JP2001322844A - Cement admixture for hardening with adiabatic curing, production process of concrete hardened body and concrete hardened body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cement admixture by the use of which a concrete composition can easily be hardened in a short time so as to exhibit high strength and a concrete hardened body also having good physical properties such as resistance to freezing and thawing, water tightness and durability can be produced, to provide this concrete hardened body which has high strength and good physical properties such as resistance to freezing and thawing water tightness and durability and can be produced in a short time at a low cost, and further to provide a production process of the concrete hardened body. SOLUTION: This cement admixture for hardening with adiabatic curing contains >=50 wt.% CaO crystals and in particular contains, as its main constituent minerals, a specific clinker composition and gypsum. This concrete hardened body production process comprises: mixing a concrete composition containing the above admixture, portland cement or blended cement, aggregate and water; and hardening the resulting concrete mix with adiabatic curing. This hardened body is produced by the above production process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cement admixture for heat-insulating curing and hardening, a method for producing a hardened concrete using the same, and a hardened concrete.

[0002]

2. Description of the Related Art In the production of hardened concrete, particularly in the manufacture of hardened concrete, such as large concrete products or prestressed concrete, which require relatively high strength at the time of demolding, hardened products having high strength are required in a short time. In addition, it is required to improve productivity. As one method for obtaining a cured product having high strength in a short time, high-temperature steam curing, that is, so-called steam curing, has been conventionally used.

[0003] The steam curing is curing by normal-pressure high-temperature steam, in which high-temperature steam generated by a boiler is blown out from a nozzle into a curing room to increase the temperature and humidity in the curing room, thereby promoting the hardening of concrete. This is a curing method for obtaining the required demolding strength at an early stage. More specifically, the production of hardened concrete by steam curing is performed, for example, as follows. Concrete mixed with fine aggregate and / or coarse aggregate, water, admixture such as water reducing agent, fluidizing agent, etc., and silica fume, etc. is added to cement and kneaded. It is poured and molded while giving vibration with a vibrator or the like. Next, this is transferred to a steam curing tank or placed in a suitable place, covered with canvas, left to cure for 1 to 5 hours, and then steam is fed in at a heating rate of 20 ° C./hour.
Raise the temperature to 60-80 ° C. and maintain this temperature for 2-3 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.

[0004] However, the production of concrete by steam curing naturally involves equipment costs and running costs associated with the steam curing equipment. In addition, steam-cured concrete can achieve the required strength at the time of demolding, but the strength decreases by 10 to 30% as compared with the standard cured concrete as the material age increases. In addition, since the accelerated concrete structure is coarse, the resistance to freezing and thawing and the watertightness are reduced, which adversely affects the durability of the concrete.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to cure a concrete composition easily and quickly to a high strength in a short time.
Moreover, it is an object of the present invention to provide a cement admixture that can be used as a concrete hardened material having good physical properties such as freeze-thaw resistance, watertightness, and durability.

It is a further object of the present invention to provide a hardened concrete product which has high strength and good physical properties such as freeze-thaw resistance, watertightness and durability, and can be produced in a short time and at low cost. It is to provide a manufacturing method of.

A further object of the present invention is to provide a hardened concrete product which can be manufactured in a short time and at low cost, has high strength, and has good physical properties such as freeze-thaw resistance, watertightness and durability. It is in.

[0008]

According to the present invention, there is provided a cement admixture for adiabatic curing containing 50% by weight or more of CaO crystals.

Further, according to the present invention (i) CaO-3CaO · SiO 2 as a main constituent minerals -2CaO · SiO ₂ - gap materials, CaO-3
CaO ・ SiO ₂ -interstitial material, CaO-2CaO ・ SiO ₂ -interstitial material, Ca
A clinker composition comprising one or more O-interstitial materials, and having a CaO crystal content of 50 to 92% by weight; and
(ii) The above-mentioned cement admixture for adiabatic curing and hardening characterized by containing gypsum is provided.

