JPH0794339B2 - Concrete for direct lining - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete for direct-casting lining, and is particularly used for a part requiring water resistance such as a lining construction of a direct-casting lining method such as a tunnel, and has water-stopping property even when it is not hardened. However, the present invention relates to a concrete for direct lining which has a small slump loss even when it is placed for a long time.

[0002]

2. Description of the Related Art Conventionally, in a shield tunnel, in the direct hitting lining method (ECL) which has been widely used, it is necessary to directly apply a lining concrete (lining) at the tail portion of the excavator simultaneously with the excavation of the shield excavator. Has become. At this time, concrete is placed between the skin plate of the shield excavator and the inner mold, and is pressed and filled in the tail void by a pressure jack or the like. At the same time, the shield excavator is propelled, so the concrete adheres to the ground,
The lining can be constructed without the need for backfill injection. Normally, the following properties are required for the concrete used for direct lining. (1) Since it is pumped from a concrete pump installed behind the excavator, it has excellent material separation resistance. (2) The tail void filling performance and the self-leveling property are excellent, and an appropriate consistency is secured. (3) Slump loss in the uncured state is small. (4) Good initial strength development to accelerate demolding time. (5) It should be possible to place it in the confined groundwater layer. In order to satisfy these conditions, various concretes for direct lining have been proposed. However, many of them have a problem that when used in a pressurized groundwater layer, the cement content is washed out by the pressurized groundwater to separate the material from the aggregate, and a predetermined concrete strength cannot be obtained. In order to solve this problem, concrete to which a separation reducing agent for special underwater concrete made of a cellulosic water-soluble polymer is added has been proposed.

[0003]

However, in the case of the direct-lining concrete for which the above-mentioned cellulosic separation reducing agent is added, even if the early-strength Portland cement is used as the cement, it is necessary to obtain the desired compressive strength. It takes about a day, and in some cases the shield machine cannot be dug during this time. Therefore, the hardening time of the lining concrete becomes a critical path of the process, and there is a problem that the construction is delayed.

Therefore, the object of the present invention is to solve the above-mentioned problems of the prior art, to show sufficient water impermeability even in an uncured state, to prevent material separation due to washing action with water, and It is intended to provide a concrete for direct lining which can keep the slump loss small for a long time after kneading and exhibits good initial strength.

[0005]

In order to achieve the above object, the present invention provides a predetermined amount of water obtained by adding an acrylic thickener to Portland cement and kneading the mixture, and diluting and adding a water reducing agent to the Portland cement mixture. It is characterized by being manufactured by kneading with the addition of water.

[0006]

According to the present invention, since an acrylic thickening agent is added to Portland cement and kneading is performed, and a predetermined amount of water to which the water reducing agent is diluted and added is added to this Portland cement mixture and kneading is performed, The water-soluble polymer of the acrylic thickener is kneaded around it and molecularly disperses in the water while attracting a part of the water, and the remaining free water is trapped in the network structure of the molecularly dispersed polymer, And the yield value of water increases. As a result, the cement particles and aggregates are wrapped in this water, exhibiting non-separability in water due to the thickening action that does not separate even when contacted with external water, and show non-breathing properties and self-leveling properties. As a result, the slump loss can be reduced for a long time by the dispersing action of the water reducing agent.

[0007]

EFFECTS OF THE INVENTION According to the present invention, it exhibits good water impermeability in an uncured state, does not cause material separation even by the washing action of water, reduces slump loss, and can be used for long-time driving. In addition to the effect that the initial strength is well expressed and that direct lining can be quickly applied, it can be applied to concrete that is required to have water resistance in an uncured state. Can be expected. [Detailed Description of the Invention] The concrete for direct lining according to the present invention is prepared by adding a predetermined amount of a thickening agent to pre-measured early-strength Portland cement or ordinary Portland cement, and kneading the mixture. By adding mixing water and mixing for a certain period of time, fresh concrete having a predetermined specification is obtained. At this time, it is known that addition of a thickening agent increases the viscosity coefficient of water and increases the amount of unit water required to obtain the same consistency. Here, in order to obtain the same strength as ordinary concrete, it is necessary to keep the water-cement ratio constant. For this reason, it is effective to add a fluidizing agent or a high-performance water reducing agent in order to prevent the unit cement amount from increasing.

