Construction method of concrete beam

Abstract

To provide a construction method of a concrete beam capable of shortening a construction period and reducing construction cost as comparing with a conventional construction method using molds.SOLUTION: A construction method of a concrete beam is to construct a concrete beam in an underground concave area 1 having an opening in a ground surface, comprises: a process of filling wast melting furnace water-pulverized slag 2 produced by pulverizing with water molten material generated in a melting treatment of general waste or industrial waste at temperature equal to 1200°C or more in an industrial waste melting furnace, making its metal iron content equal to 1 mass% or less in a magnetic separation treatment and further performing particle shape adjustment treatment, and installing and leveling on the ground surface level GL to be water-fastened, thereby forming a slag filling layer 21 in the underground concave area 1; a process of excavating the slag filling layer 21 and forming a concave part 211 corresponding to a shape of the concrete beam A; and a process of filling concrete 6 into the concave part 211.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for constructing a concrete beam in an underground recessed area that opens to the ground surface. [Background technology]

[0002] A common construction method for constructing concrete in an underground recessed area, including a method for constructing concrete beams, is to install a formwork in the underground recessed area and pour concrete into the formwork (see, for example, Patent Document 1). However, this conventional construction method using a formwork requires the work of constructing the formwork (carpentry work when constructing wood), installing the formwork, and removing the formwork, which creates problems such as the need to secure carpenters and formwork craftsmen and increases labor and material costs, leading to longer construction periods and higher construction costs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3009592 Summary of the Invention [Problem to be solved by the invention]

[0004] The problem to be solved by the present invention is to provide a method for constructing concrete beams that can shorten the construction period and reduce construction costs compared to conventional construction methods that use formwork. [Means for solving the problem]

[0005] In order to solve the above problems, the inventors have aimed to develop a method for constructing concrete beams without using formwork. They have discovered that by forming a slag-filled layer in an underground recessed area using granulated slag from a waste melting furnace, and then excavating the slag-filled layer to form a recess corresponding to the shape of the concrete beam, it is possible to construct a concrete beam without using formwork.

[0006] That is, according to one aspect of the present invention, the following concrete beam construction method is provided. A method for constructing a concrete beam in an underground recessed area that opens to the ground surface, comprising: a process of filling the underground depression with granulated waste melting furnace slag obtained by melting municipal or industrial waste at a high temperature of 1200°C or higher in a waste melting furnace, pulverizing the resulting molten material with water, reducing the metallic iron content to 1% by mass or less by magnetic separation, and further adjusting the particle size, and spreading the granulated slag evenly to the ground surface level and water-tightening it to form a slag-filled layer; Excavating the slag-filled layer to form a recess corresponding to the shape of the concrete beam; and pouring concrete into the recess. [Effects of the Invention]

[0007] According to the present invention, it is possible to construct concrete beams without using formwork, which reduces the construction time and costs compared to conventional construction methods that use formwork. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view conceptually illustrating an outline of a concrete beam construction method according to one embodiment of the present invention. [Figure 2] 1 is a cross-sectional view conceptually illustrating an outline of a conventional concrete beam construction method. DETAILED DESCRIPTION OF THE INVENTION

[0009] Fig. 1 conceptually illustrates an outline of a concrete beam construction method (hereinafter referred to as "the present invention construction method"), which is one embodiment of the present invention. On the other hand, Fig. 2 conceptually illustrates an outline of a conventional concrete beam construction method (hereinafter referred to as "the conventional construction method"). Here, in order to deepen understanding of the present invention, the conventional construction method will be explained with reference to Fig. 2 before explaining the present invention construction method.

[0010] The construction procedure for the conventional method is as follows: (1) Fill the underground depression 1 that opens to the ground surface with landfill soil or sand (hereinafter collectively referred to as "landfill soil") 20 and compact it. At this time, an unfilled portion 201 of the landfill soil 20 is secured in the area where the concrete beam A is to be constructed. (2) Mortar 40 is applied to the bottom surface of the unconstructed portion 201 to adjust the level of the formwork 30 for the concrete beam A. (3) After a predetermined number of days have passed, the pre-fabricated formwork 30 is installed and fixed. (4) The specified reinforcing bars 50 are placed and fixed in the formwork 30, and concrete 60 of the specified mix is ​​poured in. (5) After a predetermined number of days have passed, the formwork 30 is removed, and the remaining portion 11 of the underground recessed area 1 is filled with landfill soil and compacted.

[0011] As described above, conventional construction methods use formwork 30, which requires the above-mentioned work of making the formwork (carpentry work when wood is used), installing the formwork, and removing the formwork. This creates problems such as the need to secure carpenters and formwork craftsmen, and increases in labor and material costs, which leads to longer construction periods and higher construction costs.

