Diatomite chemical foaming synergistic hierarchical porous cement-based coating as well as preparation method and application thereof

Abstract

The invention discloses a diatomite chemical foaming synergistic hierarchical porous cement-based coating as well as a preparation method and application thereof. Raw materials of the cement-based coating comprise a solid component and mixing water. The solid component is prepared from the following components in parts by weight: 55 to 65 parts of cement binding material, 20 to 30 parts of diatomite powder, 3 to 5 parts of calcium peroxide powder, 3 to 5 parts of stearate powder, 0.3 to 0.8 part of fiber, 1.7 to 2.5 parts of citric acid powder, 4.5 to 6.5 parts of isobutyltriethoxysilane and 0.5 to 1.0 part of dibutyltin dilaurate. Gradient multistage pore channels are constructed through directional pore forming in a cement-based material, differential modification of pore walls / pore channels by a double-hydrophobic barrier is cooperated, and a liquid water transmission path is cut off while a water vapor diffusion channel is maintained, so that the problem of three-element balance of ventilation, water resistance and mechanical strength is solved; and the service life of the cement structure body in an extreme environment is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of cement - based material preparation, and particularly relates to a diatomite chemical foaming synergistic multi - level pore cement - based coating, its preparation method and application. Background Art

[0002] Disclosing the information of this background art section is only intended to increase the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an implication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.

[0003] Traditional cement - based materials are difficult to balance the inherent contradiction between air permeability and waterproofness, that is: although improving the denseness of cement - based materials is beneficial to blocking the penetration of liquid water, the long - term accumulation of moisture inside the cement - based materials will be caused due to the closed pores, which is easy to induce damage such as freeze - thaw cycle spalling and salt crystallization expansion. Although the porous cement - based materials formed by physical or chemical foaming help to discharge the internal moisture, the connected pores instead become the intrusion channels of liquid water and erosive ions (such as Cl⁻, SO4 2- etc.), accelerating the corrosion of steel bars inside the cement - based materials and the dissolution of the matrix. In addition, a single modification method often has one thing at the expense of another. For example, the hydrophobic agent is easy to block the pores and reduce the air permeability, while foaming and pore - forming weaken the mechanical strength, resulting in insufficient durability of the cement - based materials in extreme environments. Therefore, traditional cement - based materials have the deficiency of being difficult to balance air permeability and waterproofness in extreme environments such as deep - sea high - pressure and saline - alkali erosion. Summary of the Invention

[0004] Aiming at the above problems, the present invention provides a diatomite chemical foaming synergistic multi - level pore cement - based coating, its preparation method and application, which effectively overcomes the ternary balance problem of air permeability - waterproofness - mechanical strength and prolongs the service life of cement structures in extreme environments. Specifically, the present invention discloses the following technical solutions.

[0005] First of all, the present invention discloses a diatomite chemical foaming synergistic multi - level pore cement - based coating, the raw materials of which include solid components and mixing water, and the mass ratio of the two is 1:0.35 - 0.40. Among them, the solid components include: 55 - 65 parts by weight of cementitious materials, 20 - 30 parts by weight of diatomite powder, 3 - 5 parts by weight of calcium peroxide powder, 3 - 5 parts by weight of stearate powder, 0.3 - 0.8 parts by weight of fiber, 1.7 - 2.5 parts by weight of citric acid powder, 4.5 - 6.5 parts by weight of isobutyltriethoxysilane, and 0.5 - 1.0 parts by weight of dibutyltin dilaurate.

[0006] Furthermore, the cementitious material includes at least one of silicate cement, sulfoaluminate cement, etc., which can not only serve as a matrix for the coating to ensure good mechanical properties, but also can use the alkaline substances generated by its hydration to provide an alkaline reaction environment, thereby promoting the ion exchange reaction between the stearate and the calcium ions released by the cement hydration to generate a calcium stearate hydrophobic agent, which adheres to the pore walls of the multi-level channels to form a waterproof barrier, blocking the penetration of liquid water while maintaining the permeability of water vapor.

[0007] Furthermore, the stearate includes at least one of sodium stearate, magnesium stearate, zinc stearate, etc.

