CN109001258B - Asphalt content nondestructive testing method based on dielectric property of asphalt mixture - Google Patents
Asphalt content nondestructive testing method based on dielectric property of asphalt mixture Download PDFInfo
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Abstract
The invention discloses a nondestructive testing method for asphalt content based on the dielectric property of an asphalt mixture. The invention establishes a relation between the asphalt content and the dielectric property thereof by deducing a formula, obtains the density of the asphalt and the mineral aggregate by using data, obtains the porosity of the mixture by design, then measures the dielectric constant of the asphalt and the mineral aggregate by experiments, and directly calculates the asphalt content by measuring the dielectric constant of the asphalt mixture after inputting the data into the formula. The method has great progress in both the rationality and the experimental time of the test method, and in addition, the characteristic of nondestructive testing of the method has essential difference and advantage compared with the conventional asphalt content measurement method, and can lay a foundation for the research of the practical road engineering nondestructive testing asphalt content.
Description
Technical Field
The invention belongs to the field of road engineering, and relates to a nondestructive testing method for asphalt content based on the dielectric property of an asphalt mixture.
Background
Whether the asphalt pavement has early diseases or not is related to construction processes such as construction technology and paving quality control, and is also related to improper design of the properties, the gradation, the oil-stone ratio and the like of the selected asphalt mixture raw materials. The most common disease is oil bleeding or rutting, which is caused by improper use of asphalt. In the national standard, a marshall method is usually adopted in an asphalt mixture design method, the design core is to describe the volumes of relevant components of the asphalt mixture through parameters such as void ratio, mineral aggregate void ratio and the like, but the part of asphalt absorbed by aggregate is not calculated, and the volumes of the components of the asphalt mixture are not accurately analyzed and calculated, so that the asphalt consumption of the asphalt mixture is small and the void ratio is large. However, if only blindly considering increasing the amount of asphalt, the amount of asphalt may be too large and the void ratio may be too small, thereby reducing the thermal stability of the asphalt pavement and causing the problems of rutting and other diseases. In conclusion, the reasonable design of the asphalt-aggregate ratio adopted by the asphalt mixture is one of the keys for ensuring the construction quality and the service performance of the asphalt pavement. How to design the asphalt mixture according to a reasonable asphalt-to-stone ratio is one of the key conditions for ensuring the service performance and the service life of the asphalt pavement.
In the current engineering practice, the common methods for measuring the asphalt content are combustion method and centrifugal extraction method, but the two measurement methods can damage the mixture test piece, and the operation is complicated and long-time consuming.
Disclosure of Invention
The invention aims to provide a nondestructive testing method for asphalt content, aiming at the defects of complex operation and damage of the existing asphalt content testing of asphalt mixtures, and accurately, quickly and nondestructively calculating the asphalt content of the asphalt mixtures, so as to reflect the construction quality of actual engineering roads and provide reference for indoor monitoring of asphalt content changes of the asphalt mixtures and even road testing.
In order to achieve the purpose, the technical scheme is as follows:
the nondestructive testing method for the asphalt content based on the dielectric property of the asphalt mixture comprises the following steps:
the relationship between the asphalt content of the mixture and the dielectric constant is established as follows:
in the formula, P is the content of asphalt; e is the void ratio of the asphalt mixture; mu is the conversion ratio of the density of the asphalt and the mineral aggregate,
to conversion formula, gammaas、γsThe densities of the asphalt and the mineral aggregate respectively; k is a radical ofm、ks、kasThe dielectric constant coefficients of the asphalt mixture, the mineral aggregate and the asphalt are respectively;
wherein the content of the first and second substances,
calculating formulas of three coefficients respectively;m、s、asthe dielectric constants of the asphalt mixture, the mineral aggregate and the asphalt are respectively;
and substituting the related measurement data into a formula, and calculating to obtain the asphalt content of the asphalt mixture.
According to the scheme, the dielectric constant of the mineral aggregate is determined according to the following method:
core drilling and cutting are carried out on large mineral aggregate to obtain 3 small test pieces with the height of 12mm multiplied by the diameter of 26mm, the dielectric constant of each small test piece is measured once on the front surface and the back surface of a high-temperature test platform, and the dielectric constant value of the mineral aggregate is represented by the mean value of 6 dielectric constants measured by the 3 small test pieces.
