JP3087940B2 - High-strength wet spray concrete - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
Spraying concrete using quick-setting material mainly composed of ground and raw concrete, particularly high-strength wet spraying in the wet spraying method for construction work such as tunnels and underground structures Related to spray concrete.

[0002]

2. Description of the Related Art In a construction work of an excavated tunnel or underground space, a method of spraying concrete on an exposed surface and lining the surface to prevent the surface from collapsing is widely used.

[0003] As a concrete spraying method, a dry method and a wet method are known. The dry method is a method in which a quick-setting material is added to a kneaded material obtained by kneading cement and aggregate and supplied to a spraying device, and water is added and mixed during transportation by compressed air to spray. On the other hand, the wet construction method is a construction method in which raw concrete is supplied to a spraying device, and while being transported by compressed air, a quick-setting material is pressed in, mixed and sprayed on the way. This wet method has become the mainstream of the spraying method because it has the advantage of less dust generation than the dry method, and is easy to control the quality of the concrete and can obtain stable strength. .

A typical raw concrete used in the wet spraying method uses ordinary Portland cement as a cement, and has a unit cement amount of 350 to 370 kg / m ³ and a water cement ratio of 55 to 70% by mass. A quick-setting material containing calcium aluminate as a main component (e.g., a quick-setting material described in JP-A-63-112448) is used in an amount of 5 to 5% as cement.
10% by mass is added. The compressive strength of such a spray concrete is about 200 to 300 kgf / cm ^{2 in} 28 days of age.

[0005] Usually, after the construction of the spray concrete, the concrete is further poured into the inside of the spray concrete, and the secondary lining is applied. That is, the spray concrete itself has been constructed as a temporary temporary structure.

[0006]

By the way, recently,
For the purpose of shortening the construction period and reducing the cost, it has begun to try to eliminate the secondary lining after spraying concrete construction, or to construct with a simple secondary lining with precast concrete plate. I have. In order to carry out the construction in this way, a higher strength is required because the spraying concrete requires a higher support effect than in the past. There was a tendency for elongation of strength to deteriorate.

Therefore, the present inventors have developed a spray concrete.
As a result of intensive research on the technology to improve the strength of a 28-day-old spray-molded product to a compressive strength of 500 kgf / cm ² or more without impairing the quick-setting property essential to SUMMARY OF THE INVENTION It is an object of the present invention to provide a quick-setting, high-strength wet type which has a high strength and can provide a significantly higher support effect than conventional spray concrete in an underground structure such as a tunnel. To provide a spray concrete.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a wet shotcrete made of a quick-setting material mainly composed of calcium aluminate and a ready-mixed concrete. Anhydrous gypsum is preliminarily divided into 1.0 to 5.0 with respect to the main binding material.
Using a binder added by mass%, the amount of the binder being 40
In 0~600kg / m ^3, and water binder ratio is 50 mass%
It is characterized by using the following, and by using such a ready-mixed concrete, when a molded body molded by wet spraying is cured at 20 ° C., 500 k
An object of the present invention is to provide a high-strength wet shotcrete having an effect of exhibiting a compressive strength of gf / cm ² or more.

That is, the present invention relates to a wet-type shotcrete comprising a quick-setting material containing calcium aluminate as a main component and a ready-mixed concrete, wherein the ready-mixed concrete is made of an early-strength Portland cement. anhydrous gypsum was binding material used comprising previously adding 1.0 to 5.0 wt%, the binder amount in 400~600kg / m ^3, the
A high-strength wet shotcrete having a water binder ratio of 50% by mass or less. (Claim 1), and the binding main material is 100 to 40 parts by mass of early-strength Portland cement and 0 to 60 blast furnace slag fine powder.
It consists of parts by mass (claim 2).

Hereinafter, the present invention will be described in detail. In the present invention, the term "bonding main material" means "early high-strength Portland cement alone or a mixture of early-strength Portland cement and blast-furnace slag fine powder". What is obtained by adding anhydrous gypsum to the main binding material ".

In the present invention, it is important to use early-strength Portland cement as the cement. The reason is that in the case of ordinary Portland cement, which is generally used in the construction of spray concrete, when a test piece molded by spraying is cured at 20 ° C, 500 kgf / cm ^{2 in} 28 days of material age.
This is because it is difficult to obtain the above high strength.

