CN106767629A - A kind of method for obtaining asphalt membrane thickness - Google Patents

Abstract

The invention provides a method for obtaining the thickness of the asphalt film. Firstly, the asphalt content and relative density of the asphalt mixed aggregate are measured, and then the asphalt mixed aggregate is screened. According to the particle size of the aggregate, several grades of aggregate and corresponding grades are obtained. Ratio of sub-metering and sieving of aggregates. Then the specific surface area coefficients of several file aggregates obtained are multiplied by the sub-metering ratio of the corresponding file aggregates and then added and summed to obtain the specific surface area of the asphalt aggregate; respectively the specific surface area of the asphalt aggregate, The asphalt content of the asphalt aggregate and the asphalt relative density at 25°C were substituted into the formula to obtain the asphalt film thickness. The results of the embodiments of the present invention show that the error of the optimum asphalt-stone ratio calculated by the asphalt film thickness obtained by the method for determining the thickness of the asphalt aggregate film provided by the present invention and the actual optimum asphalt-aggregate ratio of the corresponding asphalt aggregate is 0.0 ~1.0%.

Description

A method to obtain the thickness of asphalt film

technical field

The invention belongs to the technical field of asphalt application, in particular to a method for obtaining the thickness of asphalt film.

Background technique

After the interaction between the asphalt and the aggregate, the asphalt structure produced by the asphalt on the surface of the aggregate is the decisive factor for the formation of the asphalt mixture structure. The asphalt wrapped on the aggregate surface must reach a certain thickness to ensure that the asphalt mixture has sufficient Durability, and the grading of the mix and the optimal amount of bitumen are affected by the thickness of the bitumen film and affect the adhesion of the aggregate of the mix to the bitumen. Therefore, the determination of asphalt film thickness has guiding significance for the improvement of asphalt aggregate performance.

At present, the method of obtaining the thickness of the asphalt film mainly divides the effective asphalt content by the total surface area of the aggregate, and the methods for determining the specific surface area of the asphalt mixed aggregate mainly include the specific surface area coefficient method, the density calculation method, and the corrected specific surface area coefficient method. The specific surface area of the aggregate obtained by the specific surface area coefficient method is too small, and the actual deviation is large; the recommended coefficient given in the density determination method is based on the actual measurement results, and is consistent with the "Technical Specifications for Construction of Highway Asphalt Pavement" (JTG F40-2004 ) (hereinafter referred to as the specification) there is a big difference in the standard coefficient, and in the calculation process, the sieve allowance is used instead of the sieve pass rate used in the specification; the modified specific surface area coefficient method is used in the aggregate In the process of shape assumption, different aggregates are stipulated as a uniform shape, and large errors are caused by the difference.

The specific surface area of asphalt mixture aggregates in China is generally calculated using the determination method of aggregate specific surface area coefficient in the specification: on the premise that the minimum particle size of the aggregate is 0.030mm, the surface area coefficient of the part of the aggregate with a particle size greater than 4.75mm is taken as is 0.0041, and it is only calculated once in the calculation process, that is, the specific surface area of the aggregate with a particle size greater than 4.75mm is 0.41m ² /kg; After multiplication and accumulation, the specific surface area of the part can be obtained. Finally, the specific surface area of the aggregate can be obtained by adding the specific surface area of the two parts.

However, due to continuous changes in processing technology and other aspects, the fineness of ore powder is increasing, and there is a deviation from the minimum particle size assumption of the standard derivation method, which leads to a large gap between the deduced specific surface area and the measured specific surface area of the aggregate. This also makes the obtained bitumen film thickness inaccurate. Furthermore, the traditional asphalt film calculation only considers the effective asphalt, and does not consider the influence of structural asphalt on the asphalt film thickness, which leads to a smaller asphalt film thickness calculated on this basis, which is different from that obtained by scanning electron microscopy (SEM). There is a gap in the actual observed thickness of the prepared specimen.

Contents of the invention

In view of this, the object of the present invention is to provide a method for obtaining the thickness of the asphalt film. The thickness of the asphalt film obtained by the method provided by the present invention has high accuracy and high consistency with the measured film thickness.

In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions:

The invention provides a method for obtaining the thickness of asphalt film, which is characterized in that, comprising the following steps:

(1) Determination of the asphalt content of asphalt aggregates and the relative density of asphalt at 25°C;

(2) Sieve the asphalt mixed aggregate, according to the particle size of the aggregate, obtain the fractional sieve ratio of several grades of aggregate and corresponding grades of aggregate;

(3) adding and summing after multiplying the specific surface area coefficients of several file aggregates obtained by the step (2) and the proportion of sub-metering and screening of corresponding file aggregates, to obtain the asphalt aggregate specific surface area;

The several grades of aggregates include coarse grades of aggregates, superfine grades of aggregates and middle grades of aggregates;

The particle size of the coarse-grade aggregate is not less than 2.36mm;

The particle size of the superfine grade aggregate is less than 0.15mm;

The particle size of the mid-range aggregate is not less than 0.15mm and less than 2.36mm;

(4) Substitute the specific surface area of the asphalt aggregate, the asphalt content of the asphalt aggregate, and the relative density of asphalt at 25°C into the formula shown in Formula I to obtain the asphalt film thickness.

DA described in formula I is the thickness of asphalt film;

Said SA is the specific surface area of asphalt aggregate;

Described P _b is the asphalt content of asphalt mixture aggregate;

The γ _b is the relative density of bitumen under the condition of 25°C;

The sub-meter sieve residue ratio is the mass percentage of the oversize material passing through the sieve holes of the corresponding particle size in the several grades of aggregates in the corresponding asphalt mixture aggregate.

Preferably, the fractional sieve ratio of the several grades of aggregates is the percentage of the mass of the oversize material of different grades of aggregates passing through the sieve holes with corresponding particle sizes to the total mass of the asphalt mixture aggregate.

Preferably, the specific surface area coefficient of the coarse-grade aggregate is a fixed specific surface area coefficient.

Preferably, the fixed specific surface area coefficient obtains according to the method comprising the following steps:

(a) sieving the coarse aggregate, and obtaining several secondary grades of the coarse aggregate according to the particle size of the aggregate;

(b) weighing the coarse aggregates of the several secondary files respectively to obtain the quality of the coarse aggregates of the several secondary files;

(c) Scanning the coarse aggregates of the several secondary files respectively, to obtain the scanned images of the coarse aggregates of the several secondary files;

(d) Obtain the surface area of the coarse aggregate of the several secondary files according to the scanned images of the coarse aggregate of the several secondary files;

(e) according to the surface area of the coarse aggregate of the several secondary files and the quality of the coarse aggregate of the several secondary files, obtain the fixed specific surface area coefficient of the coarse aggregate of the several secondary files;

The fixed specific surface area coefficient of the coarse aggregate of the several secondary files is the ratio of the surface area of the coarse aggregate of the several secondary files to the mass of the coarse aggregate of the several secondary files.

Preferably, the specific surface area coefficient of the superfine aggregate obtains according to the method comprising the following steps:

a. Sieve the ultra-fine aggregate to obtain the first-level ultra-fine aggregate and the second-level ultra-fine aggregate and the fractional sieve ratio of the first-level ultra-fine aggregate and the second-level ultra-fine aggregate Ratio of sub-metering and sieving of materials;

b. Using Blaine's specific surface area method to test the first-level ultrafine aggregate and the second-level ultrafine aggregate respectively, and obtain the first-level ultrafine aggregate specific surface coefficient and the second-level ultrafine aggregate specific surface area coefficient ;

The first-level ultrafine aggregate is aggregate with a particle size greater than 0.075mm and less than 0.15mm;

The secondary ultrafine aggregates are aggregates with a particle size not greater than 0.075mm.

