CN101701924A - Method for measuring thermal expansion coefficient of concrete - Google Patents
Method for measuring thermal expansion coefficient of concrete Download PDFInfo
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- CN101701924A CN101701924A CN200910232704A CN200910232704A CN101701924A CN 101701924 A CN101701924 A CN 101701924A CN 200910232704 A CN200910232704 A CN 200910232704A CN 200910232704 A CN200910232704 A CN 200910232704A CN 101701924 A CN101701924 A CN 101701924A
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Abstract
The invention discloses a method for measuring the thermal expansion coefficient of concrete, which comprises the steps of: proportioning each concrete to form into 3 test pieces; previously embedding 4 copper heads which are taken as ends for measuring the length on the surface of the each test piece when forming the each test piece; removing modules after 1 day of forming the test pieces; putting the test pieces into a standard curing room to cure; when reaching a preset curing age, putting the concrete test pieces into water with temperature of T0 to immerse, and measuring the length 1 (T0) among each two corresponding copper heads on the surface of the each test piece; moving the concrete test pieces into a thermostatic water tank with temperature of T to immerse, measuring the length 1 (T) among each two corresponding copper heads on the surface of the each test piece, and recording; measuring the distance among the same pair of the copper heads on the surface of the same test piece under each temperature for many times, taking the average value as effective data; and according to the measured length among the two copper heads on the surface of the each test piece under the different temperatures, counting the thermal expansion coefficient of concrete according to formula (1).
Description
Technical field
The invention belongs to the concrete performance analysis technical field, relate to a kind of measuring method of thermal expansion coefficient of concrete.
Background technology
Thermal expansion coefficient of concrete is meant and be not subjected to external interference, when influenced by self attributes, the variable quantity of the concrete of unit length or volume length or volume under unit temperature changes, it is one of Main physical characterisitic parameter of material, generally characterizes with average thermal linear expansion coefficient.Because the existence of hydration heat of cement and the influence of solar radiation and other environment thermal source, in xoncrete structure, particularly in large volume and Overlong Concrete Structure, produce bigger thermograde, make structure produce bigger uneven temperature distortion, and then the bigger temperature stress of generation, when temperature stress during greater than concrete tensile strength, cause defectives such as cracking, influence structural behaviour.The important parameter that xoncrete structure is carried out temperature deformation calculating is a thermal expansivity.So accurately measure different compositions, varying strength, the concrete thermal expansivity in the different length of times, for the concrete temperature deformation characteristic of abundant grasp, accurately calculate concrete temperature deformation size, instruct structural design, the permanance etc. that improves xoncrete structure has crucial meaning.
Because concrete sample is bigger, the method for measuring thermal expansion coefficient of concrete is the method for pasting strain transducer with built-in sensors or surface mostly.The method of measuring thermal expansion coefficient of concrete at present mainly contains:
1) built-in sensors measuring method
The built-in sensors method is when concrete sample is built moulding, at the inner pre-buried sensor of test specimen.Behind the concrete sample hardened forming, when temperature changed, test specimen can occurrence temperature be out of shape, and the sensor that is embedded in the concrete sample can together deform.By specific testing tool, can measure the deflection of sensor, thereby learn the deflection of concrete sample.Concrete sample can cause very big measuring error to built-in electronic sensor in temperature changing process; Simultaneously, because a certain amount of moisture in the concrete sample also can cause bigger measuring error to sensor; If sensor is carried out water-proofing treatment, then can cause sensor can not directly react the distortion of test specimen, can increase the uncertainty of measurement result.
2) strain-ga(u)ge transducer measuring method
Paste strain-ga(u)ge transducer with bonding agent on the concrete sample surface, when the test specimen temperature changes, can measure the dependent variable of foil gauge, thereby obtain the temperature deformation amount of concrete sample self with the static resistance strainometer.The strain-ga(u)ge transducer measuring method has avoided sensor pre-buried to concrete sample inside, thereby has avoided the influence of internal moisture.But because foil gauge mostly is resistance sensor, the temperature-coefficient of electrical resistance of foil gauge itself and thermal expansivity can influence the determinacy of test result; The deflection of foil gauge can only react the temperature deformation on concrete sample surface, has certain limitation for the measurement of structural entity temperature deformation.
