Method of forming an asphalt concrete beam embedded with strain sensors

Abstract

The present application relates to a kind of asphalt concrete beam forming method of embedded strain sensor, design uses special beam mould to effectively protect sensor cable in forming process, by a kind of detachable positioning line, ensure that sensor cable is safe in forming process and avoid sensor position deviation, prepare a variety of sizes, different gradation of pre-embedded strain sensor of asphalt concrete beam, effectively solve the problem of poor bonding effect of sensor and mixture caused by using space block step forming method, also can effectively simulate the actual state of sensor in the interior of asphalt pavement, and then make a good foundation for studying the measurement effectiveness and use durability of sensor when applied to road engineering monitoring, it has important significance for promoting sensor in road life cycle maintenance monitoring application.

Description

TECHNICAL FIELD

[0001] The application relates to a method for forming an asphalt concrete beam embedded with a strain sensor and belongs to the technical field of indoor experiment of road structure health monitoring. BACKGROUND

[0002] It is of great significance to obtain the internal state of a road structure in time and accurately for the whole life cycle maintenance decision and optimal design of the road, so strain sensors are more and more widely applied in the field of road structure health monitoring. However, in the actual application process, the strain measurement accuracy of the sensor applied to road engineering is affected due to the high modulus of the external armor structure of the sensor and the deformation incoordination with the asphalt mixture. The current research and a large number of simulation prove that when the sensor is embedded in the internal structure of the road, there is a certain difference between the measurement result and the true value due to the deformation incoordination with the mixture, which directly affects the application of the sensor in road engineering.

[0003] In order to analyze and design the experiment to verify the measurement effectiveness and use durability of various stress and strain sensors applied in road engineering monitoring, it is a great step to promote the application of road stress and strain sensors to verify the influence of sensor types and embedding methods on the measurement effectiveness and use durability through indoor experiments. The current methods for forming and embedding sensor asphalt mixture beams can be mainly divided into step-by-step forming method and integral forming method. Specifically, the integral forming method is to directly place the sensor at the predetermined position in the filling process, and then compact and form the mixture beam. The current problem is that the sensor is easy to deviate from the position or even be damaged under the action of the compaction load. In order to solve this problem, the step-by-step forming method is to first fill part of the asphalt mixture to a predetermined height, place a placeholder at the predetermined position of the sensor, and then compact and form the beam body. Then the placeholder is removed, and the sensor is placed, but the size and shape of the placeholder and the sensor are different, so there is a gap between the sensor and the mixture. Therefore, the gap is filled with fine materials. Then the filling is completed, and the whole beam body is compacted and formed. Although the step-by-step forming method solves the problem of position deviation and damage of the sensor in the compaction process to a certain extent, the gap between the sensor and the mixture is filled with materials after the formation, which will lead to poor deformation coordination between the sensor and the mixture, and further cause the decrease of the measurement accuracy of the sensor.

[0004] Therefore, it is of great practical value to design an asphalt mixture beam test piece in which the internal sensor is close to the actual use state, and to study an indoor experiment method for the behavior state of the strain sensor in the asphalt mixture. SUMMARY

[0005] The application provides a bituminous concrete beam forming method with embedded strain sensors, which can ensure the survival ability and position fixing effect of the embedded strain sensors under the action of a compaction load on the premise of improving the coordinated deformation performance of the sensors and bituminous mixture by using a whole forming method.

[0006] The application solves the technical problems by adopting the technical solutions of:

[0007] The bituminous concrete beam forming method with embedded strain sensors specifically comprises the following steps:

[0008] Step S1: preparing a beam mold for forming a test piece;

[0009] Step S2: preparing a detachable positioning line for fixing the sensor;

[0010] Step S3: designing and configuring bituminous components and dosages according to the road grade and pavement layer position to be studied, and mixing and preparing bituminous mixture;

[0011] Step S4: wrapping black tape on the corresponding position outside the sensor cable;

[0012] Step S5: pre-laying an oil paper layer on the bottom of the beam mold, filling the bituminous mixture obtained in step S3 into the beam mold in batches, and tamping after each layer position is filled with the bituminous mixture; when the bituminous mixture is filled to the preset layer position, the sensor is placed, the two ends of the sensor flange are respectively coated with adhesive paint, at least one circle of the detachable positioning line is wound outside the sensor, and the detachable positioning line is combined with the sensor cable and stretched out of the beam mold;

