and discharging.

[0091] However, since the fiber raw materials are generally added to the fiber mixer through fixed feeding channels, there is a phenomenon of partial clumping of the added fibers, which leads to uneven dispersion of the fibers in the concrete, thereby reducing the tensile, bending and impact strength of the ultra-high performance concrete; therefore, the present embodiment proposes a fiber mixer to improve this.

[0092] Please refer to Figures 2-6The fiber stirring machine comprises a box body 1, a feeding pipe 2 arranged in the middle of the top wall of the box body 1, a guide hopper 3 arranged directly below the feeding pipe 2, the upper and lower ends of the guide hopper 3 being open, a feeding hopper 4 fixedly connected to the outer surface of the bottom end of the guide hopper 3, and the lower end of the feeding hopper 4 being open. A conical block 5 is arranged at the bottom center of the feeding hopper 4, and the conical block 5 is connected to the inner surface of the feeding hopper 4 through a connecting rod. The outlet of the guide hopper 3 is located directly above the conical block 5, so that the discharged material of the guide hopper 3 falls on the conical block 5, and the conical block 5 makes the fibers dispersed and then enter the box body 1. The guide hopper 3 and the feeding hopper 4 are both circular truncated cone-shaped. The cross-sectional diameter of the top end of the guide hopper 3 is greater than the diameter of the outlet of the bottom end of the feeding pipe 2. When the discharged material of the feeding pipe 2 falls on the inner wall of the guide hopper 3 at different positions, it can fall on the conical block 5 under the guidance of the guide hopper 3. Preferably, the cross-sectional diameter of the top end of the guide hopper 3 is 2.0-5.0 times the diameter of the outlet of the bottom end of the feeding pipe 2, that is, the cross-sectional diameter of the top end of the guide hopper 3 is obviously greater than the diameter of the outlet of the bottom end of the feeding pipe 2, so that the guide hopper 3 can move within a certain range relative to the feeding pipe 2. Since the guide hopper 3 can move relative to the feeding pipe 2, and the guide hopper 3 and the feeding hopper 4 are connected to each other, the feeding hopper 4 can be moved, so that the fibers are further dispersed at different positions in the box body 1, avoiding uneven dispersion of the fibers in the ultra-high performance concrete due to clumping, and being beneficial to improving the tensile, bending and impact strength of the ultra-high performance concrete.

[0093] Please continue to refer to Figure 2 In order to realize the movement of the guide hopper 3 relative to the feeding pipe 2, first sliding blocks 7 are connected to the left and right outer walls of the feeding hopper 4 through connecting structures 6. The first sliding blocks 7 are slidingly arranged on first sliding rods 9, and the first sliding block 7 located on the left side of the feeding hopper 4 is threadedly connected with a threaded rod 8. The threaded rod 8 penetrates through and is threadedly connected with the first sliding block 7 at the middle part, and the two ends of the threaded rod 8 are rotationally connected with the left side wall of the box body 1 and the outer wall of the feeding pipe 2, respectively. The threaded rod 8 is driven to rotate by a driving mechanism, so that the first sliding block 7 reciprocates along the central axis of the first sliding rod 9, and the guide hopper 3 and the feeding hopper 4 reciprocate along the width direction of the box body 1 as a whole, so as to realize the dispersion of the fibers at different positions in the box body 1, so that the ultra-high performance concrete and the fiber raw materials are uniformly mixed during the stirring process, and the tensile, bending and impact strength of the ultra-high performance concrete is improved.

[0094] Specifically, please refer to Figure 6The driving mechanism comprises a mounting frame 10 mounted on the left side wall of the box body 1, a first motor 11 mounted on the bottom wall of the mounting frame 10, and a residual conical gear 12 fixedly connected to the output end of the first motor 11. The residual conical gear 12 is in turn meshingly connected with a first conical gear 13 and a second conical gear 14, which are mounted on the same gear shaft. A first gear 15 is also mounted on the gear shaft, and the first gear 15 is meshingly connected with a second gear 16. One end of the threaded rod 8 extends into the mounting frame 10 and is connected with the second gear 16. It can be understood that when the first motor 11 drives the residual conical gear 12 to rotate, the residual conical gear 12 is in turn meshingly connected with the first conical gear 13 and the second conical gear 14, so that the corresponding gear shafts of the first conical gear 13 and the second conical gear 14 are in turn positively rotated and reversely rotated, and then under the driving cooperation of the first gear 15 and the second gear 16, the threaded rod 8 is positively rotated and reversely rotated, and after the threaded rod 8 is positively rotated and reversely rotated, the guiding hopper 3 and the feeding hopper 4 are further reciprocated along the width direction of the box body 1 as a whole.

