WO2024204035A1 - Setting accelerator for trowelled finishing, concrete composition, and hardened body - Google Patents

Abstract

The purpose of the present invention is to provide: a setting accelerator for trowelled finishing, which exhibits concrete fluidity maintaining properties and can shorten the period of time between concrete placement and a point at which trowelled finishing is possible; a concrete composition; and a hardened body. Provided are: a setting accelerator for trowelled finishing, which contains an inorganic sulfate and a calcium salt of an organic acid, with the mass ratio of the inorganic sulfate and the calcium salt of an organic acid (calcium salt of organic acid/inorganic sulfate) being 20/80 to 95/5; a concrete composition that contains this setting accelerator for trowelled finishing; and a hardened body comprising this concrete composition.

Description

Setting accelerator for trowel finishing, concrete composition, and hardened product

The present invention relates to a setting accelerator for trowel finishing, a concrete composition, and a hardened concrete used primarily in the construction and civil engineering industries. The concrete composition of the present invention is a general term for cement paste, mortar, and concrete.

In concrete construction, the surface of the concrete is often finished with a trowel after it has been poured. The quality of this trowel finish can affect the cracks and strength of the concrete surface, and ultimately the durability of the concrete structure.

In this trowel finishing work, the optimal time to start the final trowel finishing work is when the bleeding starts to subside. Because the bleeding starts to subside just before the concrete starts to set, the current situation is that plasterers have to wait for hours, and this waiting time reduces work efficiency.

In order to speed up the setting of concrete, for example, Patent Document 1 below describes the addition of a setting accelerator to the concrete.

Japanese Patent Application Publication No. 08-48553

However, when setting accelerators are added to concrete, the fluidity is lost, which significantly reduces workability during pouring, leading to poor construction and the risk of construction defects.

The present invention was made in consideration of these circumstances, and aims to provide a setting accelerator for trowel finishing that retains the fluidity of concrete and shortens the time from pouring concrete to when it can be finished with a trowel. It also aims to provide a concrete composition that contains this setting accelerator for trowel finishing, and a hardened concrete body made from this concrete composition.

As a result of intensive research into solving the above problems, the inventors discovered that the above problems could be solved by a setting accelerator for trowel finishing that contains an organic acid calcium salt and an inorganic sulfate in a specific ratio, and thus arrived at the present invention. That is, the present invention is as follows.

[1] A setting accelerator for trowel finishing, comprising an organic acid calcium salt and an inorganic sulfate, wherein the mass ratio of the organic acid calcium salt to the inorganic sulfate (organic acid calcium salt/inorganic sulfate) is 20/80 to 95/5.
[2] The setting accelerator for trowel finishing according to [1], wherein the organic acid calcium salt is calcium carboxylate.
[3] The setting accelerator for trowel finishing according to [1] or [2], wherein the inorganic sulfate salt comprises at least one selected from aluminum sulfate, sodium thiosulfate, and potassium alum.
[4] The setting accelerator for trowel finishing according to any one of [1] to [3], wherein the organic acid calcium salt and the inorganic sulfate have a mass ratio of 95% or more passing through a 0.6 mm sieve.
[5] A concrete composition comprising the setting accelerator for trowel finishing according to any one of [1] to [4] and cement.
[6] The concrete composition according to [5], wherein the content of the trowel finishing setting accelerator is 0.5 to 8 kg per 1 ^m3 of the concrete composition.
[7] The concrete composition according to [5] or [6], further comprising an expansive agent.
[8] A hardened body obtained by hardening the concrete composition according to any one of [5] to [7].

The present invention provides a setting accelerator for trowel finishing that can maintain the fluidity of concrete and shorten the time from pouring concrete to when it can be finished with a trowel, a concrete composition that contains this setting accelerator for trowel finishing, and a hardened concrete body made from this concrete composition.

The trowel finishing setting accelerator, concrete composition, and hardened body of the present invention will be described in detail below, but the present invention is not limited to these embodiments. Note that "%" in this specification is based on mass unless otherwise specified. In addition, a numerical range specified using the symbol "~" includes the numerical values at both ends of "~" (upper and lower limits).

[Set accelerator for trowel finishing]
The setting accelerator for trowel finishing of the present invention (hereinafter also simply referred to as "setting accelerator") contains an organic acid calcium salt and an inorganic sulfate, and the mass ratio of the organic acid calcium salt to the inorganic sulfate (organic acid calcium salt/inorganic sulfate) is 20/80 to 95/5.

