JP4551697B2 - Sulfuric acid resistant concrete - Google Patents

Description

The present invention relates to a sulfate resistant concrete suitable for use in a place where corrosion is a problem due to sulfuric acid or sulfate.

  In places where exposed to sulfuric acid or sulfate, such as facilities in sewer facilities and hot springs, corrosion of sulfate-resistant hardened materials such as cement hardened materials by sulfuric acid or sulfate has been a problem. That is, sulfate ions contained in sewage and hot spring water are reduced by sulfate-reducing bacteria and released as hydrogen sulfide in an anaerobic environment. The diffused hydrogen sulfide is converted into sulfuric acid by the activity of bacteria (such as sulfur-oxidizing bacteria) that use hydrogen sulfide as a nutrient source. That is, bacteria such as sulfur-oxidizing bacteria are actively activated when the surface of cement hardened material (for example, concrete, hereinafter referred to as concrete) is exposed to carbon dioxide in the atmosphere and transitions from alkaline to neutral, Change concrete surface to sulfuric acid environment. When the hardened cement is kept in contact with sulfuric acid for a long period of time, corrosion progresses and hardly soluble gypsum is formed on the surface, and silicate and alumina are eluted to form silica gel and alumina gel. Furthermore, silica gel and alumina gel are also eluted, and the concrete collapses.

This action of sulfuric acid on concrete naturally depends on the acid concentration. When the pH is 2 or more (sulfuric acid concentration of 0.1% by mass or less), densification of concrete is effective from the point of suppressing penetration of corrosion factor substances into the interior. Therefore, the corrosion resistance can be improved by reducing the water cement ratio while ensuring workability by using a high performance AE water reducing agent or the like and increasing the cement ratio. On the other hand, when the concentration of sulfuric acid is high, it is difficult to cope with, for example, when the pH is lower than 2, the water-cement ratio is lowered and densified, so that there are fewer pores that can relieve the crystal growth expansion pressure of gypsum produced by sulfuric acid For this reason, cracking is induced and sulfuric acid easily penetrates. Accordingly, the corrosion resistance becomes worse on the contrary, and it is difficult to increase the resistance of the cement material itself to sulfuric acid.
Japanese Patent Laid-Open No. 10-236860

  Bacteria involved in the production of sulfuric acid (sulfur-oxidizing bacteria) are inhibited when the alkalinity of the concrete surface (pH 12-13) is maintained, but can be activated when the surface pH is 10 or less. As the pH decreases, the types of sulfur oxidizing bacteria are T. thioparus, T. versutus (pH about 10 to about 3.5), T. intermedius, T. novelllus (pH about 9 to about 2.5), T. neaporitanus (pH about 8.5 to about 4.5), T.ferrooxidans, T.thiooxidans (pH about 5.5 to about 0.5), the surface of concrete rapidly becomes acidic due to the sulfuric acid produced by the activity of the fungus, and corrosion by sulfuric acid proceeds To do. Therefore, in order to improve the durability of concrete such as sewer facilities and hot springs, in addition to sulfuric acid resistance, the neutralization of the concrete surface by carbon dioxide gas, etc., is suppressed, and the activity of bacteria is suppressed. It is important, however, little studies have been conducted focusing on sulfuric acid resistance and neutralization performance.

Accordingly, an object of the present invention is to provide sulfate-resistant concrete that is excellent in sulfuric acid resistance and slow in neutralization in a sulfuric acid corrosive environment caused by bacteria (sulfur-oxidizing bacteria) or in a normal environment.

The sulfuric acid resistant hydraulic composition according to the present invention contains Portland cement having a 3CaO · SiO ₂ amount of 60 mass% or more calculated by the Borg formula, and a limestone powder having a Blaine specific surface area of 2,000 cm ² / g or more, Inorganic powder composition having a mass part ratio of Portland cement and limestone powder of 30:70 to 100: 0, and 1 to 10 parts by mass of naphthalenesulfonic acid per 100 parts by mass of the inorganic powder composition Formalin condensate salt and a thickener.

