Asphalt modified coal gangue cement concrete and preparation method thereof

Abstract

The present application relates to the technical fields of cement concrete, in particular to a kind of asphalt modified coal gangue cement concrete and preparation method thereof.In order to solve the problem of high cost and complex process of the existing method for improving the mechanical properties of coal gangue concrete, a new asphalt modified coal gangue cement concrete and preparation method thereof are provided, which comprises: cement 2-5 parts, slag 0.6-1.2 parts, fly ash 0.2-0.4 parts, sand 6-7 parts, coal gangue aggregate 10-12, water reducing agent 0.005-0.015 parts, water 1.5-2.5 parts, asphalt crude oil 2.5-3.5 parts, by weight.The modified coal gangue cement concrete prepared by the present application significantly improves the durability, strength, workability, impermeability and deformation capacity of concrete compared to ordinary coal gangue cement concrete.In addition, the preparation method described in the present application is simple, low in cost and easy to implement.

Description

Technical Field

[0001] This invention relates to the field of cement concrete technology, specifically to an asphalt-modified coal gangue cement concrete and its preparation method. Background Technology

[0002] With the rapid development of infrastructure construction in my country, the demand for concrete materials is increasing day by day. Traditional concrete materials often require a large amount of natural sand and gravel aggregates in the preparation process. However, the mining and preparation of natural sand and gravel aggregates not only cause irreversible and serious damage to the ecological environment, but also still cannot meet the large demand for concrete and its raw materials in structural engineering. Therefore, it is urgent to find a non-natural aggregate to replace natural sand and gravel in order to alleviate the demand for concrete raw materials and the environmental pressure.

[0003] Coal gangue, a byproduct of the coal industry, has long been stockpiled in large quantities, not only occupying land resources but also potentially causing spontaneous combustion, leading to environmental pollution and resource waste. Therefore, finding a method to realize the stockpiling and resource utilization of coal gangue is of great significance for promoting the sustainable development of the coal industry. Coal gangue is a silica-alumina material, with its main chemical components being SiO2 and Al2O3, the same as the main chemical components of natural sand and gravel aggregates. In existing technologies, some scholars have attempted to use coal gangue as concrete aggregate. However, due to the disadvantages of untreated coal gangue aggregate, such as high porosity, high water absorption, and low crushing strength, directly replacing natural sand and gravel aggregate with it would significantly reduce the strength of concrete, limiting its engineering application.

[0004] To improve the mechanical properties of coal gangue concrete, admixtures, fibers, and mineral admixtures can be added. However, existing methods for improving the performance of coal gangue concrete often have drawbacks such as high cost and complex processes, which hinder the promotion and application of coal gangue concrete in engineering projects. Summary of the Invention

[0005] In order to solve the problems of high cost and complex process in existing methods for improving the mechanical properties of coal gangue concrete, this invention provides a new asphalt-modified coal gangue cement concrete and its preparation method.

[0006] This invention is achieved using the following technical solution: A type of asphalt-modified coal gangue cement concrete comprises: 2-5 parts cement, 0.6-1.2 parts slag, 0.2-0.4 parts fly ash, 6-7 parts sand, 10-12 parts coal gangue aggregate, 0.005-0.015 parts water-reducing agent, 1.5-2.5 parts water, and 2.5-3.5 parts crude asphalt, by weight.

[0007] Furthermore, the coal gangue aggregate includes 5-6 parts of fine-grained coal gangue, 3-4 parts of medium-grained coal gangue, and 2.0-3.0 parts of coarse-grained coal gangue. The particle size of the fine-grained coal gangue is 4.75-9.5 mm, the particle size of the medium-grained coal gangue is 9.5-16.5 mm, and the particle size of the coarse-grained coal gangue is 16.5-20 mm.

[0008] A method for preparing asphalt-modified coal gangue cement concrete includes the following steps: 1) preparing materials according to the weight proportions of each material in the asphalt-modified coal gangue cement concrete as described above; 2) heating crude asphalt, and then immersing coal gangue aggregate in the heated crude asphalt, so that the crude asphalt is evenly distributed on the surface of the coal gangue aggregate to form modified coal gangue aggregate; 3) mixing the modified coal gangue aggregate, cement, slag, fly ash, sand, and water and stirring evenly to form asphalt-modified coal gangue cement concrete.

