Low-carbon and environment-friendly ultra-high performance concrete and preparation method thereof

Abstract

The application belongs to the field of concrete, and discloses a low-carbon and environment-friendly ultra-high performance concrete and a preparation method thereof.The low-carbon and environment-friendly ultra-high performance concrete comprises the following raw materials in parts by weight: 13-23 parts of water, 50-70 parts of cement, 5-15 parts of silica ash, 100-138 parts of fine aggregate, 20-50 parts of quartz powder, 5-12 parts of reinforcing fiber, 1-5 parts of additive, 0-0.5 parts of calcium polyacrylate (CPA), and 0-0.2 parts of silane coupling agent.The low-carbon and environment-friendly ultra-high performance concrete provided by the application can greatly reduce the dosage of cement, silica ash and other cementitious materials and the dosage of fiber compared with traditional ultra-high performance concrete, but still maintains excellent mechanical properties and durability.

Description

Technical Field

[0001] This invention belongs to the field of concrete, and specifically relates to a low-carbon, environmentally friendly, ultra-high performance concrete and its preparation method. Background Technology

[0002] Concrete is one of the most widely used building materials in the field of civil engineering. With the increasing demands on concrete performance under different working conditions, ultra-high performance concrete (UHPC) has gradually appeared in special engineering construction. UHPC is a type of concrete with high strength, high toughness, and high durability, and has received widespread attention both domestically and internationally, with broad application prospects.

[0003] UHPC (Ultra-High-Pressure Polymer) often requires a high amount of cement during its preparation, typically 3-5 times that of ordinary concrete. Statistics show that carbon dioxide emissions from cement manufacturing account for approximately 7% of total anthropogenic carbon dioxide emissions, and the cement industry consumes about 2% of global primary energy consumption and 5% of total global industrial energy consumption. This high cement usage significantly increases carbon emissions and energy consumption throughout the UHPC production process. Furthermore, some UHPC systems require high-temperature steam curing to achieve their target performance, further increasing energy consumption. In addition, the high amount of cementitious materials and the incorporation of reinforcing fibers make the production cost of UHPC far higher than that of ordinary concrete, resulting in low economic efficiency and hindering its widespread application.

[0004] In existing technologies, the amount of cementitious material used in UHPC is typically 1000 kg / m³. 3 The fiber content is typically around 2%, and the curing method is mostly high-temperature steam curing. This results in significant carbon emissions and energy consumption during production, leading to low economic efficiency and hindering widespread adoption. Higher cementitious material content also increases the heat release during UHPC hydration. Furthermore, the increased chemical shrinkage of the cementitious material during hydration, combined with its own drying shrinkage, causes numerous microcracks within the concrete, which can even develop into macro-cracks. These internal defects directly and adversely affect the structure itself.

[0005] Therefore, developing a low-carbon, environmentally friendly, ultra-high performance concrete is of great significance for the development of low-carbon green buildings and the promotion of UHPC engineering applications. Summary of the Invention

[0006] In order to overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a low-carbon, environmentally friendly, ultra-high performance concrete.

[0007] Another objective of this invention is to provide a method for preparing the aforementioned low-carbon, environmentally friendly, ultra-high-performance concrete.

[0008] This invention modifies concrete by incorporating polymers and coupling agents, thereby controlling the amount of cementitious materials (cement and silica fume) per unit volume to 550-850 kg / m³. 3 Within the specified range, while the steel fiber content is significantly reduced, the concrete can still maintain the excellent performance of UHPC, achieving the effect of energy conservation and emission reduction.

[0009] The objective of this invention is achieved through the following solution:

[0010] A low-carbon, environmentally friendly, ultra-high-performance concrete comprises the following raw materials in parts by weight: 13-23 parts water, 50-70 parts cement, 5-15 parts silica fume, 100-138 parts fine aggregate, 20-50 parts quartz powder, 5-12 parts reinforcing fiber, 1-5 parts admixture, 0-0.5 parts calcium polyacrylate (CPA), and 0-0.2 parts silane coupling agent.

