JP5483695B2 - Crack-inhibiting spray material and spraying method using the same - Google Patents

Description

  The present invention mainly relates to a crack-suppressing type spraying material used in the civil engineering and construction industry and a spraying method using the same.

  In order to prevent collapse of exposed ground such as tunnel excavation, a spraying method using quick setting sprayed concrete in which a quick setting agent is mixed with concrete is performed (see Patent Document 1). This method usually involves preparing concrete at a cement, aggregate, and water metering and mixing plant installed at the excavation site, transporting it with an agitator car, pumping it with a concrete pump, It is a construction method that mixes with a quick-set agent fed from the other side and sprays it as a quick setting sprayed concrete onto a natural ground surface to a predetermined thickness.

In recent years, the concrete used for the spraying method has increased in the use of fine powders such as fly ash and blast furnace slag, the use of a large amount of cement and the combination of low water cement ratios for the purpose of improving water tightness and increasing strength. ing. In such a concrete blend, a water reducing agent is used in combination to ensure fluidity. Since spraying is performed by blowing concrete through pumping or air conveyance, it is considered that the higher the fluidity, the better the pumpability and the improved quality of the quick setting sprayed concrete.
However, control of fluidity with a water reducing agent will not provide sufficient fluidity if it is too small, and if it is too much, it will cause material separation, which will impair pumpability and also reduce the adhesion of sprayed concrete. In some cases, it was necessary to determine an appropriate range of use.
In addition, in order to maintain durability, it was necessary to suppress the occurrence of cracks due to drying until a secondary lining was applied or when a single shell structure was not applied. .

Short fibers are used to improve mechanical performance such as bending toughness and to prevent delamination of concrete pieces. (See Patent Document 2). Moreover, as an example of use of a short fiber, it is used for repair mortar for the purpose of suppressing shrinkage cracking (see Patent Documents 3 and 4).
However, when there is dust collection equipment as a countermeasure against dust, as in tunnel construction work, it always becomes an environment where wind acts on the spraying surface. In some cases, cracking due to shrinkage could not be sufficiently suppressed.
Conventional fibers include a monofilament type having a large fiber diameter and a converging type in which one fiber itself is as thin as 100 microns or less and is bundled into a bundle by an adhesive component. In addition to such fibers, fibrillated fibers are also known (see Patent Documents 5 and 6). Patent Document 5 relates to a repair mortar containing a pulp-like multi-branched ultrafine fiber, and describes the thickening property and anti-sagging property when trowel coating is performed, but concrete is sprayed using compressed air. It is not applied to construction materials. Further, Patent Document 6 uses fibrillated fibers for fixing elements such as anchors and prevents separation of water and cement components, but there is no description about application to a spraying method. .

Japanese Patent Publication No. 60-4149 JP 2002-193653 A JP 2005-82434 A JP 2009-110142 A JP 2003-292361 A JP 2008-138360 A

  The present invention relates to a technique for improving material separation resistance of concrete before adding a quick setting agent. In particular, in spray concrete with a low water cement ratio that uses a large amount of water reducing agent, even concrete with high fluidity has material separation resistance, can realize good pumpability, and uses conventional polymer fibers A spraying material and a spraying method capable of improving crack resistance immediately after construction even if the amount of fiber used is further reduced.

That is, the present invention is (1) rapid setting spray concrete containing cement, aggregate, water, fibrillated polymer fiber, and rapid setting agent, and the fibrillated polymer fiber is A crack-suppressing spray material characterized by a fiber diameter of 0.5 to 20 μm, a fiber length of 4 to 40 mm, and 0.001 to 2% by volume in 1 m3 of concrete excluding a quick setting agent, (2) a water reducing agent (1) crack-suppressing type spraying material, (3) cracking control type spraying material of (1) or (2) in which the slump flow of concrete excluding the quick setting agent is 40 to 65 cm, (4) ( In the crack-suppressing type spray material according to any one of 1) to (3), the spraying method is characterized in that the concrete excluding the rapid setting agent is pumped by a spraying machine, and the rapid setting agent is mixed and mixed in the course of spraying. .