In the present invention, as the blast furnace slag fine powder used in combination with the early-strength Portland cement, as the fineness increases, the strength of concrete increases, but the fluidity tends to decrease. In terms of material ratio, the pumpability becomes poor. In addition, the Brain specific surface area is 10,0
Fine materials having a fineness exceeding 00 cm ² / g are not practical because of the large labor required for production. Therefore, in the present invention, the fineness of the blast furnace slag fine powder is 4,000 c
m ² / g or more, particularly preferably about 6,000 to 8,000 cm ² / g.

The anhydrous gypsum used in the present invention is a type II anhydrous gypsum, and the percentage of the anhydrous gypsum is based on the total amount of the early-strength Portland cement and the blast furnace slag fine powder.
Preferably, the content is 1.0 to 5.0% by mass. When the amount is less than 1.0% by mass, the effect of adding anhydrous gypsum does not clearly appear (Comparative Examples 4 and 5 described below).
On the other hand, when the content exceeds 5.0% by mass, a quick setting property indispensable for shotcrete is caused (see Comparative Example 6 described later), and neither is preferable.

As gypsum, hemihydrate gypsum and dihydrate gypsum are known in addition to anhydrous gypsum (type II anhydrous gypsum). However, when gypsum other than anhydrous gypsum is used, the quick-setting property of the concrete tends to decrease. Therefore, in the present invention, the use of anhydrous gypsum (II type anhydrous gypsum) is particularly preferred. The details of the difference in the effect on the quick-setting properties of concrete between anhydrous gypsum and other hemihydrate gypsum and dihydrate gypsum are unknown, but the solubility of hemihydrate gypsum and gypsum And the dissolution rate is significantly higher than that of anhydrous gypsum.

In the present invention, the fineness of the anhydrous gypsum is not particularly limited, but is preferably 3,000 cm ² / g or more in terms of the specific surface area of the gypsum. can do.

The method of mixing the anhydrous gypsum, the early-strength Portland cement and the blast furnace slag fine powder is not particularly limited in the present invention. For example, these three types of powders are mixed in advance at a predetermined ratio, and this is mixed. The raw concrete plant can be supplied, or the raw concrete can be weighed and put into a mixer during the production of the raw concrete, and the effect remains unchanged in either case.

An important point in the present invention is that a binder obtained by previously adding anhydrous gypsum to a binder mainly composed of early-strength Portland cement is used. That is, anhydrous gypsum is kneaded in advance during the production of the raw concrete which is the base material of the spray concrete. If anhydrous gypsum is added to or mixed with a quick-setting material containing calcium aluminate as a main component or mixed with this quick-setting material, the quick-setting property is impaired. It is not preferable.

The ratio of the early-strength Portland cement and the blast-furnace slag fine powder in the binder is 100 to 40 parts by mass,
The latter is preferably from 0 to 60 parts by mass. If the blast-furnace slag fine powder exceeds 60 parts by mass, quick-setting properties are impaired, and strength development is also deteriorated (see Comparative Example 10 described later), which is not preferable.

In the present invention, the total amount of the binder composed of the early-strength Portland cement, the blast-furnace slag fine powder and the anhydrous gypsum is 400 to 600 kg / m in ready-mixed concrete.
In m ^3, and is preferably water binding agent ratio is less than 50 wt%. More preferably, the unit amount of the binder is 500 to
600 kg / m ³ , the water binder ratio is 40% by mass or less (30
４０40% by mass).

When the unit amount of the binder is less than 400 kg / m ³ , or when the ratio of the water binder is more than 50% by mass, the strength is not sufficient, and 500 kgf / c after 28 days of material age.
It is not preferable because a compressive strength of m ² or more cannot be obtained. In the present invention, the lower limit of the water binder ratio is not particularly limited, but at an extremely low water binder ratio, the fluidity is reduced, and it is difficult to transport the concrete with compressed air. However, the lower limit is practically up to about 30% by mass. Similarly, binding material amount upper limit
Is extremely high, the fluidity decreases, and it becomes difficult to transport the concrete by compressed air, so practically 600 kg / m
Up to about ³ .

Examples of the quick-setting material containing calcium aluminate as a main component include "calcium aluminate 50 to 90% by weight and alkali carbonate 10 to 40% by weight" described in JP-A-63-112448. And quick-setting material for wet spraying concrete consisting of less than 0 to 10% by weight of alkali aluminate "
Alternatively, a quick setting for wet spraying of cement mortar or concrete comprising calcium aluminate in an amount exceeding 50% by weight and alkali carbonate in an amount of less than 50% by weight described in Japanese Patent Publication No. 7-25577. Material "can be used.

