Early shrinkage testing device and testing method for cement mortar with adjustable evaporation area

Abstract

The present application relates to a kind of cement mortar early shrinkage test device and test method of adjustable evaporation area, it is suitable for concrete test technical field.The technical scheme used in the present application is: a kind of cement mortar early shrinkage test device of adjustable evaporation area, including shrinkage mould, the shrinkage mould has: support base;Cylinder mould, the mould is circumferentially divided into steel bottom film and steel outer film, wherein steel bottom film is set on the support base, steel outer film is equipped with evaporation window;Steel side mould, can be connected with the support base combination, and can close the two end ports of the cylinder mould when being connected with base;Flexible plastic baffle, it is arranged into cylinder, it is set in close contact with the inside of the cylinder mould, and the flexible plastic baffle is annularly divided into plastic bottom baffle and plastic outer baffle, wherein plastic outer baffle position corresponds evaporation window on steel outer film;Water-impermeable film, cover in the pouring cavity inner wall surrounded by the flexible plastic baffle and two ends steel side mould.

Description

TECHNICAL FIELD

[0001] The application relates to a cement mortar early shrinkage test device with adjustable evaporation area and a test method. BACKGROUND

[0002] Cement mortar is a kind of multiphase composite material composed of cement, fine aggregate and water, and is widely used in the field of building engineering. Due to the deficiency of material preparation technology, the water-binder ratio of cement mortar in the last century was usually high, the porosity in the hardened paste was large, so the compressive strength of the mortar was low, and the long-term shrinkage problem of the high water-binder ratio mortar was more obvious than the early shrinkage. After that, with the advent of high-efficiency water reducing agent, the agglomeration problem of cement particles was effectively solved, most of the free water wrapped by cement particles was released, the water consumption of cement mortar was greatly reduced, and at the same time, the industry development trend of reducing backward production capacity and optimizing product performance was met, the low water-binder ratio high-strength and super-high-strength cement mortar was gradually popularized to meet the engineering construction needs of building structure repair and reinforcement, bridge waterproofing and leakage repair, pipeline repair and river regulation. However, low water-binder ratio cement-based materials generally have the problem of large early shrinkage, which is easy to induce the initiation and development of internal micro-cracks when the base resistance is low, which brings significant cracking risk and endangers the long-term durability of the material, so it is of great scientific significance to accurately determine the early shrinkage of high-strength cement mortar under different working conditions.

[0003] The early shrinkage of cement-based materials after setting is closely related to the evaporation of internal free water, and the structure of cement mortar products is various, so it is difficult to scientifically define the influence of external environment on the early shrinkage of materials only by single evaporation amount or evaporation area, therefore, some specifications use the evaporation area to volume ratio of the test piece as a key parameter index to evaluate the early shrinkage law of cement-based materials. The current domestic standard mainly focuses on the long-term shrinkage problem of high water-binder ratio cement mortar, and there are few test methods for the early shrinkage of low water-binder ratio mortar, and in order to improve the convenience of testing, the shape of the related shrinkage test piece is usually a prism, but the distance from each part of the side surface of the prism test piece to the center of the test piece is different, which cannot well realize the goal of adjusting the evaporation area of the test piece with a set of molds, and then it is difficult to accurately determine the material shrinkage under different evaporation area to volume ratios, considering that the parameter ratio has important engineering value, it is necessary to propose a shrinkage test device with adjustable evaporation area, which can meet the test requirements of the early shrinkage of low water-binder ratio cement mortar under different working conditions as much as possible under the premise of controlling cost and ensuring analysis accuracy.

[0004] In the existing technology, the prism shrinkage test method has a wide range of applications, but this method cannot effectively measure the shrinkage of mortar under different evaporation area to volume ratios and has functional limitations. In addition, the bellows shrinkage test method is also relatively common, but this method is mainly used to test the autogenous shrinkage of materials and has a high implementation cost, which also makes it difficult to meet the above-mentioned testing requirements. The evaporation area to volume ratio parameter is an important indicator for analyzing the early shrinkage of high-strength cement mortars under different structural forms, but current testing technologies rarely consider the influence of this research parameter and fail to provide a convenient and efficient testing method. This is not conducive to understanding the causes of shrinkage cracking of materials at an early age from a theoretical perspective, and it is difficult to provide complete technical guidance for the engineering practice of high-strength and ultra-high-strength mortars. Summary of the Invention

[0005] The technical problem to be solved by the present invention is: in response to the above-mentioned problems, a cement mortar early shrinkage testing device and testing method with adjustable evaporation area are provided.

