A method for preparing low-carbon imitation stone bricks by cascading utilization of construction waste

Abstract

The present invention relates to the field of building material technology, and in particular to a method for preparing low-carbon imitation stone bricks through the cascade utilization of construction waste. The present invention first sieves construction waste to obtain construction waste coarse aggregate, construction waste fine aggregate and construction waste powder, then mixes a portion of the construction waste powder with cement, blast furnace slag, red mud, desulfurized gypsum and water to granulate to obtain unburned ceramsite coarse aggregate; then, the construction waste coarse aggregate, construction waste fine aggregate, construction waste powder and unburned ceramsite coarse aggregate are mixed with cement, iron tailings and water through model grading, and low-carbon imitation stone bricks are prepared by static pressing at room temperature. The present invention divides construction waste into two steps for cascade utilization, which can not only greatly improve the utilization rate of construction waste powder, but also achieve the purpose of high-value utilization of solid waste. The entire production process of the imitation stone bricks has low carbon emissions and low energy consumption, and the imitation stone bricks produced have good mechanical properties and a compressive strength of up to 80 MPa.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a method for preparing low-carbon imitation stone bricks by cascading construction waste. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Construction waste refers to the slag, abandoned soil, discarded materials, silt, and other waste generated by construction companies or individuals during the construction, laying, demolition, and repair of various buildings, structures, and pipelines. The vast majority of this waste is transported untreated to suburban areas or rural areas, where it is dumped in open-air piles or landfilled, consuming significant construction costs, including land acquisition fees and waste removal costs. Therefore, the resource utilization of construction waste has significant social and economic value.

[0004] In the existing technology, construction waste is mostly used as coarse aggregate for concrete. The utilization rate of construction waste powder with a particle size of less than 100μm is very low, and a large amount of construction waste powder is discarded and stored. This is because the excessively high powder content will cause the water absorption and dilution effect to be greater than the filling effect, making it difficult to improve product performance and difficult to use in concrete buildings and building materials products.

[0005] In existing technology, the use of construction waste powder, cement, organic adhesives, and curing agents to produce building materials such as imitation stone bricks requires the addition of large amounts of organic additives to improve product performance. These bricks can slowly release harmful gases and chemicals, negatively impacting human health and the surrounding environment. Without organic adhesives, imitation stone bricks require a large amount of cement to improve performance and require high-temperature steam curing after molding. This high-temperature steam curing consumes significant energy, resulting in high production costs and high carbon emissions over the product's lifecycle.

[0006] Furthermore, existing construction waste aggregate processing techniques lack scientific guidance, often requiring direct screening and reuse without grading. This results in low product density and difficulty improving performance. Furthermore, the particle size distribution of raw construction waste makes it difficult to meet grading requirements, limiting the performance of imitation stone bricks due to the raw materials. Summary of the Invention

[0007] In view of this, the present invention provides a method for preparing low-carbon imitation stone bricks through cascade utilization of construction waste, which solves the problems of low utilization rate of construction waste powder, poor product performance and high carbon emissions throughout the product life cycle.

[0008] In a first aspect, the present invention provides a method for preparing low-carbon imitation stone bricks by cascading construction waste, comprising the following steps:

[0009] Step S1: removing impurities, crushing, and screening construction waste to obtain construction waste coarse aggregate, construction waste fine aggregate, and construction waste powder; a portion of the construction waste powder is used in step S2, and the other portion is used in step S3;

[0010] Step S2: mixing the construction waste powder obtained in step S1 with cement, blast furnace slag, red mud, desulfurized gypsum and water to form pellets, controlling the pellet size to be 5-15 mm, and then placing the obtained ceramsite in a natural environment for a period of time to obtain unburned ceramsite coarse aggregate containing construction waste;

[0011] Step S3: mixing the construction waste coarse aggregate, construction waste fine aggregate and construction waste powder obtained in step S1, and the unburned ceramsite coarse aggregate obtained in step S2 with cement, iron tailings and water, and preparing low-carbon imitation stone bricks by static pressing at room temperature.

[0012] Preferably, in step S1, the particle size of the construction waste coarse aggregate is 5-15 mm; further preferably, the construction waste coarse aggregate is sieved into two particle sizes of 5-10 mm and 10-15 mm; the particle size of the construction waste fine aggregate is 0.075-5 mm; and the particle size of the construction waste powder is 0.01-0.075 mm.

[0013] Preferably, in step S2, the added amount of each component is, by weight, 20-30 parts of cement, 20-25 parts of blast furnace slag, 25-30 parts of red mud, 10-15 parts of desulfurized gypsum, 35-40 parts of construction waste powder, and 18-22 parts of water.