Preferably, the fractional sieve ratio of the first-level ultrafine aggregate is the percentage of the mass of the oversize of the first-level ultrafine aggregate passing through the sieve holes of the corresponding particle size to the total mass of the asphalt mixture aggregate ;

The fractional sieve ratio of the secondary superfine aggregate is the percentage of the mass of the oversize of the secondary superfine aggregate passing through the sieve holes with corresponding particle sizes to the total mass of the asphalt mixture aggregate.

Preferably, the specific surface area coefficient of the mid-range aggregate is obtained by modifying the fixed value of the specific surface area coefficient of the mid-range aggregate by using a modification coefficient;

The correction method is to multiply the fixed value of the specific surface area coefficient of the mid-grade aggregate with the correction coefficient.

Preferably, the correction coefficient is the ratio of the specific surface area coefficient of the primary ultrafine aggregate to a fixed value of the specific surface area coefficient of the primary ultrafine aggregate.

Preferably, the fixed value of the specific surface area coefficient is the specific surface area coefficient in the American coefficient method.

The invention provides a method for obtaining the thickness of the asphalt film. Firstly, the asphalt content and relative density of the asphalt mixed aggregate are measured, and then the asphalt mixed aggregate is screened. According to the particle size of the aggregate, several grades of aggregate and corresponding grades are obtained. Ratio of sub-metering and sieving of aggregates. Subsequent multiplication of the specific surface area coefficients of the obtained aggregates of several grades with the sub-metering ratio of the aggregates of the corresponding grades are added and summed to obtain the specific surface area of the asphalt mixed aggregates; the aggregates of the several grades include coarse grade aggregates , superfine grade aggregate and medium grade aggregate; the particle diameter of the coarse grade aggregate is not less than 2.36mm; the particle diameter of the superfine grade aggregate is less than 0.15mm; the particle diameter of the middle grade aggregate is not less than 0.15 mm and less than 2.36 mm; the specific surface area of the asphalt aggregate, the asphalt content of the asphalt aggregate, and the relative density of asphalt at 25°C are substituted into the formula shown in Formula I to obtain the thickness of the asphalt film. The method provided by the present invention takes aggregates in different particle size ranges into consideration. During the particle size analysis of mineral powder, it is found that the proportion of fine aggregates below 0.030mm particle size accounts for between 15.47% and 47.68%. The specific surface area of this part of the particles accounts for a large proportion of the entire aggregate, but the calculation method of the specific surface in the specification ignores the influence of the specific surface of the fine aggregate with a particle size below 0.030mm on the specific surface area of the entire aggregate, resulting in the specification The specific surface area of the aggregate obtained by the method is relatively small, which in turn affects the measurement accuracy of the asphalt film thickness. The method provided by the invention avoids the assumption that the minimum particle size of the aggregate is 0.030 mm in the standard method for the specific surface area of the mixed aggregate. , the problem that smaller-sized fine aggregates are neglected; the standard method only considers the influence of asphalt mixture aggregate grading on the specific surface area, and ignores the influence of the mixture aggregate material itself, which reduces the accuracy of the results. The method provided by the invention will Mineral powder with a particle size of less than 0.075mm is included to improve the calculation accuracy; the method provided by the invention does not assume the spherical shape of the stone, and in actual engineering, the stones used are mostly irregular polyhedrons with large edges and corners coincide to avoid errors caused by spherical assumptions.

The method for determining the thickness of the asphalt film provided by the present invention directly divides the amount of asphalt by the specific surface area of the aggregate, regards the asphalt absorbed by the aggregate as structural asphalt, considers the influence of structural asphalt on the thickness of the asphalt film, and avoids the use of traditional methods In this paper, only effective asphalt is considered, and the influence of structural asphalt on the thickness of asphalt film is not considered. The method for calculating the specific surface area of the aggregate provided by the invention has high accuracy in obtaining the specific surface area of the mixed aggregate, is highly consistent with the actual measured specific surface area of the aggregate, and has a more accurate asphalt film thickness.

The results of the embodiments of the present invention show that the error of the optimum asphalt-stone ratio calculated by the asphalt film thickness obtained by the method for determining the thickness of asphalt aggregate film provided by the present invention and the actual optimum asphalt-aggregate ratio of the corresponding asphalt aggregate is 0.02 %～0.11%, which proves the reliability of the method for determining the thickness of asphalt film provided by the present invention. Therefore, the method provided by the invention obtains the thickness of the asphalt film with high accuracy and high consistency with the actual measured specific surface area of the aggregate.

Furthermore, the specific surface area of coarse aggregate accounts for a small proportion in the mixed aggregate, and the fixed specific surface area coefficient is used to calculate the specific surface area of the corresponding size aggregate conveniently and quickly, without affecting the accuracy of the specific surface area of the mixed aggregate; through the American coefficient The introduction of the law corrects the original fixed specific surface area coefficient, eliminates the influence of aggregate density and specific surface area, and improves the accuracy of the specific surface area of asphalt mixture aggregates, thereby ensuring that the thickness of the asphalt film is in line with the actual test results. sex.

Description of drawings

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Fig. 1 is the relationship curve between the asphalt specific surface area obtained in the embodiment of the present invention and the optimum asphalt ratio determined by the Marshall method.

detailed description

The invention provides a method for obtaining the thickness of asphalt film, which is characterized in that, comprising the following steps:

(1) Determination of the asphalt content of asphalt aggregates and the relative density of asphalt at 25°C;

(2) Sieve the asphalt mixed aggregate, according to the particle size of the aggregate, obtain the fractional sieve ratio of several grades of aggregate and corresponding grades of aggregate;

(3) adding and summing after multiplying the specific surface area coefficients of several file aggregates obtained by the step (2) and the proportion of sub-metering and screening of corresponding file aggregates, to obtain the asphalt aggregate specific surface area;

The several grades of aggregates include coarse grades of aggregates, superfine grades of aggregates and middle grades of aggregates;

The particle size of the coarse-grade aggregate is not less than 2.36mm;

The particle size of the superfine grade aggregate is less than 0.15mm;

The particle size of the mid-range aggregate is not less than 0.15mm and less than 2.36mm;

(4) Substitute the specific surface area of the asphalt aggregate, the asphalt content of the asphalt aggregate, and the relative density of asphalt at 25°C into the formula shown in Formula I to obtain the asphalt film thickness.

DA described in formula I is the thickness of asphalt film;

Said SA is the specific surface area of asphalt aggregate;

Described P _b is the asphalt content of asphalt mixture aggregate;

The γ _b is the relative density of asphalt aggregate;

The sub-meter sieve residue ratio is the mass percentage of the oversize material passing through the sieve holes of the corresponding particle size in the several grades of aggregates in the corresponding asphalt mixture aggregate.

In the present invention, the asphalt ratio of the asphalt mixture is preferably determined before the determination of the asphalt content of the asphalt mixture aggregate and the asphalt relative density at 25°C; in the present invention, the asphalt mixture ratio is preferably The mass ratio of aggregate oil to asphalt aggregate stone.

After the bitumen ratio is obtained, the bitumen content is obtained by substituting the bitumen ratio into the formula shown in Formula II.

The _Pa in formula II is preferably the asphalt ratio, more preferably the optimum asphalt ratio.

In the present invention, the relative density of the bitumen under the condition of 25°C is preferably calculated according to the relative density specified in the conventional parameters of bitumen.

The present invention sieves asphalt mixed aggregates, and according to the particle size of the aggregates, obtains several grades of aggregates and the fractional sieving ratio of the corresponding grades of aggregates. In the present invention, the sub-sieve residue ratio of the several grades of aggregates is the percentage of the weight of the oversize of different grades of aggregates passing through the sieve holes with corresponding particle sizes to the total mass of the asphalt mixture aggregate.