The total of the organic acid calcium salt and inorganic sulfate in the setting accelerator is preferably 80% by mass or more, and more preferably 90% by mass or more, from the standpoint of ensuring the retention of concrete fluidity and shortening the time from concrete pouring until trowel finishing is possible (hereinafter also referred to as "trowel finishing time").

(Calcium salt of organic acid)
The setting accelerator of the present invention contains an organic acid calcium salt. By containing an organic acid calcium salt, the time when trowel finishing is possible can be shortened. As the organic acid calcium salt, a carboxylate calcium salt can be used, for example, calcium formate, calcium acetate, and calcium lactate can be used. Only one type of organic acid calcium can be used, or two or more types can be used. In this embodiment, it is preferable to use calcium formate from the viewpoint of shortening the time when trowel finishing is possible.

In this embodiment, the content of the organic acid calcium salt in the setting accelerator is preferably 20% by mass or more and 95% by mass or less, more preferably 30% by mass or more and 90% by mass or less, and even more preferably 40% by mass or more and 85% by mass or less. By making the content of the organic acid calcium salt 20% by mass or more, the time until trowel finishing can be completed can be shortened. Furthermore, by making it 95% by mass or less, the fluidity of the concrete can be appropriately reduced.

The organic acid calcium used in the setting accelerator of the present invention is preferably in powder form, with 95% or more passing through a 0.6 mm sieve. By making the organic acid calcium powder such that 95% or more passes through a 0.6 mm sieve, it is possible to improve trowel finishability. Good trowel finishability means that the concrete surface after trowel finish is smooth and free of pockmarks, air bubbles, and uneven finish. It also makes it easier to reduce bleeding after trowel finish.

(Inorganic sulfates)
The setting accelerator of the present invention contains an inorganic sulfate. By containing an inorganic sulfate, the fluidity retention of concrete can be improved. As the inorganic sulfate, for example, aluminum sulfate and alkali metal sulfates such as sodium sulfate, sodium thiosulfate, and potassium alum are preferable, and aluminum sulfate, sodium thiosulfate, and potassium alum are more preferable. Among them, aluminum sulfate is preferable from the viewpoint of maintaining the fluidity of the concrete produced, suppressing the total alkali amount (R ₂ O amount) of the concrete, and suppressing the alkali aggregate reaction. In addition, only one type of inorganic sulfate can be used, or two or more types can be used.

In this embodiment, the content of inorganic sulfate in the setting accelerator is preferably 5% by mass or more and 80% by mass or less, more preferably 10% by mass or more and 60% by mass or less, and even more preferably 15% by mass or more and 50% by mass or less. By making the content of inorganic sulfate 5% by mass or more, it is possible to appropriately reduce the fluidity of the concrete. In addition, by making it 80% by mass or less, it is possible to shorten the time until finishing with a trowel is possible.

In addition, the inorganic sulfate used in the setting accelerator of the present invention is preferably in powder form, and preferably 95% or more of the inorganic sulfate passes through a 0.6 mm sieve. By making the inorganic sulfate powder so that 95% or more of the inorganic sulfate passes through a 0.6 mm sieve, the finishability with a trowel can be improved. Also, bleeding after trowel finishing can be easily suppressed.

The set accelerator of the present invention has a mass ratio of organic acid calcium salt to inorganic sulfate (organic acid calcium salt/inorganic sulfate) of 20/80 to 95/5. If the mass ratio of organic acid calcium salt to inorganic sulfate is less than 20/80, the time required for trowel finishing will be shorter, but the fluidity of the concrete will be poorly maintained. If it exceeds 95/5, the fluidity of the concrete will improve and it will fall outside the slump range. The organic acid calcium salt/inorganic sulfate ratio is preferably 30/70 to 90/10, and more preferably 40/60 to 80/20.

In addition, in addition to the above-mentioned organic acid calcium salt and inorganic sulfate, the setting accelerator of this embodiment can also contain one or more of concrete expansion agents and shrinkage reducing agents within a range that does not substantially impair the object of the present invention.

[Method of manufacturing setting accelerator]
The setting accelerator of the present embodiment is produced by mixing the materials. The mixing method is not particularly limited, and an existing mixing device can be used.

[Concrete composition]
The concrete composition according to this embodiment contains a set accelerator and cement.