[0006] The technical solution adopted by the present invention is: a cement mortar early shrinkage testing device with adjustable evaporation area, characterized in that it includes a shrinkage mold, which has:

[0007] Support base;

[0008] A cylindrical mold, which is divided into a steel bottom membrane and a steel outer membrane in the circumferential direction, wherein the steel bottom membrane is arranged on the supporting base, and the steel outer membrane is provided with an evaporation window;

[0009] Steel side molds, capable of being combined with the support base and connected to the base to close the two end ports of the cylindrical mold;

[0010] A flexible plastic partition is arranged in a cylindrical shape and is closely disposed inside the cylindrical mold. The flexible plastic partition is divided into a plastic bottom partition and a plastic outer partition in an annular shape, wherein the position of the plastic outer partition corresponds to the evaporation window on the steel outer membrane;

[0011] The water-impermeable film covers the inner wall of the casting chamber surrounded by the flexible plastic partition and the steel side molds at both ends.

[0012] The steel bottom film and the steel outer film are spliced ​​together through the cooperation of the clamping groove and the clamping strip to form the cylindrical mold.

[0013] The support base is provided with a clamping groove perpendicular to the axis of the cylindrical mold at both ends corresponding to the cylindrical mold, and the steel side mold is provided with a clamping strip adapted to the clamping groove on the support base.

[0014] The cross section of the steel bottom membrane is a poor arc cross section; the cross section of the steel outer membrane is a good arc cross section.

[0015] The inner wall of the pouring chamber is coated with lubricant.

[0016] The thickness of the flexible plastic partition plate is not more than 2 mm.

[0017] The shrinkage mold is vertically arranged, and the lower end thereof is placed on a mold support provided with a supporting ring for supporting the shrinkage mold, and the supporting ring is mounted on a supporting frame.

[0018] The center of the steel side mold is provided with a through circular hole.

[0019] The plastic bottom partition plate and the plastic outer partition plate are spliced to form the cylindrical flexible plastic partition plate through the cooperation of the clamping groove and the clamping strip.

[0020] A testing method based on the early shrinkage testing device of the cement mortar with adjustable evaporation area, characterized in that, comprising:

[0021] 1) preparing a shrinkage mold assembly;

[0022] 2) assembling and erecting the shrinkage mold: placing the steel bottom mold and the supporting base, splicing the steel outer mold and the steel bottom mold into a cylindrical mold, and allowing the shrinkage measuring head to pierce the film along the through circular hole in the center of the steel side mold, and splicing a piece of steel side mold with the shrinkage measuring head and the supporting base, and sealing one end of the cylindrical mold through the steel side mold, and then erecting the shrinkage mold, and placing the end with the installed steel side mold on the mold support, and controlling the shrinkage measuring head to penetrate into the supporting ring;

[0023] 3) pouring and curing the test piece: pouring the cement mortar along the open end of the cylindrical mold, and after filling the mold, splicing another piece of steel side mold with the shrinkage measuring head and the cylindrical mold, and then preparing the setting testing sample, and placing the shrinkage mold together with the support, the setting testing sample into the curing chamber.

[0024] 4) setting time testing: after the cement mortar is formed, the penetration resistance value of the setting testing sample is measured every predetermined time interval, when the penetration resistance value of the sample approaches the preset value, the time interval is shortened, and when the penetration resistance value reaches the preset value, the initial setting time is recorded;

[0025] 5) adjusting the evaporation area of the test piece: when the cement mortar is close to initial setting, the shrinkage mold erected on the mold support is taken down and placed flat, the steel side mold at both ends of the mold is disassembled, and then the steel outer mold is disassembled, the plastic outer partition plate is removed, the evaporation area line is drawn in the evaporation window of the steel outer film, and then the film is lightly drawn along the line with a graver to obtain the evaporation surface of the test piece;

[0026] 6) shrinkage testing: the test piece is moved to the shrinkage testing chamber, and the micrometer is erected at the shrinkage measuring head at both ends of the test piece, and the initial reading of the micrometer is recorded, and then the shrinkage deformation of the test piece is observed to 72h after initial setting.

