Method for testing strength of coal gangue coarse aggregate for lime-fly ash stabilized base

Abstract

The invention relates to a coal gangue coarse aggregate strength test method for a lime-fly ash stabilized base, and belongs to the technical field of highway engineering. According to the test method, the coal gangue soaking compressive strength R is adopted as an index for judging the mechanical property of the coal gangue coarse aggregate, and the applicability of the coal gangue coarse aggregate is further verified through a two-ash stabilized base mixture 28d unconfined compressive strength test. When R is greater than or equal to 4 * Rdmin, preliminarily judging that the strength of the coal gangue coarse aggregate is qualified; otherwise, judging that the product is unqualified; after preliminary judgment is qualified, the applicability of the strength of the coal gangue coarse aggregate is further verified through 7d and 28d unconfined compressive strength tests. According to the method, the correct test method and index are adopted, scientific test judgment is conducted on the applicability of the coal gangue coarse aggregate in the lime-fly ash stabilized aggregate base layer, the coal gangue coarse aggregate can be used up under the condition that the quality of the lime-fly ash stabilized coal gangue coarse aggregate base layer is guaranteed, and opportunities are provided for reducing the cost of the lime-fly ash stabilized base layer and protecting the environment as much as possible.

Description

Technical Field

[0001] This invention relates to the field of highway engineering technology, and in particular to a test method for the strength of coarse aggregate of coal gangue used in lime-stabilized base courses. Background Technology

[0002] Coal gangue is a solid waste discharged during coal mining and washing. It is a blackish-gray rock with low carbon content and harder than coal, which is associated with coal seams during coal formation. Its discharge is large, causing serious pollution. Coal gangue coarse aggregate refers to a mixture of coal gangue with a particle size greater than 2.36 mm formed by crushing and screening.

[0003] Currently, when coarse coal gangue aggregate is used in road base courses (including subbase courses, hereinafter referred to as base courses), its mechanical properties are tested through the coarse aggregate crushing value test (an indirect indicator of strength) to assess its suitability for use in base courses. This test is conducted on the coarse coal gangue aggregate in a dry state. However, the mechanical properties of coal gangue can differ significantly between dry and wet conditions. Some coal gangue may meet the specifications for crushing value when dry, but fail to do so when wet. This is determined by the inherent properties of the coarse coal gangue aggregate itself, a factor that the coarse aggregate crushing value test does not take into account.

[0004] Furthermore, in the coarse aggregate crushing value test, only when the coarse aggregate is crushed into particles with a diameter of 2.36 mm or less (i.e., fine aggregate) is it considered crushed and reflected in the crushing value. However, in reality, large-diameter aggregates (such as aggregates with a diameter of 9.5 mm to 13.2 mm) are often crushed but cannot pass through a 2.36 mm sieve. The test result, i.e., the coarse aggregate crushing value, does not reflect this situation. This is due to a defect in the coarse aggregate crushing value test itself.

[0005] In conclusion, according to the existing test evaluation methods, the crushing value of coarse aggregate of coal gangue is misleading, or in other words, the test of the crushing value of coarse aggregate is unscientific.

[0006] The use of coarse aggregates in the base course without causing secondary pollution is an effective way to turn coal gangue waste into a valuable resource. However, in engineering practice, the aggregates used in ash-stabilized granular base courses are mostly gravel and crushed stone, while the application of coarse aggregates from coal gangue is very limited. Research has found that one reason for this is the lack of scientific testing and evaluation methods for coarse aggregates from coal gangue, leading to both successful and unsuccessful applications, thus limiting their use. Another reason is that current specifications have excessively high crushing value requirements, causing some coarse aggregates from coal gangue to be discarded due to their slightly higher crushing values. For example, the gangue produced after coal washing in coal preparation plants (called washed gangue) is clean, hard, and has uniform and stable strength, but its crushing value is sometimes only 30% to 26%, leading to waste of resources and the loss of opportunities to reduce the cost of ash-stabilized granular base courses and protect the environment. Summary of the Invention

[0007] The problem this invention aims to solve is to scientifically test and determine the applicability of coal gangue coarse aggregate in lime-stabilized granular base courses using correct test methods and indicators, so as to make full use of the lime-stabilized coal gangue coarse aggregate base course (hereinafter referred to as lime-stabilized base course) while ensuring the quality of the lime-stabilized coal gangue coarse aggregate base course.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A test method for the strength of coarse coal gangue aggregate for ash-stabilized base course. The index used to determine the mechanical properties of coarse coal gangue aggregate in this test method is the compressive strength R.