The present invention has no special requirements on the screening method, and the screening method known to those skilled in the art can be adopted, and the asphalt mixture aggregate is screened with screens of different apertures. The present invention preferably determines the sieve aperture according to the required different particle sizes to obtain coarse-grade aggregates, superfine-grade aggregates and medium-grade aggregates. The particle diameter of the coarse-grade aggregates is not less than 2.36mm. The particle size of the fine-grade aggregate is less than 0.15 mm, and the particle size of the medium-grade aggregate is not less than 0.15 mm and less than 2.36 mm.

After obtaining several grades of aggregates, the present invention preferably weighs the several grades of aggregates respectively, and compares them with the total mass of the asphalt mixed aggregates obtained before the sieving to obtain the sub-calculated sieve residue of the corresponding grades of aggregates. Proportion.

After obtaining the sub-meter sieve ratio, the present invention multiplies the specific surface area coefficients of the several grades of aggregates by the sub-meter sieve ratio of the corresponding grade aggregates, and then adds and sums them to obtain the specific surface area of the asphalt mixture aggregate.

In the present invention, the specific surface area coefficients of the several grades of aggregates are preferably obtained in different ways.

In the present invention, the specific surface area coefficient of the coarse aggregate is preferably a fixed specific surface area coefficient. The fixed specific surface area coefficient is preferably obtained by X-ray-CT technology.

After obtaining the coarse-grade aggregate, the present invention preferably screens the coarse-grade aggregate, and obtains several secondary grades of the coarse-grade aggregate according to the particle size of the aggregate. In the present invention, the number of secondary gears is preferably 2-10 gears, more preferably 4-8 gears, and most preferably 6 gears. The present invention has no special requirements on the particle size ranges of the several secondary grades, and aims to sieve the coarse grade aggregates into several grades to facilitate subsequent scanning and image processing. In the embodiment of the present invention, the sieving is preferably carried out according to the requirements in the "Test Regulations for Highway Engineering Aggregate" (JTGE42-2005) T0302-2005 standard, and the coarse-grade aggregate is sieved to obtain 6 grades several times Coarse aggregates of grade grades, specifically: coarse aggregates of not less than 2.36mm and lower than 4.75mm secondary grades, coarse aggregates of not less than 4.75mm and lower than 9.5mm secondary grades, not less than 9.5mm mm and less than 13.2mm secondary coarse aggregate, not less than 13.2mm and less than 16mm coarse aggregate, not less than 16mm and less than 19mm secondary coarse aggregate and not less than 19mm and lower than 26.5mm secondary grade coarse aggregate.

After obtaining the several secondary files of the coarse aggregate, the present invention preferably weighs the coarse aggregates of the several secondary files respectively to obtain the mass of the coarse aggregates of the several secondary files. In the present invention, it is preferred to obtain the fractional sieve ratio of the coarse aggregate of the several secondary files according to the quality of the coarse aggregate of the several secondary files. In the present invention, the fractional sieve ratio of the coarse aggregates of the several secondary files is preferably the ratio of the mass of the aggregates of the several secondary files to the total mass of the asphalt aggregate obtained in the aforementioned scheme.

In the present invention, the coarse aggregates of the several secondary files are preferably scanned separately to obtain the scanned images of the coarse aggregates of the several secondary files. Before performing the scanning, the present invention preferably takes out several pieces of stones from the coarse aggregates of the several secondary files as scanning samples of the corresponding secondary files of the aggregates of the several secondary files. In the present invention, The number of blocks is preferably 3 to 6 blocks. After obtaining the scanned samples of the aggregates of the several secondary files, the present invention preferably weighs the scanned samples of the coarse aggregates of the several secondary files respectively to obtain the mass of the scanned samples.

In the present invention, it is preferable to perform pre-scanning preparations on the scanned samples respectively to obtain samples to be scanned. The present invention has no special requirements on the preliminary preparation, and adopts the preliminary preparation methods well known to those skilled in the art. In the embodiment of the present invention, each stone in the scanning sample is preferably wrapped with tin foil to obtain the sample to be scanned. There is no special requirement for the wrapping method, and the non-contact between different stones shall prevail.

After the sample to be scanned is obtained, the present invention preferably uses a CT scanner to scan the sample to be scanned to obtain a scan image. The present invention has no special requirements on the CT scanner, and the CT scanner well known to those skilled in the art can be used. In the embodiment of the present invention, a CT scanner model YXLON.CT is preferably used. The present invention has no special requirements on the scanning method, and the scanning method well known to those skilled in the art can be used. In the embodiment of the present invention, it is specifically a scanning method that rotates while translating, and the image matrix is a matrix of 128×128. The sampling time is 0.3s.

After the scan images are obtained, the present invention preferably obtains the surface area of the coarse aggregates of the several secondary files according to the scan images of the coarse aggregates of the several secondary files. In the present invention, image processing software is preferably used to preprocess the scanned image, and the preprocessing preferably includes reducing the gray value, subject to the ability to distinguish the stone image. The present invention has no special requirements on image processing software, and image processing software well known to those skilled in the art can be used. In the embodiment of the present invention, the computing software is preferably Image image processing software.

After the scan image is preprocessed, the present invention preferably uses the calculation function of the image processing software to analyze the scan image to obtain the surface area of the scanned sample. The present invention has no special requirements on the analysis method, and it is realized by using the calculation function of the image processing software well known to those skilled in the art.

After obtaining the surface area of the scanned sample, the present invention preferably compares the surface area of the scanned sample of the coarse aggregate of the several secondary files with the mass of the scanned sample to obtain the coarse aggregate of the several secondary files The specific surface area coefficient of the scanned sample. In the present invention, the specific surface area coefficients of the scanned samples of the coarse aggregates of the several secondary grades are preferably used as the specific surface area coefficients of the coarse aggregates of the several secondary grades.

In the present invention, the specific surface coefficient of the ultra-fine aggregate is preferably obtained by the Blaine specific surface area method.

In the present invention, the ultra-fine grade aggregate is preferably screened to obtain the first-grade ultra-fine aggregate and the second-grade ultra-fine aggregate. In the present invention, the primary ultrafine aggregates are aggregates with a particle size greater than 0.075 mm and less than 0.15 mm, and the secondary ultrafine aggregates are aggregates with a particle size not greater than 0.075 mm.

After obtaining the first-level ultrafine aggregate and the second-level ultrafine aggregate, the present invention preferably weighs the first-level ultrafine aggregate and the second-level ultrafine aggregate respectively to obtain the first-level ultrafine aggregate The quality of the material and the quality of the secondary ultrafine aggregate. In the present invention, the mass of the primary superfine aggregate is preferably compared with the total mass of the asphalt mixed aggregate obtained in the aforementioned scheme to obtain the fractional sieve ratio of the primary superfine aggregate. In the present invention, the mass of the first-stage superfine aggregate is preferably compared with the total mass of the asphalt mixed aggregate obtained in the aforementioned scheme to obtain the fractional sieve ratio of the second-stage superfine aggregate.

After the weighing is completed, the present invention preferably uses Blaine's specific surface area method to test the first-level ultrafine aggregate and the second-level ultrafine aggregate to obtain the first-level ultrafine aggregate specific surface area coefficient and the second-level ultrafine aggregate. Aggregate specific surface area coefficient.

The Blaine specific surface area method described in the present invention preferably includes sample preparation, density test, volume calibration, sample layer preparation, determination of K value, determination of liquid level falling time and data integration process.

In the present invention, samples are preferably prepared respectively for the first-level ultrafine aggregate and the second-level ultrafine aggregate according to the requirements in the "Test Regulations for Highway Engineering Aggregate" (JTGE42-2005) T0302-2005, to obtain the samples to be tested. sample. The method of sample preparation in the present invention is to dry and cool the first-level ultrafine aggregate and the second-level ultrafine aggregate, and disperse the cooled aggregate to obtain the sample to be tested. The present invention has no special requirements on the methods of drying, cooling and dispersing, and methods known to those skilled in the art can be used. In the present invention, the temperature of the drying is preferably 105-115°C, and the moisture content of the aggregate after drying is preferably measured, and the measured value is that the aggregate is dried until the quality is no longer changed. . In the present invention, the cooling is preferably performed in a desiccator, and the temperature after the cooling is preferably room temperature. In the present invention, the dispersion preferably disperses the cooled aggregate by shaking, and the shaking is preferably performed in a closed bottle, and the shaking time is preferably 2-4 minutes. After the oscillation is completed, the dispersion preferably also includes stirring. In the embodiment of the present invention, specifically, the stirring is based on the distribution of the powder falling on the surface during the oscillation into the sample.