[0012] Therefore, in the present invention, as described above, it is possible to construct concrete beams without using formwork. One embodiment of the method of the present invention will be described below with reference to Figure 1. The construction procedure of the method of the present invention is as follows. (1) Granulated waste melting furnace slag 2 is filled into an underground depression 1 that opens to the ground surface, spread evenly to the ground surface level GL, and water-tightened to form a slag filled layer 21. (2) The slag filled layer 21 is excavated to form a recess 211 corresponding to the shape of the concrete beam A. (3) Mortar 4 is applied to the bottom and sides of the recess 211. (4) After a predetermined number of days have passed, a predetermined reinforcing bar 5 is placed and fixed in the recess 211, and concrete 6 of a predetermined mix is ​​poured in.

[0013] In this way, the construction method of the present invention makes it possible to construct concrete beams without using formwork, which reduces construction time and construction costs compared to conventional construction methods that use formwork 30.

[0014] In the above-described method of the present invention, mortar 4 is applied to the bottom and side surfaces of the recess 211, but this application of mortar 4 can be omitted. Since the granulated waste melting furnace slag used in the present invention has high water compaction properties, it is easy to maintain the surface condition of the granulated waste melting furnace slag 2 on the bottom and side surfaces of the recess 211 after the slag-filled layer 21 is excavated. Therefore, the application of mortar 4 can be omitted in the method of the present invention. However, from the viewpoint of ease and accuracy of application, it is preferable to apply mortar 4 to the bottom and side surfaces of the recess 211. In this case, it is preferable to spray water on the bottom and side surfaces of the recess 211 before applying mortar 4. Furthermore, in order to maintain the surface condition of the granulated waste melting furnace slag 2 for a predetermined number of days after the application of the mortar, it is preferable to perform water spraying and sheet (vinyl sheet) curing as a measure to prevent moisture evaporation, as necessary.

[0015] Next, we will explain the waste melting furnace granulated slag used in the present invention. In this specification, "waste melting furnace granulated slag" refers to slag obtained by melting municipal or industrial waste (hereinafter simply referred to as "waste") in a waste melting furnace at a high temperature of 1,200 °C or higher, pulverizing the resulting molten material with water (rapid pulverization, rapid cooling pulverization; the slag discharged from the waste melting furnace is poured into water to rapidly cool, harden, and simultaneously pulverize into particles), reducing the metallic iron content to 1% by mass or less by magnetic separation, and then subjecting the slag to particle size adjustment. Furthermore, the "particle size adjustment" in this specification is a general term for sieving and particle size adjustment, which are performed after magnetic separation (sieving and particle size adjustment methods, either crushing or grinding). The specific particle size of the waste melting furnace granulated slag obtained by this particle size adjustment is 5 mm or less. The term "particle size" refers to the sieve mesh size specified by the nominal mesh size of the sieve as specified in JIS Z 8801-1, and a particle size of 5 mm or less means that the particle passes through a sieve with a mesh size of 5 mm.

[0016] As described above, in the present invention, granulated slag from a waste melting furnace is used, and it is preferable to use slag of such quality that the design CBR value is 20% or more, the water-tight CBR value is 10% or more, and the internal friction angle is 30° or more. Of these, the design CBR value is commonly used as an index to determine whether or not a pavement material can be used as a subgrade material to support it, and the higher the design CBR value, the higher the support rate.The test method for the design CBR value is specified in JIS A 1211 (CBR test method), and a penetration test is carried out using a CBR tester consisting of a loading device, load meter, penetration piston, and penetration amount measuring device, and the CBR value (design CBR value) is calculated by reading the load at penetration amounts of 2.5 mm and 5.0 mm while penetrating a 5 cm diameter piston at 1 mm / min. In addition, the watertight design CBR value is an index for the use of backfill soil in areas where water such as groundwater is present, and JIS A 1211 (CBR test method) is also applied to the watertight CBR value, but in the watertight CBR test, the sample is not compacted with a rammer; instead, the sample is immersed in water and dropped into a mold together with the sample. After jigging, a 5 kg perforated weight plate is placed on top and left to stand for 15 minutes before penetration to determine the CBR value (watertight CBR value). On the other hand, the angle of internal friction is the angle that represents the frictional resistance portion of the soil's shear strength that is proportional to the vertical stress, and specifically, it is the maximum angle at which soil or sand can stand on its own. The angle of internal friction is determined in accordance with the test method specified in JGS 0524 (triaxial compression test of soil).

