A bridge structure and design method for improving bridge durability in marine environment

Abstract

The present invention discloses a bridge structure for improving the durability of bridges in marine environments, comprising: a bridge deck and a plurality of piers for supporting the bridge deck, an annular seat installed on the outside of the piers, the annular seat surrounding the piers, an annular space formed between the annular seat and the piers, a shock-absorbing mechanism connecting the annular seat and the piers provided in the annular space, and an annular folding cover for closing the annular space installed at the opening of the annular space. A design method for improving the durability of bridges in marine environments comprises the following steps: analyzing the depth of the ocean and the ocean dynamics at different depths; determining the size and spacing of the annular seat; preparing concrete raw materials; installing the shock-absorbing mechanism after casting the annular seat; filling with epoxy resin; and installing the annular folding cover at the opening of the annular space to close the annular space. The present invention prevents seawater from contacting the piers by providing a truncated cone-shaped annular seat, thereby making the bridge more durable.

Description

Technical Field

[0001] The present invention belongs to the technical field of bridge durability research, and in particular relates to a bridge structure and a design method for improving bridge durability in a marine environment. Background Art

[0002] Bridge structures are critical infrastructure projects. Ensuring their safety under extreme loads during design is a growing concern for relevant departments and bridge engineers. However, bridge collapses still occur, causing significant harm to society and the public. Most catastrophic bridge collapses are not caused by inherent structural defects, but rather by external extreme disasters such as river erosion, tanker trucks striking bridge piers, earthquakes, or overweight vehicles traveling on bridges.

[0003] At present, bridges are mainly reinforced concrete structures, and reinforced concrete is exposed to the external environment for a long time. Due to the erosion of wind, chloride ions, sulfates, etc. in the external environment, the reinforced concrete will be corroded, which affects the durability of the bridge. Especially in a marine environment, the concentrated salt and alkali in the ocean and the flow of seawater are more corrosive and destructive to the bridge piers, and the disasters and losses caused by the collapse of the bridge in the marine environment are greater. Therefore, the durability requirements of the bridge structure in the marine environment need to be further improved.

[0004] The piers of existing ocean bridges are generally improved in durability by preparing highly durable reinforced concrete materials or applying anti-corrosion materials on the outside. However, this method still exposes the piers to the external environment, which can only slow down the speed at which the piers are corroded or damaged. Moreover, corrosion and damage are difficult to repair, which affects the durability of the bridge. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a bridge structure and design method for improving the durability of bridges in marine environments, so as to solve the problem in the prior art that bridge piers are exposed to the outside in marine environments and are easily corroded by seawater, thereby affecting the durability of bridges.

[0006] In order to achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention provides a bridge structure for improving bridge durability in a marine environment, comprising:

[0008] A bridge deck and a plurality of piers for supporting the bridge deck, an annular seat being installed on the outside of the piers, the annular seat being arranged to surround the piers, an annular space being formed between the annular seat and the piers, a shock absorbing mechanism being provided in the annular space to connect the annular seat and the piers, the shock absorbing mechanism comprising: an inner U-shaped steel plate and an outer U-shaped steel plate, the inner U-shaped steel plate and the outer U-shaped steel plate being slidably connected, a cavity being formed between the inner U-shaped steel plate and the outer U-shaped steel plate, a plurality of elastic members being circumferentially arranged side by side in the cavity;

[0009] An annular folding cover that closes the annular space is installed at the opening of the annular space, a first threaded plate is installed at the opening of the inner ring of the annular seat, and a second threaded plate that cooperates with the first threaded plate is installed on the peripheral wall of the pier. The annular folding cover is threadedly connected to the first threaded plate and the second threaded plate.

[0010] Furthermore, the annular seat includes a front portion and a back portion arranged along the direction of coastal water flow, the front portion and the back portion are connected as a whole, the cross-sectional area of ​​the front portion is larger than the cross-sectional area of ​​the back portion, and the connection between the front portion and the back portion is streamlined.

[0011] Furthermore, a protective mechanism is installed on the circumferential side of the annular seat, and the protective mechanism includes: a mounting frame, a filter screen matching the annular seat is installed on the mounting frame, a mounting cavity is provided between the filter screen and the mounting frame, a plurality of elliptical columns are connected in parallel in a circumferential rotation in the mounting cavity, a brush is installed on the elliptical column, and the brush contacts the side wall of the annular seat to clean foreign matter adhering to the annular seat.

