CN112161583A - DEF-based cement-based composite material deformation testing method - Google Patents
DEF-based cement-based composite material deformation testing method Download PDFInfo
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- CN112161583A CN112161583A CN202010994522.3A CN202010994522A CN112161583A CN 112161583 A CN112161583 A CN 112161583A CN 202010994522 A CN202010994522 A CN 202010994522A CN 112161583 A CN112161583 A CN 112161583A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
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Abstract
A DEF-based cement-based composite material deformation testing method belongs to the field of cement-based composite material deformation testing. The test method comprises the following steps: maintaining the cement-based composite material sample in an environment with the temperature of more than 70 ℃ for more than 4h, cooling to room temperature, placing the cooled cement-based composite material sample in water, arranging a metal block on the detection surface of the cement-based composite material sample, and arranging a laser displacement sensor above the metal block; then carrying out deformation on-line measurement to obtain displacement measurement data of the cement-based composite material sample at corresponding time; establishing deformation curves of time and expansion rate, and establishing a fitting mathematical model of time-expansion rate according to curve trend of a gentle deformation stage to obtain a fitting formula of the curve at the gentle stage; and obtaining the expansion rate caused by DEF corresponding to the soaking time according to a fitting formula, thereby predicting the expansion process of the DEF and preventing the DEF in advance according to engineering requirements.
Description
Technical Field
The invention relates to a DEF-based cement-based composite material deformation testing method, and belongs to the field of cement-based composite material deformation testing.
Background
In the building engineering industry, cement mortar and concrete are the most widely used among cement-based composite materials. Delayed Ettringite Formation (DEF) is a process of forming Ettringite in cement mortar or concrete after hardening is finally completed. DEF is considered a potentially damaging reaction that affects the durability of cement mortar or concrete, and the resulting damage is usually apparent months or years later.
The expansion deformation of cement mortar or concrete caused by delayed ettringite generation (DEF) is very small in early change, the existing deformation testing means (such as dial indicators and electromagnetic induction) and devices are difficult to accurately measure, the expansion process of the cement mortar or concrete cannot be predicted, related research is difficult to progress, and many engineering quality problems are difficult to determine due to the fact that reliable data cannot be provided.
Disclosure of Invention
The invention provides a DEF-based cement-based composite material deformation testing method aiming at the problems, and aims to solve the problem that DEF deformation cannot be measured in the early stage. By adopting the testing device and the analysis method provided by the invention, the expansion deformation caused by DEF can be analyzed, and the measurement and prediction based on DEF deformation can be formed.
The purpose of the invention is realized by the following technical scheme:
a method for testing the deformation of a DEF-based cement-based composite material, comprising the steps of:
step 1: preparation and measurement
(1) Maintaining the cement-based composite material sample in an environment with the temperature of more than 70 ℃ for more than 4h to ensure that the ettringite is fully decomposed, and then cooling to room temperature to obtain a cooled cement-based composite material sample; the cement-based composite material is one of cement mortar or concrete;
(2) placing the cooled cement-based composite material sample into water, arranging a metal block on the detection surface of the cement-based composite material sample, and arranging a laser displacement sensor above the metal block; then carrying out deformation on-line measurement to obtain displacement measurement data of the cement-based composite material sample at corresponding time;
step 2: establishing a deformation curve
Establishing a deformation curve of time and expansion rate according to the obtained displacement measurement data of the cement-based composite material sample corresponding to the time, stopping measurement when the deformation curve can be divided into a water absorption expansion stage, a dissolution contraction stage and a gentle deformation stage, and preferably selecting the measurement time to be more than or equal to 28 days;
regarding a gradual deformation phase in the deformation curve as an expansion deformation caused by the DEF;
wherein the water absorption expansion stage is a stage of expansion rate increase after the cement-based composite material sample is soaked in water;
the dissolution shrinkage stage is an expansion rate reduction stage after the water absorption expansion stage is finished;
the gradual deformation stage is a stage in which the expansion rate continuously rises again after the cement-based composite material sample shrinks, and the stage is the expansion deformation caused by DEF;
according to the curve trend of the gentle deformation stage, a fitting mathematical model of time-expansion rate is established to obtain a fitting formula of the curve at the gentle stage;
and step 3: deformation prediction
According to the obtained fitting formula of the curve at the gentle stage, the expansion rate of the corresponding cement mortar or concrete structure caused by DEF under the same condition can be calculated according to the soaking time.