  By using the spray material of the present invention, it is difficult for material separation to occur even with high fluidity concrete, and it is possible to obtain concrete with excellent pumpability, reducing the amount of fiber compared to conventional polymer fibers Even so, concrete sprayed with a rapid setting agent can greatly improve the crack resistance immediately after construction. Therefore, a high-performance spray member can be obtained at low cost.

  In the present invention, “parts” and “%” are based on mass unless otherwise specified.

The cement used in the present invention includes various portland cements such as normal, early strength, ultra-early strength, low heat, and moderate heat, and various mixed cements and branes obtained by mixing blast furnace slag, fly ash, or silica with these portland cements. Filler cement mixed with limestone powder with a specific surface area exceeding 2000 cm ² / g, blast furnace slow-cooled slag fine powder, etc., and environmentally friendly cement (eco-cement) manufactured from municipal waste incineration ash and sewage sludge incineration ash Portland cements such as these can be used, and one or more of these can be used.

  The aggregate used in the present invention is not particularly limited, and any aggregate can be used as long as it does not adversely affect the performance of the concrete. For example, natural aggregates produced from rivers, mountains (land), and the sea, artificially produced artificial aggregates, and heavy aggregates can be mentioned.

  The fibrillated polymer fiber of the present invention is an external fibrillation in which a very short bundle of fibers (fibrils) comes out from the surface of the fiber, and an internal fibrillation in which each membrane layer constituting the fiber is loosened and softened. Is a polymer fiber obtained. Either type can be used, but it is preferable to use fibers that are multi-branched by external fibrillation. Types include pulp fibers, aramid fibers, vinylon fibers, acrylic fibers, and polyolefin fibers such as polyethylene fibers and polypropylene fibers. These may be used alone or in combination of two or more. Among these, it is preferable to use polyethylene fibers having a low density and hardly causing a significant increase in resistance during concrete pumping.

The fiber diameter of the fibrillated polymer fiber is preferably 0.5 to 20 μm. If the thickness is less than 0.5 μm, the mechanical energy for production is large and the cost is high, which is uneconomical. If the thickness exceeds 20 μm, the effect of reducing cracks with low addition may be reduced.
The fiber length of the fibrillated polymer fiber is preferably 4 to 40 mm. If it is less than 4 mm, material separation resistance may not be imparted. If it exceeds 40 mm, fiber balls are likely to be generated during mixing.
The amount of the fibrillated polymer fiber added is preferably 0.001 to 2% by volume in 1 m ^{3 of} cement, aggregate, water, concrete containing a fibrillated polymer fiber or a water reducing agent (excluding the quick setting agent). 0.01 to 1% by volume is more preferable. If it is less than 0.001% by volume, the material separation resistance may not be imparted. If it exceeds 2% by volume, it may be difficult to maintain the fluidity of the concrete.

The rapid setting agent used in the present invention has an action of promoting the setting of cement and imparting rapid setting property to concrete. Commercially available quick setting agents can be used. For example, a quick setting agent containing calcium aluminates, a quick setting agent containing aluminates such as lithium, sodium and potassium, and a quick setting agent containing aluminum sulfate. Calcium aluminates are mainly composed of CaO and Al ₂ O ₃ , those in which alkali metal salts such as sodium, potassium and lithium are partly dissolved, those containing SiO ₂ , SO ₃ What is contained is also included. A rapid setting agent containing any of calcium aluminates, alkali metal aluminates, and aluminum sulfate is preferable.
2-15 parts are preferable with respect to 100 parts of cement, and, as for the usage-amount of the quick setting agent of this invention, 3-10 parts are more preferable. If it is less than 2 parts, sufficient rapid setting force cannot be obtained, and if it exceeds 15 parts, long-term strength expression may be inhibited.