3) clock gauge formula dilatometer measuring method
The principle of clock gauge formula dilatometer measuring method is that the temperature deformation with concrete sample to be measured is delivered on the clock gauge, reads the temperature deformation amount under the different temperatures thus, and then calculates concrete thermal expansivity.This measuring method is simple and convenient, but its degree of accuracy is subjected to the restriction of the minimum scale (0.001mm) of clock gauge, and can not carry out the amplification and the record of swell increment, be difficult to accurate response and go out the temperature deformation amount of bulk effect than small specimen, measuring accuracy is very limited.
Summary of the invention
The present invention is directed to problems such as the degree of accuracy that exists in the above-mentioned measuring method is low, uncertain big, a kind of measuring method of thermal expansion coefficient of concrete is provided, measuring process is simple to operate, the measuring accuracy height.
Technical scheme of the present invention is: a kind of measuring method of thermal expansion coefficient of concrete, and step is as follows:
The first step, 3 test specimens of every kind of concrete mix moulding, the shape size of test specimen is identical, each test specimen when moulding at parallel pre-buried 4 copperheads in test specimen surface as the end points of measuring length, concrete sample moulding form removal after 1 day, put into standard curing room and carry out maintenance, to predetermined curing age measurement thermal expansivity;
Second step reached when being scheduled to curing age, and earlier concrete sample being put into temperature is T
0Water in soak, half an hour, that the hand-held strainmeter is put into standard curing was indoor before measuring, concrete sample soaks in water 〉=measure the length l (T between corresponding two copperheads on the test specimen surface behind the 1.5h
0) and record;
In the 3rd step, then, concrete sample is moved in the constant temperature water tank that temperature is T behind the immersions 〉=1.5h length l (T) and the record between two corresponding copperheads on the measurement test specimen surface;
The 4th step, at between the same a pair of copperhead on same test specimen surface apart from after measuring several times under each temperature, average as valid data after rejecting undesired data, according to the measurement length between two copperheads of concrete sample surface under the different temperatures, calculate concrete average thermal linear expansion coefficient α according to following formula
T wherein
0With T be concrete initial temperature and finishing temperature (℃); L (T) and l (T
0) to be respectively concrete temperature be T and T
0The time test specimen length (mm); Δ l and Δ T concrete length respectively change and temperature variation.
When soaking test specimen, two of parallel placements can the free rolling reinforcing bar in the bottom of test specimen, can reduce the restricting resistance force of concrete sample when temperature raises.
When measuring length, adopt foam heat-insulating board to cover the test specimen surface, the heat interchange of water and surrounding environment when the minimizing tank lid opens and closes keeps the constant of the interior water temperature of water tank, simultaneously for effective temperature variation that reduces hand-held strainmeter self in the measuring process.
Beneficial effect:
(1) operating process of this measuring method is simple, the measurement result good reproducibility.
(2) error of this measuring method is lower than 3.2%, can satisfy the accuracy requirement of research.
Description of drawings
The synoptic diagram of Fig. 1 concrete sample size and pre-buried copperhead position.Wherein, 1,2,3,4 is copperhead.
The temperature of Fig. 2 test specimen center over time
Thermal expansion coefficient of concrete under the different slurry volume fraction of Fig. 3 condition
Thermal expansion coefficient of concrete under the different doping quantity of fly ash conditions of Fig. 4
Embodiment
Below in conjunction with accompanying drawing the present invention is made and to specify.
Embodiment 1
(1) moulding 100mm * 100mm * 400mm prism concrete sample, 3 test specimens of every kind of concrete mix moulding, on each test specimen when moulding at parallel pre-buried 4 copperheads in test specimen surface as shown in Figure 1 as the end points of measuring length, be about 250mm along the distance between two copperheads on the test specimen length direction.Concrete sample moulding form removal after 1 day is put into standard curing room and is carried out maintenance, measures thermal expansivity to the predetermined length of time.