[0009] Furthermore, the compressive strength is the water immersion compressive strength.

[0010] Studies have shown that the compressive strength of some coal gangue when immersed in water is lower than that when dry. In order to ensure the quality of coal gangue suitable for use in base courses, this test method uses the compressive strength when immersed in water.

[0011] Furthermore, the compressive strength test was conducted according to the method of (T 0221-2005) "Test for Uniaxial Compressive Strength of Rock".

[0012] Furthermore, the standard compressive strength R is ≥ 4 times the minimum standard compressive strength R of the design compressive strength of the lime-stabilized base course. dmin .

[0013] Under conditions of no overloading or exceeding limits, the compressive stress of vehicle loads on the road surface should not exceed 0.4 MPa, and the compressive stress of vehicle loads on the base layer should be even smaller. However, in the composite design of highway pavement structures, the design compressive stress is much greater than 0.4 MPa. Considering factors such as overloading, load impact, road grade, service layer, and safety factor, the "Technical Specifications for Construction of Highway Pavement Base Layers" (JTG / T F20-2015) stipulates the standard for the design compressive strength of lime-fly ash stabilized base layers (i.e., the 7-day unconfined compressive strength standard R of lime-fly ash stabilized base layer mixtures). d (R) refers to the base course of highways and first-class roads used for extremely heavy and extra-heavy traffic. d ≥1.1MPa (This is the highest requirement in the current standard, and its R dmin =1.1MPa); when used for the subbase of secondary and lower grade highways for medium and light traffic, R d ≥0.5MPa (This is the minimum requirement in the current standard, and its R dmin=0.5MPa); In engineering practice, the compressive strength of lime-fly ash stabilized base courses is no greater than 2MPa, and the compressive strength of filler (referring to the mixture of fine aggregate and lime-fly ash, called filler because it fills the gaps between coarse aggregate) is between 1MPa and 2MPa; in the maintenance of lime-fly ash stabilized base courses, no damage caused by insufficient strength of coarse aggregate has ever been found. These situations indicate that the strength of coarse aggregate is sufficiently abundant. Based on this, research was conducted, and the results show that when coal gangue coarse aggregate is used for lime-fly ash stabilized base courses, R = 2 × R dmin (That is, the compressive strength of the coarse aggregate of coal gangue after immersion in water is equal to twice the minimum standard design compressive strength of the lime-fly ash stabilized base course) to ensure that the lime-fly ash stabilized base course will not be damaged due to insufficient strength of the coarse aggregate. In practical applications, a guarantee factor of 2 is taken, that is, R≥4×R dmin This ensures that the lime-stabilized base course will not be damaged due to insufficient strength of the coarse aggregate. In other words, when damage occurs under load, the filler and the interface between the filler and the coarse aggregate will be damaged first, rather than the coarse aggregate being crushed.

[0014] Furthermore, the test method further verifies the applicability of coal gangue coarse aggregate by conducting a 28-day unconfined compressive strength test on the lime-stabilized base course mixture.

[0015] According to the method of (JTG E51-2009) "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering", the 28-day unconfined compressive strength test of the lime-fly ash stabilized base course mixture was carried out. In the 28-day unconfined compressive strength test specimen after compression, the coarse aggregate of coal gangue should not crack. Otherwise, the coarse aggregate of coal gangue is determined to be unsuitable for lime-fly ash stabilized base course.

