JP6732521B2 - Mortar for spraying - Google Patents

Description

The present invention relates to a cement-based mortar for spraying that requires long-distance pumping to a spraying site by a transport pipe.

In tunnels, mining tunnels, underground spaces, etc., it is possible to spray cement slurry or cement-based mortar onto the target surface to prevent collapse of the exposed surface of the excavation, to prevent water leakage from the ground surface, and for finishing these surfaces. Has been done. The general spraying method of cement-based mortar is a plant installed near the excavation site, weighs and mixes cement, water and fine aggregate to make a base mortar, and transports this to the excavation site with an agitator car, From there to the spraying machine, the pump is pressure-fed through the transport pipe, and immediately before the spraying, the quick-setting agent sent separately is mixed and sprayed. The quick-setting agents are roughly classified into powder quick-setting agents such as calcium aluminate and sodium aluminate, and liquid quick-setting agents such as aluminum sulfate and sodium silicate. The powder quick-setting admixture has a strong quick-setting property and a high initial strength development property, but since it is difficult to mix with cement mortar when added, dust is likely to be generated. On the other hand, although the liquid quick-setting admixture can suppress the generation of dust, sodium silicate has a high alkali content, which causes deterioration of cement-based works, and aluminum sulfate, which is suitable for alkali-free construction, has a low quick-setting property and exhibits initial strength. The sex is not high either. As a measure to improve the spraying properties when using aluminum sulfate as a liquid quick-setting agent, it is known that using mortar slurry for adding aluminum sulfate quick-setting agent to which gypsum has been added in advance has a strength improving effect. There is. (For example, refer to Patent Document 1.) Further, calcium aluminate is added together with gypsum as a quick setting aid to concrete before water injection in advance, and sprayed concrete in which water and liquid aluminum sulfate are added thereto has quick setting property and It is known that strength development can be improved. (For example, refer to Patent Document 2.)

By the way, the transportation of the cement composition slurry from a so-called ready-mixed plant or the like to the construction site by an agitator car generally takes a long time, so that there are many problems in terms of quality and stability of the state and construction efficiency. Therefore, when transporting mortar that does not contain coarse aggregates such as concrete, unless the transport distance is too long, mortar mixed with water is mixed from a manufacturing plant adjacent to the site or a mixing device brought to the site. The slurry is pumped to the construction site with a hose or other transportation pipe. As the pumping distance becomes longer, the elapsed time from pouring water until reaching the construction site becomes longer, increasing the viscosity of the mortar slurry and the risk of clogging the pumping pipe. On the other hand, by pneumatically feeding the premix mortar containing no water, even if the premix mortar is premixed with the quick-setting aid, such a risk can be eliminated. However, the premix mortar mixes admixtures such as fine aggregate, cement, and quick-setting aid in a dry manner, and thus has poor mixability as compared with wet mixing using water as a mixing medium. Especially when an admixture such as fiber is included, the mixing property by dry mixing is likely to be further lowered. In addition, since the pressure medium after mixing does not have an adhesive effect due to the aqueous medium, it is easy to cause component separation due to the difference in specific gravity of each component of the dry mixture and the difference in air resistance due to size, and the separation may expand. Will also increase. Even if water is added or a liquid quick-setting agent is added to the premixed mortar where the components have been separated, just before spraying, it is difficult for the whole mixture to be well mixed, and the mortar in a non-homogeneous state will be sprayed. .. As a result, there are variations in the fixing rate of the mortar on the sprayed surface, and the strength of the sprayed construction may be uneven and uneven within the mortar construction, resulting in a lack of reinforcement capacity and durability. It was

JP, 10-212149, A JP-A-11-130500

Therefore, it is an object of the present invention to provide a spraying mortar that suppresses variations and can stably have high quick-setting properties and strength development properties, and that can be transported over a relatively long distance and that has excellent pumping construction efficiency.

