JP5587006B2 - Sulfuric acid resistant cement composition, sulfuric acid resistant mortar composition and sulfuric acid resistant concrete composition - Google Patents

Description

  The present invention is suitable for use in places where corrosion by sulfuric acid or sulfate is a problem, such as sewers, hot springs, chemical factories, and the like, and a sulfuric acid resistant cement composition with improved durability against acid rain, sulfuric acid resistance The present invention relates to a mortar composition and a sulfuric acid resistant concrete composition.

  In places where exposed to sulfuric acid or sulfate, such as sewers, hot springs, and chemical factories, corrosion of hardened cement by sulfuric acid or sulfate has been a problem. In recent years, corrosion of the entire structure using cement due to acid rain has also become a problem.

  Hardened cement (hardened cement paste, mortar, or concrete) forms a sparingly soluble and expandable gypsum when it comes into contact with sulfuric acid and dissolves silicic acid, alumina, etc. to produce silica or alumina gel To do. This action of sulfuric acid on the cement, which causes the expansive gypsum, silica and alumina gels to elute and easily breaks the hardened cement body, naturally depends on the acid concentration. When the pH exceeds 2 (sulfuric acid concentration of 0.1% or less), that is, when the acid concentration is low, corrosion by carbon dioxide gas or low concentration acid, or by salt showing corrosive properties such as sulfate Similarly, the penetration of corrosive substances into the interior can be suppressed by densifying the hardened cement, for example, by reducing the water-cement ratio while ensuring workability by using a high-performance AE water reducing agent. Thereby, corrosion resistance can be improved. However, when the concentration of sulfuric acid is high, it is difficult to cope only with the densification of the hardened cement. When the cement-hardened body is densified by lowering the water-cement ratio, there are fewer pores that relieve the expansion pressure due to crystal growth of gypsum produced by the acid. For this reason, for example, when the pH is very low, such as 2 or less, the gypsum is easily peeled off from the surface, and the corrosion resistance of the hardened cement body may deteriorate due to the progress of erosion. It is difficult.

  When pH is 2 or less (sulfuric acid concentration 0.1% or more), in order to prevent deterioration of the hardened cement body due to acid, the polymer cement in which the polymer is combined with the cement composition or the surface of the cement composition is corrosion resistant. An anticorrosion coating (lining) material that is coated with a material (for example, an epoxy resin or an unsaturated polyester resin) and prevents contact between a chemical corrosive substance (for example, sulfuric acid) and a cement composition is used. However, polymer cement and anticorrosion coating are not only expensive, but are not general-purpose measures because a special process is required during production or construction. Even if there is a demand for sulfuric acid resistance, the cost may be more important than the improvement of sulfuric acid resistance if the cost becomes large.

  A water-soluble organic compound having an alkali metal salt of sulfonic acid as a substituent, specifically, a water-soluble organic compound containing an alkali metal salt of naphthalenesulfonic acid, as a cement composition from which a cured product having improved sulfuric acid resistance is obtained There is known a cement composition containing 0.5 to 4 parts by mass with respect to 100 parts by mass of cement (Patent Document 1).

Japanese Patent Laid-Open No. 10-236860

As shown in Patent Document 1, the amount of water-reducing agent containing a water-soluble organic compound such as an alkali metal salt of naphthalene sulfonic acid is larger than the amount added for the purpose of ensuring fluidity. By doing so, it is known that the sulfuric acid resistance after curing the cement composition is improved. However, the cement composition of Patent Document 1 may cause material separation.
Therefore, the present invention is simple in construction, provides a cured body with improved sulfuric acid resistance, and can suppress material separation, sulfuric acid resistant cement composition, sulfuric acid resistant mortar composition, and sulfuric acid resistant material. An object is to provide a concrete composition.

  The inventors of the present invention have studied various chemical structures of a compound imparting sulfuric acid resistance, and can greatly improve the sulfuric acid resistance after curing of a cement composition, a mortar composition, or a concrete composition, and a material. The present inventors have found a compound having an optimal chemical structure that can suppress separation, and have reached the present invention.

