CN108507939A - A kind of real-time measurement apparatus and its measurement method of the variation of temperature and humidity control cement-based material length - Google Patents

Abstract

The invention discloses a real-time measuring device for the length change of temperature-controlled and humidity-controlled cement-based materials. The control unit 9 and the temperature-controlled humidity-controlled environment box 10 are also equipped with a measuring device for measuring the length change of the specimen material. The invention also discloses the measurement method of the real-time measuring device for the length change of the temperature-controlled and humidity-controlled cement-based material. The invention uses the replaceable saturated salt solution in the solution pool to realize the environmental humidity control. Matching to achieve environmental temperature control, use the length change measuring device to detect the length change of the test piece. It solves the problem of real-time monitoring of the length change of cement paste/mortar under the condition of humidity change or low temperature change, and can be used for the study of volume change of cement paste/mortar/concrete and other cement-based materials under the influence of humidity or low temperature and severe cold climate conditions with application.

Description

A real-time measurement device and its measurement for the length change of cement-based materials with temperature and humidity control method

technical field

The invention belongs to the technical field of civil engineering material performance testing instruments, and in particular relates to a real-time measuring device and a measuring method for the length change of cement-based materials with temperature and humidity control.

Background technique

Concrete materials are widely used in modern buildings. It has the advantages of low price, wide application range, and good durability. Concrete cracks. Since the performance of concrete is affected by the amount of cement, the shrinkage performance of cement directly affects the quality of cement concrete. Therefore, the shrinkage performance of cement is generally evaluated by measuring the shrinkage rate of cement mortar.

According to "JC/T 603-2004 Cement Mortar Drying Shrinkage Test Method", after the test piece is prepared, maintained, and measured with a ratio meter to measure the initial length, the test piece is moved into a curing box with a specified temperature and humidity, and then taken out after a certain period of time. Placed on a ratiometer at room temperature for measurement. The disadvantage of this method is that it cannot rule out the influence of sudden changes in the environment or other factors involved in the multiple times of moving in and out of the test piece, and the operation is complicated. The purpose of the present invention is to accurately and effectively evaluate the change of the length of cement-based materials under the condition of external environmental humidity or temperature change, and it is more in line with engineering practice to change the environmental conditions and measure the real-time change of the length of the test piece under the condition that the test piece does not move.

The existing length measurement technology is various cement mortar ratio meters, which are instruments used to measure the drying shrinkage rate of cement mortar specimens at various ages and the expansion rate of expansive cement at various ages, including thousand Sub table, upper measuring head, 90°V-shaped support, lower measuring head, standard rod, base, etc. It has the advantages of convenient use, high measurement accuracy, fast speed, and clear readings. In order to avoid the impact caused by multiple mutations in the environment, the length measuring device and the test piece can be moved into the environmental chamber together, but this cannot rule out unfavorable factors such as changes in the bracket of the measuring device and other components affected by the environment and the impact on the accuracy of the dial indicator.

The present invention proposes a temperature-controlled and humidity-controlled environmental chamber, and combines it with the length change measuring device of the ratio meter. It solves the problems caused by the original test process, and is easy to operate. It can measure the relationship between the length of cement slurry, mortar and concrete and other test pieces and the change of temperature and humidity without moving the test piece.

Contents of the invention

In order to solve the problems of the existing cement mortar shrinkage and expansion measurement device, such as complicated test operation and errors caused by multiple environmental mutations during the transfer process of the test piece, the present invention provides a real-time measurement device for temperature and humidity control of the length change of cement-based materials It can accurately and effectively evaluate the change of cement-based material length under the condition of external environmental humidity or temperature change, and it is more in line with engineering practice to change the environmental conditions and measure the real-time change of the length of the test piece without moving the test piece.

