A device and method for measuring water diffusion coefficient of cement-based materials

Abstract

The present invention discloses a device and method for determining the moisture diffusion coefficient of cement-based materials, and relates to the field of determining physical property parameters of cement-based materials. The measuring device comprises: a mold for fixing embedded pipes and casting cement-based material specimens; embedded pipes for placing temperature and humidity sensors; temperature and humidity sensors for collecting humidity data; and a portable data analyzer for analyzing humidity data and displaying results, and can be connected to a computer. The present invention can effectively determine the moisture diffusion coefficient of cement-based materials, the device is simple and portable, easy to operate, and can quickly analyze and display results, solving the problem that the moisture diffusion coefficient is difficult to determine quickly, and providing measured physical property parameters for durability analysis of cement-based materials. It is suitable for determining the moisture diffusion coefficient of cement-based materials under the same conditions in laboratory scientific research experiments and engineering sites, and can be promoted and applied as a standard device and standard method.

Description

Technical Field

[0001] The invention relates to the technical field of cement-based materials, and relates to a device and method for measuring a water diffusion coefficient. Background Art

[0002] Generally, the ambient humidity is lower than the internal humidity of cement-based materials. Due to the difference between the internal humidity of cement-based materials and the ambient humidity, the internal moisture of cement-based materials will continue to diffuse into the environment, causing the internal relative humidity of cement-based materials to continue to decrease. The decrease in internal relative humidity will cause shrinkage and cracking of cement-based materials, greatly reducing the safety and life of cement-based materials. The moisture diffusion coefficient is an important parameter for calculating the internal relative humidity of cement substrates. Therefore, it is necessary to accurately and quickly determine the moisture diffusion coefficient of cement-based materials. However, the moisture diffusion coefficient of cement-based materials is different from other parameters. The moisture diffusion coefficient is related to the age of cement-based materials, internal relative humidity, temperature, and internal pore structure. Therefore, the moisture diffusion coefficient of cement-based materials is difficult to measure simply and accurately.

[0003] At present, there is no dedicated device for measuring the moisture diffusion coefficient of cement-based materials. Some scholars have proposed their own measurement methods in relevant papers. For example, the literature (Solution of moisture diffusion coefficient of early-age concrete based on internal humidity test, Journal of Tsinghua University (Science and Technology), 2008, 48(12): 2033-2035.) proposed that the measurement device has many operating steps and a long measurement time, and it is impossible to measure the moisture diffusion coefficient of a specific age. The literature (Analysis of temperature and humidity response parameters of concrete: moisture diffusion coefficient and thermal conductivity, Materials Guide, 2021, 35(12), 12075-12080) proposed a measurement device with many operating steps, which makes the cement-based material saturated with water for too long, and it is impossible to ensure that the cement-based material is completely saturated with water.

[0004] Due to the limitations of existing measurement methods, the moisture diffusion coefficient of cement-based materials is generally taken as an empirical value in actual scientific research and engineering calculations, which is difficult to meet actual needs. Therefore, it is urgent to develop a measurement device and method that can quickly, simply and accurately measure the moisture diffusion coefficient of cement-based materials. Summary of the invention

[0005] In order to solve the above problems, the object of the present invention is to provide a device and method for measuring the moisture diffusion coefficient of cement-based materials.

[0006] The above purpose can be achieved through the following technical solutions:

[0007] A device for measuring the water diffusion coefficient of cement-based materials, characterized by comprising a mold, a pre-buried pipe, a temperature and humidity sensor, and a portable data analyzer:

[0008] The mold includes a base, embedded pipe clamps, and plug-in plates;

[0009] The embedded pipe is fixed on the mold through the reserved circular hole on the base and the embedded pipe clamp before pouring the cement-based material. One end embedded in the cement-based material is closed at the end, and two gaps are reserved on the side near the end. The two gaps are symmetrically distributed on both sides of the pipe. The embedded pipe is engraved with length scale lines, and the 0 point of the scale lines is located at the center of the gap. The scale lines are used to accurately control the embedded depth of the embedded pipe;