[0013] Step S6: continuing to fill the bituminous mixture into the beam mold on the basis of step S5 until the filling is completed, and closing the beam mold;

[0014] Step S7: bonding the adhesive paint of the sensor flange with the bituminous mixture around the sensor, and extracting the detachable positioning line from the beam mold to preliminarily complete the forming of the test piece;

[0015] Step S8: using a wheel roller to form the test piece, placing the beam mold for at least 1 hour after compaction, and obtaining the bituminous concrete beam test piece with embedded strain sensors after the temperature of the formed test piece returns to room temperature;

[0016] As a further preferred embodiment of the application, the beam mold prepared in step S1 comprises a bottom pad, a mold bottom plate, a mold top plate, a mold long side plate and a mold wide side plate, the mold bottom plate comprises two oppositely arranged long sides and two oppositely arranged short sides, the mold bottom plate is fixed on the bottom pad, and the mold long side plate is vertically arranged at the position of the long side of the mold bottom plate.

[0017] The long-side side plate of the former mold is provided with a long-side side plate groove on the side wall near the two ends, and the long-side side plate groove is perpendicular to the side of the long-side side plate of the mold;

[0018] When the long-side side plate is arranged at the long-side position of the mold base plate, the long-side side plate groove faces the inside of the beam mold, and a wide-side side plate of the mold is arranged in the long-side side plate groove opposite to the long-side side plate groove;

[0019] Screws are arranged in the holes opposite to each other in the two long-side side plates of the mold, and nuts are arranged at the ends of the screws;

[0020] The mold top plate is arranged on the top of the cavity formed by the mold base plate, the long-side side plate of the mold and the wide-side side plate of the mold, and a semicircular hole is arranged in the mold top plate corresponding to the center of the side of the wide-side side plate of the mold;

[0021] As a further preferred embodiment of the present application, the diameter of the semicircular hole is 5-10mm;

[0022] As a further preferred embodiment of the present application, a matching semicircular rubber protective sleeve is arranged at the position of the semicircular hole in the mold top plate;

[0023] As a further preferred embodiment of the present application, the detachable positioning line in step S2 is a flexible cable, and the flexible cable is fixed on the sensor by low-adhesion tape when the flexible cable is wound around the sensor;

[0024] As a further preferred embodiment of the present application, the weight calculation method of the asphalt mixture in step S3 is:

[0025] m a =1.03ρ0(a·b·c)

[0026] Wherein, a is the length of the inside of the beam mold, b is the width of the inside of the beam mold, and c is the height of the inside of the beam mold, and ρ0 is the design density of the asphalt mixture;

[0027] As a further preferred embodiment of the present application, in step S4, the sensor cable outside the sensor which has an angle between the sensor and the wide-side side plate of the beam mold is wrapped with black tape;

[0028] The sensor cable and the asphalt mixture or the beam mold are wrapped with black tape outside the contact part;

[0029] As a further preferred embodiment of the present application, in step S5, the asphalt mixture is filled in several times, and one fourth of the weight is filled each time.

[0030] Compared with the prior art, the present application has the following advantages:

[0031] 1. The asphalt concrete beam embedding strain sensor forming method provided by the application, the size of the beam mold and the component weight of the asphalt mixture can be made and configured according to actual application, effectively simulating the actual state of the sensor in the asphalt pavement, and laying a foundation for studying the measurement effectiveness and use durability of the sensor when applied to road engineering monitoring.

[0032] 2. The asphalt concrete beam embedding strain sensor forming method provided by the application, the beam mold is a specially designed structure, which can effectively protect the sensor cable, and through the setting of the detachable positioning line, black cloth and the application of adhesive coating, the survival ability and position fixing effect of the embedded sensor under the action of the compaction load are ensured. BRIEF DESCRIPTION OF DRAWINGS

[0033] The application will be further described below in combination with the drawings and examples.

[0034] Figure 1 is a structure schematic diagram of the beam mold after splitting provided by the application;

[0035] Figure 2 is a sensor processing schematic diagram provided by the application;

[0036] Figure 3 is a structure schematic diagram of the sensor embedded in the beam mold for specimen forming provided by the application;

[0037] Figure 4 is a detachable positioning line setting schematic diagram provided by the application.

