JP2023049714A - Cement composition, repairing method using the same, and concrete structure - Google Patents

Abstract

To provide a cement composition having high acid tolerance, initial cracking resistance, high adhesiveness, and fluidity retention.SOLUTION: A cement composition includes calcium aluminate and pozzolan, where the calcium aluminate includes SO3, ZrO2, and P2O5 as a chemical component, the total amount of SO3, ZrO2, and P2O5 is 0.05 mass% or more and 2.0 mass% or less with respect to 100 pts.mass of the calcium aluminate, and the content of the P2O5 (P2O5/(SO3+ZrO2+P2O5)) is 10 mass% or more and 45 mass% or less.SELECTED DRAWING: None

Description

The present invention mainly relates to a cement composition used in the civil engineering and construction fields, a repair method using the same, and a concrete structure.

In recent years, cases of deterioration of concrete structures due to sulfuric acid have been increasing, mainly in sewage treatment facilities, and research on sulfuric acid deterioration of concrete has become more common than ever before. It is known that the activity of microorganisms is the cause of the generation of sulfuric acid in sewage treatment facilities, and in addition to the use of acid-resistant materials as countermeasures against acid deterioration, the application of antibacterial agents, etc. is being studied.

As acid-resistant materials, mortar and concrete in which a large amount of blast furnace slag, fly ash, silica fume, etc. are mixed with Portland cement (see Patent Document 1), and mortar and concrete using alumina cement have been proposed (Patent Document 2, See Patent Document 3). However, there were also problems such as the occurrence of cracks in the initial stage and the decrease in fluidity.

JP-A-2000-128618 JP-A-60-180945 JP-A-01-141844

INDUSTRIAL APPLICABILITY The present invention provides a cement composition having excellent acid resistance, initial crack resistance and fluid retention, a repair method using the same, and a concrete structure.

As a result of intensive studies in view of the above problems, the present inventors found that the problems can be solved by a cement composition containing calcium aluminate and pozzolan having a predetermined chemical composition. That is, the present invention is as follows.

[1] A cement composition containing calcium aluminate and pozzolan, wherein the calcium aluminate contains _SO3 , _ZrO2 and _P2O5 as chemical components, and ₁₀₀ parts by mass of the calcium aluminate contains On the other hand, the _{total amount of SO3, ZrO2 and P2O5 is 0.05 %} by mass or more and 2.0% by mass _or less, _{and the content of P2O5 (P2O5 / ( SO3} + _ZrO2 +P ₂ O ₅ )) is 10% by mass or more and 45% by mass or less.
[2] The cement composition according to [1], wherein the pozzolan is ground granulated blast furnace slag.
[3] The cement composition according to [1] or [2], wherein the calcium aluminate has a CaO/Al ₂ O ₃ molar ratio of 0.5 or more and 2.0 or less.
[4] The cement composition according to any one of [1] to [3], further comprising a polymer for cement.
[5] The cement composition according to any one of [1] to [4], further comprising an aggregate.
[6] A concrete structure repaired using the cement composition described in any one of [1] to [5].
[7] A repair method using the cement composition according to any one of [1] to [5].

INDUSTRIAL APPLICABILITY According to the present invention, a cement composition having excellent acid resistance, initial crack resistance, and fluid retention, and a repair method using the same can be obtained.

The present invention will be described in detail below. Parts and percentages in this specification are shown on a mass basis unless otherwise specified. Moreover, the concrete mentioned in the present invention is a general term for cement paste, mortar and concrete.

[Cement composition]
The cement composition according to the present invention contains calcium aluminate and pozzolan.
Calcium aluminate used in the present invention is mainly composed of CaO and Al ₂ O ₃ obtained by mixing a calcia raw material and an alumina raw material, etc., firing in a kiln, or melting and cooling in an electric furnace. It is a general term for substances having hydration activity, and can be used either crystalline or amorphous. It is a material that cures quickly and exhibits high initial strength.