According to this sulfuric acid resistant hydraulic composition, as compared with the case where the amount of 3CaO · SiO ₂ is less than 60% by mass as the composition of Portland cement, the setting is faster and bleeding is less likely to occur. Moreover, compared with the case where the lane specific surface area of the limestone powder is less than 2000 cm ² / g, gypsum serving as a barrier against sulfuric acid or sulfate is likely to be generated, and the expansion at the time of gypsum generation is small. Moreover, if the mass part ratio of the limestone powder in the inorganic powder composition is within 70, the amount of Portland cement in the inorganic powder composition is sufficient, so that the decrease in resistance to neutralization is sufficiently prevented. Can do. Further, compared to the case where the amount of the formalin condensate salt of naphthalene sulfonic acid is less than 1 part by mass in terms of solid content with respect to 100 parts by mass of the inorganic powder composition, water reduction is sufficiently exhibited and sulfuric acid resistance It also demonstrates its properties. In addition, the sulfuric acid resistance is improved with an increase in the amount of the formalin condensate salt of naphthalene sulfonic acid. However, when the amount exceeds 10 parts by mass, the improvement effect reaches its peak, so that the amount added is not more than 10 parts by mass. Moreover, workability | operativity is good because the thickener is added.

The specific surface area of the limestone powder is preferably 8,000 cm ² / g or more.

If the limestone powder has a Blaine specific surface area of 8000 cm ² / g or more, a gypsum serving as a barrier to sulfuric acid or sulfate is likely to be produced, and the expansion during gypsum production is small. Furthermore, a sulfuric acid resistant hydraulic composition excellent in sulfuric acid resistance and workability can be obtained without using a thickener.

  The above thickener is preferably at least one selected from the group consisting of a cellulose-based water-soluble polymer, an acrylic water-soluble polymer, a biopolymer, a glycol-based water-soluble polymer, and an inorganic thickener. . By adding such a thickener, the workability of the sulfuric acid resistant hydraulic composition is improved.

  Moreover, in a sulfuric acid resistant hydraulic composition, it is preferable when a thickener is included 0.005-0.1 mass part with respect to 100 mass parts of inorganic powder compositions. If the thickener is 0.005 parts by mass or more, material separation hardly occurs and sufficient workability can be obtained. If the thickener is 0.1 part by mass or less, the viscosity does not become too high, the workability is maintained, and the setting does not take too long.

  The sulfuric acid resistant cured product according to the present invention is characterized in that the above sulfuric acid resistant hydraulic composition, aggregate and water are mixed and cured. According to this sulfuric acid resistant cured material, a sulfuric acid resistant cured material excellent in resistance to neutralization and sulfuric acid resistance can be obtained. Here, when limestone aggregate is used as the aggregate, the sulfuric acid resistance is further improved, and the amount of limestone can be increased while maintaining the amount of Portland cement, which is very preferable.

This sulfate-resistant cured product has an erosion depth of 3 mm or less when immersed in a 5% by mass sulfuric acid aqueous solution at 20 ° C for 56 days, in an environment with a carbon dioxide concentration of 5% by volume, 20 ° C and a relative humidity of 60%. Accelerated neutralization depth when exposed for 26 weeks is standard concrete made by mixing a water reducing agent with ordinary Portland cement containing 56% by mass of 3CaO · SiO ₂ by the Borg calculation. The acceleration neutralization depth is preferably 0.7 or less. Since the erosion depth is 3 mm or less when immersed in a 5% by mass sulfuric acid aqueous solution at 20 ° C. for 56 days, it is sufficient as resistance to erosion by sulfuric acid or sulfate. In addition, the accelerated neutralization depth when exposed for 26 weeks in an environment with a carbon dioxide concentration of 5% by volume, 20 ° C and relative humidity of 60% is 0.7 or less that of standard concrete. Resistance is sufficient, and the growth of bacteria (sulfur-oxidizing bacteria) is also suppressed.