[0017] The granulated slag used in the present invention is generated in a waste melting furnace, and the preferred type of waste melting furnace is a coke-bed type waste melting furnace, which adds coke and limestone as secondary materials when the waste is charged. The coke and limestone added as secondary materials provide the following effects: In other words, the addition of coke as a secondary material provides the following effects. (1) The atmospheric temperature in the lower part of the furnace reaches a high temperature of 1700-1800°C, and the waste melts completely at this high temperature, resulting in the ash in the waste melting completely (the unmelted portion disappears). (2) The atmosphere inside the furnace becomes a high-temperature reducing atmosphere (a high-temperature atmosphere without oxygen), which causes harmful substances such as heavy metals in the waste to migrate into the gas system, thereby keeping the content of harmful substances in the molten material low. As a result, the safety is comparable to that of natural sand. In addition, adding limestone as a secondary material has the following effects: (3) By adjusting the proportion of limestone added depending on the type of waste, the concentrations of the main components of the molten material (silica / SiO2, lime / CaO) can be stabilized throughout the year. (4) The stabilization of the concentration of the main components in the molten material and the high-temperature melting process facilitate the separation of the slag and metallic iron when crushed with water, improving the separation in the subsequent magnetic separation process. As a result, the metallic iron content in the resulting granulated slag from the waste melting furnace is significantly reduced. (5) The concentration of the main components in the molten material is stable throughout the year, and the quality of the resulting granulated slag from the waste melting furnace (design CBR value, design CBR value, internal friction angle, particle size distribution) is also stable throughout the year. In addition, the stable particle size distribution improves compaction performance.

[0018] In this invention, granulated waste melting furnace slag is used as a filling material for underground depressions. Conventional filling materials for underground depressions include steel slag, non-ferrous slag, and cement-based fluidized soil. However, steel slag has a high pH value, raising concerns about alkaline impacts on the surrounding area. Furthermore, it solidifies after construction, making future re-excavation extremely difficult. Non-ferrous slag has a high iron content, which can lead to iron rust on the surface after construction, resulting in poor appearance. Fluidized soil is often used to fill underground depressions, and while it is not a problem if future re-excavation is not planned, it can be difficult if future re-excavation is planned. In contrast, the granulated waste melting furnace slag used in this invention has the advantages of a neutral to slightly alkaline pH, no alkaline impact on the surrounding area, no concerns about solidification after construction, and lower cost compared to fluidized soil.

[0019] The concrete beam construction method according to the present invention can be suitably applied to repair work on the underground portions of existing facilities and foundation work for small to medium-sized structures with a height of three stories or less in the case of new construction. Furthermore, as shown in Fig. 1, the construction dimensions of the concrete beam are such that, in order to place reinforcing bars 5 in recesses 211 corresponding to the shape of the concrete beam A, the width W is approximately the same as or slightly wider than the depth D, and the depth D is 700 mm or less, preferably 500 mm or less. [Example]

[0020] As an example of the present invention, a concrete beam was constructed using the construction method of the present invention shown in Figure 1. The construction conditions were as follows: the surface area of ​​the underground recessed area 1 was approximately 100 m 2 , capacity is about 60m 3 The dimensions of concrete beam A were height (depth D): 700 mm, width W: 700 mm, and two beams were constructed, one 9 m long and one 6 m long. On the other hand, as a comparative example, concrete beams were constructed using the conventional construction method shown in Figure 2. The construction conditions were the same as those of the example. When the construction period (construction process period) and labor costs (construction costs) of the example and comparative example were compared, the example showed a reduction in the construction process period by approximately 30% and a reduction in labor costs by approximately 20% compared to the comparative example. [Explanation of symbols]

[0021] A Concrete beam 1 Underground concave area 11 Remaining part of underground depression area 2. Granulated slag from waste melting furnace 21 Slag packed bed 211 Recess 4,40 Mortar 5,50 rebar 6,60 Concrete 20 Landfill soil 201 Unbuilt area 30 Formwork

Claims

1. A method for constructing a concrete beam in an underground recessed area that opens to the ground surface, comprising: a process of filling the underground depression with granulated waste melting furnace slag obtained by melting municipal or industrial waste at a high temperature of 1200°C or higher in a waste melting furnace, pulverizing the resulting molten material with water, reducing the metallic iron content to 1% by mass or less by magnetic separation, and further subjecting the granulated slag to a particle size adjustment process, spreading the granulated slag evenly to the ground surface level, and water-tightening the granulated slag to form a slag-filled layer; Excavating the slag-filled layer to form a recess corresponding to the shape of the concrete beam; and pouring concrete into the recess.

2. The method for constructing a concrete beam according to claim 1, further comprising the step of applying mortar to the bottom and side surfaces of the recess before the step of pouring concrete into the recess.

3. 3. A method for constructing a concrete beam according to claim 1, wherein granulated waste melting furnace slag having a design CBR value of 20% or more, a water-tightened CBR value of 10% or more, and an internal friction angle of 30° or more is used.

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