UHPC-NC test piece, machining mold, machining method and application

Abstract

The invention discloses a UHPC-NC test piece, a machining mold, a machining method and application, and belongs to the technical field of building material performance testing. In order to solve the problems that at present, the UHPC-NC interface bonding performance is still subjected to static mechanical property research, and the interface form influences the repairing effect, the mold comprises a base, an assembly type cylinder, an upper cover and an interface partition plate, a round boss is arranged in the middle of the base, the assembly type cylinder is arranged on the periphery of the round boss, and the upper cover is arranged on the periphery of the round boss. The interface partition plate is vertically inserted in the middle of the split mounting type cylinder, and the upper cover is buckled on the top of the split mounting type cylinder. UHPC-NC test pieces with different interface forms are manufactured through the mold, then the UHPC-NC test pieces with different interface forms are subjected to freeze-thaw cycle erosion tests, the dynamic mechanical properties of the UHPC-NC test pieces under freeze-thaw damage are tested, the dynamic splitting tensile strength of the UHPC-NC test pieces is obtained through calculation, and a theoretical basis and technical support are provided for application of the UHPC-NC composite structure in actual engineering.

Description

Technical Field

[0001] The present invention relates to the technical field of building material performance testing, and in particular to a UHPC-NC test piece, a processing mold, a processing method and an application thereof. Background Art

[0002] In civil engineering applications, the durability and safety of concrete structures are of vital importance. UHPC has the potential to become a repair material due to its excellent mechanical properties and durability. It is widely used in the field of repair and reinforcement of damaged engineering materials. Ultra-high performance concrete (UHPC) is combined with ordinary concrete (NC) to form a new UHPC-NC material, thereby repairing the original damaged material. However, after the concrete structure is repaired and reinforced, the bonding interface between UHPC and NC is often a weak area, which is a key indicator for judging the bonding quality of new and old concrete.

[0003] In the western region, freeze-thaw cycle is one of the important factors affecting the bond strength of the interface between new and old concrete. Concrete structures in cold areas are susceptible to freeze-thaw cycles, which lead to cracks inside the concrete, degrade its mechanical properties, and affect the bond effect of the interface between new and old concrete. The degree of influence of freeze-thaw cycles on concrete performance is related to multiple factors such as low temperature and concrete water content. Therefore, when constructing in cold areas, the impact of freeze-thaw cycles on concrete performance and interface bond strength should be fully considered, and corresponding measures should be taken to improve the frost resistance and bond strength of concrete.

[0004] Therefore, it is very necessary to actively carry out mechanical property tests on UHPC-NC after combination under freeze-thaw cycles, which can serve as a theoretical basis for later application in freeze-thaw cycle environments. However, the existing studies on the UHPC-NC interface bonding performance that are currently available mainly focus on static mechanical properties, and there is still a lack of dynamic performance testing methods for the UHPC-NC interface bonding performance. Concrete structures in high-altitude cold areas will be subjected to dynamic loads such as explosions and impacts during service. After the concrete structure is destroyed, high-performance materials are usually used to repair the damaged parts. The current static mechanical performance research method cannot judge the dynamic splitting tensile strength of the interface after damage repair under freeze-thaw environments, and no research has yet shown which type of interface morphology has a better mechanical repair effect. Summary of the invention

[0005] In view of the deficiencies in the above-mentioned prior art, the object of the present invention is to provide a UHPC-NC specimen, a processing mold, a processing method and an application. Based on the requirements of the Brazilian disc splitting test, UHPC-NC specimens with different interface morphologies and circular cross-sections are manufactured by the processing mold of the present invention, and after the UHPC-NC specimens are corroded in a set freeze-thaw cycle environment, the dynamic splitting tensile strength test is performed on them to solve the problems in the background technology.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: In the first aspect, the present invention discloses a processing mold for a UHPC-NC specimen, which includes a base, an assembled cylindrical barrel, an upper cover and an interface partition. A circular boss is arranged in the middle of the base, and the assembled cylindrical barrel is arranged on the outer periphery of the circular boss. The interface partition is vertically inserted in the middle of the assembled cylindrical barrel, and the upper cover is buckled on the top of the assembled cylindrical barrel.

[0007] A further preferred embodiment of the above technical solution is as follows: the assembled cylindrical barrel is composed of multiple arc-shaped plates, and the outer wall of each arc-shaped plate is provided with a disassembly and assembly component, which includes a positioning plate, a limit shaft and an adjuster. The positioning plate is fixedly connected to the base, and the limit shaft and the adjuster are respectively connected to the arc plate and pass through the positioning plate. The adjuster is located above the limit shaft, and the opening and closing state of the assembled cylindrical barrel is adjusted by rotating the adjuster.

[0008] As a further preferred embodiment, the adjuster includes a rotating handle, a threaded rod and a connecting plate. The threaded rod is movably inserted into the positioning plate. The rotating handle and the connecting plate are respectively connected to the two ends of the threaded rod, and the connecting plate is located inside the No. 1 mounting plate on the outer wall of the arc plate.