(2) reach when setting curing age, earlier concrete sample is put into 20 ℃ of water and soak fully.Half an hour, that the hand-held strainmeter is put into standard curing was indoor before measuring, and made test specimen have identical temperature with the hand-held strainmeter.Concrete sample is measured length and the record between corresponding two copperheads on the test specimen surface soak 1.5h fully in water after.
(3) afterwards concrete sample is moved into immersion fully in 60 ℃ of constant temperature water tanks.In order to reduce the restricting resistance force of concrete sample when temperature raises, test specimen two of the parallel placements in bottom can the free rolling reinforcing bar.The heat interchange of water and surrounding environment when opening and closing in order to reduce tank lid, keep the constant of the interior water temperature of water tank, simultaneously in order effectively to reduce the temperature variation of hand-held strainmeter self in the measuring process, during test specimen length under measuring 60 ℃ of conditions, adopt and cover the test specimen surface with foam heat-insulating board.Soaking 1.5h fully in 60 ℃ of water after, measures by concrete sample length and the record between two corresponding copperheads on the test specimen surface.
(4) range observation between the same a pair of copperhead on same test specimen surface is 3 times, averages as valid data after rejecting undesired data.According to the measurement length between two copperheads of concrete sample surface under the different temperatures, calculate concrete thermal expansivity.
When specimen molding, can place the measurement terminals of a thermopair at the center of test specimen in advance, can measure temperature by the thermopair that is embedded in the test specimen center is that the temperature of center over time after 20 ℃ concrete sample was put into 60 ℃ water.
The error of this measuring method only is 3.2%, can satisfy the accuracy requirement of research.
Error calculates that process is as follows:
Concrete average thermal linear expansion coefficient α can calculate according to formula 1.
Wherein: T
0With T be concrete initial temperature and finishing temperature (℃); L (T) and l (T
0) to be respectively concrete temperature be T and T
0The time test specimen length (mm); Δ l and Δ T concrete length respectively change and temperature variation;
Measure the relative error of concrete thermal linear expansion coefficient according to formula 1
For:
σ wherein
α, σ
l, σ
TBe respectively the standard deviation of thermal expansivity, length and temperature,
Each parameter can be determined in such a way in the formula 2:
l
0For initial gauge length, get 250mm; Concrete thermal expansivity is generally 10 * 10
-6/ ℃ about; Temperature Δ T is changed to 40 ℃ in this paper test, and Δ l is about 250mm * (40 ℃) * (10 * 10
-6/ ℃) promptly 10
-1Mm; Single measurement length standard difference for the minimum scale of hand-held strainmeter half promptly 0.5 * 10
-2Mm, because every group got 4 length values, then relative error is
The standard deviation of temperature variation is 0.5 ℃.
Then formula 3 can be expressed as:
From formula 4 as can be seen the error of this measuring method be 3.2%, can satisfy the accuracy requirement of research.
Fig. 2 be temperature be 20 ℃ concrete sample be put in test specimen center, back in 60 ℃ of water temperature over time.As shown in Figure 2, concrete sample is put in 60 ℃ of water behind the 55min, and the temperature of test specimen center is identical with water temperature, illustrates that this moment, the temperature of test specimen diverse location reached balance.So concrete sample can guarantee that test specimen is identical with the temperature of water soak 1.5h fully in water after, the length between two copperheads of measurement is the length under set water temperature.
Embodiment 2
Be 0.42 at the slurry water-cement ratio, flyash replacement amount is that 25%wt, sand coarse aggregate ratio are under the experiment condition of 38%wt, the volume fraction V of slurry is respectively under 20%, 30%, 40% the condition 3 test specimens of each moulding respectively in concrete, after the moulding according to the method for embodiment 1, measure concrete thermal expansivity in the different length of times, test result as shown in Figure 3.Because the thermal expansivity of hardened cement paste is higher than the thermal expansivity of aggregate, so the slurry volume fraction increases, concrete thermal expansivity also increases thereupon.This trend with testing result shown in Figure 3 is consistent.