After the sample to be tested is obtained, the present invention preferably performs a density test on the sample to be tested. The present invention has no special requirements for the density test method, and the density test method well known to those skilled in the art can be used. In the embodiment of the present invention, the density test is preferably carried out using Archimedes' law, specifically: weighing the sample to be tested to obtain the mass of the sample to be tested; Anhydrous kerosene, put the sample to be tested into the Lee bottle, measure the volume of the overflowed anhydrous kerosene, as the volume of the sample to be tested; The volume of the sample to be tested is compared to obtain the density of the sample to be tested.

After obtaining the density of the sample to be tested, the present invention preferably performs volume calibration on the sample to be tested. The present invention has no special requirements on the volume calibration method, and the volume calibration method well known to those skilled in the art can be used. In the embodiment of the present invention, calibration is carried out according to the volume calibration method stipulated in "Highway Engineering Cement and Cement Concrete Test Regulations" (JTGE42-2005) T0504-2005, and the mercury substitution method is preferably used for the volume calibration, specifically: (1) Put two pieces of filter paper into the air-permeable cylinder along the cylinder wall, preferably use a long rod to put the filter paper into the air-permeable cylinder, and further preferably place the filter paper flat on the metal hole plate of the air-permeable cylinder , the diameter of the long rod is 1-2mm smaller than the diameter of the air-permeable cylinder; (2) after the filter paper is put into the air-permeable cylinder, mercury is preferably filled in the air-permeable cylinder, and the addition of the mercury The amount is preferably to fill up the air-permeable cylinder; (3) after filling the mercury, in order to make the surface of the mercury flush with the mouth of the air-permeable cylinder, the present invention preferably uses a thin glass plate to press the surface of the mercury , the strength of the pressing is preferably based on the absence of air bubbles or cavities between the thin glass plate and the surface of the mercury; (4) after the pressing is completed, the present invention preferably removes the thin glass plate and pours out the Said mercury, the mercury poured out is weighed to obtain the mass of the mercury; (5) repeat the steps (2) to (4), the number of repetitions is preferably 2 to 10 times, twice before and after to obtain The mass difference of the mercury is less than 0.1g; (6) take out 1 piece of filter paper, and put 3-4g of the sample to be tested into the air-permeable cylinder; (7) put the sample to be tested into After entering the air-permeable cylinder, it is preferred to fill the air-permeable cylinder with mercury, and the amount of mercury added is preferably to fill the air-permeable cylinder; (8) adopt the steps (3) and ( 4) removing air bubbles; (9) repeating the step (7) and the step (8), the number of repetitions is preferably 2 to 10 times, and the mass difference of the mercury obtained twice before and after is less than 50 mg. Complete the volume calibration of the sample to be tested.

The volume V of the sample layer in the cylinder is calculated according to the formula V=10-6×(P ₁ -P ₂ )/ _ρmercury , accurate to 5×10 ^-9 m ³ ;

Among them, V---the volume of the sample layer (m ³ );

P ₁ --- When no sample is filled, the mass of mercury (g) that fills the cylinder;

P ₂ ---- After loading the sample, the cement mass (g) that fills the cylinder;

ρ _Mercury ----- the density of mercury at the test temperature (g/cm ³ );

The standard sample size and measured sample size used in the calibration test should reach a void ratio of 0.500±0.005 in the prepared sample layer;

The present invention preferably obtains the porosity of the sample layer according to the calibrated volume by calculating the formula W=ρV(1-ε);

In the formula, W ----- the amount of sample required (kg), accurate to 1 mg;

ρ-----sample density (kg/m ³ );

V ----- the volume of the sample layer (m ³ ) measured by the method mentioned above;

ε----The porosity of the sample layer.

After completing the volume calibration, the present invention preferably carries out the preparation of the sample layer. The present invention has no special requirements on the preparation method of the sample layer, and the preparation method of the sample layer well known to those skilled in the art can be used. In the embodiment of the present invention, the preparation method of the sample layer is as follows: put the perforated plate on the flange of the air-permeable cylinder, use a ram to put a piece of filter paper on the perforated plate, lay the edge flat and press Tight; pour the sample to be tested into the air-permeable cylinder; in order to ensure the flatness of the surface of the sample layer, after the sample to be tested is poured into the air-permeable cylinder, vibrate the air-permeable cylinder; After putting the two pieces of filter paper into the air-permeable cylinder, use a tamper to compact the material to be tested in the air-permeable cylinder so that the support ring of the tamper is in contact with the top edge of the cylinder; Take out the pounder after 1 to 2 turns.

After the preparation of the sample layer is completed, the present invention preferably carries out the determination of the K value of the instrument. The present invention has no special requirements for the determination of the K value, and the method for determining the K value well known to those skilled in the art can be used. In an embodiment of the present invention, the mensuration of described K value preferably carries out the mensuration of K value according to the instrument description of Blaine specific surface area tester (Blaine specific surface area tester), specifically: the density of standard powder, the density of standard powder Input the specific surface area and the porosity of the standard powder into the Blaine specific surface area tester, and turn on the instrument to record the K value.

After the determination of the K value is completed, the present invention preferably measures the falling time of the liquid level in the manometer of the Blaine specific surface area tester. The present invention has no special requirements on the method of measuring the liquid level falling time, and the method of measuring the liquid level falling time well known to those skilled in the art can be used. In the embodiment of the present invention, the measurement method of the liquid level fall time is as follows: apply piston grease to the lower cone surface of the air-permeable cylinder equipped with the sample layer, and the thickness of the application is preferably 1-2mm; The breathable cylinder smeared with piston grease is inserted into the conical grinding port at the top of the pressure gauge. In order to ensure that the breathable cylinder and the pressure gauge are tightly connected and airtight, it is preferable to rotate the breathable cylinder 1 to 2 times; The electromagnetic pump extracts air from one arm of the pressure gauge, so that the liquid level of the original liquid in the pressure gauge rises to the lower end of the enlarged part of the pressure gauge; when the pressure gauge is left still, the liquid in the pressure gauge When the concave surface of the liquid drops to the first scale line of the pressure gauge, the timing is started, and when the concave surface of the liquid drops to the second scale line, the timing is stopped, and the liquid level falling time is obtained.

In the process of measuring the liquid level falling time, in the present invention, the temperature during the liquid level falling process is preferably controlled to be a constant temperature, and the present invention preferably measures the constant temperature during the liquid level falling process.

After the measurement of the liquid level falling time is completed, the present invention preferably performs data integration to obtain the specific surface area coefficient of the primary ultrafine aggregate and the specific surface area coefficient of the secondary ultrafine aggregate. The present invention preferably integrates data according to the specific surface area coefficient calculation formula in "Highway Engineering Cement and Cement Concrete Test Regulations" (JTG E30-2005), and the calculation formula is specifically:

Under the condition that the temperature difference during the test is not greater than ±3°C, it is calculated according to the following formula:

When the test temperature difference is greater than ±3°C, calculate according to the following formula:

In the formula:

S _c ——— the specific surface area of the tested sample (kg/m ³ )

S _S ———— specific surface area of standard sample (kg/m ³ )

T———When the test sample is tested, the time measured by the drop of the liquid level in the pressure gauge (S)

T _S —————When the test sample is tested, the time measured by the drop of the liquid level in the pressure gauge (S)

ε———The porosity of the sample layer under test

ε _S ———— The porosity in the sample layer of the standard sample

ρ———the density of the tested sample (kg/m ³ )

In the present invention, the specific surface area coefficient of the mid-range aggregate is preferably obtained by correcting the fixed value of the coefficient of the specific surface area of the mid-range aggregate by a correction coefficient, and the correction method is preferably that the mid-range aggregate The coefficient fixed value of the specific surface area is multiplied by the correction coefficient, the coefficient fixed value of the specific surface area of the mid-range aggregate is the specific surface area coefficient in the law of the American coefficient method, and the modification coefficient is preferably the one obtained by the aforementioned scheme. The ratio of the specific surface area coefficient of the superfine aggregate to the fixed value of the specific surface area coefficient of the first superfine aggregate, in the present invention, the fixed value of the specific surface area coefficient of the first superfine aggregate is the American coefficient method The specific surface area coefficient in the law.

