JP4727282B2 - Spraying material and spraying method using the same - Google Patents

Description

  The present invention relates to an admixture for spraying, a spraying material, and a spraying method using the same.

The cement concrete spraying method is one of the methods widely used for supporting tunnels and slopes due to the ease of construction and construction speed.
This construction method is mainly used on slopes that are slopes made by cutting or embankment, mainly on the inner surface of natural ground caused by tunnel excavation, highways, dams, and steep slopes.
In particular, it is necessary to protect the slope because the slope may easily collapse due to natural weathering, heavy rain, etc.

  Conventionally, in order to prevent the slope from collapsing, the method of spraying cement concrete directly on the slope has been the mainstream, and in order to increase the reinforcement effect of the slope, a method of placing a formwork on the slope has been used. (See Patent Document 1).

  As a method of placing the formwork on the slope, wire mesh and multiple rebars are placed in a grid pattern (cross-beam shape) on the slope to create a slope formwork, and each intersection of the grid-like slope formwork After the anchor is driven into the part, cement concrete is sprayed on the sloped mold to form a cement concrete frame that is a reinforced concrete structure to stabilize the slope.

Among the methods for placing a formwork on a slope, a method of using a formwork that allows the formwork to be placed directly on the slope without shaping and cutting the slope is used.
In this method, a deformable (flexible) wire mesh or reinforcing bar is directly placed on the slope, and cement concrete is sprayed onto the formed method frame.

  Even in the frame method with improved durability, when a cement concrete frame is constructed by spraying, the destruction by freezing and thawing in winter may become serious.

Freezing and thawing in cement concrete occurs because the water in the cement concrete frame changes from water to ice as the temperature decreases.
The phase change from water to ice is accompanied by volume expansion. Therefore, the volume expands when water freezes in the voids in the cement concrete hardened body such as a cement concrete frame. At this time, when there are many voids in the hardened cement body, the expansion pressure does not occur because the volume is accommodated in the voids even if water freezes. However, when there are few voids in the hardened cement concrete, the volume of ice does not fit in the voids and expansion pressure is generated, and tensile stress is generated in the hardened cement concrete. Furthermore, when such freeze-thawing is repeated, cracks develop and phenomena such as scaling and pop-out occur. In general, when there is a void amount of 3% or more, freeze-thaw does not occur remarkably.

  When sprayed, air introduced during cement concrete mixing using an AE agent tends to disappear in the pressure feeding hose, and there is a problem that the amount of air necessary for freeze-thaw resistance cannot be secured in many cases. It was.

  In addition, because slopes are often in cold mountainous areas, deterioration due to freezing and thawing becomes noticeable in winter. There was a problem that there was a case.

In spray construction, in order to increase the amount of spray per unit time, it is necessary to enlarge the slump of cement concrete, but when the slump is large, there was a problem that cement concrete flows down from the slope when sprayed .
For this reason, it was necessary to reduce the slump of cement concrete immediately after spraying to prevent the cement concrete from falling off.

Japanese Examined Patent Publication No. 58-058493

  The present invention relates to a spray admixture for improving the freeze-thaw resistance of spray cement concrete, a spray material, and a spray method using the same, and has, for example, a slope and an aesthetic that are easy to collapse. The present invention provides a spray admixture, a spray material, and a spraying method using the spray admixture sprayed on a method frame arranged in a grid pattern on the slope.

That is, the present invention comprises (1) cement and (2) hollow fine particles having an average particle diameter of 3 to 150 μm in 0.5 to 8 parts by volume in 100 parts by volume of cement concrete, (3) (3-1) water. 1A element hydroxide consisting of one or more of the group consisting of lithium oxide, potassium hydroxide and sodium hydroxide, solid content concentration of 25-45%, (3-2) aluminum hydroxide 3-3 element hydroxide in solid content concentration of 15 to 35%, and (3-3) a liquid curing accelerator containing water, containing 2 to 10 parts with respect to 100 parts of cement And (4) the spray material containing aggregate, and the slope spray material having an air amount of 3.6% by volume or more, (1 Cement) and (2) hollow fine particles having an average particle diameter of 3 to 150 μm. From 100 to 10 parts by volume of cement concrete, and (4) cement concrete containing aggregate, and (3) (3-1) lithium hydroxide, potassium hydroxide and sodium hydroxide. 1A element hydroxide consisting of one or more of the group consisting of 25 to 45% in solid content concentration, (3-2) 3B element hydroxide consisting of aluminum hydroxide in solid content concentration 15 to 35%, and (3-3) a liquid curing accelerator containing water so that the solid content concentration of the liquid curing accelerator is 40 to 65%, relative to 100 parts of cement, is 2 to 10 %. Y-tube that is mixed and sprayed, and the amount of air in the cement concrete is 3.6% by volume or more, and is attached to mix the liquid hardening accelerator with cement concrete. Mounting position is at the discharge port This is a spraying method of 0.1 to 100 m in front of the cement, the unit cement amount of cement concrete is 270 to 600 kg / m ³ , the W / C of cement concrete is 35 to 65%, This is the spraying method in which / a = 50 to 100% and the hollow fine particles are organic.

