JP2005336039A - Cement additive, cement composition, and method for crack prevention of secondary lining cement concrete of tunnel using the composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cement additive for use in a secondary lining cement concrete, which reduces drying shrinkage and increases crack resistance , a cement composition, and a method for crack prevention of the secondary lining cement concrete of a tunnel using the composition. <P>SOLUTION: The cement additive contains an expanding material, calcium aluminosilicate glass, gypsum, and a setting retarder. The expanding material of the cement additive is a calcium aluminoferrite, and the article size of the expanding material exhibits a Blaine specific surface area value of 1,000 to 4,500 cm<SP>2</SP>/g. The cement composition contains cement and the cement additive. The cement concrete is produced by blending the cement composition with water. The method for the crack prevention of the secondary lining cement concrete of the tunnel comprises the execution of the cement concrete. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a cement admixture used for secondary lining cement concrete, such as construction after primary lining on exposed ground surfaces and tunnel repair in tunnels such as roads, railways, and conduits. The present invention relates to a composition and a crack prevention method for a tunnel secondary lining cement concrete using the composition.

Conventionally, in order to prevent collapse of exposed ground such as tunnel excavation, primary covering of rapid hardening cement concrete in which rapid hardening material containing calcium aluminate, setting retarder, and gypsum as necessary is mixed with concrete. A construction method is performed (see Patent Document 1).
This primary lining method is a concrete used for the method of pouring concrete using a formwork, and is composed of a rapid hardening material and concrete containing a rapid hardening component and a setting retarder, for example, a slump value after kneading This is the use of rapid-hardening concrete that has sufficient fluidity to fill the formwork, such as about 20 cm, and has initial strength.
Further, since the concrete before the addition of the rapid hardening material is kneaded and then pumped using a concrete pump, mixed with the rapid hardening material and placed, it is also necessary to maintain its fluidity for a certain period of time.
Then, in the mixing plant installed at the excavation site, cement, aggregate, water, etc. are mixed to prepare concrete, transported with an agitator car, pumped with a concrete pump, It is mixed with a quick-hardening material pumped from the other, and is primary lining as a quick-hardening cement concrete.

  Since secondary lining concrete does not require the stability of natural ground at the time of primary lining, ordinary concrete without rapid hardening is generally used.

JP 2002-321957 A

  At the time of secondary lining concrete construction, conventional concrete is cast using a formwork, and if the early deframement is performed within 24 hours in order to increase the efficiency of the formwork, the secondary lining concrete will crack. There was a problem that it is easy to produce.

  As a result of intensive studies, the present inventor obtained knowledge that the above problems can be solved by using a specific cement admixture and by using cement concrete having a specific composition. It came to be completed.

The present invention is a cement admixture containing an expansion material, calcium aluminosilicate glass, gypsum, and a setting retarder, the expansion material is the cement admixture that is calcium aluminoferrite, the particle size of the expansion material A cement admixture having a brain specific surface area value of 1,000 to 4,500 cm ² / g, a cement composition comprising the cement and the cement admixture, the cement composition and water It is cement concrete formed by blending, and is a method for preventing cracks in a tunnel secondary lining cement concrete on which the cement concrete is applied.

The present invention will be described in detail below.
Parts and% used in the present invention are based on mass unless otherwise specified.
In the present invention, paste, cement, and concrete are collectively referred to as cement concrete.

As the expanding material used in the present invention, any of a lime-based expanding material, a calcium sulfoaluminate-based expanding material, and a calcium aluminoferrite-based expanding material can be used. Among them, the use of a calcium aluminoferrite-based expansion material containing a CaO—Al ₂ O ₃ —Fe ₂ O ₃ compound is more preferable because it is less likely to change with time at high temperatures such as in summer, and the amount used is small.
The particle size of the expandable member is generally shake - down specific surface area value (hereinafter, blur - called down value) preferably 1,000~4,500cm ² / g in, 1,500~3,500cm ² / g is more preferable. If it is less than 1,000 cm ² / g, unreacted substances may remain for a long time and the durability may be lowered. If it exceeds 4,500 cm ² / g, the hydration reaction is fast and the prescribed expansion performance may not be obtained. .
The amount of the expansion material used is preferably 1 to 13 parts, more preferably 2 to 10 parts, in 100 parts of a binder composed of cement, expansion material, calcium aluminosilicate glass, and gypsum. If it is less than 1 part, sufficient crack prevention effect may not be obtained. If it exceeds 13 parts, the strength will decrease and the amount of expansion will increase. Therefore, consideration should be given to the arrangement with bar arrangement and primary lining concrete. It is necessary and the construction may be complicated.

