CN103712855B - A kind of method of testing of concrete creep - Google Patents
A kind of method of testing of concrete creep Download PDFInfo
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- CN103712855B CN103712855B CN201310441890.5A CN201310441890A CN103712855B CN 103712855 B CN103712855 B CN 103712855B CN 201310441890 A CN201310441890 A CN 201310441890A CN 103712855 B CN103712855 B CN 103712855B
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Abstract
The method of testing of a kind of concrete creep, application small spring Creep Apparatus loads concrete sample, and its creep degree exists good dependency: use omnipotent pressure testing machine to load test specimen；The foil gauge pasted by test specimen coordinates the size of monitoring imposed load with static resistance deformeter；Spring compresses unit upper plate Place half pad of creeping, be forced into control load of creeping 20% carries out prestrain and centering, unload after load should be added to after test specimen centering Creep Stress, the deformation difference at test specimen four sides should be less than the l0% of its meansigma methods, formal loading, the deformation difference at four sides should be less than the l0% of its meansigma methods, and mean strain is less than 1% with the last phase difference of loading, after be loaded onto control load；Loading procedure should control within 2 hours, and constant temperature and humidity inserted by number by test specimen after loading indoor, carries out Continuous Observation.The present invention save fund, add carried convenient, be prevented effectively from test specimen unbalance loading, dead load ability strong, without mend carry mobile flexibly.
Description
Present disclosure relates to a kind of method of testing crept.
The loading system of background technology compression creep test is generally divided into four kinds: lever, spring, spring
Lever and fluid pressure type.Spring compression creep mechanism because its floor space is little, volume is little, loading convenient with
And the advantage such as reliable operation becomes the loading system that China's application is most, can be divided into by tension column number difference
Single pole, double-rod and three rod-types, general loading scope is at below 30t, and because concrete creep causes with contraction
Relative displacement load is reduced, need often to adjust load.Its weak point: loading tonnage is not
The bulky complex of foot and constant voltage means makes to use spring compression Creep Apparatus to carry out test the most in a large number and is limited
System, waste money, load inconvenience, mobile complicated, to take shelf space big.
Summary of the invention it is an object of the invention to provide a kind of saving fund, adds carried convenient, is prevented effectively from examination
Part unbalance loading, dead load ability are strong, without mending the method for testing carrying a kind of mobile concrete creep.
The research method of the present invention realizes according to the following steps:
(1) application small spring Creep Apparatus loads 40mm × 40mm that the coarse aggregate of 5～16mm particle diameters makes
× 160mm concrete sample, its creep degree and the 100mm using the coarse aggregate of 5～25mm particle diameters to make
There is good dependency in the creep degree of × 100mm × 400mm test specimen；
(2) use 40mm × 40mm that the coarse aggregate of 5～16mm particle diameters makes by omnipotent pressure testing machine ×
160mm concrete sample loads；
(3) the foil gauge pasted by test specimen coordinates the size of monitoring imposed load with static resistance deformeter；
(4) spring compresses unit upper plate Place half pad of creeping, and is first forced into the 20% of control load of creeping and carries out
Prestrain and centering, unload after load should add to after test specimen centering Creep Stress, now the change at test specimen four sides
Shape difference should be less than the 10% of its meansigma methods, as beyond this scope, should readjust；
The most formally loading, through loaded cycle for several times, finally will once load, the deformation difference at four sides should be less than
The 10% of its meansigma methods, mean strain and the last phase difference that loads less than 1%, after be loaded onto control load；
(6) loading procedure should control within 2 hours, because of moisture evaporation and temperature during preventing test specimen from loading
Degree change is on the impact produced of creeping；
(7) constant temperature and humidity indoor inserted by number by test specimen after loading, and carry out Continuous Observation according to predetermined age.
The present invention save fund, add carried convenient, be prevented effectively from test specimen unbalance loading, dead load ability is strong, carry without mending
Mobile flexible.
Accompanying drawing explanation
Fig. 1 spring compresses the structural representation of mechanism of creeping；
With the creep degree correlation curve of aggregate different size test specimen under Fig. 2 difference doping quantity of fly ash；
With the creep degree correlation curve of size difference aggregate test specimen under Fig. 3 difference doping quantity of fly ash.
