Method for measuring bulk density and void ratio of coarse aggregate skeleton and judging skeleton packing state

Abstract

The present invention relates to the field of road engineering, and specifically provides a method for measuring the bulk density and void ratio of a coarse aggregate skeleton and judging the bulk packing state of the skeleton. By adding an asphalt-mineral powder mortar to the coarse aggregate, the present invention increases the cohesion between the coarse aggregate aggregates, enables the aggregates in each particle size range to be evenly distributed, forms a coarse aggregate skeleton agglomerate without segregation, and does not interfere with the formation of the skeleton; uses a rotational compactor to simulate the actual skeleton interlock state of the mixture, enables the coarse aggregate skeleton to be rearranged closer to the actual skeleton condition of the road surface, has higher test reproducibility and more accurate data; defines the aggregate interlock state according to the density change rate index, which is more accurate and more convincing.

Description

Technical Field

[0001] The present invention relates to the field of road engineering, and particularly relates to a method for measuring the bulk density and void ratio of a coarse aggregate skeleton and judging the skeleton packing state. Background Art

[0002] In China, asphalt pavements mainly use skeleton-dense asphalt mixtures. The formation of the skeleton is achieved by the stone-to-stone structure of coarse aggregates. The degree of interlock of the coarse aggregate skeleton has a great influence on the performance of asphalt pavements. Therefore, accurately calculating the degree of interlock of the mineral aggregate skeleton is of great significance. For this reason, in SMA asphalt mixtures, the void ratio VCA between the coarse aggregate skeletons above the key sieve holes is defined as a measure of the interlock effect of coarse aggregates. The test method for the void ratio of the coarse aggregate skeleton in asphalt mixtures is as follows: The coarse aggregate part larger than the key sieve hole is filled into a volumetric cylinder and tamped, and the void ratio VCA in the tamped state is measured, and this value is used as a standard for measuring the interlock effect of coarse aggregates. The existing test method has the following problems: ① The mineral aggregates have a certain particle size range. The larger the nominal particle size, the easier it is to cause segregation of coarse and fine aggregates, resulting in large discreteness of test results; ② Using the tamping method to measure the skeleton density and void ratio has a large difference from the actual pavement skeleton arrangement structure, and it is not accurate enough as a standard for measuring the interlock effect of coarse aggregates; ③ The reproducibility of operations such as the tamping force and the principle of surface scraping by different people is poor, and it is greatly affected by human factors. Summary of the Invention

[0003] The present invention aims to overcome the deficiencies of the prior art and provides a method for measuring the bulk density and void ratio of a coarse aggregate skeleton and judging the skeleton packing state. Overview of the Invention:

[0005] The present invention uses the asphalt-mineral powder mortar method to increase the cohesion between coarse aggregate mineral materials, enabling aggregates in each particle size range to be evenly distributed, forming a coarse aggregate skeleton agglomerate without segregation, and without interfering with the formation of the skeleton. At the same time, under constant compaction conditions, a rotary compactor is used to simulate the kneading compaction effect of asphalt pavements for testing, simulating the actual skeleton interlock state of the mixture, making the rearrangement of the coarse aggregate skeleton closer to the actual pavement skeleton situation, greatly reducing the interference of human factors, with higher test reproducibility, more accurate data, and more practical; according to the density change rate index, the interlock state of mineral aggregates (loose skeleton state, tamped skeleton state) is defined, and the density and void ratio of the coarse aggregate skeleton are calculated, which is used as a standard for measuring the interlock effect of the mineral aggregate skeleton, more accurate and more convincing, and can be used to test the interlock state of skeleton-dense structure asphalt mixtures and SMA structure asphalt mixtures, improving the quality of asphalt pavement engineering, and having very good promotion value.

