A lightweight carbonized building block and its preparation method

Abstract

The present invention discloses a lightweight carbonized building block and a preparation method thereof. The components and their weight percentages include: 100 parts dry mix, 4-6 parts water, and 5-15 parts carbon-containing ice balls. The dry mix is composed of a cementitious material, a skeleton material, and a filler powder, the cementitious material including an air-hardening cementitious material. The carbon-containing ice balls are formed by freezing a carbon-containing solution. The present invention uses the carbon-containing ice balls to pre-seal carbon dioxide within the building block. During carbonization curing, the carbon-containing ice balls absorb heat and melt, releasing carbon dioxide and increasing internal porosity. Carbonization curing can be performed simultaneously on both the inside and outside of the building block, effectively resolving the problem of difficulty in carbonizing the interior of the carbonized building block product. Furthermore, the bulk density of the carbonized building block can be flexibly adjusted by controlling the amount of carbon-containing ice balls. The resulting building block has high strength, environmentally friendly carbon absorption, adjustable bulk density, and excellent thermal insulation and sound insulation properties, making it suitable for widespread application.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to a lightweight carbonized building block and a preparation method thereof. Background Art

[0002] The curing of carbonized building materials involves a three-phase contact reaction: gas, liquid, and solid. During traditional carbonization curing, gas diffuses from the exterior to the interior of the building material, a process significantly impacted by factors such as CO2 diffusion rate, dissolution rate, product density, moisture content, and product volume. Furthermore, during the outside-in curing process, as the carbonization reaction proceeds, the surface density of the carbonized product increases, and the diffusion rate of CO2 into the product decreases. This can lead to low carbonization curing efficiency and uneven carbonization across the product's cross-section. These issues become more pronounced with larger carbonized products.

[0003] Patent CN111892340A discloses a method for preparing low-cost steel slag carbonized bricks. 90 to 180 parts of recycled aggregate, 10 to 30 parts of steel slag powder A with a particle size of 0.1 to 1.0 mm, 30 to 60 parts of steel slag powder B with a particle size of 15 to 30 μm, and 15 to 40 parts of steel slag slurry C with a particle size of 2 to 4 μm are mixed evenly, and the bricks are pressed at a molding pressure of 10 MPa for 2 minutes to obtain brick blanks, which are then cured in a carbonization curing box for 4 to 6 hours to obtain steel slag carbonized bricks. During the carbonization curing process of the brick blanks, carbon dioxide can only diffuse from the outside to the inside of the brick blanks, resulting in low carbonization efficiency. The inside of the brick blanks is difficult to fully carbonize, and the brick blanks can only be used in small-sized brick products. Patent CN112679179 A discloses a carbonized brick containing industrial calcium slag and a preparation method thereof. The mixture is prepared by mixing 30 parts of dried, ground and sieved calcium slag powder, 70 parts of aggregate, 0.06-0.12 parts of ammonium bicarbonate and 15-25 parts of water, and then pressed, formed and carbonized to obtain a carbonized brick product. This method uses carbon dioxide generated by the decomposition of ammonium bicarbonate for internal curing. The amount of gas introduced is small, and the degree of carbonization inside the product is limited. It is not suitable for the carbonization curing process of block products. When carbon dioxide is introduced, ammonia is generated. When ammonia dissolves in water, it affects the dissolution rate of carbon dioxide in water, thereby affecting the carbonization reaction rate. It is difficult to separate it from unreacted CO2, and the waste gas treatment is difficult. In addition, the product after carbonization curing has a large volume (usually 2000kg / m 3 The construction cost is high and the efficiency is low. Summary of the Invention

[0004] The main purpose of the present invention is to address the problems and shortcomings of the existing technology and provide a lightweight carbonized building block. By introducing carbon-containing ice balls into the mixture, it can effectively solve the problems of low curing efficiency, high product density, and uneven carbonization in traditional carbonized products. The preparation method involved is relatively simple and easy to operate, which can provide a new idea for the preparation of carbonized building blocks.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A lightweight carbonized building block, comprising raw materials and their weight proportions: 100 parts of dry mix, 4-6 parts of water, and 5-15 parts of carbon-containing ice balls; wherein the dry mix consists of a cementitious material, a skeleton material, and a filling powder, the cementitious material comprising an air-hardening cementitious material; and the carbon-containing ice balls are formed by freezing a carbon-containing solution.

[0007] Furthermore, the main air-hardening mineral content in the cementitious material is 50-90%, and is composed of one or more of CS, C3S2, C2S, and C3S.