Detailed description of the invention
In the schematic diagram of the present invention shown in Fig. 1, Fig. 2 and Fig. 3, spring compresses mechanism of creeping and mainly wraps
Include: nut, spring washer, upper backup pad, column, middle gripper shoe, spring and lower supporting plate.Wherein,
Fixing connection four root posts 2 on this lower supporting plate 1, a piece spring 3 of outer socket, every two phases on every root post
The lower end line successively of adjacent spring, constitutes square, and the upper end of this spring is provided with middle gripper shoe 4, middle gripper shoe
The position of corresponding column is provided with through hole, and this column is through the through hole of middle gripper shoe, and middle gripper shoe is located at above-mentioned bullet
The upper end of spring.Test specimen is laid in middle gripper shoe upper end, and test specimen is arranged above with upper backup pad 5, and upper backup pad correspondence is stood
The position of post is provided with through hole, and the upper end of above-mentioned column is provided with screw thread, and this end of thread passes perpendicularly through upper backup pad
Four through holes, are provided with internal diameter spring shim slightly greater than it 6 on the top of this through hole, this pad is provided with
The nut 7 that above-mentioned column screw thread is corresponding.
Embodiment 1
The raw material of the present invention uses the portland cement of P II 42.5 of shallow wild cement plant production, Suizhong thermoelectricity
Stand factory produce I grade of flyash, its chemical composition, loss on ignition and specific surface area are as shown in table 1；Fine aggregate is adopted
Being 2.8 with modulus of fineness, apparent density is 2650kg/m3Natural river sand.Creep and test Plays prism
The coarse aggregate grain size that test specimen uses is different from little prism test specimen, have employed the aggregate of two kinds of different gradation: little
Test specimen uses particle diameter 5～16mm continuous grading crushed stone lime stone；Big test specimen uses continuous grading crushed stone lime stone,
Part particle diameter is 5～16mm, and part particle diameter is 5～25mm.Water reducer is naphthalene water reducer, and water-reducing rate is
21%.
Table 1 cement and the chemical composition of flyash, loss on ignition, specific surface area
The present invention takes fixing concrete sand coarse aggregate ratio, binder total amount and water-cement ratio, replaces with flyash equivalent
Cement, is prepared as the technique study dimensional effect of test specimen of the different size concrete Ying Ying to concrete creep
Ring.In mix Design, sand coarse aggregate ratio is fixed as 38%, and water-cement ratio is 0.45, benchmark group concrete water
Mud consumption is 390kg/m3, flyash replaces cement, application by the mass fraction equivalent of 0%, 30%, 60%
Water reducer adjusts the slump of concrete in the range of 90～110mm.Each content fly ash test specimen concrete
Coordinate when sample dimensions as shown in table 2.
Table 2 concrete mix
When test specimen loads, the little prism test specimen of a size of 40mm × 40mm × 160mm uses small spring
Formula Creep Apparatus loads, and the standard prism test specimen of a size of 100mm × 100mm × 400mm uses state
Spring Creep Apparatus in family's specification loads, loading stress level 33%.At (20 ± 1) DEG C, relative humidity it is
In the environment of (60 ± 5) %, application resistance strain gauge test concrete shrinkage and time deformation.
Hereinafter the data for the present invention process: comparing the identical grating aggregate size of employing is 40mm × 40
The little concrete sample of mm × 160mm and big test specimen each age of a size of 100mm × 100mm × 400mm
The creep degree of phase, with creep degree correlation curve such as Fig. 2 of aggregate different size test specimen under different doping quantity of fly ash
Shown in.
From figure 2 it can be seen that under different doping quantity of fly ash, the basic phase of creep degree curve of big small specimen
Symbol, the creep degree of small specimen is slightly larger than big test specimen, loads the later stage, and both creep degree curves are steady, difference
Maintain certain level.
The size relatively using the coarse aggregate of 5～16mm particle diameters to make is 100mm × 100mm × 400mm examination
Part creep degree with under the conditions of the creeping of same size test specimen each age that make of the coarse aggregate of 5～25mm particle diameters
Degree, often group test specimen is classified according to the difference of doping quantity of fly ash.With size difference under different doping quantity of fly ash
The creep degree correlation curve of aggregate test specimen is as shown in Figure 3.
