Die for forming cylinder test piece and forming method

Abstract

The invention relates to a mold for forming a cylindrical test piece and a forming method. The mold comprises a first shell, a second shell, a first pressing plate, a second pressing plate and a plugging piece, the first shell and the second shell are enclosed to form a cylindrical mold barrel with a cylindrical cavity; the first pressing plate and the second pressing plate are detachably fixed to the openings in the two ends of the cylindrical cavity. An exhaust hole is formed in the middle area of the side wall of the first shell and connected to the cylindrical cavity. The plugging piece is detachably connected to the exhaust hole; wherein the mold is adapted to form a cylindrical test piece in a transverse arrangement mode, and the exhaust hole faces upwards when the mold is transversely arranged. An arc-shaped compensation groove is formed in the 1 / 4-3 / 4 height of the side wall of the first shell and connected to the cylindrical cavity, and the exhaust hole is formed in the middle of the arc-shaped compensation groove. The problems that the end faces are uneven and the upper end face and the lower end face are not parallel when the cylindrical cement-based material test piece is formed are solved, and the forming quality of the cylindrical cement-based material test piece and the reliability and efficiency of mechanical property testing of the cylindrical cement-based material test piece are improved.

Description

Technical Field

[0001] This invention relates to the field of cement-based material specimen molding technology, specifically to a mold and molding method for molding cylindrical specimens. Background Technology

[0002] In the testing of properties such as compressive strength and elastic modulus of cylindrical specimens of cement-based materials (including concrete, mortar, grout, etc.), the molding quality of the cylindrical specimens directly determines the volatility and accuracy of the test data.

[0003] Currently, vertical molds are commonly used in the industry for forming cylindrical specimens. However, this method has significant technical drawbacks in practical applications. During the vertical molding process, factors such as material shrinkage or expansion, and the expulsion of air bubbles from cement-based materials, easily lead to uneven surfaces on the formed specimens. These end-face defects directly result in uneven contact of the stress-bearing surfaces during subsequent mechanical testing, causing eccentric load transfer and consequently resulting in large dispersion and distorted test strength data, failing to accurately reflect the actual performance of the material.

[0004] To address this issue, traditional vertical mold forming requires significant manpower for processes such as grinding, leveling, and repairing the end faces of the specimens. This is not only time-consuming and labor-intensive, significantly increasing the human and financial resources invested in specimen preparation, but the grinding or leveling process can also affect material properties, and the final results are often unsatisfactory, impacting the final test results. Therefore, there is an urgent need to develop a simple and easy-to-use cylindrical specimen forming mold and method. Summary of the Invention

[0005] To address the problems existing in the prior art, the purpose of this invention is to provide a mold and molding method for forming cylindrical specimens, which can form cylindrical cement-based material specimens with flat end faces and parallel upper and lower end faces without grinding or leveling.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A mold for forming cylindrical specimens includes a first outer shell, a second outer shell, a first pressure plate, a second pressure plate, and a sealing component; The first and second outer shells are used to enclose and form a cylindrical mold with a cylindrical cavity; The first pressure plate and the second pressure plate are detachably fixed to the openings at both ends of the cylindrical cavity; The sidewall of the first housing has one or more vent holes in the central region, and the vent holes are connected to the cylindrical cavity. The sealing element is detachably connected to the vent. The mold is adapted to form cylindrical specimens in a horizontal manner, with the vent holes facing upwards when the mold is horizontal.

[0007] Furthermore, the areas of the first and second pressure plates are both larger than the end face area of ​​the cylindrical mold, and they are parallel and fitted to the end face of the cylindrical mold.

[0008] Furthermore, both the first and second outer shells are provided with connecting ears at their mating edges. The connecting ears are fastened with bolts and nuts to form a closed cylindrical mold between the first and second outer shells.