In the step 1 (1), the curing is preferably carried out at 70-100 ℃ for 4-10 h.
In the step 1 (1), after curing for more than 4 hours in an environment of more than 70 ℃, autoclaving can also be carried out, wherein the temperature of autoclaving is 180-200 ℃, the pressure is 1-2 MPa, and the time is more than 10 hours.
In step 1 (2), the laser displacement sensor is adopted for online deformation measurement, the laser displacement sensor is further provided with a fixing support and a lifting device in a matching mode, the lifting device is arranged on the objective table and used for adjusting the distance between the laser displacement sensor and the cement-based composite material sample, the lifting device is connected with the laser displacement sensor through the fixing support, and the fixing support is used for fixing the laser displacement sensor.
In the step (2) of the step 1, the cooled cement-based composite material sample, the metal block and water are all arranged in an environment box; and the cooled cement-based composite material sample is completely immersed in water, and the metal block is partially immersed in the water.
The environment box is a stainless steel container provided with a heat-insulating layer, is provided with a heating device and is used for maintaining the temperature stability in a test environment, and the temperature control precision is less than or equal to +/-1 ℃.
The metal block is preferably made of corrosion-resistant stainless steel, such as 304 stainless steel.
In step 1 (2), the laser displacement sensor is also connected with a computer.
In step 1 (2), the measurement accuracy of the laser displacement sensor is less than or equal to 0.2 μm.
The lifting device adopts one of gears, screws, fixing pins or hydraulic pressure to realize lifting, and the lifting range is 0-20 cm.
The invention discloses a DEF-based cement-based composite material deformation testing method, which has the advantages that:
the method comprises the steps of measuring the micro deformation of a sample by using a measuring device with the precision of less than or equal to 0.2 micrometer, providing the deformation of a cement-based composite material (cement mortar or concrete) which is subjected to high temperature of more than 70 ℃ to fully decompose ettringite and then cooled to normal temperature in a water environment, establishing a sample deformation curve according to measurement data, and if the deformation curve has three stages of I water absorption expansion, II dissolution shrinkage and III slow deformation, taking the curve in the III slow deformation stage as a prediction curve based on DEF deformation to obtain a deformation rule, determining the characteristics of the deformation curve based on DEF, performing engineering prejudgment on the expansion rate caused by DEF, and adjusting the mixing ratio of the components of the cement-based composite material if the expansion rate is not in accordance with the engineering requirements.
Drawings
FIG. 1 is a schematic diagram of the step 1 measurement process in the DEF-based cement mortar deformation test method in example 1 of the present invention;
FIG. 2 is a deformation curve of time and expansion ratio obtained by the DEF-based cement mortar deformation test method in example 1 of the present invention;
FIG. 3 is a schematic view showing the structure of an apparatus used in the measurement process in the DEF-based cement mortar deformation test method in example 1 of the present invention;
FIG. 4 is a deformation curve of time and expansion ratio obtained by the DEF-based cement mortar deformation test method in example 2 of the present invention;
in the above figures, 1 is a laser displacement sensor, 2 is a metal block, 3 is water, 4 is a cement-based composite material sample, 5 is a fixed support, 6 is a lifting device, 7 is an object stage, and 8 is an environment box.
Detailed Description
The present invention will be described in further detail with reference to examples.
In the following embodiment, the structural schematic diagram of the adopted testing device is shown in fig. 3, and the testing device comprises a laser displacement sensor 1, wherein the laser displacement sensor 1 is further provided with a fixing support 5 and a lifting device 6 in a matching manner, the lifting device 6 is arranged on an object stage 7 and is used for adjusting the distance between the laser displacement sensor 1 and a cement-based composite material sample, the lifting device 6 is connected with the laser displacement sensor 1 through the fixing support 5, and the fixing support 5 is used for fixing the laser displacement sensor 1.
During measurement, the measurement schematic diagram is shown in fig. 1, and the cooled cement-based composite material sample 4, the metal block 2 and the water 3 are all arranged in an environment box 8; and the cooled cement-based composite material sample 4 is completely immersed in water, the metal block 2 is partially immersed in the water, the metal block 2 is arranged on the detection surface of the cement-based composite material sample 4, and the laser displacement sensor 1 is arranged above the metal block 2.
