Concrete composition for tunnel lining and method for manufacturing tunnel lining concrete using the same

Abstract

The present invention provides a tunnel lining concrete composition and a method for manufacturing the same, which can be used with blast furnace cement type C concrete to achieve strength development equivalent to that of blast furnace cement type B concrete, and can also suppress the occurrence of cracks due to drying shrinkage. [Solution] The present invention provides a density of 3500 cm 2 The present invention provides a concrete composition for tunnel lining comprising blast furnace cement containing blast furnace slag fine powder at a concentration of 60% to 70% by mass of the cement mass, and a sulfate, and a method for producing the concrete composition for tunnel lining comprising mixing an additive containing sulfate with the concrete raw material containing the blast furnace cement.

Description

[Technical Field]

[0001] The present invention relates to a tunnel lining concrete composition and a method for producing tunnel lining concrete using the same. [Background technology]

[0002] In the construction of tunnel lining concrete, concrete is poured into the centering formwork, and after the concrete hardens, the centering formwork is removed, the centering trolley is moved to the next section, and this process is repeated to pour the tunnel lining concrete. The centering formwork must not be removed until the poured concrete reaches the required strength, and this is often done about 12 to 20 hours after the concrete pouring is completed. The compressive strength of the concrete at the time of demolding is 2 to 3 N / mm². 2 It is stated that this is used as a guideline (Non-Patent Document 1).

[0003] In recent years, with the growing desire for a low-carbon society, the construction industry is also expected to reduce the amount of carbon dioxide emitted during material manufacturing. In particular, blast furnace slag powder has a carbon dioxide intensity of 20.9 kg / t during manufacturing, which is significantly lower than that of Portland cement (798.1 kg / t) (Non-Patent Literature 2), and is expected to be a suitable alternative binder. When blast furnace cement is mixed with blast furnace slag powder, Type A contains more than 5% by mass but less than or equal to 30% by mass, Type B contains more than 30% by mass but less than or equal to 60% by mass, and Type C contains more than 60% by mass but less than or equal to 70% by mass, with Type C blast furnace cement having the lowest CO2 emissions. However, due to delayed setting and insufficient strength development, almost only Type B blast furnace cement is used on the market. If Type C blast furnace cement could be used in tunnel lining concrete, it would be possible to suppress salt damage and alkali-aggregate reaction, as well as to effectively utilize by-products and reduce carbon dioxide emissions, but there are many challenges in using Type C blast furnace cement in actual structures.

[0004] A hydraulic composition has been proposed consisting of blast furnace slag fine powder, limestone fine powder, and two or more stimulants with different rates of calcium ion elution. It has been reported that, despite containing blast furnace slag fine powder, it has setting time and strength development properties equivalent to ordinary Portland cement (Patent Document 1).

[0005] Research has been conducted in the past to improve the initial strength development of blast furnace cement, and there are reports of using hardening accelerators mainly composed of nitrates and nitrites to address this issue (Patent Document 2). [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2014-148434 [Patent Document 2] Japanese Patent Publication No. 2020-128316

[0007] [Non-Patent Document 1] Yu Tsuchida et al., "Improving the Quality of Tunnel Lining Concrete Using Two Tunnel Lining Centering Units": Proceedings of the 67th Annual Scientific Conference of the Japan Society of Civil Engineers, pp. 9-10, VI-005, 2012. http: / / library.jsce.or.jp / jsce / open / 00035 / 2012 / 67-06 / 67-06-0005.pdf [Non-Patent Document 2] Yukihiko Nagao: On the CO2 reduction effect of blast furnace slag fine powder on concrete, Concrete Engineering, Vol. 48, No. 9, pp. 62-65, 2010.9 https: / / www.jstage.jst.go.jp / article / coj / 48 / 9 / 48_9_9_62 / _pdf / -char / ja [Overview of the project] [Problems that the invention aims to solve]

[0008] The composition described in Patent Document 1 is not a commonly used cement conforming to JIS R 5210, and therefore has the problem of being difficult to manufacture in a typical ready-mixed concrete plant. Furthermore, since the amount of ions leached from the powder and the chemical reactions change significantly with ambient temperature, it is considered that adjustment of fluidity and desired strength enhancement cannot be obtained, especially in low-temperature environments.