The present invention solves its technical problem and realizes through the following technical solutions:

A real-time measuring device for the length change of temperature-controlled and humidity-controlled cement-based materials, comprising a closed temperature-controlled and humidity-controlled environment box (10), a temperature control part (8) and a humidity control part (9);

The temperature control and humidity control environment box (10) is provided with several closable ports (11) on the side wall, and the temperature control part (8) includes a number of ports that can be inserted into the temperature control and humidity control environment box from the ports (11). (10) the thermal rod (7), the thermal rod (7) comprises a sealed rod body (71), the rod body (71) is hollow, and the bottom of the rod body (71) is stored with heat absorbing and cooling of liquid ammonia (72);

The humidity control part (9) includes a solution pool (91), filled with a saturated saline solution (93) in the solution pool (91), and a detachable cover on the solution pool (91) is provided with a partition (94 ), a push plate (92) is installed on the side wall of the solution pool (91), and a through hole (12) is also provided on the side wall of the temperature and humidity control environment box (10), the solution pool (91) through the through hole (12) to slide in and out of the temperature and humidity control environment box (10), the push plate (92) is located outside the temperature control and humidity control environment box (10), and the push plate ( The diameter of 92) is greater than the diameter of through hole (12);

A measuring device is also installed in the temperature-controlled and humidity-controlled environment box (10), and the measuring device includes a base (4) on which a support (3) for clamping the test piece (2) is installed , the test piece (2) is connected with a measuring instrument (1) for measuring the length change of the test piece (2), and the measuring instrument (1) is installed outside the temperature and humidity control environment box (10);

A thermo-hygrometer (6) for reading the temperature and humidity around the test piece (2) is also installed in the temperature and humidity control environment box (10).

Further, cooling fins (73) are installed on the outside of the upper part of the rod body (71).

Further, a sealing rubber ring (74) is bonded to the outer wall of the rod body (71), and the material of the sealing rubber ring (74) is low temperature resistant silicone rubber.

Further, a positioning hole is opened on the top of the temperature and humidity control environment box (10), the foam board (5) is set in the positioning hole, and a temperature and humidity meter (6) is inserted on the foam board (5) ), the temperature-hygrometer (6) stretches into the temperature and humidity control environment box (10).

Further, the measuring instrument (1) is a dial gauge; or the measuring instrument (1) is an electronic displacement sensor.

Further, the material used for the rod body (71) is steel.

Further, the material used in the temperature-controlled and humidity-controlled environment box (10) is plexiglass, or a transparent, low-temperature resistant material, and the low-temperature resistant range is -30°C to 30°C.

Further, the material used for the bracket (3) is Invar alloy.

Further, the test piece (2) shrinks during the temperature drop process, and the temperature at which ice is formed in the test piece (2) leading to a sudden increase in length is determined as the freezing temperature of the test piece (2).

A method for measuring the real-time measurement device for the length change of the temperature-controlled and humidity-controlled cement-based material, comprising the following steps:

(1) Keep the temperature constant and control the humidity change

1) Select an experimental environment with a temperature greater than 0°C, and keep the temperature constant during the experiment, close all ports (11) of the temperature-controlled and humidity-controlled environmental box (10) and keep them sealed;

2) Configure saturated salt solutions with different solutes according to the equilibrium relative humidity value of the saturated salt solution at the reference experimental temperature;

3) At normal temperature, read the ambient humidity at this time, measure the initial length of the test piece (2) and record the initial length, and then place it stably on the length measuring device. The test piece (2) is 40mm×40mm× 160mm standard cement mortar specimen;

4) Calibration of the length measuring device and zeroing of the measuring instrument (1);

5) During the test, put a saturated salt solution into the solution pool (91), push it into the temperature-controlled humidity-controlled environment box (10), maintain a constant humidity for 14 days, read the readings of the measuring instrument (1) and the temperature-humidity meter (6) temperature and humidity values and records;

6) Arrange the environmental humidity values that can be maintained by different solute saturated salt solutions from high to low, and carry out the test of step (5) in sequence until the test is completed when the experimental humidity is reduced from 97% RH to 22% RH;

7) Data processing, error analysis, obtaining the relationship between the length of the cement mortar specimen and the change in humidity;

(2) Keep the humidity constant and control the temperature change

1) Make several hot rods (7), fill them with different volumes of liquid ammonia, and store the prepared hot rods (7) in a freezer at -40°C;

