JPH08245255A - Low powder spraying concrete composition - Google Patents

Abstract

PURPOSE: To enable application with a general-purpose device without increasing the force feed resistance in a spraying device at the time of application by specifying the compounding ratio of a dust decreasing agent and the slump value by a high-performance water-reducing agent of a concrete compsn. CONSTITUTION: Normal Portland cement and, according to conditions, high-early- strength Portland cement and blast furnace cement are used as cement components. Aggregate including natural, artificial and by-product aggregate all having the max. grain size of about 15mm is compounded therewith at 50 to 80wt.% of the total weight of the compsn. and water is compounded therewith at 50 to 65 pts.wt. per 100 pts.wt. cement component according to a dry or wet system of the compounding ratio of ordinary spraying concrete. A quick setting agent which may be an inorg. salt-based or cement-based agent is compounded with the compsn. at 5 to 7 pts.wt. per 100 pts.wt. cement component and a powder decreasing agent which is of a cellulose-, acrylic-, acrylamide- or polyvinyl alcohol- based agent, at 1.0 to 0.3 pt.wt. per 100 pts.wt. cement component. The high-performance water reducing agents are compounded with the compsn. in such a manner that the slump value attains 15.0 to 22.0cm.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is applicable to underground structures such as tunnels, shotcrete used for repairing and reinforcing existing concrete, covering excavation slopes, reinforcing, and the like, particularly in tunnel construction. The present invention relates to a low dust sprayed concrete composition that can be used when the NATM method is used.

[0002]

2. Description of the Related Art Conventional sprayed concrete contains cement, aggregate, water, quick-setting agent, etc. as active ingredients. For example, a cellulosic thickener for suppressing dust amount during construction, Dust reducing agents such as acrylic thickeners and reinforcing materials such as steel fibers are added for reinforcing concrete after spraying.

As a spraying device for constructing such sprayed concrete, a rotor type having a nozzle,
Pump type devices are usually used, but at present, various improved devices are used depending on the concrete composition. For example, when the dust reducing agent is blended, the viscosity of the concrete composition increases, and it is necessary to increase the pressure-feeding resistance that conveys the composition to the nozzle. Therefore, a spraying device with an increased pressure-feeding force is used. Has been done.
A method is also known in which the dust reducing agent is conveyed in a separate system, and is mixed with the concrete composition at the tip of the nozzle and sprayed, but in this case as well, a separate system pipe for supplying the dust reducing agent must be provided.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a sprayed concrete composition containing a dust reducing agent and effectively reducing the amount of dust at the time of construction. It is an object of the present invention to provide a low-dust sprayed concrete composition that can be sprayed by a general-purpose device without causing an increase in pumping resistance.

[0005]

According to the present invention, in a sprayed concrete composition containing a cement component, aggregate, water, a quick-setting agent and a dust reducing agent, the mixing ratio of the dust reducing agent is set to the cement component. 0.1 to 0.
A low-dust sprayed concrete composition is provided which is 3 parts by weight and further blended with a high-performance water reducing agent to give a slump value of 15.0 to 22.0 cm.

The present invention will be described in more detail below. The composition of the present invention contains a cement component, an aggregate, water, a quick-setting agent, a dust reducing agent and a high-performance water reducing agent as active ingredients, and in particular, the mixing ratio of the dust reducing agent and the high-performance water reducing agent is a specific amount. Therefore, even when the dust reducing agent is blended, the pressure-feeding pressure (for example, 50 to 100 kgf / c) in an ordinary spraying device is used.
It has fluidity that can be sprayed at m ² ) and can sufficiently suppress dust generation during construction.
This composition can be used for spraying concrete in underground structures such as tunnels, repairing and reinforcing existing concrete, covering excavation slopes and reinforcing.

As the above-mentioned cement component, usually ordinary Portland cement can be used, but depending on the spraying place and conditions, early strength Portland cement or blast furnace cement can also be used.

The aggregate is not particularly limited as long as it is one that is usually used in concrete, and natural aggregate,
Both artificial aggregates and by-product aggregates can be used.
The maximum particle size is preferably about 15 mm, and it is desirable that the particle size is not flat or angular. The blending ratio of the aggregate is not particularly limited, but is preferably 50 to 80% by weight, and particularly preferably 70 to 80% by weight based on the total amount of the composition.

The water may be added in a mixing ratio usually used for shotcrete, and can be mixed according to a dry method or a wet method. For example, it is desirable to mix the cement component in an amount of 50 to 65 parts by weight with respect to 100 parts by weight.

The quick-setting admixture is a component for exerting concrete strength early after construction, and both an inorganic salt-based quick-setting admixture and a cement-based quick-setting admixture can be used. It can be appropriately selected and blended according to the conditions. The mixing ratio of the quick-setting agent is not particularly limited, and is preferably 5 to 7 parts by weight with respect to 100 parts by weight of the cement component.

The dust reducing agent is a component that suppresses dust during spraying, and is hydroxyethyl cellulose,
Cellulose dust reducing agents such as hydroxymethyl cellulose and cellulose ether; acrylic dust reducing agents; acrylamide dust reducing agents such as polyacrylamide; polyvinyl alcohol dust reducing agents such as polyethylene oxide. The mixing ratio of the dust reducing agent is 0.1 to 0.3 with respect to 100 parts by weight of the cement component.
Parts by weight, preferably 0.2 to 0.25 parts by weight.
If it is less than 0.1 parts by weight, the desired dust suppressing effect cannot be obtained, and if it exceeds 0.3 parts by weight, the viscosity increases,
The desired fluidity cannot be obtained, and the desired slump value cannot be obtained even by blending a high-performance water reducing agent described later.

