Preparation method of coal gangue combustion slag machine-made aggregate and preparation method for applying coal gangue combustion slag machine-made aggregate to cement concrete

Abstract

The invention discloses a preparation method of coal gangue combustion slag machine-made aggregate and a preparation method of cement concrete, and belongs to the technical field of cement concrete materials. The preparation method of the coal gangue combustion slag machine-made aggregate comprises the following steps: S1, processing coal gangue combustion slag graded broken stones and machine-made sand on a large scale through combined equipment; s2, preparing cement concrete from the industrial coal gangue combustion slag graded broken stone and the machine-made sand. The invention discloses a preparation method for applying coal gangue burning slag machine-made aggregate to cement concrete. The problem that ordinary cement concrete is large in dead weight is critically overcome and solved; the problems of engineering materials, environmental protection, land resources and the like are solved; the laying period is short, simple and fast; the problem of high cost of cement concrete is solved, and the cost is low; the anti-freezing agent has great benefit to the overall anti-freezing performance of a heavy freezing area, can effectively prolong the service life of cement concrete, and saves the maintenance cost.

Description

Technical Field

[0001] This invention belongs to the field of cement concrete materials technology, specifically relating to a method for preparing coal gangue slag aggregate and its application in the preparation of cement concrete. Background Technology

[0002] Highway construction currently requires a large amount of sand and gravel. With the implementation of environmental protection policies, the requirements for sand and gravel mining and processing will become increasingly stringent, and sand and gravel will gradually become a scarce resource. Coal gangue, as a solid industrial waste, has large emissions, occupies a lot of land, and seriously pollutes the environment, severely impacting people's lives, production, and physical and mental health.

[0003] Therefore, how to rationally utilize coal gangue slag is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a method for preparing coal gangue slag aggregate and its application in the preparation of cement concrete.

[0005] The technical solution adopted in this invention is: A method for preparing coal gangue slag aggregate includes the following steps: S1. Processing coal gangue slag graded crushed stone and manufactured sand on a large scale using combined equipment; The combined equipment is either a combination of cone crusher and impact crusher or a combination of hammer crusher and impact crusher.

[0006] S2. Prepare cement concrete from graded crushed stone and manufactured sand made from coal gangue slag.

[0007] Furthermore, in S2, the coal gangue slag graded crushed stone is impregnated before preparing cement concrete.

[0008] Furthermore, in the hammer crusher-impact crusher combination, a shaping machine is subsequently used.

[0009] A method for preparing cement concrete using coal gangue slag aggregate, wherein the concrete mix proportion is: cement dosage of 365 kg / m³. 3 The water-cement ratio is 0.46 and it contains 0.6% water-reducing agent, with a fine-to-coarse aggregate ratio of 0.82:1.0.

[0010] Furthermore, the cement concrete is applied to cement concrete precast blocks, cement concrete products, and cement concrete base courses for highways.

[0011] Compared with the prior art, the present invention has the following advantages: 1. Coal gangue and slag aggregate cement concrete overcomes some of the shortcomings of traditional crushed stone concrete, and solves the problem of material acquisition difficulties. Its overall technical characteristics and advantages are: ① It keyly overcomes and solves the problem of the heavy weight of ordinary cement concrete; ② It solves problems related to engineering materials, environmental protection, and land resources; ③ It has a short laying cycle and is simple and quick; ④ It solves the problem of high cost of cement concrete, while having a lower cost; ⑤ It has great benefits for the overall frost resistance in heavily frozen areas, can effectively extend the service life of cement concrete, and save maintenance costs.

[0012] 2. Coal gangue slag = self-igniting coal gangue = coal gangue that has completely combusted = commonly known as "fire-burned gangue". Coal gangue is a general term encompassing non-spontaneously combusted coal gangue, coal gangue that is in the process of spontaneous combustion, and coal gangue that has completely spontaneously combusted (coal gangue slag). The main differences between non-spontaneously combusted coal gangue and coal gangue that has completely spontaneously combusted (coal gangue slag) are: ① The rock properties and engineering properties are completely different; ② The quantity of coal gangue slag is much smaller than that of unburned coal gangue, limiting the selection options; ③ Even when used in cement concrete, non-spontaneously combusted coal gangue does not achieve good performance, uniformity, and stability. However, research has shown that using graded crushed stone and manufactured sand from coal gangue slag can achieve excellent performance, uniformity, and stability. The combustible impurities in the coal gangue slag are eliminated, and the strength of sandstone in the original rock is improved after combustion. The strength of mudstone, argillaceous sandstone, or argillaceous shale in the original rock is also improved after combustion, and the strength uniformity and stability are better.