2) Read the humidity of the experimental environment at this time, measure the initial length of the test piece (2) and record the initial length, then place it stably on the length measuring device, and the test piece (2) is 40mm×40mm×160mm standard cement Mortar test piece;

3) Calibration of the length measuring device and zeroing of the measuring instrument (1);

4) Take out a hot rod (7), insert it into the temperature and humidity control environment box (10) from the port (11), the bottom of the rod body (71) extends into the temperature and humidity control environment box (10), And the upper part of the rod body (71) is located outside the temperature and humidity control environment box (10), and the connection between the hot rod (7) and the temperature and humidity control environment box (10) is kept sealed;

5) Read the temperature of the thermo-hygrometer (6), maintain the current temperature for 1 hour, read and record the reading of the measuring instrument (1);

6) Add one hot rod (7) each time, repeat the test steps (4) and (5) until the temperature drops to -18°C;

7) Reduce one hot rod (7) each time, repeat the test steps (4) and (5) until the temperature rises to 4°C;

8) End the experiment and put all the hot rods (7) back into the freezer at -40°C;

9) Data processing and error analysis to obtain the relationship between the length of the test piece (2) and the temperature change.

The beneficial effects of the present invention are:

1. The present invention installs the standard test piece (40mm × 40mm × 160mm) made of cement-based material on the length measuring device at normal temperature and does not move any more. A sealed plexiglass box is used to establish an independent space. A push-pull detachable saturated salt solution pool is set in the side through hole, and the ambient humidity is maintained by filling the pool with saturated salt solution, and different solute saturated salt solutions are configured for separate tests, so that the environmental humidity of this test is controlled at 22% to 97% RH. Thus, the relationship between the length of the specimen and the humidity of the environment can be obtained directly.

2. In the present invention, the standard test piece (40mm×40mm×160mm) made of cement-based material is installed on the length measuring device and no longer moves, and a sealed plexiglass box is used to establish an independent space, and several openings are opened on the box body , Place the hot rod, and control the change of the ambient temperature through the matching of the hot rod with different volumes of liquid ammonia inside and the number of the placed hot rod, so that the temperature of the test environment can be controlled between -20°C and 25°C. Thus, the relationship between the length of the test piece and the ambient temperature can be obtained directly, and the freezing temperature of the test piece can also be obtained through the volume expansion at a certain temperature.

Description of drawings

Fig. 1 is a three-dimensional structural schematic diagram of a temperature-controlled and humidity-controlled environmental chamber of the present invention;

Fig. 2 is the structural representation of heating rod among the present invention;

Fig. 3 is a schematic structural view of the solution pool in the present invention.

Explanation of reference signs:

1-measuring instrument, 2-test piece, 3-bracket, 4-base, 5-foam board, 6-thermo-hygrometer, 7-hot rod, 71-rod body, 72-liquid ammonia, 73-radiating fin, 74 -rubber ring, 8-temperature control part, 9-humidity control part, 91-solution pool, 92-push plate, 93-saturated salt solution, 94-partition, 10-temperature and humidity control environment box, 11-port , 12-through holes.

Detailed ways

The present invention will be further described in detail below through the specific examples, the following examples are only descriptive, not restrictive, and cannot limit the protection scope of the present invention with this.

On the basis of the existing length measurement technology, the present invention provides a real-time measurement device for the length change of cement-based materials with temperature control and humidity control, which includes a temperature control and humidity control environment box and a length change measurement device, which can realize the temperature higher than 0 The real-time measurement of the length change of the specimen when the humidity changes and the real-time measurement of the length change of the specimen under low temperature conditions.

As shown in Figures 1 to 3, a real-time measuring device for the length change of temperature-controlled and humidity-controlled cement-based materials includes a closed temperature-controlled and humidity-controlled environmental box 10, the box material is plexiglass, and other transparent low-temperature resistant materials can also be used (-30°C to 30°C range) materials instead. A number of closable openings 11 are provided on the side wall of the temperature and humidity control environment box 10 for installing other components to realize temperature control or humidity control, and the connection between the box body and other components is kept sealed.