[0012] Furthermore, the annular seat is in the shape of a truncated cone.

[0013] Furthermore, the gap between the annular space and the shock absorbing mechanism is filled with epoxy resin.

[0014] The present invention also provides a design method for improving the durability of a bridge in a marine environment, comprising the following steps:

[0015] A1: Analyze ocean depth and ocean dynamics at different depths based on the ocean environment;

[0016] A2: Determine the size of the annular seat and the distance between the two annular seats;

[0017] A3: Use silicate and active clinker to prepare concrete raw materials, and have the durability of the concrete raw materials tested by a testing agency;

[0018] A4: After the bridge piers and annular seat are cast, the shock absorbing mechanism is installed in the annular space between the bridge piers and the annular seat;

[0019] A5: Fill the gap between the annular space and the shock absorbing mechanism with epoxy resin;

[0020] A6: Install the annular folding cover at the opening of the annular space to close the annular space.

[0021] Furthermore, in step A2, when analyzing ocean wave energy, the size of the annular seat 3 is determined by the following formula:

[0022]

[0023] Among them, F i is the wave force of the i-th segment, F is the total wave force, ε is the inertia force coefficient, ρ is the seawater density, ω is the velocity force coefficient, d i is half the diameter of the cross section of the annular seat 3 in the i-th section, v i is the horizontal velocity of the wave particle in the i-th segment; H i is the height of the cross section of the annular seat 3 in the i-th section; t is the time variable.

[0024] Furthermore, in step A3, preparing the concrete raw materials includes the following steps:

[0025] B1: Prepare multiple groups of concrete test specimens by selecting different ratios of silicate and active clinker;

[0026] B2: Place the concrete test piece in a testing device for testing. The testing device is a permeability tester. During the test, the water environment in the testing device needs to simulate the marine environment, including seawater density, salinity, height difference, and seawater dynamics.

[0027] B3: Analyze the impermeability of multiple groups of concrete test specimens in the testing organization based on the similarity principle;

[0028] B4: Select the ratio of silicate to active clinker from a group of concrete test pieces with the highest impermeability to prepare concrete raw materials.

[0029] As described above, the bridge structure and design method for improving the durability of bridges in marine environments of the present invention have the following beneficial effects: by providing a truncated cone-shaped annular seat, contact between seawater and bridge piers is avoided, thereby preventing seawater from washing and corroding the bridge piers; an annular space is left between the annular seat and the bridge piers to prevent seawater from penetrating the annular seat and corroding the bridge piers from the inside; the annular space and the shock-absorbing mechanism reduce vibrations on the bridge piers caused by the flow of seawater or collisions with large marine organisms; an annular folding cover is provided at the opening of the annular space to seal the annular space, thereby preventing seawater or external gas from penetrating the annular space and corroding the bridge piers; the annular folding cover is provided at the opening of the annular space to seal the annular space, thereby preventing seawater or external gas from penetrating the annular space and corroding the bridge piers; The cover is retractable and foldable, which improves the shock absorption capacity and thus greatly improves the durability of the bridge; the annular folding cover is screwed into the annular space through the cooperation of the first threaded plate and the second threaded plate, which is convenient for installation and disassembly; the size of the annular seat is determined by analyzing the marine dynamics in the marine environment, thereby improving the structural stability of the annular seat; the concrete raw materials prepared using silicate and active clinker have higher density, impermeability and corrosion resistance; the shock-absorbing mechanism prevents the flow of seawater from causing damage to the bridge piers by the annular seat; by filling the annular space with epoxy resin, the compressive strength, rigidity and bonding degree are enhanced, making the bridge more durable.