The present invention is an alkali metal salt of polystyrene sulfonic acid which is used at a pH of 2 or less exposed to sulfuric acid or sulfate, and whose weight average molecular weight is 10,000 to 2,000,000 with respect to 100 parts by mass of cement . The present invention relates to a sulfuric acid resistant cement composition containing 1 to 20 parts by mass of a homopolymer , and a sulfuric acid resistant mortar composition and a sulfuric acid resistant concrete composition using the same.

  The sulfuric acid-resistant cement composition according to the present invention, and the sulfuric acid-resistant mortar composition and sulfuric acid-resistant concrete composition using the same are simple in construction without requiring a special process at the time of construction. Separation can be suppressed, and the sulfuric acid resistance of a cured product obtained using these compositions can be improved.

2 is a photograph (40 magnifications) of a cross section of a specimen of Comparative Example 1. 2 is a photograph (40 magnifications) of a cross section of a specimen of Example 2. FIG. It is a photograph (40 magnifications) of the cross section of the specimen of Example 14.

The sulfuric acid resistant cement composition, sulfuric acid resistant mortar composition and sulfuric acid resistant concrete composition of the present invention will be described in detail.
The sulfuric acid resistant cement composition of the present invention is a polymer of a compound having an unsaturated ring and each ring of the unsaturated ring having one or more sulfo groups with respect to 100 parts by mass of the cement and / or its 0.1-20 mass parts of organic compounds which are salts are included.

  Examples of the cement used in the present invention include Portland cement and mixed cement specified by JIS. Specifically, ordinary Portland cement, early strength Portland cement, super early strength Portland cement, moderately hot Portland cement, low heat Portland cement, sulfate resistant Portland cement, and their low alkali type Portland cement, blast furnace cement, fly ash Examples thereof include cement and silica cement.

The organic compound used in the present invention is a polymer of a compound having an unsaturated ring and each unsaturated ring having one or more sulfo groups (—SO ₃ H) and / or a salt thereof. Among these organic compounds, one type may be used, or two or more types may be used in combination. These have an unsaturated ring, and each ring of the unsaturated ring has a polycondensation of a compound having one or more sulfo groups (—SO ₃ H) and formaldehyde, and / or an unsaturated ring, and Each unsaturated ring is produced by polymerization using a compound having one or more sulfo groups as a monomer and / or sulfonation of a polymer having an unsaturated ring.

  The mechanism of improving the sulfuric acid resistance of a hardened cement according to the present invention is not completely elucidated, but the organic compound used in the present invention is produced when the hardened cement is exposed to sulfuric acid. It is understood that it affects the generation of. That is, it is presumed that the organic compound used in the present invention is adsorbed on gypsum produced by the reaction between sulfuric acid and cement by the sulfo group, and the crystal growth is efficiently controlled. As a result, the expansibility of gypsum is suppressed, and a dense gypsum layer is formed on the cement particle surface. This prevents sulfuric acid erosion, thereby suppressing further reaction of the cemented hardened body of sulfuric acid and improving sulfuric acid resistance. Then it is understood.

  The organic compound used in the present invention has an unsaturated ring, and the unsaturated ring may be a single ring or a condensed ring. The unsaturated ring may be substituted with an alkyl group having 1 to 4 carbon atoms such as a hydroxy group or a methyl group.

  Further, the unsaturated ring may be a carbocyclic ring or a heterocyclic ring. Examples of the carbocycle include at least one selected from the group consisting of a benzene ring, a naphthalene ring, and an anthracene ring.

  Each ring of the unsaturated ring has one or more sulfo groups. In the case of a single ring, this means that the ring has one or more sulfo groups, and in the case of a condensed ring, a condensed ring. Each ring (nucleus) that forms a ring has one or more sulfo groups. For example, a naphthalene ring refers to a case where two benzene rings (nuclei) each have one or more sulfo groups.

  The organic compound used in the present invention includes a polycondensate of formaldehyde with a compound having an unsaturated ring and each ring of the unsaturated ring having one or more sulfo groups. Examples of the compound having an unsaturated ring and each unsaturated ring having one or more sulfo groups include phenolsulfonic acid, phenoldisulfonic acid, and naphthalenedisulfonic acid.