The _calcium aluminate according to the present invention contains _SO3 , _ZrO2 and _P2O5 as chemical components.
It contains _SO3 , _ZrO2 and _P2O5 as chemical components in _calcium aluminate. SO ₃ in calcium aluminate is preferably 0.01 mass % or more and 0.9 mass % or less, more preferably 0.03 mass % or more and 0.25 mass % or less. ZrO ₂ is preferably 0.01 mass % or more and 0.7 mass % or less, more preferably 0.03 mass % or more and 0.25 mass % or less. P ₂ O ₅ is preferably 0.01% by mass or more and 0.6% by mass or less, more preferably 0.03% by mass or more and 0.5% by mass or less.

Note that "calcium aluminate contains _SO3 , _{ZrO2 ,} and _P2O5 as chemical components" means that _SO3 , _ZrO2 , and _P2O5 are each identified by X-ray diffraction measurement _. Although no peak is observed _, it refers to a _state in _which each content can be measured by fluorescent X-ray measurement _. It is presumed that

In the calcium aluminate according to the present invention, the total amount _{of SO3} , _ZrO2 and _P2O5 is 0.05% by mass or more from the viewpoint of having excellent acid resistance, initial crack resistance, and fluidity retention. 0% by mass or less, preferably 0.07% by mass or more and 1.7% by mass or less, and more preferably 0.1% by mass or more and 1.5% by mass or less.

Furthermore, the content of P ₂ O ₅ (P ₂ O ₅ /(SO ₃ +ZrO ₂ +P ₂ O ₅ )) is 10% by mass or more and 45% by mass or less from the viewpoint of having initial crack resistance and fluidity retention, It is preferably 12% by mass or more and 43% by mass or less, more preferably 15% by mass or more and 40% by mass or less. Also, the amounts of SO ₃ , ZrO ₂ and P ₂ O ₅ can be measured by X-ray fluorescence diffraction (XRF).

The total amount of SO ₃ , ZrO ₂ and P ₂ O ₅ is 0.05% by mass or more and 2.0% by mass from the viewpoint of high fluidity retention effect, low kneading resistance, high strength development, and suppression of cracking. %, preferably 0.07% by mass or more and 1.7% by mass or less, and more preferably 0.1% by mass or more and 1.5% by mass or less.

The total amount _{of SO3} , _ZrO2 and _P2O5 with respect to 100 parts by mass of _calcium aluminate is 0.05% by mass or more and 2.0% by mass or _less , or the content of _P2O5 ( _P2O5 /(SO ₃ +ZrO ₂ +P ₂ O ₅ )) is 10% by mass or more and 45% by mass or less, for example, each content in the raw material is measured, and the desired total amount is obtained. , SO ₃ , ZrO ₂ , and P ₂ O ₅ may be adjusted.

Among calcium aluminates, the molar ratio between CaO and Al ₂ O ₃ (CaO/Al ₂ O ₃ molar ratio) is preferably 0.5 or more and 2.0 or less, more preferably 0.7 or more and 1.8. The following are more preferable. When the molar ratio is within the above range, the curing time can be further shortened and the initial strength development can be enhanced.
In order to make the molar ratio of CaO and Al ₂ O ₃ within the above range, for example, the blending of raw materials when producing calcium aluminate may be adjusted.

When obtaining calcium aluminate industrially, it may contain impurities. Specific examples thereof include SiO ₂ , Fe ₂ O ₃ , MgO, TiO ₂ , MnO, Na ₂ O, K ₂ O, SrO, Cr ₂ O ₃ , Nb ₂ O ₅ , Ga ₂ O ₃ and Y _{2 . O3} , _ThO2 , NiO _{, SeO2} , _Li2O , _Rb2O , _As2O3 , ZnO, S, Cl, F and the like. The presence of these impurities poses no particular problem as long as they do not substantially hinder the object of the present invention. Specifically, if the total content of these impurities is 10% or less, there is no particular problem.