Further, according to the present invention, concrete hardening is performed by kneading a concrete composition containing the cement admixture, Portland cement or mixed cement, aggregate, and water, and curing by adiabatic curing. An article manufacturing method is provided.

Further, according to the present invention, there is provided a cured concrete product obtained by the above-mentioned method.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The cement admixture for adiabatic curing of the present invention contains 50% by weight or more of CaO crystals. The CaO crystals are 3CaO.SiO ₂ , 2CaO.Si constituting normal cement.
In O _2, unlike what _{3CaO · Al 2 O 3, 4CaO} · Al 2 O 3 · Fe 2 O 3 CaO with other substances such as such becomes combined with crystals, essentially consisting of CaO only crystals is there.

[0013] The CaO crystal can be present in the admixture as a clinker composed of a mixture with other crystals. Examples of the clinker, and specific examples, quicklime _{clinker, CaO-Al 2 O 3 -CaSO} 4 clinker, CaO-CaSO _{4 clinker, CaO-Al 2 O 3 -SiO} 2 -CaSO 4 clinker, CaO-Al ₂ O
Various clinkers such as a _3- CaSO ₄ clinker, a CaO—SiO ₂ —CaSO ₄ clinker, and a mixture thereof are exemplified.

As the cement admixture for adiabatic curing and hardening of the present invention, in particular, those containing a clinker composition containing CaO crystals and interstitial substances as main constituent minerals are preferable. Also,
In addition to CaO crystals and interstitial materials, alite (3CaO
₂ ) and / or those containing a clinker composition containing belite (2CaO · SiO ₂ ) are also preferred. More _{specifically, CaO-3CaO · SiO 2 -2CaO} · SiO 2 as a main constituent minerals - gap materials, CaO-3CaO · SiO ₂ - gap materials, CaO-2CaO · SiO ₂ -
A clinker composition containing one or more of interstitial substances and CaO-interstitial substances and having a CaO crystal content of 50 to 92% by weight (hereinafter referred to as clinker composition (i)). Is preferable, and further, since the specific clinker composition and the one containing gypsum have a heat generation property suitable for adiabatic curing and do not impair the workability of concrete,
More preferred.

The interstitial material is similar to a mineral that fills a space between alite and belite in a cement clinker mineral. Specifically, for example, a calcium ferrite mineral such as 2CaO.Fe ₂ O ₃ or a 3CaO. Calcium aluminate mineral such as Al ₂ O ₃ or 6CaO ・ Al ₂ O ₃・ Fe ₂ O ₃ , 4CaO ・
_{Al 2 O 3 · Fe 2 O} 3, and calcium, such as _{6CaO · Al 2 O 3 · Fe} 2 O 3 alumino can be mentioned ferrite minerals.

When the cement admixture for adiabatic curing of the present invention contains the clinker composition (i), the preferred content is 50 to 95% by weight as the ratio of the clinker composition (i) to the total amount of the admixture. can do.

As the gypsum, commercially available general gypsum or the like can be used. Specifically, for example, anhydrous gypsum, hemihydrate gypsum, gypsum dihydrate, or a mixture thereof can be used.

[0018] The content of the gypsum in the cement admixture for adiabatic curing of the present invention can be 5 to 50% by weight.

In the method for producing a hardened concrete product of the present invention, a concrete composition containing the cement admixture for heat-insulating curing and hardening, Portland cement or mixed cement, aggregate, and water is kneaded and hardened by heat-insulating curing. Let it.

The mixing ratio of the cement admixture for adiabatic curing and curing in the concrete composition is 15 to 50 kg / m ^3.
It can be.

Examples of the portland cement include ordinary portland cement, early-strength portland cement, white portland cement and the like. Examples of the mixed cement include blast furnace cement, fly ash cement, silica cement and the like. The aggregate is not particularly limited, and fine aggregate and / or coarse aggregate used for ordinary concrete can be used.

