CN105759017A - Device and method for evaluating anti-crack performance of external squares and internal circles of cement-based materials - Google Patents
Device and method for evaluating anti-crack performance of external squares and internal circles of cement-based materials Download PDFInfo
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- CN105759017A CN105759017A CN201610240940.7A CN201610240940A CN105759017A CN 105759017 A CN105759017 A CN 105759017A CN 201610240940 A CN201610240940 A CN 201610240940A CN 105759017 A CN105759017 A CN 105759017A
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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 invention discloses a device and a method for evaluating the anti-crack performance of external squares and internal circles of cement-based materials.The device comprises forms and strain acquisition systems.The forms comprise square bottom plates, eccentric cylindrical inner rings are arranged in the bottom plates, and strain gauges which are connected with the strain acquisition systems are arranged on the inner walls of the inner rings; detachable borders are arranged at the edges of the bottom plates.The method includes steps of determining the maximum aggregate particle sizes and designing the forms; pouring the cement-based materials into the forms and arranging the forms under identical temperature and humidity conditions; stripping the forms, adhering the strain gauges on the inner walls of the inner rings, connecting the strain gauges with the strain acquisition systems and measuring strain sudden change moments; measuring the widths of crack of test pieces in specified time; comparing the crack time and the widths of the crack of various groups of materials and determining that the materials with the long crack time and the small widths of the crack are materials with good anti-crack performance.The device and the method have the advantage that problem of long test periods and unsuitability for observing crack of existing methods for evaluating the anti-crack performance can be solved by the aid of the device and the method.
Description
Technical field
The present invention relates to construction material performance evaluation, particularly to a kind of cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus and evaluation methodology.
Background technology
Since commonly using pumping commodity pig cement-based material, the crack of cement-based material structure is increasingly severe, especially early crack.The contraction of cement-based material is its build-in attribute, when cement-based material is owing to shrinking the deformation produced more than its ultimate value, may result in material cracks.According to studies have reported that, the crack caused due to cement-based material contraction distortion accounts for the 80% of total crack.Therefore, the anti-cracking performance evaluating cement-based material becomes the important indicator evaluating cement-based material performance.
Considering cost and the difficulty of evaluation methodology, the cement-based material anti-cracking performance evaluation methodology being currently mainly used mainly has two kinds: flat band method and ring method.Flat band method is mainly used in evaluating the cracking that causes due to hydration reaction of cement-based material, actual with engineering does not correspond；Ring method can evaluate the cracking that cement-based material causes due to hydration reaction and dry dehydration simultaneously, but its there is test period length, crack location is uncertain causes crack to observe the problems such as difficulty, have impact on it and promote the use of.
Therefore, a kind of new cement-based material anti-cracking performance evaluating apparatus and evaluation methodology are needed at present badly so that it is when meeting engineering reality, the test period can be shortened and facilitate crack to observe.
Summary of the invention
It is an object of the invention to overcome deficiency of the prior art, it is provided that a kind of cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus and evaluation methodology, it is possible to resolve test period length that existing evaluation methodology exists, the problem that crack should not be observed.
In order to solve above-mentioned technical problem, the present invention provides a kind of cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus, including mould and strain acquisition system, described mould includes square floor, it is provided with off-centre operation cylindricality internal ring in described base plate, the inwall of described internal ring is provided with the foil gauge being connected with described strain acquisition system；Described bottom edge is provided with detachable frame.
The axial location of described internal ring is 1:1 to the distance of described a pair length of side of mould, and to described mould, the distance of the length of side is 5:3 by another.
The length of side of described mould is 24 times of test specimen maximum diameter of aggrogate.
The height of described mould is 3 times of test specimen maximum diameter of aggrogate.
The external diameter of described internal ring is 12 times of test specimen maximum diameter of aggrogate.
Described base plate is made up of steel, and its thickness is 3-5mm.
Described internal ring is made up of steel, and its wall thickness is 1-2mm.
Described frame is made up of steel, and its thickness is 3-5mm.