[0009] Furthermore, the sidewall of the first outer shell is provided with an arc-shaped compensation groove in the region of 1 / 4 to 3 / 4 of the length direction. The arc-shaped compensation groove is connected to the cylindrical cavity, and the exhaust port is opened in the middle of the arc-shaped compensation groove.

[0010] Furthermore, the volume of the arc-shaped compensation groove is quantitatively designed based on the expected shrinkage rate of the cement-based material, and the volume of the arc-shaped compensation groove is greater than the expected shrinkage volume.

[0011] Furthermore, it also includes a filler for filling the arc-shaped compensation groove, the filler being adapted to the shape of the arc-shaped compensation groove.

[0012] A method for molding cylindrical specimens, used for molding cylindrical specimens of expansive cement-based materials, includes the following steps: Step 1: Enclose the first outer shell and the second outer shell to form a cylindrical mold with a cylindrical cavity; Step 2: Fix and seal the first pressure plate to one end of the cylindrical mold, seal the vent hole with the sealing component, stand the cylindrical mold upright, pour the expansive cement-based material into the cylindrical cavity until it is slightly higher than the cylindrical cavity, and then scrape it level. Step 3: Fix and seal the second pressure plate to the other end of the cylindrical mold cylinder, place the cylindrical mold cylinder horizontally with the vent hole facing upward, remove the sealing piece on the vent hole, use the vent hole to expel air bubbles, and seal the vent hole with the sealing piece after venting is completed. Step 4: After static curing to the specified age, remove the mold to obtain a cylindrical specimen with flat and parallel upper and lower end faces.

[0013] A method for molding cylindrical specimens, used for molding cylindrical specimens of shrinkage cement-based materials, includes the following steps: Step 1: Enclose the first outer shell and the second outer shell to form a cylindrical mold with a cylindrical cavity; Step 2: Fix and seal the first pressure plate to one end of the cylindrical mold, seal the vent hole with the sealing piece, stand the cylindrical mold upright, pour shrinkage cement-based material into the cylindrical cavity and arc-shaped compensation groove until it is slightly higher than the cylindrical cavity, and then scrape it level. Step 3: Fix and seal the second pressure plate to the other end of the cylindrical mold, place the cylindrical mold horizontally so that the arc-shaped compensation groove and the vent hole face upward, remove the sealing piece on the vent hole, and the shrinkage cement-based material in the arc-shaped compensation groove flows into the cylindrical cavity by gravity to compensate for the shrinkage of the shrinkage cement-based material in the cylindrical cavity. The air bubbles are discharged through the vent hole. After the venting is completed, seal the vent hole with the sealing piece. Step 4: After static curing to the specified age, remove the mold to obtain a cylindrical specimen with flat and parallel upper and lower end faces.

[0014] Furthermore, it is also used to mold cylindrical specimens of expansive cement-based materials, including the following steps: before step 1, the arc-shaped compensation groove is filled with a filler.

[0015] Furthermore, during the pouring of cement-based materials, air bubbles in the cement-based materials are removed through tamping, vibration, and compaction.

[0016] In summary, the present invention has the following advantages: (1) The cylindrical specimen molding die provided by the present invention can ensure that the end face of the formed cylindrical cement-based material specimen is flat and the upper and lower end faces are parallel. The die avoids unevenness defects on the end face through the fixing effect of the cylindrical mold cylinder and the first and second pressure plates, and prevents the end face from tilting or shifting. From the source of forming, it ensures that the upper and lower end faces of the specimen are flat and smooth, strictly maintain a parallel state, and fully meet the standard requirements of mechanical testing for the appearance and size of the specimen. (2) The cylindrical specimen molding die provided by this invention can improve the stability of specimen strength testing: Based on the flat and parallel end face structure, the specimen can achieve uniform contact of the stress surface in mechanical tests such as compressive strength, axial compressive strength, and elastic modulus. The load transfer is free from eccentric loading and stress concentration, effectively avoiding the problem of large dispersion of test data caused by end face defects in traditional mold specimens. The test results can truly and objectively reflect the mechanical properties of the material itself, greatly improving the effectiveness and stability of strength data.