  Here, it is preferable that the use of the above-mentioned sulfate-resistant cured product is a sewer pipe, a concrete facility of a sewerage treatment plant, or a concrete facility of a hot spring area. By using this sulfate-resistant hardened material in concrete facilities in sewer pipes, sewage treatment plants and hot springs where sulfuric acid and sulfates are likely to be generated, corrosion becomes difficult.

  According to the sulfuric acid resistant hydraulic composition and the sulfuric acid resistant hydraulic cured product according to the present invention, the sulfuric acid resistant hydraulic composition is excellent in sulfuric acid resistance and can be neutralized.

  Hereinafter, preferred embodiments of the sulfuric acid resistant hydraulic composition and the sulfuric acid resistant cured product according to the present invention will be described.

  First, the sulfuric acid resistant hydraulic composition will be described. The sulfuric acid resistant hydraulic composition is composed of Portland cement, limestone powder, a formalin condensate salt of naphthalenesulfonic acid, and a thickener.

Portland cement contains 3CaO · SiO _{2 in an} amount of 60% by mass or more according to the Borg calculation. Examples of Portland cement include early-strength Portland cement, ultra-early-strength Portland cement, and sulfate-resistant Portland cement. The amount of 3CaO · SiO ₂ by the Borg formula is calculated by the following formula from the chemical component of the cement (analyzed in accordance with JIS R 5202 “Chemical analysis method of Portland cement”).

3CaO · SiO ₂ (mass%) =
4.071 × CaO (mass%) − 7.6 × SiO ₂ (mass%) − 6.718 × Al ₂ O ₃ (mass%)
−1.43 × Fe ₂ O ₃ −2.852 × SO ₃ (mass%)

In general, as the amount of formalin condensate salt of naphthalene sulfonic acid or thickener added to Portland cement increases, the setting of Portland cement composition delays, so the amount of 3CaO · SiO _{2 that} rapidly sets is 64 mass% or more. It is preferable to use an existing early strong cement or a very early strong cement. These cements are also preferable in that they have a small particle size and are difficult to cause bleeding.

The specific surface area (measured according to JIS R 5201 “Physical testing method for cement”) of the limestone powder is 2000 cm ² / g or more. Although the mechanism of expression of sulfuric acid resistance of limestone powder has not been clarified, it is thought that it is related to the fact that gypsum serving as a barrier is easily generated and that the expansion at the time of gypsum generation is small. Limestone powder is an optional component. Further, when a finer limestone powder having a Blaine specific surface area of 8000 cm ² / g or more is used as the limestone powder, a cement composition excellent in sulfuric acid resistance and workability can be obtained without using a thickener. Such a composition is preferable in that the composition becomes simple.

  In addition, the inorganic powder composition composed of Portland cement and limestone powder is preferably a mixture of Portland cement and limestone powder with a mass part ratio of about 30:70 to 100: 0. If the mass part ratio of the limestone powder in the inorganic powder composition is within 70, since the amount of Portland cement in the inorganic powder composition is sufficient, it is possible to sufficiently prevent a decrease in resistance to neutralization. . In order to increase the resistance to neutralization, it is desirable that the mass part ratio of the limestone powder in the inorganic powder composition is 60 or less. That is, it is more preferable that the mass part ratio of Portland cement and limestone powder is about 40:60 to 100: 0.

  The addition amount of the naphthalenesulfonic acid formalin condensate salt is 1 to 10 parts by mass in terms of solid content with respect to 100 parts by mass of the inorganic powder composition which is a mixture of cement and limestone powder. When the amount of the naphthalene sulfonic acid formalin condensate added is 1 part by mass or more, water reduction is exhibited and the sulfuric acid resistance is sufficiently exhibited. Further, although the sulfuric acid resistance is improved with the addition amount of the formalin condensate salt of naphthalene sulfonic acid, the effect of improving the sulfuric acid resistance is peaked at 10 parts by mass or more, so the addition amount is 10 parts by mass.