[0014] Preferably, in step S2, the obtained ceramsite is placed in a natural environment for 25-30 days.

[0015] Preferably, the cement in step S2 and step S3 is sulphoaluminate cement. Preferably, the fineness of the sulphoaluminate cement is 400m 2 / kg±10m 2 / kg; the fineness of the iron tailings is 50m 2 / kg±5m 2 / kg.

[0016] Preferably, in step S3, the ratio of construction waste coarse aggregate, construction waste fine aggregate, construction waste powder, unburned ceramsite coarse aggregate, cement and iron tailings is determined according to the closest packing model, and the improved Andreasen & Andersen model is used for fitting, and the raw material ratio is obtained after fitting.

[0017] Furthermore, the fitting results are calculated by weight as follows: 2-10 parts of construction waste powder, 10-20 parts of construction waste fine aggregate, 10-20 parts of construction waste coarse aggregate, 10-20 parts of unburned ceramsite coarse aggregate, 25-35 parts of cement, 25-35 parts of iron ore tailings, and 12-20 parts of water. Further preferably, the construction waste coarse aggregate comprises 5-10 mm sized construction waste coarse aggregate and 3-8 parts sized construction waste coarse aggregate; and the unburned ceramsite coarse aggregate comprises 5-12 parts sized construction waste coarse aggregate and 3-8 parts sized construction waste coarse aggregate.

[0018] Preferably, in step S3, the pressure of the normal temperature static pressing molding is 20-30 MPa.

[0019] Preferably, the method further comprises step S4: subjecting the low-carbon imitation stone bricks obtained in step S3 to natural curing for 2-4 days, and then carbonization curing in a CO2 environment. Preferably, the CO2 concentration is 10-30%, the carbonization pressure is 0.1-0.6 MPa, and the carbonization time is 2-4 hours. Preferably, the CO2 environment is industrial flue gas.

[0020] Furthermore, the carbonized imitation stone bricks in step S4 are subjected to natural curing for 7-14 days to obtain high-performance low-carbon imitation stone bricks. Furthermore, the obtained high-performance low-carbon imitation stone bricks are surface treated using a shot blasting machine or a water mill.

[0021] In a second aspect, the present invention provides a low-carbon imitation stone brick obtained by the method for preparing low-carbon imitation stone bricks by utilizing construction waste steps as described in the first aspect.

[0022] In a third aspect, the present invention provides an application of the low-carbon imitation stone bricks in the field of construction.

[0023] It can be seen from the above technical solution that the present invention has achieved the following beneficial effects:

[0024] (1) The present invention uses unburned expanded clay prepared from construction waste powder as coarse aggregate, and uses it together with construction waste coarse aggregate and construction waste fine aggregate as raw materials to prepare imitation stone bricks. The construction waste is divided into two steps for cascade utilization, which can not only greatly improve the utilization rate of construction waste powder, but also effectively reduce the dead weight of imitation stone bricks and improve thermal insulation effect. At the same time, it can absorb a large amount of solid waste such as construction waste, red mud, iron tailings, blast furnace slag, etc., thereby achieving the purpose of high-value utilization of solid waste.

[0025] (2) The entire production process of the imitation stone bricks of the present invention is carried out at room temperature, avoiding the use of high-temperature firing technology. It is not only green, energy-saving and environmentally friendly, but also has a cost that is at least 30% lower than that of natural stone bricks, which has significant social and economic benefits.

[0026] (3) The raw materials of the present invention are designed and proportioned based on the improved Andreasen & Andersen model, which can enable the materials to achieve the most dense stacking, thereby obtaining high density, high strength, high durability, and high impermeability. The compressive strength of the imitation stone brick can reach 80MPa.

[0027] (4) The imitation stone bricks of the present invention have a low cement content and use CO2 carbonization instead of traditional high-temperature curing, which gives full play to the carbon sequestration potential of solid waste, reduces energy consumption, consumes carbon dioxide, and shortens the curing cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute undue limitations thereon. It is obvious that one of ordinary skill in the art could derive other drawings based on these drawings without inventive effort.

[0029] Figure 1 This is a schematic flow chart of the preparation process of the low-carbon imitation stone brick of the present invention;

[0030] Figure 2 1 is the raw material particle size distribution and optimized gradation diagram of Example 1 and Example 2 of the present invention;

[0031] Figure 3 This is a picture of the surface texture of the imitation stone brick product prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0033] As pointed out in the background art, the utilization rate of construction waste powder in the existing technology is low, and the product performance is low. At the same time, there will be high carbon emissions in the process of utilizing construction waste.