[0008] Furthermore, the fibers include at least one of polyethylene fibers, polypropylene fibers, polyvinyl alcohol fibers, polyacrylonitrile fibers, basalt fibers, and carbon fibers. Optionally, the fibers are 12 to 24 mm in length. These fibers help inhibit shrinkage cracking and improve the performance of the protective coating formed by the cement-based coating.

[0009] Furthermore, the fineness of the diatomaceous earth powder is 200-325 meshes. The fineness of the calcium peroxide powder is 400-800 meshes.

[0010] Furthermore, the fineness of the stearate powder is 800-1250 mesh. The fineness of the citric acid powder is 300-600 mesh.

[0011] Secondly, the present invention discloses a method for preparing the diatomite chemical foaming synergistic multi-stage pore cement-based coating, comprising the following steps: (1) The isobutyltriethoxysilane, dibutyltin dilaurate and mixing water are mixed and allowed to stand to obtain activated mixing water.

[0012] (2) The cement binder, diatomaceous earth, calcium peroxide, stearate, fiber, and citric acid powder are uniformly mixed to obtain a solid component.

[0013] (3) The solid components are mixed evenly with activated mixing water to obtain the cement-based coating.

[0014] Finally, the present invention discloses the application of the diatomaceous earth chemical foaming synergistic multi-stage pore cement-based coating in the fields of marine engineering, water conservancy and hydropower engineering, road engineering, bridge engineering, tunnel engineering, etc.

[0015] Furthermore, the application method is: applying the cement-based coating to the surface of the substrate, and forming a protective coating after hardening and forming. Optionally, the thickness of the protective coating is 1.5-2.0 mm.

[0016] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects: Aiming at the deficiency that the traditional cement-based materials are difficult to balance breathability and waterproofness, after the diatomite chemical foaming synergistic multi-level pore channel cement-based coating provided by the present invention is coated on the surface of the substrate to form a protective coating, gradient multi-level pore channels are constructed by directional pore formation therein, and the differential modification of the pore walls / pore channels by the synergistic double hydrophobic barriers cuts off the liquid water transmission path while maintaining the water vapor diffusion channel, thus overcoming the ternary balance problem of breathability-waterproofness-mechanical strength. For this purpose, first, the present invention uses the porous structure of diatomite as the main channel for water vapor diffusion. Secondly, calcium peroxide is used to react with water to slowly release oxygen for pore formation, so as to form gradient multi-level pore channels with the pores of the diatomite. The pore channels with such structural characteristics not only ensure the breathability of the coating, enabling water vapor to diffuse freely, but also use micropores to prevent liquid water from entering, thus achieving the effect of "breathable but not water-permeable". Thirdly, since the reaction of calcium peroxide with water is easily interfered by the calcium ions generated by cement hydration, which affects the uniformity of the distribution of the constructed gradient multi-level pore channels. For this reason, on the one hand, the present invention uses citric acid to form a stable chelate with calcium ions, reducing the calcium ion concentration, thereby reducing the interference with the reaction of calcium peroxide with water, making the oxygen release and foaming process of calcium peroxide synchronous with the initial setting of the coating, facilitating the bubbles generated to be "locked" by the gradually solidified cement network, reducing merger and escape, and forming uniformly distributed micron-sized pores, and constructing gradient multi-level pore channels with the pores of the diatomite. On the other hand, calcium stearate water repellent is formed by the reaction of the stearate with calcium ions. It not only reduces the calcium ion concentration, but also the calcium stearate is loaded on the surface of the multi-level pore channels. Together with the waterproof film formed by the isobutyltriethoxysilane and dibutyltin dilaurate, it blocks the permeation of liquid water through the protective coating, realizing the function of breathable but not water-permeable. At the same time, the fibers help to inhibit the generation of shrinkage cracks and improve the mechanical properties of the protective coating, thus overcoming the ternary balance problem of breathability-waterproofness-mechanical strength and effectively extending the service life of the cement structure in extreme environments. Description of the Drawings

[0017] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0018] Figure 1 Physical sample diagram of the cement-based coating prepared for Example 1 below Figure 2 Water contact angle test diagram of Example 1 below

[0019] Figure 3 Physical sample diagram of the cement-based coating prepared for Example 4 below

[0020] Figure 4 It is the water contact angle test diagram for the following Example 4.

