Preparation method of coal gangue autoclaved aerated concrete and application of regulator thereof

Abstract

A preparation method of coal gangue autoclaved aerated concrete and application of a regulator thereof, the regulator comprising a combination of one or more of silica fume, silica sol, sodium tripolyphosphate, etc. A coal gangue autoclaved aerated concrete, raw materials of the coal gangue autoclaved aerated concrete comprising more than 50% of coal gangue in total mass of the raw materials of the coal gangue autoclaved aerated concrete. A method for preparing coal gangue autoclaved aerated concrete, comprising: step 1: decarburization treatment of the coal gangue, the decarburization treatment comprising photoelectric sorting and / or water washing flotation; after the decarburization treatment, the carbon content of the gangue is less than or equal to 7%; step 2: mixing and stirring the raw materials of the coal gangue autoclaved aerated concrete, then pouring and standing, cutting and demolding, pre-curing, autoclaved curing to obtain the autoclaved aerated concrete. The method can greatly shield or reduce the influence of carbon content and low activity of coal gangue and improve the compressive strength of the product by multi-stage decarburization, single-doped and multi-doped complex doped regulator.

Description

Technical Field

[0001] This invention relates to a technology for preparing autoclaved aerated concrete, specifically a technology for preparing autoclaved aerated concrete from coal gangue. Background Technology

[0002] With the rapid development of industry and infrastructure projects, a large amount of solid waste is generated. Coal gangue is a type of solid waste separated during coal mining; it is a blackish-gray rock that is associated with coal during coal formation. The main mineral components of coal gangue are clay minerals (kaolinite, montmorillonite, illite, etc.), quartz, dolomite, pyrite, and other minerals. The environmental harm caused by large-scale coal gangue accumulation is obvious, including land occupation, land subsidence, soil erosion, desertification, and ecological damage. The accumulation and prolonged exposure of coal gangue also makes it prone to spontaneous combustion, resulting in serious environmental problems such as dust and the emission of harmful gases (CO, CO2, SO2, H2S).

[0003] Currently, coal gangue in my country is mainly used in road construction, power generation, and building materials, accounting for 56%, 32%, and 12% of the total utilization rate of coal gangue, respectively. Therefore, increasing the application of coal gangue in building materials is an important way to achieve resource utilization of coal gangue, comprehensive environmental management, social development, and economic improvement.

[0004] Autoclaved aerated concrete (AAC) blocks have a unit volume weight that is one-third that of clay bricks, thermal insulation performance that is 3-4 times that of clay bricks, sound insulation performance that is twice that of clay bricks, impermeability performance that is more than twice that of clay bricks, and fire resistance performance that is 6-8 times that of reinforced concrete. The masonry strength of the blocks is approximately 80% of the block's own strength (compared to 30% for red bricks). They are particularly suitable for interior and exterior infill walls in high-rise buildings and underground infill walls (except for walls with special requirements), and their construction characteristics are also excellent.

[0005] Autoclaved aerated concrete (AAC) is a porous silicate product made primarily from siliceous and calcareous materials, with the addition of a foaming agent. It is produced through processes such as raw material preparation, batching and pouring, foaming and static curing, cutting and shaping, autoclaving and curing, sorting and packaging. Its typical characteristic is that the pores in the product are formed by chemical reactions.

[0006] The raw materials used in the production of autoclaved aerated concrete (AAC) are divided into four main categories: basic materials, gas-generating materials, conditioning materials, and structural materials. Basic materials constitute the main body of AAC, accounting for over 95% of the total product weight. These include two main categories: siliceous materials (primarily SiO2) and calcareous materials (primarily CaO). Siliceous raw materials are primarily sourced from quartz sand, accounting for 55%–65% of the product weight. Calcium-rich raw materials are mainly sourced from cement and lime, accounting for over 30% of the product weight.

[0007] Since sand is a non-renewable mineral resource, developing coal gangue to replace siliceous materials not only provides an effective way to save energy, conserve soil, utilize waste, and protect the environment, but also offers a sustainable development path for autoclaved aerated concrete (AAC) production enterprises to reduce costs and improve efficiency. However, the low volcanic ash activity of raw coal gangue hinders its application in AAC preparation. While spontaneous combustion can largely solve the problem of high carbon content and improve raw material activation to some extent, the carbon dioxide, sulfur dioxide, nitrogen oxides, and soot emitted during combustion severely pollute the atmosphere. Furthermore, spontaneous combustion of coal gangue exhibits significant regionality, specificity, and incompleteness. Therefore, spontaneous combustion or combustion methods cannot solve the industrial application problem of coal gangue in AAC preparation. Additionally, in related technologies, AAC prepared using coal gangue often has low compressive strength, failing to meet relevant national standards. Therefore, there is an urgent need to study a technology that incorporates coal gangue in a large amount into the raw materials for preparing autoclaved aerated concrete (AAC). This technology should be able to be stably applied in industrialization, and the resulting products should have high compressive strength and meet national quality standards. Summary of the Invention

[0008] This invention aims to solve the problems existing in the preparation of autoclaved aerated concrete using coal gangue in related technologies, and provides a technology for preparing autoclaved aerated concrete using a larger amount of coal gangue. The resulting product has high compressive strength and meets national quality standards.

[0009] To address the aforementioned limitations, this invention proposes a modifier for coal gangue autoclaved aerated concrete, coal gangue autoclaved aerated concrete, and a method for preparing the same.

[0010] A modifier for autoclaved aerated concrete made from coal gangue, wherein the modifier is selected from:

[0011] Group 1: Silica ash;

[0012] And / or, Group 2: silica sol;

[0013] The regulator accounts for 3.0% to 15.0% of the total mass of the raw materials in the coal gangue autoclaved aerated concrete.

[0014] Further: If the regulator is a first group and a second group, the mass ratio of the first group to the second group is (2:3) to (5:2).

[0015] A modifier for autoclaved aerated concrete made from coal gangue, wherein the modifier is selected from:

[0016] Group 1: Silica ash;

[0017] And / or at least one of the second, third, and fourth groups;

[0018] The second group is silica sol;

[0019] The third group is sodium tripolyphosphate;

[0020] The fourth group consists of at least one of glass fiber powder, hydroxypropyl methylcellulose, and lignin sulfonate.

[0021] The regulator accounts for 3.0% to 15.0% of the total mass of the raw materials in the coal gangue autoclaved aerated concrete.

[0022] Further: If the regulator includes a first group and a third group, the mass ratio of the first group to the third group is 5:2;

[0023] Further: If the regulator includes a first group and a fourth group, the mass ratio of the first group to the fourth group is (5:1) to (5:4).

[0024] A type of autoclaved aerated concrete (AAC) made from coal gangue, wherein the raw materials for AAC include:

[0025] Coal gangue, wherein the mass of the coal gangue accounts for more than 50% of the total mass of the raw materials for autoclaved aerated concrete made from coal gangue; and the carbon content of the coal gangue is less than or equal to 7%.

[0026] The regulators mentioned above account for 3.0% to 15.0% of the total mass of the raw materials in the coal gangue autoclaved aerated concrete.

[0027] Furthermore: the raw materials for the coal gangue autoclaved aerated concrete include the following components, all by mass:

[0028] The coal gangue is 50-70 parts;

[0029] 0.65 to 0.75 parts of warm water at 50℃ to 60℃;

[0030] The regulator is 3 to 15 parts;

[0031] 12-20 parts lime;

[0032] 10-20 parts cement;

[0033] 2-8 parts plaster;

[0034] 0.05 to 0.12 parts of aluminum powder.

