JP2019218223A - Hardening accelerator for concrete surface finishing - Google Patents

Abstract

To provide a hardening accelerator for concrete surface finishing capable of ensuring good surface finish and shortening the duration from concrete casting to the time surface finishing becomes possible, even in a cold season.SOLUTION: A hardening accelerator for concrete surface finishing of this invention contains aluminum sulfate and/or potassium alum and a flow regulator, in which the aluminum sulfate and/or potassium alum is 70 parts by mass or more and 95 parts by mass or less, and the flow regulator is 5 parts by mass or more and 30 parts by mass or less.SELECTED DRAWING: None

Description

  The present invention relates to a hardening accelerator for concrete surface finishing of concrete mainly used in the field of civil engineering and construction. The concrete of the present invention is a general term for cement paste, mortar and concrete.

  The construction industry is said to have a lot of so-called 3K (dangerous, hard, dirty) work. The Ministry of Land, Infrastructure, Transport and Tourism has stated in its White Paper on Land, Infrastructure, Transport and Tourism and its Priority Policy that it is aiming for a new 3K (paying well, taking vacations, giving hope) and reforming the construction industry. For example, in concrete works, the policy is to promote work efficiency, labor saving and light labor under the keyword “i-Construction”. Under these circumstances, it is desired to reduce overtime in connection with improving the working environment of workers at construction sites.

In the concrete work, after the concrete is cast, the surface is finished. The quality of this surface finish affects the cracking and strength of the concrete, and ultimately the durability of the concrete structure. Examples of the surface finish of concrete include a metal iron, a wooden iron, a plastic iron, a hard iron iron, and the like, and a soldering iron finish, and a vibrator finish for smoothing with a surface finishing vibrator. This is done using a trowel.
Regarding the surface finishing by the iron or the like, when the final surface finishing operation is started, the time when bleeding starts to be drawn is the optimal time, and the work cannot be performed until that time. At that time, it is right before the time when the concrete starts to set, and it is the present situation that plasterers are waiting for many hours, especially in concrete casting in cold weather when the outside temperature is low. In many cases, the waiting time causes a decrease in work efficiency and leads to overtime.

  A method of adding a setting accelerator to concrete, for example, a method of adding aluminum sulfate (Patent Literature 1 and Patent Literature 2) is also conceivable for the purpose of accelerating the setting and hardening of concrete and shortening the waiting time until the start of setting. However, in this case, the consistency of the concrete is reduced during transportation, the workability at the time of casting is remarkably deteriorated, the construction does not work well, and there is a possibility of causing a construction defect.

  Further, a setting regulator is used in the existing technology for shortening the construction period by using a setting accelerator and a setting regulator in combination with quick-setting cement (Patent Document 3). However, in this case, the setting modifier may delay the setting of the concrete during the on-site casting in the cold season, so that the work time until the surface finishing by the iron may be delayed.

Regarding the surface finishing process of concrete, a method using a surface finishing machine (Patent Document 4), a method using roughening mat in combination with a curing mat (Patent Document 5), and a method using a resin film to perform ironing (Patent Document 5) Document 6), a method of vacuum degassing from a concrete surface through a filter mat (Patent Document 7), a method of using a nonwoven fabric sheet (Patent Documents 8 and 9), and the like are known. However, there have been problems such as the necessity of using special equipment and materials, and the need for extra steps and finishing requiring special techniques, which is troublesome.
Furthermore, for surface finishing using an iron, special materials and equipment are required by using a surface finishing agent such as a polymer dispersion (Patent Document 10), a surfactant (Patent Document 11), or an aqueous curing agent (Patent Document 12). And technologies that do not have been developed. However, although these surface finishing agents can improve the quality of ironing on the concrete surface, it is impossible to shorten the time until ironing is possible, and it is impossible to shorten the process.

French Patent No. 2031950 JP 08-48553 A JP-A-5-321463 Japanese Patent No. 2046553 JP-A-06-172060 JP-A-10-018566 Japanese Patent No. 03398716 JP-A-2000-015619 Japanese Patent No. 5830051 Japanese Patent No. 1887894 Japanese Patent No. 4574316 JP 2014-173246 A

As described above, the conventional technology for the surface finishing process of concrete requires special equipment and labor to increase durability, and it is also possible to perform surface finishing (particularly iron finishing) from concrete casting. It was not possible to shorten the time, and as a result, it was impossible to shorten the process. It is also important to have a so-called surface finish (iron finish in the case of iron finish) that can secure a sufficient time for performing a wide range of surface finish operations.
Therefore, the present invention provides a hardening accelerator for concrete surface finishing capable of ensuring good surface finish and shortening the time from concrete casting to surface finishing even during the cold season. With the goal.