[0027] The beneficial effects of the present application are:

[0028] The application combines steel bottom mold, steel outer mold, steel side mold, etc. to form a detachable and assembled cylindrical shrinkage mold, and further combines flexible plastic partition plate and water-impermeable film to further simplify the demolding operation, avoid disturbing the test piece in the early age stage, and effectively reduce the frictional resistance between the cylindrical test piece and the steel mold, thereby greatly improving the shrinkage test precision.

[0029] In the application, after the plastic outer partition plate is taken out, a preset size of film can be drawn on the water-impermeable film through the evaporation window on the steel outer film, so as to quickly form a preset size of evaporation area.

[0030] The application realizes the vertical casting of the cylindrical shrinkage test piece by the method of standing the shrinkage mold on the shrinkage support and allowing the shrinkage test head at one end of the mold to penetrate into the support supporting ring, so that the related operation is more simple and convenient, and the casting quality of the test piece is improved. After the steel outer mold, the plastic outer partition plate and the water-impermeable film are removed, the distance from any point on the exposed surface of the cylindrical test piece to the center of the test piece is equal, which guarantees the uniformity of evaporation of the test piece and the accuracy of shrinkage test.

[0031] The application draws an evaporation area line on the surface of the water-impermeable film along the length direction of the test piece, so as to quickly and efficiently adjust the size of the exposed surface of the cylindrical test piece. The test method has the characteristics of simple operation and low implementation cost, and a set of mold can be repeatedly used on the basis of the method to obtain the early shrinkage rule of cement mortar under different evaporation area and volume ratio conditions. Therefore, the method also has the characteristics of high application efficiency and excellent data stability, and can better meet various engineering technical requirements. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a schematic diagram of the steel mold assembly of the application;

[0033] Figure 2 It is a local schematic diagram of the assembly splicing of the application;

[0034] Figure 3 It is a schematic diagram of the partition plate and steel mold combination of the application;

[0035] Figure 4 It is a schematic diagram of the mold vertical casting top surface of the application;

[0036] Figure 5 It is a schematic diagram of the mold vertical casting bottom surface of the application;

[0037] Figure 6 It is a schematic diagram of the appearance of the mold after casting of the application;

[0038] Figure 7 It is a schematic diagram of the test piece after the steel outer mold, side mold and outer partition plate are removed of the application;

[0039] Figure 8Schematic diagram of shrinkage test after setting up the evaporation surface in the present invention;

[0040] Figure 9 This is a schematic diagram of the shrinking mold when the steel outer mold of the present invention is opened;

[0041] Figure 10 Schematic diagram of the steel outer mold disconnection structure and shrinkage test of the present invention;

[0042] Figure 11 Schematic diagram of the mold support with a clamp of the present invention.

[0043] In the figure: 1. Steel bottom mold; 1-1. Support base; 2. Steel outer mold; 3. Steel side mold; 3-1. Center hole of side mold; 4. Mold bracket; 4-1. Foot; 4-2. Vertical steel rod; 4-3. Horizontal steel rod; 4-4. Support steel ring; 5. Flexible plastic partition; 5-1. Plastic bottom partition; 5-2. Plastic outer partition; 6. Water-impermeable film; 7. Cylinder mold; 7-1. Inferior arc section; 7-2. Superior arc section; 8. Slot; 9. Shrinkage probe; 10. Casting mouth; 11. Shrinkage specimen; 12. Evaporation surface of specimen; 13. Micrometer; 14. Clamp. DETAILED DESCRIPTION

[0044] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0045] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0046] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0047] It should be noted that the directional words such as "upper", "lower", "left", and "right" described in the embodiments of the present application are described based on the angles shown in the accompanying drawings and should not be understood as limiting the embodiments of the present application. In addition, in the context, it should be understood that when it is mentioned that an element is connected to another element "on" or "under", it can not only be directly connected to the other element "on" or "under", but also be indirectly connected to the other element "on" or "under" through an intermediate element.

