Concrete crack prefabricating device and preparation method of crack concrete test block

Abstract

The application discloses a concrete crack prefabricating device and a preparation method of a cracked concrete test block, wherein the concrete crack prefabricating device comprises a cracked concrete mold and a crack inducing device; the cracked concrete mold comprises a bottom mold, a side mold and a detachable rib plate; four lower blind holes are arranged on the bottom mold; the side mold is arranged on the bottom mold and is detachably connected with the bottom mold; a side blind hole is arranged on the side mold; and the detachable rib plate is arranged on the top of the side mold and is provided with an upper blind hole. The concrete crack prefabricating device is simple in structure, convenient in demolding and reusable, and the non-through cracks of the concrete test block prepared by the device are basically consistent with the cracks in an engineering site in terms of appearance, sharp end micro-crack area, crack surface roughness, crack trend tortuosity, aggregate splitting and aggregate pull-out ratio, and the like, and thus the demand of the research on the influence of the crack width of the cracked concrete on the durability of the concrete can be met.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of concrete crack making, and particularly relates to a concrete crack prefabrication device and a preparation method of a non-penetrating crack concrete test block. BACKGROUND

[0002] In today's era, reinforced concrete is still the most widely used and largest amount of building material, which is stable in nature, high in safety factor and long in service life, and provides a foundation guarantee for the sustainable development of economy and society. Concrete crack is one of the major technical problems in the field of building engineering, and is considered as a "cancer" stubborn disease that cannot be avoided in the engineering construction and health service stage. After the concrete cracks, harmful substances erode the concrete base material and structural steel through the gap, causing durability problems such as concrete carbonation corrosion and steel corrosion. The research on concrete crack repair is of great significance to improve the use function and service life of building structure engineering, and the crack repair technology is hailed as the "surgical knife" to treat crack problems. Common concrete crack repair technologies include cement grouting technology, chemical grouting technology, epoxy mortar repair technology, permeation crystallization technology and biological self-repairing technology, etc.

[0003] At present, crack repair technology is gradually popularized in entity engineering disease treatment, but the crack repair effect of concrete under different construction environments or service environment conditions is very different, which leads to great difficulty in quality control of crack repair engineering, and even threatens the health service of the repaired engineering building. The urgent task is to fully carry out indoor research on different crack repair technologies according to different working conditions and different service environments, put forward concrete crack repair technologies with good adaptability and different repair functions, and carry out in-depth research on the durability of repaired concrete. In addition, nondestructive testing and quality evaluation of repair effect also play a decisive role in the popularization and application of concrete repair technology. The basic conditions for carrying out indoor crack repair test aiming at the above contradictions are: preparing crack concrete test blocks with stable performance, batch production and the same crack characteristics as entity concrete, and having nondestructive testing conditions, which do not affect the nondestructive testing and quality evaluation of crack repair effect.

[0004] Patent No. CN111157307A discloses a self-repairing cement-based material test piece crack making method, which uses a pressure testing machine to prepare a concrete through crack, but a certain amount of fiber must be contained in the induced crack concrete to maintain the overall integrity of the cracked test piece, which is inconsistent with the crack characteristics of actual engineering concrete without fiber. Although the detachable stainless steel throat clamp can control the crack width, it cannot lengthen the crack width. Patent No. CN109612802A discloses a concrete crack making method, which specifically uses an expansion method to induce concrete test block cracking, and induces concrete cracking by pouring expansion agent into the concrete row drill hole. Although the crack characteristics are similar to actual engineering, the crack width control is difficult. The use of expansion agent changes the composition of the concrete at the crack. In addition, the invention adds iron wire when pouring concrete to control the concrete test block from breaking into two halves, which interferes with the propagation of acoustic signals in ultrasonic non-destructive testing. Patent No. CN103175721B discloses a device for making natural cracks in concrete test pieces, which specifically uses a three-point load to induce concrete test block cracking, and controls the slow cracking of concrete by precisely applying load. However, plain concrete is a brittle material, and the three-point bending process requires a very high loading rate to avoid brittle fracture. More importantly, the crack width obtained by this method is limited in a very narrow range, and usually only simulates the cracking of the superficial layer of concrete. In summary, the existing methods for making concrete cracks in indoor tests are complex, have low repeatability, and have large differences in crack characteristics from engineering entities, resulting in poor applicability of indoor test results in engineering. SUMMARY

[0005] The present application aims to at least partially solve one of the technical problems in the related art. To this end, embodiments of the present application propose a concrete crack precast device and a method for preparing a crack concrete test block.

