A high-performance autoclaved aerated concrete and its preparation process

Abstract

The present invention relates to the technical field of concrete. The present invention discloses a high-performance autoclaved aerated concrete and a preparation process, which comprises raw materials in the following parts by weight: 25-35 parts of quartz sand, 18-22 parts of quicklime, 12-18 parts of cement, 3-5 parts of foaming agent, 5-8 parts of ulexite powder and an appropriate amount of water, with a water-cement ratio of 0.5-0.55. The foaming agent is aluminum powder and silicon powder. The preparation process comprises the following steps: (1) raw material pretreatment; (2) mixing; (3) forming; (4) steam curing. The present invention has the properties of high strength and light weight. By reasonably blending raw materials such as quartz sand, quicklime, and cement, and cooperating with ulexite powder to optimize the crystal structure, a reasonable bubble structure with a gradient distribution of large and small bubbles is formed inside the concrete, improving the heat insulation and sound insulation properties of the material, and the prepared concrete has high compressive strength.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and specifically to a high-performance autoclaved aerated concrete and a preparation process thereof. Background Art

[0002] Autoclaved aerated concrete (AAC) is widely used in the construction industry due to its light weight, heat insulation, sound insulation and other characteristics. Traditional autoclaved aerated concrete uses siliceous materials (such as quartz sand) and calcareous materials (such as cement, quicklime) as the matrix, forms a porous structure through the foaming of aluminum powder, and then generates tobermorite crystals through autoclave curing. However, the existing technology has the following problems:

[0003] The tobermorite crystal structure is loose, resulting in insufficient mechanical properties;

[0004] The porosity uniformity formed by the foaming process is poor, and large-diameter pores are prone to become stress concentration points; the compressive strength is generally lower than 5 MPa, which limits its application in high-rise buildings. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-performance autoclaved aerated concrete and a preparation process thereof, so that the prepared concrete has a small dry density, a high compressive strength, and a high strength-density ratio.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] The high-performance autoclaved aerated concrete of the present invention comprises the following raw materials in parts by weight: 25-35 parts of quartz sand, 18-22 parts of quicklime, 12-18 parts of cement, 3-5 parts of foaming agent, 5-8 parts of ulexite powder, 0.1-0.3 part of foam stabilizer and an appropriate amount of water, the water-cement ratio is 0.5-0.55, and the foaming agent is aluminum powder and silicon powder with a mass ratio of 3:(4-5).

[0008] Preferably, the foaming agent is aluminum powder and silicon powder with a mass ratio of 3:5. Aluminum powder pretreatment: Take aluminum powder with a particle size of 50-100 μm, and then coat the aluminum powder with aluminum phosphate sol, dry it, and the coating thickness is 1-2 μm; Silicon powder pretreatment: Wash and dry with a hydrochloric acid solution with a mass content of 5% and then ball mill it to a particle size of less than 200 nm, and the volume ratio of silicon powder to hydrochloric acid solution is 0.5.

[0009] Preferably, the particle size of the quicklime is 50-100 μm, and 30-40% of the quicklime needs to be modified: coat the quicklime with stearic acid, dry it, and the coating thickness is 1-2 μm; The ulexite powder is selected with a particle size of 5-15 μm, and then coated with a silane coupling agent and dried, and the coating thickness is 0.5-1 μm.

[0010] Preferably, the cement used is sulfoaluminate cement.

[0011] Preferably, it includes 5-10 parts of glass micro-powder with a particle size ≤ 10 μm.

[0012] Preferably, the foam stabilizer is a compound of sodium dodecyl sulfate, hydroxypropyl methylcellulose and nano-SiO 2 in a mass ratio of 1:0.5:0.4.

[0013] Preferably, it includes the following raw materials in parts by weight: 30 parts of quartz sand, 20 parts of quicklime, 15 parts of cement, 4.0 parts of foaming agent, 6.0 parts of ulexite powder, 8.0 parts of glass micro-powder, 0.2 part of foam stabilizer and an appropriate amount of water, with a water-cement ratio of 0.52.

[0014] Preferably, the aluminum phosphate sol is prepared by the following method: using aluminum sulfate Al 2 (SO 4 ) 3 and sodium dihydrogen phosphate NaH 2 PO 4 , respectively preparing an aluminum sulfate solution and an aqueous sodium dihydrogen phosphate solution, slowly dropping the sodium dihydrogen phosphate solution into the aluminum sulfate solution, stirring while dropping, controlling the pH value of the reaction system between 3-5 and reacting for 1 hour, aging for 12 hours, and then washing and filtering with water to obtain the aluminum phosphate sol.

