JP5707684B2 - Sulfuric acid resistant mortar composition, sulfuric acid resistant concrete composition and cured body thereof - Google Patents

Description

  The present invention relates to a sulfuric acid resistant mortar composition and a sulfuric acid resistant concrete composition excellent in sulfuric acid resistance in places where corrosion due to sulfuric acid or sulfate such as sewerage and hot springs is a problem, and hardened bodies thereof.

  In places exposed to sulfuric acid or sulfate such as sewers and hot springs, corrosion of hardened cement by sulfuric acid has been a problem. This problem of corrosion is not limited to limited areas such as sewers and hot springs, and in recent years, it has become a problem of the entire structure using cement due to corrosion by acid rain.

  When a hardened cement (mortar or concrete) is kept in contact with sulfuric acid for a long time, it forms hardly soluble gypsum and produces silica gel and alumina gel. The silica gel and alumina gel are eluted, and the hardened cement body is liable to collapse. This action of sulfuric acid on hardened cement, in particular concrete, naturally depends on the acid concentration. When the pH is 2 or more (sulfuric acid concentration 0.1% or less), the concrete is dense as in the case of corrosion due to carbon dioxide gas or low-concentration acid, or corrosive salts such as sulfate. For example, by reducing the water-cement ratio while ensuring workability by using a high-performance AE water reducing agent or the like, it is possible to suppress the penetration of corrosive substances into the concrete, thereby improving the corrosion resistance. be able to. However, when the concentration of sulfuric acid is high, it is difficult to cope with only the densification of concrete. For example, when the pH is lower than 2 and the concrete is densified by lowering the water-cement ratio, the number of pores that relieve the expansion pressure due to crystal growth of gypsum produced by sulfuric acid is reduced, and cracks and the like are induced. If sulfuric acid penetrates into the cracks, the corrosion resistance of the concrete may deteriorate, and it is difficult to expect the cement material itself to be resistant to sulfuric acid.

  As a method of preventing deterioration of the cement cured body due to sulfuric acid when the pH is lower than 2, a method of adding 1 to 10 parts by mass of a naphthalenesulfonate condensate in a large amount with respect to 100 parts by mass of the composition containing cement. It has been proposed (see Patent Documents 1, 2, and 3).

JP 2004-331458 A JP 2004-331459 A JP-A-2005-336012

  However, further improvement in sulfuric acid resistance has been desired.

  Therefore, an object of the present invention is to provide a sulfuric acid resistant mortar composition, a sulfuric acid resistant concrete composition, and a cured product thereof having higher sulfuric acid resistance than conventional ones.

The present invention include a cement, a fine aggregate, the number seen containing an average molecular weight of from 2000 to 4000 and a weight average molecular weight of 3,000 to 6,000 and a naphthalenesulfonic Sanshiochijimigo was further coarse aggregate and limestone powder The present invention relates to a sulfuric acid resistant concrete composition characterized by the following.
Further, the present invention is obtained by curing the above Ki耐 sulfate concrete composition, a cured product.

According to engagement Ru resistance sulfate concrete composition of the present invention, it is possible to provide a benzalkonium Nkurito cured product excellent in resistance to sulfuric acid.

It is a molecular weight calibration curve using standard polystyrene sulfonic acid. It is a gel filtration chromatogram of naphthalenesulfonate condensate NS1. It is a molecular weight distribution curve of naphthalene sulfonate condensate NS1. It is a gel filtration chromatogram of naphthalenesulfonate condensate NS2. It is a molecular weight distribution curve of naphthalene sulfonate condensate NS2. It is a gel filtration chromatogram of naphthalenesulfonate condensate NS3. It is a molecular weight distribution curve of naphthalene sulfonate condensate NS3.

The sulfuric acid resistant mortar composition and sulfuric acid resistant concrete composition according to the present invention will be described in detail.
The sulfuric acid resistant mortar composition of the present invention contains cement, fine aggregate, and a naphthalene sulfonate condensate having a number average molecular weight of 2000 to 6000 and a weight average molecular weight of 3000 to 30000.

