CN109856374A - A kind of concrete self-shrinkage test method - Google Patents

A kind of concrete self-shrinkage test method Download PDF

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Publication number
CN109856374A
CN109856374A CN201811600444.3A CN201811600444A CN109856374A CN 109856374 A CN109856374 A CN 109856374A CN 201811600444 A CN201811600444 A CN 201811600444A CN 109856374 A CN109856374 A CN 109856374A
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test
concrete
self
shrinkage
humidity
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CN109856374B (en
Inventor
郑新国
程冠之
郁培云
蒋睿
谢永江
刘竞
李书明
曾志
董全霄
李世达
杨德军
刘相会
潘永健
谢清清
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China Academy of Railway Sciences Corp Ltd CARS
Railway Engineering Research Institute of CARS
China State Railway Group Co Ltd
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China Academy of Railway Sciences Corp Ltd CARS
Railway Engineering Research Institute of CARS
China Railway Corp
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Abstract

The present invention relates to a kind of concrete self-shrinkage test methods, belong to concrete shrinkage deformation measuring technology.It covers moisturizing and curing membrane, and the demoulding after final set immediately after concreting, pastes test copper sheet, it is put into hygrometer, environmental sealing is carried out using moisturizing and curing membrane, is fixed on shrinks on testing jig vertically, long mode is vertically surveyed using contact method and tests contraction, records humidity and shrinkage value.The present invention substitutes traditional plastic foil using moisturizing and curing membrane and is sealed to test specimen, can exclude dry effect of contraction caused by plastics membrane permeability, maintain humidity in film, accurately test the self-shrinking value of different concrete.