  The present inventors have conducted studies to solve the above problems, and by combining aluminum sulfate and / or potassium alum with a fluidizing agent in a special range, it is possible to ensure good ironing finish, and It has been found that a hardening accelerator for concrete surface finishing can be obtained which can be shortened from the time when concrete is cast to the time when ironing is possible even in the final period. That is, the present invention is as follows.

[1] comprising aluminum and / or potassium alum and a flow regulator;
A curing accelerator for concrete surface finishing, wherein the aluminum sulfate and / or potassium alum is 70 parts by mass or more and 95 parts by mass or less, and the flow regulator is 5 parts by mass or more and 30 parts by mass or less.
[2] The hardening accelerator for concrete surface finishing according to [1], wherein the flow regulator is at least one of a melamine compound, an oxycarboxylic acid, and an oxycarboxylate.
[3] Concrete 1 m ³ 4 kg / m ³ was mixed with respect to, the time from immediately after driving of the concrete until it becomes possible trowel finish, following 8 hours at ambient temperature 5 ° C., in the following 4 hours at ambient temperature 20 ° C. The curing accelerator for concrete surface finishing according to [1] or [2].
[4] Slump or slump flow 90 minutes after the completion of mixing of the concrete mixed with the concrete surface finishing hardening accelerator is compared with concrete of the same composition except that the concrete surface hardening accelerator is not mixed. The hardening accelerator for concrete surface finishing according to any one of [1] to [3], wherein the slump is ± 2 cm, and the slump low is ± 5 cm.

  By using the hardening accelerator for concrete surface finishing of the present invention, good surface finish properties can be ensured, and the time from concrete casting to surface finishing can be shortened even in the cold season. As a result, it is possible to improve the work efficiency of the plasterer and to improve the efficiency of the construction site.

Hereinafter, the present invention will be described in detail.
Note that “parts” and “%” used in this specification are based on mass unless otherwise specified. In the following, a description will be given of ironing as a preferred example of surface finishing, but the same can be said for other surface finishing.

Since the hardening accelerator for concrete surface finishing of the present invention can shorten the time required for surface finishing such as ironing, it leads to an increase in work efficiency of plasterers. Normally, after casting concrete, plasterers often wait for more than half a day after the occurrence of bleeding has ceased and before final finishing, and this waiting time has impaired the efficiency of the construction site .
By using the hardening accelerator for concrete surface finishing of the present invention, it is possible to shorten the time until the final ironing is performed, and it is possible to improve the construction efficiency at the construction site.

The hardening accelerator for concrete surface finishing of the present invention contains aluminum and / or potassium alum and a flow regulator. These proportions are such that aluminum sulfate and / or potassium alum are 70 parts or more and 95 parts or less, the flow regulator is 5 parts or more and 30 parts or less, and aluminum sulfate and / or potassium alum are preferably 80 parts or more and 95 parts or less. Parts or less, and the flow regulator is 5 parts or more and 15 parts or less.
If the amount of the aluminum sulfate and / or potassium alum is less than 70 parts and the flow modifier exceeds 30 parts, the effect of shortening the time from immediately after the concrete is poured until ironing can be performed may not be obtained. If the amount of the aluminum sulfate and / or potassium alum exceeds 95 parts and the amount of the flow regulator is less than 5 parts, a highly accurate ironing property may not be obtained.

Further, the total of aluminum sulfate and / or potassium alum and the flow modifier in the hardening accelerator for concrete surface finishing is preferably 85% or more, more preferably 90% or more. When it is 85% or more, the construction efficiency of the ironing work at the construction site can be further improved.
In addition to the aluminum sulfate and / or potassium alum and the flow regulator, a water reducing agent, a high performance water reducing agent, an AE water reducing agent, a high performance AE water reducing agent, a fluidizing agent, a defoaming agent, a thickener, a rust inhibitor , A deicing agent, a shrinkage reducing agent, a setting regulator, a fibrous substance such as vinylon fiber, acrylic fiber, and carbon fiber; a polymer dispersion for cement admixture; an anion exchanger such as hydrotalcite; More than one species can be used without substantially inhibiting the purpose of the present invention.

