JP2001322852A - Slump-reducing, spraying admixture, spraying cement concrete and spraying method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a slump-reducing, spraying admixture which is capable of drastically reducing the slump value of cement concrete when spraying work with the cement concrete is executed, preventing concrete drooling from being caused and adjusting concrete hardness to a value appropriate to perform trowelling of the concrete after spraying. SOLUTION: This admixture comprises a clay mineral and a water-absorbing high polymer compound and optionally, further additionally contains an aluminum-containing material, an alkali metal carbonate and/or a calcareous material(s).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention preferably uses a spray admixture for reducing slumps added to cement concrete when spraying cement concrete on slopes to prevent landslides and rocks from falling, and the like. It relates to spraying cement concrete and spraying method. In the present invention, mortar and concrete are collectively called cement concrete.

[0002]

2. Description of the Related Art Conventionally, concrete has been sprayed to stabilize a slope in order to prevent landslides on the slope and collapse of rocks and the like.

[0003] As a method for stabilizing the slope, usually, concrete is supplied to a concrete pump installed on a flat place, the concrete is transported through a pipe, and mixed with compressed air during the transportation, and the slope is sloped. Spraying method. In this method, ironing is often performed after spraying, and a component that promotes the setting and hardening of cement, such as a quick setting agent, is not used, or even if a component that promotes the setting and hardening of cement is used, Only a component having a low coagulability is added.

[0004] In addition, as a method of stabilizing the slope, there is also known a greening method in which a vegetation base is formed by spraying in order to finish the landscape as harmonious as possible without leaving a trace of spraying work. Have been. In this method, a water retention material containing a water-absorbing polymer is used to improve the water retention of the vegetation base.

[0005]

However, the slope is often a steep cliff with a steep slope, and when spraying the entire slope, a concrete pump is installed on a flat ground and the place where the spray can be performed. It is necessary to transport concrete up to the pipe. If soft concrete is supplied in consideration of pumpability, there is a problem that the concrete flows down the slope after spraying, and it is not possible to carry out sufficient construction.

[0006] On the other hand, the use of concrete having a certain degree of hardness lowers the pumpability. For this reason, when spraying on a vast slope, the concrete transportation distance will be long, so a concrete pump must be added during the transportation of concrete, which is extremely disadvantageous in terms of workability and economic efficiency. There was a problem of becoming.

[0007] The present invention has been made in order to solve the above problems, and the purpose of the present invention is to provide a slump-reducing spray admixture of the present invention, even if the slump of cement concrete is as soft as 15 cm or more. An object of the present invention is to provide a spray admixture for slump reduction, which does not run down a slope, has good pumping properties, is easy to iron, and has good workability.

[0008]

That is, the present invention relates to a spray admixture for reducing a slump, comprising a clay mineral and a water-absorbing polymer compound, and further comprising an aluminum-containing substance. The present invention is a spray admixture for reducing slump, which further comprises an alkali metal carbonate and / or lime. A sprayed cement concrete comprising cement and the spray admixture for reducing slump. The spraying method is characterized in that the slump reducing spray admixture and the cement concrete obtained by carrying air in the pipe are mixed and mixed immediately before spraying to the construction site and sprayed.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The slump reducing spray admixture of the present invention (hereinafter referred to as a slump reducing agent) reduces the fluidity of cement concrete sprayed during slope spraying work immediately before spraying. 7 for cement concrete without admixture
It means that a slump can be reduced by 0% or more. Therefore, the fluidity of the cement concrete sprayed on the slope is reduced, and the cement concrete does not run down from the slope having a steep slope after spraying, and has a hardness sufficient to perform ironing. Of cement concrete is obtained.

[0011] The cement of the present invention is generally available on the market in the form of various types of Portland cements such as ordinary, fast, medium heat, super fast, and low heat, and various mixed cements obtained by mixing fly ash, blast furnace slag, etc. with these portland cements. ,
And commercially available fine particle cement and the like. Portland cement or mixed cement may be used after being pulverized.

The clay mineral of the present invention exhibits water absorbency in the presence of water, and also decreases the fluidity of cement concrete and increases tackiness.