[0030] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to make the purpose, technical solutions and beneficial effects of the present invention more clear, the present invention provides the following drawings for illustration:

[0032] Figure 1 A front view of an embodiment of the present invention;

[0033] Figure 2 For the embodiment of the present invention Figure 1 A magnified view of the middle part A;

[0034] Figure 3 Schematic diagram of the structure of the shock absorbing mechanism according to an embodiment of the present invention;

[0035] Figure 4 This is a schematic structural diagram of an annular seat according to an embodiment of the present invention;

[0036] Figure 5 is a top cross-sectional view of a shock absorbing mechanism according to an embodiment of the present invention;

[0037] Figure 6 Schematic diagram of the installation of the protection mechanism according to an embodiment of the present invention;

[0038] Figure 7 Flowchart of an embodiment of the present invention.

[0039] The markings in the accompanying drawings are as follows: 1. Bridge deck; 2. Bridge pier; 201. Second threaded plate; 3. Annular seat; 301. First threaded plate; 302. Frontal portion; 303. Back portion; 4. Annular space; 5. Shock-absorbing mechanism; 501. Inner U-shaped steel plate; 502. Outer U-shaped steel plate; 503. Elastic part; 6. Annular folding cover; 7. Protective mechanism; 701. Mounting frame; 702. Filter screen; 703. Mounting cavity; 704. Elliptical column; 705. Brush. DETAILED DESCRIPTION

[0040] See also Figures 1 to 7 The present invention provides a bridge structure for improving the durability of a bridge in a marine environment, comprising: a bridge deck 1 and a plurality of piers 2 for supporting the bridge deck 1, an annular seat 3 being installed on the outer side of the pier 2, the annular seat 3 being arranged to surround the pier 2, an annular space 4 being formed between the annular seat 3 and the pier 2, a shock absorbing mechanism 5 connecting the annular seat 3 and the pier 2 being provided in the annular space 4, the shock absorbing mechanism 5 comprising: an inner U-shaped steel plate 501 and an outer U-shaped steel plate 502, the inner U-shaped steel plate 501 and the outer U-shaped steel plate 502 being slidably connected, a cavity being formed between the inner U-shaped steel plate 501 and the outer U-shaped steel plate 502, a plurality of elastic members 503 being circumferentially arranged side by side in the cavity;

[0041] An annular folding cover 6 that closes the annular space 4 is installed at the opening of the annular space 4, a first threaded plate 301 is installed at the opening of the inner ring of the annular seat 3, and a second threaded plate 201 that cooperates with the first threaded plate 301 is installed on the peripheral wall of the pier 2. The annular folding cover 6 is threadedly connected to the first threaded plate 301 and the second threaded plate 201.

[0042] The working principle of the above technical solution is as follows: Figure 1 According to the fact that the deeper the depth in the ocean, the greater the water pressure, the annular seat 3 is set to a truncated cone shape. At the same time, due to the tidal energy, wave energy and current energy generated during the movement of seawater in the marine environment, a shock absorbing mechanism 5 is set in the annular space 4. Figure 5 As shown, in order to reduce the vibration of the bridge pier 2 caused by the flow of seawater or the impact of large marine organisms, an annular folding cover 6 is provided at the opening of the annular space 4. The inner ring and outer ring of the annular folding cover 6 are respectively installed with threaded mounting plates that cooperate with the second threaded plate 201 and the first threaded plate 301. After the shock absorbing mechanism 5 is installed in the annular space 4, the annular folding cover 6 is screwed into the opening of the annular space 4 through threads to close the annular space 4.

[0043] The beneficial effects of the above technical solution are as follows: by providing a truncated cone-shaped annular seat 3, contact between seawater and the bridge pier 2 is avoided, and the seawater is prevented from washing and corroding the bridge pier 2; an annular space 4 is left between the annular seat 3 and the bridge pier 2 to prevent seawater from penetrating the annular seat 3 and corroding the bridge pier 2 from the inside; the annular space 4 and the shock-absorbing mechanism 5 reduce the vibration of the bridge pier 2 caused by the flow of seawater or the impact of large fish; an annular folding cover 6 is provided at the opening of the annular space 4 to close the annular space 4, and prevent seawater or external gas from penetrating the annular space 4 and corroding the bridge pier 2 and the shock-absorbing mechanism 5; the annular folding cover 6 is retractable and foldable, which improves the shock-absorbing ability, thereby greatly improving the durability of the bridge; the annular folding cover 6 is screwed into the annular space 4 through the cooperation of the first threaded plate 301 and the second threaded plate 201, which is convenient for installation and disassembly.