[0009] A further preferred embodiment of the above technical solution is as follows: the interface partition plate includes a basic mother plate, an adjusting sub-plate and a pushing piece, the basic mother plate is connected to the circular boss, and both ends of the basic mother plate are abutted against the inner wall of the assembled cylindrical tube, the adjusting sub-plate and the pushing piece are installed on the basic mother plate in cooperation, a number of elastic rubber columns are connected to the adjusting sub-plate, the pushing piece is in contact with the elastic rubber columns, one side of the basic mother plate is used to form a predetermined specimen interface morphology, and one side of the adjusting sub-plate is used to form a variable specimen interface morphology.

[0010] As a further preferred embodiment, a plurality of rectangular protrusions are provided on one side of the basic motherboard, and a plurality of limiting columns are evenly distributed on the other side thereof, and gaps are opened between the rectangular protrusions and the limiting columns. Each limiting column includes two L-shaped baffles that are spaced apart and symmetrical to each other, and a gap is provided between the two L-shaped baffles.

[0011] As a further preferred embodiment, the adjusting sub-plate includes a T-shaped column and an elastic arc panel. A plurality of T-shaped columns are provided and distributed on one side of the elastic arc panel. The T-shaped column is clamped in the gap between two L-shaped baffles. The elastic arc panel is located on the outside of the basic mother plate. The pushing piece is inserted in the gap and passes through the gap between adjacent limit columns to abut against the elastic arc panel.

[0012] As a further preferred embodiment, the mold also includes an interface adjustment component. When the interface shape of the adjustment sub-plate needs to be changed, the interface adjustment component is movably inserted into the basic motherboard. The interface adjustment component pushes the push piece to move in the direction of the elastic arc panel, pushing the elastic arc panel from an arc shape to a serrated shape.

[0013] In a second aspect, the present invention further discloses a method for processing a UHPC-NC specimen, wherein the UHPC-NC specimen is manufactured using the above-mentioned processing mold, and the method comprises the following steps: The arc-shaped plates are combined to form an assembled cylindrical tube, and an interface partition is installed in the assembled cylindrical tube; According to the design interface morphology requirements of the UHPC-NC specimen, NC was added to one side of the interface partition. After the curing was completed, the interface partition was removed, and UHPC was added to fill the assembled cylinder, and the curing continued. If it is necessary to make a UHPC-NC specimen with a zigzag interface, use the interface adjustment component to push the push piece to change the elastic arc panel from an arc to a zigzag shape, then add NC on one side of the elastic arc panel, remove the interface partition after curing, add UHPC to fill the assembled cylinder, and continue curing; After the curing is completed, the arc plates are driven away from each other by turning the rotary handle using the threaded rod to open the assembled cylindrical barrel and take out the UHPC-NC specimen.

[0014] In a third aspect, the present invention further discloses a UHPC-NC specimen, which is prepared by the above-mentioned processing method of a UHPC-NC specimen.

[0015] In a fourth aspect, the present invention further discloses a method for testing the dynamic splitting tensile strength of an interface of a UHPC-NC specimen under freeze-thaw damage, comprising the following steps: S1: For UHPC-NC specimens with different interface morphologies, the number of freeze-thaw cycles is determined according to the freeze-thaw degradation proportional coefficient, and the UHPC-NC specimens are subjected to freeze-thaw cycle erosion for a set number of times; S2: Place the UHPC-NC specimen after freeze-thaw cycle erosion on the SHPB test bench, so that the bonding interface of the UHPC-NC specimen is at the same level as the center of the incident rod. Use the incident rod and the transmission rod to clamp the UHPC-NC specimen, and set different impact air pressure levels to perform impact tests on the UHPC-NC specimen. S3: Calculate the dynamic splitting tensile strength of the UHPC-NC specimen based on the load it is subjected to.

[0016] Preferably, in step S1, the freeze-thaw degradation proportional coefficient is determined by the ratio of the number of indoor freeze-thaw cycles to the number of natural freeze-thaw cycles when the UHPC-NC specimen reaches the same freeze-thaw damage degree, and its value range is 10-15, and the number of freeze-thaw cycles is 0-200 times.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention bonds UHPC and NC to form a cylindrical specimen through a processing mold, and the position of the partition is the bonding interface between UHPC and NC. The processing mold is composed of three circumferentially distributed arc plates, and the position of the arc plates is adjusted by disassembling and assembling components to open the assembled cylindrical barrel composed of three arc plates, which is conducive to rapid demolding of the UHPC-NC specimen after processing, avoiding the existing mold from causing a large disturbance to the UHPC-NC specimen due to demolding, and ensuring the accuracy of the subsequent test results of the splitting tensile strength of the bonding interface of the UHPC-NC specimen.