Examples of the clay mineral include beidellite, kaolinite, halloysite, montmorillonite, pyrophyllite, vermiculite, mica, chlorite, saponite, sepiolite, and acid clay, which are mainly composed of layered aluminosilicates. May be used alone or in combination. Among them, bentonite containing montmorillonite as a main component is preferable because it is easily gelled when a metal ion having a valence of 2 or more such as aluminum ion or calcium ion is present, and is produced in large quantities at low cost.

The water-absorbing polymer compound of the present invention exhibits water absorption in the presence of water, and also decreases the fluidity of cement concrete and increases the adhesiveness.

As the water-absorbing polymer compound, poly-N-
3-dimensional crosslinked polymer containing vinylacetamide as a main component, starch-polyacrylonitrile copolymer, saponified vinylester-ethylenically unsaturated carboxylic acid copolymer, self-crosslinked polyacrylic acid salt obtained by reversed phase suspension polymerization method Examples thereof include a reaction product of a polyvinyl alcohol-based polymer and a cyclic acid anhydride, a polyacrylate cross-linked product, and a vinyl alcohol-acrylate copolymer, but are not particularly limited as long as they exhibit water absorption. Not something.

The particle size of the water-absorbing polymer compound is preferably 500 μm or less from the viewpoint that the water absorption rate is high and the fluidity of cement concrete is easily reduced instantaneously.

The water absorption capacity of the water-absorbing polymer compound is determined to be 1% of its own weight because the fluidity of cement concrete is apt to decrease.
0 times or more is preferable, and 30 times or more is more preferable.

The amount of the water-absorbing polymer compound used is preferably 0.05 to 30 parts by mass, more preferably 0.2 to 20 parts by mass, based on 100 parts by mass of the clay mineral. If the amount is less than 0.05 parts by mass, the fluidity of the cement concrete does not decrease when used in combination with the clay mineral, and the sprayed cement concrete may not flow down the slope, and if it exceeds 30 parts by mass, the strength expression may be impaired. There is.

In the present invention, it is preferable to further include an aluminum-containing substance in the spray admixture for reducing slump.

The aluminum-containing material of the present invention reduces the fluidity of sprayed cement concrete and increases the initial strength. As the aluminum-containing substance, one or more members selected from the group consisting of alkali metal aluminates such as sodium aluminate, potassium aluminate, and lithium aluminate, aluminum sulfate, aluminum hydroxide, and calcium aluminates are preferable. Among these, calcium aluminates are preferred from the viewpoint of strength development.

Calcium aluminates are CaO and Al ₂ obtained by mixing a raw material containing calcia and a raw material containing alumina, followed by heat treatment such as firing in a kiln or melting in an electric furnace. O ₃ is a general term for a substance having hydration activity and having a main component of CaO and / or Al ₂
Part of O ₃ is an alkali metal oxide, an alkaline earth metal oxide, silicon oxide, titanium oxide, iron oxide, an alkali metal halide, an alkaline earth metal halide, an alkali metal sulfate, and an alkaline earth metal. It is a substance obtained by dissolving a small amount of a compound substituted with a sulfate or the like, or a compound containing CaO and Al ₂ O ₃ as main components. The mineral form may be either crystalline or amorphous.

Among calcium aluminates, amorphous calcium aluminates are preferable from the viewpoint of reaction activity, and a non-heated product obtained by quenching a heat-treated product corresponding to a 12CaO · 7Al ₂ O ₃ (C ₁₂ A ₇ ) composition is preferred. Crystalline calcium aluminate is more preferred.

The particle size of the calcium aluminate is preferably 3000 cm ² / g or more in terms of Blaine value, and is preferably 4000 cm ² / g.
cm ² / g or more is more preferable. If it is less than 3000 cm ² / g, there is a possibility that a sufficient effect of reducing fluidity may not be obtained.

