A low-carbon ramming concrete material, its preparation method and application

Abstract

The present invention belongs to the technical field of building materials, and discloses a low-carbon ramming concrete material, a preparation method thereof and an application. The low-carbon ramming concrete material comprises the following raw materials in parts by mass: 10-25 parts of low-carbon ramming concrete cementitious material, 5-15 parts of water, 0.1-2 parts of admixture, 0.5-1 part of fiber, 30-45 parts of coarse aggregate, and 25-40 parts of sand; wherein, the low-carbon ramming concrete cementitious material comprises the following raw materials in parts by mass: 5-15 parts of composite calcined powder, 1-6 parts of limestone powder, 0-6 parts of aggregate washing slag, 1 part of gypsum, and 2-6 parts of ordinary portland cement. The low-carbon ramming concrete material of the present invention has high mechanical properties and excellent durability, and does not require artificial addition of pigments, and the color can be regulated during the production process by adjusting the raw materials.

Description

Technical Field

[0001] The invention belongs to the technical field of building materials, and particularly relates to a low-carbon rammed concrete material and a preparation method and application thereof. Background Art

[0002] Traditional rammed earth is a construction technology with a long and widespread history of traditional housing construction in rural my country, primarily used for the construction of load-bearing walls and fences. It has the advantages of using local materials, simple construction techniques, low cost, energy conservation, and environmental protection. However, there are some shortcomings: 1) Traditional rammed earth buildings use clay and glutinous rice as binders, resulting in low overall strength of the rammed earth walls. In addition, the earth material has poor durability, especially its waterproof and impermeability properties. The wall foundation is easily affected by moisture and falls off, which can seriously cause collapse. 2) The wall's exterior color is monotonous, lacking decorative effect and poor aesthetic appeal. Although the color can be adjusted by adding color powder, this adjustment method will cause the color of the earth to be masked, losing its natural hue.

[0003] Modern rammed concrete is a mixture of rammed earth and cement added to natural soil. While cement improves its strength, the production process emits significant amounts of CO2, impacting the environment. Relying solely on cement to increase strength contradicts the energy-saving and environmentally friendly principles of rammed earth. Existing technologies often use the addition of colored cement to adjust color, which also results in high carbon emissions. Furthermore, colored cement is in low production, expensive, and difficult to control. If the addition ratio isn't precisely adjusted, defects such as holes, honeycombs, and surface cracks can easily appear. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the deficiencies in the existing technology and provide a low-carbon rammed concrete material and its preparation method and application, which has high mechanical properties and excellent durability, and does not require the artificial addition of pigments. The color can be controlled during the production process by adjusting the raw materials.

[0005] In order to solve the technical problem raised by the present invention, the present invention provides a low-carbon rammed concrete material, comprising the following raw materials in parts by mass: 10 to 25 parts of low-carbon rammed concrete cementitious material, 5 to 15 parts of water, 0.1 to 2 parts of admixture, 0.5 to 1 part of fiber, 30 to 45 parts of coarse aggregate, and 25 to 40 parts of sand; wherein the low-carbon rammed concrete cementitious material comprises the following raw materials in parts by mass: 5 to 15 parts of composite calcined powder, 1 to 6 parts of limestone powder, 0 to 6 parts of aggregate washed slag, 1 part of gypsum, and 2 to 6 parts of ordinary Portland cement.

[0006] In the above solution, the composite calcined powder is a product of calcining a mixture of clay and dolomite powder.

[0007] In the above solution, the preparation method of the composite calcined powder is as follows: Mix clay and dolomite powder, and then calcine at a temperature of 600 - 850°C for 1 - 3 hours. After the calcination is completed, immediately take it out and cool it naturally to room temperature.

[0008] Further, when mixing clay and dolomite powder, the mass ratio of clay is 70 - 90%, and the mass ratio of dolomite powder is 10 - 30%.

[0009] Further, the clay is a kaolin - type mineral clay material mainly composed of silicon dioxide and alumina during the mining process. Its SiO₂ content is 40 - 65%, Al₂O₃ content is 15 - 50%, CaO content is 0.01 - 5%, Fe₂O₃ content is 0.01 - 10%, and MgO content is 0.1 - 5%.

