Cement mortar early-stage shrinkage testing device capable of regulating and controlling evaporation area and testing method

Abstract

The invention relates to a cement mortar early-stage shrinkage testing device capable of regulating and controlling the evaporation area and a testing method. The method is suitable for concrete testing. According to the technical scheme, the cement mortar early-stage shrinkage testing device capable of regulating and controlling the evaporation area comprises a shrinkage mold, and the shrinkage mold is provided with a supporting base; the cylindrical mold is annularly divided into a steel bottom film and a steel outer film, the steel bottom film is arranged on the supporting base, and the steel outer film is provided with an evaporation window; the steel side die can be combined and connected with the supporting base and can seal two end openings of the cylindrical die when being connected with the base; the flexible plastic partition plate is arranged to be cylindrical and tightly attached to the interior of the cylindrical mold, the flexible plastic partition plate is annularly divided into a plastic bottom partition plate body and a plastic outer partition plate body, and the position of the plastic outer partition plate body corresponds to the evaporation window in the steel outer film; the waterproof film covers the inner wall of a pouring cavity defined by the flexible plastic partition plate and the steel side molds at the two ends.

Description

Technical Field

[0001] The invention relates to a cement mortar early shrinkage testing device and a testing method capable of adjusting the evaporation area, which are applicable to the technical field of concrete testing. Background Art

[0002] Cement mortar is a multiphase composite material composed of cement, fine aggregate and water, and is widely used in the field of construction engineering. Limited by the inadequacy of material preparation technology, the water-cement ratio of cement mortar in the last century was usually high, and the porosity inside the hardened slurry was large, so the compressive strength of the mortar was low, and compared with the early shrinkage, the long-term shrinkage problem of high water-cement ratio mortar was more obvious. Since then, with the advent of high-efficiency water reducers, the agglomeration problem of cement particles has been effectively solved, releasing most of the free water wrapped in cement particles, greatly reducing the mixing water consumption of cement mortar. At the same time, in line with the industrial development trend of reducing backward production capacity and optimizing product performance, high-strength and ultra-high-strength cement mortars with low water-cement ratios have been gradually promoted to meet the construction needs of building structure repair and reinforcement, bridge waterproofing and leak repair, pipeline maintenance and river regulation. However, cement-based materials with low water-cement ratio generally have the problem of large early shrinkage, which can easily induce the initiation and development of internal microcracks when the matrix resistance is low, bringing significant cracking risks and endangering the long-term durability of the material. Therefore, accurately measuring the early shrinkage of high-strength cement mortar under different working conditions is of great scientific significance.

[0003] The early shrinkage of cement-based materials after solidification is closely related to the evaporation of internal free water. However, the structural forms of cement mortar products are diverse. It is difficult to scientifically define the influence of the external environment on the early shrinkage of materials with only a single evaporation amount or evaporation area. Therefore, some specifications use the evaporation area to volume ratio of the specimen as a key parameter indicator to evaluate the early shrinkage law of cement-based materials. The current domestic standards mainly focus on the long-term shrinkage of high water-cement ratio cement mortars, and rarely provide test methods for the early shrinkage of low water-cement ratio mortars. In order to improve the convenience of testing, the relevant shrinkage specimens are usually prisms. However, the distances from the side parts of the prism specimens to the center of the specimens are different, which cannot well achieve the goal of adjusting the evaporation area of ​​the specimens with a set of molds, and it is difficult to accurately measure the material shrinkage under different evaporation area to volume ratios. Considering that this parameter ratio has important engineering value, it is necessary to propose a shrinkage test device with adjustable evaporation area to meet the test requirements of early shrinkage of low water-cement ratio cement mortars under different working conditions as much as possible while controlling costs and ensuring analysis accuracy.

[0004] In the prior art, the prism shrinkage test method has a wide range of applications, but this method cannot well 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 self-shrinkage of materials, and the execution cost is relatively high, and it is also difficult to meet the above test requirements. The evaporation area to volume ratio parameter is an important indicator for analyzing the early shrinkage of high-strength cement mortar under different structural forms, but current testing technology rarely considers the influence of this research parameter, and fails to provide a convenient and efficient testing method, which is not conducive to grasping the causes of shrinkage and cracking of materials at an early age from a theoretical level, 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 view of the above-mentioned problems, a cement mortar early shrinkage testing device and a testing method with adjustable evaporation area are provided.