[0018] 2. The processing mold of the present invention is provided with an interface partition, and the interface partition is composed of a side with a fixed shape and a side with a variable shape. The test piece with a rectangular interface shape can be processed through the fixed shape side of the interface partition, and the test piece with an arc interface shape can be produced through the variable shape side without deformation. In addition, it can also cooperate with an interface adjustment component. During the process of inserting the interface adjustment component into the interface partition, the adjustment sub-plate is pushed and deformed into a sawtooth shape through the insertion rod, and the sawtooth interface shape is produced by using the deformed interface partition. In general, the mold can realize the processing of UHPC-NC test pieces with three different interface shapes, which is conducive to the later testing of the splitting tensile strength of UHPC-NC test pieces under different interface shapes, and obtaining more comprehensive UHPC-NC test piece performance analysis results.

[0019] 3. Based on the freeze-thaw degradation proportional coefficient, the present invention converts the number of freeze-thaw cycles under the test conditions into the corresponding number in the actual engineering scenario, determines the number of freeze-thaw cycles required for the test, and then uses the Brazilian disc splitting test method as a basis to test the dynamic splitting tensile strength of the bonding interface of the UHPC-NC specimen using the Brazilian splitting test combined with the SHPB device. This method can more accurately simulate the tensile failure form of the UHPC-NC composite structure in actual engineering, and the obtained dynamic splitting tensile strength test results are basically consistent with the actual mechanical properties.

[0020] 4. The method of the present invention is scientific and reasonable, and the test results are accurate and reliable. The dynamic splitting tensile strength of different interfaces can be measured, so as to obtain the interface type that can improve the interface bonding strength. It can be extended to the dynamic tensile strength of different types of concrete bonding interfaces, providing a theoretical basis for the later application of UHPC in different environments to repair and reinforce concrete structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0022] Figure 1 It is a schematic diagram of the overall structure of a processing mold for a UHPC-NC specimen of the present invention; Figure 2 It is a structural schematic diagram of the disassembly and assembly components of the present invention; Figure 3 A diagram showing the matching relationship between the disassembly and assembly components and the arc-shaped plate of the present invention; Figure 4 A diagram showing the positional relationship between the assembled cylindrical tube and the interface partition of the present invention; Figure 5 It is a schematic structural diagram of the interface partition of the present invention; Figure 6 It is a structural schematic diagram of the basic motherboard of the present invention; Figure 7 It is a schematic structural diagram of the push member of the present invention; Figure 8 This is a diagram of the original state of the elastic arc panel of the present invention; Fig. 9 It is a schematic diagram of the elastic arc panel of the present invention changing from an arc shape to a sawtooth shape; Fig.10 A diagram showing the matching relationship between the push member and the elastic arc panel of the present invention; Fig.11 A diagram showing the matching relationship between the interface adjustment component and the interface partition of the present invention; Fig.12 The temperature rise and fall mechanism and the high and low temperature duration diagram of the present invention; Fig.13 It is a schematic diagram of clamping the UHPC-NC specimen of the present invention on the SHPB test bench; Fig.14 It is a partially enlarged schematic diagram of the loading method of the UHPC-NC specimen of the present invention; Fig.15 The dot-line graph of the dynamic splitting tensile strength of the UHPC-NC specimens with three interface morphologies of the present invention under different freeze-thaw cycles and an impact gas pressure of 0.1 MPa; Fig.16 The dynamic splitting tensile strength dot-line graph of the UHPC-NC specimens with three interface morphologies of the present invention under different freeze-thaw cycles and an impact gas pressure of 0.125 MPa; Fig.17The dynamic splitting tensile strength dot-line graph of the UHPC-NC specimens with three interface morphologies of the present invention under different freeze-thaw cycles and an impact gas pressure of 0.15 MPa; In the figure: 1. base; 11. circular boss; 2. assembled cylindrical tube; 21. arc plate; 3. upper cover; 4. interface partition; 41. basic motherboard; 411. rectangular protrusion; 412. limit column; 413. gap; 42. adjusting sub-plate; 421. T-shaped column; 422. elastic arc panel; 43. push piece; 431. plane plate; 432. push plate; 5. disassembly and assembly component; 51. positioning plate; 52. limit shaft; 53. regulator; 531. rotating handle; 532. threaded rod; 533. connecting plate; 6. interface adjustment component; 61. cover plate; 62. plug rod; 621. cone; 622. first cylinder; 623. second cylinder; 7. elastic rubber column; 8. incident rod; 9. transmission rod; 10. rigid pad; 20. strain gauge. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0024] Example 1: Reference Figure 1-Figure 11 The present invention provides a processing mold for a UHPC-NC specimen, which includes a base 1, an assembled cylindrical barrel 2, an upper cover 3 and an interface partition 4. A circular boss 11 is arranged in the middle of the base 1, and a card slot is opened in the middle of the circular boss 11. The assembled cylindrical barrel 2 is spliced ​​by a plurality of arc-shaped plates 21, and the assembled cylindrical barrel 2 is arranged on the outer periphery of the circular boss 11. The interface partition 4 is vertically inserted in the middle of the assembled cylindrical barrel 2 and matched with the card slot. The upper cover 3 is buckled on the top of the assembled cylindrical barrel 2. The upper cover 3 is a conical structure with an exhaust hole on the top. When making the specimen, it needs to be placed on a vibrating table for vibration. The upper cover 3 can prevent the material in the assembled cylindrical barrel 2 from overflowing due to vibration.

