CN108828198A - Early concrete crack-induced test device - Google Patents
Early concrete crack-induced test device Download PDFInfo
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- CN108828198A CN108828198A CN201810599286.8A CN201810599286A CN108828198A CN 108828198 A CN108828198 A CN 108828198A CN 201810599286 A CN201810599286 A CN 201810599286A CN 108828198 A CN108828198 A CN 108828198A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/38—Concrete; ceramics; glass; bricks
- G01N33/383—Concrete, cement
Abstract
The present invention provides a kind of early concrete crack-induced test device, including：One piece of rectangle steel substrate, the six-edged steel column at bottom plate both ends, concave character type steel side template, several cuboid blocks and the cuboid block with the edge of a knife.It is fluted along longitudinal direction in the middle part of bottom plate, for placing cuboid block and the cuboid block with the edge of a knife.Spacing, quantity and the blade angle between cuboid block on bottom plate between six-edged steel column and with the edge of a knife can be adjusted freely, and the cuboid block with the edge of a knife is also adjustable to react influence of the different constraint types to concrete cracking at a distance from concrete sample upper surface.The optical fiber grating temperature and strain transducer different from traditional resistor foil gauge can be longitudinally arranged when test between concrete upper surface and the edge of a knife, measurement accuracy high stability accurately can completely monitor well the contraction after concreting, temperature deformation and cracking situation.
Description
Technical field
The present invention relates to the test device of early-age concrete restrained shrinkage cracking and the sides of inducing concrete cracking
Method.
Background technique
With the development of the times and social progress, the civil constructions demands such as Super High, large span, labyrinth form
To the properties of concrete material, more stringent requirements are proposed.Therefore, the high-strength high property of various admixtures and additive is mixed
Energy concrete comes into being.But researcher and construction personnel's discovery, high-strength high-performance concrete are split being more prone to produce in early days
Seam, has seriously affected the durability of structure.Concrete cracking is mainly due to inside concrete or the moist gradient and temperature on surface
Spending gradient, constantly variation causes distortional stress in hydration process, and when influence that stress suffers restraints can be in concrete structure office
Portion generates stress and concentrates, and when the development of distortional stress is more than the development of tensile strength, just leads to concrete structure early crack
Generation.Simultaneously because nowadays the cement fineness increase in concrete material, the ratio of mud are lower, microfine mineral admixture
Using so that structure has stronger cracking sensitivity.There is expert to point out that the later concrete that cracks, infiltration coefficient can improve
Several grades.So in order to avoid or reduce Practical Project in concrete cracking phenomena, early period the crack resistance to concrete
Can be carried out evaluation is just particularly important.
For the method for test concrete early age shrinkage cracking, various countries have no unified standard.Concrete is limiting at present
Under the conditions of the test method of cracking performance be broadly divided into flat band method, ring method and prism method.These test methods can be from calmly
Property aspect the cracking trend and rule of concrete material in structural engineering are evaluated, predict the excellent of its cracking resistance
It is bad, specific evaluation index can also be quantified, although can solve certain problems respectively still has deficiency, there is very big office
It is sex-limited.Prism method is the promising approach currently used for evaluating concrete early stage restrained shrinkage cracking performance, but testing equipment
Cost is higher, stringent to the sensitivity requirement of instrument, and is not convenient for testing at the scene.Ring method is most widely used, letter
It is single easy to operate, but cracking sensitivity is poor and crack generation is irregular.Flat band method is the user recommended in China's specification
Method, but the generation in crack still has deficiency in terms of the quantization in crack and observation also than more random.
Concrete cracking induction device according to the present invention not only substantially can control position and the quantity of crack generation
It can also accurately observe the size of concrete shrinkage and temperature deformation, increase to test specimen gap observation and the accurate of assessment of cracking
Property.Test method is simple and effective, easy to operate.
Summary of the invention
The present invention provides a kind of easy to operate, and institute's measured data is accurate, and the early stage that can be convenient to construction site field survey is mixed
Solidifying soil cracking induction experiment device and method.Constraint is applied simultaneously to test piece end and bottom, and constraint type is adjustable,
The distribution situation in more than qualitatively observation test specimen crack its strain can generate rule with quantitative analysis.