[0038] In the figure: 1 is a bottom pad, 2 is a mold bottom plate, 3 is a mold long side plate, 4 is a hole, 5 is a long side plate groove, 6 is a mold wide side plate, 7 is a mold top plate, 8 is a sensor flange, 9 is an adhesive coating, 10 is black cloth, 11 is asphalt mixture, 12 is a semicircular hole, 13 is a detachable positioning line, and 14 is a low-adhesion tape. DETAILED DESCRIPTION

[0039] The application will be further described below in combination with the drawings and examples. In the description of the present application, it should be understood that the terms "left side", "right side", "upper part", "lower part" and the like indicate the orientation or positional relationship shown in the drawings, and are only used for the convenience of describing the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and "first", "second" and the like do not represent the importance of the parts, and therefore cannot be understood as limiting the application. The specific dimensions used in the present embodiment are only used to illustrate the technical solutions and do not limit the protection scope of the application.

[0040] As set forth in the background, the current forming method for asphalt concrete beam, most of the sensor under the action of compaction load is prone to position deviation even failure, the reason is mainly due to the one-time injection of asphalt mixture causes the sensor can not be fixed in the preset position, subsequent compaction, can not bear the compaction load. Therefore, the present application provides a kind of asphalt concrete beam forming method of embedded strain sensor, it is through the design using special beam mold to effectively protect sensor cable in the forming process, and then through the sensor black cloth covering, smearing adhesive coating mode to ensure that sensor cable safety and enhance the adhesion between sensor and asphalt mixture in the forming process, then in the forming process using special detachable positioning line 13 to fix the sensor position, and then after filling is completed, the detachable positioning line is extracted along the sensor cable path;Since the sensor has been pressed on the predetermined position by asphalt mixture, the adhesive coating 9 on the sensor flange 8 also completes the adhesion with asphalt mixture, so when the detachable positioning line is extracted, the low-adhesion adhesive tape 14 automatically falls off and does not cause the sensor position to change. Finally, the whole one-time forming method is adopted to compact and form the asphalt concrete beam embedded with strain sensor.

[0041] Next, the asphalt concrete beam forming method provided by the present application is specifically described, which specifically includes the following steps:

[0042] Step S1: make a beam mold for forming a test piece;One of the highlights of the present application is the special mold structure of the beam mold. The size of the mold can be adjusted according to the actual test requirements, and the mold can be easily disassembled later. Figure 1 As shown, the beam mold includes a bottom pad 1, a mold bottom plate 2, a mold top plate 7, a mold long side plate 3 and a mold wide side plate 6. The mold bottom plate includes two oppositely arranged long sides and two oppositely arranged short sides. The mold bottom plate is fixed on the bottom pad. The mold long side plate is vertically arranged at the long side position of the mold bottom plate. The long side plate recesses 5 are respectively formed on the side walls near the two ends of the aforementioned mold long side plate, and the long side plate recesses are perpendicular to the side edges of the mold long side plate. When the mold long side plate is arranged at the long side position of the mold bottom plate, the long side plate recesses face the inside of the beam mold. The mold wide side plate is inserted into the oppositely arranged long side plate recesses. In this way, the mold bottom plate, the mold long side plate and the mold wide side plate form a hollow chamber structure. Since there is a distance between the ends of the mold long side plate and the long side plate recesses, in order to better ensure the stability of the chamber structure, a plurality of evenly distributed holes 4 are arranged between the long side plate recesses and the ends, which are perpendicular to the side edges of the mold long side plate. The screws are inserted into the holes of the two oppositely arranged mold long side plates, and the ends of the screws are fixed by nuts. By tightening the nuts, the chamber structure can be stabilized. After the test piece is formed, the beam mold can be disassembled by unscrewing the nuts.

[0043] The mold top plate in the beam mold is used to seal the cavity structure. Since the sensor cable needs to be led out when the sensor is embedded in the structure, in order not to damage the overall structure of the beam mold, a semi-circular hole 12 is opened at the center of the side of the mold top plate corresponding to the wide side plate of the mold. The sensor cable can then extend out from the semi-circular hole.