[0035] Furthermore: the strength grade of the coal gangue autoclaved aerated concrete meets the requirements of grades A2.0 to A5.0 in the following table:

[0036]

[0037] A method for preparing autoclaved aerated concrete from coal gangue, the method comprising:

[0038] Step 1: The coal gangue is subjected to decarbonization treatment, which includes photoelectric separation and / or water washing flotation; after the decarbonization treatment, the carbon content of the gangue is ≤7%;

[0039] Step 2: Using the above-mentioned raw materials for coal gangue autoclaved aerated concrete, prepare the coal gangue autoclaved aerated concrete;

[0040] The strength grade of the coal gangue autoclaved aerated concrete meets the requirements of grades A2.0 to A5.0 in the following table:

[0041]

[0042] Furthermore, after the decarburization treatment, the carbon content of the gangue is ≤3%.

[0043] Further: Step 2 includes: mixing and stirring the raw materials of the coal gangue autoclaved aerated concrete, then pouring and stopping, cutting and demolding, pre-curing in the autoclave, and autoclaving to obtain coal gangue autoclaved aerated concrete.

[0044] Compared with related technologies, the present invention has the following advantages:

[0045] This invention discloses a regulator for autoclaved aerated concrete (AAC) made from coal gangue. Specifically selected based on the unique characteristics of coal gangue raw materials, and employing single-admixture, double-admixture, and composite admixture techniques, the comprehensive performance of the obtained AAC products is significantly improved. The regulator of this invention encapsulates carbon particles in coal gangue, shielding or reducing the adverse effects of carbon in the coal gangue. It also has an activating effect, increasing the pozzolanic activity of the coal gangue raw materials for AAC preparation, promoting the full hydration reaction, and improving the hydration quality and strength of the product. Therefore, the regulator combines the functions of an activator that enhances the reactivity of the raw materials for AAC preparation and a regulator that improves the strength of the product, thus possessing significant innovative value. Using the regulator of this invention is beneficial for improving the durability, sealing, impermeability, corrosion resistance, impact resistance, and wear resistance of the product.

[0046] In another aspect, the autoclaved aerated concrete (AAC) prepared from coal gangue, due to the use of the aforementioned regulator, achieves a large-scale application of coal gangue in AAC. This not only effectively reduces the preparation cost of AAC but also solves the environmental problems caused by coal gangue and saves on the treatment costs associated with coal gangue disposal. Furthermore, the use of the regulator can compensate for and enhance the pozzolanic activity of the coal gangue raw material in AAC, promoting the full hydration reaction, improving the hydration quality and strength of the product, and thus enhancing its durability, sealing properties, impermeability, corrosion resistance, impact resistance, and wear resistance.

[0047] Another aspect of this invention relates to a method for preparing autoclaved aerated concrete (AAC) from coal gangue. By using the aforementioned regulator, this method enables the large-scale application of coal gangue in AAC, effectively reducing the preparation cost of AAC and solving the environmental problems caused by coal gangue, while also saving on the treatment costs associated with coal gangue disposal. Furthermore, the use of the regulator can compensate for and enhance the pozzolanic activity of the coal gangue raw material in AAC, promoting the full hydration reaction, improving the hydration quality and strength of the product, and ultimately enhancing its durability, sealing properties, impermeability, corrosion resistance, impact resistance, and wear resistance. Attached Figure Description

[0048] Figure 1 Photographs of coal gangue autoclaved aerated concrete products from Experimental Examples 1-3 of an embodiment of the present invention;

[0049] Figure 2 is an XRD diffraction pattern of autoclaved aerated concrete made of coal gangue according to another embodiment of the present invention; wherein, (1) is the quantitative XRD pattern of No. 1 coal gangue; (2) is the quantitative XRD pattern of No. 2 coal gangue; and (3) is the XRD pattern of No. 7 sample of No. 1 coal gangue (Experimental Example 1).

[0050] Figure 3 This is a SEM image of autoclaved aerated concrete made from coal gangue according to another embodiment of the present invention;

[0051] Figure 4 This is a flowchart of the physical decarbonization treatment of coal gangue raw material according to another embodiment of the present invention;

[0052] Figure 5 is a photograph of the coal gangue autoclaved aerated concrete products of Experimental Examples 4-6 of another embodiment of the present invention; (1) is Experimental Example 6; (2) is Experimental Example 5; (3) is Experimental Example 4;

[0053] Figure 6 These are photographs of coal gangue autoclaved aerated concrete products from Experimental Examples 7-8 of another embodiment of the present invention;

[0054] Figure 7 This is the XRD diffraction pattern of No. 4 coal gangue material according to another embodiment of the present invention;

[0055] Figure 8 This is a comparison photo of the exterior. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below. However, it should be understood that the description herein is merely illustrative and not intended to limit the scope of the invention.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. All characterization techniques mentioned herein can be found in relevant descriptions in the prior art, and will not be repeated here.

[0058] To further understand the present invention, the present invention will be further described in detail below with reference to the preferred embodiments.

[0059] Coal gangue is a mixture of various rock fragments with a complex composition. Chemically, it consists of inorganic matter and a small amount of organic matter. The inorganic matter primarily comprises minerals and water, with dozens of elements constituting the mineral components, generally SiO2 and Al2O3 as the main components. It also contains varying amounts of Fe2O3, CaO, MgO, SO3, K2O, Na2O, P2O3, and trace amounts of rare metals (such as titanium, vanadium, and cobalt). The organic matter content in coal gangue increases with the coal content, and it mainly includes carbon, hydrogen, oxygen, nitrogen, and sulfur. The total content of inorganic matter (SiO2 and Al2O3) in coal gangue is generally above 70%, and in some cases exceeds 90%. The SiO2 content is generally above 50%, and in some cases reaches 80%. Therefore, coal gangue has inherent potential as a siliceous material for autoclaved aerated concrete (AAC) production.

[0060] However, compared to other minerals with pozzolanic activity (including fly ash from power plants), the minerals composing coal gangue tend to have better crystallinity, higher degree of chemical molecular order, and tighter arrangement, resulting in a more stable chemical structure. Therefore, raw coal gangue has very low pozzolanic activity. At the same time, the presence of combustible carbon in coal gangue generally poses a certain obstacle to its direct utilization. Class I and II coal gangue have a carbon content ≤6% (lower calorific value below 420 kcal); Class III coal gangue has a carbon content of 6%–20%, falling between Class II and Class IV; Class IV coal gangue has a carbon content ≥20% and a higher calorific value (lower calorific value ≥1400 kcal / kg).

[0061] Our long-term research has revealed significant differences in the form and structure of carbon in coal gangue and fly ash. In coal gangue, carbon is mostly mixed, interwoven, and encapsulated with various minerals such as quartz, alumina, and carbonates, or exists as various carbonate mineral phases such as calcite, mica, kaolinite, and illite. In contrast, carbon in fly ash is primarily in the form of coarse and porous coke particles or semi-coke particles, mixed within the aluminosilicate glass (generally accounting for about 70%) and other crystalline minerals (mullite, quartz, hematite, etc.) of the fly ash raw materials. Unlike fly ash, coal gangue exhibits lower pozzolanic activity. Therefore, to address the issue of activating coal gangue and achieving stable industrial application in the preparation of autoclaved aerated concrete (AAC) using large-volume coal gangue, a stable, reliable, cost-effective, and industrially suitable method is needed to solve both the activation problem of coal gangue and the compressive strength problem of the resulting products.