Early concrete crack-induced test device, which is characterized in that including：One piece of rectangle steel substrate (1), steel column
(9), four pieces of concave character type steel side templates, bolt (6), cuboid block (13), the cuboid block (8) with the edge of a knife, grating strain
Sensor (10), grating temperature sensor (14), optical fiber (11), (FBG) demodulator (12).Early concrete crack-induced test dress
It is set to I-shaped, intermediate elongated, both ends local wide and all devices are steel.Four pieces of side templates each other and with
It is connected by bolt (6) between bottom plate (1).The centre of bottom plate (1) is provided with groove (7), and is disposed at bottom plate (1) both ends
It constrains steel column (9), height, the height of side template of steel column (9) are consistent with the height of concrete sample.In bottom plate (1)
Cuboid block (13) and the cuboid block (8) with the edge of a knife can be placed at portion's groove (7).Cuboid block (13) and have knife
Cuboid block (8) length direction of mouth is identical as groove (7) length direction, cuboid block (13) and the cuboid with the edge of a knife
Block (8) width direction is identical as the opening width of groove (7).Different height can be placed at bottom plate (1) central slot (7)
Cuboid block (13).Placing height and groove at the groove (7) at cuboid block (8) of the arrangement with the edge of a knife are not being needed
(7) identical and equal with the upper surface of bottom plate (1) the cuboid block (13) of height；It is rectangular with the edge of a knife needing to arrange
At groove (7) at body block (8), the cuboid block of different height can be placed below the cuboid block (8) with the edge of a knife
(13).Height h according to placed cuboid block (13) in groove (7) is different, and cuboid block (8) distance with the edge of a knife is mixed
The spacing of solidifying soil test specimen upper surface is adjusted to different height forms and then reacts the degree of its inducing concrete test specimen cracking；
Bottom plate (1) both ends are equipped with steel column (9) it acts as end restraint is provided to concrete, and bottom plate (1) central slot (7) is for putting
The cuboid block (8) with the edge of a knife is set to provide the upper table of middle part constraint or placing height and bottom plate (1) to concrete
The equal cuboid block (13) in face is with the effect to concrete without induced cracking.
Before concreting, placing height at the groove (7) at cuboid block (8) of the arrangement with the edge of a knife is not being needed
Cuboid block (13) identical as the height of groove (7) and equal with the upper surface of bottom plate (1)；The edge of a knife is had needing to arrange
Cuboid block (8) at groove (7) at, pass through with the edge of a knife cuboid block (8) below place different height length
The edge of a knife of cuboid block (8) of cube block (13) adjustment with the edge of a knife is at a distance from concrete sample upper surface.Then by four pieces
After the completion of side template is assembled, smear mineral grease in die trial bottom and inside, guarantee concrete sample in addition to by steel column (9) and
Edge of a knife constraint is outer, and bottom plate (1) and side template do not limit the contraction distortion of test specimen.Above casting concrete to the edge of a knife with side form
Plate top surface suspends at half height to be poured, and will place soft transparent sebific duct in concrete surface after its vibration compacting
(15).The optical fiber for being welded with grating strain transducer (10) and grating temperature sensor (14) is penetrated in advance in sebific duct (15)
(11).Optical fiber (11) is longitudinally arranged along test specimen, is chosen away from test specimen apical side height according to test demand, substantially in the edge of a knife
With concrete sample top surface at one third to half height.It is extremely concordant with side template to continue casting concrete, to
After concrete vibrating is closely knit, sebific duct (15) are extracted.It slightly vibrates and is supported after striking off surface of test piece with trowel in upper paving plastic film
Shield removes side template and concrete sample is put into the observation and calculating for carrying out crack under experimental condition to required age.Passing through will
Data in (FBG) demodulator (12) import observation test specimen in computer and are embedded with the strain value at sensor position, pass through gap observation
Instrument reads fracture width.