  Examples of the organic compound used in the present invention also include a polymer having an unsaturated ring and a monomer having a compound in which each ring of the unsaturated ring has one or more sulfo groups. In this case, it may be a homopolymer having one kind of compound as a monomer or a copolymer having two or more kinds as a monomer. For example, a homopolymer of a compound having an ethylenically unsaturated bond such as styrene sulfonic acid or vinyl naphthalene having a sulfo group substituted on each benzene ring (core), or a copolymer thereof.

  The organic compound used in the present invention may be in the form of a salt, and examples thereof include alkali metal salts such as sodium salts and alkaline earth metal salts such as calcium salts. The organic compounds and salts thereof may be used alone or in combination of two or more.

  As an organic compound used in the present invention, polystyrenesulfonic acid and / or a salt thereof is a homopolymer containing a repeating unit represented by the following formula (1), or a monomer containing a unit represented by the following formula (1). And a copolymer of a monomer having an unsaturated double bond such as styrene or α-methylstyrene and having or not having a sulfo group as a substituent on the benzene ring, acrylonitrile, or methyl methacrylate. May be.

  In the above formula, R and R ′ each independently represent hydrogen or an alkyl group having 1 to 4 carbon atoms, and M represents an alkali metal such as hydrogen, lithium, sodium or potassium, or an alkaline earth such as magnesium or calcium. Indicates metal. As the organic compound having a sulfo group used in the present invention, a homopolymer of styrene sulfonic acid and / or a salt thereof is preferably used.

  The organic compound used in the present invention is preferably a polymer compound, and when the organic compound is a homopolymer of polystyrene sulfonic acid and / or a salt thereof, the weight average molecular weight is 10,000 to 2,000,000. 000 is preferable, and more preferably 20,000 to 1,000,000. When the weight average molecular weight of the polystyrene sulfonic acid and / or salt thereof is 10,000 or more, the sulfuric acid resistance can be secured, and when the weight average molecular weight is 2,000,000 or less, the viscosity does not increase. Here, the weight average molecular weight is a value calculated in terms of a calibration curve of polystyrene sulfonic acid and p-toluenesulfonic acid by a gel filtration chromatography (GFC) method.

  The amount of the organic compound used in the present invention is 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, more preferably 1 to 5 parts by weight, and still more preferably 100 parts by weight of cement. 2 to 4 parts by mass. The amount of the organic compound is based on the solid content. When the amount of the organic compound is less than 0.1 parts by mass with respect to 100 parts by mass of the cement, the effect of improving the sulfuric acid resistance is small, and when it exceeds 20 parts by mass, not only the cost becomes disadvantageous, The fresh properties and curability of the cement composition may be deteriorated, which is not preferable.

  The sulfuric acid resistant cement composition of the present invention preferably further contains 30 to 400 parts by mass of limestone fine powder with respect to 100 parts by mass of cement. The limestone fine powder used in the present invention is more preferably 50 to 350 parts by mass, still more preferably 70 to 300 parts by mass, and particularly preferably 80 to 250 parts by mass with respect to 100 parts by mass of cement. . When the amount of fine limestone powder is within the above range, it becomes possible to produce a denser gypsum layer when the cement hardened body made of the cement composition is exposed to sulfuric acid, and the hardened body has a sulfuric acid resistance. The effect which improves further can also be expected.

As the limestone fine powder, one having a brain specific surface area of preferably 2000 to 20000 cm ² / g can be used. Blaine specific surface area of powder limestone fines, more preferably 2500~15000cm ² / g, more preferably 3000~10000cm ² / g, particularly preferably be used those 4000~7000cm ² / g. When the Blaine specific surface area of the limestone fine powder is within the above range, material separation can be suppressed and good workability can be maintained. Here, the Blaine specific surface area of the limestone fine powder is a value measured according to JIS R 5201 “cement physical test method”.

  The sulfuric acid resistant mortar composition of the present invention further contains fine aggregate in addition to the sulfuric acid resistant cement composition. As the fine aggregate used in the present invention, river sand, land sand, sea sand, crushed sand, blast furnace slag fine aggregate, limestone fine aggregate and the like can be used. The fine aggregate contained in the sulfuric acid resistant mortar composition is preferably 50 to 800 parts by weight, more preferably 100 to 650 parts by weight, and even more preferably 150 to 500 parts by weight, particularly 100 parts by weight of cement. Preferably it is 150-400 weight part, Most preferably, it is 180-300 weight part.

