Device and method for detecting flame retardance of tunnel flame-retardant asphalt

Abstract

A device for detecting the flame retardance of tunnel flame-retardant asphalt comprises a support, two plug boards, a cutting knife, a forming box body, a tray, a flame gun and a heating wire, the tray, the flame gun and the heating wire are arranged on the support, a bottom plate of the forming box body is a detachable bottom plate, each plug board is provided with a plurality of occupied columns, and the occupied columns are arranged on the bottom plate of the forming box body. The inserting plates are detachably installed at the top of the forming box body, the space between an inner cavity of the forming box body and the occupied columns forms a flame-retardant asphalt forming space, the forming box body is supported on the tray, the scratching knife is used for forming scratches on the top face of a formed flame-retardant asphalt block, and the heating wire is used for being inserted into blind holes formed after the occupied columns of the formed flame-retardant asphalt block are removed. The flame gun is located above the forming box body and corresponds to the opening in the top face. The device is simple in structure and low in improvement cost, and can simulate the extreme working condition of tunnel flame-retardant asphalt and test the flame retardance of the flame-retardant asphalt under the extreme working condition.

Description

Technical Field

[0001] The present invention relates to the field of municipal engineering, and particularly to a device and method for detecting the flame retardant performance of tunnel flame retardant asphalt. Background Art

[0002] A tunnel is an engineering structure buried in the ground. The tunnel pavement is paved with an asphalt layer to reduce vehicle tire noise and dust emission.

[0003] With the gradual increase in the ownership of new energy vehicles, the probability of the batteries equipped in new energy vehicles exploding and burning in tunnels is also gradually increasing. The burning new energy battery directly burns the asphalt layer laid in the tunnel, causing the asphalt layer to burn and generating a large amount of toxic gases, which is extremely harmful in a closed environment such as a tunnel. In order to reduce the risk of such hazards, the asphalt laid in the tunnel usually uses flame retardant asphalt. After being burned, the surface part of the flame retardant asphalt decomposes and releases gas to form a flame retardant layer, thereby exerting the flame retardant property. However, considering the factors of environmental temperature change and initial damage during the long-term use process of the flame retardant asphalt layer laid in the tunnel, for example, under high temperature (the temperature of a certain tunnel can reach 50°C) and scratch conditions, the change in the flame retardant performance of the set flame retardant asphalt needs to be detected. In addition, the minimum laying thickness at which a certain flame retardant asphalt achieves the flame retardant effect is also data that municipal construction personnel need to know.

[0004] Therefore, designing a device for detecting the flame retardant performance of flame retardant asphalt with a simple structure and convenient detection is a technical problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] One of the purposes of the present invention is to provide, in view of the deficiencies of the prior art, a device for detecting the flame retardant performance of tunnel flame retardant asphalt, which has a simple structure, low transformation cost, can simulate the extreme working conditions of tunnel flame retardant asphalt, and can test the flame retardant performance of flame retardant asphalt under extreme working conditions.

[0006] Another purpose of the present invention is to provide a method for detecting the flame retardant performance of tunnel flame retardant asphalt under extreme working conditions by using the above device, which is simple and convenient to operate, can accurately and objectively reflect the flame retardant performance of flame retardant asphalt, and meets the actual requirements.

[0007] One of the technical solutions to achieve one of the purposes of the present invention is: a device for detecting the flame retardancy of tunnel flame-retardant asphalt, including a bracket, a plug-in board, a cutter, a forming box body, and a tray, a blowtorch, and a heating wire arranged on the bracket. The forming box body is formed by connecting a lower box body and an upper box body as a whole. The cross-section of the lower box body is rectangular, and the bottom plate is a detachable bottom plate. The cross-section of the upper box body is trapezoidal, and the top surface is open. A plurality of through holes are evenly arranged on the side wall where the waist of the upper box body is located. The number of the plug-in boards is two, and a plurality of positioning columns are arranged on each plug-in board. The number of the positioning columns is adapted to the through holes on the side wall where the waist is located. Each plug-in board is detachably installed on the top of the forming box body through the positioning columns passing through the corresponding through holes. The inner cavity of the forming box body and the space between each positioning column form a forming space for the flame-retardant asphalt. The forming box body is supported on the tray. The cutter is used to form scratches on the top surface of the formed flame-retardant asphalt block. The heating wire is used to be inserted into the blind hole formed after removing the positioning column from the formed flame-retardant asphalt block. The blowtorch is located above the forming box body, corresponding to the open top surface.