As the impurity compound, calcium aluminoferrite such as 4CaO.Al ₂ O ₃ .Fe ₂ O ₃ , 6CaO.2Al ₂ O ₃ .Fe ₂ O ₃ , 6CaO.Al _{2 O} 3.2Fe ₂ O ₃ , 2CaO. Calcium ferrites such _{as Fe2O3} and _CaO.Fe2O3 , _{galenite 2CaO.Al2O3.SiO2} , _{anorthite CaO.Al2O3.2SiO2 and other} calcium aluminosilicates, _merbinite 3CaO.MgO.2SiO ₂ , Akermanite _{2CaO.MgO.2SiO2} , _calcium magnesium silicate such as monticelite CaO.MgO.SiO2, tricalcium _silicate 3CaO.SiO2 _, dicalcium silicate 2CaO.SiO2, lankinite 3CaO.2SiO2 _, wollastonite Calcium silicate such as _CaO.SiO2 , calcium titanate _CaO.TiO2 , _calcium alnate _{3CaO.Al2O3 ,} free lime, leucite ( _K2O , _Na2O ) _{.Al2O3.SiO2 ,} etc. may contain. In the present invention, these crystalline or amorphous materials may be mixed.

The particle size of the calcium aluminate according to the present invention is not particularly limited, but the Blaine specific surface area is preferably in the range of 3000 to 9000 cm ² /g, more preferably in the range of about 4000 to 8000 cm ² /g. . When it is 3,000 cm ² /g or more, sufficient strength development can be easily obtained, and when it is 9,000 cm ² /g or less, handling can be improved.
The Blaine specific surface area is determined according to JIS R 5201 (physical test method for cement).

The pozzolan according to the present invention plays a role of promoting the effect of preventing a decrease in strength due to conversion of calcium aluminate and the effect of improving acid resistance. Pozzolans are not particularly limited, and include ground granulated blast furnace slag, fly ash, silica fume, pulp sludge incineration ash, sewage sludge incineration ash, and waste glass powder. can be used. Among them, it is preferable to use ground granulated blast furnace slag.

The fineness of the ground granulated blast furnace slag is not particularly limited, but is usually in the range of about 3000 to 9000 cm ² /g in Blaine specific surface area. The fineness of fly ash and silica fume is not particularly limited, but usually fly ash has a Blaine specific surface area of about 3000 to 9000 cm 2 /g, and silica fume has a BET specific surface area of about 3000 to 9000 cm ² /g. is in the range of about 2 to 20 m ² /g.

In the present invention, the mixing ratio of calcium aluminate and pozzolan is not particularly limited. is more preferred. The pozzolan is preferably 20 to 70 parts, more preferably 30 to 60 parts.

When the amount of calcium aluminate is 30 parts or more and the amount of pozzolan is 70 parts or less, it becomes easier to achieve excellent acid resistance, resistance to initial cracking, and fluid retention. Further, when the amount of calcium aluminate is 80 parts or less and the amount of pozzolan is 20 parts or more, a reduction in strength due to conversion does not occur, and sufficient acid resistance can be easily obtained.

The cement composition of the present invention preferably further contains a polymer for cement. Polymers for cement (hereinafter referred to as polymers) include, but are not limited to, aqueous polymer dispersions, re-emulsified powder resins, water-soluble polymers, and liquid polymers. Aqueous polymer dispersions include synthetic rubber latex such as natural rubber latex, acrylic rubber, styrene-butadiene rubber (SBR), chloroprene rubber (CR), ethylene-vinyl acetate copolymer (EVA), and polyacrylate (PAE). ) and other resin emulsions. Forms of the polymer include re-emulsified powder type and liquid type. These are used to improve adhesion and durability between mortar and existing concrete.

The amount of the polymer to be used is preferably 1 to 15 parts, more preferably 3 to 10 parts in terms of solid content, per 100 parts of the binder composed of calcium aluminate and pozzolan. If it is 1 part or more, high adhesion to existing concrete and the like and improvement in durability can be expected. When the content is 15 parts or less, economic efficiency can be maintained while an improvement in the effect is expected.

The method of mixing the polymer is not particularly limited, but in the case of powder, it may be mixed with cement in advance, mixed with other materials at the time of kneading, or suspended or dissolved in water. In the case of a liquid, there is a method of simultaneously adding it with other materials during kneading, or a method of mixing it with water and using it.

The cement composition of the present invention preferably further contains aggregate.
As aggregates used in the present invention, fine aggregates and coarse aggregates similar to those used in ordinary cement mortar and concrete can be used. 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, and heavy aggregates can be used, and a combination thereof is also possible. In particular, silica sand, limestone aggregate, and lime sand are preferably used in applications where the effect of maintaining fluidity is high and the effect of low kneading resistance is intended.

