JP2018104982A - Construction method of spray concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a construction method of a spray concrete which has a better quick-setting quality and a good consistency of concrete even using a liquid quick-setting agent.SOLUTION: There is provided a construction method of a spray concrete which includes a quick-setting assistant agent containing alkaline metal aluminate, limes and plasters, and a liquid quick-setting agent, and is characterized in that after a base concrete is produced, the quick-setting assistant agent is added to the base concrete and mixed, the mixed concrete is pressure-fed, and the liquid quick-setting agent is added using a spray nozzle tip.SELECTED DRAWING: None

Description

  The present invention relates to a method for constructing shotcrete using a liquid quick-setting agent.

  In construction work in excavated tunnels and underground spaces, it has been widely practiced to lining concrete by adding a powder quick-set agent to the excavated exposed surface to prevent collapse of the exposed surface ( (See Patent Documents 1 and 2). As the powder quick setting agent, a quick setting agent containing calcium aluminate as a main component and containing aluminate, alkali metal carbonate or the like is known. Although this powder quick setting agent is excellent in quick setting property, there are problems such as a large amount of dust generation and a large amount of rebound of the sprayed concrete.

As a measure for solving this problem, a technique using a liquid quick-setting agent has been proposed (see Patent Documents 3 and 4). Inferior in comparison is a major issue.
As a solution to the problem when using a liquid quick-set agent, there has been proposed a method in which inorganic salts having an effect for improving quick setting properties such as a powder quick-set agent are used in addition to the liquid quick-set agent (Patent Document) 5 and 6). Specifically, it is a method of adding inorganic salts such as powdered aluminum sulfate and calcium aluminate in addition to the liquid accelerating agent. As a method for adding inorganic salts, it can be contained in the spray concrete used as a base, but immediately before spraying concrete is sprayed, it is mixed with water or a liquid quick-setting agent to form a slurry. It is said that the method of mixing things just before the spraying concrete is discharged is preferable from the viewpoint of reducing dust.

Japanese Patent Publication No. 60-004149 JP 09-019910 A JP-T-2001-509124 Japanese Patent Laid-Open No. 10-087358 JP 2002-220270 A JP 2007-055831 A

However, the method of slurrying the powder quick-setting agent immediately before spraying requires a dedicated mixing device at the tip of the spray nozzle and has many practical problems such as a complicated structure of the spraying device. . On the other hand, when the powder quick-setting agent is contained in the base concrete, the concrete consistency is generally poor, and the pumpability of the concrete during spraying is hindered.
Accordingly, an object of the present invention is to provide a method for constructing shotcrete having good quick setting properties without affecting the pumpability of concrete even when a liquid quick setting agent is used. is there.

  Therefore, the present inventor, as a result of various studies on the effective rapid accelerator and its addition method, in the case of using the rapid accelerator that contains alkali metal aluminate, limes and gypsum, The present invention has been completed by finding a method for constructing sprayed concrete that has no hindrance to the pumpability of concrete and has good quick setting even in spraying using a liquid quick setting agent.

That is, the present invention provides the following [1] to [3].
[1] A method for constructing shotcrete containing a quick setting aid containing an alkali metal aluminate, limes and gypsum, and a liquid quick set, wherein the quick setting aid is produced after the base concrete is manufactured. A method for constructing sprayed concrete, in which an agent is added to the base concrete, kneaded, the kneaded concrete is pumped, and a liquid quick setting agent is added at the tip of the spray nozzle.
[2] A method for constructing shotcrete containing a quick setting aid containing an alkali metal aluminate, limes and gypsum and a liquid quick set, and after manufacturing the base concrete, the drum of the track agitator A spraying concrete in which the quick setting aid is added to the base concrete in the drum of the track agitator, kneaded, the kneaded concrete is pumped, and the liquid quick setting agent is added at the tip of the spray nozzle. Construction method.
[3] The method for constructing shotcrete according to [1] or [2], wherein the liquid quick setting agent is mainly composed of aluminum sulfate.

  By using the method for constructing shotcrete of the present invention, shotcrete having a good quick setting property can be constructed even when a liquid quick setting agent is used. As a result, it is possible to construct shotcrete that takes advantage of the characteristics of the liquid quick-setting agent that the amount of dust generated is small and the amount of rebound is small.