[0021] Figure 5 It is the water contact angle test diagram for the following Example 5.

[0022] Figure 6 It is the water contact angle test diagram for the following Example 6.

[0023] Figure 7 It is the water contact angle test diagram for the following Example 8. Specific implementation mode

[0024] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The experimental methods without specific conditions noted in the following embodiments are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0025] Unless otherwise defined, all professional and scientific terms used in the present invention have the same meaning as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can all be obtained by conventional means. Unless otherwise specified, the reagents or raw materials used in the present invention are used in the conventional manner in the art or according to the product instructions.

[0026] In addition, any methods and materials similar or equivalent to the described content can be applied to the method of the present invention. The technical solution of the present invention will be further described below in conjunction with the accompanying drawings of the specification and specific embodiments.

[0027] Example 1 The preparation of a diatomite chemical foaming synergistic multi - pore channel cement - based coating includes the steps: (1) Take solid components: 65 parts by weight of 42.5 ordinary Portland cement, 20 parts by weight of diatomite powder with a fineness of 300 meshes, 5 parts by weight of calcium peroxide powder with a fineness of 800 meshes, 3 parts by weight of sodium stearate powder with a fineness of 1000 meshes, 0.3 parts by weight of polyethylene fiber with a length of 15 mm, 1.7 parts by weight of citric acid powder with a fineness of 500 meshes, 4.5 parts by weight of isobutyltriethoxysilane, and 0.5 parts by weight of dibutyltin dilaurate. Then take mixing water which is 0.35 times the mass of the solid components, and set aside.

[0028] (2) Mix the isobutyltriethoxysilane, dibutyltin dilaurate and the mixing water, and let it stand for 5 min to obtain activated mixing water.

[0029] (3) Stir and dry - mix the cement, diatomite, calcium peroxide, sodium stearate, polyethylene fiber, and citric acid powder for 15 min to obtain solid components.

[0030] (4) Mix and stir the solid component with mixing water for 2 min to obtain the cement-based coating, as Figure 1 shown.

[0031] Performance test: The water vapor transmission rate and tensile strength of the cement-based coating prepared in this example were tested according to the standards of JG / T 309-2011 and GB / T 16777-2008, respectively. In addition, the water contact angle of the cement-based coating was tested using an optical contact angle measuring instrument (model JC2000D3M) (as Figure 2 shown). The test results are shown in the following table: .

[0032] Example 2 Preparation of a diatomite chemical foaming synergistic multi-level pore cement-based coating, comprising the steps of: (1) Take solid components: 60 parts by weight of 42.5 ordinary Portland cement, 24 parts by weight of diatomite powder with a fineness of 200 meshes, 4.5 parts by weight of calcium peroxide powder with a fineness of 500 meshes, 3.5 parts by weight of magnesium stearate powder with a fineness of 1250 meshes, 0.6 parts by weight of polyacrylonitrile fiber with a length of 24 mm, 2 parts by weight of citric acid powder with a fineness of 300 meshes, 5 parts by weight of isobutyltriethoxysilane, and 0.8 parts by weight of dibutyltin dilaurate. Then take mixing water with a mass 0.37 times that of the solid components and set aside.

[0033] (2) Mix the isobutyltriethoxysilane, dibutyltin dilaurate with the mixing water, and let it stand for 5 min to obtain activated mixing water.

[0034] (3) Stir and dry-mix the cement, diatomite, calcium peroxide, magnesium stearate, polyacrylonitrile fiber, and citric acid powder for 15 min to obtain a solid component.

[0035] (4) Mix and stir the solid component with the mixing water for 2 min to obtain the cement-based coating.

[0036] Performance test: The water vapor transmission rate, tensile strength, and water contact angle of the cement-based coating prepared in this example were tested using the same method as in Example 1 above, and the results are shown in the following table: .