[0034] In view of this, the present invention provides a method for preparing low-carbon imitation stone bricks by cascading construction waste, comprising the following steps:

[0035] Step S1: removing impurities, crushing, and screening construction waste to obtain construction waste coarse aggregate, construction waste fine aggregate, and construction waste powder; a portion of the construction waste powder is used in step S2, and the other portion is used in step S3;

[0036] Step S2: mixing the construction waste powder obtained in step S1 with cement, blast furnace slag, red mud, desulfurized gypsum and water to form pellets, controlling the pellet size to be 5-15 mm, and then placing the obtained ceramsite in a natural environment for a period of time to obtain unburned ceramsite coarse aggregate containing construction waste;

[0037] Step S3: mixing the construction waste coarse aggregate, construction waste fine aggregate and construction waste powder obtained in step S1, and the unburned ceramsite coarse aggregate obtained in step S2 with cement, iron tailings and water, and preparing low-carbon imitation stone bricks by static pressing at room temperature.

[0038] The construction waste described in the present invention includes slag, waste concrete, waste bricks and stones, etc.

[0039] The cement described in steps S2 and S3 of the present invention is sulfoaluminate cement. The present invention does not restrict its source; commercially available aluminum sulfate cement can be used. In the prior art, the cementitious material in construction waste bricks is generally based on Portland cement. However, the present invention utilizes sulfoaluminate cement as the cementitious material, leveraging its early and high strength characteristics to significantly enhance the strength of the stone. Furthermore, due to the micro-expansion of sulfoaluminate cement during its hydration process, it solves the problem of self-shrinkage and cracking in conventional imitation stone bricks.

[0040] The impurity removal of the present invention is preferably manual and mechanical sorting to remove impurities. The present invention does not limit the method of crushing and screening the construction waste powder, and methods well known to those skilled in the art can be used.

[0041] In the present invention, the particle size of the construction waste coarse aggregate is 5-15 mm; preferably, it is further sieved into two particle sizes of 5-10 mm and 10-15 mm; the particle size of the construction waste fine aggregate is 0.075-5 mm; and the particle size of the construction waste powder is 0.01-0.075 mm.

[0042] In step S2 of the present invention, the added amounts of the components are, by weight, 20-30 parts of cement, 20-25 parts of blast furnace slag, 25-30 parts of red mud, 10-15 parts of desulfurized gypsum, 35-40 parts of construction waste powder, and 18-22 parts of water.

[0043] The ceramsite obtained in step S2 of the present invention is placed in a natural environment for 25-30 days. The ceramsite in the prior art is generally formed by firing, which requires a large amount of energy. However, the ceramsite of the present invention contains an appropriate amount of sulfoaluminate cement, which can enable the ceramsite to rapidly increase in strength during placement in a natural environment, avoid the sintering process, and save energy.

[0044] In step S3 of the present invention, the ratio of construction waste coarse aggregate, construction waste fine aggregate, construction waste powder, unburned ceramsite coarse aggregate, cement and iron tailings is determined according to the closest packing model, and the improved Andreasen & Andersen model is used for fitting. The present invention takes into account the particle size distribution of construction waste coarse aggregate, construction waste fine aggregate and the content of construction waste powder, guides the particle size distribution of ceramsite granulation according to the closest packing model, and maximizes the utilization rate of powder and aggregates of various particle sizes. Specifically, formula (I) is used as the objective function, and the least squares method is used to obtain the optimal fit between the composite material and the target curve, so that when the raw material particle size distribution changes, the particle size distribution and weight fraction of the unburned ceramsite prepared are dynamically adjusted according to the calculation, so that the aggregate ratio reaches the highest density.

[0045]

[0046] Where P(D) is the cumulative percentage of particles under the sieve; D is the current particle size (μm); D min is the minimum particle size (μm); D max is the maximum particle size (μm); q is the distribution coefficient, which ranges from 0.18 to 0.23.

[0047] According to the calculation results of formula (I), the proportions of each component are obtained, by weight: 2-10 parts of construction waste powder, 10-20 parts of construction waste fine aggregate, 10-20 parts of construction waste coarse aggregate, 10-20 parts of unburned ceramsite coarse aggregate, 25-35 parts of cement, 25-35 parts of iron ore tailings, and 12-20 parts of water. Further preferably, the construction waste coarse aggregate comprises 5-12 parts of 5-10mm coarse aggregate and 3-8 parts of 10-15mm coarse aggregate; and the unburned ceramsite coarse aggregate comprises 5-12 parts of 5-10mm coarse aggregate and 3-8 parts of 10-15mm coarse aggregate. Further screening of the coarse aggregate particle size facilitates achieving a higher density.