[0009] Furthermore, nitrate and nitrite-based hardening accelerators tend to reduce long-term strength compared to materials without them, and their rapid hydration reaction makes it difficult to achieve the desired fluidity.

[0010] The present invention provides a tunnel lining concrete composition and a method for manufacturing the same, which can be used with blast furnace cement type C concrete to achieve strength development equivalent to that of blast furnace cement type B concrete, and can also suppress the occurrence of cracks due to drying shrinkage. [Means for solving the problem]

[0011] The present invention provides the following [1] to [7]. [1] Density 3500cm 2 Blast furnace cement containing blast furnace slag fine powder of 60% by mass and 70% by mass or less of 5000 / g or more, Sulfates and A concrete composition for tunnel lining, including the following: [2] The composition according to [1], wherein the sulfate is a thiosulfate. [3] The composition according to [1] or [2], wherein the blast furnace cement is blast furnace cement type C. [4] The composition according to any one of [1] to [3], wherein the sulfate content (on an anhydrous basis) is 0.5 to 2.0 parts by mass per 100 parts by mass of blast furnace cement. [5] A composition according to any one of items [1] to [4], wherein the water-bonding material ratio is 40 to 60%. [6] Density 3500cm 2A method for manufacturing a concrete composition for tunnel lining, comprising mixing an additive containing sulfate with a concrete raw material containing blast-furnace cement containing blast-furnace slag fine powder of more than 5000 and less than 5000 / g and more than 60 mass% and less than or equal to 70 mass% of the cement mass. 〔7〕A method for constructing concrete for tunnel lining, comprising placing the composition according to any one of 〔1〕~〔5〕 in a tunnel.

Advantages of the Invention

[0012] According to the present invention, by adding sulfate to a concrete raw material containing blast-furnace cement, high-strength concrete can be obtained without worrying about the influence on fluidity. According to the present invention, the demand for blast-furnace cement type C can be increased, while general-purpose cement such as ordinary Portland cement can be used, and it is easy to manufacture in an ordinary ready-mixed concrete factory. Further, the addition time of sulfate is not limited, and the same effect can be obtained during the preparation of the concrete raw material or on-site. Therefore, it is clear that the concrete composition of the present invention is suitable for use in tunnel lining.

Embodiments for Carrying Out the Invention

[0013] [1. Concrete Composition] The concrete composition contains blast-furnace cement and sulfate.

[0014] [1.1 Blast-Furnace Cement] Blast-furnace cement is a cement containing blast-furnace slag fine powder. The content of blast-furnace slag fine powder in blast-furnace cement is preferably more than 60 mass% and less than or equal to 70 mass%, and blast-furnace cement type C (JIS R5211:2009) is more preferable.

[0015] - Blast-Furnace Slag Fine Powder - Blast-furnace slag fine powder is obtained by pulverizing blast-furnace water-quenched slag or adding gypsum thereto. The specific surface area of blast-furnace slag fine powder is usually 2,500 cm 2 / g to 10,000 cm 2The value is / g, preferably 3,500 or more and less than 5,000 (approximately 4,000 cm³). 2 The density is 2.80 g / cm³. 3 The above is preferable (JIS A6206:2013). As such blast furnace slag fine powder, blast furnace slag fine powder 4000 (JIS A6206:2013) is preferred.

[0016] -Method for manufacturing blast furnace cement- The method for producing blast furnace cement is not particularly limited, but one example is to add blast furnace slag to cement such as Portland cement. Examples of Portland cement include ordinary Portland cement, rapid-hardening Portland cement, ultra-rapid-hardening Portland cement, moderate-heat Portland cement, low-heat Portland cement, sulfate-resistant Portland cement, and their low-alkali forms, of which ordinary Portland cement and rapid-hardening Portland cement are preferred. It is preferable that the Portland cement meets the standards of JIS R5210:2009. The conditions for adding blast furnace slag powder to the cement should be adjusted so that the amount of blast furnace slag powder added is greater than 60% by mass and less than or equal to 70% by mass of the cement mass. For example, either a single addition or sequential addition is acceptable, and the addition and mixing may be carried out using appropriate equipment.

[0017] [1.2 Sulfates] In this specification, sulfates refer to sulfates, salts in which the atoms constituting the sulfate are substituted with other atoms (e.g., thiosulfates, sulfites, bisulfites, dithionites, pyrosulfates, pyrobisulfites), or anhydrous forms thereof. Examples of salts include alkali metals (sodium, potassium, etc.) and alkaline earth metals (calcium, magnesium, etc.). Preferred sulfates are thiosulfates (e.g., sodium thiosulfate) and anhydrous thiosulfates.