The present inventor, as a result of examination for solving the above problems, Portland cement, gypsum, calcium aluminate and pre-prepared unmixed water premixed mortar containing fine aggregate, with an alkali-free liquid quick setting agent Water is post-added immediately before spraying to make a mortar for spraying, and if the aggregate used for the premix mortar is a specific one, the fine aggregate and cement or other admixtures in the process of premixing The auxiliaries have extremely good mixing properties, and even when the premix mortar in such a mixed state is pressure-fed by a transport pipe over a relatively long distance, the mortar-containing components are not separated and the homogeneous mixed state is maintained. It was found that even if a liquid quick-setting admixture and water were kneaded and sprayed on this, there was no variation in the fixability on the sprayed surface, and high fixability was generally seen and sprayed. The strength of the mortar construction was high, and there was no variation, so the present invention was completed.

That is, the present invention is a spray mortar represented by the following (1) to (4).
(1) A spraying mortar containing the following premix mortar (A) and 5 to 9.5 parts by mass of an alkali-free liquid quick-setting admixture and water based on 100 parts by mass of the Portland cement content in the premix mortar.
A: Portland cement 100 parts by mass, anhydrous gypsum 2.5 to 8 parts by mass, and the molar ratio of CaO and Al ₂ O ₃ as chemical components (CaO and /Al ₂ O ₃ ) is 2.2 to 2.4. 3 to 8 parts by mass of an amorphous calcium aluminate and a bulk specific gravity of 2.4 to 2. Premix mortar containing 130 to 350 parts by mass of fine aggregate of 9 and containing no water.
(2) The spray mortar according to (1) above, wherein the premix mortar contains water reducing agents. (3) The mortar for spraying according to (1) or (2) above, wherein the premix mortar contains short fibers.
(4) The spraying mortar according to any one of (1) to (3) above, wherein the alkali-free liquid quick-setting agent is aluminum sulfate having a solid content concentration of 30 to 53 mass %.

According to the present invention, in the cement mortar spraying construction, for example, since it is possible to perform mortar pressure feed with a long distance from the mortar plant to the spraying site, there is no transshipment of the mortar to the agitator car, and the agitator car itself is also unnecessary In addition, since the premixed mortar of unfilled water is pressure-fed to the spraying equipment at the spraying site, there is no particular problem even if the mortar remains in the transport pipe. Since the supply of mortar can be stopped freely, construction efficiency is greatly improved.

The premix mortar constituting the spraying mortar of the present invention is a dry mixed mortar before pouring water, and therefore does not contain water, and Portland cement, a specific fine aggregate, anhydrite, and CaO as a contained chemical component. This is a mortar containing amorphous calcium aluminate whose specified molar ratio of Al ₂ O ₃ (CaO/Al ₂ O ₃ ) is specified.

The Portland cement required to be contained in the premix mortar may be any Portland cement, and specific examples thereof include various types of Portland cement having normal strength, early strength, super-early strength, moderate heat, low heat and sulfate resistance. Further, a mixed cement containing Portland cement such as blast furnace cement may be used. Among these, ordinary Portland cement is preferable from the viewpoint of economy and versatility. The particle size of Portland cement is not particularly limited as long as it satisfies the JIS standard (JIS R 5210) of 2500 cm ² /g or more. It is preferable that the particle size is similar to that of a general commercial product (for example, approximately 2900 to 3400 cm ² /g).

Any anhydrous gypsum, including anhydrous calcium sulfate (CaSO ₄ ), can be used as the essential anhydrous gypsum contained in the premix mortar. It is preferable to use anhydrous gypsum having a Blaine specific surface area of 1.5 to 2 times the Blaine specific surface area of the Portland cement to be contained, since the miscibility with Portland cement, the reaction activity, the production cost, etc. are likely to fall within an appropriate range. To do. The content of anhydrous gypsum is 2.5 to 8 parts by mass with respect to 100 parts by mass of the Portland cement content in the premix mortar. If it is less than 2.5 parts by mass, the curing is delayed and the development of strength and the like is sluggish, which is not preferable. Further, if it exceeds 8 parts by mass, setting is delayed and it may cause expansion cracks, which is not preferable. Although a small amount of gypsum is contained in Portland cement, since this is a constituent component of Portland cement, it is included in Portland cement itself and is not included in anhydrous gypsum contained in premix mortar.

