CN101000338A - Method for measuring concrete setting time based on strain time on-line measuring - Google Patents
Method for measuring concrete setting time based on strain time on-line measuring Download PDFInfo
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- CN101000338A CN101000338A CN 200710026217 CN200710026217A CN101000338A CN 101000338 A CN101000338 A CN 101000338A CN 200710026217 CN200710026217 CN 200710026217 CN 200710026217 A CN200710026217 A CN 200710026217A CN 101000338 A CN101000338 A CN 101000338A
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Abstract
A method for measuring setting time of concrete based on on-line measurement of strain temperature includes fixing transducers in concrete template to be measured in advance, setting parameters of said transducers before concrete is poured and carrying out on-line measurement automatically on strain and temperature in solidifying course of concrete to obtain variation curve of general strain to time and variation curve of temperature to time, using the first coincided time point of two said curves as the solidified time of concrete.
Description
Technical field
The present invention relates to civil engineering work, specifically relate to a kind of based on strain temperature on-line measurement cement concrete after cast the situation of solidifying or judge the measuring method whether concrete solidifies.
Background technology
Cement concrete is used in civil engineering work in a large number, concrete is monitored concrete process of setting or is determined concrete setting time, to understanding concrete various performance such as tension pressure and shear resistance, anti-leakage, elastic property etc., accurately measure concrete contraction, creep, it is extremely important to determine whether concrete can carry.Especially be significant for engineering construction control of large-sized concrete structure (bridge etc.) etc., yet in concrete solidification process, owing to changed to high-intensity curing from the state of dissolving by variation of temperature and concrete material, be accompanied by tangible material contracts distortion, so judge whether concrete solidifies or determine concrete setting time, the stand under load situation of xoncrete structure is made analyzed very difficulty accurately.At present concrete solidifying adopted two class method of discrimination, a class is test point, electrical measuring method, and another kind of is parametric method.
The test point method is the concrete presetting period to be defined as the initial set test point be sink to apart from test specimen template bottom surface (4 ± 1) mm; And being defined as the final set test point, concrete final setting time sinks to test specimen 0.5mm.Obvious this definition solidify the concrete flowing property of main reflection, can not ensure concrete intensity, be mainly used in the mensuration in the laboratory.
Electrical measuring method is mainly monitored electrical characteristics such as resistance, electric capacity or the resistivity etc. of concrete at hydration process.According to these electrical measurements over time rule determine concrete setting time.Because electrical measuring method relies on the electron ion motion in the grout, be applicable to the concrete in age early.More than two kinds of methods be suitable for reflection early age concrete specific, the concrete final setting time that records approximately is 4～6 hours.
The parameter measurement method is to infer concrete setting time by measuring concrete material parameters such as concrete bullet mould, intensity or rigidity.Make concrete material in the shortest curing time, material parameter and if long-term the same (more than 98%) under (standard 28 days) curing condition, can think that then this time is exactly concrete setting time.Concrete measuring method can be with the mechanical measurement of material property, ultrasound wave, Fibre Optical Sensor etc.
Said method is owing to exist the definition of different concrete settings, so the concrete setting time of measuring also differs greatly.In addition, existing method generally is difficult to the concrete of construction is carried out the on-line measurement of on-the-spot process of setting.
Summary of the invention
In order to overcome the deficiencies in the prior art, the purpose of this invention is to provide a kind of concrete setting Method Of Time Measurement based on the strain temperature on-line measurement.