[0010] The temperature and humidity sensor is placed in the pre-buried pipe during measurement, and the gap between the temperature and humidity sensor and the pre-buried pipe is sealed with a sealing ring and sealant;

[0011] The portable data analyzer can collect, store and analyze humidity data in real time through wired or wireless communication with temperature and humidity sensors, calculate the moisture diffusion coefficient curve based on the data, and display the moisture diffusion coefficient curve and its curve fitting formula on the screen in real time. The portable data analyzer can also be directly connected to a computer.

[0012] Preferably, the base is composed of a bottom surface and four side surfaces, a small circular hole is reserved in the center of the bottom surface for demoulding, and all the side surfaces are fixed on the bottom surface, wherein three side surfaces are of equal height, the height of the fourth side surface is half of the height of the other three side surfaces, and three semicircular holes are reserved on the upper edge of the fourth side surface for placing the embedded pipes, and two bolt holes are reserved on the fourth side surface for fixing the plug plate; there are three embedded pipe clamps, all of which are placed on the outside of the fourth side surface, and the positions correspond to the three semicircular holes reserved on the fourth side surface, and the embedded pipe clamps are fixed to the fourth side surface; corresponding to the fourth side surface The two adjacent sides are higher than the fourth side and have slots for placing the plug-in board; the height of the plug-in board is the same as that of the fourth side, and the thickness is the same as that of the fourth side, and both ends can be inserted into the reserved slots. The plug-in board is reserved with three semicircular holes. After the plug-in board is inserted into the two side slots, the plug-in board and the three semicircular holes on the fourth side form three circular holes, and the three circular holes and the three embedded pipe clamps form an embedded pipe channel. Two bolt holes are reserved on the plug-in board, and their positions are the same as the vertical positions of the bolt holes on the fourth side; a handle is fixed to the outer sides of the two side surfaces adjacent to the fourth side respectively, so as to facilitate the transportation of the mold.

[0013] Preferably, the width of the gap at the end of the embedded pipe buried in the cement-based material is 1 to 3 mm, and a material that prevents slurry from penetrating but allows water to diffuse is pasted outside the gap. The embedding depths of the three embedded pipes are set by the scale lines on the pipe body according to test needs, and the maximum embedding depth is not more than 10 cm.

[0014] Preferably, the material pasted outside the gap at the end of the embedded pipe can be a single layer of water-permeable gauze.

[0015] Preferably, the height of the three sides of the mold at the same height is 40 to 60 mm.

[0016] A method for measuring a water diffusion coefficient of a cement-based material, comprising the following steps:

[0017] S1. Place three embedded pipes on the mold base and fix the embedded pipes with embedded pipe clamps;

[0018] S2. After fixing the three embedded pipes, insert the plug plate into the base and connect it to the side with two screws to further fix the embedded pipes and the plug plate;

[0019] S3. Use a film or paper to block the circular hole on the bottom surface, cast the cement-based material specimen, and after curing for 1 day, demould and cure;

[0020] S4. After the specimens have been cured to the test age, they are vacuum-saturated with water. First, place the specimens in a vacuum container, then start the vacuum pump, and reduce the absolute pressure in the vacuum container to (1-5) kPa within 5 minutes, maintain the vacuum for 3 hours, and then, while the vacuum pump is still running, inject enough distilled water or deionized water until the specimens are submerged. Normal pressure should be restored after the specimens are immersed for 1 hour, and the immersion should continue for (18±2) hours. The vacuum saturation temperature is the temperature required for the target test;

[0021] S5. After the vacuum saturation is completed, take the test piece out of the water and wipe off the excess water on the surface. Keep the temperature and humidity constant in the environment required by the target test, and seal the other five surfaces of the test piece except the surface with the embedded pipe;

[0022] S6. After sealing, place the temperature and humidity sensor in the pre-buried pipe and seal the gap between the temperature and humidity sensor and the pre-buried pipe.