[0006] Specific Content of the Invention:

[0007] In the first aspect, the present invention provides a method for measuring the bulk density and void ratio of a coarse aggregate skeleton, comprising the following steps:

[0008] (1) Prepare a coarse aggregate mineral mixture: Configure the mineral mixture according to the gradation requirements. Determine the key sieve holes that play a skeletal role based on the type of asphalt mixture and the nominal maximum particle size. Screen out the particles above the key sieve holes in the mineral mixture for later use;

[0009] (2) Add asphalt and mineral powder to the coarse aggregate and mix to prepare a mineral mixture sample;

[0010] (3) Compact the above mixture sample after mixing;

[0011] (4) Put the sample into a combustion furnace for testing. After the sample cools down after the test, use a sieve to screen out the coarse aggregate, and weigh its mass and record it as M, that is, the mass of the coarse aggregate;

[0012] (5) Calculate the bulk density ρ of the coarse aggregate skeleton i (g / cm 3 )

[0013] Further, the amounts of asphalt and mineral powder in step (2) are as follows:

[0014]

[0015] P 矿粉 = P 沥青 ×FB

[0016] In the formula, P 沥青 is the asphalt dosage, %; H is the thickness of the asphalt-mineral powder mortar film, μm; P ≥4、75 , P 4、75 , P 2.36 , P 1.18 are the passing rates of the particle sizes greater than 4.75 mm and the particle sizes of 4.75 mm, 2.36 mm, and 1.18 mm under the key sieve holes of the mineral aggregate, %, where the passing rate of the part greater than 4.75 mm is only calculated once for the corresponding part of the maximum particle size; FA ≥4.75 , FA 4.75 , FA 2.36 , FA 1.18 are the specific surface area coefficients of the particle sizes greater than 4.75 mm and the particle sizes of 4.75 mm, 2.36 mm, and 1.18 mm of the mineral aggregate, m 2 / kg; ρ 沥青 is the density of asphalt, g / cm 3 ; FB is the powder-to-binder ratio, that is, the mass ratio of mineral powder to asphalt; P 矿粉 is the mineral powder dosage, %.

[0017] In this article, the P 沥青, P 矿粉 Both are the mass percentages of asphalt and mineral powder in the mixture sample.

[0018] In the above step (2), the passing rate of the mineral powder through 0.6 mm is 100%.

[0019] Preferably, in the above step (2), flocculent lignin fibers are externally added to the mineral aggregate mixture sample, and the dosage of the lignin fibers is 0.1% - 0.3%.

[0020] In this article, the dosage of the lignin fibers mentioned is the mass percentage of the lignin fibers in the mixture sample.

[0021] Preferably, in the above step (2), to ensure the cohesion between the mineral aggregates, make the mineral aggregate particles evenly dispersed and non-segregating, and at the same time not interfere with the mineral aggregate mixture skeleton, the thickness H of the mineral powder slurry film is 20 μm - 30 μm, and the powder - binder ratio FB is 1.8 - 2.5.

[0022] Preferably, in the above step (2), to increase the viscosity between the mineral aggregate mixture particles, make the gradation non-segregating, the mixing temperature is reduced by 10 - 15 °C compared with the temperature of the conventional asphalt mixture. For ordinary base asphalt, the mixing temperature is controlled at 130 °C - 135 °C, and for modified asphalt, the mixing temperature is controlled at 150 °C - 155 °C.

[0023] Further, the specific operation of compacting the mineral aggregates in the above step (3) is as follows:

[0024] Weigh a mixture sample with a mass of m and add it to a cylindrical test mold, and conduct a rotational compaction test using a rotational compactor, and record the rotational compaction height h at the i - th time i (mm).

[0025] Preferably, in the above step (3), the mass m of the mixture sample is 5000 - 7000 g.

[0026] Preferably, the radius r in the above step (3) is 50 or 75 mm.

[0027] Further, in the above step (3), the vertical pressure of the loading device of the rotational compactor is 600 kPa ± 18 kPa, the effective internal rotational angle is 1.16° ± 0.02°, and the rotational compaction speed is 30 r / min ± 0.5 r / min.

[0028] Further, in the above step (3), the number of rotational compaction times is not less than 20 times;

[0029] Preferably, the number of rotational compaction times is 20 times.

[0030] Further, the test method in step (4) is carried out in accordance with "Test Procedures for Bitumen and Bituminous Mixtures in Highway Engineering" T0735-2011;

[0031] Preferably, the screen aperture in step (4) is 0.6 mm.

[0032] Further, in step (5) above, the bulk density ρ i of the coarse aggregate skeleton is calculated as follows:

[0033]

[0034] where ρ i is the bulk density of the coarse aggregate skeleton at the i-th rotational compaction, g / cm 3 ; M is the mass of the coarse aggregate, g; r is the radius of the cylindrical test mold, mm; h i is the height of the i-th rotational compaction.