The calcium aluminosilicate glass (hereinafter referred to as CAS glass) used in the present invention includes a raw material containing calcia (CaO), a raw material containing alumina (Al ₂ O ₃ ), and a raw material containing silicic acid (SiO ₂ ). It is a generic term for substances having hydration activity, which are mainly mixed with CaO, Al ₂ O ₃ , and SiO ₂ , obtained by mixing and calcining in a kiln or heat treatment such as melting in an electric furnace.
Further, a part of CaO and / or Al ₂ O ₃ is an alkali metal oxide, an alkaline earth metal oxide, titanium oxide, iron oxide, an alkali metal halide, an alkaline earth metal halide, an alkali metal sulfate, In addition, a substance substituted with alkaline earth metal sulfate or the like, or a substance mainly composed of CaO, Al ₂ O ₃ , and SiO ₂ contains a substance in which a small amount thereof is dissolved.
And as a mineral form, it is a vitreous obtained by quenching a melt with compressed air, high-pressure water, or the like.
The component ratio of the CAS glass is preferably CaO 30 to 60 parts, Al ₂ O ₃ 20 to 60 parts, and SiO ₂ 5 to 25 parts, CaO 30 to 55 parts, Al ₂ O ₃ 30 to 60 parts, and SiO ₂ 10 to 20 parts is more preferred. If CaO is less than 30 parts or Al ₂ O ₃ exceeds 60 parts, the rapid hardening may be inferior. If CaO exceeds 60 parts or Al ₂ O ₃ is less than 20 parts, a large amount of setting retarder may be used. Even if they are used together, they are instantly linked, which is not preferable from the viewpoint of workability. If SiO ₂ is less than 5 parts, long-term strength growth cannot be expected, and if it exceeds 25 parts, the initial strength may be small.
Further, the glass quality in the CAS glass is preferably 80 parts or more.
The particle size of the CAS glass is preferably 3,000 cm ² / g or more in Blaine value, 4,000 cm ² / g or more is more preferable. If it is less than 3,000 cm ² / g, rapid hardening and initial strength development may be reduced.

As the gypsum used in the present invention, any commercially available gypsum can be used, but in view of strength development, use of type II anhydrous gypsum and / or natural anhydrous gypsum is preferable.
The particle size of the gypsum is preferably 3,000 cm ² / g or more in Blaine value, 4,000~7,000cm ² / g is more preferable. If it is less than 3,000 cm ² / g, the initial strength development may decrease.
The amount of gypsum used is preferably 30 to 80 parts, more preferably 35 to 70 parts, in 100 parts of the rapid hardening component made of CAS glass and gypsum. If it is less than 30 parts, the long-term strength development may be small, and if it exceeds 80 parts, the initial strength development may be small.

  The amount of the rapid hardening component used is preferably 5 to 30 parts, more preferably 10 to 25 parts, in 100 parts of a binder composed of cement, an expanding material, and a rapid hardening component. If it is less than 5 parts, the initial strength development may be small, and if it exceeds 30 parts, the long-term strength may be small.

The setting retarder used in the present invention is capable of maintaining the workability of cement concrete and is a material that can ensure the pumpability. As the setting retarder, any of powder, slurry, or liquid can be used.
Examples of the setting retarder include organic acids and alkali metal carbonates. In these, it is preferable to use together organic acids and alkali metal carbonates at the point which can control hardening time and the intensity | strength expression property after hardening is favorable.

  The organic acid is an organic acid or a salt thereof, specifically, oxycarboxylic acid such as citric acid, gluconic acid, tartaric acid, and malic acid, or one or more of these salts can be used. The salt is preferably a sodium salt or potassium salt. Among these, the setting time is increased in direct proportion to the amount used, it is easy to control, and when the setting retarder is used in a slurry admixture, it does not easily cause a chemical reaction with the calcium component, and the slurry does not generate heat easily. In terms of surface, organic acid salts are preferred, and oxycarboxylates are more preferred.