[0011] The water in question is tap water.

[0012] The cement is P.II 52.5 Portland cement, and its material properties meet the following requirements: 28-day compressive strength ≥ 52.5 MPa, 28-day flexural strength ≥ 7.0 MPa, and specific surface area ≥ 300 m². 2 / kg.

[0013] The silica fume has an average particle size of 1-1.5 μm and a specific surface area ≥20 m². 2 / g, with a silica content ≥95% by mass.

[0014] The fine aggregate is ordinary quartz sand with a particle size of 26-110 mesh.

[0015] The quartz powder has a particle size of 325-800 mesh.

[0016] The reinforcing fiber is at least one of micro steel fiber, milled steel fiber, and end-hooked steel fiber, preferably end-hooked steel fiber.

[0017] The additive is a polycarboxylate superplasticizer with a solid content ≥35%.

[0018] The silane coupling agent is at least one of vinyl silane coupling agents and amino silane coupling agents, preferably vinyltriethoxysilane.

[0019] The preparation method of the above-mentioned low-carbon and environmentally friendly ultra-high performance concrete includes the following steps:

[0020] (1) Add calcium polyacrylate and silane coupling agent to water and stir, then set aside;

[0021] (2) Add the additive to water and mix for later use;

[0022] (3) Add cement, silica fume, fine aggregate and quartz powder to a concrete mixer and mix;

[0023] (4) Add the two mixed solutions obtained in steps (1) and (2) to the concrete mixer and mix.

[0024] (5) Add the reinforcing fibers to the concrete mixer and mix, then fill the mold;

[0025] (6) The desired product is obtained after demolding and curing.

[0026] The temperature of the water in step (1) is 60-80℃. No continuous heating is required during the stirring process. Stir until no crystalline calcium polyacrylate particles are visible to the naked eye in the solution.

[0027] The amount of water used in steps (1) and (2) is half of the total water consumption.

[0028] The stirring time in step (3) is 3-5 minutes.

[0029] The stirring time in step (4) is 8-10 minutes.

[0030] The stirring time in step (5) is 4-6 minutes; preferably 4 minutes. The specific operation is: stirring in the forward direction for 2 minutes, stirring in the reverse direction for 1 minute, and finally stirring in the forward direction for 2 minutes.

[0031] The demolding time in step (6) is 1 day after pouring, and the curing method is to cover with geotextile and water for 9 days.

[0032] The mechanism of this invention is as follows:

[0033] The calcium polyacrylate in this invention's formulation is typically used as a mud treatment agent in drilling fluids to improve their performance. Because calcium polyacrylate has a long dissolution time in water, other chemical reagents are usually added as co-solvents for dissolution. However, in this invention's preparation process, only water at 60-80°C is used for dissolution. Compared to water at normal temperature, warm water accelerates the dissolution rate of calcium polyacrylate and makes its dissolved solid phase more uniformly dispersed, which plays an important role in the uniformity of subsequent mixing. Adding calcium polyacrylate to concrete promotes cement hydration, repairs the internal pore structure of the matrix, and improves the microstructure composition. Simultaneously, calcium polyacrylate can improve the transition zone between aggregates and cement in the finished concrete, thereby enhancing the mechanical properties of the concrete. Calcium polyacrylate also has a water loss reduction effect, effectively mitigating the large drying shrinkage phenomenon caused by the decrease in internal relative humidity in the early stages of UHPC (Ultra-High-Pressure Polymer).