[0015] The preparation process of the high-performance autoclaved aerated concrete of the present invention includes the following steps: (1) Raw material pretreatment: pre-wetting the quartz sand to a moisture content of 8-12%, and activating the ulexite powder at 105 °C for 2 hours; (2) Mixing: mixing all raw materials to obtain a slurry; (3) Molding: pouring the slurry into a mold and standing at 82-85 °C for 2 hours, demolding and cutting into shape; (4) Steam curing: subjecting the cut product to high-pressure steam curing.

[0016] Preferably, in the step (2) mixing: successively adding quartz sand, quicklime, cement, glass micro-powder, ulexite, dry mixing for 5 minutes, then adding silica powder, foam stabilizer and water, wet mixing for 8-10 minutes, standing for 0.5 hour, and then adding aluminum powder and wet mixing for 5-8 minutes to obtain a slurry; in the step (4) steam curing: sending the cut product into a steam curing chamber and heating it to 205 °C at a rate of 30-40 °C / h, maintaining a constant temperature at 1.52-1.55 MPa for 8 hours, and then cooling to room temperature at a cooling rate of 12-13 °C / h.

[0017] The mechanism of action of the present invention:

[0018] Quartz sand is the main silica source for concrete. In concrete, it serves as a skeletal material, providing support for other components and enhancing the overall structural stability of the concrete. At the same time, it participates in the hydration reaction, reacting with other substances to form gelling products, which helps to improve the strength of the concrete. Quicklime is an important calcium source. In concrete, quicklime reacts with water to form calcium hydroxide, providing an alkaline environment for subsequent hydration reactions and promoting the hydration of other cementitious materials. Among them, quicklime coated with stearic acid can slow down its hydration rate, avoid excessive reaction in the early stage, and ensure the workability of the concrete during mixing and forming processes.

[0019] Aluminum powder and silica fume react with water in an alkaline environment to produce hydrogen gas, creating pores inside the concrete, thereby reducing the weight of the concrete and achieving lightweighting. Since the aluminum powder is coated with aluminum phosphate sol and the addition time of the aluminum powder is controlled during mixing, its participation in the gasification reaction can be delayed. Sulfoaluminate cement has a lower pH value compared to ordinary Portland cement, which also relatively delays the gas evolution effect. Part of the quicklime not coated with stearic acid reacts with water first to form calcium hydroxide, releasing a large amount of heat at the same time, providing conditions for the gas production of silica fume. The silica fume generates gas. Due to the relatively small gas production of silica fume, small bubbles are first produced densely in the concrete, and then the coated quicklime continuously hydrolyzes and releases heat, providing an alkaline condition for the gas production of aluminum powder. Aluminum powder will produce a large number of relatively large bubbles during the steam curing stage under high temperature and high pressure. Sodium dodecyl sulfate, as a surfactant, can reduce the surface tension at the gas-liquid interface, making it easier for bubbles to form and stabilize; hydroxypropyl methylcellulose has thickening and water retention effects, which can increase the strength and stability of the bubble liquid film; nano-SiO 2 can fill on the surface of the bubbles, enhancing the stability of the bubbles, preventing the bubbles from merging and bursting, ensuring the uniformity of the internal bubble structure of the concrete, and enabling the formed concrete to form a structure with uniformly distributed large bubbles as the main part and small bubbles densely distributed in the gaps between the large bubbles.