The temperature control component 8 includes a number of hot rods 7 that can be inserted into the temperature-controlled and humidity-controlled environment box 10 through the openings 11. The hot rods 7 include a hollow rod body 71, and the material used for the rod body is steel. Liquid ammonia 72 for absorbing heat and cooling is stored at the bottom of the rod body 71, and the rod body 71 is closed to prevent accidents caused by leakage of liquid ammonia. Radiating fins 73 are installed on the outside of the upper part of the rod body 71 to enhance the cooling performance of liquid ammonia. The outer wall of the rod body 71 is also bonded with a rubber ring 74, in order to make the sealing effect of the hot rod 7 better with the temperature and humidity control environment box 10 during work. The rubber ring 74 forms an angle of 45° with the rod body 71, and the rubber ring 74 materials used are low temperature resistant silicon rubber. When the hot rod 7 is in use, the bottom of the rod body 71 stretches into the temperature-controlled and humidity-controlled environment box 10, and the top of the rod body 71 is located outside the temperature-controlled and humidity-controlled environment box 10. The connection remains sealed. The present invention utilizes the melting and boiling point characteristics of ammonia (melting point -77°C, boiling point -33°C), which is easy to boil and evaporate, and is used for heat absorption and cooling. The liquid ammonia 72 is stored in the hot rod 7 made of steel, and the seal is sealed to prevent accidents caused by ammonia leakage during the test. Before use, the hot rod 7 equipped with liquid ammonia 72 is stored in a freezer at -40°C (according to the melting and boiling point of ammonia, ammonia is liquid at this time); when in use, the hot rod 7 is taken out and inserted into the temperature and humidity control environment box 10, Put the hot rod 7 back into the original storage cabinet after use, and the ammonia becomes liquid again, which can be reused. According to the size of the temperature control and humidity control environment box 10 and the temperature range that needs to be tested, the volume of liquid ammonia 72 that is loaded into the hot rod 7 is determined. The number of rods 7 is used to adjust the temperature change in the temperature and humidity control environment box 10. The device can control the test temperature between -20°C and 25°C.

The humidity control unit 9 includes a solution pool 91 filled with a saturated saline solution 93 . The detachable cover on the solution pool 91 is provided with a partition 94, which is convenient for replacing the saturated saline solution 93 in the solution pool 91, and changes the contact state between the saturated saline solution 93 and the temperature and humidity control environment box 10 through the partition 94. A push plate 92 is installed on a side wall of the solution pool 91, and a through hole 12 is also opened on the side wall of the temperature and humidity control environment box 10, and the solution pool 91 can slide in and out of the temperature and humidity control environment through the through hole 12 Box 10, push plate 92 is positioned at temperature control humidity control environment box 10 outsides, and the diameter of push plate 92 is greater than the diameter of through hole 12, after solution pool 91 enters temperature control humidity control environment box 10, push plate 92 can withstand through The holes 12 ensure the sealing of the temperature-controlled and humidity-controlled environment box 10 . Under normal temperature conditions, by changing the type of saturated salt solution 93, the test humidity can be controlled at 22% to 97% RH. The invention uses a saturated salt solution to control the environmental humidity in the box, and configures different solute saturated salt solutions to change the environmental humidity for testing. The present invention chooses normal temperature 25 ℃ to carry out the experiment, can refer to the following relative humidity values of different solute saturated salt solutions at 25 ℃ [Hua Youping. Humidity adjustment methods using various aqueous solutions [J]. Surface Technology, 1979 (4)] .

Saturated potassium acetate solution: 22.51±0.32%RH

Saturated magnesium chloride solution: 32.78±0.16%RH

Saturated potassium carbonate solution: 43.16±0.39%RH

Saturated magnesium nitrate solution: 52.89±0.22%RH

Saturated sodium chloride solution: 75.29±0.12%RH

Saturated potassium chloride solution: 84.34±0.26%RH

Saturated potassium nitrate solution: 93.58±0.55%RH

Saturated potassium sulfate solution: 97.30±0.45%RH

According to the kind of saturated saline solution 93, the material of the solution pool 91 can be glass or organic plastic.