[0010] Further, the particle size of the clay is < 80μm, and the residue on a 45μm square - hole sieve is 10 - 30%. The specific surface area is 400 - 600m 2 / kg, and the moisture content is < 1%.

[0011] Further, the dolomite powder is fine particles collected by a dust collector or selected by a powder - selecting device during the dry production process of concrete aggregates. Its MgO content is 15 - 25%, CaO content is 30 - 40%, and the loss on ignition is 45 - 60%.

[0012] Further, the fineness of the dolomite powder is that the residue on a 45μm square - hole sieve is 10 - 20%. The specific surface area is 300 - 500m 2 / kg, and the moisture content is < 1%.

[0013] Further, the color of the clay is yellow and gradually turns pink with the increase of the calcination temperature during the calcination process.

[0014] Further, the color of the dolomite powder is yellowish or reddish, and it gradually becomes lighter with the increase of the calcination temperature during the calcination process. After the calcination temperature is higher than 750°C, it turns into grayish - white.

[0015] In the above solution, the limestone powder is fine particles collected by a dust collector or selected by a powder - selecting device during the dry production process of concrete aggregates, and the color of the limestone powder is slightly white.

[0016] In the above solution, the aggregate washing residue is the washed powder collected during the wet production process of concrete aggregates. When washing the aggregates, the light particles in the aggregates enter the water, and then it is the industrial waste after precipitation and pressure filtration. Its main components are stone powder and soil, and the color is yellowish.

[0017] In the above solution, the fineness of the limestone powder and the aggregate water-washed slag is 10-20% residue on a 45μm square-hole sieve, the specific surface area is 300-500 m 2 / kg, and the water content is <1%.

[0018] In the above solution, the gypsum is one or more of natural gypsum, desulfurized gypsum, and fluorogypsum.

[0019] In the above solution, the admixture is compounded from a polycarboxylate water-reducing mother liquor and a slump-keeping mother liquor, or is a naphthalene-based water-reducing agent.

[0020] In the above solution, the fiber is one of PP fiber, PVA fiber, and POM fiber, with a length of 6-12 mm and a diameter of 0.1-0.5 mm.

[0021] In the above solution, the coarse aggregate is continuously graded gravel with a particle size of 5-25 mm.

[0022] In the above solution, the sand is machine-made sand, specifically medium sand in Zone II with a particle size below 5 mm, a fineness modulus of 2.3-3.0, a powder content below 15%, and an MB value of methylene blue ≤ 1.4.

[0023] The present invention also provides a preparation method for a low-carbon ramming concrete material, including the following steps:

[0024] 1) Add calcined clay, limestone powder, dolomite powder, filter press residue, gypsum, and ordinary portland cement into a stirring device, and stir evenly to obtain a low-carbon ramming concrete binder;

[0025] 2) Add coarse aggregate, sand, fiber admixture, and water to the low-carbon ramming concrete binder, and stir evenly to obtain a low-carbon ramming concrete material.

[0026] In the above solution, the stirring rate in step 1) is 30-50 r / min, and the stirring time is 2-3 min.

[0027] In the above solution, the stirring rate in step 2) is 10-30 r / min, and the stirring time is 3-5 min.

[0028] In the above solution, the slump of the low-carbon ramming concrete material is 50-150 mm, and the Vebe consistency is 5-30 s.

[0029] The present invention also provides an application of the low-carbon ramming concrete material in landscape architecture. Specifically, the low-carbon ramming concrete material is used to manufacture building components such as ramming concrete columns, ramming concrete walls, ramming concrete blocks, and ramming concrete hanging boards. The application method is as follows:

[0030] 1) Pouring into the mold: Layer the mixed low-carbon ramming concrete material into a pre-installed mold;

[0031] 2) Compaction: After each layer of low-carbon ramming concrete material is loaded into the mold, it is compacted with a pneumatic rammer.

[0032] 3) Maintenance: After maintenance, demolding is carried out to obtain the ramming concrete building component.