Angle at the top of cuboid block (8) with the edge of a knife between angle [alpha], that is, two inclined-plane of edge of a knife vertex junction of the edge of a knife
It can be different size, the rule in crack is generated by its inducing concrete test specimen of the reaction of different sizes of blade angle.Simultaneously
The quantity and spacing of cuboid block (8) with the edge of a knife also can freely adjust, and further reacting it influences concrete sample cracking
The case where.
Bottom plate (1) both ends of the present invention are steel column (9) and are provided with groove (7) among bottom.
Side template (2) of the present invention, (3), (4), (5) are four pieces of concave character type steel side templates.
Height, side template (2), (3), (4), the height of (5) of steel column (9) of the present invention are consistent with the height of test specimen.
Several grooves (7) are evenly arranged in the middle part of bottom plate (1) of the present invention.
Steel column (9) of the present invention is equilateral hexagonal prisms, and side length, quantity and spacing arrangement are freely adjustable, and then react it
To the size of concrete sample degree of restraint.
Cuboid block (13) length direction placed at bottom plate (1) central slot (7) of the present invention and groove (7) length side
To identical, cuboid block (13) width direction is identical as the opening width of groove (7).
The height selection gist test demand of cuboid block (13) of the present invention is chosen.Arrangement is not being needed with the edge of a knife
Placing height is identical as the height of groove (7) and equal with the upper surface of bottom plate (1) at groove (7) at cuboid block (8)
Cuboid block (13)；It is needing to arrange at the groove (7) at the cuboid block (8) with the edge of a knife, it can be in the length for having the edge of a knife
The cuboid block (13) of different height is placed below cube block (8).
The present invention is different according to the height h of placed cuboid block (13) in groove (7), the cuboid block with the edge of a knife
(8) spacing apart from concrete sample upper surface is adjustable for different height forms and then to react the examination of its inducing concrete
The degree of part cracking.
Angle [alpha] of the present invention with the edge of a knife at the top of the cuboid block (8) of the edge of a knife is (between two inclined-plane of edge of a knife vertex junction
Angle) can be different size, pass through its inducing concrete test specimen of the reaction of different sizes of blade angle generate crack rule
Rule.It also can freely adjust simultaneous with the quantity and spacing of the cuboid block (8) of the edge of a knife, further reacting it influences concrete
The case where test specimen cracks.
Bottom plate (1) both ends of the present invention are used to provide end restraint, bottom plate (1) central slot to concrete equipped with steel column (9)
(7) it is used to place the cuboid block (8) with the edge of a knife to provide middle part constraint or placing height and bottom plate to concrete
(1) the equal cuboid block (13) in upper surface is with the effect to concrete without induced cracking.
The different arrangements and band that the present invention passes through the quantity and spacing of steel column (9) and the cuboid block (8) with the edge of a knife
There is the angle of the edge of a knife of the cuboid block (8) of the edge of a knife to choose the influence of reacting it to concrete cracking, break previous constraint and
The randomness that the fixed induced fractures of knife-edge positions generate.
Contraction distortion is early, and shrinkage stress is small, and the generation in crack is substantially in the edge of a knife in view of concrete early stage generates by the present invention
Top occurs along the arranged direction of the edge of a knife, so being longitudinally arranged optical fiber light between concrete sample upper surface and the edge of a knife
Grid strain transducer (10).There is one two between the concrete sample upper surface and the edge of a knife of flat tests device in specification
The distance of centimetre.Optical fiber (11) is longitudinally arranged along test specimen, is chosen away from test specimen apical side height according to test demand, substantially in knife
Mouth is with concrete sample top surface at half height.The arrangement height and grating strain of grating temperature sensor (14)
Sensor (10) unanimously, but does not need to be arranged in above the edge of a knife of the pane (8) with the edge of a knife.
The present invention is become using (FBG) demodulator (12) acquisition grating temperature sensor (14) and grating strain transducer (10) center
The wavelength value of change connect the contraction that can monitor test specimen, temperature variations with computer by USB interface.
The present invention by using area of cracks total on values of shrinkage strain correction factor and concrete unit area product pair
The cracking resistance of concrete is evaluated.