[0025] like Figure 2-Figure 4 As shown, each arc plate 21 is connected to the base 1 through a disassembly and assembly component 5, wherein the disassembly and assembly component 5 includes a positioning plate 51, a limiting shaft 52 and an adjuster 53, the positioning plate 51 is fixedly connected to the base 1, the limiting shaft 52 and the adjuster 53 are respectively connected to the arc plate 21 and penetrate the positioning plate 51, the adjuster 53 is located above the limiting shaft 52, and the opening and closing state of the assembled cylindrical tube 2 is adjusted by screwing the adjuster 53; in this embodiment, three positioning plates 51 are provided and are evenly arranged in an annular direction at the edge of the base 1, the limiting shaft 52 penetrates and is connected to the positioning plate 51 and is threadedly connected to the No. 2 mounting disk on the outer wall of the arc plate 21.

[0026] Specifically, the regulator 53 includes a rotating handle 531, a threaded rod 532 and a connecting disk 533. The threaded rod 532 is movably arranged on the positioning plate 51. The threaded rod 532 and the positioning plate 51 are threadedly matched. The rotating handle 531 and the connecting disk 533 are respectively connected to the two ends of the threaded rod 532, and the connecting disk 533 is located inside the No. 1 mounting disk on the outer wall of the arc plate 21. When the rotating handle 531 is screwed, the rotating handle 531 drives the threaded rod 532 to rotate, and synchronously makes the connecting disk 533 rotate inside the No. 1 mounting disk. Through the cooperation of the threaded rod 532 and the positioning plate 51, the three arc plates 21 are close to each other and spliced ​​together to form an assembled cylindrical tube 2, or the three arc plates 21 are moved away from each other to open the assembled cylindrical tube 2 to realize demolding of the processed specimen.

[0027] like Figure 5-Figure 11 As shown, the interface partition 4 is a strip plate with different interface shapes on both sides. The interface partition 4 is installed in the slot. The contact surfaces between the interface partition 4 and the assembled cylindrical tube 2 are both arc-shaped surfaces, so that when the interface partition 4 is installed in the assembled cylindrical tube 2, the interface partition 4 can fit completely with the assembled cylindrical tube 2. In the process of making the test piece, the interface partition 4 can be extracted from the assembled cylindrical tube 2.

[0028] Specifically, the interface partition plate 4 includes a basic mother plate 41, an adjusting sub-plate 42 and a push piece 43. The basic mother plate 41 is connected to the circular boss 11, and both ends of the basic mother plate 41 are in contact with the assembled cylindrical tube 2. The adjusting sub-plate 42 and the push piece 43 are both connected to the basic mother plate 41. One side of the basic mother plate 41 is used to form a predetermined specimen interface shape, and one side of the adjusting sub-plate 42 is used to form a variable specimen interface shape. A plurality of elastic rubber columns 7 (such as Fig.11 ), the push member 43 is in contact with the elastic rubber column 7.

[0029] like Figure 6 As shown, a plurality of rectangular protrusions 411 are provided on one side of the basic motherboard 41, and a plurality of limiting columns 412 are evenly distributed on the other side thereof, and a gap 413 is opened between the rectangular protrusions 411 and the limiting columns 412, and each limiting column 412 includes two L-shaped baffles that are spaced apart and symmetrical to each other, and the adjusting sub-plate 42 is connected to the basic motherboard 41 through the plurality of limiting columns 412, and the pushing member 43 is installed in the gap 413 and extends to cooperate with the adjusting sub-plate 42, and the pushing member 43 and the adjusting sub-plate 42 are connected through an elastic rubber column 7.

[0030] like Figure 8As shown, the adjusting sub-plate 42 includes a T-shaped column 421 and an elastic arc panel 422. The T-shaped column 421 is provided with a plurality of L-shaped baffles fixedly connected to the same limiting column 412. The elastic arc panel 422 is connected to the T-shaped column 421, and the elastic arc panel 422 is located on the outside of the basic mother plate 41. The pushing member 43 includes a plane plate 431 and a push plate 432. The push plates 432 are provided with a plurality of push plates evenly arranged on one side of the plane plate 431. The top of the other side of the plane plate 431 is set as a smooth arc surface. The plane plate 431 is inserted in the gap 413. After the push plate 432 passes through the gap between two adjacent limiting columns 412, its end abuts against the elastic arc panel 422.