Examples of alkali metal carbonates (hereinafter referred to as alkali carbonates) include carbonates such as lithium carbonate, sodium carbonate, and potassium carbonate, and bicarbonates such as sodium hydrogen carbonate and potassium hydrogen carbonate. In terms of good strength development later, alkali metal carbonates are preferable, and potassium carbonate is more preferable.
When the organic acid and the alkali carbonate are used in combination, the mixing ratio of the two is preferably 5 to 200 parts, more preferably 10 to 100 parts, with respect to 100 parts of the alkali carbonate. If the amount is less than 5 parts, the setting time cannot be controlled, and the pumpability of cement concrete may be reduced and the hose may be blocked. If the amount exceeds 200 parts, the strength development may be reduced.

  The amount of setting retarder used varies depending on the transport time, working time, temperature, etc. of cement concrete, so it is difficult to determine uniquely, but usually 0.1 to 10 parts per 100 parts of binder. Preferably, 0.3 to 7 parts is more preferable. If it is less than 0.1 part, the curing time cannot be controlled, and the pumpability of cement concrete may be reduced and the hose may be clogged or the strength development may be reduced. If it exceeds 7 parts, the strength development will be reduced. There is a case.

  Here, as the cement, various portland cements such as normal, early strength, moderate heat, low heat, and super early strength that are usually marketed, various mixed cements in which fly ash, blast furnace slag, etc. are mixed with these portland cements, In addition, eco-cement and the like can be mentioned, and these can be used after being finely powdered. Among these, ordinary Portland cement and / or early-strength Portland cement are preferable.

As the aggregate used in the present invention, either a fine aggregate or a coarse aggregate can be used.
Examples of the fine aggregate include natural sand, quartz sand, crushed sand, and lime sand. Examples of the coarse aggregate include river gravel, mountain gravel, crushed stone, and lime gravel.
The maximum particle size of the coarse aggregate is preferably 5 to 25 mm. If it exceeds 25 mm, the construction cross section becomes thick, and construction such as the cover thickness and rebar spacing may have to be considered.
The fine aggregate ratio (S / a) of cement concrete used in the present invention varies depending on the unit water amount, fluidity, FM value of fine aggregate, etc., but is usually preferably 40% or more, and 45 to 60%. Is more preferable. If it is less than 40%, the hose is clogged, the pumpability becomes worse, and there is a case where a jumper can be formed after cement concrete is put into the formwork.

  In the present invention, the water binder ratio (W / P) is preferably 35 to 65%, more preferably 40 to 60%. If it is less than 35%, the viscosity of cement concrete increases, and workability and pumpability may be reduced. If it exceeds 65%, durability may not be obtained.

In the present invention, it is further possible to use a water reducing agent.
The water reducing agent is to obtain fluidity, and both liquid and powder can be used. Specific examples include lignin sulfonate and its derivatives, and high performance water reducing agents. Two or more types can be used. Among these, a high-performance water reducing agent is preferable in terms of large setting delay effect, fluidity, and pumpability.

High-performance water reducing agents include polyol derivatives such as polyethylene glycol, aromatic sulfonic acid-based high-performance water reducing agents, polycarboxylic acid-based high-performance water reducing agents, and polyethylene-based high-performance water reducing agents containing ethylene glycol chains and sulfonic acid groups. A performance water-reducing agent, a melamine-based high-performance water-reducing agent, and a mixture thereof can be used. Among these, aromatic sulfonic acid-based, polycarboxylic acid-based, and polyether-based high-performance water reducing agents are preferable because they have a large setting retarding effect, fluidity, and pumpability.
The amount of water reducing agent used is preferably 0.2 to 3 parts, more preferably 0.5 to 2 parts, relative to 100 parts of the binder. If it is less than 0.2 part, the pumpability of the cement concrete is small and the fluidity may not be maintained. If it exceeds 3 parts, the setting of the cement concrete becomes poor, and it is not economical and the initial strength development may be small.

  The setting of the cement concrete of the present invention starts from the time when it is mixed with water by a mixer, and the setting time is preferably 2 to 180 minutes, more preferably 5 to 120 minutes. If it is less than 2 minutes, the hose may be blocked, and the cement concrete may not be sufficiently filled in the tornell formwork. If it exceeds 180 minutes, the strength development will be reduced, and the formwork will be unframed, resulting in tunnel lining. There is a risk that the workability of the machine will deteriorate.