[0016] Furthermore, the specific steps of the experimental method are as follows: 1. Determine the compressive strength R of coal gangue coarse aggregate. The test was conducted according to the method of (T 0221-2005) "Test for Uniaxial Compressive Strength of Rock" to obtain the compressive strength R of coal gangue coarse aggregate; 2. Determine the minimum standard value R of the design compressive strength of the lime-stabilized base course. dmin According to Table 4.2.6 of the "Technical Specifications for Construction of Highway Pavement Base Course" (JTG / T F20-2015), the minimum standard value of the design compressive strength R of the lime-fly ash stabilized base course is determined. dmin ; 3. Preliminary assessment of compressive strength R≥4×R dmin If the strength of the coarse aggregate of coal gangue is within acceptable limits, it is preliminarily determined to be qualified; otherwise, it is determined to be unqualified. 4. Verify the applicability of the strength of the coal gangue coarse aggregate. The design of the lime-fly ash stabilized base course mixture was carried out in accordance with the requirements of (JTG / T F20-2015) "Technical Specifications for Construction of Highway Pavement Base Course". The 7-day unconfined compressive strength test of the lime-fly ash stabilized base course mixture was carried out in accordance with the method of (JTG E51-2009) "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering". The 7-day unconfined compressive strength R7 was obtained. When R7 < R dmin At that time, there are two situations: (1) If the coarse aggregate of coal gangue does not crack, but the filler is damaged, the design of the two-ash stabilized base course mixture is unqualified and should be redesigned to improve the strength of the filler. (2) If the coarse aggregate of coal gangue cracks, then the coarse aggregate of coal gangue is not suitable for the two-ash stabilized base course; When R7≥R dmin If the design of the lime-stabilized base course mixture is qualified, then the following verification should be performed: The 28-day unconfined compressive strength test of lime-fly ash stabilized base course mixture was conducted according to the method of (JTG E51-2009) "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering". In the 28-day unconfined compressive strength test specimens after compression, if the coarse aggregate of coal gangue does not crack, the strength of the coarse aggregate of coal gangue is determined to be suitable for the two-ash stabilized base course; otherwise, the coarse aggregate of coal gangue is determined not to be suitable for the two-ash stabilized base course.

[0017] Furthermore, after the coal gangue coarse aggregate compressive strength test specimens are prepared in step 1, they are completely immersed in water for at least 24 hours.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The present invention uses the water immersion compressive strength as the mechanical performance index of coal gangue coarse aggregate to determine its applicability in lime-fly ash stabilized base course, which is scientific and accurate; the prior art uses the crushing value to determine its applicability in lime-fly ash stabilized base course, which is misleading and unscientific.

[0019] 2. Based on extensive and detailed experimental research, data analysis, and long-term practical experience in engineering construction, maintenance, and upkeep, this invention has realistically determined the standard for water immersion compressive strength. This ensures the quality of the lime-stabilized base course and allows for the full utilization of coal gangue coarse aggregate, resulting in high economic value and significant environmental benefits—large usage without causing secondary pollution.

[0020] 3. This invention has a wide range of applications and can also be used to determine the applicability of other coarse stone aggregates in lime-stabilized aggregate base courses. Detailed Implementation

[0021] The technical solution and effects of the present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0022] The quicklime, fly ash, stone chips, and coal gangue coarse aggregate used in the following examples and comparative examples are commercially available products. Specifically: the quality of the quicklime, fly ash, and stone chips all meet the requirements of (JTG / T F20-2015) "Technical Specifications for Construction of Highway Pavement Base Course". Specifically: the quicklime is Grade II quicklime, purchased from the Bai Li Shi Factory in Wuliang Town, Yuzhou City, Henan Province, and is used after being slaked into hydrated lime; the fly ash has a total SiO2, Al2O3, and Fe2O3 content greater than 70%, and its loss on ignition does not exceed 20%, purchased from Zhiqiang Fly Ash Refining Plant in Pingdingshan High-tech Zone; the stone chips have excellent gradation and a particle size not exceeding 2.36 mm, purchased from Jianhong Building Materials Stone Factory in Jia County; and the coal gangue coarse aggregate is a mixture with a particle size of 2.36 mm to 31.5 mm.

[0023] In addition, in the following examples and comparative examples, the quality mix design of the lime-stabilized base course mixture (including the gradation of the aggregate mixture - the gradation of the coal gangue coarse aggregate and the stone chip mixture) only gives the design results. The design method is carried out in accordance with the requirements of (JTG / T F20-2015) "Technical Specifications for Construction of Highway Pavement Base Course", which is a mature technology and will not be elaborated here.