The amount of the aluminum-containing substance to be used is preferably 0.5 to 100 parts by mass, more preferably 2 to 50 parts by mass, per 100 parts by mass of the clay mineral. If it is less than 0.5 parts by mass, the fluidity of the sprayed cement concrete does not decrease,
The sprayed cement concrete may flow down the slope, and the initial strength increasing effect may be small. If it exceeds 100 parts by mass, the curing may be too fast, and the ironing work afterwards may be difficult.

In the present invention, it is preferable that the alkali metal carbonate and / or lime is further contained in the spray admixture for reducing slump.

The alkali metal carbonate of the present invention improves the initial strength. Examples of the alkali metal carbonate include sodium carbonate, potassium carbonate, lithium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, and lithium hydrogen carbonate. Among them, sodium carbonate is preferred because of its large initial strength effect.

The use amount of the alkali metal carbonate is preferably 5 to 300 parts by mass with respect to 100 parts by mass of the clay mineral.
15 to 150 parts by mass is more preferred. If the amount is less than 5 parts by mass, the strength may be impaired. If the amount exceeds 300 parts by mass, the fluidity may increase, and the sprayed cement concrete may flow down the slope to impair the long-term intensity.

The limes of the present invention improve the initial strength. Examples of the limes include quick lime and slaked lime. Of these, slaked lime is preferred because it does not significantly affect the strength development.

The amount of lime used is preferably 5 to 150 parts by mass, more preferably 15 to 50 parts by mass, based on 100 parts by mass of the clay mineral. If the amount is less than 5 parts by mass, the fluidity does not decrease, and it may be difficult to improve the initial strength expression. If it exceeds 150 parts by mass, the long-term intensity expression may be impaired.

The amount of the slump reducing agent of the present invention is preferably 1 to 8 parts by mass with respect to 100 parts by mass of cement.
2 to 4 parts by mass are more preferred. If the amount is less than 1 part by mass, the effect of reducing the slump is not recognized, and the sprayed cement concrete may flow down the slope, and if it exceeds 8 parts by mass, the strength development may be impaired.

The water-cement ratio (W / C) of the present invention is 30 to
70% is preferred. If it is less than 30%, the viscosity of the cement concrete becomes large, which impairs the pumping performance, and the spraying workability may be reduced. If it exceeds 70%, it may adversely affect the strength development and the coagulation property. .

The aggregate of the present invention is not particularly limited, but preferably has as high an aggregate strength as possible. Examples of the aggregate include fine aggregate and coarse aggregate. Examples of fine aggregate include sea sand, mountain sand, and river sand, which are natural aggregates collected from the sea, mountains, and rivers, and crushed stones (eg, lime sand, etc.) cut out from mountains, crushed, and adjusted in particle size. Examples of the coarse aggregate include river gravel as natural aggregate and lime gravel as crushed stone.

In the present invention, by mixing a slump reducing agent immediately before spraying on a slope, a spray cement concrete with reduced slump is obtained, and the slope can be sprayed.

As a method of mixing the slump reducing agent, there is a method of using a device for transporting by pneumatic transportation, and mixing and mixing the cement concrete which is pneumatically transported through a Y-shaped pipe and the slump reducing agent. When it is desired to suppress the generation of dust and the like, spraying may be performed by adding a dust reducing agent to the cement concrete side in advance, or making a slump reducing agent into a slurry.

As the spraying method of the present invention, either a dry spraying method or a wet spraying method can be used. In the case of spraying as concrete, for example, cement, aggregate, and water are put into a concrete mixer at a concrete manufacturing plant, kneaded and mixed, transported to a spraying site by an agitator truck, and conveyed by air with a spraying machine, and mixed. There is a method of spraying by combining with a slump reducing agent in a pipe. or,
When spraying as mortar, mortar is manufactured in a concrete manufacturing plant and sprayed, or dry mortar premixed with cement and dried fine aggregate is kneaded with water by a continuous mixer or batch kneading mixer, and air transported Then, there is a method in which the mixture is sprayed with the slump reducing agent by a mixing pipe.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a detailed description will be given based on embodiments.