[0031] The mold described above can be used to manufacture UHPC-NC specimens with rectangular and arc-shaped interface shapes. According to the experimental requirements for various interface shapes of UHPC-NC specimens, an interface adjustment component 6 is also provided in this embodiment. The interface adjustment component 6 is used to change the shape of the adjustment sub-plate 42, so as to transform the elastic arc panel 422 into a serrated panel, thereby realizing the manufacture of UHPC-NC specimens with a serrated interface shape.

[0032] Specifically, if Fig.11 As shown, the interface adjustment member 6 includes a cover plate 61 and an insertion rod 62. A plurality of insertion rods 62 are provided and are evenly connected to the bottom of the cover plate 61. A handle is provided on the top of the cover plate 61 to facilitate grasping the insertion rod 62 when it is placed in the gap 413. Each insertion rod 62 is composed of a cone 621, a first cylinder 622 and a second cylinder 623 connected from bottom to top. A diameter-changing transition section is provided between the first cylinder 622 and the second cylinder 623. The diameter of the first cylinder 622 is smaller than that of the second cylinder 623. The rectangular shape of the first cylinder 622 near the push member 43 is An arc-shaped long groove is provided on one side of the protrusion 411, and the diameter of the second cylinder 623 is matched with the diameter of the arc-shaped long groove; when it is necessary to produce a UHPC-NC specimen with a serrated interface morphology, the interface adjustment component 6 is movably inserted into the basic motherboard 41, and the push piece 43 is pushed to move in the direction of the elastic arc panel 422 by the insertion rod 62, and the elastic arc panel 422 is deformed from an arc surface to a serrated shape by the push plate 432, and when the insertion rod 62 is inserted into the bottom of the gap 413, the second cylinder 623 is used to cooperate with the arc-shaped long groove to press against the push piece 43.

[0033] Embodiment 2: Based on the above embodiment 1, the present invention further provides a method for processing a UHPC-NC specimen, and uses the processing mold of the present invention to complete the processing and production of UHPC-NC specimens with different interface forms, as follows: First, by adjusting the disassembly assembly 5, the three arc-shaped plates 21 are brought close to each other and tightly assembled to form an assembled cylindrical tube 2, and the interface partition plate 4 is inserted into the assembled cylindrical tube 2 and clamped in the clamping groove on the circular boss 11; Then, according to the interface morphology of the UHPC-NC specimen to be made, the pre-configured NC (ordinary concrete, see Table 1 for specific mix ratio) is added to the left area or the right area of ​​the interface partition 4. Before adding, a layer of release agent can be applied on the interface partition 4 on the side where the material is to be added. The release agent is vaseline. The mold is placed in a curing room for 28 days at a curing temperature of 20°C ± 2°C and a relative humidity of 95%. Then, the interface partition 4 is removed, and the configured UHPC (ultra-high performance concrete, see Table 2 for specific mix ratio) is filled into the mold, and it is placed in the curing room again for 28 days at a curing temperature of 20°C ± 2°C and a relative humidity of 95%. Table 1 Ordinary concrete mix ratio (kg / m 3 ): ; Table 2 UHPC mix ratio (kg): ; After the curing is completed, the UHPC-NC specimen is formed. The UHPC-NC specimen is gradually formed by rotating the rotating handle 531 to drive the threaded rod 532 to rotate. Since the connecting plate 533 is installed on the arc plate 21, the connecting plate 533 rotates synchronously with the threaded rod 532, driving the arc plate 21 to move away from the UHPC-NC specimen, so that the UHPC-NC specimen can be quickly demolded. After the UHPC-NC specimen is made, 1 / 7 of the overall height of the two ends of the UHPC-NC specimen is cut off to eliminate the influence of uneven distribution of end aggregate and roughness on subsequent tests. The final height of the UHPC-NC specimen is 50 mm.

[0034] like Figure 8 As shown, the original form of the interface partition 4 can be used to process UHPC-NC specimens with two interface forms, namely, rectangular interface and arc interface. If a UHPC-NC specimen with a sawtooth interface needs to be made, the interface adjustment member 6 is required. The operator grasps the handle and inserts the insertion rod 62 into each arc-shaped long groove. During the downward insertion process of the insertion rod 62, the plane plate 431 is pushed to move by the insertion rod 62, so that the push plate 432 connected to the other side of the plane plate 431 pushes the elastic arc panel 422, so that the elastic arc panel 422 is deformed from an arc surface to a sawtooth shape, as shown in FIG. Fig. 9 As shown, when the insertion rod 62 is inserted into the bottom of the gap 413, the second cylinder 623 cooperates with the arc-shaped long groove to press against the push piece 43 to prevent the deformed serrated panel from automatically recovering under the action of the elastic rubber column 7.

