CN212722893U - Concrete early-age shrinkage deformation characteristic cone measuring device - Google Patents

Abstract

The utility model provides a concrete early age shrinkage deformation characteristic toper survey device has the awl point under, the uncovered and ascending toper examination mould in awl end, and toper examination mould inner wall is provided with antiseized layer, the toper examination mould is pyramid examination mould [5] that has triangle-shaped side more than three. Compared with the prior cone sample technical method, the geometrical characteristic that the angle of the cone angle is kept unchanged when the isotropic length is deformed is kept, so that the state of external constraint force applied to the sample in the volume deformation process is kept unchanged, the measured deformation characteristic is more accurate and closer to an ideal state than the prior art, and meanwhile, the manufacturing cost of the test mold is effectively reduced. And because the inner wall of the side surface of the test mold is a plane instead of a cambered surface, the sheet-shaped film can be directly used as the anti-sticking layer of the inner wall of the test mold, so that the test operation is simpler and more convenient.

Description

Concrete early-age shrinkage deformation characteristic cone measuring device

Technical Field

The utility model relates to a concrete early age shrinkage deformation characteristic toper survey device.

Background

2 when the concrete is mixed with water, the concrete shrinks or expands and deforms during the process of setting and aging, but the concrete shrinks and deforms totally. The shrinkage deformation characteristic of the concrete, particularly the shrinkage deformation characteristic of the early age is an important technical index for evaluating the crack resistance of the concrete, and has practical significance for preventing the concrete member from generating early cracks in concrete engineering, wherein the early age concrete is the concrete mixed by adding water within 3 days, and is characterized in that the concrete is not completely solidified in the determination process of the shrinkage deformation characteristic of the early age concrete.

3 the nature of concrete deformation is a volume change. Since the deformation characteristics of concrete are considered to be isotropic, it is desirable to measure the deformation characteristics of concrete in a state where the concrete to be measured is not restrained by external force in any direction. When the concrete sample has external force constraint in a certain direction to limit the deformation, the change of the volume of the concrete sample causes the change of the shape, and the length deformation in the free direction is influenced, especially before the tested concrete is completely solidified. For example, in the measuring method specified in the national standard of "test method for long-term performance and durability of ordinary concrete" GB/T50082-. As the mortar sample is measured in the plastic corrugated pipe in the measuring method of American standard ASTM C1698-09, when the sample deforms, the volume deformation effect of the sample can generate an amplifying effect on the deformation of the corrugated pipe in the length direction due to the constraint action of the pipe wall of the corrugated pipe.

4 the shrinkage deformation speed of the concrete in different age stages is different, and even expansion can occur, while the curing degree of the concrete samples in different age stages is different, and the influence effect on the length deformation in the measuring direction caused by the volume change effect is also different. Another uncertainty in the measurement results that can be attributed to this effect is: differences in the characteristics of the deformation process will cause differences in the measurement results. Namely: in the measurement method of the prior art, the measured accumulated deformation amounts are different due to the difference of the characteristics of the deformation process.

The conventional concrete early-age shrinkage deformation characteristic measuring method imposes constraints on a sample in multiple directions and has different influences on each direction due to volume change, so that a large uncorrectable error exists in a measuring result.

6 to overcome the defect, the Chinese patent application "method for measuring shrinkage deformation characteristics of concrete in early age" (application publication No. CN 110187084A) discloses a scheme for measuring shrinkage deformation characteristics of mortar samples in early age concrete in a cone test mould. CN110187084A utilizes the geometric characteristic that the angle of the cone sample is kept unchanged when the cone sample deforms in the isotropic length, so that the state of external constraint force applied to the sample in the volume deformation process is kept unchanged, the defect that the deformation characteristic in the measuring direction is changed due to the fact that the constraint force between the sample and a test mold is changed when the sample deforms in the traditional technology is overcome, and the measured deformation characteristic is more accurate and closer to the ideal state.

