Steam pressurized concrete slab and preparation method thereof

Abstract

The invention relates to the technical field of building materials, and provides a steam pressurized concrete slab and a preparation method thereof.The steam pressurized concrete slab is prepared from, by weight, 100 parts of cement, 40-60 parts of quick lime, 20-30 parts of slaked lime, 8-15 parts of gypsum, 4-6 parts of aluminum powder, 2-4 parts of kaolin, 2-4 parts of bentonite, 0.6-1 part of steel fiber, 0.3-0.6 part of polyacrylonitrile fiber and 0.3-0.5 part of dispersing agent. The steel fibers are composed of first steel fibers and second steel fibers, and the first steel fibers and the second steel fibers are different in fiber length. According to the technical scheme, the problem of insufficient drying shrinkage of the autoclaved aerated concrete slab in the related technology is solved.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a steam-pressurized concrete slab and its preparation method. Background Technology

[0002] Autoclaved aerated concrete (AAC) panels are porous silicate concrete products made primarily from cement, lime, and silicate materials, with aluminum powder as a foaming agent, and cured under high temperature and pressure steam. Due to their advantages such as light weight, good thermal insulation, fire resistance, and high workability, they are widely used in the exterior walls, interior partitions, and roofing panels of industrial and civil buildings, making them one of the ideal materials for green building.

[0003] However, with the rapid development of industrialized construction, higher requirements have been placed on the comprehensive performance of autoclaved aerated concrete (AAC) panels. Especially in high-rise buildings, large-span structures, and regions with significant temperature differences, the panels will experience drying shrinkage due to moisture loss. If the shrinkage is too large or uneven, it can easily lead to cracks at wall joints and surface finishes, severely affecting the building's aesthetics, functionality, and safety. Therefore, developing an AAC panel with low drying shrinkage and its preparation method is of great significance for improving building reliability and supporting technological upgrades in the industry. Summary of the Invention

[0004] This invention proposes a steam-pressurized concrete slab and its preparation method, which solves the problem of insufficient drying shrinkage in related technologies.

[0005] The technical solution of the present invention is as follows: This invention proposes a steam-pressurized concrete slab, comprising the following raw materials in parts by weight: 100 parts cement, 40-60 parts quicklime, 20-30 parts hydrated lime, 8-15 parts gypsum, 4-6 parts aluminum powder, 2-4 parts kaolin, 2-4 parts bentonite, 0.6-1 part steel fiber, 0.3-0.6 parts polyacrylonitrile fiber, and 0.3-0.5 parts dispersant. The steel fiber is composed of a first steel fiber and a second steel fiber, wherein the first steel fiber and the second steel fiber have different fiber lengths.

[0006] As a further technical solution, the fiber length of the first steel fiber is 12~15mm, and the fiber length of the second steel fiber is 6~9mm.

[0007] As a further technical solution, the mass ratio of the first steel fiber to the second steel fiber is 7:4~5, preferably 7:4.5.

[0008] As a further technical solution, the quicklime is pretreated quicklime, and the preparation method of the pretreated quicklime includes the following steps: A1. Methacryloxysilane is added to solvent I and mixed, then quicklime is added and mixed again, and finally dried to obtain a premix. A2. After adding polylactic acid to solvent II and mixing, a mixture is obtained; A3. Spray the mixture onto the surface of the premixed material, dry it to form a coating layer, and obtain pretreated quicklime.

[0009] In this invention, quicklime is first surface-treated with methacryloyloxysilane, and then coated with a layer of polylactic acid. This effectively slows down the hydration reaction rate of quicklime, avoiding the rapid reaction of quicklime with water, which could lead to defects in the internal structure of the concrete slab. By reducing the reactivity of quicklime, the pore structure of the prepared concrete slab is made more uniform, effectively improving the tensile strength of the concrete slab.

[0010] As a further technical solution, solvent I is anhydrous ethanol; solvent II is N,N-dimethylformamide.