The blending ratio of the aggregate is preferably 0 to 1000 parts, more preferably 50 to 400 parts, per 100 parts of the binder composed of calcium aluminate and pozzolan. When it is 0 part or more, it is possible to have initial crack resistance and fluid retention. When the amount is 1000 parts or less, excellent acid resistance, initial crack resistance, and fluid retention can be obtained.

The particle size of the cement composition of the present invention is not particularly limited because it depends on the purpose and application of use, but usually the Blaine specific surface area is preferably 3000 to 8000 cm ² /g, more preferably 4000 to 6000 cm ² /g. more preferred. When it is 3000 cm ² /g or more, sufficient strength development is obtained, and when it is 8000 cm ² /g or less, good workability can be exhibited.

In the present invention, known cement may be used in combination. As well-known cements, various Portland cements such as normal, high early strength, ultra high early strength, low heat, and moderate heat, various mixed cements obtained by mixing these Portland cements with blast furnace slag, fly ash, or silica, and white cement , filler cement mixed with fine cement, limestone powder, etc., fine powder of slow-cooled blast furnace slag, waste-utilizing cement, so-called eco-cement, etc., and one or more of these can be used in combination.

In the present invention, in addition to aggregates such as sand and gravel, admixture materials such as fine powder of limestone and fine powder of slow-cooled blast furnace slag, water reducing agents, AE water reducing agents, high performance water reducing agents, high performance AE water reducing agents, and gas foaming substances, antifoaming agents, thickeners, rust inhibitors, antifreeze agents, shrinkage reducing agents, setting modifiers, fibers, clay minerals such as bentonite, and anion exchangers such as hydrotalcite, etc. or Two or more kinds can be used as long as the object of the present invention is not substantially impaired.

In the present invention, the method of mixing each material is not particularly limited, and each material may be mixed at the time of construction, or may be partially or wholly mixed in advance.
As a mixing device, any existing device can be used, for example, a tilting mixer, an omni mixer, a Henschel mixer, a V-type mixer, and a Nauta mixer can be used.

[Repair method, concrete structure]
The repair method according to the present invention is a repair method using the above-described cement composition of the present invention.
As the repair method, for example, there is a construction of repairing the cross section after removing the deteriorated portion of the concrete. There are various types of degraded concrete for cross-section repair, some repair large areas, others repair partial small areas, and the repair method is selected according to the repair area and the amount of repair material applied. be done. If the area is relatively large, the spraying method or grouting material is often used. In addition, if there is a wall or member thickness, a formwork is assembled and grout material is injected. On the other hand, if the area to be repaired is small, it will be done with a trowel. When partially repairing a cross section, although the area is small, the coating thickness of the repairing material is often thick, and a method of applying multiple layers is used. Although the cement composition of the present invention can be used in any construction method, the trowel coating method is particularly suitable.

By the repair method as described above, a concrete structure repaired using the cement composition of the present invention is obtained.

Examples will be described in detail below, but the present invention is not limited to these examples.

[Experimental example 1]
(Preparation of calcium aluminate)
Calcium carbonate and aluminum oxide are mixed so that the CaO/Al ₂ O ₃ molar ratio shown in Table 1 below is obtained, and SO ₃ , ZrO ₂ and P ₂ O ₅ after melting have the ratio shown in Table 1. _SO3 raw material (gypsum), _ZrO2 raw material (zirconium oxide), _P2O5 raw material (calcium phosphate) are added _, calcined at 1,500 ° C to synthesize clinker, and the Blaine specific surface area is measured using a ball mill. and pulverized to 3,000 cm ² /g to prepare various calcium aluminates.

(Preparation of cement composition)
The types and amounts of calcium aluminate and pozzolan shown in Table 1 were blended as shown in Table 1 to prepare a cement composition. Next, 200 parts by mass of fine aggregate and 0.03 parts by mass of water reducing agent are mixed with 100 parts by mass of cement composition (100 parts by mass of binder consisting of calcium aluminate and pozzolan) to prepare mortar and maintain fluidity. Performance, acid resistance evaluation, and crack acceleration test were evaluated. For comparison, the same procedure was carried out using ordinary Portland cement instead of calcium aluminate. The results are also shown in Table 1.