Purpose of the present invention is achieved through the following technical solutions:
A kind of concrete setting Method Of Time Measurement based on the strain temperature on-line measurement is characterized in that may further comprise the steps:
(1) buries sensor underground: imbed vibrating string type strain transducer and temperature sensor in measured inside in advance, vibrating string type strain transducer is connected data acquisition device with temperature sensor with the water conservancy project lead at concrete component;
(2) measure automatically: set the sampling time parameter of surveying instrument before concrete begins to pour into a mould, and start measurement automatically, at concrete process of setting on-line measurement is carried out in strain and temperature, measuring intervals of TIME was less than 30 minutes;
(3) determine the concrete setting time: strain and the temperature data gathered are handled, obtained the time dependent curve d of the overall strain amount ε of detected concrete
VtThe temperature variation of/dt～t (rate of strain that vibrating wire sensor is measured) and detected concrete is change curve α in time
cD (Δ T)/dt～t (concrete thermal expansion rate of strain), first time point that two curves overlap is concrete setting time; Wherein, α
cRepresent concrete thermal expansivity, ε
CtThe overall strain amount of expression detected concrete, the t express time, T represents temperature.
The burial place of described vibrating string type strain transducer and temperature sensor surpasses 15cm apart from the concrete surface degree of depth.
Described step (2) is carried out on-line measurement at concrete process of setting to strain and temperature, and measuring intervals of TIME is less than 30 minutes being according to the overall strain amount of detected concrete change curve d ε in time
VtThe temperature variation of/dt～t and detected concrete is change curve α in time
cD (Δ T)/dt～t rendering request and deciding, in theory, the time is short more good more, considers actual demands of engineering, and getting 30 minutes also is to meet the demands fully, preferred 10 minutes/time of measuring intervals of TIME of the present invention.
The concrete derivation of setting time is as follows:
1. vibrating string type sensor strain measurement principle
Vibrating string type sensor is a vibrating string type strain transducer, and its measuring principle is to utilize the sinusoidal excited frequency and the relation of vibratory string tension force: for the vibratory string of given length, when vibratory string was subjected to tension variation, the excited frequency of vibratory string also can change.By giving the vibratory string exciting, measure the excited frequency of vibratory string and just can instead release the current suffered stretch-draw of vibratory string.When the sensor completion of processing, and behind the given reference state, for any state, can obtain Tension Difference with the vibratory string of reference state, thereby ask strain under this state relative reference state by Hooke's law by the measurement of vibratory string frequency.Usually, the strain measurement that vibratory string is measured can be written as:
Wherein: ε
v: the measurement strain of vibratory string; F: the frequency of vibratory string; P: the tension force of vibratory string
2. the correction of temperature variation generation
Suppose to have temperature variation simultaneously, if vibratory string can free thermal expansion (contraction), obviously the measurement strain stress of temperature variation offset of sinusoidal in measuring process
vDo not have influence influence in other words to ignore.But vibrating string type sensor obviously can not free expansion in the sensing process, and it must change along with the distortion of measured body, if the thermal expansivity of body and vibratory string not simultaneously, therefore vibratory string will measure and the additional strain that produces.Then actual body is because of being subjected to the strain stress of power stretching (or compression)
hFor:
ε
h＝ε
v-ΔT(α
h-α
v) (2)
Wherein: α
h, α
vIt is respectively the thermal expansivity of measured body and vibratory string; Δ T is the change amount of temperature.