[0035] Second, the present invention provides a method for measuring the void content VCA (%) of the mineral aggregate skeleton according to the above-mentioned bulk density of the coarse aggregate skeleton, and the calculation formula is as follows:

[0036]

[0037] where VCA is the void content of the mineral aggregate skeleton, %; ρ b is the bulk specific gravity of the coarse aggregate, g / cm 3 .

[0038] Third, the present invention also provides a method for judging the state of the mineral aggregate skeleton according to the above-mentioned bulk density of the coarse aggregate, and the specific steps are as follows:

[0039] Calculate the density change rate n i according to the following formula:

[0040] n i = ρ i - ρ i-1

[0041] where n i is the density change rate of the mineral aggregate skeleton at the i-th rotational compaction, g / cm 3 ; ρ i and ρ i-1 are the bulk densities of the coarse aggregate skeleton at the i-th and (i-1)-th rotational compactions, respectively.

[0042] When n i is (0.02 ± 0.002) g / cm 3 , then the mineral aggregate mixture reaches the starting state of stone-stone contact, that is, a loose state skeleton; when n iIs (0.01 ± 0.002) g / cm 3 When it is, the mineral aggregate mixture reaches the framework interlock state at this time, that is, the interlock state framework.

[0043] The advantages and beneficial effects of the present invention are as follows:

[0044] (1) The present invention uses mineral powder, asphalt, and fibers to form an asphalt-mineral powder mortar. By controlling the indexes of the asphalt-mineral powder mortar film thickness and powder-binder ratio, the mortar has strong adhesion and workability, which can make the mineral aggregate form a stable coarse aggregate framework mass, and does not interfere with the framework. It makes the mineral aggregate particles in each particle size range evenly distributed and does not segregate, reducing the discreteness of the test and making the data more accurate.

[0045] (2) The present invention performs kneading through rotational compaction, simulating the rolling state of a road surface roller. At the same time, under the action of the mineral powder mortar, the coarse aggregate mineral aggregate framework is rearranged to form a more robust interlock structure, more accurately simulating the framework structure of the mixture under the rolling state.

[0046] (3) The present invention directly reads the height value through a rotational compaction device. Compared with the current method of filling the large voids on the surface with suitable aggregates, scraping it roughly flat with a straightedge, and visually making the protruding and sunken parts on the surface approximately equal, the method of the present invention directly omits this step, greatly reducing the influence of human error and improving the accuracy and reproducibility of the test.

[0047] (4) The present invention fixes the compaction power through a rotational compaction device. Compared with the current method of using three-time loading and ramming, the present invention reduces the influence of human error and improves the accuracy and reproducibility of the test.

[0048] (5) The present invention uses the index of the bulk density change rate as the standard for judging the state of the coarse aggregate framework, which can more accurately measure the interlock effect of the coarse aggregate in the mixture, and is used to test the interlock state of the framework dense structure asphalt mixture and the SMA structure asphalt mixture, improving the quality of the asphalt pavement project. Description of the Drawings

[0049] Figure 1 The discrete state of the coarse aggregate obtained by the T0309-2005 method;

[0050] Figure 2 The discrete state of the coarse aggregate obtained by the present invention. Detailed Embodiments

[0051] The following further details the present invention through specific implementation examples. The following examples are only descriptive and not restrictive, and the protection scope of the present invention cannot be limited thereby.

[0052] Example 1:

[0053] Taking the SMA-13 modified asphalt mixture as an example, the calculation process of the skeleton density and the skeleton void ratio is described in detail as follows:

[0054] (1) Prepare the coarse aggregate mixture: Configure the aggregate mixture according to the SMA-13 gradation requirements. Determine the key sieve hole of 4.75 mm that plays a skeletal role according to the type of asphalt mixture and the nominal maximum particle size, and screen out the particles larger than 4.75 mm in the aggregate mixture for standby.

[0055] (2) Determine the amount of asphalt-powder mortar: According to the powder-bitumen ratio FB and the thickness H of the asphalt-powder mortar film, calculate the powder dosage P 矿粉 (%), asphalt dosage P 沥青 (%) according to the following formula, and prepare the aggregate mixture sample according to the calculated ratio.