[0034] Silane coupling agents possess two active functional groups: one that bonds to polymers and the other that reacts with inorganic surfaces. These groups enhance interfacial connections between inorganic and inorganic materials, between organic and organic materials, and between organic and inorganic materials. Adding vinyltriethoxysilane to calcium polyacrylate allows the vinyl groups to react with the polyacrylate polymer and adhere to the polymer surface, while the ethoxy groups hydrolyze to form hydroxyl groups. When the mixture is added to the concrete, the hydroxyl groups bridge and couple with the hydrated calcium silicate formed by the hydration of the cementitious material. The addition of the silane coupling agent improves the permeability and spreadability of the organic polymer within the concrete, making the resulting three-dimensional interpenetrating network more pronounced and effectively reducing the formation of microcracks within the concrete in the early stages.

[0035] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0036] This invention provides a low-carbon, environmentally friendly ultra-high performance concrete. Compared with traditional ultra-high performance concrete, it significantly reduces the amount of cement, silica fume, and other cementitious materials, as well as the amount of fiber, while still maintaining excellent mechanical and durability properties. The modified low-carbon, environmentally friendly ultra-high performance concrete has a 28-day compressive strength ≥140MPa, a 28-day flexural strength ≥35MPa, a 28-day water absorption rate ≤0.6%, and a workability ≥210mm. Compared with existing technologies, this invention significantly reduces the total carbon dioxide emissions and energy consumption during the production process, which is of great significance for developing low-carbon green buildings and promoting the application of UHPC engineering. Attached Figure Description

[0037] Figure 1 This is a flowchart of a method for preparing low-carbon, environmentally friendly, ultra-high-performance concrete according to the present invention. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0039] Unless otherwise specified, all reagents used in the examples are commercially available.

[0040] The specific raw materials and specifications used in the examples and comparative examples are as follows:

[0041] Cement: P.Ⅱ52.5 Portland cement, with material properties meeting the following requirements: 28-day compressive strength ≥ 52.5 MPa, 28-day flexural strength ≥ 7.0 MPa, and specific surface area ≥ 300 m². 2 / kg.

[0042] Silica fume: average particle size 1.5μm, specific surface area ≥20m² 2 / g, with a silica content ≥95% by mass.

[0043] Fine aggregate: Quartz sand, particle size 26-110 mesh.

[0044] Quartz powder: particle size 325 mesh.

[0045] Reinforcing fiber: hook-shaped ordinary steel fiber with a diameter of 0.22mm, a length of 14mm, and a tensile strength greater than 2000MPa.

[0046] Additive: Polycarboxylate superplasticizer, solid content ≥35%.

[0047] Calcium polyacrylate (CPA): density 3 g / cm³ 3 The content of the substance is ≥99.8%, and the molecular weight is 2.5-3 million.

[0048] Silane coupling agent: Vinyltriethoxysilane, molecular formula C8H 18 03Si, mass content ≥98%, colorless and transparent liquid.

[0049] Mixer: HJS-60 twin-shaft forced mixer, with a mixing motor power of 3.0kW, a tilting discharge motor power of 1.5kW, and a mixer speed of 55±5 revolutions per minute.

[0050] In the following examples and comparative examples, 1 part = 10 kg.

[0051] Example 1:

[0052] This embodiment describes a low-carbon, environmentally friendly, ultra-high-performance concrete, the raw materials of which include, by weight: 14 parts water, 68 parts cement, 12 parts silica fume, 131 parts fine aggregate, 20 parts quartz powder, 7 parts reinforcing fiber, 4 parts admixture, 0.1 parts calcium polyacrylate (CPA), and 0.1 parts silane coupling agent.

[0053] This embodiment describes a method for preparing low-carbon, environmentally friendly, ultra-high-performance concrete, with the following specific steps:

[0054] (1) Add calcium polyacrylate and silane coupling agent to water at 70°C and stir for later use. The amount of water used is half of the total amount of water used.

[0055] (2) Add the additive to the water and mix for later use, wherein the amount of water used is half of the total amount of water used;

[0056] (3) Add cement, silica fume, fine aggregate and quartz powder to a concrete mixer and mix for 4 minutes;

[0057] (4) Add the two mixed solutions obtained in steps (1) and (2) to a concrete mixer and mix for 8 minutes;

[0058] (5) Add the reinforcing fiber to the concrete mixer and mix for 4 minutes. The specific operation is: mix forward for 2 minutes, mix reverse for 1 minute, and finally mix forward for 2 minutes before filling the mold.