[0062] Example 1

[0063] like Figure 1 As shown, a modifier for autoclaved aerated concrete made from coal gangue, wherein the modifier is selected from:

[0064] Group 1: Silica ash;

[0065] And / or, Group 2: silica sol;

[0066] Further: If the regulator uses the first group and the second group, the mass ratio of the first group to the second group is (2:3) to (5:2), for example, it can be 2:5, 1:1, 1:2, 2:3, 3:2, 3:4 or 3:5, etc., but the present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0067] The modifier accounts for 3.0% to 15.0% of the total mass of the raw materials in the coal gangue autoclaved aerated concrete. For example, it can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. The present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0068] The average particle size of silica fume is 0.1–0.3 μm, with over 80% having a fineness of less than 1 μm. Its specific surface area is 20–28 m². 2 / g. Its fineness and specific surface area are about 80 to 100 times that of cement and 50 to 70 times that of fly ash.

[0069] During its formation, silica fume undergoes a phase transformation under the influence of surface tension, resulting in amorphous, non-crystalline spherical particles with relatively smooth surfaces. Some particles are aggregates of multiple spherical particles bonded together. It is a highly reactive volcanic ash material with a large specific surface area, dispersed within the gaps between other coarse particles. It hydrates with alkaline oxides to form a gel, and under high temperature and pressure conditions, it readily forms tobermorite, increasing the strength of the finished product.

[0070] Using an appropriate amount of silica fume in autoclaved aerated concrete made from coal gangue can help compensate for the insufficient SiO2 in coal gangue, increase the density of the product, increase the strength of the product, improve the durability of the product, and improve the product's impermeability, corrosion resistance, impact resistance and wear resistance.

[0071] Silica sol is a dispersion system containing a large number of hydrated SiO2 particles, characterized by its high surface free energy. It has low viscosity and can penetrate anywhere water can, resulting in excellent dispersibility and permeability when mixed with other substances. When the water in silica sol evaporates, the colloidal particles firmly adhere to the surface of the object, forming silicon-oxygen bonds between the particles, making it an excellent adhesive.

[0072] In coal gangue autoclaved aerated concrete (AAC), silica sol plays a crucial role not only in its good dispersibility and permeability but also in encapsulating low-hardness, non-hydrothermal-synthetic carbon-like powder particles. These particles then undergo a hydrothermal synthesis reaction with Ca(OH)₂, forming monoalkali hydrates CSH-(I) and CSH gel near the carbon particles. This partially recrystallizes into tobermorite, shielding the carbon-like particles from affecting the strength of the product and improving its strength and other physical properties. Furthermore, the small particle size of silica sol helps increase the density of the pore walls in the coal gangue autoclaved concrete, thereby enhancing the product's sealing and impermeability, and further improving its physical strength.

[0073] Due to its dispersibility, permeability, and large specific surface area, silica sol penetrates into the interior of coal gangue carbon particles during slurry preparation, forming a network-like coating around them. When alkaline raw materials such as cement and lime are added, the silica sol, being nano-sized silica, reacts with the hydrated calcium hydroxide in the cement and lime to form hydrated calcium silicate (CSH(I)), resulting in strong adhesion between the raw materials (including carbon particles) within the green body. With the implementation of autoclaving, most of this hydrated calcium silicate gradually transforms into well-crystallized tobermorite, increasing the strength of the coal gangue autoclaved aerated concrete (AAC), thereby avoiding or reducing the impact of carbon in the coal gangue on its strength. Therefore, silica sol also acts as a modifier for coal gangue.

[0074] Example 2

[0075] A modifier for autoclaved aerated concrete made from coal gangue, wherein the modifier is selected from:

[0076] Group 1: Silica ash;

[0077] And / or at least one of the second, third, and fourth groups;

[0078] The second group is silica sol;

[0079] The third group is sodium tripolyphosphate;

[0080] The fourth group consists of at least one of glass fiber powder, hydroxypropyl methylcellulose, and lignin sulfonate.

[0081] The modifier accounts for 3.0% to 15.0% of the total mass of the raw materials in the coal gangue autoclaved aerated concrete. For example, it can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. The present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0082] Further: If the regulator includes a first group and a third group, the mass ratio of the first group to the third group is 5:2;

[0083] Further: If the regulator includes a first group and a fourth group, the mass ratio of the first group to the fourth group is (5:1) to (5:4), for example, it can be 5:1, 5:2, 5:3 or 5:4. The present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0084] Research has shown that the above-mentioned ratio of regulators can achieve better compressive strength of the product. The method of using regulators can be determined according to the actual situation. They can be used individually, or in combination or in multiple ways. Mixed use can not only reduce costs, but also exert synergistic effects and achieve better product strength.

[0085] The regulator includes a first group and a third group, for example, the regulator is a first group and a third group, or the regulator is a first group, a second group, and a third group; or the regulator is a first group, a second group, a third group, and a fourth group; or other combinations including a first group and a third group.

[0086] The regulator includes a first group and a fourth group. For example, the regulator is a first group and a fourth group, or the regulator is a first group, a second group, and a fourth group; or the regulator is a first group, a second group, a third group, and a fourth group; or other combinations including a first group and a fourth group.

[0087] Preferably, the regulator is silica fume;

[0088] Alternatively, the regulator may be silica fume and silica sol;

[0089] Alternatively, the regulator may be silica fume or sodium tripolyphosphate;

[0090] Alternatively, the regulator may be silica fume or glass fiber powder;

[0091] Alternatively, the regulator may be silica fume or hydroxypropyl methylcellulose;

[0092] Alternatively, the regulator may be silica fume or lignin sulfonate;

[0093] Alternatively, the regulator may be silica sol;

[0094] Alternatively, the regulator may be silica fume, silica sol, or sodium tripolyphosphate;

[0095] Alternatively, the regulator may be silica fume, silica sol, or glass fiber powder;

[0096] However, the present invention is not limited to the combinations listed, and other unlisted combinations are equally applicable within the scope of the above description of the modifiers of the present invention.

[0097] Sodium tripolyphosphate (STP) aqueous solutions are quite stable at room temperature. However, heating, adding acid, or adding alkali promotes hydrolysis, resulting in a decreasing content of sodium tripolyphosphate, which eventually reverts to its original orthophosphate form. The hydrolysis reaction is as follows:

[0098] Na5P3O 10 +H₂O→Na₂HPO₄+NaH₂PO₄

[0099] For example, sodium tripolyphosphate hexahydrate is stable at 80℃, but it dehydrates and decomposes into sodium dihydrogen phosphate and sodium pyrophosphate at 85-120℃, and then recombines into sodium tripolyphosphate at temperatures above 120℃.

[0100] Sodium tripolyphosphate (STP) possesses numerous excellent properties, making it suitable for application in autoclaved aerated concrete (AAC) made from coal gangue. Firstly, it leverages its complexing effect on metal ions in the raw materials, preventing metal aggregation and thus avoiding uneven density in the finished product. Secondly, its strong dispersing power for solid particles stimulates the activity and dissolution of SiO2 and CaO in the raw materials, promoting thorough hydration reactions and improving the hydration quality and strength of the finished product. Thirdly, it increases the fluidity of the slurry and promotes hydrolytic stability.

[0101] Glass fiber powder is made by cutting, grinding and sieving specially drawn continuous glass fiber filaments. It is widely used as a filler and reinforcing material in various thermosetting and thermoplastic resins.

[0102] Performance indicators: Density: 2.254 g / cm³ 3Moisture content: <0.5% Fiber diameter: 9-13μm Aspect ratio: 4:1-8:1 Particle size: 300-400 Fiber composition: E glass (alkali content <0.5%) C glass (alkali content <12%).