  In the present invention, a quick setting aid containing an alkali metal aluminate, limes and gypsum is used as the quick setting aid, and the quick setting aid is added and kneaded after the base concrete is manufactured. This is a method for constructing sprayed concrete in which the concrete is pumped and a liquid quick setting agent is added at the tip of the spray nozzle. Further, after the base concrete is put into the drum of the track agitator, the quick setting aid is put into the drum and kneaded. Here, concrete includes mortar.

  As a method for producing concrete containing a rapid setting aid, a method of adding water to a concrete mixer together with cement and aggregate and performing kneading, followed by adding water and kneading (hereinafter sometimes referred to as “batch kneading”) And a method of adding a quick setting aid after the base concrete is manufactured and kneading again (hereinafter sometimes referred to as “post-addition”).

However, as a result of studying the method for producing concrete using the quick setting aid in the present invention, in the case of batch kneading, concrete cohesion (false condensation) is likely to occur, and a large amount of water reducing agent is necessary to eliminate this. It was found necessary to add. Furthermore, when the amount of water reducing agent used is increased, a concrete with stable pumpability can be obtained because of the post elongation phenomenon that the fluidity of the concrete increases with the passage of the kneading time after kneading. It turned out that there was a problem that it was difficult to be. In addition, with the addition of a large amount of water reducing agent and the post elongation phenomenon of fluidity, it was found that the quick setting property when adding a liquid quick setting agent was also affected, and a stable quality shotcrete was obtained. I found it difficult.

On the other hand, in the case of post-addition, it was found that stable fluid concrete with less influence of the kneading time can be obtained without excessively increasing the amount of water reducing agent added. Surprisingly, it has been found that the amount of the water reducing agent can be blended with a setting amount that is less than half that of the batch kneading. The fact that the amount of water reducing agent can be reduced has great economic merit. Furthermore, it was found that the compounding amount of the quick setting aid can be increased as compared with the batch kneading, and it has been found that spray construction with improved quick setting performance can be performed. The present invention has found a method for constructing shotcrete that is particularly effective when a specific quick setting aid is used.

(Quick setting aid)
The quick setting aid in the present invention is used to supplementarily improve the quick setting property of shotcrete, and contains alkali metal aluminate, limes and gypsum.

  Examples of the alkali metal aluminate used in the present invention include sodium aluminate, potassium aluminate and the like, and commercially available reagents or industrial products can be used. Sodium aluminate is particularly preferable. The blending amount of the alkali metal aluminate in 100 parts by mass of the quick setting aid is preferably 5 to 50 parts by mass from the viewpoint of the consistency of the concrete and the strength development of the shotcrete. More preferably, it is 10-40 mass parts.

  The lime used in the present invention refers to a composition containing a lime component such as a heat treatment product containing quick lime, slaked lime, or free lime (hereinafter referred to as “quick lime clinker composition”), and these are used alone or in combination of two kinds. The above can be used together. Among these, it is particularly preferable to use a quicklime clinker composition.

The quicklime clinker composition is a heat treatment product containing free quicklime and calcium silicate such as trisilicate silicate (CaO.3SiO ₂ ). What contains 50 mass% or more as free lime is preferable. The quicklime clinker composition is produced by heat-treating a composition containing a CaO raw material, an Al ₂ O ₃ raw material, an Fe ₂ O ₃ raw material, an SiO ₂ raw material, a CaSO ₄ raw material, etc. at a temperature of 1300 to 1600 ° C. An electric furnace, a rotary kiln or the like is used for the heat treatment. The heat treatment product is subjected to pulverization, classification, and the like, and the particle size is adjusted to a Blaine specific surface area of 2,000 to 6,000 cm ² / g.

The blending amount of limes in 100 parts by mass of the quick setting aid is preferably 10 to 70 parts by mass from the viewpoint of concrete consistency and strength development of shotcrete. More preferably, it is 15-65 mass parts.

  Examples of the gypsum used in the present invention include anhydrous gypsum, dihydrate gypsum, hemihydrate gypsum, and the like, but anhydrous gypsum is preferable. The blending amount of gypsum in 100 parts by mass of the quick setting aid is preferably 5 to 70 parts by mass from the viewpoint of concrete consistency and strength development of shotcrete. More preferably, it is 10-65 mass parts.