[0008] In the above solution, the gelling material accounts for 10-25% of the mass of the dry mixture.

[0009] In the above solution, the cementitious material is composed of one or more of low-carbon cement, steel slag, and magnesium slag.

[0010] In the above solution, the skeleton material accounts for 40-60% of the weight of the dry mixed material.

[0011] In the above scheme, the skeleton material can be selected from one or more of aggregate screened materials, crushed waste concrete, crushed waste sintered bricks, etc., with a particle size of 5 to 10 mm and a crushing value of 10 to 30%; the filling powder can be selected from one or more of ground filter press soil, heavy calcium powder, sand making building dust ash, etc., with an 80um sieve residue of 10 to 20%.

[0012] Furthermore, the skeleton material is preferably aggregate undersize material; and the filling powder is preferably ground filter press soil.

[0013] In the above solution, the particle size of the carbon-containing ice balls is 1 to 10 mm, preferably 5 to 10 mm.

[0014] In the above scheme, the carbon-containing solution is obtained by placing it in a vacuum, sealed water-containing container under temperature control, then introducing carbon dioxide gas to a constant pressure, and then maintaining the temperature and pressure.

[0015] In the above scheme, the vacuum pressure is -0.09 to -0.08 MPa.

[0016] In the above scheme, the temperature of the temperature control treatment (heat holding temperature) is 5-25°C; the pressure used in the pressure holding step is 5-20 MPa; and the pressure is maintained until the concentration of carbon dioxide in 100g of water is above 5g.

[0017] Furthermore, the temperature of the temperature control treatment is 5-10°C.

[0018] In the above solution, the purity of the carbon dioxide gas is ≥95 vol%.

[0019] In the above scheme, the temperature used in the freezing step is lower than 0°C; preferably -10 to -1°C.

[0020] The method for preparing the above-mentioned lightweight carbonized building block specifically comprises the following steps:

[0021] 1) Preparation of carbon-containing ice balls: placing a mold containing water in a sealed container; evacuating the container with a negative pressure pump; controlling the temperature; then introducing carbon dioxide gas to a constant pressure; maintaining the temperature and pressure to obtain a carbon-containing solution; freezing the solution; recovering unused carbon dioxide in the container; and opening the container to remove the obtained carbon-containing ice balls.

[0022] 2) Evenly mix the gelling material, skeleton material, filling powder and water weighed in proportion to obtain a wet mixture;

[0023] 3) Block body forming: the wet mixture is mixed with carbon-containing ice balls according to a proportion, and pressed into shape to obtain a block body;

[0024] 4) Carbonization curing: The obtained block body is subjected to carbonization curing to obtain the carbonized block product.

[0025] In the above scheme, the sealed container in step 1) can withstand an air pressure of 20 MPa and has a cooling function; the carbon dioxide content in the carbon-containing solution is 5.5-8.0 g / 100 g water.

[0026] In the above scheme, the compression molding step in step 3) adopts a static pressure molding method, the molding pressure is 10 to 30 MPa, preferably 20 to 30 MPa; the pressing time is 3 to 10 seconds.

[0027] In the above scheme, the process parameters adopted in the carbonization curing step in step 4) include: CO2 concentration of 20-60 vol%, pressure of 0.1-0.3 MPa, temperature of 20-40°C, and curing time of 4-12 hours.

[0028] The carbonized blocks prepared according to the above scheme have better thermal insulation and sound insulation effects than traditional carbonized solid building materials; their bulk density varies from 1600 to 2000 kg / m 3 Adjustable within the range.

[0029] The principle of the present invention is:

[0030] The present invention uses vacuuming and introducing carbon dioxide and pressurizing to increase the partial pressure of carbon dioxide, while simultaneously performing temperature control, which can effectively increase the solubility of carbon dioxide in water to form a carbon-containing solution, and then performs a cooling and freezing process to solidify the carbon dioxide in the ice ball to obtain a carbon-containing ice ball.