[0023] S7. The portable data analyzer starts to collect, store and analyze the data on the temperature and humidity sensor (3) in real time, calculates the moisture diffusion coefficient curve based on the data, and displays the moisture diffusion coefficient curve and its curve fitting formula on the screen in real time.

[0024] Preferably, the three pre-buried pipes have different buried depths. After determining the maximum buried depth of the pre-buried pipe, the greater the difference between the maximum buried depth and the minimum buried depth, the better. The buried depth of the third pre-buried pipe is the average of the maximum buried depth and the minimum buried depth. The lower the strength of the cement-based material, the greater the maximum buried depth of the pre-buried pipe, but the maximum buried depth is not greater than 10 cm.

[0025] Preferably, the specimen can be sealed by using aluminum foil tape, or by using paraffin or butter, and then wrapped with plastic wrap or covered with a silicone sleeve.

[0026] Preferably, when the test piece is cast, the embedded pipe is kept in a horizontal state, and the casting thickness is the same as the side height of the mold.

[0027] Preferably, the ambient temperature should be kept constant with a variation range of less than 0.5°C; the lower the ambient humidity, the more accurate the moisture diffusion coefficient curve. To speed up the test progress, the wind speed along the surface of the specimen can be increased.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) Since the cement-based material is uneven in the vertical direction when it is poured, the present invention places the embedded pipe horizontally, takes the surface with the embedded pipe as the dry surface, and performs sealing treatment on the other five surfaces, so that when the humidity inside the cement-based material diffuses, the cement-based material in the humidity diffusion direction is uniform;

[0030] (2) The present invention adopts a pre-buried pipe method, designs a pipe clamp to fix the pre-buried pipe, and at the same time, a scale line is engraved on the pre-buried pipe body, so as to achieve precise control of the humidity measurement position and effectively prevent the position of the pre-buried pipe from changing during the pouring process of the cement-based material;

[0031] (3) A layer of gauze is pre-pasted at the reserved gap at the embedded end of the embedded pipe, which effectively prevents mortar from entering the embedded pipe when pouring cement-based materials, and does not affect the temperature and humidity sensor to measure the temperature and humidity of the cement-based material at the gap;

[0032] (4) The present invention adopts a vacuum saturation method to fully saturate the interior of the cement-based material with water, which greatly reduces the time for increasing the humidity inside the cement-based material. The vacuum saturation equipment is mature and easy to operate;

[0033] (5) The measuring device disclosed in the present invention can be produced in a standardized manner, has a short measuring time, is easy to operate, and solves the problem of measuring the water diffusion coefficient of cement-based materials at a specific age;

[0034] (6) The present invention can be connected to the temperature and humidity sensor by wire or wirelessly through a portable data analyzer to collect, store and analyze temperature and humidity data in real time, and display the moisture diffusion coefficient curve and function value of cement-based materials in real time. It is suitable for laboratory scientific research and for use on engineering sites, and can be promoted and applied as a standard device and standard method. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0036] Fig. 1 is a schematic diagram of the measuring process of the present invention.

[0037] Figure 2 The top view of the mold.

[0038] Figure 3 This is the front view of the mold.

[0039] Figure 4 This is the front view of the plugboard.

[0040] Figure 5 This is a top view of the plugboard.

[0041] Figure 6 This is a detailed drawing of the embedded pipe end.

[0042] Figure 7 These are the front view, top view and side view of the embedded pipe clamp.

[0043] Figure 8 This is a graph of the water diffusion coefficient measured in Example 2.