Cement is not particularly limited, and examples include various types of Portland cement, such as normal, early strength, extra early strength, low heat and medium heat, various mixed cements in which Portland cement is mixed with blast furnace slag, fly ash or silica fume, environmentally friendly cement (eco-cement) made from municipal waste incineration ash or sewage sludge incineration ash, commercially available fine particle cement, white cement, etc. It is also possible to use various types of cement in a fine powder form. It is also possible to use cement that has been adjusted by increasing or decreasing the amount of components normally used in cement (such as gypsum). Furthermore, it is also possible to use a combination of two or more of these.

The set accelerator of the present invention is preferably contained in an amount of 0.5 to 8 kg per 1 ^m3 of concrete composition, more preferably 2.5 to 5 kg, and even more preferably 3 to 4 kg. By making the content of the set accelerator 0.5 to 8 kg per 1 ^m3 of concrete composition, the effect of shortening the time until trowel finishing can be achieved is easily obtained, and the fluidity retention of concrete can be improved.

The setting accelerator is preferably contained in an amount of 0.10 to 2 parts by mass per 100 parts by mass of cement, more preferably 0.45 to 1.7 parts by mass, and even more preferably 0.55 to 1.4 parts by mass. By making the content of the setting accelerator 0.10 to 2 parts by mass per 100 parts by mass of cement, it becomes easier to shorten the time required for trowel finishing, and the fluidity retention of the concrete can be improved.

The concrete composition preferably contains aggregate. The aggregate to be used may be the same fine or coarse aggregate as that used in ordinary cement mortar or concrete. That is, river sand, river gravel, mountain sand, mountain gravel, crushed stone, crushed sand, limestone aggregate, lime sand, silica sand, colored sand, artificial aggregate, blast furnace slag aggregate, sea sand, sea gravel, artificial lightweight aggregate, heavy weight aggregate, etc. may be used, and combinations of these are also possible.

The concrete composition may contain a water-reducing agent. When the concrete composition contains a water-reducing agent, it is easier to improve the fluidity retention. Examples of water-reducing agents include polyol derivatives, lignin sulfonates and their derivatives, and high-performance water-reducing agents, and one or more of these may be used in combination. Among these, high-performance water-reducing agents are preferred from the viewpoint of fluidity retention.

Examples of high-performance water-reducing agents include formalin condensates of alkylarylsulfonates, formalin condensates of naphthalenesulfonates, formalin condensates of melaminesulfonates, and polycarboxylic acid polymer compounds, and one or more of these may be used in combination. Among these, polycarboxylic acid polymer compounds are preferred because of their high fluidity retention effect.

The amount of the high performance water reducing agent used is preferably 0.05 to 3 parts by mass, and more preferably 0.1 to 2 parts by mass, per 100 parts by mass of cement. When the amount is 0.05 to 3 parts by mass, the effect of maintaining sufficient fluidity is easily obtained.
The high-range water-reducing agent can be in liquid or powder form, but it is preferable to use a powder water-reducing agent that is premixed with the concrete composition of the present invention, as this reduces workability and physical property fluctuations during on-site use.

The concrete composition may contain an expansive material. By using the set accelerator of the present invention in a concrete composition containing an expansive material, it is possible to impart a certain degree of expansiveness to the concrete, while improving the fluidity of the concrete and shortening the time from pouring to when the concrete can be finished with a trowel, thereby reducing subsequent shrinkage and cracking. Also, a shrinkage-reducing agent may be used instead of or in addition to the expansive material.

The expansive agent is not particularly limited, and any agent that generates expansion hydrates and expands concrete or mortar can be used. As the expansive agent, those containing free lime, free magnesia, calcium ferrite, ettringite, lime, ettringite-lime composite, and hauyne are preferred, as they tend to suppress shrinkage and exert their expansive effect when combined with the organic acid calcium salt and inorganic sulfate contained in the setting accelerator.

The particle size of the expansive agent is preferably 2000 to 9000 cm ² /g, more preferably 3000 to 8000 cm ² /g, in terms of Blaine specific surface area. With a specific surface area of 2000 cm ² /g or more, the hydration reaction proceeds well, while with a specific surface area of 9000 cm ² /g or less, the hydration reaction does not proceed too quickly, making it easier to obtain the desired expansion.
In this specification, the Blaine specific surface area can be determined in accordance with JIS R 5201.