[0044] In one embodiment of the present invention, the annular seat 3 includes a front portion 302 and a back portion 303 arranged along the direction of coastal water flow, the front portion 302 and the back portion 303 are connected as a whole, the cross-sectional area of ​​the front portion 302 is larger than the cross-sectional area of ​​the back portion 303, and the connection between the front portion 302 and the back portion 303 is streamlined.

[0045] The working principle of the above technical solution is as follows: Figure 4 In a high-altitude marine environment, when only the influence of the height difference is considered, the seawater flows downward, so the front portion 302 is easily eroded by the seawater, and the seawater erosion on the back portion 303 side is relatively weak. The cross-sectional area of ​​the front portion 302 is set to be larger than the cross-sectional area of ​​the back portion 303, so that the surface area of ​​the front portion 302 affected by the seawater erosion is larger, thereby improving the pressure resistance of the front portion 302.

[0046] The beneficial effects of the above technical solution are as follows: through the design of the above structure, the compressive resistance of the annular seat 3 is improved. At the same time, the cross-sectional area of ​​the back portion 303 where the seawater flow pressure is smaller is smaller than the cross-sectional area of ​​the front portion 302, which saves the reinforced concrete material of the back portion 303 and saves costs. The connection between the front portion 302 and the back portion 303 is streamlined, which makes the seawater flow smoothly and is not easy to cause damage to the connection between the front portion 302 and the back portion 303, further improving the durability and economy of the annular seat 3.

[0047] In one embodiment of the present invention, a protective mechanism 7 is installed on the circumferential side of the annular seat 3, and the protective mechanism 7 includes: a mounting frame 701, a filter screen 702 matching the annular seat 3 is installed on the mounting frame 701, and a mounting cavity 703 is provided between the filter screen 702 and the mounting frame 701, and a plurality of elliptical columns 704 are connected in a circumferentially rotating manner side by side in the mounting cavity 703, and a brush 705 is installed on the elliptical column 704, and the brush 705 contacts the side wall of the annular seat 3 for cleaning foreign matter adhering to the annular seat 3.

[0048] The working principle of the above technical solution is as follows: Figure 6 When the seawater flows to the elliptical column 704 , it drives the elliptical column 704 to rotate, thereby driving the brush 705 to rotate to clean foreign matter adhering to the annular seat 3 .

[0049] The beneficial effects of the above technical solution are as follows: through the design of the above structure, the elliptical column 704 can be driven to rotate by the flow of seawater, and the rotation of the elliptical column 704 reduces the frontal impact of the seawater flow on the annular seat 3, thereby improving the durability of the annular seat 3; and the rotation of the elliptical column 704 will drive the brush 705 to rotate to clean foreign matter adhering to the annular seat 3, thereby preventing foreign matter in the marine environment from adhering and causing corrosion damage to the annular seat 3 due to microbial activity, thereby further improving the durability of the annular seat 3; and by setting the filter screen 702, the elliptical column 704 is protected to prevent marine biological activities from damaging the elliptical column 704, and to prevent larger marine organisms or seabed garbage from entering the installation cavity 703, thereby further improving the durability of the annular seat 3 and the bridge.

[0050] In one embodiment of the present invention, the annular seat 3 is in the shape of a truncated cone.

[0051] The working principle and beneficial effects of the above technical solution are as follows: Figure 4 The annular seat 3 is set to a truncated cone shape, which improves the bearing capacity of the annular seat 3 at depth and makes the bridge more durable.

[0052] In one embodiment of the present invention, the gap between the annular space 4 and the shock absorbing mechanism 5 is filled with epoxy resin.

[0053] The working principle and beneficial effects of the above technical solution are as follows: Figure 2 By filling the gap between the annular space 4 and the shock-absorbing mechanism 5 with epoxy resin, the compressive strength, rigidity and bonding degree are enhanced, making the bridge more durable.