[0037] Example 3 Preparation of a diatomite chemical foaming synergistic multi-level pore cement-based coating, comprising the steps of: (1) Take solid components: 55 parts by weight of 42.5 ordinary Portland cement, 30 parts by weight of diatomite powder with a fineness of 325 mesh, 3 parts by weight of calcium peroxide powder with a fineness of 500 mesh, 5 parts by weight of zinc stearate powder with a fineness of 800 mesh, 0.8 parts by weight of basalt fiber with a length of 12 mm, 2.5 parts by weight of citric acid powder with a fineness of 600 mesh, 6.5 parts by weight of isobutyltriethoxysilane, and 1.0 part by weight of dibutyltin dilaurate. Then take mixing water which is 0.4 times the mass of the solid components and set aside.

[0038] (2) Mix the isobutyltriethoxysilane, dibutyltin dilaurate with the mixing water and let it stand for 5 min to obtain activated mixing water.

[0039] (3) Stir and dry-mix the cement, diatomite, calcium peroxide, zinc stearate, basalt fiber, and citric acid powder for 15 min to obtain solid components.

[0040] (4) Mix and stir the solid components with the mixing water for 2 min to obtain the cement-based coating.

[0041] Performance test: Use the same method as in Example 1 above to test the water vapor transmission rate, tensile strength, and water contact angle of the cement-based coating prepared in this example. The results are shown in the following table: 。

[0042] Example 4 Preparation of a diatomite chemical foaming synergistic multi-level pore cement-based coating, including the steps: (1) Take solid components: 65 parts by weight of 42.5 ordinary Portland cement, 5 parts by weight of calcium peroxide powder with a fineness of 800 mesh, 3 parts by weight of sodium stearate powder with a fineness of 1000 mesh, 0.3 parts by weight of polyethylene fiber with a length of 15 mm, 1.7 parts by weight of citric acid powder with a fineness of 500 mesh, 4.5 parts by weight of isobutyltriethoxysilane, and 0.5 part by weight of dibutyltin dilaurate. Then take mixing water which is 0.35 times the mass of the solid components and set aside.

[0043] (2) Mix the isobutyltriethoxysilane, dibutyltin dilaurate with the mixing water and let it stand for 5 min to obtain activated mixing water.

[0044] (3) Stir and dry-mix the cement, calcium peroxide, sodium stearate, polyethylene fiber, and citric acid powder for 15 min to obtain solid components.

[0045] (4) Mix and stir the solid components with the mixing water for 2 min to obtain the cement-based coating, as Figure 3 shown.

[0046] Performance test: Using the same method as in Example 1 above, the water vapor transmission rate, tensile strength, and water contact angle (as Figure 4 shown) of the cement-based coating prepared in this example were tested, and the results are shown in the following table: .

[0047] Example 5 Preparation of a diatomite chemical foaming synergistic multi-level pore cement-based coating, including the steps of: (1) Take solid components: 60 parts by weight of 42.5 ordinary Portland cement, 24 parts by weight of diatomite powder with a fineness of 200 mesh, 3.5 parts by weight of magnesium stearate powder with a fineness of 1250 mesh, 0.6 parts by weight of polyacrylonitrile fiber with a length of 24 mm, 2 parts by weight of citric acid powder with a fineness of 300 mesh, 5 parts by weight of isobutyltriethoxysilane, and 0.8 parts by weight of dibutyltin dilaurate. Then take 0.37 times the mass of the solid components of mixing water and set aside.

[0048] (2) Mix the isobutyltriethoxysilane, dibutyltin dilaurate with the mixing water and let it stand for 5 min to obtain activated mixing water.

[0049] (3) Stir and dry-mix the cement, diatomite, magnesium stearate, polyacrylonitrile fiber, and citric acid powder for 15 min to obtain solid components.

[0050] (4) Mix and stir the solid components with the mixing water for 2 min to obtain the cement-based coating.

[0051] Performance test: Using the same method as in Example 1 above, the water vapor transmission rate, tensile strength, and water contact angle (as Figure 5 shown) of the cement-based coating prepared in this example were tested, and the results are shown in the following table: .