[0013] 3. Industrial solid waste, when stockpiled in large quantities—environmentally friendly, land-consuming, and polluting. Conventional crushed stone mining results in significant land occupation, resource depletion, and environmental impact. However, its large-scale, fully replaceable application in cement concrete allows for substantial consumption, turning waste into treasure—a win-win situation. Especially for railway transport over distances of approximately 500km, the cost remains comparable to conventional crushed stone. Coal gangue slag has a low density and low thermal conductivity, reducing the frost depth of roads after application to cement concrete. This greatly benefits the overall frost resistance in heavily frozen areas, effectively extending the service life of cement concrete and saving on maintenance costs.

[0014] 4. With the large-scale construction of highways and infrastructure, the utilization of coal gangue ash in engineering projects has broad prospects. The large-scale consumption and application of accumulated coal gangue ash can solve problems related to engineering materials, environmental protection, and land resources, achieving multiple benefits. Therefore, research on the properties of coal gangue, especially its application in road engineering, will generate significant economic, environmental, and social benefits, and is of great significance.

[0015] 5. Environmental and social benefits are often difficult to quantify. Through a detailed investigation and study of the base price of coal gangue slag, processing costs of crushed material, and transportation costs across the province, this study compares the direct cost of using coal gangue slag crushed stone in highway engineering with that of conventional crushed stone aggregates to determine the direct impact of coal gangue slag crushed stone application on project costs. Simultaneously, the study also reflects the direct value of land savings based on land acquisition costs. Attached Figure Description

[0016] Figure 1 It is the failure mode of coal gangue aggregate concrete; Figure 2 This is a schematic diagram of cement concrete with 6% water-reducing agent for coal gangue aggregate; Figure 3 This is the discharge state of coal gangue aggregate concrete; Figure 4 It refers to the preparation state of coal gangue slag; Figure 5 It is cement concrete made from coal gangue slag; Figure 6 This is a schematic diagram of the on-site preparation of coal gangue slag aggregate. Figure 1 ; Figure 7 This is a schematic diagram of the on-site preparation of coal gangue slag aggregate. Figure 2 . Detailed Implementation

[0017] To better understand the purpose, structure, and function of this invention, the invention will be described in further detail below with reference to the accompanying drawings.

[0018] This invention is applicable to cement concrete precast blocks, cement concrete products, and cement concrete base courses for highways, etc.

[0019] A method for preparing coal gangue slag aggregate includes the following steps: S1. Through combined equipment, large-scale, refined processing of graded coal gangue slag crushed stone and manufactured sand with good technical indicators such as well-formed, square-shaped particles and high particle crushing value; such as... Figure 4 , Figure 6 , Figure 7 As shown.

[0020] The combined equipment is either a combination of cone crusher and impact crusher or a combination of hammer crusher and impact crusher.

[0021] Coal gangue slag is a medium-hardness rock. For crushing, the jaw crusher's coarse crushing stage is omitted. Furthermore, based on the principles of multiple impacts and grinding, a two-stage crushing process of medium and fine crushing is preferred. Recommended equipment combinations are "cone crusher-impact crusher" and "hammer crusher-impact crusher (including a shaping machine)". Using these two methods to crush the coal gangue slag will yield coal gangue slag crushed stone of the appropriate particle size.

[0022] Using large-scale mining crushing equipment, high-quality "coal gangue slag graded crushed stone" and "coal gangue slag manufactured sand" were processed on a large scale, and then applied to the base course of secondary highways as "5% cement stabilized slag crushed stone". A test section was paved and a comprehensive technical parameter study was conducted, which achieved the technical level of 4.5% cement stabilized conventional crushed stone and met the requirements of the "Specification".

[0023] S2. Prepare cement concrete from graded crushed stone made from coal gangue and slag, and manufactured sand. For example... Figure 5 As shown.