Description

A kind of concrete self-shrinkage test method
Technical field
The present invention relates to a kind of concrete self-shrinkage test method and materials, belong to concrete shrinkage deformation measuring technology.
Background technique
Contraction after concrete coagulation hardening mainly includes chemical shrinkage, self-constriction and dry contraction.Chemical shrinkage refers to The reduction of solid and liquid absolute volume in the slurry due to caused by hydrated cementitious.Self-constriction refers to that hydrated cementitious causes self-desiccation Caused contraction.It is dry to shrink the contraction for referring to that concrete generates in nonsaturated air because outwardly scattering and disappearing moisture.Wherein, Since chemical shrinkage can be compensated by the formation of microscopic void, so not being embodied in macroscopical cubic deformation of concrete all On, macro manifestations are known as self-constriction.
Due to self-constriction phenomenon in high-strength concrete, self-compacting concrete and mass concrete highly significant, even It will cause the concrete cracking under the conditions of thermostatted water is supported, therefore application of the self-constriction of accurate test concrete to concrete is instructed It is of great significance.For the accurate test of self-constriction, it is critical to exclude the influence of following factors: (1) humidity of ambient atmosphere Intrusion and evaporation;(2) lifting of temperature;(3) stress caused by external loads or limiter.Domestic traditional self-constriction is surveyed at present Method for testing is to be sealed after the concrete is cured with plastic film, is placed in isoperibol and is tested.And it is tested about self-constriction The research of method, which focuses primarily upon, to be excluded stress interference and tests since pouring.Chinese patent (publication number: CN 202182880 U) a kind of self-contraction determinator is disclosed, it by concreting into die trial, and is sealed with plastic film, finally Be placed in 20 ± 2 DEG C of environment test concrete since pouring to the self-constriction of any age.Chinese patent (publication number: CN 102590485 B) a kind of frame concrete shrinkage test device is disclosed, it eliminates template and the stress of concrete is interfered. These test methods are all made of plastic film seal to exclude the interference of humidity variation, but plastic film seal is limited, interior humidity It is difficult to ensure, just inevitably generates dry shrink when concrete is in environment of the relative humidity lower than 100%.Therefore it surveys The self-constriction data obtained are bigger than normal, not can accurately reflect the self-constriction of concrete.
Summary of the invention
In view of the deficiency of current test method and material property, the present invention changes test method using new material Into the influence of dry contraction can be excluded by devising one kind, the method for self-constriction after accurate test concrete final set.This method letter It is single, easy to operate, without the device of complex and expensive, it can accurately test the self-shrinking value of different concrete.
The technical solution adopted by the present invention is that: a kind of concrete self-shrinkage test method, using moisturizing and curing membrane as close The self-constriction of closure material test concrete.
The curing film is by gas-impermeable plastics film surface layer, microporous permeable Breathable nonwoven bottom and water storage high molecular material Middle layer composition.
Concrete surface air humidity can be maintained 95% or more under close-fitting state by the curing film.
Comprise the steps of: 1) formation of concrete test specimen, every three are one group;2) pre- in forming surface covering immediately after forming The curing film first sprinkled water;3) humidity sensor is pasted in demoulding after final set in the middle part of test specimen, copper is pasted in test specimen one end middle position Piece;4) using the curing film environmental sealing test specimen sprinkled water in advance, keep curing film closely connected with concrete sample;5) test specimen is posted into copper One end of piece upward, is fixed on the contraction testing jig equipped with amesdial vertically;6) test specimen is placed in temperature is 20 DEG C ± 2 DEG C, It is conserved in the environment of relative humidity 60% ± 5%;7) periodic logging humidity sensor reading and amesdial reading.
The concrete sample having a size of 100mm*100mm*400mm, the copper sheet be thickness 1mm ~ 2mm, side length 20mm ~ The square of 40mm, the hygrometer range are 0 ~ 100%RH, resolution ratio 0.1%RH, and the amesdial precision is ± 0.001mm.
The amount that the curing film is sprinkled water in advance before wrapping up test specimen is 80 ~ 180g/m2
Routine observation humidity data and situation is pasted, when humidity is lower than 95%, timely moisturizing and again is carried out to curing film It carries out and closely pastes.
Amesdial numerical value is periodically read, when the deviation of the test value of one group of three test specimen and average value is respectively less than 15%, is taken The average value of three test values is as test result;When one of test specimen test value and average value deviation be greater than 15%, and When other two test value difference is less than 15%, take the average value of other two value as test result;Otherwise it retests.
The present invention has the advantages that the macromolecule water storage material in curing film can be such that water is unlikely to when absorbing suitable quantity of water Flowing discharges water to test specimen, and can compensate the permeability of plastic film, maintains humidity >=95% in film.This method is simple, Device easy to operate, without complex and expensive;Compared to conventional plastic film seal, this method can compensate plastic foil water vapor permeability and System humidity caused by hydrated cementitious reduces, maintenance system interior humidity, excludes dry effect of contraction;Difference can accurately be tested Concrete is from final set to the self-shrinking value of each age.
Specific embodiment
It by the feature that the present invention will be described in detail and can achieve the effect that, elaborated below with reference to embodiment.
Embodiment 1
C30 concrete mix:
1 C30 concrete mix (unit g/m of table3)
Cement Flyash Sand Stone (5 ~ 10mm) Stone (10 ~ 20mm) Water Water-reducing agent Air entraining agent
288 72 716 467.2 700.8 155 1.8 0.4
According to 1 match ratio of table, concrete is mixed and stirred to the die trial for being packed into 100*100*400mm, the preparatory watering 100g/ of covering immediately m2Curing film, the demoulding after final set pastes the copper sheet of 30*30mm in concrete one end immediately.Then test specimen three are divided into One group, using preparatory watering 100g/m2Water-saving moist keeping maintenance film package, and be put into hygrometer, expose copper sheet, lap-joint's glue Band sealing.Upward by test specimen copper sheet finally, be fixed on the contraction testing jig equipped with amesdial vertically, be placed in temperature be 20 DEG C ± 2 DEG C, in the fog room of relative humidity 60% ± 5%.
Periodic logging humidity reads amesdial and reads, and continuous 28 days, and calculate shrinkage value.It the results are shown in Table 2 and table 3;
2 test specimen interior humidity record sheet of table
3 test specimen of table shrinks record sheet
Age/d 1 3 7 14 28
Shrink microstrain 0.00 -4.17 -13.67 -20.83 -25.00
From the data of table 2 it can be seen that water-saving moist keeping maintenance film moisturizing has good stability;
Can be seen that C30 concrete 28d age self-constriction microstrain from the data of table 3 is -25.00.
Embodiment 2
C50 concrete mix:
4 C50 concrete mix (unit g/m of table3)
Cement Flyash Miberal powder Sand Stone (5 ~ 10mm) Stone (10 ~ 20mm) Water Water-reducing agent
363 48.5 72 704 422 633 155 2.5
According to 4 match ratio of table, concrete is mixed and stirred to the die trial for being packed into 100*100*400mm, the preparatory watering 100g/ of covering immediately m2Curing film, blank control group plastic covering film;The demoulding after final set pastes the copper of 30*30mm in concrete one end immediately Piece.Then it is divided into one group for test specimen three, experimental group is using watering 100g/m in advance2Water-saving moist keeping maintenance film package, and put Enter hygrometer, exposes copper sheet, lap-joint's rubber belt sealing;Blank control group is not handled.Upward by two groups of test specimen copper sheets finally, it erects It is directly fixed on the contraction testing jig equipped with amesdial, being placed in temperature is 20 DEG C ± 2 DEG C, the fog room of relative humidity 60% ± 5% In.
Periodic logging humidity reads amesdial and reads, and continuous 28 days, and calculate shrinkage value.It the results are shown in Table 5 and table 6;
5 test specimen interior humidity record sheet of table
6 test specimen of table shrinks record sheet
From the data of table 5 it can be seen that water-saving moist keeping maintenance film can guarantee the saturated humidity in experimental group.
The total contraction microstrain that can be seen that concrete 28d age from the data of table 6 is -358.33, self-constriction microstrain It is the 22.09% of the total shrinkage value of -79.17, Zhan.
Comparative example
C50 concrete mix:
7 C50 concrete mix (unit g/m of table3)
Cement Flyash Miberal powder Sand Stone (5 ~ 10mm) Stone (10 ~ 20mm) Water Water-reducing agent
363 48.5 72 704 422 633 155 2.5
According to 7 match ratio of table, concrete is mixed and stirred to the die trial for being packed into 100*100*400mm, test group is equal with blank control group Plastic covering film immediately;The demoulding after final set pastes the copper sheet of 30*30mm in concrete one end immediately.Then by test specimen three It is divided into one group, experimental group uses plastic film wrapped, and is put into hygrometer, exposes copper sheet, lap-joint's rubber belt sealing;Blank control Group is not handled.Upward by two groups of test specimen copper sheets finally, it is fixed on the contraction testing jig equipped with amesdial vertically, being placed in temperature is 20 DEG C ± 2 DEG C, in the fog room of relative humidity 60% ± 5%.
Periodic logging humidity reads amesdial and reads, and continuous 28 days, and calculate shrinkage value.It the results are shown in Table 8 and table 9;
8 test specimen interior humidity record sheet of table
9 test specimen of table shrinks record sheet
From the data of table 8 it can be seen that the experimental group interior humidity of plastic film wrapped is declining always in 28d curing period, coagulation Native local environment humidity and not up to saturated humidity;
The self-constriction microstrain for using plastic film seal to measure be can be seen that from the data of table 9 as the total shrinkage value of -258.33, Zhan 72.09%, self-shrinking value is obviously bigger than normal.