[0059] (6) Demolding is performed 1 day after pouring, followed by curing with geotextile for 9 days to obtain a 1m² layer. 3 The intended product.

[0060] Example 2:

[0061] This embodiment describes a low-carbon, environmentally friendly, ultra-high-performance concrete. The difference between this embodiment and Embodiment 1 is that the raw materials in the indicated weight proportions are: 15 parts water, 63 parts cement, 10 parts silica fume, 127 parts fine aggregate, 26 parts quartz powder, 8 parts reinforcing fiber, 3 parts admixture, 0.1 parts calcium polyacrylate (CPA), and 0.1 parts silane coupling agent.

[0062] Example 3:

[0063] This embodiment describes a low-carbon, environmentally friendly, ultra-high-performance concrete. The difference between this embodiment and Embodiment 1 is that the raw materials in the indicated weight proportions are: 16 parts water, 56 parts cement, 15 parts silica fume, 121 parts fine aggregate, 31 parts quartz powder, 9 parts reinforcing fiber, 3 parts admixture, 0.1 parts calcium polyacrylate (CPA), and 0.1 parts silane coupling agent.

[0064] Example 4:

[0065] This embodiment describes a low-carbon, environmentally friendly, ultra-high-performance concrete. The difference between this embodiment and Embodiment 1 is that the raw materials in the indicated weight proportions are: 18 parts water, 59 parts cement, 8 parts silica fume, 114 parts fine aggregate, 37 parts quartz powder, 10 parts reinforcing fiber, 3 parts admixture, 0.15 parts calcium polyacrylate (CPA), and 0.1 parts silane coupling agent.

[0066] Example 5:

[0067] This embodiment describes a low-carbon, environmentally friendly, ultra-high-performance concrete. The difference between this embodiment and Embodiment 1 is that the raw materials in the indicated weight proportions are: 20 parts water, 54 parts cement, 12 parts silica fume, 105 parts fine aggregate, 42 parts quartz powder, 11 parts reinforcing fiber, 2 parts admixture, 0.2 parts calcium polyacrylate (CPA), and 0.1 parts silane coupling agent.

[0068] Comparative Example 1:

[0069] The difference from Example 1 is that no calcium polyacrylate and silane coupling agent were incorporated.

[0070] Comparative Example 2:

[0071] The difference from Example 1 is that the raw materials in this example include, by weight, 20 parts water, 90 parts cement, 20 parts silica fume, 105 parts fine aggregate, 42 parts quartz powder, 15 parts reinforcing fiber, and 2 parts additives.

[0072] That is, the sum of the mass parts of cement and silica fume is greater than 105 parts, the mass parts of reinforcing fiber are greater than 14 parts, and no calcium polyacrylate and silane coupling agent are added.

[0073] Comparative Example 3:

[0074] The difference from Example 1 is that the raw materials in this example include, by weight, 20 parts water, 80 parts cement, 25 parts silica fume, 105 parts fine aggregate, 42 parts quartz powder, 15 parts reinforcing fiber, and 2 parts additives.

[0075] That is, the sum of the mass parts of cement and silica fume is greater than 100 parts, the mass parts of reinforcing fiber are greater than 14 parts, and no calcium polyacrylate and silane coupling agent are added.

[0076] Comparative Example 4:

[0077] The difference from Example 1 is that the raw materials in this example include, by weight, 20 parts water, 75 parts cement, 20 parts silica fume, 105 parts fine aggregate, 42 parts quartz powder, 15 parts reinforcing fiber, and 2 parts additives.

[0078] That is, the sum of the mass parts of cement and silica fume is greater than 95 parts, the mass parts of reinforcing fiber are greater than 14 parts, and no calcium polyacrylate and silane coupling agent are added.