[0054] The present invention provides a design method for improving the durability of a bridge in a marine environment, comprising the following steps:

[0055] A1: Analyze ocean depth and ocean dynamics at different depths based on the ocean environment;

[0056] A2: Determine the size of the annular seat 3 and the spacing between the two annular seats 3;

[0057] A3: Use silicate and active clinker to prepare concrete raw materials, and have the durability of the concrete raw materials tested by a testing agency;

[0058] A4: After the bridge pier 2 and the annular seat 3 are cast, the shock absorbing mechanism 5 is installed in the annular space 4 between the bridge pier 2 and the annular seat 3;

[0059] A5: Fill the gap between the annular space 4 and the shock absorbing mechanism 5 with epoxy resin;

[0060] A6: Install the annular folding cover 6 at the opening of the annular space 4 to close the annular space 4.

[0061] The working principle of the above technical solution is as follows: when designing a bridge, the tidal energy, wave energy, ocean current energy, and temperature and salinity differences at different depths generated during the movement of seawater are determined according to the marine environment. Then, a finite element analysis is performed on the annular seat 3 according to the wave energy to determine the structural dimensions of the annular seat 3. In order to avoid different pressures at different depths in the ocean, the annular seat 3 is determined to be a truncated cone. Then, the diameters of the upper and lower bottom surfaces of the annular seat 3 are analyzed according to the wave energy. The spacing between the annular seats 3 is determined by analyzing the width of passing ships to prevent damage to the annular seats 3 caused by ship collisions. The temperature differences and salinity at different depths are analyzed. The lowest temperature and the highest salinity are selected as the standard to determine the ratio of silicate and active clinker to prepare concrete specimens, wherein the active clinker includes blast furnace slag, volcanic ash, fly ash, and diatomaceous earth; the concrete specimens are tested by a testing agency, wherein the testing agency is an impermeability tester, which mainly tests the impermeability of concrete. After the test is qualified, concrete raw materials are prepared by the raw ingredients that have passed the test, and then cast to form an annular seat 3, and then the shock-absorbing mechanism 5 is installed in the annular space 4, and the gap between the annular space 4 and the shock-absorbing mechanism 5 is filled with epoxy resin, and then the annular folding cover 6 is installed at the opening of the annular space 4 to close the annular space 4.

[0062] The beneficial effects of the above technical solution are as follows: by analyzing the ocean dynamics in the marine environment to determine the size of the annular seat 3, the structural stability of the annular seat 3 is improved; the concrete raw materials prepared using silicate and active clinker have higher density, impermeability and corrosion resistance; the shock-absorbing mechanism 5 prevents the flow of seawater from causing damage to the bridge pier 2 by the annular seat 3; by filling the annular space 4 with epoxy resin, the compressive strength, rigidity and bonding degree are enhanced, making the bridge more durable.

[0063] In one embodiment of the present invention, in step A2, when analyzing ocean wave energy, the size of the annular seat 3 is determined by the following formula:

[0064]

[0065] Among them, F i is the wave force of the i-th segment, F is the total wave force, ε is the inertia force coefficient, ρ is the seawater density, ω is the velocity force coefficient, d i is half the diameter of the cross section of the annular seat 3 in the i-th section, v i is the horizontal velocity of the wave particle in the i-th segment; H i is the height of the cross section of the annular seat 3 in the i-th section; t is the time variable.

[0066] The working principle and beneficial effects of the above technical solution are as follows: by selecting the maximum wave force previously experienced in the current marine environment as a standard and performing finite element analysis, when the annular seat 3 is affected by wave energy, the most stable side wall shape and structural dimensions of the annular seat 3 under the influence of wave energy are calculated by using the above formula, thereby improving the stability of the annular seat 3 in the marine environment and ensuring the durability of the bridge.

[0067] In one embodiment of the present invention, in step A3, preparing the concrete raw materials includes the following steps:

[0068] B1: Prepare multiple groups of concrete test specimens by selecting different ratios of silicate and active clinker;

[0069] B2: Place the concrete test piece in a testing device for testing. The testing device is a permeability tester. During the test, the water environment in the testing device needs to simulate the marine environment, including seawater density, salinity, height difference, and seawater dynamics.

[0070] B3: Analyze the impermeability of multiple groups of concrete test specimens in the testing organization based on the similarity principle;

[0071] B4: Select the ratio of silicate to active clinker from a group of concrete test pieces with the highest impermeability to prepare concrete raw materials.