Detailed description of the invention
Fig. 1 is the device of the invention bottom plate perspective view
Fig. 2 is the perspective view of the device of the invention bottom plate and four side templates composition
Fig. 3 is the device of the invention bottom plate, four side templates, cuboid block and the cuboid block composition with the edge of a knife
Perspective view
Fig. 4 is the perspective view of cuboid and the cuboid block with the edge of a knife of the invention
Fig. 5 is the cross-sectional view of cuboid and the cuboid block with the edge of a knife of the invention
Fig. 6 is overall schematic of the invention
Specific embodiment
Cuboid block (13) and the cuboid block (8) with the edge of a knife, bottom are placed at steel substrate (1) central slot (7)
Steel column (9) on plate (1), cuboid block (8) its spacing quantity with the edge of a knife etc. difference arrangement according to test demand and
Design needs to be determined.
(2), (3), (4), (5) four pieces of concave character type steel side templates are connected on steel substrate (1) by bolt (6),
Fixation is attached also by bolt (6) between four pieces of side templates
Before concreting, mineral grease is smeared on the inside of die trial bottom (1) and side form (2), (3), (4), (5), is guaranteed
For concrete sample other than being constrained by steel column (9) and the edge of a knife, bottom plate (1) and side template (2), (3), (4), (5) do not limit coagulation
The contraction distortion of soil.
Influence in view of the temperature rise of concrete early hydration to test specimen shrinkage cracking, when test pass optical fiber grating temperature
Sensor (14) and strain transducer (10) are buried simultaneously, to monitor test specimen internal temperature rise curve, assess the size of its temperature deformation
To carry out temperature-compensating to test specimen contraction distortion.
Grating temperature sensor (14) and grating strain transducer (10) are welded on optical fiber (11), to prevent temperature
Sensor (14) and strain transducer sensor (10) bending change position and damage, and optical fiber (11) is penetrated transparent hose
(15) in, optical fiber (11) is impaired when preventing casting concrete while can be with the position of observation sensor.And in transparent hose
(15) pipe is outer smears lubricant, in order to subsequent extraction.
The position and quantity of fiber Bragg grating strain sensor (10) have the length of the edge of a knife according to bottom plate recess place strap
Depending on the quantity of cube fast (8) and position.Short transverse is arranged in the top of knife-edge positions and with test specimen top surface at a distance of certain
At distance, 2-4 fiber Bragg grating strain sensor (10) is arranged above each edge of a knife.
Fiber grating temperature sensor (14) test specimen center arrangement several, short transverse and above-mentioned strain transducer
(10) position is identical.
Optical fiber (11) described above is longitudinally arranged along test specimen, is chosen away from test specimen apical side height according to test demand,
Substantially in the edge of a knife and concrete sample top surface at half height.
Influence in view of variation of ambient temperature to measurement result also needs one optical fiber grating temperature of arrangement in the environment
Sensor (14), to monitor the variation of environment temperature at any time.
Fiber-optic grating sensor (14), (10) are different from traditional resistor foil gauge, without just being glued after concrete initial set
Patch measurement.So measurement accuracy is high and stability accurately can completely monitor that well the contraction after concreting, temperature become
Shape and cracking situation, and about 1.5h can be firmly combined with concrete.When the grating (14) and (10) being embedded in concrete by
When being influenced to concrete shrinkage and temperature change, the axial strain of fiber Bragg grating strain sensor (14) and grating temperature sensing
The temperature strain of device (10), which will change, to be eventually led to the wavelength of grating (14) and (10) center and changes.
(FBG) demodulator (12) is connected to detect the wavelength of grating (14), (10) center with fiber-optic grating sensor (14), (10)
Variation.It is connect between (FBG) demodulator (12) and computer by data collecting card, is carried out by online observation and is deposited for data with computer
It stores up, the strain value of concrete is calculated by acquisition software observation at sensor (14), (10).
Pre- mixed concrete is poured between in a mold at away from top surface design height, is about tried in the edge of a knife and concrete
Between part at half height, then vibrated until laitance occurs in concrete surface up and down using artificial.