[0020] Ulexite powder: Ulexite decomposes into calcium oxide (CaO) and boron oxide (B 2 O 3 ) in a steam curing environment under high temperature and high pressure. The latter dissolves in an alkaline solution to form boric acid (H 3 BO 3 ), which further dissociates into borate ions (B 3+ ). The B 3+ ions generated by the decomposition of ulexite diffuse into the tobermorite crystal structure. The B 3+ has a smaller radius and partially replaces Si 4+ in the silicon-oxygen tetrahedron of the tobermorite crystal, forming a tighter B-O-Si bond; another part of B 3+ enters the crystal interlayer and combines with calcium ions (Ca 2+)(They) combine to form composite ions, compress the layer spacing, and optimize the crystal structure, thus significantly enhancing the compressive strength of the concrete. At the same time, combined with the micro-aggregate filling effect of glass powder, it can fill the pores inside the concrete, improve the compactness of the concrete, reduce the porosity, and thus enhance the strength of the concrete. Using the coated ulexite powder can improve the interfacial compatibility between ulexite and components such as quartz, cement, and foam stabilizer, and improve the uniformity of the overall system.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention has high strength and lightweight properties. By reasonably blending raw materials such as quartz sand, quicklime, and cement, optimizing the crystal structure with ulexite powder, the synergistic effect of aluminum powder and silicon powder in the foaming agent, and combining with the foam stabilizer to stabilize the bubbles, a reasonable bubble structure with a gradient distribution of large and small bubbles is formed inside the concrete, improving the heat insulation and sound insulation properties of the material. The prepared concrete has a small dry density, a high compressive strength, and a high strength-density ratio. Specific embodiments

[0022] For those not specifying specific conditions in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0023] The following high-performance autoclaved aerated concrete in each example includes the following raw materials: quartz sand, quicklime, cement, foaming agent, ulexite powder, glass powder, foam stabilizer, and an appropriate amount of water, with a water-cement ratio of 0.52. Here, the water-cement ratio in the present invention refers to the weight ratio of the amount of water used to the amount of ash used, and the amount of ash used is the total mass of cement and quicklime.

[0024] The foaming agent is aluminum powder and silicon powder with a mass ratio of 3:5. Pretreatment of aluminum powder: Take aluminum powder with a particle size of 50 - 100 μm, and then coat the aluminum powder with aluminum phosphate sol, dry it, and the coating thickness is 1 - 2 μm; Pretreatment of silicon powder: Wash and dry with a 5% hydrochloric acid solution by mass content, and then ball mill it to a particle size less than 200 nm, and the volume ratio of silicon powder to hydrochloric acid solution is 0.5.

[0025] Select quicklime with a particle size of 50 - 100 μm, and 40% of the quicklime needs to be modified: Coat the quicklime with stearic acid, dry it, and the coating thickness is 1 - 2 μm; Select ulexite powder with a particle size of 5 - 15 μm, and then coat it with a silane coupling agent, dry it, and the coating thickness is 0.5 - 1 μm.

[0026] The aluminum phosphate sol is prepared by the following method:

[0027] Raw materials: Aluminum sulfate Al with a molar ratio of 1:6 2 (SO 4 ) 3 and sodium dihydrogen phosphate NaH 2 PO4 All are analytical pure reagents. Reaction process: Prepare aluminum sulfate solution and sodium dihydrogen phosphate aqueous solution respectively. The amount of water added is twice the amount of water required for complete dissolution. Slowly add the sodium dihydrogen phosphate solution to the aluminum sulfate solution while stirring. The reaction equation is:

[0028] (Al 2 (SO 4 ) 3 +6NaH 2 PO 4 =2Al(H 2 PO 4 ) 3 +3Na 2 SO 4 ;

[0029] Control the reaction temperature at 75 - 80 °C. During the dropping process, control the pH value of the reaction system between 3 - 5 by dropping sodium hydroxide or hydrochloric acid solution, react for 1 hour, age for 12 hours, then wash and filter with water to obtain aluminum phosphate sol.

[0030] Method for coating aluminum powder with aluminum phosphate sol: Under the condition of 20 - 25 °C, add aluminum powder to an appropriate amount of deionized water, ultrasonically disperse for 10 - 30 minutes to make the aluminum powder uniformly dispersed in water to form a suspension. Slowly add the aluminum phosphate sol to the aluminum powder suspension, stir for 2 hours, age for 12 hours, and then wash and filter with deionized water to obtain.

[0031] Method for coating quicklime with stearic acid: Dissolve stearic acid fully with absolute ethanol, add quicklime, stir at 65 - 70 °C for 2 hours, age for 12 hours, and then wash and filter with absolute ethanol to obtain.

[0032] Sulfoaluminate cement is used as the cement.

[0033] Sodium dodecyl sulfate, hydroxypropyl methylcellulose and nano - SiO 2 are compounded according to the mass ratio of 1:0.5:0.4 as the foam stabilizer.