The proportions of Portland cement or mixed cement, aggregate, and water in the concrete composition are not particularly limited, and may be the same as those of a normal concrete composition. The compounding ratio of the portland cement or the mixed cement is preferably 400 kg / m ³ or more, more preferably 500 kg / m ³ or more, in the whole composition. Further, the water / cement ratio is preferably 45% or less, and more preferably 35% or less.

The concrete composition used in the method for producing a hardened concrete product of the present invention further comprises various admixtures such as a water reducing agent, a fluidizing agent, an AE agent, blast furnace slag, limestone fine powder, fly ash and silica. An admixture such as fume can be included.

Further, the concrete composition may include a cement hardening accelerator. Specifically, for example, an inorganic material-based hardening accelerator such as an alkali metal salt, an alkaline earth metal salt, or a trivalent metal salt, or an organic material-based hardening accelerator such as triethanolamine or glycerin, or a mixture thereof. A mixture or the like can be used. The compounding ratio of the cement hardening accelerator in the concrete composition is the Portland cement or the mixed cement.
The amount can be 10 parts by weight or less, preferably 0.05 to 5 parts by weight, more preferably 0.1 to 2 parts by weight in terms of anhydride per 100 parts by weight.

The adiabatic curing is to cure the concrete composition, cover its surface with a material having a low thermal conductivity, reduce the amount of heat released from the concrete, and promote the development of the strength of the concrete hardened material. That means. Specifically, thermal conductivity 0.1 kcal / mh ° C. or less, more preferably
It is carried out by covering the concrete composition with a heat insulating material made of a material having a temperature of 0.05 kcal / mh or less and having a thickness of 0.5 to 15 cm, more preferably 0.3 to 3 cm, or a heat insulating material having an equivalent heat insulating ability. it can. Specifically, for example, a method of surrounding a mold filled with a concrete composition with a foamed resin member such as styrofoam or urethane foam, or providing a film layer such as an aluminum-evaporated polyester film on both surfaces of a fiber layer such as glass wool or cotton. It can be performed by a method of covering the form with a sheet member that has been used.

The heat insulating material has a low thermal conductivity,
Those which do not deform even when used for a long time, have low specific gravity, and have high mechanical strength are preferred. Further, a material having a small water absorption and a low water permeability is preferable in order to prevent a decrease in thermal conductivity and workability due to water vapor released from the concrete composition.

The hardening by the adiabatic curing can be carried out during part or all of the period from when the concrete composition becomes a solid hardened material and further when the concrete composition is hardened until the strength further increases. Specifically, for example, it can be performed from the time when the concrete composition is put in a mold until the time when the concrete composition is released.

The hardened concrete of the present invention is a hardened concrete obtained by the above-mentioned manufacturing method.

The hardened concrete of the present invention has a higher strength and a dense structure as compared with the hardened concrete cured by steam. This means that in the production method of the present invention, self-heating derived from the admixture is obtained from inside the concrete composition,
While this heat energy is not released from the inside of the concrete by adiabatic curing, the strength appears in a short time, whereas steam curing gives strength in a short time by forcibly applying heat energy from the outside. It is thought that it is.

The use of the hardened concrete product of the present invention is not particularly limited, and it can be used in the same manner as a general hardened concrete product, but it can be particularly preferably used as a prestressed concrete or the like.

[0031]

The cement admixture for heat-insulating curing of the present invention is capable of hardening the concrete composition to a high strength in a short time by blending it with the concrete composition and performing heat-insulating curing. It is possible to provide a hardened concrete having a dense structure, which has good physical properties such as watertightness and durability.

According to the method for producing a hardened concrete product of the present invention, a hardened concrete product having a dense structure having high strength and good physical properties such as freeze-thaw resistance, watertightness and durability can be prepared in a short time. It can be manufactured at low cost. In particular, it is a production method effective at low temperatures where the strength of the concrete hardened material is hardly obtained.

The hardened concrete product of the present invention can be manufactured in a short time and at low cost, has high strength, and has good physical properties such as freeze-thaw resistance, watertightness and durability. Can be.