  The sulfuric acid resistant concrete composition of the present invention further comprises coarse aggregate in the sulfuric acid resistant mortar composition. As the coarse aggregate used in the present invention, gravel, crushed stone, blast furnace slag coarse aggregate, limestone coarse aggregate and the like can be used. The coarse aggregate is preferably 200 to 320 parts by mass, more preferably 230 to 290 parts by mass, and further preferably 250 to 270 parts by mass with respect to 100 parts by mass of cement. If the blending amount of the coarse aggregate is within the above range, good fresh properties can be obtained.

  The sulfuric acid resistant cement composition of the present invention, and the sulfuric acid resistant mortar composition and the sulfuric acid resistant concrete composition using the same can be premixed prior to kneading. When adding water and kneading, it is preferable to prepare by adding an organic compound, fine aggregate and other admixtures. As described above, the sulfuric acid resistant cement composition of the present invention, and the sulfuric acid resistant mortar composition and the sulfuric acid resistant concrete composition using the same can be prepared by a simple method. Can be prepared easily and inexpensively in a facility or the like that forms the film.

  The sulfate-resistant cement composition of the present invention, and the sulfate-resistant mortar composition and sulfate-resistant concrete composition using the same are a base cement, an organic compound having a sulfo group, limestone fine powder, and water. In addition, aggregates such as sand and gravel, AE agents that are compounds of lignin, naphthalene, polyol, polycarboxylic acid, etc. to adjust fresh properties, AE water reducing agent, high performance water reducing agent, high performance Chemical admixtures such as AE water reducing agent, medium performance water reducing agent, high function water reducing agent, multifunctional water reducing agent, thickener, antifoaming agent, air amount adjusting agent, curing accelerator, curing retarder, reinforcing steel rust inhibitor Even if a known additive such as the above is added, no problem occurs, and it can be used as a paste, mortar, or concrete material by a conventionally known construction method. Further, the curing can be produced not only by room temperature curing but also by steam curing or heat curing.

  A cured product obtained by curing any one composition selected from the group consisting of a sulfuric acid resistant cement composition, a sulfuric acid resistant mortar composition and a sulfuric acid resistant concrete composition of the present invention is in contact with an aqueous solution containing sulfuric acid. By doing so, a dense gypsum layer is formed on the surface. In these cured bodies having a gypsum layer on the surface, sulfuric acid erosion is prevented by the gypsum layer, and the sulfuric acid resistance is improved.

  The sulfuric acid resistant cement composition of the present invention, and the sulfuric acid resistant mortar composition and sulfuric acid resistant concrete composition using the same are concrete structures such as hot spring facilities, sewerage facilities, chemical factories, etc. where excellent sulfuric acid resistance is required. It can be suitably used for concrete products using cement such as objects, pipes, U-shaped grooves, and concrete piles. Furthermore, it can apply to the surface of those concrete products, and can apply as an anticorrosion coating material which forms an anticorrosion coating layer, and a repair material with respect to a degradation part.

  Hereinafter, the contents of the present invention will be described in more detail with reference to Examples and Comparative Examples. Note that the present invention is not limited to these examples.