[0103] Its application in autoclaved aerated concrete (AAC) made from coal gangue can enhance its low-temperature crack resistance and fatigue resistance, improve its high-temperature stability, and extend its service life.

[0104] Hydroxypropyl methylcellulose (HPMC), also known as hydroxypropyl methylcellulose, is a type of nonionic cellulose mixed ether. Its aqueous solution exhibits surface activity. It has high transparency and stable performance. Different specifications of HPMC have different gelation temperatures, and its solubility varies with viscosity; the lower the viscosity, the greater the solubility. The solubility of HPMC in water is not affected by pH.

[0105] When applied in autoclaved aerated concrete made from coal gangue, it promotes the bonding of raw materials, facilitates molding and demolding, and increases the strength of the finished product.

[0106] Calcium lignosulfonate (abbreviated as calcium lignosulfonate) is a multi-component high molecular weight polymer anionic surfactant. It appears as a light yellow to dark brown powder with a slightly aromatic odor. Its molecular weight is generally between 800 and 10,000. It has strong dispersibility, binding and chelating properties.

[0107] When used as a concrete water-reducing agent, adding 0.25-0.3% of the cement content can reduce water consumption by 10-14% or more, improve concrete workability, significantly improve operational performance, and have good effects such as strengthening and preventing cracking.

[0108] Silica fume, silica sol, and sodium tripolyphosphate act as both activators and reinforcing agents, promoting the hydration reaction of coal gangue in the preparation of autoclaved aerated concrete (AAC), thereby significantly improving the compressive strength of the product. This additive, possessing both activating and reinforcing properties, solves the technical problem of using large quantities of coal gangue in the preparation of AAC. Furthermore, the preparation method is stable and reliable, allowing for industrial application. This addresses the long-standing problem of the industrial application of coal gangue in AAC, thus possessing significant innovative value.

[0109] Glass fiber powder, hydroxypropyl methylcellulose, and calcium lignosulfonate act as fiber reinforcement. It can be understood that adding sodium tripolyphosphate, glass fiber powder, hydroxypropyl methylcellulose, and lignosulfonate is a further improvement on the silica fume and silica sol solution; alternatively, only silica fume or silica sol can be used as a modifier.

[0110] Example 3

[0111] Based on Example 1 or 2, a coal gangue autoclaved aerated concrete is provided, wherein the raw materials for the coal gangue autoclaved aerated concrete include:

[0112] The coal gangue constitutes more than 50% of the total mass of the raw materials for autoclaved aerated concrete; for example, it can be 55%, 60%, 65% or 70%. This invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable. The carbon content of the coal gangue is less than or equal to 7%; for example, it can be 1%, 2%, 3%, 4%, 5%, 6% or 7%. This invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0113] The regulator described in Example 1 or 2 accounts for 3.0% to 15.0% of the total mass of the raw materials for autoclaved aerated concrete made from coal gangue. For example, it can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. This invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0114] Example 4

[0115] Based on Example 3, the raw materials for the coal gangue autoclaved aerated concrete further include the following components, all by mass:

[0116] The amount of coal gangue is 50 to 70 parts; for example, it can be 50, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64 or 70. The present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0117] 0.65 to 0.75 parts of warm water at 50℃ to 60℃; for example, it can be warm water at 50℃, 52℃, 54℃, 56℃, 58℃ or 60℃. This invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable. The number of parts of warm water can be, for example, 0.65, 0.66, 0.67, 0.68, 0.69, 0.7, 0.71, 0.72, 0.73, 0.74 or 0.75 parts. This invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0118] The regulator is 3 to 15 parts; for example, it can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14 or 15 parts. The present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0119] 12 to 20 parts of lime; for example, it can be 12, 13, 14, 15, 16, 17, 18, 19 or 20 parts. The present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0120] 10 to 20 parts of cement; for example, it can be 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20 parts. This invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0121] 2 to 8 parts of plaster; for example, it can be 2, 3, 4, 5, 6, 7 or 8 parts. This invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0122] The aluminum powder is 0.05 to 0.12 parts. For example, it can be 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11 or 0.12 parts. The present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0123] Cement and lime are the main sources of calcium-based raw materials for coal gangue autoclaved aerated concrete, accounting for about 30% of the product weight.

[0124] Furthermore: the strength grade of the coal gangue autoclaved aerated concrete meets the requirements of grades A2.0 to A5.0 in the following table:

[0125]

[0126]

[0127] Example 5

[0128] Based on Example 3 or 4, a method for preparing coal gangue autoclaved aerated concrete (AAC) is provided, which uses the above-mentioned coal gangue AAC raw materials to prepare AAC; the method includes:

[0129] Step 1: Decarbonize the coal gangue, the decarbonization process including photoelectric separation and / or water washing flotation;

[0130] After the decarburization treatment, the carbon content of the gangue is less than or equal to 7%; for example, it can be 1%, 2%, 3%, 4%, 5%, 6% or 7%. The present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0131] Step 2: Mix and stir the raw materials of the coal gangue autoclaved aerated concrete described in Example 3 or 4, then pour, stop, cut and demold, pre-cur in front of the autoclave, and autoclave to obtain the coal gangue autoclaved aerated concrete.

[0132] The strength grade of the coal gangue autoclaved aerated concrete meets the requirements of A2.0-A5.0 in the table below, for example, it can be A2.0, A2.5, A3.5 or A5.0.

[0133] Table 1 Compressive Strength and Dry Density Requirements

[0134]

[0135]

[0136] The table above is selected from "GB / T11968-2020 Autoclaved Aerated Concrete Blocks".

[0137] Practice has shown that for coal gangue processed by electro-optical separation and water washing flotation, a carbon content of less than 3% has almost no significant impact on the production of finished products (see...). Figure 1 This experiment used raw material #3. Autoclaved aerated concrete (AAC) was prepared using coal gangue raw material after photoelectric dry separation. For raw materials with a carbon content exceeding 7%, further treatment with water washing and flotation is necessary to obtain raw materials with a carbon content below 7%, thus achieving favorable application conditions. Therefore, multi-stage physical decarbonization using electro-optical separation and water washing flotation ensures that the carbon content of the coal gangue is ≤7%. This allows coal gangue with a carbon content above 7% to meet application requirements after only two stages of separation, thereby expanding the scope of usable coal gangue and fundamentally solving the problem of coal gangue resource utilization.

[0138] For gangue with a carbon content of 7% or less, using regulators (reinforcing agents) or a combination of multiple regulators (reinforcing agents) can produce better qualified products, and the compressive strength of the products can be significantly enhanced. After decarburization by the above physical methods, the coal gangue fines with a carbon content of less than 7% are further ball-milled to a particle size of ≤15% residue on a 200-mesh sieve, and then proceed with subsequent raw material mixing steps.

[0139] The XRD diffraction pattern of the coal gangue autoclaved aerated concrete sample of the present invention shows that the main mineral composition of the sample is tobermorite, CSH gel, anhydrite, quartz, dolomite, calcite, calcium carbide, pseudowollastonite, hydrous kaolinite and other minerals (see Figure 2).

[0140] like Figure 3 As shown, SEM (scanning electron microscopy) revealed that the hydrothermal synthesis products of coal gangue autoclaved aerated concrete mainly consist of platy tobermorite, acicular CSH, hydrated calcium sulfoaluminate, and other unreacted minerals. The CSH gel binds a large number of high-strength tobermorite crystals together with other phases, while the distribution of unreacted minerals is not too concentrated, thus ensuring good strength and stability of the product.

