Concrete composition, synthetic segment, and method for manufacturing the synthetic segment

Abstract

This enables the realization of concrete compositions, synthetic segments, and methods for manufacturing synthetic segments, all made of concrete that is environmentally friendly, maintains high strength over long periods, and exhibits excellent adhesion to steel materials and formability. [Solution] The concrete that makes up reinforced concrete is made of cement and 3000cm 2 / g~10000cm 2 Concrete is composed of blast furnace slag fine powder having a specific surface area of ​​ / g, water, admixtures, and aggregate, and satisfies the following formulas (i) to (iii), and the cement is either ordinary Portland cement, high-early-strength Portland cement, or ultra-high-early-strength Portland cement. 28≦C / (C+GGBFS)×100≦70…(i) 20≦W / (C+GGBFS)×100≦50…(ii) 0.1≦SP / (C+GGBFS)×100≦5 …(iii)

Description

[Technical Field]

[0001] This invention relates to a concrete composition, a synthetic segment, and a method for producing a synthetic segment. [Background technology]

[0002] Conventionally, tunnel segments used in shield tunneling have been applied to a wide range of tunnel structures, including those for roads, railways, and utilities such as wiring and piping. In recent years, in particular, tunnel construction in soft ground and deep underground ground has been increasing. In such ground conditions, the external forces acting on the tunnel segments are high, so composite segments, which are a composite structure in which steel and concrete are integrated, are used because they are highly durable and economically superior (see, for example, Patent Document 1).

[0003] Patent Document 1 describes a composite segment formed by integrally forming a steel shell and concrete, which is constructed according to structural requirements for when the steel shell (including the steel shell body, skin plate, reinforcing bars, etc.) and concrete together bear the load.

[0004] On the other hand, with the growing awareness of global environmental protection in recent years, there is a widespread demand for environmentally friendly concrete. For example, as shown in Patent Document 2, it is known that replacing the cement content in concrete with blast furnace slag powder is important in reducing CO2 emissions during concrete production.

[0005] Patent Document 2 describes a concrete composition comprising a binder, water, fine aggregate, coarse aggregate, and an admixture, wherein the binder contains 70% by mass or more of the following blast furnace cement, and the admixture contains, as part thereof, the following water-soluble vinyl copolymer in an amount of 0.1 to 5.0% by mass of the binder, and contains 15 to 60% by mass of water, and furthermore, the amount of calcium hydroxide remaining after the hydration reaction of the binder per cubic meter of the concrete composition 3A concrete composition using blast-furnace cement, characterized in that it is 5 kg or more per hit, is described.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, conventional high-replacement type blast-furnace slag concrete has a softer fluidity (slump and slump flow) immediately after mixing compared to normal concrete, and there is a risk that molding during the production of composite segments will become difficult. In addition, in the case of conventional high-replacement type blast-furnace slag concrete, there is a problem that cracks due to autogenous shrinkage are likely to occur compared to normal concrete, resulting in a decrease in quality. Furthermore, there are problems such as a smaller amount of calcium hydroxide generated inside the hardened body after hardening compared to normal concrete, and a tendency for neutralization to progress, and there is room for improvement in this regard.

[0008] The present invention has been made in view of the above circumstances, and an object thereof is to provide a composite segment made of concrete that is excellent in environmental performance, has high strength over a long period of time, and is excellent in adhesion and formability to steel materials, and a method for producing the composite segment.

Means for Solving the Problems

[0009] To solve the above problems, the present invention employs the following configuration. [1] A concrete composition containing cement, blast-furnace slag fine powder having a specific surface area of 3000 cm 2 / g to 10000 cm 2 / g, water, admixture, and aggregate, Satisfying the following formulas (i) to (iii), The cement is any one of ordinary Portland cement, early-strength Portland cement, or ultra-early-strength Portland cement, and the concrete composition. 28 ≦ C / (C + GGBFS) × 100 ≦ 70 …(i) 20 ≦ W / (C + GGBFS) × 100 ≦ 50 …(ii) 0.1 ≦ SP / (C + GGBFS) × 100 ≦ 5 …(iii) However, in formulas (i) to (iii), C is the mass of cement (kg), GGBFS is the mass of granulated blast-furnace slag fine powder (kg), W is the mass of water (kg), and SP is the mass of admixture (kg). [2] A synthetic segment including a steel shell made of steel and concrete obtained by filling and curing the concrete composition described in [1] in the inner space surrounded by the steel shell, and forming at least the inner surface of the tunnel. [3] The synthetic segment according to [2], wherein the unit water amount in the concrete composition is 175 kg / m 3 or less. [4] The synthetic segment according to [2], wherein the admixture contains polycarboxylic acid or polycarboxylate. [5] The concrete composition further contains an expansive agent, The synthetic segment according to [2], wherein the expansive agent contains at least 40 mass% or more of a calcium composition. [6] The synthetic segment according to [5], wherein the unit amount of the expansive agent in the concrete composition is 20 to 40 kg / m 3 . [7] Anti-cracking reinforcing bars are arranged inside the synthetic segment up to 70 mm in the radial direction of the tunnel radius from the surface of the inner surface of the tunnel, ] The synthetic segment according to [2], wherein the anti-cracking reinforcing bars are formed by shaping round steel bars with a diameter of 6 to 12 mm into a mesh shape, and the distance between adjacent round steel bars in the uniaxial direction is 50 to 200 mm. [8] The compressive strength of the concrete composition hardened by the concrete compressive strength test method specified in JIS A 1108:2018 is 40 N / mm² after 28 days of age. 2 The above is the synthetic segment described in [2]. [9] The synthetic segment according to [2], characterized in that the concrete composition further comprises a hardening accelerator.

[10] A method for manufacturing a composite segment that forms at least the interior surface of a tunnel, comprising a steel shell made of steel material and concrete formed by filling the interior space surrounded by the steel shell, When forming the concrete by pouring the concrete composition into the steel shell, The concrete composition includes cement and 3000 cm 2 / g~10000cm 2 It contains blast furnace slag fine powder with a specific surface area of ​​ / g, water, an admixture, and aggregate. The following equations (i) through (iii) are satisfied, A method for manufacturing a composite segment, using concrete in which the cement is one of ordinary Portland cement, high-early-strength Portland cement, or ultra-high-early-strength Portland cement. 28≦C / (C+GGBFS)×100≦70…(i) 20≦W / (C+GGBFS)×100≦50…(ii) 0.1≦SP / (C+GGBFS)×100≦5 …(iii) However, in equations (i) to (iii), C is the mass of cement (kg), GGBFS is the mass of blast furnace slag powder (kg), W is the mass of water (kg), and SP is the mass of the admixture (kg).