Regarding the use of the AE water reducing agent, the concrete of the present invention is used in a tunnel lining or the like, and it is expected that the concrete will be subjected to a freeze-thaw action. Just do it. Here, both the early-strength Portland cement and the ordinary Portland cement used in the present invention are known cements, and the outline of their components and properties is as follows. In the following description, C: CaO, S: SiO
₂ is shown.

<Early Strength Portland Cement> The early strength Portland cement has a content of tricalcium silicate (C ₃ S) of 62 as a chemical composition according to the Bogue equation in order to secure the early development of strength of 1 to 3 days. It is set to ~ 66%.
In the direct lining method, the demolding time affects the progress of the excavator, so early demolding is required. Therefore, also in the present invention, early strength Portland cement was used in the experiment for confirming the effect. The amount used is set to about 350 to 400 kg / m ^{3 for} reinforced concrete (RC) and about 500 to 600 kg / m ³ for steel fiber concrete (SFC).

<Ordinary Portland Cement> The chemical composition of ordinary Portland cement according to the Bogue equation is that the content of tricalcium silicate (C ₃ S) is 49 to 52% and the content of dicalcium silicate (C ₂ S) is. 22-26%, the former contributing to early strength and the latter controlling long-term strength after 28 days of age. This makes it possible to obtain a well-balanced strength expression in the short and short term.

<Thickening Agent> The thickening agent used in the present invention is an acrylic thickening agent, and as its property, it prevents the cement component from flowing away even when it is washed with water, and prevents material separation. It is widely known that this is possible, but it has excellent filling properties and self-leveling properties, and almost no breathing. Also,
Compared with cellulosic thickeners, it exhibits excellent curing properties in developing initial strength. Examples of the main component of the thickening agent include polyacrylamide, modified polyacrylamide, and partially hydrolyzed polyacrylamide. The amount of addition is 0.6 to 1.2% with respect to the weight of cement used for conventional underwater non-separable concrete, but the finished concrete unit volume (1
Addition of 1 to 2.2 kg per m ³ ) makes it possible to secure the predetermined fluidity and pot life.

Even when this thickening agent is added, the viscosity decreases as the material temperature rises, so it is preferable to increase the addition amount of the thickening agent according to the operating temperature. The addition amount is preferably about 3 kg / m ³ .

<Fluidizing agent> When the fluidizing agent is added, the cement particles move from the aggregating system to the dispersing system. At this time, the viscosity of the suspension is reduced and the yield value is greatly reduced. In this state, the fluidity of concrete is remarkably improved. However, the suspension is a thermodynamically unstable system, in which cement particles aggregate and settle, so that the fluidity of concrete disappears in a short time. This phenomenon appears as slump loss. A naphthalene sulfonate-based, polycarboxylate-based, melamine sulfonate-based, or lignin-based dispersant is suitable as the main component of the known fluidizing agent.

<High-performance AE water reducing agent> The high-performance AE water reducing agent is a dispersant that improves the slump loss of the above-mentioned fluidizing agent. In the high-performance AE water reducing agent, the dispersion of the cement particles is promoted by the dispersant, which lowers the viscosity and the yield value of the dispersion system, and fluidizes the concrete. Furthermore, the aggregation of cement particles can be prevented by the sustained release of the dispersant. The water reducing mechanism for increasing the viscosity of the dispersant by keeping the viscosity constant by reducing the amount of viscosity reduction caused by dispersion of cement particles is the same as that of the fluidizing agent. Known high performance A
As the water reducing agent E, polycarboxylic acid ether-based composites, aminosulfonic acid condensate-based or lignin derivatives, anionic special polymer activators and the like are used.

<Addition amount of superplasticizer or high-performance AE water reducing agent> In the present invention, the superplasticizer or high-performance AE water reducing agent was used for controlling the increase of slump loss due to the thickening action of the thickener. The lower limit of the addition amount was set to 3% of the cement weight in order to secure a slump flow of 350 mm after 3 hours from the kneading, and the upper limit was set to 4% of the cement weight to prevent material separation. Since the consistency of the material changes depending on the cement brand, the type of aggregate used, the coarse grain ratio, etc., in order to obtain a predetermined slump flow, it is preferable to carry out a test kneading using an actually used material, It is preferable to allow for a slight increase or decrease in the set value.