[0018] The sulfate content is typically 0.5 parts by mass or more, preferably 0.6 parts by mass or more, and more preferably 0.7 parts by mass or more, per 100 parts by mass of blast furnace cement. The upper limit is typically 2.0 parts by mass or less, preferably 1.8 parts by mass or less, and more preferably 1.5 parts by mass or less. Therefore, it is typically 0.5 to 2.0 parts by mass, preferably 0.6 to 1.8 parts by mass, and more preferably 0.7 to 1.5 parts by mass.

[0019] [1.3 Aggregates] Concrete compositions typically include aggregates as concrete raw materials other than blast furnace cement. The aggregates are usually a combination of fine and coarse aggregates.

[0020] -Fine aggregate- Examples of fine aggregates include sand, gravel, crushed stone; granulated slag; recycled aggregates, etc.; and aggregates with relatively small particle sizes such as silica, clay, zircon, high alumina, silicon carbide, graphite, chromium, chromomagnesia, and magnesia.

[0021] -Coarse aggregate- Examples of coarse aggregates include sand, gravel, crushed stone; granulated slag; recycled aggregates, etc.; and refractory aggregates such as silica, clay, zircon, high alumina, silicon carbide, graphite, chromium, chromium-magnesium, and magnesia.

[0022] [1.4 Water] The concrete composition may contain water. Examples include tap water, water other than tap water (river water, lake water, well water, groundwater, industrial water, etc.), and recovered water (supernatant water, sludge water).

[0023] [1.5 Other Concrete Raw Materials] The concrete composition may contain components other than those listed above as concrete raw materials. Other components include, for example, chemical admixtures. Chemical admixtures may be any admixtures for concrete or mortar that contain a chemical substance as an active ingredient. Examples of chemical admixtures include water-reducing agents, high-performance AE water-reducing agents, AE water-reducing agents, high-performance water-reducing agents, water-soluble polymers, polymer emulsions, air-entraining agents, cement wetting agents, expansive agents, waterproofing agents, retarders, thickeners, flocculants, drying shrinkage reducing agents, strength enhancers, effect enhancers, defoaming agents, other surfactants, and other chemical admixtures intended to improve concrete function. Examples of active ingredients in chemical admixtures include polycarboxylic acids and / or their salts, carboxyl group and / or salt-containing compounds (CA agents), sulfonic acid group and / or salt-containing compounds (SA agents), and kraft lignin. Examples of CA agents include sodium polyacrylate and sodium gluconate. Examples of SA agents include sodium lignin sulfonate and naphthalene sulfonic acid.

[0024] Furthermore, other components may include known materials that can be added to cement compositions, such as fine powders like fly ash, cinder ash, clinker ash, husk ash, silica fume, silica powder, calcium carbonate, limestone powder, and gypsum, in addition to chemical admixtures. These other components may be one type or a combination of two or more types.

[0025] [1.6 Water binding material mass ratio] In concrete compositions, the water-binding material ratio (W / B: (water / blast furnace cement) × 100) is preferably 40% or more, more preferably 42% or more, and even more preferably 44% or more. The upper limit is preferably 60% or less, more preferably 55% or less, and even more preferably 50% or less. Therefore, 40-60% is preferred, 42-55% is more preferred, and 45-50% is even more preferred.

[0026] [1.7 Uses of Concrete Compositions] The concrete composition is useful for tunnel lining applications because it can exhibit fluidity and strength enhancement effects even at low temperatures and can develop strength at an early stage.

[0027] [2. Method for manufacturing the concrete composition] The above concrete composition can be manufactured by mixing an additive containing sulfate with a concrete raw material containing blast furnace cement. Examples of the concrete raw material include the components exemplified above. The concrete raw material may be kneaded (using a device such as a forced kneading mixer as necessary) together with the sulfate or before adding the sulfate, and post-treatments such as grinding, drying, shaping, and classification may be performed as necessary. The sulfate may be added as a dry powder or dissolved or dispersed in a solvent such as water and then added. In the case of post-addition, it may be added on-site.