A measuring device is also installed in the temperature-controlled and humidity-controlled environment box 10 . The measuring device includes a base 4 on which a bracket 3 for clamping the test piece 2 is installed. The material used for the bracket 3 is Invar alloy. Invar alloy has a low coefficient of thermal expansion (between -20°C and 20°C, the average value of the coefficient of thermal expansion is about 1.6×10 ^-6 /°C, which is about 1/10 of that of concrete materials). When the temperature changes, the length of the test piece 2 changes with the temperature, and the accurate measurement of the length change of the test piece 2 is realized because the deformation of the support 3 is small due to the influence of temperature. Specimen 2 is a standard cement mortar specimen of 40mm×40mm×160mm; the size of specimen 2 can also be changed according to test requirements to measure the length change of cement slurry or concrete material. The test piece 2 is connected with a measuring instrument 1 for measuring length changes, and the measuring instrument 1 is a dial gauge installed outside the temperature-controlled and humidity-controlled environment box 10 to prevent the accuracy of the dial gauge 1 from being affected by temperature and humidity changes in the box; the dial gauge 1 It can also be replaced by an electronic displacement sensor, which can be connected with a computer to achieve more accurate real-time monitoring of changes in the length of the test piece and reduce manpower.

This measuring device can be used to simultaneously monitor the freezing temperature of test piece 2. During the temperature drop process, the specimen 2 will shrink. However, if a large amount of ice is suddenly formed in the specimen 2, the length of the specimen 2 will suddenly increase, and the temperature at this time is the freezing temperature of the specimen 2.

A thermo-hygrometer 6 for reading the temperature and humidity around the test piece is also installed in the temperature-controlled humidity-controlled environment box 10 . The temperature-hygrometer 6 is fixed by the foam board 5, and the top of the temperature and humidity control environment box 10 is provided with a positioning hole, the foam board 5 is arranged in the positioning hole, and the temperature-hygrometer 6 is inserted on the foam board 5, and the temperature-hygrometer 6 Stretch into temperature control humidity control environment box 10. The temperature and humidity meter 6 can be replaced by an electronic temperature and humidity meter, which can be connected with a computer to realize more accurate real-time monitoring of temperature and humidity changes in the cabinet. Combined with an electronic displacement sensor, the length change and temperature or humidity relationship.

The measuring method of a real-time measuring device for the length change of a temperature-controlled and humidity-controlled cement-based material of the present invention comprises the following steps:

(1) Keep the temperature constant and control the humidity change

1) Select an experimental environment with a temperature greater than 0°C, and keep the temperature constant during the experiment, close all the ports 11 of the temperature-controlled and humidity-controlled environmental box 10 and keep them sealed;

2) Configure saturated salt solutions with different solutes according to the equilibrium relative humidity value of the saturated salt solution at the reference experimental temperature;

3) At normal temperature, read the ambient humidity at this time, measure the initial length of the test piece 2 and record the initial length, and then place it stably on the length measuring device;

4) Calibration of the length measuring device and zeroing of the measuring instrument 1;

5) During the test, the solution pool 91 is pulled out of the temperature-controlled and humidity-controlled environment box 10 through the push plate 92, and the partition 94 is opened to put a saturated saline solution into the solution pool 91. Push the solution pool 91 filled with saturated saline solution into the temperature-controlled humidity-controlled environment box 10, maintain a constant humidity for 14 days, read the readings of the measuring instrument 1 and the temperature and humidity values of the thermo-hygrometer 6 and record them;

6) Arrange from high to low according to the environmental humidity values that can be maintained by different solute saturated salt solutions, and carry out the test in step 5 in sequence until the humidity drops from 97% RH to 22% RH and end the test;

7) Data processing, error analysis, obtaining the relationship between the length of the cement mortar specimen and the change in humidity;