[0141] like Figure 4 As shown, the beneficial effects of the physical decarbonization method used in one embodiment of the present invention are explained below:

[0142] (1) The calorific value of black gangue separated by photoelectric sorting machine is about 3200 kcal or more. The company sells it as energy recovery, and the current market price is 300 yuan / ton. A production line with a daily processing capacity of 2000 tons of coal gangue can recover about 400 tons of black gangue with higher calorific value per day, which can generate an income of about 120,000 yuan.

[0143] (2) The white gangue (raw material with slightly higher calcium and magnesium content) separated by the photoelectric separator has a carbon content of about 10% (calorific value of about 650 kcal), which is material No. 2 used in this experiment. With excellent separation results, the carbon content of the white gangue (raw material with slightly higher calcium and magnesium content) can be controlled below 5% (calorific value ≤ 350 kcal / kg), which is material No. 1 used in this experiment. A production line with a daily coal gangue processing capacity of 2000t can separate approximately 300t / day of white gangue calcium-magnesium material, which, after hammer crushing / screening, is used as raw material for autoclaved aerated concrete (capable of meeting the annual production of 1 million m³). 3 Materials used in large-scale autoclaved aerated concrete production;

[0144] (3) The calorific value of the coal gangue raw material after black coal and white calcium magnesium gangue are separated by photoelectric separator is about 900 kcal. A production line with a daily coal gangue processing capacity of 2000t can sort about 500t of coal gangue raw material per day. After hammer crushing / screening, it can be directly used as raw material for sintered bricks (which can meet the material needs of a production line with an annual output of 150 million sintered bricks).

[0145] (4) The calorific value of the fine material separated by a 1.5cm spherical screen is about 1350 kcal. A production line with a daily processing capacity of 2000t of coal gangue produces about 800t of separated fine material per day, which can be sold as low-calorific-value fuel to cement plants, sintered brick and stone enterprises, etc., to generate revenue for enterprises. At the same time, it can also be used as a raw material for autoclaved aerated concrete after further washing (flotation).

[0146] (5) If all the fine material separated by the 1.5cm sluice screen is washed and floated, approximately 300 tons / day of coal slime with a calorific value of over 3000 kcal / kg can be extracted, generating an additional 90,000 yuan / day in revenue for the enterprise. The daily output of fine material after washing (flotation) reaches approximately 500 tons, and the carbon content in the fine material will be less than 3% (below 200 kcal / kg). This is the No. 3 material used in this experiment. When used or blended into the raw materials for autoclaved aerated concrete or sintered hollow bricks, the influence of coal will be further reduced, alleviating production pressure.

[0147] If conditions permit, the raw materials (2), (3), and (4) after photoelectric dry separation can be further washed (flotated) with water, which is more conducive to the purity of the raw materials of coal gangue autoclaved aerated concrete and sintered hollow bricks, reduces the impact of carbon content on the production quality of the two ecological building materials, and improves the compressive strength of the products.

[0148] The flotation reagents used in the water washing flotation are formulated experimentally based on the type of coal gangue to be flotated, and their dosage is determined according to the amount of coal gangue being processed. The flotation reagents are purchased from commercially available flotation reagent manufacturers.

[0149] Wet flotation, also known as wet washing technology, involves the following process: Coal gangue, after being crushed and screened, is mixed with reagents and fed into a flotation machine. This process separates the gangue minerals from the coal powder and other organic matter. The separated coal powder and other organic matter can be used as fuel or sold. The gangue and other minerals obtained after separation are used as raw materials for autoclaved aerated concrete.

[0150] Furthermore, after the decarburization treatment, the carbon content of the gangue is ≤3%, for example, 0.10%, 0.20%, 0.30%, 0.40%, 0.50%, 0.60%, 0.70%, 0.80%, 0.90%, 1.00%, 2.00%, 2.50%, or 3%. The present invention is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0151] Example 6

[0152] The present invention will be further illustrated by the following experimental examples:

[0153] When raw coal and gangue enter the plant, their carbon content is all above 20%, and their calorific value is above 1500 kcal / kg.

[0154] After photoelectric separation, the carbon content of coal gangue is reduced to about 10%, and the calorific value is about 750 kcal / kg (the No. 2 material used in this experiment originated from this). When the separation process is different or the separation effect is particularly good, the carbon content of coal gangue is reduced to about 5%, and the calorific value is about 350 kcal / kg (the No. 1 material used in this experiment also originated from this). After photoelectric separation, the carbon content of coal gangue can be reduced to below 3% and the calorific value to below 200 kcal / kg after water washing and flotation (the No. 3 material used in this experiment).

[0155] Although the coal gangue, after physical decarbonization treatment, undergoes further hammer crushing and screening, the raw material particle size is generally still relatively coarse, failing to meet the particle size requirements for the hydration reaction of the main raw material in coal gangue autoclaved aerated concrete (AAC). The fine coal gangue used in AAC requires further deep grinding in a ore mill to achieve a particle size of ≤15% residue on a 200-sieve. This is also a necessary measure for the mechanical activation of the coal gangue raw material. When using dry grinding, it is important to implement environmental protection measures to prevent dust emissions; when using wet grinding, the purpose of fine grinding of raw materials and preparation of slurry can be achieved in one step.

[0156] When preparing autoclaved aerated concrete from coal gangue raw materials that have undergone photoelectric dry separation, for raw materials with a carbon content of 7% or more, it is generally necessary to adopt further enhanced physical decarbonization measures, and it is generally not advisable to adopt them.

[0157] For raw materials with a carbon content of 7% or more, if no further carbon reduction technology measures are adopted, the appearance of the products after demolding is found to be poor, the mechanical strength is poor, and the air bubbles are difficult to control.

[0158] Although coal gangue with a carbon content of 3% to 7% (see raw material #1 in this experiment) and a high silicon content can generally be used to prepare qualified coal gangue autoclaved aerated concrete without the addition of auxiliary agents, better qualified products can be prepared by using regulators (reinforcing agents) or using multiple regulators (reinforcing agents) in combination, which greatly improves the compressive strength of the products.

[0159] The chemical composition of the coal gangue raw material used in autoclaved aerated concrete after the above pretreatment is as follows:

[0160] Table 2 Chemical composition of coal gangue raw materials used in autoclaved aerated concrete (AAC).

[0161] Coal gangue <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> CaO MgO <![CDATA[Na2O]]> <![CDATA[K2O]]> <![CDATA[SO3]]> C 1#(％) 61.79 10.28 5.84 9.07 4.44 0.62 1.80 2.06 3.7 2#(％) 48.46 14.73 7.37 8.65 3.93 0.29 1.90 1.85 6.8 3#(％) 76.73 13.96 3.45 3.15 0.06 -- 1.55 0.10 -- 4#(％) 36.18 12.09 13.53 19.24 3.57 0.26 1.67 2.92 10.9

[0162] The mineral composition of the coal gangue raw material used in autoclaved aerated concrete after the above pretreatment is as follows:

[0163] Table 3 Mineral Composition of Coal Gangue Raw Material

[0164]

[0165] The cement and lime used in this invention have the following composition:

[0166] Table 4 Composition of cement and lime materials

[0167]

[0168] Other materials used in this invention are as follows:

[0169] plaster:

[0170] This experiment used analytical grade dihydrate gypsum from Fuchen Company, with a CaSO4·2H2O content ≥99%.

[0171] Aluminum powder:

[0172] This experiment used aluminum powder, which is still in normal use by most autoclaved aerated concrete companies, as the air-generating agent.