[0024] Furthermore, in the following examples and comparative examples, only the test results of the compressive strength test are given. The test methods, procedures and requirements are carried out in accordance with relevant test procedures, which are also mature technologies, and will not be elaborated here. Example 1

[0025] Known conditions for Example 1: A certain highway is a Class I highway with heavy traffic. The applicability of coarse coal gangue aggregate in a lime-stabilized base course is determined. The coal gangue used is washed gangue from the Tianzhuang Coal Preparation Plant in Pingdingshan City. Its main components are Al2O3, SiO2, and Fe2O3, with a combined content of 78%–91%. It also contains CaO, MgO, Na2O, K2O, P2O5, SO3, and trace rare elements (gallium, vanadium, titanium, cobalt).

[0026] To verify whether the strength of the coarse aggregate of coal gangue used in this embodiment is suitable for use in the base course, the strength test method for coarse aggregate of coal gangue used in the lime-fly ash stabilized base course was adopted. The specific steps are as follows: 1. Determine the compressive strength R of coal gangue coarse aggregate. The compressive strength of coal gangue coarse aggregate was obtained by conducting a water immersion compressive strength test according to the method of (T 0221-2005) "Test for Uniaxial Compressive Strength of Rock".

[0027] In this step, a large piece of washed gangue with a minimum size (particle size) of 10cm is taken, fixed on a cutting table, and a 5cm×5cm×5cm cubic compressive strength specimen is cut from the large piece of washed gangue using a diamond saw blade cutter. It is required that the compressive strength specimen be completely taken from the interior of the original washed gangue (that is, all faces of the compressive strength specimen are cut out, and the surface of the original washed gangue is not left on the compressive strength specimen). After the coal gangue coarse aggregate compressive strength specimen is cut, it is immediately completely immersed in water. In this embodiment, the immersion time of the compressive strength specimen is 26 hours. Before the compressive strength test, the specimen is taken out of the water, and the water on the surface of the specimen is wiped dry with a dry cloth. Then the compressive strength test is carried out according to the method of (T0221-2005) "Rock Uniaxial Compressive Strength Test".

[0028] In this embodiment, the failure loads of the six washed gangue compressive strength test specimens were 10990N, 11480N, 11360N, 11340N, 11680N, and 11520N, respectively. The calculated test result R≈4.6MPa.

[0029] 2. Determine the minimum standard value R of the design compressive strength of the lime-stabilized base course. dmin According to Table 4.2.6 of (JTG / T F20-2015) "Technical Specifications for Construction of Highway Pavement Base Course", the minimum standard design compressive strength of the lime-fly ash stabilized base course, i.e., R, is determined. dmin =1.1MPa, then 4×R dmin =4 × 1.1 MPa = 4.4 MPa.

[0030] 3. Preliminary assessment of compressive strength Since R≈4.6MPa>4×R dmin =4.4MPa, then the strength of the coarse aggregate of coal gangue is preliminarily determined to be qualified.

[0031] 4. Verify the applicability of the strength of the coal gangue coarse aggregate. The design of the lime-fly ash stabilized base course mixture was carried out in accordance with the requirements of (JTG / T F20-2015) "Technical Specifications for Construction of Highway Pavement Base Course". The 7-day unconfined compressive strength test of the lime-fly ash stabilized base course mixture was carried out in accordance with the method of (JTG E51-2009) "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering".

[0032] In this step, the design mix ratio of the lime-fly ash stabilized base course mixture is: hydrated lime: fly ash: stone chips: coal gangue coarse aggregate = 8:17:15:60; the specimens are made according to (T 0843-2009) "Method for making specimens of inorganic binder stabilized materials (cylindrical)" in (JTG E51-2009) "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering", with a specimen diameter × height = φ150mm × 150mm, and the compressive strength test is carried out according to (T 0805-1994) "Test Method for Unconfined Compressive Strength of Inorganic Binder Stabilized Materials".