[0044] In the figure: 1, mold; 2, embedded pipe; 3, temperature and humidity sensor; 4, portable data analyzer; 5, mold base; 6, embedded pipe clamp; 7, plug plate; 8, mold bottom; 9, mold side; 10, mold side; 11, mold side; 12, mold side; 13, mold handle; 14, sealant sealing treatment between temperature and humidity sensor and embedded pipe; 15, embedded pipe anti-seepage slurry material; 16, reserved gap at embedded end of embedded pipe; 17, sealing treatment of non-dry surface of concrete specimen; 18, sealing ring between temperature and humidity sensor and embedded pipe; 19, computer; 20, card slot; 21, reserved bolt hole on side (12); 22, reserved semicircular hole on side (12); 23, circular hole in the center of mold bottom; 24, reserved bolt hole on plug plate (7); 25, reserved semicircular hole on plug plate (7); 26, scale line on embedded pipe (2). DETAILED DESCRIPTION

[0045] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] Embodiment 1: As shown in Figures 1-7, a device for measuring the water diffusion coefficient of cement-based materials includes: 1. mold; 2. embedded pipe; 3. temperature and humidity sensor; 4. portable data analyzer; 5. mold base; 6. embedded pipe clamp; 7. plug-in board; 8. mold bottom; 9. mold side; 10. mold side; 11. mold side; 12. mold side; 13. mold handle; 14. sealant sealing treatment between the temperature and humidity sensor and the embedded pipe; 15. embedded pipe anti-seepage slurry Materials; 16. Reserved gap at the end of the embedded pipe; 17. Sealing treatment of the non-dry surface of the concrete specimen; 18. Sealing ring between the temperature and humidity sensor and the embedded pipe; 19. Computer; 20. Card slot; 21. Reserved bolt hole on the side (12); 22. Reserved semicircular hole on the side (12); 23. Round hole in the center of the bottom surface of the mold; 24. Reserved bolt hole on the plug plate (7); 25. Reserved semicircular hole on the plug plate (7); 26. Scale line on the embedded pipe (2).

[0047] The mold (1) comprises a base (5), a pre-buried pipe clamp (6), and a plug plate (7);

[0048] The embedded pipe (2) is fixed on the mold through the reserved circular hole on the base (5) and the embedded pipe clamp (6) before the cement-based material is poured. One end embedded in the cement-based material is closed at the end, and two gaps (16) are reserved on the side near the end. The two gaps (16) are symmetrically distributed on both sides of the pipe. The embedded pipe (2) is engraved with length scale lines (26), and the zero point of the scale lines is located at the center of the gap. The scale lines are used to accurately control the embedding depth of the embedded pipe (2);

[0049] The temperature and humidity sensor (3) is placed in the pre-buried pipe (2) during measurement, and the gap between the temperature and humidity sensor (3) and the pre-buried pipe (2) is sealed (16) with a sealing ring (18) and a sealing glue;

[0050] The portable data analyzer (4) can collect, store and analyze humidity data in real time by means of wired or wireless communication with the temperature and humidity sensor (3), calculate a moisture diffusion coefficient curve based on the data, and display the moisture diffusion coefficient curve and its curve fitting formula on a screen in real time. The portable data analyzer (4) can also be directly connected to a computer (19).

[0051] The base (5) is composed of a bottom surface (8), a side surface (9), a side surface (10), a side surface (11), and a side surface (12). A small circular hole (23) is reserved in the center of the bottom surface (8) for demoulding. All the side surfaces are fixed on the bottom surface (8). The side surfaces (9), (10), and (11) are of equal height. The height of the side surface (12) is half of the height of the other three side surfaces. Three semicircular holes (22) are reserved on the upper edge of the side surface (12) for placing the embedded pipe (2). Two bolt holes (21) are reserved on the side surface (12) for fixing the plug plate (7). There are three embedded pipe clamps (6) in total, all of which are placed outside the side surface (12) and their positions correspond to the three semicircular holes (22) reserved on the side surface (12). The embedded pipe clamps (6) are fixed to the side surface (12). The side surface (10) and the side surface (11) are connected to the side surface (12). The side surface (10) and the side surface (11) are adjacent to each other, and a slot (20) is reserved on the part of the side surface (10) and the side surface (11) that is higher than the side surface (12) for placing the plug plate (7); the height of the plug plate (7) is the same as that of the side surface (12); the thickness of the plug plate (7) is the same as that of the side surface (12); both ends of the plug plate (7) can be inserted into the slots (20) reserved on the side surface (10) and the side surface (11); three semicircular holes (25) are reserved on the plug plate (7); after the plug plate (7) is inserted into the side surface (10) and the side surface (11), the plug plate (7) and the three semicircular holes on the side surface (12) form three circular holes; the three circular holes (25) and the three embedded pipe clamps (6) form an embedded pipe channel; two bolt holes (24) are reserved on the plug plate (7), and the positions are the same as the vertical positions of the bolt holes (21) on the side surface (12); a handle (13) is fixed on the outer side of the side surface (10) and the side surface (11) respectively, so as to facilitate the transportation of the mold (1).