[0024] In concrete engineering, aggregates with particle sizes of 2mm or less than 1mm should be avoided as much as possible; Because coal gangue slag has a high water absorption rate (and has previously lost too much water), pre-wetting is beneficial, but it should not be saturated with water. A method for applying coal gangue slag aggregate to the preparation of cement concrete includes the following steps: S1. 1. Cement concrete mix proportions Table 1. Summary of Slag Concrete Mix Proportions and Workability

[0025] The mix proportions of coal gangue, slag, and crushed stone shown in Table 1 represent perfect and successful mix proportions. With a water-reducing agent content of 0.6%, the slump is 245 mm, the slump spread is 550 mm, and good cohesiveness and water retention are observed. Figure 2 and Figure 3 The cement content in this mix design is 365 kg / m³. 3 The water-cement ratio is 0.46, with 0.6% water-reducing agent added, and the fine-to-coarse aggregate ratio is 0.82:1.0. Cement concrete with this mix proportion can achieve the standard C42 strength grade.

[0026] 2. Properties of cement concrete Slump: 245mm, spread: 550mm, workability: good cohesiveness and water retention.

[0027] 3. Performance of cement concrete for road use Compressive strength: This experiment was based on mature empirical data for C30 concrete. The aggregates of each grade were replaced by a 1.1x coefficient, and the use and dosage of water-reducing agents were also investigated. The compressive strength test results after dimensional conversion are shown in Tables 2 and 3 below, illustrating the failure modes of coal gangue aggregate concrete. Figure 1 The data results are analyzed as follows: It is worth mentioning that a mix design was also tested—based on a conventional C30 crushed stone aggregate mix design, the coarse aggregate and sand were replaced by an equal volume, while the proportions of other raw materials (cement, water, and 3% water-reducing agent) remained unchanged. The resulting slag concrete was dry and hard, with no slump, and could not be formed using conventional methods. The main reason for the failure of this mix design was the high water absorption rate and poor particle permeability of coal gangue. To achieve good workability, the amount of water or water-reducing agent needed to be increased. Therefore, in subsequent tests, the amount of water-reducing agent was tentatively increased to 6%.

[0028] Table 2 Compressive strength (MPa) of 28-day slag aggregate and conventional aggregate concrete (Test site 1, group 1)

[0029] Table 3 Compressive strength (MPa) of slag aggregate and conventional aggregate concrete from 7d to 28d (Test site 2, group 2)

[0030] 3.1 The slag aggregate concrete reached the C30 level at 7 days of age, but the strength hardly increased from 7 to 14 days. Then, the compressive strength increased rapidly again from 14 to 28 days to the C41.6 level. The strength continued to increase from 28 to 90 days, but very slowly.

[0031] 3.2 The expected intensity level was C30, but the actual intensity reached C41.6, far exceeding expectations; 3.3 The cement dosage in this group of tests was 365 kg / m³. 3 The strength was at a medium level compared to all previous tests, but the strength was the highest among all tests. If measured by the ratio of strength to cement dosage, it offers the best cost-effectiveness.

[0032] 3.4, by Figure 1 It is evident that the macroscopic compressive failure morphology of concrete specimens prepared with coal gangue and slag aggregates mixed with water-reducing agents is similar to that of ordinary aggregate concrete, both exhibiting a conical shape after failure. However, the cross-section of ordinary aggregate concrete mostly shows delamination between the aggregate and the interface, while the cross-section of coal gangue aggregate concrete mostly shows fracture of the aggregate itself.

[0033] Therefore, it can be inferred that grade C40 is close to the limit of the best performance that coal gangue slag aggregate can achieve, and it is recommended to use it in concrete with a maximum strength grade of C35 in engineering applications.

[0034] The results of the concrete splitting strength test are shown in Figure 3.

[0035] Results and data analysis: 1. The standard deviations of the two sets of tests were small, and the splitting strength of the slag concrete increased at a relatively uniform rate with age. 2. The tensile strength of cement concrete is usually measured using splitting tensile strength, which is generally only 1 / 10 to 1 / 20 of the compressive strength, and this ratio decreases as the concrete strength grade increases. Concrete generally does not rely on its tensile strength during operation. However, tensile strength is crucial for crack resistance, and in structural design, it is an important indicator for determining the crack resistance of concrete. It is also sometimes used to indirectly measure the bond strength between concrete and reinforcing steel.

[0036] Based on empirical data, the recommended design parameters for cement concrete are as follows: for C15 to C80, the ratio of compressive strength to splitting tensile strength is 7.9 to 16.1, while for the commonly used C25 to C45, the ratio is 9.4 to 11.8.

[0037] The measured ratio of compressive strength to splitting tensile strength of cement concrete made from coal gangue and slag aggregate is 12.2 for C32.3 and 10.9 for C35.4. This deviates slightly from empirical values ​​but remains within a reasonable range. Furthermore, slag aggregate concrete does not exhibit the superior "compression-tensile (splitting) ratio" of cement-stabilized slag crushed stone, primarily because the cement plays a greater role in the tensile process of concrete (not depending on the aggregate).