By using the spraying admixture or spraying material of the present invention, the deterioration due to freezing and thawing, which causes a fatal defect in the cement concrete frame sprayed on the frame during the winter period, is improved. In particular, 1) use of a liquid curing accelerator ensures sag prevention and initial strength, and reduces the initial freeze-thaw action. 2) Conventionally, spray cement concrete is susceptible to freeze-thaw effect because the void volume is small, the hollow fine particles and the additive child to cement concrete composition, to ensure voids spraying cement concrete, longer-term In addition, there is an effect that it is possible to ensure durability against freezing and thawing.

Parts and% used in the present invention are based on mass unless otherwise specified.
In the present invention, cement paste, mortar, and concrete are collectively referred to as cement concrete.

  The hollow fine particles used in the present invention have cavities encapsulated in the particles, and there are inorganic hollow organic particles and organic hollow fine particles, and the shape of the hollow fine particles is not broken even during spraying, The encapsulated cavity is introduced into the cement concrete hardened body and contributes to freeze-thaw resistance, and is introduced by an AE agent or the like and has an effect different from that of air that disappears when sprayed.

Examples of the inorganic hollow fine particles include ceramic hollow fine particles, shirasu balloons, glass balloons, silica balloons, fly ash balloons, and the like. These inorganic hollow fine particles include those produced, those obtained as by-products from thermal power plants, and those obtained from the natural world. Among these, mullite ceramic hollow fine particles having high particle strength are preferable. Moreover, freeze-thaw resistance may not be obtained with some silica balloons.
If the inorganic hollow microparticle composition contains soluble silica other than Al ₂ O ₃ or SiO ₂ , the hollow microparticle shell may be broken and freeze-thaw resistance may be reduced. is there.

The composition of the organic hollow fine particles is mainly composed of a copolymer of acrylonitrile, vinylidene chloride, methyl methacrylate, methacrylonitrile, acrylic ester, methacrylic ester, styrene, and vinyl acetate, It is preferable that the main component is a copolymer of acrylonitrile, vinylidene chloride, methyl methacrylate, and methacrylonitrile.
It is possible to enclose liquids and gases such as n-butane, isobutane, isopentane, and neopentane inside the organic hollow fine particles.

The average particle size of the hollow fine particles is preferably 3 to 150 μm, more preferably 10 to 60 μm.
If it is less than 3 μm, sufficient freeze-thaw resistance may not be obtained, and if it exceeds 150 μm, the strength may decrease.
The ratio of the cavities in the hollow fine particles is not particularly limited, but is preferably 20% by volume or more of the hollow fine particles, and more preferably 40% by volume or more from the viewpoint of freeze-thaw resistance.
The amount of the hollow fine particles used is preferably 0.5 to 8 parts by volume, more preferably 3 to 5 parts by volume, in 100 parts by volume of cement concrete mixed and kneaded with materials other than the liquid curing accelerator. If it is less than 0.5 part by volume, the sprayed cement concrete may be affected by freezing and thawing, and if it exceeds 8 parts by volume, the compressive strength of the sprayed cement concrete may be reduced.

The liquid curing accelerator used in the present invention is not particularly limited as long as it accelerates the setting of cement. Examples of main ones include lithium hydroxide, potassium hydroxide, and sodium hydroxide as 1A element hydroxides. In addition, since the curing is accelerated when the 3B element is used supplementarily, it is preferable to contain it in the curing accelerator. As a main thing of the hydroxide of 3B element, aluminum hydroxide is mentioned, for example. In addition, for the purpose of agglomeration effect and acceleration of hardening, alkali metal carbonates, nitrates, nitrites, sulfates, and silicates can be used, and one or more of these can be used. .
The solid content concentration of the liquid curing accelerator is preferably 40 to 65%, more preferably 55 to 60%. If the solid content concentration is less than 40%, dripping may occur, and if it exceeds 65%, the viscosity increases when pumped to sprayed cement concrete, and workability may be deteriorated.