  The reason why sulfuric acid resistance is improved by the formalin condensate salt of naphthalene sulfonic acid is not clear, but the SEM observation of the cured product soaked in sulfuric acid solution shows a dense layer of gypsum that is not usually seen on the surface It is conceivable that this gypsum layer acts as a barrier to suppress the permeation of sulfuric acid. The composition of Portland cement dissolves in a sulfuric acid solution and precipitates gypsum, but the gypsum precipitation mechanism was changed by the formalin condensate salt of naphthalenesulfonic acid, and the above-mentioned dense gypsum layer was formed. Inferred.

  As the formalin condensate salt of naphthalene sulfonic acid, for example, the trade name “Mighty 100” or “Mighty 150” from Kao Co., Ltd., the product name “Axelito 550” from Nissan Chemical Industries, Ltd. Products sold under the trade name "Sunflow PS" from Flow Corporation can be used. These products are commercially available as high performance water reducing agents for concrete.

  In addition, materials such as Portland cement, limestone powder, formalin condensate salt of naphthalene sulfonic acid, thickener, etc. constituting the sulfuric acid resistant hydraulic composition are added to the cement composition or the cement composition paste, respectively. Can be used. In this case, some or all of them can be mixed and used in advance. When mixed and used in advance, it is preferable to use a powder of the formalin condensate salt of naphthalenesulfonic acid. The method of mixing and using in advance is suitable for uniformly mixing a thickener with a small amount of addition or fine powder that is difficult to mix with a concrete mixer.

In addition, thickening agents, Ru Oh cellulose-based water-soluble polymer. Here, examples of the cellulose-based water-soluble polymer include alkyl celluloses such as methyl cellulose, hydroxyethyl cellulose, and hydroxypropyl methyl cellulose, hydroxyalkyl cellulose, hydroxyalkylalkyl cellulose, and the like . Of this, preferably, a hydroxycarboxylic cellulose-based water-soluble polymers. These thickeners are used to improve the workability of high fluid concrete production or plastering mortar.

  Furthermore, the thickener is preferably used in an amount in the range of 0.005 to 0.1 parts by mass, more preferably 0.02 to 0.07 parts by mass with respect to 100 parts by mass of the inorganic powder composition. If the thickener is 0.005 parts by mass or more, material separation hardly occurs and sufficient workability can be obtained. Further, when the thickener is 0.1 part by mass or less, the viscosity does not become too high, workability is maintained, and the setting does not take too long.

  In normal concrete production, the use of a thickener for formalin condensate is not added in such an amount that the cement and water are separated. This is a method unique to hydraulic compositions. The reason why the use amount of the thickener may be smaller than the general use amount in the high fluidity concrete is presumed to be because the viscosity of the thickener increases due to gelation of the thickener. In general, the formalin condensate salt of naphthalene sulfonic acid and the cellulose-based water-soluble polymer are said to be incompatible with the cellulose-based water-soluble polymer, but the above-mentioned sulfuric acid-resistant water In a cement composition obtained by adding a small amount of a cellulose-based water-soluble polymer to a formalin condensate salt of naphthalenesulfonic acid in a hard composition, the combination of both can be performed without any problem.

  Moreover, you may add inorganic powders, such as fine powder of a blast furnace slag, a fly ash, a silica fume which are used with a normal cement, mortar, and concrete to a hydraulic composition. Furthermore, chemical admixtures for mortar or concrete can also be used.

  Moreover, a sulfate-resistant hardened material, such as concrete and mortar, can be produced by mixing aggregate and water with such a sulfate-resistant hydraulic composition and curing the mixture. In this case, when limestone aggregate is used as the aggregate, the sulfuric acid resistance is further improved. This seems to be the same factor as the effect of the addition of limestone powder to the cement, but using limestone as an aggregate is very preferable because the amount of limestone can be increased while maintaining the amount of cement.