According to the scheme, the dielectric constant of the asphalt is determined according to the following method:
5 cylindrical molds with the diameter of 40mm and the thickness of 9.5mm are manufactured, the upper ends of the molds are opened, the periphery and the lower ends of the molds are closed, asphalt is heated and poured into the molds, the molds are kept still for cooling, the upper surfaces of the molds are scraped, the molds are broken, asphalt blocks are taken out, cores are drilled on the asphalt blocks, asphalt block test pieces with the diameter of 25mm and the thickness of 9.5mm meeting the measurement requirements are obtained, the asphalt block test pieces are placed into a constant temperature box with the temperature of 25 ℃ for heat preservation for 30min before measurement, the temperature of the asphalt block test pieces is kept consistent with the measurement temperature of a mixture, the positive and negative measurement of each test piece is carried out once, and the average value.
According to the scheme, the dielectric constant of the mixture is determined according to the following method:
preparing a mixture test piece, and using a rotary compaction molding test piece to control the porosity of the test piece to be within the range of 4 +/-0.5%; drilling and cutting the molded test piece to obtain a cylindrical test piece with the height of 150mm multiplied by the diameter of 100 mm;
measuring by using a Percometer (PM for short) of a dielectric constant instrument, selecting a proper probe, then selecting a correct probe mode in the PM to measure air, namely calibrating the PM, and preheating the PM for 1-2 minutes after calibration is finished;
before the test, the probe is lifted and placed at a position 5-10cm above the test piece, and the index E of the PM is 1.0, so that the normal work of the PM is determined;
and (3) measuring the upper surface, the lower surface, the left surface, the right surface and the middle part of the upper surface and the lower surface of the asphalt mixture for 5 times, recording the dielectric constant value and the measurement temperature after each measurement is finished, and taking the average value of 10 measurements to represent the dielectric constant value of the asphalt mixture.
The invention relates to a method for directly calculating the content of asphalt by deducing a formula, establishing a relation between the content of the asphalt and the dielectric property of the asphalt, obtaining the density of the asphalt and mineral aggregate by using data, obtaining the void ratio of the mixture by design, measuring the dielectric constant of the asphalt and the mineral aggregate by experiments, and directly calculating the content of the asphalt by measuring the dielectric constant of the asphalt mixture after inputting the data into the formula. The method has great progress in both the rationality and the experimental time of the test method, and in addition, the characteristic of nondestructive testing of the method has essential difference and advantage compared with the conventional asphalt content measurement method, and can lay a foundation for the research of the practical road engineering nondestructive testing asphalt content.
The method comprises the following specific steps:
(1) the PM is used for measuring the dielectric constant of the asphalt mixture to accelerate the test progress and shorten the test time, various constants in a formula need to be measured at one time in the early stage of the measurement method, about 10 hours are consumed, the asphalt content of the mixture can be inversely calculated by measuring the dielectric constant of the asphalt mixture, under the condition that the types of mineral aggregate and asphalt are not changed, the asphalt content of a plurality of mixtures can be rapidly measured and calculated, the average time for measuring and calculating each mixture is 15 minutes, and the time for measuring each asphalt mixture by a conventional combustion method and a centrifugal separation method is more than half a day.
(2) Can realize the nondestructive measurement of the asphalt content of the asphalt mixture under the indoor condition
The method adopts a formula inverse algorithm, utilizes a PM instrument to perform nondestructive measurement on the dielectric constant of the asphalt mixture, substitutes the formula for the dielectric constant to perform inverse calculation, can directly obtain the asphalt content of the mixture, does not need to damage a test piece, and compared with the conventional destructive measurement method, can further perform other experiments on the test piece of the mixture after the asphalt content is measured, thereby laying a research foundation for researching the relation between the mechanical property of the asphalt mixture and the asphalt content in the future.
(3) Can lay a foundation for the research of the nondestructive testing of the asphalt content in the actual road engineering
The measurement method adopts a formula inverse algorithm, and in practical road engineering application, if the void ratio of a road surface measurement point can be accurately obtained, the asphalt content of the corresponding measurement point of the road can be rapidly measured without damage. In addition, after the relationship between the dielectric property and the void ratio of the asphalt mixture is established in the future, the dielectric constants of different positions of the pavement can be detected by using the road ground penetrating radar to obtain the void ratio of the corresponding position of the pavement, and then the asphalt content of the whole pavement is obtained through back calculation by the method and is used for evaluating the construction quality.