Described base plate lower surface is fixedly installed bearing.
The present invention also provides for a kind of evaluation methodology based on described cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus, comprises the following steps:
(1) maximum diameter of aggrogate in existing N kind cement-based material is determined；
(2) above-mentioned mould is designed according to maximum diameter of aggrogate；
(3) mix cement sill according to each group of match ratio, build to mould, floating being placed under same temperature damp condition of vibrating；
Form removal after (4) one days, pastes foil gauge on internal ring inwall, and is connected with strain acquisition system by foil gauge, and every 15min gathers a strain data, and the moment that the strain recorded is undergone mutation is the cracking moment of test specimen；
(5) within the time of regulation, measure the fracture width of test specimen；
(6) contrasting cracking time and the fracture width of each group of material, the material that cracking time is of a specified duration, fracture width is little is the material that anti-cracking performance is good.
The invention has the beneficial effects as follows:
1, the present invention is by the cooperation of the base plate of mould, internal ring and frame, it is possible to produce cement-based material square-outside and round-inside test specimen easily, and the eccentric setting of described test specimen inner circle is basic for the evaluation that cement-based material anti-cracking performance evaluation offer is good；
2, the present invention can shorten the test period, improve the ageing of device: existing evaluation methodology exists the problem of test period length, and the long test period increases the time cost of test, reduces it ageing；
3, present invention may determine that test specimen crack location, improve the accuracy of device: existing evaluation methodology exists the crack location of test specimen and has the problem of randomness, is unfavorable for the observation of crack progressing, reduces its accuracy.
Accompanying drawing explanation
Fig. 1: inventive die plan structure schematic diagram；
Fig. 2: A-A cross-sectional view of the present invention；
Fig. 3: test specimen plan structure schematic diagram after form removal of the present invention；
Fig. 4: B-B cross-sectional view of the present invention；
Fig. 5: C-C cross-sectional view of the present invention.
Accompanying drawing marks: 1, frame；2, internal ring；3, base plate；4, bearing；5, foil gauge；6, cement-based material；7, test specimen crack location.
Detailed description of the invention
Below in conjunction with accompanying drawing, the invention will be further described.
As shown in accompanying drawing 1 to Fig. 5, a kind of cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus, including mould and strain acquisition system, described mould includes square floor 3, and described base plate 3 is made up of steel, and its thickness is 3-5mm；Off-centre operation cylindricality internal ring 2 it is provided with in described base plate 3, the inwall of described internal ring 2 is provided with the foil gauge 5 being connected with strain acquisition system, wherein, the axial location of described internal ring 2 is 1:1 to the distance of described a pair length of side of mould, to described mould, the distance of the length of side is 5:3 by another, further, described internal ring 2 is made up of steel, and its wall thickness is 1-2mm；Described base plate 3 edge is provided with detachable frame 1, and described frame 1 is made up of steel, and its thickness is 3-5mm；Described base plate 3 lower surface is fixedly installed bearing 4.
In the present invention, the length of side of described mould is 24 times of test specimen maximum diameter of aggrogate, i.e. L=24Dmax；The height of described mould is 3 times of test specimen maximum diameter of aggrogate, i.e. H=3Dmax；The external diameter of described internal ring 2 is 12 times of test specimen maximum diameter of aggrogate, i.e. D0=12Dmax, and, due to the eccentric setting of described internal ring 2, in Fig. 2, eccentric dimension D1=3Dmax, D2=9Dmax。
Based on the evaluation methodology of above-mentioned cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus, comprise the following steps:
Firstly, for existing several (being assumed to be N kind) cement-based material 6, it is determined that in N kind material, maximum diameter of aggrogate is Dmax, and according to maximum diameter of aggrogate DmaxDesign above-mentioned mould；
Secondly, mix cement sill 6 according to each group of match ratio, build to mould (between described frame 1 and internal ring 2), vibrate and floating be placed on same temperature humidity (recommended temperature 20 ± 2 DEG C, relative humidity 60 ± 5%) under condition, form removal after one day, after form removal, test specimen is as shown in Figures 3 to 5；After form removal, foil gauge 5 is pasted in position on internal ring 2 inwall, as shown in Figure 5, and foil gauge 5 is connected with strain acquisition system, every 15min gathers a strain data, and undergo mutation moment of (usual Sudden Changing Rate is 30-70 μ ε) of the strain recorded is the cracking moment t of test specimen；
Now, test specimen crack location 7 as it is shown on figure 3, measure the fracture width ω of test specimen in the time (generally selecting test specimen to build 28 days, 60 days or 90 days) of regulation；
Finally, contrasting the cracking time t and fracture width ω of each group of material, the material that cracking time is of a specified duration, fracture width is little is the material that anti-cracking performance is good.