7 while CN110187084A can improve the accuracy of the measurement result to the ideal state, there are some factors that hinder the popularization and application.

Firstly, the manufacturing cost of the cone test mold is high, because concrete is a mixture containing coarse aggregate, the deformation of the concrete in the early age period is mainly contributed by the deformation of a mortar part, and in order to avoid the error generated by the deformation characteristic of the measured sample due to the deviation of the content of the coarse aggregate in the measured sample and the actual mixing ratio, the volume of the sample cannot be selected to be too small. As described in CN110187084A, "test mode with cone angle of 60 °; the diameter of the bottom surface of the cone can be 170mm when the aggregate diameter of the common concrete is less than or equal to 40 mm; the diameter of the bottom surface of the cone with the particle diameter less than or equal to 30mm of the aggregate can be selected to be 115 mm; the diameter of the bottom surface of the cone is 225mm when the particle diameter of the aggregate is less than or equal to 60 mm. "

9 meanwhile, the 3-day shrinkage rate of the concrete shrinkage in the early age is generally 1000 multiplied by 10^-6Within the order of magnitude, for example, the vertical shrinkage of a test piece having a cone base diameter of 170mm corresponding to a cone angle of 60 ° is about 0.15mm, and for such a minute amount of shrinkage displacement of the test piece, and the measurement method and apparatus using the test mold as a reference, the test mold is required to have sufficient rigidity to prevent a test error caused by occurrence of a micro-deformation of the shape of the test mold.

The test mold 10 is therefore usually made of steel or cast iron and requires a sufficient thickness of the mold wall. Taking a test mold with a cone bottom diameter of 170mm as an example, the thickness of the test mold wall is generally required to be more than 5 mm. If larger volumes of sample are used, thicker wall thicknesses are required. The manufacturing process of the prior art trial mold is generally formed by cutting machining on the basis of a large-volume steel block, or formed by casting a rough mold and then cutting finish machining, or formed in one step by adopting a precision casting process. If the test mold is made of other materials, such as "the test mold can also be made of rigid materials such as engineering plastics and aluminum alloy" described in CN110187084A, a larger thickness of the test mold wall is required or a reinforced structural design is adopted to ensure that the deformation of the test mold and the test mold wall is small enough to control the measurement error caused by the deformation within an allowable range. It follows that the manufacturing cost is high for the actual demand of small lot size.

This deficiency 11 is particularly disadvantageous in applications where larger volumes of sample are used. For concrete mixtures, the larger the sample volume is, the smaller the dispersion error of the coarse aggregate proportion is, and the more representative the measured deformation characteristic is; meanwhile, the increase of the size of the sample can increase the total deformation of the sample in the same ratio, so that the measuring device can obtain larger measuring displacement, the deformation resistance technical indexes of the micro-displacement measuring device and the precision requirements of a measuring system and a micro-displacement measuring sensor can be reduced, and the related cost of the measuring device can be further reduced. Under the existing manufacturing technology, the relation between the small-batch manufacturing cost of the cast cone test mold and the volume thereof is approximately equal ratio in a certain range, and the volume increasing factor of the integral cutting processing increases the manufacturing cost progressively. Taking the example that the diameter of the bottom surface of the cone can be selected as 170mm when the aggregate diameter of common concrete is less than or equal to 40mm, according to the estimation of 3 test molds matched with the existing set of early-age concrete shrinkage deformation characteristic measuring device, the manufacturing cost of the test molds and parts related to the size of the test molds becomes an important component of the comprehensive manufacturing cost of the whole set of measuring device, and the increase of the size of the test molds leads to the rapid increase of the comprehensive manufacturing cost of the whole set of measuring device.

12 the conical test mold limits the selection of the anti-sticking layer on the inner wall of the test mold

13 the main purposes of the anti-sticking layer on the inner wall of the trial mold are as follows: the test method has the advantages that the measurement error caused by the constraint of the adhesive force of the concrete test sample and the test mold wall on the test mold deformation is within the allowable degree, and the test sample is conveniently demoulded from the test mold after the test is completed.