[0009] Principle Explanation: ① Oxidation Reaction: Asphalt is mainly composed of hydrocarbons, including a large amount of aromatic hydrocarbons, saturated hydrocarbons, resins, and asphaltenes. Coal gangue contains inorganic minerals, small amounts of coal and organic matter, sulfides, and oxides. The hydrocarbon organic components in asphalt can undergo oxidation reactions with the oxides in coal gangue, producing carboxylic acids, aldehydes, ketones, or alcohols, forming waxy, oily, or crystalline substances, thus significantly improving the rheological properties and density of concrete; ② Physical Interaction Reaction: Coal gangue has a rough surface and high porosity, resulting in a large contact area with fluid asphalt; it is more likely to form an interlocking interface structure with asphalt. Microscopic morphology reveals a "honeycomb structure" at the interface between aggregate and asphalt, forming a denser interwoven network structure, indicating a very strong physical interaction between coal gangue and asphalt; In addition, asphalt also has the following effects: Isolation function: As an organic material, asphalt can form a protective film on the outside of coal gangue aggregate, effectively isolating the direct contact between coal gangue and cement paste, and avoiding the impact of high water absorption of aggregate on hydration reaction; Anti-corrosion function: The asphalt layer can provide a certain degree of anti-corrosion protection for coal gangue, preventing or slowing down the erosion of coal gangue and surrounding cement slurry by acids, alkalis and other chemicals. Interface improvement effect: As an interface material, the asphalt layer can improve the interfacial bonding between coal gangue and cement paste, increase the bonding strength of the interface, and thus improve the overall strength and stability of concrete. Reduced micro-defects: The asphalt layer fills the micro-defects on the surface of coal gangue, reducing micro-cracks and pores inside the concrete, thereby improving the density and durability of the concrete. Improved thermal properties: Asphalt has certain thermal resistance properties, which can reduce the temperature change range of coal gangue in the thermal environment, reduce the internal stress caused by temperature changes, and thus reduce thermal cracking. Reducing porosity: The asphalt coating can fill the microscopic pores on the surface of coal gangue, reducing the porosity inside the concrete and making the concrete structure more compact. A denser structure helps improve the compressive strength of the concrete. Preventing water penetration: Asphalt has excellent waterproof properties, which can prevent water from entering the concrete and reduce the corrosive effect of water on the internal structure of the concrete, especially in harsh environments such as freeze-thaw cycles, thus maintaining the strength of the concrete. Reduce stress concentration: The asphalt layer can act as a buffer layer, reducing internal stress concentration caused by the difference in thermal expansion coefficients between coal gangue and cement paste, reducing the risk of internal cracks in concrete, and thus helping to maintain the strength of concrete. Increase the elastic modulus of aggregates: The asphalt layer increases the elastic modulus of coal gangue aggregates, making the aggregates less prone to deformation under pressure, thereby transferring more stress to the cement paste and improving the overall strength of the concrete. Lubricating effect: Asphalt has lubricating properties and can form a smooth film on the surface of coal gangue. During concrete mixing, this asphalt film can reduce the friction between aggregates, making the concrete mixture easier to flow and thus improving workability; Reduced adhesion: The asphalt layer can reduce the direct adhesion between coal gangue and cement paste, avoiding the increase in internal friction of the mixture due to excessive adhesion, thereby making the concrete mixture exhibit better fluidity during mixing, transportation and pouring. Improving the coating properties of cement paste: Asphalt film can improve the coating properties of cement paste on coal gangue aggregate, making it easier for cement paste to evenly cover the surface of aggregate and form a uniform and stable mixture, which helps to improve the workability of concrete. Improved particle shape: The asphalt layer fills the irregular shape on the surface of coal gangue, making the aggregate shape smoother and reducing the content of needle-like and flaky particles, which is beneficial to the fluidity and filling properties of concrete mixtures. Reduced water absorption: Coal gangue usually has a certain degree of water absorption, while the asphalt layer can reduce the absorption of water by coal gangue, avoid excessive water loss in the mixture, and maintain the fluidity and plasticity of the cement paste. Enhanced stability: The asphalt layer provides an additional protective layer, making the coal gangue aggregate less susceptible to damage during transportation and construction, reducing the instability of the mixture caused by aggregate breakage, and thus improving workability; Formation of a waterproof layer: Asphalt coats the surface of coal gangue, forming a waterproof layer. This waterproof layer can effectively prevent water from penetrating into the concrete, thereby improving the concrete's impermeability. Improved adhesion: After the modified coal gangue is coated with asphalt, the adhesion between the coal gangue and cement mortar is enhanced, making the entire concrete structure more robust and less susceptible to damage from water penetration. Buffer layer function: As a buffer layer, the asphalt layer can provide a "soft connection" between coal gangue aggregate and cement paste. This connection allows for more relative sliding between aggregates under load, thereby improving the overall deformation capacity of concrete. Strain compatibility: The deformation capacity of asphalt is closer to that of cement paste, which helps improve the strain compatibility between the two. When concrete is subjected to external loads, the asphalt layer can coordinate the deformation of coal gangue and cement paste, reduce internal stress concentration, and thus improve the overall deformation capacity. Reduce rigidity differences: Coal gangue aggregate itself has relatively high rigidity, and the addition of asphalt can reduce this rigidity difference, making the entire concrete structure more uniform under stress, which helps to improve the overall deformation capacity. Improved interfacial bonding: The asphalt film can enhance the bond between coal gangue and cement paste, making the interface between aggregate and paste less prone to damage during deformation, thereby improving the deformation capacity of concrete. Reduced temperature impact: Asphalt has good temperature stability and can maintain its deformability at different temperatures. Therefore, asphalt-coated coal gangue aggregate concrete exhibits more stable deformation performance when subjected to temperature changes and is less prone to cracking due to temperature differences.