[0034] The preparation method of high-performance autoclaved aerated concrete in the following embodiments includes the following steps: (1) Raw material pretreatment: Pre-wet the quartz sand to a water content of 10% (the water used is included in the water-cement ratio), and activate the ulexite powder at 105°C for 2 hours; (2) Mixing: Add quartz sand, quicklime, cement, glass powder, and ulexite in sequence. After dry mixing for 5 minutes, add silica fume, foam stabilizer, and water, wet mix for 8 - 10 minutes, let stand for 0.5 hour, and then add aluminum powder and wet mix for 5 - 8 minutes to obtain the slurry; (3) Molding: Pour the slurry into the mold and let stand at 82 - 85°C for 2 hours, then demold and cut into shape; (4) Steam curing: Send the cut product into the steam curing chamber and heat it up to 205°C at a rate of 30 - 40°C / h, keep it at a constant temperature of 1.52 - 1.55 MPa for 8 hours, and then cool it down to room temperature at a rate of 12 - 13°C / h.

[0035] The raw materials used in the present invention are:

[0036] Quartz sand, with a particle size of 0.25 - 0.5 mm, SiO 2 The mass content is ≥98%.

[0037] Quicklime: Quicklime with a CaO mass content ≥98%.

[0038] Silica fume refers to elemental silicon powder, and aluminum powder refers to elemental aluminum powder.

[0039] Sulfoaluminate cement: High belite sulfoaluminate cement purchased from Nanjing Leputai New Material Technology Co., Ltd., strength grade: 42.5.

[0040] Ulexite powder: Purchased from Dalian Wobiwo Mining Co., Ltd., Ca 2 B 6 O 11 ·5H 2 The O mass content is ≥98%.

[0041] Glass powder: Glass powder of model JHD - 0058 from Shijiazhuang Jihan East New Material Technology Co., Ltd., with a particle size of 2000 mesh.

[0042] Sodium dodecyl sulfate: Zhechuang brand K12 sodium dodecyl sulfate purchased from Shaoxing Zhechuang Chemical Co., Ltd.

[0043] Hydroxypropyl methylcellulose: Purchased from Shanghai Chenqi Chemical Technology Co., Ltd., model HPMC - 7.5 - 100,000 viscosity.

[0044] Nano SiO 2 : Purchased from Xuzhou Jiechuang New Material Technology Co., Ltd., brand: Hongwu, CAS: 7631869.

[0045] Stearic acid: Purchased from Jiangyin Zhuoqi Trading Co., Ltd., brand and model: Kangqiao 1842.

[0046] Silane coupling agent: The silane coupling agent KH-560 from Dongguan Shanyi Plastic Co., Ltd. was used.

[0047] Each embodiment of the present invention uses the components in Table 1 (the dosage is in parts by weight).

[0048] Table 1

[0049]

[0050] The control examples of the present invention are as follows:

[0051] Control Example 1, the difference from Example 1 is that the foaming agent uses aluminum powder with a particle size of 50-100 μm.

[0052] Control Example 2, the difference from Example 1 is that the foaming agent is aluminum powder and silicon powder with a mass ratio of 4:5, the particle size of aluminum powder is 50-100 μm, the particle size of silicon powder is less than 200 nm, and the aluminum powder and silicon powder are not pretreated.

[0053] Control Example 3, the difference from Example 1 is that borocalcite is replaced with an equal amount of quartz sand.

[0054] Control Example 4, the difference from Example 1 is that the foam stabilizer uses sodium dodecyl sulfate.

[0055] Control Example 5, the difference from Example 1 is that ordinary Portland cement is used.

[0056] Control Example 6, the difference from Example 1 is that quicklime is not subjected to sexual treatment and glass micro powder is not used.

[0057] Control Example 7, the difference from Example 1 is that the preparation method is: the preparation method of high-performance autoclaved aerated concrete: including the following steps: (1) Raw material pretreatment: Pre-wet the quartz sand to a moisture content of 10% (this water is included in the water-cement ratio); (2) Mixing: Mix all the raw materials simultaneously to obtain a slurry; (3) Molding: Pour the slurry into a mold and let it stand at 60-65 °C for 2 hours, then demold and cut into shape; (4) Steam curing: Send the cut product into a steam curing chamber and heat it to 180 °C at a rate of 30-40 °C / h, keep it at a constant temperature of 1.4-1.5 MPa for 8 hours, and then cool it to room temperature at a cooling rate of 15-20 °C / h.