The aluminum sulfate referred to in the present invention is represented by the general formula Al ₂ (SO ₄ ) ₃ .nH ₂ O, where n is in the range of 0 to 18. As aluminum sulfate, anhydrous aluminum sulfate and aluminum sulfate of various numbers of water of crystallization exist, and any of them can be used in the present invention. Also, dried aluminum sulfate obtained by drying aluminum sulfate 18 hydrate at, for example, 105 ° C. for 24 hours can be used.

  Aluminum sulfate is preferably a powder, and its average particle size is not limited. However, it is usually preferably 500 μm or less, more preferably 325 μm or less. When the average particle size of the aluminum sulfate is 500 μm or less, the ironing property is improved, and the bleeding after the ironing is easily reduced.

The potassium alum referred to in the present invention is a kind of alum and is a double salt containing potassium ion, hydrated aluminum ion and sulfate ion. A compound represented by the general formula AlK (SO ₄ ) ₂ .nH ₂ O, wherein n is 0 to 12 can be used.

The potassium alum is preferably a powder, and the average particle size thereof is not limited, but is usually preferably 500 μm or less, more preferably 325 μm or less. When the average particle diameter of the potassium alum is 500 μm or less, the ironing property becomes good, and the bleeding after the ironing becomes easy to be contained.
The measurement of the average particle size was measured by a laser diffraction / scattering type particle size distribution meter manufactured by Horiba, Ltd.

  Of the aluminum sulfate and potassium alum, aluminum sulfate is preferred in the present invention, and anhydrous aluminum sulfate is more preferred. With aluminum sulfate, the ironing start time in the cold season can be shortened, and the ironing time can be ensured in a range where the workability is good. In addition, if it is an anhydride of aluminum sulfate, rapid hardening due to the influence of water can be prevented well, and a practical ironing time can be secured.

  The flow control agent used in the present invention refers to a uniform setting and hardening while maintaining appropriate fluidity of the concrete by slowing down the rapid setting and hardening action of concrete by aluminum sulfate and / or potassium alum to some extent. And an admixture that can reduce the time from concrete casting to ironing.

The flow regulator is preferably at least one of a melamine compound, an oxycarboxylic acid, and an oxycarboxylic acid salt.
The melamine-based compound is preferably a powdered melamine-based compound, and examples thereof include methylol melamine condensate, melamine sulfonate, and melamine sulfonate formalin condensate. Specifically, a product name “Seakament FF” manufactured by Sika Japan Co., Ltd. can be used.

  Examples of the oxycarboxylic acid include tartaric acid, citric acid, gluconic acid, and the like, and examples of the oxycarboxylic salt include salts of the above oxycarboxylic acid. These may be used alone or as a mixture of two or more.

  Among the above, the melamine-based compound is a material that imparts dispersibility to concrete by adhering to the surface of cement particles, and has a good mixability between aluminum sulfate and / or potassium alum and the cement composition. And the effect of the present invention is more easily exhibited.

Therefore, a melamine-based compound is preferable as the flow regulator, but a mixture of the melamine-based compound and an oxycarboxylic acid and / or an oxycarboxylate is preferable from the viewpoint of the effect of shortening the time until ironing is possible. . At this time, the mass ratio of the melamine compound to the oxycarboxylic acid and / or oxycarboxylate is [melamine compound]: [oxycarboxylic acid and / or oxycarboxylate] = 40: 60 to 95: 5. The ratio is preferably 80:20 to 90:10, and more preferably 80:20 to 90:10.
The oxycarboxylic acid used in combination with the melamine compound is preferably tartaric acid from the viewpoint of further improving the effects of the present invention.

The hardening accelerator for concrete surface finishing of the present invention is preferably used in an amount of 2 to 10 kg / m ³ per 1 m ^{3 of} concrete, more preferably ⁴ to 8 kg / m ³ . When it is 2 kg / m ³ or more, the effect of shortening the time from immediately after the concrete is poured to when ironing can be performed is easily obtained. When the content is 10 kg / m ³ or less, the effect of shortening the time from immediately after the concrete is poured to when ironing can be performed can be easily obtained, and the fluidity retention of the concrete can be favorably maintained.