Experimental Example 1 Using a 10 liter mortar mixer, cement 1
00 parts by mass, 300 parts by mass of fine aggregate, 0.5 parts by mass of water reducing agent, and 55 parts by mass of water were mixed, and a slump 18 ± 2 cm
Was prepared. In a mortar, 100 parts by mass of a clay mineral, 10 parts by mass of a water-absorbing polymer compound, 10 parts by mass of an aluminum-containing substance, and 5 parts by mass of an alkali metal carbonate shown in Table 1
3 parts by mass of the slump reducing agent consisting of 0 parts by mass was mixed with 100 parts by mass of the cement, and the mixture was stirred for 10 seconds. After that, sagging and compressive strength were measured. Table 1 shows the results.

(Materials used) Cement: ordinary Portland cement, specific gravity 3.16,
Commercially available fine aggregate: river sand from Himekawa water system, Niigata prefecture, specific gravity 2.62 Water reducing agent: polycarboxylic acid-based high-performance water reducing agent Clay mineral: bentonite containing montmorillonite as a main component, commercially available water-absorbing polymer compound: poly-N -A three-dimensional crosslinked polymer containing vinylacetamide as a main component, particle size 25 µm, water absorption 30 times, commercially available aluminum-containing substances: calcium aluminates, amorphous C ₁₂ A ₇ , specific gravity 2.92, Blaine specific surface area 590
0 cm ² / g alkali metal carbonate: commercial product, sodium carbonate

(Measurement Method) Water Absorption Ratio: A water-absorbing polymer compound was immersed, and the water absorption ratio =
It was calculated from the formula of [(mass of swollen water-absorbing polymer compound) / (mass of charged water-absorbing polymer compound)]-1. Drip: Spray mortar is sprayed on an inclined surface having a slope of 100/1000, and the case where spray mortar is not dripped at all is marked as O. When there was no, it was evaluated as x. Compressive strength: Specimens were prepared in a mold frame of 4 cm × 4 cm × 16 cm, and the compressive strength of a predetermined age was measured.

[0040]

[Table 1]

Experimental Example 2 100 parts by mass of a clay mineral, 1 part by mass of a water-absorbing polymer compound,
The procedure was performed in the same manner as in Experimental Example 1 except that a slump reducing agent composed of 50 parts by mass of the aluminum-containing substance and 50 parts by mass of the alkali metal carbonate shown in Table 2 was mixed, and slump, sag and workability were measured. Table 2 shows the results.

(Measurement method) Slump: According to JIS A 1118. Workability: A spray mortar was sprayed on a mold having a width of 10 cm, a length of 40 cm and a thickness of 10 cm, and the surface of the mold was habitually molded with a trowel and the workability of the trowel finish was evaluated. The case where molding was easily performed without applying force to the hand was evaluated as ○, the case where molding was performed when applying force was evaluated as △, and the case where molding was impossible even when force was applied was evaluated as x.

[0043]

[Table 2]

Experimental Example 3 100 parts by mass of clay mineral, 1 part by mass of water-absorbing polymer compound,
A slump reducing agent consisting of 10 parts by mass of an aluminum-containing substance and 50 parts by mass of an alkali metal carbonate was mixed in parts by mass shown in Table 3, and the same procedure as in Experimental Example 1 was carried out except that slump, sagging and compressive strength were measured. Was. Table 3 shows the results.

[0045]

[Table 3]

Experimental Example 4 100 parts by mass of clay mineral, 1 part by mass of water-absorbing polymer compound,
Same as Experimental Example 1 except that 10 parts by mass of an aluminum-containing substance and a slump reducing agent composed of limes and an alkali metal carbonate in parts by mass shown in Table 4 were mixed, and slump, sagging and compressive strength were measured. went. Table 4 shows the results.