[0173] Silica ash:

[0174] Provided by a company in Ningxia, with SiO2 content ≥93% and specific surface area ≥18m². 2 / g

[0175] Silica sol:

[0176] This experiment used S-1430B water glass type silica sol, and its performance indicators are as follows:

[0177] Table 5 Performance Indicators of Water Glass-type Silica Sol

[0178] <![CDATA[SiO2]]> <![CDATA[Na2O]]> Specific gravity (25℃) <![CDATA[Viscosity (25°C, mm 2 / S)]]> Average particle size (nm) Stable period 29～31 ≤0.5 1.19～1.21 ≤6.5 10～16 ≥1 year

[0179] The compressive strength testing method in this invention uses destructive testing, which involves subjecting the material to pressure exceeding its limits. The purpose of this method is to assess the material's ultimate compressive strength and to record and analyze the failure process. Common destructive tests for evaluating the compressive strength of building structures typically use a pressure testing machine; the compressive strength testing equipment used in this invention is the RFP-03 intelligent force gauge.

[0180] Experimental Example 1:

[0181] Formulation and preparation process of raw material #1 (carbon content 3.7%) + 3% silica fume (C / S = 0.62):

[0182] (1) Mix 58.3 parts of material #1, 3 parts of silica fume, and 0.65 parts of 60℃ warm water for 5 minutes;

[0183] (2) While stirring continuously, quickly add 16 parts lime, 18.9 parts cement, and 3.8 parts gypsum and continue stirring for 2.5 minutes;

[0184] (3) Add 0.09 parts of aluminum powder while stirring continuously for 40 seconds;

[0185] (4) After stopping the mixing, quickly pour the mixed slurry into the prepared steel mold in one go;

[0186] (5) Then the poured mold is placed in a constant temperature and humidity chamber with a temperature of 60℃ and a relative humidity of 95% for 3.0h to complete the static stopping process such as foaming, shaping and solidification.

[0187] (6) Then use a wire saw to cut off the bread top that is higher than the mold and then demold it;

[0188] (7) After demolding, the green body is placed in a constant temperature and humidity chamber with a temperature of 80℃ and a relative humidity of 95% for 4 hours for pre-curing (pre-curing before the autoclave).

[0189] (8) Quickly transfer the pre-cured green body into the experimental small autoclave for autoclaving. The curing regime is as follows: uniformly increase the temperature from room temperature to 105℃ for 10 min, uniformly increase the temperature from 105℃ to 125℃ for 75 min, uniformly increase the temperature from 125℃ to 190℃ for 75 min, maintain the temperature at 190℃ (autoclave pressure 1.25MPa) for 8 h, uniformly exhaust the gas to reduce the pressure (temperature) for 2 h until the pressure inside the autoclave drops to 0 (at this time the temperature is still above 110℃), and remove the green body from the autoclave when the temperature inside the autoclave drops to a safe temperature below 60℃ (to prevent burns).

[0190] The tested dry density is 528 kg / m³. 3 At that time, its compressive strength reached 2.71 MPa (see sample #7).

[0191] Experimental Example 2:

[0192] Formulation and preparation process of raw material #1 (carbon content 3.7%) + 3% silica sol (C / S = 0.62):

[0193] (1) Add 61.3 parts of material #1, 3 parts of silica sol, and 0.65 parts of 60℃ warm water and stir for 5 minutes;

[0194] (2) While stirring continuously, quickly add 16 parts lime, 18.9 parts cement, and 3.8 parts gypsum and continue stirring for 2.5 minutes;

[0195] (3) Add 0.09 parts of aluminum powder while stirring continuously for 40 seconds;

[0196] (4) After stopping the mixing, quickly pour the mixed slurry into the prepared steel mold in one go;

[0197] (5) Then the poured mold is placed in a constant temperature and humidity chamber with a temperature of 60℃ and a relative humidity of 95% for 3 hours to complete the static stopping process such as foaming, shaping and solidification.

[0198] (6) Then use a wire saw to cut off the bread top that is higher than the mold and then demold it;

[0199] (7) After demolding, the green body is placed in a constant temperature and humidity chamber with a temperature of 80℃ and a relative humidity of 95% for 4 hours for pre-curing (pre-curing before the autoclave).

[0200] (8) Quickly transfer the pre-cured green body into the experimental small autoclave for autoclaving. The curing regime is as follows: uniformly increase the temperature from room temperature to 105℃ for 10 min, uniformly increase the temperature from 105℃ to 125℃ for 75 min, uniformly increase the temperature from 125℃ to 190℃ for 75 min, maintain the temperature at 190℃ (autoclave pressure 1.25MPa) for 8 h, uniformly exhaust the gas to reduce the pressure (temperature) for 2 h until the pressure inside the autoclave drops to 0 (at this time the temperature is still above 110℃), and remove the green body from the autoclave when the temperature inside the autoclave drops to a safe temperature below 60℃ (to prevent burns).

[0201] The tested dry density is 526 kg / m³. 3 At that time, its compressive strength reached 2.81 MPa (see sample #5).

[0202] Experimental Example 3:

[0203] Formulation and preparation process of raw material #1 (carbon content 3.7%) + 3% silica sol + 3% silica fume (C / S = 0.62):

[0204] (9) Add 58.3 parts of material #1, 3 parts of silica sol, 3 parts of silica fume, and 0.65 parts of 60℃ warm water and stir for 5 minutes;

[0205] (10) While stirring continuously, quickly add 16 parts lime, 18.9 parts cement, and 3.8 parts gypsum and continue stirring for 2.5 minutes;

[0206] (11) Add 0.09 parts of aluminum powder while stirring continuously for 40 seconds;

[0207] (12) After stopping the mixing, quickly pour the mixed slurry into the prepared steel mold in one go;

[0208] (13) Then the poured mold is placed in a constant temperature and humidity chamber with a temperature of 60℃ and a relative humidity of 95% for 3.0h to complete the static stopping process such as foaming, shaping and solidification.

[0209] (14) Then use a wire saw to cut off the bread head that is higher than the mold and then demold it;

[0210] (15) The demolded blank is placed in a constant temperature and humidity chamber with a temperature of 80℃ and a relative humidity of 95% for 6 hours for pre-curing (pre-curing before the autoclave).

[0211] (16) Quickly transfer the pre-cured green body into the experimental small autoclave for autoclaving. The curing regime is as follows: uniformly increase the temperature from room temperature to 105℃ for 10 min, uniformly increase the temperature from 105℃ to 125℃ for 75 min, uniformly increase the temperature from 125℃ to 190℃ for 75 min, maintain the temperature at 190℃ (autoclave pressure 1.25MPa) for 8 h, uniformly exhaust the gas to reduce the pressure (temperature) for 2 h until the pressure inside the autoclave drops to 0 (at this time the temperature is still above 110℃), and remove the green body from the autoclave when the temperature inside the autoclave drops to a safe temperature below 60℃ (to prevent burns).

[0212] The tested dry density is 543 kg / m³. 3 At that time, its compressive strength reached 3.02 MPa (see sample #8).

[0213] Experiment Example 4:

[0214] Raw material #2 (carbon content 6.9%, 483 kcal / kg) + silica fume + silica sol + glass fiber powder (C / S = 0.78);

[0215] (1) Add 60 parts of No. 2 raw material, 5 parts of silica fume, 3 parts of silica sol, 3 parts of glass fiber powder, and 0.75 parts of 60℃ warm water and stir for 10 minutes;

[0216] (2) While stirring continuously, quickly add 16 parts lime, 16 parts cement, and 3 parts gypsum and continue stirring for 2.5 minutes;

[0217] (3) Add 0.09 parts of aluminum powder while stirring continuously for 40 seconds;

[0218] (4) After stopping the mixing, quickly pour the mixed slurry into the prepared steel mold in one go;

[0219] (5) Then the poured mold is placed in a constant temperature and humidity chamber with a temperature of 60℃ and a relative humidity of 95% for 3 hours to complete the static stopping process such as foaming, shaping and solidification.