[11] The method for producing a synthetic segment according to

[10] , wherein the concrete composition has a slump of 9 cm or less immediately after mixing.

[12] The method for producing a synthetic segment according to

[10] , wherein the unit water content in the concrete composition is 175 kg / m3 or less.

[13] The method for manufacturing the synthetic segment according to

[10] , wherein the admixture contains a polycarboxylic acid or a polycarboxylate.

[14] The concrete composition further contains an expansion agent. The method for manufacturing the synthetic segment according to

[10] , wherein the expansion agent contains at least 40% by mass or more of a calcium composition.

[15] Anti-cracking reinforcing bars are arranged inside the synthetic segment up to 70 mm in the tunnel radius direction from the inner surface of the tunnel. The method for manufacturing the synthetic segment according to

[10] , wherein the anti-cracking reinforcing bars are formed by shaping steel bars with a diameter of 6 to 12 mm into a mesh shape, and the concrete is placed so that the distance between adjacent steel bars in the uniaxial direction is 50 to 200 mm.

[16] After placing the concrete composition, any one of air curing, sealed curing, moist curing, or steam curing is performed. The method for manufacturing the synthetic segment according to

[10] .

[17] The method for manufacturing the synthetic segment according to

[10] , characterized in that the concrete composition further contains a curing accelerator.

[18] After placing the concrete composition, steam curing is performed at 50°C or lower for 6 hours or more, and then air curing, sealed curing, or moist curing is performed. The method for manufacturing the synthetic segment according to

[10] .

[19] The amount of the unit expansion agent in the concrete composition is 20 to 40 kg / m 3 The method for manufacturing the synthetic segment according to

[14] . [Effect of the Invention]

[0010] According to the present invention, it is possible to provide a concrete composition, a synthetic segment, and a method for manufacturing a synthetic segment made of concrete that are excellent in environmental performance, have high strength over a long period of time, and are excellent in adhesion and formability to steel materials. [Brief Description of the Drawings]

[0011] [Figure 1] It is a partial perspective view showing a synthetic segment of a shield tunnel according to an embodiment of the present invention. [Figure 2] Figure 1 is a perspective view showing the composite segment. [Figure 3] Figure 1 is a perspective view showing the composite segment. [Figure 4] These are photographs showing the surface condition of synthetic segment simulation test specimens according to the examples, with (a) showing concrete of type N and (b) showing concrete of type BC. [Figure 5] This graph shows the temperature profile of steam curing in the example. [Figure 6] This is a plan view showing the arrangement of strain gauges in the embodiment, where (a) is in the X2 direction in Figure 1, (b) is in the X3 direction in Figure 1, and (c) is in the X1 direction in Figure 1. [Modes for carrying out the invention]

[0012] The following describes embodiments of the present invention, including a concrete composition, a synthetic segment, and a method for producing the synthetic segment.

[0013] (Composite segment) The composite segment of this embodiment comprises a steel shell made of steel material, and concrete made of reinforced concrete that fills the internal cavity surrounded by the steel shell and is formed at least on the internal surface of the tunnel. The concrete constituting the reinforced concrete is made of cement and 3000 cm 2 / g~10000cm 2 This concrete composition is hardened from blast furnace slag fine powder having a specific surface area of ​​1 / g, water, an admixture, and aggregate. The concrete composition satisfies the following formulas (i) to (iii). The cement is a synthetic segment, which is either ordinary Portland cement, high-early-strength Portland cement, or ultra-high-early-strength Portland cement. 28≦C / (C+GGBFS)×100≦70…(i) 20≦W / (C+GGBFS)×100≦50…(ii) 0.1≦SP / (C+GGBFS)×100≦5 …(iii) However, in equations (i) to (iii), C is the mass of cement (kg), GGBFS is the mass of blast furnace slag powder (kg), W is the mass of water (kg), and SP is the mass of the admixture (kg).

[0014] As shown in Figures 1 to 3, the composite segment 1 is arc-shaped. The composite segment 1 in this embodiment constitutes a segment ring R, which is a structural member of the circular cross-section tunnel lining constructed on the inner wall of the shield tunnel 100 excavated by the shield tunneling method. In this embodiment, the composite segment 1 has a steel shell filled with concrete 14. The shield tunnel 100 has a structure in which segment ring Rs, which are formed by connecting arc-shaped composite segments 1 in the circumferential direction, are connected in the segment ring axis direction.

[0015] Here, in composite segment 1, the arc direction is called the tunnel circumferential direction X1 (circumferential direction), the short side direction perpendicular to the arc direction is called the tunnel axis direction X2, and the height direction of composite segment 1 is called the tunnel radial direction X3. Also, in the tunnel radial direction X3, the outer side is called the ground side (tunnel ground side), and the inner side is called the interior side (tunnel interior side).

[0016] In the shield tunneling method, multiple composite segments 1 are connected along the inner wall of the excavated tunnel hole in the natural ground in the circumferential direction X1 and the axial direction X2 of the tunnel to construct a cylindrical wall. The composite segment 1 is formed as a hexahedron in the shape of an arc, having a curvature approximately equal to the curvature of the inner surface of the excavated tunnel hole.

[0017] As shown in Figure 1, the composite segment 1 comprises a main girder 11, a joint plate 12, a skin plate 13, and infill concrete (hereinafter simply referred to as concrete 14). In the composite segment 1, a pair of main girders 11, 11 facing each other in the tunnel axis direction X2, a pair of joint plates 12, 12 facing each other in the tunnel circumferential direction X1, and a skin plate 13 positioned on the outer circumferential surface side of the main girders 11 and joint plates 12 that form the four sides thereof, constitute a steel shell 10 in which concrete 14 is filled inside. That is, the concrete 14 is filled into the internal cavity surrounded by the steel shell 10, and a concrete surface made of reinforced concrete is formed at least on the internal surface of the tunnel.

[0018] Furthermore, the composite segment 1 includes an inter-ring joint 20 provided on the inter-ring joint surface 11a of the main girder 11, and a segment joint 30 provided on the segment joint surface 12a of the joint plate 12. The shield tunnel 100 is a tunnel structure that extends in the tunnel axis direction X2 by connecting segment rings R, each consisting of arc-shaped composite segments 1 connected in the tunnel circumferential direction X1 by segment joints 30, to each other in the tunnel axis direction X2 by inter-ring joints 20.

