Super-large particle size graded broken stone mixture and design method thereof

Abstract

The invention relates to the technical field of pavement materials, in particular to an oversized-particle-size graded broken stone mixture and a design method.The mineral aggregate grading is improved and optimized, the CBR value of the mixture can reach 300-600, the mechanical property can be improved by 50% or above, an optimal water content determining method is provided, the coarse aggregate volume fraction index is adopted, and the particle size of the mixture can be increased by 50% or above. The test result is high in reliability, the engineering guidance is high, the mineral aggregate skeleton interlocking structure evaluation method is provided, the design efficiency is improved, the mechanical property of the mixture can be fully guaranteed, and the method is suitable for popularization and application. Therefore, the problem that an existing graded broken stone mixture design method cannot guarantee the compaction performance and the mechanical stability of the mixture is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of pavement materials, and particularly relates to an ultra-large-size graded crushed stone mixture and a design method thereof. Background Art

[0002] The ultra-large-size graded crushed stone mixture is improved and innovated on the basis of the traditional graded crushed stone. The nominal maximum particle size reaches 53 mm, and the mass ratio of coarse particles with a particle size above 19 mm reaches more than 40%. It has a good framework interlock structure, greatly improving the bearing capacity and anti-deformation ability of the pavement. In addition, the ultra-large-size graded crushed stone mixture belongs to granular materials, has a good effect on preventing reflective cracks, has little impact on traffic interruption during construction, and does not require maintenance after construction, and can achieve rapid opening to traffic, and has wide applicability in the major repair projects of old cement pavements at the end of the service life of national and provincial trunk highways.

[0003] At present, the design of the ultra-large-size graded crushed stone mixture mainly refers to the design method of the traditional graded crushed stone mixture. First, the compaction test is carried out on the mixture at different water contents by the heavy compaction method, then the maximum dry density of the mixture at different water contents is measured, and the water content-maximum dry density relationship curve is drawn. The water content corresponding to the highest point of the curve is taken as the optimum water content, and then the mechanical properties of the mixture at the optimum water content are verified. However, this method is not applicable to the ultra-large-size graded crushed stone mixture, and there are mainly the following three problems: (1) Compaction method problem: The nominal maximum particle size of the mineral aggregate in the ultra-large-size graded crushed stone mixture reaches 53 mm, and the mass ratio of coarse particles with a particle size above 19 mm reaches more than 40%. Therefore, using the traditional heavy compaction test is likely to cause the crushing of coarse-grained crushed stones, affecting the mineral aggregate gradation and mechanical properties of the mixture. (2) Discreteness problem of the maximum dry density: Due to the high content of coarse-grained crushed stones above 19 mm in the ultra-large-size graded crushed stone mixture, segregation is likely to occur in the mixture during mixing and compaction, resulting in difficulty in accurately measuring the maximum dry density of the compacted mixture, and the discreteness of the test results is very large. Therefore, it is difficult to scientifically evaluate the compaction characteristics of the mixture. (3) The overall bearing capacity and mechanical properties of the ultra-large-size graded crushed stone mixture mainly depend on the framework interlock structure formed by coarse-grained crushed stones. However, the traditional graded crushed stone design method does not have an evaluation standard for the mineral aggregate framework interlock structure, and cannot design the mechanical properties of the mixture in advance. Only the mechanical properties of the mixture are verified after the event, with low design efficiency and easy rework due to insufficient mechanical properties.

[0004] In summary, a design method applicable to the ultra-large-size graded crushed stone mixture is needed, which can not only ensure the compaction performance of the mixture but also improve the mechanical properties of the mixture. Summary of the Invention

[0005] The object of the present invention is to provide an extra-large particle size graded crushed stone mixture and a design method, aiming to solve the problem that the existing design methods for graded crushed stone mixtures cannot guarantee the compaction performance and mechanical stability of the mixtures.