[0220] (6) Then use a wire saw to cut off the bread top that is higher than the mold and then demold it;

[0221] (7) After demolding, the green body is placed in a constant temperature and humidity chamber with a temperature of 80℃ and a relative humidity of 95% for 8 hours for pre-curing (pre-curing before the autoclave).

[0222] (8) The pre-cured green body is quickly transferred to a small experimental autoclave for autoclaving (the hydrothermal synthesis reaction continues inside the green body to generate sufficient hydration products and achieve the necessary crystallinity, so that the product obtains good properties). The curing regime is as follows: uniformly increase the temperature from room temperature to 105℃ for 10 min (during which the vent valve is in the open state), uniformly increase the temperature from 105℃ to 125℃ for 75 min, uniformly increase the temperature from 125℃ to 190℃ for 75 min, hold the temperature at 190℃ (autoclave pressure 1.25MPa) for 8 h, uniformly exhaust the gas to reduce the pressure and temperature for 2 h, and remove the product from the autoclave when the pressure inside the autoclave drops to 0 and the humidity inside the autoclave drops to a safe temperature below 60℃.

[0223] The tested dry density is 542 kg / m³. 3 Its compressive strength reaches 2.89 MPa.

[0224] Experimental Example 5:

[0225] Formula for raw material #2 (carbon content 6.9%, calorific value 483kcal / kg) + silica fume + sodium tripolyphosphate (C / S = 0.78);

[0226] (1) Add 60 parts of material #2, 5 parts of silica fume, 2 parts of sodium tripolyphosphate, and 0.75 parts of 60℃ warm water and stir for 10 minutes;

[0227] (2) While stirring continuously, quickly add 16 parts lime, 16 parts cement, and 3 parts gypsum and continue stirring for 2.5 minutes;

[0228] (3) Add 0.09 parts of aluminum powder while stirring continuously for 40 seconds;

[0229] (4) After stopping the mixing, quickly pour the mixed slurry into the prepared steel mold in one go;

[0230] (5) Then the poured mold is placed in a constant temperature and humidity chamber with a temperature of 60℃ and a relative humidity of 95% for 3 hours to complete the static stopping process such as foaming, shaping and solidification.

[0231] (6) Then use a wire saw to cut off the bread top that is higher than the mold and then demold it;

[0232] (7) The demolded blank is placed in a constant temperature and humidity chamber with a temperature of 80℃ and a relative humidity of 95% for 10 hours for pre-curing (pre-curing before the autoclave).

[0233] (8) Quickly transfer the pre-cured green body into the autoclave for autoclaving (the hydrothermal synthesis reaction continues inside the green body to generate sufficient hydration products and achieve the necessary crystallinity, so that the product obtains good properties). The curing regime is as follows: room temperature to 105℃ for 10 min (during which the vent valve is in the open state), 105 to 125℃ for 75 min, 125 to 190℃ for 75 min, 190℃ (autoclave pressure 1.25MPa) constant temperature for 8 h, uniformly exhaust and depressurize for 2 h, reduce the autoclave pressure to 0, and remove the green body from the autoclave when the humidity inside the autoclave drops to a safe temperature below 60℃.

[0234] The tested dry density is 539 kg / m³. 3 Its compressive strength reaches 2.78 MPa.

[0235] Experimental Example 6:

[0236] Silica fume + silica sol formulation

[0237] Formula for raw material #2 (carbon content 6.9%, calorific value 483kcal / kg) silica fume + silica sol (C / S = 0.78);

[0238] (1) Add 60 parts of material #2, 5 parts of silica fume, 3 parts of silica sol, and 0.75 parts of 60℃ warm water and stir for 10 minutes;

[0239] (2) While stirring continuously, quickly add 16 parts lime, 16 parts cement, and 3 parts gypsum and continue stirring for 2.5 minutes;

[0240] (3) Add 0.09 parts of aluminum powder while stirring continuously for 40 seconds;

[0241] (4) After stopping the mixing, quickly pour the mixed slurry into the prepared steel mold in one go;

[0242] (5) Then the poured mold is placed in a constant temperature and humidity chamber with a temperature of 60℃ and a relative humidity of 95% for 3.0h to complete the static stopping process such as foaming, shaping and solidification.

[0243] (6) Then use a wire saw to cut off the bread top that is higher than the mold and then demold it;

[0244] (7) The demolded blank is placed in a constant temperature and humidity chamber with a temperature of 80℃ and a relative humidity of 95% for 12 hours for pre-curing (pre-curing before the autoclave).

[0245] (8) The pre-cured green body is quickly transferred to a small experimental autoclave for autoclaving (the hydrothermal synthesis reaction continues inside the green body to generate sufficient hydration products and achieve the necessary crystallinity, so that the product obtains good properties). The curing regime is as follows: uniformly increase the temperature from room temperature to 105℃ for 10 min (during which the vent valve is in the open state), uniformly increase the temperature from 105℃ to 125℃ for 75 min, uniformly increase the temperature from 125℃ to 190℃ for 75 min, hold the temperature at 190℃ (autoclave pressure 1.25MPa) for 8 h, uniformly exhaust the gas to reduce the pressure and temperature for 2 h, and remove the product from the autoclave when the pressure inside the autoclave drops to 0 and the humidity inside the autoclave drops to a safe temperature below 60℃.

[0246] The tested dry density is 546 kg / m³. 3 Its compressive strength reaches 2.86 MPa.

[0247] Experiment Example 7:

[0248] Silica fume + silica sol formulation

[0249] Formula for raw material #4 (carbon content 10.9%, calorific value 766 kcal / kg) silica fume + silica sol (C / S = 0.83);

[0250] (1) Add 52 parts of No. 4 material, 8 parts of silica fume, 5 parts of silica sol, and 0.75 parts of 60℃ warm water and stir for 10 minutes;

[0251] (2) While stirring continuously, quickly add 18 parts lime, 14 parts cement, and 3 parts gypsum and continue stirring for 2.5 minutes;

[0252] (3) Add 0.12 parts of aluminum powder while stirring continuously for 45 seconds;

[0253] (4) After stopping the mixing, quickly pour the mixed slurry into the prepared steel mold in one go;

[0254] (5) Then the poured mold is placed in a constant temperature and humidity chamber with a temperature of 60℃ and a relative humidity of 95% for 2.5 hours to complete the static stopping process such as foaming, shaping and solidification.

[0255] (6) Then use a wire saw to cut off the bread top that is higher than the mold and then demold it;

[0256] (7) The demolded blank is placed in a constant temperature and humidity chamber with a temperature of 80℃ and a relative humidity of 95% for 12 hours for pre-curing (pre-curing before the autoclave).

[0257] (8) The pre-cured green body is quickly transferred to a large autoclave on the production line for autoclaving (to accelerate the hydrothermal synthesis reaction inside the green body, generate sufficient hydration products and achieve the necessary crystallinity, so that the product obtains good properties). The curing regime is as follows: In the autoclave on the production line, the air inside the autoclave is discharged for 30 minutes by steam replacement from other autoclaves. At this time, the temperature inside the autoclave has been uniformly raised to about 105℃. The temperature is uniformly increased from 105℃ to 190℃ for 120 minutes. The temperature is kept constant at 190℃ (autoclave pressure 1.25MPa) for 8 hours. Steam is slowly discharged (displacing the steam inside the autoclave with other autoclaves) for about 60 minutes. The autoclave pressure drops to 0.80MPa. At this time, the temperature inside the autoclave is about 160℃. Then, the pressure and temperature are uniformly reduced for 1.0 hour until the autoclave pressure drops to 0 and the temperature inside the autoclave drops below 130℃ before the product is removed from the autoclave.