<Materials used>
Pozzolan (A): ground granulated blast furnace slag, Blaine specific surface area 6000 cm ² /g, commercially available product Pozzolan (B): fly ash, Blaine specific surface area 4300 cm ² /g, commercial product Pozzolan (C): Pozzolan A and Pozzolan B Pozzolane (D): Silica fume, BET specific surface area of 10 m ² /g, commercial product Ordinary Portland cement (abbreviated as OPC): Commercial product Water: Tap water Fine aggregate: Silica sand N50, manufactured by Nihon Gyogyo Water reducing agent: Melamine sulfonic acid powder water reducing agent

<Test method>
- Fluidity retention: Measured according to JIS R 5201, and the flow value after 20 minutes was subtracted from the flow value immediately after kneading to confirm the fluidity retention effect.
Fluidity retention effect = Flow value immediately after kneading - Flow value after 20 minutes ・Acid resistance evaluation: A specimen cured in water at 20 ° C until the material age of 28 days was immersed in a 5% concentration sulfuric acid solution for 3 months. Then, the acid resistance was evaluated from the change in appearance and weight loss of the specimen.
The evaluation criteria are: × if the appearance changes significantly and the mass change rate is ± 5% or more, and △ if the appearance changes significantly or the mass change rate is ± 5% or more. In the case of ◯, both the change in appearance and the change in mass did not meet the above conditions.
· Crack test: A concrete flat plate of 30 cm wide × 30 cm long × 6 cm thick was cast so as to have a thickness of 1 cm. The crack length was measured after 12 hours in a constant temperature and humidity room at 20° C. and 60% humidity with an air blower blowing the test piece with a wind speed of 3 m/sec.

From Table 1, it can be seen that the cement composition of the present invention is excellent in fluidity retention effect, acid resistance and initial crack resistance.

[Experimental example 2]
Experimental Example 1 No. To 100 parts of the binder containing 60 parts of calcium aluminate (1) and 40 parts of pozzolan (A) of 1-3, a polymer was blended in terms of solid content as shown in Table 2 to maintain fluidity. The same procedure as in Example 1 was conducted except that an adhesion test was conducted in addition to the evaluation of acid resistance. The results are also shown in Table 2.

<Materials used>
Polymer (A): commercial acrylic rubber (45% solids)
Polymer (B): commercially available styrene-butadiene rubber (45% solids)
Polymer (C): Commercially available polyacrylate, re-emulsified powder type

From Table 2, it can be seen that the cement composition of the present invention does not change the fluidity retention effect even when the polymer is blended, the adhesive strength is improved, and the acid resistance is excellent.

[Experimental example 3]
The deteriorated portion of the concrete sewage pipe corroded by sulfuric acid was removed and repaired by troweling using the cement composition of the present invention (mortar of No. 2-3 in Experimental Example 2). One year passed after the repair, but no particular abnormality was observed.
It can be seen that the cement composition of the present invention and the repair method using the same enable durable repair of concrete structures.

The cement composition and the repair method using the same of the present invention have excellent acid resistance, initial crack resistance, and fluidity retention, and therefore can be widely applied in the civil engineering and construction fields such as sewage treatment facilities.

Claims (7)

A cement composition comprising calcium aluminate and pozzolan,
_The calcium aluminate contains _SO3 , _ZrO2 and _P2O5 as chemical components,
The total amount of SO ₃ , ZrO ₂ and P ₂ O ₅ is 0.05% by mass or more and 2.0% by mass or less with respect to 100 parts by mass of the calcium aluminate,
The cement composition, wherein the P ₂ O ₅ content (P ₂ O ₅ /(SO ₃ +ZrO ₂ +P ₂ O ₅ )) is 10% by mass or more and 45% by mass or less. 2. The cement composition according to claim 1, wherein said pozzolan is ground granulated blast furnace slag. The cement composition according to claim ₁ or 2, wherein the calcium aluminate has a CaO/ _Al2O3 molar ratio of 0.5 or more and 2.0 or less. 4. The cement composition according to any one of claims 1 to 3, further comprising a polymer for cement. 5. The cement composition according to any one of claims 1 to 4, further comprising an aggregate. A concrete structure repaired using the cement composition according to any one of claims 1 to 5. A repair method using the cement composition according to any one of claims 1 to 5.