The present invention preferably sieves the mid-range aggregate, and obtains several secondary grades of the mid-grade aggregate according to the particle size of the aggregate. In the present invention, the number of secondary gears is preferably 2-9 gears, more preferably 3-8 gears, and most preferably 4 gears. The present invention has no special requirements on the sieving method, and the sieving method well known to those skilled in the art can be used. The present invention preferably uses sieves with particle diameters of 0.3mm, 0.6mm, 1.18mm and 2.36mm for sieving . In the embodiment of the present invention, the screening is preferably carried out according to the requirements in the T0302-2005 standard of "Test Regulations for Highway Engineering Aggregate", and the mid-range aggregates are screened to obtain 4 grades and several secondary grades of mid-grade aggregates , specifically: not less than 0.15mm and lower than 0.3mm secondary file, not less than 0.3mm and lower than 0.6mm secondary file, not less than 0.6mm and lower than 1.18mm secondary file and not lower than 1.18 mm and lower than the 2.36mm secondary file.

After obtaining the intermediate grade aggregates of the several secondary grades, the present invention preferably weighs the intermediate grade aggregates of the several secondary grades respectively to obtain the mass of the intermediate grade aggregates of the several secondary grades. In the present invention, it is preferable to compare the quality of the middle grade aggregates of the several secondary grades with the total mass of the asphalt mixed aggregate obtained in the aforementioned scheme to obtain the fractional ratio of the intermediate grade aggregates of the several secondary grades.

In the present invention, the specific surface area coefficients of several grades of aggregates obtained are multiplied by the sub-metering and sieving ratios of corresponding grades of aggregates, and then added and summed to obtain the specific surface area of the asphalt mixture aggregate.

After obtaining the specific surface area of the asphalt aggregate, the present invention substitutes the specific surface area of the asphalt aggregate, the asphalt content of the asphalt aggregate, and the relative density of the asphalt aggregate into the formula shown in Formula I to obtain the thickness of the asphalt film.

The DA in Formula I is the thickness of the asphalt film; the SA is the specific surface area of the asphalt aggregate; the P _b is the bitumen content of the asphalt aggregate; the γ _b is the relative density of the asphalt aggregate.

The invention provides a method for obtaining the thickness of the asphalt film. Firstly, the asphalt content and relative density of the asphalt mixed aggregate are measured, and then the asphalt mixed aggregate is screened. According to the particle size of the aggregate, several grades of aggregate and corresponding grades are obtained. Ratio of sub-metering and sieving of aggregates. Subsequent multiplication of the specific surface area coefficients of the obtained aggregates of several grades with the sub-metering ratio of the aggregates of the corresponding grades are added and summed to obtain the specific surface area of the asphalt mixed aggregates; the aggregates of the several grades include coarse grade aggregates , superfine grade aggregate and medium grade aggregate; the particle diameter of the coarse grade aggregate is not less than 2.36mm; the particle diameter of the superfine grade aggregate is less than 0.15mm; the particle diameter of the middle grade aggregate is not less than 0.15 mm and less than 2.36 mm; the specific surface area of the asphalt aggregate, the asphalt content of the asphalt aggregate, and the relative density of asphalt at 25°C are substituted into the formula shown in Formula I to obtain the thickness of the asphalt film. The method provided by the present invention takes aggregates in different particle size ranges into consideration. During the particle size analysis of mineral powder, it is found that the proportion of fine aggregates below 0.030mm particle size accounts for between 15.47% and 47.68%. The specific surface area of this part of the particles accounts for a large proportion of the entire aggregate, but the calculation method of the specific surface in the specification ignores the influence of the specific surface of the fine aggregate with a particle size below 0.030mm on the specific surface area of the entire aggregate, resulting in the specification The specific surface area of the aggregate obtained by the method is relatively small, which in turn affects the measurement accuracy of the asphalt film thickness. The method provided by the invention avoids the assumption that the minimum particle size of the aggregate is 0.030 mm in the standard method for the specific surface area of the mixed aggregate. , the problem that smaller-sized fine aggregates are neglected; the standard method only considers the influence of asphalt mixture aggregate grading on the specific surface area, and ignores the influence of the mixture aggregate material itself, which reduces the accuracy of the results. The method provided by the invention will Mineral powder with a particle size of less than 0.075mm is included to improve the calculation accuracy; the method provided by the invention does not assume the spherical shape of the stone, and in actual engineering, the stones used are mostly irregular polyhedrons with large edges and corners coincide to avoid errors caused by spherical assumptions. The results of the embodiments of the present invention show that the error of the optimum asphalt-stone ratio calculated by the asphalt film thickness obtained by the method for determining the thickness of asphalt aggregate film provided by the present invention and the actual optimum asphalt-aggregate ratio of the corresponding asphalt aggregate is 0.02 %～0.11%, which proves the reliability of the method for determining the thickness of asphalt film provided by the present invention. Therefore, the method provided by the invention obtains the thickness of the asphalt film with high accuracy and high consistency with the actual measured specific surface area of the aggregate.

Furthermore, the specific surface area of coarse aggregate accounts for a small proportion in the mixed aggregate, and the fixed specific surface area coefficient is used to calculate the specific surface area of the corresponding size aggregate conveniently and quickly, without affecting the accuracy of the specific surface area of the mixed aggregate; through the American coefficient The introduction of the law corrects the original fixed specific surface area coefficient, eliminates the influence of aggregate density and specific surface area, and improves the accuracy of the specific surface area of asphalt mixture aggregates, thereby ensuring that the thickness of the asphalt film is in line with the actual test results. sex.

The method for obtaining the thickness of the asphalt film provided by the present invention will be described in detail below in conjunction with the examples, but they should not be interpreted as limiting the protection scope of the present invention.

In the embodiment of the present invention, asphalt adopts South Korea Ssangyong (S-OIL brand) A grade No. 70 road petroleum asphalt; coarse aggregate adopts limestone crushed stone produced by Ganxian Xinyuan Stone Factory; fine aggregate adopts Xixian Expressway LM-1 0-2.36mm machine-made sand and limestone slag produced by the self-built material yard of the standard asphalt mixing station. JL-2 is the 0-2.36mm machine-made sand and limestone slag produced by the self-built material yard of the LM-2 standard asphalt mixing station of Xixian Expressway, and JL-3 is produced by the self-built material yard of the LM-3 standard asphalt mixing station of Xixian Expressway 0 ~ 2.36mm machine-made sand and limestone slag powder.

The technical requirements of road asphalt and the test results of road petroleum asphalt are shown in Table 1.

Table 1 Road asphalt requirements and test results of the road asphalt used

The technical indicators of the asphalt aggregate used for testing in the present invention are shown in Table 2, Table 3 and Table 4. The results show that all technical indicators of raw materials meet the technical requirements of JTG F40-2004.

Table 2 Coarse aggregate technical indicators in asphalt mixed aggregate

Table 3 Coarse aggregate technical indicators in asphalt mixed aggregate

Table 4 Technical indicators of ore powder quality in asphalt mixed aggregate

Example 1

The aggregates are prepared according to the asphalt aggregate gradation shown in Table 5, where GF is the median value of the standard gradation, and GJ is the embedded skeleton gradation.