Here, when forming a sulfuric acid-resistant hardened | cured material, it is good to knead | mix the water amount with respect to the cement component in a sulfuric acid-resistant hydraulic composition as 30-60 mass% by water / cement ratio. If the water / cement ratio is less than 30% by mass, the sulfuric acid resistance tends to decrease. If the water / cement ratio exceeds 60% by mass, the setting tends to be slow and the water tightness tends to decrease. The unit water amount during kneading is preferably 120 to 175 kg / m ³ . When the amount of water is less than 120 kg / m ³ , the workability of the production of concrete molding tends to decrease, while when the amount exceeds 175 kg / m ³ , the amount of aggregate in the concrete decreases and the properties as concrete deteriorate. Tend to. The total amount of water and cement in 1 m ^{3 of} concrete is preferably 160 to 300 L.

  Thus, using a sulfuric acid resistant hydraulic composition, kneading with aggregate and water, molding and curing, the sulfuric acid resistant hydraulic composition is 5% by mass sulfuric acid aqueous solution (pH approximately 0.3). It is preferable that the depth of erosion when immersed in a glass for 20 days at 20 ° C. is 3 mm or less. More preferably, the erosion depth is 2 mm or less.

  Here, the measurement conditions and measurement method of the erosion depth when immersed in a 5% by mass sulfuric acid aqueous solution are as follows. Building Material Testing Center Standard JSTM C 7401: 1999 “Testing method for chemical resistance of concrete by solution immersion” [1999 5 May 28, revised Building Materials Testing Center]. That is, the adjusted concrete is placed in a mold having a size of 10 cm × 10 cm × 40 cm, and after one day of material age, it is removed from the mold and cured in water at 20 ° C. until the material age is 28 days. Then, it is dried for one day in a constant temperature and humidity room at 20 ° C. and a relative humidity of 60%. Furthermore, of the 6 surfaces of the concrete specimen, one surface (exposed surface) of 10 cm × 40 cm perpendicular to the placement surface is left, and the other 5 surfaces are coated with deformed silicone resin. After the silicone resin is cured, the specimen is immersed in a 5% by mass sulfuric acid aqueous solution for 56 days. Further, after washing the surface of the specimen with water, cut it with a concrete cutter in the long axis direction at a width of about 2 cm from the end face.

  The erosion depth is measured as follows. First, let L (= 10 cm) be the distance between the exposed surface of the concrete before dipping and the back surface of the exposed surface (the length of one side of the inner dimensions of the mold). Then, in order to stain the non-eroded area, a phenolphthalein solution (phenolphthalein solution specified in 4.4 (indicator) of JIS K 8001) is sprayed on the cross section of the specimen cut after immersion. Thereby, the area | region which shows the basicity which is not eroded is colored magenta. Therefore, the width in the direction perpendicular to the exposed surface in the reddish purple region is measured with a caliper, and the width is defined as L1 (cm). Then, the erosion depth can be determined by L-L1 (cm), and it can be seen that the erosion depth is eroded by the sulfuric acid aqueous solution by the depth of L-L1 (cm). In addition, the erosion depth is the average of the results of measurements at three locations (the center of the exposed surface and the position 1 cm inside from each end of the exposed surface).

Further, the accelerated neutralization depth when the above-mentioned sulfidation-resistant cured product is allowed to stand for 26 weeks in an atmosphere of carbon dioxide gas concentration of 5% by volume at 20 ° C. and relative humidity of 60% by mass is calculated by the Borg calculation. It is 0.7 times or less of the accelerated neutralization depth of the reference concrete made by mixing a normal water-containing agent with ordinary Portland cement containing ₃ % by mass of 3CaO · SiO ₂ at the same water cement ratio. If the ratio of the accelerated neutralization depth exceeds 0.7 times, bacteria (sulfur-oxidizing bacteria) will propagate, which is not preferable.