[0058] According to the national standard "Autoclaved Aerated Concrete Blocks", standard number GB / T 11969-2020, standard specimens were prepared and the concrete properties detected are shown in Table 2.

[0059] Table 2

[0060]

[0061] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high performance autoclaved aerated concrete, characterized in that: The raw materials include the following parts by weight: 25-35 parts of quartz sand, 18-22 parts of quicklime, 12-18 parts of cement, 3-5 parts of foaming agent, 5-8 parts of colemanite powder, 0.1-0.3 parts of foam stabilizer and appropriate amount of water, with a water-cement ratio of 0.5-0.

55. The foaming agent is aluminum powder and silicon powder in a mass ratio of 3: (4-5); the foaming agent is aluminum powder and silicon powder in a mass ratio of 3:

5. Aluminum powder pretreatment: take a particle size of 50- 100μm aluminum powder, then coated with aluminum phosphate sol, dried, and the coating thickness is 1-2μm; silicon powder pretreatment: cleaned and dried with 5% hydrochloric acid solution, ball milled to a particle size of less than 200nm, the volume ratio of silicon powder to hydrochloric acid solution is 0.5; quicklime with a particle size of 50-100μm is selected, and 30-40% quicklime is modified: quicklime is coated with stearic acid, dried, and the coating thickness is 1-2μm; The colemanite powder has a particle size of 5-15 μm, is coated with a silane coupling agent, and is dried, with a coating layer thickness of 0.5-1 μm.

2. The high performance autoclaved aerated concrete according to claim 1, characterized in that: The cement is sulphoaluminate cement.

3. The high performance autoclaved aerated concrete according to claim 2, characterized in that: The invention comprises 5-10 parts of glass powder with a particle size of ≤10 μm.

4. The high performance autoclaved aerated concrete according to claim 3, characterized in that: The foam stabilizer is prepared by mixing sodium lauryl sulfate, hydroxypropyl methylcellulose and nano-SiO2 in a mass ratio of 1:0.5:0.

4.

5. The high performance autoclaved aerated concrete according to claim 4, characterized in that: The method comprises the following raw materials in parts by weight: 30 parts of quartz sand, 20 parts of quicklime, 15 parts of cement, 4.0 parts of foaming agent, 6.0 parts of calcium borate powder, 8.0 parts of glass micropowder, 0.2 parts of foam stabilizer and appropriate amount of water, with a water-cement ratio of 0.

52.

6. The high performance autoclaved aerated concrete according to claim 5, characterized in that: The aluminum phosphate sol is prepared by the following method: aluminum sulfate Al2(SO4)3 and sodium dihydrogen phosphate NaH2PO4 are used in a molar ratio of 1:6 to prepare an aluminum sulfate solution and a sodium dihydrogen phosphate aqueous solution respectively, and the sodium dihydrogen phosphate solution is slowly added dropwise to the aluminum sulfate solution while stirring, the pH value of the reaction system is controlled between 3 and 5, the reaction is carried out for 1 hour, the reaction is aged for 12 hours, and then the reaction is carried out with water and filtered to obtain the aluminum phosphate sol.

7. A process for preparing high performance autoclaved aerated concrete according to any one of claims 3 to 6, characterized in that: The method comprises the following steps: (1) raw material pretreatment: pre-wetting quartz sand to a moisture content of 8-12%, and activating colemanite powder at 105° C. for 2 hours; (2) mixing: mixing all raw materials to obtain slurry; (3) molding: pouring the slurry into a mold and leaving it at 82-85° C. for 2 hours, demolding and cutting into shape; and (4) steam curing: steam curing the cut product under high pressure.

8. The process for preparing high performance autoclaved aerated concrete according to claim 7, characterized in that: The step (2) of mixing is as follows: quartz sand, quicklime, cement, glass powder and colemanite are added in sequence, and dry mixed for 5 minutes, followed by adding silicon powder, foam stabilizer and water, and wet mixed for 8-10 minutes, and allowed to stand for 0.5 hours, and then adding aluminum powder and wet mixed for 5-8 minutes to obtain slurry; the step (4) of steam curing is as follows: the cut product is sent to a steam curing chamber and heated to 205°C at 30-40°C / h, maintained at a constant temperature for 8 hours at a pressure of 1.52-1.55MPa, and then cooled to room temperature at a rate of 12-13°C / h.

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