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

[0007] Support base;

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

[0009] A steel side mold, which can be connected to the support base and can close the two end ports of the cylindrical mold when connected to the base;

[0010] A flexible plastic partition is arranged in a cylindrical shape and is closely disposed inside the cylindrical mold, and 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 film;

[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 grooves and the clamping strips to form the cylindrical mold.

[0013] The support base is provided with a clamping groove perpendicular to the axis of the cylindrical mold at two 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 minor arc cross section; the cross section of the steel outer membrane is a major arc cross section.

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

[0016] The thickness of the flexible plastic partition does not exceed 2 mm.

[0017] The shrinking mold is arranged vertically, and its lower end 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.

[0018] A through circular hole is provided at the center of the steel side mold.

[0019] 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.

[0020] A testing method for cement mortar early shrinkage testing device based on the adjustable evaporation area, characterized by comprising:

[0021] 1) Prepare shrink mold assembly;

[0022] 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 shrink probe to pierce the film along the through circular hole in the center of the steel side mold, and splice a piece of steel side mold with a shrink probe to the support base, and seal one end of the cylindrical mold through the steel side mold. After that, erect the shrink mold, place one end of the installed steel side mold on the mold bracket, and control the shrink probe to penetrate into the support ring;

[0023] 3) Casting and curing test pieces: Pour cement mortar along the open end of the cylindrical mold until the mold is filled. Then, splice another steel side mold with a shrinkage probe to the cylindrical mold, and then prepare the coagulation test specimen. Put the shrinkage mold together with the bracket and coagulation specimen into the curing room.

[0024] 4) Setting time test: After the cement mortar is formed, the penetration resistance value of the setting test sample is measured at preset time intervals. When the penetration resistance value of the sample is close to the preset value, the measurement time interval is shortened. When the penetration resistance value reaches the preset value, it is recorded as the initial setting time;

[0025] 5) Control the evaporation area of ​​the specimen: When the cement mortar is about to set, remove the shrinkage mold on the mold bracket and lay it flat. First, disassemble the steel side molds at both ends of the mold, then disassemble the steel outer mold, remove the plastic outer partition, draw the evaporation area line in the evaporation window of the steel outer film, and then use a carving knife to gently scratch the film along the line to obtain the evaporation surface of the specimen;

[0026] 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 test specimen until 72 hours after initial setting.

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

[0028] The present invention combines a steel bottom mold, a steel outer mold, a steel side mold, etc. to form a detachable and assembled cylindrical shrinkage mold, and combines a flexible plastic partition and a waterproof film to further simplify the demolding operation, avoid disturbing the specimen at an early age stage, and effectively reduce the friction between the cylindrical specimen and the steel mold, thereby greatly improving the shrinkage test accuracy.

[0029] In the present invention, after the plastic outer partition is taken out, a film of a preset size can be cut out on the water-impermeable film through the evaporation window on the steel outer film, thereby quickly forming an evaporation area of ​​a preset size.

[0030] The present invention realizes the vertical casting of cylindrical shrinkage specimens by placing the shrinkage mold on a shrinkage bracket and allowing the shrinkage probe at one end of the mold to penetrate the bracket support ring, making the related operation easier and more convenient, thereby improving the casting quality of the specimens. After removing the steel outer mold, the plastic outer partition and the impermeable film, the distance from any point on the exposed surface of the cylindrical specimen to the center of the specimen is equal, ensuring the uniformity of specimen evaporation and the accuracy of shrinkage test.

