A method for predicting the occurrence of rutting on the surface of concrete slabs.

Abstract

To provide a prediction method for a formation period of wheel tracks on a concrete slab surface that can measure an initial fine crack formed in a concrete so as to predict the period in which the surface breaks to form wheel tracks.SOLUTION: A prediction method for formation period of wheel tracks on a concrete slab surface comprises: making a vehicle travel on a plurality of test bodies differing in condition of concrete under different conditions; measuring the number of times of a travel of the vehicle while the surface of concrete is held in a sound state and the number of times of a travel of the vehicle at which the surface of concrete has a fine crack; combining the conditions of the concrete and conditions of the vehicle to prepare a plurality of combination models; selecting a proper combination model for the concrete slab where the vehicle travels; and predicting the formation period of wheel tracks on the surface of the concrete slab based upon a result of the combination model.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for predicting the occurrence of ruts on the surface of a concrete slab. [Background technology]

[0002] In recent years, with the expansion of mail order businesses, large logistics warehouses need to move a lot of luggage in a short time. The transportation of luggage by automatic guided vehicles (AGVs) has become essential. For example, one logistics warehouse has a 10,000m 2 In a warehouse of over 1,000 meters in size, hundreds of AGVs run around almost all day, all year round. AGVs are required to carry as much cargo as possible and transport it as fast as possible. Therefore, in areas where AGVs run frequently, the tracks of the AGV's wheels become visible in a short period of time, and over time the surface wears away, leaving ruts about 2mm to 5mm deep.

[0003] These ruts increase the vibrations and shocks that AGVs experience when they are moving, leading to damage to the AGV and failures and malfunctions of the equipment on board.

[0004] One possible countermeasure to prevent ruts on concrete slabs is to soften the material on the AGV wheel surface or to select a hard material (such as metal plates like iron or stainless steel) whose surface does not easily wear away. However, improving AGVs is fundamentally difficult from the construction side. On the other hand, in large-area logistics warehouses, changing to expensive floor materials would significantly increase costs, so at present, relatively inexpensive specifications such as applying a surface reinforcing material to the concrete slab are the basis. At this stage, it is not clear what type of slab specifications can withstand repeated AGV runs and for how long.

[0005] The following Patent Document 1 proposes a method for diagnosing or predicting deterioration of concrete. This method aims to diagnose or predict the type of deterioration occurring in the concrete to be diagnosed (for example, deterioration caused by alkali aggregate reaction (ASR), delayed ettringite formation (DEF), frost damage, fire damage, salt damage, or rebar corrosion due to neutralization, etc.) and the degree (magnitude) of deterioration of the concrete. In addition, when multiple types of deterioration occur in the concrete to be diagnosed, the method aims to diagnose the main cause (factor) of concrete deterioration from each type of deterioration, the degree of each deterioration, and the degree of each deterioration. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-18233 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the method described in Patent Document 1 does not target cracks that occur when the wheels of an AGV repeatedly run over a concrete surface.

[0008] In view of the above circumstances, the present invention provides a method for predicting the time when ruts will appear on the surface of a concrete slab, which is capable of predicting the period from when the surface breaks down until the ruts grow by measuring the initial microcracks that appear on the concrete surface. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention employs the following means. In other words, the method of the present invention for predicting the time when ruts will appear on the surface of a concrete slab involves running vehicles under different conditions over a number of test specimens with different concrete conditions, measuring the number of times the vehicle runs until the concrete surface is maintained in a healthy state and the number of times the vehicle runs until fine cracks appear on the concrete surface, combining the concrete conditions and the vehicle conditions to prepare a number of combination models, selecting an appropriate combination model for the concrete slab on which the vehicle will run, and predicting the time when ruts will appear on the surface of the concrete slab based on the results of the combination model.

[0010] In the method for predicting the time when ruts will occur on the surface of a concrete slab configured as described above, vehicles with different conditions are run on multiple test specimens to prepare multiple combination models in advance. An appropriate combination model is selected, and based on the results of the combination model, the time when ruts will occur on the surface of a concrete slab on which a vehicle actually runs can be predicted. Therefore, by measuring the initial microscopic cracks that occur on the concrete surface, it is possible to predict the period until the surface breaks down and grows into ruts.

[0011] In addition, in the method of predicting the time of rut formation on the surface of a concrete slab according to the present invention, the concrete conditions may be one or more combinations of the concrete mix, the type of aggregate, the finishing method, the type of surface reinforcement material, and the amount of application of the surface reinforcement material.

[0012] In the method for predicting the occurrence of rutting on the surface of a concrete slab configured as described above, a combination model is prepared by using one or more combinations of concrete conditions including the concrete mix, aggregate type, finishing method, type of surface reinforcement material, and amount of application of the surface reinforcement material, and the combination model can be prepared by using one or more combinations of concrete conditions, and the combination model can predict the occurrence of rutting more accurately based on the specific concrete conditions.

[0013] In addition, in the method of predicting the time of rut formation on the surface of a concrete slab according to the present invention, the vehicle conditions may be one or a combination of the shape of the wheels, the material of the wheels, and the load amount.

[0014] In the method for predicting the occurrence of wheel ruts on the surface of a concrete slab configured as above, a combination model is prepared by using one or more combinations of the wheel shape, wheel material, and load weight as vehicle conditions, and the occurrence of wheel ruts can be predicted more accurately based on the specific vehicle conditions. Effect of the Invention

[0015] According to the method of the present invention for predicting the time when ruts will appear on the surface of a concrete slab, by measuring the initial microscopic cracks that appear on the concrete surface, it is possible to predict the period until the surface breaks down and grows into ruts. [Brief description of the drawings]

[0016] [Figure 1] 1 is a graph showing the relationship between the number of repeated runs of the AGV wheels and the amount of wear (wheel rut depth) on the concrete surface. [Diagram 2] This is a photograph showing the (1) sound condition of a concrete surface. [Diagram 3] This is a photograph showing the state of microcracks (2) on the surface of concrete. [Figure 4] This is a photograph showing the state of ruts (3) on a concrete surface. [Diagram 5] This is a photograph showing the expansion of rut depth on the concrete surface (4). [Figure 6] FIG. 1 is a diagram showing the relationship between the number of repeated runs for each combination (1) sound, (2) occurrence of fine cracks, and the amount of applied load. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, a method for predicting the occurrence time of ruts on the surface of a concrete slab according to an embodiment of the present invention will be described. For example, the method for predicting the occurrence time of ruts will be described for ruts that occur on the surface of a floor slab of a building such as a large logistics warehouse where AGVs (vehicles) run.

[0018] As the AGV wheels repeatedly run over the concrete, the concrete surface is gradually damaged, and fine cracks first appear. These fine cracks grow into ruts as the destruction progresses in the depth direction. Note that fine cracks are less than 0.1 mm (the width visible with a magnifying glass) to about 0.5 mm.

[0019] Figure 1 is a graph showing the relationship between the number of repeated runs of the AGV wheels and the amount of wear (track depth) on the concrete surface. Note that the regions shown in Figure 1, (1) sound, (2) fine cracks, (3) tracks, and (4) increased track depth, are based on the graph for a load of 400 kgf.

[0020] Figure 2 shows a photograph of (1) an example of a healthy road. Figure 3 shows a photograph of (2) an example of fine cracks. Figure 4 shows a photograph of (3) an example of ruts (a ruler is shown in the center of the photograph). Figure 5 shows a photograph of (4) an example of ruts that have become deeper (a ruler is shown in the center of the photograph, and the width of the ruts in this photograph is about 5 cm).

[0021] As shown in Figure 1, before the wheels run over the concrete, the surface is in a sound state with no cracks (see "(1) Sound"). As the wheels run over it repeatedly, microcracks appear on the concrete surface (see "(2) Microcracks appear"). The microcracks gradually increase in number and width, but do not progress in the depth direction for a while. After that, the concrete surface begins to break down, and ruts appear in the depth direction little by little (see "(3) Ruts appear"), and then the depth of the ruts increases (see "(4) Increasing rut depth").

[0022] In logistics warehouses, when the condition progresses from (3) ruts appearing to (4) rut depth increasing, the area requiring repairs must be divided, the program must be changed to prevent AGVs from entering, and a period of about one week must be allowed for the repair material to fully harden. There are concerns that this work will lead to a reduction in the amount of movement of the logistics warehouse. On the other hand, since a certain amount of area must be reserved for repairs, a vicious cycle is created in which many areas that are repaired at the same time are left unattended until the condition progresses to (4) rut depth increasing. Therefore, it is ideal to check the slabs of logistics warehouses while they are in the condition of (2) microcracks appearing, and repair them partially in a short period of time.

[0023] The relationship between (1) soundness and (2) occurrence of microcracks is shown in the image in FIG. 6 as an example. The horizontal axis of FIG. 6 indicates the number of repeated runs of the AGV while maintaining (1) a sound state. In other words, the horizontal axis of FIG. 6 indicates the number of repeated runs of the AGV from (1) a sound state until (2) microcracks begin to occur. The vertical axis of FIG. 6 indicates the number of repeated runs of the AGV from (2) the beginning of the occurrence of microcracks until (3) the beginning of the occurrence of ruts. The number of repeated runs from (1) soundness until (2) occurrence of microcracks is obtained for each combination model by changing the concrete conditions and AGV conditions (vehicle conditions). The concrete conditions are the concrete mix, the type of aggregate, the finishing method such as polishing, the type of surface reinforcement material, and the amount of application of the surface reinforcement material. The AGV conditions are the shape of the wheel (flat or drum type), the material of the wheel surface (hardness), and the load (weight of the AGV). The relationship between (1) the sound length and (2) the length at which microcracks appear is that if the concrete surface is extremely hard and the wheel load is extremely light in comparison, the sound length (1) will not change to microcracks (2), and ruts will not appear permanently. Also, the more repeated runs that are made from (1) a sound state (a clean state with absolutely no cracks on the concrete slab surface) until (2) microcracks appear, the more repeated runs that are made from (2) a microcrack will gradually grow larger, causing the surface of the concrete slab to begin to collapse and (3) ruts will begin to appear.

[0024] In this way, by obtaining data on the number of repetitions from (1) soundness to (3) the appearance of ruts through tests on a combination model using multiple test specimens, it is possible to reflect this in the selection of slab specifications that match the AGV specifications and operating conditions in actual projects, as well as in maintenance plans. In addition, it is possible to (2) investigate the AGV running path in an actual project when microcracks are present, and to provide partial reinforcement according to practical application.

[0025] The procedure is as follows. (Step 1) Conduct repeated wheel running tests on test specimens that combine concrete and AGV conditions.

[0026] (Step 2) (1) The relationship between the number of repeated runs required for soundness and (2) the number of repeated runs required for the occurrence of microcracks is understood for each combination model (see Figure 6).

[0027] (Step 3) · We propose combinations of slab specifications and wheel materials that suit the AGV specifications and driving conditions. Select a combination model that matches (is close to) the actual conditions of the AGV and concrete slab that will be used. Predict the timing of rutting based on the test results of that combination model. (2) At the stage before rutting occurs and when fine cracks appear, the timing of slab surface checks based on the number of repeated runs is proposed. -Suggests early maintenance timing.

[0028] (Step 4) (2) Carry out partial repairs when microcracks have developed, to extend the life of the road before ruts form.

[0029] In the method for predicting the time when ruts will occur on the surface of a concrete slab, which is configured as described above, multiple combination models are prepared in advance by running AGVs under different conditions on multiple test specimens. By selecting an appropriate combination model, it is possible to predict the time when ruts will occur on the surface of a concrete slab on which an AGV will actually run, based on the results of the combination model. Therefore, by measuring the initial microscopic cracks that occur on the concrete surface, it is possible to predict the period until the surface breaks down and grows into ruts.

[0030] In addition, a combination model is prepared by using one or more combinations of concrete mix, aggregate type, finishing method, surface reinforcement type, and surface reinforcement application amount as concrete conditions, and the timing of rutting can be predicted more accurately based on the specific concrete conditions.

[0031] In addition, a combination model is prepared by setting one or more combinations of the wheel shape, wheel material, and load capacity as AGV conditions, which makes it possible to more accurately predict the occurrence of wheel ruts based on the specific AGV conditions.

[0032] In addition, during the design stage, slab specifications can be selected according to the AGV specifications and driving conditions, and wheel materials can be selected to suit the slab specifications.

[0033] In addition, (2) the time to check the slab surface can be determined based on the number of repeated runs at which fine cracks appear.

[0034] In addition, it is possible to grasp the timing of maintenance before ruts form, and select simple and inexpensive partial repairs, enabling repair work to be carried out with minimal reduction in the operating rate of the logistics warehouse.

[0035] The above describes one embodiment of the wind load evaluation method for exterior materials according to the present invention. However, the present invention is not limited to the above-described embodiment and can be modified as appropriate without departing from the spirit of the present invention.

[0036] For example, in the embodiment described above, a combination model was prepared with the concrete mix, type of aggregate, finishing method, type of surface reinforcement material, and amount of application of the surface reinforcement material as the concrete conditions, but the present invention is not limited to this. It is sufficient to set one or more combinations of the concrete mix, type of aggregate, finishing method, type of surface reinforcement material, and amount of application of the surface reinforcement material as the concrete conditions.

[0037] In the above embodiment, a combination model is prepared with the wheel shape, wheel material, and load weight as the AGV conditions, but the present invention is not limited to this. One or more combinations of the wheel shape, wheel material, and load weight may be set as the AGV conditions.

[0038] In the above embodiment, the AGV is used as an example of the vehicle, but the present invention is not limited to this. The type of vehicle can be set appropriately.

Claims

1. Vehicles with different conditions were run over multiple test specimens with different concrete conditions, measuring the number of times the vehicle is driven until the surface of the concrete is kept in a healthy state and the number of times the vehicle is driven until microcracks appear on the surface of the concrete, and preparing a plurality of combination models by combining the conditions of the concrete, the conditions of the vehicle, and the number of times the vehicle is driven; Selecting an appropriate combination model for a concrete slab on which the vehicle runs, and predicting the time when ruts will occur on the surface of the concrete slab based on the result of the combination model; A method for predicting the time when ruts will occur on the surface of a concrete slab, wherein the concrete conditions are one or more combinations of concrete mix, type of aggregate, finishing method, type of surface reinforcement material, and amount of application of the surface reinforcement material.

2. 2. The method for predicting the occurrence of ruts on the surface of a concrete slab according to claim 1, wherein the vehicle conditions are one or more combinations of the shape of the wheels, the material of the wheels, and the load.

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