[0019] The composite segment 1 is assembled by a staggered arrangement in which the connection positions of adjacent segment rings R in the tunnel circumferential direction X1 are shifted in the tunnel circumferential direction X1 along the tunnel axis X2. In other words, one A-ring R and the other B-ring R of adjacent segment rings R are arranged alternately along the tunnel axis X2.

[0020] Within the concrete 14 of composite segment 1, multiple reinforcing bars (not shown, crack-preventing bars described later) extending in an arc shape in the tunnel circumferential direction X1 are arranged on the tunnel interior side and the tunnel ground side, and reinforcing ribs are placed as needed. The size of composite segment 1 can be changed as appropriate depending on transportability, assembly, etc. The curvature of the arc of composite segment 1 is appropriately determined by the cross-section of the tunnel to be excavated.

[0021] Synthetic segment 1 will be explained in more detail using Figures 2 and 3. The composite segment 1 is constructed in a roughly arc-shaped form by filling the area surrounded by a steel shell 10 consisting of a thin rectangular steel plate curved into an arc shape with concrete 14.

[0022] As mentioned above, the skin plate 13 is installed on the ground side of the composite segment 1. The skin plate 13 is made of steel plate and is positioned to close the ground-side openings between the pair of main girders 11, 11 and the pair of joint plates 12, 12, which are assembled in a frame-like manner. The skin plate 13 is fixed to the ground-side periphery of the main girders 11 and joint plates 12 by welding. The skin plate 13 prevents concrete 14 from flowing out to the outside and also prevents water and soil from the ground from penetrating into the steel shell 10. It can also be used as formwork when pouring concrete 14.

[0023] A pair of main girders 11, 11 are arranged parallel to each other with a gap in the tunnel axis direction X2, and the ends of each main girder 11, 11 in the tunnel circumferential direction X1 are connected by joint plates 12. Skin plates 13 are welded to the ground-side periphery of each of the pair of main girders 11, 11 and the pair of joint plates 12, 12. In other words, the composite segment 1 forms a steel shell 10 framed by the pair of main girders 11, 11, the pair of joint plates 12, 12, and the skin plates 13. Concrete 14 is filled inside this steel shell 10.

[0024] The main girder 11 is provided with inter-ring joints 20 for connecting with other composite segments 1 adjacent to it in the tunnel axis direction X2. Multiple inter-ring joints 20 (four in this case) are provided on the surface of the main girder 11 facing the tunnel axis direction X2 (inter-ring joint surface 11a). The inter-ring joints 20 connect the composite segments 1 in the tunnel axis direction X2.

[0025] The inter-ring joint 20 includes a pair of first male joints 21 provided at intervals in the tunnel circumferential direction X1 on one of the opposing inter-ring joint surfaces 11a, and a pair of first female joints 22 provided at the same position as the first male joints 21 in the tunnel circumferential direction X1 on the other of the opposing inter-ring joint surfaces 11a. The opposing first male joints 21 and first female joints 22 are fitted together between adjacent composite segments 1 in the tunnel axial direction X2. As such inter-ring joints 20, well-known types such as bolted joints, pin joints, snap-fit ​​joints, or mechanical joints can be used.

[0026] As shown in Figure 3, the first male joint 21 is positioned at the center of the inter-ring joint surface 11a of the main girder 11 in the tunnel radial direction X3 (segment thickness direction) and has a shape that protrudes from the inter-ring joint surface 11a. The first female joint 22 has a shaft portion 211 extending from the inter-ring joint surface 11a and an engaging portion 212 that expands towards the tunnel interior side and the tunnel ground side at the protruding end of the shaft portion 211. As shown in Figure 2, the first female joint 22 has a pair of retaining pieces 221 that are movable towards the tunnel interior side and the tunnel ground side so as to clamp the first male joint 21 in the segment thickness direction and are biased toward the center in the tunnel thickness direction by a spring member 222. The first male joint 21 engages while being clamped between the pair of retaining pieces 221 of the first female joint 22. The first male joint 21 engages while spreading the pair of retaining pieces 221 against the biasing force of the spring member 222. In the ring joint 20, the engaging portion 212 of the first male joint 21 fits into the inner side of the pair of retaining pieces 221, and the pair of retaining pieces 221 hold the shaft portion 211, thereby preventing it from coming out in the tunnel axial direction X2.

[0027] The joint plate 12 is provided at both ends in the tunnel circumferential direction X1 and includes segment joints 30 that correspond to inter-piece joints, bringing the segment joint surfaces 12a of the joint plate 12 of other composite segments 1 adjacent to the tunnel circumferential direction X1 into contact with each other. In other words, multiple (two in this case) segment joints 30 are arranged near the segment joint surfaces 12a, connecting the composite segments 1 in the tunnel circumferential direction X1.

[0028] The segment joint 30 has a second male joint 31 provided at one end in the tunnel axial direction X2 and a second female joint 32 provided at the other end in the tunnel axial direction X2. On one inter-ring joint surface 11a side, the second male joint 31 is provided at one end in the tunnel circumferential direction X1 and the second female joint 32 is provided at the other end. The opposing second male joint 31 and second female joint 32 are fitted together between composite segments 1 adjacent to each other in the tunnel circumferential direction X1. As such segment joints 30, well-known types such as bolted joints, pin joints, snap-fit ​​joints, or mechanical joints can be used.

[0029] As shown in Figure 2, the second male joint 31 is positioned at intervals in the tunnel radial direction X3 (segment thickness direction) on the inter-ring joint surface 11a of the main girder 11 and has a pair of engaging protrusions 311 that protrude from the inter-ring joint surface 11a. The second female joint 32 has a pair of engaging holes 321 into which the second male joint 31 can be inserted in the tunnel axial direction X2. As shown in Figure 1, the segment joint 30 is prevented from coming out in the tunnel circumferential direction X1 by the engagement of the pair of engaging protrusions 311 of the second male joint 31 with the pair of engaging holes 321 of the second female joint 32 when they are inserted through it.

[0030] As shown in Figure 1, the concrete 14 is filled within the steel shell 10 so as to be flush with the tunnel cavity. The concrete 14 of the manufactured composite segment 1 has hardened after filling. On the other hand, the concrete mixed before hardening is referred to as the "concrete composition" and is used separately from the concrete 14. The concrete composition constituting the concrete 14 is appropriately selected from ordinary concrete, high-strength concrete, high-flow concrete, fiber-reinforced concrete, etc., depending on the stress acting on the tunnel lining and the cross-sectional shape of the tunnel. The concrete 14 may also contain deformed steel bars made of SD295A, SD345, SD390, SD490 steel, etc. Here, the deformed steel bars may be of D13 or greater.

