JP2000233959A - Clinker ground material, high-early-strength cement composition containing the same, concrete and concrete product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a cement clinker composition which is capable of providing concrete containing the composition with good workability until placing of the concrete is completed, and also providing the concrete with high-early-strength after the placing, by using as main mineral constituents of the composition, at least a specified amount of CaO crystals and a specified amount of an interstitial material and further if necessary, alite and belite. SOLUTION: This clinker ground material is produced by grinding a cement clinker composition having at least one main mineral composition selected from 3CaO.SiO2-2 CaO.SiO2-CaO-interstitial material, 3CaO.SiO2-CaO-interstitial material, 2CaO.SiO2-CaO- interstitial material and CaO-interstitial material systems, into grains having such grain size as to provide an about 3,000-6,000 cm2/g specific surface area, to form the objective clinker ground material containing 50-92 wt.% CaO crystals. This high- early-strength cement composition is produced by blending 3-30 pts.wt. of the clinker ground material, 0-10 pts.wt. of a hardening accelerator and 100 pts.wt. of portland cement or mixed cement together, wherein as the hardening accelerator used, a salt of a metal such as alkali metal, alkaline earth metal or trivalent metal, or an organic substance such as triethanolamine is preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a clinker pulverized product,
And a high-strength cement composition, concrete and concrete products containing the same. More specifically, the present invention relates to an early-strength cement composition having good workability and early-strength, concrete and concrete products thereof, and a clinker pulverized product therefor.

[0002]

2. Description of the Related Art Conventionally, for example, to produce a concrete product in a short time, steam curing is used as follows. That is, fine aggregates and / or coarse aggregates, water, admixtures such as a water reducing agent and a fluidizing agent, and a mixture such as silica fume are added to cement and mixed, and the kneaded concrete is formed into a mold. Casting and shaping while giving vibration with a vibrator. Next, this is transferred to a steam curing tank or placed in an appropriate place and covered with a can bath, left to cure for 1 to 5 hours, and then steam is fed in.
The temperature is raised to 60 to 80 ° C. at a rate of temperature increase of 60 ° C./hour, and this temperature is maintained for 2 to 3 hours. After that, the supply of steam is stopped to allow the water to cool naturally, and the mold is removed to obtain a concrete product.

[0003] However, this conventional method still requires a long time from the molding of the concrete to the demolding, and the production cycle with one mold is usually about one cycle per day. Also, the time required for curing and demolding of centrifugally formed concrete products such as fume pipes and concrete piles is substantially the same as that of ordinary concrete products, except that the molding method is different. The production amount per unit is about once a day. Therefore, it has been strongly desired to improve the productivity by increasing the rotational efficiency of the formwork in order to reduce the cost.

[0004] In order to improve the production efficiency, a cement composition is used in which a predetermined amount of lithium, aluminum, gallium, thallium sulfate or a double sulfate containing these metals is added to cement. A method of curing at a high temperature is described in JP-A-60-21839. According to this method, steam curing is performed directly without pre-curing, and rapid high-temperature curing at a heating rate of 40 ° C./hour or more and a curing temperature of 80 ° C. or more can be performed. It is said that the nature can be improved.

[0005] It is said that the pre-curing is not required in this method because ettringite is formed early by the action of the above-mentioned sulfate or double sulfate. Therefore, it was difficult to obtain desired workability. Therefore, in order to actually produce a concrete product or the like using the cement composition, concrete to which a sulfate or a double sulfate is not added is first kneaded in advance, and the kneaded material is transported to a place where the formwork is installed, and the formwork of the formwork is formed. It must be transferred to another mixer installed nearby, where sulfates and double sulfates are added and kneaded again before pouring or pouring into the mold within a short time. Such a transfer operation to the mixer significantly impairs productivity, and it is very difficult to put this mixer to practical use in this type of operation for mass production. In this case, if the amount of sulfate or double sulfate is reduced, the hydration reaction can be delayed to a certain extent.However, since the hardening of concrete is delayed, it is not possible to remove the mold in a short time, and the productivity can be increased. Disappears. Incidentally, the above problem is not limited to concrete, but is also true of mortar.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in the conventional cement or concrete, and has good workability until the end of concrete casting. It is an object of the present invention to provide a cement or a concrete which can be hardened at an early stage after being cast into a high strength concrete and a pulverized clinker therefor.