[0006] The concrete crack precast device according to the embodiments of the present application comprises a crack concrete mold and a crack inducing device. The crack concrete mold comprises a bottom mold provided with a lower blind hole, a side mold provided on the bottom mold and detachably connected with the bottom mold, and the side mold is provided with a side blind hole, and a detachable rib plate provided on the top of the side mold and provided with an upper blind hole.

[0007] The concrete crack precast device according to the embodiments of the present application has a simple structure, is easy to operate, is convenient to demold, and can be repeatedly used. The induced concrete test block prepared by the device has a crack that is a non-through crack, and the crack characteristics are basically consistent with those of the cracks in the engineering site in terms of appearance, sharp tip micro-crack area, crack surface roughness, crack direction tortuosity, aggregate splitting, and aggregate pull-out ratio. The device can meet the demand for studying the influence of crack width of cracked concrete on the durability of concrete.

[0008] Optionally, the side mold is in a quadrangular prism shape, and the side mold comprises two long side molds and two short side molds, and the long side mold and the short side mold are detachably connected.

[0009] Optionally, the side blind hole is arranged on one of the long side molds, and the number of the side blind hole on the long side mold is 3-5 times that of the lower blind hole.

[0010] Optionally, the detachable rib plate is provided in two, and the two detachable rib plates are arranged on the top of the two long side molds in a spaced manner along a first preset direction, at least two upper blind holes are arranged on each detachable rib plate in a spaced manner along a second preset direction, and the positions of the upper blind holes and the lower blind holes correspond to each other in a third preset direction.

[0011] Optionally, the two ends of the detachable rib plate are arranged on the two long side molds through a spring buckle, the first preset direction is consistent with the length direction of the long side mold, the second preset direction is consistent with the length direction of the detachable rib plate, the second preset direction is perpendicular to the first preset direction, and the third preset direction is perpendicular to each of the first preset direction and the second preset direction.

[0012] Optionally, the crack inducing device comprises a slit width adjusting assembly, the slit width adjusting assembly comprises a plurality of embedded long nuts, the plurality of embedded long nuts correspond to the upper blind holes and the lower blind holes one by one, and the embedded long nuts are arranged in the upper blind holes and the lower blind holes.

[0013] Optionally, the slit width adjusting assembly further comprises a slit width adjusting rod and a connecting screw, the connecting screw is matched with the embedded long nut, and the two ends of the slit width adjusting rod are connected with the embedded long nut through the connecting screw.

[0014] Optionally, the crack inducing device further comprises a non-penetrating auxiliary member, the non-penetrating auxiliary member comprises a non-penetrating auxiliary plate, a plurality of embedded special nuts, and a fixing bolt, the plurality of embedded special nuts correspond to the side blind holes one by one, the embedded special nuts are arranged in the side blind holes, and the non-penetrating auxiliary plate is arranged on the embedded special nut through the fixing bolt.

[0015] Optionally, the crack inducing device further comprises a three-point loading device, the three-point loading device comprises a pressure applying cylindrical profile and a pressure bearing semi-cylindrical profile, and the pressure applying cylindrical profile is matched with the non-penetrating auxiliary member.

[0016] The method for preparing a cracked concrete test block by using the concrete crack prefabricating device according to the embodiment of the present application comprises the following steps:

[0017] S1, assembling a cracked concrete mold: inserting the embedded long nut into the lower blind hole of the bottom mold, inserting the embedded special-shaped nut into the side blind hole of the side mold, placing the detachable rib plate at the top end of the side mold, pressing the spring snap, and then inserting the embedded long nut into the upper blind hole of the detachable rib plate to assemble the cracked concrete mold;

[0018] S2, pouring concrete: layering and vibrating and compacting the concrete mixture into the cracked concrete mold, and opening the spring snap after hardening, and sequentially removing the detachable rib plate, the side mold and the bottom mold to obtain a concrete test block to be induced to crack, the concrete test block comprising an A face, a B face, a C face and a D face;