[0031] The concrete 14 is formed in a plate shape that is rectangular in plan view. The concrete 14 is in contact with the inner surface of the skin plate 13. Each side of the concrete 14 is in contact with the side plates (main girder 11, joint plate 12) of the steel shell 10.

[0032] The concrete 14 of this embodiment contains cement and 3000 cm² immediately after construction. 2 / g~10000cm 2 It contains blast furnace slag fine powder with a specific surface area of ​​1 / g, water, admixtures, and aggregates. After construction, the concrete 14 hardens and integrates with the steel shell 10 and reinforcing bars to form reinforced concrete.

[0033] In the tunnel radial direction X3 from the tunnel's internal surface, crack-preventing reinforcement bars are placed inside composite segments 1 up to 70 mm in diameter. These crack-preventing reinforcement bars are made of steel bars with a diameter of 6 to 12 mm formed into a mesh, with a spacing of 50 to 200 mm between adjacent steel bars in the axial direction.

[0034] Next, the concrete composition of concrete 14 will be described in more detail. As described above, the concrete composition of this embodiment contains cement and 3000 cm² immediately after construction. 2 / g~10000cm 2 It contains blast furnace slag fine powder with a specific surface area of ​​ / g, water, admixtures, and aggregates. The composition of concrete 14 is described below.

[0035] For the cement, for example, ordinary Portland cement, rapid-hardening Portland cement, or ultra-rapid-hardening Portland cement can be used. When constructing a composite segment structure, a short construction period may be required, in which case it is advisable to use rapid-hardening Portland cement or ultra-rapid-hardening Portland cement, which have excellent hardening speed. In addition, fly ash cement may be used as the cement to suppress alkali-aggregate reaction.

[0036] Blast furnace slag fine powder is obtained by rapidly cooling molten slag, which is formed simultaneously with pig iron in a blast furnace, with water to produce water-granulated slag, and then crushing the water-granulated slag. It has a relatively large specific surface area compared to blast furnace slab, which is mixed into blast furnace cement. By mixing blast furnace slag fine powder with concrete 14, the latent water-hardening properties of the blast furnace slag fine powder are activated, making it possible to maintain a high strength in the hardened concrete 14 for a long period of time.

[0037] In this embodiment, blast furnace slag fine powder is used, with a specific surface area of ​​3000 cm². 2 / g~10000cm 2 Use a specific surface area within the range of / g. If the specific surface area falls below the lower limit, the hardening reaction of the concrete 14 is significantly suppressed, the hardening rate decreases, the hardening time to reach the desired hardness increases, and there is a risk of defects such as material segregation, which is undesirable. Also, if the specific surface area exceeds the upper limit, the hardening of the concrete 14 proceeds rapidly, and cracks occur, which is undesirable.

[0038] The proportion of cement in a concrete composition relative to the total amount of cement and blast furnace slag powder must satisfy the following formula (i).

[0039] 28≦C / (C+GGBFS)×100≦70…(i)

[0040] In equation (i), C is the mass of cement (kg), and GGBFS is the mass of blast furnace slag powder (kg).

[0041] If C / (C+GGBFS)×100 is less than 28, that is, if the proportion of cement to the total amount of cement and blast furnace slag fine powder is less than 28%, the hardening rate of the concrete 14 will decrease, the hardening time to reach the desired hardness will increase, and there is a risk of problems such as material segregation, which is undesirable. On the other hand, if C / (C+GGBFS)×100 exceeds 70, that is, if the proportion of cement to the total amount of cement and blast furnace slag fine powder exceeds 70%, there will be an excess of cement, and it will not be possible to reduce the CO2 intensity, which is undesirable. The range of C / (C+GGBFS)×100 may be 30 or more and 60 or less, or 35 or more and 50 or less.

[0042] The CO2 emissions per unit of material that make up concrete are as follows: cement: 755.5 kg-CO2 / t, blast furnace slag powder: approximately 40.21 kg-CO2 / t, aggregate: approximately 7.09 kg-CO2 / t. The CO2 emissions from cement are significantly higher than those from other materials. Therefore, reducing the amount of cement used and replacing it with blast furnace slag powder is an effective way to reduce CO2 emissions during concrete production.

[0043] Furthermore, in concrete compositions in which cement is replaced with a large amount of blast furnace slag fine powder, the high affinity of blast furnace slag fine powder to admixtures such as high-performance AE water-reducing agents results in a greater dispersion effect and higher fluidity in the concrete. In addition, the latent hydraulic properties of blast furnace slag fine powder enhance strength over the long term, and especially after 91 days of age, the floor slab concrete becomes as tough as or stronger than ordinary concrete.

[0044] Furthermore, at the contact surface between the steel shell 10 (hereinafter referred to as the steel plate) and the concrete composition, the free water in the concrete tends to accumulate relatively easily due to the influence of surface tension, which may lead to the formation of more voids and a decrease in adhesion between the two. In contrast, the concrete composition containing blast furnace slag fine powder exhibits latent hydraulic properties due to the silica (SiO2) and alumina (Al2O3) contained in the blast furnace slag fine powder, which leads to a long-term active hydration reaction with water, consuming the accumulated water and forming a dense cementitious body. Through such a reaction, the concrete composition becomes denser at the contact surface between the concrete composition and the steel plate, and the water is consumed, improving the adhesion between the concrete composition and the steel plate, allowing the external load to be transmitted more effectively between the composite segments 1.

[0045] In addition to the configuration of the synthetic segment 1 shown in Figure 1, it is also possible to apply a synthetic segment in which, for example, the skin plate 13 is omitted.

[0046] Water enhances the fluidity of the concrete composition during construction and also affects the hardness of the concrete 14 after hardening; therefore, the amount of water in the concrete composition is an important factor. The ratio of water to the total amount of cement, blast furnace slag powder, and water in the concrete composition must satisfy the following formula (ii).

[0047] 20≦W / (C+GGBFS)×100≦50…(ii)

[0048] In equation (ii), C is the mass of cement (kg), GGBFS is the mass of blast furnace slag powder (kg), and W is the mass of water (kg).

[0049] If W / (C+GGBFS)×100 is less than 20, that is, if the ratio of water to the total amount of cement and blast furnace slag fine powder is less than 20%, the fluidity of the concrete composition will decrease, making it impossible to form concrete 14, and variations in strength will occur, which is undesirable. On the other hand, if W / (C+GGBFS)×100 exceeds 50, that is, if the ratio of water to the total amount of cement and blast furnace slag fine powder exceeds 50%, there will be an excess of water, and the strength of the concrete after hardening will decrease significantly. The range of W / (C+GGBFS)×100 may be 20 or more and 45 or less, or 25 or more and 40 or less.