Table 5 Asphalt aggregate gradation

In strict accordance with the requirements in the "Test Regulations for Highway Engineering Aggregate" (JTGE42-2005) T0302-2005, sampling was carried out to obtain the asphalt mixed aggregate to be tested, and the fine aggregate was selected as JL-1, and the asphalt mixed aggregate to be tested was weighed , to obtain the total mass of the asphalt mixture aggregate, and screen the asphalt mixture aggregate with screens of different apertures. Grade coarse aggregate with particle size not less than 2.36mm, superfine aggregate with particle size less than 0.15mm and medium grade aggregate with particle size greater than 0.15mm and less than 2.36mm are obtained.

1. Using X-ray-CT technology as the method for measuring the specific surface area coefficient of coarse aggregate, the specific operation steps are as follows:

(1) Screening

Use the four-point method to divide the aggregates that have been taken, and screen them step by step according to the requirements in the "Test Regulations for Highway Engineering Aggregate" (JTGE42-2005) T0302-2005 to obtain 2.36mm ~ 4.75mm , 4.75mm～9.5mm, 9.5mm～13.2mm, 13.2mm～16mm, 16mm～19mm, and 19mm～26.5mm, 6 levels of coarse aggregate with different particle sizes.

(2) weighing

Weigh the coarse aggregates with 6 grades of particle diameters obtained in step (1), obtain the quality of the 6 grades of coarse aggregates respectively, compare them with the total mass of the asphalt mixed aggregates, and obtain the fractions of the 6 grades of coarse aggregates respectively. Calculate the ratio of sieve residue.

(3) Preparation of samples

Three stones were taken out from 6 grades of coarse aggregates with different particle sizes, and each stone was wrapped with three layers of paper to ensure that there was no contact between the stones and the stones in preparation for the later image processing.

(4) scan

Put the wrapped stones into the box, put them into the YXLON.CT scanner for scanning, adopt the scanning method of translation and rotation, the image matrix is 128×128 matrix, and the sampling time of scanning is 0.3s , start the instrument to scan, and wait for the output of the scan result.

(5) Image processing

Use the Image image processing software to process the scanning results and remove the parts with lower gray values, so as to obtain the scanning results of the required aggregates, and obtain the coarse aggregates with 6 particle sizes through the calculation function in the image processing software. Surface area and volume.

(6) Determination of specific surface area coefficient

Comparing the surface area and mass of the coarse aggregates with 6 grades of particle sizes, the specific surface area coefficients of the 6 grades of particle diameters are obtained respectively.

The test results of the coarse aggregate are shown in Table 6.

Table 6 Coarse aggregate CT scanning test results

aggregate size 19～26.5 16～19 13.2～16 9.5～13 4.75～9. 2.36～4.7 Quality (quantity mm (g)) 692 507 333 106.6 385.6 65.3 Surface area (cm ² ) 1360.55 1170.97 1232.51 571.80 303.38 103.71 Volume (cm ³ ) 255.9 184.9 122.3 39.19 14.13 2.33 Specific surface area system 0.19 0.23 0.37 0.53 0.78 1.64 Density (g/cm ³ ) 2.704 2.742 2.723 2.72 2.731 2.702

2. Superfine aggregate specific surface area test

(a) According to the requirements in "Test Regulations for Highway Engineering Aggregate" (JTGE42-2005) T0302-2005, sieve the ultrafine aggregate into first-class ultrafine aggregate with particle size greater than 0.075mm and less than 0.15mm and particle size The secondary ultra-fine aggregate not greater than 0.075mm, and weigh the mass respectively, and then compare the mass of the primary ultra-fine aggregate and the mass of the secondary ultra-fine aggregate with the total mass of the asphalt mixture aggregate , to obtain the sub-meter sieve ratio of the first-grade ultrafine aggregate and the sub-meter sieve ratio of the second-level ultra-fine aggregate.

(b) Sample preparation: According to the requirements in "Test Regulations for Highway Engineering Aggregate" (JTGE42-2005) T0302-2005, dry the sample to be measured at 110°C, cool it to room temperature in a desiccator, and In a 100ml airtight bottle, vibrate vigorously for 2 minutes to break up the agglomerated sample and loosen the sample. After standing still for 2 minutes, open the bottle cap and stir gently to distribute the fine powder falling on the surface during the loosening process to the whole sample.

(c) Sample density test: weigh the sample to be tested to obtain the quality of the sample to be tested; after the Lee's bottle is filled with anhydrous kerosene, the sample is poured into the Lee's bottle, and the liquid medium is fully Under the condition that the temperature is kept constant, the density of the sample is calculated using physical principles, that is, the volume of the spilled anhydrous kerosene is measured as the volume of the sample to be tested; the mass of the sample to be tested and the The volume of the sample to be tested is compared to obtain the density of the sample to be tested.

(d) Calibration of the instrument: Check the various parts of the Blaine specific surface area tester to ensure that it meets the specification requirements, and check the tightness of the instrument.

(e) Calibrate the volume of the sample layer: use the mercury substitution method to calculate the volume of the sample layer, specifically: (1) put two pieces of filter paper into the air-permeable cylinder along the cylinder wall, preferably use a long stick to put the filter paper into In the air-permeable cylinder, it is further preferred to place the filter paper flat on the metal hole plate of the air-permeable cylinder, and the diameter of the long rod is 1-2 mm smaller than the diameter of the air-permeable cylinder; After the filter paper is put into the air-permeable cylinder, it is preferable to fill mercury in the air-permeable cylinder, and the addition of the mercury is preferably to fill up the air-permeable cylinder; (3) after filling the mercury, in order to make the surface of the mercury and the air-permeable cylinder The mouth of the air-permeable cylinder is flush. In the present invention, a thin glass plate is preferably used to press the surface of the mercury. The pressing force is preferably such that no air bubbles or cavities exist between the thin glass plate and the surface of the mercury. (4) after the pressing is completed, the present invention preferably removes the thin glass plate and then pours out the mercury, and weighs the poured out mercury to obtain the mass of the mercury; (5) repeat Described steps (2)～(4), repetition times are preferably 2～10 times, the mass difference value of described mercury obtained twice before and after is less than 0.1g as the criterion; (6) take out 1 piece of filter paper, to described Put 3-4g of the sample to be tested in the air-permeable cylinder; (7) after putting the sample to be tested into the air-permeable cylinder, preferably fill the air-permeable cylinder with mercury, the amount of mercury added Preferably be filled with described air-permeable cylinder; (8) adopt described step (3) and described step (4) to remove air bubble; (9) repeat described step (7) and described step (8), repetition times It is preferably 2 to 10 times, and the volume calibration of the sample to be tested is completed and the porosity of the sample layer is measured as the difference between the mass of the mercury obtained twice is less than 50 mg.

(f) Use standard samples to calibrate the test equipment, and the standard samples should be kept at room temperature before use.

(g) Prepare the sample layer: put the perforated plate on the flange of the air-permeable cylinder, put a piece of filter paper on the perforated plate with a tamping stick, lay the edge flat and press it tightly; put 2.000g～5.000g Pour the sample into the air-permeable cylinder; in order to ensure the flatness of the surface of the sample layer, after the sample to be tested is poured into the air-permeable cylinder, vibrate the air-permeable cylinder; put the second piece of filter paper into the After the air-permeable cylinder, use a tamper to compact the material to be tested in the gas-permeable cylinder, so that the support ring of the tamper is in contact with the top edge of the cylinder; after the tamper is completed, rotate the tamper for 1 to 2 turns Then remove the tamper.

(h) Determination of K value: According to the requirements of the instrument, input the density, specific surface area and determined porosity of the standard powder into the instrument, turn on the instrument to measure and record the K value.