  The neutralization depth is measured in accordance with JIS A 1153 “Accelerated neutralization test method for concrete”. That is, a concrete specimen is prepared by using a mold having dimensions of 10 cm × 10 cm × 40 cm and waiting for curing for two days. In the pre-curing stage, after removing the specimen from the mold, it is placed in a wet state (water or an atmosphere having a relative humidity of 95% or more) at a temperature of 20 ° C. until the age of 4 weeks. Then, it is allowed to stand in a constant temperature and humidity chamber having a relative humidity of 60% and a temperature of 20 ° C. until the material age is 8 weeks. In addition, during the age of 7 to 8 weeks, the driving surface, bottom surface, and both end surfaces of the specimen are sealed so as to block carbon dioxide. Then, as described above, the sample is allowed to stand for 26 weeks under environmental conditions of a temperature of 20 ° C., a relative humidity of 60%, and a carbon dioxide concentration of 5% by volume. The neutralization depth is measured by cutting the specimen in accordance with JIS A 1152 “Measurement of neutralization depth of concrete” and applying the phenol cover specified in 4.4 (indicator) of JIS K 8001 to the cut surface. Spray the rain solution. Then, in the cross section having a region colored reddish purple and a region not colored, the region not colored reddish purple was evaluated as a neutralized region, and neutralized from the surface of the specimen. Measure depth.

Here, as an influence of the type of cement on the neutralization depth, it is said that early strength Portland cement has a neutralization rate of about 0.7 times that of normal Portland cement. However, as described above, the concrete containing 0.7% by mass of 3CaO · SiO ₂ in Portland cement containing limestone powder, formalin condensate salt of naphthalene sulfonic acid and thickener is neutral to 0.7 or less of the standard concrete ratio. It was found that it can be suppressed to the conversion rate. The mechanism to suppress such neutralization has not been clarified, but such concrete has a strength statement superior to the above-mentioned standard concrete made with ordinary Portland cement at the same cement ratio. It is guessed.

  The ratio of accelerated neutralization depth is more preferably 0.5 times or less. The smaller the accelerated neutralization depth is, the longer the alkali on the concrete surface is kept, so that it is possible to suppress bacterial activity on the surface.

  Such sulfuric acid-resistant hydraulic compositions and sulfuric acid-resistant cured products are used in sewer pipes, sewerage treatment plants, pipes and other sewer related facilities, hot springs, chemical factories, etc. that require excellent sulfuric acid resistance. It can be advantageously applied as a structure, secondary product, or repair material. 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. You can use things. In addition to the hot spring facility's bathtub, bathroom interior materials, and internal facilities, the hot spring resort's concrete facilities include the foundations and walls of hot springs that are affected by hot spring water and hot spring steam, underground beams, and concrete. Examples include used tunnels, utility poles, and paving concrete.

  Hereinafter, the content of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

(ii) リグニンスルホン酸系減水剤（LS）
(iii) 増粘剤：セルロース系水溶性高分子（CE）
（４）骨材
(i) 細骨材：
・海砂（S）：密度2.59g/cm³、粗粒率2.57、福岡市博多産
(ii) 粗骨材：
・砕石（G）2005：密度2.69g/cm³、粗粒率6.68、山口市宮野産
（５）練混ぜ水：
・水道水（Ｗ） [Materials used]
The following materials were used in carrying out each example.
(1) Portland cement (C)
(i) Ordinary Portland cement (N)
3CaO · SiO ₂ content: 56% by mass (Borg calculation)
Blaine specific surface area: 3250cm ² / g
(ii) Early strong Portland cement (H)
3CaO · SiO ₂ content: 67% by mass (Borg calculation)
Blaine specific surface area: 4500cm ² / g
(2) Limestone powder Limestone powder (LSP): Specific surface area 6400cm ² / g (measured by the brain method)
(3) Admixture
(i) Naphthalenesulfonic acid formalin condensate salt (NS)