[0052] The width of the gap (16) at the end of the pre-buried pipe (2) buried in the cement-based material is 1 to 3 mm, and a material (15) that prevents slurry from penetrating but allows water to diffuse is pasted outside the gap. The embedding depth of the three pre-buried pipes (2) is set according to test requirements through the pipe body scale line (26), and the maximum embedding depth is not greater than 10 cm.

[0053] The material (15) pasted outside the gap at the end of the embedded pipe (2) can be a single layer of water-permeable gauze.

[0054] The heights of the side surface (9), the side surface (10) and the side surface (11) are 40 to 60 mm.

[0055] A method for measuring a water diffusion coefficient of a cement-based material, characterized in that it comprises the following steps:

[0056] S1, placing three embedded pipes (2) on the mold base (5), and fixing the embedded pipes (2) by embedded pipe clamps (6);

[0057] S2. After the three embedded pipes (2) are fixed, the plug plate (7) is inserted into the base (5) and connected to the side (12) with two screws to further fix the embedded pipes (2) and the plug plate (7);

[0058] S3, plug the circular hole (23) on the bottom surface (8) with a film or paper, then cast the cement-based material specimen, and after curing for 1 day, demould and cure;

[0059] S4. After the specimens have been cured to the test age, they are vacuum-saturated with water. First, place the specimens in a vacuum container, then start the vacuum pump, and reduce the absolute pressure in the vacuum container to (1-5) kPa within 5 minutes, maintain the vacuum for 3 hours, and then, while the vacuum pump is still running, inject enough distilled water or deionized water until the specimens are submerged. Normal pressure should be restored after the specimens are immersed for 1 hour, and the immersion should continue for (18±2) hours. The vacuum saturation temperature is the temperature required for the target test;

[0060] S5. After the vacuum saturation is completed, remove the test piece from the water and wipe off the excess water on the surface. Keep the ambient temperature and humidity constant at the temperature and humidity required by the target test, and perform sealing treatment (17) on the other five surfaces of the test piece except the surface with the embedded pipe (2);

[0061] S6. After the sealing process, the temperature and humidity sensor (3) is placed in the pre-buried pipe (2), and the gap between the temperature and humidity sensor (3) and the pre-buried pipe (2) is sealed;

[0062] S7, the portable data analyzer (4) starts to collect, store and analyze the data on the temperature and humidity sensor (3) in real time, calculates the moisture diffusion coefficient curve based on the data, and displays the moisture diffusion coefficient curve and its curve fitting formula on the screen in real time.

[0063] Furthermore, the three pre-buried pipes (2) have different buried depths. After determining the maximum buried depth of the pre-buried pipe (2), the greater the difference between the maximum buried depth and the minimum buried depth, the better. The buried depth of the third pre-buried pipe (2) is the average of the maximum buried depth and the minimum buried depth. The lower the strength of the cement-based material, the greater the maximum buried depth of the pre-buried pipe (2), but the maximum buried depth is not greater than 10 cm.

[0064] Furthermore, the specimen can be sealed by using aluminum foil tape, or by using paraffin or butter, and then wrapped with plastic wrap or covered with a silicone sleeve.