[0016]

[Example] <Experimental Example 1: SFC blend> (1) Materials used (per 1 m ³ ) Coarse aggregate (crushed stone) 882 kg Fine aggregate (river sand) 590 kg Early strength Portland 600 kg Cement mixing water 210 kg High performance AE water reduction Agent 25 kg Viscosity agent 1-3 kg (mixing is performed by changing the addition amount) Steel fiber 79 kg (2) Kneading process (using a 50-liter forced kneading mixer) Aggregate empty kneading + cement + thickening agent 60 seconds ＋ Mixing water ＋ High performance 4 minutes AE water reducing agent ＋ Steel fiber 90 seconds (3) Slump test result Slump 24.0 cm flow 695 mm 3 hours after slump 23.8 cm flow 520 mm (4) Compression test result (material age) 24 hours) σ _24hr = 161kgf / cm ² <Experimental example 2: RC compounding> (1) Materials used (per 1 m ³ ) Coarse aggregate (crushed stone) _960kg Fine aggregate (river sand) 800kg Early strength Portland 400kg Cement Mixing water 180kg High-performance AE water reducing agent 14kg Thickening agent 1-3kg (mixing is performed by changing the addition amount) (2) Mixing process (using a 50-liter forced kneading mixer) Aggregate kneading as appropriate + cement ＋ Viscous agent 60 seconds ＋ Mixing water ＋ High performance 4 minutes AE water reducing agent (3) Slump test result Slump 24.0 cm flow 645 mm 3 hours after slump 22.5 cm flow 438 mm (4) Compression test result (material 36 hours) σ _36hr = 170kgf / cm ²

<Experimental results> (1) Relationship between the amount of thickener added and the slump flow As shown in FIG.
In order to secure m), it is preferable that the added amount of the thickener is 2.2 kg (per 1 m ^{3 of} concrete) or less. If the amount added is less than 1 kg (per 1 m ^{3 of} concrete), the uniform thickening effect cannot be exhibited. Therefore, 1 to 2.2 kg (per 1 m ^{3 of} concrete) can be recommended as an appropriate value for the amount of thickener added. (2) Relationship between high-performance AE water reducing agent addition amount, slump flow, and 24-hour compressive strength From Fig. 2, it is possible to determine the lower limit value from the relationship with the prescribed slump flow and the upper limit value from the relationship with the 24-hour compressive strength. it can. As a result, it was found that the addition amount of 3 to 4% by weight of cement is suitable.

[Brief description of drawings]

FIG. 1 is a characteristic curve diagram showing the relationship between the amount of thickener added and slump flow.

[Figure 2] High-performance AE water reducing agent addition amount and slump flow, 2
The characteristic curve figure which showed the relationship with 4-hour compressive strength.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location C04B 28/04 E21D 11/10 C // (C04B 28/04 24:26 H 24:18) B (72) Inventor Shinsuke Ishikawa, Oi-cho, Iruma-gun, Saitama 1168, Kamei, Kameikubo, Kagoi, Institute of Technology Research, Ando Construction Co., Ltd. (56) Reference JP-A-3-161304 (JP, A)

Claims (3)

[Claims] 1. A direct-lining lining characterized by being produced by adding an acrylic thickener to Portland cement and kneading the mixture, and then kneading the Portland cement mixture with a predetermined amount of a water reducing agent and water. concrete. 2. The concrete for direct lining according to claim 1, wherein the acrylic thickener is added in an amount of 1 to 2.2 kg / m ^{3 with} respect to a unit volume of the concrete to be produced. . 3. The water reducing agent is selected from polycarboxylic acid-based, aminosulfonic acid-based or lignin-based water reducing agents, and the amount of the water reducing agent added is 3 to 3 of the Portland cement cement weight ratio.
It is 4%, The concrete for direct-casting linings in any one of Claim 1 or Claim 2 characterized by the above-mentioned.