[0017] (3) The cylindrical specimen molding method provided by the present invention will produce a slight deviation from the cylinder at 1 / 4 to 3 / 4 of the side height. Since the central area of ​​the cylindrical specimen is greatly affected by the end friction force when the mechanical properties of the specimen are tested, the slight defect will not change the failure mode of the specimen, will not cause a large stress concentration or reduce the load-bearing capacity of the specimen. Therefore, the slight defect generated in the middle of the specimen has little effect on the mechanical property test results of the specimen.

[0018] (4) The cylindrical specimen molding method provided by the present invention is simple and easy to implement, with low energy consumption and carbon emissions: The operation process of this mold is not complicated compared with the traditional vertical mold. At the same time, the molded specimen does not require subsequent grinding and leveling, which saves the energy consumption of grinding equipment, reduces the production and use of grinding consumables and leveling materials, and reduces the additional carbon emissions caused by material loss. It simplifies the preparation process and meets the industry development requirements of low carbon, environmental protection, energy saving and consumption reduction. Attached Figure Description

[0019] Figure 1 This is an overall schematic diagram of the mold for the expansive concrete cylindrical specimen in an embodiment of the present invention; Figure 2 This is a top view of the mold for the cylindrical expansive concrete specimen in an embodiment of the present invention. Figure 3 This is a perspective view of the unfolded inner wall of the mold of the expansive concrete cylindrical specimen in an embodiment of the present invention; Figure 4 This is an overall schematic diagram of the mold for the shrinkage concrete cylindrical specimen in an embodiment of the present invention; Figure 5 This is a top view of the mold for a shrinkage concrete cylindrical specimen in an embodiment of the present invention.

[0020] Figure 6 This is a cross-sectional view of the inner wall of the mold cylinder for the shrinkage concrete cylindrical specimen in an embodiment of the present invention. Figure 7 for Figure 6 A schematic diagram of the AA cross section.

[0021] In the picture: 11-First outer shell, 12-Second outer shell, 13-Connecting ear; 21 - First pressure plate, 22 - Second pressure plate; 31-Exhaust port, 32-Sealing component; 4-Arc-shaped compensation groove. Detailed Implementation

[0022] The present invention will now be described in further detail.

[0023] A mold for forming a cylindrical specimen includes a first outer shell 11, a second outer shell 12, a first pressure plate 21, a second pressure plate 22, and a sealing component 32; The first and second outer shells are used to enclose and form a cylindrical mold cylinder with a cylindrical cavity; preferably, both the first and second outer shells are semi-circular outer shells.

[0024] Specifically, both the first and second outer shells are provided with connecting ears 13 at their mating edges. The connecting ears are fastened with bolts and nuts to form a closed cylindrical mold between the first and second outer shells.

[0025] The first pressure plate and the second pressure plate are detachably fixed to the two ends of the cylindrical cavity. The area of ​​the first pressure plate and the second pressure plate is larger than the end face area of ​​the cylindrical mold, and they are parallel and fitted to the end face of the cylindrical mold to constrain the end face of the specimen. The sidewall of the first outer casing has one or more exhaust holes 31 in the central region. The exhaust holes are connected to the cylindrical cavity and are used to discharge gas from the cylindrical cavity. The sealing element is detachably connected to the vent hole to control the opening and closing of the vent hole; The mold is used to form cylindrical specimens in a horizontal position, with the vent holes facing upwards when the mold is horizontal.