  A dispersant can be further added to the quick setting aid of the present invention. As a dispersing agent, the water reducing agent for cement etc. which are generally marketed can be used, for example. Examples of the dispersant include polyacrylic acid, polycarboxylic acid, melamine sulfonic acid, lignin sulfonic acid, naphthalene sulfonic acid, and polyol. When used as a quick-set aid premixed with other components, a powdery one is used. The blending amount of the dispersant in 100 parts by mass of the quick setting aid is 15 parts by mass or less in terms of solid content from the viewpoint of concrete consistency and strength development of shotcrete. More preferably, it is 1-10 mass parts.

  A setting retarder can be further added to the rapid setting aid of the present invention as required. As the setting retarder, a commercially available one can be used. Examples thereof include organic acids such as citric acid, gluconic acid, malic acid, and tartaric acid, or salts thereof, boric acid salts such as boric acid and sodium borate, phosphates, and saccharides. Of these, one or more are used. The use of a setting retarder is effective in summer when the base concrete has a high kneading temperature.

  The blending amount of the setting retarder in 100 parts by mass of the quick setting aid is 2 parts by mass or less in terms of solid content from the viewpoint of ensuring the consistency of the concrete and not having a large effect on the quick setting property of the shotcrete. . More preferably, it is 1.5 parts by mass or less.

In addition to the above components, the rapid setting agent of the present invention contains inorganic salts such as alkali metal carbonates, bicarbonates, sulfates and nitrates, or alkaline earth metal sulfates, nitrates and nitrites. be able to. Specific examples include alkali metal carbonates such as sodium carbonate, potassium carbonate, and lithium carbonate. These are effective in increasing the strength of shotcrete by blending an appropriate amount.

(Sprayed concrete)
The cement used in the shotcrete of the present invention is not particularly limited, and various portland cements such as normal, early strength, ultra-early strength, low heat and moderate heat, fly ash, fine limestone powder, etc. A mixed cement obtained by mixing Moreover, even if it is 1 type of the said cement, it may be 2 or more types.

  In addition, the aggregate used in the present invention is not particularly limited, and any aggregate used for the production of ordinary concrete or mortar can be used.

In addition to the dispersant added to the quick setting aid, a cement water reducing agent is usually added to the base concrete to adjust the consistency of the concrete. The cement water reducing agent used here is usually liquid. Although the kind is not specifically limited, When the water reducing agent for cement is mix | blended with the quick setting aid, it is desirable to use the water reducing agent for cement of the same kind. The addition amount of the water reducing agent for cement is preferably 0.1 to 2.0% by mass with respect to cement.

  For shotcrete, in addition to the cement water reducing agent, if necessary, an AE agent, a fluidizing agent, a thickener, an expansion material, a shrinkage reducing agent, and cement Addition of polymers, waterproofing materials, rust preventives, antifreezing agents, water retention agents, pigments, anti-whitening agents, foaming agents, antifoaming agents, water repellents, various fibers, etc. is not prevented.

(Construction of shotcrete)
First, base concrete is manufactured by a concrete manufacturing apparatus provided near a ready-mixed manufacturing plant or a spraying construction site. When manufactured in a ready-mixed plant, the base concrete is put into the drum of the track agitator and transported to the spraying site.

  In the spray construction site, a quick setting aid is added to the base concrete in consideration of the time when the pumpability of the concrete can be secured. When transported by the track agitator, the quick setting aid can be put into the base concrete in the drum of the track agitator and kneaded by rotating at high speed.

  The amount of the quick setting aid added to the base concrete is preferably 1.0 to 5.5% by mass with respect to the cement in the concrete. If it is less than 1.0% by mass, there is a possibility that sufficient quick setting property cannot be imparted. On the other hand, if it exceeds 5.0% by mass, the consistency of the concrete is impaired, and pumping is not possible. There is a risk of trouble. More preferably, it is 1.5-4.0 mass%.

  The concrete to which the quick setting aid is added is pumped, mixed with the liquid quick setting agent at the tip of the spray nozzle, and sprayed onto the exposed surface of the excavation such as a tunnel. About a spraying system, when performing spraying construction using a liquid quick-setting agent, the spraying apparatus and spraying system generally used can be utilized.