The water reducing agent used in the present invention imparts fluidity to concrete, and any commercially available water reducing agent (AE water reducing agent, high performance water reducing agent, high performance AE water reducing agent) can be used.
Examples of the water reducing agent include polycarboxylic acid-based, melamine-based, naphthalene sulfonic acid-based, and lignin sulfonic acid-based water reducing agents. Among these, it is preferable to use a polycarboxylic acid-based water reducing agent that easily obtains high fluidity with low addition.
Although the usage-amount of a water reducing agent is not specifically limited, What is necessary is just to use it in the range which does not have a bad influence on the strength development property of quick setting shotcrete. Although it varies depending on the aggregate and cement used, it is generally used in the range of 0.5 to 3 parts relative to the cement. If it is less than 0.5 part, sufficient fluidity may not be obtained, and if it exceeds 3 parts, strength development may be inhibited.

  The workability of the concrete of the present invention is not particularly limited, but it is also possible to use a concrete having a hardness that cannot be measured by a slump flow (measurable by a slump value). As concrete which gave the water reducing agent and gave high fluidity, the range of 40-65 cm is preferable by slump flow. If it exceeds 65 cm, the adhesion of concrete when sprayed may be reduced.

Although the spraying method of this invention is not specifically limited, What is necessary is just the method of merging and mixing and spraying a quick setting agent just before spraying the concrete sent by pressure. Concrete pumping methods include, for example, a method in which mixed concrete is packed in a hopper and air transported, a method in which mixed concrete is packed in a hopper and pumped into the concrete with a piston pump, and compressed air is introduced in the middle and air transported. Either may be used.
For the quick setting agent, both powder and liquid can be used. In the case of powder, an addition system that feeds air may be used, and in the case of liquid, a plunger type or piston type liquid pump may be used. . When a liquid quick-setting agent is added, compressed air may be introduced into the mist before mixing with concrete and mixed with concrete.

  In the present invention, an antifoaming agent, a thickener, a rust inhibitor, a defrosting agent, a shrinkage reducing agent, an expansion material, a polymer emulsion, a setting modifier, and an acrylic ester are added within a range that does not affect the effects of the present invention. Various additives such as plasticizers, anion exchangers such as hydrotalcite, blast furnace granulated slag fine powder, blast furnace annealed slag fine powder, limestone fine powder, fly ash, silica fume, Furthermore, it is possible to use together 1 type, or 2 or more types in the group consisting of admixtures such as γ-dicalcium silicate, clay mineral, gypsum and the like.

"Experiment 1"
The concrete of the composition shown in Table 1 was mixed with the types and amounts (volume%) of fibers shown in Tables 2 and ³ to produce 0.9 m ³ of concrete. This concrete was pumped by a concrete pumping machine “MKW-25SMT” under a spraying pressure of 0.4 MPa and a set discharge rate of 10 m ³ / h. Compressed air was introduced at a position 3 m behind the Y-shaped pipe where the rapid setting agent was joined, and the concrete was conveyed by air. From one side of the Y-shaped pipe, the rapid setting agent was pneumatically fed so as to be 7 parts with respect to 100 parts of cement, and mixed and mixed with the concrete and sprayed as quick setting sprayed concrete. For the concrete before the addition of the quick setting agent, the slump flow and the flow time of the V funnel were measured. For fast setting concrete sprayed with the addition of a quick setting agent, the compressive strength and crack resistance were measured. The results are shown in Tables 2 and 3.

(Materials used)
Coarse aggregate: Gravel from Himekawa, Itoigawa City, Niigata Prefecture, surface dry condition, specific gravity 2.66, maximum dimension 10mm
Fine aggregate: Himekawa Sakegawa gravel, Itoigawa City, Niigata Prefecture, surface dry condition, specific gravity 2.62, maximum dimension 5mm
Cement: Ordinary Portland cement, commercial high-performance water reducing agent: polycarboxylate-based, commercial product quick-setting agent: calcium aluminate-based, commercial product fiber A: polyethylene fibrillated fiber (fiber made into multi-branched by external fibrillation) ), Manufactured by Mitsui Chemicals, brand Chemibest FDSS-2 equivalent (average fiber length adjusted to 6 mm), fiber diameter 5-15 μm, density 0.98 g / cm ³
Fiber B: Non-fibrillated polyethylene fiber, manufactured by Toyobo Co., Ltd., brand Dyneema SK-71 equivalent (fiber length adjusted to 6 mm), fiber diameter 5 to 15 μm, density 0.97 g / cm ³
Fiber C: non-fibrillated vinylon fiber, manufactured by Kuraray, brand RECS-2, fiber length 6 mm, fiber diameter 14 μm, density 1.3 g / cm ³ , convergence type,
Fiber D: Fiber obtained by cutting fiber C into a fiber length of 2 mm, density 1.3 g / cm ³