[0028] [3. Construction method for tunnel lining concrete] The concrete composition can be used for tunnel lining. The tunnel lining can be carried out by placing the concrete composition according to a conventional method. For example, in a section of the inner wall surface of the tunnel, the above concrete composition is driven between the centering formwork, cured to harden the concrete, and then the formwork is moved to the next section, and this operation is repeated to place the tunnel lining concrete. [Examples]

[0029] Hereinafter, the present invention will be described with reference to examples. Note that the examples are one aspect for explaining the present invention and are not intended to limit the present invention.

[0030] [Experiment - 1 (Example 1, Comparative Examples 1 and 2: 21 - 22 °C)] [Materials used] Ordinary Portland cement (N: density: 3.16 g / cm 3 , specific surface area: 3320 cm 2 / g), blast furnace cement type B (BB: density: 3.04 g / cm 3 , specific surface area: 3870 cm 2 / g) Blast furnace slag fine powder 4000 (BFS; density: 2.89 g / cm³) 3 , Specific surface area: 4620cm 2 / g) Crushed sand (S1; from Hachioji and Miyama, density: 2.63 g / cm³) 3 FM=3.10), mountain sand (S2; produced in Kururi, Kimitsu City, density: 2.59 g / cm³) 3 (FM=1.70) Crushed stone 2005 (G; from Oji and Miyama, density: 2.65 g / cm³) 3 ,Actual rate=59.0%) High-performance AE water-reducing agent (1) (Ad1: Standard type I, polycarboxylic acid compound), High-performance AE water-reducing agent (2) (Ad2: Standard type I, polycarboxylic acid compound, lignin sulfonate) Additive (AA: Thiosulfate powder)

[0031] (Concrete mix design) The concrete mixes for Example 1 and Comparative Examples 1 and 2 are shown in Table 1. In Comparative Example 2 and Example 1, the BFS and N mixes were adjusted to conform to the specifications for blast furnace cement type C (BC). [Table 1]

[0032] (Measurement items) Slump test (SL): Compliant with JIS A 1101 Air volume: Complies with JIS A 1128 Concrete temperature (CT): Conforms to JIS A 1156 Compressive strength (standard curing): In accordance with JIS A 1108. Measured at 7 and 28 days of age. Compressive strength (cured at 20°C): Compliant with JIS A 1108. Measured at 7 and 28 days of age. Compressive strength (in-sealed curing): Compliant with JIS A 1108. Measured at 7 and 28 days of age. Compressive strength (simulated material): Based on JIS A 1107. Measured at 7 days and 28 days of age. Length change test: Measured using the dial gauge method in accordance with JIS A 1129; specimens were demolded 24 hours after casting, cured in water at 20°C for one week, and stored in an environment of 20°C and 60% relative humidity.

[0033] (Test conditions) The target slump was 21 cm and the target air content was 4.5%, and the target performance was adjusted by changing the addition rate of chemical admixtures. The target slump was 21 ± 2.5 cm and the target air content was 4.5 ± 1.5%. Concrete was manufactured at a ready-mixed concrete plant, transported by agitator truck for approximately 40 minutes, and measured for slump, air content, and concrete temperature upon arrival at the site. After that, the concrete was left at the site for 30 minutes while being agitated, and the slump, air content, and concrete temperature were measured again to create test specimens and simulated specimens. AA was added to the agitator truck at the time of shipment from the ready-mixed concrete plant. The simulated body was 1m square and constructed in two layers of 0.5m each, using a rod-shaped vibrator. It was demolded after 7 days. At 28 days, a Φ100mm core was taken from the outer perimeter of the simulated body, where strength development was least likely, and its compressive strength was measured.

[0034] (Test results 1: Slump test, air content, concrete temperature)

[0035] [Table 2]

[0036] All formulations met the target values ​​upon arrival at the site and within 30 minutes of arrival. It was confirmed that the addition of AA did not adversely affect the freshness of the product (Table 2).

[0037] (Test result 2: Compressive strength)

[0038] [Table 3]

[0039] Comparative Example 2 showed lower strength than Comparative Example 1 at all ages and curing methods. The compressive strength test of Example 1 showed higher compressive strength than Comparative Example 1 regardless of age or curing method, confirming that it can raise the strength development of blast furnace type C concrete up to that of blast furnace type B concrete (Table 3).