The arrangement of inside concrete sensor：It is longitudinally put into according to design position with grating temperature in concrete surface
Sensor (14), grating strain transducer (10), optical fiber (11) transparent hose (15).Stretch out the optical fiber of sebific duct (15) one end
(11) clamp end with wooden clamp (16), sebific duct (15) other end can slightly pull optical fiber (11) make its it is exceptionally straight do not move,
Keep temperature sensor (14) and strain transducer sensor (10) fixed by adjusting the position of wood clamp (16) fiber clamping (11)
In pre-designed position.
Pour remaining part concrete to side template (2), (3), (4), (5) either flush, it is artificial after the completion of pouring on
Lower vibration compacting is until laitance occurs in concrete surface.Surface layer's concrete paved with trowel closely knit, then sebific duct (15) are slow
Slow extraction, then beaing die trial keeps concrete and fiber-optic grating sensor (14), (10) bonding intact, synchronous deformation.
Slightly vibrating after striking off surface of test piece with trowel, paving plastic film was conserved to required age in upper surface, removed side
Behind template (2), (3), (4), (5), concrete sample is put into the observation and calculating that crack is carried out under experimental condition.Passing through will
Data in (FBG) demodulator (12) import observation test specimen in computer and are embedded with the strain value at sensor position, pass through gap observation
Instrument reads fracture width, and fracture length is measured with vernier caliper,
Crack takes broken line to be added the final lengths of crack thus when not being straight line.
Data processing：Concrete sample initial cracking time is observed, according to each period crack situation (quantity, length, width
Degree) calculate total cracking face of average area of cracks, cracking the crack number and unit area of maximum cracking width, unit area
The values of shrinkage strain and temperature deformation value of long-pending and corresponding time.Contraction strain and cracking state joint are got up overall merit
The cracking resistance of test specimen and crack generate the relationship between rule and contraction strain.
The present invention provide example 1 embody the experimental rig edge of a knife at a distance from concrete sample upper surface difference to coagulation
The influence of native cracking behaviors simultaneously provides specific cracking evaluation parameter.
Crack-induced test device is using device shown in abstract of the invention in example 1, on the edge of a knife and concrete sample
The distance on surface is divided into two kinds of situations of 20mm and 35mm and is tested respectively, and the opening angle of the edge of a knife is selected as 74 degree.
Simultaneously in order to consider influence of the interior curing agent to concrete cracking situation, test cooperation is such as shown in table 1.Wherein
S-A indicates that the volume of interior curing agent (high hydroscopic resin) is 0, and it is cement that S-L-B, S-L-C, which respectively indicate interior curing agent volume,
0.05% and 0.2%.
1 concrete cracking of table tests match ratio Kg/m3
Mix and stir requirement：Before concreting, coarse-fine aggregate and cement is poured into carry out dry mixing in concrete mixer first
30s is again stirring for 100s to mixing water is added after mixing.Then the lightweight aggregate that pre-suction water process is added stirs 60s,
It merges interior curing agent with other materials uniformly, the step is omitted when not adding interior curing agent.Finally concrete mix is poured
It builds in crack-induced test device shown in Fig. 1.
Pre- mixed concrete is poured between in a mold to away from being vibrated up and down to concrete after at the 10mm of top surface using artificial
When laitance occurs in surface, the transparent hose of optical fiber grating temperature and strain transducer is had according to abovementioned steps insertion, is poured surplus
Lower part concrete to side template either flush.Sebific duct is slowly extracted out again after manually slightly vibrating up and down after the completion of pouring.
It is dried after specimen molding with electric fan, wind direction is parallel to surface of test piece, wind speed 4m/s-5m/s, the contraction to test specimen
Value and crack developing situation are observed.