Specific embodiments of the invention:
Contrast the anti-cracking performance of two groups of cement mortar mix ratio A and B.The match ratio of mortar A and B is as shown in table 1 below.Water used is tap water；Cement is P.O42.5 Portland cement；Sand is medium sand, modulus of fineness 2.65, maximum particle diameter Dmax=5mm.
Before evaluation, according to maximum particle diameter Dmax=5mm show that the dimensional parameters of the present embodiment mould is respectively as follows: the length of side L=120mm of mould, mold height H=15mm, internal ring 2 outer diameter D0=60mm, the eccentric dimension D of internal ring 21=15mm, D2=45mm.Often group match ratio uses three moulds, needs six moulds altogether.Then, the match ratio shown in table 1 builds test specimen, and the test specimen built is placed in temperature 20 ± 2 DEG C, form removal after maintenance one day when relative humidity 60 ± 5%.
Table 1 cement mortar mix ratio (kg/m3)
After form removal, foil gauge 5 is pasted in position on internal ring 2 inwall, as shown in Figure 5, and is connected with strain acquisition system by foil gauge 5, and every 15min gathers a strain data.In the moment that record strain is undergone mutation, each test specimen cracking time t is as shown in table 2.
Table 2 test specimen cracking time (h)
After test specimen has built 28 days, measure the fracture width ω of each test specimen, as shown in table 3.
Table 3 test specimen fracture width (mm)
The result of the test of contrast table 2 and table 3, the cracking time of B group match ratio material is of a specified duration compared with the cracking time of A group match ratio material, 62.92 (h) > 51.25 (h)；The fracture width of B group match ratio material is little compared with the fracture width of A group match ratio material, 1.77 (mm) < 2.17 (mm).
Finally conclude that the anti-cracking performance of B group material is better than A group material.
Claims (10)
1. a cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus, including mould and strain acquisition system, it is characterized in that, described mould includes square floor, it is provided with off-centre operation cylindricality internal ring in described base plate, the inwall of described internal ring is provided with the foil gauge being connected with described strain acquisition system；Described bottom edge is provided with detachable frame.
2. cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus according to claim 1, it is characterised in that the axial location of described internal ring is 1:1 to the distance of described a pair length of side of mould, to described mould, the distance of the length of side is 5:3 by another.
3. cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus according to claim 1, it is characterised in that the length of side of described mould is 24 times of test specimen maximum diameter of aggrogate.
4. cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus according to claim 1, it is characterised in that the height of described mould is 3 times of test specimen maximum diameter of aggrogate.
5. cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus according to claim 1, it is characterised in that the external diameter of described internal ring is 12 times of test specimen maximum diameter of aggrogate.
6. cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus according to claim 1, it is characterised in that described base plate lower surface is fixedly installed bearing.
7. cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus according to claim 1, it is characterised in that described base plate is made up of steel, and its thickness is 3-5mm.
8. cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus according to claim 1, it is characterised in that described internal ring is made up of steel, and its wall thickness is 1-2mm.
9. cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus according to claim 1, it is characterised in that described frame is made up of steel, and its thickness is 3-5mm.