The environment box 8 is a stainless steel container provided with a heat-insulating layer and a heating device, and the temperature control precision is less than or equal to +/-1 ℃.
The metal block 2 is made of corrosion-resistant stainless steel, such as 304 stainless steel.
The laser displacement sensor 1 is also connected with a computer, and the computer is used for receiving and processing the measurement data.
The measurement precision of the laser displacement sensor 1 is less than or equal to 0.2 mu m.
The lifting device 6 adopts a gear mode to realize lifting, and the lifting range is 0-20 cm.
Example 1
Preparing a standard cement mortar sample, wherein the size of the cement mortar sample is as follows: 40mm 160mm, the cement mortar uses 80% ordinary portland cement and 20% powdered ore, add water to mix, after shaping, put into steam of 90-100 duC and maintain 10 hours, put into water after cooling, adopt the way shown in figure 1 to carry on the online measurement of deformation for 800 hours, draw the measured data obtained and get the deformation curve as shown in figure 2. Obviously, the deformation curve is divided into three stages, line fitting is carried out on the gentle deformation stage, the relation between DEF-based deformation expansion rate and time is established, and the expansion rate of cement mortar with the same composition at different moments under the same curing condition can be calculated accordingly.
Example 2
Preparing a standard cement mortar sample, wherein the size of the cement mortar sample is 40mm x 160mm, the raw materials of the cement mortar sample are 80% of ordinary portland cement and 20% of mineral powder, adding water for mixing, forming, curing (the curing environment is 70 +/-5 ℃ and normal pressure steam curing for 6h + autoclaving, the autoclaving temperature is 180-200 ℃, the pressure is 1MPa, and the time is 10h), cooling, then placing in water, and performing deformation online measurement for 800 hours, wherein the deformation curve is shown in figure 4. Obviously, the deformation curve is divided into three stages, line fitting is carried out on the gentle deformation stage, the relation between DEF-based deformation expansion rate and time is established, and the expansion rate of cement mortar with the same composition at different moments under the same curing condition can be calculated accordingly.
Example 3
Preparing a standard concrete sample, wherein the concrete sample is prepared from 80% of ordinary portland cement, 10% of mineral powder and 10% of sand as raw materials, adding water for mixing, and curing after molding, wherein the curing environment is as follows: the method comprises the steps of maintaining for 6 hours at 70 +/-5 ℃ under normal pressure steam, cooling, putting into water at 40 ℃, performing deformation online measurement for 800 hours, obviously finding out that a deformation curve is divided into three stages, performing line fitting on a gentle deformation stage, establishing a DEF-based relation between deformation expansion rate and time, and calculating expansion rate of cement mortar with the same composition at different moments under the same maintenance condition.
Claims (10)
1. A DEF-based cement-based composite deformation test method is characterized by comprising the following steps of:
step 1: preparation and measurement
(1) Maintaining the cement-based composite material sample in an environment with the temperature of more than 70 ℃ for more than 4h to ensure that the ettringite is fully decomposed, and then cooling to room temperature to obtain a cooled cement-based composite material sample; the cement-based composite material is one of cement mortar or concrete;
(2) placing the cooled cement-based composite material sample into water, arranging a metal block on the detection surface of the cement-based composite material sample, and arranging a laser displacement sensor above the metal block; then carrying out deformation on-line measurement to obtain displacement measurement data of the cement-based composite material sample at corresponding time;
step 2: establishing a deformation curve
Establishing deformation curves of time and expansion rate according to the obtained displacement measurement data of the cement-based composite material sample corresponding to the time, and stopping measurement when the deformation curves can be divided into a water absorption expansion stage, a dissolution contraction stage and a gentle deformation stage;
regarding a gradual deformation phase in the deformation curve as an expansion deformation caused by the DEF;
wherein the water absorption expansion stage is a stage of expansion rate increase after the cement-based composite material sample is soaked in water;
the dissolution shrinkage stage is an expansion rate reduction stage after the water absorption expansion stage is finished;
the gradual deformation stage is a stage in which the expansion rate continuously rises again after the cement-based composite material sample shrinks, and the stage is the expansion deformation caused by DEF;
according to the curve trend of the gentle deformation stage, a fitting mathematical model of time-expansion rate is established to obtain a fitting formula of the curve at the gentle stage;
and step 3: deformation prediction
And inputting the soaking time according to the obtained fitting formula of the curve at the gentle stage to obtain the corresponding expansion rate of the cement mortar or the concrete structure caused by DEF under the same condition.