The hardening accelerator for concrete surface finishing of the present invention is mixed with 4 kg / m ³ (preferably ² to 10 kg / m ³ ) with respect to 1 m ^{3 of} concrete, and immediately after the concrete is poured in until the ironing becomes possible. The time is preferably 8 hours or less at an environmental temperature of 5 ° C, and 4 hours or less at an environmental temperature of 20 ° C. When the temperature is 8 hours or less at an environmental temperature of 5 ° C. and 4 hours or less at an environmental temperature of 20 ° C., it is possible to secure a good iron-finished surface and shorten the time from concrete casting to iron-iron finishing. .

  It is more preferable that the time from the time immediately after the concrete is poured to the time when ironing can be performed is 2 to 8 hours at an environmental temperature of 5 ° C. Further, at an environmental temperature of 20 ° C., it is more preferable that the heating time is 1 to 4 hours.

  The hardening accelerator for concrete surface finishing of the present invention can be used for any concrete, and is not affected by the type of cement. Examples of the cement include, for example, various portland cements such as ordinary, fast, ultra-high, low heat, and moderate heat, and various mixed cements obtained by mixing blast furnace slag, fly ash, or silica with these portland cements, limestone powder, and blast furnace. Examples include filler cement mixed with finely-cooled slag fine powder and the like, and eco-friendly cement (eco-cement) manufactured using municipal waste incineration ash and sewage sludge incineration ash as raw materials. Portland cement is preferred because of its availability, and ordinary Portland cement is most preferred.

  The aggregate used for the concrete that is the subject of the present invention is not particularly limited, and may be any aggregate that is produced naturally and whose grain size is adjusted by an artificially produced aggregate.

  In the present invention, the method of mixing the respective materials is not particularly limited, and the respective materials may be mixed at the time of construction, or a part or all of them may be mixed in advance. As the mixing device, any existing device can be used, and examples thereof include a tilting mixer, an omni mixer, a Henschel mixer, a V-type mixer, a pro-share mixer, and a Nauter mixer.

  The hardening accelerator for concrete surface finishing as described above is such that the slump or slump flow 90 minutes after the completion of mixing of the concrete mixed with the hardening accelerator for concrete surface finishing does not mix the hardening accelerator for concrete surface finishing. Compared to concrete of the same composition, the slump preferably has ± 2 cm and the slump low has ± 5 cm. With such a slump or a slump flow, it is possible to secure a good iron-finished surface and to shorten the time from concrete placement to the time when ironing is possible. More preferably, the slump is ± 1.5 cm, and the slump is ± 3 cm.

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

(Example 1)
Unit cement amount 310 kg / m ³ , unit water amount 170.5 kg / m ³ , s / a = 43%, air amount 4.5 ± 1.5%, slump 12 ± 2.5 cm, water reducing agent addition rate: cement × 1 0.0% concrete was prepared using a 50 L twin screw mixer.

The materials used for the preparation of the concrete are as follows.
Cement: ordinary Portland cement, commercially available product, Blaine specific surface area 3200 cm ² / g.
- Coarse aggregate: crushed stone, density 2.64g / ^cm 3.
・ Fine aggregate: Washed sea sand. Chloride content 0.02%. Density 2.62 g / cm ³ .
・ Water: Tap water ・ Water reducing agent: Lignin-based water reducing agent, manufactured by GCP

Further, various mixing ratios were adjusted as shown in Table 1 below using the following materials (inorganic compounds and flow control materials) to prepare a concrete surface finishing hardening accelerator for concrete. 6 kg / m ^{3 of the} produced concrete surface finishing hardening accelerator was mixed with 1 m ^{3 of} concrete, and each measurement was carried out.
In addition, the hardening accelerator for concrete surface finishing was charged into the biaxial mixer after the concrete kneading was completed and mixed for 30 seconds. All tests were performed in a 5 ° C. constant temperature room.

(1) Inorganic compound Inorganic compound A: anhydrous aluminum sulfate reagent Inorganic compound B: dried aluminum sulfate reagent Inorganic compound C: aluminum sulfate 18 hydrate (powder), average particle size 325 μm, commercially available product Inorganic compound D: potassium alum 12 Water salt (powder), average particle size 305 μm, commercial product

(2) Flow control agent Flow control agent A: powdered melamine-based compound, Cicament FF (manufactured by Cika Co., Ltd.)
Flow regulator B: tartaric acid, reagent Flow regulator C: sodium gluconate, reagent

"Test method"
Iron finishing time: 24 pieces of 30 cm × 30 cm × 10 cm formwork were prepared, filled with concrete, and the concrete surface was ironed one by one every hour from the concrete casting. Check the condition of the concrete surface 24 hours after ironing, suitable for ironing that satisfies two conditions: (1) the concrete surface is smooth, and (2) no settlement is seen from the top of the concrete formwork. In addition, the shortest time from when the concrete was poured to when ironing was possible was measured.
The time is preferably within 8 hours from the viewpoint of work efficiency and the like.