[0033] In this embodiment, the failure loads of 13 unconfined compressive strength test specimens of lime-stabilized base course mixture at 7 days were 25620N, 24920N, 24560N, 25270N, 23680N, 24920N, 24920N, 24390N, 23860N, 26510N, 24740N, 24740N, and 24210N, respectively. The calculated test result R7≈1.4MPa.

[0034] Since R7≈1.4MPa>R dmin =1.1MPa, then the design of the lime-stabilized base course mixture is qualified, and then the following verification is carried out.

[0035] According to the method of (JTG E51-2009) "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering", the 28-day unconfined compressive strength test of the lime-fly ash stabilized base course mixture was carried out. In the compressed specimen, if the coarse aggregate of coal gangue did not crack, the strength of the coarse aggregate of coal gangue was determined to be suitable for lime-fly ash stabilized base course; otherwise, the coarse aggregate of coal gangue was determined to be unsuitable for lime-fly ash stabilized base course.

[0036] The strength of the compressive strength test specimens of the lime-fly ash stabilized base course mixture mainly develops within 28 days. Its 28-day unconfined compressive strength is very close to the strength of the lime-fly ash stabilized base course engineering entity. Therefore, the 28-day unconfined compressive strength test of the lime-fly ash stabilized base course mixture can accurately characterize the working state of the engineering entity. Furthermore, the compressive stress exerted by vehicle loads on the lime-fly ash stabilized base course is much smaller than the compressive stress at which the 28-day unconfined compressive strength test specimens of the lime-fly ash stabilized base course mixture fail under pressure. Therefore, as long as the coarse coal gangue aggregate is not crushed in the 28-day unconfined compressive strength test specimens of the lime-fly ash stabilized base course mixture, it can be guaranteed that it will not be crushed in the lime-fly ash stabilized base course.

[0037] In this embodiment, since the coarse aggregate of coal gangue did not crack, the strength of the coarse aggregate of coal gangue was determined to be suitable for the two-ash stabilized base course. Comparative Example 1

[0038] The known conditions for Comparative Example 1 are the same as those for Example 1. This comparative example is a common lime-fly ash stabilized base course mixture, and the designed mass mix ratio is: hydrated lime: fly ash: stone chips: coal gangue coarse aggregate = 10:18:20:52. The experiment was conducted according to the method of Example 1.

[0039] In this comparative example, the failure loads of 13 unconfined compressive strength test specimens of lime-stabilized base course mixture at 7 days were 26530N, 25820N, 25620N, 25710N, 25090N, 24550N, 27410N, 25750N, 25860N, 26260N, 26970N, 25880N, and 25920N, respectively. The calculated test result is R7≈1.5MPa.

[0040] Since R7≈1.5MPa>R dmin =1.1MPa, and in the specimens after the 28-day unconfined compressive strength test of the lime-fly ash stabilized base course mixture, no cracking of the coarse aggregate of coal gangue was observed. Therefore, the strength of the coarse aggregate of coal gangue is determined to be suitable for lime-fly ash stabilized base course. Example 2

[0041] Known conditions for Example 2: A certain highway is a Class I highway with heavy traffic. Determine the applicability of coal gangue coarse aggregate in a lime-stabilized base course. The coal gangue is taken from the gangue pile of the Fourth Mine of China Pingmei Shenma Energy Chemical Group Co., Ltd. Its main components are Al2O3, SiO2 and Fe2O3, with a combined content of 70% to 86%. It also contains CaO, MgO, Na2O, K2O, P2O5, SO3 and trace rare elements (gallium, vanadium, titanium, cobalt).

[0042] To verify whether the strength of the coarse aggregate of coal gangue used in this embodiment is suitable for use in the base course, the strength test method for coarse aggregate of coal gangue used in the lime-fly ash stabilized base course was adopted. The specific steps are as follows: 1. Determine the compressive strength R of coal gangue coarse aggregate. The experimental method is the same as step 1 of Example 1.

[0043] In this embodiment, the failure loads of the six coal gangue compressive strength test specimens are 10350N, 10880N, 10780N, 10940N, 11090N, and 11010N, respectively. The calculated test result is R≈4.3MPa.

