A six-face fully-enclosed UHPC wrapped core concrete standard test block and a manufacturing device and method thereof

Abstract

The application relates to a six-surface fully-enclosed UHPC wrapped core concrete standard test block and a manufacturing device and method thereof, and relates to the field of ultra-high performance concrete. The application comprises a core concrete block, a peripheral UHPC wrapping layer which completely wraps the six surfaces of the core concrete block to form an integrated closed shell, and a plurality of permanent UHPC positioning columns which are embedded in the surface of the core concrete block and extend into the interior of the peripheral UHPC wrapping layer. The height of the permanent UHPC positioning column is equal to the designed thickness of the peripheral UHPC wrapping layer, and the permanent UHPC positioning column is used for supporting and positioning the core concrete block when the peripheral UHPC wrapping layer is poured, and is permanently retained after molding. The application first proposes a six-surface fully-enclosed composite test block structure, and through reverse thinking of the permanent positioning column, the technical difficulty that the core concrete cannot be accurately centered in the fully-enclosed process is completely solved, high-precision control of the wrapping layer thickness is realized, and the mechanical authenticity of the axial compression test is ensured.

Description

Technical Field

[0001] This invention relates to the field of ultra-high performance concrete, specifically to a standard test block of six-sided fully enclosed UHPC-encased core concrete and its manufacturing apparatus and method. Background Technology

[0002] Ultra-high performance concrete (UHPC), with its superior properties such as ultra-high strength, high durability, and low porosity, has shown broad application prospects in bridge, marine engineering, and structural reinforcement. However, the heavy weight and high cost of UHPC structures limit their widespread application in large-volume structures. To address this, UHPC-encased concrete composite structures have emerged, utilizing UHPC as an outer shell to encase a core of ordinary or high-strength concrete, aiming to improve structural performance while controlling costs.

[0003] In civil engineering research and experimentation, standardized test blocks are urgently needed to accurately study the confinement effect of ultra-high performance concrete (UHPC) on the core concrete and the mechanical constitutive relationship of composite structures. Theoretically, a six-sided fully enclosed cubic block is the ideal model for obtaining the true mechanical parameters under axial compression. However, to fabricate such a block, the core concrete block must first be precisely suspended and fixed in the center of the mold, and then the outer UHPC is poured to form a uniformly thick encapsulating layer, especially a thin-walled encapsulation with a thickness ≤20mm.

[0004] The existing technology has the following main drawbacks: (1) Existing UHPC reinforcement is mostly U-shaped, round tube or flat plate wrapping, which only reinforces part of the surface of beams and columns. It cannot achieve full six-sided enclosure. Corrosive media may still invade from the unwrapped surface, and cannot achieve true full isolation.

[0005] (2) For the six-sided fully enclosed process, there is an inherent contradiction: once the positioning components are placed, they cannot be removed. The traditional approach is to use spacers or temporary supports, but these components either need to be removed after demolding, leaving holes that need to be filled, which damages the integrity of the UHPC shell; or they remain permanently, becoming foreign objects that cause local debonding and stress concentration. More importantly, during the pouring and vibration process, these temporary spacers are very prone to displacement, causing the core concrete to deviate from the center, resulting in a serious unevenness in the thickness of the wrapping layer (the deviation can reach more than 2-3 mm), and even causing the test blocks to be scrapped.

[0006] (3) If the core concrete block is not centered, the stress distribution will be distorted, the failure mode will be changed, the measured bearing capacity will be low, the data will be highly discrete, completely deviating from the experimental assumption of axial compression, and reliable constitutive relation data cannot be provided.

[0007] Therefore, developing a six-sided fully enclosed composite test block that can achieve precise centering of the core concrete, ensure the integrity and continuity of the UHPC shell, and is easy to operate, as well as its manufacturing method, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] To address at least one technical problem in the background art, this invention provides a six-sided fully enclosed UHPC-wrapped core concrete standard test block and its fabrication device and method. It proposes for the first time a six-sided fully enclosed composite test block structure, and through the reverse thinking of permanent positioning columns, completely solves the technical problem of the core concrete not being able to be precisely centered in the fully enclosed process, achieving high-precision control of the wrapping layer thickness and ensuring the mechanical authenticity of the axial compression test.