[0008] A camera device is arranged on the bracket. The camera of the camera device is located above the forming box body and corresponds to the open top surface.

[0009] The cutter includes a mounting shaft and at least two blades assembled on the mounting shaft by screw fit. Locking nuts are screwed on both sides of each blade.

[0010] The blade is in an arc-shaped structure, and the cutting edge is a serrated cutting edge.

[0011] Slots are arranged on both pairs of opposite sides at the bottom of the lower box body. The bottom plate is inserted and fitted between the two slots to form a detachable connection with the lower box body.

[0012] The center of the upper surface of the tray is coated with red.

[0013] One of the technical solutions to achieve the second purpose of the present invention is: a method for detecting the flame retardancy of flame-retardant asphalt by using any of the above devices, including the steps:

[0014] 1) After assembling the bottom plate and the plug-in board in place, pour molten flame-retardant asphalt into the forming box body until the molten flame-retardant asphalt naturally solidifies and forms a flame-retardant asphalt block;

[0015] 2) Disassemble the plug-in board, form a blind hole in the flame-retardant asphalt block, and insert the heating wire into the blind hole formed in the flame-retardant asphalt block through the through hole;

[0016] 3) Flip the forming box body 180°, tap the bottom plate and the side plate to separate the flame-retardant asphalt block from the inner wall of the forming box body, and disassemble the bottom plate;

[0017] 4) Reset the forming box body. After adjusting the interval distance between adjacent blades of the cutting knife, make scratches on the top surface of the flame-retardant asphalt block, and support it on the tray.

[0018] 5) Control the heating wire to heat up. After reaching the specified temperature, take out the heating wire, turn on the flame gun to burn the top surface of the flame-retardant asphalt block, so that the temperature of the surface of the burning point on the top surface of the flame-retardant asphalt block rises to 350 - 450 °C, the heating-up time is 10 s, the holding time is 50 - 60 s, and record the change of the flame-retardant asphalt block until the burning is completed.

[0019] 6a) If the top surface of the flame-retardant asphalt block in the forming box body expands upward and the upper surface of the tray is observed during the process, it is judged that the asphalt of this thickness and type is unqualified.

[0020] 6b) If a depression appears on the top surface of the flame-retardant asphalt block in the forming box body, it is judged that the asphalt of this thickness and type does not meet the requirements.

[0021] 6c) If the top surface of the flame-retardant asphalt block in the forming box body expands upward and the upper surface of the tray is not observed during the process, it is judged that the asphalt of this thickness and type is qualified.

[0022] Further, the flame-retardant asphalt described in step 1) includes the following components:

[0023] Asphalt 85 - 90 wt%;

[0024] Flame retardant 10 wt%;

[0025] Synergist 0 - 5 wt%;

[0026] Among them, the synergist is any one or more of montmorillonite, antimony oxide and its derivatives, zinc borate, and organotin compounds. The flame retardant includes 60 - 90 wt% of hydroxide and 10 - 40 wt% of the mixture of halloysite nanotubes and ferrocene, and the mass ratio of halloysite nanotubes to ferrocene is 1:2 - 2:1; the hydroxide is any one or more of aluminum hydroxide, magnesium hydroxide, and calcium hydroxide.

[0027] Preferably, the angle between the straight line where the blind hole is located and the horizontal plane in step 2) is 35 - 55°, preferably 45°. The vertical projection length of each blind hole is 1 / 4 - 3 / 4 of the height of the forming box body. The number of scratches in step 4) is 1 - 3, the width of the scratches is 1 / 6 - 1 / 4 of the width of the upper opening of the upper box body, and the depth of each scratch does not exceed 1 / 4 of the thickness of the flame-retardant asphalt block.

[0028] Preferably, the specified temperature in step 5) is 45 - 65 °C.