[0011] As a further technical solution, in step A1, the mass ratio of quicklime to methacryloxysilane is 80:0.5~0.8, preferably 80:0.7.

[0012] As a further technical solution, in step A3, the thickness of the coating layer is 0.08~1.12mm.

[0013] As a further technical solution, in step A3, the premixed material is placed in a coating machine, the mixture is sprayed, dried, and a coating layer is formed to obtain pretreated quicklime.

[0014] As a further technical solution, the particle size of the quicklime is 400-500 mesh.

[0015] As a further technical solution, the dispersant includes one or both of stearic acid and dodecylbenzenesulfonic acid.

[0016] This invention also proposes a method for preparing steam-pressurized concrete slabs, comprising the following steps: S1. After mixing the raw materials, a concrete slab is obtained by casting. S2. After steam curing the concrete slab blank, a steam-pressurized concrete slab is obtained.

[0017] As a further technical solution, the autoclaving is performed by steam curing the concrete slab at 190~200℃ and 1.2~1.5MPa for 8~12 hours.

[0018] The working principle and beneficial effects of this invention are as follows: This invention prepares a steam-pressurized concrete slab. By adding polyacrylonitrile fibers and steel fibers of different lengths, the drying shrinkage of the concrete slab can be effectively reduced. Polyacrylonitrile fibers have a high elastic modulus and good dispersibility, and can be uniformly distributed in the concrete matrix. However, their rigid support effect in preventing crack propagation is relatively limited. Steel fibers, on the other hand, have excellent rigid support performance, which can compensate for the lack of rigidity reinforcement of polyacrylonitrile fibers. The synergistic effect of the two can effectively reduce the drying shrinkage of the concrete slab and prevent crack formation. However, although longer steel fibers can effectively prevent further crack propagation, their effect on inhibiting the formation of microcracks is limited. The introduction of short steel fibers can reduce the shrinkage of the concrete slab and prevent crack formation. Therefore, the use of a combination of long and short steel fibers further reduces the drying shrinkage of the concrete slab. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] In the following examples and comparative examples: The cement is silicate cement, type: PO-42.5; manufacturer: Wuxi Jianghuai Building Materials Technology Co., Ltd. Quicklime, model: 0407; manufacturer: Shijiazhuang Yuanjiang Mineral Products Trading Co., Ltd. Quicklime, type: 13; manufacturer: Lingshou County Chengyu Mineral Products Processing Plant; Aluminum powder, average diameter 20μm; Kaolin, with an average particle size of 800 mesh; Bentonite, average particle size 1000 mesh; Polylactic acid, model: FY201; manufacturer: Suzhou Jiangcangfa Plastics Co., Ltd. Polyacrylonitrile fiber, average diameter: 8~12μm, average length: 6~10mm; Manufacturer: Shandong Yongxing New Material Co., Ltd. Gypsum, model: 0014, manufacturer: Yuyao Xinshi Gypsum Products Co., Ltd.; First steel fiber, average diameter: 0.5~1mm, average fiber length: 12~15mm, manufacturer: Anping County Zhihui Engineering Materials Co., Ltd.; The second steel fiber has an average diameter of 0.5-1mm and an average fiber length of 6-9mm. It is manufactured by Anping County Zhihui Engineering Materials Co., Ltd. Example 1 A steam-pressurized concrete slab comprises the following raw materials in parts by weight: 100 parts cement, 40 parts quicklime, 20 parts hydrated lime, 8 parts gypsum, 4 parts aluminum powder, 2 parts kaolin, 2 parts bentonite, 0.6 parts steel fiber, 0.3 parts polyacrylonitrile fiber, and 0.3 parts stearic acid. The steel fiber is composed of a first steel fiber and a second steel fiber in a mass ratio of 7:4. A method for preparing a steam-pressurized concrete slab includes the following steps: S1. After mixing the raw materials, the concrete slab is obtained by casting. S2. After steam curing the concrete slab blank for 8 hours at 190℃ and 1.5MPa, a steam-pressurized concrete slab is obtained.