[0033] In the above solution, the single-layer height of the mold filling does not exceed 120 mm.

[0034] In the above solution, the maintenance is natural maintenance. [[ID=IO]]

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1) The low-carbon ramming concrete material of the present invention has high mechanical properties and good durability. Calcium carbonate in stone powder and filter press residue can chemically react with active aluminate in calcined clay to form calcium aluminate hydrate. After dolomite is lightly calcined, it forms certain active magnesium oxide components. In the initial stage of hydration, magnesium hydroxide with a certain expansibility can be formed, having certain micro-expansibility and initial strength. In the later stage of hydration, the active magnesia material can react with active silica in calcined clay to form gelling magnesium silicate gel, ensuring the growth of later strength and optimizing the pore structure of the cementitious material.

[0037] 2) The low-carbon ramming concrete material of the present invention is close to the original color of the soil. The main raw materials, clay and dolomite stone powder, in the low-carbon ramming concrete cementitious material are both close to the original color of the soil. After preparing the ramming concrete, the overall color is uniform. Without artificially adding pigments, an aesthetic effect can be achieved, and color control can be realized during the production process by adjusting the raw materials. When the present invention is applied, ramming concrete layers of multiple colors can be poured in sequence to form a soil-colored ramming concrete wall, hanging board, etc., with a more layered appearance effect.

[0038] 3) The low-carbon ramming concrete material of the present invention has the advantage of low carbon. The calcination temperature of clay and dolomite stone powder is lower than the firing temperature of Portland cement clinker, reducing carbon dioxide emissions during the fuel firing process. Calcined clay is easier to grind than Portland cement clinker, reducing the energy consumed in the production process for co-grinding. The main component of the stone powder or filter press residue in the cementitious material is calcium carbonate, which can directly react with the aluminous raw materials in calcined clay, while Portland cement clinker needs to decarbonize limestone and react with siliceous, aluminous, and ferrous raw materials, thereby reducing carbon dioxide emissions. Using industrial tail ore powder, filter press residue, etc. as raw materials can achieve comprehensive utilization of resources and reduce the production cost of ramming concrete buildings. Specific Embodiments

[0039] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with embodiments, but the content of the present invention is not limited to the following embodiments.

[0040] In the following examples, the properties of each raw material used are as follows:

[0041] The clay is a kaolin-type mineral clay material with silicon dioxide and alumina as the main components during the mining process, and its color is yellow; after testing, its SiO2 content is 56.8%, Al2O3 content is 35.6%, CaO content is 0.3%, Fe2O3 content is 1.7%, and MgO content is 0.34%; its particle size is <80μm, and the residue on a 45μm square-hole sieve is 15.7%, and the specific surface area is 510m 2 / kg, and the water content is 0.3%.

[0042] The dolomite powder is fine particles collected by a dust collector or selected by a powder separator during the dry production process of concrete aggregates. Its color is yellowish, close to the original color of the soil; after testing, its MgO content is 19.05%, CaO content is 33.6%, and the loss on ignition is 46.8%; its fineness is the residue on a 45μm square-hole sieve is 12.8%, and the specific surface area is 550m 2 / kg, and the water content is 0.1%.

[0043] The limestone powder is fine particles collected by a dust collector or selected by a powder separator during the dry production process of concrete aggregates, and its color is slightly white; after testing, its fineness is the residue on a 45μm square-hole sieve is 18.2%, and the specific surface area is 470m 2 / kg, and the water content is 0.2%.

[0044] The aggregate washing residue is the washed powder collected during the wet production process of concrete aggregates, and its main components are stone powder and soil, and its color is yellowish; after testing, its fineness is the residue on a 45μm square-hole sieve is 15.5%, and the specific surface area is 490m 2 / kg, and the water content is 0.3%.

[0045] The admixture is compounded from polycarboxylate water-reducing mother liquor and slump-keeping mother liquor in a mass ratio of 5:5, and the solid content is 10%; the coarse aggregate is continuously graded gravel with a particle size of 5 - 25mm; the sand is machine-made sand, specifically medium sand in Zone II with a particle size below 5mm, the fineness modulus is 2.3 - 3.0, the powder content is less than 15%, and the methylene blue MB value ≤ 1.4.