[0029] Adopting the above technical solution has the following beneficial effects:

[0030] 1. The device for detecting the flame retardancy of tunnel flame retardant asphalt includes a bracket, a plug-in board, a cutter, a forming box body, and a tray, a blowtorch, and a heating wire arranged on the bracket. The forming box body is formed by connecting a lower box body and an upper box body as a whole. The cross-section of the lower box body is rectangular, and the bottom plate is a detachable bottom plate. The cross-section of the upper box body is trapezoidal, and the top surface is open, that is, the bottom of the forming box body can be opened or closed through the bottom plate. A number of through holes are evenly arranged on the side wall where the waist of the upper box body is located. The number of plug-in boards is two, and a number of positioning posts are arranged on each plug-in board. The number of positioning posts is adapted to the through holes on the side wall where the waist is located. Each plug-in board is detachably installed on the top of the forming box body through the positioning posts passing through the corresponding through holes. The inner cavity of the forming box body and the space between each positioning post form a forming space for the flame retardant asphalt. When the filled flame retardant asphalt is formed into a block, the plug-in board can be disassembled, and the positioning posts on the plug-in board can be pulled out from the formed flame retardant asphalt block to form blind holes in the formed flame retardant asphalt block for installing the heating wire. Moreover, the set structure can ensure the normal installation or disassembly of the plug-in board. The forming box body is supported on the tray. The cutter is used to form scratches on the top surface of the formed flame retardant asphalt block to simulate the damage formed during the use of the tunnel flame retardant asphalt layer. The heating wire is used to be inserted into the blind holes formed after the positioning posts are withdrawn from the formed flame retardant asphalt block and uniformly heated to heat the flame retardant asphalt block to simulate a high-temperature environment. The blowtorch is located above the forming box body, corresponding to the open top surface. When the heating wire heats the flame retardant asphalt block to a specified temperature, the blowtorch is turned on to burn the top surface of the flame retardant asphalt block, and thus the flame retardancy of the flame retardant asphalt under real conditions can be simulated, effectively meeting the requirements for detecting the flame retardancy of tunnel flame retardant asphalt.

[0031] 2. A camera device is arranged on the bracket. The camera of the camera device is located above the forming box body and corresponds to the open top surface. During the test, the phenomenon of melting through and re-accumulation may occur. By determining whether the central area of the upper surface of the tray is captured by the camera device, it can be determined whether the melting-through phenomenon occurs, ensuring the accuracy of the test results.

[0032] 3. The cutter includes a mounting shaft and at least two blades assembled on the mounting shaft by screw threads. Locking nuts are screwed on both sides of each blade, so that the distance between adjacent two blades can be adjusted according to actual needs. The blade is in an arc-shaped structure, and the cutting edge is a serrated cutting edge. The serrated cutting edge can be used to cut scratches with thickness and depth on the surface of the flame retardant asphalt block, or cut scratches with the required width by fitting two or more blades according to needs, effectively meeting the requirements for detecting the flame retardancy of tunnel flame retardant asphalt.

[0033] 4. The detection method of the present invention first forms a flame-retardant asphalt block with a specific shape through a forming box body. The asphalt block of this shape has a small upper projection area and a large lower projection area. When the upper surface of the flame-retardant asphalt block is burned by a flame, the flame-retardant asphalt block of this shape can simulate the actual distress environment where the surface of the tunnel flame-retardant asphalt layer is locally heated and the heat is transferred downward, ensuring an accurate feedback on the flame-retardant performance of the tunnel flame-retardant asphalt. In addition, scratches are formed on the surface of the flame-retardant asphalt block and the temperature is raised to a specified temperature to simulate the extreme working environment of the tunnel flame-retardant asphalt layer, ensuring an accurate feedback on the flame-retardant performance of the tunnel flame-retardant asphalt. The bottom plate at the bottom of the forming box body is disassembled, and the forming box body is supported on a tray. The formed accommodation space can not only prevent the overflow of the flame-retardant asphalt block after being burned, resulting in inaccurate performance measurement results, but also avoid causing external environmental pollution. Moreover, the melting-through phenomenon of the flame-retardant asphalt can be observed through the center of the upper surface of the tray, avoiding false detection.

[0034] 5. The detection method of the present invention relies on the fact that after the flame-retardant asphalt is burned, it releases gas to form a flame-retardant layer, thereby exerting the flame-retardant property. Depending on the residual morphology of each flame-retardant asphalt block sample after burning, the flame-retardant performance of each flame-retardant asphalt block is judged. The thickness of the qualified flame-retardant asphalt block can also be adjusted to determine the appropriate laying thickness, meeting the actual needs of judging the flame-retardant performance of the flame-retardant asphalt in the laboratory and determining the laying thickness, and ensuring the accuracy of the experimental results.