[0007]

That is, the present invention relates to the following pulverized clinker. (1) The main mineral composition is 3CaO.SiO ₂ -2CaO.
SiO ₂ -CaO- gap material based clinker composition, the main mineral composition 3CaO · SiO ₂ -CaO- gap material based clinker composition, the main mineral composition is 2CaO · SiO ₂ -CaO-
An interstitial substance clinker composition, wherein the main mineral composition is any one or more pulverized CaO-interstitial substance clinker compositions, characterized by containing 50 to 92% by weight of CaO crystals. Clinker crushed material.

[0008] The present invention also relates to the following high-strength cement composition. (2) Portland cement or mixed cement 100
3. An early-strength cement composition comprising 3 to 30 parts by weight of the pulverized clinker product according to claim 1 and 0 to 10 parts by weight of a cement hardening accelerator. (3) The early-strength cement composition according to (2), wherein the cement hardening accelerator is one or more of an alkali metal salt, an alkaline earth metal salt, a trivalent metal salt, and an organic substance. (4) The metal salt which is a cement hardening accelerator is sodium sulfate, potassium sulfate, aluminum sulfate, iron sulfate, magnesium nitrate, calcium nitrate, calcium nitrite,
The early-strength cement composition according to the above (2), which is one or more of sodium carbonate. (5) The early-strength cement composition according to the above (2), wherein the cement setting accelerator is triethanolamine and / or glycerin.

Furthermore, the present invention relates to the following concrete and concrete products. (6) The above-mentioned (2), (3) or (4), an early-strength cement composition,
Concrete characterized by using an aggregate and water as raw materials, and kneading the raw materials or a mixture obtained by adding a concrete admixture (material) to the raw materials. (7) Concrete, characterized in that the concrete of (6) is poured into a mold, cured in the air, cured, demolded, and left in the air or cured in water. Product. (8) The concrete of the above (6) is poured into a mold and immediately put into a steam curing tank or a steam cure is performed by supplying a steam with a cover provided, and the steam cure is performed for 30 minutes to 1 hour.
After raising the temperature to 0 to 85 ° C, the supply of steam was stopped, and after the strength of the concrete became 10 MPa or more, the steam curing was completed. After demolding, the product was left in the air or cured in water. A concrete product characterized by that:

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The pulverized clinker according to the present invention comprises:
The main mineral composition is 3CaO.SiO ₂ -2CaO.SiO ₂ −
CaO-intercalated substance clinker composition, main mineral composition is 3
CaO · SiO ₂ -CaO-interstitial material clinker composition,
The main mineral composition is 2CaO.SiO ₂ -CaO-intercalated substance clinker composition, or the main mineral composition is any one or more pulverized CaO-intercalated substance clinker composition, and the CaO crystal is It is characterized by containing 50 to 92% by weight. That is, the clinker pulverized product of the present invention has at least CaO as a main mineral composition.
A pulverized clinker composition containing crystals and interstitial substances, which may or may not contain alite (3CaO.SiO ₂ ) and / or belite (2CaO.SiO ₂ ),
It contains 50 to 92% by weight of aO crystals.

The above-mentioned interstitial material is similar to a mineral that fills a space between alite and belite in the cement clinker mineral, and specifically, for example, a calcium ferrite mineral such as 2CaO.Fe ₂ O ₃ , 3CaO.Al Calcium aluminate mineral such as ₂ O ₃ or 6CaO.A
_{l 2 O 3 · Fe 2 O} 3, 4CaO · Al 2 O 3 · Fe 2 O 3, 6C
calcium etc. _{aO · 2Al 2 O 3 · Fe} 2 O 3 alumino a ferrite minerals. The main mineral composition is at least C
By containing the aO crystal and the interstitial material, CaO plays a role of generating heat during hydration and accelerating cement hardening of the hydration product, and the interstitial material acts as a flux of CaO and hydrates CaO. It plays the role of suppressing the speed and the effect of promoting cement hardening without greatly impairing workability can be obtained only when both coexist.

The content of CaO crystals contained in the clinker composition is 50 to 92% by weight.
If the content is less than 0%, the desired early strength cannot be obtained. On the other hand, if the content exceeds 92%, the amount of the interstitial material is relatively reduced, which also makes it difficult to obtain desired properties. is there.