[0048] The pressure of the static pressing molding at room temperature in step S3 of the present invention is 20-30 MPa. This molding pressure is conducive to the preparation of imitation stone bricks with excellent mechanical properties.

[0049] The present invention further includes step S4: subjecting the low-carbon imitation stone bricks obtained in step S3 to natural curing for 2-4 days, followed by carbonization in a CO2 environment with a CO2 concentration of 10-30%. Preferably, the CO2 environment is industrial flue gas, with a carbonization pressure of 0.1-0.6 MPa and a carbonization time of 2-4 hours. This rapid carbonization further increases matrix density, improves product performance, and simultaneously achieves CO2 capture, reducing the product's carbon emission coefficient.

[0050] The present invention further subjects the carbonized imitation stone bricks in step S4 to natural curing for 7-14 days to obtain high-performance, low-carbon imitation stone bricks. The present invention uses CO2 curing and natural curing instead of traditional high-temperature steam curing, significantly reducing material CO2 emissions and production energy consumption while shortening curing time.

[0051] Furthermore, the present invention uses a shot blasting machine or a water mill to perform surface treatment on the obtained high-performance low-carbon imitation stone bricks, thereby obtaining a surface with natural stone textures such as flamed surface, litchi surface and terrazzo effects, which has a good ornamental effect.

[0052] The schematic diagram of the preparation process of the low-carbon imitation stone brick of the present invention is as follows Figure 1 shown.

[0053] The technical solution of the present invention is further described below with reference to specific embodiments.

[0054] Example 1

[0055] The construction waste including slag, waste concrete and waste bricks and stones are collected, sundries are removed, crushed and sieved to obtain construction waste coarse aggregate with particle size of 5-10mm and 10-15mm, construction waste fine aggregate with particle size of 0.075-5mm and construction waste powder with particle size of 0.01-0.075mm.

[0056] After drying, sulphoaluminate cement, blast furnace slag, red mud, desulfurized gypsum and construction waste powder are mixed according to the following weight parts: 30 parts of sulphoaluminate cement, 20 parts of blast furnace slag, 25 parts of red mud, 10 parts of desulfurized gypsum, 35 parts of construction waste powder and 18 parts of water.

[0057] The mixed material was fed into a pelletizer with a diameter, angle, and speed of 60 cm, 45°, and 25 rpm, respectively. The pellet size was controlled to 5-15 mm. The resulting ceramsite was then placed in a natural environment for 28 days to produce unburned ceramsite containing construction waste. The ceramsite was then sieved into two particle sizes: 5-10 mm and 10-15 mm, which served as unburned ceramsite coarse aggregate.

[0058] Sulphoaluminate cement, iron tailings, construction waste powder, construction waste coarse aggregate, construction waste fine aggregate and unburned ceramsite coarse aggregate were selected as the artificial stone substrate, and the improved Andreasen & Andersen model was used for fitting. The fitting diagram is shown in the figure. Figure 2 , and obtain the mixing ratio, by mass, 28 parts of cement, 28 parts of iron tailings, 3 parts of construction waste powder, 15 parts of construction waste fine aggregate, 7 parts of 5-10mm construction waste coarse aggregate, 5 parts of 10-15mm construction waste coarse aggregate, 8 parts of 5-10mm unburned ceramsite coarse aggregate, 4 parts of 10-15mm unburned ceramsite coarse aggregate, and 14 parts of water.

[0059] The base materials were mixed, filled into a 300*600*30 artificial stone mold, and molded under a pressure of 25 MPa.

[0060] The formed stone was first subjected to natural curing for 3 days and then carbonized in a CO2 environment with a CO2 concentration of 30%, a carbonization pressure of 0.6 MPa, and a carbonization time of 4 hours. After carbonization, the stone was further subjected to natural curing for 14 days to obtain the high-performance carbonized imitation stone brick.

[0061] Use water mill for surface treatment to make the product reach the natural stone texture of terrazzo, such as Figure 3 shown.

[0062] Example 2

[0063] The construction waste including slag, waste concrete and waste bricks and stones are collected, sundries are removed, crushed and sieved to obtain construction waste coarse aggregate with particle size of 5-10mm and 10-15mm, construction waste fine aggregate with particle size of 0.075-5mm and construction waste powder with particle size of 0.01-0.075mm.