[0052] Example 6 Preparation of a diatomite chemical foaming synergistic multi-level pore cement-based coating, including the steps of: (1) Take solid components: 65 parts by weight of 42.5 ordinary Portland cement, 20 parts by weight of diatomite powder with a fineness of 300 mesh, 5 parts by weight of calcium peroxide powder with a fineness of 800 mesh, 0.3 parts by weight of polyethylene fiber with a length of 15 mm, 1.7 parts by weight of citric acid powder with a fineness of 500 mesh, 4.5 parts by weight of isobutyltriethoxysilane, and 0.5 parts by weight of dibutyltin dilaurate. Then take 0.35 times the mass of the solid components of mixing water and set aside.

[0053] (2) Mix the isobutyltriethoxysilane, dibutyltin dilaurate with the mixing water and let it stand for 5 min to obtain the activated mixing water.

[0054] (3) Mix the cement, diatomite, calcium peroxide, polyethylene fiber, and citric acid powder and stir dry for 15 min to obtain the solid component.

[0055] (4) Mix and stir the solid component with the mixing water for 2 min to obtain the cement-based coating.

[0056] Performance test: Use the same method as in Example 1 above to test the water vapor transmission rate, tensile strength, and water contact angle of the cement-based coating prepared in this example (as Figure 6 shown), and the results are shown in the following table: .

[0057] Example 7 Preparation of a diatomite chemical foaming synergistic multi-level pore cement-based coating, including the steps: (1) Take the solid components: 55 parts by weight of 42.5 ordinary Portland cement, 30 parts by weight of diatomite powder with a fineness of 325 mesh, 3 parts by weight of calcium peroxide powder with a fineness of 500 mesh, 5 parts by weight of zinc stearate powder with a fineness of 800 mesh, 0.8 parts by weight of basalt fiber with a length of 12 mm, 6.5 parts by weight of isobutyltriethoxysilane with a fineness, and 1.0 part by weight of dibutyltin dilaurate. Then take 0.4 times the mass of the solid components of the mixing water and set aside.

[0058] (2) Mix the isobutyltriethoxysilane, dibutyltin dilaurate with the mixing water and let it stand for 5 min to obtain the activated mixing water.

[0059] (3) Mix the cement, diatomite, calcium peroxide, zinc stearate, and basalt fiber and stir dry for 15 min to obtain the solid component.

[0060] (4) Mix and stir the solid component with the mixing water for 2 min to obtain the cement-based coating.

[0061] Performance test: Use the same method as in Example 1 above to test the water vapor transmission rate, tensile strength, and water contact angle of the cement-based coating prepared in this example, and the results are shown in the following table: .

[0062] Example 8 Preparation of a diatomite chemical foaming synergistic multi-level pore cement-based coating, including the steps: (1) Take solid components: 60 parts by weight of 42.5 ordinary Portland cement, 24 parts by weight of diatomite powder with a fineness of 200 mesh, 4.5 parts by weight of calcium peroxide powder with a fineness of 500 mesh, 3.5 parts by weight of magnesium stearate powder with a fineness of 1250 mesh, 0.6 parts by weight of polyacrylonitrile fiber with a length of 24 mm, 2 parts by weight of citric acid powder with a fineness of 300 mesh, 0.8 parts by weight of dibutyltin dilaurate. Then take 0.37 times the mass of the solid components of mixing water and set aside.

[0063] (2) Mix the dibutyltin dilaurate with the mixing water and let it stand for 5 min to obtain activated mixing water.

[0064] (3) Stir and dry-mix the cement, diatomite, calcium peroxide, magnesium stearate, polyacrylonitrile fiber, and citric acid powder for 15 min to obtain solid components.

[0065] (4) Mix and stir the solid components with the mixing water for 2 min to obtain the cement-based coating.

[0066] Performance test: Use the same method as in Example 1 above to test the water vapor transmission rate, tensile strength, and water contact angle (as Figure 7 shown) of the cement-based coating prepared in this example. The results are shown in the following table: .