The basic requirements for using a separate barrier film 14 are: the isolation film has the advantages that the isolation film is required to be kept in a close-fitting state with a test mold wall, no wrinkle occurs during vibration molding of a test sample, otherwise gaps or wrinkle spaces which are not close to each other are filled or compacted by concrete mortar in a subsequent test process, so that the measurement shrinkage is seriously distorted; the isolation film has enough antibody volume compression deformability, or the isolation film is thin enough to enable the influence of volume deformation caused by sample extrusion on the sample deformation measurement value in the whole test process to be within an error allowable range; and the isolation film has flexibility so that the restriction on the deformation of the concrete sample is smaller than the allowable error range. For cone trial molding, it is difficult to ensure the implementation of the conditions by using an independent isolation film, and it is more difficult to achieve all the requirements simultaneously.

15 in practical application, the cone sample method is more inclined to choose a scheme of coating a lubricant on the wall surface when the test wall coating film is combined with the sample for forming, but the scheme has the defects that the test wall coating film is easily scratched by concrete aggregate, and the technical requirement of coating the lubricant during forming is increased. In addition, because of no isolation of an independent film, the demoulding operation of the test sample after the test is finished is difficult, and once the test sample is adhered to the test mould, the test mould is difficult to remove and even can be scrapped.

Disclosure of Invention

16 to the above insufficiency, the utility model provides a concrete early age shrinkage deformation characteristic cone shape measuring device that replaces conical examination mould with polyhedron pyramid examination mould that the side constitutes as the plane.

The utility model provides a concrete early age shrinkage deformation characteristic toper survey device has the awl point under, the uncovered and ascending toper examination mould at the awl end, and toper examination mould inner wall is provided with antiseized layer, the toper examination mould is the pyramid examination mould that has triangle-shaped side more than three.

18 the utility model provides a concrete early age shrinkage deformation characteristic toper survey device to the pyramid replaces the circular cone, has remain the advantage of toper examination mould. When in use, the mixed concrete or mortar is vibrated in a test mould into a pyramid sample with a downward cone tip. When the sample undergoes length deformation in the same proportion during solidification and aging, the angle of the taper angle of each side surface is unchanged, and the height deformation rate of the taper is equal to the isotropic length deformation rate. Therefore, when the sample in the tapered test mold is deformed, the height of the upper surface of the sample in the test mold (the distance between the bottom and the tip of the cone, i.e., the measured value of the device of the present invention) changes, and the constraint stress condition between the sample and the test mold remains unchanged.

The utility model provides a concrete early age shrinkage deformation characteristic toper survey device, pyramid examination mould cuts the concatenation with the flat board and forms, compares with current cone sample technical method, and the angle of its cone angle when having kept "isotropic length deformation keeps unchangeable geometric characteristics for the outside constraint power state that the sample received in taking place the volume deformation process remains unchanged, thereby when making the deformation characteristic of surveying more accurate than prior art, more being close to ideal state" advantage, effectively reduced the manufacturing cost of examination mould. And because the inner wall of the side surface of the test mold is a plane instead of a cambered surface, the sheet-shaped film can be directly used as the anti-sticking layer of the inner wall of the test mold, so that the test operation is simpler and more convenient.

More than three triangular side faces forming the test die are identical isosceles triangles so as to facilitate manufacturing and reduce test errors.

The wall body of the test mold forming more than three triangular side surfaces of the test mold is formed by connecting at least two parts in a detachable way, and the separation line of each part is the waist edge of the triangular side surface. The meaning of the method comprises that one or more test mould wall units bearing a single triangular side face are detachably connected with other parts, or test mould wall units bearing a plurality of adjacent triangular side faces are detachably connected with other parts.