[0064] After drying, sulphoaluminate cement, blast furnace slag, red mud, desulfurized gypsum and construction waste powder are mixed according to the following weight parts: 25 parts of sulphoaluminate cement, 25 parts of blast furnace slag, 30 parts of red mud, 15 parts of desulfurized gypsum, 40 parts of construction waste powder and 22 parts of water.

[0065] The mixed material is fed into a pelletizer with a diameter, angle, and rotation speed of 60 cm, 45°, and 25 rpm, respectively. The pellet size is controlled to be 5-10 mm. The resulting ceramsite is then placed in a natural environment for 28 days to produce unburned ceramsite coarse aggregate containing construction waste.

[0066] Sulphoaluminate cement, iron tailings, construction waste powder, construction waste coarse aggregate, construction waste fine aggregate and unburned ceramsite coarse aggregate were selected as the artificial stone substrate, and the improved Andreasen & Andersen model was used for fitting. The fitting diagram is shown in the figure. Figure 2 , and obtain the mixing ratio, by mass, 32 parts of cement, 30 parts of iron tailings, 10 parts of construction waste powder, 17 parts of construction waste fine aggregate, 10 parts of 5-10mm construction waste coarse aggregate, 3 parts of 10-15mm particle size construction waste coarse aggregate, 12 parts of 5-10mm unburned ceramsite coarse aggregate, 3 parts of 10-15mm particle size unburned ceramsite coarse aggregate, and 14 parts of water.

[0067] The base materials were mixed, filled into a 300*600*30 artificial stone mold, and molded under a pressure of 25 MPa.

[0068] The formed stone was first subjected to natural curing for 3 days and then carbonized in a CO2 environment with a CO2 concentration of 30%, a carbonization pressure of 0.6 MPa, and a carbonization time of 4 hours. After carbonization, the stone was further subjected to natural curing for 14 days to obtain the high-performance carbonized imitation stone brick.

[0069] Use a water grinder for surface treatment to give the product the natural stone texture of terrazzo.

[0070] Comparative Example 1

[0071] The construction waste including slag, waste concrete and waste bricks and stones are collected, sundries are removed, crushed and sieved to obtain construction waste coarse aggregate with particle size of 5-10mm and 10-15mm, construction waste fine aggregate with particle size of 0.075-5mm and construction waste powder with particle size of 0.01-0.075mm.

[0072] Sulphoaluminate cement, iron tailings, construction waste powder, construction waste coarse aggregate and construction waste fine aggregate were selected as the artificial stone base material. The improved Andreasen&Andersen model was used to fit the mix ratio, which is 28 parts by mass of cement, 28 parts of iron tailings, 3 parts of construction waste powder, 15 parts of construction waste fine aggregate, 15 parts of 5-10mm construction waste coarse aggregate, 9 parts of 10-15mm construction waste coarse aggregate, and 14 parts of water.

[0073] The base materials were mixed, filled into a 300*600*30 artificial stone mold, and molded under a pressure of 25 MPa.

[0074] The formed stone was first subjected to natural curing for 3 days and then carbonized in a CO2 environment with a CO2 concentration of 30%, a carbonization pressure of 0.6 MPa, and a carbonization time of 4 hours. After carbonization, the stone was further subjected to natural curing for 14 days to obtain the high-performance carbonized imitation stone brick.

[0075] Use a water grinder for surface treatment to give the product the natural stone texture of terrazzo.

[0076] Comparative Example 2

[0077] The construction waste including slag, waste concrete and waste bricks and stones are collected, sundries are removed, crushed and sieved to obtain construction waste coarse aggregate with particle size of 5-10mm and 10-15mm, construction waste fine aggregate with particle size of 0.075-5mm and construction waste powder with particle size of 0.01-0.075mm.

[0078] Sulphoaluminate cement, iron tailings, construction waste powder, construction waste coarse aggregate and construction waste fine aggregate were selected as the artificial stone base material. The improved Andreasen&Andersen model was used to fit the mix ratio, which was 26 parts by mass of cement, 26 parts of iron tailings, 10 parts of construction waste powder, 15 parts of construction waste fine aggregate, 20 parts of 5-10mm construction waste coarse aggregate, 6 parts of 10-15mm construction waste coarse aggregate, and 14 parts of water.

[0079] The base materials were mixed, filled into a 300*600*30 artificial stone mold, and molded under a pressure of 25 MPa.

[0080] The formed stone was first subjected to natural curing for 3 days and then carbonized in a CO2 environment with a CO2 concentration of 30%, a carbonization pressure of 0.6 MPa, and a carbonization time of 4 hours. After carbonization, the stone was further subjected to natural curing for 14 days to obtain the high-performance carbonized imitation stone brick.

