CN102288623B - Method and device for determining water content of fresh concrete mixture based on dielectric constant - Google Patents
Method and device for determining water content of fresh concrete mixture based on dielectric constant Download PDFInfo
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- CN102288623B CN102288623B CN 201110127241 CN201110127241A CN102288623B CN 102288623 B CN102288623 B CN 102288623B CN 201110127241 CN201110127241 CN 201110127241 CN 201110127241 A CN201110127241 A CN 201110127241A CN 102288623 B CN102288623 B CN 102288623B
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Abstract
The invention discloses a method and a device for determining the water content of a fresh concrete mixture based on dielectric constant. According to the method, a relative dielectric constant of concrete is tested based on the propagation rate attenuation of an electromagnetic wave in the fresh concrete mixture and the reflection principle of the electromagnetic wave on a metal plate of a testing device, and then, in accordance with the principle that the relative dielectric constant is relatively sensitive to water, the propagation velocity of the electromagnetic wave in the fresh concrete mixture is enabled to vary so as to lead to the variation of the relative dielectric constant, thus the water content of the fresh concrete mixture can be measured. The method has the characteristics of no contact between an electromagnetic transmitting and receiving device and a tested object, large testing area and wide water ratio testing range. The method can be used for overcoming the defect that the traditional method is insufficient in concrete adaptability, largely impacted by environment, inaccurate and unreliable, has greatly increased precision and speed in testing the relative dielectric constant of concrete, and has the characteristics of great simplicity in manufacturing testing device, good simplicity and convenience, accurate test results and outstanding operation easiness.
Description
Technical field
The present invention relates to the fresh concrete mixture water cut test method based on specific inductive capacity, also relate to the device that is applied to fresh concrete mixture measurement of water-content coefficient, be mainly used in concrete mixing plant, working-yard or other test places and measure the water percentage of fresh concrete mixture, belong to the cement concrete building material field.
Background technology
The water consumption of concrete mix has very important impact to its serviceability, mechanical property and permanance, and the Practical Project construction exists water consumption bigger than normal more, causes the problem that later concrete mechanical property and endurance quality descend.The water percentage of accurately, measuring efficiently, rapidly the fresh concrete mixture is controlled very important for the concrete quality of production.
Existing standard, standard have proposed multiple fresh concrete mixture measurement of water ratio method, and practical operation adopts the form of water-cement ratio to represent more.Adopt the methods such as fried dry method, WATER-WASHING METHOD such as basis " concrete for hydraulic structure testing regulations " (DL/T 5150-2001) regulation, its complicated operation, consuming time longer.In addition, bibliographical information has been arranged additive method is such as alcohol firing method, NEUTRON METHOD, capacitance method, time domain reflectometry, electric-resistivity method etc.It is larger that these method measurement results are affected by near the matter water-containing state sample and the probe, and the result who records has uncertainty, accurately the water percentage of representative species integral body.A lot of scholars have put forward the measurement of the rear concrete of sclerosis and Water Content in Mortar, but yet there are no report for the measuring method of the fresh concrete mixture water percentage that is in flow state.
Specific inductive capacity has reflected the fundamental characteristics of medium, it is a very important parameter, it is relevant with factors such as material composition, structure, density, because each component of concrete mix all can exert an influence to the electromagnetic property of medium, and the relative dielectric constant of cement, silica sand, stone is generally between 2-8, and free water is under certain frequency, its relative dielectric constant is about 80, the relative dielectric constant of air is stabilized in 1, wherein to concrete mix what have the greatest impact is the content of water.Along with the increase of water cut in the fresh concrete mixture, the relative dielectric constant of concrete mix promptly increases, and this mensuration for fresh concrete mixture water cut provides theoretical foundation.
The present invention is directed to concrete is the inhomogeneous compound substance of a kind of polycomponent, its specific inductive capacity depends on the characteristics of the distribution situation between specific inductive capacity, volumetric concentration and each component of coarse-fine aggregate, water, cement and each component of mineral admixture, for the fresh concrete mixture provides a kind of test speed fast, degree of accuracy is high, continuously, practical measurement of water ratio new method.
Summary of the invention
The object of the invention aims to provide a kind of fresh concrete mixture water cut test method and proving installation.
The object of the invention adopts following technical proposals to realize.
A kind of method of testing fresh concrete mixture moisture content of the present invention, it is the method based on dielectric constant, utilize decay and the reflection of electromagnetic wave on metallic plate of electromagnetic wave propagation rate in concrete mix, with electromagnetic wave receiver, record the two way travel time of GPR ripple in concrete, through type (1) calculates concrete relative dielectric constant ε again, according to survey relative dielectric constant data, relative dielectric constant and moisture content relation curve that the substitution experiment is set up, obtain the moisture content of fresh concrete mixture to be measured
ε＝c
2t
2/4h
2 (1)
Wherein, c is the speed that electromagnetic wave is propagated in a vacuum, c=0.3m/ns, t be electromagnetic wave from being transmitted into the two way travel time of reception, unit is ns, h is the fixed thickness of device, unit is m.
The method of test fresh concrete mixture water percentage of the present invention, specifically carry out successively as follows:
1), concrete-agitating to be measured is even, put into the device of test fresh concrete mixture water percentage, and closely knit until there is not obvious bubble to emerge on shaking table, after finishing at surface coverage layer of polyethylene film;
2), the device that transmits and receives of ground penetrating radar is placed on the lateral surface that test fresh concrete mixture water percentage device has the opposite of sheet metal, the fresh concrete mixture is tested;
3), in the test process, get 3-5 position horizontal survey, get the mean value that it records;
4), the mean value that records is analyzed, get the two way travel time of ground penetrating radar ripple in concrete, more resulting data are calculated the relative dielectric constant of fresh concrete mixture;
5), according to the survey relative dielectric constant, relative dielectric constant and water percentage relation curve that substitution experiment is set up obtain the water percentage of fresh concrete mixture to be measured.
A kind of device of testing fresh concrete mixture water percentage of the present invention, it comprises that main body, sheet metal, described main body are the rectangle cell body, be made into by polymethylmethacrylate (PMMA) plate, described sheet metal is close on the inwall of a side of main body seamless, between other side panels of described sheet metal and main body cavity is arranged, suitable for reading opening wide.
The device of test fresh concrete mixture water percentage of the present invention is considered the border to electromagnetic impact, large 3 to 4 times than the antenna of the transmitter-receiver device of ground penetrating radar of the body interior sizes of design.
In the device of test fresh concrete mixture water percentage of the present invention, described sheet metal is steel plate.
Principle of work of the present invention is: ground exploring radar antenna sends electromagnetic wave, by propagating in the concrete of PMMA plate in device, behind the sheet metal that runs into the device back, electromagnetic wave can be reflected back by the steel plate shielding, pass again the receiving trap that medium arrives ground penetrating radar, electromagnetic wave can be obtained in the time of propagating, concrete relative dielectric constant can be got as calculated according to the time.Because the relative dielectric constant of fresh concrete mixture is mainly determined by water, so can obtain its water percentage.
Advantage of the present invention:
Method of the present invention utilizes propagation and the principle of reflection on proving installation sheet metal of electromagnetic wave in concrete to test concrete relative dielectric constant.Relative dielectric constant increases and increases along with water cut rapidly, utilizes its relative dielectric constant indirectly to characterize the water percentage of fresh concrete mixture.The electromagnetic wave transmitter-receiver device does not contact with measured object, and test area is large, and the water cut test scope is large.The method has overcome classic method to not strong, affected by environment large, inaccurate, the insecure shortcoming of concrete adaptability, precision and the speed of fresh concrete mixture water cut test have greatly been improved, the method has proving installation and makes simple, easy, test result is accurate, easy-operating characteristics.
The present invention is fit to the test of different mixture ratio fresh concrete mixture water percentage, if reasonable in design, be equally applicable to the test of water percentage of the mixture (sand-cement slurry etc., lime mortar) of other Binder Materials, utilize the inventive method can obtain accurately, easily the water percentage of fresh concrete mixture by nondestructive technique.
Description of drawings
Fig. 1 is apparatus of the present invention structural representation.
Fig. 2 is method of testing schematic diagram of the present invention
Fig. 3 fresh concrete mixture relative dielectric constant and water percentage experimental data matched curve synoptic diagram
Embodiment
Fig. 1 is the apparatus structure synoptic diagram of test fresh concrete mixture water percentage of the present invention.This device comprises main body 1, sheet metal 2, described main body 1 is the rectangle cell body, the polymethylmethacrylate plate less by relative dielectric constant is made into, described sheet metal 2 is close on the inwall of a side of main body 1 seamless, between other side panels of described sheet metal and main body cavity 3 is arranged, be used for adding fresh concrete mixture sample, loam cake can be opened, consider the border to electromagnetic impact, main body 1 inside dimension of design is than the transmitter-receiver device of ground penetrating radar 4 large 3～4 times.The one side of present embodiment device is steel plate, and another side is used for putting the transmitter-receiver device 4 of ground penetrating radar.
The applicable frequency range of the embodiment of the invention is that device thickness is at least 100mm greater than 400MHz, and width is greater than 250mm, highly is not less than 150mm.Its test operation: at first the concrete that stirs is poured in the device, is filled as far as possible the fresh concrete mixture, be no less than 2/3 height, through closely knit until there is not obvious bubble to emerge on shaking table, after finishing at surface coverage layer of polyethylene film; The test ground penetrating radar emitting antenna of usefulness and receiving antenna 4 are placed on the device side begin test, will survey a plurality of points in the test process, keep as far as possible test result accurately, reliability, get 3-5 position horizontal survey, get its measurement mean value; The data of test are got two way travel time in the concrete through the Radan5.0 software analysis, calculate concrete relative dielectric constant through formula (1) again; Utilize great many of experiments to set up relation curve (Fig. 3 has considered different condition, and revises) between relative dielectric constant and its water percentage; The relative dielectric constant substitution Fig. 3 relation curve that records, extrapolate the water percentage of fresh concrete mixture.