  Concrete fluidity retention: Concrete surface finishing hardening accelerator for each condition, assuming slump or slump flow value of concrete not mixed with concrete surface finishing hardening accelerator at 90 minutes immediately after pouring concrete Was evaluated as a slump or a slump flow value of concrete mixed with.

  Compressive strength: For concrete filled in a formwork of φ10 × 20 cm, the strength at the age of 24 hours was measured in accordance with JISA1108 “Test method for compressive strength of concrete”. The compressive strength of the concrete mixed with the hardening accelerator for concrete surface finishing under each condition was evaluated by setting the concrete not mixed with the hardening accelerator for concrete surface finishing as 100.

  Visual observation of the concrete surface: The iron surface was subjected to ironing at a time suitable for ironing, and the concrete surface was observed as white. .

Concrete ironing: 30 minutes after the time to reach the optimum condition for ironing, to evaluate whether sufficient time is available for a widespread ironing operation The surface of concrete cast into a 30cm × 30cm × 20cm formwork is finished with iron, (1) ironing can be done, (2) when the concrete surface is visually checked, there is no pock, air bubbles or unevenness of finish, A sample satisfying the two conditions of being smooth was evaluated as having a high iron finish, and the sample satisfying (1) but having a slight unevenness in (2) was evaluated as Δ, (1) and All of those that could not satisfy either of (2) were evaluated as x. ○ or ○ indicates that the iron finish is acceptable.
Tables 1 and 2 also show the results of the above tests.

  From Table 1, it can be seen that the hardening accelerator for concrete surface finishing of the present invention significantly shortens the time that the concrete immediately after kneading can be ironed to a slump of 12 ± 2.5 cm in a 5 ° C. environment. It can be seen that the compressive strength is increased without adversely affecting the fluidity of the powder.

  From Table 2, it can be seen that the concrete surface finishing hardening accelerator of the present invention can finish the concrete surface in a good condition in a 5 ° C. environment and can sufficiently secure the ironing work time.

"Example 2"
The test was performed in the same manner as in Example 1 except that the test was performed in a constant temperature room at 20 ° C. The test results are shown in Tables 3 and 4.

  From Table 3, it can be seen that the hardening accelerator for concrete surface finishing of the present invention significantly shortens the time in which a concrete immediately after kneading can be ironed to a slump of 12 ± 2.5 cm in a 20 ° C. environment. It can be seen that the compressive strength is increased without adversely affecting the fluidity of the powder.

  From Table 4, it can be seen that the concrete surface finishing hardening accelerator of the present invention can finish the concrete surface in a good condition in a 20 ° C. environment and can sufficiently secure the ironing work time.

(Example 3)
The same evaluation as in Example 1 was performed, except that the concrete to be mixed was a high-fluidity concrete having a slump flow of 65 cm as described below. The test results are shown in Tables 5 and 6.

Water binder ratio = 40%, unit cement amount 300 kg / m ³ , unit fly ash amount 220 kg / m ³ , s / a = 50%, slump flow 65 cm, air amount = 5%, water reducing agent addition rate: binder × 1.5% high fluidity concrete.
Fly ash: Fly ash class I specified in JIS A 6201 “Fly ash for concrete”. Water reducer manufactured by Shikoku Electric Power Co., Inc .: Polycarboxylate-based high-performance AE water reducer, manufactured by GCP

  Table 5 shows that the hardening accelerator for concrete surface finishing of the present invention significantly shortens the time that ironing can be performed on high-fluidity concrete in which the concrete immediately after kneading has a slump flow of 65 cm in a 5 ° C environment. It can be seen that the compressive strength is increased without adversely affecting the fluidity of the powder.

  From Table 6, it can be seen that the hardening accelerator for concrete surface finishing of the present invention can finish the concrete surface in a good condition even in a 5 ° C. environment with respect to high-fluid concrete in which the concrete immediately after kneading has a slump flow of 65 cm. It turns out that the work time of the ironing can be sufficiently secured.