[0050] Furthermore, the unit water content in the concrete composition is 175 kg / m³. 3 The following is preferable. This makes it possible to further increase the strength of the concrete 14.

[0051] In this embodiment, the admixture may be formulated to improve the formability of the concrete composition and its ability to fill the steel shell 10 and reinforcing bars. The admixture may also be formulated to improve the fluidity of the concrete composition. Furthermore, the admixture may be formulated to reduce the amount of water while maintaining the fluidity of the concrete composition.

[0052] The ratio of admixture to the total amount of cement and blast furnace slag powder in a concrete composition must satisfy the following formula (iii).

[0053] 0.1≦SP / (C+GGBFS)×100≦5 …(iii)

[0054] In equation (iii), SP is the mass of the admixture (kg), C is the mass of the cement (kg), and GGBFS is the mass of the blast furnace slag powder (kg).

[0055] SP / (C+GGBFS)×100 should be 0.1 or greater to obtain the desired effects of the admixture. That is, if the admixture ratio relative to the total amount of cement and blast furnace slag fine powder is 0.1% or more, the admixture's effects of improving moldability and filling properties, improving fluidity, and reducing water content can be fully realized. On the other hand, if SP / (C+GGBFS)×100 exceeds 5, that is, if the admixture ratio relative to the total amount of cement and blast furnace slag fine powder exceeds 5%, the effect of adding the admixture saturates. The range of SP / (C+GGBFS)×100 may be 0.2 or more and 4 or less, 0.5 or more and 3 or less, or 1 or more and 2 or less.

[0056] The admixture is more preferably one containing a polycarboxylic acid or a polycarboxylate salt. By incorporating a polycarboxylic acid or polycarboxylate salt as an admixture, the formability and filling properties of the concrete composition can be improved. For example, MasterGlenium 8000E manufactured by Pozzolith Solutions, Inc. can be used as an admixture.

[0057] Furthermore, admixtures such as AE agents, AE water-reducing agents, and fluidizing agents may be included.

[0058] The concrete composition of this embodiment may further contain an expansive agent. By incorporating an expansive agent, the occurrence of cracks in the hardened concrete 14 can be suppressed. Furthermore, it is preferable that the expansive agent contains at least 40% by mass of a calcium composition. In this embodiment, since blast furnace slag fine powder with a relatively low calcium content is incorporated into the concrete composition, the amount of alkaline components in the concrete composition is reduced. By incorporating an expansive agent containing at least 40% by mass of a calcium composition, the amount of calcium hydroxide contained in the hardened concrete 14 increases, thereby suppressing the neutralization of the concrete 14. CaO can be used as an example of a calcium composition. In addition to CaO, the expansive agent may contain Al2O3 and SO3 as mineral components. As an expansive agent, for example, Denka Power CSA Type S manufactured by Denka Co., Ltd. can be used.

[0059] The unit expansion amount of the concrete composition is 20-40 kg / m³. 3 Preferably, the unit expansion amount is 20 kg / m³. 3 By doing so, cracking of the concrete 14 after hardening can be suppressed. Unit expansion amount is 40 kg / m 3 The effect saturates beyond a certain point, so the unit expansion amount is 40 kg / m³. 3 The following is acceptable.

[0060] There are no particular restrictions on the aggregates included in the concrete composition; crushed stone can be used as coarse aggregate, and gravel or mountain sand can be used as fine aggregate. The coarse and fine aggregates may be used in combination.

[0061] The concrete composition of this embodiment may further contain a hardening accelerator. By incorporating a hardening accelerator into the concrete composition, the strength can be more effectively improved, and the quality of the composite segment is enhanced. Furthermore, the formwork in contact with the concrete composition can be removed earlier. This is particularly effective in winter when concrete hardening is inhibited.

[0062] The hardening accelerator can be any material conforming to the hardening accelerators specified in JIS A 6204:2011 "Chemical Admixtures for Concrete". The unit amount of the hardening accelerator in the concrete composition is preferably in the range of 1.0 to 3.0% relative to the amount of the binder. However, the amount of hardening accelerator may be in the range of 0.1 to 5.0% relative to the amount of binder, and should be determined considering the temperature and other conditions at the concrete placement site.

[0063] The hardening accelerator may be either a calcium silicate-based or a nitrite-based (e.g., calcium nitrite, lithium nitrite, or other nitrites).

[0064] The concrete composition used in the composite segment 1 of this embodiment needs to have high fluidity in order to improve the moldability of the composite segment 1. Specifically, the slump immediately after mixing needs to be 9 cm or less. If the slump exceeds 9 cm, the fluidity becomes excessive, making it difficult to form the concrete 14.

[0065] Slump shall be measured in accordance with the concrete slump test method specified in JIS A 1101:2020. Slump flow shall be measured in accordance with the concrete slump flow test method specified in JIS A 1150:2020.

[0066] In this embodiment, it is desirable that the concrete exhibits the following properties.

[0067] [Uniaxial compressive strength of concrete at 28 days of age: 40 N / mm²] 2 [End] The uniaxial compressive strength of concrete, measured in accordance with JIS A 1108:2018 "Test Method for Compressive Strength of Concrete," should preferably be 40 N / mm² at 28 days of age. 2 It is preferable that the above conditions are met.

[0068] [Surface cracking: should not occur] When cracks occur, water and oxygen can easily penetrate the concrete, increasing the risk of rebar corrosion. Additionally, the infiltration of carbon dioxide increases, raising the risk of concrete carbonation. Therefore, it is desirable to prevent surface cracking. Furthermore, mixing blast furnace slag powder into concrete increases self-shrinkage during hardening, making cracking more likely. For this reason, it is preferable to mix in an appropriate amount of expansive agent.

[0069] In this embodiment, crack-preventing reinforcing bars are placed inside the composite segment 1, extending 70 mm in the tunnel radial direction X3 from the tunnel's internal surface. The crack-preventing reinforcing bars are formed from steel bars with a diameter of 6 to 12 mm in a mesh-like structure, and the concrete 14 is poured so that the spacing between adjacent steel bars in one axial direction is 50 to 200 mm, thereby suppressing the occurrence of cracks.

[0070] (Compressive strength) The compressive strength of the concrete in composite segment 1 is a representative physical property of the strength of concrete 14, and it affects the load-bearing capacity and carbonation resistance of composite segment 1 (higher strength leads to densification of concrete 14, making it difficult for carbon dioxide to penetrate).