[0095] Further, please refer to Figures 3-5The worm 19 is rotatably connected in the first sliding block 7 on the left side of the feeding hopper 4, wherein the central axis of the worm 19 is perpendicular to the central axis of the first sliding rod 9. The worm 19 is meshingly connected with a worm wheel 20, and the worm wheel 20 is interference-fitted with a residual gear 21 on the wheel shaft, that is, the worm wheel 20 and the residual gear 21 are installed on the same wheel shaft. The teeth on the residual gear 21 are used for intermittently meshingly connecting with the teeth on a second rack 22. The second rack 22 is installed on a second sliding block 23, and the second sliding block 23 is slidingly arranged on a second sliding rod 24, and the two ends of the second sliding rod 24 are installed on the inner wall of the first sliding block 7. A spring 25 is sleeved on the second sliding rod 24, and the two ends of the spring 25 are respectively abutted against the second sliding block 23 and the inner wall of the first sliding block 7. In this embodiment, the end of the connecting structure 6 away from the feeding hopper 4 is connected with the lower surface of the second sliding block 23, and specifically, the connecting structure 6 includes a horizontal rod and a vertical rod connected with each other. A sliding groove for the vertical rod to slide is formed in the bottom wall of the first sliding block 7. The outer surface of the two ends of the worm 19 is also interference-fitted with a third gear 18, and the third gear 18 is meshingly connected with a first rack 17 installed on the lower surface of the top wall of the box body 1. In the process that the first sliding block 7 moves from one end of the threaded rod 8 to the other end, the third gear 18 is meshingly connected with the first rack 17 to drive the worm 19 to rotate, and under the transmission cooperation of the worm 19 and the worm wheel 20, the residual gear 21 is driven to rotate. When the teeth on the residual gear 21 cooperate with the second rack 22, the second sliding block 23 will slide on the second sliding rod 24 and compress the spring 25, and when the teeth on the residual gear 21 are disengaged from the second rack 22, the second sliding block 23 will move reversely under the reset action of the spring 25. Since the second sliding block 23 is connected with the feeding hopper 4 through the connecting structure 6, the guiding hopper 3 and the feeding hopper 4 are simultaneously reciprocated along the front-back direction of the box body 1 in the process that they move along the width direction of the box body 1, and the fibers are further dispersed at different positions of the box body 1 so as to be fully dispersed.

[0096] It should be noted that the reciprocating movement of the guiding hopper 3 and the feeding hopper 4 along the front-back direction of the box body 1 is in the process that they move from the left side of the box body 1 to the right side or in the process that they move from the right side of the box body 1 to the left side, rather than in the process that they move from the center of the box body 1 to the edge, that is, the guiding hopper 3 and the feeding hopper 4 are not obliquely moved from the center of the box body 1 to the edge. Instead, they are reciprocated along the front-back direction of the box body 1 in the process that the box body 1 moves laterally to the left or to the right in one direction, so that the fibers can be fully dispersed at different positions of the box body 1.

[0097] It needs to be further explained that the guide hopper 3 and the feeding hopper 4 can move left and right along the box body 1 and can also move forward and backward along the box body 1, and the characteristics that the circular table-shaped guide hopper 3 will not interfere with the feeding pipe 2 after moving forward and backward and left and right are fully utilized; it needs to be noted that when the edge of the guide hopper 3 is close to the feeding pipe 2, the inner wall of the guide hopper 3 is close to the feeding pipe 2 in the front and back direction; therefore, when the guide hopper 3 and the feeding hopper 4 move left and right, the limit position of the movement should be spaced apart from the feeding pipe 2 by a certain distance, so as to avoid the front and back reciprocating movement of the guide hopper 3 from colliding with the feeding pipe 2 when the guide hopper 3 is too close to the feeding pipe 2.

[0098] Further, please continue to refer to Figure 1 The box body 1 is further provided with a stirring structure 26, the stirring structure 26 comprising a second motor and a stirring paddle, the second motor being installed on the side wall of the box body 1, and the output end of the second motor being connected with the stirring paddle. The bottom wall of the box body 1 is provided with a discharging structure 27, the discharging structure 27 comprising a discharging channel and a flow guide block, the flow guide block being arranged on the bottom wall of the box body 1 and being used for guiding the uniformly stirred ultra-high performance concrete into the discharging channel, and the opening and closing of the discharging channel can be controlled through a valve.

[0099] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application.

[0100] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "illustrative embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example.

[0101] It is apparent that the described embodiments are only some, but not all, of the embodiments of the present application. Reference to "an embodiment" in this text means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. The appearances of the phrase "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. As those skilled in the art will appreciate, embodiments described herein can be combined with other embodiments in various ways. All other embodiments obtained by combining the embodiments described herein in various ways are within the scope of the present application.

[0102] Although the embodiments of the present application have been shown and described, it will be appreciated by those skilled in the art that changes can be made in these embodiments without departing from the principles and the scope of the application, which is defined by the claims and their equivalents.