The clinker composition is alite (3CaO.Si)
O ₂ ) and belite (2CaO · SiO ₂ ) may or may not be contained. Those containing these greatly suppress the hydration rate of CaO, and these hydrates contribute to the strength development of cement.

The above-mentioned clinker composition is prepared by mixing calcareous raw materials, clay raw materials, silica stone, slag, gypsum and the like so as to have the above-mentioned composition, and then preparing the raw material mixture at 1300 to 1600 ° C. using a rotary kiln or the like. It is manufactured by baking and firing sufficiently until the desired clinker mineral composition is obtained at the temperature.

When the clinker composition is fired, a mineralizer (flux) can be added to the raw material to improve the production efficiency. As the mineralizer, those generally used when calcining cement-based compounds can be used, and CaSO ₄ , CaF ₂ , Fe ₂ O ₃ , MgO, Al ₂ O ₃
A compound containing, for example, gypsum, fluorite, serpentine, or the like may be added to the raw material in an amount of about 10% by weight or less and fired.

For the pulverization of the clinker composition, a pulverizer used for pulverizing cement, such as a ball mill or a roll mill, can be used. In general, as the particle size of the pulverized product increases, the higher the degree of fineness, the sooner the cement strength appears, and the higher the heat of hydration tends to be. This fineness is equal to or higher than that of Portland cement or mixed cement used for mixing.
000-6000 cm ² / g is suitable. Preferably, the specific surface area (plane) is equivalent to that of the early-strength Portland cement.
It is desirable to set it to about 000 to 5000 cm ² / g.

The high-strength cement of the present invention comprises Portland cement or mixed cement, or the above-mentioned pulverized clinker, and contains a cement hardening accelerator as required. The amount of these components is 3 to 30 parts by weight of the pulverized clinker and 100 to 1 part by weight of Portland cement or mixed cement.
0 parts by weight. The mixing ratio of the pulverized clinker to Portland cement or the mixed cement is set to 3 to 30 parts by weight. If the mixing ratio of the pulverized clinker is less than 3 parts by weight, the desired early strength of the present invention cannot be obtained. On the other hand, if the mixing ratio of the clinker pulverized product exceeds 30 parts by weight, the expansion is excessive and the concrete may be broken, which is not preferable.

The portland cement is ordinary portland cement, fast-strength portland cement, white portland cement or the like. The mixed cement is blast furnace cement, fly ash cent, silica cement and the like.

The early-strength cement of the present invention exhibits a more remarkable effect when a cement hardening accelerator is added in addition to the above-mentioned clinker pulverized material. Inorganic substances and organic substances can be used as the cement setting accelerator. Examples of the inorganic substance-based cement hardening accelerator include alkali metal salts, alkaline earth metal salts, and trivalent metal salts. Specifically, sulfites, sulfates, carbonates, rhodanes, thiosulfates, formates, and the like, for example, sodium sulfate,
Potassium sulfate, aluminum sulfate, ferrous sulfate, ferric sulfate, magnesium nitrate, calcium nitrate, calcium nitrite, sodium carbonate, and the like can be used. Examples of the organic substance-based cement hardening accelerator include triethanolamine and glycerin. One or more of these can be used. Also, among these cement hardening accelerators, sodium sulfate,
Potassium sulfate, aluminum sulfate, iron sulfate or triethanolamine is preferred, and sodium sulfate is particularly preferred.

The amount of the cement hardening accelerator added is 10% by weight or less, preferably 0.05 to 5% by weight in terms of anhydride, based on Portland cement or mixed cement.
More preferably, the content is 0.1 to 2% by weight. In addition, even if it is added in excess of 10% by weight, the effect of the addition is small, and there is a possibility that the long-term strength of the concrete is rather lowered.

In the early-strength cement of the present invention, when the above-mentioned pulverized clinker and a cement hardening accelerator are used in combination,
A higher synergistic effect is exhibited than in the case of adding each alone, and concrete hardening is remarkably accelerated, and a high strength of 10 MPa or more after 2-3 hours after steam curing is obtained. Therefore, the mold can be removed in a short time, and the production efficiency of the concrete product can be increased.

The concrete of the present invention is obtained by adding an aggregate (fine aggregate and / or coarse aggregate) and water to the above-mentioned high-strength cement as a raw material, and adding a concrete admixture ( Material) is kneaded. aggregate,
The mixing amount of water and the admixture (material) may be within the range of the mixing amount of ordinary concrete. The type of aggregate and admixture (material) may be any as long as it is used for ordinary concrete.