Test result is as shown in table 2, wherein：
Number 1 indicates that the test edge of a knife is 20mm at a distance from concrete sample upper surface, and the volume of interior curing agent is 0 in material
Number 2 indicates that the test edge of a knife is 20mm at a distance from concrete sample upper surface, and the volume of interior curing agent is in material
0.05%
Number 3 indicates that the test edge of a knife is 20mm at a distance from concrete sample upper surface, and the volume of interior curing agent is in material
0.2%
Number 4 indicates that the test edge of a knife is 35mm at a distance from concrete sample upper surface, and the volume of interior curing agent is 0 in material
Number 5 indicates that the test edge of a knife is 35mm at a distance from concrete sample upper surface, and the volume of interior curing agent is in material
0.05%
Number 6 indicates that the test edge of a knife is 35mm at a distance from concrete sample upper surface, and the volume of interior curing agent is in material
0.2%
2 concrete cracking test result of table
Test display crack location mainly near above the edge of a knife, illustrates that the edge of a knife can obvious inducing concrete cracking.
It can be seen from Table 2 that：1 test specimen initial cracking time of number is earliest, and maximum crack width is maximum.
Compared with 1 test specimen of number, total area of cracks reduces respectively on 2 test specimen of number and 4 test specimen unit area of number
18.53% and 12.71%, maximum crack width reduce respectively 26.03% and 28.77%, values of shrinkage strain reduce respectively
28.65% and 43.58%.
Compared with 2 test specimen of number, total area of cracks reduces 30.5% respectively on 3 test specimen of number and 5 test specimen unit area of number
With 22.63%, maximum crack width reduce respectively 33.33% and 20.37%, values of shrinkage strain reduce 47.56% respectively
With 53.28%.
With the increase of interior conserving material volume and the edge of a knife at a distance from concrete sample upper surface, crack quantity, width
Degree, total area of cracks are substantially reduced phenomenon.
Crack-resistant performance of concrete deliberated index：By using on values of shrinkage strain correction factor and concrete unit area
The product of total area of cracks evaluates the crack resistance of concrete.Correction factor is denoted as K, total area of cracks on unit area
It is denoted as A.
As values of shrinkage strain ε < 50, adjusted coefficient K takes 1
When values of shrinkage strain 50≤ε < 100, adjusted coefficient K takes 0.95
When values of shrinkage strain 100≤ε < 150, adjusted coefficient K takes 0.9
When values of shrinkage strain 150≤ε < 200, adjusted coefficient K takes 0.85
As values of shrinkage strain ε >=200, adjusted coefficient K takes 0.8
I grade of crack resistance：KA≥400
II grade of crack resistance：300≤KA < 400
III grade of crack resistance：200≤KA < 300
IV grade of crack resistance：100≤KA < 200
V grade of crack resistance：KA < 100.
Claims (6)
1. early concrete crack-induced test device, which is characterized in that including：One piece of rectangle steel substrate (1), steel column (9),
Four pieces of concave character type steel side templates, bolt, cuboid block (13), the cuboid block (8) with the edge of a knife, grating strain transducer
(10), grating temperature sensor (14), optical fiber (11), (FBG) demodulator (12)；
The early concrete crack-induced test device is I-shaped, intermediate elongated, both ends local wide and all devices are
Steel；It is bolted between four pieces of side templates and bottom plate (1)；
The centre of bottom plate (1) is provided with groove (7), and is disposed with constraint steel column (9), the height of steel column (9), side form at bottom plate both ends
The height of plate is consistent with the height of concrete sample；
Cuboid block (13) or/and the cuboid block (8) with the edge of a knife are placed at bottom plate (1) central slot (7)；
Cuboid block (13) and cuboid block (8) length direction with the edge of a knife are identical as groove (7) length direction；Cuboid block
(13) cuboid block (8) width direction and with the edge of a knife is identical as the opening width of groove (7)；
The cuboid block (13) that different height can be placed at bottom plate (1) central slot (7) is not needing arrangement with the edge of a knife
Placing height is identical as the height of groove (7) and equal with the upper surface of bottom plate (1) at groove (7) at cuboid block (8)
Cuboid block (13)；It is needing to arrange at the groove (7) at the cuboid block (8) with the edge of a knife, in the cuboid for having the edge of a knife
The cuboid block (13) of different height is placed below block (8) or only places the cuboid block (8) for having the edge of a knife；
Height according to placed cuboid block (13) in groove (7) is different, and the cuboid block (8) with the edge of a knife is apart from concrete
The spacing of test specimen upper surface is adjusted to different height forms and then reacts the degree of its inducing concrete test specimen cracking；
Bottom plate (1) both ends are equipped with steel column (9) to provide end restraint to concrete, and bottom plate (1) central slot (7) is for placing band
There is the cuboid block (8) of the edge of a knife to provide middle part constraint to concrete；The either upper surface of only placing height and bottom plate (1)
Equal cuboid block (13) is with the effect to concrete without induced cracking.