[0031] The present invention draws an evaporation area line on the surface of a water-impermeable film along the length direction of the specimen, and the film is drawn in a way to quickly and efficiently adjust the exposed surface size of the cylindrical specimen. The test method has the characteristics of simple operation and low implementation cost. At the same time, based on the method, a set of molds can be used repeatedly to obtain the early shrinkage law of cement mortar under different evaporation area to volume ratios. Therefore, the method also has the characteristics of high application efficiency and excellent data stability, and can better meet various engineering technology requirements. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0033] Figure 2 It is a partial schematic diagram of the assembly of the present invention;

[0034] Figure 3 It is a schematic diagram of the assembly of the partition plate and the steel mold of the present invention;

[0035] Figure 4 This is a schematic diagram of the top surface of the mold for vertical casting of the present invention;

[0036] Figure 5 This is a schematic diagram of the bottom surface of the mold of the present invention when it is vertically cast;

[0037] Figure 6 This is a schematic diagram of the appearance of the mold after casting of the present invention;

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

[0039] Figure 8A schematic diagram of a shrinkage test after setting an evaporation surface in the present invention;

[0040] Fig. 9 It is a schematic diagram of the shrinking mold when the steel outer mold of the present invention is opened;

[0041] Fig.10 It is a schematic diagram of the disconnection structure and shrinkage test of the steel outer mold of the present invention;

[0042] Fig.11 It is a schematic diagram of a mold support with a clamp according to 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 seat; 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 port; 11. Shrinkage specimen; 12. Evaporation surface of specimen; 13. Micrometer; 14. Fixture. 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 described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0046] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" 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 other meanings.

[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 at 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 is also necessary to understand that when it is mentioned that an element is connected to another element "upper" or "lower", it can not only be directly connected to another element "upper" or "lower", but also indirectly connected to another element "upper" or "lower" through an intermediate element.

[0048] Embodiment 1: This embodiment is a cement mortar early shrinkage testing device with adjustable evaporation area, including a shrinkage mold and a mold support.

[0049] In this example, the shrink mold includes a support base 1-1, a cylindrical mold 7, a steel side mold 3, a flexible plastic partition 5 and a waterproof film 6, etc.

[0050] In this embodiment, the cylindrical mold 7 is divided into two parts in the circumferential direction: a steel bottom mold 1 and a steel outer mold 2. The cross section of the steel bottom mold is a minor arc cross section 7-1 formed by dividing the cylindrical cross section, and the cross section of the steel outer mold is a major arc cross section 7-2 formed by dividing the cylindrical cross section. The wall thickness of the bottom mold minor arc cross section 7-1 and the major arc cross section 7-2 of the outer mold are the same. The inner diameter of the cylindrical mold 7 is 40 mm, the outer diameter is 45 mm, the wall thickness is 2.5 mm, and the length is 300 mm. The center angle corresponding to the minor arc cross section 7-1 of the bottom mold 1 is 120°, and the center angle corresponding to the major 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. The detachable splicing of the mold includes bolt connection, clamp connection, pin connection, slot connection or buckle connection, wherein the slot 8 includes a rectangular slot, a T-shaped slot, a circular slot or a V-shaped slot, and is equipped with a clip adapted to the slot, the slots 8 are respectively arranged at both ends of the steel bottom film 1 in the circumferential direction and are arranged parallel to the axis, and the clips are arranged at both ends of the steel outer film 2 in the circumferential direction; the clips include bite-type clips, clamp-type clips, splicing clips or press-type clips.

[0052] In this embodiment, the steel bottom mold 1 and the supporting base 1-1 arranged thereunder are an integral structure. The supporting base 1-1 is 310 mm long, 45 mm wide, and 20 mm high. The square side mold 3 has a side length of 45 mm and a wall thickness of 5 mm.

[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 respectively located at the two ends of the steel outer film 2.

[0054] In this example, the steel side mold 3 can be combined and connected with the support base 1-1, and can close the two end ports of the cylindrical mold 7 when connected with the base. The steel side mold 3 is connected through the card slot on the card bar base. After the steel side mold 3 is spliced ​​with the support base 1-1, the structure fits with the two ends of the cylindrical mold 7, and the length of the two pieces of steel side mold 3 after being fitted 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, and a through circular hole 3-1 is provided at the center of the steel side mold 3 for passing the shrinkage probe 9 extending from the cylindrical mold 7. The through circular hole 3-1 has a diameter of 8 mm, and a gap of 3 mm is left between the through circular hole 3-1 and the shrinkage probe 9 in the diameter direction.

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

[0057] In this embodiment, the mold support 4 is composed of a foot 4-1, four vertical steel rods 4-2, four horizontal steel rods 4-3, and a supporting ring 4-4. One end of the four horizontal steel rods 4-3 is fixed to the four vertical steel rods 4-2 respectively, and the other end is fixed to the supporting ring 4-4. The inner diameter of the supporting ring 4-4 ​​is 45mm. The supporting ring 4-4 ​​is arranged parallel to the foot 4-1 and is about 130mm higher than the foot 4-1. When the shrink mold is arranged vertically, the lower end of the shrink mold can be supported on the supporting ring 4-4, and the central through hole of the supporting ring 4-4 ​​can provide an installation space for the shrink probe 9.

[0058] The testing method of the cement mortar early shrinkage testing device based on the adjustable evaporation area in this embodiment includes the following steps:

[0059] 1) Prepare the shrink mold assembly: fit the plastic bottom partition 5-1 and the outer partition 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 5 and the inner surface of the steel side mold 3, and then evenly spread the impermeable film 6 on the plastic partition 5 and the steel side mold 3;

[0060] 2) Assembling and erecting the shrink mold: placing the steel bottom mold 1 and the supporting base 1-1 flat, splicing the steel outer mold 2 and the steel bottom mold 1 into a steel cylindrical mold 7 through a sliding slot, and at the same time allowing the shrinkage probe 9 to pierce the film 6 along the circular hole 3-1 in the center of the steel side mold 3, and splicing a piece of steel side mold 3 with a shrinkage probe 9 and the supporting base 1-1 through the slot 8, then erecting the shrink mold, and placing one end of the installed steel side mold 3 on the mold bracket 4, so that the shrinkage probe 9 penetrates the bracket support ring 4-4;

[0061] 3) Casting and curing test piece 11: Cast cement mortar along the open part of the cylindrical mold 7 until the mold 7 is filled, and then splice another steel side mold 3 with a shrinkage probe 9 with the steel cylindrical mold 7 through the slot 8, and then prepare the condensation test sample, and put the shrinkage mold together with the bracket 4 and the condensation sample into the curing room;

[0062] 4) Setting time test: After the cement mortar is formed, the penetration resistance value of the setting test sample is measured, and the measurement time interval is 20 minutes. When the penetration resistance value of the sample is close to 0.3MPa, the measurement time interval is adjusted to 10 minutes. When the penetration resistance value reaches 0.3MPa, it is recorded as the initial setting time;

[0063] 5) Controlling the evaporation area of ​​the specimen 11: When the cement mortar is about to set initially, the shrinkage mold erected on the mold support 4 is removed and laid flat, and the steel side molds 3 at both ends of the mold are first disassembled, and then the steel outer mold 2 is disassembled, and the plastic outer partition 5-2 is removed. Then, the evaporation area line is drawn on the surface of the impermeable film 6 along the length direction of the specimen, and then the film 6 is lightly scratched along the line with a carving knife to obtain the evaporation surface 12 of the cylindrical specimen 11, thereby ensuring that the distance from any point on different evaporation surfaces 12 to the center of the specimen 11 is the same;

[0064] 6) Shrinkage test: Move the test piece 11 to the shrinkage test room, set up the micrometer 13 at the shrinkage probes 9 at both ends of the test piece 11, record the initial reading of the micrometer 13, and then observe the shrinkage deformation of the test piece 11 until 72 hours after initial setting.

[0065] To ensure that the area of ​​the evaporation surface 12 marked by the engraving knife in step 5) is the preset area, in this embodiment, the engraving knife is equipped with an auxiliary mechanism, which has a linear guide, a first slider, an arc guide, a second slider and a range limiting slider, etc., wherein 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; an angle scale is formed on the arc guide, 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 cooperate with the locking mechanism thereon to lock the position, and the second slider can move along the arc guide on the arc guide, between the range limiting slider and the first slider.

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

[0067] In this example, when the outer partition plate 5 - 2 cannot be pulled out in some special cases, the evaporation surface can be directly scratched on the outer partition plate 5 - 2 and the water-impermeable film 6 with a carving knife.