  The solid content concentration of the liquid curing accelerator of the 1A element hydroxide is preferably 25 to 45 parts, more preferably 30 to 40 parts. If it is less than 25 parts, the sprayed cement concrete may sag, and if it exceeds 45 parts, the trowel finish may not be possible.

  Moreover, 15-35 parts is preferable and, as for the solid content density | concentration of the liquid hardening accelerator of the hydroxide content of 3B element, 20-30 parts is more preferable. If it is less than 15 parts, the initial strength may be deteriorated, and if it exceeds 35 parts, cracks may occur.

  The amount of the liquid curing accelerator used is preferably 2 to 10 parts, more preferably 3 to 8 parts, relative to 100 parts of cement. If it is less than 2 parts, the sprayed cement concrete may slide down, and if it exceeds 10 parts, the compressive strength may be significantly impaired.

  Here, as cement, various Portland cements specified in JIS R 5210, various mixed cements specified in JIS R 5211, JIS R 5212, and JIS R 5213, and mixed admixtures more than specified in JIS Blast furnace cement, fly ash cement, silica cement, and filler cement mixed with limestone powder and the like.

Further, the aggregate preferably has a low water absorption rate and a high aggregate strength, and the fine aggregate ratio and the maximum dimension of the aggregate are not particularly limited as long as spraying can be performed.
River sand, mountain sand, lime sand, quartz sand, and the like can be used as the fine aggregate, and river gravel, mountain gravel, lime gravel, and the like can be used as the coarse aggregate.

  In the present invention, in addition to cement, aggregate, hollow fine particles, and liquid curing accelerator, a water reducing agent and a setting retarder can be used in combination as long as the object of the present invention is not substantially inhibited.

  As the water reducing agent, naphthalene sulfonic acid formalin condensate, melamine sulfonic acid formalin condensate, polycarboxylic acid polymer compound and the like can be used.

  The setting retarder adjusts the setting of cement concrete, and specific examples thereof include oxycarboxylic acid and salts thereof, phosphates, and sugars.

Furthermore, in this invention, it is preferable to use a fiber from the surface of the impact resistance of the hardened | cured material of spray cement concrete, and the improvement of elasticity.
As the fiber, either inorganic fiber or organic fiber can be used.
Examples of inorganic fibers include glass fibers, carbon fibers, rock wool, stone brocade, ceramic fibers, and metal fibers. Organic fibers include vinylon fibers, polyethylene fibers, polypropylene fibers, polyacrylic fibers, and cellulose fibers. , Polyvinyl alcohol fiber, polyamide fiber, pulp, hemp, wood wool, and wood chip. Among these, metal fiber and vinylon fiber are preferable in terms of economy.
The length of the fiber is preferably 50 mm or less, and more preferably 5 to 30 mm in terms of pumpability and mixing properties. If it exceeds 50 mm, the quick setting sprayed cement concrete may be blocked during feeding.
The aspect ratio of the fiber is not particularly limited.
The amount of fiber used is preferably 0.1 to 3 parts by volume, more preferably 0.4 to 1.5 parts by volume, in 100 parts by volume of sprayed cement concrete. If the amount is less than 0.1 parts by volume, the effect of improving impact resistance and elasticity may be small.

In the spraying method of the present invention, conventionally used spraying equipment or the like can be used.
Moreover, as the spraying method of the present invention, various spraying methods according to the required physical properties, economy, workability, and the like are possible. For example, in the wet spraying method, cement, fine aggregate (coarse aggregate is also used if necessary), and water (water reducing agent is also used if necessary) and kneaded are pumped with air using a hose. A Y-tube is installed in the middle of the hose, and the admixture for spraying is pneumatically fed from one side of the hose using a spray admixture supply device (the type of pump is not particularly limited), and then merged and mixed. The method of spraying is mentioned.
The mixing of the admixture for spraying onto the cement concrete is preferably carried out by mixing the spray admixture onto the cement concrete by simultaneous mixing with showering or spraying air that allows the admixture for spraying to uniformly enter.

  The mounting position of the Y-shaped tube in the pumping hose is preferably 0.1 to 100 m before the discharge port, and more preferably 3 to 20 m in consideration of the mixing property and pumping property. If it exceeds 100m, problems such as hose blockage may occur.

  As the slope spraying method using the spray material used in the present invention, the spray material may be sprayed directly onto the slope, but in order to increase the reinforcing effect, in addition to the main bars, It is preferable to form reinforcing frame skeletons by arranging reinforcing bars, and the frame manufacturing method is more preferable.