[0079] According to GB-T 17671-1999 "Test Method for Strength of Cement Mortar (ISO Method)", the compressive strength and flexural strength of concrete specimens from Examples 1-5 and Comparative Examples 1-4, with a curing age of 28 days, were tested. The specimen size was 40mm × 40mm × 160mm. The water absorption rate of each specimen was tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". Simultaneously, referring to JGJ-T 283-2012 "Technical Specification for Application of Self-Compacting Concrete", the flowability of the concrete was tested using the jump table test method.

[0080] Table 1 shows the test results of various physical properties of Examples 1-5 and Comparative Examples 1-4.

[0081]

[0082] The performance test results show that the mechanical properties of low-carbon and environmentally friendly ultra-high performance concrete without modified calcium polyacrylate are reduced. However, the performance of low-carbon and environmentally friendly ultra-high performance concrete with modified calcium polyacrylate is still excellent compared with comparative examples 2-4, even with a reduction in the amount of cement, silica fume and reinforcing fiber. This greatly reduces carbon emissions and energy consumption during the production process, while effectively controlling production costs. This is of great significance for the development of low-carbon green buildings and the promotion of UHPC engineering applications.

[0083] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A low-carbon, environmentally friendly, ultra-high performance concrete, characterized in that, It is made from the following raw materials in parts by weight: 13-23 parts water, 50-70 parts cement, 5-15 parts silica fume, 100-138 parts fine aggregate, 20-50 parts quartz powder, 5-12 parts reinforcing fiber, 1-5 parts admixture, 0-0.5 parts calcium polyacrylate, and 0-0.2 parts silane coupling agent. The reinforcing fiber is at least one of micro-fine steel fiber, milled steel fiber, and end-hooked steel fiber; The silane coupling agent is vinyltriethoxysilane; The low-carbon, environmentally friendly, ultra-high-performance concrete is prepared by the following method: (1) Add calcium polyacrylate and silane coupling agent to water and stir, then set aside; (2) Add the additive to the water and mix for later use; (3) Add cement, silica fume, fine aggregate, and quartz powder to a concrete mixer and mix. (4) Add the two mixed solutions obtained in steps (1) and (2) to the concrete mixer and mix. (5) Add the reinforcing fibers to the concrete mixer and mix, then load into the mold; (6) The desired product is obtained after demolding and curing; The temperature of the water in step (1) is 60-80℃; The demolding time in step (6) is 1 day after pouring, and the curing method is to cover with geotextile and water for 9 days.

2. The low-carbon, environmentally friendly, ultra-high-performance concrete according to claim 1, characterized in that: The cement is P.II 52.5 silicate cement, and its material properties meet the following requirements: 28-day compressive strength ≥ 52.5 MPa, 28-day flexural strength ≥ 7.0 MPa, and specific surface area ≥ 300 m². 2 / kg; The silica fume has an average particle size of 1-1.5 μm and a specific surface area ≥20 m². 2 / g, silica content ≥95%; The fine aggregate is ordinary quartz sand with a particle size of 26-110 mesh; The quartz powder has a particle size of 325-800 mesh.

3. The low-carbon, environmentally friendly, ultra-high-performance concrete according to claim 1, characterized in that: The additive is a polycarboxylate superplasticizer.

4. The low-carbon, environmentally friendly, ultra-high-performance concrete according to claim 1, characterized in that: The amount of water used in steps (1) and (2) is half of the total water consumption.

5. The low-carbon, environmentally friendly, ultra-high-performance concrete according to claim 1, characterized in that: The stirring time in step (3) is 3-5 minutes; The stirring time in step (4) is 8-10 minutes.

6. The low-carbon, environmentally friendly, ultra-high-performance concrete according to claim 1, characterized in that: The stirring time in step (5) is 5 minutes. The specific operation is as follows: stir forward for 2 minutes, stir backward for 1 minute, and finally stir forward for 2 minutes.

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