[0048] Example 1: This example is a cement mortar early shrinkage testing device with adjustable evaporation area, including a shrinkage mold and a mold bracket.

[0049] The shrinkage mold in this example includes a support base 1-1, a cylindrical mold 7, a steel side mold 3, a flexible plastic partition 5, and a water-impermeable film 6.

[0050] In this embodiment, the cylindrical mold 7 is circumferentially divided into two parts, a steel bottom film 1 and a steel outer film 2. The cross section of the steel bottom mold is a poor arc cross section 7-1 formed by dividing the cross section of a cylinder, and the cross section of the steel outer mold is a good arc cross section 7-2 formed by dividing the poor arc cross section of the cylinder. The wall thickness of the poor arc cross section 7-1 of the bottom mold is the same as that of the good arc cross section 7-2 of the outer mold. The inner diameter of the cylindrical mold 7 is 40 mm, the outer diameter is 45 mm, the wall thickness is 2.5 mm, the length is 300 mm, the corresponding central angle of the poor arc cross section 7-1 of the bottom mold 1 is 120°, and the corresponding central angle of the good arc cross section 7-2 of the outer mold 2 is 240°.

[0051] In this example, the cylindrical mold 7 is formed by splicing the steel bottom film 1 and the steel outer film 2 in a detachable connection manner. The detachable splicing of the mold includes bolt connection, clamp connection, latch connection, slot connection, or buckle connection. The slot 8 includes a rectangular slot, a T-shaped slot, a circular slot, or a V-shaped slot, and is equipped with a clamping strip matched with the slot. The slot 8 is arranged at the circumferential ends of the steel bottom film 1 and is parallel to the axis. The clamping strip is arranged at the circumferential ends of the steel outer film 2. The buckle includes a snap buckle, a hoop buckle, a splicing buckle, or a pressing buckle.

[0052] In this embodiment, the steel bottom mold 1 and the support base 1-1 arranged below it are of an integral structure. The support base 1-1 is 310 mm long, 45 mm wide, and 20 mm high. The square side mold 3 is 45 mm long and 5 mm thick.

[0053] In this embodiment, the steel outer film 2 is provided with an evaporation window, which is a rectangular window. The two long sides of the rectangular window are parallel to the axis of the cylindrical mold 7, and the two short sides of the rectangular window are located at the two ends of the steel outer film 2.

[0054] In this example, the steel side mold 3 can be connected to the support base 1-1 and can close the two end ports of the cylindrical mold 7 when connected to the base. The steel side mold 3 is connected through the slot on the clamping strip base. After splicing the steel side mold 3 with the support base 1-1, the two pieces of steel side mold 3 are fitted with the two ends of the cylindrical mold 7, and the length of the two pieces of steel side mold 3 after fitting with the two ends of the cylindrical mold 7 is equal to the length of the support base 1-1.

[0055] In this embodiment, the steel side mold 3 is aligned with the center of the cylindrical mold 7. The center of the steel side mold 3 is provided with a through-hole 3-1 for the shrinkage probe 9 extending out of the cylindrical mold 7. The diameter of the through-hole 3-1 is 8 mm, and a gap of 3 mm is left between the through-hole 3-1 and the shrinkage probe 9 in the diameter direction.

[0056] In the embodiment, the flexible plastic partition plate 5 is arranged in a cylindrical shape, which is circumferentially divided into a bottom partition plate 5-1 and an outer partition plate 5-2. The plastic bottom partition plate 5-1 and the plastic outer partition plate 5-2 are arc-shaped plates. The wall thickness of the plastic arc-shaped plate 5 is 1 mm. During testing, the plastic arc-shaped plate 5 is placed on the inner surface of the cylindrical mold 7 and can be seamlessly attached to the inner surface of the cylindrical mold 7. The outer partition plate 5-2 can seal the evaporation window on the outer steel film 2.