[0031] The obtained carbon-containing ice balls are mixed evenly with a gelling material containing an air-containing hard component, a skeleton material, a filling powder and water in proportion to obtain a wet mixture, which is then subjected to static pressing, carbonization and curing in sequence to prepare a carbonized building block. During the carbonization and curing process of the building block obtained by the present invention, carbon dioxide in the curing environment diffuses from the outer surface of the building block to the inner surface, and a carbonization reaction occurs. Due to the heat transfer of the carbonization environment temperature and the heat release of the carbonization reaction, the temperature inside the building block increases, and the carbon-containing ice balls are heated and melted into a carbon-containing aqueous solution. In addition, as the temperature increases (the Henry coefficient decreases), the solubility of carbon dioxide in the carbon-containing aqueous solution decreases, and the carbon dioxide is released from the aqueous solution and diffuses outward from the pores inside the building block. Disperse and participate in the internal carbonization reaction; the internal and external carbonization reactions proceed simultaneously, which can effectively solve the problems of traditional carbonization curing process in which only the outside of the block is carbonized, the external carbonized layer becomes increasingly dense (as the carbonization reaction proceeds), and it becomes increasingly difficult for carbon dioxide to diffuse into the interior of the block (the larger the size of the carbonized product, the less likely the interior of the carbonized product is to be carbonized); in addition, after the carbon-containing ice balls melt, the holes left behind can provide channels for the external carbon dioxide to diffuse, which can further increase the degree of carbonization reaction, while reducing the bulk density of the carbonized block and improving its thermal insulation and heat insulation properties. The present invention can flexibly adjust the bulk density of the carbonized block by controlling the amount of carbon-containing ice balls added.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) The present invention introduces carbon-containing ice ball block bodies into a mixture with carbonization properties. During the curing process, the carbon-containing ice balls absorb heat and release carbon dioxide. Internal and external carbonization curing are carried out simultaneously, which increases the carbonization efficiency and effectively improves the carbonization depth of the product. This solves the problem of low carbonization degree and low efficiency of carbonized block products.

[0034] 2) The present invention can flexibly adjust the bulk density of the carbonized building block by controlling the amount of carbon-containing ice balls added; at the same time, the carbonization channel inside the product is opened, which is more conducive to the diffusion of carbon dioxide into the product, and the carbonization efficiency is higher;

[0035] 3) The carbon dioxide adsorption or desorption process of the present invention does not consume or release additional adsorbents, and no toxic or harmful substances are generated in the product and the curing process. It has good environmental benefits and is suitable for promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a process flow chart of the lightweight carbonized building blocks according to an embodiment of the present invention;

[0037] Figure 2 Schematic diagram of the structure of the mold used to prepare carbon-containing ice balls in the present invention; (a) is a top view, and (b) is a front view. DETAILED DESCRIPTION

[0038] The present invention will be further explained below with reference to the following examples, which are provided for illustrative purposes only and are not intended to limit the scope of the present invention.

[0039] In the following examples, the two low-carbon cements used in the dry mix were provided by Huaxin Jinlong Cement (Yunxian) Co., Ltd. The main mineral compositions and their weight percentages of the No. 1 low-carbon cement were: C3S 20%, β-C2S 14%, C3S2 7%, CS 26%, and SiO2 20%; the main mineral compositions and their weight percentages of the No. 2 low-carbon cement were: C3S 10%, β-C2S 14%, C3S2 11%, CS 38%, and SiO2 16%. The steel slag used in the dry mix was provided by Wuhan Iron and Steel Co., Ltd., with a ground particle size of 30 to 80 μm. The main mineral compositions and their weight percentages were: γ-C2S 37%, C3S 10%, portlandite 11%, calcite 1%, quartz 4%, ferrocene 22%, wustite 10%, and magnetite 4%.

[0040] The filter press soil and undersize material used in the dry mix are provided by Huaxin Cement Yangxin Aggregate Plant. The moisture content of the filter press soil is 18%, and the fineness after drying and grinding is 80um and the residue is 20%. Its main mineral composition and mass percentage are: calcite 63%, quartz 13%, clinochlore 4%, muscovite 6%, and dolomite 9%; the particle size of the undersize material is 5-10mm, and the crushing value is 28%. The main mineral composition and mass percentage are: calcite 49%, quartz 20%, kaolin 6%, muscovite 15%, clinochlore 3%, and dolomite 2%.

[0041] The chemical compositions of the five raw materials are shown in Table 1.

[0042] Table 1 Chemical composition of raw materials (wt%)

[0043] CaO <![CDATA[SiO2]]> <![CDATA[Al2O3]]> <![CDATA[Fe2O3]]> MgO <![CDATA[SO3]]> 1# low carbon cement 52.75 32.68 4.16 2.86 3.67 0.65 2# low carbon cement 51.47 36.03 4.07 2.76 2.20 0.39 steel slag 40.04 13.27 6.33 21.01 9.05 0.77 Screen material 26.18 30.76 9.11 3.07 1.11 3.18 filter press soil 31.09 26.28 7.85 2.42 0.93 2.45

[0044] The water used in the following examples is tap water from the laboratory of the Technology Research Institute of Huaxin Cement Co., Ltd.