As seen from Figure 3, under different doping quantity of fly ash, the basic phase of creep degree curve of different aggregate test specimens
Symbol, the creep degree of little aggregate test specimen is slightly larger than big aggregate test specimen, loads the later stage, and both creep degree curves are put down
Surely, difference maintains certain level.
The most each test specimen creep degree has good dependency.Therefore to use 5～16mm
The limestone of continuous grading, on the basis of the test specimen of a size of 100mm × 100mm × 400mm, it is different
The creep degree of age is as unit 1, with the test specimen of a size of 40mm × 40mm × 160mm and a size of
100mm × 100mm × 400mm, uses the test specimen creep degree of 5～16mm continuous grading limestone to compare
Relatively, processing through data, the creep degree statistical result of each age is as shown in table 3.
As seen from Table 3, load the proportionate relationship between the creep degree of three kinds of test specimens of later stage gradually stable, take
Often the meansigma methods of group last 4 numerical value of test specimen Relative creep degree carries out being calculated the phase of different test specimen creep degree
Close coefficient.
(1) prism with match ratio concrete sample a size of 40mm × 40mm × 160mm and chi are calculated
Very little for the correlation coefficient between the prism creep degree of 100mm × 100mm × 400mm:
Variation correlation coefficient k=(1.036+1.050+1.049+1.046)/4=1.045 when doping quantity of fly ash is 0%；
When doping quantity of fly ash is 30%, correlation coefficient k=(1.087+1.049+1.062+1.064)/4=1.066；
When doping quantity of fly ash is 60%, correlation coefficient k=(1.022+0.997+1.009+1.020)/4=1.012.
Three correlation coefficienies are averaged and are obtained same match ratio concrete 40mm × 40mm × 160mm test specimen
Creep degree be the correlation coefficient of 100mm × 100mm × 400mm test specimen creep degree be k=1.04.
Tri-kinds of different sizes of table 3-2, the creep degree contrast of different aggregate test specimens
(2) calculate 5-16mm coarse aggregate make 100mm × 100mm × 400mm test specimen creep degree with
Under the conditions of Tong 5-25mm coarse aggregate make test specimen creep degree between correlation coefficient:
Creep degree correlation coefficient k=(0.933+0.926+0.927+0.900)/4=0.922 when doping quantity of fly ash is 0%；
When doping quantity of fly ash is 30%, correlation coefficient k=(0.918+0.920+0.917+0.910)/4=0.916；
When doping quantity of fly ash is 60%, correlation coefficient k=(0.989+0.926+0.922+0.933)/4=0.943.
The creep degree correlation coefficient of three kinds of doping quantity of fly ash is averaged and is obtained what 5～16mm coarse aggregates made
100mm × 100mm × 400mm test specimen creep degree with under the conditions of 5～25mm coarse aggregates make test specimen Xu
Correlation coefficient between variation is k=0.93.
(3) according to the creep degree correlation coefficient obtained in (1) and (2), it can be deduced that use 5～16mm particle diameters
The creep degree of 40mm × 40mm × 160mm test specimen that coarse aggregate makes and the thick bone using 5～25mm particle diameters
Correlation coefficient between 100mm × 100mm × 400mm test specimen creep degree that material makes is k=1.12.
Loading system holds lotus capacity calculation, and the present invention uses spring to compress mechanism of creeping, and coefficient of elasticity is 0.6-1
KN/mm, elastic limit are 4 steel spring composition groups of springs of 10kN, concrete sample a size of 40
Mm × 40mm × 160mm, Mei Tai mechanism loads a test specimen.According to conventional experimental result, it is assumed that spring
Coefficient of elasticity is 1kN/mm, and the contraction strain taking concrete is 300 × 10-6, creep degree is 30 × 10-6/ MPa,
It is that 30kN calculates according to loaded load, can draw:
Groups of springs initial deformation is: Xs=F/K=30/4=7.5mm；
In formula, Xs is that groups of springs deforms (mm)；F is load (kN)；K is groups of springs coefficient of elasticity (kN/mm)
After concrete loading due to contraction and the deformation produced of creeping it is:
Xc=Xsh+Xcr=L0(εsh+εcrσ)
=160 × [400 × 10-6+50×10-6×25×103/ (40 × 40)]=0.138 (mm)
X in formulac(mm) is deformed for concrete sample；XshThe deformation (mm) caused for contraction；XcrFor
Creep the deformation (mm) caused；L0For concrete sample length (mm)；εshFor contraction strain；εcrFor
Concrete creep degree (10-6/MPa)；σ is the stress (MPa) of concrete sample
Shrink and the load reduction degree produced of creeping is 1.84%, less than 2%, experimentation carries without mending.