[0046] Example 1

[0047] A low-carbon ramming concrete material, comprising the following raw materials in parts by mass: 10 parts of low-carbon ramming concrete cementitious material, 6 parts of water, 0.3 parts of admixture, 0.5 parts of PVA fiber with a length of 6mm and a diameter of 0.2mm, 43.2 parts of coarse aggregate, and 40 parts of sand; among them, the low-carbon ramming concrete cementitious material comprises the following raw materials in parts by mass: 5 parts of composite calcined powder, 1 part of limestone powder, 1 part of desulfurized gypsum, and 3 parts of ordinary Portland cement.

[0048] The preparation method of the composite calcined powder is as follows: Mix clay and dolomite powder according to the mass ratio of 70% for clay and 30% for dolomite powder, and then calcine at 850°C for 1 hour. After the calcination is completed, take it out immediately and cool it naturally to room temperature.

[0049] The preparation method of the low-carbon ramming concrete material includes the following steps:

[0050] 1) Add calcined clay, limestone powder, dolomite powder, filter press residue, gypsum and ordinary Portland cement into the mixing equipment, and stir at a rate of 50 r / min for 2 minutes to obtain the low-carbon ramming concrete cementitious material;

[0051] 2) Add coarse aggregate, sand, fiber admixture and water to the low-carbon ramming concrete cementitious material, and stir at a rate of 30 r / min for 3 minutes to obtain the low-carbon ramming concrete material.

[0052] Use the low-carbon ramming concrete material to manufacture ramming concrete columns. The application method is as follows:

[0053] 1) Molding: Layer by layer load the mixed low-carbon ramming concrete material into the pre-installed mold, and the single-layer height during molding does not exceed 120 mm;

[0054] 2) Compacting: After each layer of low-carbon ramming concrete material is loaded into the mold, use a pneumatic rammer to compact it;

[0055] 3) Maintenance: After natural maintenance, demold to obtain the ramming concrete building component.

[0056] Example 2

[0057] A low-carbon ramming concrete material, including the following raw materials in parts by mass: 15 parts of low-carbon ramming concrete cementitious material, 9 parts of water, 0.4 parts of admixture, 0.5 parts of PP fiber with a length of 8 mm and a diameter of 0.3 mm, 39 parts of coarse aggregate, 36 parts of sand; among them, the low-carbon ramming concrete cementitious material includes the following raw materials in parts by mass: 8 parts of composite calcined powder, 2 parts of limestone powder, 1 part of natural gypsum, 4 parts of ordinary Portland cement.

[0058] The preparation method of the composite calcined powder is as follows: Mix clay and dolomite powder according to the mass ratio of 75% for clay and 25% for dolomite powder, and then calcine at 700°C for 2 hours. After the calcination is completed, take it out immediately and cool it naturally to room temperature.

[0059] The preparation method of the low-carbon ramming concrete material includes the following steps:

[0060] 1) Add calcined clay, limestone powder, dolomite powder, filter press residue, gypsum and ordinary Portland cement into the mixing equipment, and stir at a rate of 45 r / min for 2 minutes to obtain the low-carbon ramming concrete cementitious material;

[0061] 2) Add coarse aggregate, sand, fiber admixture and water to the low-carbon ramming concrete cementitious material, and stir at a rate of 25 r / min for 4 min to obtain the low-carbon ramming concrete material.

[0062] Use the low-carbon ramming concrete material to manufacture ramming concrete walls. The application method is as follows:

[0063] 1) Molding: Layer the mixed low-carbon ramming concrete material into a pre-installed mold, and the single-layer height during molding does not exceed 120 mm;

[0064] 2) Compacting: After each layer of low-carbon ramming concrete material is loaded into the mold, compact it with a pneumatic rammer;

[0065] 3) Curing: Demold after natural curing to obtain the ramming concrete building component.