[0038] Table 4 Splitting strength of slag concrete from 7d to 28d

[0039] 4. Main experimental conclusions or engineering application conclusions 4.1 Within the commonly used cement dosage range, cement concrete made from coal gangue, slag, and crushed stone aggregate can easily reach a strength grade of C25 or even as high as C40, which is sufficient to meet the requirements of cement concrete engineering for even the protection projects in heavily frozen areas.

[0040] 4.2 Due to the high water absorption rate and poor particle bleeding properties of coal gangue slag crushed stone aggregate, strict mix design should be adopted in engineering applications. The cement content should not be too low, and the concrete should be kept in good workability to avoid the problem of low early strength (7d~14d), which is not conducive to construction.

[0041] 4.3 Concrete specimens of grade C40 prepared from coal gangue and slag crushed stone aggregate with added water-reducing agent showed similar macroscopic compressive failure modes to ordinary aggregate concrete, both exhibiting a conical shape after failure. However, the cross-section of ordinary aggregate concrete mostly showed delamination between the aggregate and the interface, while the cross-section of coal gangue aggregate concrete mostly showed fracture of the aggregate itself.

[0042] Therefore, it can be inferred that grade C40 is close to the limit of the best performance that coal gangue slag aggregate can achieve. In engineering applications, it is recommended to use it in concrete with a maximum strength grade of C35. It is also recommended not to use coal gangue slag crushed stone concrete in major components such as bridges and culverts.

[0043] 4.4 Due to the characteristics of coal gangue and slag crushed stone aggregates, which have "high water absorption and poor particle bleeding," a large amount of water is usually required. Slag crushed stone concrete is best suited for use with water-reducing agents that are "widely used in engineering and have a high cost-performance ratio"—① This avoids a significant increase in water consumption, thus preventing problems such as "difficulty in adjusting concrete workability and low early strength"; ② Using water-reducing agents reduces water consumption, which is more conducive to achieving good workability indicators such as slump, cohesion, fluidity, and workability in concrete, thereby ensuring the strength and uniformity of concrete components; ③ From an economic perspective, it helps to achieve optimal cement utilization efficiency and overall cost-effectiveness.

[0044] 5. According to empirical data, the recommended design parameter values ​​for cement concrete are 7.9 to 16.1 for compressive strength to splitting tensile strength for C15 to C80 concrete, while the commonly used ratio for C25 to C45 is 9.4 to 11.8.

[0045] The measured ratio of compressive strength to splitting tensile strength of cement concrete made from coal gangue and slag aggregate is approximately 12.2 to 10.9 for grades C30 to C35. This is slightly different from the empirical value, but still within a reasonable range. Moreover, slag aggregate concrete does not exhibit the excellent "compression-tensile (splitting) ratio" of cement-stabilized slag crushed stone, mainly because the cement plays a greater role in the tensile process of concrete (not depending on the aggregate).

[0046] The prepared cement concrete is used in cement concrete precast blocks, cement concrete products, and cement concrete base courses for highways.

[0047] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A method for preparing coal gangue slag aggregate, characterized in that: Includes the following steps: S1. Through combined equipment, large-scale processing of coal gangue slag graded crushed stone and manufactured sand; The combined equipment is either a combination of cone crusher and impact crusher or a combination of hammer crusher and impact crusher. S2. Prepare cement concrete from graded crushed stone and manufactured sand made from coal gangue slag.

2. The method for preparing coal gangue slag aggregate according to claim 1, characterized in that: In step S2, the coal gangue slag graded crushed stone is impregnated before preparing cement concrete.

3. The method for preparing coal gangue slag aggregate according to claim 2, characterized in that: In the hammer crusher-impact crusher combination, a shaping machine is subsequently used.

4. A method for preparing cement concrete using coal gangue slag aggregate, characterized in that: The mix proportion for preparing cement concrete is: cement dosage 365 kg / m³. 3 The water-cement ratio is 0.46 and it contains 0.6% water-reducing agent, with a fine-to-coarse aggregate ratio of 0.82:1.

0.

5. A method for preparing cement concrete using coal gangue slag aggregate, characterized in that: The cement concrete is used in cement concrete precast blocks, cement concrete products, and cement concrete base courses for highways.

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