If remembering the contraction of test specimen in advance and creeping higher than the numerical value set in this example, coefficient of elasticity can be selected less
Groups of springs, generally, all disclosure satisfy that test specimen is not required in loading 1 year mend the requirement carried.
Claims (1)
1. the method for testing of a concrete creep, it is characterised in that:
(1) application small spring Creep Apparatus loads 40mm × 40mm that the coarse aggregate of 5～16mm particle diameters makes
× 160mm concrete sample, its creep degree and the 100mm using the coarse aggregate of 5～25mm particle diameters to make
There is good dependency in the creep degree of × 100mm × 400mm test specimen；
(2) use 40mm × 40mm that the coarse aggregate of 5～16mm particle diameters makes by omnipotent pressure testing machine ×
160mm concrete sample loads；
(3) the foil gauge pasted by test specimen coordinates the size of monitoring imposed load with static resistance deformeter；
(4) spring compresses unit upper plate Place half pad of creeping, and is first forced into the 20% of control load of creeping and carries out
Prestrain and centering, unload after load should add to after test specimen centering Creep Stress, now the change at test specimen four sides
Shape difference should be less than the 10% of its meansigma methods, as beyond this scope, should readjust；
The most formally loading, through loaded cycle for several times, finally will once load, the deformation difference at four sides should be less than
The 10% of its meansigma methods, mean strain and the last phase difference that loads less than 1%, after be loaded onto control load；
(6) loading procedure should control within 2 hours, because of moisture evaporation and temperature during preventing test specimen from loading
Degree change is on the impact produced of creeping；
(7) constant temperature and humidity indoor inserted by number by test specimen after loading, and carry out Continuous Observation according to predetermined age.
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| CN108692834B (en) * | 2018-06-11 | 2020-01-21 | 河海大学 | Be used for verifying concrete stress test device under internal load effect |
| CN111721627B (en) * | 2020-06-11 | 2021-04-02 | 燕山大学 | Device and testing method for ultra-early tensile creep of cement-based material |
| CN113295527B (en) * | 2021-05-24 | 2022-12-09 | 燕山大学 | Device for measuring stress relaxation of fiber reinforced composite bar and measuring method thereof |
| CN113533025B (en) * | 2021-07-22 | 2022-12-20 | 燕山大学 | Loading device for durability test of concrete member and measuring method thereof |
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| CN201034921Y (en) * | 2007-04-27 | 2008-03-12 | 同济大学 | Concrete in compression slowly changing experiment tester |
| CN102235952A (en) * | 2010-04-30 | 2011-11-09 | 长江水利委员会长江科学院 | Concrete creep testing system |
| CN103063515A (en) * | 2012-12-20 | 2013-04-24 | 清华大学 | Tensile creep test device for cement-based materials |
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| JP3955247B2 (en) * | 2002-08-30 | 2007-08-08 | 嘉昭 佐藤 | Concrete shrinkage cracking test equipment |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN201034921Y (en) * | 2007-04-27 | 2008-03-12 | 同济大学 | Concrete in compression slowly changing experiment tester |
| CN102235952A (en) * | 2010-04-30 | 2011-11-09 | 长江水利委员会长江科学院 | Concrete creep testing system |
| CN103063515A (en) * | 2012-12-20 | 2013-04-24 | 清华大学 | Tensile creep test device for cement-based materials |
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| 磨细矿渣和粉煤灰对高性能砼徐变性能的影响;赵庆新 等;《武汉理工大学学报》;20051130;第27卷(第11期);第35-38页 * |
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