Detailed Description
The following examples further illustrate the technical solutions of the present invention, but should not be construed as limiting the scope of the present invention.
Preparation of test samples of asphalt mixture
The test adopts a rotary compaction molding test piece, and the asphalt selected from the asphalt is SBS modified asphalt provided by high and new material stocks Co., Ltd, China Hubei province; the aggregate selected is limestone produced by a certain stone factory in the county of Hubei province and basalt produced by a certain stone factory in the province of Hubei province; the mineral powder is ground by limestone; the same aggregate was graded in the same way and two sets of linearly varying oilstone ratios were used as variables, where the asphalt to basalt mineral density ratio μ was calculated to be 0.3812 and the asphalt to limestone mineral density ratio μ was calculated to be 0.4012.
Wherein 5 test pieces are respectively prepared from basalt SMA-13 according to the oilstone ratio of 3.1%, 3.6%, 4.1%, 4.6% and 5.1%, the test pieces are respectively numbered as SMA-13-1, SMA-13-2, SMA-13-3, SMA-13-4 and SMA-13-5, limestone AC-20 is respectively prepared from the basalt SMA-13 according to the oilstone ratio of 3.8%, 4.3%, 4.8%, 5.3% and 5.8%, the test pieces are respectively numbered as AC-20-1, AC-20-2, AC-20-3, AC-20-4 and AC-20-5, and the porosity of the rotary compaction test piece is controlled within the range of 4% +/-0.5%. And then, drilling and cutting the molded test piece to obtain a cylindrical test piece with the height of 150mm multiplied by the diameter of 100 mm.
Debugging PM
Selecting a probe SF169 with the diameter of 60mm to be connected with a PM host, opening the PM, and selecting a correct measurement mode according to the model of the probe, wherein the correct setting is shown in H169C on the upper left of a display screen; and then calibrating the PM, placing the probe in the air, displaying the E of 1.0 on a screen at the moment, namely successfully calibrating, and starting to measure after preheating for 1-2 minutes.
Start measurement
Vertically placing the probe above the mixture test piece, enabling the edge of the probe to be tangent to the circumference of the mixture, displaying the value of E on a PM screen at the moment, and recording after data are stable; and 5 times of measurement is carried out on the symmetrical part, the same five times of measurement is carried out on the reverse side of the mixture, the average value of 10 times of measurement is taken as the dielectric constant value of the whole mixture, finally, the rest 9 test pieces are measured according to the same steps, and the obtained dielectric constant data are summarized in the following table 1.
TABLE 1 dielectric constant test data for blends
Measuring the dielectric constant value of aggregates
Selecting large-size basalt and limestone mineral aggregates, drilling and cutting the basalt and limestone mineral aggregates to obtain 3 small test pieces with the height of 12mm and the diameter of × mm, respectively measuring the dielectric constants of the small test pieces once on the front side and the back side of a high-temperature test platform, representing the dielectric constant value of the mineral aggregates by the mean value of 6 dielectric constants measured by the 3 small test pieces, and finally obtaining the k of the basalt through conversions0.8357, k of limestones0.7433;
measuring the dielectric constant value of asphalt
The asphalt is measured by the method, the asphalt is heated and poured into a mould, the mould is kept stand and cooled, the upper surface of the asphalt is strickled off, the mould is broken, the asphalt block is taken out, the core is drilled to obtain an asphalt block test piece which meets the measurement requirement, the diameter of the asphalt block test piece is 25mm, the thickness of the asphalt block test piece is 9.5mm, the asphalt block test piece is placed into a constant temperature box with the temperature of 25 ℃ for heat preservation for 30min before measurement, the temperature of the asphalt block test piece is kept consistent with the measurement temperature of the mixture, the positive and negative of each test piece are measured once, the average value of 10 measured values is taken as the dielectric constantas0.5012;
substitution calculation
Densifying the above asphalt mineral aggregateDegree ratio mu, void ratio e, and conversion coefficient k of dielectric constant of mineral aggregatesDielectric constant conversion coefficient k of asphaltasAnd a dielectric constant conversion coefficient k of the mixed materialmThe calculated value of the asphalt content is obtained by calculation finally after being substituted into a formula, the comparison condition of the calculated value and the design value is shown in table 2, the values are all less than 3% from the result of average relative error, the calculation result is accurate, and the method has feasibility.