[0034]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

[0035]

Example 1 Production of cement admixture (1) Limestone, quartzite, clay, iron raw material, and anhydrous gypsum are shown in Table 1
The raw material mixtures were prepared so as to have the compositions shown in Table 2 by mixing them at different weight ratios (Nos. 1 and 2). This raw material was baked in a rotary kiln to produce a clinker. The conditions for baking were 1300 ° C for 120 minutes for No. 1, and No. 2
About 1500 ° C. for 60 minutes. These have a Blaine value (measured as specified in JIS R 5201) of 4500 ± 100c
It was pulverized with a pot mill until it reached about m ² / g. The degree of baking of the obtained ground clinker was measured by 4N hydrochloric acid consumption according to the standard test method of the Japan Lime Society, which is used as a method for evaluating the activity of limestone. As shown in Table 3, the obtained clinker compositions Nos. 1 and 2 contained CaO crystals and interstitial materials together with alite (3CaO.SiO ₂ ) and belite (2CaO.SiO ₂ ).

[0036]

[Table 1]

[0037]

[Table 2]

[0038]

[Table 3]

Each of the obtained powders of clinker compositions No. 1 and No. 2 was mixed with anhydrous type II gypsum having a Blaine value of about 6000 cm ² / g so as to have a content of 10% by weight. Cement admixture (Cement admixture 1 and cement admixture 2)
I got

[0040]

Example 2 Production of cement admixture (2) Hard burnt lime with a consumption of about 100 ml of 4N hydrochloric acid was pulverized by a pot mill until the Blaine value became about 4500 ± 100 cm ² / g. Next, this was mixed with a type II anhydrous gypsum having a Blaine value of about 6000 cm ² / g so as to have a content of 10% by weight to obtain a cement admixture (cement admixture 3).

[0041]

Example 3 and Comparative Examples 1 to 3 (Production of Cured Product)
At 20 ° C., a cured product was produced. Cement admixture 1, ordinary Portland cement, fine aggregate and coarse aggregate,
Water and admixture (High performance water reducing agent manufactured by Taiheiyo Cement Corporation,
Concrete containing the product name “CP-300”) in the proportions shown in Table 4 was prepared. In the tables, the mixing ratio of the admixture is represented by Cx%, that is, by weight of the admixture with respect to 100 parts by weight of cement. After kneading the concrete, cast it into a steel formwork (diameter 10cm x height 20cm) and heat-insulate it as shown in Table 4 or leave the formwork without insulation as it is And cured to produce a cured product.

As shown in FIG. 1, the insulation curing was carried out by placing nine concrete-casting molds 11 in a 10-cm-thick styrofoam container 12 and covering the molds with glass fiber insulation 13. This was performed by covering with a 10 cm styrofoam lid 14.

[0043]

[Table 4]

The mold was released 18 hours after the start of curing, and the compressive strength was measured immediately. Also, 14 days after the completion of curing, the compressive strength was measured. Table 5 shows the results.

[0045]

[Table 5]

As is evident from the results in Table 5, the cured product of Example 3 was 37.5MP at the time of demolding as compared with the comparative example.
It can be seen that a remarkable early strength effect is exhibited. Also, it can be seen that the strength on the 14th day corresponding to the shipping order of the concrete product is not inferior at all.

[0047]

Example 4 and Comparative Examples 4 to 7 (Production of cured product)
At 5 ° C., a cured product was produced. Cement admixture
3, early strength Portland cement, fine aggregate and coarse aggregate,
Water and admixture (High performance water reducing agent manufactured by Taiheiyo Cement Corporation,
Concrete containing the product name “CP-300”) in the proportions shown in Table 6 was prepared. After kneading the concrete, cast it into a steel formwork (diameter 10 cm x height 20 cm) and heat-insulate it as shown in Table 6 or leave the formwork without insulation as it is And cured to produce a cured product.