[0035] The following further explains in conjunction with the drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic structural diagram of the present invention;

[0037] Figure 2 is an axonometric view of the forming box body of the present invention;

[0038] Figure 3 is a schematic diagram of the cooperation between the forming box body and the plug-in board of the present invention;

[0039] Figure 4 is a schematic structural diagram of the cutter of the present invention;

[0040] Figure 5 is a partial axonometric view of the cutter of the present invention;

[0041] Figure 6 is a schematic diagram of step 1) of Embodiment 2;

[0042] Figure 7 is a schematic diagram of step 2) of Embodiment 2;

[0043] Figure 8 is a schematic diagram of step 4) of Embodiment 2;

[0044] Figure 9Schematic diagram of the result of Example 2;

[0045] Figure 10 Schematic diagram of the result of Example 3;

[0046] Figure 11 Schematic diagram of the result of Example 4.

[0047] In the drawings, 1 is a bracket, 2 is a plug-in board, 21 is a placeholder post, 3 is a cutting knife, 31 is a mounting shaft, 32 is a blade, 4 is a forming box body, 41 is a lower box body, 42 is an upper box body, 43 is a bottom plate, 44 is a through hole, 45 is a slot, 5 is a tray, 6 is a blowtorch, 7 is a heating wire, 8 is a camera device, and 81 is a camera. Detailed implementation manners

[0048] Example 1

[0049] See Figures 1 to 5, the device for detecting the flame retardancy of tunnel flame-retardant asphalt includes a bracket 1, a plug-in board 2, a cutter 3, a forming box body 4, and a tray 5, a blowtorch 6, and a heating wire 7 provided on the bracket. Specifically, the tray is made of iron material, and the center of the upper surface of the tray is coated with red, which forms a significant distinction from the peripheral color. The cutter 3 includes a mounting shaft 31 and three blades 32 assembled on the mounting shaft 31 by screw fit. Locking nuts are screwed on both sides of each blade 32. In this embodiment, each blade 32 has an arcuate structure, and the cutting edge is a serrated cutting edge. The forming box body 4 is formed by connecting a lower box body 41 and an upper box body 42 as a whole. The cross-section of the lower box body 41 is rectangular, and the bottom plate 43 is a detachable bottom plate. Specifically, slots 45 are provided on both pairs of sides at the bottom of the lower box body 41, and the bottom plate 43 is inserted and fitted between the two slots 45 to form a detachable connection with the lower box body 41. The cross-section of the upper box body 42 is trapezoidal, and the top surface is open. Specifically, the angle between the side wall where the waist of the upper box body is located and the horizontal plane is 45°. The height, width, and length of the entire forming box body are 50 mm, 50 mm, and 100 mm respectively. A number of through holes 44 are evenly provided on the side wall where the waist of the upper box body 42 is located. Specifically, the number of through holes on a single side wall is eleven, divided into three columns. The number of the first column is four, the number of the second column is three, and the number of the third column is four. The number of the plug-in boards 2 is two, and a number of positioning posts 21 are provided on each plug-in board 2. The number of the positioning posts 21 is adapted to the through holes 44 on the side wall where the waist is located. That is, the number of the positioning posts on each plug-in board is also eleven, and the distribution is the same as that of the through holes. Each plug-in board 2 is detachably installed on the top of the forming box body 4 through the positioning posts 21 passing through the corresponding through holes 44. The inner cavity of the forming box body and the space between the positioning posts form a forming space for the flame-retardant asphalt. In this embodiment, the vertical projection of the extended length of each positioning post is 1 / 2 of the height of the forming box body, that is, the vertical projection length is 50 mm. The forming box body 4 is supported on the tray 5. The cutter 3 is used to form scratches on the top surface of the formed flame-retardant asphalt block. The heating wire 7 is used to be inserted into the blind holes formed after removing the positioning posts from the formed flame-retardant asphalt block. The blowtorch 6 is located above the forming box body 4, corresponding to the open top surface.

[0050] To ensure accurate test results, a camera device 8 is provided on the bracket 1. The camera 81 of the camera device is located above the forming box body 4 and corresponds to the open top surface.