2. the apparatus according to claim 1, which is characterized in that the angle [alpha] of the edge of a knife at the top of the cuboid block (8) with the edge of a knife
Angle i.e. between two inclined-plane of edge of a knife vertex junction can be different size, pass through its induction of the reaction of different sizes of blade angle
The rule in concrete sample generation crack；It can freely be adjusted simultaneous with the quantity and spacing of the cuboid block (8) of the edge of a knife, into one
The case where its influence concrete sample cracking of step reaction.
3. the apparatus according to claim 1, which is characterized in that steel column (9) be equilateral hexagonal prisms, side length, quantity and
Away from can freely adjust, and then react its size to concrete sample degree of restraint.
4. the apparatus according to claim 1, which is characterized in that grating strain transducer (10) is arranged in the length with the edge of a knife
Above the edge of a knife of cube block (8) between concrete sample upper surface；The arrangement height and grating of grating temperature sensor (14)
Strain transducer (10) is consistent.
5. the test method of application such as claim 1-4 any one described device, it is characterized in that：
Before concreting, placing height and groove at the groove (7) at cuboid block (8) of the arrangement with the edge of a knife are not being needed
(7) identical and equal with the upper surface of bottom plate (1) the cuboid block (13) of height；It is needing to arrange the cuboid with the edge of a knife
At groove (7) at block (8), by the cuboid block for placing different height below the cuboid block (8) with the edge of a knife
(13) edge of a knife of cuboid block (8) of the adjustment with the edge of a knife is at a distance from concrete sample upper surface；
Then by after the completion of four pieces of side templates assembly, mineral grease is smeared in die trial bottom and inside, guarantees that concrete sample removes
Constrained by steel column (9) and the edge of a knife outer, bottom plate (1) and side template do not limit the contraction distortion of test specimen；By grating strain transducer
(10), grating temperature sensor (14) is welded on optical fiber (11), is then penetrated in soft transparent sebific duct (15)；It is pouring
Pause pours at concrete one third to half height, will place soft transparent in concrete surface after its vibration compacting
Sebific duct (15)；It is extremely concordant with side template to continue casting concrete, is extracted after concrete vibrating is closely knit, then by round tube (15)；Slightly
Add vibrate strike off surface of test piece with trowel after conserve in upper paving plastic film to required age, remove side template for concrete sample
It is put into the observation and calculating that crack is carried out under experimental condition；It is tried by importing to observe in computer by the data in (FBG) demodulator (12)
Part is embedded with the strain value at sensor position, reads fracture width by crack observer.
6. method according to claim 5, it is characterized in that：According to the edge of a knife in the middle part of bottom plate (1) and concrete sample upper surface
Distance difference, the quantity of the edge of a knife different, quantity of bottom plate (1) end steel column (9) and side length differential responses test dress with angle
The influence to concrete cracking behavior is set, the randomness of previous constraint and the fixed induced fractures generation of knife-edge positions is broken；And it gives
Specific cracking evaluation parameter out, multiplies by using values of shrinkage strain correction factor and total area of cracks on concrete unit area
Product evaluates the cracking resistance of concrete.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810599286.8A CN108828198B (en) | 2018-06-12 | 2018-06-12 | Early concrete crack induction testing device |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810599286.8A CN108828198B (en) | 2018-06-12 | 2018-06-12 | Early concrete crack induction testing device |
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| Publication Number | Publication Date |
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| CN108828198A true CN108828198A (en) | 2018-11-16 |
| CN108828198B CN108828198B (en) | 2021-08-20 |
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