[0009] To achieve the above objectives, the present invention provides a standard test block of six-sided fully enclosed UHPC-encased core concrete, comprising: Core concrete block; The outer UHPC cladding layer completely encloses the six sides of the core concrete block, forming an integrated closed shell; Multiple permanent UHPC positioning posts are embedded in the surface of the core concrete block and extend into the interior of the outer UHPC wrapping layer; The height of the permanent UHPC positioning column is equal to the designed thickness of the outer UHPC wrapping layer. It is used to support and position the core concrete block when the outer UHPC wrapping layer is poured, and is permanently retained after molding.

[0010] Furthermore, the diameter of the permanent UHPC positioning post is 3mm to 8mm, its height is 15mm to 30mm, and the height / diameter ratio is ≤5.

[0011] Furthermore, the end of the permanent UHPC positioning post that contacts the inner wall of the external mold is hemispherical or conical.

[0012] Furthermore, the plurality of permanent UHPC positioning posts are arranged at the center point, at the four corner points, or in an array on each surface of the core concrete block.

[0013] A device for fabricating a standard test block with a six-sided fully enclosed UHPC-encased core concrete, comprising: The external mold has an internal cavity that matches the external dimensions of the standard test block; Multiple permanent UHPC positioning posts, with a height equal to the thickness of the outer UHPC wrapping layer, are fixed at one end to the surface of the core concrete block, and the other end abuts against the inner wall of the outer mold before the outer UHPC wrapping layer is poured, so as to accurately support and position the core concrete block at the center of the inner cavity of the outer mold. The permanent UHPC positioning column remains permanently inside the outer UHPC wrapping layer after the casting is completed.

[0014] Furthermore, it includes: the permanent UHPC positioning post is connected to the surface of the core concrete block by pre-embedding or integral casting.

[0015] Furthermore, the external mold is a segmented combination mold, and its demolding direction is parallel to the axial direction of the positioning column.

[0016] A method for fabricating a standard test block with a six-sided fully enclosed UHPC-encased core concrete, comprising the following steps: Step 1: Precast core concrete cube test blocks. To ensure the bonding strength between the core concrete test block and the outer UHPC wrapping layer, the surface of the core concrete test block is roughened and the surface laitance layer of the concrete is removed before the permanent UHPC positioning column is installed before pouring the outer UHPC wrapping layer. Step 2, Prefabrication and Installation of Positioning Posts: Prefabricate permanent UHPC positioning posts with a height tolerance of ≤ ±0.1mm, and fix them to the surface of the core concrete block according to the predetermined arrangement; Step 3: Core concrete block placement: Place the core concrete block with permanent UHPC positioning posts into the outer mold, so that the free end of each permanent UHPC positioning post directly abuts against the inner wall of the outer mold, and the core concrete block automatically occupies the center of the outer mold. Step 4, Casting of the outer UHPC wrapping layer: Cast the outer UHPC material into the outer mold and compact it with vibration; Step 5, Curing and Demolding: Curing is carried out according to the UHPC curing system. After reaching the required curing age, the product is demolded.

[0017] Furthermore, in step 1, the prefabrication accuracy of the permanent UHPC positioning post is a height tolerance of ≤ ±0.1mm.

[0018] Furthermore, the method can achieve a positioning accuracy of ≤±0.5mm for the distance between each face of the core concrete block and the inner wall of the external mold.

[0019] The beneficial effects of this invention are as follows: 1. For the first time, a standard test block with a six-sided fully UHPC-enclosed core concrete core was proposed, providing a standardized test platform for studying the true mechanical constitutive relationship of composite structures under ideal axial compression.

[0020] 2. The ingenious use of permanent positioning posts solves the inherent contradiction of the inability to remove positioning components in a fully enclosed process, turning unmanageable waste into valuable resources, which is a major breakthrough in technological thinking.

[0021] 3. Positioning accuracy is guaranteed by the height precision of the pre-set positioning column, rather than relying on on-site adjustments. This achieves a positioning accuracy of ≤±0.3mm for the distance between each surface of the core concrete and the inner wall of the mold, and a coating layer thickness deviation of ≤0.5mm, an improvement of an order of magnitude compared to existing technologies (±2-3mm). This fundamentally ensures the axial stress state of the specimen, making the test data authentic and reliable.