  As the liquid accelerator used in the present invention, any generally used liquid accelerator can be used, but a liquid accelerator containing aluminum sulfate as an active ingredient is particularly preferable. This liquid accelerator is usually prepared as an aqueous solution by mixing powdered aluminum sulfate (or its hydrate) with water, but is not limited to this, and a soluble aluminum component and a sulfur source such as sulfuric acid. The aluminum sulfate may be prepared as an aqueous solution. Further, addition of other components is not prevented as long as the features of the present invention are not impaired. Examples of other components include precipitated silica and alkanolamine. 15 mass% or more is preferable, as for the aluminum sulfate content in a liquid quick setting agent, 20-35 mass% is more preferable, and 22-30 mass% is further more preferable. The amount of the liquid quick-setting agent is preferably 3 to 15% by mass, more preferably 5 to 13% by mass with respect to the cement in the concrete, from the viewpoint of the balance between rapid setting performance and long-term strength development.

The spraying construction method of the present invention can produce sprayed concrete having excellent quick setting properties by using a quick setting aid, even when a liquid quick setting agent is used. In addition, by using the quick setting aid of the present invention, it is possible to construct shotcrete that makes use of the characteristics of the liquid quick setting agent that the amount of dust generated is small and the amount of rebound is small.

  Hereinafter, more specific examples will be described. However, the present invention is not limited to the following examples.

Example 1
The mortar was used to evaluate differences due to the method of adding the quick setting aid.

[Materials used]
(1) Sodium aluminate: commercial product, powder (2) Quicklime clinker composition: A mixed powder of quicklime, clay and gypsum was fired at 1450 ° C. to obtain a heat treatment product containing 65% by mass of free lime. Main components other than free lime were tricalcium silicate (3CaO · SiO ₂ ) and anhydrous gypsum (CaSO ₄ ). The heat-treated product was coarsely crushed and further pulverized by a mill to obtain a quicklime clinker composition having a Blaine specific surface area of 3,200 cm ² / g.
(3) Gypsum: Anhydrous gypsum; Commercial product (4) Water reducing agent for cement (powder type): Polycarboxylic acid-based high-performance water reducing agent “NF-100” (manufactured by Taiheiyo Materials Co., Ltd.)
(5) Water reducing agent for cement (liquid type): High performance water reducing agent “NT1000H” (manufactured by BASF)
(6) Cement: Ordinary Portland cement (manufactured by Taiheiyo Cement, density: 3.16 g / cm ³ )
(7) Fine aggregate: JIS sand (8) Water: Tap water (9) Liquid quick setting agent: Aluminum sulfate-based liquid quick setting agent (aluminum sulfate content; 27% by mass)

[Preparation of quick setting aid]
22 parts by mass of sodium aluminate, 56 parts by mass of quicklime clinker composition, 15 parts by mass of gypsum, and 7 parts by mass of a water reducing agent for cement (powder type) were mixed with a mixer to obtain a quick setting aid.

〔Evaluation test〕
(1) Evaluation of fluidity The fluidity of the mortar after the addition of the quick setting aid was evaluated by a 15-stroke flow value of a flow test according to JIS R 5201. Moreover, it visually evaluated about the tightness of the mortar.
(2) Rapid setting evaluation The rapid setting evaluation was performed by a proctor penetration resistance test using mortar.
Addition of quick setting aid and water reducing agent for cement (liquid type) as shown in the table to a mortar formulation with a sand cement ratio (mass ratio) of 2.5 and a water cement ratio (mass ratio) of 50% And kneaded for 1 minute with a mortar mixer. The mortar was added with a 7% by mass liquid setting agent with respect to the cement, stirred for 5 seconds using a hand mixer, and then measured for a proctor penetration resistance value. The measurement was performed at each material age after 30 seconds, 60 seconds, 90 seconds, 120 seconds, and 360 seconds, with 0 seconds immediately after the addition of the liquid accelerating agent. The results are shown in Table 1.
(3) Compressive strength As with the quick setting evaluation test, a liquid quick setting agent was added and the kneaded mortar was quickly packed into a mold to obtain a specimen for a compressive strength test. The compressive strength test was performed at a material age of 3 hours, 1 day, and 28 days.