  Here, the reinforcing bars are made of wire mesh, reinforcing bars, etc., which are combined to form a framework frame, sprayed with cement concrete, and made into a cement-concrete framework integrated with the reinforcing bars. .

Spraying is applied to the legal frame skeleton arranged in this way using a spray material, and the part protruding from the reinforcing bar frame of the legal frame skeleton is troweled, so that the construction of the legal frame is maintained so as to maintain the aesthetic appearance.

In the case of mortar, spray cement concrete to be applied to the slope is preferably 270-600kg / m ³ unit cement and 35-65% W / C. In the case of concrete, s / a = 50 ˜100% is preferable, and the compressive strength at the age of 4 weeks is preferably 15 N / mm ² or more.

  Hereinafter, the present invention will be described in detail based on experimental examples.

Experimental example 1
Using a concrete blend with a unit cement amount of 430kg / m ³ , W / C of 55% and s / a of 70%, adjusting the amount of water reducing agent so that the slump is about 18cm, the hollow shown in Table 1 Base concrete was prepared by mixing fine particles.
5 parts of liquid hardening accelerator (hereinafter referred to as accelerator) is pumped to 100 parts of cement in the base concrete, and is pressed into the base concrete together with compressed air into a branch pipe attached 10m before the discharge port. The air content and relative dynamic elastic modulus of the base concrete were measured. The results are also shown in Table 1.
The spray was sprayed at a discharge rate of 3 m ³ / h with a compressed air of 7 m ³ / min through a 2-inch 40 m pressure hose.
For comparison, a base concrete containing 5% by volume of air with an AE agent without mixing hollow fine particles was also sprayed in the same manner.
After spraying, a sample was cut out from the resulting cured body and subjected to a freeze-thaw test. The results are also shown in Table 1.

<Materials used>
Hollow fine particles A: SiO ₂ / Al ₂ O ₃ / Fe ₂ O ₃ = 63/33/4, ceramic hollow fine particles, average particle size 50 μm
Hollow fine particle B: Copolymer of acrylonitrile / methyl methacrylate / vinylidene chloride = 55/36/9, average particle size 40 μm
Hollow fine particle C: methacrylate / acrylonitrile = 26/74 copolymer, average particle size 40 μm
Accelerator A: Water / sodium hydroxide / aluminum hydroxide = 42/33/25, solid content concentration 58%
Cement: Ordinary Portland cement, density 3.16g / cm ³
Fine aggregate: Sand, from Himekawa, Niigata, density 2.62g / cm ³ , FM2.86
Coarse aggregate: Gravel, produced in Himekawa, Niigata Prefecture, density 2.63g / cm ³ , particle size 12mm or less AE agent: alkyl ether ion surfactant, commercially available water reducing agent: polycarboxylic acid-based high-performance water reducing agent water: industrial water

<Measurement method>
Average particle size of hollow fine particles: Measured using a commercially available laser diffraction particle size meter: JIS A 1128 “Measured according to the test method using air pressure of fresh concrete Relative kinematic modulus: Freeze-thaw test, JIS A In accordance with 1148 “Concrete Freeze-Thaw Test Method”, Method A Underwater Freeze-Thaw Test, the relative dynamic elastic modulus after 300 cycles of freeze-thaw was measured. In addition, what was destroyed before reaching 300 cycles was regarded as defective.

  Inorganic hollow microparticles are inferior in relative dynamic elastic modulus to organic hollow microparticles because some of the particles are destroyed when they collide with the wall surface during spraying. On the other hand, the organic hollow fine particles exhibit high relative dynamic elastic modulus without being broken so much even during spraying because the particles themselves have elasticity.

Experimental example 2
The same operation as in Experimental Example 1 was performed except that the hollow fine particles shown in Table 2 were used. The results are also shown in Table 2.

<Materials used>
Hollow fine particles D: Copolymer of methacrylate / acrylonitrile = 26/74, average particle size of 3 μm
Hollow fine particle E: A copolymer of methacrylate / acrylonitrile = 26/74, average particle size 10 μm
Hollow fine particles F: Copolymer of methacrylate / acrylonitrile = 26/74, average particle size 60 μm
Hollow fine particles G: Copolymer of methacrylate / acrylonitrile = 26/74, average particle size 150 μm

  From the table, when the average particle size is 1 to 60 μm, the relative kinematic modulus is 60 to 90% compared to that before being subjected to freezing and thawing. I understand that

Experimental example 3
Experimental example except that the accelerator shown in Table 3 was used, and the hollow fine particles B were sprayed using 3% by volume in 100% by volume of the base concrete, the spraying state was confirmed, and the relative dynamic elastic modulus was measured. Same as 1. The results are also shown in Table 3.