[0022] 4. The permanently retained UHPC positioning posts are not only harmless, but also serve as miniature shear keys, enhancing the interfacial bond strength and shear resistance between the outer UHPC wrapping layer and the core concrete block.

[0023] 5. The traditional and complex centering adjustment steps are simplified into three steps: installation, mold placement, and pouring, which improves construction efficiency by more than 50%, requires no professional skills, and greatly increases the yield of finished products.

[0024] 6. The UHPC shell is free of holes, foreign objects, and secondary interfaces, and has the same lifespan as the structure, avoiding the risks of aging and cracking at the filling points in traditional methods.

[0025] 7. By flexibly adjusting the specimen size and wrapping thickness, the product's application scenarios can be comprehensively expanded. From pedestrian walkways in urban areas to wall decorations inside and outside buildings, the specimen blocks of this invention possess multiple advantages such as high strength, impermeability, and corrosion resistance. Especially in frigid regions, facing the challenges of low-temperature freeze-thaw cycles and corrosive environments such as salting for snow melting, this invention, with its excellent frost resistance and stability, can effectively resist natural erosion, significantly extend its service life, and reduce maintenance costs. It also injects innovative momentum into the construction of green buildings and smart cities, truly achieving a deep integration of technological innovation and market demand, and has broad application prospects and extremely high promotional value. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the test block of the present invention; Figure 2 This is a flowchart of the method of the present invention.

[0027] In the diagram: 1-core concrete block; 2-outer UHPC wrapping layer; 3-permanent UHPC positioning column. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0030] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0031] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0032] Furthermore, the terms "installation," "setup," "equipped with," "connection," "linking," and "socketing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0033] To achieve the above objectives, refer to Figure 1 This invention provides a standard test block for a six-sided fully enclosed UHPC-encased core concrete, comprising: Core concrete block 1; The outer UHPC wrapping layer 2 completely encloses the six sides of the core concrete block 1, forming an integrated closed shell; Multiple permanent UHPC positioning posts 3 are embedded in the surface of the core concrete block 1 and extend into the interior of the outer UHPC wrapping layer 2; The height of the permanent UHPC positioning column 3 is equal to the designed thickness of the outer UHPC wrapping layer 2. It is used to support and position the core concrete block 1 when the outer UHPC wrapping layer 2 is poured, and is permanently retained after molding.

[0034] To further optimize the technical solution, the diameter of the permanent UHPC positioning post 3 is 3mm to 8mm, its height is 15mm to 30mm, and the height / diameter ratio is ≤5.

[0035] To further optimize the technical solution, the end of the permanent UHPC positioning post 3 that contacts the inner wall of the external mold is hemispherical or conical.

[0036] To further optimize the technical solution, the multiple permanent UHPC positioning columns 3 are arranged at the center point, at the four corner points, or in an array on each surface of the core concrete block 1. The number and arrangement of the positioning columns can be flexibly selected according to the actual vibration intensity during the pouring of the outer UHPC wrapping layer.

[0037] This invention also provides a device for fabricating a standard test block of UHPC-encased core concrete with six fully enclosed sides, comprising: The external mold has an internal cavity that matches the external dimensions of the standard test block; Multiple permanent UHPC positioning posts, with a height equal to the thickness of the outer UHPC wrapping layer, are fixed at one end to the surface of the core concrete block, and the other end abuts against the inner wall of the outer mold before the outer UHPC wrapping layer is poured, so as to accurately support and position the core concrete block at the center of the inner cavity of the outer mold. The permanent UHPC positioning column remains permanently inside the outer UHPC wrapping layer after the casting is completed.

[0038] Further optimization of the technical solution includes: the permanent UHPC positioning column is connected to the surface of the core concrete block by pre-embedding or integral casting.

[0039] Further optimization of the technical solution includes: the external mold is a segmented combination mold, and its demolding direction is parallel to the axial direction of the positioning column.