[0021] Example 2 A steam-pressurized concrete slab comprises the following raw materials in parts by weight: 100 parts cement, 50 parts quicklime, 25 parts hydrated lime, 12 parts gypsum, 5 parts aluminum powder, 3 parts kaolin, 3 parts bentonite, 0.8 parts steel fiber, 0.5 parts polyacrylonitrile fiber, and 0.4 parts stearic acid. The steel fiber is composed of a first steel fiber and a second steel fiber in a mass ratio of 7:4. A method for preparing a steam-pressurized concrete slab includes the following steps: S1. After mixing the raw materials, the concrete slab is obtained by casting. S2. After steam curing the concrete slab blank for 10 hours at 195℃ and 1.3MPa, steam-pressurized concrete slab is obtained.

[0022] Example 3 A steam-pressurized concrete slab comprises the following raw materials in parts by weight: 100 parts cement, 60 parts quicklime, 30 parts hydrated lime, 15 parts gypsum, 6 parts aluminum powder, 4 parts kaolin, 4 parts bentonite, 1 part steel fiber, 0.6 parts polyacrylonitrile fiber, and 0.5 parts stearic acid. The steel fiber is composed of a first steel fiber and a second steel fiber in a mass ratio of 7:4. A method for preparing a steam-pressurized concrete slab includes the following steps: S1. After mixing the raw materials, the concrete slab is obtained by casting. S2. After steam curing the concrete slab blank for 12 hours at 200℃ and 1.2MPa, a steam-pressurized concrete slab is obtained.

[0023] Example 4 The only difference between this embodiment and Embodiment 2 is that the mass ratio of the first steel fiber to the second steel fiber in this embodiment is 7:4.5.

[0024] Example 5 The only difference between this embodiment and Embodiment 2 is that the mass ratio of the first steel fiber to the second steel fiber in this embodiment is 7:5.

[0025] Example 6 The only difference between this embodiment and Embodiment 2 is that the quicklime in this embodiment is pretreated quicklime, and the preparation method of the pretreated quicklime is as follows: A1. Methacryloxysilane was added to anhydrous ethanol (the mass-volume ratio of quicklime to anhydrous ethanol was 1 g: 7 mL), and then quicklime was added and mixed at 40°C for 2 h. After drying, a premix was obtained; wherein the mass ratio of quicklime to methacryloxysilane was 80:0.5. A2. Polylactic acid is added to N,N-dimethylformamide (the mass-volume ratio of polylactic acid to N,N-dimethylformamide is 1g:100mL) and mixed to obtain a mixture. A3. Add the premixed material to the coating machine, spray the mixture, and dry to form a 0.1mm coating layer to obtain pretreated quicklime.

[0026] Example 7 The only difference between this embodiment and Embodiment 6 is that the mass ratio of quicklime to methacryloyloxysilane in this embodiment is 80:0.7.

[0027] Example 8 The only difference between this embodiment and Embodiment 6 is that the mass ratio of quicklime to methacryloyloxysilane in this embodiment is 10:0.1.

[0028] Example 9 The only difference between this embodiment and Example 6 is that the quicklime in this embodiment is modified quicklime. The preparation method of modified quicklime is as follows: Methacryloxysilane is added to anhydrous ethanol (the mass-volume ratio of quicklime to anhydrous ethanol is 1g:7mL), mixed, and then quicklime is added and mixed. After drying, modified quicklime is obtained; the mass ratio of quicklime to methacryloxysilane is 80:0.5.

[0029] Comparative Example 1 The only difference between this comparative example and Example 2 is that the first steel fiber is replaced with a second steel fiber of equal mass in this comparative example.

[0030] Comparative Example 2 The only difference between this embodiment and Embodiment 2 is that the second steel fiber is replaced with the first steel fiber of equal mass in this comparative example.