The amount of expansive agent used is preferably 5 to 30 kg/ ^m3 per 1 ^m3 of concrete composition, and more preferably ^about 10 to 25 kg/m3. When the amount is 5 kg/m3 or ^more , the shrinkage compensation effect is easily obtained, and when the amount is 30 kg/m3 ^{or less} , it is possible to prevent the amount of expansion from becoming too large, which would otherwise cause a decrease in strength.

The concrete composition may contain an alkali metal carbonate. When the concrete composition contains an alkali metal carbonate, it is easier to improve the fluidity retention. Examples of alkali metal carbonates include sodium carbonate, potassium carbonate, lithium carbonate, sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, etc., and these can also be combined.

The concrete composition may contain a siliceous fine powder. The concrete composition containing the siliceous fine powder is likely to have good fluidity retention. Examples of the siliceous fine powder include latent hydraulic substances such as granulated blast furnace slag powder, fly ash, and pozzolanic substances such as silica fume, among which silica fume is preferred. The type of silica fume is not limited, but from the viewpoint of fluidity, it is more preferred to use silica fume containing 10% or less of _ZrO2 as an impurity or acidic silica fume. The acidic silica fume refers to a silica fume that exhibits an acidity of pH 5.0 or less when 1 g of silica fume is added to 100 cc of pure water and stirred.

　Concrete compositions can also contain antifoaming agents to the extent that it does not adversely affect performance. Antifoaming agents are used to reduce the amount of air entrained during mixing. There are no particular limitations on the type of antifoaming agent, so long as it does not significantly adversely affect the strength properties of the hardened mortar, and both liquid and powdered forms can be used. Examples include polyether-based antifoaming agents, polyhydric alcohol-based antifoaming agents such as esters of polyhydric alcohols and alkyl ethers, alkyl phosphate-based antifoaming agents, and silicone-based antifoaming agents.

In addition, the concrete composition may contain one or more of the following additives, provided that they do not adversely affect performance: shrinkage reducing agents, gas foaming substances, air entraining agents, rust inhibitors, water repellents, antibacterial agents, colorants, antifreeze agents, limestone fine powder, slowly cooled blast furnace slag fine powder, sewage sludge incineration ash and its molten slag, municipal waste incineration ash and its molten slag, and pulp sludge incineration ash; thickeners; shrinkage reducing agents; polymers; clay minerals such as bentonite and sepiolite; and anion exchangers such as hydrotalcite.

[Hardened body]
The hardened body according to the present embodiment is formed by hardening a concrete composition and water. The hardened body is usually formed by kneading the concrete composition with water, and the concrete, which is a hydraulic material, undergoes a hydration reaction and hardens. The amount of water used for mixing is not particularly limited, but is preferably 10 to 70 parts by mass, more preferably 14 to 65 parts by mass, and even more preferably 16 to 60 parts by mass, relative to 100 parts by mass of the concrete composition. By setting the amount of water used for mixing within the above range, the effect of retaining fluidity can be enhanced.

The hardened body is produced by kneading a set accelerator, cement, and water to produce a cement composition, and then hardening the concrete composition.
The mixing of the materials is not particularly limited, and each material may be mixed at the time of construction, or some or all of the materials may be mixed in advance. For example, when mixing some of the materials in advance, the concrete composition other than the setting accelerator and water can be mixed at a high temperature, and the setting accelerator can be mixed at the construction site. As a mixing device, any existing device such as a tilting mixer, an omni mixer, a Henschel mixer, a V-type mixer, a Plosser mixer, and a Nauta mixer can be used.

The temperature at which the concrete composition hardens is preferably 20°C or lower, more preferably 18°C or lower, and even more preferably 15°C or lower. By using the setting accelerator of the present invention, the time until finishing with a trowel can be shortened and the fluidity retention effect can be improved, even if the hardening (curing) is performed at a low temperature of 20°C or lower. In other words, the setting accelerator of the present invention can be used particularly effectively at low temperatures.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

<Measurement method>
The concrete compositions prepared in the respective experimental examples were evaluated by the following methods.
(slump)
The slump of the base concrete was measured immediately after mixing (0 min), 30 min later (immediately after adding the setting accelerator), 60 min later, and 90 min later in accordance with JIS A 1150. When the base concrete of mix No. 1 was used, the slump after 60 min was considered to be good when it was in the range of 15.5 to 20.5 cm, and when the base concrete of mix No. 2 was used, the slump after 60 min was considered to be good when it was in the range of 12.5 to 17.5 cm.
(First departure time)
The initial time was measured in accordance with JIS A 1147: 2019. A case in which the initial time was shortened by 60 minutes or more compared to a reference example in which no setting accelerator was added was deemed to have obtained good results.
(Bleeding pull time)
The bleeding time was determined by measuring the bleeding according to the concrete bleeding test method (JIS A 1123), and the time when bleeding was no longer observed was defined as the bleeding time.