[0066] Example 3

[0067] A low-carbon ramming concrete material, comprising the following raw materials in parts by mass: 20 parts of low-carbon ramming concrete cementitious material, 12 parts of water, 1.2 parts of admixture, 0.8 parts of POM fiber with a length of 10 mm and a diameter of 0.4 mm, 35 parts of coarse aggregate, and 31 parts of sand; among them, the low-carbon ramming concrete cementitious material comprises the following raw materials in parts by mass: 9 parts of composite calcined powder, 6 parts of limestone powder, 1 part of fluorogypsum, and 4 parts of ordinary Portland cement.

[0068] The preparation method of the composite calcined powder is as follows: Mix clay and dolomite powder according to the mass ratio of clay accounting for 90% and dolomite powder accounting for 10%, then calcine at a temperature of

[0069] The preparation method of the low-carbon ramming concrete material comprises the following steps:

[0070] 1) Add calcined clay, limestone powder, dolomite powder, filter press residue, gypsum and ordinary Portland cement to a stirring device, and stir at a rate of 35 r / min for 3 min to obtain the low-carbon ramming concrete cementitious material;

[0071] 2) Add coarse aggregate, sand, fiber admixture and water to the low-carbon ramming concrete cementitious material, and stir at a rate of 15 r / min for 5 min to obtain the low-carbon ramming concrete material.

[0072] Use the low-carbon ramming concrete material to manufacture ramming concrete blocks. The application method is as follows:

[0073] 1) Molding: Layer the mixed low-carbon ramming concrete material into a pre-installed mold, and the single-layer height during molding does not exceed 120 mm;

[0074] 2) Compacting: After each layer of low-carbon ramming concrete material is loaded into the mold, compact it with a pneumatic rammer;

[0075] 3) Maintenance: After natural maintenance, demold to obtain the rammed concrete building component.

[0076] Example 4

[0077] A low-carbon rammed concrete material, comprising raw materials in the following mass parts: 25 parts of low-carbon rammed concrete cementitious material, 15 parts of water, 2 parts of admixture, 1 part of PP fiber with a length of 12 mm and a diameter of 0.5 mm, 31 parts of coarse aggregate, and 26 parts of sand; wherein, the low-carbon rammed concrete cementitious material comprises raw materials in the following mass parts: 15 parts of composite calcined powder, 1 part of limestone powder, 3 parts of aggregate water-washed slag, 1 part of desulfurized gypsum, and 5 parts of ordinary Portland cement.

[0078] The preparation method of the composite calcined powder is as follows: Mix clay and dolomite powder according to the mass ratio of clay accounting for 80% and dolomite powder accounting for 20%, then calcine at 750 °C for 2 h, immediately take out after the calcination ends, and naturally cool to room temperature.

[0079] The preparation method of the low-carbon rammed concrete material comprises the following steps:

[0080] 1) Add calcined clay, limestone powder, dolomite powder, filter press residue, gypsum and ordinary Portland cement into a stirring device, and stir at a rate of 30 r / min for 3 min to obtain the low-carbon rammed concrete cementitious material;

[0081] 2) Add coarse aggregate, sand, fiber admixture and water to the low-carbon rammed concrete cementitious material, and stir at a rate of 10 r / min for 5 min to obtain the low-carbon rammed concrete material.

[0082] Use the low-carbon rammed concrete material to manufacture rammed concrete wall panels, and the application method is as follows:

[0083] 1) Molding: Layer by layer load the mixed low-carbon rammed concrete material into a pre-installed mold, and the single-layer height during molding does not exceed 120 mm;

[0084] 2) Compacting: After each layer of low-carbon rammed concrete material is loaded into the mold, use a pneumatic rammer to compact it;

[0085] 3) Maintenance: After natural maintenance, demold to obtain the rammed concrete building component.

[0086] Test the finished low-carbon rammed concrete materials prepared in Examples 1 to 4. The colors of the finished products are close to the original color of the soil. Test their working performance, mechanical performance and durability performance, and the results are shown in Table 1. The results show that the low-carbon rammed concrete material of the present invention has excellent working performance and mechanical performance, while the chloride ion diffusion coefficient and the water penetration height reflect its durability performance. The data shows that the chloride ion diffusion coefficient is lower than that of ordinary Portland cement concrete, and the water penetration height is the data tested under the condition of a water pressure of 1.2 MPa and maintained for 24 h, indicating excellent water resistance.