(Measuring method)
Slump flow: compliant with JIS A 1150. Measures the expanded concrete diameter when the slump cone is removed.
V funnel: Based on JSCE-F 512-2007. Measure the time for concrete to pass through the V funnel.
Compressive strength: The compressive strength at the age of 24 hours is that the pin placed on the pull-out formwork 25cm wide x 25cm long is covered with quick setting sprayed concrete from the surface of the pullout formwork, and the pin is placed from the back side of the formwork Drawing, the drawing strength at that time was determined, and the compressive strength was calculated from the formula of (compressive strength) = (drawing strength) × 4 / (test specimen contact area). The compressive strength at the age of 28 days was determined by spraying rapidly setting sprayed concrete onto a formwork of width 50 cm x length 50 cm x thickness 20 cm. Measured and determined compressive strength.
Crack resistance: Using an L-shaped wall made of concrete, quick setting sprayed concrete was sprayed on an area of about 1 m ² so as to have a thickness of 10 cm. Immediately after the spraying, a wind with a wind speed of 5 m was blown for 20 days, and the time when cracks occurred was confirmed.

"Experimental example 2"
The experiment was performed in the same manner as in Experimental Example 1 except that the concrete shown in Table 1 was mixed with the fiber shown in Table 4 at 0.1% by volume to produce a 0.9 m ³ concrete. The results are shown in Table 4.

(Materials used)
Fiber E: Polyethylene fibrillated fiber (fiber made into a multi-branched shape by external fibrillation), Mitsui Chemicals, brand Chemibest FDSS-2 equivalent (average fiber length adjusted to 2 mm), fiber diameter 5-15 μm
Fiber F: Polyethylene fibrillated fiber (fiber made into a multi-branched shape by external fibrillation), Mitsui Chemicals, brand Chemibest FDSS-2 equivalent (average fiber length adjusted to 12 mm), fiber diameter 5-15 μm
Fiber G: Polyethylene fibrillated fiber (fiber made into a multi-branched shape by external fibrillation), Mitsui Chemicals, brand Chemibest FDSS-2 equivalent (average fiber length adjusted to 30 mm), fiber diameter 5-15 μm
Fiber H: Polyethylene fibrillated fiber (fiber made into a multi-branched form by external fibrillation), Mitsui Chemicals, brand Chemibest FDSS-2 equivalent (average fiber length adjusted to 40 mm), fiber diameter 5-15 μm

  By using the spray material of the present invention, it is difficult for material separation to occur even with high fluidity concrete, and it is possible to obtain concrete with excellent pumpability, reducing the amount of fiber compared to conventional polymer fibers Even so, concrete sprayed with a rapid setting agent can greatly improve the crack resistance immediately after construction. Therefore, it is possible to obtain a high-performance spray member at a lower cost than using a non-fibrillated polymer fiber to take measures against cracks. Therefore, it is widely used in tunnel construction in the civil engineering field. be able to.

Claims (4)

Cement, aggregate, water, fibrillated polymer fiber, and quick setting shot concrete containing a quick setting agent, the fibrillated polymer fiber having a fiber diameter of 0.5 to 20 μm, fiber long 4 to 40 mm, crack suppression type spraying material, which is a 0.001% by volume in the concrete 1 m ^3, except for quick-setting admixture. The crack suppressing spray material according to claim 1, further comprising a water reducing agent. The crack-suppressing spray material according to claim 1 or 2, wherein the slump flow of the concrete excluding the rapid setting agent is 40 to 65 cm. The crack-suppressing type spray material according to any one of claims 1 to 3, wherein the concrete excluding the rapid setting agent is pumped by a spraying machine, and the rapid setting agent is mixed and mixed in the course of spraying. Spraying method.