[0056]

[0057] In the formula, P ≥4.75 is 100%, P 4、75 , P 2.36 , P 1.18 are all 0. The specific surface area coefficients of aggregates of each particle size are shown in Table 7. The density ρ 沥青 of asphalt is approximately 1 g / cm 3 .

[0058] The asphalt-powder mortar has a great influence on the cohesion between aggregate mixtures. If the asphalt-powder mortar is too thin, it will affect the cohesion of the mixture and prevent the coarse and fine particles from being evenly distributed; if the asphalt-powder mortar is too thick, it will interfere with the skeleton and affect the interlock of the skeleton. Therefore, it is necessary to strictly select the thickness of the asphalt-powder mortar film according to the requirements. In this case, 25 μm is selected. The same is true for the powder-bitumen ratio FB. In this case, the powder-bitumen ratio FB of 2.0 is selected. According to the formula, the asphalt dosage p 沥青 is 3.4%, and the powder dosage P 矿粉 is 6.8%. To further increase the viscosity of the powder mortar, the dosage of flocculent lignin fiber is selected as 0.2%.

[0059] (3) Rotational compaction test: Mix the mixture sample in a mixing pot according to the determined ratio. Use SBS(1-D) as the asphalt, and set the asphalt mixing temperature to 150 °C. Weigh 6000 g of the mixture sample and add it to a cylindrical mold with a radius r of 75 mm. Set the number of rotational compaction times to 20 times, conduct the rotational compaction test, and record the height h i (mm) of the i-th rotational compaction, as shown in Table 1.

[0060] Table 1 The height of the i-th compaction

[0061] Compaction times i (times) 1 2 3 4 5 6 7 8 9 10 Height h (mm) 205.7 200.5 196.9 194.4 192.3 190.6 189.2 187.9 186.9 186.1 Compaction times i (times) 11 12 13 14 15 16 17 18 19 20 Height h (mm) 185.3 184.6 183.9 183.4 182.9 182.5 182.0 181.7 181.2 181.0

[0062] (4) Combustion furnace test: According to the method of T0735-2011 in "Test Procedures for Bitumen and Bituminous Mixtures in Highway Engineering", all samples were put into the combustion furnace for testing. After the test was completed and the samples cooled, the above part was sieved out with a 0.6 mm sieve mesh, and its mass was weighed as 5359 g.

[0063] (5) Determine the skeleton state: According to the formula

[0064]

[0065] Calculate the density change rate. As shown in Table 2, when n i is (0.02 ± 0.002) g / cm 3 , the number of gyratory compaction is 4 times. At this time, the mineral aggregate mixture reaches the starting state of stone-stone contact, that is, the loose state skeleton; when n i is (0.01 ± 0.002) g / cm 3 , the number of gyratory compaction is 9 times. At this time, the mineral aggregate mixture reaches the skeleton interlock state, that is, the interlock state skeleton.

[0066] Table 2 The skeleton density of the i-th compaction

[0067] Compaction times i (times) 1 2 3 4 5 6 7 8 9 10 <![CDATA[Skeleton density (g / cm 3 )]]> 1.4742 1.513 1.540 1.560 1.577 1.591 1.603 1.614 1.623 1.630 <![CDATA[Rate of density change (g / cm 3 )]]> — 0.038 0.027 0.020 0.017 0.014 0.012 0.011 0.009 0.007 Compaction times i (times) 11 12 13 14 15 16 17 18 19 20 <![CDATA[Skeleton density (g / cm 3 )]]> 1.636 1.643 1.649 1.654 1.658 1.662 1.667 1.669 1.673 1.676 <![CDATA[Rate of change of density (g / cm 3 )]]> 0.006 0.006 0.006 0.005 0.004 0.004 0.005 0.003 0.004 0.003

[0068] (6) Calculate the bulk density ρ i of the coarse aggregate skeleton, and calculate the void ratio VCA(%) of the coarse aggregate skeleton according to the bulk specific gravity ρ b of the coarse aggregate. Among them, ρ b is 2.791 g / cm 3 :

[0069] The mineral aggregate mixture reaches the starting state of stone-stone contact, that is, the loose state skeleton:

[0070]

[0071] The mineral aggregate mixture reaches the skeleton interlock state, that is, the interlock state skeleton:

[0072]

[0073]

[0074] Comparative Example 1:

[0075] Compare the present invention with the method of T0309-2005 in the current specification. The experimental steps of the present invention are the same as those in Example 1.

