Coal-fired slag asphalt mixture and preparation method thereof

Abstract

The invention discloses a coal-fired furnace slag asphalt mixture and a preparation method thereof, and belongs to the technical field of building material preparation. According to the invention, coal-fired furnace slag, limestone, asphalt and other raw materials are combined to obtain the furnace slag asphalt mixture with proper gradation, and the furnace slag asphalt mixture is used for a middle surface layer of an asphalt pavement, so that a technical basis is provided for scientific and reasonable selection and application of furnace slag aggregate in road engineering, and the method has important significance for reducing the total amount of furnace slag, relieving the treatment pressure of furnace slag and improving the construction efficiency. And the method plays a positive role in providing qualified raw materials for road engineering, meets the social development requirements of resource conservation and environmental friendliness, and has remarkable social benefits and economic benefits.

Description

Technical Field

[0001] The invention belongs to the technical field of building material preparation, and particularly relates to a coal-fired furnace slag asphalt mixture and a preparation method thereof. Background Art

[0002] The coal gangue of the coal industry and the coal ash slag of coal-fired units in thermal power plants are the coal solid wastes with the largest and most concentrated emissions. Among them, the coal ash slag includes fly ash and coal-fired slag, of which fly ash accounts for 80% to 90% of the total ash slag and slag accounts for 10% to 20%. The main chemical composition and mineral composition of coal-fired slag are similar to those of fly ash and natural mineral aggregates, but because its particle size is larger than that of fly ash, it is difficult to stimulate its volcanic ash activity by direct use. In addition, the slag particles show a "popcorn"-like porous structure at the microscopic level, so compared with natural mineral aggregates, they have the disadvantages of higher water absorption, lower density and strength, which leads to a low development and utilization rate of slag. The emission of slag will occupy a large amount of land resources, and the dissolved metal ions may cause environmental pollution. How to deal with the slag produced after the combustion of a large amount of coal has become an urgent problem to be solved.

[0003] The research on the resource utilization of slag in my country started late, with a low utilization rate and a single utilization method. Slag is usually ball-ground into powder to replace part of cement-based cementitious materials or as an aggregate for cement concrete. With the development of highway transportation, asphalt mixture, the main road construction material, is used in huge quantities. Large-scale mining of aggregates such as limestone will cause environmental damage. Coal slag is a green material for paving roads. If it can be recycled and used in asphalt pavement, it can reduce the cost of stone mining and the impact on the environment, and promote the green and sustainable development of road engineering materials. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a coal-fired slag asphalt mixture and a preparation method thereof, so as to solve the technical problems of low utilization rate of coal-fired slag and poor performance of ordinary asphalt mixture.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: to provide a coal slag asphalt mixture, the raw materials used include, by mass, 783-935 parts of limestone aggregate, 94-142 parts of coal slag, 45-55 parts of asphalt and 15-20 parts of mineral powder.

[0006] The main components of coal slag are calcium (Ca), silicon (Si) and aluminum (Al), accounting for more than 77% of the total mass, which is similar to the natural aggregates used in highway projects. In addition, iron (Fe), potassium (K), magnesium (Mg), sodium (Na), sulfur (S), chlorine (Cl) and phosphorus (P) account for about 20% of the total mass. The main phases of coal slag are mullite (aluminum silicate), quartz (silicon dioxide) and calcium feldspar (calcium aluminum silicate), among which calcium feldspar has a certain activity and can react chemically with the acidic components in asphalt to form chemical bonds, thereby enhancing the bonding force between asphalt and coal slag. Limestone aggregate provides a solid skeleton and good high-temperature stability for asphalt mixture; the combination of coal slag, asphalt and mineral powder improves the economy, compression resistance and crack resistance of the material, and improves the density and water resistance of the mixture. Mineral powder mainly plays a filler and synergist role, further optimizing the road performance of the mixture. Through reasonable raw material ratios, effective synergy between coal-fired slag and other materials can be achieved, the performance of asphalt mixture can be improved, and a balance between environmental protection and performance can be achieved.

[0007] On the basis of the above technical solution, the present invention can also be improved as follows:

[0008] Furthermore, the raw materials used include, by mass, 838 parts of limestone aggregate, 94 parts of coal-fired slag, 48 parts of asphalt, and 20 parts of mineral powder.

[0009] Furthermore, the raw materials used include, by mass, 783 parts of limestone aggregate, 142 parts of coal-fired slag, 45 parts of asphalt and 15 parts of mineral powder.

[0010] Furthermore, the raw materials used include, by mass, 935 parts of limestone aggregate, 110 parts of coal-fired slag, 55 parts of asphalt, and 18 parts of mineral powder.