[0051] Embodiment 2

[0052] The method for detecting the flame retardancy of tunnel flame-retardant asphalt using the detection device of Embodiment 1, the components of the flame-retardant asphalt are:

[0053] Asphalt 85 wt%;

[0054] Flame retardant 10 wt%;

[0055] Synergist 5 wt%;

[0056] Among them, the synergist is montmorillonite, and the flame retardant includes 90 wt% hydroxide and a mixture of 10 wt% halloysite nanotubes and ferrocene. The mass ratio of halloysite nanotubes to ferrocene is 1:2; the hydroxide is calcium hydroxide.

[0057] Including the steps:

[0058] 1) After assembling the bottom plate and the plug-in board in place, pour molten flame-retardant asphalt into the forming box until the molten flame-retardant asphalt solidifies naturally to obtain a flame-retardant asphalt block.

[0059] 2) Disassemble the plug-in board, form blind holes on the flame-retardant asphalt block, and insert the heating wire through the holes into the blind holes formed on the flame-retardant asphalt block.

[0060] 3) Flip the forming box 180°, tap the bottom plate and the side plate to separate the flame-retardant asphalt block from the inner wall of the forming box, and disassemble the bottom plate.

[0061] 4) Reset the forming box. After adjusting the interval distance between adjacent blades of the cutting knife, draw scratches on the top surface of the flame-retardant asphalt block. The number of scratches is three, running through the flame-retardant asphalt block along the width direction. Then support the forming box (including the inner flame-retardant asphalt block) on the tray.

[0062] 5) Control the heating wire to increase the temperature. After reaching 60 °C, take out the heating wire, turn on the flame gun to burn the top surface of the flame-retardant asphalt block, so that the temperature of the surface of the burning point on the top surface of the flame-retardant asphalt block rises to 450 °C. The heating-up time is 10 s, the holding time is 60 s, and record the change of the flame-retardant asphalt block until the burning is completed.

[0063] 6) If the top surface of the flame-retardant asphalt block in the forming box expands upward and the upper surface of the tray is not observed during the process, it is judged that the flame retardancy of this type of asphalt with this thickness is qualified, as Figures 6 - 9 shown.

[0064] Example 3

[0065] Select the commercial flame retardant ammonium polyphosphate, with an addition amount of 10 wt%, and other operations are the same as in Example 2. The results are as Figure 10 shown. The top surface of the flame-retardant asphalt block in the forming box expands upward and the upper surface of the tray is observed during the process, indicating that there is a melting-through phenomenon during the burning process. It is judged that the flame retardancy of this type of asphalt with this thickness is unqualified.

[0066] Example 4

[0067] Select commercial flame retardant hydroxides, specifically a mixture of aluminum hydroxide and magnesium hydroxide, with a weight ratio of 1:2 between the two. The addition amount of the commercial flame retardant hydroxides is 10 wt%, and other operations are the same as in Example 2. The results are as Figure 11 shown. There are depressions on the top surface of the flame retardant asphalt block in the formed box body, indicating that the flame retardant layer formed by the released gas when the flame retardant asphalt block is burned has poor efficacy, and it is judged that the flame retardant performance of this type of asphalt with this thickness does not meet the requirements.

Claims

1. An apparatus for detecting the flame retardancy of tunnel flame retardant asphalt, characterized in that, It includes a bracket (1), a plug-in board (2), a cutting knife (3), a forming box body (4), and a tray (5), a blowtorch (6), a heating wire (7) arranged on the bracket. The forming box body (4) is formed by connecting a lower box body (41) and an upper box body (42) into a whole. The cross-section of the lower box body (41) is rectangular, and the bottom plate (43) is a detachable bottom plate. The cross-section of the upper box body (42) is trapezoidal, and the top surface is open. A plurality of through holes (44) are evenly arranged on the side wall where the waist is located of the upper box body (42). The number of the plug-in boards (2) is two. A plurality of positioning posts (21) are arranged on each plug-in board (2). The number of the positioning posts (21) is adapted to the through holes (44) on the side wall where the waist is located. Each plug-in board (2) is detachably installed on the top of the forming box body (4) through the positioning posts (21) passing through the corresponding through holes (44). The space between the inner cavity of the forming box body and the positioning posts forms a forming space for the flame-retardant asphalt. The forming box body (4) is supported on the tray (5). The cutting knife (3) is used to form scratches on the top surface of the formed flame-retardant asphalt block. The heating wire (7) is used to be inserted into the blind holes formed after removing the positioning posts from the formed flame-retardant asphalt block. The blowtorch (6) is located above the forming box body (4), corresponding to the open top surface.