  Examples of the cement used in the present invention include ordinary Portland cement, early strength Portland cement, super early strength Portland cement, sulfate-resistant Portland cement, moderately hot Portland cement, low heat Portland cement, blast furnace cement, fly ash cement, silica fume cement, and alumina. A cement etc. can be mentioned.

  The naphthalene sulfonate condensate used in the present invention has a number average molecular weight of 2000 to 6000, preferably 2000 to 5000, more preferably 2050 to 4500, and still more preferably 2080 to 4000. The naphthalene sulfonate condensate has a weight average molecular weight of 3000 to 30000, preferably 3050 to 20000, more preferably 3100 to 10000, and still more preferably 3150 to 6000. If the number average molecular weight and the weight average molecular weight of the naphthalene sulfonate condensate are within the above ranges, sufficient sulfuric acid resistance can be obtained.

The reason why the sulfuric acid resistance is improved by the number average molecular weight and the weight average molecular weight being in the above ranges is not clear. However, the following mechanism is estimated.
Sulfuric acid erosion means that sulfate ions generated in the environment such as sewers and hot springs react with calcium ions eluted from mortar and concrete to form brittle gypsum. This is a phenomenon in which mortar structures and concrete structures are eroded by the cycle of formation.
In the naphthalene sulfonate condensate having a specific number average molecular weight and weight average molecular weight within the scope of the present invention, the sulfonic acid group following the naphthalene structure is adsorbed on polyvalent cations such as calcium ions on the cement particle surface, It is thought that the elution of calcium ions is suppressed or the reaction with sulfate ions is suppressed by covering the cement particle surface with a bulky and rigid naphthalene structure and the subsequent polymer.

  That is, when a naphthalene sulfonate condensate having a specific number average molecular weight and a weight average molecular weight coexists in a mortar composition or a concrete composition, a specific number average molecular weight and a weight average molecular weight are compared with the case where no naphthalene sulfonate condensate coexists. A naphthalene sulfonate condensate having a number average molecular weight and a weight average molecular weight coats the cement surface to form a gypsum gently, and to form a densely oriented gypsum layer to prevent sulfuric acid erosion and resistance. It is presumed to improve sulfuric acidity.

  As the naphthalenesulfonate condensate, a formalin condensate of naphthalenesulfonate optionally substituted with one or more alkyl groups can be used, and the substituent includes carbon atoms such as a methyl group and an ethyl group. 1-3 alkyl groups are mentioned. The naphthalenesulfonate condensate is a salt with an alkali metal such as sodium (Na) or potassium (K), an alkaline earth metal such as magnesium (Mg) or calcium (Ca), ammonium or an amine. Is preferred.

  As the naphthalene sulfonate condensate, as long as the number average molecular weight and the weight average molecular weight are within the above ranges, they are commercially available as dispersants for use in high performance dispersants, pigments, dyes, agricultural chemical wettable powders and the like for concrete. Can be used. In addition, the naphthalene sulfonate condensate is a product obtained by removing and purifying unreacted monomers, even if unreacted monomers remaining in the production of the polymer are mainly composed of naphthalene sulfonate condensate. It may be a mixture of additives and the like.

  As described above, in general, organic polymer-based commercial products include, in addition to the main component responsible for the main purpose of dispersion if a dispersant, residual monomers and polymerization inhibitors, lubricants, preservatives that were not involved in the polymerization, Although an antifoamer, dye, etc. may coexist, the number average molecular weight and weight average molecular weight in the present invention mean the number average molecular weight and the weight average molecular weight of the main component.

  In the present invention, the number average molecular weight and the weight average molecular weight are determined when the molecular weight of the naphthalene sulfonate condensate is measured by gel filtration chromatography (GFC: Gel Filtration Chromatography). Using the maximum peak of the high molecular weight peak intensity (area) detected at the beginning of the measurement as the main component peak, the number average molecular weight and weight average molecular weight of the main component peak alone are calculated in terms of the calibration curve of a standard substance (for example, polystyrene) What you did.

  The naphthalene sulfonate condensate is preferably 0.3 to 5 parts by mass, more preferably 0.4 to 4 parts by mass, and still more preferably 0.5 to 3. 5 parts by mass. When the blending amount of the naphthalene sulfonate condensate is within the above range, the obtained cement cured product can sufficiently obtain sulfuric acid resistance.