[0006] To achieve the above object, in the first aspect, the present invention provides a design method for an extra-large particle size graded crushed stone mixture, comprising the following steps:

[0007] Screen the mineral materials to obtain the screening results;

[0008] Based on the screening results, synthesize the mineral material gradation;

[0009] Based on the mineral material gradation, conduct a compaction experiment after mixing three kinds of coarse particle size materials evenly, and calculate the void ratio of the coarse aggregate skeleton in the mixture after compaction;

[0010] Based on the mineral material gradation and moisture content, conduct a vibrating compaction experiment after mixing the mineral materials evenly to obtain the volume ratio of the coarse aggregate in the mixture under different moisture contents;

[0011] Draw a relationship curve based on the moisture content and the volume ratio of the coarse aggregate, and take the highest point of the relationship curve as the optimum moisture content;

[0012] Based on the optimum moisture content and the mineral material gradation, conduct a vibrating compaction test after mixing the mineral materials evenly, test the void ratio of the coarse aggregate skeleton and the volume ratio of the coarse aggregate, and test the CBR value;

[0013] Based on the void ratio of the coarse aggregate skeleton I, the void ratio of the coarse aggregate skeleton II, and the volume ratio of the coarse aggregate, conduct a skeleton structure determination to obtain the optimum ratio of the extra-large particle size graded crushed stone mixture.

[0014] Among them, in the step of "screening the mineral materials to obtain the screening results", the mineral materials include four specifications of mineral materials: 20mm - 40mm, 10mm - 20mm, 5mm - 10mm, and 0 - 5mm.

[0015] Among them, in the step of "conducting a compaction experiment after mixing three kinds of coarse particle size materials evenly based on the mineral material gradation and calculating the void ratio of the coarse aggregate skeleton in the mixture after compaction", the specifications of the three kinds of coarse particle size materials are 20mm - 40mm, 10mm - 20mm, and 5mm - 10mm, and the mixing ratio is 45:18:11.

[0016] Among them, in the step of "conducting a vibrating compaction experiment based on the mineral material gradation and moisture content after mixing the mineral materials evenly to obtain the volume ratio of the coarse aggregate in the mixture under different moisture contents", the moisture contents are five kinds of moisture contents: 3%, 3.5%, 4%, 4.5%, and 5%.

[0017] Among them, in the step of "performing a vibration compaction experiment after uniformly mixing the mineral materials based on the mineral material gradation and water content to obtain the coarse aggregate volume ratio of the mixture at different water contents", the calculation formula for the coarse aggregate volume ratio ρ is as follows:

[0018]

[0019]

[0020] In the formula:

[0021] ρ—the volume ratio of coarse aggregates larger than 19 mm in the specimen, in percentage (%);

[0022] m 0 —the mass of coarse aggregates larger than 19 mm in the specimen, in grams (g);

[0023] γ 19 —the combined bulk specific gravity of coarse aggregates larger than 19 mm, in grams per cubic centimeter (g / cm 3 );

[0024] V—the volume of the specimen, in cubic centimeters (cm 3 );

[0025] P 1 、P 2 —the blending ratios of two kinds of mineral materials of 20 mm - 40 mm and 10 mm - 30 mm, in percentage (%);

[0026] γ 1 、γ 2 —the bulk specific gravities of two kinds of mineral materials of 20 mm - 40 mm and 10 mm - 30 mm, in grams per cubic centimeter (g / cm 3 ).

[0027] Among them, in the step of "judging the skeleton structure based on the first coarse aggregate skeleton void ratio, the second coarse aggregate skeleton void ratio, and the coarse aggregate volume ratio to obtain the optimal ratio of the super-large particle size graded crushed stone mixture", the skeleton structure judgment criterion is: VCA mix < VCA DRC and ρ 1 ≥ 39%.

[0028] In the second aspect, a super-large particle size graded crushed stone mixture, adopting the super-large particle size graded crushed stone mixture design method described in the first aspect, includes 20 mm - 40 mm: 10 mm - 20 mm: 5 mm - 10 mm: 0 - 5 mm = 45:18:11:26, the optimal water content is 3.98%, the coarse aggregate volume ratio of the mixture under the optimal ratio is 43.84%, and the CBR value is 354.

[0029] A design method for super-large particle size graded crushed stone mixture of the present invention includes the following steps: screening the mineral materials to obtain the screening results; synthesizing the mineral material gradation based on the screening results; performing a compaction experiment on the mixture of three coarse particle size materials after mixing them evenly based on the mineral material gradation, and calculating the first coarse aggregate skeleton void ratio in the compacted mixture; performing a vibrating compaction experiment on the mineral materials after mixing them evenly based on the mineral material gradation and water content to obtain the coarse aggregate volume ratio of the mixture at different water contents; plotting a relationship curve based on the water content and the coarse aggregate volume ratio, and taking the highest point of the relationship curve as the optimum water content; performing a vibrating compaction test on the mineral materials after mixing them evenly based on the optimum water content and the mineral material gradation, testing the coarse aggregate skeleton void ratio and the coarse aggregate volume ratio, and testing the CBR value; performing a skeleton structure determination based on the first coarse aggregate skeleton void ratio, the second coarse aggregate skeleton void ratio, and the coarse aggregate volume ratio to obtain the optimum proportion of the super-large particle size graded crushed stone mixture. The present invention improves and optimizes the mineral material gradation. The CBR value of the mixture can reach 300-600, and the mechanical properties can be improved by more than 50%. A method for determining the optimum water content is proposed. The coarse aggregate volume ratio index is adopted, that is, the water content corresponding to the highest point of the water content - coarse aggregate volume ratio relationship curve is the optimum water content. The test results are highly reliable and have strong engineering guidance. A method for evaluating the mineral aggregate interlock structure is proposed, which improves the design efficiency and can fully guarantee the mechanical properties of the mixture, thus solving the problem that the existing design method for graded crushed stone mixture cannot guarantee the compaction performance and mechanical stability of the mixture. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0031] Figure 1 It is the curve of the coarse aggregate volume ratio changing with the water content.

[0032] Figure 2 It is the design flow chart of the super-large particle size graded crushed stone mixture.

[0033] Figure 3 It is the flow chart of a design method for the super-large particle size graded crushed stone mixture provided by the present invention. Detailed Embodiments

[0034] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0035] Please refer to Figures 1 to 3 , in a first aspect, the present invention provides a design method for super-large particle size graded crushed stone mixture, including the following steps:

[0036] S1 Screen the mineral materials to obtain the screening results;

[0037] The mineral materials include four specifications of mineral materials: 20mm - 40mm, 10mm - 20mm, 5mm - 10mm, and 0 - 5mm.

[0038] Specifically, the screening results of the four specifications of mineral materials of 20mm - 40mm, 10mm - 20mm, 5mm - 10mm, and 0 - 5mm are shown in Table 1, and the bulk specific gravity of the mineral materials is shown in Table 2.

[0039] Table 1 Screening Results of Each Grade of Mineral Materials

[0040]

[0041]

[0042] Table 2 Bulk Specific Gravity of Each Grade of Mineral Materials

[0043] S2 Synthesize the mineral material gradation based on the screening results;

[0044] Specifically, synthesize the mineral material gradation according to engineering experience. The synthesized mineral material gradation is shown in Table 3.

[0045] Table 3 Synthesized Mineral Material Gradation

[0046]

[0047] S3 Based on the mineral material gradation, conduct a compaction experiment after mixing three kinds of coarse particle size materials evenly, and calculate the void ratio of the coarse aggregate skeleton in the compacted mixture one;

[0048] The specifications of the three kinds of coarse particle size materials are 20mm - 40mm, 10mm - 20mm, and 5mm - 10mm, and the mixing ratio is 45:18:11.

[0049] Specifically, three types of coarse aggregate with particle sizes of 20 mm - 40 mm, 10 mm - 20 mm, and 5 mm - 10 mm are mixed evenly in a ratio of 45:18:11. The vibration compaction test is carried out according to the method T 0309 in the "Test Regulations for Aggregates in Highway Engineering" (JTG 3432 - 2024), and the void ratio VCA of the coarse aggregate skeleton in the compacted mixture is calculated. DRC = 38.07%

[0050] S4 performs a vibration compaction test after mixing the mineral aggregates evenly based on the mineral aggregate gradation and water content, and obtains the volume ratio of coarse aggregates in the mixture at different water contents.

[0051] The water contents are five water contents of 3%, 3.5%, 4%, 4.5%, and 5%.

[0052] The calculation formula for the volume ratio ρ of the coarse aggregates is as follows:

[0053]

[0054]

[0055] In the formula:

[0056] ρ —— The volume ratio of coarse aggregates above 19 mm in the specimen, in percentage (%);

[0057] m 0 —— The mass of coarse aggregates above 19 mm in the specimen, in grams (g);

[0058] γ 19 —— The combined bulk specific gravity of coarse aggregates above 19 mm, in grams per cubic centimeter (g / cm 3 );

[0059] V —— The volume of the specimen, in cubic centimeters (cm 3 );

[0060] P 1 、P 2 —— The blending ratios of two types of mineral aggregates of 20 mm - 40 mm and 10 mm - 30 mm, in percentage (%);

[0061] γ 1 、γ 2 —— The bulk specific gravities of two types of mineral aggregates of 20 mm - 40 mm and 10 mm - 30 mm, in grams per cubic centimeter (g / cm 3 ).

[0062] Specifically, according to the aggregate gradation in Table 3, vibration compaction tests were carried out at five water contents of 3%, 3.5%, 4%, 4.5%, and 5% in accordance with Method T 0309 in the "Test Regulations for Highway Engineering Aggregates" (JTG 3432-2024). Then, the coarse aggregate volume ratio ρ of the mixture at different water contents was tested, as shown in Table 4. The curve of water content versus coarse aggregate volume ratio is as Figure 1 shown.

[0063] Table 4 Coarse aggregate volume ratio of the mixture at different water contents

[0064]

[0065]

[0066] In the formula:

[0067] ρ—the volume ratio of coarse aggregates larger than 19 mm in the specimen, in percentage (%);

[0068] m 0 —the mass of coarse aggregates larger than 19 mm in the specimen, in grams (g);

[0069] γ 19 —the combined bulk specific gravity of coarse aggregates larger than 19 mm, in grams per cubic centimeter (g / cm3);

[0070] V—the volume of the specimen, in cubic centimeters (cm3);

[0071] P 1 、P 2 —the blending ratios of two kinds of aggregates with particle sizes of 20 mm - 40 mm and 10 mm - 30 mm, in percentage (%);

[0072] γ 1 、γ 2 —the bulk specific gravities of two kinds of aggregates with particle sizes of 20 mm - 40 mm and 10 mm - 30 mm, in grams per cubic centimeter (g / cm3).

[0073] S5 Draw a relationship curve based on the water content and the coarse aggregate volume ratio, and take the highest point of the relationship curve as the optimal water content;

[0074] Specifically, Figure 1 the optimal water content was determined to be 3.98% from the highest point of the water content - coarse aggregate volume ratio curve;

[0075] S6 Based on the optimal water content and the aggregate gradation, the aggregates were mixed evenly and then vibration compaction tests were carried out to test the void ratio of the coarse aggregate skeleton and the coarse aggregate volume ratio, and the CBR value was also tested;

[0076] Specifically, a vibration compaction test is carried out at a water content of 3.98% according to the aggregate gradation in Table 3 to test the void ratio VCA of the coarse aggregate skeleton in the compacted specimen mix and the volume ratio ρ of the coarse aggregate 1 , and the CBR value of the specimen is tested. The test results are shown in Table 5

[0077] Table 5 Test results of the mixture at the optimum water content

[0078]

[0079]

[0080] S7 determines the skeleton structure based on the first void ratio of the coarse aggregate skeleton, the second void ratio of the coarse aggregate skeleton, and the volume ratio of the coarse aggregate to obtain the optimal ratio of the super-large-size graded crushed stone mixture

[0081] The above-mentioned skeleton structure determination criterion is: VCA mix <VCA DRC and ρ 1 ≥39%.

[0082] Specifically, for the skeleton structure determination: according to the test results in Table 5, it can be seen that VCA mix = 37.97 ≤ VCA DRC = 38.07%, and ρ 1 > 39%, indicating that the designed super-large-size graded crushed stone mixture has a good skeleton interlocking structure

[0083] Verification of mechanical properties: CBR = 354 > 300, indicating good mechanical properties

[0084] According to the above design process, the optimal ratio of the super-large-size graded crushed stone mixture obtained based on the selected aggregates is: 20mm - 40mm: 10mm - 20mm: 5mm - 10mm: 0 - 5mm = 45:18:11:26, the optimum water content is 3.98%, the volume ratio of the coarse aggregate in the mixture under the optimal ratio is 43.84%, and the CBR value is 354, meeting the specification technical requirements

[0085] In the second aspect, a super-large-size graded crushed stone mixture adopts the super-large-size graded crushed stone mixture design method described in the first aspect, including 20mm - 40mm: 10mm - 20mm: 5mm - 10mm: 0 - 5mm = 45:18:11:26, the optimum water content is 3.98%, the volume ratio of the coarse aggregate in the mixture under the optimal ratio is 43.84%, and the CBR value is 354

[0086] Beneficial effects:

[0087] (1) The gradation of aggregates was improved and optimized: For traditional graded crushed stone mixtures, the nominal maximum size of aggregates does not exceed 31.5, the coarse aggregates larger than 19 mm do not exceed 25%, and the CBR value of the mixture is not higher than 300. In the super-large size graded crushed stone mixture, the nominal maximum size of aggregates is larger, reaching 53 mm, and the content of coarse aggregates larger than 19 mm is higher, reaching more than 40%. Therefore, the coarse aggregates in the mixture are more likely to form a framework interlocking structure, the CBR value of the mixture can reach 300 - 600, and the mechanical properties can be improved by more than 50%.

[0088] (2) The compaction method of the mixture was optimized: It was proposed to use the vibration compaction method for the compaction test of the super-large size graded crushed stone mixture, avoiding the crushing of coarse aggregates caused by the traditional heavy compaction method, which affects the aggregate gradation and overall bearing capacity of the mixture.

[0089] (3) A method for determining the optimum moisture content was proposed: When determining the optimum moisture content of traditional graded crushed stone mixtures, the maximum dry density index is used, that is, the moisture content corresponding to the highest point of the moisture content - maximum dry density curve is the optimum moisture content. However, due to the high content of coarse aggregates in the super-large size graded crushed stone mixture, the discreteness of density test results is large, it is difficult to measure accurately, and the reliability of the test results is not high. For the super-large size graded crushed stone mixture, it is proposed to use the coarse aggregate volume ratio index, that is, the moisture content corresponding to the highest point of the moisture content - coarse aggregate volume ratio relationship curve is the optimum moisture content. The test results have high reliability and strong engineering guidance.

[0090] (4) A method for evaluating the aggregate framework interlocking structure was proposed: The aggregate framework interlocking structure in the mixture is directly related to the mechanical properties of the mixture. The stronger the framework interlocking structure, the better the mechanical properties. In the design process of traditional graded crushed stone mixtures, there is a lack of evaluation of the aggregate framework structure, and only the CBR test is used to verify the mechanical properties afterwards, which belongs to post-control. The design efficiency is low, it is difficult to predict the mechanical properties of the mixture in advance, and it is easy to cause rework due to insufficient mechanical properties. In the design process of the super-large size graded crushed stone mixture, it is proposed to use the double indexes of VCAmix < VCA DRC and ρ 1 ≥ 39% to evaluate the aggregate framework structure, which can fully guarantee the mechanical properties of the mixture.

[0091] The above-disclosed is only a preferred embodiment of a super-large size graded crushed stone mixture and its design method of the present invention. Of course, it cannot be used to limit the scope of the rights of the present invention. Those of ordinary skill in the art can understand all or part of the processes of implementing the above embodiments, and the equivalent changes made according to the claims of the present invention still fall within the scope covered by the invention.