2. The device for detecting the flame retardancy of tunnel flame retardant asphalt according to claim 1, characterized in that, A camera device (8) is arranged on the bracket (1). The camera (81) of the camera device is located above the forming box body (4), and corresponds to the open top surface.

3. The device for detecting the flame retardancy of tunnel flame retardant asphalt according to claim 1, wherein The cutting knife (3) includes a mounting shaft (31), and at least two blades (32) assembled on the mounting shaft (31) by thread fitting. Locking nuts are thread-fitted on both sides of each blade (32).

4. The device for detecting the flame retardancy of tunnel flame retardant asphalt according to claim 3, wherein The blade (32) is in an arch structure, and the cutting edge is a serrated cutting edge.

5. The device for detecting the flame retardancy of tunnel flame-retardant asphalt according to claim 1 or 2, characterized in that, Slots (45) are arranged on both pairs of opposite sides at the bottom of the lower box body (41). The bottom plate (43) is inserted and fitted between the two slots (45) to form a detachable connection with the lower box body (41).

6. The device for detecting the flame retardancy of tunnel flame retardant asphalt according to claim 1, characterized in that, The center of the upper surface of the tray (5) is coated red.

7. A method for detecting the flame retardant performance of flame retardant asphalt using any one of the devices according to claims 1-6, characterized in that, It includes the steps: 1) After assembling the bottom plate and the plug-in board in place, pour molten flame-retardant asphalt into the forming box body until the molten flame-retardant asphalt naturally solidifies and forms to obtain a flame-retardant asphalt block. 2) Disassemble the plug-in board, form blind holes in the flame-retardant asphalt block, and insert the heating wire into the blind holes formed in the flame-retardant asphalt block through the through holes. 3) Flip the forming box body 180°, tap the bottom plate and the side plates to separate the flame-retardant asphalt block from the inner wall of the forming box body, and disassemble the bottom plate. 4) Reset the forming box body, adjust the interval distance between adjacent blades of the cutting knife, then scratch the top surface of the flame-retardant asphalt block and support it on the tray. 5) Control the heating wire to increase the temperature. After reaching the specified temperature, take out the heating wire, turn on the flame gun to burn the top surface of the flame-retardant asphalt block, so that the temperature of the surface of the burning point on the top surface of the flame-retardant asphalt block rises to 350 - 450 °C, the heating-up time is 10 s, the holding time is 50 - 60 s, and record the change situation of the flame-retardant asphalt block until the burning is completed. 6a) If the top surface of the flame-retardant asphalt block in the forming box body expands upward and the upper surface of the tray is observed during the process, it is judged that the asphalt of this thickness and type is unqualified. 6b) If there is a depression on the top surface of the flame-retardant asphalt block in the forming box, it is determined that this type of asphalt with this thickness does not meet the requirements; 6c) If the top surface of the flame-retardant asphalt block in the forming box expands upward and the upper surface of the tray is not observed during the process, it is determined that this type of asphalt with this thickness is qualified.

8. The method according to claim 7, wherein The flame-retardant asphalt described in step 1) includes the following components: 85 - 90 wt% of asphalt; 10 wt% of flame retardant; 0 - 5 wt% of synergist; Among them, the synergist is any one or more of montmorillonite, antimony oxide and its derivatives, zinc borate, and organotin compounds. The flame retardant includes 60 - 90 wt% of hydroxide and 10 - 40 wt% of a mixture of halloysite nanotubes and ferrocene, and the mass ratio of halloysite nanotubes to ferrocene is 1:2 - 2:1; the hydroxide is any one or more of aluminum hydroxide, magnesium hydroxide, and calcium hydroxide.

9. The method according to claim 7, wherein In step 2), the angle between the straight line where the blind hole is located and the horizontal plane is 35 - 55°, preferably 45°. The vertical projection length of each blind hole is 1 / 4 - 3 / 4 of the height of the forming box. In step 4), the number of scratches is 1 - 3, the width of the scratches is 1 / 6 - 1 / 4 of the width of the upper opening of the upper box body, and the depth of each scratch does not exceed 1 / 4 of the thickness of the flame-retardant asphalt block.

10. The method according to claim 7, wherein In step 5), the specified temperature is 45 - 65 °C.

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