Method for predicting the timing of repairs on the surface of concrete slabs
By measuring Mohs hardness and deriving linear functions, the method predicts concrete surface repair timing, addressing durability assessment in minor damage and enabling efficient maintenance planning.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- SHIMIZU CORP
- Filing Date
- 2022-09-02
- Publication Date
- 2026-07-22
AI Technical Summary
Existing methods fail to assess the durability of concrete surfaces in a state of minor damage, such as scratches or impacts, leading to potential damage and malfunctions in automatic guided vehicles (AGVs) due to rut formation.
A method involving driving a wheel with a predetermined load on the concrete surface, measuring Mohs hardness, deriving an approximate formula, and calculating the number of drives required to reach a Mohs hardness of 2, using linear functions to predict repair timing.
Enables determination of concrete surface durability in minor damage states, allowing for timely maintenance planning and reducing labor and costs by simulating wear under controlled conditions.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention relates to a method for predicting the repair timing of the surface of a concrete slab.
Background Art
[0002] In recent years, with the expansion of the mail-order business, it has become necessary to move a large number of packages in a short time in large logistics warehouses. The transportation of packages by automatic guided vehicles (hereinafter, AGV: Automatic Guided Vehicle) has become essential. For example, in a certain logistics warehouse, several hundred AGVs are running almost non-stop throughout the year. Therefore, at locations with a high running frequency, running tracks of wheels can be seen on the surface of the concrete slab in a short period, and the surface wears over time to form ruts. Such ruts lead to an increase in vibration and impact during the running of AGVs, resulting in damage to AGVs, failures of mounted devices, and malfunctions, which has become a problem.
[0003] In Patent Document 1 below, a method for diagnosing or predicting the deterioration of concrete has been proposed. 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 formation of ettringite (DEF), freezing damage, fire damage, salt damage, or corrosion of reinforcing bars due to carbonation, etc.) and the degree of deterioration of the concrete (the magnitude of deterioration). Also, when multiple types of deterioration occur in the concrete to be diagnosed, it aims to diagnose the type of each deterioration, the degree of each deterioration, and the main cause (factor) in the deterioration of the concrete from the degree of each deterioration.
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0005] There is a need for a method to assess the durability of a concrete surface in a state of minor damage, such as from scratches or impacts.
[0006] In view of the above circumstances, the present invention provides a method for predicting the timing of repairs to a concrete slab surface that can determine the durability of the concrete surface when it is in a state of slight damage. [Means for solving the problem]
[0007] To achieve the above objective, the present invention employs the following means. In other words, the method for predicting the timing of repairs on a concrete slab surface according to the present invention involves driving a wheel equipped with a predetermined load onto the concrete surface, then measuring the Mohs hardness of the concrete surface by varying the number of times the wheel is driven, calculating the relationship between the Mohs hardness for each number of drives, deriving an approximate formula, and calculating the number of drives required to reach a Mohs hardness of 2.
[0008] Furthermore, in the method for predicting the timing of repairs to the surface of a concrete slab according to the present invention, the approximation formula is a linear function.
[0009] Furthermore, in the method for predicting the timing of repairs to a concrete slab surface according to the present invention, the number of runs required to reach a Mohs hardness of 2 when the load is 200 kgf is three times the number of runs required to reach a Mohs hardness of 2 when the load is 600 kgf.
[0010] Furthermore, in the method for predicting the timing of repairs to the surface of a concrete slab according to the present invention, if a coating material is applied to the surface of the concrete, the approximate formula is derived by including the relationship value at the number of runs that exceeds the state in which the Mohs hardness remains substantially constant, even if the number of runs is increased. [Effects of the Invention]
[0011] According to the method for predicting the timing of repairs to a concrete slab surface based on the present invention, the durability of the concrete surface can be determined when it is in a state of minor damage. [Brief explanation of the drawing]
[0012] [Figure 1] This is a perspective view showing a Mohs hardness tester used in a method for predicting the timing of repairs on the surface of concrete slabs. [Figure 2] This graph shows the relationship between the number of runs and the change in hardness when a wheel loaded with 600 kgf is repeatedly driven over concrete. [Figure 3] The images show the condition of the concrete surface after repeated wheel runs: (a) a photograph showing the concrete surface after 100,000 runs, and (b) a photograph showing the concrete surface after 300,000 runs. [Figure 4] This graph shows the relationship between the number of runs and the change in hardness when wheels loaded with 400 kgf and 600 kgf are repeatedly driven over concrete. [Figure 5] This graph shows the change in hardness and the number of runs when a wheel loaded with 600 kgf is repeatedly driven over concrete, both with and without a coating (Figure 2). [Figure 6] This illustrates a method for predicting the timing of repairs to the surface of a concrete slab. [Figure 7] This image illustrates a method for predicting the repair timing of a concrete slab surface after applying a coating material. [Modes for carrying out the invention]
[0013] The following describes a method for predicting the timing of repairs to the surface of a concrete slab according to an embodiment of the present invention.