The present invention is not limited to concrete, but can be applied to spray mortar by replacing all coarse aggregate with fine aggregate, which is also included in the present invention. is there. The spraying concrete can be applied by any conventional wet method, and the present invention is not limited to a specific wet method.

[0023]

Next, examples of the present invention will be described together with comparative examples.
The present invention will be specifically described, but the present invention is not limited to the following examples.

Here, the materials used in the following Examples and Comparative Examples will be described together.・ Anhydrite: manufactured by Daiichi Cement Co., Ltd. [Brain specific surface area 78
00cm ² / g] ・ Cement: Portland cement made by Nippon Cement Co., Ltd .: Ordinary Portland cement made by Nippon Cement Co., Ltd. ・ Blast furnace slag: “Fine Cementment made by Daiichi Cement Co., Ltd.
20A (trade name) "[shake - down specific surface area of 6200cm ² / g] · Kyuyuizai: Nihon Cement Co., Ltd." Asanosu - Pas - Natomu (trade name) "[calcium aluminate - as a main component the door] and fine Aggregate: Fuji River water system sand [coarse grain ratio 2.8] ・ Coarse aggregate: crushed sand from Ome [maximum particle size 13mm] ・ Admixture: NMB-water reducing agent “NT-1000 (brand name)”

In the following Examples and Comparative Examples, tests of "rapid setting property of spray concrete" and "compression strength" are as follows. "Quick setting of spray concrete"
Evaluation was made visually and by touch. The `` compressive strength '' was measured with a specimen sprayed into a 15 × 15 × 53 cm form when the material age was 24 hours, and when the material age was 28 days, it was molded by spraying it into a wooden box. A core having a diameter of 10 cm and a height of 20 cm was cut out from the concrete block and measured.

The test block sprayed into a 15 × 15 × 53 cm formwork and the concrete block sprayed into a wooden box are:
Cured to the prescribed age in a room at 20 ± 3 ° C. Spraying was carried out using a "need gun" manufactured by Nippon Pribrico and a "Q gun" manufactured by Nippon Priblico as a quick-setting material supply device. In both the examples and the comparative examples, the supply device of the quick setting material was adjusted so that the addition rate of the quick setting material was 6% by mass with respect to the binder.

(Examples 1 to 7, Comparative Examples 1 to 3)
As shown in Table 2, spraying experiments were carried out while changing the composition of the concrete, and quick setting and compressive strength were measured. As the binder, a mixture of early strength Portland cement mixed with anhydrous gypsum at an internal ratio of 2.0% by mass was used.

Comparative Example 1 is a performance test of a normal spray concrete using ordinary Portland cement. The content of this concrete was 60% by mass of fine aggregate and no water reducing agent was added. The slump was 12 cm. The raw concretes of Examples 1 to 7 and Comparative Examples 2 and 3 have slumps.
It was prepared by changing the fine aggregate ratio and the addition ratio of the water reducing agent so as to be 14 ± 2 cm. Table 1 shows the results.

[0029]

[Table 1]

As is clear from Table 1, in Examples 1 to 7 in the range of the amount of the binder ( 400 to 600 kg / m ³ ) and the water binder ratio (50% by mass or less) specified in the present invention,
A material having a high compressive strength of a material age of 28 days or more of 500 kgf / cm ² or more was obtained.

On the other hand, Comparative Example 1 using ordinary Portland cement and using early-strength Portland cement, but the amount of binder was 350 kg / m outside the range specified in the present invention.
³ Comparative Example 2 was used, both wood age 28 days compressive strength was 500 kgf / cm ² or less of ^{262kgf / cm 2, 342kgf / cm} 2. In addition, using early strength Portland cement, the amount of binder is 500 kg / m ³ within the range specified in the present invention,
In Comparative Example 3 in which the water binder ratio was 55% by mass outside the range specified in the present invention, the quick setting property was slightly poor, and the material age was 28%.
The daily compressive strength was 381 kgf / cm ² .