(i) Determination of liquid level fall time: during the liquid level fall process, the temperature is controlled to be a constant temperature, and the temperature is measured. Apply piston grease to the lower cone surface of the breathable cylinder equipped with the sample layer, and the thickness of the smear is preferably 1 to 2mm; insert the breathable cylinder coated with piston grease into the conical grinding port at the top of the pressure gauge, in order to Ensure that the air-permeable cylinder and the pressure gauge are tightly connected and airtight, preferably rotate the air-permeable cylinder for 1 to 2 turns; use a micro electromagnetic pump to extract air from one arm of the pressure gauge, so that the inside of the pressure gauge The liquid level rises to the lower end of the enlarged part of the pressure gauge; when the pressure gauge is left still, the timing starts when the concave surface of the liquid in the pressure gauge drops to the first scale line of the pressure gauge, and when the concave surface of the liquid drops Stop timing when the second mark line is reached to obtain the liquid level drop time.

(j) It is carried out under the condition that the temperature difference of the test is not greater than ±3°C, so the specific surface area of the sample is calculated according to the formula:

In the formula:

S _c ——— the specific surface area of the tested sample (kg/m ³ )

S _S ———— specific surface area of standard sample (kg/m ³ )

T———When the test sample is tested, the time measured by the drop of the liquid level in the pressure gauge (S)

T _S —————When the test sample is tested, the time measured by the drop of the liquid level in the pressure gauge (S)

ε———The porosity of the sample layer under test

ε _S ———— The porosity in the sample layer of the standard sample

ρ———the density of the tested sample (kg/m ³ ).

The test results of medium-grade aggregates are shown in JL-1 in Table 7.

Table 7 Blaine specific surface area tester test results for mid-range aggregates

3. Medium-grade aggregate specific surface area coefficient

According to the requirements in the T0302-2005 standard of "Test Regulations for Highway Engineering Aggregate" (JTGE42-2005), the mid-range aggregate is screened to obtain the mid-grade aggregate with a particle size range of 4 grades. The mid-range aggregates in the 4 particle size ranges are respectively weighed to obtain the mass of the mid-range aggregates in the 4 particle size ranges. Then compared with the total mass of asphalt mixed aggregate, the proportion of sub-metering and sieve residue of the fourth-grade aggregate is obtained respectively.

The fixed value of the specific surface area coefficient of the 4th grade aggregate adopts the corresponding specific surface area coefficient value in the American coefficient law. As shown in Table 8.

In step 2, the specific surface area of the 0.075mm-0.15mm aggregate aggregate is 50.6m ² /kg, and the specific surface area of the 0.075mm-0.15mm aggregate aggregate in the American coefficient law is 57.35m ² /kg, taking 0.882 (50.6/57.35) as The correction coefficient is to modify the fixed value of the specific surface area coefficient of the medium-grade aggregate, that is, multiply the specified value of the specific surface area coefficient of the fourth-grade aggregate by the correction coefficient, 1.18mm～2.36mm, 0.6mm～1.18mm, 0.3mm～ 0.6mm and 0.15mm～0.3mm correspond to specific surface area coefficients of 2.53m ² /kg, 5.42m ² /kg, 10.84m ² /kg and 21.68m ² /kg respectively.

Table 8 Specific surface area coefficient in the American coefficient law of medium-grade aggregates

The obtained specific surface area coefficients of the aggregates of different particle sizes are multiplied and summed to obtain the specific surface area of the asphalt mixture aggregate. Among them, the measurement results of specific surface area of GF graded coarse aggregate files are shown in Table 9. Table 10 shows the specific surface area measurement results of GF graded ultrafine aggregates and medium-grade aggregates. The specific surface area of the GF graded mixed aggregate thus obtained is 11.85m ² /kg;

According to the Marshall design method, the optimum asphalt ratio of GF graded asphalt mixture aggregate is 4.0, and the optimum ratio of asphalt mixture of GJ graded asphalt mixture is 3.9.

Table 9 GF graded coarse aggregate specific surface area measurement results

Table 10 GF graded fine aggregate specific surface area measurement results

Substitute the specific surface area of the obtained aggregate into the formula, (I):

The obtained bitumen film thickness is 3.15, as shown in Table 13.

Example 2

Measure the thickness of the asphalt film according to the scheme described in Example 1. The difference from Example 1 is that the measured object is the GJ embedded extrusion skeleton gradation prepared according to the asphalt mixture aggregate gradation shown in Table 5. . The measurement results of the specific surface area of the GJ graded coarse aggregate are shown in Table 11, and the measurement results of the specific surface area of the GJ graded ultrafine aggregate and medium-grade aggregate are shown in Table 12. The specific surface area of each grade of aggregate is added to obtain GJ The gradation specific surface area is 11.68m2/kg. Also using the formula shown in Formula I, the thickness of the asphalt film is 3.12, as shown in Table 13.

Table 11 Calculation of specific surface area of GJ graded coarse aggregate

Table 12 Calculation of specific surface area of GJ graded fine aggregate

Example 3

The asphalt film thickness is measured according to the scheme described in Example 1. The difference from Example 1 is that the measured object is the JP-1 gradation prepared according to the asphalt aggregate gradation shown in Table 5. The specific surface area of JP-1 gradation is 11.47m ² /kg, and the optimum asphalt ratio of JP-1 gradation AC-20 asphalt mixture determined by Marshall compaction method is 3.8%. Also using the formula shown in Formula I, the thickness of the asphalt film is 3.09, as shown in Table 13.

Example 4

The asphalt film thickness is measured according to the scheme described in Example 1. The difference from Example 1 is that the measured object is the JP-2 gradation prepared according to the asphalt aggregate gradation shown in Table 5. The specific surface area of JP-2 gradation is 12.27m ² /kg, and the optimum asphalt ratio of JP-2 gradation AC-20 asphalt mixture determined by Marshall compaction method is 4.1%.

Example 5

The asphalt film thickness is measured according to the scheme described in Example 1, and the difference from Example 1 is that the measured object is the JP-3 gradation prepared according to the asphalt aggregate gradation shown in Table 5, The specific surface area of JP-3 gradation is 10.78m ² /kg, and the optimum asphalt ratio of JP-3 gradation AC-20 asphalt mixture determined by Marshall compaction method is 3.6%.

Table 13 Asphalt film thickness of different grades

In order to verify the reliability of the calculation results of the new calculation method, the optimum asphalt-stone ratios corresponding to the five gradations were calculated using the optimum film thickness (3.25 μm). (JTGF40-2004), using the Marshall compaction method to determine, JP-1, JP-2, JP-3 three different gradations of AC-20 asphalt mixture optimal asphalt ratio, the results were 3.8%, 4.0 %, 3.6%. The calculated results are compared with the optimum asphalt ratio determined by the Schell design method.

Table 14 The asphalt ratio corresponding to different graded mixtures

It can be seen from Table 14 that the determined optimal asphalt film thickness, aggregate specific surface area, and asphalt relative density at 25°C are combined with the method for determining the asphalt film thickness provided by the present invention to back-calculate, and the asphalt content and asphalt ratio are obtained, as shown in Table 14 Inversely calculated bitumen content and inversely calculated asphalt ratio data are shown. The asphalt-stone ratio obtained by inverse calculation of the optimal asphalt film thickness was compared with the actual asphalt dosage.

The obtained asphalt film thickness is calculated to obtain the asphalt ratio. For the same material and different gradation, the error between the actual asphalt ratio and the calculated asphalt ratio is between 0% and 1%, which proves the method for determining the asphalt film thickness provided by the present invention reliability.

Example 6

The specific surface area of the asphalt aggregate was measured according to the scheme described in Example 1. The difference from Example 1 is that in the selection process of the asphalt aggregate, the fine aggregate is JL-2. The specific surface area of the final asphalt aggregate is 11.24, and the optimum asphalt-stone ratio of the asphalt aggregate determined according to the Marshall design method is 3.9.