The amorphous calcium aluminate essential contained in the (A) premix mortar has a molar ratio (CaO/Al ₂ O ₃ ) of 2.2 to 2.4 containing CaO and Al ₂ O ₃ as main chemical components. Inorganic hydration active substance contained in 1., the raw material mixture serving as the CaO source and the Al ₂ O ₃ source in consideration of the content molar ratio (CaO/Al ₂ O ₃ ), preferably until melting Obtained by heating. Therefore, as in the case of using a natural mineral raw material, impurities other than CaO and Al ₂ O ₃ which are mainly derived from the raw material used should be included within a range that does not impair the effects of the present invention, regardless of the existing form. Is acceptable. The amorphous calcium aluminate does not have to be in a completely glassy state, and may have a structure in which vitrification is advanced. Specifically, the vitrification rate is preferably 50% or more, and more preferably 90% or more. The higher the vitrification is, the higher the reaction activity becomes. The vitrification rate can be adjusted by, for example, cooling treatment from a high temperature when the molten state is reached. Generally, the faster the quenching rate, the higher the vitrification rate of calcium aluminate obtained. Further, by containing such an amorphous calcium aluminate as an essential component in the premix mortar, it is possible to sufficiently compensate for the lack of quick-setting force when a quick-setting agent having a relatively low quick-setting property is used. Further, if the content molar ratio (CaO/Al ₂ O ₃ ) is less than 2.2, it becomes difficult to improve the adhesiveness and the strength development, and if it exceeds 2.4, the condensation proceeds too quickly and the water content is shortly after pouring. It is not preferable because there is a risk of binding. The content of the amorphous calcium aluminate is 3 to 8 parts by mass with respect to 100 parts by mass of the Portland cement content in the premix mortar. If the amount is less than 3 parts by mass, the quick-setting property of the spray mortar after addition of the liquid quick-setting agent and particularly the initial strength development property cannot be improved, which is not preferable. On the other hand, if the amount exceeds 8 parts by mass, there is a possibility that the mortar for spraying after water injection may end the condensation before reaching the spraying surface, which is not preferable.

The fine aggregate that is essential in the (A) premix mortar has a central particle size of 0.4 mm or more and a particle content of 0.05 to 3.5 mm of 99 mass% or more and a bulk specific gravity of 2. It is a fine aggregate of 4 to 2.9. The fine aggregate may be made of any material as long as it is inert to water and satisfies the bulk specific gravity. Specific examples thereof include natural aggregates such as silica sand and limestone sand, and crushed sand such as andesite, sandstone, and basalt. If the bulk specific gravity is less than 2.4, material separation is likely to occur due to the difference in specific gravity between powder components such as cement and calcium aluminate during pressure feeding, and the volume contained in the mortar increases, so the cured product after spraying The strength and durability may be sluggish, which is not preferable. Further, if the bulk specific gravity exceeds 2.9, the air pressure feeding resistance increases depending on the particle size, and the pressure feeding speed is slower or more likely to sink than other powder components, and the mixing uniformity as a premix mortar is improved. It is not preferable because it may not be possible to secure it. Further, the fine aggregate to be used has, in addition to the specific gravity, a central particle diameter of 0.4 mm or more and a particle content rate of 0.05 to 3.5 mm of 99% by mass or more. .. When fine aggregate with such a particle size is used, pre-mixing tends to form a large amount of intergranular fine aggregate particles, and relatively fine powder such as cement particles or gypsum can be dispersed appropriately among the intergranular particles. The mixed state can be easily obtained and the degree of mixing can be increased. Further, if the central particle size is less than 0.4 mm, the fine particles in the premix mortar increase, and the mixing property decreases, which is not preferable. Further, even if the central particle size is 0.4 mm or more, if the particle size range of the fine aggregate is too wide than 0.05 to 3.5 mm, the fine aggregate according to the particle size during air pressure feeding is formed. It is not preferable because a separation tendency appears. Therefore, it is necessary that the fine aggregate used has a particle size of 0.05 to 3.5 mm in which 99% by mass or more (including 100% by mass) of all the aggregates belong. The content of the fine aggregate is 130 to 350 parts by mass with respect to 100 parts by mass of the Portland cement content in the premix mortar. If the amount is less than 130 parts by mass, the proportion of fine powder components increases, which may deteriorate the kneading property after water injection, which is not preferable. Further, if it exceeds 350 parts by mass, the strength of the mortar may decrease, which is not preferable.