(2) Keep the humidity constant and control the temperature change

1) Make several hot rods 7 and fill them with different volumes of liquid ammonia, and store the prepared hot rods 7 in a freezer at -40°C;

2) read the experimental environment humidity at this time, measure the initial length of the test piece 2 and record the initial length, then place it stably on the length measuring device, and cover the partition plate 94 on the solution pool 91, push plate 92 and The side wall of the temperature-controlled and humidity-controlled environment box 10 is tightly attached to maintain good sealing;

3) Calibration of the length measuring device and zeroing of the measuring instrument 1;

4) Take out a hot rod 7 and insert it into the temperature and humidity control environment box 10 from the port 11. The bottom of the rod 71 extends into the temperature and humidity control environment box 10, and the upper part of the rod 71 is located in the temperature and humidity control environment. Outside the box 10, the connection between the hot rod 7 and the temperature and humidity control environment box 10 is kept sealed;

5) Read the temperature of the thermo-hygrometer 6, maintain the current temperature for 1 hour, read and record the reading of the measuring instrument 1;

6) Add one hot rod each time, and repeat steps 4 and 5 of this test until the temperature drops to -18°C;

7) Reduce one hot rod each time, and repeat steps 4 and 5 of this test until the temperature rises to 4°C;

8) End the experiment and put all the hot rods 7 back into the freezer at -40°C;

9) Data processing and error analysis to obtain the relationship between the length of the test piece 2 and the temperature change.

The above is only a preferred embodiment of the present invention, it should be pointed out that, for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications can also be made. It should be regarded as the protection scope of the present invention.

Claims (10)