[0044] The diameter of the semi-circular hole ranges from 5 to 10 mm. A matching semi-circular rubber protective sleeve is installed at the location of the semi-circular hole to avoid damaging the sensor cable.

[0045] Step S2: Fabricate a detachable positioning line for fixing the sensor; Another innovation of this application is the use of a flexible cable as a detachable positioning line. This flexible cable has high temperature resistance. Because it is made of a flexible material, the sensor and the asphalt mixture 11 are fully bonded after the specimen is formed, and the flexible cable can be pulled out at this time.

[0046] Step S3: Based on the road grade and pavement layer design, configure the asphalt components and dosage, and mix to produce asphalt mixtures. The asphalt mixture formula ratio can also be matched and configured according to the actual construction site to ensure that the test results are closer to the actual working conditions. Considering the loss during the molding process, the weight of the mixed asphalt mixture should preferably be 1.03 times the theoretically required weight. Therefore, the calculation method for the required weight of the asphalt mixture is as follows:

[0047] m a =1.03ρ0(a·b·c)

[0048] Where a is the length of the inner side of the beam mold, b is the width of the inner side of the beam mold, c is the height of the inner side of the beam mold, and ρ0 is the design density of the asphalt mixture.

[0049] Step S4: In this application, to ensure the sensor cable remains intact during the molding process, special treatment is required for the sensor. For example, black tape 10 is used to wrap the main stress-bearing parts of the sensor cable. This wrapping improves the pressure-bearing capacity of the stress-bearing parts. Furthermore, since the asphalt mixture is heated during pouring, the black tape has high-temperature resistance, thus maintaining the integrity of the sensor cable. Here, the stress-bearing part of the sensor cable is typically located at the angle between the sensor and the wide side plate of the beam mold (where a bend occurs). Figure 2 As shown, at the location where the sensor cable directly contacts the asphalt mixture or beam mold, the sensor cable at the aforementioned location is wrapped with black tape.

[0050] Step S5: First, lay a layer of parchment paper at the bottom of the beam mold. Then, fill the beam mold with the asphalt mixture obtained in Step S3 in several batches, filling one-quarter of the weight each time. After each batch of asphalt mixture is filled, compact it. When the asphalt mixture reaches the preset layer, place the sensor. To ensure the sensor is fixed in the preset position... Figure 2 As shown, adhesive coating is applied to both ends of the sensor flange. The filled asphalt mixture can bond with the adhesive coating in a timely manner, and the sensor is initially fixed in the preset position. Figure 4 As shown, at least one turn of the removable positioning wire is then wrapped around the outside of the sensor to further secure it. The removable positioning wire is attached to the sensor cable and extends out of the beam mold through the semi-circular hole in the top plate of the mold. The removable positioning wire is also reinforced and fixed to the sensor flange with low-tack tape.

[0051] Step S6: Based on step S5, continue filling the beam mold with asphalt mixture until the filling is complete, then seal the beam mold. Figure 3 As shown;

[0052] Step S7: At this time, the sensor has been compacted into the preset position by the asphalt mixture located on top of the sensor. The adhesive coating on the sensor flange is also bonded to the asphalt mixture around the sensor. Therefore, when the detachable positioning line is pulled out, it can automatically fall off without causing the sensor position to shift. Pull the detachable positioning line out from the beam mold along the sensor cable path to initially complete the molding specimen.

[0053] Step S8: Use a roller to compact the specimen. During the compaction process, take care to protect the sensor cable from direct load. After compaction, let the beam mold stand for at least 1 hour. After the temperature of the molded specimen returns to room temperature, disassemble the beam mold to obtain the concrete beam specimen with the embedded strain sensor.

[0054] The asphalt concrete beam with pre-embedded strain sensors obtained by the above molding method effectively solves the problem of poor bonding between the sensor and the mixture caused by the step-by-step molding method using placeholder blocks. It can also effectively simulate the actual state of the sensor inside the asphalt pavement, thus laying the foundation for studying the measurement effectiveness and durability of the sensor when applied to road engineering monitoring. It is of great significance for promoting the application of sensors in the maintenance and monitoring of the entire life cycle of roads.