  As the fine aggregate used in the present invention, river sand, land sand, sea sand, crushed sand, blast furnace slag fine aggregate and the like can be used. The fine aggregate is preferably 200 to 320 parts by mass, more preferably 230 to 290 parts by mass, and still more preferably 250 to 270 parts by mass with respect to 100 parts by mass of cement. If the amount of fine aggregate is within the above range, good fresh properties can be obtained.

  The sulfuric acid resistant concrete composition of the present invention further comprises coarse aggregate and fine limestone powder in the sulfuric acid resistant mortar composition. As the coarse aggregate used in the present invention, gravel, crushed stone, blast furnace slag coarse aggregate or 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 still more 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.

  In addition, a limestone aggregate can also be used as a fine aggregate and / or a coarse aggregate.

  The use of fine limestone powder further improves the sulfuric acid resistance of the mortar hardened body and the concrete hardened body. The reason why the sulfuric acid resistance is improved is not clear, but it is considered that gypsum serving as a barrier against sulfuric acid is easily generated by the fine powder of limestone, and that the expansion at the time of generating the gypsum is related.

Blaine specific surface area of powder limestone fines (JIS R 5201 measured in accordance with "Physical testing methods for cement") is a 2000~10000cm ² / g, preferably 3000~80000cm ² / g, particularly preferably 4000~6000cm ² / g.

The sulfuric acid resistant concrete composition of the present invention further contains water, and the water / cement ratio (mass ratio of water to cement) is 30 to 70 mass%, preferably 40 to 60 mass%, particularly preferably 45 to 58 mass%. %.
When the water / cement ratio is less than 30% by mass, the sulfuric acid resistance tends to decrease, and when the water / cement ratio exceeds 70% by mass, the setting is delayed and the water tightness tends to decrease.

In order to obtain a sulfuric acid resistant concrete composition having excellent sulfuric acid resistance, the preferred blending amounts are as follows.
Water: 120 to 200 kg / m ³ , preferably 140 to 180 kg / m ³ , particularly preferably 150 to 170 kg / m ³ ,
Cement: 200 to 400 kg / m ³ , preferably 220 to 380 kg / m ³ , particularly preferably 250 to 350 kg / m ³ ,
Limestone fine powder: 20 to 150 kg / m ³ , preferably 40 to 130 kg / m ³ , particularly preferably 60 to 120 kg / m ³ ,
Fine aggregate: 500 to 1000 kg / m ³ , preferably 600 to 900 kg / m ³ , particularly preferably 650 to 800 kg / m ³ ,
Coarse aggregate: 800-1400 kg / m ³ , preferably 900-1200 kg / m ³ , particularly preferably 1000-1100 kg / m ³ ,
Naphthalenesulfonate condensate: 4 to 40 kg / m ³ , preferably 6 to 25 kg / m ³ , particularly preferably 8 to 15 kg / m ³ ,
It is.
If it is the said range, it has moderate intensity | strength and fluidity | liquidity, a workability is favorable, and the concrete composition excellent in sulfuric acid resistance is obtained.

  The sulfuric acid-resistant mortar composition or sulfuric acid-resistant concrete composition of the present invention is a water-reducing agent as necessary, and a water-soluble thickener or an inorganic material to reduce aggregate separation, as with normal mortar and concrete. A thickener may be added.

  Examples of the water reducing agent include water reducing agents such as lignin sulfonic acid, naphthalene sulfonic acid, and polycarboxylic acid. Moreover, the use of an AE water reducing agent is also possible. From the viewpoint of compatibility with the naphthalene sulfonate condensate, use of lignin sulfonic acid or naphthalene sulfonic acid is preferred.