(Examples 8, 9 and Comparative Examples 4 to 8)
As shown in (1), raw concrete was manufactured by using a pre-mixed and pre-mixed material in the early-strength Portland cement by changing the proportion of anhydrous gypsum, and a spraying construction experiment was performed using this and the quick-setting material, and Quick setting and compressive strength were measured
(Examples 8, 9 and Comparative Examples 4 to 6). Also, as a comparison,
Spraying of a combination of ordinary Portland cement and anhydrous gypsum was performed in the same manner (Comparative Examples 7 and 8). Table 2 shows the basic composition of the raw concrete used in Examples 8 and 9 and Comparative Examples 4 to 8. The slump was adjusted by adding the water reducing agent. Table 3 shows the results. Table 3 also shows Example 3 (an example in which anhydrous gypsum was mixed with early-strength Portland cement at 2.0% by mass).

[0033]

[Table 2]

[0034]

[Table 3]

From Table 3, it can be seen that in Examples 8 and 9 in which the addition amount of anhydrous gypsum to the binder (1.0 to 5.0% by mass) specified in the present invention is within the range, the compressive strength of 28 days old is intended by the present invention. Do
High strength of 500 kgf / cm ² or more was obtained.

On the other hand, in Comparative Examples 4 and 7 where no gypsum was added, 411 of 500 kgf / cm ² or less intended in the present invention was used.
kgf / cm ^2, it was 381kgf / cm ^2. In addition, even when anhydrous gypsum was added, the amount of the additive was out of the range specified in the present invention in Comparative Examples 5 and 6, and even though the amount was in the range specified in the present invention, ordinary Portland cement was used. In Comparative Example 8 using No. 6, no compression strength intended in the present invention was obtained.

(Comparative Example 9) The quick setting properties of the case where anhydrous gypsum was added to the ready-mixed concrete together with the cement and the like and the case where it was mixed with the quick-setting material and then added to the ready-mixed concrete were compared. . The anhydrous gypsum equivalent to 2.0% by mass added to Example 3 was mixed with a quick setting material also equivalent to 6.0% by mass, and the mixture was mixed at the same blending ratio as in Example 3 except for anhydrous gypsum (unit bonding). A wet spraying experiment was carried out by press-fitting the raw concrete with a material weight of 500 kg / m ³ ). As a result, the quick setting property of the concrete was worse than that of Example 3, and dripping and peeling after adhesion were remarkable.

(Examples 10 to 12 and Comparative Example 10) As shown in Table 4 below, raw concrete was manufactured by changing the ratio of the early-strength Portland cement and the blast-furnace slag fine powder as the binder, and spraying was performed. Experiments were performed to determine the quick setting and compressive strength. The addition rate of anhydrous gypsum was constant at 2.0% by mass of the main binder. The basic composition of the raw concrete is the same as in Table 2 described above. Table 4 shows the results. Table 4 shows Example 3 (anhydrous gypsum in early strength Portland cement, 2.0%
Mass%) is also shown.

[0039]

[Table 4]

As is apparent from Table 4, in Examples 10 to 12 in which the early-strength Portland cement and the blast furnace slag fine powder of 60% by mass or less were used as the binding main material, the fast-strength Portland cement plain binding main material was used. It was recognized that the 28-day-old compressive strength was improved as compared with Example 3 used. On the other hand, in Comparative Example 10 in which the binder was used in which a large amount of blast furnace slag fine powder was blended as much as 70% by mass, the quick-setting properties were slightly poor, and the 28-day compressive strength was as low as 391 kgf / cm ^2. Met.

[0041]

As described in detail above, the high-strength wet-spray concrete according to the present invention has an effect of obtaining a significantly higher strength than the conventional wet-spray concrete. Therefore, according to the present invention, in a subterranean structure such as a tunnel, a remarkably higher support effect can be obtained as compared with the conventional spray concrete, and the practical value is extremely high.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C04B 22:14 18:14 24:00) 103: 12 111: 00 (56) References JP-A-3-122040 (JP, A JP-A-6-33057 (JP, A) JP-A-63-112448 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 28/04 C04B 22/08 C04B 103: 12

Claims (2)

(57) [Claims] 1. A wet shotcrete comprising a quick-setting material mainly composed of calcium aluminate and a ready-mixed concrete, wherein the ready-mixed concrete is obtained by adding anhydrous gypsum to a binding main material based on an early-strength Portland cement in advance. A binder obtained by adding 1.0 to 5.0 mass% is used, the amount of the binder is 400 to 600 kg / m ³ , and the water binder ratio is 5
High-strength wet shotcrete characterized by being at most 0 mass%. 2. The high-strength wet spray concrete according to claim 1, wherein the main binder comprises 100 to 40 parts by mass of early-strength Portland cement and 0 to 60 parts by mass of blast furnace slag fine powder. G.