The main purpose of the detachable side wall body of the test mold is to conveniently clean the inner wall of the test mold. The inner wall of the test mould can cause the situation that the wall surface is not tightly adhered to the isolation film after the mortar is bonded, so that the test error is caused, the inner wall is required to be cleaned frequently to keep clean, and the operation of cleaning the inner wall can be more convenient by separating the inner wall from the side wall body. Another useful effect is that the test mold can be easily removed by disengaging the side walls in the event of a difficult sample removal. Meanwhile, the side wall body can be detached, so that the operation of arranging the anti-sticking layer is more convenient.

Drawings

Fig. 1 is a schematic structural diagram of an embodiment of the present invention, in which: 1-probe frame, 2-sample, 3-displacement measuring target, 4-displacement sensor probe and 5-test mold;

fig. 2 is a top view of fig. 1 (sample 2 is not shown), and fig. 3 is an enlarged view of I in fig. 2, in which: 1-a probe frame, 3-a displacement measuring target, 4-a displacement sensor probe, 51-a fixed part side wall body and 52-a detachable part side wall body;

fig. 4 is an axial cross-sectional view of the trial mold 5 of fig. 1, in which: 51-a fixed part side wall body of the pyramid test mold, and 52-a detachable part side wall body of the pyramid test mold;

fig. 5 is a schematic structural diagram (top view) of another embodiment of the present invention, in which: 6-framework, 7-lateral wall body;

fig. 6 is a schematic structural diagram (partial) of another embodiment of the present invention, in which: 81-side wall of nail, and 82-side wall of nail.

Detailed Description

1. A concrete early age shrinkage deformation characteristic cone measuring device is shown in figure 1, and comprises a pyramid test mould 5, a test mould cone tip is downward, a test mould cone bottom is open, a probe frame 1 is arranged on the test mould cone bottom, a displacement sensor probe 4 is arranged on the probe frame, and a displacement measuring target 3 matched with the probe. During operation, a concrete or mortar sample 2 is poured from the conical bottom, a target is placed in the center of the upper surface of the sample, and a probe is used for detecting the height change of the target in the solidification and aging processes on the central axis aiming at the target.

The test mold structure is made of steel plates, is quadrangular pyramid-shaped and is formed by four triangular side faces as shown in figures 2 and 4. Three of the triangular sides are formed by folding a flat plate to form a fixed part side wall 51, and one of the triangular sides is a movable part side wall 52 detachably connected to the fixed part. The two parts are detachably connected by screws passing through holes on the edge of the side wall body of the movable part and screw holes on the edge section of the side wall body of the fixed part (as shown in figure 3). The inner walls of the assembled side surfaces of the test molds are four same isosceles triangles.

2. A triangular pyramid test mould is shown in figure 5, and comprises a steel triangular frame 6 and three isosceles triangle engineering plastic plates as side wall bodies 7 of the test mould, wherein a yin-yang groove structure is arranged between the waist edges of the triangles, and the three triangles are matched in the frame by the yin-yang grooves to form the triangular pyramid test mould during assembly.

3. A hexagonal pyramid-shaped test mould is composed of three side wall units, each of which has two triangular sides, and a folded edge between two side wall units and with holes for screw connection. As shown in fig. 6, the paper side wall 81 and the paper side wall 82 are screwed to each other.

In practical applications, the non-side wall may not be an isosceles triangle or may be a non-strict isosceles triangle.

Claims (3)

1. A conical testing device for the early-age shrinkage deformation characteristic of concrete is provided with a conical testing mold with a lower conical tip and an upward conical bottom opening, wherein an anti-sticking layer is arranged on the inner wall of the conical testing mold.

2. The concrete early-age shrinkage-deformation characteristic cone measuring device according to claim 1, wherein three or more triangular side surfaces forming the test mold are identical isosceles triangles.

3. The concrete early-age shrinkage deformation characteristic cone measuring device according to claim 1 or 2, wherein the test mold wall body forming the three or more triangular side surfaces of the test mold is composed of at least two parts detachably connected, and the parting line of each part is the waist edge of the triangular side surface.

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