[0081] Use a water grinder for surface treatment to give the product the natural stone texture of terrazzo.

[0082] Comparative Example 3

[0083] The construction waste including slag, waste concrete and waste bricks and stones are collected, sundries are removed, crushed and sieved to obtain construction waste coarse aggregate with particle size of 5-10mm and 10-15mm, construction waste fine aggregate with particle size of 0.075-5mm and construction waste powder with particle size of 0.01-0.075mm.

[0084] After drying, sulphoaluminate cement, blast furnace slag, red mud and desulfurized gypsum are mixed according to the following weight parts: 30 parts of sulphoaluminate cement, 20 parts of blast furnace slag, 25 parts of red mud, 10 parts of desulfurized gypsum and 18 parts of water.

[0085] The mixture was fed into a pelletizer with a diameter, angle, and speed of 60 cm, 45°, and 25 rpm, respectively. The pellet size was controlled to 5-15 mm. The resulting ceramsite was then placed in a natural environment for 28 days to produce unburned ceramsite free of construction waste. The ceramsite was then sieved into two particle sizes: 5-10 mm and 10-15 mm, which served as unburned ceramsite coarse aggregate.

[0086] Sulphoaluminate cement, iron tailings, construction waste powder, construction waste coarse aggregate, construction waste fine aggregate and unburned ceramsite coarse aggregate were selected as the artificial stone base material. The improved Andreasen&Andersen model was used to fit the mix ratio, which is calculated by mass as follows: 28 parts of cement, 28 parts of iron tailings, 3 parts of construction waste powder, 15 parts of construction waste fine aggregate, 7 parts of 5-10mm construction waste coarse aggregate, 5 parts of 10-15mm construction waste coarse aggregate, 8 parts of 5-10mm unburned ceramsite coarse aggregate, 4 parts of 10-15mm unburned ceramsite coarse aggregate, and 14 parts of water.

[0087] The base materials were mixed, filled into a 300*600*30 artificial stone mold, and molded under a pressure of 25 MPa.

[0088] The formed stone was first subjected to natural curing for 3 days and then carbonized in a CO2 environment with a CO2 concentration of 30%, a carbonization pressure of 0.6 MPa, and a carbonization time of 4 hours. After carbonization, the stone was further subjected to natural curing for 14 days to obtain the high-performance carbonized imitation stone brick.

[0089] Use a water grinder for surface treatment to give the product the natural stone texture of terrazzo.

[0090] Comparative Example 4

[0091] The construction waste including slag, waste concrete and waste bricks and stones are collected, sundries are removed, crushed and sieved to obtain construction waste coarse aggregate with particle size of 5-10mm and 10-15mm, construction waste fine aggregate with particle size of 0.075-5mm and construction waste powder with particle size of 0.01-0.075mm.

[0092] After drying, sulphoaluminate cement, blast furnace slag, red mud and desulfurization gypsum are mixed according to the following weight parts: 30 parts of sulphoaluminate cement, 20 parts of blast furnace slag, 25 parts of red mud, 10 parts of desulfurization gypsum, 35 parts of construction waste powder and 18 parts of water.

[0093] The mixture was fed into a pelletizer with a diameter, angle, and speed of 60 cm, 45°, and 25 rpm, respectively. The pellet size was controlled to 5-15 mm. The resulting ceramsite was then placed in a natural environment for 28 days to produce unburned ceramsite free of construction waste. The ceramsite was then sieved into two particle sizes: 5-10 mm and 10-15 mm, which served as unburned ceramsite coarse aggregate.

[0094] Without fitting the densest packing model, calculated by mass, there are 28 parts of cement, 28 parts of iron tailings, 5 parts of construction waste powder, 15 parts of construction waste fine aggregate, 15 parts of 5-10mm construction waste coarse aggregate, 10 parts of 10-15mm construction waste coarse aggregate, 15 parts of 5-10mm unburned ceramsite coarse aggregate, 10 parts of 10-15mm unburned ceramsite coarse aggregate, and 14 parts of water.

[0095] The base materials were mixed, filled into a 300*600*30 artificial stone mold, and molded under a pressure of 25 MPa.

[0096] The formed stone was first subjected to natural curing for 3 days and then carbonized in a CO2 environment with a CO2 concentration of 30%, a carbonization pressure of 0.6 MPa, and a carbonization time of 4 hours. After carbonization, the stone was further subjected to natural curing for 14 days to obtain the high-performance carbonized imitation stone brick.

[0097] Use a water grinder for surface treatment to give the product the natural stone texture of terrazzo.