[0011] Furthermore, the particle size of the coal-fired slag is 0.01-4.75 mm, and the moisture content is 9-12%; the particle size of the limestone aggregate is 0.01-19 mm.

[0012] The invention also discloses a method for preparing a coal-fired slag asphalt mixture, comprising the following steps: mixing and stirring raw materials according to a proportion at 140-160° C. for 30-60 minutes to obtain the coal-fired slag asphalt mixture.

[0013] The beneficial effects of the present invention are:

[0014] 1. The present invention uses coal-fired slag with a particle size of 0.001-4.75 mm, which accounts for nearly 80% of the total slag mass, significantly reducing the number of screening times, simplifying the production process, and allowing the coal-fired slag to be used in large quantities and efficiently in coal-fired slag asphalt mixtures, thereby increasing the utilization of coal-fired slag, thereby achieving resource utilization of waste and optimization of asphalt mixture performance.

[0015] 2. The bulk density of the coal-fired slag asphalt mixture prepared by the present invention is 2.324 g / cm 3 The bulk density of ordinary asphalt mixture is 2.423g / cm 3 The gross volume density of coal-fired slag asphalt mixture is lower than that of ordinary asphalt mixture, with a decrease of about 4.1%. Under the condition of the same paving thickness of the road surface (the road mixture is calculated per cubic meter), the amount of asphalt used is reduced, saving costs.

[0016] 3. The maximum flexural strain of the coal-fired slag asphalt mixture prepared by the present invention is 2736με, and the maximum flexural strain of the ordinary asphalt mixture is 2346με, which indicates that the coal-fired slag asphalt mixture has good ductility and plasticity under stress, and can withstand large deformation at low temperature without being easily broken. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Design of synthetic gradation diagram for coal-fired slag asphalt mixture;

[0018] Figure 2 The effect of slag content on the optimal oil-stone ratio;

[0019] Figure 3 The effect of slag content on the relative density of gross volume;

[0020] Figure 4 The influence of slag content on convection value;

[0021] Figure 5 The effect of slag content on the void ratio of aggregate;

[0022] Figure 6 The effect of slag content on asphalt saturation;

[0023] Figure 7 The effect of slag content on Marshall stability. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention are described below to facilitate the understanding of the present invention by those skilled in the art. If the specific conditions are not specified in the examples, the methods are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturers are not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the attached claims, these changes are obvious, and all inventions and creations using the concept of the present invention are protected.

[0025] The particle size of the limestone aggregate used in the present invention has five grades, namely 19mm, 16mm, 10-15mm, 5-10mm and 0.01-5mm. The grading results of the coal slag asphalt mixture are shown in Tables 1 and Figure 1 shown.

[0026] Table 1 Designed synthetic gradation of coal-fired slag asphalt mixture

[0027] Screen size (mm) Slag synthesis gradation (mm) 26.5 100 19 95 16 81 13.2 75.9 9.5 60.1 4.75 40.5 2.36 25.3 1.18 19.6 0.6 14.3 0.3 10 0.15 5.6 0.075 3.1

[0028] The mixture is mainly composed of aggregate and asphalt. The aggregate particle size composition, that is, the synthetic gradation, must meet the requirements of the upper and lower limits of the specification. Table 1 shows the mass ratio of aggregates of each particle size used in the embodiment. Figure 1 It explains the relationship between the composite gradation adopted in the implementation case and the specification requirements.

[0029] The limestone aggregate used in the following examples was purchased from Chongqing Wansheng Economic Development Zone Qunhonglong Building Materials Co., Ltd., coal-fired slag was obtained from Tianjin Beijiang Power Plant, asphalt was purchased from Chongqing Zhixiang Paving Technology Engineering Co., Ltd., and mineral powder was purchased from Chongqing Wansheng Economic Development Zone Qunhonglong Building Materials Co., Ltd.

[0030] Example 1

[0031] A coal-fired furnace slag asphalt mixture comprises the following raw materials by mass: 838 parts of limestone aggregate, 94 parts of coal-fired furnace slag, 48 parts of asphalt and 20 parts of mineral powder.

[0032] The method for preparing the coal-fired furnace slag asphalt mixture comprises the following steps: mixing the raw materials according to the proportion at 150° C. for 45 minutes to obtain the coal-fired furnace slag asphalt mixture.

[0033] Example 2

[0034] A coal-fired furnace slag asphalt mixture comprises the following raw materials by mass: 783 parts of limestone aggregate, 142 parts of coal-fired furnace slag, 55 parts of asphalt and 20 parts of mineral powder.

[0035] The method for preparing the coal-fired furnace slag asphalt mixture comprises the following steps: mixing the raw materials according to the proportion at 140° C. for 60 minutes to obtain the coal-fired furnace slag asphalt mixture.