The premix mortar constituting the spray mortar of the present invention may contain components other than the above components as long as they do not impair the effects of the present invention. Examples of the components that can be contained include powdery water reducing agents, dry mixing aids, setting accelerators, and short fibers, all of which are used in mortar and concrete.

It is preferable to contain a powdery water reducing agent from the viewpoints of reducing the amount of unit water in the mortar and improving the kneading efficiency after water injection. Water-reducing agents include those referred to as water-reducing agents, dispersants, high-performance water-reducing agents, high-performance AE water-reducing agents, AE water-reducing agents, and the like, and their active ingredients are not particularly limited, and examples include polycarboxylic acids and salts thereof. , Naphthalenesulfonic acid formalin condensate, ligninsulfonic acid naphthalene condensate, and the like. When the water reducing agents are mixed, the content is preferably 0.1 to 0.6 parts by mass with respect to 100 parts by mass of the Portland cement content in the premix mortar. When a liquid admixture is used, it is not premixed in the premix mortar but is added at the time of adding a liquid quick-setting agent or water as described below.

The premix mortar constituting the spray mortar of the present invention preferably contains short fibers. The short fiber is not particularly limited as long as it is a fiber made of a material such as an organic polymer that can be used for mortar or concrete, carbon, steel, glass, or ceramics. Preferably, an organic polymer is used because it has folding resistance and corrosion resistance and is relatively inexpensive. The length of the short fibers is not particularly limited, but is preferably 5 to 20 mm, more preferably 10 to 12 mm. The fiber diameter is also not particularly limited, but it is preferably 1 mm or less in order to obtain a sufficient fiber blending effect. By containing the short fibers, the crack resistance of the mortar construction is improved. Also, the toughness of the construction is improved. In order to exert such an effect, the content of the short fiber is preferably about 0.03 to 0.25% by volume of the whole premix mortar.

The spray mortar of the present invention can be obtained by adding an alkali-free liquid quick-setting admixture and water to the premix mortar. It is desirable to add the alkali-free liquid quick-setting admixture and water to the premix mortar as soon as possible before spraying. The alkali-free liquid quick-setting agent and water may be added substantially at the same time, but preferably, the alkali-free quick-setting agent is first added, and water is preferably poured into a mixture of the alkali-free quick-setting agent. If water is injected from an early stage during the premix mortar pumping, the condensation will proceed and the pumping will be hindered, and it will be indispensable to remove the residue in the pipe after the pumping is stopped. The device for addition is not particularly limited, and a liquid quick-setting agent supply pipe and a water supply pipe are provided, for example, in a Y shape, to the pressure-feeding pipe to which the premix mortar pressure-fed in the pressure-feeding pipe is pressure-fed. Connect them through confluent parts such as pipes, double pipes, etc., or use a mortar spraying device equipped with a liquid quick-setting admixture and water addition mechanism.

The alkali-free liquid quick-setting admixture added to the premix mortar is a liquid quick-setting admixture that does not contain alkali metal components such as alkali metal compounds as much as possible. By adding such a quick-setting agent, the mortar finishes setting in a short time, and good spray adhesion can be obtained. The specific active ingredient of the alkali-free liquid quick-setting admixture used in the present invention is not limited as long as it does not contain an alkali metal component, but is preferably aluminum sulfate. More preferably, aluminum sulfate having a concentration (effective solid content) of 30 to 53 mass% is used because it has good compatibility with Portland cement. The amount of the alkali-free liquid quick-setting admixture added to the premix mortar is 5 to 9.5 parts by mass in terms of liquid mass with respect to 100 parts by mass of the cement content in the premix mortar. If the amount of addition exceeds 9.5 parts by mass, the tendency to form instantaneously increases, but the long-term strength developability decreases, so it is not preferable, and if the amount of addition less than 5 parts by mass, the rapid setting property is insufficient and sufficient adhesion cannot be achieved, and the mortar construction product It is not preferable because it hinders the fixing of the toner.