[0065] Furthermore, when the test piece is cast, the embedded pipe (2) is kept in a horizontal state, and the casting thickness is the same as the height of the side surface (9), the side surface (10), and the side surface (11) of the mold (1).

[0066] Furthermore, the ambient temperature should be kept constant with a variation range of less than 0.5°C; the lower the ambient humidity, the more accurate the moisture diffusion coefficient curve. To speed up the test progress, the wind speed along the surface of the specimen can be increased.

[0067] Example 2: A method for measuring the water diffusion coefficient of cement-based materials using a measuring device. The measuring device is used to select C30 concrete, and the specific mix ratio is as follows:

[0068] Cement: water: sand: stone: fly ash = 240: 186: 750: 1150: 60

[0069] The following steps are involved:

[0070] S1, the height of the mold side (9), (10), (11) is 50 mm, and three embedded pipes (2) are placed on the mold base (5). The embedded depths of the three embedded pipes (2) are 20 mm, 60 mm, and 100 mm, respectively. The embedded pipes (2) are fixed by embedded pipe clamps (6), and the gap (16) at the end of the embedded pipes is 2 mm wide;

[0071] S2. After the three embedded pipes (2) are fixed, the plug plate (7) is inserted into the base (5) and connected to the side (12) with two screws to further fix the embedded pipes (2) and the plug plate (7);

[0072] S3, plug the circular hole (23) on the bottom surface (8) with a film or paper, then cast the C30 concrete specimen, and after curing for 1 day, demould and place it in a standard concrete curing room for curing;

[0073] S4. When the specimens are cured for 28 days, vacuum saturate the specimens with water. First, place the specimens in a vacuum container, then start the vacuum pump, and reduce the absolute pressure in the vacuum container to 3kPa within 5 minutes, maintain the vacuum for 3 hours, and then, while the vacuum pump is still running, inject enough distilled water or deionized water until the specimens are submerged. Normal pressure should be restored after the specimens are immersed for 1 hour, and the immersion should continue for 18 hours. The vacuum saturation temperature is 23°C;

[0074] S5. After the vacuum saturation is completed, remove the test piece from the water and wipe off the excess water on the surface. In an environment with a temperature of 23±0.3°C and a humidity of 30%, perform an aluminum foil tape sealing treatment (17) on the other five surfaces of the test piece except the surface with the embedded pipe (2);

[0075] S6. After the sealing process, the temperature and humidity sensor (3) is placed in the pre-buried pipe (2), and a sealing ring and a sealing adhesive are used to seal the gap between the temperature and humidity sensor (3) and the pre-buried pipe (2);

[0076] S7, the portable data analyzer (4) starts to collect, store and analyze the data on the temperature and humidity sensor (3) in real time, calculates the moisture diffusion coefficient curve based on the data, and displays the moisture diffusion coefficient curve and its curve fitting formula on the screen in real time.

[0077] The specific calculation process of moisture diffusion coefficient is as follows:

[0078] The calculation formula of relative humidity inside the specimen with respect to time and position is as follows:

[0079]

[0080] Wherein, H is the relative humidity inside the specimen; x is the depth of the calculated position from the drying surface of the specimen. In this embodiment, the values ​​of x at the positions measured by the three temperature and humidity sensors (3) are 20 mm, 60 mm, and 100 mm, respectively; t is the time from the start of drying of the specimen; m, n, a, and b are constants, whose values ​​are obtained by fitting the humidity change over time at the three positions of the specimen measured by the three temperature and humidity sensors (3) through formula (1). In this embodiment, based on the 7-day test data, the values ​​of m, n, a, and b are fitted to be 1.0054, 2.206, 0.66, and 0.94, respectively. Since the values ​​of m, n, a, and b are obtained by fitting, as the measurement time increases, the values ​​of m, n, a, and b will also change, but gradually tend to be stable.