[0036] Example 3

[0037] A coal-fired furnace slag asphalt mixture comprises the following raw materials, measured by weight: 783 parts of limestone aggregate, 142 parts of coal-fired furnace slag, 45 parts of asphalt and 15 parts of mineral powder.

[0038] The method for preparing the coal-fired furnace slag asphalt mixture comprises the following steps: mixing the raw materials according to the proportion at 160° C. for 30 minutes to obtain the coal-fired furnace slag asphalt mixture.

[0039] Example 4

[0040] A coal-fired furnace slag asphalt mixture comprises the following raw materials by mass: 935 parts of limestone aggregate, 110 parts of coal-fired furnace slag, 55 parts of asphalt and 18 parts of mineral powder.

[0041] The method for preparing the coal-fired furnace slag asphalt mixture comprises the following steps: mixing the raw materials according to the proportion at 155° C. for 40 minutes to obtain the coal-fired furnace slag asphalt mixture.

[0042] Comparative Example

[0043] The difference between this comparative example and Example 1 is that coal-fired furnace slag is omitted, and the remaining components and implementation conditions are the same as those of Example 1 to obtain an asphalt mixture.

[0044] Experimental example

[0045] The raw materials used in Examples 1, 2 and Comparative Example are shown in Table 2.

[0046] Table 2 Weight parts of raw materials used in Examples 1, 2 and Comparative Examples

[0047]

[0048]

[0049] The mixtures prepared in Examples 1 and 2 and the comparative example were subjected to a Marshall test, and the test standard was based on the Technical Specification for Highway Asphalt Pavement Construction (JTG F40-2004). The results are as follows: Figure 2-Figure 7 As shown in the figure, it can be seen that the optimal asphalt-stone ratio of the mixture increases with the increase of slag content, and the degree of increase is uneven. The higher the slag content, the more significant the increase; with the increase of slag content, the density of the mixture decreases significantly, which is related to the low density of slag; the Marshall stability of asphalt mixture with slag is higher than that of asphalt mixture without slag.

[0050] The mixtures prepared in Examples 1, 2 and the comparative example were subjected to low-temperature bending tests. The test standards refer to the "Test Procedures for Asphalt and Asphalt Mixtures in Highway Engineering" (JTG3441-2024). The results of the low-temperature bending tests are shown in Table 3. It can be seen from the table that the maximum bending strain of the mixture increases first and then decreases with the increase of the slag content, reaching a peak value in Example 1, that is, slag is beneficial to the improvement of the low-temperature crack resistance of the mixture, but excessive content will weaken this effect. The increase in the amount of asphalt makes the mixture have better stress relaxation ability at low temperatures; as the slag content increases further, due to the poor mechanical strength of the slag aggregate particles, it is more prone to brittle cracking at low temperatures.

[0051] Table 3 Results of low temperature bending test of mixture

[0052] Flexural strength / MPa Maximum bending strain / με Bending stiffness modulus / MPa Example 1 9.18 2736 3355 Example 2 9.03 2696 3349 Comparative Example 8.86 2346 3777

[0053] In summary, Example 1 has the best effect. The high-temperature stability of the asphalt mixture increases first and then decreases with the increase in the amount of slag aggregate. The addition of slag aggregate will improve the low-temperature crack resistance of the mixture.

Claims

1. A coal-fired slag asphalt mixture, characterized in that: The raw materials used include, by weight: 783-935 parts of limestone aggregate, 94-142 parts of coal slag, 45-55 parts of asphalt and 15-20 parts of mineral powder.

2. The coal-fired furnace slag asphalt mixture according to claim 1, characterized in that: The raw materials used include, by mass, 838 parts of limestone aggregate, 94 parts of coal slag, 48 parts of asphalt and 20 parts of mineral powder.

3. The coal-fired furnace slag asphalt mixture according to claim 1, characterized in that: The raw materials used include, by mass, 783 parts of limestone aggregate, 142 parts of coal slag, 45 parts of asphalt and 15 parts of mineral powder.

4. The coal-fired furnace slag asphalt mixture according to claim 1, characterized in that: The raw materials used include, by mass, 935 parts of limestone aggregate, 110 parts of coal slag, 55 parts of asphalt and 18 parts of mineral powder.

5. The coal-fired furnace slag asphalt mixture according to any one of claims 1 to 4, characterized in that: The particle size of the coal-fired slag is 0.001-4.75 mm, and the moisture content is 9-12%; the particle size of the limestone aggregate is 0.001-19 mm.

6. The method for preparing coal-fired furnace slag asphalt mixture according to any one of claims 1 to 5, characterized in that: The following steps are involved: The raw materials are mixed according to the proportion and stirred at 140-160° C. for 30-60 minutes to obtain a coal-fired slag asphalt mixture.

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