[0076] (1) Prepare 20 portions of coarse aggregate mixtures of SMA-13 gradation type, and sieve out the particles larger than 4.75 mm in the mineral aggregate mixture for standby.

[0077] (2) Divide 20 samples into 2 groups on average, and conduct tests according to the method of the present invention and the T0309-2005 method in the current specification respectively. The test results are shown in the following table:

[0078] Table 3 Void ratio of coarse aggregate skeleton obtained by two methods

[0079]

[0080] (3) Analysis of test results:

[0081] ① When comparing the method of the present invention with T0309-2005, the ranges of this method are 0.7 and 0.8, and the ranges of the T0309-2005 method are 2.6 and 2.1. The numerical discreteness of the method of the present invention is smaller. There are three main reasons: a. For the T0309-2005 aggregate, the test is carried out by manual ramming. The repeatability of the force, depth, position, etc. of manual ramming is poor, and there will be a large deviation in the ramming result. However, for the method of the present invention, the fixed force value and rotation angle of the gyratory compaction are adopted, and the discreteness will be much smaller; b. For the T0309-2005 scraping method, manual scraping is used, and the principle is that the raised and sunken parts on the surface are roughly the same by eye. In this way, the human influence is extremely large. However, for the method of the present invention, a gyratory compaction device is adopted, and the flatness of the top surface stress surface is extremely good, and there is no interference from human factors at all; c. For the T0309-2005 method, the aggregate is directly rammed, and there is no bonding force between the aggregates, which will cause segregation. There are three states in the test cylinder: the interlock between coarse aggregates, the interlock between fine aggregates, and the interlock between coarse and fine aggregates. The differences in states will all affect the accuracy of the test results, and the discreteness will also increase. However, the method of using mineral powder-asphalt mortar in the present invention can solve this problem. As shown in Figure 1 、 Figure 2 Comparison of the discreteness of coarse aggregates by the two methods shown.

[0082] ② From the test means of the two methods, the test void ratio VCA of the method of the present invention is smaller than that of the T0309-2005 method, and it is closer to the actual interlock state of the asphalt pavement. The main reason is that the method of the present invention adopts gyratory compaction to simulate the actual rolling form of the pavement. Through the viscosity increasing and lubricating effects of asphalt-mineral powder mortar, the coarse aggregate skeleton is rearranged during the test, which is closer to the actual interlock effect of the coarse aggregate skeleton in the asphalt pavement and is closer to the actual situation. Therefore, VCA will be smaller.

[0083] Experimental example 1:

[0084] Verify the feasibility of using asphalt-mineral powder mortar to increase the viscosity between skeleton aggregates and reduce segregation. The experimental steps of the present invention are the same as those in Example 1.

[0085] (1) First, a set of asphalt-mineral powder mortar ratios that meet the requirements are adapted through experiments. The asphalt-mineral powder mortar film thickness is 25μm, the powder-to-glue ratio is 2.0, and the lignin fiber content is 0.2%. Based on this, the powder-to-glue ratio is fixed to determine the most suitable asphalt-mineral powder mortar film thickness; then the most suitable powder-to-glue ratio is determined by fixing the asphalt-mineral powder mortar film thickness. The test results are as follows:

[0086] Table 4 Test results of different ingredients

[0087]

[0088] (2) Analysis of test results:

[0089] ① Determination of the thickness of asphalt-mineral powder mortar film: According to the test data of group ah, when the thickness of the mortar film is less than 20μm, the mortar film is too thin, and the aggregate is still loose and segregated. The segregation and lack of lubrication of the asphalt film lead to a large VCA of the coarse aggregate skeleton. When the thickness of the mortar film is greater than 30μm, the mortar film is too thick, the aggregate is completely covered, and although the mixture is uniform, the VCA begins to increase. This is mainly because the mortar film interferes with the skeleton. Therefore, the thickness of the asphalt-mineral powder mortar film should be controlled at 20-30μm, which ensures the uniform mixing of the coarse aggregate skeleton without interfering with the skeleton and affecting the accuracy of the test results. Within this range, the variability of the VCA value is very small.

[0090] ② Determination of the powder-binder ratio: According to the test data of group IM, when the powder-binder ratio is less than 1.8, the bonding strength of the mixed aggregate is insufficient, the surface is oily, there is more free asphalt, the aggregate is segregated, and the VCA value is too large; when the powder-binder ratio is greater than 2.7, there is no bonding strength between the mixed aggregates, most of the asphalt is absorbed by the mineral powder, and the VCA value is also too large. Therefore, it is advisable to control the powder-binder ratio within 1.8-2.5, which can ensure the uniform mixing of the coarse aggregate skeleton and the bonding strength between the coarse aggregates so that the aggregates do not segregate. Within this range, the variability of the VCA value is very small.

[0091] Experimental Example 2:

[0092] This embodiment provides two skeleton state judgment methods and judgment results, wherein the total mass m of the aggregate in this experimental example is the same as that in Example 1.

[0093] (1) Prepare 20 portions of two commonly used aggregates, limestone and basalt, respectively. Take the coarse aggregate mineral mixture of the same SMA-13 ​​grading type as an example, and sieve out particles larger than 4.75 mm in the mineral mixture for later use.

[0094] (2) 20 samples of limestone and basalt aggregate were divided into two groups, each with 10 samples. One group was tested according to the T0309-2005 method in the current specification. The test results are as follows:

[0095] Table 5 Void ratio of coarse aggregate skeleton measured by T0309-2005 method

[0096]

[0097] (3) Compact another group of limestone and basalt respectively 1, 2, 3, 4, 6, 8, 10, 12, 14, and 16 times by gyratory compaction, and conduct aggregate screening tests after compaction is completed. Calculate the aggregate breakage value Q(%) during gyratory compaction of the aggregate by the following formula.

[0098]

[0099] In the formula, m is the total mass (g) of the aggregate; m i is the mass (g) of the aggregate on the i-type sieve before the test, where i is each sieve of the standard sieve, such as 0.075mm, 1.18mm, 2.36mm, 4.75mm, 9.5mm, 13.2mm, 16mm, 19mm, 26.5mm; m i ′ is the mass (g) of the aggregate on the i-type sieve after the test.

[0100] Table 6 Test results measured by gyratory compaction

[0101]

[0102] (4) Analysis of test results:

[0103] ① The first group of limestone and basalt aggregates was tested by the T0309-2005 method. It can be found from the test data that the discreteness of the test results is large. Therefore, the average value of 10 groups of data is used as the test result. The loose void ratio of limestone is 44.6%, and the interlocked void ratio is 42.6%; the loose void ratio of basalt is 45.8%, and the interlocked void ratio is 43.4%.

[0104] ② The second group of limestone and basalt aggregates was tested by the method of the present invention. It can be found from the test data that the breakage point of limestone starts from the third time, and the breakage point of basalt starts from the fourth time. At this time, the loose void ratios are all close to those of the T0309-2005 method. At this time, the density change rates are 0.021 and 0.019. After verification, it is feasible to use a density change rate of 0.02 to characterize the loose state.

[0105] ③ It was found through experiments that the crushing point of the limestone aggregate in the present invention began to increase from the 8th time, and the crushing point of the basalt aggregate began to increase from the 12th time. At this time, the crushed materials of the aggregates were all within the range of 1%, and their crushing was caused by the brittle fracture of needle-like and flaky particles. When it was greater than 1%, the crushing of the aggregates would occur between square particles. Therefore, the void ratio reached when the aggregate interlock was at 1% could be used as the interlock state. Through the above data, it was found that when the crushing value was 1%, the density change rates were 0.009 and 0.011. After verification, it was feasible to use a density change rate of 0.01 to characterize the interlock state.

[0106] In summary, through the test results of the two kinds of rocks, it was found that it was more scientific and accurate to use the density change rate as the evaluation criterion to determine the loose state and interlock state of the aggregates.