[0031] Test case The steam-pressurized concrete slabs prepared in Examples 1-9 and Comparative Examples 1-2 were used as test samples, and the following performance tests were conducted: According to GB / T 11969-2020 "Test Methods for Performance of Autoclaved Aerated Concrete", compressive strength, drying shrinkage value, and surface cracks were tested for each group of samples. For the drying shrinkage value test, a standard specimen of 40mm×40mm×160mm was used, and the test results are shown in Table 1 below. For the compressive strength test, a standard specimen of 100mm×100mm×100mm was used, and the test results are shown in Table 2 below. Table 1. Drying shrinkage values ​​and crack presence / absence determination results for Examples 1-5 and Comparative Examples 1-2

[0032] The drying shrinkage values ​​of Examples 1-5 were lower than those of Comparative Examples 1-2, and no cracks were generated in Examples 1-5 after steam pressurization. This indicates that the addition of polyacrylonitrile fibers and steel fibers of different lengths in this invention reduces the drying shrinkage value of steam-pressurized concrete slabs and improves their crack resistance.

[0033] Table 2. Compressive strength test results of Examples 2, 6-9

[0034] The compressive strength of Examples 6-8 is higher than that of Examples 2 and 9, indicating that the addition of pretreated quicklime obtained by first modifying quicklime with methacryloyloxysilane and then coating it with polylactic acid improves the compressive strength of steam-pressurized concrete slabs.

[0035] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A steam-pressurized concrete slab, characterized in that, The raw materials include the following components by weight: 100 parts cement, 40-60 parts quicklime, 20-30 parts hydrated lime, 8-15 parts gypsum, 4-6 parts aluminum powder, 2-4 parts kaolin, 2-4 parts bentonite, 0.6-1 part steel fiber, 0.3-0.6 parts polyacrylonitrile fiber, and 0.3-0.5 parts dispersant. The steel fiber is composed of a first steel fiber and a second steel fiber, and the first steel fiber and the second steel fiber have different fiber lengths.

2. The steam-pressurized concrete slab according to claim 1, characterized in that, The first steel fiber has a fiber length of 12-15 mm, and the second steel fiber has a fiber length of 6-9 mm.

3. The steam-pressurized concrete slab according to claim 1, characterized in that, The mass ratio of the first steel fiber to the second steel fiber is 7:4~5.

4. A steam-pressurized concrete slab according to claim 1, characterized in that, The quicklime is pretreated quicklime, and the preparation method of the pretreated quicklime includes the following steps: A1. Methacryloxysilane is added to solvent I and mixed, then quicklime is added and mixed again, and finally dried to obtain a premix. A2. After adding polylactic acid to solvent II and mixing, a mixture is obtained; A3. Spray the mixture onto the surface of the premixed material, dry it to form a coating layer, and obtain pretreated quicklime.

5. A steam-pressurized concrete slab according to claim 4, characterized in that, In step A1, the mass ratio of quicklime to methacryloxysilane is 80:0.5~0.

8.

6. A steam-pressurized concrete slab according to claim 4, characterized in that, In step A3, the thickness of the coating layer is 0.08~0.12mm.

7. A steam-pressurized concrete slab according to claim 1, characterized in that, The quicklime has a particle size of 400-500 mesh.

8. A steam-pressurized concrete slab according to claim 1, characterized in that, The dispersant includes one or both of stearic acid and dodecylbenzenesulfonic acid.

9. A method for preparing a steam-pressurized concrete slab, used to manufacture a steam-pressurized concrete slab as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. After mixing the raw materials, a concrete slab is obtained by casting. S2. After steam curing the concrete slab blank, a steam-pressurized concrete slab is obtained.

10. The method for preparing a steam-pressurized concrete slab according to claim 9, characterized in that, The autoclaving is performed by steam curing the concrete slab at 190~200℃ and 1.2~1.5MPa for 8~12 hours.

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