[0098] Comparative Example 5

[0099] The construction waste including slag, waste concrete and waste bricks and stones are collected, sundries are removed, crushed and sieved to obtain construction waste coarse aggregate with particle size of 5-10mm and 10-15mm, construction waste fine aggregate with particle size of 0.075-5mm and construction waste powder with particle size of 0.01-0.075mm.

[0100] After drying, sulphoaluminate cement, blast furnace slag, red mud, desulfurized gypsum and construction waste powder are mixed according to the following weight parts: 30 parts of sulphoaluminate cement, 20 parts of blast furnace slag, 25 parts of red mud, 10 parts of desulfurized gypsum, 35 parts of construction waste powder and 18 parts of water.

[0101] The mixed material was fed into a pelletizer with a diameter, angle, and speed of 60 cm, 45°, and 25 rpm, respectively. The pellet size was controlled to 5-15 mm. The resulting ceramsite was then placed in a natural environment for 28 days to produce unburned ceramsite containing construction waste. The ceramsite was then sieved into two particle sizes: 5-10 mm and 10-15 mm, which served as unburned ceramsite coarse aggregate.

[0102] Sulphoaluminate cement, iron tailings, construction waste powder, construction waste coarse aggregate, construction waste fine aggregate and unburned ceramsite coarse aggregate were selected as the artificial stone substrate, and the improved Andreasen & Andersen model was used for fitting. The fitting diagram is shown in the figure. Figure 2 , and obtain the mixing ratio, by mass, 28 parts of cement, 28 parts of iron tailings, 3 parts of construction waste powder, 15 parts of construction waste fine aggregate, 7 parts of 5-10mm construction waste coarse aggregate, 5 parts of 10-15mm construction waste coarse aggregate, 8 parts of 5-10mm unburned ceramsite coarse aggregate, 4 parts of 10-15mm unburned ceramsite coarse aggregate, and 14 parts of water.

[0103] The base materials were mixed, filled into a 300*600*30 artificial stone mold, and molded under a pressure of 25 MPa.

[0104] The formed stone is naturally cured for 7 days. After the strength reaches the surface treatment requirements, it is surface treated with a water mill to achieve the natural stone texture of terrazzo.

[0105] Test example

[0106] The compressive strength and flexural strength of the imitation stone bricks obtained in Examples 1-2 and Comparative Examples 1-4 were measured according to GB / T 41919-2022. The results are shown in Table 1.

[0107] Table 1 Mechanical properties test results of imitation stone bricks

[0108] Examples / Comparative Examples Compressive strength / MPa Flexural strength / MPa Construction waste powder utilization rate / % Example 1 86.7 11.2 6.63 Example 2 83.8 10.8 12.35 Comparative Example 1 80.4 9.9 3.06 Comparative Example 2 77.9 9.2 9.71 Comparative Example 3 85.8 10.8 3.06 Comparative Example 4 75.6 9.1 9.76 Comparative Example 5 79.8 10.3 6.63

[0109] Note: The utilization rate of construction waste powder is the ratio of the total amount of construction waste powder to the total amount of dry materials (excluding water). For example, in Example 1, the utilization rate of construction waste powder is:

[0110] (35 / (30+20+25+10+35)*(8+4)+3) / (28+28+3+15+7+5+8+4)=6.63%.

[0111] As can be seen from Table 1, the products of Examples 1 and 2 of the present invention maintain high compressive strength (above 83 MPa) and flexural strength (above 10.5 MPa) when the utilization rate of construction waste powder exceeds 6%. The strength of Comparative Examples 1 and 2, which do not add unfired ceramsite, is significantly reduced. Comparative Example 2, which adds a higher amount of construction waste powder, has a lower compressive strength and flexural strength than Comparative Example 1, indicating that increasing the amount of construction waste powder will have a negative impact on the mechanical strength of the imitation stone brick. The unfired ceramsite in Comparative Example 3 does not add construction waste powder, and its compressive strength and flexural strength are similar to those of Example 1, slightly lower than that of Example 1, indicating that adding construction waste powder to the unfired ceramsite not only improves the powder utilization rate but also has a positive impact on the mechanical properties. The product of Comparative Example 4, which does not have the closest packing, has the worst mechanical properties. The mechanical strength of the imitation stone brick prepared according to the raw material ratio obtained by the closest packing is significantly improved. The mechanical properties of the product of Comparative Example 5 are worse than those of the product of Example 1, indicating that carbon dioxide curing of the imitation stone bricks can further improve the mechanical strength of the product.