[0044] 2. Determine the minimum standard value R of the design compressive strength of the lime-stabilized base course. dmin According to Table 4.2.6 of (JTG / T F20-2015) "Technical Specifications for Construction of Highway Pavement Base Course", the minimum standard design compressive strength of the lime-fly ash stabilized base course, i.e., R, is determined. dmin =1.1MPa, then 4×R dmin=4 × 1.1 MPa = 4.4 MPa.

[0045] 3. Preliminary assessment of compressive strength Since R≈4.3MPa<4×R dmin =4.4MPa, then the strength of the coarse aggregate of coal gangue is preliminarily determined to be unqualified.

[0046] If the strength of the coarse aggregate of coal gangue is initially determined to be unqualified, then the strength of the coarse aggregate of coal gangue is determined to be unsuitable for the two-ash stabilized base course. Example 3

[0047] Known conditions for Example 3: A certain highway is a Class I highway with heavy traffic. Determine the applicability of coal gangue coarse aggregate in a lime-stabilized base course. The coal gangue is taken from the gangue pile of the Sixth Mine of China Pingmei Shenma Energy Chemical Group Co., Ltd. Its main components are Al2O3, SiO2 and Fe2O3, with a combined content of 75% to 89%. It also contains CaO, MgO, Na2O, K2O, P2O5, SO3 and trace rare elements (gallium, vanadium, titanium, cobalt).

[0048] To verify whether the strength of the coarse aggregate of coal gangue used in this embodiment is suitable for use in the base course, the strength test method for coarse aggregate of coal gangue used in the lime-fly ash stabilized base course was adopted. The specific steps are as follows: 1. Determine the compressive strength R of coal gangue coarse aggregate. The experimental method is the same as step 1 of Example 1.

[0049] In this embodiment, the failure loads of the six coal gangue compressive strength test specimens are 11250N, 11280N, 11230N, 11240N, 11290N, and 11220N, respectively. The calculated test result is R≈4.5MPa.

[0050] 2. Determine the minimum standard value R of the design compressive strength of the lime-stabilized base course. dmin According to Table 4.2.6 of (JTG / T F20-2015) "Technical Specifications for Construction of Highway Pavement Base Course", the minimum standard design compressive strength of the lime-fly ash stabilized base course, i.e., R, is determined. dmin =1.1MPa, then 4×R dmin =4 × 1.1 MPa = 4.4 MPa.

[0051] 3. Preliminary assessment of compressive strength Since R≈4.5MPa>4×R dmin =4.4MPa, then the strength of the coarse aggregate of coal gangue is preliminarily determined to be qualified.

[0052] 4. Verify the applicability of the strength of the coal gangue coarse aggregate. The design of the lime-fly ash stabilized base course mixture was carried out in accordance with the requirements of (JTG / T F20-2015) "Technical Specifications for Construction of Highway Pavement Base Course". The 7-day unconfined compressive strength test of the lime-fly ash stabilized base course mixture was carried out in accordance with the method of (JTG E51-2009) "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering".

[0053] In this step, the design mass mix ratio of the lime-fly ash stabilized base course mixture is: hydrated lime: fly ash: stone chips: coal gangue coarse aggregate = 10:20:15:55; the specimens are made according to (T 0843-2009) "Method for making specimens of inorganic binder stabilized materials (cylindrical)" in (JTG E51-2009) "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering", with a specimen diameter × height = φ150mm × 150mm, and the compressive strength test is carried out according to (T 0805-1994) "Test Method for Unconfined Compressive Strength of Inorganic Binder Stabilized Materials".

[0054] In this embodiment, the failure loads of 13 unconfined compressive strength test specimens of lime-stabilized base course mixture at 7 days were 24850N, 24790N, 25510N, 24410N, 25380N, 24080N, 24110N, 24920N, 24810N, 24820N, 24410N, 23850N, and 26560N, respectively. The calculated test result R7≈1.4MPa.

[0055] Since R7≈1.4MPa>R dmin =1.1MPa, then the design of the lime-stabilized base course mixture is qualified, and then the following verification is carried out.