[0057] In the embodiment, the mold support 4 is composed of a foot base 4-1, four vertical steel rods 4-2, four horizontal steel rods 4-3, and a support circular ring 4-4. One end of each of the four horizontal steel rods 4-3 is fixed to one of the four vertical steel rods 4-2, and the other end is fixed to the support circular ring 4-4. The inner diameter of the support circular ring 4-4 is 45 mm. The support circular ring 4-4 is arranged in parallel with the foot base 4-1 and is about 130 mm higher than the foot base 4-1. When the shrinkage mold is arranged vertically, the lower end of the shrinkage mold can be supported on the support circular ring 4-4. The central through hole of the support circular ring 4-4 can provide installation space for the shrinkage measuring head 9.

[0058] In the embodiment, the testing method based on the cement mortar early shrinkage testing device with adjustable evaporation area includes the following steps:

[0059] 1) Prepare the shrinkage mold assembly: attach the plastic bottom partition plate 5-1 and the plastic outer partition plate 5-2 to the inner surface of the steel bottom mold 1 and the inner surface of the steel outer mold 2, respectively. Then, apply vaseline lubricant on the exposed surface of the plastic partition plate 5 and the inner surface of the steel side mold 3. Finally, evenly spread the water-impermeable film 6 on the plastic partition plate 5 and the steel side mold 3.

[0060] 2) Assemble and erect the shrinkage mold: place the steel bottom mold 1 on the support base 1-1, and assemble the steel cylinder mold 7 by sliding the steel outer mold 2 onto the steel bottom mold 1 through the sliding clamping groove. At the same time, make the shrinkage measuring head 9 pierce the film 6 along the central circular hole 3-1 of the steel side mold 3, and assemble the steel side mold 3 with the shrinkage measuring head 9 onto the support base 1-1 through the clamping groove 8. Then, erect the shrinkage mold, and place the end of the steel side mold 3 with the shrinkage measuring head 9 on the mold support 4, so that the shrinkage measuring head 9 penetrates the support circular ring 4-4 of the support.

[0061] 3) Pour and cure the test piece 11: pour the cement mortar into the open end of the cylindrical mold 7 until the mold 7 is filled. Then, assemble the steel cylinder mold 7 with the steel side mold 3 through the clamping groove 8. After that, prepare the setting test sample, and place the shrinkage mold together with the support 4 and the setting test sample into the curing chamber.

[0062] 4) Test the setting time: measure the penetration resistance value of the setting test sample after the cement mortar is formed. The measurement time interval is 20 minutes. When the penetration resistance value of the sample approaches 0.3 MPa, the measurement time interval is adjusted to 10 minutes. When the penetration resistance value reaches 0.3 MPa, the initial setting time is recorded.

[0063] 5) Regulating the evaporation area of the test piece 11: When the initial setting of the cement mortar is close, the shrinkage mold standing on the mold support 4 is removed and placed flat, the steel side mold 3 at both ends of the mold is removed first, then the steel outer mold 2 is removed, the plastic outer partition plate 5-2 is removed, and then the evaporation area line is drawn on the surface of the water-impermeable film 6 along the length direction of the test piece, and then the film 6 is lightly drawn along the line with a graver to obtain the evaporation surface 12 of the cylindrical test piece 11, so as to ensure that the distance from any point on the different evaporation surfaces 12 to the center of the test piece 11 is the same;

[0064] 6) Shrinkage test: The test piece 11 is moved to the shrinkage test chamber, the micrometer 13 is arranged at the shrinkage measuring head 9 at both ends of the test piece 11, and the initial reading of the micrometer 13 is recorded, and then the shrinkage deformation of the test piece 11 is observed until 72 hours after the initial setting.