Claims (3)
1. method of testing fresh concrete mixture water percentage, it is characterized in that: described method is the method based on fresh concrete mixture specific inductive capacity, utilize decay and the reflection of electromagnetic wave on steel plate of electromagnetic wave propagation rate in the fresh concrete mixture, record the two way travel time of ground penetrating radar ripple in fresh concrete with electromagnetic wave receiver, through type (1) calculates the relative dielectric constant ε of fresh concrete again, in the relative dielectric constant and water percentage relation curve according to survey relative dielectric constant data substitution experiment foundation, obtain the water percentage of fresh concrete mixture to be measured
ε=c
2t
2/4h
2 （1）
Wherein c is the speed that electromagnetic wave is propagated in a vacuum, c=0.3m/ns, t be electromagnetic wave from being transmitted into the two way travel time of reception, unit is ns, h is the fixed thickness of device, unit is m;
Specifically carry out successively as follows:
1), fresh concrete to be measured is stirred, put into the device of test fresh concrete mixture water percentage, and closely knit until there is not obvious bubble to emerge on shaking table, after finishing at surface coverage layer of polyethylene film;
2), the device that transmits and receives of ground penetrating radar is placed on the lateral surface that test fresh concrete mixture water percentage device has the opposite of steel plate, the fresh concrete mixture is tested;
3), in the test process, get 3-5 position horizontal survey, get the mean value that it records;
4), the mean value that records is analyzed, get the two way travel time of ground penetrating radar ripple in fresh concrete, more resulting data are calculated the relative dielectric constant of fresh concrete mixture;
5), according to relative dielectric constant and water percentage relation curve that survey relative dielectric constant substitution experiment is set up, obtain the water percentage of fresh concrete mixture to be measured.
2. device of testing fresh concrete mixture water percentage, it is characterized in that: it comprises that main body (1), steel plate, main body (1) are the rectangle cell body, be made into by the polymethylmethacrylate plate, steel plate is close on the inwall of a side of main body (1) seamless, cavity (3) is arranged, suitable for reading opening wide between other side panels of steel plate and main body (1).
3. the device of test fresh concrete mixture water percentage as claimed in claim 3 is characterized in that: large 3 to 4 times than the antenna of the transmitter-receiver device (4) of ground penetrating radar of described main body (1) inside dimensions.
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| CN103175852B (en) * | 2011-12-20 | 2015-12-16 | 航天信息股份有限公司 | A kind of stored grain moisture on-line measuring device and method thereof |
| CN103808624A (en) * | 2014-02-21 | 2014-05-21 | 北京林业大学 | Wood moisture content detection method based on radar waves |
| CN104965231A (en) * | 2015-07-30 | 2015-10-07 | 中国科学院电子学研究所 | Concrete water content detection device and method |
| CN105116055B (en) * | 2015-09-10 | 2017-11-17 | 山东大学 | Concrete device for detecting water content and method and the aqueous amount adjustment method based on the device |
| CN105527305A (en) * | 2015-12-02 | 2016-04-27 | 江苏科技大学 | Concrete strength detection method based on electromagnetic properties of material |
| CN106908489A (en) * | 2017-02-24 | 2017-06-30 | 河海大学 | A kind of non-destructive determination method of grinding coagulation soil moisture content |
| CN107290596A (en) * | 2017-07-14 | 2017-10-24 | 中国神华能源股份有限公司 | The Dielectric Coefficient method and system of railway ballast |
| CN108535219B (en) * | 2018-04-08 | 2021-05-14 | 北京环境特性研究所 | Tool device for measuring reflectivity and method for manufacturing sample for measuring reflectivity |
| CN108931562B (en) * | 2018-06-15 | 2021-01-19 | 武汉理工大学 | Nondestructive testing method for dielectric constant of large-size uneven mixture |
| CN110320247A (en) * | 2019-07-09 | 2019-10-11 | 中国农业大学 | Plant haulm water content damage-free measuring apparatus and method |
| CN110715963A (en) * | 2019-07-16 | 2020-01-21 | 武汉大学 | Method for detecting ice content of concrete |
| CN112630235B (en) * | 2020-12-01 | 2022-03-08 | 同济大学 | Concrete setting time detecting system based on patch antenna |
| CN113075390A (en) * | 2021-03-22 | 2021-07-06 | 青岛理工大学 | Concrete internal moisture and chloride ion synchronous transmission sensing device |
| CN115575417B (en) * | 2022-08-03 | 2023-10-31 | 华能应城热电有限责任公司 | Coal moisture detection method and device |
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