An example of the concrete manufacturing process will be described below. (1) The concrete is poured into a mold, cured in the air, cured, and then removed from the mold, and left in the air or cured in water. (2) The concrete is poured into a mold and immediately put into a steam curing tank or a steam is cured by supplying steam with a cover provided, and 50 to 85 hours in 30 minutes to 1 hour.
After the temperature was raised to ℃, the supply of steam was stopped, and after the strength of the concrete became 10 MPa or more, the steam curing was terminated.
After demolding, leave in the air or cure in water.

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 [Preparation of mortar] Limestone, silica stone, clay, iron raw material, and anhydrous gypsum were blended in the proportions shown in Table 1, and a raw material mixture was prepared to have the composition shown in Table 2. This raw material is roasted in a rotary kiln at 13
Clinker is manufactured by baking at 00 to 1600 ° C. and a residence time of 60 to 120 minutes.
It was pulverized with a pot mill to about 00 cm ² / g. The degree of baking was controlled by the consumption of 4N hydrochloric acid. This method is used as a method for evaluating the activity of limestone, and the consumption of 4N hydrochloric acid was measured according to the Japan Lime Society standard test method.
As shown in Table 2, the obtained clinker compositions (Nos. 1 to 11)
Are alite (3CaO.SiO ₂ ) and belite (2CaO.
It contains CaO and interstitial material together with SiO ₂ ). The clinker composition of Sample No. 11 is an example in which the amount of CaO is less than the range of the present invention.

[0026]

[Table 1]

[0027]

[Table 2]

Using the clinker pulverized product (No. 1 to 11: 80 g), sand (19 g) was added to a commercially available ordinary Portland cement (1000 g).
10g), water (380g), water reducing agent (10g), cement setting accelerator
(Anhydrous sodium sulfate: 10 g) and mortar (No.
1 to 11) were prepared. As a comparative example, a mortar was prepared in which clinker pulverized material was not added to ordinary Portland cement (Sample No. 12: ordinary mortar cement: 1000 g, Na ₂ SO ₄ : 10)
g, sand: 2000 g, water: 380 g, water reducing agent: 10 g). The water reducing agent used was a commercially available naphthalene-based high-performance water reducing agent. The kneading procedure is as follows. Clinker pulverized product and sodium sulfate, which are admixtures, were added to cement in advance, mixed well, and kneaded. First, water and a water reducing agent are put into a kneading bowl, a kneading machine is started, and cement and an admixture are charged for 30 seconds. The sand is charged for the next 30 seconds and then mixed for 60 seconds. The kneading was stopped for 20 seconds, and the mixture was scraped off. The kneading was started again and kneaded for 120 seconds to obtain mortar. The flow value of the obtained mortar immediately after kneading showed a value of 150 to 220 mm, and sufficient workability was secured. The prepared mortar was subjected to a setting test, standard curing, and steam curing, and its strength was measured.

[Coagulation test] The setting time is measured by filling the kneaded mortar (Nos. 1 to 12) into a setting ring and measuring the start and end times of setting using an automatic setting tester (Bigger needle method). did. Table 3 shows the results of the setting test. The clinker No. in the table indicates the type of the clinker pulverized material used for the mortar, and corresponds to the clinker No. in Table 2. As is clear from the setting test results, the setting start time and setting time of the samples of the present invention (No. 1 to 10) are significantly shortened as compared with the comparative sample (No. 12) using only ordinary cement. It turns out that there is.

[0030]

[Table 3]

[ Strength Test by Standard Curing] The above mortar (N
o.1 ~ 12) in a formwork (4cm x 4cm x 16cm)
After an hour, capping was performed, and after curing in a humid empty box at 20 ° C. for 6 hours, the mold was released. After the mold was released, it was further cured in a humid empty box at 20 ° C., and the compressive strength was measured. The compression strength was measured according to JIS R 5201. The results are shown in Table 4. As is clear from the results, the compressive strength after 6 hours from the water injection was 0.59 to 2.3 in the comparative samples (Nos. 11 and 12).
6N / mm ² , but the samples of the present invention (Nos.
/ mm ² , and the same tendency was observed for the compressive strength after one day. It can be seen that the initial strength of the present invention was remarkably improved as compared with the comparative example.