(Materials used) Lime: Commercial product, slaked lime

[0048]

[Table 4]

Experimental Example 5 100 parts by mass of cement, 300 parts by mass of fine aggregate, 55 parts by mass of water, and 1.0 part by mass of a water reducing agent were mixed to prepare a mortar. The mortar was pressure-fed by 200 m with a squeeze pump. A confluence pipe is provided in the middle of the pressure feeding, and a slump reducing agent composed of 100 parts by mass of a clay mineral, 1 part by mass of a water-absorbing polymer compound, 10 parts by mass of an aluminum-containing substance, and 50 parts by mass of an alkali metal carbonate is added to 100 parts by mass of cement. 3
The air was conveyed from one of the mass part and the confluence pipe using a powder supply device, was mixed and mixed with the mortar by the confluence pipe, and was sprayed on a slope having a steep slope. The height difference between the position of the pump provided on the ground and the position where the slope was sprayed was 54 m. The slump of the mortar sprayed on the slope was less than 1 cm. The compressive strength is 6.9 N / m for one day of age.
m ² , and was 38.1 N / mm ² at a material age of 28 days. In addition, there is no dripping from the place where the slope was sprayed when spraying,
It could be confirmed that ironing was easy and there was no problem in strength development.

Experimental Example 6 For comparison, the same operation as in Experimental Example 5 was performed except that no slump reducing agent was used. The slump of the mortar sprayed on the slope was 23.0 cm. Further, when spraying, dripping was often observed from the point where the slope was sprayed, and it was difficult to finish the iron because the mortar dripped and flowed down.

Experimental Example 7 100 parts by mass of cement, 240 parts by mass of fine aggregate, coarse aggregate 6
0 parts by mass, 55 parts by mass of water, and 1.0 part by mass of a water reducing agent were mixed to prepare a concrete. The concrete was pumped 100 m by a concrete pump. A confluence pipe is provided in the middle of the pressure feeding, and a slump reducing agent composed of 100 parts by mass of a clay mineral, 1 part by mass of a water-absorbing polymer compound, 10 parts by mass of an aluminum-containing substance, and 50 parts by mass of an alkali metal carbonate is added to 100 parts by mass of cement. 3 parts by weight of the confluent pipe, air was conveyed from one of the converging pipes using a powder supply device, mixed and mixed with the concrete by the confluent pipe, and sprayed on a slope having a steep slope. The height difference between the position of the pump provided on the ground and the position of the place where the slope was sprayed was 21 m. The slump of concrete sprayed on the slope was less than 1 cm. or,
Compressive strength, 7.4 N / mm ² in one day the age, was 38.8N / mm ² at an age of 28 days. Furthermore, it was confirmed that there was no sagging from the place where the slope was sprayed when spraying, that ironing was easy, and that there was no problem with the strength development.

(Materials used) Coarse aggregate: gravel from Himekawa, Niigata Prefecture, specific gravity 2.64

Experimental Example 8 For comparison, the same operation as in Experimental Example 7 was carried out except that no slump reducing agent was used. The slump of concrete sprayed on the slope was 23.5 cm. Furthermore, dripping was often seen from the point where the slope was sprayed when spraying, and it was difficult to finish the iron because the mortar dripped and flowed down.

[0054]

The transportation distance of concrete has been long,
If there is a height difference between the position of the pump provided on the ground and the position of the point where the slope is sprayed, it is necessary to make the concrete slump 15 cm or more in consideration of the pumpability of the pump, and concrete with slump 15 cm or more There was a problem that it dripped when sprayed on the slope. However, the slump-reducing agent of the present invention can significantly reduce the slump of the cement concrete at the time of spraying, can prevent dripping, and can be adjusted to an appropriate hardness for ironing. Also, age 1
Good slope spraying can be performed without impairing the strength development on the day.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C04B 28/02 C04B 28/02 E02D 17/20 104 E02D 17/20 104B // C04B 103: 44 C04B 103: 44

Claims (5)

[Claims] 1. A spray admixture for slump reduction, comprising a clay mineral and a water-absorbing polymer compound. 2. The spray admixture for slump reduction according to claim 1, further comprising an aluminum-containing substance. 3. The spray admixture for slump reduction according to claim 1, further comprising an alkali metal carbonate and / or lime. 4. A sprayed cement concrete comprising a cement and the spray admixture for slump reduction according to claim 1. 5. The spray admixture for slump reduction according to any one of claims 1 to 3, and a cement concrete obtained by carrying air through a pipe, are mixed and mixed immediately before being sprayed to a construction site, and sprayed. A spraying method characterized by comprising: