Testing device and method for analyzing influence of internal relative humidity on concrete self-constriction by adjusting temperature field

Abstract

The invention discloses a test device and method for analyzing the influence of internal relative humidity on concrete self-constriction by adjusting a temperature field, and relates to the technical field of concrete testing, the test device comprises a constriction mold assembly, the constriction mold assembly is composed of an outer plate, an inner plate, two side plates and a bottom plate, an embedded type strain sensor and an embedded type humidity sensor are arranged in the shrinkage mold assembly, the output end of the embedded type strain sensor and the output end of the embedded type humidity sensor are connected with a controller, the output end of the controller is connected with a heater and a refrigerator, and water tanks are arranged on the two sides of the shrinkage mold assembly. The shrinkage die assembly is connected with the heater, the refrigerator and the water tank through guide pipes. According to the invention, the thin-wall arc-shaped shrinkage test piece can be conveniently prepared, and a uniform and controllable temperature field is established around the shrinkage test piece, so that the effective conduction of the temperature in the shrinkage test piece is ensured, the quantitative regulation and control of the relative humidity gradient rate in the test piece are further realized, and the theoretical research requirements of concrete self-shrinkage are met.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete testing, and in particular to an experimental device and method for analyzing the influence of internal relative humidity on concrete autogenous shrinkage by adjusting the temperature field. Background Technique

[0002] Concrete shrinkage can cause the initiation and development of microcracks inside the matrix, deteriorating the mechanical properties and durability of the material. Therefore, its development law and evolution mechanism have received extensive attention. The shrinkage of concrete after setting consists of autogenous shrinkage and drying shrinkage. Among them, the volume stability of low water-binder ratio concrete is mainly related to autogenous shrinkage, and the autogenous shrinkage of concrete is closely related to the cement hydration reaction. During the cement hydration process, the absolute volume of concrete decreases, and at the same time, the hydration products are interconnected to form a supporting skeleton, thus forming microscopic pores. After that, the hydration reaction consumes part of the pore water, resulting in a decrease in the internal relative humidity of the concrete and an increase in capillary negative pressure, which further exacerbates the autogenous shrinkage of the concrete. After the concrete sets, the self-drying process of the unsaturated pores is the main driving force for the autogenous shrinkage of the matrix, and the internal relative humidity of the concrete is the key parameter reflecting the law of pore self-drying. Therefore, it is of great scientific significance to accurately and efficiently analyze the evolution mechanism of concrete autogenous shrinkage starting from the internal relative humidity.

[0003] Internal curing is a typical measure to inhibit the autogenous shrinkage of concrete by regulating the internal relative humidity of the matrix. When applied in engineering, materials capable of storing water, such as ceramsite and expanded shale, are usually selected and mixed with the concrete to construct a uniformly dispersed micro water storage system inside the matrix. When the cement hydration causes the internal humidity of the concrete to decrease, the water storage material slowly releases water under the action of the humidity difference, delaying the rate of decrease of the internal relative humidity and inhibiting the autogenous shrinkage of the matrix. However, although internal curing can effectively maintain the pore humidity inside the concrete, the effect of this method generally lacks regularity and cannot efficiently achieve quantitative control of the internal humidity. Therefore, this method is difficult to effectively support the correlation analysis between the internal relative humidity and autogenous shrinkage. To meet the urgent needs of related research, it is necessary to propose a new experimental device and testing method to quantitatively regulate the internal relative humidity of the matrix and provide technical support for the theoretical research of concrete autogenous shrinkage.

[0004] In the prior art, it is common to control the relative humidity inside concrete through internal curing measures, but this method cannot achieve quantitative control of the internal relative humidity well and is difficult to meet the relevant testing requirements. The evolution law of internal relative humidity is an important indicator for analyzing the autogenous shrinkage of concrete, but current testing technologies rarely provide accurate and efficient testing methods. Analyzing the influence mechanism of the internal relative humidity variation rate on the time-varying characteristics of autogenous shrinkage is not conducive to establishing a perfect shrinkage constraint mechanism from a theoretical level, and it is difficult to provide complete technical guidance for the shrinkage control of concrete. In order to overcome the above shortcomings, we use environmental factors, such as external temperature field or external humidity field, as analysis variables to adjust the internal relative humidity and achieve the shrinkage test objectives. Different from the external humidity field, the temperature field can directly affect the evolution law of the relative humidity inside the matrix through heat conduction when the concrete is sealed and cured. Therefore, a test device and method for analyzing the influence of internal relative humidity on the autogenous shrinkage of concrete by adjusting the temperature field is proposed. Summary of the invention

[0005] The purpose of the new invention is to provide a test device and method for analyzing the influence of internal relative humidity on concrete autogenous shrinkage by adjusting the temperature field. It can easily prepare thin-walled arc-shaped shrinkage specimens and establish a uniform and controllable temperature field around the shrinkage specimens, thereby ensuring that the temperature is effectively conducted inside the shrinkage specimens, and then achieving quantitative control of the relative humidity change rate inside the specimens, meeting the theoretical research needs of concrete autogenous shrinkage, and solving the problems raised in the above-mentioned background technology.

[0006] In order to achieve the above object, the present invention provides the following technical solutions: A test device for analyzing the influence of internal relative humidity on concrete autogenous shrinkage by adjusting a temperature field, comprising a shrinkage mold assembly, wherein the shrinkage mold assembly comprises a bottom plate, an outer plate and an inner plate both of which have semicircular arc cross-sections are arranged on the top of the bottom plate, the inner plate is located in the outer plate, and side plates are arranged at both ends of the outer plate and the inner plate; An embedded strain sensor and an embedded humidity sensor are arranged inside the shrinking mold assembly, the output ends of the embedded strain sensor and the embedded humidity sensor are connected to a controller through lines, the output ends of the controller are connected to a heater and a refrigerator through lines, water tanks are arranged on both sides of the shrinking mold assembly, and the outer plate and the side plate are respectively connected to the heater, the refrigerator and the water tank through conduits.

[0007] Preferably, a foam board is arranged between the outer panel and the inner panel, and the upper surface of the foam board is in close contact with the inner wall of the outer panel, and a shrinkage specimen with a semicircular arc cross-section for testing concrete is arranged between the foam board and the inner panel, and the thickness of the shrinkage specimen does not exceed 50 mm. After the foam board is pulled out, an outer panel cavity is formed between the outer panel and the specimen, and a bottom panel cavity is formed between the inner panel and the bottom panel.

[0008] Preferably, the side plates are rectangular plates, the length and width dimensions of the side plates are respectively equal to the outer diameter and outer radius dimensions of the cross-section of the outer plate, the width of the bottom plate is equal to the outer diameter dimension of the cross-section of the outer plate, and the length of the bottom plate is equal to the length after the two side plates are spliced with the outer plate.

[0009] Preferably, the inner plate can be made of a thin-walled copper plate or a stainless steel heating plate.

[0010] Preferably, the embedded strain sensor includes an embedded strain gauge, a vibrating wire strain sensor, a non-contact optical sensor and a distributed optical fiber sensor, and the embedded humidity sensor includes a digital humidity sensor, a piezoelectric humidity sensor and a built-in humidity sensor.

[0011] Preferably, the temperature control range of the heater is 20°C to 100°C, and the temperature control range of the cooler is -20°C to 20°C.

[0012] Preferably, when the shrinkage specimen is subjected to a long-term shrinkage test, a sealed test chamber is arranged outside, and the sealed test chamber is connected to the heater, the cooler and the water tank respectively through arranged conduits.

[0013] Preferably, an arc-shaped bottom film is arranged on the side of the outer plate away from the bottom plate, and an airbag for replacing the inner plate is arranged in the inner cavity of the outer plate.

[0014] The present invention also provides a test method for analyzing the influence of internal relative humidity on the autogenous shrinkage of concrete by adjusting the temperature field. The test is carried out by using the above-mentioned test device for analyzing the influence of internal relative humidity on the autogenous shrinkage of concrete by adjusting the temperature field, and specifically includes the following steps: S1. Assemble the shrinkage mold assembly: First, apply vaseline on the contact surfaces of the inner plate, the side plates, the bottom plate and the foam board with the shrinkage specimen, and spread a plastic film on the surface coated with vaseline. Then, splice the outer plate, the inner plate and the bottom plate into an assembly without side plates, and then place the foam board inside and make it fit with the inner wall of the outer plate; S2. Install and calibrate the embedded sensors: Position and install the embedded strain sensor and the embedded humidity sensor along the axis position of the shrinkage specimen. During the installation process, check the position and direction of the sensors multiple times to ensure that the deviation error between the axis of the sensor and the target axis does not exceed 2°. After installation, calibrate the sensitivity and initial reading of the sensors; S3. Pour the shrinkage specimen: Install one side plate of the shrinkage mold assembly, then erect the mold, pour the concrete from the open end on the other side of the mold, and slowly vibrate the concrete. After pouring, install another side plate at the open end of the mold, and at the same time move the mold to the shrinkage test chamber; S4. Assemble the test system: When the concrete is about to set, lay the whole flat, remove the side panels and the outer panel, then take out the foam panel, respectively place temperature probes in the cavity left by the foam panel in the mold and in the cavity between the bottom panel and the inner panel, then install the outer panel and the side panel back into the mold, and then use conduits to connect the outer panel with the heater, the refrigerator, the outer panel with the water tank, the side panel with the heater, the refrigerator, and the side panel with the water tank, wherein the conduit on the outer panel extends into the outer panel cavity in the mold, and the conduit on the side panel extends into the bottom panel cavity, and at the same time, connect one end of the embedded strain sensor, the embedded humidity sensor, the heater, and the refrigerator to the controller; S5. Test the relative humidity inside the shrinkage specimen: after the initial setting of the concrete, read the time-varying data of the relative humidity inside the shrinkage specimen on the controller to obtain the evolution law of the relative humidity inside the shrinkage specimen under the standard ambient temperature. Thereafter, set the test temperature on the controller, control the heater or refrigerator to introduce the gas of the set temperature into the outer plate cavity and the bottom plate cavity, and obtain the time-varying characteristics of the relative humidity inside the shrinkage specimen under different temperature conditions. S6. Test the autogenous shrinkage of shrinkage specimens: Based on the evolution law of relative humidity inside the shrinkage specimens under different temperature conditions, set the controller program to adjust the temperature field inside the outer plate cavity and the bottom plate cavity of the specimen at different test ages, or let the controller intelligently identify the real-time humidity status and automatically adjust the temperature field value according to the set program, thereby changing the rate of change of relative humidity inside the concrete, so as to control the relative humidity inside the concrete at the target value at a specific age. At the same time, read the shrinkage results of the shrinkage specimens and analyze the theoretical relationship between the relative humidity inside the concrete and autogenous shrinkage.

[0015] In summary, the present invention has the following beneficial effects: 1. The present invention proposes a detachable and assembled arc cross-section shrinkage mold, and establishes a controllable temperature rise and fall system on the top and bottom surfaces of the mold to achieve variable control of the external temperature field of the shrinkage specimen. At the same time, the design of the thin-walled arc specimen enables the temperature to be uniformly transmitted along the radial direction of the arc, thereby ensuring the effectiveness and stability of the temperature effect. The test device is exquisitely constructed and easy to operate, providing the necessary equipment foundation for analyzing the correlation mechanism between the relative humidity inside the concrete and the shrinkage. At the same time, through the design of the detachable mold, space is created for establishing a controllable temperature field around the specimen at an early age stage, so that the analysis and testing of the relative humidity and shrinkage inside the concrete can be carried out earlier to meet various testing needs.

[0016] 2. The present invention establishes an intelligent environmental control system for concrete shrinkage testing. By transmitting the internal relative humidity of the concrete and the shrinkage test data to the controller, the real-time state of the interior of the concrete can be analyzed by setting existing programs. Then, the set program in the controller drives the heating or refrigeration device to operate according to the established test requirements, realizing the quantitative analysis of the internal relative humidity and autogenous shrinkage of the concrete. Compared with the environmental control system of traditional curing chambers, it has the characteristics of small floor area, low energy consumption, high automation degree, good stability, etc., and can efficiently promote the implementation and development of relevant theoretical research.

[0017] 3. The testing method mentioned in the present invention can accurately measure the early autogenous shrinkage of high-strength and ultra-high-strength concrete components with small wall thickness, meeting the needs of new technology research and development under the current industrial upgrading trend, and having great market practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the early autogenous shrinkage testing device of the present invention without side plates; Figure 2 It is an exploded view of the components of the autogenous shrinkage mold assembly of the present invention; Figure 3 It is a schematic assembly diagram of the autogenous shrinkage mold assembly without side plates of the present invention; Figure 4 It is a schematic diagram of the early autogenous shrinkage testing device without side plates when the inner plate of the present invention adopts a stainless steel heating plate; Figure 2 ; Figure 5 It is a schematic diagram of the arc-shaped bottom mold component during open-pour of the present invention; Figure 6 It is a schematic diagram of the inflatable airbag component during open-pour of the present invention; Figure 7 It is a schematic diagram of the autogenous shrinkage mold before and after airbag inflation during open-pour of the present invention; Figure 8 It is a schematic diagram of the long-term autogenous shrinkage testing device using a sealed test chamber of the present invention; Figure 9 It is a schematic diagram of the hollow cylindrical cross-section shrinkage test piece adapted to the test system of the present invention.

[0019] In the figures: 1. Autogenous shrinkage mold assembly; 101. Outer plate; 1011. Outer plate cavity; 102. Inner plate; 103. Side plate; 104. Bottom plate; 1041. Bottom plate cavity; 105. Foam board; 2. Embedded strain sensor; 3. Embedded humidity sensor; 4. Heater; 5. Refrigerator; 6. Controller; 7. Water tank; 8. Conduit; 9. Shrinkage test piece; 10. Sealed test chamber; 11. Arc-shaped bottom mold; 12. Airbag. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0021] Embodiment 1: As Figures 1 - 3 shown, a test device for analyzing the influence of internal relative humidity on the autogenous shrinkage of concrete by adjusting the temperature field includes a shrinkage mold assembly 1. The shrinkage mold assembly 1 includes a bottom plate 104. An outer plate 101 and an inner plate 102 with semi-circular cross-sections are provided on the top of the bottom plate 104. The inner plate 102 is located inside the outer plate 101. In this embodiment, the inner plate 102 is made of a copper plate with good thermal conductivity. Side plates 103 are provided at both ends of the outer plate 101 and the inner plate 102. Slots can be opened at the joints of the outer plate 101, the side plates 103 and the bottom plate 104, and they are assembled by detachable splicing. A foam board 105 is provided between the outer plate 101 and the inner plate 102, and the upper surface of the foam board 105 is closely attached to the inner wall of the outer plate 101. A shrinkage specimen 9 in the shape of a semi-circular cross-section of test concrete is provided between the foam board 105 and the inner plate 102. The thickness of the shrinkage specimen 9 does not exceed 50 mm. After the foam board 105 is drawn out, an outer plate cavity 1011 is formed between the outer plate and the specimen 9, and a bottom plate cavity 1041 is formed between the inner plate 102 and the bottom plate 104.

[0022] An embedded strain sensor 2 and an embedded humidity sensor 3 are provided inside the shrinkage mold assembly 1. The output ends of the embedded strain sensor 2 and the embedded humidity sensor 3 are connected to a controller 6 through lines. The output end of the controller 6 is connected to a heater 4 and a cooler 5 through lines. Water tanks 7 are provided on both sides of the shrinkage mold assembly 1. The outer plate 101 and the side plates 103 are connected to the heater 4, the cooler 5 and the water tanks 7 respectively through ducts 8. A controllable temperature rising and falling system is established to realize the variable control of the external temperature field of the shrinkage specimen, providing a necessary equipment basis for efficiently analyzing the correlation mechanism between the internal relative humidity of concrete and autogenous shrinkage, and facilitating the early autogenous shrinkage test of concrete.

[0023] The following specifically describes this embodiment. The inner diameter of the outer plate 101 is 120 mm, the outer diameter of the inner plate 102 is 60 mm, the lengths of the outer plate 101 and the inner plate 102 are both 500 mm, the wall thickness is 5 mm. The mold side plate 103 is a rectangular plate with a length of 130 mm, a width of 65 mm and a wall thickness of 5 mm. The mold bottom plate 104 has a height of 20 mm, a width of 130 mm and a length of 510 mm. The foam board 105 attached to the inner surface of the outer plate 101 is 30 mm thick, thereby controlling the wall thickness of the shrinkage specimen 9 in the shape of an arc cross-section to be 30 mm.

[0024] In this embodiment, one end of the controller 6 is connected to the embedded strain sensor 2 and the embedded humidity sensor 3, and the other end is connected to the heater 4 and the refrigerator 5. The hot air and cold air generated by the heater 4 and the refrigerator 5 enter the outer plate cavity 1011 and the bottom plate cavity 1041 of the mold through the conduit 8, and another conduit 8 is provided to connect the outer plate cavity 1011 and the bottom plate cavity 1041 with the water tank 7, and the air guide pipe 8 in the water tank 7 extends below the liquid surface.

[0025] According to the device in the above embodiment, a test method for analyzing the effect of internal relative humidity on concrete autogenous shrinkage by adjusting the temperature field is adopted, which specifically includes the following steps: S1, assembling the shrink mold assembly 1: first, applying vaseline on the contact surfaces of the inner panel 102, the side panel 103, the bottom panel 104 and the foam panel 105 with the shrink test piece 9, and spreading a plastic film on the surface coated with vaseline, and then assembling the outer panel 101, the inner panel 102 and the bottom panel 104 into an assembly without the side panel 103, and then placing the foam panel 105 inside and making it fit with the inner wall of the outer panel 101; S2. Install and calibrate the embedded sensors: Position and install the embedded strain sensor 2 and the embedded humidity sensor 3 along the axis of the shrinkage specimen 9. During the installation process, check the position and direction of the sensors several times to ensure that the deviation error between the sensor axis and the target axis does not exceed 2°. After installation, calibrate the sensor sensitivity and initial reading to ensure that the test results are accurate and reliable. S3, casting shrinkage test piece 9: install the side plate 103 on one side of the shrinkage mold assembly 1, then erect the mold, pour concrete from the open opening on the other side of the mold, and slowly vibrate the concrete to improve the compactness of the concrete around the embedded strain sensor 2 and the embedded humidity sensor 3 to prevent the test results from being affected by voids or cracks. After the casting is completed, install another side plate 103 at the open opening of the mold, and move the mold to the shrinkage test room; S4, assemble the test system: when the concrete is about to begin to set, lay the above-mentioned whole flat, remove the side panel 103 and the outer panel 101, then take out the foam panel 105, and respectively place temperature probes in the cavity left by the foam panel 105 in the mold and in the cavity between the bottom panel 104 and the inner panel 102 to check the test temperature. During the process, the plastic film on the concrete surface layer should be avoided from being disturbed. Then, the outer panel 101 and the side panel 103 are installed back into the mold, and then the conduit 8 is used to connect the outer panel 101 with the heater 4, the refrigerator 5, the outer panel 101 with the water tank 7, the side panel 103 with the heater 4, the refrigerator 5, and the side panel 101 with the water tank 7, wherein the conduit 8 on the outer panel 101 extends into the outer panel cavity 1011 in the mold, and the conduit 8 on the side panel 103 extends into the bottom panel cavity 1041. At the same time, one end of the embedded strain sensor 2, the embedded humidity sensor 3, the heater 4 and the refrigerator 5 is connected to the controller 6; S5. Measure the relative humidity inside the shrinkage specimen 9: After the concrete begins to set, read the time-varying data of the relative humidity inside the shrinkage specimen 9 on the controller 6 to obtain the evolution law of the relative humidity inside the shrinkage specimen 9 under standard ambient temperature. Thereafter, set the test temperature on the controller 6, and control the heater 4 or the cooler 5 to introduce gas at the set temperature into the outer plate cavity 1011 and the bottom plate cavity 1041 to obtain the time-varying characteristics of the relative humidity inside the shrinkage specimen 9 under different temperature conditions; S6. Measure the autogenous shrinkage of the shrinkage specimen 9: Combining the evolution law of the relative humidity inside the shrinkage specimen 9 under different temperature conditions that have been measured, set the program of the controller 6 to regulate the temperature field in the outer plate cavity 1011 and the bottom plate cavity 1041 of the specimen at different test ages, or the controller 6 intelligently identifies the real-time humidity state and automatically adjusts the temperature field value according to the set program, thereby changing the rate of change of the relative humidity inside the concrete, so as to control the relative humidity inside the concrete at the target value at a specific age. At the same time, read the shrinkage result of the shrinkage specimen 9 and analyze the theoretical relationship between the relative humidity inside the concrete and the autogenous shrinkage.

[0026] Example 2: As Figure 4 shown, the difference from Example 1 is that the material of the inner plate 102 is replaced with a temperature-controllable stainless steel heating plate, thereby changing the way of regulating the bottom temperature of the shrinkage specimen 9 by transferring temperature through cold and hot gases in the inner plate 10 in Example 1, and directly controlling the test temperature of the inner plate 102 at the bottom of the shrinkage specimen 9. Thus, a target temperature field can be established more accurately, and each conduit 8 extending into the bottom plate cavity 1041 can be removed. This example is applicable to the test method of controlling the relative humidity inside the concrete by single heating, which is beneficial to improving the accuracy of the test.

[0027] Example 3: As Figures 5 - 7 shown, the difference from Example 1 is that by setting the Figures 5 - 6 arc-shaped bottom mold 11 and the airbag 12 in it, the vertical pouring method of pouring from the side plate 103 position of the mold in Example 1 is changed to the Figure 7 open-pouring method of directly pouring on the foam board 105 in it, thereby effectively increasing the pouring area of the mold and solving the problems of difficult pouring and low density of low-fluidity concrete. To implement this example, use the arc-shaped bottom mold 11 to support the outer plate 101, remove the inner plate 102 during mold making, place the uninflated airbag 12, and after pouring the concrete, inflate the airbag 12 through the air vent hole on the side plate 103. As Figure 6 shown, after inflation, the cross-section of the airbag 12 is semi-circular, and the outer diameter of the cross-section of the airbag 12 is the same as the outer diameter of the inner plate 102, so as to play the role of replacing the inner plate 102 to prepare the thin-walled shrinkage specimen 9. Before the autogenous shrinkage test, replace the airbag 12 with the bottom plate 102, and then refer to the test steps 4-6 in Example 1 for shrinkage test. This example enriches the preparation method of the specimen 9 and can better meet the shrinkage test requirements of different concretes Example 4: As Figure 8 shown, the difference from Example 1 is that this example is mainly used to analyze the relationship between the relative humidity inside the concrete and the long-term autogenous shrinkage. The corresponding initial measurement time of shrinkage is adjusted from the initial setting of the concrete to after the demolding and curing of the shrinkage specimen 9. The shrinkage specimen 9 does not need to be tested with the mold, and only a plastic film is wrapped on the surface. Therefore, the demolded shrinkage specimen 9 is placed in the sealed test chamber 10, and the conduits 8 connecting the heater 4, the cooler 5, and the water tank 7 to the shrinkage mold assembly 1 in Example 1 are connected to the sealed test chamber 10. The subsequent test method refers to Steps 5 and 6 in the test procedure of Example 1. The application of the sealed test chamber 10 and the adjustment of the test system increase the test space and improve the operability of the test, thereby realizing the synchronous test of multiple groups of shrinkage specimens 9 while facilitating monitoring.