[0056] According to the method of (JTG E51-2009) "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering", the 28-day unconfined compressive strength test of the lime-fly ash stabilized base course mixture was carried out. In the compressed specimen, if the coarse aggregate of coal gangue did not crack, the strength of the coarse aggregate of coal gangue was determined to be suitable for lime-fly ash stabilized base course; otherwise, the coarse aggregate of coal gangue was determined to be unsuitable for lime-fly ash stabilized base course.

[0057] In this embodiment, since the coarse aggregate of coal gangue has cracked, the strength of the coarse aggregate of coal gangue is determined to be unsuitable for the two-ash stabilized base course.

[0058] It should be noted that the above embodiments are illustrative of the technical solutions of the present invention and not limiting thereof. Equivalent substitutions or other modifications made by those skilled in the art based on the prior art, as long as they do not exceed the concept and scope of the technical solutions of the present invention, should be included within the scope of the claims of the present invention.

Claims

1. A test method for the strength of coarse coal gangue aggregate for ash-stabilized base course, wherein the mechanical properties of the coarse coal gangue aggregate determined by this test method are: compressive strength R.

2. The test method according to claim 1, characterized in that, The compressive strength mentioned is the compressive strength after immersion in water.

3. The test method according to claim 1, characterized in that, The compressive strength test was conducted according to the method of (T 0221-2005) "Test for Uniaxial Compressive Strength of Rock".

4. The test method according to claim 1, characterized in that, The standard compressive strength R is ≥ 4 times the minimum standard compressive strength R of the design compressive strength of the lime-stabilized base course. dmin .

5. The test method according to claim 1, characterized in that, The test method also includes a 28-day unconfined compressive strength test of the lime-stabilized base course mixture to further verify the applicability of coal gangue coarse aggregate.

6. The test method according to claim 1, characterized in that, The specific steps of the experimental method are as follows: 1) Determine the compressive strength R of coal gangue coarse aggregate. The test was conducted according to the method of (T 0221-2005) "Test for Uniaxial Compressive Strength of Rock" to obtain the compressive strength R of coal gangue coarse aggregate; 2) Determine the minimum standard value R of the design compressive strength of the lime-stabilized base course. dmin According to Table 4.2.6 of the "Technical Specifications for Construction of Highway Pavement Base Course" (JTG / T F20-2015), the minimum standard value of the design compressive strength R of the lime-fly ash stabilized base course is determined. dmin ; 3) Preliminary assessment of compressive strength R≥4×R dmin If the strength of the coarse aggregate of coal gangue is within acceptable limits, it is preliminarily determined to be qualified; otherwise, it is determined to be unqualified. 4) Verify the suitability of the strength of the coal gangue coarse aggregate. The design of the lime-fly ash stabilized base course mixture was carried out in accordance with the requirements of (JTG / T F20-2015) "Technical Specifications for Construction of Highway Pavement Base Course". The 7-day unconfined compressive strength test of the lime-fly ash stabilized base course mixture was carried out in accordance with the method of (JTG E51-2009) "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering". The 7-day unconfined compressive strength R7 was obtained. When R7 < R dmin At that time, there are two situations: (1) If the coarse aggregate of coal gangue does not crack, but the filler is damaged, the design of the two-ash stabilized base course mixture is unqualified and should be redesigned to improve the strength of the filler. (2) If the coarse aggregate of coal gangue cracks, then the coarse aggregate of coal gangue is not suitable for the two-ash stabilized base course; When R7≥R dmin If the design of the lime-stabilized base course mixture is qualified, then the following verification should be performed: The 28-day unconfined compressive strength test of lime-fly ash stabilized base course mixture was conducted according to the method of (JTG E51-2009) "Test Procedure for Inorganic Binder Stabilized Materials in Highway Engineering". In the 28-day unconfined compressive strength test specimens after compression, if the coarse aggregate of coal gangue does not crack, the strength of the coarse aggregate of coal gangue is determined to be suitable for the two-ash stabilized base course; otherwise, the coarse aggregate of coal gangue is determined not to be suitable for the two-ash stabilized base course.

7. The test method according to claim 6, characterized in that, After the coal gangue coarse aggregate compressive strength test specimens are prepared in step 1, they are completely immersed in water for at least 24 hours.