[0065] In order to ensure that the area of the evaporation surface 12 drawn by the graver in step 5) is the preset area, an auxiliary mechanism is installed for the graver in this embodiment, which has a linear guide, a first slider, an arc guide, a second slider, and a range limiting slider, etc. The linear guide can be detachably installed on the steel outer mold 2, and the linear guide is arranged parallel to the axis of the cylindrical mold 7, and the first slider is installed on the linear guide. The arc guide is arranged concentrically with the cylindrical mold 7, and one end of the arc guide is fixedly installed on the first slider. The arc guide is provided with an angle scale, and the second slider and the range limiting slider can be installed on the arc guide. The range limiting slider can move along the arc guide on the arc guide and be locked in position by cooperating with the locking mechanism thereon, and the second slider can move along the arc guide between the range limiting slider and the first slider.

[0066] In this embodiment, the graver can be installed on the second slider, and when the graver is installed on the second slider, the tip of the graver faces the axis of the cylindrical mold 7.

[0067] In some special cases, the outer partition plate 5-2 cannot be pulled out, and the graver can be directly used to draw the evaporation surface on the outer partition plate 5-2 and the water-impermeable film 6.

[0068] Example 2: As Figure 9As shown, the difference from Example 1 is that a pouring port 10 is provided on the top surface of the steel outer mold 2, the outer partition 5-2, and the impermeable film 6. The side length of the pouring port 10 is 1 / 3-1 / 2 of the inner diameter of the cylindrical mold 7. Cement mortar is poured through the pouring port 10. After the slurry fills the mold, the pouring port 10 is sealed with an impermeable film, thereby simplifying the specimen casting process and achieving the preparation of shrinkage specimens 11 without using the mold holder 4. The cylindrical mold 7 of this embodiment is the same size as that of Example 1, with an inner diameter of 40 mm and an outer diameter of 45 mm. Therefore, the length and width dimensions of the pouring port 10 are set to 20×20 mm. Compared with Example 1, this embodiment omits the mold holder 4, has lower requirements on equipment, and is more convenient to operate. However, this embodiment is mainly used for pouring cement mortar with good fluidity to ensure the casting quality through the self-compacting of the slurry.

[0069] Example 3: Figure 10 As shown, the difference from Example 1 is that the steel outer mold 2 is broken along the longitudinal section into two parts, forming an evaporation window between the two parts. The outer partition 5-2 inside the steel outer mold 2 remains unchanged, used to support the casting of the shrinkage test piece 11. The spacing between the two outer molds 2 at the fracture is no greater than the inner diameter of the cylindrical mold 7. After the slurry solidifies, the steel side mold 3 is removed, and the outer mold 2 is retained. The outer partition 5-2 is directly pulled out, exposing the empty area between the two outer molds 2. Then, using the outer mold 2 to position, the film 6 in the empty area is scratched to obtain the evaporation surface of the shrinkage test piece 11. The cylindrical mold 7 in this embodiment has the same dimensions as that in Example 1, with an inner diameter of 40 mm and an outer diameter of 45 mm. Therefore, the spacing between the two outer molds 2 at the fracture is set to 25 mm. Compared with Example 1, the mold 7 in this embodiment is more standardized, and the model size of the outer mold 2 corresponds to the exposed evaporation area of ​​the test piece 11, which helps to improve the comparability of shrinkage test results and the accuracy of shrinkage analysis.

[0070] Example 4: Figure 11 As shown, the difference from Example 1 lies in the installation of a clamp 14 on the upper portion of the mold support 4 to secure the upright shrinkage mold. This prevents the mold from tipping over during casting, particularly when the mold is long, thereby improving operational stability. Compared to Example 1, this embodiment primarily targets elongated cylindrical molds 7 with aspect ratios greater than 8, ensuring the feasibility and reliability of upright casting of test specimens 11. This meets the diverse needs of shrinkage testing and supports a variety of test types.

Claims

1. A cement mortar early shrinkage testing device with adjustable evaporation area, characterized in that: The invention comprises a shrink mold having: Support base; A cylindrical mold, which is divided into a steel bottom membrane and a steel outer membrane in the circumferential direction, wherein the steel bottom membrane is arranged on the supporting base, and the steel outer membrane is provided with an evaporation window; Steel side molds, capable of being combined with the support base and connected to the base to close the two end ports of the cylindrical mold; A flexible plastic partition is arranged in a cylindrical shape and is closely disposed inside the cylindrical mold. The flexible plastic partition is divided into a plastic bottom partition and a plastic outer partition in an annular shape, wherein the position of the plastic outer partition corresponds to the evaporation window on the steel outer membrane; The water-impermeable film covers the inner wall of the casting chamber surrounded by the flexible plastic partition and the steel side molds at both ends.