[0035] Example 3: According to the method in Example 2 above, three types of UHPC-NC specimens with rectangular interface (specimen 1), arc-shaped interface (specimen 2), and sawtooth interface (specimen 3) required for the test were prepared. Based on the freeze-thaw environment in Jiuquan City, Gansu Province, the dynamic splitting tensile strength test of the interface under the influence of freeze-thaw damage was carried out for UHPC-NC specimens with different interface forms according to the following method, as follows: Firstly, the number of freeze-thaw cycles of the manufactured UHPC-NC specimens was determined according to the freeze-thaw degradation proportional coefficient, and the UHPC-NC specimens were subjected to freeze-thaw cycle erosion for a set number of times; Introducing freeze-thaw degradation proportionality coefficient K a , the value is 12. Considering that the annual freeze-thaw cycles in Jiuquan, Gansu Province are 100-130 times, 115 times is taken as the annual freeze-thaw cycles. Therefore, the number of indoor freeze-thaw cycles in a year is N =115 / K a ≈10 times, with a 5-year cycle, considering the degradation of the dynamic splitting tensile strength of the UHPC-NC bonding interface, the freeze-thaw cycles are set to 0, 50, 100, 150, and 200 times. Combined with the temperature in the western region, 25°C is selected as the highest temperature to simulate the summer temperature, and -20°C is selected to simulate the lowest temperature in winter. In order to allow the water to fully freeze and melt, the lowest temperature is kept constant for 2 hours and the highest temperature is kept constant for 1 hour. The setting is as follows: Fig.12 The UHPC-NC specimens were subjected to freeze-thaw cycle corrosion according to the heating and cooling mechanism and high and low temperature duration shown in the figure. The heating and cooling mechanism and high and low temperature duration were set according to the environmental conditions and test requirements of the western region. The freeze-thaw cycle corrosion includes spraying stage, cooling stage, low temperature constant temperature stage, heating stage and high temperature constant temperature stage, and the duration of each stage is 5min, 2h, 2h, 1h, 1h, a total of 6 hours and 5 minutes.

[0036] Then, the UHPC-NC specimens after freeze-thaw cycle erosion were placed on the SHPB test bench so that the bonding interface of the UHPC-NC specimens and the center of the incident rod were at the same horizontal plane. The UHPC-NC specimens were clamped by the incident rod and the transmission rod, and the impact test was carried out on the UHPC-NC specimens at different impact air pressure levels. After the UHPC-NC specimen is subjected to the above treatment, the UHPC-NC specimen is placed on a SHPB (separated Hopkinson pressure bar test system) test bench, and the UHPC-NC specimen is clamped by an incident rod 8 and a transmission rod 9, and a strain gauge 20 is provided on the transmission rod 9, and the transmission wave of the transmission rod 9 is captured by the strain gauge 20, and a rigid pad is provided on the contact surface between the incident rod 8, the transmission rod 9 and the UHPC-NC specimen, and the curvature of the rigid pad is adapted to the outer wall of the UHPC-NC specimen to avoid the stress concentration at the stress point of the UHPC-NC specimen. Then, different impact air pressure levels are set to perform impact tests. The greater the impact air pressure, the higher the dynamic splitting tensile strength of the bonding interface of the UHPC-NC specimen (i.e., the strain rate effect). According to the actual laboratory conditions, and to ensure that the specimen is destroyed under dynamic impact to set the corresponding gradient, specifically, the impact air pressure of the present invention is 0.1MPa~0.15MPa.

[0037] In this embodiment, Fig.13 , Fig.14 As shown, a SHPB test loading device with a straight cone variable cross-section of 74 mm in diameter is used, the elastic modulus of the rigid pad 10 is 210 GPa, the elastic wave velocity in the rigid pad 10 is 5172 m / s, and the density of the rigid pad 10 is 7850 kg / m 3 ; The length of the incident rod 8 is 3.2m, the length of the transmission rod 9 is 1.8m, the UHPC-NC specimen is placed on the SHPB test bench, the UHPC-NC bonding interface and the center of the incident rod are in the same horizontal plane, the UHPC-NC specimen is clamped by the incident rod 8 and the transmission rod 9, a rigid pad 10 is provided on the contact surface of the incident rod 8, the transmission rod 9 and the UHPC-NC specimen, and the curvature of the rigid pad is adapted to the outer wall of the UHPC-NC specimen, the clamping method is as follows Fig.14 As shown, the impact test on the UHPC-NC specimens was carried out by setting the impact gas pressure to 0.1MPa, 0.125MPa and 0.15MPa respectively.

[0038] During the impact test, the stress wave is transmitted to the UHPC-NC specimen through the rigid pad 10, and the interface crack initiation point occurs at the center of the UHPC-NC specimen, causing a main crack perpendicular to the loading direction to appear in the center, and then the main crack expands to both sides to split the UHPC-NC specimen into two parts.