[0112] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing low-carbon imitation stone bricks by cascading construction waste, characterized in that: The steps include: Step S1: removing impurities, crushing, and screening the construction waste to obtain construction waste coarse aggregate, construction waste fine aggregate, and construction waste powder; Part of the construction waste powder is used in step S2, and the other part is used in step S3; Step S2: mixing the construction waste powder obtained in step S1 with cement, blast furnace slag, red mud, desulfurized gypsum and water to form pellets, controlling the pellet size to be 5-15 mm, and then placing the obtained ceramsite in a natural environment for a period of time to obtain unburned ceramsite coarse aggregate containing construction waste; Step S3: mixing the construction waste coarse aggregate, construction waste fine aggregate and construction waste powder obtained in step S1, and the unburned ceramsite coarse aggregate obtained in step S2 with cement, iron tailings and water, and preparing low-carbon imitation stone bricks by static pressing at room temperature; Step S4: The low-carbon imitation stone bricks obtained in step S3 are first subjected to natural curing for 2-4 days, and then carbonized in a CO2 environment; the carbonized low-carbon imitation stone bricks are further subjected to natural curing for 7-14 days to obtain high-performance low-carbon imitation stone bricks; In step S3, the proportions of construction waste coarse aggregate, construction waste fine aggregate, construction waste powder, unburned ceramsite coarse aggregate, cement and iron tailings are determined according to the closest packing model, and the improved Andreasen & Andersen model is used for fitting.

2. The method for preparing low-carbon imitation stone bricks by cascading construction waste as claimed in claim 1, characterized in that: In step S1, the particle size of the coarse aggregate of construction waste is 5-15 mm; the particle size of the fine aggregate of construction waste is 0.075-5 mm; the particle size of the construction waste powder is 0.01-0.075 mm; in step S3, the fineness of the cement is 400 mm. 2 / kg±10 m 2 / kg; the fineness of the iron tailings is 50m 2 / kg±5 m 2 / kg.

3. The method for preparing low-carbon imitation stone bricks by cascading construction waste as claimed in claim 1, characterized in that: In step S2, the added amounts of the components are as follows, by weight: 20-30 parts of cement, 20-25 parts of blast furnace slag, 25-30 parts of red mud, 10-15 parts of desulfurized gypsum, 35-40 parts of construction waste powder, and 18-22 parts of water.

4. The method for preparing low-carbon imitation stone bricks by cascading construction waste as claimed in claim 1, characterized in that: In step S2, the obtained ceramsite is placed in a natural environment for 25-30 days; in step S3, the pressure of the static pressing molding at room temperature is 20-30 MPa.

5. The method for preparing low-carbon imitation stone bricks by cascading construction waste as claimed in claim 1, characterized in that: The cement in step S2 and step S3 is both sulphoaluminate cement.

6. The method for preparing low-carbon imitation stone bricks by cascading construction waste as claimed in claim 1, characterized in that: The fitting results are calculated by weight: 2-10 parts of construction waste powder, 10-20 parts of construction waste fine aggregate, 10-20 parts of construction waste coarse aggregate, 10-20 parts of unburned ceramsite coarse aggregate, 25-35 parts of cement, 25-35 parts of iron tailings, and 12-20 parts of water.

7. The method for preparing low-carbon imitation stone bricks by cascading construction waste as claimed in claim 6, characterized in that: Among the construction waste coarse aggregate, 5-12 parts of construction waste coarse aggregate with a particle size of 5-10mm are used, and 3-8 parts of construction waste coarse aggregate with a particle size of 10-15mm are used; among the unburned ceramsite coarse aggregate, 5-12 parts of unburned ceramsite coarse aggregate with a particle size of 5-10mm are used, and 3-8 parts of unburned ceramsite coarse aggregate with a particle size of 10-15mm are used.

8. The method for preparing low-carbon imitation stone bricks by cascading construction waste as claimed in claim 1, characterized in that: The obtained high-performance low-carbon imitation stone bricks are surface-treated by a shot blasting machine or a water mill.

9. The method for preparing low-carbon imitation stone bricks by cascading construction waste as claimed in claim 1, characterized in that: The concentration of CO2 in the carbonization process is 10-30%, the carbonization pressure is 0.1-0.6 MPa, and the carbonization time is 2-4 hours.

10. The method for preparing low-carbon imitation stone bricks by cascading construction waste as claimed in claim 1, characterized in that: The CO2 environment is industrial flue gas.

11. A low-carbon imitation stone brick obtained by the method for preparing low-carbon imitation stone bricks by utilizing construction waste steps as claimed in any one of claims 1 to 10.

12. Use of the low-carbon imitation stone brick according to claim 11 in the field of construction.

Images