Further, the amount of water added to the premix mortar is not particularly limited, and may be any amount that can react with components having hydration reaction activity such as cement and anhydrite in a substantially sufficient manner. As an example of the amount of water added, the amount of water added is 10 to 25 parts by mass with respect to 100 parts by mass of the cement content. Preferably, the amount of water added is 13 to 20 parts by mass in order to improve the kneading property at the time of water injection and the mortar strength manifestation property.

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the described examples. The examples were carried out in an environment of 20 (±1)° C. unless otherwise specified.

[Preparation of calcium aluminate]
With CaCO ₃ and Al ₂ O ₃ commercial industrial chemicals, as the value of the molar ratio of CaO and _{Al 2 O 3 (CaO / Al} 2 O 3) is obtained calcium aluminate representing below Hyoryou The ingredients were blended and a raw material mixture was prepared with a Henschel mixer. This raw material mixture was fired at about 1600° C. (±50° C.) for 60 minutes using an electric furnace and immediately taken out of the furnace after the firing time had elapsed. Nitrogen gas for cooling was sprayed onto the surface of the fired lump (clinker) taken out at a flow rate of about 30 ml/sec to rapidly cool it to obtain a cooled product. In addition, in order to adjust the vitrification rate, a part of the clinker was sprayed while reducing the flow rate of nitrogen gas. Each clinker was crushed with an all-steel ball mill and subjected to a classifier to adjust the Blaine specific surface area to about 5000 cm ² /g. As the sized powder, the calcium aluminate powder represented by CA1 to CA5 below was obtained. The vitrification rate of calcium aluminate is obtained by quantifying the mass of each mineral contained in the calcium aluminate clinker having a mass of M1 by an internal standard method using a powder X-ray diffractometer, and calculating the total sum of the contained mineral phases. The mass; M2 was calculated, the rest was regarded as a pure glass phase, and the vitrification rate was calculated by the following formula.
Vitrification rate (%)=(1-M2/M1)×100

[Prepared calcium aluminate]
CA1; content molar ratio (CaO/Al ₂ O ₃ ) 2.3, vitrification rate 90%
CA2; content molar ratio (CaO/Al ₂ O ₃ ) 2.4, vitrification rate 90%
CA3; content molar ratio (CaO/Al ₂ O ₃ ) 2.2, vitrification rate 90%
CA4; content molar ratio (CaO/Al ₂ O ₃ ) 2.3, vitrification rate 50%
CA5; Molar content ratio (CaO/Al ₂ O ₃ ) 1.7, vitrification rate 90%

[Preparation of premix mortar]
Calcium aluminate powder represented by the above-mentioned CA1 to CA5, ordinary Portland cement (commercial item. Blaine specific surface area 3200 cm ² /g, density 3.15), classification treatment of commercial industrial anhydrous gypsum represented by the following CS1 to CS2 Products, fine aggregates represented by SG1 to SG8 below, powdery polycarboxylic acid-based high-performance water reducing agent (commercially available product), polypropylene short fibers having a length of 12 mm (referred to as FW1. commercially available product), and having a length of 10 mm. Materials selected from polyvinyl short fibers (commercially available as FW2) were put into a Henschel mixer all at once so that the compounding amounts shown in Table 1 were obtained. This mixer was dry-mixed for about 2 minutes to prepare a premix mortar.