[0071] (Method for manufacturing synthetic segments) The manufacturing method for the composite segment 1 of this embodiment, as shown in Figures 2 and 3, involves forming reinforced concrete by pouring a concrete composition onto reinforcing bars placed inside the steel shell 10. The concrete composition poured at this time is the concrete described above. That is, the concrete composition consists of cement and 3000 cm 2 / g~10000cm 2 The concrete used is composed of blast furnace slag fine powder having a specific surface area of ​​ / g, water, an admixture, and aggregate, satisfying the above formulas (i) to (iii), and the cement being either ordinary Portland cement, high-early-strength Portland cement, or ultra-high-early-strength Portland cement.

[0072] This concrete composition has a slump of 9 cm or less immediately after mixing and exhibits excellent fluidity, making it suitable for use in forming the composite segment 1. Furthermore, because it satisfies the above formula (ii), the amount of water can be kept low, improving the strength of the hardened concrete 14 and allowing it to maintain high strength over a long period of time.

[0073] After the concrete composition is placed, it is preferable to perform curing by air curing, sealed curing, wet curing, or steam curing. This allows the strength of the hardened concrete 14 to be increased to the desired strength.

[0074] It is preferable to perform steam curing on the composite segment into which the concrete composition has been placed, followed by air curing, sealed curing, or wet curing. By curing in this procedure, the compressive strength of the concrete composition can be efficiently improved. Furthermore, while self-shrinkage cracking during hardening is a concern in concrete compositions that generally contain a large amount of blast furnace slag powder, the occurrence of self-shrinkage cracking can be suppressed by performing this steam curing and the subsequent various curing methods.

[0075] Specifically, the composite segments are first left to stand in the air for 1 to 3 hours after concrete placement. Then, the composite segments are sealed using curing sheets or similar materials, and steam pipes are connected to the sealed space to supply steam. While maintaining a humidity of 70-95% inside the sealed space, the temperature is raised at a rate of 15°C / hr to a maximum temperature of over 20°C but not exceeding 50°C, and this temperature is maintained for 6 to 10 hours after reaching it. After that, natural cooling is allowed while maintaining a humidity of 70-95%, and when the temperature inside the sealed space reaches 20°C or below the ambient temperature, the seal is opened, and air curing, sealed curing, or wet curing is performed.

[0076] The humidity inside the sealed space may be 75-95% or 80-95%. The heating rate may be 20°C / hr or less or 15°C / hr or less. The maximum temperature may be 25°C to 50°C or 30°C to 45°C. Alternatively, the internal temperature of the concrete composition under steam curing may be set to less than 65°C. The holding time after reaching the maximum temperature may be 6 hours to 9 hours or 6 hours to 8 hours. Furthermore, during the holding period after reaching the maximum temperature, it is preferable to keep the temperature fluctuation from the target temperature to less than ±5°C.

[0077] According to this embodiment, a composite segment 1 made of concrete 14 with excellent adhesion to steel can be constructed. Furthermore, by replacing a portion of the cement with blast furnace slag powder, the hexavalent chromium content derived from cement in the concrete 14 can be effectively suppressed, resulting in an environmentally friendly product. In addition, the occurrence of initial cracks can also be suppressed. Furthermore, by replacing a portion of the cement with blast furnace slag powder, the fluidity of the concrete composition is increased, improving the filling and moldability of the concrete composition into the steel shell 10 during the manufacturing of the synthetic segment 1.

[0078] Furthermore, according to this embodiment, by limiting the amount of water per unit, a synthetic segment structure exhibiting even higher strength can be obtained.

[0079] Furthermore, according to this embodiment, by using an admixture containing polycarboxylic acid or a polycarboxylic acid salt, the filling and moldability of the synthetic segment 1 during construction can be further improved.

[0080] Furthermore, according to this embodiment, by including an expansive material containing a calcium composition, surface cracking of the concrete on the upper surface of the composite segment is more effectively suppressed, and more calcium hydroxide is generated in the hardened concrete, thereby more effectively improving the carbonation resistance.

[0081] Furthermore, according to this embodiment, the unit amount of the expansion material is 20 to 40 kg / m³. 3 By restricting this, the crack suppression effect can be improved, and the carbonation resistance can be improved more effectively.

[0082] Furthermore, according to this embodiment, crack-preventing reinforcing bars are arranged inside the composite segment up to 70 mm in the tunnel radial direction X3 from the tunnel's internal surface. The crack-preventing reinforcing bars are formed in a mesh pattern of steel bars with diameters from 6 mm to 12 mm, and by setting the spacing between adjacent steel bars in the axial direction to 50 mm or more and 200 mm or less, the crack-preventing effect of the reinforcing bars on the surface of the concrete 14 can be made more effective.

[0083] Furthermore, according to this embodiment, the compressive strength of concrete 14 at 28 days of age is 40 N / mm². 2 As a result, the mechanical performance of composite segment 1 can be made suitable even in the initial stages of service.

[0084] Furthermore, according to this embodiment, by limiting the unit amount of hardening accelerator to 1.0 to 3.0% relative to the amount of binder, the strength of the concrete composition can be more effectively improved, and the quality of the composite segment is enhanced. In addition, the formwork in contact with the concrete composition can be removed earlier.

[0085] Next, examples of actions taken to support the effects of the synthetic segment and the method for producing the synthetic segment according to the above-described embodiments will be explained below. [Examples]

[0086] Concrete was prepared using the materials shown in Table 1 and Table 2 by mixing cement, blast furnace slag powder, water, admixtures, and aggregate in the specified mixing ratios. Specific examples of cement, blast furnace slag powder, water, admixtures, and aggregate are shown in Table 1. Table 2 shows the concrete mixes for ordinary concrete (N) and blast furnace type C (BC).

[0087] Here, we will explain the symbols used in Tables 1 to 3. W: Water, N: Ordinary Portland cement, CGGSS: Carbonated steel slag fine powder (water, chelate), S: Fine aggregate, G: Coarse aggregate, SP: Admixture (High-performance AE water-reducing agent). Here, mix N is the mix for ordinary concrete, and mix BC is a mix in which a certain proportion of cement is replaced with carbonated steel slag.

[0088] Table 1 shows the concrete materials used in the performance evaluation test. In Table 1, blast furnace slag fine powder has a specific surface area of ​​4340 cm². 2 The material used was a calcium compound containing 40% or more by mass. The fine aggregate was made from land sand. The coarse aggregate was made from crushed stone. The admixture was made from polycarboxylic acid as the main component.