As shown in FIG. 1, the insulation curing was carried out by putting nine molds 11 in which concrete was cast into a 10 cm thick styrofoam container 12 and covering the molds with a glass fiber insulation 13. This was performed by covering with a 10 cm styrofoam lid 14.

[0049]

[Table 6]

The mold was released 16 hours after the start of curing, and the compressive strength was measured immediately. The compressive strength was measured 7 days after the completion of curing. Table 7 shows the results.

[0051]

[Table 7]

As is evident from the results in Table 7, it can be seen that the cured product of Example 4 exerts a remarkable early strength effect at the time of demolding as compared with the comparative example.

The strength of the cured product of Example 4 on the 14th day after completion of curing was also measured. Further, as a comparative example, a concrete having the same composition as that of Comparative Example 5 was prepared, kneaded, and poured into a steel mold (diameter 10 cm × height 20 cm). The temperature was monitored by a pair, and steam curing was performed by controlling the concrete temperature according to the pattern shown in FIG. The mold was released 16 hours after the start of steam curing, and the compressive strength was measured immediately. Further, the compressive strength was measured 7 days and 14 days after the completion of the curing (Comparative Example 7). Table 8 shows the results.

[0054]

[Table 8]

As is evident from the results in Table 8, the cured product of Example 4 using both the adiabatic curing and the cement admixture can secure the same strength as the steam curing at the time of demolding.
It can be seen that the strength increases more than the cured product by steam curing as the material age passes on days 14 and 14.

[0056]

Reference Examples 1 and 2 Concrete having the same composition as in Example 4 (Reference Example 1) and concrete having the same composition as Comparative Example 7 (Reference Example 2) were prepared, kneaded and mixed with a steel mold (diameter 10 cm).
× 20 cm in height) and cured under so-called standard curing conditions. That is, after the casting, the mold was allowed to stand overnight at 20 ° C. in the open air, and then demolded. The obtained cured product was further allowed to stand in water at 20 ° C. for 28 days. The compression strength of the cured product after standing for 28 days was measured.
As a result, the compression strength of the cured product of Reference Example 1 was 67.5 MPa, and the compression strength of the cured product of Reference Example 2 was 68.8 MPa.

[0057]

(Examples 5 to 6 and Comparative Examples 8 to 9) (Production of hardened material of high-flowable concrete) As shown in Table 9, the outside air temperature was set to 20 ° C or 5 ° C.
° C, using cement admixture 2, ordinary Portland cement, limestone fine powder, fine aggregate and coarse aggregate, water, and admixture (high performance water reducing agent manufactured by Taiheiyo Cement Corporation, trade name “CP-3
00 ") in the proportions shown in Table 9 were prepared. In the tables, the mixing ratio of the admixture is represented by Px%, that is, parts by weight of the admixture with respect to 100 parts by weight of cement, cement admixture and limestone fine powder in total.
The slump flow of this high fluidity concrete was 60-65 cm. After mixing this concrete, steel formwork (diameter
(10 cm × 20 cm in height), and cured by adiabatic curing to produce a cured product.

As shown in FIG. 1, the heat-insulating curing was performed by placing nine concrete-cast molds 11 in a 10-cm-thick styrofoam container 12 and covering the molds with a glass fiber heat-insulating material 13. This was performed by covering with a 10 cm styrofoam lid 14.

[0059]

[Table 9]

The mold was released 18 hours after the start of curing, and the compressive strength was measured immediately. The compressive strength was measured 7 days after the completion of curing. Table 10 shows the results.

[0061]

[Table 10]

It can be seen that the cured products of Examples 5 and 6 using both the heat-insulating curing and the cement admixture are significantly superior in 18-hour strength to those of the comparative example. In particular, it can be seen that the cured product of Example 6 in which both the adiabatic curing and the cement admixture were used in a low-temperature environment reached a strength of 30 MPa, which can sufficiently withstand demolding of a large member 18 hours after the start of curing. .