[Materials used]
In the implementation, the following raw materials were used.
(1) Cement:
Ordinary Portland cement [manufactured by Ube Industries, Ltd.], Blaine specific surface area 3270 cm ² / g (measured according to JIS R 5201-1997 “Physical test of cement”. The porosity of the sample bed was 0.50.)
(2) Limestone fine powder:
Limestone fine powder for roads [manufactured by Ube Materials Co., Ltd.], Blaine specific surface area 4500 cm ² / g (measured according to JIS R 5201-1997 “Physical test of cement”. The porosity of the sample bed was 0.47. .)
(3) Organic compound having a sulfo group:
Examples of organic compounds:
Homopolymers of sodium polystyrene sulfonate: Polynus PS-1 (weight average molecular weight 20,000), Polynus PS-5 (weight average molecular weight 75,000), Polynus PS-50 (weight average molecular weight 500,000), Polynas PS -100 (weight average molecular weight 1,000,000) [manufactured by Tosoh Corporation]. All were 20 mass% aqueous solution (Gel filtration chromatography (GFC method, measured with the calibration curve of polystyrene sulfonic acid and p-toluenesulfonic acid)).
Organic compounds of comparative examples:
Sodium 1,5-naphthalenedisulfonate [reagent, powder, purity 95% by mass or more]
(4) AE water reducing agent:
No. 70 [manufactured by BASF Pozzolith Co., Ltd.] (complex of lignin sulfonic acid compound and polyol)
(5) Air amount adjusting agent:
Micro Air 404 [manufactured by BASF Pozzolith Co., Ltd.] (Ingredients Polyalkylene glycol derivative)
(6) Aggregate: Sea sand (water absorption 1.34%, surface dry density 2.59 g / cm ³ , FM 2.66) and crushed sand (water absorption 1.36%, surface dry density 2.68 g / cm ³ , FM 2.79) 1: 1 mixture (7) Mixing water:
Water and sewage

[Preparation of mortar composition]
Mortar compositions were prepared with the blending amounts shown in Table 1 according to the mixing method in JIS R5201-1997 “Cement physical test”. Specifically, a mortar composition was prepared as follows.
In a kneading bowl, 160 g of water, a predetermined amount of an organic compound, and 0.029 g of an air amount adjusting agent are added. Then, 291 g of cement and 291 g of fine limestone powder are added, and kneaded for a predetermined time with a Hobart mixer. 582 g of aggregate was added and further kneaded to obtain a mortar composition. In Comparative Example 1, 1.45 g of AE water reducing agent was added instead of the organic compound.

[Fresh property test]
Using the obtained mortar composition, in a method described in “Cement physical test method 11. Flow test” of JIS R5201-1997, a value measured without giving a hit (hereinafter referred to as “0 hit flow”). ) And the presence or absence of separation of the mortar composition was visually confirmed. The results are shown in Table 2. The case where material separation occurred in the mortar composition was evaluated as x, the case where material separation slightly occurred was evaluated as Δ, and the case where material separation did not occur was evaluated as ○.

[Preparation of cured product]
Pour the prepared mortar composition into a cylindrical form with a diameter of 5 cm and a height of 10 cm. After curing at 65 ° C. for a whole day and night, demolding, and then at a temperature of 20 ° C. and a relative humidity (RH) of 90% or more for 6 days Cured with moisture to obtain a cured mortar, which was used as a test specimen.

[Evaluation of sulfuric acid resistance (1)]
A sulfuric acid resistance test was conducted based on the “JIS chemical test method by immersion in concrete solution”. Specifically, the specimen after curing was immersed in a 5% by mass sulfuric acid aqueous solution (pH of about 0.3, 20 ± 2 ° C.), and the specimen was taken out from the sulfuric acid aqueous solution after a soaking period of 1 week and 13 weeks. . The removed specimen was washed with water using a brush, the moisture was wiped off with a towel, and the mass was measured. The mass reduction rate was calculated | required by the following formula | equation (2). The results are shown in Table 2. Further, in order to clarify the effect of improving the sulfuric acid resistance, the ratio of the mass reduction rate of each example and the comparative example when the mass reduction rate of the comparative example 1 is set to 1 is also shown in Table 2 in parentheses.
Mass reduction rate (%) = (mass of specimen before being immersed in sulfuric acid aqueous solution−mass of specimen after being immersed in sulfuric acid aqueous solution for a predetermined period) / (mass of specimen before being immersed in sulfuric acid aqueous solution) × 100 ... (2)

[Evaluation of sulfuric acid resistance (2)]
For the specimens of Comparative Example 1, Example 2 and Example 14, the cut surface in the vicinity of the exposed surface of the specimen that had been immersed for 13 weeks, washed with water, and cut with a dry cutter was digital microscope (manufactured by Moritex Corporation). And a COOLPIX 950 equipped with a Nikon relay lens. The light source used was MME250 manufactured by Moritex Corporation. Photographs of the results obtained are shown in FIGS. 1 to 3 (Comparative Example 1, Example 2 and Example 14).