[0040] refer to Figure 2 The present invention also provides a method for manufacturing a standard test block of UHPC-enclosed core concrete with six sides fully enclosed, comprising the following steps: Step 1: Precast core concrete cube test blocks. To ensure the bonding strength between the core concrete test block and the outer UHPC wrapping layer, the surface of the core concrete test block is roughened and the surface laitance layer of the concrete is removed before the permanent UHPC positioning column is installed before pouring the outer UHPC wrapping layer. Step 2, Prefabrication and Installation of Positioning Posts: Prefabricate permanent UHPC positioning posts with a height tolerance of ≤ ±0.1mm, and fix them to the surface of the core concrete block according to the predetermined arrangement; Step 3: Core concrete block placement: Place the core concrete block with permanent UHPC positioning posts into the outer mold, so that the free end of each permanent UHPC positioning post directly abuts against the inner wall of the outer mold, and the core concrete block automatically occupies the center of the outer mold. Step 4, Casting of the outer UHPC wrapping layer: Cast the outer UHPC material into the outer mold and compact it with vibration; Step 5, Curing and Demolding: Curing is carried out according to the UHPC curing system. After reaching the required curing age, the product is demolded.

[0041] To further optimize the technical solution, in step 1, the prefabrication accuracy of the permanent UHPC positioning post is a height tolerance of ≤ ±0.1mm.

[0042] Further optimization of the technical solution allows the method to achieve a positioning accuracy of ≤±0.5mm between the distance between each surface of the core concrete block and the inner wall of the external mold.

[0043] Example 1: 150mm cube standard test block (20mm thick UHPC outer layer, center point arrangement)

[0044] (1) Test block structure design

[0045] This embodiment provides a standard test block with a six-sided UHPC-encased core concrete core, with overall dimensions of 150mm × 150mm × 150mm. Its structure includes: Core concrete block 1: The dimensions are 110mm×110mm×110mm. It is made of C50 ordinary concrete and can be used after 28 days of standard curing.

[0046] The outer UHPC cladding layer 2 is uniformly wrapped around the six sides of the core concrete block 1, with a designed thickness of t=20mm. The UHPC material used has a compressive strength ≥120MPa and contains 2% steel fiber by volume.

[0047] Permanent UHPC positioning posts 3: A total of 6 posts are positioned at the geometric center points of the six faces of the core concrete block 1. The positioning posts 3 are made of the same material as the outer UHPC cladding layer 2. The geometric parameters of the positioning posts 3 are: diameter d = 5mm, height h = t = 20mm, slenderness ratio = 4. One end is flat and pre-embedded approximately 2mm deep into the surface of the core concrete block 1; the other end is hemispherical and abuts against the inner wall of the mold during fabrication.

[0048] (2) Positioning device and manufacturing method

[0049] The positioning device in this embodiment includes a core concrete block 1 with a permanent UHPC positioning post 3 and an external mold. The external mold is a standard cubic steel mold of 150mm×150mm×150mm with a smooth inner wall.

[0050] The production method is as follows: Step 1: Prefabrication and installation of positioning columns (integral casting type) Precast permanent UHPC positioning posts 3: Using a special silicone mold, UHPC is poured according to the mix ratio, vibrated and smoothed, and cured for 3 days (strength reaches 85%). After demolding, the actual heights of the 6 permanent UHPC positioning posts 3 are measured to be 20.00mm, 20.01mm, 19.99mm, 20.00mm, 20.02mm and 20.00mm, with all tolerances ≤ ±0.1mm.

[0051] Fabrication of Core Concrete Block 1: Shallow holes, 2mm deep, are pre-drilled at the bottom of the core concrete mold, matching the diameter of the permanent UHPC positioning posts 3. Six permanent UHPC positioning posts 3 are placed into the pre-drilled holes on each of the six sides, with the flat ends facing inwards. After mold closing, C50 concrete is poured and vibrated for curing. After demolding, the permanent UHPC positioning posts 3 are firmly embedded in the surface of the core concrete block 1.

[0052] Step 2: Core concrete pouring

[0053] The core concrete block 1 with the permanent UHPC positioning post 3 is placed into the outer mold. Since the height of the permanent UHPC positioning post 3 is precisely equal to the designed outer UHPC wrapping layer thickness of 20mm, its hemispherical end naturally abuts against the inner wall of the outer mold. Without any measurement or adjustment, the core concrete block 1 is automatically and precisely centered in the mold.