The high-performance water reducing agent is a component that imparts fluidity when it is made into shotcrete, and includes a high-performance AE water reducing agent in addition to the usual high-performance water reducing agent. Specifically, polyglycol ester, naphthalene sulfonic acid formalin high condensate, sulfonated melamine formalin condensate, polystyrene sulfonate, hydroxypolyacrylate, copolymer of unsaturated dicarboxylic acid and olefin, isobutylene-styrene maleic acid. Examples of the copolymer include an isobutylene-acrylic acid ester-maleic acid copolymer, an isobutylene-styrene-acrylic acid ester-maleic copolymer, and an aromatic aminosulfonic acid polymer compound. The blending ratio of the high-performance water reducing agent is such that the slump value of the shotcrete during spraying is 15.0 to 22.0 cm, preferably 18.0.
It is blended appropriately so as to be 20.0 cm. If the slump value is less than 15.0 cm, the flowability of the shotcrete concrete composition is insufficient, and if it exceeds 22.0 cm, the fluidity is sufficient, but the separation of other components such as aggregates. Occurs, and a uniform composition cannot be obtained. The mixing ratio of the high-performance water reducing agent may be set to the slump value and can be appropriately selected according to other compositions. For example, 0.5 to 2.0 with respect to 100 parts by weight of the cement component. It can be blended in the range of parts by weight. The slump value is a value measured according to JIS A 1101 (concrete slump test method).

In the composition of the present invention, in addition to the above-mentioned essential components, various fiber reinforcing materials such as steel fibers, AE agents, etc. are blended within the range where the slump value and low dust resistance are secured. You can also At this time, when the high-performance AE water reducing agent is used as the high-performance water reducing agent, the AE agent is already blended. It is desirable to adjust the air content in the composition of the present invention to preferably 4 to 6% by this AE agent because the fluidity of the composition, the material separability and the like can be easily adjusted.

To prepare and use the compositions of the present invention,
For example, it can be prepared by a method such as adding a dust reducing agent to a cement component, aggregate, water, and a quick-setting agent, and further adding a high-performance water reducing agent and uniformly stirring and mixing in a raw plant or on-site. . The prepared composition can be sprayed from the nozzle onto the spraying surface by a normal spraying device with a normal pressure-feeding pressure of 50 to 100 kgf / cm ² .

[0015]

The shotcrete composition of the present invention is
Since the dust reducing agent and the high-performance water reducing agent are mixed in a predetermined amount and the slump value is adjusted within a predetermined range, the dust concentration is 5 mg / m.
^{It is} possible to maintain the low dustiness of ³ or less and the rebound rate of 25% or less, and to spray by normal pressure feeding pressure by a general-purpose spraying device. Therefore, even if a dust reducing agent (thickener) is added, sufficient construction capacity (for example, 5 m ³
/ Hr or more).

[0016]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples below, but the present invention is not limited thereto.

[0017]

Example 1 Normal Portland cement (specific gravity 3.1)
6, specific surface area 3350 cm ² / g) 360 parts by weight, river sand (specific gravity 2.655, water absorption 1.98%, coarse grain ratio 2.8)
0) 1036 parts by weight, river gravel (specific gravity 2.68, water absorption 1.00%, maximum particle size 15 mm) 690 parts by weight, cement mineral powder quick setting agent 25 parts by weight and river water 202 parts by weight are mixed. Then, 0.9 parts by weight of cellulose ether as a dust reducing agent and 4.7 parts by weight of polyglycol ester as a high performance water reducing agent were uniformly stirred and mixed to prepare a shotcrete concrete composition. The water-cement ratio (W / C) of the obtained composition was 56%, and the amount of air was 4.5 ± 1.5.
%, Fine aggregate ratio (s / a) is 60%, JIS A1101
The slump value measured by the method was 20 ± 2.5 cm.

Next, the composition thus obtained was applied to a spraying device (piston type concrete pump type, pressure feeding pressure 50 to 100 kg).
f / cm ² ) and sprayed on the bedrock at a speed of 6.7
Sprayed at m ³ / hr. Each measurement shown below was performed. Table 1 shows the results.

Dust concentration; spraying with a digital dust meter 1
The dust concentration was measured after 6 minutes. Bounce rate: It was calculated by spraying 2 m ^{3 of} concrete and measuring the weight of the dropped sample. Pull-out test: Measured by KODAN 702. Core compressive strength; measured by KODAN 704.

[0020]

[Table 1]

[0021]

Comparative Example 1 A composition was prepared in the same manner as in Example 1 except that the superplasticizer was not added. The water-cement ratio (W / C) of the obtained composition was 56%, and the amount of air was 4.5 ± 1.5.
%, Fine aggregate ratio (s / a) is 60%, JIS A 1101
The slump value measured by the method was 8 ± 2 cm. Next, when the composition thus obtained was charged into a spraying apparatus similar to that in Example 1 and spraying was attempted, the viscosity of the composition was high and spraying could not be sufficiently carried out.

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Claims (1)

[Claims] 1. A sprayed concrete composition containing a cement component, aggregate, water, a quick-setting agent and a dust reducing agent, wherein the mixing ratio of the dust reducing agent is 0.1 to 100 parts by weight of the cement component. A low dust sprayed concrete composition, characterized in that the slump value is 15.0 to 22.0 cm by adding 0.3 parts by weight and a high performance water reducing agent.