[0063]

Example 7 A prestressed concrete product was manufactured in an environment corresponding to a severe cold season at an outside temperature of 3 ° C.
Cement admixture 2, early-strength Portland cement, fine aggregate and coarse aggregate, water, and an admixture (high performance water reducer manufactured by Taiheiyo Cement Corporation, trade name "CP-300") are blended in the proportions shown in Table 11. , Kneading, concrete with slump 6cm, air volume 5%. Put this concrete in a plate shape (length 5000mm
× 2000 mm × 200 mm thick) was filled in a concrete product form, compacted with a table vibrator, and immediately covered with a 5 mm thick heat insulating sheet having the structure shown in FIG. . The heat insulating sheet of FIG.
A heat insulating layer 22 made of a foam sheet is provided between layers of the vinyl sheet 21. Sixteen hours after the start of the heat-insulating curing, the heat-insulating sheet was removed, the cured product was released, and the cured product was lifted using a hook previously attached to the cured product, moved to the yard, and a prestress was introduced. No abnormality was observed in the cured product through demolding, transportation and introduction of prestress.

[0064]

Example 8 Concrete having the same composition as that used in Example 7 was placed in a mold (diameter 10 cm × height 2) at an ambient temperature of 3 ° C.
0 cm), covered with the same heat-insulating sheet as used in Example 7, heat-insulated and cured for 16 hours, demolded, and immediately measured for compressive strength of the obtained cured product. , 38MPa, 35M capable of introducing sufficient prestress
It was confirmed that the strength reached Pa or more.

[0065]

Comparative Example 9 The operation was performed in the same manner as in Example 8 except that concrete having the composition shown in Table 11 without the cement admixture 2 was used, and the compressive strength of the cured product immediately after demolding was measured.
It was 22 MPa, and it was confirmed that the strength did not reach the prestress-introducable level.

[0066]

[Table 11]

[Brief description of the drawings]

FIG. 1 is a top view (FIG. 1A) and a side view (FIG. 1B) showing an embodiment of adiabatic curing in an embodiment of the present application.

FIG. 2 is a sectional view showing a structure of a heat insulating sheet used for heat insulating curing in the embodiment of the present invention.

FIG. 3 is a graph showing a temperature control pattern of steam curing performed in Comparative Example 7 of the present application.

[Explanation of symbols]

 11: Formwork 12: Styrofoam container 13: Glass fiber insulation 14: Styrofoam lid 21: Vinyl sheet 22: Heat insulation layer

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) // (C04B 28/04 (C04B 28/04 7:00 7:00 22:06 22:06 22:14) 22: 14) B 111: 20 111: 20 111: 76 111: 76 (72) Inventor: Yoshihisa Kaneda 2-4-2, Daisaku, Sakura-shi, Chiba Pref. Taiheiyo Cement Co., Ltd. Sakura Research Institute (72) Inventor: Kure Nyo Tochigi Kinugaoka, Moka Pref., Japan Oriental Construction Co., Ltd. Technical Research Institute F-term (reference) 4G012 PA04 PA10 PB03 PB11 PC03 PC12 PC13 PE05 RA05

Claims (4)

[Claims] 1. A cement admixture containing 50% by weight or more of CaO crystals for adiabatic curing. (I) CaO-3CaO.SiO ₂ as a main constituent mineral
-2CaO · SiO ₂ - gap material, CaO-3CaO · SiO ₂ - gap material, CaO-2CaO · SiO ₂ - gap material, CaO- gap material, of 1
Containing at least two or more species and having a CaO crystal content of 50 to 9
2. The cement admixture for heat-insulating curing according to claim 1, further comprising 2% by weight of a clinker composition, and (ii) gypsum. 3. A concrete composition comprising the cement admixture for heat insulating curing according to claim 1 or 2, portland cement or mixed cement, aggregate, and water, and the mixture is cured by heat insulating curing. A method for producing a hardened concrete product. 4. A hardened concrete product produced by the production method according to claim 3.