[0258] The tested dry density is 547 kg / m³. 3 Its compressive strength reaches 2.65 MPa.

[0259] Experimental Example 8:

[0260] Silica fume + silica sol + hydroxypropyl methylcellulose formula

[0261] Formula for raw material #4 (carbon content 10.9%, calorific value 766kcal / kg): silica fume + silica sol + hydroxypropyl methylcellulose (C / S = 0.81);

[0262] (1) Add 55 parts of material #4, 5 parts of silica fume, 3 parts of silica sol, and 3 parts of hydroxypropyl methylcellulose, and 0.75 parts of 60℃ warm water and stir for 10 minutes.

[0263] (2) While stirring continuously, quickly add 18 parts lime, 14 parts cement, and 3 parts gypsum and continue stirring for 2.5 minutes;

[0264] (3) Add 0.010 parts of aluminum powder while stirring continuously for 45 seconds;

[0265] (4) After stopping the mixing, quickly pour the mixed slurry into the prepared steel mold in one go;

[0266] (5) Then the poured mold is placed in a constant temperature and humidity chamber with a temperature of 60℃ and a relative humidity of 95% for 3.0h to complete the static stopping process such as foaming, shaping and solidification.

[0267] (6) Then use a wire saw to cut off the bread top that is higher than the mold and then demold it;

[0268] (7) The demolded blank is placed in a constant temperature and humidity chamber with a temperature of 80℃ and a relative humidity of 95% for 12 hours for pre-curing (pre-curing before the autoclave).

[0269] (8) The pre-cured green body is quickly transferred to a small experimental autoclave for autoclaving (to accelerate the hydrothermal synthesis reaction inside the green body, generate sufficient hydration products and achieve the necessary crystallinity, so that the product obtains good properties). The curing regime is as follows: In the autoclave on the production line, the air inside the autoclave is discharged for 30 minutes by steam replacement from other autoclaves. At this time, the temperature inside the autoclave has been uniformly raised to about 105℃. The temperature is uniformly increased from 105℃ to 190℃ for 120 minutes. The temperature is kept constant at 190℃ (autoclave pressure 1.25MPa) for 8 hours. Steam is slowly discharged (displacing the steam inside the autoclave with other autoclaves) for about 60 minutes. The autoclave pressure drops to 0.80MPa. At this time, the temperature inside the autoclave is about 160℃. Then, the pressure and temperature are uniformly reduced for 1.0 hour until the autoclave pressure drops to 0 and the temperature inside the autoclave drops below 130℃ before the product is removed from the autoclave.

[0270] The tested dry density is 421 kg / m³. 3 Its compressive strength reaches 2.02 MPa.

[0271] Comparative Example 1:

[0272] The steps in Example 2 are the same as in Example 2, except that no regulator was added. The oven-dry density was measured to be 539 kg / m³. 3 Its compressive strength reached 2.32 MPa, which is lower than the compressive strength of the product in Example 2.

[0273] Comparative Example 2

[0274] The steps in Example 8 are the same as in Example 2, except that no regulator was added. The oven-dry density was measured to be 539 kg / m³. 3 Its compressive strength reached 1.278 MPa, which is far lower than the compressive strength of the product in Example 8.

[0275] Table 6. Relationship between the performance of the coal gangue autoclaved aerated concrete of this invention and the regulator.

[0276]

[0277] As shown in Table 6, using the regulator of this invention significantly improves the compressive strength of autoclaved aerated concrete (AAC) made from coal gangue compared to methods without regulators under the same conditions. All products prepared using the method of this invention meet the compressive strength requirements of B05 in the national standard GB / T11968-2020 (see Table 7). Furthermore, using a mixed regulator results in better compressive strength of the AAC compared to using a single regulator, demonstrating that the use of multiple regulators significantly improves product quality. Table 6 also shows that material #4, with its low silica content (36.18%) and high carbon content (10.9%), after adding the regulator, not only breaks the industry convention that silica raw materials with silica content below 40% cannot be used to prepare AAC, but also achieves the excellent compressive strength of grade A2.5 B05 in Table 7 (Example 7). The compressive strength of the product with the same carbon content in Comparative Example 2 falls far short of this strength standard. Example 8, due to its different formulation, has a different density grade, but its compressive strength has reached the A2.0 grade B04 standard in Table 6. Here, A represents the strength grade, and B represents the density grade. This is because when coal gangue with the aforementioned high carbon content is added in large quantities to autoclaved aerated concrete raw materials, the quality of the prepared product is generally substandard. However, the addition of the aforementioned regulator greatly enhances the compressive strength of the product, allowing the utilization of the aforementioned high-carbon coal gangue, while also reducing the cost of processing coal gangue with high carbon content.

[0278] In the preparation of autoclaved aerated concrete, density grade mainly involves the adjustment of pores. Therefore, if a sample of any density grade is successfully prepared under the same strength grade, it can be inferred that qualified products of other density grades under the same strength grade can also be obtained by adjusting the density grade.

[0279] Table 7 Compressive Strength and Dry Density Requirements

[0280]

[0281] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for producing coal gangue autoclaved aerated concrete, characterized by, 4# coal gangue raw material chemical composition: SiO2 36.18%, Al2O3 12.09%, Fe2O3 13.53%, CaO 19.24%, MgO 3.57%, Na2O 0.26%, K2O 1.67%, SO3 2.92%; 4# coal gangue raw material carbon content 10.9%, heat value 766kcal / kg; autoclaved aerated concrete C / S = 0.83; (1) 52 parts of 4# coal gangue raw material, 8 parts of silica fume + 5 parts of silica sol, 0.75 parts of warm water at 60℃, stirring for 10min; (2) Under the condition of continuous stirring, quickly add 18 parts of lime, 14 parts of cement, 3 parts of gypsum, continue to stir for 2.5min; (3) Under the condition of continuous stirring, add 0.12 parts of aluminum powder and stir for 45S; (4) After stopping stirring, the prepared slurry is quickly injected into the prepared steel mold at one time; (5) Then put the poured mold into the constant temperature and humidity box with temperature of 60℃ and relative humidity of 95% for 2.5h to complete the foaming, shaping and solidification and static process; (6) Then cut off the bread head higher than the mold with a steel wire saw, and then demold; (7) Put the demolded body into the constant temperature and humidity box with temperature of 80℃ and relative humidity of 95% for 12h of pre-curing; (8) Quickly put the pre-cured body into the large autoclave on the production line for autoclave curing, and the curing system is as follows: the air in the autoclave is discharged for 30min by replacing the steam in other autoclaves, at this time the temperature in the autoclave has been uniformly raised to 105℃, the temperature is uniformly raised to 105-190℃ for 120min, the pressure is 1.25MPa at 190℃ for 8h, the steam is slowly discharged, the steam in the autoclave is replaced to other autoclaves, the pressure is reduced to 0.80Mpa for 60min, at this time the temperature in the autoclave is 160℃, then the steam is uniformly discharged to reduce the pressure and temperature for 1.0h, the pressure is reduced to 0, the temperature in the autoclave is reduced to below 130℃, and then the autoclave is taken out; The absolute dry density of the coal gangue autoclaved aerated concrete is 547 kg / m 3 and the compressive strength reaches 2.65 MPa.

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