(ii) Lignin sulfonic acid water reducing agent (LS)
(iii) Thickener: Cellulosic water-soluble polymer (CE)
(4) Aggregate
(i) Fine aggregate:
・ Sea sand (S): density 2.59g / cm ³ , coarse grain ratio 2.57, produced in Hakata, Fukuoka
(ii) Coarse aggregate:
・ Crumbled stone (G) 2005: Density 2.69g / cm ³ , Coarse grain ratio 6.68, Product from Miyano, Yamaguchi City (5) Mixing water:
・ Tap water (W)

[Concrete adjustment]
First, a hydraulic composition composed of Portland cement, limestone powder, and an admixture was prepared by mixing at a ratio shown in Table 1. That is, the hydraulic composition of Comparative Example 1 serving as the reference concrete was mixed with 0.25 parts by mass of a lignin sulfonic acid-based water reducing agent with respect to 100 parts by mass of ordinary Portland cement having an amount of 3CaO · SiO ₂ of 56% by mass. The limestone powder is not mixed. The hydraulic composition of Comparative Example 2 was obtained by adding a formalin condensate salt (NS) 1 of naphthalenesulfonic acid to a mixture of 65 parts by mass of ordinary Portland cement having a 3CaO · SiO ₂ content of 56% by mass and 35 parts by mass of limestone powder. .92 parts by mass and cellulose-based water-soluble polymer (CE) 0.033 parts by mass are mixed. The hydraulic composition of Example 1 was prepared by adding a formalin condensate salt (NS) of naphthalene sulfonic acid to a mixture of 65 parts by weight of early strength Portland cement having an amount of 3CaO · SiO ₂ of 67% by mass and 35 parts by mass of limestone powder. 1.92 parts by mass and cellulose water-soluble polymer (CE) 0.033 parts by mass are mixed.

Next, concrete was prepared from these hydraulic compositions by using a 50 L pan-type forced kneading mixer of aggregate and water. The amount of kneading was 30 L per batch. Table 2 shows the water cement ratio (W / C) when making concrete for each of Comparative Examples 1 and 2 and Example 1, and water, Portland cement, limestone powder (LSP), sea sand (S), and crushed stone. (G), unit amounts (kg / m ³ ) of formalin condensate salt (NS) of naphthalene sulfonic acid, lignin sulfonic acid-based water reducing agent (LS), and cellulose-based water-soluble polymer (CE). Table 2 also shows the slump measured by the slump test. The amount of air mixed into the concrete was adjusted to 4.5% ± 1.5% according to JIS A 5308 ordinary concrete.

The slump and the amount of air were measured according to the following test method.
Slump measurement: Measured in accordance with JIS A 1101 “Concrete slump test method”.

[Sulfuric acid immersion test]
The measurement conditions and measurement method of the erosion depth when immersed in a 5% by mass sulfuric acid aqueous solution were in accordance with the above-mentioned Building Material Testing Center Standard JSTM C 7401: 1999 “Testing method for chemical resistance of concrete by solution immersion”. That is, as described above, the concrete prepared in a mold having a size of 10 cm × 10 cm × 40 cm was placed, cured in water at 20 ° C. until the age of 28 days, and then kept at a constant temperature of 20 ° C. and a relative humidity of 60% by mass. Dry in a constant humidity room for 1 day. After that, among the 6 surfaces of the concrete specimen, leave one surface (exposed surface) 10 cm × 40 cm perpendicular to the placement surface, and apply the modified silicone resin to the other 5 surfaces. Then, after the silicone resin was cured, the specimen was immersed in a 5% by mass sulfuric acid aqueous solution.

  After 56 days of immersion (56 days of immersion material), the surface of the specimen was washed with water, then cut with a concrete cutter to a thickness of about 2 cm from the end face (10 cm x 10 cm), and eroded by spraying with a phenolphthalein solution. The depth was measured. For the remaining specimens, the cut surface was protected with resin and returned to the immersion test, and the erosion depth was measured in the same manner 91 days after immersion (immersion material age 91 days) and 364 days (immersion material age 364 days). did.