[Classified anhydrous gypsum]
CS1; Blaine specific surface area 4800 cm ² /g
CS2; Blaine specific surface area 6400 cm ² /g

[Fine aggregate used in combination]
The unit of the central particle size is mm. The abundance ratio within the specified particle size range represents the content ratio of the fine aggregate having a particle size of 0.05 mm to 3.5 mm in the total fine aggregate.
SG1; limestone fine aggregate, bulk specific gravity; 2.7, central particle size; 0.6, abundance within the specified particle size range; >99%
SG2; silica sand fine aggregate, bulk specific gravity; 2.6, central particle size; 1.2, abundance within the specified particle size range: >99%
SG3; basalt crushed sand, bulk specific gravity; 2.9, central particle size; 0.6, abundance within the specified particle size range; >99%
SG4; silica sand fine aggregate, bulk specific gravity; 2.6, central particle size; 0.4, abundance within the specified particle size range; >99%
SG5; silica sand fine aggregate, bulk specific gravity; 2.6, central particle size; 0.2, abundance within the specified particle size range; >99%
SG6; silica sand fine aggregate, bulk specific gravity; 2.6, central particle size; 0.6, abundance within the specified particle size range; 63%
SG7; crushed andesite sand, bulk specific gravity; 2.4, central particle size; 0.6, abundance in the specified particle size range; >99%
SG8; fine aggregate of expanded shale, specific gravity; 1.6, central particle size; 0.6, abundance within the specified particle size range; 99%

[Preparation of mortar for spraying]
The produced premix mortar was pressure-fed with compressed air by a pump through a resin hose pipe having a length of about 50 m and an inner diameter of 4.0 cm. Water to be separately fed was added from a water addition port provided on the side surface near the tip of the hose pipe to be pressure-fed so that the premixed mortar and the water fed under pressure can be combined in the pipe. Wet premix mortar mixed and mixed with water is a ring-shaped quick-setting agent having multiple addition ports provided around the mortar passage in the device by a spraying device connected to the pipe port on the discharge side of the combined product. The alkali-free liquid quick-setting agent was added from the addition section in a shower state. The mortar that passed through this quick-setting-agent-added portion was sprayed through a nozzle for spraying. The alkali-free liquid quick-setting admixture used here has aluminum sulfate as an active ingredient, and the solid content concentration of the active ingredient is 48 mass% (SA1), 42 mass% (SA2) and 51 mass% (SA3). There are three types. Table 2 shows the amounts of the liquid quick-setting agent and water added to 100 parts by mass of Portland cement in the premix mortar.

[Evaluation of quick-setting property of spray mortar]
To the mortar for spraying produced as described above, the Proctor penetration resistance value was measured after 30 seconds, 60 seconds, 180 seconds and 300 seconds of the addition of the liquid quick-setting agent to evaluate the quick-setting property. .. Measurement method of Proctor penetration resistance conforms to Japan Society of Civil Engineers concrete standard Sashikata term "for Shotcrete quick-setting admixture quality standard" Annex "Madokayui time measurement method of the mortar by penetration resistance" of the cross-sectional area 0.125 cm ² A proctor needle was used. Table 3 shows the measurement results of the penetration resistance value. Here, "-" described in the table indicates that the mortar was hardened and the penetration resistance could not be measured. Further, according to become "> 16 (N / mm ^2)" is possible is driving the Proctor needle, but beyond the measurement limit of the fleet (maximum 16N / mm ^2). Moreover, the thing which did not deserve measurement was shown as "x", because no condensation was observed.

[Evaluation of spray fixing property of spray mortar]
Immediately after the preparation, the spray mortar prepared as described above was used for spraying using a mortar spray gun. The spraying was done by spraying onto the following objects. That is, the spraying mortar was sprayed at a flow rate of 160 ml/min toward a 3 mm square concrete flat plate surface having a thickness of 9 mm, which was vertically installed at a position about 100 cm away from the nozzle hole of the mortar spraying gun. To evaluate the fixing property of the sprayed product, the bounce (rebound) of the spray mortar from the flat plate surface was examined by visual observation, and when the bounce was not substantially seen, the rebound was judged to be "no", and the bounce did not occur. We judged that there was a rebound "Yes". In addition, the mortar sprayed on the flat plate surface was judged to have good adhesiveness when it continued to adhere without sagging or peeling off, and all other conditions were "poor". It was decided. Also, after such spraying for 3 minutes, the supply of the premix mortar is stopped for 30 minutes, the spraying is interrupted, the supply of the premix mortar is restarted, and the spraying is performed again. If there is a hindrance to the mortar's transportation pipe pumping, or if there is a spraying failure such as a decrease in the spraying amount of the mortar for spraying, it is judged that the pumping property is ``poor'', these phenomena are not seen, and smooth pumping is possible, When the variation in the sprayed amount was not observed, the pumpability was judged to be “good”. The results are shown in Table 4.