[0010] Furthermore, the coal gangue aggregate is obtained by crushing, rinsing, and screening coal gangue to obtain fine-grained coal gangue, medium-grained coal gangue, and coarse-grained coal gangue. The particle size of fine-grained coal gangue is 4.75–9.5 mm, the particle size of medium-grained coal gangue is 9.5–16.5 mm, and the particle size of coarse-grained coal gangue is 16.5–20 mm.

[0011] Furthermore, 5-6 parts of fine-grained coal gangue, 3-4 parts of medium-grained coal gangue, and 2.0-3.0 parts of coarse-grained coal gangue are taken.

[0012] The beneficial effects of this invention are as follows: The coal gangue concrete prepared by this invention solves the problem of adverse chemical reactions between heavy metals in coal gangue and the external environment; at the same time, the modified coal gangue cement concrete prepared by this invention significantly improves durability, strength, workability, impermeability and deformation capacity of concrete compared with ordinary coal gangue cement concrete; in addition, the preparation method described in this invention is simple, low-cost and easy to implement. Attached Figure Description

[0013] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 The image shows the microstructure of the asphalt-modified coal gangue cement interface in Example 1 (the microstructure images of the asphalt-modified coal gangue prepared in Examples 1-4 are basically the same). Figure 2 The microstructure of the unmodified coal gangue cement interface in the comparative example; Figure 3 The image shows the morphology of the coal gangue coated with asphalt in Example 1 (the morphology images of the asphalt-modified coal gangue prepared in Examples 1-4 are basically the same). Figure 4 The morphology of unmodified coal gangue in the comparative example; Figure 5 This is the test block used in Example 1 for testing the compressive strength of concrete specimens; Figure 6 This is a test block for testing the compressive strength of concrete specimens in the comparative example; Figure 7 The modified coal gangue concrete impermeability test block in Example 1; Figure 8 This is a test block for the impermeability testing of modified coal gangue concrete used in the comparative example. Figure 9 The stress-strain curves of concrete in Examples 1-4 and Comparative Examples are shown. Detailed Implementation

[0016] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.

[0017] In this description, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. It should also be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joint" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0018] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.

[0019] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0020] A type of asphalt-modified coal gangue cement concrete comprises: 2-5 parts cement, 0.6-1.2 parts slag, 0.2-0.4 parts fly ash, 6-7 parts sand, 10-12 parts coal gangue aggregate, 0.005-0.015 parts water-reducing agent, 1.5-2.5 parts water, and 2.5-3.5 parts crude asphalt. By weight, the coal gangue aggregate includes 5-6 parts fine-grained coal gangue, 3-4 parts medium-grained coal gangue, and 2.0-3.0 parts coarse-grained coal gangue. The particle size of the fine-grained coal gangue is 4.75-9.5 mm, the particle size of the medium-grained coal gangue is 9.5-16.5 mm, and the particle size of the coarse-grained coal gangue is 16.5-20 mm.