  Examples of the water-soluble thickener include one selected from acrylic water-soluble polymers, biopolymers, glycol-based water-soluble polymers, and cellulose-based water-soluble polymers, or a mixture thereof. Examples of the acrylic water-soluble polymer include a copolymer of acrylamide and acrylic acid, polyacrylic acid, and the like. Examples of biopolymers include β-1, 3 glucan, water-soluble polysaccharides and the like. Examples of the glycol-based water-soluble polymer include polyalkylene glycol, glycol distearate, and fiber glycolic acid. Examples of the cellulose-based water-soluble polymer include alkyl celluloses such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose, hydroxyalkyl cellulose, and hydroxyalkylalkyl cellulose.

  Examples of the inorganic thickener include one selected from attapulgite, sepiolite, bentonite, talc, silica fume, and the like, or a mixture thereof.

  The sulfuric acid resistant mortar composition or sulfuric acid resistant concrete composition of the present invention can be premixed with cement and other components prior to kneading, but water is added to the cement and kneaded. At this time, it is preferable to adjust by adding other components. Moreover, a sulfuric acid resistant concrete hardening body is obtained by shape | molding, curing, and hardening the sulfuric acid resistant mortar composition or sulfuric acid resistant concrete composition knead | mixed by adding water. The curing method is not particularly limited.

  Such a sulfuric acid resistant mortar composition and a sulfuric acid resistant concrete composition of the present invention can be used in sewerage pipes, sewerage treatment plants, pipes and other facilities related to sewerage, or hot spring facilities, which are required to have excellent sulfuric acid resistance. It can be advantageously applied as structures, secondary products, and repair materials used in hot spring related facilities, chemical factories, etc., such as water supply and drainage facilities and waterway structures for agriculture and drainage in hot spring areas. In concrete facilities related to sewage treatment, for example, pumping stations, sedimentation tanks, distribution tanks, reaction tanks, sludge storage tanks, communication channels, sludge digestion tanks, etc., the sulfuric acid resistant concrete composition or sulfuric acid resistant concrete of the present invention is used. A cured product can be used. In addition to hot spring facilities such as bathtubs, bathroom interior materials and internal equipment, the hot spring facilities include foundations and walls of hot springs affected by hot spring water and hot spring steam, underground beams, and tunnels using concrete. The sulfuric acid resistant concrete composition and the sulfuric acid resistant concrete hardened body of the present invention can be used for utility poles, pavement concrete and the like.

  Hereinafter, the contents of the present invention will be described more specifically with reference to examples and comparative examples. Note that the present invention is not limited to these examples.

[Materials used]
The following materials were used.
(1) Cement (C):
Normal Portland cement: Blaine specific surface area 3270 cm ² / g
(2) Limestone fine powder Limestone fine powder (LSP): Blaine specific surface area 4500 cm ² / g
(3) Aggregate (i) Fine aggregate Sea sand (S1) (surface dry density 2.59 g / cm ³ , coarse particle ratio 2.66)
Crushed sand (S2) (surface dry density 2.68 g / cm ³ , coarse particle ratio 2.79)
(Ii) Coarse aggregate (G)
Hard sandstone crushed stone (surface dry density 2.70 g / cm ³ , coarse particle ratio 6.61)
(4) AE water reducing agent (Pozoris No. 70)
Lignin sulfonic acid, solid content: 48% by mass
(5) Mixing water (W)
Tap water (6) Naphthalene sulfonate condensate Number-average molecular weight of naphthalene sulfonate formalin condensate represented by the following formula (1) by gel filtration chromatography (GFC) under the following conditions The weight average molecular weight was measured, and three types of naphthalene sulfonate condensates having different number average molecular weights and weight average molecular weights were used.

(Naphthalenesulfonate condensate)
A formalin condensate of naphthalene sulfonate represented by the following formula (1) was used.

[Measurement conditions for gel filtration chromatography]
GFC apparatus: PU-2085plus type system column manufactured by JASCO Corporation: GMPW manufactured by Tosoh Corporation (inner diameter 7.8 mm × length 300 mm)
Eluent: 50 mM LiCl aqueous solution / CH ₃ CN = 60/40 (volume ratio)
Injection volume: 10 μL
Eluent flow rate: 0.6 mL / min
Column temperature: 40 ° C
Detector: UV absorption type (wavelength 260nm)
Standard samples: polystyrene sulfonic acid, p-toluenesulfonic acid

[Measurement of molecular weight]
As shown in Table 1, the relationship between the molecular weight of polystyrene sulfonic acid and p-toluenesulfonic acid and the retention time was measured, and a calibration curve shown in FIG. 1 was created from the measurement results.