Example 7

The specific surface area of the asphalt aggregate was measured according to the scheme described in Example 1. The difference from Example 1 is that in the selection process of the asphalt aggregate, the fine aggregate is JL-3. The final specific surface area of the asphalt aggregate is 12.8, and the optimum asphalt-stone ratio of the asphalt aggregate determined according to the Marshall design method is 4.2.

Example 8

The specific surface area of the asphalt aggregate was measured according to the scheme described in Example 1. The difference from Example 1 is that in the selection process of the asphalt aggregate, the fine aggregate is JL-2. The final specific surface area of the asphalt aggregate is 12.27, and the optimum asphalt-stone ratio of the asphalt aggregate determined according to the Marshall design method is 4.1.

The relationship between the specific surface area of the asphalt aggregate measured in Examples 1, 6, 7 and 8 and the optimum asphalt ratio is shown in the relationship curve between the asphalt specific surface area and the optimum asphalt ratio measured by the Marshall method in Figure 1. Figure 1 shows that the specific surface area of the asphalt mixed aggregate obtained according to the scheme of the present invention has a specific consistent trend with the optimum asphalt-stone ratio measured by the Marshall method, and the aggregate specific surface area has a good correlation with the optimum asphalt-stone ratio.

Comparative example 1

According to the gradation GF in Table 15, the asphalt mixture aggregate was prepared, and the specific surface area of the asphalt mixture aggregate was measured according to the method in the specification to be 5.02, and the optimum asphalt mixture aggregate ratio determined according to the Marshall design method was 4.0.

Comparative example 2

According to the gradation GJ in Table 15, the asphalt mixture aggregate was prepared, and the specific surface area of the asphalt mixture aggregate was measured according to the method in the specification to be 5.12, and the optimum asphalt mixture aggregate ratio determined according to the Marshall design method was 3.9.

Table 15 Grading of asphalt mixture for comparative example

Table 16 Aggregate specific surface area and corresponding optimum asphalt ratio determined by standardized method

The data in Table 16 shows that the specific surface area of GF-graded asphalt aggregates is smaller than that of GJ-graded asphalt aggregates; through the Marshall design method, the optimal asphalt ratio of GF-graded asphalt aggregates is greater than that of GJ grades The best asphalt-stone ratio of asphalt mixture aggregate. The specific surface area of asphalt aggregate determined by the standard method has poor correlation with the optimum asphalt-stone ratio.

The above is only a preferred embodiment of the present invention, and it should be pointed out that for those of ordinary skill in the art, some improvements and modifications can be made without departing from the principle of the present invention. It should be regarded as the protection scope of the present invention.

Claims (9)

1. it is a kind of obtain asphalt membrane thickness method, it is characterised in that comprise the following steps：

(1) determine pitch and mix pitch relative density under the conditions of the bitumen content and 25 DEG C gathered materials；

(2) screening pitch mixing is gathered materials, and according to the grain size for gathering materials, is obtained some shelves and is gathered materials point meter sieve gathered materials with corresponding shelves Remaining ratio；

(3) point meter that the specific surface area coefficient and corresponding shelves for some shelves that the step (2) is obtained gathering materials gather materials tails over ratio Summation is added after multiplication, pitch is obtained and is mixed specific surface area of gathering materials；

Some shelves gather materials gather materials including thick shelves, ultra-fine shelves gather materials and gather materials with middle-grade；

The particle diameter that the thick shelves gather materials is not less than 2.36mm；

The particle diameter that the ultra-fine shelves gather materials is less than 0.15mm；

The middle-grade particle diameter for gathering materials is not less than 0.15mm and less than 2.36mm；

(4) pitch is mixed into specific surface area of gathering materials, pitch respectively and mixes pitch under the conditions of the bitumen content gathered materials and 25 DEG C Relative density substitutes into formula shown in Formulas I, obtains asphalt membrane thickness.

$DA=\frac{P_b}{{\mathrm{\γ}}_b\×SA}\×10---I;$

DA described in formula I is asphalt membrane thickness；

The SA is the specific surface area that pitch mixing is gathered materials；

The P_bFor the bitumen content that pitch mixing is gathered materials；

The γ_bIt is pitch relative density under the conditions of 25 DEG C；Described point of meter tails over ratio for some shelves gather materials by corresponding grain The oversize of footpath size perforations accounts for the mass percent that the corresponding pitch mixing is gathered materials.

2. method according to claim 1, it is characterised in that point meter that some shelves gather materials tails over ratio for different shelves Gather materials and account for the percentage that the pitch mixes gross mass of gathering materials by the quality of the oversize of corresponding grain size sieve aperture.

3. method according to claim 1, it is characterised in that the specific surface area coefficient that the thick shelves gather materials compares table for fixation Area coefficient.

4. the determination method of specific surface according to claim 3, it is characterised in that the fixed specific surface area coefficient according to The method for comprising the following steps is obtained:

A () is gathered materials the thick shelves and is sieved, according to the grain size for gathering materials, obtain some secondary shelves of the coarse aggregate；

B () weighs respectively to the coarse aggregate of some secondary shelves, obtain the quality of the coarse aggregate of some secondary shelves；

C () is scanned respectively to the coarse aggregate of some secondary shelves, obtain the scanning of the coarse aggregate of some secondary shelves Figure；

D () obtains the surface area of the coarse aggregate of some secondary shelves according to the scanning figure of the coarse aggregate of some secondary shelves；

E () obtains according to the quality of the coarse aggregate of the surface area and some secondary shelves of the coarse aggregate of some secondary shelves The fixed specific surface area coefficient of the coarse aggregate of some secondary shelves；

The fixed specific surface area coefficient of the coarse aggregate of some secondary shelves is the surface area of the coarse aggregate of some secondary shelves With the ratio of the quality of the coarse aggregate of some secondary shelves.

5. method according to claim 1, it is characterised in that the ultra-fine specific surface area coefficient for gathering materials according to including with The method of lower step is obtained：

A, to it is described it is ultra-fine gather materials sieve, obtain that one-level is ultra-fine to gather materials gather materials and the one-level ultra-fine collection ultra-fine with two grades Point meter of material tails over ratio and two grades of ultra-fine point meters for gathering materials tail over ratio；

B, using Blain specific surface method it is ultra-fine to the one-level gather materials and it is described two grades it is ultra-fine gather materials test respectively, obtain To ultra-fine specific surface coefficient and the two grades of ultra-fine specific surface area coefficients that gather materials of gathering materials of one-level；

The one-level is ultra-fine to gather materials for particle diameter gathers materials more than 0.075mm and less than 0.15mm grades；

Described two grades ultra-fine to gather materials for particle diameter no more than 0.075mm grades and gathers materials.

6. method according to claim 5, it is characterised in that it is described that the ultra-fine point meter for gathering materials of the one-level tails over ratio One-level is ultra-fine to gather materials and account for the percentage that the pitch mixes gross mass of gathering materials by the quality of the oversize of corresponding grain size sieve aperture Than；

It is the described two grades ultra-fine sieves gathered materials by corresponding grain size sieve aperture that the described two grades ultra-fine point meters for gathering materials tail over ratio The quality of upper thing accounts for the percentage that the pitch mixes gross mass of gathering materials.

7. method according to claim 5, it is characterised in that the middle-grade specific surface area coefficient for gathering materials is using modification Coefficient is modified to the coefficient fixed value of the middle-grade specific surface area gathered materials and obtains；

The method of the amendment is that the coefficient fixed value of the middle-grade specific surface area gathered materials is multiplied with the correction factor.

8. method according to claim 7, it is characterised in that the correction factor is the ultra-fine ratio table for gathering materials of the one-level The ratio of the fixed value of area coefficient and the ultra-fine specific surface area coefficient that gathers materials of one-level.

9. the method according to claim 7 or 8, it is characterised in that the fixed value of the specific surface area coefficient is system of the U.S. Specific surface area coefficient in number method rule.