[0014] Figure 1 is a perspective view showing a Mohs hardness tester used in a method for predicting the timing of repairs on the surface of a concrete slab. After driving on the surface of concrete with wheels having a specified load weight, the Mohs hardness of the concrete surface is measured. When measuring the Mohs hardness, the Mohs hardness tester 1 shown in Fig. 1 is used.
[0015] The Mohs hardness tester 1 has a plurality of pen-shaped test pens 10. The tip portions 11 of the plurality of test pens 10 are each formed of a different type of mineral. The hardness of the surface is evaluated by scratching the surface of the object with the tip portion 11 of the test pen 10 and checking whether the surface is damaged. Table 1 shows the minerals of the tip portion 11 of the test pen 10 and their descriptions.
[0016]
Table 1
[0017] Fig. 2 is a graph showing the change in the number of driving cycles and hardness when a wheel loaded with 600 kgf is repeatedly driven on concrete. The measurement of Mohs hardness is performed by changing the number of driving cycles of the wheel. As shown in Fig. 2, the relationship values between the Mohs hardness for each number of driving cycles are calculated. Up to 100,000 cycles, the hardness decreases linearly and reaches hardness 1 at 100,000 cycles. After that, from 200,000 to 300,000 cycles, it returns to hardness 2 and becomes constant.
[0018] Fig. 3 shows the state of the concrete surface due to repeated driving of the wheel, (a) is a photograph showing the concrete surface after 100,000 cycles, and (b) is a photograph showing the concrete surface after 300,000 cycles. As shown in Fig. 3(a), at 100,000 cycles, the concrete surface is scraped and becomes powdery, and the aggregate (sand) can be seen partially. As shown in Fig. 3(b), at 300,000 cycles, the aggregate can be seen everywhere, and it can be seen that the surface is worn deeply in some parts.
[0019] As shown in Figure 2, the hardness is 2 for 200,000 to 300,000 cycles, but this is an evaluation of the cement filling the aggregate, and the hardness of the aggregate itself is higher than 2. Since the AGV's wheels are in contact with the surface of the aggregate, the hardness does not change at 2, but it is thought that once the aggregate comes off, the amount of wear will increase rapidly, forming ruts.
[0020] Therefore, on a concrete surface, the point at which it reaches a hardness of 2 for the first time can be considered the abrasion threshold. As explained in Table 1 regarding hardness, a hardness of 2 is such that it can be scratched with a fingernail, indicating that the concrete surface is in a fairly brittle state.
[0021] In this test with a 600 kgf load, the results up to 100,000 cycles yielded the approximate formula shown in equation (1) below, indicating that a hardness of 2 is reached at approximately 84,000 cycles. The approximate relationship between the number of cycles and hardness is a linear function. The number of cycles required to derive the approximate formula varies depending on the combination of the hardness of the concrete slab surface, the load value, the wheel material, etc. Measurements should be taken until a proportional relationship can be determined; in this embodiment, for example, the approximate formula can be derived from more than 50,000 cycles.
[0022]
number
[0023] In equation (1), when Y=2, X=8.39 (83,900 times).
[0024] Figure 4 is a graph showing the change in hardness and the number of runs when wheels loaded with 400 kgf and 600 kgf are repeatedly driven over concrete. As shown in Figure 4, the approximate formula for a 400 kgf load is given by equation (2) below, and it takes approximately 139,000 cycles to reach a hardness of 2.
[0025]
number
[0026] In equation (2), when Y=2, X=13.91 (139,100 times).
[0027] With a 400kgf load, the approximately 139,000 cycles required to reach hardness level 2 is about 1.65 times more than the approximately 84,000 cycles required with a 600kgf load. Since a 600kgf load is 1.50 times more than a 400kgf load, it can be considered that the load and the number of cycles are roughly proportional. Therefore, assuming a load of 200kgf, it can be predicted that it will take approximately 251,700 cycles, about three times more, to reach hardness level 2.
[0028] Figure 5 is a graph showing the change in hardness and the number of runs when a wheel loaded with 600 kgf is repeatedly driven over concrete, both with and without a coating (Figure 2). The case with a coating refers to concrete that has been coated with a material that provides abrasion resistance to the concrete surface. As shown in Figure 5, when the coating material is applied, no change in hardness is observed from 20,000 to 60,000 cycles. From 60,000 to 100,000 cycles, the hardness decreases. This is thought to be due to the wear-resistant effect of the coating material, but this effect is thought to have been lost after 60,000 cycles. In this case, since the hardness is thought to decrease linearly after 100,000 cycles, it can be calculated that the hardness reaches 2 at approximately 121,000 cycles using the following equation (3).
[0029]
number
[0030] In equation (3), when Y=2, X=12.1 (121,000 times).
[0031] Therefore, in the case of concrete using this coating material, it can be predicted that it can withstand 182,000 loads at 400 kgf and 364,000 loads at 200 kgf.
[0032] Figures 2, 4, and 5 show the results of tests on concrete specimens prepared to simulate a concrete slab. The abrasion resistance of a concrete slab surface varies depending on the concrete mix, pressing method (manual pressing, mechanical pressing), and curing method (watering, sheeting, immersion). Furthermore, various coatings for abrasion resistance are available from many manufacturers, and their effectiveness differs depending on the amount applied, the application method, and the degree of penetration into the concrete. Additionally, AGV wheels have various conditions, including the load capacity, shape, and material hardness. Therefore, it is necessary to conduct tests on combinations of concrete slab specifications, wheel materials, and load capacity that are planned for actual site use.
[0033] However, actual usage conditions may involve wheel loads of, for example, 100 kgf to 200 kgf, and the number of runs required to reach hardness level 2 could exceed 1 million. Conducting a test with consistent conditions from start to finish would require considerable time and effort. Therefore, by using the method described above, the concrete surface can be accelerated to wear down with a larger load than the actual load, and the actual number of runs can be calculated by obtaining results in a short time.
[0034] Figure 6 shows an image illustrating a method for predicting the timing of repairs to the surface of a concrete slab. For example, measure multiple hardness levels (with different number of runs) under a 600 kgf load. Calculate the number of runs required to reach hardness level 2 using an approximate formula. If the actual load is 200 kgf, triple the number of runs. If necessary, conduct hardness measurements at the actual site. Consider the timing and method of repairs in advance.
[0035] Figure 7 shows an image illustrating a method for predicting the timing of repairs to the concrete slab surface when a coating material is applied. For example, measure multiple hardness levels (with different number of runs) under a 600 kgf load. Include a period where the hardness remains constant during the measurement. Measure again when the hardness decreases due to the loss of the coating's effect. From the data measured after the hardness decrease, calculate the number of runs required to reach a hardness of 2 using an approximate formula. If the actual load is 200 kgf, triple the number of runs. If necessary, conduct hardness measurements at the actual site. Consider the timing and method of repair in advance.
[0036] Furthermore, this method allows for easy measurement of surface hardness even in actual field conditions. By periodically measuring changes in concrete surface hardness, it's possible to calculate when hardness level 2 will be reached. Therefore, maintenance timing and repair methods can be considered early, before large ruts develop, minimizing labor and costs.
[0037] The procedure is as follows: (Step 1) • Conduct wheel running tests on test specimens that combine concrete mix, finishing method, coating material type, wheel material (hardness), and load capacity (AGV weight).
[0038] (Step 2) • Measure the Mohs hardness of the concrete surface after multiple runs.
[0039] (Step 3) • Obtain an approximate formula from the decrease in hardness due to the number of runs. • Calculate the number of runs required to reach hardness level 2. • Calculate the number of trips based on the actual load capacity.
[0040] (Step 4) • Reflect this in the slab specifications. • Consider the wheel material and load capacity. • Develop a maintenance plan.
[0041] You may also repeat steps 3 and 4 by regularly conducting hardness measurements in actual buildings.
[0042] This method for predicting the timing of repairs to a concrete slab surface allows for the determination of the durability of the concrete surface while it is in a state of minor damage.
[0043] Furthermore, test results can be obtained faster than conducting tests under actual usage conditions, resulting in reduced time, cost, and effort in testing.
[0044] Furthermore, the results obtained from the tests allow for consideration of slab specifications tailored to the AGV's specifications and driving conditions during the design phase.
[0045] Furthermore, hardness measurement is easy in the actual field, allowing for an understanding of the concrete surface condition.
[0046] Furthermore, maintenance schedules can be planned in advance, minimizing effort and costs.
[0047] Although one embodiment of the wind load evaluation method for exterior materials according to the present invention has been described above, the present invention is not limited to the above embodiment and can be modified as appropriate without departing from the spirit of the invention.
[0048] The Sustainable Development Goals (SDGs) are 17 international goals adopted at the UN Summit in September 2015. The method for predicting the timing of repairs to concrete slab surfaces according to this embodiment can contribute to achieving some of the 17 SDGs, such as Goal 9, "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation."
Claims
1. A method for predicting the timing of repairs to a concrete slab surface, comprising: driving a wheel equipped with a predetermined load onto the concrete surface; measuring the Mohs hardness of the concrete surface while varying the number of wheel runs; calculating the relationship between the Mohs hardness for each run; deriving an approximate formula; and calculating the number of runs required to reach a Mohs hardness of 2.
2. The method for predicting the timing of repairs to a concrete slab surface according to claim 1, wherein the approximation formula is a linear function.
3. A method for predicting the timing of repairs to a concrete slab surface according to claim 1 or 2, wherein the number of trips required to reach a Mohs hardness of 2 when the applied load is 200 kgf is three times the number of trips required to reach a Mohs hardness of 2 when the applied load is 600 kgf.
4. A method for predicting the timing of repairs to a concrete slab surface according to claim 1 or 2, wherein, if a coating material is applied to the surface of the concrete, the approximate formula is derived by including the relationship value at the number of runs that exceeds the state in which the Mohs hardness remains substantially constant even when the number of runs is increased.