Method for manufacturing reinforced roadbed material

Abstract

To provide a reinforced roadbed material that does not cause reverse fault-type fracture and to provide a method for producing the same.SOLUTION: A reinforced roadbed material comprises a slag whose rate of expansion (%) measured by a water immersion expansion test is lower than a rate of strain (%) leading to a compressive failure of the reinforced roadbed material measured by a compression test of the reinforced roadbed material after curing cement.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a reinforced roadbed material using steelmaking slag, which is one of the by-products of a steelworks, and a method for manufacturing the same.

Background Art

[0002] For an asphalt-paved roadbed, materials to be used are selected in consideration of the stability and durability of the roadbed. The materials used as roadbed materials are defined in the civil engineering common specifications and paving regeneration manuals of each prefecture, and are required to satisfy various characteristics such as modified CBR.

[0003] It is well known that steelmaking slag generated as a by-product of a steelworks is one of the materials for roadbed materials. However, since calcium oxide contained therein reacts with moisture such as rainwater and causes deposition expansion, when used as a roadbed material, in order to suppress the expansion of steelmaking slag after the construction of the roadbed, pretreatment such as aging is performed in advance, and it has been common to add cement to the pretreated steelmaking slag to form a stable treatment mixture.

[0004] By the way, a reinforced roadbed material containing steelmaking slag is required not to cause a reverse fault type of fracture caused by the expansion of the steelmaking slag in addition to having desired strength, filling property, compaction property, etc. Therefore, conventionally, a large safety factor has been uniformly set and excessive pretreatment has been performed, and the current situation is that it has not yet been clarified to what extent the expansion of the steelmaking slag should be suppressed to avoid a reverse fault type of fracture. Here, the reverse fault type of fracture refers to a phenomenon in which a horizontal compressive force acts on the roadbed due to the expansion of the steelmaking slag after the consolidation of the roadbed material, a fault occurs in the roadbed, and the roadbed on one side of the fault rises above the roadbed on the other side, causing the roadbed to bulge in the vicinity of the fault.

[0005] As prior art related to roadbed materials, for example, Patent Documents 1 and 2 propose methods for estimating future developed strength from unconsolidated soil cement, and Patent Document 3 proposes a method for estimating the compressive strength of a predetermined age according to the construction conditions at the construction site of soil cement. Further, although Patent Document 4 proposes a method for evaluating the filling property, compacting property, etc. of concrete from the viewpoints of construction site management and rationalization, none of them mention avoiding reverse fault failure due to expansion after consolidation of the roadbed material.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] The problem of the present invention is to propose a reinforced roadbed material that does not cause reverse fault type failure due to expansion of slag and a manufacturing method thereof.

Means for Solving the Problems

[0008] The present invention is a reinforced roadbed material composed of a mixture of cement and slag, wherein the expansion rate (%) of the slag in the water immersion expansion test of the slag is lower than the strain rate (%) leading to compressive failure of the reinforced roadbed material in the compressive test of the reinforced roadbed material after cement curing. In the present invention, the reinforced roadbed material refers to a stable treatment mixture of slag and cement.

[0009] In the above-described reinforced roadbed material, the water immersion expansion test is preferably the water immersion expansion test for steel slag for roads in JIS A 5015 (performed for 100 days), and the compression test is preferably performed at a compression rate of 0.1 to 1% / min. Regarding the water immersion expansion test, a continuous accelerated water immersion expansion test may be performed at a water temperature of 80°C for 40 days.

[0010] Further, the present invention provides a method for manufacturing a reinforced roadbed material composed of a mixture of cement and slag. In this method, a compression test is performed on the reinforced roadbed material after cement curing to obtain the strain rate at which the reinforced roadbed material reaches compressive failure, and the expansion rate of the slag is obtained by a water immersion expansion test. The expansion rate of the slag is compared with the strain rate at which the reinforced roadbed material reaches compressive failure, and cement is added and mixed with the slag under the condition that the expansion rate is lower than the strain rate. This is a method for manufacturing a reinforced roadbed material. In order to make the expansion rate of the slag lower than the strain rate at which compressive failure occurs in the present invention, it is preferable to apply any one or two or more of the following methods: using slag that has been subjected to aging treatment for a longer time, using slag with a lower CaO or MgO concentration, or reducing the amount of cement added.

[0011] In the above manufacturing method, the water immersion expansion test is preferably the water immersion expansion test for steel slag for roads in JIS A 5015, and the compression test is preferably performed at a compression rate of 0.1 to 1% / min.

Advantages of the Invention

[0012] According to the present invention, the strain rate (%) at which the reinforced roadbed material reaches compressive failure after cement curing is regarded as being caused by the expansion of the slag. This strain rate (%) is compared with the expansion rate (%) obtained by the water immersion expansion test of the steelmaking slag. By making the expansion rate (%) lower than the strain rate (%), the expansion of the slag can be suppressed, and the shear failure of the reinforced roadbed material caused thereby can be avoided.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0014] The present invention is based on a new finding that in a reinforced roadbed material, when the expansion rate (%) in the water immersion expansion test of slag is lower than the strain rate (%) at which the reinforced roadbed material reaches compressive failure in the compression test of the reinforced roadbed material after cement curing, it is possible to avoid causing reverse fault type failure due to the expansion of the material after consolidation, and thereby, it is possible to set the amount of cement added that will not cause reverse fault type failure in the future.