[0067] Example 9 Preparation of a diatomite chemical foaming synergistic multi-level pore cement-based coating, including the steps: (1) Take solid components: 55 parts by weight of 42.5 ordinary Portland cement, 30 parts by weight of diatomite powder with a fineness of 325 mesh, 3 parts by weight of calcium peroxide powder with a fineness of 500 mesh, 5 parts by weight of zinc stearate powder with a fineness of 800 mesh, 0.8 parts by weight of basalt fiber with a length of 12 mm, 2.5 parts by weight of citric acid powder with a fineness of 600 mesh, 6.5 parts by weight of isobutyltriethoxysilane. Then take 0.4 times the mass of the solid components of mixing water and set aside.

[0068] (2) Mix the isobutyltriethoxysilane with the mixing water and let it stand for 5 min to obtain activated mixing water.

[0069] (3) Stir and dry-mix the cement, diatomite, calcium peroxide, zinc stearate, basalt fiber, and citric acid powder for 15 min to obtain solid components.

[0070] (4) Mix and stir the solid components with the mixing water for 2 min to obtain the cement-based coating.

[0071] Performance test: The water vapor transmission rate, tensile strength, and water contact angle of the cement-based coating prepared in this example were tested using the same method as in Example 1 above. The results are shown in the following table: 。

[0072] The foregoing are only the preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A diatomite chemically foamed and multi - hierarchical pore - channel cement - based coating, characterized in that The raw materials of the coating include a solid component and mixing water, and the mass ratio of the two is 1: 0.35 - 0.40; wherein, the solid component includes: 55 - 65 parts by weight of a cementitious material, 20 - 30 parts by weight of diatomite powder, 3 - 5 parts by weight of calcium peroxide powder, 3 - 5 parts by weight of stearate powder, 0.3 - 0.8 parts by weight of fiber, 1.7 - 2.5 parts by weight of citric acid powder, 4.5 - 6.5 parts by weight of isobutyltriethoxysilane, and 0.5 - 1.0 parts by weight of dibutyltin dilaurate.

2. The diatomaceous earth chemically foamed and multi - level pore - channel cement - based coating according to claim 1, wherein, The cementitious material includes at least one of portland cement and sulfoaluminate cement.

3. The diatomaceous earth chemically foamed and multi-stage pore channel cement-based coating according to claim 1, wherein The stearate includes at least one of sodium stearate, magnesium stearate, and zinc stearate.

4. The diatomite chemically foamed and multi - level pore - channel cement - based coating according to claim 1, characterized in that, The fiber includes at least one of polyethylene fiber, polypropylene fiber, polyvinyl alcohol fiber, polyacrylonitrile fiber, basalt fiber, and carbon fiber; optionally, the length of the fiber is 12 - 24 mm.

5. The diatomite chemically foamed and multi - level pore - channel cement - based coating according to any one of claims 1 - 4, characterized in that, The fineness of the diatomite powder is 200 - 325 mesh; optionally, the fineness of the calcium peroxide powder is 400 - 800 mesh.

6. The diatomite chemically foamed and multi - level pore - channel cement - based coating according to any one of claims 1 - 4, wherein, The fineness of the stearate powder is 800 - 1250 mesh; optionally, the fineness of the citric acid powder is 300 - 600 mesh.

7. The preparation method of the diatomite chemically foamed and multi - stage pore - channel cement - based coating according to any one of claims 1 - 6, characterized in that, It includes the following steps: (1) Mix the isobutyltriethoxysilane, dibutyltin dilaurate with the mixing water and let it stand still to obtain activated mixing water; (2) Mix the cementitious material, diatomite, calcium peroxide, stearate, fiber, and citric acid powder evenly to obtain a solid component; (3) Mix the solid component with the activated mixing water evenly to obtain the cement-based coating.

8. Application of the diatomite chemical foaming synergistic multi-level pore cement-based coating according to any one of claims 1 - 7, or the cement-based coating obtained by the preparation method according to claim 7 in ocean engineering, water conservancy and hydropower engineering, road engineering, bridge engineering or tunnel engineering.

9. The application according to claim 8, wherein The method of this application is: coat the cement-based coating on the surface of the substrate, and a protective coating can be formed after hardening and shaping.

10. The application according to claim 9, characterized in that, The thickness of the protective coating is 1.5 - 2.0 mm.

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