This moment vibratory string overall strain ε
VtEqual the overall strain ε of body
Ht(comprising the thermal expansion strain) and be:
ε
vt＝ε
v+ΔTα
v＝ε
ht＝ε
h+ΔTα
h (3)
Usually vibrating wire sensor fixes two ends and protection by a steel sleeve.Any measurement body links to each other if the vibrating wire sensor of band steel sleeve is got along well or its distortion is not subjected to the constraint of body, then when temperature variation, and the strain stress that vibratory string is measured
vBe exactly that vibratory string and steel sleeve thermal expansion cause.Then steel sleeve is subjected to the strain stress of stretching (or compression)
s, be written as by formula (2):
ε
s＝ε
v-ΔT(α
s-α
v) (4)
Wherein: α
sIt is the thermal expansivity of steel sleeve.At this moment, the vibratory string overall strain equals the overall strain ε of steel sleeve
St, get by formula (3):
ε
vt＝ε
v+ΔTα
v＝ε
st＝ε
s+ΔTα
s (5)
3. the measurement mechanism analysis of concrete setting process
If sinusoidal sensor is imbedded in the concrete component, and suppose that concrete is in complete curdled appearance, then concrete rigidity is greater than the rigidity of vibratory string steel sleeve, and concrete is because of being subjected to the strain stress of power stretching (or compression) in measuring process
c, can be written as by formula (2):
ε
c＝ε
v-ΔT(α
c-α
v) (6)
Wherein: α
cIt is concrete thermal expansivity.The vibratory string overall strain equals concrete overall strain ε
Ct, and by (3):
ε
vt＝ε
v+ΔTα
v＝ε
ct＝ε
c+ΔTα
c (7)
But for concrete from the state of dissolving to solidifying fully because the change and the variation of temperature of phase are arranged, vibrating wire sensor is measured the implication more complicated of strain representative.Just pour into a mould the initial stage at concrete, concrete is in the state of dissolving, be that concrete rigidity can be assumed to be zero, but concrete temperature begins progressively to raise, at this moment vibratory string overall strain (relatively before the concrete depositing) equals the strain of steel sleeve, and the strain of steel sleeve is only caused by thermal expansion, promptly has:
ε
vt＝ε
v+ΔTα
v＝ε
st＝ΔTα
s (8)
But as time passes, concrete progressively solidifies, the no longer free thermal expansion of steel sleeve, formula (8) is false gradually, to the concrete full solidification, then formula (8) is false fully, and formula (7) begins to play a leading role, but the strain in the formula (7) is that at this moment steel sleeve has had initial strain ε because of thermal expansion causes the relative concrete of vibratory string before the relative concrete depositing
0, concrete strain simultaneously also only is because temperature variation produces, and promptly has:
ε
vt＝ε
v+ΔTα
v＝ε
ct+ε
0＝ε
0+ΔTα
c (9)
Because for each process of setting, ε
0Be time-independent.Therefore can get the time differentiate respectively formula (8), (9):
Between the firm casting cycle of concrete, formula (10) is set up, and after the concrete setting, formula (11) is set up.Therefore,, can record the temperature of concrete setting process if when vibrating wire sensor is measured strain, just can be in the hope of three curve d ε
Vt/ dt～t, α
sD (Δ T)/dt～t and α
cD (Δ T)/dt～t is then by curve d ε
Vt/ dt～t and α
cConcrete setting time t can be measured or define to first point that d (Δ T)/dt～t begins to overlap continuously
Cr
Compared with prior art, the invention has the beneficial effects as follows:
(1) directly reflects concrete rigidity, begin to overlap,, just mean the rigidity of concrete rigidity greater than steel sleeve so the result that vibratory string is measured obeys concrete rate of strain because concrete thermal expansion rate of strain and vibratory string are measured rate of strain;
(2) can carry out on-line monitoring to large-scale concrete engineering.
Description of drawings
Fig. 1 is the temperature situation of change in time of 2G cross section concrete placement among the embodiment 1;
Fig. 2 is the situation of change in time of the overall strain amount after the smooth treatment among the embodiment 1;
Fig. 3 is a 2G cross section strain transducer rate curve among the embodiment 1;
Fig. 4 is a 3G cross section strain transducer rate curve in the embodiment of the invention 2;
Fig. 5 is a 4G cross section strain transducer rate curve in the inventive embodiments 3;
Fig. 6 is a 5G cross section strain transducer rate curve in the inventive embodiments 4.
Embodiment
Below in conjunction with embodiment and accompanying drawing the present invention is further described, but the scope of protection of present invention is not limited to the scope that embodiment represents.
A kind of concrete setting Method Of Time Measurement based on the strain temperature on-line measurement may further comprise the steps:
(1) buries sensor underground: imbed vibrating string type strain transducer and temperature sensor in measured inside in advance, vibrating string type strain transducer is connected data acquisition device with temperature sensor with the water conservancy project lead at concrete component; The burial place of vibrating string type strain transducer and temperature sensor surpasses 15cm apart from the concrete surface degree of depth.