  The erosion depth depends on the surface cut at the age of each measurement, from the size of the concrete before immersion (L = 10cm: the size of the inside dimensions of the formwork), phenolphthalein solution (JIS K 8001 4.4 (indicator) The phenolphthalein solution defined in (1)) was obtained from a value (L-L1) obtained by subtracting the width (L1) in the direction perpendicular to the exposed surface in the region colored (red purple). The erosion depth was the average of 3 locations (center of exposed surface and 1 cm inside from both ends of exposed surface). The results of the sulfuric acid test are shown in the column of “Erosion depth (mm) when immersed in 5% sulfuric acid aqueous solution” in Table 3.

  As shown in Table 3, it was found that the erosion depth of Comparative Example 1 after 56 days of immersion was deeply eroded to 8.0 mm. On the other hand, the erosion depths of Comparative Example 2 and Example 1 after 56 days of immersion were as shallow as 1.5 mm and 1.1 mm, respectively, and it was found that the resistance to erosion by the sulfuric acid aqueous solution was high.

[Accelerated neutralization test]
The neutralization depth was measured in accordance with JIS A 1153 “Concrete accelerated neutralization test method”. That is, as described above, after preparation and pre-curing of the specimen, the specimen is cured in an atmosphere having a carbon dioxide gas concentration of 5% by volume and a relative humidity of 60% by mass at 20 ° C., and neutralized after 26 weeks. The depth was measured. As a neutralization promotion test apparatus, ELH-10S manufactured by Onishi Thermal Engineering Co., Ltd. was used. The results of the neutralization promotion test are shown in the column “Ratio to the accelerated neutralization depth of the reference concrete” in Table 3. Here, the accelerated neutralization depth in Comparative Example 1 is set to 1, and the ratio of each of the accelerated neutralization depths in Comparative Example 2 and Example 1 to the accelerated neutralization depth in Comparative Example 1 is “reference”. It is shown in the column “Ratio to accelerated neutralization depth of concrete”. The accelerated neutralization depth of the reference concrete (after 26 weeks) was about 15 mm when the water-cement ratio was 55% by mass.

  As shown in Table 3, the ratio of accelerated neutralization depth of Comparative Example 2 was 1, and it was found that neutralization was progressing to the same extent as Comparative Example 1. On the other hand, the ratio of the accelerated neutralization depth of Example 1 was 0.4, and it was found that the resistance to neutralization was sufficiently high as compared with Comparative Example 1.

  From the results of the sulfuric acid immersion test and the accelerated neutralization test, it was found that Example 1 has a high erosion depth of 1.1 mm and high resistance to erosion by sulfuric acid aqueous solution, and high resistance to neutralization. In this way, concrete that is highly resistant to erosion by sulfuric acid and sulfate and neutralization by carbonic acid, such as sewer pipes, sewage treatment plants and pipes exposed to high concentrations of sulfuric acid and sulfate, or carbonic acid, etc. It was found that it is suitable for structures, secondary products and repair materials used in sewerage related facilities, hot springs, chemical factories, etc.

Claims (2)

An inorganic powder composition containing a Portland cement having a 3CaO.SiO ₂ amount of 60 mass% or more calculated by the Borg formula, and a limestone powder having a Blaine specific surface area of 2,000 cm ² / g or more ;
Fine aggregate,
Coarse aggregate,
Sulfuric acid resistant concrete containing water,
The Portland cement and parts by weight ratio of the limestone powder 30: 70-100: 0 der is,
A formalin condensate salt of naphthalene sulfonic acid having from 1 to 10 parts by weight with respect to the inorganic powder to 100 parts by mass of the composition, to include a water-soluble, high molecular cellulose of 0.005 to 0.1 parts by weight Characteristic sulfuric acid resistant concrete . ^2. The sulfate-resistant concrete according to claim 1, wherein the limestone powder has a Blaine specific surface area of 2,000 to 6,400 cm ² / g .