Embodiment 3
At binder total amount is 400kg/m
3Water-cement ratio is 0.42, sand coarse aggregate ratio is to experimentize under the condition of 38%wt, the massfraction of flyash in slurry is respectively 3 test specimens of each moulding under 0,0.1,0.2,0.3,0.4 the condition, test the thermal expansivity of different doped fly ash concretes behind the standard curing 28d according to the method for embodiment 1, as shown in Figure 4.Under the identical situation of gel material content, along with the increase of doping quantity of fly ash, the porosity of cement stone increases, and causes concrete thermal expansivity to reduce.This trend with testing result shown in Figure 4 is consistent.
This measuring method was both simple as can be seen by embodiment, the measurement result good reproducibility, and also error is also little.
Claims (4)
1. the measuring method of a thermal expansion coefficient of concrete is characterized in that, step is as follows:
The first step, 3 test specimens of every kind of concrete mix moulding, the shape size of test specimen is identical, each test specimen when moulding at parallel pre-buried 4 copperheads in test specimen surface as the end points of measuring length, concrete sample moulding form removal after 1 day, put into standard curing room and carry out maintenance, to predetermined curing age measurement thermal expansivity;
Second step reached when being scheduled to curing age, and earlier concrete sample being put into temperature is T
0Water in soak, half an hour, that the hand-held strainmeter is put into standard curing was indoor before measuring, concrete sample soaks in water 〉=measure the length l (T between corresponding two copperheads on the test specimen surface behind the 1.5h
0) and record;
In the 3rd step, then, concrete sample is moved in the constant temperature water tank that temperature is T behind the immersions 〉=1.5h length l (T) and the record between two corresponding copperheads on the measurement test specimen surface;
The 4th step, at between the same a pair of copperhead on same test specimen surface apart from after measuring several times under each temperature, average as valid data after rejecting undesired data, according to the measurement length between two copperheads of concrete sample surface under the different temperatures, calculate concrete average thermal linear expansion coefficient α according to following formula
L (T) and l (T
0) to be respectively concrete temperature be T and T
0The time test specimen length (mm); Δ l and Δ T concrete length respectively change and temperature variation.
2. the measuring method of thermal expansion coefficient of concrete as claimed in claim 1 is characterized in that, when soaking test specimen, two of parallel placements can the free rolling reinforcing bar in the bottom of test specimen.
3. the measuring method of thermal expansion coefficient of concrete as claimed in claim 1 is characterized in that, when measuring length, adopts foam heat-insulating board to cover the test specimen surface.
4. the measuring method of thermal expansion coefficient of concrete as claimed in claim 3 is characterized in that, the size of foam heat-insulating board is identical with test specimen surface configuration size, leaves two slits in the position of the pre-buried copperhead of test specimen upper surface.
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Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101865865A (en) * | 2010-06-12 | 2010-10-20 | 水利部交通运输部国家能源局南京水利科学研究院 | Noncontact-type test method of early-period thermal expansion coefficient of concrete dam and equipment thereof |
| CN102384927A (en) * | 2011-11-23 | 2012-03-21 | 河海大学 | Measuring device for early-aged cement-based material thermal expansion coefficient under different environmental conditions and measuring method |
| CN103630084A (en) * | 2013-12-11 | 2014-03-12 | 中国建筑第八工程局有限公司 | Integral constrained deformation measuring method under concrete frame structure seasonal temperature difference action |
| CN104280290A (en) * | 2014-09-26 | 2015-01-14 | 同济大学 | Device for testing stress-strain of plastic concrete/mortar and use method of device |