TABLE 2 comparison of asphalt content design value and calculated value of each asphalt mixture test piece
Claims (4)
1. The nondestructive testing method for the asphalt content based on the dielectric property of the asphalt mixture is characterized by comprising the following steps of:
the relationship between the asphalt content of the mixture and the dielectric constant is established as follows:
in the formula, P is the content of asphalt; e is the void ratio of the asphalt mixture; mu is the conversion ratio of the density of the asphalt and the mineral aggregate,
to conversion formula, gammaas、γsThe densities of the asphalt and the mineral aggregate respectively; k is a radical ofm、ks、kasThe dielectric constant coefficients of the asphalt mixture, the mineral aggregate and the asphalt are respectively;
wherein the content of the first and second substances,
calculating formulas of three coefficients respectively;m、s、asthe dielectric constants of the asphalt mixture, the mineral aggregate and the asphalt are respectively;
and substituting the related measurement data into a formula, and calculating to obtain the asphalt content of the asphalt mixture.
2. The nondestructive testing method for the content of the asphalt based on the dielectric property of the asphalt mixture as claimed in claim 1, wherein the dielectric constant of the mineral aggregate is determined by the following method:
core drilling and cutting are carried out on large mineral aggregate to obtain 3 small test pieces with the height of 12mm multiplied by the diameter of 26mm, the dielectric constant of each small test piece is measured once on the front surface and the back surface of a high-temperature test platform, and the dielectric constant value of the mineral aggregate is represented by the mean value of 6 dielectric constants measured by the 3 small test pieces.
3. The nondestructive testing method for the content of asphalt based on the dielectric property of the asphalt mixture as claimed in claim 1, wherein the dielectric constant of the asphalt is determined by the following method:
5 cylindrical molds with the diameter of 40mm and the thickness of 9.5mm are manufactured, the upper ends of the molds are opened, the periphery and the lower ends of the molds are closed, asphalt is heated and poured into the molds, the molds are kept still for cooling, the upper surfaces of the molds are scraped, the molds are broken, asphalt blocks are taken out, cores are drilled on the asphalt blocks, asphalt block test pieces with the diameter of 25mm and the thickness of 9.5mm meeting the measurement requirements are obtained, the asphalt block test pieces are placed into a constant temperature box with the temperature of 25 ℃ for heat preservation for 30min before measurement, the temperature of the asphalt block test pieces is kept consistent with the measurement temperature of a mixture, the positive and negative measurement of each test piece is carried out once, and the average value.
4. The nondestructive testing method for the asphalt content based on the dielectric property of the asphalt mixture as claimed in claim 1, wherein the dielectric constant of the mixture is determined by the following method:
preparing a mixture test piece, and using a rotary compaction molding test piece to control the porosity of the test piece to be within the range of 4 +/-0.5%; drilling and cutting the molded test piece to obtain a cylindrical test piece with the height of 150mm multiplied by the diameter of 100 mm;
measuring by using a dielectric constant instrument PM, selecting a proper probe mode in the PM to measure air after selecting the proper probe, namely calibrating the PM, and preheating the PM for 1-2 minutes after the calibration is finished;
before the test, the probe is lifted and placed at a position 5-10cm above the test piece, and the index E of the PM is 1.0, so that the normal work of the PM is determined;
and (3) measuring the upper surface, the lower surface, the left surface, the right surface and the middle part of the upper surface and the lower surface of the asphalt mixture for 5 times, recording the dielectric constant value and the measurement temperature after each measurement is finished, and taking the average value of 10 measurements to represent the dielectric constant value of the asphalt mixture.
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| CN110361427A (en) * | 2019-08-12 | 2019-10-22 | 武汉理工大学 | A kind of asphalt mixture gradation evaluation method based on dielectric property |
| CN114428049B (en) * | 2021-09-13 | 2022-07-26 | 中国石油化工股份有限公司 | Method for calculating asphalt content of ancient carbonate reservoir |
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