[0055] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0056] The meaning of "and / or" as used in this application includes situations where each exists alone or both exist simultaneously.

[0057] The term "connection" as used in this application can mean a direct connection between components or an indirect connection between components through other components.

[0058] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method of forming a strain sensor embedded asphalt concrete beam, characterized by: Specifically comprising the following steps: Step S1: making a beam mold for forming a test piece, the beam mold comprising a bottom base plate (1), a mold bottom plate (2), a mold top plate (7), a mold long side side plate (3), and a mold wide side side plate (6); Step S2: making a detachable positioning line (13) for fixing the sensor; Step S3: designing and configuring the asphalt component and dosage according to the road grade to be studied and the pavement layer position, and mixing and making the asphalt mixture (11); Step S4: wrapping black tape (10) on the corresponding position outside the sensor cable, specifically wrapping black tape (10) on the sensor cable outside the position where the sensor cable appears an angle between the sensor and the mold wide side side plate (6) of the beam mold; wrapping black tape (10) on the outside of the part of the sensor cable in contact with the asphalt mixture (11) or the beam mold; Step S5: laying an oil paper on the inside bottom of the beam mold in advance, filling the asphalt mixture (11) obtained in step S3 into the beam mold in batches, and tamping after each filling of the asphalt mixture (11) to complete a layer; when the asphalt mixture (11) is filled to the preset layer position, placing the sensor, applying adhesive coating (9) to the two ends of the sensor flange (8), wrapping at least one circle of detachable positioning line (13) outside the sensor, and extending the detachable positioning line (13) out of the beam mold in conjunction with the sensor cable; Step S6: continuing to fill the asphalt mixture (11) into the beam mold on the basis of step S5 until the filling is completed, and closing the beam mold; Step S7: bonding the adhesive coating (9) of the sensor flange (8) with the asphalt mixture (11) around the sensor, drawing out the detachable positioning line (13) from the beam mold, and preliminarily completing the forming of the test piece; Step S8: rolling the test piece, placing the beam mold for at least 1 hour after compaction, and obtaining the concrete beam test piece with the embedded strain sensor after the temperature of the test piece returns to room temperature.

2. The method of claim 1, wherein: The mold bottom plate (2) comprises two oppositely arranged long sides and two oppositely arranged short sides, and the mold bottom plate (2) is fixed on the bottom base plate (1), and the mold long side side plate (3) is vertically arranged at the position of the long side of the mold bottom plate (2); The aforementioned mold long side side plate (3) is provided with a long side side plate groove (5) on the side wall near each end, and the long side side plate groove (5) is vertically arranged at the side of the mold long side side plate (3); a plurality of uniformly distributed holes (4) are also vertically arranged at the position between the long side side plate groove and the end of the mold long side side plate (3); When the mold long side side plate (3) is arranged at the position of the long side of the mold bottom plate (2), the long side side plate groove (5) faces the inside of the beam mold, and the mold wide side side plate (6) is inserted into the oppositely arranged long side side plate grooves (5); Two long side plates (3) of the mold are oppositely provided with holes (4) in which screws are arranged, and the ends of the screws are fixed by nuts; a top plate (7) is arranged on the top of the cavity formed by the bottom plate (2), the long side plates (3) and the wide side plates (6), and a semicircular hole (12) is arranged on the center of the side of the wide side plate (6) of the top plate (7).

3. The method of claim 2, wherein: The diameter of the semicircular hole (12) is 5-10mm.

4. The method of claim 3, wherein: A matching semicircular rubber protective sleeve is arranged at the position of the semicircular hole (12) of the top plate (7) of the mold.

5. The method of claim 4, wherein: The detachable positioning line (13) in step S2 is a flexible cable which is fixed on the sensor by low-adhesion tape (14) when being wound around the sensor.

6. The method of claim 5, wherein: The calculation method of the required weight of the asphalt mixture (11) in step S3 is: ma=1.03ρ0(a·b·c) Wherein, a is the length of the inside of the beam mold, b is the width of the inside of the beam mold, c is the height of the inside of the beam mold, and ρ0 is the design density of the asphalt mixture (11).

7. The method of claim 1, wherein: In step S5, the asphalt mixture (11) is filled in several times, and one fourth of the weight is filled in each time.

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