1. A real-time measuring device for temperature-controlling-humidity-controlling cement-based material length variation, characterized in that: comprising a closed temperature-controlling-humidity environment box (10), a temperature control unit (8) and a humidity control unit (9); The temperature control and humidity control environment box (10) is provided with several closable ports (11) on the side wall, and the temperature control part (8) includes a number of ports that can be inserted into the temperature control and humidity control environment box from the ports (11). (10) the thermal rod (7), the thermal rod (7) comprises a sealed rod body (71), the rod body (71) is hollow, and the bottom of the rod body (71) is stored with heat absorbing and cooling of liquid ammonia (72); The humidity control part (9) includes a solution pool (91), filled with a saturated saline solution (93) in the solution pool (91), and a detachable cover on the solution pool (91) is provided with a partition (94 ), a push plate (92) is installed on the side wall of the solution pool (91), and a through hole (12) is also provided on the side wall of the temperature and humidity control environment box (10), the solution pool (91) through the through hole (12) to slide in and out of the temperature and humidity control environment box (10), the push plate (92) is located outside the temperature control and humidity control environment box (10), and the push plate ( The diameter of 92) is greater than the diameter of through hole (12); A measuring device is also installed in the temperature-controlled and humidity-controlled environment box (10), and the measuring device includes a base (4) on which a bracket (3) for clamping the test piece (2) is installed , the test piece (2) is connected with a measuring instrument (1) for measuring the length change of the test piece (2), and the measuring instrument (1) is installed outside the temperature and humidity control environment box (10); A thermo-hygrometer (6) for reading the temperature and humidity around the test piece (2) is also installed in the temperature and humidity control environment box (10). 2. A real-time measuring device for temperature and humidity control of cement-based material length change according to claim 1, characterized in that: a cooling fin (73) is installed on the outside of the upper part of the rod body (71). 3. A real-time measuring device for temperature and humidity control cement-based material length change as claimed in claim 1, characterized in that: a sealing rubber ring (74) is bonded to the outer wall of the rod body (71), and The material of the sealing rubber ring (74) is low temperature resistant silicone rubber. 4. The real-time measuring device for the length change of a temperature-controlled humidity-controlled cement-based material as claimed in claim 1, characterized in that: the top of the temperature-controlled humidity-controlled environment box (10) is provided with a positioning hole, and the foam The board (5) is arranged in the positioning hole, and a thermo-hygrometer (6) is inserted on the foam board (5), and the thermo-hygrometer (6) extends into the temperature-controlled and humidity-controlled environment box (10). 5. A real-time measuring device for temperature and humidity control cement-based material length change as claimed in claim 1, characterized in that: the measuring instrument (1) is a dial gauge; or the measuring instrument (1) is Electronic displacement sensor. 6. A real-time measuring device for the length change of the temperature-controlled and humidity-controlled cement-based material according to claim 1, characterized in that: the material used for the rod body (71) is steel. 7. The real-time measuring device for the length change of a temperature-controlled humidity-controlled cement-based material as claimed in claim 1, characterized in that: the material used in the temperature-controlled humidity-controlled environment box (10) is plexiglass, or transparent . Low temperature resistant materials, the low temperature resistant range is -30°C to 30°C. 8. A real-time measuring device for temperature and humidity control cement-based material length change as claimed in claim 1, characterized in that: the material used for the bracket (3) is Invar alloy. 9. The real-time measuring device for the length change of a temperature-controlled and humidity-controlled cement-based material as claimed in claim 1, characterized in that: the test piece (2) shrinks during the temperature reduction process, and the test piece (2) ) is the temperature at which ice is formed in it to cause a sudden increase in length, which is determined as the freezing temperature of the specimen (2). 10. A measuring method based on the real-time measuring device for the length change of the temperature-controlled and humidity-controlled cement-based material according to claims 1 to 9, characterized in that: comprising the following steps: (1) Keep the temperature constant and control the humidity change 1) Select an experimental environment with a temperature greater than 0°C, and keep the temperature constant during the experiment, close all ports (11) of the temperature-controlled and humidity-controlled environmental box (10) and keep them sealed; 2) Configure saturated salt solutions with different solutes according to the equilibrium relative humidity value of the saturated salt solution at the reference experimental temperature; 3) At normal temperature, read the ambient humidity at this time, measure the initial length of the test piece (2) and record the initial length, and then place it stably on the length measuring device. The test piece (2) is 40mm×40mm× 160mm standard cement mortar specimen; 4) Calibration of the length measuring device and zeroing of the measuring instrument (1); 5) During the test, put a saturated salt solution into the solution pool (91), push it into the temperature-controlled humidity-controlled environment box (10), maintain a constant humidity for 14 days, and read the readings of the measuring instrument (1) and the temperature-humidity meter (6) temperature and humidity values and records; 6) Arrange the environmental humidity values that can be maintained by different solute saturated salt solutions from high to low, and carry out the test of step (5) in sequence until the test is completed when the experimental humidity is reduced from 97% RH to 22% RH; 7) Data processing, error analysis, obtaining the relationship between the length of the cement mortar specimen and the change in humidity; (2) Keep the humidity constant and control the temperature change 1) Make several hot rods (7), fill them with different volumes of liquid ammonia, and store the prepared hot rods (7) in a freezer at -40°C; 2) Read the humidity of the experimental environment at this time, measure the initial length of the test piece (2) and record the initial length, then place it stably on the length measuring device, and the test piece (2) is 40mm×40mm×160mm standard cement Mortar test piece; 3) Calibration of the length measuring device and zeroing of the measuring instrument (1); 4) Take out a hot rod (7), insert it into the temperature and humidity control environment box (10) from the port (11), the bottom of the rod body (71) extends into the temperature and humidity control environment box (10), And the upper part of the rod body (71) is located outside the temperature and humidity control environment box (10), and the connection between the hot rod (7) and the temperature and humidity control environment box (10) is kept sealed; 5) Read the temperature of the thermo-hygrometer (6), maintain the current temperature for 1 hour, read and record the reading of the measuring instrument (1); 6) Add one hot rod (7) each time, repeat the test steps (4) and (5) until the temperature drops to -18°C; 7) Reduce one hot rod (7) each time, repeat the test steps (4) and (5) until the temperature rises to 4°C; 8) End the experiment and put all the hot rods (7) back into the freezer at -40°C; 9) Data processing and error analysis to obtain the relationship between the length of the test piece (2) and the temperature change.