2. A DEF-based cement-based composite material deformation test method as defined in claim 1, wherein in step 1 (1), the curing conditions are 70-100 ℃ for 4-10 h.
3. A DEF-based cement-based composite material deformation test method as defined in claim 1, wherein in step 1 (1), after curing at 70 ℃ or higher for 4 hours or longer, autoclaving is further performed at 180-200 ℃ under 1-2 MPa for 10 hours or longer.
4. A DEF-based cement-based composite deformation testing method as claimed in claim 1, wherein in step 1 (2), a laser displacement sensor is used for online measurement of deformation, the laser displacement sensor is further provided with a fixing bracket and a lifting device in a matching manner, the lifting device is arranged on a stage and used for adjusting the distance between the laser displacement sensor and a cement-based composite sample, the lifting device is connected with the laser displacement sensor through the fixing bracket, and the fixing bracket is used for fixing the laser displacement sensor.
5. A DEF-based cement-based composite material deformation test method as defined in claim 4, wherein the lifting device is adapted to lift in a range of 0-20 cm by using one of gears, screws, fixed pins or hydraulic pressure.
6. The DEF-based cement-based composite deformation testing method of claim 1, wherein in step 1 (2), the cooled cement-based composite specimen, the metal block, and water are all placed in an environmental tank; and the cooled cement-based composite material sample is completely immersed in water, and the metal block is partially immersed in the water.
7. A DEF-based cement-based composite deformation test method according to claim 6, wherein the environmental chamber is a stainless steel container provided with an insulating layer and provided with a heating device for maintaining temperature stability in the test environment with a temperature control accuracy of ≦ 1 ℃.
8. The method of claim 1, wherein the metal block is a corrosion resistant stainless steel.
9. A DEF-based cement-based composite deformation test method as defined in claim 1, wherein in step 1 (2), the laser displacement sensor is further connected to a computer; the measurement precision of the laser displacement sensor is less than or equal to 0.2 mu m.
10. A test method for deformation of a DEF-based cement-based composite material according to claim 1, wherein the measurement time is 28 days or more.
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| CN202010994522.3A CN112161583A (en) | 2020-09-21 | 2020-09-21 | DEF-based cement-based composite material deformation testing method |
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Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1547000A (en) * | 2003-12-09 | 2004-11-17 | 中国建筑材料科学研究院 | Cement mortar and concrete shrinkage stress testing method |
| CN102072704A (en) * | 2010-11-11 | 2011-05-25 | 清华大学 | Non-contact laser displacement measurement system used for cement-based materials |
| US8949067B1 (en) * | 2010-09-17 | 2015-02-03 | Ofi Testing Equipment, Inc. | Device and method for measuring material volume changes |
| CN109238376A (en) * | 2018-11-09 | 2019-01-18 | 中南大学 | A kind of device and method monitoring steam-cured cement-based material in the process deformation and stress |
| CN110595936A (en) * | 2019-10-14 | 2019-12-20 | 哈尔滨工业大学 | Device and method for testing wet expansion coefficient of composite material under humid filling condition |
-
2020
- 2020-09-21 CN CN202010994522.3A patent/CN112161583A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1547000A (en) * | 2003-12-09 | 2004-11-17 | 中国建筑材料科学研究院 | Cement mortar and concrete shrinkage stress testing method |
| US8949067B1 (en) * | 2010-09-17 | 2015-02-03 | Ofi Testing Equipment, Inc. | Device and method for measuring material volume changes |
| CN102072704A (en) * | 2010-11-11 | 2011-05-25 | 清华大学 | Non-contact laser displacement measurement system used for cement-based materials |
| CN109238376A (en) * | 2018-11-09 | 2019-01-18 | 中南大学 | A kind of device and method monitoring steam-cured cement-based material in the process deformation and stress |
| CN110595936A (en) * | 2019-10-14 | 2019-12-20 | 哈尔滨工业大学 | Device and method for testing wet expansion coefficient of composite material under humid filling condition |
Non-Patent Citations (1)
| Title |
|---|
| 戴民等: "基于DEF的砂浆变形分析", 《混凝土》 * |
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