[0081] The calculation formula of water diffusion coefficient is as follows:

[0082]

[0083] By using formula (2), the curve of the change of the water diffusion coefficient with the relative humidity inside the specimen can be plotted in real time. Figure 8 shown.

[0084] Figure 8 The middle curve is obtained by substituting the m, n, a, and b values ​​obtained by fitting formula (1) into formula (2). Since the actual ambient humidity is 30%, the minimum relative humidity value inside the specimen is also 30%. Therefore, Figure 8 The data of the solid line part of the middle curve can be verified by comparing the humidity data calculated by the diffusion equation with the actual measured humidity data, but the data of the dotted line part can only be drawn by formula (2). Existing experiments show that when the humidity is below 50%, the moisture diffusion coefficient changes little with humidity. Therefore, in actual tests, the lower the ambient humidity, the larger the humidity range of the measured moisture diffusion coefficient. It is recommended that the ambient humidity should be lower than 50% during the test.

[0085] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

Claims

1. A device for measuring water diffusion coefficient of cement-based materials, characterized in that: It comprises a mold (1), a pre-buried pipe (2), a temperature and humidity sensor (3), and a portable data analyzer (4); The mold (1) comprises a base (5), a pre-buried pipe clamp (6), and a plug plate (7); The embedded pipe (2) is fixed on the mold through the reserved circular hole on the base (5) and the embedded pipe clamp (6) before the cement-based material is poured. One end embedded in the cement-based material is closed at the end, and two gaps are reserved on the side near the end. The two gaps are symmetrically distributed on both sides of the pipe. The embedded pipe (2) is engraved with length scale lines, and the zero point of the scale lines is located at the center of the gap. The scale lines are used to accurately control the embedding depth of the embedded pipe (2); The temperature and humidity sensor (3) is placed in the pre-buried pipe (2) during measurement, and a sealing ring and a sealing glue are used to seal the gap between the temperature and humidity sensor (3) and the pre-buried pipe (2); The portable data analyzer (4) collects, stores, and analyzes humidity data in real time by means of wired or wireless communication with the temperature and humidity sensor (3), calculates a moisture diffusion coefficient curve based on the data, and displays the moisture diffusion coefficient curve and its curve fitting formula on a screen in real time. The portable data analyzer (4) is directly connected to a computer; The base (5) is composed of a bottom surface (8), a side surface (9), a side surface (10), a side surface (11), and a side surface (12). A small circular hole is reserved in the center of the bottom surface (8) for demoulding. All the side surfaces are fixed on the bottom surface (8). The side surfaces (9), (10), and (11) are of equal height. The height of the side surface (12) is half the height of the other three side surfaces. Three semicircular holes are reserved on the upper edge of the side surface (12) for placing the embedded pipe (2). Two bolt holes are reserved on the side surface (12) for fixing the plug plate (7). There are three embedded pipe clamps (6) in total, all of which are placed outside the side surface (12) at positions corresponding to the three semicircular holes reserved on the side surface (12). The embedded pipe clamps (6) are fixed to the side surface (12). The side surfaces (10) and (11) are connected to the side surfaces. The sides (12) are adjacent to each other, and the side (10) and the side (11) are higher than the side (12) and have slots for placing the plug plate (7); the height of the plug plate (7) is the same as that of the side (12), the thickness of the plug plate (7) is the same as that of the side (12), and both ends are inserted into the slots reserved on the side (10) and the side (11). The plug plate (7) has three semicircular holes reserved. After the plug plate (7) is inserted into the side (10) and the side (11), the plug plate (7) and the three semicircular holes on the side (12) form three circular holes, and the three circular holes and the three embedded pipe clamps (6) form embedded pipe channels. Two bolt holes are reserved on the plug plate (7), and the positions are the same as the vertical positions of the bolt holes on the side (12); a handle (13) is fixed on the outer side of the side (10) and the side (11) respectively, so as to facilitate the transportation of the mold (1).