Claims

1. An optimization method for partially replacing steel fiber with modified bamboo fiber in UHPC, characterized in that: The specific steps include: Step S1: selecting fresh bamboo, cutting bamboo tubes, and pre-treating the bamboo tubes to obtain bamboo strips; Step S2: modifying the bamboo strips to produce modified bamboo fibers of a preset length; Step S3, mixing 1.0% by volume of end hook steel fiber, 1.0% by volume of modified bamboo fiber of preset length, and ultra-high performance concrete in a fiber mixer; Step S4: Filling the hybrid fiber ultra-high performance concrete obtained in step S3 into a mold and vibrating it into shape; Curing and hardening the formed concrete to prepare hybrid fiber ultra-high performance concrete structural components; The step S2 specifically includes: Chemical methods are used to modify bamboo strips; The bamboo strips were placed in an oven at 103°C for 6 h to completely dehydrate the bamboo fibers. Prepare a 4% sodium chlorite solution, add glacial acetic acid to adjust the pH value of the solution, and heat it in a constant temperature water bath at 80°C. Place the dehydrated bamboo fiber in a beaker and seal the beaker with plastic wrap. The treatment time is 2 to 5 hours. Wash the solution remaining on the surface of the bamboo slices with deionized water; The delignified bamboo samples were placed in an oven at 60°C for 15 min; Dry at room temperature for 2 h; A single bundle of modified bamboo fiber is obtained by decomposing the bamboo material using a bamboo decomposition machine; The fiber mixer comprises a box body (1), a feed pipe (2) is provided on the top wall of the box body (1), a guide bucket (3) is provided directly below the feed pipe (2), the bottom end of the guide bucket (3) is fixedly connected to the feed hopper (4), a conical block (5) is provided at the center of the bottom of the feed hopper (4), and the outlet of the guide bucket (3) is located directly above the conical block (5), at least the guide bucket (3) is in the shape of a truncated cone, the cross-sectional diameter of the top end of the guide bucket (3) is larger than the outlet diameter of the bottom end of the feed pipe (2), the outer wall of the feed hopper (4) is connected to a first slider (7) through a connecting structure (6), the first slider (7) is slidably provided on a first slide bar (9), and the first slider (7) reciprocates along the central axis of the first slide bar (9) under the action of a driving mechanism; The first slider (7) is internally connected to a worm (19) for rotation, wherein the central axis of the worm (19) is perpendicular to the central axis of the first slider (9), and the worm (19) is meshedly connected to a worm wheel (20), and a residual gear (21) is interference-fitted on the wheel shaft of the worm wheel (20), and the gear teeth on the residual gear (21) are used to mesh with a second rack (22), and the second rack (22) is mounted on a second slider (23), and the second slider (23) is slidably arranged on a second slider (24), and a spring (25) is sleeved on the second slider (24). The end of the connecting structure (6) away from the feed hopper (4) is connected to the second slider (23), and the outer surface of at least one end of the worm (19) is interference-fitted with a third gear (18), and the third gear (18) is meshedly connected to the first rack (17) mounted on the lower surface of the top wall of the box body (1).

2. The optimization method for partially replacing steel fiber with modified bamboo fiber in UHPC according to claim 1, characterized in that , the pre-processing in step S1 specifically includes: Whole material process: remove branches and tips from the bamboo tube and cut the bamboo tube into single stems; Bamboo chip making process: split the bamboo tube into bamboo chips of specific size; Inner layer removal process: remove the green and yellow parts of the bamboo slices.

3. The optimization method for partially replacing steel fiber with modified bamboo fiber in UHPC according to claim 1, characterized in that , the step S3 specifically includes: Pour cement, silica fume, micro mineral powder, quartz powder, fly ash and quartz sand into the fiber mixer and dry mix for 5 minutes. ; Add mixing water and stir 5 ; Add 1.0% volume of end hook steel fiber and 1.0% volume of modified bamboo fiber, stir for 10 .

4. The optimization method for partially replacing steel fiber with modified bamboo fiber in UHPC according to claim 1, characterized in that , the step S4 specifically includes: The mixed fiber ultra-high performance concrete was poured into the mold coated with the release agent, and the vibration time was set to 3 minutes on the vibration table to vibrate and form the test block, and the test block was smoothed and formed; After the specimens were formed, they were placed in a standard curing room for 2 days; After the test block was demoulded, it was placed in a cement rapid curing box and the heating rate was set to , raised to 72 h for 3 days, and then The rate was adjusted back to room temperature.

5. The optimization method for partially replacing steel fiber with modified bamboo fiber in UHPC according to claim 1, characterized in that: The cross-sectional diameter of the top end of the guide bucket (3) is 2.0-5.0 times that of the bottom end outlet of the feed pipe (2).

6. The optimization method for partially replacing steel fiber with modified bamboo fiber in UHPC according to claim 1, characterized in that: The driving mechanism comprises a first motor (11), an output end of the first motor (11) is fixedly connected to a residual bevel gear (12), the residual bevel gear (12) is meshed with a first bevel gear (13) and a second bevel gear (14) in sequence, the first bevel gear (13) and the second bevel gear (14) are mounted on the same gear shaft, and the gear shaft drives a threaded rod (8) to rotate through a transmission mechanism, and the middle portion of the threaded rod (8) passes through a first slider (7) and is threadedly connected thereto.

7. The optimization method for partially replacing steel fiber with modified bamboo fiber in UHPC according to claim 1, characterized in that: A stirring structure (26) is further provided inside the box body (1), and a discharge structure (27) is provided on the bottom wall of the box body (1).

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