  From the results shown in Table 2, the cured products composed of the mortar compositions of Examples 1 to 16 have a mass reduction rate after immersion in sulfuric acid as low as -1.6% to 3.4% in 1 week, and 13 weeks. However, it was 0.1% to 55.9%, and it was confirmed that the sulfuric acid resistance was improved. On the other hand, in Comparative Example 1 in which an AE water reducing agent was added to the mortar composition, it was 6.7% in 1 week and 79.1% in 13 weeks. 16 is 0.51 or less in 1 week and 0.71 or less in 13 weeks, and it can be seen that it is small. On the other hand, in Comparative Examples 2 to 4 in which an organic compound having only one unsaturated ring (naphthalene ring) was added to the mortar composition, the ratio was 5.8 to 7.0% per week. Then, it was confirmed that it was as large as 0.87 or more.

  Furthermore, in the mortar compositions of Examples 1 to 16, a small number of material separations were confirmed, almost no material separation occurred, and more than or equal to Comparative Example 1 to which an AE water reducing agent was added. It was confirmed that the construction was simple without requiring a special process because the fluidity was ensured.

  In particular, the mortar composition (Examples 2 to 4, 6 to 8, 10 to 12, and 14 to 16) in which 1 part by mass or more of the organic compound used in the present invention is added to 100 parts by mass of the cement is the above organic. Compared with the mortar composition (Example 1, 5, 9, 13) which added less than 1 mass part of compounds, fluidity | liquidity and sulfuric acid resistance are improving more.

  Further, as can be seen from FIGS. 1 to 3, the thickness of the gypsum layer was the thinnest in Comparative Example 1, and many gypsums peeled off from the specimen were observed in the sulfuric acid aqueous solution. From this, it is surmised that the gypsum layer produced in Comparative Example 1 is highly expansible and peeled off from the surface of the specimen as the gypsum layer grew and the protective layer on the surface decreased, so that the sulfuric acid resistance was also lowered.

  The sulfuric acid resistant cement composition of the present invention, and the sulfuric acid resistant mortar composition and sulfuric acid resistant concrete composition using the same are likely to be exposed to sulfuric acid or sulfate in hot springs, sewer facilities, chemical factories, etc. It is not only applicable to concrete structures and concrete products used in high places, but also has high durability against acid rain, which has become a problem in recent years, so it is useful as a composition for forming general concrete products. high.

Claims (6)

Used at a pH of 2 or less exposed to sulfuric acid or sulfate,
1 to 20 parts by mass of a homopolymer of an alkali metal salt of polystyrene sulfonic acid having a weight average molecular weight of 10,000 to 2,000,000 with respect to 100 parts by mass of cement. Composition. 1.33 to 4 parts by mass of a homopolymer of an alkali metal salt of polystyrene sulfonic acid is contained with respect to 100 parts by mass of cement , and 30 to 400 parts by mass of fine limestone powder having a Blaine specific surface area of 2000 to 20000 cm ² / g. , claim 1 Symbol placement of sulfuric acid cement composition. The sulfuric acid resistant cement composition according to claim 1 or 2, wherein the homopolymer of an alkali metal salt of polystyrene sulfonic acid is a homopolymer of sodium polystyrene sulfonate. A sulfuric acid resistant mortar composition, wherein the sulfuric acid resistant cement composition according to any one of claims 1 to 3 further comprises 50 to 800 parts by mass of fine aggregate with respect to 100 parts by mass of cement . The sulfuric acid resistant mortar composition according to claim 4 , further comprising 200 to 320 parts by mass of coarse aggregate with respect to 100 parts by mass of cement . Any one selected from the group consisting of the sulfuric acid resistant cement composition according to any one of claims 1 to 3, the sulfuric acid resistant mortar composition according to claim 4 , and the sulfuric acid resistant concrete composition according to claim 5 . A sulfate-resistant cured body, which is obtained by curing one composition and has a gypsum layer formed on the surface by contacting with an aqueous solution containing sulfuric acid.