[0039] To ensure the reliability of the test data, the SHPB impact splitting test needs to meet two basic assumptions: (1) One-dimensional elastic wave assumption: the incident rod 8 and the transmission rod 9 are always within the elastic range during the test, and the propagation of stress waves in the incident rod 8 and the transmission rod 9 can be approximately regarded as a one-dimensional wave; (2) Uniformity assumption: during the test, the stress and strain in the specimen are uniformly distributed along the length of the specimen.

[0040] According to the propagation principle of one-dimensional elastic wave, the displacement at the end face of the incident rod 8 is for: ; Since the displacement of the end face of the transmission rod 9 is only related to the transmitted wave, the displacement at the end face of the transmission rod 9 is for: ; Using the displacement of the end face of the incident rod 8 Subtract the displacement at the end of the transmission rod 9 , and the overall displacement of the specimen is obtained ,Right now: ; Loads at the end faces of incident rod 8 and transmission rod 9 and Respectively expressed as: ; ; Therefore, the average load on both ends of the specimen is: ; According to the equilibrium assumption, We can get: ; In the above formula: C 0 is the wave speed, is the incident wave, is the reflected wave, is the transmitted wave, t For time, is the load on the end face of the incident rod 8, is the load on the end face of the transmission rod 9, P ( t ) is the load on the UHPC-NC specimen, and They respectively represent the cross-sectional area and elastic modulus of the compression rods (i.e., the incident rod 8 and the transmission rod 9) of the SHPB test loading device.

[0041] In the present invention, the dynamic splitting tensile strength of the specimen needs to capture the data of the transmitted wave. After the strain gauge 20 obtains the electrical signal, the experimental data is collected through the strain gauge, and the transmitted wave is obtained after data processing. The strain gauge in this embodiment adopts the model SDY2107B ultra-dynamic strain gauge produced by Beidaihe Practical Electronic Technology Research Institute.

[0042] Finally, the dynamic splitting tensile strength of the UHPC-NC specimens was calculated based on the loads they were subjected to; The test data of the UHPC-NC specimen after loading the impact gas pressure were analyzed. First, according to the formula Calculate the load on the UHPC-NC specimen.

[0043] Then, according to the obtained load on the UHPC-NC specimen, the dynamic splitting tensile strength of the UHPC-NC specimen is calculated, and the calculation formula is as follows: ; In the formula, is the dynamic splitting tensile strength of the UHPC-NC specimen, is the maximum load on the UHPC-NC specimen, n is the number of freeze-thaw cycles, is the inner diameter of the homemade mold, L is the height of the UHPC-NC specimen.

[0044] In this embodiment, the splitting tensile strength test after freeze-thaw corrosion was performed on the prepared specimens 1, 2 and 3, respectively, wherein: n The values ​​are 0, 50, 100, 150, 200 respectively. , L =50mm, under the impact gas pressure of 0.1MPa, 0.125MPa, and 0.15MPa, the splitting tensile strength of UHPC-NC specimens with three different interface morphologies was calculated. ， The results are shown in Table 3, Table 4 and Table 5 respectively.

[0045] Table 3 Dynamic splitting tensile strength of UHPC-NC specimen with rectangular bonding interface (specimen 1): ; Table 4 Dynamic splitting tensile strength of UHPC-NC specimen with arc-shaped bonding interface (specimen 2): ; Table 5 Dynamic splitting tensile strength of UHPC-NC specimen with serrated bonding interface (specimen 3): ; The comparison results of interface dynamic splitting tensile strength under different interface morphologies are shown in Figure 15-17As shown in the figure, after analysis, specimen 3 (i.e., the UHPC-NC specimen with a sawtooth interface) performed well in terms of dynamic splitting tensile strength, and its performance was significantly higher than that of the UHPC-NC specimens with a rectangular interface and an arc interface. It can be seen that in actual engineering applications, the concrete interface to be repaired can be processed into a sawtooth shape, which is expected to effectively improve the structural strength after repair. This has an important practical significance for improving the overall quality of the project and ensuring the long-term stable operation of the project, and can provide valuable reference and guidance for actual engineering practice.

[0046] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A processing mold for a UHPC-NC specimen, characterized in that: The mold comprises a base (1), an assembled cylindrical barrel (2), an upper cover (3) and an interface partition (4); a circular boss (11) is arranged in the middle of the base (1); the assembled cylindrical barrel (2) is arranged on the outer periphery of the circular boss (11); the interface partition (4) is vertically inserted in the middle of the assembled cylindrical barrel (2); and the upper cover (3) is buckled on the top of the assembled cylindrical barrel (2); The assembled cylindrical tube (2) is assembled by splicing a plurality of arc-shaped plates (21). The outer wall of each arc-shaped plate (21) is provided with a disassembly assembly (5). The disassembly assembly (5) comprises a positioning plate (51), a limiting shaft (52) and an adjuster (53). The positioning plate (51) is fixedly connected to the base (1). The limiting shaft (52) and the adjuster (53) are respectively connected to the arc-shaped plate (21) and penetrate the positioning plate (51). The opening and closing state of the assembled cylindrical tube (2) is adjusted by screwing the adjuster (53).