[0045] The carbon dioxide used in the carbonization curing in the following examples was provided by Wuhan Runhuahui Oxygen Cylinder Inspection Co., Ltd. Dongxin Branch, and its purity was greater than 95 vol%.

[0046] Example 1

[0047] A lightweight carbonized building block, the preparation process of which comprises the following steps:

[0048] 1) Preparation of carbon-containing ice balls: A spherical ice mold with a particle size of 5 mm was selected and filled with water up to the water inlet; the mold containing water was placed in a sealed container; a vacuum pump was used to evacuate the container to a pressure of -0.09 MPa; the temperature inside the container was controlled to 8°C; 95 vol% carbon dioxide was introduced into the container using a pressure pump until the pressure inside the container reached 20 MPa; the temperature and pressure were maintained until the solubility of carbon dioxide in water in the mold reached 8.0 g per 100 g of water; the temperature inside the container was cooled to -10°C until the carbon-containing solution was completely frozen into carbon-containing ice balls; unused carbon dioxide in the container was recycled; and the carbon-containing ice balls were removed from the mold.

[0049] 2) Block forming: 10 parts of No. 1 low-carbon cement, 15 parts of steel slag, 55 parts of undersize material, 20 parts of filter press soil and 6 parts of water were mixed to prepare a wet mix; carbon-containing ice balls were mixed with the mix and then pressed at a molding pressure of 30 MPa for 5 seconds to prepare a block;

[0050] 3) Carbonization curing: The carbonization curing process parameters are set as carbon dioxide concentration 25 vol%, pressure 0.1 MPa, temperature 25° C., and the block body is cured for 10 hours to obtain a carbonized block product.

[0051] 4) Block size: length 390mm*width 190mm*height 190mm.

[0052] In Example 1, the mass ratio of ice balls to dry mix was controlled at 5:100 (1#), 10:100 (2#), and 15:100 (3#), respectively. The carbonized blocks were tested for carbon fixation, carbonization weight gain, carbonization depth, compressive strength, absolute dry density, and thermal conductivity. The results are shown in Table 2.

[0053] Table 2 Performance test results of carbonized blocks obtained in Example 1

[0054]

[0055] Example 2

[0056] A lightweight carbonized building block, the preparation process of which comprises the following steps:

[0057] 1) Preparation of carbon-containing ice balls: A spherical ice mold with a particle size of 7 mm was selected and filled with water up to the water inlet; the mold containing water was placed in a sealed container; a vacuum pump was used to evacuate the container to a pressure of -0.085 MPa; the internal temperature of the container was controlled to 5°C; 99 vol% carbon dioxide was introduced into the container using a pressure pump to a pressure of 10 MPa; the temperature and pressure were maintained until the solubility of carbon dioxide in water in the mold reached 6.5 g per 100 g of water; the internal temperature of the container was cooled to -5°C until the carbon-containing solution was completely frozen into carbon-containing ice balls; unused carbon dioxide in the container was recycled; and the carbon-containing ice balls were removed from the mold.

[0058] 2) Block forming: 15 parts of steel slag or 2# low-carbon cement, 55 parts of undersize material, 30 parts of filter press soil powder and 5 parts of water were mixed evenly to prepare a wet mix; 10 parts of carbon-containing ice balls were mixed evenly with 100 parts of the mix and then pressed at a molding pressure of 20 MPa for 6 seconds to prepare a block body;

[0059] 3) Carbonization curing: The carbonization curing process parameters are set as carbon dioxide concentration 30 vol%, pressure 0.2 MPa, temperature 30° C., and the block body is cured for 12 hours to obtain a carbonized block product.

[0060] 4) Block size: length 390mm*width 190mm*height 190mm.

[0061] In Example 2, carbonized blocks with only steel slag (4#) and only 2# low carbon cement (5#) were tested for carbon fixation, carbonization weight gain rate, carbonization depth, compressive strength, absolute dry density and thermal conductivity. The results are shown in Table 3.

[0062] Table 3 Performance test results of carbonized blocks obtained in Example 2

[0063]

[0064]

[0065] Comparative Example 1

[0066] A carbonized block was prepared using a process similar to that of Example 1, except that: 1) the mixture did not contain carbon-containing ice balls, and the mass ratio of dry mix to water was 100:7; 2) the curing time during carbonization was 10 hours (for Example 6) and 48 hours (for Example 7), respectively. The carbonized blocks were tested for carbon fixation, carbonization weight gain, carbonization depth, compressive strength, absolute dry bulk density, and thermal conductivity. The results are shown in Table 4.