[0019] S3, inducing the concrete test block to crack: placing the non-penetrating auxiliary plate on the embedded special-shaped nut on the A face of the concrete test block and tightening the fixing bolt, inserting the pressure cylinder profile into the side of the non-penetrating auxiliary plate, symmetrically placing two pressure-bearing semi-cylinder profiles under the B face of the concrete test block, and then slowly applying load through the hydraulic universal testing machine to induce cracks to be generated and developed in the tension zone of the concrete test block, and finally closing the hydraulic universal testing machine and removing the three-point loading device;

[0020] S4, installing a crack width adjusting assembly: installing at least two groups of crack width adjusting assemblies on the C face and the D face of the concrete test block in a direction perpendicular to the crack, one group of the crack width adjusting assemblies being located at the crack tip and the other group of the crack width adjusting assemblies being located at the crack opening, tightening the crack width adjusting rod at the crack tip to close the crack tip of the concrete test block, and elongating or shortening the crack width adjusting rod at the crack opening to make the crack of the concrete test block freely open and close;

[0021] S5, curing the crack: filling structural curing material into the gap between the non-penetrating auxiliary plate and the concrete test block, and removing all the crack inducing devices after hardening to complete the preparation of the non-penetrating cracked concrete test block.

[0022] The method for preparing a cracked concrete test block according to the embodiment of the present application is easy to operate, low in cost, and strong in repeatability, and can be widely applied to the research on concrete crack detection technology, crack repair technology, crack repair material development, and the service mechanical properties and durability of cracked concrete, and has important value for scientifically evaluating the influence of the cracks of engineering structure concrete on the safety of service buildings. BRIEF DESCRIPTION OF DRAWINGS

[0023] Fig. 1 is a structural schematic diagram of a crack concrete mold of an embodiment of the present application.

[0024] Fig. 2 is a crack inducing schematic diagram of a concrete test block of an embodiment of the present application.

[0025] Fig. 3 is a structural schematic diagram of a non-penetrating crack test block of an embodiment of the present application.

[0026] Reference signs:

[0027] bottom mold 1; lower blind hole 101;

[0028] side mold 2; side blind hole 201;

[0029] concrete test block 3; A face 301; B face 302; C face 303; D face 304.

[0030] detachable rib plate 4; upper blind hole 401; spring buckle 402;

[0031] non-penetrating auxiliary member 5; non-penetrating auxiliary plate 501; pre-buried special-shaped nut 502; fixing bolt 503;

[0032] slit width adjusting assembly 6; slit width adjusting rod 601; pre-buried long nut 602; connecting screw 603;

[0033] structural curing material 7;

[0034] three-point loading device 8; pressure applying cylindrical profile 801; pressure bearing semi-cylindrical profile 802. DETAILED DESCRIPTION

[0035] The embodiments of the present application are described in detail below with reference to the accompanying drawings. The embodiments described below by reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0036] As Figs. 1-3 shown, the concrete crack prefabrication device according to the embodiment of the present application comprises a crack concrete mold and a crack inducing device, the crack concrete mold is used for making a concrete test block 3, and the crack inducing device is applied to the concrete test block 3 and is used for inducing cracks on the concrete test block 3.

[0037] The crack concrete mold comprises a bottom mold 1, a side mold 2 and a detachable rib plate 4, the bottom mold 1 is provided with a lower blind hole 101; the side mold 2 is arranged on the bottom mold 1, and the side mold 2 and the bottom mold 1 are detachably connected, that is, the side mold 2 and the bottom mold 1 can be combined together or separated, and the detachable rib plate 4 is arranged on the top of the side mold 2, the detachable rib plate 4 is provided with an upper blind hole 401, and the detachable rib plate 4 and the side mold 2 can also be combined together or separated, and the detachable rib plate 4 and the side mold 2 are convenient to disassemble and can be repeatedly used.

[0038] The crack inducing device is matched with each of the lower blind hole 101, the side blind hole 201 and the upper blind hole 401, so that the crack inducing device can be connected with the crack concrete mold, the concrete test block 3 made is connected with part of the crack inducing device, and a fulcrum is provided for the crack inducing test in the later stage.