Claims

1. A method for designing a super-large particle size graded crushed stone mixture, characterized by: The following steps are involved: Screening the mineral material to obtain the screening result; synthesizing mineral gradation based on the screening results; Based on the grading of the mineral material, the three coarse-grained materials are mixed evenly and then subjected to a compaction test, and the skeleton gap ratio of the coarse aggregate in the compacted mixture is calculated; The mineral materials are mixed evenly based on the mineral material gradation and moisture content, and then a vibration compaction experiment is performed to obtain the coarse aggregate volume ratio of the mixture at different moisture contents; Draw a relationship curve based on the moisture content and the volume ratio of the coarse aggregate, and take the highest point of the relationship curve as the optimal moisture content; Based on the optimum moisture content and the gradation of the ore, the ore is mixed evenly and then subjected to a vibration compaction test, the coarse aggregate skeleton gap ratio 2 and the coarse aggregate volume ratio are tested, and the CBR value is tested; The skeleton structure is determined based on the coarse aggregate skeleton gap ratio 1, the coarse aggregate skeleton gap ratio 2 and the coarse aggregate volume ratio to obtain the optimal proportion of the super-large particle size graded crushed stone mixture.

2. The method for designing a super-large particle size graded crushed stone mixture according to claim 1, characterized in that: In "screening the mineral material to obtain a screening result", the mineral material includes four specifications of 20mm-40mm, 10mm-20mm, 5mm-10mm, and 0-5mm.

3. The method for designing a super-large particle size graded crushed stone mixture according to claim 1, characterized in that: In "Based on the mineral grading, the three coarse-grained materials are mixed evenly and then compacted, and the coarse aggregate skeleton gap ratio in the compacted mixture is calculated", the specifications of the three coarse-grained materials are 20mm~40mm, 10mm~20mm, and 5mm~10mm, and the mixing ratio is 45:18:

11.

4. The method for designing a super-large particle size graded crushed stone mixture according to claim 1, characterized in that: In "Based on the mineral grading and moisture content, the minerals are mixed evenly and then subjected to vibration compaction experiment to obtain the coarse aggregate volume ratio of the mixture at different moisture contents", the moisture contents are 3%, 3.5%, 4%, 4.5% and 5%.

5. The method for designing a super-large particle size graded crushed stone mixture according to claim 1, characterized in that: In "Based on the gradation and moisture content of the mineral material, the mineral material is mixed evenly and then subjected to a vibration compaction test to obtain the coarse aggregate volume ratio of the mixture at different moisture contents", the calculation formula of the coarse aggregate volume ratio ρ is: Where: ρ——Volume ratio of coarse aggregate larger than 19 mm in the specimen, expressed as percentage (%); m0——the mass of coarse aggregate larger than 19 mm in the specimen, in grams (g); γ 19 - The synthetic bulk density of coarse aggregate larger than 19 mm, expressed in grams per cubic centimeter (g / cm 3 ); V is the volume of the specimen, in cubic centimeters (cm 3 ); P1, P2——the blending ratio of 20mm~40mm and 10mm~30mm mineral materials, in percentage (%); γ1, γ2 - gross volume density of two types of mineral materials with a diameter of 20 mm to 40 mm and 10 mm to 30 mm, in grams per cubic centimeter (g / cm 3 ).

6. The method for designing a super-large particle size graded crushed stone mixture according to claim 1, characterized in that: In "Determine the skeleton structure based on the coarse aggregate skeleton gap ratio 1, the coarse aggregate skeleton gap ratio 2, and the coarse aggregate volume ratio to obtain the optimal ratio of the super-large particle size graded crushed stone mixture", the skeleton structure determination standard is: VCA mix <VCA DRC And ρ1≥39%.

7. An ultra-large particle size graded crushed stone mixture, using the ultra-large particle size graded crushed stone mixture design method according to any one of claims 1 to 6, characterized in that: Including 20mm~40mm:10mm~20mm:5mm~10mm:0~5mm=45:18:11:26, the optimal moisture content is 3.98%, the coarse aggregate volume ratio of the mixture under the optimal ratio is 43.84%, and the CBR value is 354.

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