[0015] Figure 1 shows a plurality of specimens with a diameter of 100 mm and a height / diameter ratio of 1.27, which were prepared by using steelmaking slag with a particle size adjusted to 0 - 40 mm, adding 1.0 - 5.0 mass% of cement to the steelmaking slag, mixing and compacting it (the water content ratio was adjusted to the water content ratio sufficient for the 28-day solidification of cement), and performing sealed curing. It is a graph showing the relationship between the strain rate (%) at compressive failure and the amount of cement added (%) of the obtained specimens. Also, Table 1 shows the investigation results of the amount of cement added (%) of each specimen, the strain rate (%) at compressive failure of each specimen, the expansion rate (%) of the steelmaking slag, and the applicability.

[0016] In this investigation, the particle size distribution of steelmaking slag was measured in accordance with JIS A 1102, and relative particle sizes were created using the measured particle sizes. Adjustments were made so that there was no particle size difference in each specimen (adjusted to a relative particle size where the maximum particle size of the slag was 1 / 4 or less of the diameter of the specimen). Also, the tamping of the mixture was carried out in accordance with E011 and F007 in the test manual, and the compression speed in the compression test was set to 0.2 mm / min. Further, the strain rate (%) at the time of compression failure was obtained by creating a load-strain curve from the compression test results and converting the strain at the maximum load in the load-strain curve into the strain rate. The expansion rate (%) of the steelmaking slag was obtained from the water immersion expansion test (a test for estimating the final expansion rate) of JIS A5015 steel slag for road use. For applicability, those with an expansion rate (%) obtained from the water immersion expansion test of the steelmaking slag lower than the strain rate (%) at the time of compression failure were marked with 〇, and those with a difference between the strain rate (%) and the expansion rate (%) of 0.2% or more were marked with ◎, and those with an expansion rate (%) higher than the strain rate (%) at the time of compression failure were marked with ×.

[0017]

Table 1

[0018] In Table 1, Examples 1 to 3 are cases where the added cement amount was 1.5 mass%, Examples 4 to 6 are cases where the added cement amount was 3.5 mass%, and Example 7 is a case where the added cement amount was 5.0 mass%. However, the expansion rate (%) was lower than the strain rate (%) at the time of fracture in all cases, and the result was that it was applicable. On the other hand, in Comparative Examples 1 to 4, the expansion rate (%) was higher than the strain rate (%) at the time of fracture in all cases, and it was found to be inapplicable.

[0019] In the present invention, it is preferable that the rolling speed in the compression test be 0.1 to 1% / min. The reason is that it was considered that the stress when the steelmaking slag expands in a constrained state can be intentionally induced. For this purpose, it is important to make the rolling speed as small as possible and not to affect the strain rate (%) leading to compressive failure. This is because the results shown in Figure 2 were obtained from preliminary tests.

[0020] In the present invention, a compression test is performed on the reinforced roadbed material after cement curing to determine the strain rate leading to the compressive failure of the reinforced roadbed material, and the expansion rate of the slag is determined by a water immersion expansion test. The expansion rate of the slag is compared with the strain rate leading to the compressive failure of the roadbed material, and it is manufactured by adding cement and mixing it with the slag under the condition that the expansion rate is lower than the strain rate. For this purpose, it is preferable to use slag whose particle size is adjusted in the range of 0 to 40 mm. The amount of cement to be added is preferably determined in the range of 1 to 5 mass% according to the required roadbed support force. The mixing of the slag and the cement is preferably carried out by humidifying the slag the day before ramming and mixing it with the cement immediately before ramming. Also, the sealed curing is preferably carried out under the conditions of a temperature of 20°C and a humidity of 98%.

Industrial Applicability

[0021] According to the present invention, it is possible to provide a reinforced roadbed material that does not cause reverse fault type failure and a method for manufacturing the same.

Claims

1. In a method for manufacturing a reinforced roadbed material comprising a mixture of cement and slag, a compression test is performed on the reinforced roadbed material after cement curing to determine the strain rate leading to compressive failure of the reinforced roadbed material, and the expansion rate of the slag is determined by a water immersion expansion test. The expansion rate of the slag is compared with the strain rate leading to compressive failure of the reinforced roadbed material, and cement is added and mixed with the slag under the condition that the expansion rate is lower than the strain rate. A method for manufacturing a reinforced roadbed material, characterized in that.

2. The method for manufacturing a reinforced roadbed material according to claim 1, wherein the water immersion expansion test is a water immersion expansion test of JIS A 5015 steel slag for roads.

3. The method for manufacturing a reinforced roadbed material according to claim 1, wherein the compression test is performed at a pressure reduction rate of 0.1 to 1% / min.

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