2. A UHPC-NC specimen processing mold according to claim 1, characterized in that: The regulator (53) comprises a rotating handle (531), a threaded rod (532) and a connecting plate (533). The threaded rod (532) is movably inserted into the positioning plate (51). The rotating handle (531) and the connecting plate (533) are respectively connected to two ends of the threaded rod (532). The connecting plate (533) is located inside a No. 1 mounting plate on the outer wall of the arc plate (21).

3. A UHPC-NC specimen processing mold according to claim 1, characterized in that: The interface partition (4) comprises a base mother plate (41), an adjusting sub-plate (42) and a push piece (43); the base mother plate (41) is connected to the circular boss (11), and both ends of the base mother plate (41) are in contact with the inner wall of the assembled cylindrical tube (2); the adjusting sub-plate (42) and the push piece (43) are mounted on the base mother plate (41) in cooperation; one side of the base mother plate (41) is used to form a predetermined specimen interface morphology, and one side of the adjusting sub-plate (42) is used to form a variable specimen interface morphology.

4. A UHPC-NC specimen processing mold according to claim 3, characterized in that: A plurality of rectangular protrusions (411) are provided on one side of the basic motherboard (41), a plurality of limiting columns (412) are evenly distributed on the other side thereof, and a gap (413) is provided between the rectangular protrusions (411) and the limiting columns (412), and each limiting column (412) includes two mutually symmetrical L-shaped baffles, and a gap is provided between the two L-shaped baffles.

5. A UHPC-NC specimen processing mold according to claim 4, characterized in that: The regulating sub-plate (42) comprises a T-shaped column (421) and an elastic arc panel (422); a plurality of T-shaped columns (421) are provided and distributed on one side of the elastic arc panel (422); the T-shaped column (421) is clamped in the interval between two L-shaped baffles; the elastic arc panel (422) is located outside the base mother plate (41); and the push piece (43) is inserted into the gap (413) and passes through the gap between adjacent limiting columns (412) to abut against the elastic arc panel (422).

6. A UHPC-NC specimen processing mold according to claim 5, characterized in that: The mould further comprises an interface adjustment component (6). When the interface morphology of the adjustment sub-plate (42) needs to be changed, the interface adjustment component (6) is movably inserted into the basic mother plate (41), and the interface adjustment component (6) pushes the push member (43) to move in the direction of the elastic arc panel (422), thereby pushing the elastic arc panel (422) from an arc shape to a sawtooth shape.

7. A method for processing a UHPC-NC specimen, characterized in that: The method of manufacturing a UHPC-NC specimen using a processing mold for a UHPC-NC specimen according to any one of claims 1 to 6 comprises the following steps: Assembling the arc-shaped plates (21) to form an assembled cylindrical tube (2), and installing an interface partition plate (4) in the assembled cylindrical tube (2); According to the design interface morphology requirements of the UHPC-NC specimen, NC is added to one side of the interface partition (4), and after curing, the interface partition (4) is removed, and UHPC is added to fill the assembled cylindrical tube (2), and the curing is continued; If a UHPC-NC specimen with a sawtooth interface is produced, the interface adjustment member (6) is used to push the push member (43) to change the elastic arc panel (422) from an arc shape to a sawtooth shape, and then NC is added to one side of the elastic arc panel (422). After curing is completed, the interface partition (4) is removed, and UHPC is added to fill the assembled cylindrical tube (2), and curing is continued; After the curing is completed, the rotating handle (531) is rotated and the threaded rod (532) is used to drive the arc plates (21) away from each other so that the assembled cylindrical barrel (2) is opened and the UHPC-NC specimen is taken out.

8. A UHPC-NC specimen, characterized in that: The UHPC-NC specimen is prepared by the processing method of claim 7.

9. The method for testing the interface dynamic splitting tensile strength of a UHPC-NC specimen under freeze-thaw damage according to claim 8, characterized in that: The following steps are involved: S1: Determine the number of freeze-thaw cycles according to the freeze-thaw degradation proportional coefficient, and subject the UHPC-NC specimen to a set number of freeze-thaw cycle erosions; S2: placing the UHPC-NC specimen after freeze-thaw cycle erosion on the SHPB test bench, so that the bonding interface of the UHPC-NC specimen and the center of the incident rod (8) are in the same horizontal plane, and a rigid pad (10) is arranged on the contact surface between the incident rod (8), the transmission rod (9) and the UHPC-NC specimen, and the curvature of the rigid pad (10) is adapted to the outer wall of the UHPC-NC specimen. The UHPC-NC specimen is clamped by the incident rod (8) and the transmission rod (9), and the UHPC-NC specimen is subjected to an impact test at different impact air pressure levels; S3: Calculate the dynamic splitting tensile strength of the UHPC-NC specimen based on the load it is subjected to.

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