[0089] [Table 1]

[0090] [Table 2]

[0091] Table 2 also shows the CO2 emissions during the manufacturing of each concrete composition. These CO2 emissions were calculated using the following formula (A), assuming CO2 intensity for cement and blast furnace slag powder were 755.5 kg-CO2 / t and 40.21 kg-CO2 / t, respectively. The CO2 intensity for cement is based on the cement variety inventory data list in "Overview of LCI Data for Cement," published on April 1, 2024, by the Japan Cement Association. The CO2 intensity for blast furnace slag powder is based on the Japan Concrete Institute's Research Committee Report on Environmental Impact Assessment of Cement and Concrete, published in September 2024.

[0092] CO2 emissions from concrete composition (kg / m³) 3) = {755.5 × cement mix ratio (kg / m 3 ) + 40.21 × amount of blast furnace slag fine powder added (kg / m³ 3 ) + 7.09 x aggregate content (kg / m 3 )} / 1000 …(A)

[0093] Table 3 shows the compressive strength of hardened concrete at 7 days and 28 days of age. Table 3 shows the unconfined compressive strength (N / mm²) of ordinary concrete mix (N) and blast furnace type C (BC) concrete at 7 days and 28 days of age based on the compressive strength test results. 2 This indicates that...

[0094] [Table 3]

[0095] Furthermore, test castings were also performed on a steel shell. Using a synthetic segment simulant test specimen that mimicked the synthetic segment of the embodiment described above, the N and BC concretes described above were cast onto this synthetic segment simulant test specimen under conditions of 20°C during mixing. The cast concrete was then subjected to wet curing under conditions of 20°C, and the surface condition (presence and properties of surface cracks) was visually inspected after 28 days of curing (age 28 days). The synthetic segment simulant test specimen (steel shell) had a thickness of 150 mm, a short side width of 624 mm, an inner circumference of 958 mm, and an outer circumference of 1075 mm.

[0096] Figure 4(a) shows the inner surface of a composite segment simulation test specimen with concrete N poured on it. Figure 4(b) shows the inner surface of a composite segment simulation test specimen with concrete BC poured on it. Figures 4(a) and (b) are images taken after each concrete was poured, moist-cured for 28 days, demolded, and the surface was dried.

[0097] As shown in Figures 4(a) and (b), concrete placement tests on the synthetic segment simulation specimens revealed that no cracks occurred on the concrete surface of either the N concrete or the BC concrete. The N concrete and BC concrete used in these tests had a uniaxial compressive strength of 42 N / mm² at 28 days of age, as shown in Table 3. 2 , 44.3 N / mm 2 Therefore, 40 N / mm 2 It is preferable that the above conditions are met.

[0098] Furthermore, as shown in Table 1, performance evaluation tests based on examples showed that ordinary Portland cement emits 755.5 kg-CO2 / t of carbon dioxide (CO2) during manufacturing. In contrast, blast furnace slag powder is produced by micronizing blast furnace granulated slag, a by-product of steelmaking, and although there are various theories regarding its CO2 emission intensity, it is low at 40.21 kg-CO2 / t. Therefore, replacing ordinary Portland cement with blast furnace slag powder is effective in reducing carbon dioxide (CO2) emissions during concrete manufacturing. As shown in Table 2, the CO2 emission of concrete N is 277.5 kg / m³. 3 The CO2 emissions from BC concrete are 116.6 kg / m³. 3 Therefore, although it is difficult to define a clear reduction rate due to variations in the assumptions for CO2 intensity and the unclear intensity of the admixture Ex, it has been found that blast furnace type C concrete generally produces about 50% less CO2 emissions during production compared to ordinary concrete.

[0099] We will also explain the results of our investigation into concrete compositions with added hardening accelerators. Table 4 shows the mix designs of concrete compositions with added hardening accelerators. Here, for the materials used in the mix design table, all materials except for fine aggregate S1 and coarse aggregate G1 are the same as those shown in Table 1. The density of fine aggregate S1 is 2.68 g / cm³. 3 The density of coarse aggregate G1 is 2.72 g / cm³. 3 The CO2 consumption per unit is the same as in Table 1. In this example (Table 4), an amount equivalent to 2.0% of the binder material was used.

[0100] [Table 4]

[0101] Table 5 shows the compressive strength (N / mm²) of the formulations shown in Table 4. 2 This shows that, generally, the more blast furnace slag powder is substituted for cement, the lower the strength up to 28 days of age. Although a similar trend is observed in the concrete compositions BB, BC2 and the reference example of the present invention, the compressive strength at 28 days of age is sufficiently high. The BB mix exhibits sufficient strength for demolding even at 1 day of age. The BC2 mix exhibits high strength from 1 day of age due to steam curing. On the other hand, in the reference example, the compressive strength at 28 days of age was 40 N / mm². 2 Although it exceeds that limit, the compressive strength at 1 day of age is 10.0 N / mm². 2 It was less than [amount missing]. Here, the demolding process uses 10.0 N / mm². 2 The material must exhibit the above compressive strength, and from a manufacturing cost perspective, it is preferable that it can be demolded at 1 day of age.

[0102] [Table 5]

[0103] Figure 5 shows the temperature pattern of steam curing performed on the BC2 formulation. Figure 6 shows the arrangement of concrete strain gauges installed after curing was released. Waterproof metal base gauges (WFKM-60-11-10LJQTA) were used as concrete strain gauges. After measuring the strain behavior of the concrete for six months, the strain values ​​remained within ±200 με, confirming that no abnormal shrinkage or expansion occurred. Although the amount of blast furnace slag fine powder added increased the auto-shrinkage during hardening, the amount of shrinkage was kept small. Furthermore, if the concrete composition reaches a temperature of around 70°C during hardening, ettringite may be formed in a delayed manner after hardening, potentially causing abnormal expansion of the concrete composition. Such abnormal expansion was not observed with the steam curing method described in the present invention, and the delayed formation of ettringite can be suppressed. As described above, the method for manufacturing synthetic segments by steam curing can suppress auto-shrinkage due to the influence of blast furnace slag fine powder and abnormal expansion due to ettringite that may occur after the hardening of the concrete composition, thereby improving the compressive strength of the concrete composition.

[0104] Here, the following values ​​are provided as reference values ​​for the shrinkage strain (-) and expansion strain (+) of concrete, respectively. (Concrete shrinkage strain) The "2022 Standard Specifications for Concrete, Design Section, Part 4, Table 2.3.1, p.242" specifies standard values ​​for concrete shrinkage strain to prevent harmful cracking. According to this, shrinkage strain in environments where composite segments are applied should be kept below 300 με. (Expansion strain of concrete) When concrete expands excessively, there is a concern that it may develop cracks that are harmful to the concrete. Generally, in the mortar bar method (JIS A 1146), which evaluates the harmfulness of expansion due to alkali-silica reaction, an expansion strain of 1000 με or more in a test specimen is judged to be harmful. Based on this, it is appropriate to set the standard value for concrete expansion strain at 1000 με.