[0039] The use method of the concrete crack prefabricating device will be described below. Figs. 1-3 Briefly describe the use method of the concrete crack prefabricating device, first, the bottom mold 1 and the side mold 2 are assembled, then the detachable rib plate 4 is connected with the side mold 2, that is, the crack concrete mold is assembled, then the crack concrete mold is poured with concrete, after the concrete is hardened, the detachable rib plate 4, the side mold 2 and the bottom mold 1 are removed, the concrete test block 3 is obtained, then the concrete test block 3 is connected with the crack inducing device, and the crack inducing device is used to induce the concrete crack.

[0040] The concrete crack prefabricating device has the advantages of simple structure, simple operation, convenient demolding and reusability, the crack of the concrete test block prepared and induced by the concrete crack prefabricating device is basically consistent with the characteristics of the non-through crack and the crack in the engineering site in appearance, tip micro-crack area, crack surface roughness, crack direction tortuosity, aggregate splitting and aggregate pull-out ratio, and can meet the demand of the research on the influence of the crack width of the cracked concrete on the durability of the concrete.

[0041] As shown in the drawings, Figs. 1-3 The concrete crack prefabricating device comprises a crack concrete mold and a crack inducing device, the crack concrete mold comprises a bottom mold 1, a side mold 2 and a detachable rib plate 4, the crack concrete mold is in the shape of a long rectangular cuboid without a cover, the side mold 2 is in the shape of a quadrangular prism, the side mold 2 comprises two long side molds and two short side molds, the long side mold and the short side mold are detachably connected, and the bottom mold 1 and the side mold 2 are also detachably connected. The material of the bottom mold 1 and the side mold 2 can be rigid resin material or stainless steel plate.

[0042] The bottom mold 1 is provided with at least four lower blind holes 101, and the four lower blind holes 101 can be arranged at the four corners of the bottom mold 1. One of the long side molds is provided with side blind holes 201, and the number of the side blind holes 201 on the long side mold is 3-5 times that of the lower blind holes 101, and the side blind holes 201 are uniformly distributed on the long side mold.

[0043] The two detachable ribs 4 are arranged on the top of the two long side molds in the first preset direction, and at least two upper blind holes 401 are arranged on each detachable rib 4 in the second preset direction. The positions of the upper blind holes 401 and the lower blind holes 101 correspond to each other in the third preset direction. The first preset direction is consistent with the length direction of the long side mold, the second preset direction is consistent with the length direction of the detachable rib 4, the second preset direction is perpendicular to the first preset direction, and the third preset direction is perpendicular to each of the first preset direction and the second preset direction. Optionally, when the first preset direction and the second preset direction are in the horizontal direction, the third preset direction is the vertical direction.

[0044] The two ends of the detachable rib 4 are arranged on the two long side molds through the spring buckle 402, and the spring buckle 402 is used to fix the detachable rib 4 on the two long side molds, increase the overall stability of the cracked concrete mold, and reduce the defects of the concrete test block caused by the instability of the mold. The materials of the detachable rib 4 and the spring buckle 402 are stainless steel plates, and the connection mode of the end of the detachable rib 4 and the spring buckle 402 is plane welding. The bottom mold 1, the side mold 2, the upper blind hole 401, the lower blind hole 101, the side blind hole 201 and the detachable rib 4 of the cracked concrete mold are uniformly coated with a release agent before use, and the release agent can be selected from one of water-based and oil-based.

[0045] The inner diameters of the lower blind hole 101 and the upper blind hole 401 are the same, and a strong magnet with a magnetic force ≥14500 Gauss is embedded in each of the lower blind hole 101, the side blind hole 201 and the upper blind hole 401. The lower blind hole 101 and the upper blind hole 401 are used to embed the embedded long nut 602, and the side blind hole 201 is used to embed the embedded special-shaped nut 502. The embedded long nut 602 and the embedded special-shaped nut 502 belong to the crack inducing device, the embedded long nut 602 and the embedded special-shaped nut 502 are made of stainless steel material with an iron content not less than 71.5%, the embedded long nut 602 and the embedded special-shaped nut 502 have strong bonding force with the strong magnet, and the bottom end of the embedded long nut 602 and the special-shaped end of the embedded special-shaped nut 502 are sealed. The strong magnet embedded in the lower blind hole 101, the side blind hole 201 and the upper blind hole 401 firmly fixes the embedded long nut 602 and the embedded special-shaped nut 502 in the cracked concrete mold, avoids falling caused by vibration, and effectively guarantees the quality and survival rate of the embedded long nut 602 and the embedded special-shaped nut 502.

[0046] The concrete test block 3 made of the crack concrete mold includes an A surface 301, a B surface 302, a C surface 303 and a D surface 304. The A surface 301 is a top surface of the concrete test block 3, and the A surface 301 is provided with a pre-buried special-shaped nut 502; the B surface 302 is a bottom surface of the concrete test block 3; the C surface 303 and the D surface 304 are two side surfaces of the concrete test block 3, and the C surface 303 and the D surface 304 are oppositely arranged and provided with a pre-buried long nut 602.

[0047] The crack inducing device includes a non-penetrating auxiliary member 5, a three-point loading device 8 and a crack width adjusting assembly 6. The non-penetrating auxiliary member 5 includes a non-penetrating auxiliary plate 501, a pre-buried special-shaped nut 502 and a fixing bolt 503. The pre-buried special-shaped nut 502 is provided with a plurality of pre-buried special-shaped nuts 502 corresponding to the side blind hole 201, that is, each pre-buried special-shaped nut 502 corresponds to one side blind hole 201, and the pre-buried special-shaped nut 502 can be pre-buried in the side blind hole 201. After the pre-buried special-shaped nut 502 is inserted into the side blind hole 201, the pre-buried special-shaped nut 502 can have strong bonding force with the strong magnet in the side blind hole 201. The fixing bolt 503 cooperates with the pre-buried special-shaped nut 502, and the non-penetrating auxiliary plate 501 is arranged on the pre-buried special-shaped nut 502 through the fixing bolt 503, that is, the non-penetrating auxiliary plate 501 is arranged on the A surface 301 of the concrete test block 3 through the fixing bolt 503. The non-penetrating auxiliary plate 501 is a resin-based or metal-based plate with high toughness and high strength, which can deform synchronously with the load-bearing concrete and is not damaged in integrity. The non-penetrating auxiliary member 5 is used for preparing a non-penetrating crack, so that the crack of the prepared concrete test block 3 is a non-penetrating crack.

[0048] The three-point loading device 8 includes one pressing cylindrical profile 801 and two pressure-bearing semi-cylindrical profiles 802, and the three-point loading device 8 is made of super-hard steel with HRC 68-70. The pressing cylindrical profile 801 is cut into a U shape along the axis in the middle. The pressing cylindrical profile 801 cooperates with the non-penetrating auxiliary plate 501, specifically, the pressing cylindrical profile 801 is inserted from the middle of the side surface of the non-penetrating auxiliary plate 501, and the two pressure-bearing semi-cylindrical profiles 802 are symmetrically placed below the bottom surface, that is, the B surface 302 of the concrete test block 3. The three-point loading device 8 is used for inducing and developing the concrete crack. By slowly applying load through the hydraulic universal testing machine, the crack is induced to develop and extend to the penetration in the tension area of the bottom surface of the concrete test block 3, and the crack concrete test block 3 is obtained.

[0049] The seam width adjusting assembly 6 comprises embedded long nuts 602, seam width adjusting rods 601 and connecting screws 603. The embedded long nuts 602 are in one-to-one correspondence with the upper blind holes 401 and the lower blind holes 101, that is, each upper blind hole 401 and each lower blind hole 101 corresponds to one embedded long nut 602, and the embedded long nuts 602 can be embedded in the upper blind holes 401 and the lower blind holes 101. Since the upper blind holes 401 and the lower blind holes 101 are each provided with a powerful magnet, the embedded long nuts 602 inserted into the upper blind holes 401 and the lower blind holes 101 can have strong binding force with the powerful magnets.

[0050] The connecting screws 603 cooperate with the embedded long nuts 602, and the two ends of the seam width adjusting rods 601 are connected to the embedded long nuts 602 through the connecting screws 603. The inner thread at one end of the seam width adjusting rod 601 is left-handed thread, and the inner thread at the other end is right-handed thread, which respectively cooperate with the outer threads of the bolts at the two ends. When the seam width adjusting rod 601 rotates clockwise, the distance between the seam width adjusting rod 601 and the bolts at the two ends shortens, and when the seam width adjusting rod 601 rotates counterclockwise, the distance between the seam width adjusting rod 601 and the bolts at the two ends lengthens, thereby adjusting the width of the crack.

[0051] When installing the seam width adjusting assembly 6, the seam width adjusting assembly 6 needs to be installed on the C face 303 and the D face 304 of the concrete test block 3 respectively. At least two groups of seam width adjusting assemblies 6 are arranged on the C face 303 and the D face 304, and the length direction of the seam width adjusting rod 601 is perpendicular to the direction of the crack, that is, two groups of seam width adjusting assemblies 6, three groups of seam width adjusting assemblies 6, four groups of seam width adjusting assemblies 6 or more groups of seam width adjusting assemblies 6 can be arranged on the C face 303 and the D face 304 of the concrete test block 3, and the number of groups of seam width adjusting assemblies 6 can be selected according to actual needs. The seam width adjusting assemblies 6 on the C face 303 and the D face 304 are arranged at intervals and are perpendicular to the direction of the crack.

[0052] After the seam width adjusting assembly 6 is installed, the seam width adjusting rod 601 at the crack tip is tightened, and the concrete crack tip is closed. The seam width adjusting rod 601 at the seam opening is stretched or tightened, and the seam width of the concrete test block 3 can be adjusted accordingly, and the obtained wedge-shaped crack morphology is consistent with the crack morphology of the engineering entity. The seam width adjusting assembly is used for adjusting the width of the concrete crack.

[0053] After the completion of the crack width adjustment, structural curing material is poured into the fixed gap between the non-penetrating auxiliary member 5 and the concrete test block 3, which serves to stabilize the crack morphology, maintain the crack width, and limit the crack depth. After hardening, all crack-inducing devices are removed, and the preparation of the crack concrete test block with the preset crack width and crack depth is completed. The crack morphology characteristics meet the preparation requirements of the non-penetrating crack concrete test block in engineering practice. The structural curing material is a resin material, cement mortar, or resin mortar with the same ultrasonic wave speed as the hardened concrete material, which meets the requirements of non-destructive testing of cracks.

[0054] The structural curing material can be ordinary portland cement with a strength grade not less than 42.5, which is mixed and stirred with cement, standard sand, water, and acrylic emulsion in a mass ratio of 1:2:0.1:0.3; or an epoxy resin with an initial viscosity not less than 150, which is mixed and stirred with epoxy resin, ethylenediamine, cement, and sand in a mass ratio of 1:0.15:0.08:2:5.

[0055] In order to make the technical solutions of the present application easier to understand, the following refers to Figs. 1-3 The method for preparing a crack concrete test block using the crack concrete preparation device is further described, which includes the following steps:

[0056] S1, assembling the crack concrete mold: inserting the embedded long nut 602 into the lower blind hole 101 of the bottom mold 1, inserting the embedded special-shaped nut 502 into the side blind hole 201 of the side mold 2, placing the detachable rib plate 4 at the top end of the two long side molds, pressing the spring buckle 402, fixing the detachable rib plate 4 on the side mold 2, then inserting the embedded long nut 602 into the upper blind hole 401 of the detachable rib plate 4, and assembling the crack concrete mold;

[0057] S2, pouring concrete: layering the concrete mixture into the crack concrete mold and vibrating and compacting, after 24 hours of pre-curing under standard curing conditions, opening the spring buckle 402, sequentially removing the detachable rib plate 4, the side mold 2, and the bottom mold 1, and obtaining the concrete test block 3 to be induced to crack, which includes the A face 301, the B face 302, the C face 303, and the D face 301;

[0058] S3, inducing concrete test block cracking: first, place the non-penetrating auxiliary plate 501 on the embedded irregular nut 602 of the A face 301 of the concrete test block 3, and fix the non-penetrating auxiliary plate 501 on the A face 301 of the concrete test block 3 by tightening the fixing bolt 503, then insert the pressure cylinder profile 801 from the side of the non-penetrating auxiliary plate 501, and place the two pressure-bearing half-cylinder profiles 802 symmetrically below the B face 302 of the concrete test block 3, then slowly apply load by the hydraulic universal testing machine, induce cracks in the tension zone of the concrete test block 3 to generate and develop, and finally turn off the hydraulic universal testing machine and remove the three-point loading device;

[0059] S4, installing joint width adjusting assembly: at least two groups of joint width adjusting assemblies 6 are installed on the C face 303 and the D face 304 of the concrete test block 3 in a direction perpendicular to the crack, one group of joint width adjusting assemblies 6 is located at the crack tip, and the other group of joint width adjusting assemblies 6 is located at the crack opening, then the joint width adjusting rod 601 is installed on the embedded long nut 602 by tightening the connecting screw 603, the joint width adjusting rod 601 at the crack tip is tightened to close the crack tip of the concrete test block 3, and the joint width adjusting rod 601 at the crack opening is elongated or contracted to make the crack opening of the concrete test block 3 freely open and close, so that the width of the crack of the concrete test block can be adjusted as required;

[0060] S5, solidifying the crack: after the joint width adjustment is completed, structural curing material is filled into the gap between the non-penetrating auxiliary plate 501 and the concrete test block 3, and after hardening, all crack inducing devices are removed to complete the preparation of the non-penetrating crack concrete test block.

[0061] Optionally, when pouring concrete, the concrete mixture is poured into the crack concrete mold in three layers and vibrated and compacted. After standing in a room at 20±2℃ for 24-48 hours, the mold is removed to obtain the crack-inducing concrete test block. The obtained crack-inducing concrete test block is placed in a curing room with a temperature of 20±2℃ and a humidity of more than 95% for 28 days of curing.

[0062] Specifically, when adding structural curing material to the gap between the non-penetrating auxiliary plate 501 and the concrete test block 3, a baffle is pasted on the outer side of the upper part of the concrete test block 3 with epoxy glue, the top of the baffle is higher than the non-penetrating auxiliary plate 601, and the width of the baffle is adapted to the length and width of the concrete test block 3, so that after the gap is filled with structural curing material, the baffle can block the overflow of the curing material, which is helpful for the molding of the structural curing material. After the structural curing material is molded, the baffle is removed.

[0063] The crack of the crack concrete test block is non-penetrating, and the ultrasonic wave can form a complete loop between the transmitting and receiving transducers in the nondestructive testing process, and the ultrasonic wave propagation speed of the structural curing material is the same as that of the base concrete, so that the nondestructive testing demand of the cracked concrete can be met. The method for preparing the crack concrete test block is simple and has high repeatability, the crack characteristics are consistent with engineering entities, the crack width of the concrete test block can be adjusted and controlled, the crack characteristics are stable for a long time, and the test block can be used for concrete crack detection technology research, crack repair technology research, crack repair material research and development, crack repair concrete mechanical property and durability test and the like.

[0064] 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 is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0065] In addition, the terms "first", "second" are only for descriptive purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise specifically limited.

[0066] In the present application, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integral; it can be mechanical connection, or electrical connection or communication with each other; it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements or the interaction relationship of two elements, unless otherwise specifically defined. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0067] In the present application, unless specifically stated and limited otherwise, a first feature "on" or "under" a second feature can be directly in contact with the second feature, or indirectly in contact with the second feature through an intermediate medium. Also, a first feature "over", "above" and "on top of" a second feature can be directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. A first feature "under", "below" and "underneath" a second feature can be directly below or obliquely below the second feature, or simply means that the first feature is horizontally lower than the second feature.

[0068] In the present application, the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" mean that a particular feature, structure, material, or characteristic being described is included in at least one embodiment or example of the present application. The illustrative appearances of the above-mentioned terms in various places in the specification are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. Moreover, the terms "first", "second", "third", etc. are used herein merely as identifiers for different elements, regions, or layers, and are not intended to be taken literally, unless otherwise specified.

[0069] Although the above-mentioned embodiments have been shown and described, it is to be understood that these embodiments are exemplary only, and are not to be taken as limiting the scope of the present application, and that changes, modifications, substitutions and variations can be made to the above-mentioned embodiments by those skilled in the art without departing from the scope of the present application.