[0087] Table 1

[0088]

[0089] The above embodiments are merely examples given for clear illustration and not limitations on the implementation. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here, and the obvious changes or modifications derived therefrom still fall within the protection scope of this invention

Claims

1. A low-carbon rammed concrete material, characterized in that: The invention comprises the following raw materials in parts by weight: 10-25 parts of low-carbon rammed concrete cementitious material, 5-15 parts of water, 0.1-2 parts of admixture, 0.5-1 parts of fiber, 30-45 parts of coarse aggregate, and 25-40 parts of sand; the admixture is a mixture of polycarboxylic acid water-reducing mother liquor and collapse-preventing mother liquor, or a naphthalene-based water-reducing agent; The low-carbon rammed concrete cementitious material comprises the following raw materials in parts by weight: 5-15 parts of composite calcined powder, 1-6 parts of limestone powder, 0-6 parts of aggregate washed slag (not 0), 1 part of gypsum, and 2-6 parts of ordinary Portland cement. The composite calcined powder is prepared by mixing clay and dolomite powder in a ratio of 70-90% by weight of clay and 10-30% by weight of dolomite powder, calcining the mixture at a temperature of 600-850° C. for 1-3 hours, immediately removing the mixture after calcination, and naturally cooling the mixture to room temperature. The aggregate washed slag is the washed powder collected during the wet production process of concrete aggregate; The low-carbon rammed concrete material has a slump of 50-150 mm and a Vebe consistency of 5-30 s. The application method is as follows: the mixed low-carbon rammed concrete material is loaded into a mold in layers, each layer is compacted with a pneumatic rammer, and after all layers are loaded, the material is cured and demoulded to obtain a rammed concrete building component.

2. The low-carbon rammed concrete material according to claim 1, characterized in that: The clay has a SiO2 content of 40-65%, an Al2O3 content of 15-50%, a CaO content of 0.01-5%, a Fe2O3 content of 0.01-10%, and a MgO content of 0.1-5%. The particle size of the clay is less than 80 μm, and the residue on a 45 μm square sieve is 10-30%. The specific surface area is 400-600 m 2 / kg, moisture content <1%.

3. The low-carbon rammed concrete material according to claim 1, characterized in that: The dolomite powder has an MgO content of 15-25%, a CaO content of 30-40%, and a loss on ignition of 45-60%. The fineness of the dolomite powder, limestone powder, and aggregate washed slag is 10-20% on a 45 μm square sieve, and the specific surface area is 300-500 m 2 / kg, moisture content <1%.

4. The low-carbon rammed concrete material according to claim 1, characterized in that: The gypsum is one or more of natural gypsum, desulfurized gypsum, and fluorinated gypsum; the fiber is one of PP fiber, PVA fiber, and POM fiber, with a length of 6 to 12 mm and a diameter of 0.1 to 0.5 mm; the coarse aggregate is continuously graded crushed stone with a particle size of 5 to 25 mm; and the sand is second-zone medium sand with a particle size of less than 5 mm.

5. A method for preparing a low-carbon rammed concrete material according to any one of claims 1 to 4, characterized in that: The following steps are involved: 1) Add composite calcined powder, limestone powder, aggregate washed slag, gypsum and ordinary Portland cement into a mixing device and mix them evenly to obtain low-carbon rammed concrete cementitious material; 2) Add coarse aggregate, sand, fiber, admixture and water to the low carbon rammed concrete cementitious material, stir evenly, and obtain the low carbon rammed concrete material.

6. The method for preparing low-carbon rammed concrete material according to claim 5, characterized in that: The stirring rate in step 1) is 30-50 r / min, and the stirring time is 2-3 min; the stirring rate in step 2) is 10-30 r / min, and the stirring time is 3-5 min.

7. Use of the low-carbon rammed concrete material according to any one of claims 1 to 4 in garden landscape architecture.

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