10. one kind based on the evaluation methodology of cement-based material square-outside and round-inside anti-cracking performance evaluating apparatus described in the claims 1, it is characterised in that comprise the following steps:
(1) maximum diameter of aggrogate in existing N kind cement-based material is determined；
(2) mould described in the claims 1-9 is designed according to maximum diameter of aggrogate；
(3) mix cement sill according to each group of match ratio, build to mould, floating being placed under same temperature damp condition of vibrating；
Form removal after (4) one days, pastes foil gauge on internal ring inwall, and is connected with strain acquisition system by foil gauge, and every 15min gathers a strain data, and the moment that the strain recorded is undergone mutation is the cracking moment of test specimen；
(5) within the time of regulation, measure the fracture width of test specimen；
(6) contrasting cracking time and the fracture width of each group of material, the material that cracking time is of a specified duration, fracture width is little is the material that anti-cracking performance is good.
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| CN201610240940.7A CN105759017A (en) | 2016-04-18 | 2016-04-18 | Device and method for evaluating anti-crack performance of external squares and internal circles of cement-based materials |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107561251A (en) * | 2017-09-22 | 2018-01-09 | 北京建筑大学 | A kind of cement-based material cracking sensitivity test device and method of testing |
| CN108535459A (en) * | 2018-05-03 | 2018-09-14 | 华南理工大学 | A kind of crack resistance |
| CN110261226A (en) * | 2019-07-09 | 2019-09-20 | 武汉理工大学 | A kind of ultra-high performance concrete cracking resistance system safety testing device and method |
| CN111024503A (en) * | 2019-12-30 | 2020-04-17 | 中建七局第四建筑有限公司 | Annular test device for measuring internal tensile stress and crack development of soil body in real time |
| CN111351814A (en) * | 2020-04-13 | 2020-06-30 | 全球能源互联网研究院有限公司 | Anti-cracking performance evaluation method for epoxy material |
| CN113049791A (en) * | 2021-02-08 | 2021-06-29 | 同济大学 | Plastic shrinkage cracking and reducing method for cement mortar |
| CN113484505A (en) * | 2021-07-20 | 2021-10-08 | 福州大学 | Non-uniform annular constraint shrinkage testing device and testing method |
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| CN104374897A (en) * | 2014-11-25 | 2015-02-25 | 大连理工大学 | Method for determining early-stage concrete crack resistance by adopting elliptical ring test specimen |
| CN205581107U (en) * | 2016-04-18 | 2016-09-14 | 天津大学 | Circle crack resistance can appraise device in cement -based materials foreign side |
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| EP0376116B1 (en) * | 1988-12-29 | 1994-10-05 | Hochtief Aktiengesellschaft Vorm. Gebr. Helfmann | Method for identifying the position of a crack in reinforcing steel |
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107561251A (en) * | 2017-09-22 | 2018-01-09 | 北京建筑大学 | A kind of cement-based material cracking sensitivity test device and method of testing |
| CN108535459A (en) * | 2018-05-03 | 2018-09-14 | 华南理工大学 | A kind of crack resistance |
| CN110261226A (en) * | 2019-07-09 | 2019-09-20 | 武汉理工大学 | A kind of ultra-high performance concrete cracking resistance system safety testing device and method |
| CN111024503A (en) * | 2019-12-30 | 2020-04-17 | 中建七局第四建筑有限公司 | Annular test device for measuring internal tensile stress and crack development of soil body in real time |
| CN111351814A (en) * | 2020-04-13 | 2020-06-30 | 全球能源互联网研究院有限公司 | Anti-cracking performance evaluation method for epoxy material |
| CN111351814B (en) * | 2020-04-13 | 2023-03-31 | 全球能源互联网研究院有限公司 | Anti-cracking performance evaluation method for epoxy material |
| CN113049791A (en) * | 2021-02-08 | 2021-06-29 | 同济大学 | Plastic shrinkage cracking and reducing method for cement mortar |
| CN113484505A (en) * | 2021-07-20 | 2021-10-08 | 福州大学 | Non-uniform annular constraint shrinkage testing device and testing method |
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Application publication date: 20160713 |