[0021] A method for preparing asphalt-modified coal gangue cement concrete includes the following steps: 1) Preparing materials according to the weight proportions of each material in the asphalt-modified coal gangue cement concrete as described above, wherein the coal gangue aggregate is obtained by crushing, rinsing with water, and sieving coal gangue to obtain fine-grained coal gangue, medium-grained coal gangue, and coarse-grained coal gangue. The particle size of the fine-grained coal gangue is 4.75–9.5 mm, the particle size of the medium-grained coal gangue is 9.5–16.5 mm, and the particle size of the coarse-grained coal gangue is… The particle size is 16.5-20mm, with 5-6 parts fine-grained coal gangue, 3-4 parts medium-grained coal gangue, and 2.0-3.0 parts coarse-grained coal gangue; 2) Heat the crude asphalt, then immerse the coal gangue aggregate in the heated crude asphalt, so that the crude asphalt is evenly distributed on the surface of the coal gangue aggregate to form modified coal gangue aggregate; 3) Mix the modified coal gangue aggregate, cement, slag, fly ash, sand, and water evenly to form asphalt-modified coal gangue cement concrete.

[0022] To verify the performance of the asphalt-modified coal gangue concrete described in this invention, cement concrete prepared by the above preparation method and the material proportions shown in Table 1 (Examples 1-4) was poured or pressed into shape, then cured at room temperature and its performance was tested. The results were compared with unmodified coal gangue cement concrete (comparative example) and the test results are shown in Table 2.

[0023] Table 1 Concrete Parts in Examples 1-4 and Comparative Examples

[0024] Table 2 shows the test results of the mechanical and durability properties of the concrete mix proportions in Examples 1-4 and the comparative examples.

[0025] The test results above show that the concrete prepared by the above method not only slightly improves the 28-day strength of the material, but also effectively improves the workability of cement concrete and significantly enhances its impermeability and ductility, thus exhibiting a good comprehensive modification effect.

[0026] In addition, from Figure 9 It can be seen that: Example 1 has the highest strength, a smooth strain curve, and good continuity; Examples 2-4 have strengths of around 32 MPa; Example 2 has the largest ultimate strain because of the relatively high content of sand and good workability; Example 3 has a lower ultimate strain and poor deformation capacity; Example 4 has good continuity; The comparative example, due to the lack of modification treatment on the coal gangue, has a strain curve with almost no decreasing stage, very poor deformation capacity, and is brittle.

[0027] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.

Claims

1. A method for preparing asphalt-modified coal gangue cement concrete, characterized in that, The process includes the following steps: 1) Prepare materials according to the following weight proportions of each material in an asphalt-modified coal gangue cement concrete: 2-5 parts cement, 0.6-1.2 parts slag, 0.2-0.4 parts fly ash, 6-7 parts sand, 10-10.9 parts coal gangue aggregate, 0.005-0.015 parts water-reducing agent, 1.5-2.5 parts water, and 2.5-3.5 parts crude asphalt; 2) Heat the crude asphalt, and then immerse the coal gangue aggregate in the heated crude asphalt, so that the crude asphalt is evenly distributed on the surface of the coal gangue aggregate to form modified coal gangue aggregate; 3) Mix the modified coal gangue aggregate, cement, slag, fly ash, sand, and water evenly to form asphalt-modified coal gangue cement concrete.

2. The method for preparing asphalt-modified coal gangue cement concrete according to claim 1, characterized in that, Coal gangue aggregate is obtained by crushing, rinsing, and screening coal gangue to obtain fine-grained coal gangue, medium-grained coal gangue, and coarse-grained coal gangue. The particle size of fine-grained coal gangue is 4.75-9.5 mm, the particle size of medium-grained coal gangue is 9.5-16.5 mm, and the particle size of coarse-grained coal gangue is 16.5-20 mm.

3. The method for preparing asphalt-modified coal gangue cement concrete according to claim 2, characterized in that, Take 5-6 parts of fine-grained coal gangue, 3-4 parts of medium-grained coal gangue, and 2.0-3.0 parts of coarse-grained coal gangue.

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