<Materials used>
Accelerator A: Water / lithium hydroxide / aluminum hydroxide = 42/42/16, solid content 58%
Accelerator c: Water / potassium hydroxide / aluminum hydroxide = 40/28/32, solid content 60%

<Measurement method>
Spraying conditions: the shotcrete, after sprayed to a thickness of 20cm on the slopes of 1 m ² of inclination 60 °, allowed to stand for 1 hour, if that sprayed is slipping over half Not possible, little shear If it fell, it was acceptable.

  When the accelerator is less than 2 parts, the accelerator may fall off, and when it exceeds 10 parts, since the amount of alkali contained in the accelerator is large, the compressive strength quickly reaches a peak, and the freeze-thaw resistance is reduced. Therefore, the use amount of the accelerator is preferably 2 to 10 parts.

Experimental Example 4
Per 100 parts cement in the mortar, using 4 parts accelerator shown in Table 4, the amount of the unit cement mortar formulation ^{420kg / m 3, W / C} = 50%, the hollow fine particles mortar S / C = 3 B was used in the same manner as in Experimental Example 1 except that 3% by volume of B was used for spraying, the compressive strength after spraying was measured, and the spraying state, trowel finish, and cracking were confirmed. The results are also shown in Table 4.

<Materials used>
Accelerator D: Water / sodium hydroxide / aluminum hydroxide = 35/35/30, solid content 65%
Accelerator O: Water / lithium hydroxide / aluminum hydroxide = 40/45/15, solid content 60%
Accelerator: Water / potassium hydroxide / aluminum hydroxide = 50/35/15, solid content 50%
Accelerator key: Water / potassium hydroxide / aluminum hydroxide = 45/35/20, solid content 55%
Accelerator ： Water / potassium hydroxide / aluminum hydroxide = 60/25/15, solid content 40%
Accelerator ke: water / potassium hydroxide / aluminum hydroxide = 65/35/0, solid content 35%
Accelerator co: Water / potassium hydroxide / aluminum hydroxide = 33/23/44, solid content concentration 67%

<Measurement method>
Iron finishing: Apply iron to the surface of the mortar 2 hours after spraying. Yes, if it was possible to do it as desired, but not if it was difficult to finish with a trowel or was dull.
Compressive strength: In accordance with JIS R 5201, the strength of the material one day was measured. Cracks: Surface observation after the passage of 1 day, acceptable if there were no cracks, not acceptable if there were cracks.

Claims (6)

(1) cement, (2) hollow fine particles having an average particle size of 3 to 150 μm, 0.5 to 8 parts by volume in 100 parts by volume of cement concrete, (3) (3-1) lithium hydroxide, potassium hydroxide And 1A element hydroxide consisting of one or more of the group consisting of sodium hydroxide in a solid content concentration of 25 to 45%, (3-2) 3B element hydroxide consisting of aluminum hydroxide A spraying material comprising 15 to 35% in solid content concentration and (3-3) 2 to 10 parts of a liquid curing accelerator containing water with respect to 100 parts of cement. The spray material according to claim 1, further comprising (4) an aggregate. Furthermore, the slope spray material of Claim 1 or 2 whose air amount is 3.6 volume% or more. (1) cement, (2) cement concrete comprising hollow fine particles having an average particle size of 3 to 150 μm, 0.5 to 8 parts by volume in 100 parts by volume of cement concrete, and (4) aggregate. (3) (3-1) 1A element hydroxide consisting of one or more of the group consisting of lithium hydroxide, potassium hydroxide and sodium hydroxide in a solid content concentration of 25 to 45%, (3-2) 3B element hydroxide composed of aluminum hydroxide in a solid content concentration of 15 to 35%, and (3-3) the solid content concentration of the liquid curing accelerator is 40 to 65%. A spraying method comprising mixing 2 to 10 parts of a liquid curing accelerator containing water with 100 parts of cement and spraying the mixture. Furthermore, the amount of air in the cement concrete is 3.6% by volume or more, and the attachment position of the Y-shaped tube attached for mixing the liquid hardening accelerator with cement concrete is 0.1 to 100 m before the discharge port. The spraying method according to claim 4 . The unit amount of cement concrete is 270-600kg / m ³ , cement concrete W / C is 35-65%, cement concrete s / a = 50-100%, hollow fine particles are organic The spraying method according to claim 4 or 5.