Prefabricated parts for the impact zone of the main ditch cover of the blast furnace

Abstract

The present invention relates to a prefabricated part for the impact zone of the main trench cover of a blast furnace. The prefabricated part is an arched member formed by splicing three prefabricated parts, namely, the top, left and right parts. The prefabricated part is hoisted on the inner wall of the steel shell of the main trench cover of the blast furnace that is impacted by molten iron by bolts pre-buried in the prefabricated part. The top prefabricated part is designed to be wide at the top and narrow at the bottom to avoid falling off due to its own gravity during use. The shape of the outer wall of the prefabricated part is consistent with the inner wall of the steel shell of the main trench cover where the prefabricated part is arranged. The inner wall of the top prefabricated part is a plane structure, and the inner walls of the left and right prefabricated parts are arc structures. When the prefabricated part is installed, the refractory fiber cotton is laid, so that it can better fit the inner wall of the steel shell of the main trench cover that is deformed by repeated use. Refractory castables are poured and filled in the remaining parts of the inner wall of the steel shell of the main trench cover around the prefabricated part that are not impacted or less impacted by molten iron. The impact zone of the main trench cover of the blast furnace is prefabricated, so as to extend the overall service life of the main trench cover.

Description

Technical Field

[0001] The invention relates to the field of auxiliary equipment for a main trench cover of an iron tapping furnace, in particular to the field of a local structure of an impact zone of a main trench cover, and specifically refers to a prefabricated part of an impact zone of a main trench cover of an iron tapping furnace. Background Art

[0002] The main trench cover is mainly used on the main trench of the iron-making process to prevent the splashing of molten iron during the iron-making process of the blast furnace. The impact area of ​​the main trench cover is at the tail of this structure, about 8 meters away from the iron-making port. Because this point is exactly where the molten iron falls, this part will be subjected to the thermal shock and erosion of the molten iron, causing the structure here to be easily damaged and burned through, and the refractory life of other parts is not synchronized. Summary of the invention

[0003] The purpose of the present invention is to overcome the disadvantages of the prior art and provide a prefabricated part for the impact zone of the main ditch cover of the blast furnace which is resistant to erosion and wear and can be replaced at any time.

[0004] In order to achieve the above-mentioned object, the prefabricated parts of the impact zone of the main ditch cover of the blast furnace iron tapping according to the present invention are as follows:

[0005] The prefabricated part in the impact zone of the main trench cover of the blast furnace iron-outlet has the following main features: the prefabricated part structure is composed of three prefabricated part components, namely, a top prefabricated part, a left prefabricated part and a right prefabricated part; the three prefabricated part components are spliced ​​into an arch structure, which is hoisted on the inner wall of the main trench cover steel shell at the position where the main trench cover of the blast furnace iron-outlet is impacted by molten iron for use; the prefabricated part also includes an internal steel structure; the top prefabricated part of the prefabricated part is a structure that is wide at the top and narrow at the bottom, so as to avoid falling off due to its own gravity during use; the shape of the outer wall of the prefabricated part is consistent with the inner wall of the main trench cover steel shell where the prefabricated part is arranged; the inner wall of the top prefabricated part is a planar structure; the left prefabricated part and the right prefabricated part are The inner wall of the prefabricated part is in an arc structure; the outer wall of the prefabricated part is pre-embedded with bolts, the bolts are welded and fixed to the internal steel structure of the prefabricated part, the prefabricated part is connected and fixed to the main trench cover steel shell through nuts through the bolts, the prefabricated part is fitted with the inner wall of the main trench cover steel shell through refractory fiber cotton, and is used to fit with the inner wall of the main trench cover steel shell that is deformed due to repeated use, the inner wall of the main trench cover steel shell is filled with casting material with the same thickness as the prefabricated part around the part of the prefabricated part that is not or less impacted by molten iron, which is used to make the arched structure spliced ​​by three prefabricated parts bear force to each other and thus be more firm, and the internal steel structure is a mesh structure welded by steel elements and pre-embedded in the prefabricated part.

[0006] Preferably, the internal steel structure includes a steel mesh welded by steel elements and bolts welded and fixed to the steel mesh, the steel mesh is cast inside the prefabricated part, and the bolts hoist the prefabricated part to the inner wall of the main trench cover steel shell.

[0007] Preferably, the end of the preform has a thickened section, the cross section of the thickened section is wedge-shaped and gradually thickens from top to bottom, and the thickened section is integrally formed with the preform.

[0008] Preferably, the upward angle of the wedge is 5°.

[0009] Preferably, the refractory fiber wool has a thickness of 20 mm and a temperature resistance of 1200°C.

[0010] Preferably, the thickness of the top prefabricated component is 180 mm.

[0011] Preferably, the lateral distance between the bolts is 440 mm to 460 mm, and the longitudinal distance between the bolts is 750 mm to 780 mm.

[0012] Preferably, the length of the bolt is 150-160 mm, and the embedded depth is 60-70 mm.

[0013] Preferably, the prefabricated part is made of refractory castable, and the refractory castable is made of raw materials such as corundum, mullite and silicon carbide. Alumina powder and silicon powder are added to the matrix of the refractory castable according to the composition ratio of mullite.

[0014] Preferably, the amount of corundum added is 40-47%, the amount of mullite added is 28-35%, the amount of silicon carbide added is 4-5%, the amount of alumina powder added is 10%-13%, and the amount of silicon micropowder added is 4%-5%.

[0015] Preferably, the corundum is white corundum produced by electric melting, and the Al 2 O 3 Content ≥99%, Fe 2 O 3 The content is ≤0.2%, which is used to increase wear resistance, erosion resistance and slag erosion resistance.

[0016] Preferably, the mullite is made by sintering, and the Al 2 O 3 The content of SiO is ≥76%, 2 The content is ≥22%, which is used to improve the thermal shock stability of the preform.

[0017] Preferably, the alumina powder is activated alumina powder or α-Al 2 O 3 One or a mixture of two of the powders, the alumina powder and the silicon powder generate mullite at high temperature, producing mullite whiskers, which are used to increase the toughness of the prefabricated parts and improve structural spalling.

[0018] Preferably, the SiO 2 The content is ≥92%. On the one hand, it can reduce the amount of water added to the castable, and on the other hand, it reacts with alumina powder at high temperature to form mullite.

[0019] Preferably, the prefabricated part further comprises cement, wherein the Al 2 O 3 The content of Al is 69-71%, and the content of CaO is ≤30%, which is used to make the prefabricated part have the preset strength for use.

[0020] Preferably, an admixture is further added to the prefabricated part, wherein the content of low-temperature explosion-proof fiber in the admixture is 0.05-0.1%, the content of water reducing agent is 0.1-0.2%, and the content of retarder is 0.02-0.05%.

[0021] The prefabricated parts of the impact zone of the main ditch cover of the blast furnace iron tapping of the present invention are subjected to baking treatment to avoid cracking, explosion and the like during use. The prefabricated parts are resistant to erosion and wear and are replaceable. The defect that the impact zone of the main ditch cover of the blast furnace iron tapping is easily damaged can be improved, thereby achieving the purpose of extending the overall service life of the main ditch cover of the blast furnace iron tapping. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of assembling the prefabricated parts in the impact zone of the main ditch cover of the blast furnace iron tapping according to the present invention.

[0023] Figure 2 It is a schematic diagram of the prefabricated parts of the impact zone of the main ditch cover of the blast furnace iron-out according to the present invention.

[0024] Figure 3 It is a partial cross-sectional schematic diagram of the impact zone of the main ditch cover of the blast furnace iron-out according to the present invention.

[0025] Figure 4 It is a schematic diagram of the prefabricated part after the steel shell of the impact zone of the blast furnace main ditch cover is cut.

[0026] Figure 5 It is a schematic diagram of a prefabricated part after partial cutting of the steel shell in the impact zone of the main ditch cover of the blast furnace iron tapping according to the present invention.

[0027] Reference numerals:

[0028] 1 Main trench cover steel shell

[0029] 2 Top prefab

[0030] 3 Right prefab

[0031] 4 Left prefab

[0032] 5. Refractory fiber cotton

[0033] 6 Bolts

[0034] 7 Nut

[0035] 8 Lifting holes

[0036] 9 Anchor

[0037] 10. Pouring side wall castable

[0038] 11. Casting the end casting material

[0039] 12 Pour the top castable DETAILED DESCRIPTION

[0040] In order to more clearly describe the technical content of the present invention, further description is given below in conjunction with specific embodiments.

[0041] like Figures 1 to 5 As shown, the prefabricated parts of the impact zone of the main trench cover of the blast furnace of the present invention include a top prefabricated part 2, a right prefabricated part 3, a left prefabricated part 4 and the internal steel structure thereof, the outer wall of the prefabricated parts has pre-embedded bolts connected to the main trench cover shell steel structure through nuts, and the connection between the top prefabricated part 2, the right prefabricated part 3 and the left prefabricated part 4 and the main trench cover shell steel structure 1 is paved with refractory fiber wool 5. Three prefabricated components are spliced ​​into an arch structure, which is hoisted on the inner wall of the steel shell of the blast furnace main trench cover impacted by molten iron for use.

[0042] As a preferred embodiment of the present invention, the internal steel structure includes a steel mesh welded from steel elements and bolts 6 welded and fixed to the steel mesh. The steel mesh is cast inside the prefabricated part to support and strengthen the refractory material prefabricated part. The bolts 6 are used to hoist the top prefabricated part 2, the right prefabricated part 3 and the left prefabricated part 4 to the inner wall of the main trench cover steel shell 1.

[0043] As a preferred embodiment of the present invention, the prefabricated parts are composed of a top prefabricated part 2, a right prefabricated part 3 and a left prefabricated part 4. The top prefabricated part 2 is designed to be wide at the top and narrow at the bottom to avoid falling off due to its own gravity during use. The right prefabricated part 3 and the left prefabricated part 4 are installed on both sides of the top prefabricated part, and the three prefabricated part assemblies form a structurally firm arch structure.

[0044] As a preferred embodiment of the present invention, the outer walls of the top prefabricated part 2, the right prefabricated part 3 and the left prefabricated part 4 are pre-embedded with bolts 6, which are welded and fixed to the steel structure inside the prefabricated parts. The top prefabricated part 2, the right prefabricated part 3 and the left prefabricated part 4 are connected to the main trench cover steel shell 1 through nuts 7 through the bolts 6, which facilitates the disassembly and replacement of the prefabricated parts. In a specific embodiment of the present invention, the internal steel structure is fixedly installed through the hoisting holes 8.

[0045] As a preferred embodiment of the present invention, the shapes of the outer walls of the top prefabricated part 2, the right prefabricated part 3 and the left prefabricated part 4 are consistent with the inner wall of the main trench cover steel shell 1 where the prefabricated parts are arranged, the inner wall of the top prefabricated part 2 is a plane structure, and the inner walls of the right prefabricated part 3 and the left prefabricated part 4 are arc structures.

[0046] As a preferred embodiment of the present invention, a space for pouring refractory castables is reserved around the spliced ​​arched prefabricated parts. After the castables are filled with a thickness equivalent to that of the prefabricated parts, the arched structure formed by the spliced ​​three prefabricated parts is subjected to mutual force, thereby being more solid. Figure 1 and 3 As shown, according to different pouring positions, the castables can be divided into castables 10 for pouring side walls, castables 11 for pouring ends, and castables 12 for pouring tops.

[0047] As a preferred embodiment of the present invention, the prefabricated parts can be better fitted with the inner wall of the main trench cover steel shell that is deformed due to repeated use by laying refractory fiber wool during installation.

[0048] As a preferred embodiment of the present invention, the ends of the top preform 2, the right preform 3 and the left preform 4 have thickened sections, the cross-section of the thickened sections is wedge-shaped, gradually thickening from top to bottom, and the thickened sections are integrally formed with the preforms.

[0049] As a preferred embodiment of the present invention, the upward angle of the wedge is 5°.

[0050] As a preferred embodiment of the present invention, the refractory fiber cotton 5 has a thickness of 20 mm and a temperature resistance of 1200°C.

[0051] As a preferred embodiment of the present invention, the thickness of the top prefabricated member 2 is 180 mm.

[0052] As a preferred embodiment of the present invention, the lateral distance of the bolts 6 is 440 mm to 460 mm, and the longitudinal distance is 750 mm to 780 mm.

[0053] As a preferred embodiment of the present invention, the length of the bolt 6 is 150-160 mm, and the embedded depth is 60-70 mm.

[0054] As a preferred embodiment of the present invention, the prefabricated part is made of refractory castable, and the refractory castable is made of raw materials such as corundum, mullite and silicon carbide. Alumina powder and silicon powder are added to the matrix of the refractory castable according to the composition ratio of mullite.

[0055] As a preferred embodiment of the present invention, the addition amount of the corundum is 40-47%, the addition amount of the mullite is 28-35%, the addition amount of the silicon carbide is 4-5%, the addition amount of the alumina powder is 10%-13%, and the addition amount of the silicon micropowder is 4%-5%.

[0056] As a preferred embodiment of the present invention, the corundum is white corundum produced by electric melting, and the Al 2 O 3 Content ≥99%, Fe 2 O 3 The content is ≤0.2%, which is used to increase wear resistance, erosion resistance and slag erosion resistance.

[0057] As a preferred embodiment of the present invention, the mullite is made by sintering, and the Al 2 O 3 The content of SiO is ≥76%, 2 The content is ≥22%, which is used to improve the thermal shock stability of the preform.

[0058] As a preferred embodiment of the present invention, the alumina powder is activated alumina powder or α-Al 2 O 3 One or a mixture of two of the powders, the alumina powder and the silicon powder generate mullite at high temperature, producing mullite whiskers, which are used to increase the toughness of the prefabricated parts and improve structural spalling.

[0059] As a preferred embodiment of the present invention, the SiO 2 The content is ≥92%. On the one hand, it is used to reduce the amount of water added to the castable, and on the other hand, it can react with alumina powder at high temperature to form mullite.

[0060] As a preferred embodiment of the present invention, the prefabricated part further comprises cement, wherein the Al 2 O 3 The content of Al is 69-71%, and the content of CaO is ≤30%, which is used to make the prefabricated parts have the strength required for use.

[0061] As a preferred embodiment of the present invention, an admixture is further added to the prefabricated part, wherein the content of low-temperature explosion-proof fiber in the admixture is 0.05-0.1%, the content of water reducing agent is 0.1-0.2%, and the content of retarder is 0.02-0.05%.

[0062] In the embodiment of the present invention, the proportion of the prefabricated castable of the impact zone of the main channel cover of the blast furnace is shown in Table 1 below, and the performance index of the castable is shown in Table 2 below. The refractory castable has a plate-shaped corundum addition amount of 44%, a mullite addition amount of 33.8%, a silicon carbide content of 4%, an alumina powder addition amount of 10.2%, and a silicon powder addition amount of 4%. The performance index at this time is the best.

[0063] As a preferred embodiment of the present invention, the refractory prefabricated parts are cured for 48 hours and then baked at 600°C.

[0064] Table 1 Ratio of castables for prefabricated parts in the impact zone of the main trench cover of the blast furnace

[0065]

[0066]

[0067] Table 2 Performance indicators of the castables in the examples

[0068]

[0069] In a specific embodiment of the present invention, Figure 1 and 3 As shown, the refractory material of the molten iron impact zone of the main trench cover that is easily damaged is designed as a prefabricated part. The prefabricated part includes a refractory material casting body and a steel structure grid and bolts 6 pre-buried in the refractory material. After pouring and baking, the prefabricated part is connected to the steel shell of the main trench cover by bolts 6 with nuts 7. A 20mm refractory fiber cotton 5 is laid between the main structure of the main trench cover and the prefabricated part to play the role of heat insulation and buffer pad. By improving the traditional casting material into a prefabricated part, the impact zone of the main trench cover can achieve the purpose of being resistant to molten iron erosion, wear-resistant, and easy to replace, thereby achieving the requirement of improving the overall material life of the main trench cover. Among them, Figure 1 and Figure 3 These are schematic diagrams of the main trench cover flipped 90° to the left.

[0070] like Figure 2 As shown, the shape of the prefabricated part of the present invention is a flat top shape with arc shapes on both sides. The flat top and arc structure correspond to the shape of the outer shell steel structure; the thickness of the plane structure is 180mm, the end is wedge-shaped, gradually thickened, and its upward angle is 5°.

[0071] like Figure 4 and 5As shown, the impact zone prefabricated part is connected to the main trench cover shell steel structure 1 by bolts 6 embedded in the top surface with nuts 7, and a layer of 20 mm refractory fiber wool 5 with a temperature resistance of 1200° C. is pre-laid on the shell steel structure during connection. After the installation is completed, refractory castables with a thickness equivalent to that of the prefabricated part are poured at the locations where anchors 9 are arranged in the main trench cover steel shell 1 around the prefabricated part, and the pouring of the refractory castables has a better fixing effect on the prefabricated part.

[0072] The refractory castable used for the prefabricated part is a corundum mullite castable, which has the characteristics of good wear resistance and thermal shock stability. The prefabricated part needs to be cured and baked at a baking temperature of 600° C. In the embodiment, the refractory fiber wool can be a high-temperature fiber blanket.

[0073] The installation steps for the prefabricated parts in the impact zone of the main ditch cover of the blast furnace are as follows:

[0074] (1) After the prefabricated parts and the main trench cover shell steel structure are installed, they are fixed with nuts;

[0075] (2) pouring refractory castable with a thickness equivalent to that of the prefabricated part at the locations where anchors are arranged in the main trench cover steel shell around the prefabricated part.

[0076] The technical solution of the present invention has been applied in multiple embodiments in actual production, which significantly improves the service life of the main ditch of the blast furnace. For example, the average service life of the first embodiment in the application of the main ditch of the blast furnace with a capacity of 5000 cubic meters is increased by 53%, and the average service life of the second embodiment in the application of the main ditch of the blast furnace with a capacity of 4500 cubic meters is increased by 46%; the average service life of the third embodiment in the application of the main ditch of the blast furnace with a capacity of 3500 cubic meters is increased by 71%; the average service life of the fourth embodiment in the application of the main ditch of the blast furnace with a capacity of 2500 cubic meters is increased by 56%.

[0077] The specific implementation scheme of this embodiment can refer to the relevant description in the above embodiment, which will not be repeated here.

[0078] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0079] It should be noted that, in the description of the present invention, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, the meaning of "plurality" refers to at least two.

[0080] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0081] The prefabricated part of the impact zone of the main ditch cover of the blast furnace iron tapping adopts the present invention to avoid cracking, explosion and the like during use by strengthening the material performance and refining the manufacturing process, thereby achieving the performance of anti-scouring and wear resistance and being replaceable.

[0082] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

Claims

1. A prefabricated part for the impact zone of the main ditch cover of a blast furnace, characterized in that: The structure of the prefabricated part is composed of three prefabricated part assemblies, namely, a top prefabricated part, a left prefabricated part and a right prefabricated part. The three prefabricated part assemblies are spliced ​​into an arch structure, which is hoisted on the inner wall of the main trench cover steel shell of the blast furnace iron-out main trench cover where the molten iron impacts the main trench cover. The prefabricated part also includes an internal steel structure. The top prefabricated part of the prefabricated part is a structure that is wide at the top and narrow at the bottom, so as to avoid falling off due to its own gravity during use; the shape of the outer wall of the prefabricated part is consistent with the inner wall of the main trench cover steel shell where the prefabricated part is arranged, the inner wall of the top prefabricated part is a plane structure, and the inner walls of the left prefabricated part and the right prefabricated part are an arc structure; the outer wall of the prefabricated part is pre-embedded with bolts, which are welded and fixed to the internal steel structure of the prefabricated part, and the prefabricated part is connected and fixed to the main trench cover steel shell by nuts through the bolts. The prefabricated parts are fitted with the inner wall of the main trench cover steel shell through refractory fiber cotton, and are used to fit with the inner wall of the main trench cover steel shell that is deformed due to repeated use. The inner wall of the main trench cover steel shell is filled with a casting material with the same thickness as the prefabricated parts around the parts of the prefabricated parts that are not or less impacted by molten iron, so as to make the arched structure spliced ​​by the three prefabricated parts bear force to each other and become more solid. The internal steel structure is a mesh structure welded by steel elements and embedded in the prefabricated parts. The end of the prefabricated parts has a thickened section. The cross-section of the thickened section is wedge-shaped and gradually becomes thicker from the back to the front. The thickened section is integrally formed with the prefabricated parts. The internal steel structure includes a steel mesh welded by steel elements and bolts welded and fixed to the steel mesh. The steel mesh is arranged inside the prefabricated parts, and the bolts hoist the prefabricated parts to the inner wall of the main trench cover steel shell.

2. The prefabricated part of the impact zone of the main ditch cover of the blast furnace according to claim 1, characterized in that: The upward angle of the wedge is 5°.

3. The prefabricated part of the impact zone of the main channel cover of the blast furnace according to claim 1, characterized in that: The thickness of the fire-resistant fiber cotton is 20 mm and the temperature resistance is 1200°C.

4. The prefabricated part of the impact zone of the main channel cover of the blast furnace according to claim 1, characterized in that: The thickness of the top prefabricated part is 180 mm.

5. The prefabricated part of the impact zone of the main channel cover of the blast furnace according to claim 1, characterized in that: The transverse distance of the bolts is 440 mm to 460 mm, and the longitudinal distance is 750 mm to 780 mm.

6. The prefabricated part of the impact zone of the main channel cover of the blast furnace according to claim 1, characterized in that: The length of the bolt is 150-160 mm, and the embedded depth is 60-70 mm.

7. The prefabricated part of the impact zone of the main ditch cover of the blast furnace according to any one of claims 1 to 6, characterized in that: The prefabricated part is made of refractory castables. The raw materials of the refractory castables include corundum, mullite and silicon carbide. Alumina powder and silicon powder are added to the matrix of the refractory castables according to the composition ratio of mullite.

8. The prefabricated part of the impact zone of the main ditch cover of the blast furnace according to claim 7, characterized in that: The addition amount of the corundum is 40-47%, the addition amount of the mullite is 28-35%, the addition amount of the silicon carbide is 4-5%, the addition amount of the alumina powder is 10-13%, and the addition amount of the silicon micropowder is 4-5%.

9. The prefabricated part of the impact zone of the main channel cover of the blast furnace according to claim 7, characterized in that: The corundum is white corundum made by electric melting method, the Al2O3 content of the white corundum is ≥99%, and the Fe2O3 content is ≤0.2%, and is used to increase wear resistance, erosion resistance and slag erosion resistance.

10. The prefabricated part of the impact zone of the main channel cover of the blast furnace according to claim 7, characterized in that: The mullite is made by sintering, the Al2O3 content of the mullite is ≥76%, and the SiO2 content is ≥22%, and is used to improve the thermal shock stability of the prefabricated part.

11. The prefabricated part of the impact zone of the main channel cover of the blast furnace according to claim 7, characterized in that: The alumina powder is one of active alumina powder and α-Al2O3 powder or a mixture of the two. The alumina powder and silicon powder generate mullite at high temperature to produce mullite whiskers, which are used to increase the toughness of the prefabricated parts and improve structural peeling.

12. The prefabricated part of the impact zone of the main channel cover of the blast furnace according to claim 7, characterized in that: The SiO2 content of the silicon micropowder is ≥92%, which is used to reduce the amount of water added to the castable and reacts with alumina powder at high temperature to form mullite.

13. The prefabricated part of the impact zone of the main channel cover of the blast furnace according to claim 7, characterized in that: The prefabricated part is also made of cement, wherein the Al2O3 content of the cement is 69-71% and the CaO content is ≤30%, so as to make the prefabricated part have a preset service strength.

14. The prefabricated part of the impact zone of the main channel cover of the blast furnace according to claim 7, characterized in that: The prefabricated part is further added with an admixture, wherein the content of the low-temperature explosion-proof fiber in the admixture is 0.05-0.1%, the content of the water reducing agent is 0.1-0.2%, and the content of the retarder is 0.02-0.05%.

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