[0032]

[Table 4]

[ Strength Test by Steam Curing] The above mortar (N
o.1 to 12) were placed in a mold (4 cm × 4 cm × 16 cm), and after curing for about 30 minutes (capping was performed during this time), steam curing was performed. This steam curing is heated to 60 ° C in one hour,
Immediately after 2 hours, the temperature was lowered to 20 ° C., followed by demolding. After removal from the mold, it was cured in a humid empty box at 20 ° C. Compressive strength JIS R520
Measured according to 1. The results are shown in Table 5. As is evident from the results, the compression strength after 4 hours was lower than that of the comparative example.
(No. 12) is about 7 N / mm ² , whereas the samples of the present invention (Nos. 1 to 10) are all about 17 to 20 N / mm ² , which is much higher. Thus, it can be seen that the strength of the cured product of the cement composition of the present invention is higher than that of the comparative example even in a simple steam curing treatment, and that the initial strength is excellent.

[0034]

[Table 5]

Example 2 [Curing accelerator addition test] The clinker pulverized product of the present invention (clinker No. 5 of Example 1), ordinary Portland cement, cement hardening accelerator, sand,
Mortar was prepared by blending water and a water reducing agent at the ratios shown in Table 6 (Nos. 21 to 25). As a comparative example, a mortar to which the above-mentioned pulverized clinker and cement hardening accelerator were not added was prepared (No. 26). Sodium sulfate, potassium sulfate, aluminum sulfate, ferrous sulfate, and triethanolamine were used as cement setting accelerators, respectively. As the water reducing agent, a commercially available naphthalene sulfonate-based high-performance water reducing agent was used. In addition, what used sodium sulfate, potassium sulfate, aluminum sulfate, and ferrous sulfate as a cement hardening promoting substance was added to cement in advance, and after sufficient mixing, kneading was performed. In the case of triethanolamine, it was premixed with water and water reducing agent before being added to the cement. The kneading procedure is as follows. Using a kneading machine, knead the cement and sand for 15 seconds. Water and a water reducing agent are put into a kneading bowl while continuing to knead for another 15 seconds, and then kneaded for 60 seconds. Next, kneading was once stopped, scraping was performed for 20 seconds, kneading was started again, and kneading was performed for 120 seconds to prepare a mortar of a test specimen.

The strength test was performed in the following procedure. First, mortar (No. 21-26) is cast into a mold (4cm x 4cm x 16cm), capping is performed after about 2 hours, and after curing in a moist empty box for 1 day, the mold is released. Immediately after, the compressive strength was measured. The compression strength was measured according to JIS R5201. The results are summarized in Table 6. As is clear from the test results, the sample according to the present invention has higher compressive strength and superior early strength than the comparative sample (mortar No. 26).

[0037]

[Table 6]

Example 3 [Strength of Concrete] Normal Portland Cement, Clinker No. 9 of Example 1
Ground matter, anhydrous sodium sulfate, fine aggregate and coarse aggregate,
Concrete containing water and an admixture in the proportions shown in Table 7 was prepared (Nos. 31 to 35). Table 8 shows the mixing ratio and the like. After kneading this concrete, steel formwork (diameter 10cm x height 20c
m), and immediately put into a steam curing tank to feed steam, the temperature was raised to 60 ° C. in one hour, and then the steam was stopped and allowed to cool. Three hours after the water injection, it was taken out of the steam curing tank, and after demolding, the compressive strength was measured immediately. Further, after the mold was released, it was left at room temperature, and the compressive strength was measured 1, 7 and 14 days later. The result is shown in FIG. Furthermore, after mixing these concretes (No. 31 to 35), a steel formwork (diameter 10
cm × 20 cm in height), left as it is in a humid air-conditioned room at 20 ° C. without steam curing, and measured the compressive strength after 1, 7 and 14 days. The result is shown in FIG.

[0039]

[Table 7]

[0040]

[Table 8]

Example 4 [Concrete product test] Table 9
Knead the concrete material of the composition shown in the above with a mixer,
Concrete having a slump of 10 cm and an air volume of 5.5% was produced. This concrete was filled in a box-shaped reinforced concrete product form shown in FIG. 3, and after compaction with a rod-shaped vibrator, the upper surface was immediately covered with a canvas, and steam was fed between the form and the canvas. After the temperature was raised to ° C, the supply of steam was stopped. Four hours after water injection, the canvas was removed and the mold was removed. The crane was lifted using a hook attached in advance and moved to the yard. No abnormality was found in the concrete product through the removal and transportation. Furthermore, using the same concrete as above, it was molded in a mold (diameter 10 cm x height 20 cm), and the molded product was steam-cured under the same conditions as the concrete product for 4 hours.
One day later, the compressive strength was measured to be 17.9M.
Pa and 34.9 MPa.