Claims (8)

1. a kind of concrete self-shrinkage test method, which is characterized in that test coagulation as sealing material using moisturizing and curing membrane The self-constriction of soil.
2. a kind of concrete self-shrinkage test method according to claim 1, it is characterised in that: the curing film is by impermeable Gas plastic film surface layer, microporous permeable Breathable nonwoven bottom and water storage high molecular material middle layer composition.
3. a kind of concrete self-shrinkage test method according to claim 1, it is characterised in that: the curing film is closely connected Concrete surface air humidity can be maintained 95% or more under state.
4. a kind of concrete self-shrinkage test method according to claim 1, it is characterised in that comprise the steps of: 1) at Type concrete sample, every three are one group;2) curing film sprinkled water in advance is covered in forming surface immediately after forming;3) it is torn open after final set Mould pastes humidity sensor in the middle part of test specimen, copper sheet is pasted in test specimen one end middle position;4) using the curing film packet sprinkled water in advance Sealed test piece is wrapped up in, keeps curing film closely connected with concrete sample;5) one end that test specimen is posted copper sheet upward, is fixed on is equipped with vertically On the contraction testing jig of amesdial;6) test specimen is placed in temperature is 20 DEG C ± 2 DEG C, is conserved in the environment of relative humidity 60% ± 5%; 7) periodic logging humidity sensor reading and amesdial reading.
5. a kind of concrete self-shrinkage test method according to claim 4, it is characterised in that: the concrete sample ruler Very little is 100mm*100mm*400mm, and the copper sheet is the square of thickness 1mm ~ 2mm, side length 20mm ~ 40mm, the hygrometer range For 0 ~ 100%RH, resolution ratio 0.1%RH, the amesdial precision is ± 0.001mm.
6. a kind of concrete self-shrinkage test method according to claim 4, it is characterised in that: the curing film is wrapping up The amount sprinkled water in advance before test specimen is 80 ~ 180g/m2
7. a kind of concrete self-shrinkage test method according to claim 4, it is characterised in that: routine observation humidity data With paste situation, when humidity is lower than 95%, curing film is carried out timely moisturizing and carried out again closely to paste.
8. a kind of concrete self-shrinkage test method according to claim 4, it is characterised in that: periodically read amesdial number Value takes the average value of three test values as surveying when the deviation of the test value of one group of three test specimen and average value is respectively less than 15% Test result;When one of test specimen test value and average value deviation be greater than 15%, and other two test value difference be less than When 15%, take the average value of other two value as test result;Otherwise it retests.
CN201811600444.3A 2018-12-26 2018-12-26 Concrete self-shrinkage test method Active CN109856374B (en)

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