[Evaluation of Strength Development of Spray Mortar]
Immediately after the preparation, the mortar for spraying after water injection prepared as described above was filled in a molding frame having inner dimensions of 40×40×160 mm. This was left standing in the indoor air for 9 hours and then demolded. The demolded product was placed in a constant temperature oven at 20° C. (±1° C.) until a predetermined material age was reached to obtain specimens with an age of 3 hours, 1 day, and 7 days, respectively. The uniaxial compressive strength of each specimen was measured with an Amsler type compressive strength tester. The results are also shown in Table 4. In addition, those that were uncured at a predetermined age were described as "unmoldable" and the strength test could not be performed.

[Evaluation of flaking resistance of spray mortar]
A hitting test was carried out as an evaluation of the peeling resistance of a part of the sprayed mortar prepared as described above after water injection. The impact test was carried out by a method in conformity with "Stripping prevention effect (impact test) 2005.4 by addition of synthetic fiber of Annex 8-5 of civil engineering standard specifications of East Japan Railway Company". That is, using the sprayed mortar after the water injection, a 15 cm×15 cm×60 cm prismatic sample was prepared by frame molding, and placed and fixed on a horizontal desk with an arbitrary 15 cm×60 cm surface as the bottom surface. A 770-gram hammer was swung down like a pendulum from a height of about 30 cm from the test piece on a vertical surface at a position 2 to 4 cm from the bottom surface, and hit by the weight of the hammer. Although cracks occurred when the number of hits increased, the hits were repeated until the cover concrete fell off by about 1 cm ² or more, and the number of hits until the fall off was measured. The test was performed three times for each mortar. The results are shown in Table 5.

From the results of Tables 3 and 4, it can be seen that the mortar for spraying of the product of the present invention has a quick-setting property for sufficiently securing the adhesive property during spraying. Further, from the results of Table 4, the spraying mortar of the present invention has an excellent fixing rate at the time of spraying, and since the mortar in a good mixed state is sprayed, there is no variation in the fixability. In addition, it can be seen from the results in Table 4 that the spraying mortar of the present invention exhibits a high initial strength expression despite the dry spraying using the alkali-free liquid quick-setting admixture. Further, from the results shown in Table 5, in the mortar for spraying of the present invention in which fibers are mixed, the adhesiveness and the strength are not decreased due to the separation and uneven distribution of the fibers even after the pressure-feeding process, and the crack fracture by the impact is suppressed. It is understood that the fiber mixing effect is sufficiently exhibited.

Claims (3)

Containing the following premix mortar (A) and 100 parts by mass of Portland cement content in the premix mortar, 5 to 9.5 parts by mass of an alkali-free liquid quick-setting agent and water are contained ,
Mortar for spraying, wherein the alkali-free liquid quick-setting agent is aluminum sulfate having a solid content concentration of 30 to 53 mass % .
A: 100 parts by mass of Portland cement, 2.5-8 parts by mass of anhydrous gypsum, and the molar ratio of CaO and Al ₂ O ₃ (CaO and /Al ₂ O ₃ ) as chemical components is 2.2 to 2.4. 3 to 8 parts by mass of a certain amorphous calcium aluminate and a bulk specific gravity of 2.4 to 2. with a content of particles having a central particle size of 0.4 mm or more and a particle size of 0.05 to 3.5 mm of 99% by mass or more. Premixed mortar containing 130 to 350 parts by mass of fine aggregate of 9 and containing no water. The spray mortar according to claim 1, wherein the premix mortar contains a water reducing agent. The spray mortar according to claim 1 or 2, wherein the premix mortar contains short fibers.