[0026] A method for molding cylindrical specimens, using the aforementioned mold to mold cylindrical specimens of expansive cement-based materials, includes the following steps: Step 1: Enclose the first outer shell and the second outer shell to form a cylindrical mold with a cylindrical cavity; Step 2: Fix and seal the first pressure plate to one end of the cylindrical mold, seal the vent hole with the sealing component, stand the cylindrical mold upright, pour the expansive cement-based material into the cylindrical cavity until it is slightly higher than the cylindrical cavity, and then scrape it level. Step 3: Fix and seal the second pressure plate to the other end of the cylindrical mold cylinder, place the cylindrical mold cylinder horizontally with the vent hole facing upward, remove the sealing piece on the vent hole, use the vent hole to expel air bubbles, and seal the vent hole with the sealing piece after venting is completed. Step 4: After static curing to the specified age, remove the mold to obtain a cylindrical specimen with flat and parallel upper and lower end faces.

[0027] In order to form shrinkage concrete cylindrical specimens, the present invention improves upon the above mold: an arc-shaped compensation groove 4 is provided on the side wall of the first outer shell in the region of 1 / 4 to 3 / 4 of the length direction. The arc-shaped compensation groove is connected to the cylindrical cavity and is used to compensate for volume loss by gravity when the material shrinks. The vent is opened in the middle of the arc-shaped compensation groove.

[0028] The volume of the arc-shaped compensation groove is quantitatively designed based on the expected shrinkage rate of the cement-based material, and the volume of the arc-shaped compensation groove is slightly larger than the expected shrinkage rate of the target concrete.

[0029] A method for molding cylindrical specimens, using an improved mold to mold cylindrical specimens of shrinkage cement-based materials, includes the following steps: Step 1: Enclose the first outer shell and the second outer shell to form a cylindrical mold with a cylindrical cavity; Step 2: Fix and seal the first pressure plate to one end of the cylindrical mold, stand the cylindrical mold upright, seal the vent hole with the sealing part, pour shrinkage cement-based material into the cylindrical cavity and arc-shaped compensation groove until it is slightly higher than the cylindrical cavity, and then scrape it level. Step 3: Fix and seal the second pressure plate to the other end of the cylindrical mold cylinder, place the cylindrical mold cylinder horizontally so that the arc-shaped compensation groove and the vent hole face upwards, remove the sealing parts on the vent hole. When the material shrinks and settles, causing the liquid level to drop, the slurry temporarily stored in the arc-shaped compensation groove flows downwards back to the cylindrical cavity under the action of gravity to compensate for the shrinkage volume and discharge the gas through the vent hole. After the venting is completed, seal the vent hole with the sealing parts. Step 4: After static curing to the specified age, remove the mold to obtain a cylindrical specimen with flat and parallel upper and lower end faces.

[0030] To enable the improved mold to be suitable for molding specimens of both shrinkage-based and expansion-based cementitious materials, the present invention also includes a filler for filling the arc-shaped compensation groove, the filler being adapted to the shape of the arc-shaped compensation groove. The molding method involves filling the arc-shaped compensation groove with the filler before step 1 when molding expansion-based cementitious materials.

[0031] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings: Example 1 illustrates the specific fabrication process of an expansive grout cylindrical specimen with a molding size of Φ60mm×120mm. Step 1, refer to Figures 1-3 The first and second outer shells are spliced ​​together and fastened with connecting ears to ensure that the first pressure plate fits against the end face of the mold body, forming a complete cylindrical mold cylinder. The outer wall thickness of the cylindrical mold cylinder is 10mm, and the diameter of the cylindrical cavity is 60mm and the height is 120mm. Step 2: Erect the cylindrical mold cylinder and fix the first pressure plate as the base plate to the bottom of the cylindrical mold cylinder with bolts. The dimensions of the first pressure plate are 120mm × 120mm on each side and 10mm thick. Step 3: Prepare and pour the grouting material. Mix the grouting material according to the design mix ratio, pour it to a level slightly higher than the volume of the cylindrical cavity, and then scrape off the excess grouting material. Step 4: Tighten the bolts and nuts of the second pressure plate to fix the sealing assembly. After ensuring a seal, place the cylindrical mold horizontally and open the three circular vent holes on the upper side wall to release air bubbles in the grout. The diameter of the vent holes is 10mm, and the interval between each pair of vent holes is 8mm. After venting for 1 hour, seal the vent holes with a sealing component (bolt or pressure block). Step 5: After allowing the specimen to cure at the specified age, remove the mold to obtain a regular cylindrical specimen.

[0032] Example 2 illustrates the specific fabrication process of a shrinkage cylindrical concrete specimen with molding dimensions of Φ150mm × 300mm. Step 1, refer to Figures 4-7 The first and second outer shells are spliced ​​together and secured with connecting lugs to ensure that the first pressure plate fits snugly against the end face of the mold body, forming a complete cylindrical mold cylinder. The outer wall thickness of the cylindrical mold cylinder is 15mm, the diameter of the cylindrical cavity is 150mm, and the height is 300mm. The arc-shaped compensation groove has a slot length of 150mm and is located within a side wall length range of 75mm to 225mm. The central angle of the arc-shaped compensation groove is designed to be 90°, and the bottom radius is 8.25mm. The two ends of the arc-shaped compensation groove transition to the side wall with rounded arcs, and a vent hole with a diameter of 15mm is opened in the middle of the arc-shaped compensation groove. The calculated volume of the arc-shaped compensation groove is 2649.375mm². 3 It accounts for 0.05% of the total mold volume.

[0033] Step 2: Erect the cylindrical mold cylinder and fix the first pressure plate as the base plate to the bottom of the cylindrical mold cylinder with bolts. The first pressure plate has a side length of 300mm × 300mm and a thickness of 10mm. Step 3: Concrete preparation and pouring. Mix concrete according to the design mix ratio, prepare concrete according to the target volume shrinkage rate, pour from the top of the cylindrical mold to a volume slightly higher than the cylindrical cavity volume, and then scrape off the excess concrete; Step 4: Tighten the bolts and nuts of the second pressure plate to fix the sealing assembly. After ensuring the seal, place the cylindrical mold horizontally with the side wall area with the arc-shaped compensation groove facing upward. Then open the vent hole on the upward-facing side wall and vent for 1 hour before closing the vent hole. Step 5: Static curing. After the shrinkage cement-based material settles, the slurry temporarily stored in the arc-shaped compensation groove flows back into the cylindrical cavity under gravity to compensate for the volume loss caused by shrinkage, and the gas is discharged through the vent in the middle. After the concrete has set, the mold is removed to obtain a cylindrical specimen with flat and parallel ends.

[0034] This invention achieves comprehensive technical advantages covering molding quality, testing reliability, operational convenience, and environmental friendliness through the synergistic effects of multiple dimensions, including mold structure, molding method, adaptability design, and generalization modification. The specific synergistic relationships are as follows: 1. Synergistic effect of transverse forming structure and end-plate constraint: solving end-face defects at the source. The horizontal molding process allows air bubbles to be vented out along the vent holes on the upper sidewall, avoiding air bubble residue on the end face. The pressure plates at both ends are fastened with bolts to form a rigid constraint, preventing the end face from deforming or tilting due to material shrinkage or expansion. The combination of the two processes works simultaneously from the two dimensions of venting and constraint, ultimately achieving flat and strictly parallel upper and lower end faces of the specimen.

[0035] 2. Synergistic effect of arc-shaped compensation groove and directional vent: precisely solves the dual pain points of shrinkage materials. The arc-shaped compensation groove provides shrinkage compensation volume, and the vent hole in the middle of the groove simultaneously discharges the gas trapped in the slurry flow during the shrinkage process. The two form a closed-loop design of compensation and venting, which not only avoids end face concavity, but also reduces internal porosity to a certain extent, thereby improving the molding quality and mechanical properties of shrinkage material specimens at the same time.

[0036] 3. Coordination of the split shell structure and filler design: Achieving the versatility of a single mold with dual adaptability. The split structure of the two halves of the shell provides convenient space for the installation and removal of the filler. The filler allows the same mold to quickly switch between expanding materials (to seal the arc-shaped compensation groove) and shrinking materials (to remove the filler). It retains the advantages of easy demolding and cleaning of the two halves of the shell, and breaks through the limitation of traditional molds that only adapt to a single material. It achieves a dual improvement in versatility and convenience, with a significant synergistic effect.

[0037] The technical effects of this invention break through the conventional understanding of the prior art: 1. Minor defects in the middle of the specimen do not affect the mechanical testing: This breaks through the traditional understanding that specimens must be completely regular.

[0038] It is generally believed in the industry that if a cylindrical specimen has defects that deviate from the cylindrical shape (such as the small bulge or depression in the middle caused by the arc-shaped compensation groove in this invention), it will lead to stress concentration during mechanical testing, reduce the load-bearing capacity, and affect the authenticity of the test results.

[0039] An unexpected benefit of this application: Since the defect is located only in the middle region of the mold cylinder sidewall, spanning 1 / 4 to 3 / 4 of its length, and the failure mode of the specimen in mechanical testing is mainly affected by the frictional constraint zone at the ends, the small defect in the middle region neither changes the failure mode of the specimen nor causes significant stress concentration, and its impact on the test results is negligible. This effect exceeds conventional understanding, achieving a reconciliation between allowing for minor structural defects and ensuring the reliability of test data, providing a new design approach for mold structure optimization.

[0040] 2. Improved test data stability without the need for end face grinding or leveling: Breaking away from the traditional approach that grinding or leveling is the only way to correct defects.

[0041] Conventional technical expectation: Due to end-face defects, specimens formed by traditional vertical molds must be ground or leveled to reduce the dispersion of test data; if the grinding or leveling process is omitted, the uneven end face of the specimen will lead to uneven stress and even worse data stability.

[0042] The unexpected benefit of this application is that, through the collaborative design of horizontal placement, pressure plates, and adaptive venting / compensation, a flat and parallel end face is ensured from the molding stage. This not only eliminates the need for grinding or leveling, saving subsequent processes, but also achieves uniform contact of the stress-bearing surfaces and unbiased load transfer, truly reflecting the material's inherent properties. This effect overturns the traditional understanding that grinding or leveling is necessary to improve test stability, achieving a reverse optimization of simplified processes and improved quality—an unexpected benefit that existing technologies cannot achieve.

[0043] 3. One mold can be used for two types of materials with different properties, and the molding quality of both materials is not compromised: breaking through the industry convention of molds having only one function.

[0044] Conventional technical expectations: The molding requirements of expansive and shrinking cement-based materials are contradictory. The former expands while the latter shrinks. According to traditional thinking, two sets of special equipment need to be designed for the mold. If one mold is forced to be used, it will inevitably lead to a decrease in the molding quality of one of the cement-based materials (for example, shrinking materials without arc-shaped compensation grooves will result in side depressions, while expansive materials with arc-shaped compensation grooves will result in obvious side bulges).

[0045] The unexpected benefits of this application are: through the synergy of the detachable filler and the dual-structure mode, the two molding modes can be switched simply by removing and installing the filler. When used with expansive materials, the filler seals the arc-shaped compensation groove, ensuring a regular inner wall of the mold and efficient venting through the axial vent. When used with shrinking materials, the filler is removed, and the arc-shaped compensation groove and the central vent work together, resulting in specimens with flat end faces and reliable test data in both modes. Furthermore, the switching operation is simple and requires no replacement of the mold body. This achievement balances versatility and specialization, significantly reducing equipment investment costs and representing an innovative point that exceeds the expectations of conventional mold design.

[0046] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A mold for forming cylindrical specimens, characterized in that, It includes a first outer shell, a second outer shell, a first pressure plate, a second pressure plate, and a sealing component; The first and second outer shells are used to enclose and form a cylindrical mold with a cylindrical cavity; The first pressure plate and the second pressure plate are detachably fixed to the openings at both ends of the cylindrical cavity; The sidewall of the first housing has one or more vent holes in the central region, and the vent holes are connected to the cylindrical cavity. The sealing element is detachably connected to the vent. The mold is adapted to form cylindrical specimens in a horizontal manner, with the vent holes facing upwards when the mold is horizontal.