[0042]

[Table 9]

In the above embodiments, a naphthalene-based high-performance water reducing agent is used as a water reducing agent. However, the present invention is not limited to this, and admixtures generally used in the cement concrete field, melamine-based, lignin-based, Polycarboxylic acid-based water reducing agents, fluidizing agents, and AE agents can be used. Also,
It is also possible to use admixtures such as blast furnace slag, limestone fine powder, fly ash, and silica fume.

[0044]

According to the cement composition of the present invention, in molding of a concrete product or construction of ready-mixed concrete, it is possible to obtain fluidity enough to secure a sufficient construction time and to develop the necessary strength at an early stage. To speed up demolding. In particular, in the production of concrete products, it is possible to express the shipping strength early without performing steam curing, and to remove the mold in a short time with a small amount of steam curing. The benefits are great.

[Brief description of the drawings]

FIG. 1 is a graph showing test results of Example 3.

FIG. 2 is a graph showing test results of Example 3.

FIG. 3 is a perspective view of a mold used in Example 4.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme court ゛ (Reference) C04B 22:08 22:14 22:08 22:10 24:12 24:02) 103: 14 111: 00 ( 72) Inventor Masahiko Yoneda 6-7 Uehonmachi, Sakata City, Yamagata Prefecture Inside Maeda Advanced Technology Research Institute Co., Ltd. (72) Inventor Masaki Ishimori 2-4-2 Daisaku, Sakura City, Chiba Prefecture Pacific Ocean Cement Co., Ltd. 72) Inventor Koichi Soeda 2-4-2 Daisaku, Sakura City, Chiba Pref. Pacific Term Cement Co., Ltd. Sakura Laboratory F-term (reference) 4G012 MA00 MA01 MB06 MB12 PB03 PB04 PB08 PB10 PB20 PC04 PE05

Claims (8)

[Claims] 1. The main mineral composition is 3CaO.SiO ₂ -2C.
aO · SiO ₂ -CaO- gap material based clinker composition, the main mineral composition 3CaO · SiO ₂ -CaO- gap material based clinker composition, the main mineral composition is 2CaO · SiO ₂ -Ca
O-intercalated substance clinker composition, main mineral composition is CaO
-A pulverized clinker, which is one or more pulverized clinker-based clinker compositions, which contains 50 to 92% by weight of CaO crystals. 2. The clinker pulverized product 3 according to claim 1, based on 100 parts by weight of Portland cement or mixed cement.
An early-strength cement composition containing from about 30 parts by weight to about 0 to 10 parts by weight of a cement hardening accelerator. 3. The early-strength cement composition according to claim 2, wherein the cement hardening accelerator is one or more of an alkali metal salt, an alkaline earth metal salt, a trivalent metal salt, and an organic substance. 4. A metal salt as a cement hardening accelerator,
The early-strength cement composition according to claim 2, which is one or more of sodium sulfate, potassium sulfate, aluminum sulfate, iron sulfate, magnesium nitrate, calcium nitrate, calcium nitrite, and sodium carbonate. 5. The early-strength cement composition according to claim 2, wherein the cement setting accelerator is triethanolamine and / or glycerin. 6. A kneaded mixture of the early-strength cement composition of claim 2, 3 or 4 as a raw material, and a kneaded mixture of the raw material or an admixture (material) for concrete added to the raw material. Concrete characterized by that. 7. The method according to claim 6, wherein the concrete according to claim 6 is poured into a mold, cured in the air, cured, demolded, and left in the air or cured in water. Concrete products. 8. The concrete of claim 6 is poured into a formwork and immediately put into a steam curing tank, or steam curing is performed by feeding steam with a cover provided, and the steam curing is performed for 30 minutes to 1 hour.
After raising the temperature to 50 to 85 ° C. in a time, the supply of steam is stopped, and after the concrete strength reaches 10 MPa or more, the steam curing is finished. After the mold is released, the concrete is left in the air or cured in water. A concrete product characterized by being manufactured.