[0067] Table 4 Performance test results of carbonized blocks obtained in Comparative Example 1

[0068]

[0069] Comparative Example 2

[0070] A carbonized building block, the preparation process of which is substantially the same as that of Example 1, except that: 1) the mass ratio of carbon-containing ice balls to dry mix is controlled to 18:100 (8#), 21:100 (9#), and 24:100 (10#), respectively; the carbonized building blocks are tested for carbon fixation, carbonization weight gain rate, carbonization depth, compressive strength, absolute dry bulk density, and thermal conductivity. The results are shown in Table 5.

[0071] Table 5 Performance test results of carbonized blocks obtained in Comparative Example 2

[0072]

[0073] Comparative Example 3

[0074] A carbonized block was prepared using a process similar to that of Example 2, except that carbon-free ice balls prepared by freezing pure water at 1 atmosphere and -5°C were incorporated, eliminating the need for carbon dioxide absorption. The block containing only steel slag was designated 11#, and the block containing only 2# low-carbon cement was designated 12#. The carbonized blocks were tested for carbon fixation, carbonization weight gain, carbonization depth, compressive strength, absolute dry density, and thermal conductivity. The results are shown in Table 6.

[0075] Table 6 Performance test results of carbonized blocks obtained in Comparative Example 3

[0076]

[0077] Remark:

[0078] 1. Carbonization depth: After carbonization curing, the cross section of the block body is sprayed with 1wt% phenolphthalein alcohol solution, and the height direction of the block cross section does not show the depth of red.

[0079] 2.

[0080] 3.

[0081] The present invention is not limited to the above-described embodiments. Persons skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are deemed to be within the scope of protection of the present invention. Any matters not described in detail in this specification constitute prior art known to those skilled in the art.

Claims

1. A lightweight carbonized building block, characterized in that: The raw materials and their weight percentages include: 100 parts of dry mix, 4-6 parts of water, and 5-15 parts of carbon-containing ice balls; wherein the dry mix is composed of a gelling material, a skeleton material, and a filling powder, and the gelling material includes an air-hardening gelling material; the carbon-containing ice balls are formed by freezing a carbon-containing solution; The main gas-hardening mineral content in the cementitious material is 50-90%, and it is composed of one or more of CS, C3S2, C2S, and C3S; The cementitious material accounts for 10-25% of the mass of the dry mix; The carbon-containing solution is obtained by temperature-controlling the solution in a vacuum, sealed water-containing container, then introducing carbon dioxide gas to a constant pressure, and then maintaining the temperature and pressure; the temperature of the temperature-control treatment is 5 to 25° C.; the pressure used in the pressure-maintaining step is 5 to 20 MPa; and the pressure is maintained until the concentration of carbon dioxide per 100 g of water is greater than 5 g; The particle size of the carbon-containing ice balls is 1 to 10 mm; The obtained carbon-containing ice balls are uniformly mixed with a cementitious material containing an air-hard component, a skeleton material, a filling powder, and water in proportion to prepare a wet mixture, and then statically pressed and carbonized to prepare carbonized blocks; The process parameters adopted in the carbonization curing step include: CO2 concentration 20~60vol%, pressure 0.1~0.3MPa, temperature 20~30℃, and curing time 4~12h.

2. The lightweight carbonized building block according to claim 1, characterized in that: The particle size of the carbon-containing ice balls is 5 to 10 mm.

3. The lightweight carbonized building block according to claim 1, characterized in that: The cementitious material is composed of one or more of low-carbon cement, steel slag and magnesium slag.

4. The lightweight carbonized building block according to claim 1, characterized in that: The skeleton material is composed of one or more of aggregate undersize, crushed waste concrete, and crushed waste sintered bricks, with a particle size of 5-10 mm and a crushing value of 10-30%; the filling powder is composed of one or more of ground filter press soil, heavy calcium powder, and dust collected from sand making buildings, with an 80 μm sieve residue of 10-20%.

5. The method for preparing the lightweight carbonized building block according to any one of claims 1 to 4, characterized in that: The specific steps include: 1) Evenly mix the cementitious material, skeleton material, filling powder and water weighed in proportion to obtain a wet mixture; 2) Block body forming: the wet mixture is mixed with carbon-containing ice balls according to a proportion, and pressed into shape to obtain a block body; 3) Carbonization curing: The obtained block body is subjected to carbonization curing to obtain the carbonized block product.

6. The preparation method according to claim 5, characterized in that Step 2) The compression molding step adopts a static pressure molding method with a molding pressure of 10-30 MPa.

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