[0068] Example 2: Fig. 9As shown, the difference from Example 1 is that a pouring port 10 is opened 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 realizing the preparation of the shrinkage specimen 11 without using the mold support 4. The cylindrical mold 7 of this embodiment is the same size as that of Example 1, with an inner diameter of 40mm and an outer diameter of 45mm, so the length × width size of the pouring port 10 is set to 20×20mm. Compared with Example 1, this embodiment omits the mold support 4, has lower requirements on equipment, and is more convenient to operate. However, this embodiment is mainly used for casting cement mortar with good fluidity to ensure the casting quality through the self-compacting of the slurry.

[0069] Example 3: Fig.10 As shown, the difference from Example 1 is that the steel outer mold 2 is broken along the longitudinal section and divided into two parts, and an evaporation window is formed between the two parts. The outer partition 5-2 on the inner side of the steel outer mold 2 remains unchanged, and is used to support the casting of the shrinkage test piece 11. The spacing between the two outer molds 2 at the fracture is not greater than the inner diameter of the cylindrical mold 7. After the slurry solidifies, the steel side mold 3 is removed, and then the outer mold 2 is retained, and the outer partition 5-2 is directly pulled out to expose the empty area between the two outer molds 2. Then, with the help of the outer mold 2 for positioning, the film 6 in the empty area is cut to obtain the evaporation surface of the shrinkage test piece 11. The cylindrical mold 7 of this embodiment is the same size as that of Example 1, with an inner diameter of 40mm and an outer diameter of 45mm. Therefore, the spacing between the two outer molds 2 at the fracture is set to 25mm. Compared with Example 1, the mold 7 described in this embodiment is more standardized, and the model size of the outer mold 2 has a corresponding relationship with the exposed evaporation area of ​​the test piece 11, which is conducive to improving the comparability of the shrinkage test results and the accuracy of the shrinkage analysis.

[0070] Example 4: Fig.11 As shown, the difference from Example 1 is that a clamp 14 is provided on the upper part of the mold support 4 to fix the upright shrinkage mold, especially when the mold is long, to prevent it from tipping over due to pouring, and to improve the stability of the operation. Compared with Example 1, this embodiment is mainly aimed at the slender cylindrical mold 7 with an aspect ratio greater than 8, to ensure the feasibility and reliability of the upright pouring of the test piece 11, to meet different shrinkage test requirements, and to support the diversification 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, wherein the shrink mold has: Support base; A cylindrical mold, which is divided into a steel bottom film and a steel outer film in the circumferential direction, wherein the steel bottom film is arranged on the supporting base, and the steel outer film is provided with an evaporation window; A steel side mold, which can be connected to the support base and can close the two end ports of the cylindrical mold when connected to the base; A flexible plastic partition is arranged in a cylindrical shape and is closely disposed inside the cylindrical mold, and 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 film; 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 grooves and the clamping strips to form the cylindrical mold.

3. The cement mortar early shrinkage testing device with adjustable evaporation area according to claim 1 is characterized in that: The support base is provided with a clamping groove perpendicular to the axis of the cylindrical mold at two 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 is characterized in that: The cross section of the steel bottom membrane is a minor arc cross section; the cross section of the steel outer membrane is a major arc cross section.

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

6. The cement mortar early shrinkage testing device with adjustable evaporation area according to claim 1 is 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 is characterized in that: The shrinking mold is arranged vertically, and its lower end 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 is 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 shrink probe to pierce the film along the through circular hole in the center of the steel side mold, and splice a piece of steel side mold with a shrink probe to the support base, and seal one end of the cylindrical mold through the steel side mold. After that, erect the shrink mold, place one end of the installed steel side mold on the mold bracket, and control the shrink probe to penetrate into the support ring; 3) Casting and curing test pieces: Pour cement mortar along the open end of the cylindrical mold until the mold is filled. Then, splice another steel side mold with a shrinkage probe to the cylindrical mold, and then prepare the coagulation test specimen. Put the shrinkage mold together with the bracket and coagulation 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 time intervals. When the penetration resistance value of the sample is close to the preset value, the measurement time 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 on the mold bracket and lay it flat. First, disassemble the steel side molds at both ends of the mold, then disassemble the steel outer mold, remove the plastic outer partition, draw the evaporation area line in the evaporation window of the steel outer film, and then use a carving 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 test specimen until 72 hours after initial setting.

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