2. The cement mortar early shrinkage testing device with adjustable evaporation area according to claim 1 is characterized in that: The steel bottom film and the steel outer film are spliced ​​together through the cooperation of the clamping groove and the clamping strip to form the cylindrical mold.

3. The cement mortar early shrinkage testing device with adjustable evaporation area according to claim 1, characterized in that: The support base is provided with a clamping groove perpendicular to the axis of the cylindrical mold at both ends corresponding to the cylindrical mold, and the steel side mold is provided with a clamping strip adapted to the clamping groove on the support base.

4. The cement mortar early shrinkage testing device with adjustable evaporation area according to claim 1, characterized in that: The cross section of the steel bottom membrane is a poor arc cross section; the cross section of the steel outer membrane is a good arc cross section.

5. The cement mortar early shrinkage testing device with adjustable evaporation area according to claim 1, characterized in that: The inner wall of the pouring chamber is coated with lubricant.

6. The cement mortar early shrinkage testing device with adjustable evaporation area according to claim 1, characterized in that: The thickness of the flexible plastic partition does not exceed 2 mm.

7. The cement mortar early shrinkage testing device with adjustable evaporation area according to claim 1, characterized in that: The shrinking mold is arranged vertically, and the lower end thereof is placed on a mold bracket. The mold bracket has a supporting ring for supporting the shrinking mold, and the supporting ring is installed on the supporting frame.

8. The cement mortar early shrinkage testing device with adjustable evaporation area according to claim 1, characterized in that: A through circular hole is provided at the center of the steel side mold.

9. The cement mortar early shrinkage testing device with adjustable evaporation area according to claim 1, characterized in that: The plastic bottom partition and the plastic outer partition are spliced ​​together through the cooperation of the clamping groove and the clamping strip to form the cylindrical flexible plastic partition.

10. A testing method for cement mortar early shrinkage testing device with adjustable evaporation area according to any one of claims 1 to 9, characterized in that: include: 1) Prepare shrink mold assembly; 2) Assembling and erecting the shrink mold: Place the steel bottom mold and the support base flat, splice the steel outer mold and the steel bottom mold into a cylindrical mold, and at the same time allow the shrinkage probe to pierce the film along the through-hole in the center of the steel side mold. Splice a piece of steel side mold with a shrinkage probe to the support base, and seal one end of the cylindrical mold through the steel side mold. Then erect the shrink mold, place the installed end of the steel side mold on the mold bracket, and control the shrinkage probe to penetrate into the support ring; 3) Casting and curing test specimens: Pour cement mortar along the open end of the cylindrical mold until the mold is filled. Then, join another steel side mold with a shrinkage probe to the cylindrical mold. Then, prepare the setting test specimen. Place the shrinkage mold together with the bracket and setting specimen into the curing room. 4) Setting time test: After the cement mortar is formed, the penetration resistance value of the setting test sample is measured at preset intervals. When the penetration resistance value of the sample approaches the preset value, the measurement interval is shortened. When the penetration resistance value reaches the preset value, it is recorded as the initial setting time; 5) Control the evaporation area of ​​the specimen: When the cement mortar is about to set, remove the shrinkage mold standing on the mold support and lay it flat. First, disassemble the steel side molds at both ends of the mold, then disassemble the steel outer mold and remove the plastic outer partition. Draw the evaporation area line in the evaporation window of the steel outer film, and then use a knife to gently scratch the film along the line to obtain the evaporation surface of the specimen; 6) Shrinkage test: Move the specimen to the shrinkage test room, set up a dial gauge at the shrinkage probes at both ends of the specimen, record the initial reading of the dial gauge, and then observe the shrinkage deformation of the specimen until 72 hours after initial setting.

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