<Preparation of base concrete>
Base concrete was prepared according to the mix ratio shown in Table 1 below. Two types of base concrete were prepared: Mix No. 1, which used a high-performance water-reducing agent, and Mix No. 2, which used a water-reducing agent. The water-reducing agent was added in the amount of 0.8% cement for Mix No. 1 and 1.0% cement for Mix No. 2.
The materials used are shown below.
(Materials used)
Cement: Ordinary Portland cement (commercially available)
Water: Tap water Fine aggregate: River sand from Himekawa River Coarse aggregate: Crushed stone from Himekawa River Water reducing agent: Polycarboxylic acid high performance water reducing agent (manufactured by GCP Chemicals Co., Ltd., product name: Super 100phx)
Lignin sulfonic acid-based water reducing agent (manufactured by GCP Chemicals, product name: WRDA)

(Experimental Example 1)
The set accelerator was prepared in the amounts shown in Table 2 below, and added 30 minutes after the completion of mixing of the base concrete of Mixture No. 1, and mixed to prepare a concrete composition. The slump and initial slump time were measured after a predetermined time had elapsed from the completion of mixing of the base concrete. The environmental temperature for all tests was 10°C. The results are shown in Table 2.

 

 

(Raw materials used)
Calcium formate: Asahi Chemical Industry Co., Ltd., 98% passing through 0.6 mm sieve
Anhydrous aluminum sulfate: Taimei Chemical Industry Co., Ltd., 100% passing through 0.6 mm sieve
Powdered aluminum sulfate 14-hydrate: manufactured by Taimei Chemical Industry Co., Ltd., 98% passing through a 0.6 mm sieve (crushed product used)
Potassium alum: manufactured by Taimei Chemical Industry Co., Ltd., 100% passed through a 0.6 mm sieve
Sodium thiosulfate: Air Water Performance Chemicals, Inc., 98% passing through 0.6 mm sieve

As shown in Table 2, No. 1-2 to 1-5, which are examples of the present invention, were able to shorten the initial start time and achieve a slump value equivalent to that when no setting accelerator was added.

(Experimental Example 2)
The setting accelerator was prepared in the amounts shown in Table 3 below, and added 30 minutes after the completion of mixing of the base concrete of Mixture No. 1, and mixed to prepare a concrete composition. The slump, initial bleeding time, and bleeding time were measured after a predetermined time had elapsed from the completion of mixing of the base concrete. The results are shown in Table 3.

 

 

As shown in Table 3, good results were obtained in Test Nos. 2-2 to 2-10, which are examples of the present invention. In particular, Test Nos. 2-2 to 2-4, which used aluminum sulfate, had a setting acceleration effect and were able to moderately reduce fluidity. Test Nos. 2-11 to 2-16, in which the ratio of organic acid calcium salt to inorganic sulfate was outside the range of the present invention, and Test Nos. 2-17 to 2-20, in which only one of the components was used, were unable to maintain slump.

(Experimental Example 3)
The setting accelerator was prepared in the amounts shown in Table 4 below, and added 30 minutes after the completion of mixing of the base concrete of Mixture No. 2, and mixed to prepare a concrete composition. The slump, initial bleeding time, and bleeding time were measured after a predetermined time had elapsed from the completion of mixing of the base concrete. The results are shown in Table 4.

 

 

As shown in Table 4, even when a lignin sulfonic acid-based water-reducing agent is used, it has been confirmed that the use of the setting accelerator of the present invention improves slump retention and shortens the initial settling time and bleeding time.

(Experimental Example 4)
The organic acid calcium was used to prepare the setting accelerator in the amounts shown in Table 5 below, using calcium formate and calcium acetate. Thirty minutes after the completion of mixing the base concrete of Mixture No. 1, the accelerator was added and mixed to prepare a concrete composition. The slump, initial bleeding time, and bleeding time were measured after a predetermined time had elapsed since the completion of mixing the base concrete. The results are shown in Table 5.