[0028] Among them, in Example 4, since the autogenous shrinkage test is carried out after the demolding and curing of the shrinkage specimen 9, when formulating the cross-sectional style of the shrinkage specimen 9, there is no need to consider the problem that the concrete in the early age is not yet hardened and the strength is insufficient. Therefore, the cross-sectional style of the shrinkage specimen 9 is more diverse. Since the production of the shrinkage specimen 9 with a semi-circular arc cross-section is difficult, specimens with a hollow cylindrical cross-section with relatively simple structure can be used in the long-term shrinkage test, such as Figure 9 shown. Compared with the shrinkage specimen 9 with a semi-circular arc cross-section, the formwork style of the hollow cylindrical cross-section has the characteristics of strong versatility and low implementation cost. Therefore, the difficulty of making the mold and pouring the shrinkage specimen 9 is greatly reduced. Among them, the shrinkage specimen 9 with a hollow cylindrical cross-section has higher requirements for formwork support and more constraints in the early stage, which is not conducive to improving the accuracy of early shrinkage test. In the long-term shrinkage test, after the shrinkage specimen 9 with a hollow cylindrical cross-section reaches a certain strength, the support formwork can be removed and then the shrinkage test can be carried out. The test method refers to Example 4.

[0029] It should be noted that in this article, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0030] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A test device for analyzing the effect of internal relative humidity on concrete autogenous shrinkage by adjusting the temperature field, characterized in that: The shrinking mold assembly (1) comprises a bottom plate (104), an outer plate (101) and an inner plate (102) both of which have semicircular arc cross-sections are arranged on the top of the bottom plate (104), the inner plate (102) is located inside the outer plate (101), and side plates (103) are arranged at both ends of the outer plate (101) and the inner plate (102); An embedded strain sensor (2) and an embedded humidity sensor (3) are arranged inside the shrinking mold assembly (1); the output ends of the embedded strain sensor (2) and the embedded humidity sensor (3) are connected to a controller (6) via lines; the output end of the controller (6) is connected to a heater (4) and a refrigerator (5) via lines; water tanks (7) are arranged on both sides of the shrinking mold assembly (1); and the outer plate (101) and the side plate (103) are respectively connected to the heater (4), the refrigerator (5) and the water tank (7) via conduits (8).

2. A test device for analyzing the effect of internal relative humidity on concrete autogenous shrinkage by adjusting the temperature field according to claim 1, characterized in that: A foam plate (105) is arranged between the outer plate (101) and the inner plate (102), and the upper surface of the foam plate (105) is closely attached to the inner wall of the outer plate (101). A shrinkage test piece (9) in the shape of a semicircular arc cross section for testing concrete is arranged between the foam plate (105) and the inner plate (102), and the shrinkage test piece (9) has a thickness of no more than 50 mm. After the foam plate (105) is pulled out, an outer plate cavity (1011) is formed between the outer plate and the test piece (9), and a bottom plate cavity (1041) is formed between the inner plate (102) and the bottom plate (104).

3. The test device for analyzing the effect of internal relative humidity on concrete autogenous shrinkage by adjusting the temperature field according to claim 1, characterized in that: The side panels (103) are rectangular panels, the length and width of the side panels (103) are respectively equal to the cross-sectional outer diameter and outer radius of the outer panel (101), the width of the bottom panel (104) is equal to the cross-sectional outer diameter of the outer panel (101), and the length of the bottom panel (104) is equal to the length of the side panels (103) on both sides and the outer panel (101) after being spliced.

4. The test device for analyzing the effect of internal relative humidity on concrete autogenous shrinkage by adjusting the temperature field according to claim 1, characterized in that: The inner plate (102) may be a thin-walled copper plate or a stainless steel heating plate.

5. The test device for analyzing the effect of internal relative humidity on concrete autogenous shrinkage by adjusting the temperature field according to claim 1, characterized in that: The embedded strain sensor (2) comprises an embedded strain gauge, a vibrating wire strain sensor, a non-contact optical sensor and a distributed optical fiber sensor, and the embedded humidity sensor (3) comprises a digital humidity sensor, a piezoelectric humidity sensor and a built-in humidity sensor.

6. The test device for analyzing the effect of internal relative humidity on concrete autogenous shrinkage by adjusting the temperature field according to claim 1, characterized in that: The temperature control range of the heater (4) is 20°C to 100°C, and the temperature control range of the refrigerator (5) is -20°C to 20°C.

7. The test device for analyzing the effect of internal relative humidity on concrete autogenous shrinkage by adjusting the temperature field according to claim 1, characterized in that: When the shrinkage test piece (9) is subjected to a long-term shrinkage test, a sealed test box (10) is arranged outside the shrinkage test piece (9), and the sealed test box (10) is respectively connected to the heater (4), the refrigerator (5) and the water tank (7) by means of a conduit (8).