[0040] (Test result 3: Length change test)

[0041] [Table 4]

[0042] Compared to Comparative Example 1, Example 1 showed a shrinkage reduction rate of 10% or more after a drying period of 13 weeks (Table 4).

[0043] Experiment-2 (Example 2, Comparative Examples 3 and 4: approximately 17°C) (Materials used) Aside from the additives, the experiment is the same as in Experiment-1. Additive (AAW: 45% aqueous solution of thiosulfate)

[0044] (Concrete mix design) The concrete mix designs for Example 2 and Comparative Examples 3 and 4 are shown in Table 5. In Comparative Example 4 and Example 1, the BFS and N mix designs were adjusted to conform to the BC standard.

[0045] [Table 5]

[0046] (Measurement items) This is the same as Experiment-1.

[0047] (Test conditions) The target slump was 21 cm and the target air content was 4.5%, and the target performance was adjusted by changing the addition rate of chemical admixtures. The target slump was 21 ± 2.5 cm and the target air content was 4.5 ± 1.5%. Concrete was manufactured at a ready-mixed concrete plant, transported by agitator truck for approximately 40 minutes, and the slump test, air content, and concrete temperature were measured upon arrival at the site. In Comparative Examples 3 and 4, the slump test, air content, and concrete temperature were measured again 30 minutes after arrival at the site, and then test specimens and symmetrical specimens were taken. In Example 2, where AAW was added, AAW was added to the agitator truck 30 minutes after arrival at the site, stirred at medium speed for 60 seconds, and then the slump test, air content, and concrete temperature were measured. The concrete was left at the site for 30 minutes while agitating, and then the slump test, air content, and concrete temperature were measured again to create test specimens and symmetrical specimens. The conditions for the symmetrical specimens and the locations for core sampling were the same as in Example 1.

[0048] (Test results 1: Slump test, air content, concrete temperature)

[0049] [Table 6]

[0050] All formulations met the target values ​​upon arrival at the site, 30 minutes after arrival, and after AAW addition. It was confirmed that the addition of AAW did not adversely affect the freshness of the product, and the target values ​​were met even under the stringent condition of 30 minutes after addition (Table 6).

[0051] (Test result 2: Compressive strength)

[0052] [Table 7]

[0053] Comparative Example 4 exhibited lower strength than Comparative Example 3 across all ages and curing methods. The compressive strength test of Example 2 showed higher compressive strength than Comparative Example 3, regardless of age or curing method, confirming that it could raise the strength of blast furnace type C concrete to that of blast furnace type B concrete, even at low temperatures where strength development is generally difficult.

[0054] (Test result 3: Length change test)

[0055] [Table 8]

[0056] Compared to Comparative Example 3, Example 2 showed a shrinkage reduction rate of 10% or more after a drying period of 13 weeks. The samples of Examples 1 and 2 were able to exhibit strength development similar to concrete using blast furnace cement type B (Comparative Examples 1 and 3) at both concrete temperatures of 20°C or above and 20°C or below, and were also able to exhibit a shrinkage reduction effect of 10% or more after a drying period of 13 weeks. These results indicate that the concrete composition of the present invention is useful for tunnel lining applications because it can exhibit fluidity and strength enhancement effects regardless of ambient temperature, especially at low temperatures, and that by using blast furnace cement type C, it is possible to reduce CO2 emissions and utilize blast furnace slag as a by-product.

Claims

1. Density 3500cm ２ Blast furnace cement containing blast furnace slag fine powder at a concentration of 60% by mass and 70% by mass or less of 5000 / g or more, Sulfates and A concrete composition for tunnel lining, including the following:

2. The composition according to claim 1, wherein the sulfate is a thiosulfate.

3. The composition according to claim 1 or 2, wherein the blast furnace cement is blast furnace cement type C.

4. The composition according to claim 1 or 2, wherein the sulfate content (on an anhydrous basis) is 0.5 to 2.0 parts by mass per 100 parts by mass of blast furnace cement.

5. The composition according to claim 1 or 2, wherein the water-bonding material ratio is 40 to 60%.

6. Density 3500cm ２ A method for producing a concrete composition for tunnel lining, comprising mixing an additive containing sulfate with a concrete raw material containing blast furnace cement that contains blast furnace slag fine powder at a concentration of 60% to 70% by mass of the cement mass.

7. A method for constructing tunnel lining concrete, comprising pouring the composition described in claim 1 or 2 into a tunnel.

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