[0105] The strain generated in the specimens of this embodiment was kept within ±200 με, which is smaller than the shrinkage and expansion strains indicated in the official technical guidelines. This indicates that the specimens of this embodiment exhibit stable shrinkage and expansion behavior. It was also found that cracking on the concrete surface can be suppressed during the manufacturing of the composite segments.

[0106] Although embodiments of the concrete composition, synthetic segment, and method for manufacturing the synthetic segment according to the present invention have been described above, the present invention is not limited to the embodiments described above and can be modified as appropriate without departing from the spirit of the invention.

[0107] Furthermore, it is possible to replace the components in the above-described embodiments with well-known components as appropriate, without departing from the spirit of the present invention.

[0108] The above describes an embodiment in which the concrete composition is used in a composite segment, but the concrete composition can also be used in the manufacture of other concrete members such as RC segments and box culverts. Unlike composite segments, RC segments are manufactured without using a steel shell, by pouring the concrete composition into a formwork constructed with reinforcing bars, and then allowing it to harden and cure. Box culverts, for example, are manufactured by pouring the concrete composition into formwork incorporating reinforcing bars for each component, such as the side walls, base slab, and top plate, allowing them to harden and cure to produce precast members, and then assembling them on-site to complete the structure. [Explanation of symbols]

[0109] 1. Composite segment 10 steel shell 11 Main girder 11a Inter-ring joint surface 12 Joint plates 12a Segment joint surface 13 Skin Plates 14 Concrete 20 Ring joints 30-segment joint 100 Shield Tunnel X1 Tunnel Circumferential Direction X2 Tunnel Axis X3 Tunnel Radius Direction

Claims

1. Cement and 3000 cm ２ / g~10000cm ２ A concrete composition comprising blast furnace slag fine powder having a specific surface area of ​​ / g, water, an admixture, and aggregate, From equation (i) below, (iii) is satisfied, The cement is one of ordinary Portland cement, rapid-hardening Portland cement, or ultra-rapid-hardening Portland cement, in this concrete composition. 28≦C / (C+GGBFS)×100≦70…(i) 20≦W / (C+GGBFS)×100≦50…(ii) 0.1≦SP / (C+GGBFS)×100≦5…(iii) However, in equations (i) to (iii), C is the mass of cement (kg), GGBFS is the mass of blast furnace slag powder (kg), W is the mass of water (kg), and SP is the mass of the admixture (kg).

2. A composite segment comprising a steel shell made of steel material and concrete formed by filling the internal cavity surrounded by the steel shell with the concrete composition described in claim 1 and hardening it, thereby forming at least the internal cavity surface of a tunnel.

3. The unit water content in the aforementioned concrete composition is 175 kg / m³. ３ The synthetic segment according to claim 2, which is as follows:

4. The synthetic segment according to claim 2, wherein the admixture comprises a polycarboxylic acid or a polycarboxylate salt.

5. The concrete composition further contains an expansive agent, The synthetic segment according to claim 2, wherein the expansive material contains at least 40% by mass of the calcium composition.

6. The unit expansion amount of the concrete composition is 20 to 40 kg / m³. ３ The synthetic segment according to claim 5.

7. Crack-preventing reinforcing bars are placed inside the composite segment extending 70 mm in the radial direction from the surface of the tunnel's interior. The composite segment according to claim 2, wherein the crack-preventing reinforcement is formed by shaping steel bars with a diameter of 6 to 12 mm into a mesh, and the distance between adjacent steel bars in the axial direction is 50 to 200 mm.

8. The compressive strength of the concrete composition, as measured by the concrete compressive strength test method specified in JIS A 1108:2018, after 28 days of curing, is 40 N / mm². ２ The synthetic segment described in claim 2 is as described above.

9. The synthetic segment according to claim 2, characterized in that the concrete composition further includes a hardening accelerator.

10. A method for manufacturing a composite segment that forms at least the interior surface of a tunnel, comprising a steel shell made of steel material and concrete formed by filling the interior space surrounded by the steel shell, When forming the concrete by pouring the concrete composition into the steel shell, The concrete composition includes cement and 3000 cm ２ / g~10000cm ２ It contains blast furnace slag fine powder with a specific surface area of ​​ / g, water, an admixture, and aggregate. From equation (i) below, (iii) is satisfied, A method for manufacturing a composite segment, using concrete in which the cement is one of ordinary Portland cement, high-early-strength Portland cement, or ultra-high-early-strength Portland cement. 28≦C / (C+GGBFS)×100≦70…(i) 20≦W / (C+GGBFS)×100≦50…(ii) 0.1≦SP / (C+GGBFS)×100≦5…(iii) However, in equations (i) to (iii), C is the mass of cement (kg), GGBFS is the mass of blast furnace slag powder (kg), W is the mass of water (kg), and SP is the mass of the admixture (kg).

11. The method for producing a synthetic segment according to claim 10, wherein the concrete composition has a slump of 9 cm or less immediately after mixing.

12. The method for producing a synthetic segment according to claim 10, wherein the unit water content in the concrete composition is 175 kg / m³ or less.

13. The method for producing a synthetic segment according to claim 10, wherein the admixture comprises a polycarboxylic acid or a polycarboxylate salt.

14. The concrete composition further contains an expansive agent, The method for producing a synthetic segment according to claim 10, wherein the expansive material contains at least 40% by mass of the calcium composition.

15. A method for producing a synthetic segment according to claim 10, wherein after placing the concrete composition, curing is performed by air curing, sealed curing, wet curing, or steam curing.

16. Crack-preventing reinforcing bars are placed inside the composite segment extending 70 mm in the radial direction from the surface of the tunnel's interior. The method for manufacturing a composite segment according to claim 10, wherein the crack-preventing reinforcement is formed by shaping steel bars with a diameter of 6 to 12 mm into a mesh, and the concrete is poured so that the distance between adjacent steel bars in one axial direction is 50 to 200 mm.

17. The method for producing a synthetic segment according to claim 10, characterized in that the concrete composition further contains a hardening accelerator.

18. A method for producing a synthetic segment according to claim 10, wherein after placing the concrete composition, steam curing is performed at 50°C or below for 6 hours or more, and then air curing, sealed curing, or wet curing is performed.

19. The unit expansion amount of the concrete composition is 20 to 40 kg / m³. ３ The method for producing a synthetic segment according to claim 14.

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