(2) automatically measure: the parameters such as sampling time 10min, monitoring sensor that before concrete begins to pour into a mould, set surveying instrument, and startup is measured automatically, at concrete process of setting on-line measurement is carried out in strain and temperature, measuring intervals of TIME was less than 30 minutes;
(3) determine the concrete setting time: strain and the temperature data gathered are handled, obtained the time dependent relation curve d of the overall strain amount ε of detected concrete
VtThe time dependent curve α of the temperature variation of/dt～t and detected concrete
cD (Δ T)/dt～t, first time point that two curves overlap is concrete setting time; Wherein, α
cBe concrete thermal expansivity, ε
CtBe the overall strain amount of detected concrete, the t express time, T represents temperature.
Embodiment 1:
Be numbered the JMZX-215AT type flush type temperature strain meter of imbedding gold sign indicating number high-tech company, Changsha on the 2G sections at Xijiang River bridge, the burial place of vibrating string type strain transducer and temperature sensor is 20cm apart from the concrete surface degree of depth.Automatic data acquisition system (ADAS) also adopts the JMZX-32 vibratory string acquisition module of the said firm, and this module can be measured strain and temperature simultaneously, at concrete process of setting on-line measurement is carried out in strain and temperature, and measuring intervals of TIME is 10 minutes/time.Fig. 1 is the temperature variations figure of concrete placement, as shown in the figure, temperature survey is rational as can be seen from this figure, temperature has a jump after concrete depositing, and this is that it is higher than environment temperature (evening in winter) because the concrete initial temperature is water temperature substantially, along with concrete aquation produces heat, temperature progressively raises, and finishes concrete in aquation and progressively solidifies, and temperature progressively reduces again; Fig. 2 is the overall strain amount situation of change in time after the smooth treatment,---the thermal expansion strain of the overall strain of sensor measurement, steel sleeve---the thermal expansion strain of steel sleeve, concrete---solid concrete that three curves are respectively among the figure: vibratory string.The variation tendency of these three curves and variation of temperature trend are similar, but the details difference, and different amplitudes constantly are all different, but as can be seen in the variation tendency of later stage vibratory string with concrete the same substantially, be poor constant.Can be by smooth treatment so that temperature curve because of measuring discontinuous that disturbance produces, oscillatory occurences occurs when avoiding asking rate of strain; Fig. 3 is a 2G cross section strain transducer rate curve among the embodiment 1, as shown in Figure 3, really begin to have overlapped through sinusoidal rate of strain and the concrete thermal expansion strain that records behind the certain hour, therefore from overlap starting point (round dot the figure) can in the hope of, concrete setting time is 27 hours.
Embodiment 2:
Be numbered measurement on the 3G sections at Xijiang River bridge, measuring method is with embodiment 1.Measurement result as shown in Figure 4, the feature of example 1 demonstration---sinusoidal rate of strain that records and concrete thermal expansion strain begin to overlap really behind the certain hour, and it is 31.8 hours that same coincidence starting point by them can obtain concrete setting time as can be seen from this figure.Measuring equipment and process conditions are with embodiment 1.
Embodiment 3:
Be numbered measurement on the 4G sections at Xijiang River bridge, measuring intervals of TIME is 30 minutes/time; Other measuring methods are with embodiment 1.Measurement result as shown in Figure 5, measurement result has the same characteristics of embodiment 1; Recording concrete setting time is 29.2 hours.Measuring equipment and process conditions are with embodiment 1.
Embodiment 4:
Be numbered measurement on the 5G sections at Xijiang River bridge, measuring method is with embodiment 1, measurement result as shown in Figure 6, measurement result has the same characteristics of embodiment 1; The setting time that records is 28.7 hours.Measuring equipment and process conditions are with embodiment 1.