2. The device for measuring water diffusion coefficient of cement-based materials according to claim 1, characterized in that: The width of the gap between the ends of the pre-buried pipes (2) buried in the cement-based material is 1 to 3 mm, and a material that prevents slurry from penetrating but allows water to diffuse is pasted outside the gap. The embedding depths of the three pre-buried pipes (2) are set according to test requirements through the scale lines on the pipe body, and the maximum embedding depth is not greater than 10 cm.

3. A cement-based material water diffusion coefficient measuring device according to claim 2, characterized in that: The material pasted outside the gap at the end of the embedded tube (2) is a single layer of water-permeable gauze.

4. The device for measuring water diffusion coefficient of cement-based materials according to claim 1, characterized in that: The heights of the side surface (9), the side surface (10), and the side surface (11) are 40 to 60 mm.

5. A method for measuring the water diffusion coefficient of cement-based materials according to claim 1, characterized in that: The following steps are involved: S1, placing three embedded pipes (2) on the mold base (5), and fixing the embedded pipes (2) by embedded pipe clamps (6); S2. After the three embedded pipes (2) are fixed, the plug plate (7) is inserted into the base (5) and connected to the side (12) with two screws to further fix the embedded pipes (2) and the plug plate (7); S3, plug the circular hole on the bottom surface (8) with a film or paper, then cast the cement-based material specimen, and after curing for 1 day, demould and cure; S4. After the specimens have been cured to the test age, they are saturated with water under vacuum. First, the specimens are placed in a vacuum container, and then the vacuum pump is started. The absolute pressure in the vacuum container is reduced to (1-5) kPa within 5 minutes. The absolute pressure is maintained for 3 hours. Then, with the vacuum pump still running, sufficient distilled water or deionized water is injected until the specimens are submerged. Normal pressure should be restored after the specimens are immersed for 1 hour, and the immersion should continue for (18±2) hours. The vacuum saturation temperature is the temperature required for the target test. S5. After the vacuum saturation is completed, the test piece is taken out of the water, and the excess water on the surface is wiped off. The temperature and humidity are kept constant in the environment at the temperature and humidity required by the target test, and the other five surfaces of the test piece are sealed except for the surface with the embedded pipe (2); S6. After the sealing process, the temperature and humidity sensor (3) is placed in the pre-buried pipe (2), and the gap between the temperature and humidity sensor (3) and the pre-buried pipe (2) is sealed; S7, the portable data analyzer (4) starts to collect, store and analyze the data on the temperature and humidity sensor (3) in real time, calculates the moisture diffusion coefficient curve based on the data, and displays the moisture diffusion coefficient curve and its curve fitting formula on the screen in real time.

6. The measuring method of the cement-based material water diffusion coefficient measuring device according to claim 5, characterized in that: The three pre-buried pipes (2) have different buried depths. After determining the maximum buried depth of the pre-buried pipe (2), the greater the difference between the maximum buried depth and the minimum buried depth, the better. The buried depth of the third pre-buried pipe (2) is the average value of the maximum buried depth and the minimum buried depth. The lower the strength of the cement-based material, the greater the maximum buried depth of the pre-buried pipe (2), but the maximum buried depth is not greater than 10 cm.

7. The measuring method of the cement-based material water diffusion coefficient measuring device according to claim 5, characterized in that: The specimen is sealed with aluminum foil tape, paraffin wax or butter, and then wrapped with plastic wrap or covered with a silicone sleeve.

8. The measuring method of the cement-based material water diffusion coefficient measuring device according to claim 5, characterized in that: When the test piece is cast, the embedded pipe (2) is kept in a horizontal state, and the casting thickness is the same as the height of the side surface (9), the side surface (10), and the side surface (11) of the mold (1).

9. The measuring method of the cement-based material water diffusion coefficient measuring device according to claim 5, characterized in that: The ambient temperature was kept constant with a variation of less than 0.5°C. The lower the ambient humidity, the more accurate the moisture diffusion coefficient curve. To speed up the test, the wind speed along the surface of the specimen was increased.

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