8. The test device for analyzing the effect of internal relative humidity on concrete autogenous shrinkage by adjusting the temperature field according to claim 1, characterized in that: A curved bottom membrane (11) is provided on a side of the outer plate (101) away from the bottom plate (104), and an air bag (12) that can be used to replace the inner plate (102) is provided in the inner cavity of the outer plate (101).

9. A test method for analyzing the effect of internal relative humidity on concrete autogenous shrinkage by adjusting the temperature field, characterized in that: The test device for analyzing the effect of internal relative humidity on concrete autogenous shrinkage by adjusting the temperature field as described in any one of claims 1 to 8 is used, and specifically comprises the following steps: S1, assembling the shrink mold assembly (1): first, applying vaseline on the contact surfaces of the inner plate (102), the side plate (103), the bottom plate (104) and the foam plate (105) with the shrink test piece (9), and spreading a plastic film on the surface coated with vaseline, then assembling the outer plate (101), the inner plate (102) and the bottom plate (104) into an assembly without the side plate (103), and then placing the foam plate (105) inside and making it fit with the inner wall of the outer plate (101); S2. Install and calibrate the embedded sensors: Position and install the embedded strain sensor (2) and the embedded humidity sensor (3) along the axis of the shrinkage specimen (9). During the installation process, check the position and direction of the sensors several times to ensure that the deviation error between the sensor axis and the target axis does not exceed 2°. After installation, calibrate the sensor sensitivity and initial reading. S3, casting shrinkage test piece (9): installing a side plate (103) on one side of the shrinkage mold assembly (1), then erecting the mold, pouring concrete from the open opening on the other side of the mold, and slowly vibrating the concrete. After the casting is completed, another side plate (103) is installed at the open opening of the mold, and the mold is moved to the shrinkage test room; S4. Assemble the test system: When the concrete is about to set, lay the whole body flat, remove the side plate (103) and the outer plate (101), then take out the foam plate (105), and respectively place temperature probes in the cavity left by the foam plate (105) in the mold and in the cavity between the bottom plate (104) and the inner plate (102), then install the outer plate (101) and the side plate (103) back into the mold, and then use the conduit (8) to connect the outer plate (101) to the heater (4) and the cooler (5). (101) and a water tank (7), a side plate (103) and a heater (4), a refrigerator (5), and a side plate (101) and a water tank (7), wherein the conduit (8) on the outer plate (101) extends into the outer plate cavity (1011) in the mold, and the conduit (8) on the side plate (103) extends into the bottom plate cavity (1041), and at the same time, one end of the embedded strain sensor (2), the embedded humidity sensor (3), the heater (4) and the refrigerator (5) are connected to the controller (6); S5. Testing the relative humidity inside the shrinkage specimen (9): after the concrete has initially set, the time-varying data of the relative humidity inside the shrinkage specimen (9) is read on the controller (6) to obtain the evolution law of the relative humidity inside the shrinkage specimen (9) under the standard ambient temperature. Thereafter, the test temperature is set on the controller (6), and the heater (4) or the refrigerator (5) is controlled to introduce gas of the set temperature into the outer plate cavity (1011) and the bottom plate cavity (1041), so as to obtain the time-varying characteristics of the relative humidity inside the shrinkage specimen (9) under different temperature conditions. S6. Testing the autogenous shrinkage of the shrinkage specimen (9): Based on the evolution law of the relative humidity inside the shrinkage specimen (9) under different temperature conditions that have been measured, the controller (6) program is set to control the temperature field inside the specimen outer plate cavity (1011) and the bottom plate cavity (1041) at different test ages, or the controller (6) intelligently identifies the real-time humidity state and automatically adjusts the temperature field value according to the set program, thereby changing the rate of change of the relative humidity inside the concrete, thereby controlling the relative humidity inside the concrete to a target value at a specific age, and at the same time reading the shrinkage result of the shrinkage specimen (9) to analyze the theoretical relationship between the relative humidity inside the concrete and autogenous shrinkage.

Images