[0054] Step 3: Location Verification

[0055] The distances between each face of the core concrete block 1 and the inner wall of the outer mold were measured using vernier calipers. The measured data were 20.03mm, 19.98mm, 20.01mm, 20.02mm, 19.99mm, and 20.00mm, all within 20±0.3mm, which meets the requirements.

[0056] Step 4: Casting of the outer UHPC

[0057] Slowly pour the prepared permanent UHPC positioning pillars 2 from the top into the outer mold. Since the permanent UHPC positioning pillars 3 are only 5mm in diameter, they will not obstruct the flow of the UHPC slurry. Place the mold on a vibrating table and vibrate for 2 minutes to ensure compaction.

[0058] Step 5: Curing and Demolding

[0059] After pouring, cover with plastic film and cure in a standard curing room (20±2℃, relative humidity ≥95%) for 28 days. During demolding, because the end of the positioning post 3 is hemispherical, the contact area with the inner wall of the mold is small, making it easy to separate, and the positioning post 3 remains intact.

[0060] (3) Effect verification

[0061] Completed core concrete block 1 Figure 1 As shown, the specimens are intact, without any holes, repair marks, or visible cracks. Three core concrete blocks were randomly selected for cross-section measurement. The average thickness of the outer UHPC wrapping layer was 20.02 mm, with a standard deviation of only 0.18 mm. Axial compressive strength tests were conducted according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete." The measured average compressive strength was 156.8 MPa, with a coefficient of variation of 2.8%. All specimens exhibited a typical symmetrical crushing failure mode, proving that this embodiment successfully produced high-quality standard specimens that meet design requirements.

[0062] Example 2: 150mm cube test block (15mm thick wrapping layer, with corner points arranged)

[0063] This embodiment has the same main structure as Embodiment 1, the difference being: Positioning post height: h=15mm.

[0064] Positioning post arrangement: Four-corner point arrangement. One positioning post is placed at each of the four corner points of each face of the core concrete block (120mm×120mm×120mm), with four posts per face, for a total of 24 posts across the six faces.

[0065] Applicable Scenarios: Suitable for experiments requiring in-depth study of the shear strength of the interface between the UHPC cladding and the core concrete. The 24 positioning columns act as 24 miniature shear keys, providing stronger interfacial mechanical bonding. Interface push-out tests verified that the interfacial shear strength of the specimen in this embodiment is approximately 30% higher than that of Example 1, but it causes a slight weakening of approximately 3% in the cross-section of the outer UHPC cladding, making it suitable for scenarios with specific shear strength requirements.

[0066] Example 3: Preferred Scheme for Using a Segmented Mold

[0067] This embodiment optimizes the external mold based on Embodiment 1 or Embodiment 2. The external mold adopts a segmented combination mold, which is composed of two L-shaped steel plates joined together by bolts. During demolding, the fastening bolts are loosened first, allowing the two mold pieces to separate horizontally along the parting surface. This demolding direction is parallel to the axial direction of the permanent UHPC positioning post 3 (perpendicular to the core concrete surface). This design avoids the lateral shear force generated on the permanent UHPC positioning post 3 during demolding using a traditional integral mold, and is especially suitable for permanent UHPC positioning posts with smaller diameters (e.g., 3mm). Comparative tests show that using this embodiment, the integrity rate of the positioning post during demolding can reach over 98%, while the integrity rate using an integral mold is approximately 90%.

[0068] Experimental Example: Comparing the effects of different positioning methods on the accuracy and mechanical properties of the specimen.

[0069] Three groups of 150mm cube specimens were prepared, with a designed wrapping layer thickness of 20mm. Group A adopted the technical solution of this invention (center point arrangement, 6 rods). Group A used a 5mm permanent UHPC positioning post; Group B used the traditional padding method (temporary plastic pads, removed and used to fill holes after vibration); Group C had no positioning measures and relied on manual visual centering. Ten test blocks were prepared for each group. The test results are as follows:

[0070] Experimental conclusions: Group A (the present invention) specimens exhibited the most uniform coating thickness, the highest mechanical properties, and the least data dispersion. The failure mode met theoretical expectations, fully demonstrating the technical superiority and inventiveness of the present invention. Particularly noteworthy is that the interfacial shear strength of Group A was significantly higher than that of Groups B and C, directly proving the interfacial reinforcement function of the permanent UHPC positioning post, achieving a qualitative leap from defect to reinforcement.