Claims

1. A precast concrete crack device, characterized in that, Includes: a cracked concrete mold and a crack induction device, wherein the cracked concrete mold includes, The bottom mold has a lower blind hole. A side mold is provided on the bottom mold, and the side mold and the bottom mold are detachably connected. The side mold is provided with a side blind hole. A detachable rib is provided on the top of the side mold, and an upper blind hole is provided on the detachable rib. The crack induction device includes a non-penetrating auxiliary component, which includes a non-penetrating auxiliary plate, a pre-embedded irregular nut, and a fixing bolt. There are multiple pre-embedded irregular nuts, and each pre-embedded irregular nut corresponds to a side blind hole. The pre-embedded irregular nut is located in the side blind hole. The non-penetrating auxiliary plate is mounted on the pre-embedded irregular nut by the fixing bolt. The crack induction device includes a crack width adjustment component, which includes a pre-embedded long nut. There are multiple pre-embedded long nuts, and each pre-embedded long nut corresponds to an upper blind hole and a lower blind hole. The pre-embedded long nuts are disposed in the upper blind hole and the lower blind hole. The seam width adjustment assembly further includes a seam width adjustment rod and a connecting screw. The connecting screw cooperates with the pre-embedded long nut, and both ends of the seam width adjustment rod are connected to the pre-embedded long nut through the connecting screw. The crack induction device further includes a three-point loading device, which includes a pressure-applying cylindrical profile and a pressure-bearing semi-cylindrical profile, wherein the pressure-applying cylindrical profile cooperates with the non-penetrating auxiliary component.

2. The precast concrete crack device according to claim 1, characterized in that, The side mold is in the shape of a quadrangular prism, and includes two long side molds and two short side molds, which are detachably connected.

3. The precast concrete crack device according to claim 2, characterized in that, One of the long side molds is provided with the side blind hole, and the number of the side blind holes on the long side mold is 3-5 times that of the lower blind hole.

4. The precast concrete crack device according to claim 3, characterized in that, There are two detachable ribs, which are spaced apart on the top of the two long side molds along a first preset direction. Each detachable rib is provided with at least two upper blind holes spaced apart along a second preset direction, and the positions of the upper blind holes and the lower blind holes correspond one-to-one in a third preset direction.

5. The precast concrete crack device according to claim 4, characterized in that, Both ends of the detachable rib are attached to the two long side molds by spring hooks. The first preset direction is consistent with the length direction of the long side molds, the second preset direction is consistent with the length direction of the detachable rib, the second preset direction is perpendicular to the first preset direction, and the third preset direction is perpendicular to each of the first preset direction and the second preset direction.

6. A method for preparing cracked concrete test blocks using the precast concrete crack device according to claim 5, characterized in that, Includes the following steps: S1. Assemble the cracked concrete mold: Insert the pre-embedded long nut into the lower blind hole of the bottom mold, insert the pre-embedded irregular nut into the side blind hole of the side mold, place the detachable rib plate on the top of the side mold, press the spring buckle, and then insert the pre-embedded long nut into the upper blind hole of the detachable rib plate to assemble the cracked concrete mold. S2. Pouring concrete: The concrete mixture is poured into the cracked concrete mold in layers and vibrated to compact it. After hardening, the spring buckle is opened, and the detachable rib, the side mold and the bottom mold are removed in sequence to obtain the concrete test block to be induced to crack. The concrete test block includes surface A, surface B, surface C and surface D. S3. Inducing cracking in concrete test blocks: First, place the non-penetrating auxiliary plate on the pre-embedded irregular nut on the A side of the concrete test block and tighten the fixing bolts. Then, insert the pressure-applying cylindrical profile into the side of the non-penetrating auxiliary plate. Place the two pressure-bearing semi-cylindrical profiles symmetrically below the B side of the concrete test block. Then, slowly apply the load through the hydraulic universal testing machine to induce cracks to form and develop in the tension zone of the concrete test block. Finally, turn off the hydraulic universal testing machine and remove the three-point loading device. S4. Install the crack width adjustment components: Install at least two sets of the crack width adjustment components on the C and D surfaces of the concrete test block along the direction perpendicular to the crack. One set of the crack width adjustment components is located at the tip of the crack, and the other set of the crack width adjustment components is located at the opening of the crack. Tighten the crack width adjustment rod at the tip of the crack to close the crack tip of the concrete test block, and lengthen or contract the crack width adjustment rod at the opening of the crack to allow the concrete crack to open and close freely. S5. Curing Cracks: Fill the gap between the non-penetrating auxiliary plate and the concrete test block with structural curing material. After hardening, remove all the crack induction devices to complete the preparation of the non-penetrating crack concrete test block.

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