[0107] Table 7 Specific surface area of each mineral aggregate particle size

[0108]

[0109]

Claims

1. A method for measuring the bulk density of coarse aggregate skeleton, characterized in that, It includes the following steps: (1) Configure the mineral aggregate mixture according to the gradation requirements. Determine the key sieve pores that play a skeletal role based on the type of asphalt mixture and the nominal maximum particle size, and screen out the particles above the key sieve pores in the mineral aggregate mixture for standby; (2) Add asphalt and mineral powder to the particles screened out and reserved in step (1) and mix them to prepare a mineral aggregate mixture sample; (3) Compact the above mixture sample after mixing; (4) Put the sample into a combustion furnace for testing. After the sample cools down after the test, use a sieve to screen out the coarse aggregate, and weigh its mass and record it as M, that is, the mass of the coarse aggregate; (5) Calculate the bulk density ρ of the coarse aggregate skeleton i ; The dosages of the asphalt and mineral powder in step (2) are as follows: Wherein, P 沥青 is the asphalt content, %; H is the thickness of the asphalt-mineral powder mortar film, μm; P >4、75 , P 4、75 , P 2.36 , P 1.18 are respectively the passing rates under the key sieve holes of aggregates with particle sizes greater than 4.75 mm and particle sizes of 4.75 mm, 2.36 mm, and 1.18 mm, %, and the passing rate of the part greater than 4.75 mm is only calculated once for the corresponding part of the maximum particle size; FA >4.75 , FA 4.75 , FA 2.36 , FA 1.18 are respectively the specific surface area coefficients of aggregates with particle sizes greater than 4.75 mm and particle sizes of 4.75 mm, 2.36 mm, and 1.18 mm, m 2 / kg; ρ 沥青 is the density of the asphalt, g / cm 3 ; FB is the powder-bitumen ratio, that is, the mass ratio of mineral powder to asphalt; P 矿粉 is the mineral powder content, %; The sieve aperture of the sieve in step (4) is 0.6 mm; The bulk density ρ of the coarse aggregate skeleton in step (5) i is calculated by the following formula: Among them, ρ i is the bulk density of the coarse aggregate skeleton during the i-th rotational compaction, g / cm³; M is the mass of the coarse aggregate, g; r is the radius of the cylindrical test mold, mm; h i is the height of the i-th rotational compaction, mm.

2. The method for measuring the bulk density of coarse aggregate skeleton according to claim 1, characterized in that, The thickness of the asphalt-mineral powder mortar film is 20 - 30 μm.

3. The method for measuring the bulk density of coarse aggregate skeleton according to claim 1, characterized in that, The powder-to-bitumen ratio FB is 1.8 - 2.

5.

4. The method for measuring the bulk density of coarse aggregate skeleton according to claim 1, characterized in that, The mineral aggregate mixture sample in step (2) also includes flocculent lignin fiber; The dosage of the flocculent lignin fiber is 0.1% - 0.3%.

5. The method for measuring the bulk density of coarse aggregate skeleton according to claim 1, characterized in that, In step (2), For ordinary matrix asphalt, the mixing temperature is 130°C - 135°C; For modified asphalt, the mixing temperature is 150°C - 155°C.

6. The method for measuring the bulk density of coarse aggregate skeleton according to claim 1, characterized in that, The specific operation process of step (3) is: Weigh a mixture sample with a mass of m and add it to a cylindrical test mold. Conduct a rotational compaction test using a rotational compactor and record the rotational compaction height h at the i-th time. i .

7. The method for measuring the bulk density of coarse aggregate skeleton according to claim 6, characterized in that, The mass m of the mixture sample is 5000 - 7000 g.

8. The method for measuring the bulk density of coarse aggregate skeleton according to claim 6, characterized in that, The radius r of the cylindrical test mold is 50 or 75 mm.

9. The method for measuring the bulk density of coarse aggregate skeleton according to claim 6, characterized in that, In step (3), The number of times of rotational compaction is not less than 20 times; The vertical pressure of the loading device of the rotational compactor is 600 kPa ± 18 kPa, the effective internal rotation angle is 1.16° ± 0.02°, and the rotational compaction speed is 30 r / min ± 0.5 r / min.

10. The method for measuring the bulk density of the coarse aggregate skeleton according to claim 1, wherein, The passing rate of the mineral powder with a particle size of 0.6 mm in step (2) is 100%.

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