2. The mold according to claim 1, characterized in that, The areas of the first and second pressure plates are both larger than the end face area of ​​the cylindrical mold, and they are parallel and fitted to the end face of the cylindrical mold.

3. The mold according to claim 1, characterized in that, Both the first and second outer shells have connecting ears at their mating edges. The connecting ears are fastened with bolts and nuts to form a closed cylindrical mold between the first and second outer shells.

4. The mold according to any one of claims 1-3, characterized in that, The side wall of the first outer shell is provided with an arc-shaped compensation groove in the region of 1 / 4 to 3 / 4 of the length direction. The arc-shaped compensation groove is connected to the cylindrical cavity, and the exhaust port is opened in the middle of the arc-shaped compensation groove.

5. The mold according to claim 4, characterized in that, The volume of the arc-shaped compensation groove is quantitatively designed based on the expected shrinkage rate of the cement-based material, and the volume of the arc-shaped compensation groove is greater than the expected shrinkage volume.

6. The mold according to claim 5, characterized in that, It also includes fillers for filling the arc-shaped compensation grooves, the fillers being adapted to the shape of the arc-shaped compensation grooves.

7. A method for molding a cylindrical specimen, characterized in that, The process of molding an expansive cement-based cylindrical specimen using the mold according to any one of claims 1-3 includes the following steps: Step 1: Enclose the first outer shell and the second outer shell to form a cylindrical mold with a cylindrical cavity; Step 2: Fix and seal the first pressure plate to one end of the cylindrical mold, seal the vent hole with the sealing component, stand the cylindrical mold upright, pour the expansive cement-based material into the cylindrical cavity until it is slightly higher than the cylindrical cavity, and then scrape it level. Step 3: Fix and seal the second pressure plate to the other end of the cylindrical mold cylinder, place the cylindrical mold cylinder horizontally with the vent hole facing upward, remove the sealing piece on the vent hole, use the vent hole to expel air bubbles, and seal the vent hole with the sealing piece after venting is completed. Step 4: After static curing to the specified age, remove the mold to obtain a cylindrical specimen with flat and parallel upper and lower end faces.

8. A method for molding a cylindrical specimen, characterized in that, The molding of a shrinkage cement-based cylindrical specimen using the mold as described in claim 4 or 5 includes the following steps: Step 1: Enclose the first outer shell and the second outer shell to form a cylindrical mold with a cylindrical cavity; Step 2: Fix and seal the first pressure plate to one end of the cylindrical mold, seal the vent hole with the sealing piece, stand the cylindrical mold upright, pour shrinkage cement-based material into the cylindrical cavity and arc-shaped compensation groove until it is slightly higher than the cylindrical cavity, and then scrape it level. Step 3: Fix and seal the second pressure plate to the other end of the cylindrical mold, place the cylindrical mold horizontally so that the arc-shaped compensation groove and the vent hole face upward, remove the sealing piece on the vent hole, and the shrinkage cement-based material in the arc-shaped compensation groove flows into the cylindrical cavity by gravity to compensate for the shrinkage of the shrinkage cement-based material in the cylindrical cavity. The air bubbles are discharged through the vent hole. After the venting is completed, seal the vent hole with the sealing piece. Step 4: After static curing to the specified age, remove the mold to obtain a cylindrical specimen with flat and parallel upper and lower end faces.

9. The molding method according to claim 8, characterized in that, It is also used to form cylindrical specimens of expansive cement-based materials, including the following steps: before step 1, the arc-shaped compensation groove is filled with a filler.

10. The molding method according to any one of claims 7-9, characterized in that, During the pouring of cement-based materials, air bubbles in the cement-based materials are removed by tamping, vibration, and compaction.

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