  The chromatogram of the formalin condensate of three types of naphthalene sulfonates measured with the above conditions and a GFC apparatus and the molecular weight distribution curves measured with a detector are shown in FIGS.

  Table 2 shows the measurement results of the molecular weight distribution. The peak top molecular weight in Table 2 is the molecular weight converted based on the calibration curve calculated from polystyrene sulfonic acid and p-toluenesulfonic acid, which are standard samples, from the retention time of the maximum value of the largest peak in the molecular weight distribution curve. is there. Moreover, the solid content concentration in Table 2 refers to a value obtained by drying the naphthalene sulfonate condensate at 105 ° C. for 3 days and dividing the mass after drying by the mass before drying.

[Preparation of concrete composition]
The preparation of the concrete composition includes ordinary Portland cement (C), fine limestone powder (LSP), fine aggregate (S: S1, S2), coarse aggregate (G) and naphthalene sulfonate condensate (NS1, NS2, NS3) is mixed at the ratio shown in Table 3, and stirred for 30 seconds with a biaxial forced kneading mixer, and then tap water (W) is poured into the mixer at the ratio shown in Table 3 and further stirred for 150 seconds. Went.

[Evaluation test method for hardened concrete]
(1) Sulfuric acid resistance of hardened concrete The concrete composition prepared was placed in a cylindrical form having a diameter of 10 cm and a height of 20 cm. After 1 day of age, the form was removed from the form and the material was washed in water at 20 ° C. The specimen was cured until age 28 days to obtain a specimen of a hardened concrete. This specimen was immersed in a 5% by mass sulfuric acid aqueous solution, taken out at immersion periods of 4 weeks, 8 weeks and 13 weeks. After the surface of the specimen was washed with water, the moisture on the surface was wiped off and the mass was measured. The mass change rate was determined by the following formula. The results are shown in Table 4.
Mass change 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

[Consideration of results of sulfuric acid resistance test]
As shown in Table 4, in the immersion periods of 4 weeks and 8 weeks, there is no significant difference in mass change rate between Examples 1 and 2 and Comparative Example 1, but after 13 weeks of immersion, Comparative Example 1 is compared. Since the mass change rate of Examples 1 and 2 was small, it was found that Examples 1 and 2 were excellent in sulfuric acid resistance. Thus, it was found that a cured concrete body obtained by curing a concrete composition containing a naphthalene sulfonate condensate having a number average molecular weight and a weight average molecular weight within the scope of the present invention has high sulfuric acid resistance.

Claims (7)

Water 120~200kg / ^{m 3,} a cement 200~400kg / ^{m 3,} limestone powder 20~ 130 kg / ^{m 3,} fine aggregates 500~1000kg / ^{m 3,} coarse aggregate 1000 ~1400kg / ^{m 3} and a number average molecular weight Sulfate-resistant concrete composition comprising 8 to 40 kg / m ³ of naphthalene sulfonate condensate having a weight average molecular weight of 3000 to 6000. The sulfuric acid resistant concrete composition according to claim 1, which does not contain a thickener. The sulfate-resistant concrete composition according to claim 1 or 2 , wherein the naphthalene sulfonate condensate has a number average molecular weight of 2000 to 3418 and a weight average molecular weight of 3000 to 5110. The sulfate-resistant concrete composition according to any one of claims 1 to 3, wherein the naphthalene sulfonate condensate has a number average molecular weight of 2000 to 2141 and a weight average molecular weight of 3000 to 3231. The sulfate-resistant concrete composition according to any one of claims 1 to 4 , comprising 0.3 to 5 parts by mass of a naphthalene sulfonate condensate based on solid content with respect to 100 parts by mass of cement. The weight ratio of water / cement is 30 to 70 wt%, any one sulfuric acid concrete composition according to claim 1-5. A sulfate-resistant concrete cured body obtained by curing the sulfate-resistant concrete composition according to any one of claims 1 to 6 .

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