| CN105445318A (en) * | 2015-01-21 | 2016-03-30 | 长沙理工大学 | Temperature expansion testing method of semi-rigid base material of inorganic binding material |
| CN106226348A (en) * | 2016-10-17 | 2016-12-14 | 中国建筑第八工程局有限公司 | A kind of service check method of cement expansive material |
| CN108226216A (en) * | 2016-12-22 | 2018-06-29 | 株式会社三丰 | Linear expansion coefficient determining method and measurement device |
| CN110530916A (en) * | 2019-07-17 | 2019-12-03 | 太原理工大学 | The measuring method of inside concrete thermal stress distribution in a kind of thermal histories |
| CN111122836A (en) * | 2020-01-16 | 2020-05-08 | 中铁第五勘察设计院集团有限公司 | Shrinkage value testing system, die system and shrinkage value testing method |
| CN111462839A (en) * | 2020-04-21 | 2020-07-28 | 浙江水利水电学院 | Multiscale prediction method for thermal expansion coefficient of hardened cement mortar |
| CN111487279A (en) * | 2020-04-22 | 2020-08-04 | 河海大学 | Determination method for early-age thermal expansion coefficient of pervious concrete |
| CN111505046A (en) * | 2020-04-21 | 2020-08-07 | 浙江水利水电学院 | Prediction method of concrete early-age thermal expansion coefficient multi-scale model |
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2009
- 2009-11-27 CN CN200910232704A patent/CN101701924A/en active Pending
Cited By (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101865865A (en) * | 2010-06-12 | 2010-10-20 | 水利部交通运输部国家能源局南京水利科学研究院 | Noncontact-type test method of early-period thermal expansion coefficient of concrete dam and equipment thereof |
| CN101865865B (en) * | 2010-06-12 | 2011-12-28 | 水利部交通运输部国家能源局南京水利科学研究院 | Noncontact-type test method of early-period thermal expansion coefficient of concrete dam and equipment thereof |
| CN102384927A (en) * | 2011-11-23 | 2012-03-21 | 河海大学 | Measuring device for early-aged cement-based material thermal expansion coefficient under different environmental conditions and measuring method |
| CN103630084A (en) * | 2013-12-11 | 2014-03-12 | 中国建筑第八工程局有限公司 | Integral constrained deformation measuring method under concrete frame structure seasonal temperature difference action |
| CN103630084B (en) * | 2013-12-11 | 2017-01-11 | 中国建筑第八工程局有限公司 | Integral constrained deformation measuring method under concrete frame structure seasonal temperature difference action |
| CN104280290A (en) * | 2014-09-26 | 2015-01-14 | 同济大学 | Device for testing stress-strain of plastic concrete/mortar and use method of device |
| CN105445318A (en) * | 2015-01-21 | 2016-03-30 | 长沙理工大学 | Temperature expansion testing method of semi-rigid base material of inorganic binding material |
| CN106226348A (en) * | 2016-10-17 | 2016-12-14 | 中国建筑第八工程局有限公司 | A kind of service check method of cement expansive material |
| CN108226216A (en) * | 2016-12-22 | 2018-06-29 | 株式会社三丰 | Linear expansion coefficient determining method and measurement device |
| CN108226216B (en) * | 2016-12-22 | 2021-11-16 | 株式会社三丰 | Method and apparatus for measuring linear expansion coefficient |
| CN110530916A (en) * | 2019-07-17 | 2019-12-03 | 太原理工大学 | The measuring method of inside concrete thermal stress distribution in a kind of thermal histories |
| CN111122836A (en) * | 2020-01-16 | 2020-05-08 | 中铁第五勘察设计院集团有限公司 | Shrinkage value testing system, die system and shrinkage value testing method |
| CN111462839A (en) * | 2020-04-21 | 2020-07-28 | 浙江水利水电学院 | Multiscale prediction method for thermal expansion coefficient of hardened cement mortar |
| CN111505046A (en) * | 2020-04-21 | 2020-08-07 | 浙江水利水电学院 | Prediction method of concrete early-age thermal expansion coefficient multi-scale model |
| CN111505046B (en) * | 2020-04-21 | 2022-09-16 | 浙江水利水电学院 | Prediction method of concrete early-age thermal expansion coefficient multi-scale model |
| CN111462839B (en) * | 2020-04-21 | 2023-10-13 | 浙江水利水电学院 | Multiscale prediction method for thermal expansion coefficient of hardened cement mortar |
| CN111487279A (en) * | 2020-04-22 | 2020-08-04 | 河海大学 | Determination method for early-age thermal expansion coefficient of pervious concrete |
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