The measurement result of embodiment 1～4 as seen, the concrete time that utilization this method is measured approximately is between 27～31 hours, such in-site measurement presentation of results the present invention can measure the concrete setting time effectively, measurement result is reliable.Measurement concrete setting time method of the present invention had both been considered the index of concrete flowability also reasonably to have comprised concrete rigidity index, was a kind of method of reasonably determining concrete setting.
Claims (3)
1, a kind of concrete setting Method Of Time Measurement based on the strain temperature on-line measurement is characterized in that may further comprise the steps:
(1) buries sensor underground: imbed vibrating string type strain transducer and temperature sensor in measured inside in advance, vibrating string type strain transducer is connected data acquisition device with temperature sensor with the water conservancy project lead at concrete component;
(2) measure automatically: set the sampling time parameter of surveying instrument before concrete begins to pour into a mould, and start measurement automatically, at concrete process of setting on-line measurement is carried out in strain and temperature, measuring intervals of TIME was less than 30 minutes;
(3) determine the concrete setting time: strain and the temperature data gathered are handled, and the overall strain amount that obtains detected concrete is change curve d ε in time
VtThe temperature variation of/dt～t and detected concrete is change curve α in time
cD (Δ T)/dt～t, first time point that two curves overlap is concrete setting time; Wherein, α
cRepresent concrete thermal expansivity, ε
CtThe overall strain amount of expression detected concrete, the t express time, T represents temperature.
2, measuring method according to claim 1 is characterized in that, the burial place of described vibrating string type strain transducer and temperature sensor surpasses 15cm apart from the concrete surface degree of depth.
3, measuring method according to claim 1 is characterized in that, the measuring intervals of TIME of described step (2) is 10 minutes/time.
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| CN102323396A (en) * | 2011-06-27 | 2012-01-18 | 中国建筑第二工程局有限公司 | Solid simulation test device for mass concrete and test construction method thereof |
| CN102590483B (en) * | 2011-12-29 | 2015-12-16 | 江苏苏博特新材料股份有限公司 | The method of testing of setting time of cement-based material |
| CN102590483A (en) * | 2011-12-29 | 2012-07-18 | 江苏博特新材料有限公司 | Testing method for setting time of cement-based material |
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| WO2013097172A1 (en) * | 2011-12-30 | 2013-07-04 | 江苏博特新材料有限公司 | Method for testing setting time of cement-based material |
| CN103913560A (en) * | 2013-01-05 | 2014-07-09 | 中交武汉港湾工程设计研究院有限公司 | Real-time monitoring system of condensing state of concrete and real-time monitoring method |
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| CN104155432A (en) * | 2014-08-07 | 2014-11-19 | 福建江夏学院 | Intelligent measuring method for setting time of cement-based material |
| CN104155432B (en) * | 2014-08-07 | 2015-10-28 | 福建江夏学院 | Setting time of cement-based material intelligence assay method |
| CN104807982A (en) * | 2015-04-08 | 2015-07-29 | 天津大学 | Method for determining final setting time of concrete based on strain sensors |
| CN104807982B (en) * | 2015-04-08 | 2019-06-04 | 天津大学 | A kind of concrete final setting time based on strain transducer determines method |
| CN110757645A (en) * | 2018-07-27 | 2020-02-07 | 北新集团建材股份有限公司 | Detection method and control method for hydration process of gypsum slurry |
| CN109297865A (en) * | 2018-10-09 | 2019-02-01 | 山西省交通科学研究院 | A kind of measuring method of the early age structural stress of Cement Concrete Pavement Slab |
| CN109297865B (en) * | 2018-10-09 | 2021-03-23 | 山西省交通科学研究院 | Method for measuring early-age structural stress of cement concrete pavement slab |
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| CN114199647A (en) * | 2021-12-13 | 2022-03-18 | 四川大学 | Rock mass in-situ stress curing method and curing system |
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