As shown in Table 1, it is understood that in the case of batch kneading, it is necessary to add a large amount of water reducing agent in order to ensure the predetermined fluidity, and the fluidity is likely to vary with the passage of the kneading time. On the other hand, in the case of post-addition, it can be seen that a predetermined fluidity can be obtained with an amount of water reducing agent that is less than half that of batch kneading, and that a stable flow value can be secured regardless of the kneading time.
In addition, in the case of batch kneading, a decrease in the flow value is observed when the addition amount of the quick setting aid is increased. In order to ensure the pumpability of concrete, it is desired that 150 mm or more is secured as the 15-stroke flow value in this test. On the other hand, in the case of post-addition, it is possible to ensure fluidity to some extent even if the addition amount of the quick setting aid is increased, and as a result, by adding the liquid quick setting agent, high quick setting is achieved. It can be seen that it can be obtained.
Specifically, in the case of batch kneading, the blending that secures a flow of 150 mm or more from 0 minutes (immediately after kneading) to 30 minutes is in the range of 2.0 to 2.5% by mass as the amount of quick setting aid added. However, in the case of post-addition, up to 3.5% by mass is possible. With consideration given to the amount, if the quick-setting property as compared with 30 seconds of Proctor penetration resistance value for 1.39~1.63N / mm ² in the batch kneading, in post-addition is 3.36N / mm ² And more than double the performance can be obtained. Furthermore, it is possible to obtain performance with a high 3-hour age and 1-day age strength.
In addition, when the water reducing agent addition rate was 0.6% by mass with respect to cement in the batch kneading, the flow decreased and measurement was impossible after 15 minutes.

(Example 2)
Using the quick setting aid in the present invention, a construction test of shotcrete with a liquid quick setting agent was carried out.
First, base concrete was manufactured in a ready-mixed concrete plant. The cement (C) is ordinary Portland cement, the aggregate is fine crushed sand (surface dry density; 2.66 g / cm ³ ) as fine aggregate (S), and crushed stone 1505 (surface dry density; 2.) as coarse aggregate (G). 74 g / cm ³ ) was used. Table 2 shows the concrete composition.
The manufactured concrete was loaded onto a truck agitator and transported to the simulated tunnel spraying site.
At the construction site, the quick setting aid prepared with the same composition as in Example 1 was put into the tank of the track agitator and kneaded at high speed for 60 seconds. The addition amount of the quick setting aid was 2.5% by mass with respect to the cement.
The concrete to which the quick setting aid was added was pumped by a pump, and the same liquid quick setting agent as in Example 1 was added 0.5 m before the spray nozzle. The addition rate of the liquid quick-setting agent to cement was 7.2% by mass as an actual measurement value. The shotcrete to which the liquid quick-setting agent was added was sprayed onto the pull-out test formwork and the wooden formwork. As evaluation of the curing performance of the sprayed concrete, a pull-out test was conducted according to JSCE-G561 for the 3-hour age and 1-day age after setting, and the compressive strength test was 28 days old. The test was carried out on a specimen (diameter 5 cm × length 10 cm) in which the core was cored from a wooden formwork specimen. In addition, about the spraying property after quick setting agent addition, it evaluated by visual observation and touch.
The concrete was sprayed well, showed good adhesion from the side of the simulated tunnel to the top, and the amount of concrete rebound was small. Moreover, after adding the quick setting aid and kneading, spraying was completed in about 30 minutes, but during that time, the pumpability of the concrete was good.
Regarding strength development, the 3-hour age strength was 2.3 N / mm ² , the 1-day age strength was 6.9 N / mm ² , and the 28-day age strength was 29.2 N / mm ² , which was good. It was.

Claims (3)

A method for constructing shotcrete containing a quick setting aid containing alkali metal aluminate, lime and gypsum, and a liquid quick setting agent,
After the base concrete is manufactured, the quick setting aid is added to the base concrete, kneaded, the kneaded concrete is pumped, and a liquid quick setting agent is added at the tip of the spray nozzle. Concrete construction method. A method for constructing shotcrete containing a quick setting aid containing alkali metal aluminate, lime and gypsum, and a liquid quick setting agent,
After manufacturing the base concrete, put it into the drum of the track agitator, add the quick setting aid to the base concrete in the drum of the track agitator, knead, pump this kneaded concrete, and at the tip of the spray nozzle A method for constructing shotcrete characterized by adding a liquid quick-setting agent. The method for constructing shotcrete according to claim 1 or 2, wherein the liquid quick setting agent contains aluminum sulfate as an active ingredient.