[0072] The working principle of the above technical solution is as follows: when preparing concrete raw materials, first select different proportions of silicate and active clinker to prepare multiple groups of concrete test specimens, and according to the similarity principle, make the concrete test specimens into proportionally reduced versions of the preset bridge pier 2 and annular seat 3. Then, the water environment in the water permeability tester simulates the complex marine environment according to the similarity principle (initial conditions, boundary conditions, geometric conditions, physical conditions), and then place the concrete test specimens in the water permeability tester for water permeability testing. Finally, through finite element analysis, the silicate and active clinker ratio of the group of concrete test specimens with the strongest water permeability is selected to prepare concrete raw materials.

[0073] Beneficial effects of the above technical solution: Through the design of the above method, the proportion of raw materials for preparing concrete with the strongest impermeability in the marine environment is obtained, the impermeability of the concrete raw materials is enhanced, and the durability of the bridge is improved.

[0074] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A bridge structure for improving bridge durability in a marine environment, characterized in that: include: A bridge deck and a plurality of piers for supporting the bridge deck, an annular seat being installed on the outside of the piers, the annular seat being arranged to surround the piers, an annular space being formed between the annular seat and the piers, a shock absorbing mechanism being provided in the annular space to connect the annular seat and the piers, the shock absorbing mechanism comprising: an inner U-shaped steel plate and an outer U-shaped steel plate, the inner U-shaped steel plate and the outer U-shaped steel plate being slidably connected, a cavity being formed between the inner U-shaped steel plate and the outer U-shaped steel plate, a plurality of elastic members being circumferentially arranged side by side in the cavity; An annular folding cover is installed at the opening of the annular space to close the annular space, a first threaded plate is installed at the opening of the inner ring of the annular seat, a second threaded plate that cooperates with the first threaded plate is installed on the peripheral wall of the pier, and the annular folding cover is threadedly connected to the first threaded plate and the second threaded plate; The annular seat includes a front portion and a back portion arranged along the direction of coastal water flow, the front portion and the back portion are connected as a whole, the cross-sectional area of ​​the front portion is larger than the cross-sectional area of ​​the back portion, and the connection between the front portion and the back portion is streamlined; A protective mechanism is installed on the circumferential side of the annular seat, and the protective mechanism includes: a mounting frame, a filter screen matching the annular seat is installed on the mounting frame, a mounting cavity is provided between the filter screen and the mounting frame, a plurality of elliptical columns are connected in parallel in the mounting cavity for circumferential rotation, and a brush is installed on the elliptical column, the brush contacts the side wall of the annular seat and is used to clean foreign matter adhering to the annular seat; The design method for improving bridge durability in marine environments includes the following steps: A1: Analyze ocean depth and ocean dynamics at different depths based on the ocean environment; A2: Determine the size of the annular seat and the distance between the two annular seats; A3: Use silicate and active clinker to prepare concrete raw materials, and have the durability of the concrete raw materials tested by a testing agency; A4: After the bridge piers and annular seat are cast, the shock absorbing mechanism is installed in the annular space between the bridge piers and the annular seat; A5: Fill the gap between the annular space and the shock absorbing mechanism with epoxy resin; A6: Install the annular folding cover at the opening of the annular space to close the annular space.

2. The bridge structure for improving bridge durability in a marine environment according to claim 1, characterized in that: The annular seat is in the shape of a truncated cone.

3. The bridge structure for improving bridge durability in a marine environment according to claim 2, characterized in that: The gap between the annular space and the shock absorbing mechanism is filled with epoxy resin.

4. The bridge structure for improving bridge durability in a marine environment according to claim 3, characterized in that: In step A3, preparing the concrete raw materials includes the following steps: B1: Select different proportions of silicate and active clinker to prepare multiple groups of concrete test specimens; B2: Place the concrete test piece in a testing device for testing. The testing device is a permeability tester. During the test, the water environment in the testing device needs to simulate the marine environment, including seawater density, salinity, height difference, and seawater dynamics. B3: Analyze the impermeability of multiple groups of concrete test specimens in the testing organization based on the similarity principle; B4: Select the ratio of silicate to active clinker from a group of concrete test pieces with the highest impermeability to prepare concrete raw materials.

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