 

 

(Raw materials used)
Calcium acetate: Yoneyama Chemical Industry Co., Ltd., 98% passing through 0.6 mm sieve (coarse particles removed)

Good results were also obtained when calcium acetate was used as the organic acid calcium.

(Experimental Example 5)
A setting accelerator was prepared with a mixing ratio of 80% by mass of calcium formate as an organic acid calcium salt and 20% by mass of aluminum sulfate as an inorganic sulfate salt, and the additive amounts shown in Table 5 were added 30 minutes after the completion of mixing of the base concrete of Mixture No. 1, and the concrete composition was prepared by kneading. The slump, initial time, and bleeding time were measured after a predetermined time had elapsed from the completion of mixing of the base concrete. The results are shown in Table 6.

 

 

As shown in Table 6, when a small amount of setting accelerator was added, the initial set time was longer, and when a large amount was added, the decrease in slump was suppressed.

(Experimental Example 6)
A setting accelerator was prepared with a mixing ratio of 80% by mass of calcium formate as an organic acid calcium salt and 20% by mass of aluminum sulfate as an inorganic sulfate salt. The calcium formate and aluminum sulfate were used with the raw materials shown in Table 7 for the portion passing through a 0.6 mm sieve. The prepared setting accelerator was measured for slump, initial bleeding time, and bleeding time after a predetermined time had elapsed from the completion of mixing the base concrete. The results are shown in Table 7.

 

 

(Experimental Example 7)
Using a concrete composition containing an expansive additive, the effect of the addition of a setting accelerator on the expansion rate was confirmed. Also, the slump and initial set time were confirmed.
The composition of the base concrete containing the expansive agent used in Experimental Example 7 is shown in Table 8.
The expansive agent used was an ettringite-lime composite (Denka Power CSA) or a lime-based (Pacific Materials Hyperexpan). The binder in Table 8 is the total amount of C (cement) and the expansive agent.

As the setting accelerator, the setting accelerators shown in Table 9 were used. As a comparative example, a setting accelerator consisting of aluminum sulfate, a water reducing agent, and a retarder was used.
The water-reducing agent and retarder used in Test No. 7-2 were as follows:
・Water reducing agent: Lignosulfonic acid type ・Retarder: Tartaric acid

The set accelerator was prepared in the amount shown in Table 9 below, and 30 minutes after the completion of mixing the base concrete containing the expansive agent of Mixture No. 3, the set accelerator was added and mixed to prepare a concrete composition. The expansion rate was measured a predetermined number of days after the completion of mixing the base concrete containing the expansive agent. The results are shown in Table 9.
The expansion coefficient was measured based on the test method for expansive additives for concrete specified in JIS A 6202.

As shown in Table 9, in Test Nos. 7-3 to 7-5, which are examples of the present invention, no difference in the expansion rate was observed compared to Test No. 7-1, in which no setting accelerator was added. In Test No. 7-2, which does not contain an organic acid (calcium formate), the expansion rate was reduced to about one-third of that of Test No. 7-1, in which no setting accelerator was added. Even when added to a concrete composition containing an expansive agent, the setting accelerator of the present invention can obtain an expansion rate equivalent to that of a concrete composition to which no setting accelerator is added, or can suppress a decrease in the expansion rate.

By using the setting accelerator for trowel finishing of the present invention, the fluidity of concrete can be maintained and the time from concrete pouring to trowel finishing can be shortened, making it applicable widely in the civil engineering and construction fields.

Claims (8)

Contains an organic acid calcium salt and an inorganic sulfate,
The mass ratio of the organic acid calcium salt to the inorganic sulfate (organic acid calcium salt/inorganic sulfate) is 20/80 to 95/5. The setting accelerator for trowel finishing according to claim 1, wherein the organic acid calcium salt is calcium carboxylate. The setting accelerator for trowel finishing according to claim 1 or 2, wherein the inorganic sulfate comprises at least one selected from aluminum sulfate, sodium thiosulfate, and potassium alum. The setting accelerator for trowel finishing according to claim 1 or 2, wherein the organic acid calcium salt and the inorganic sulfate have a mass ratio of 95% or more that passes through a 0.6 mm sieve. A concrete composition containing the setting accelerator for trowel finishing according to claim 1 or 2 and cement. The concrete composition according to claim 5, wherein the content of the trowel finishing setting accelerator is 0.5 to 8 kg per 1 ^m3 of the concrete composition. The concrete composition according to claim 5, further comprising an expansive agent. A hardened body obtained by hardening the concrete composition according to claim 5.