[0071] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A standard test block with a six-sided fully enclosed UHPC-encased core concrete, characterized in that, include: Core concrete block; The outer UHPC cladding layer completely encloses the six sides of the core concrete block, forming an integrated closed shell; Multiple permanent UHPC positioning posts are embedded in the surface of the core concrete block and extend into the interior of the outer UHPC wrapping layer; The height of the permanent UHPC positioning column is equal to the designed thickness of the outer UHPC wrapping layer. It is used to support and position the core concrete block when the outer UHPC wrapping layer is poured, and is permanently retained after molding.

2. The standard test block of six-sided fully enclosed UHPC-encased core concrete as described in claim 1, characterized in that, The permanent UHPC positioning post has a diameter of 3mm to 8mm and a height of 15mm to 30mm, with a height / diameter ratio ≤ 5.

3. A standard test block with a six-sided fully enclosed UHPC-encased core concrete as described in claim 1, characterized in that, The end of the permanent UHPC positioning post that contacts the inner wall of the external mold is hemispherical or conical.

4. A standard test block with a six-sided fully enclosed UHPC-encased core concrete as described in claim 1, characterized in that, The multiple permanent UHPC positioning posts are arranged at the center point, at the four corner points, or in an array on each surface of the core concrete block.

5. A device for fabricating a standard test block with a six-sided fully enclosed UHPC-encased core concrete, characterized in that, include: The external mold has an internal cavity that matches the external dimensions of the standard test block; Multiple permanent UHPC positioning posts, with a height equal to the thickness of the outer UHPC wrapping layer, are fixed at one end to the surface of the core concrete block, and the other end abuts against the inner wall of the outer mold before the outer UHPC wrapping layer is poured, so as to accurately support and position the core concrete block at the center of the inner cavity of the outer mold. The permanent UHPC positioning column remains permanently inside the outer UHPC wrapping layer after the casting is completed.

6. The apparatus for fabricating a six-sided fully enclosed UHPC-encased core concrete standard test block as described in claim 5, characterized in that, include: The permanent UHPC positioning post is connected to the surface of the core concrete block by pre-embedding or integral casting.

7. The apparatus for fabricating a six-sided fully enclosed UHPC-encased core concrete standard test block as described in claim 5, characterized in that, include: The external mold is a segmented combination mold, and its demolding direction is parallel to the axial direction of the positioning column.

8. A method for fabricating a standard test block with a six-sided fully enclosed UHPC-encased core concrete, characterized in that, Includes the following steps: Step 1: Precast core concrete cube test blocks. To ensure the bonding strength between the core concrete test block and the outer UHPC wrapping layer, the surface of the core concrete test block is roughened and the surface laitance layer of the concrete is removed before the permanent UHPC positioning column is installed before pouring the outer UHPC wrapping layer. Step 2, Prefabrication and Installation of Positioning Posts: Prefabricate permanent UHPC positioning posts with a height tolerance of ≤ ±0.1mm, and fix them to the surface of the core concrete block according to the predetermined arrangement; Step 3: Core concrete block placement: Place the core concrete block with permanent UHPC positioning posts into the outer mold, so that the free end of each permanent UHPC positioning post directly abuts against the inner wall of the outer mold, and the core concrete block automatically occupies the center of the outer mold. Step 4, Casting of the outer UHPC wrapping layer: Cast the outer UHPC material into the outer mold and compact it with vibration; Step 5, Curing and Demolding: Curing is carried out according to the UHPC curing system. After reaching the required curing age, the product is demolded.

9. The method for determining the compressive strength of a standard test block with a six-sided fully enclosed UHPC-encased core concrete as described in claim 8, characterized in that, In step 1, the prefabrication accuracy of the permanent UHPC positioning post is a height tolerance of ≤ ±0.1mm.

10. The method for determining the compressive strength of a standard test block with a six-sided fully enclosed UHPC-encased core concrete as described in claim 9, characterized in that... The method can achieve a positioning accuracy of ≤±0.5mm between the distance between each face of the core concrete block and the inner wall of the external mold.

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