"Example 4"
The same evaluation as in Example 3 was performed except that the test was performed in a constant temperature room at 20 ° C. The test results are shown in Tables 7 and 8.

From Table 7, it can be seen that the hardening accelerator for concrete surface finishing of the present invention significantly shortens the time that ironing can be performed on high-fluidity concrete in which the concrete immediately after kneading has a slump flow of 65 cm in a 20 ° C. environment. It can be seen that the compressive strength is increased without adversely affecting the fluidity of the powder.
No. 7-27 (No. 8-27) and No. 7-27. In No. 7-28 (No. 8-28), the ironing time was shortened and the ironing property was good, but the slump flow was too large and the compressive strength was too low to be practical. Was.

  From Table 8, the hardening accelerator for concrete surface finishing of the present invention can be finished in a good condition on the concrete surface, even in a 20 ° C environment, with respect to high-fluid concrete in which the concrete immediately after kneading has a slump flow of 65 cm. It turns out that the work time of the ironing can be sufficiently secured.

"Example 5"
Example 1 was the same as Example 1 except that the blending of the inorganic compound and the flow modifier constituting the hardening accelerator for concrete surface finishing and the amount of the hardening accelerator for concrete surface finishing used were changed as shown in Tables 9 and 10. Performed similarly. The results are shown in Tables 9 and 10.

  From Table 9, it can be seen that the hardening accelerator for concrete surface finishing of the present invention significantly shortens the time in which a concrete immediately after kneading can be ironed to a 12 cm slump concrete in a 5 ° C. environment, even if the amount of addition is changed. However, it is understood that the fluidity of the concrete is not adversely affected and the compressive strength is increased.

  From Table 10, it can be seen that the concrete surface finishing hardening accelerator of the present invention can be finished in a good condition on the concrete surface even in a 5 ° C. environment, even if the amount of addition is changed, and the ironing work time can be sufficiently secured. Understand.

"Example 6"
The test was carried out in the same manner as in Example 5 except that the amount of the hardening accelerator for concrete surface finishing was changed as shown in Tables 11 and 12 in a constant temperature room at 20 ° C. The results are shown in Tables 11 and 12.

  From Table 11, it can be seen that even when the amount of the hardening accelerator for concrete surface finishing of the present invention changed at 20 ° C., the time immediately after kneading can be ironed to 12 cm slump concrete even when the amount of addition is changed. However, it is understood that the fluidity of the concrete is not adversely affected and the compressive strength is increased.

  From Table 12, it can be seen that the concrete surface finishing hardening accelerator can be finished in a good condition on the concrete surface even when the added amount is changed in an environment of 20 ° C., and a sufficient ironing work time can be secured.

  The hardening accelerator for concrete surface finishing of the present invention greatly shortens the time that ironing can be performed in a low-temperature environment, makes it possible to finish the concrete surface in good condition, does not adversely affect the fluidity of the concrete, Strength also increases. Especially in a low-temperature environment, the waiting time from concrete placing to ironing start can be greatly reduced, so it is suitable for civil engineering and construction fields, which leads to more efficient operation of plasterers and improves the efficiency of construction sites. .

Claims (4)

Comprising aluminum and / or potassium alum and a flow regulator;
A curing accelerator for concrete surface finishing, wherein the aluminum sulfate and / or potassium alum is 70 parts by mass or more and 95 parts by mass or less, and the flow regulator is 5 parts by mass or more and 30 parts by mass or less.   The hardening accelerator for concrete surface finishing according to claim 1, wherein the flow regulator is at least one of a melamine compound, an oxycarboxylic acid, and an oxycarboxylic acid salt. 4 kg / m ^{3 of} 1 m ^{3 of} concrete is mixed, and the time from immediately after the concrete is poured until ironing is possible is 8 hours or less at an environmental temperature of 5 ° C. and 4 hours or less at an environmental temperature of 20 ° C. 3. The hardening accelerator for concrete surface finishing according to 1 or 2.   The slump or slump flow 90 minutes after the completion of mixing of the concrete mixed with the concrete surface finishing hardening accelerator, compared with concrete of the same composition except that the concrete surface finishing hardening accelerator is not mixed, The curing accelerator for concrete surface finishing according to any one of claims 1 to 3, wherein the curing accelerator is ± 2 cm for a slump and ± 5 cm for the slump low.