  By using the cement concrete of the present invention, drying shrinkage is reduced and crack resistance is increased.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.

Using a concrete blend of W / P 57%, S / a 47%, and binder P unit amount of 300 kg / m ³ , 73 parts of cement, 7 parts of expansion material shown in Table 1, CAS glass A and Concrete was prepared by kneading using 20 parts of a rapid hardening component, which is an equivalent mixture of gypsum, and 0.3 part of a setting retarder with respect to 100 parts of a binder.
Slump, air amount, curing time, compressive strength, and drying shrinkage of the prepared concrete were measured at a test execution temperature of 20 ° C. The results are also shown in Table 1.

<Materials used>
Cement: Ordinary Portland cement, 3 kinds of mixture, Blaine value 3,420cm ² / g, Density 3.14g / cm ³
Expansion material: Calcium aluminoferrite, density 3.06g / cm ³
CAS glass A: CaO / Al ₂ O ₃ / SiO ₂ = 50/45/10, Vitrification rate 100%, Blaine value 5,050 cm ² / g
Gypsum: crushed anhydrous gypsum, 4,900 cm ² / g of brain value
Setting retarder: Citric acid / potassium carbonate 3/7 weight ratio fine aggregate: Himekawa Sakegawa sand, Itoigawa city, Niigata prefecture, density 2.60g / cm ³ , FM = 2.82
Coarse aggregate: Gravel from Himekawa, Itoigawa City, Niigata Prefecture, density 2.67g / cm ³ , maximum aggregate size 25mm

<Measurement method>
Slump: Measured according to JIS A 1101 “Slump test method of concrete”: Measured according to JIS A 1128 “Test method using air pressure of fresh concrete” Curing time: Compressed when the concrete temperature rises by 1 ° C after mixing Strength: Measured according to JIS A 1108 “Concrete compressive strength test method” 18 hours after casting Drying shrinkage: Covered with concrete on the concrete surface to prevent drying until demolding, JIS A 6202 “For concrete Inflated material "Measured by method B, starting material age after 18 hours

The cement shown in Table 2, an expanded material having a brain value of 2,820 cm ² / g, a rapid hardening component that is an equal mixture of CAS glass A and gypsum, and 0.3 part of a setting retarder and 100% of water for a binder. The same procedure as in Example 1 was performed except that 0.7 parts of the agent was mixed and concrete was prepared. The results are also shown in Table 2.

<Materials used>
Water reducing agent: Polycarboxylic acid-based high-performance water reducing agent, liquid, commercially available product

Same as Example ² except that 73 parts of cement, 7 parts of expanded material with a brane value of 2,820 cm ² / g, and 20 parts of the quick hardening component which is a mixture of CAS glass and gypsum shown in Table 3 were used. It was. The results are also shown in Table 3.

<Materials used>
CAS glass B: CaO / Al ₂ O ₃ / SiO ₂ = 50/45/5, Vitrification rate 100%, Blaine value 5,100 cm ² / g
CAS glass C: CaO / Al ₂ O ₃ / SiO ₂ = 50/45/20, Vitrification rate 100%, Blaine value 5,050 cm ² / g
CAS glass D: CaO / Al ₂ O ₃ / SiO ₂ = 50/45/25, 100% vitrification, brain value 5,000 cm ² / g

Using a composition of 73 parts of cement, 7 parts of an expansion material having a brain value of 2,820 cm ² / g, and 20 parts of a rapid hardening component which is an equal mixture of CAS glass A and gypsum, W / P and S / a shown in Table 4 The same procedure as in Example 2 was conducted except that a water reducing agent was used. The results are also shown in Table 4.

Claims (6)

  A cement admixture comprising an expansion material, calcium aluminosilicate glass, gypsum, and a setting retarder.   The cement admixture according to claim 1, wherein the expansion material is calcium aluminoferrite. The cement admixture according to claim 1 or 2, wherein the particle size of the expansion material is 1,000 to 4,500 cm ² / g in terms of the specific surface area of the brain.   A cement composition comprising cement and the cement admixture according to any one of claims 1 to 3.   Cement concrete formed by blending the cement composition according to claim 4 and water.   A method for preventing cracks in a tunnel secondary lining cement concrete, comprising applying the cement concrete according to claim 5.