JP4290473B2 - Sulfuric acid resistant cement composition and sulfuric acid resistant cement cured product - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sulfuric acid resistant cement composition and a sulfuric acid resistant concrete suitable for use in places where corrosion due to sulfuric acid or sulfate is a problem, such as in sewers and hot springs.
[0002]
[Prior art]
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. Furthermore, in recent years, corrosion due to acid rain has become a problem not only in limited places such as sewers and hot springs, but also in the entire structure using cement.
[0003]
When the hardened cement (concrete) is kept in contact with sulfuric acid for a long period of time, it forms hardly soluble plaster, and silicic acid, alumina and the like are eluted to produce silica and alumina gel. This action of sulfuric acid on concrete naturally depends on the acid concentration. When the pH is not lower than 2 (sulfuric acid concentration of 0.1% or less), as in the case of corrosion by carbon dioxide, sulfate, or low-concentration acid, densification of the concrete may lead to the inside of the corrosive substance. It is effective from the point of suppressing the penetration of water, and 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. However, when the concentration of sulfuric acid is high, it is difficult to cope with it. For example, when the pH is lower than 2, it is difficult to expect the cement material itself to be resistant to sulfuric acid.
[0004]
As a method for preventing deterioration of the cement cured product due to sulfuric acid when the pH is lower than 2, use of a polymer cement in which a polymer is combined with a cement composition has been proposed, and the surface of the cement cured product is treated with a corrosion-resistant material (for example, , Epoxy resin, unsaturated polyester resin), and anticorrosion coating (lining) methods have also been proposed. A method of adding a formalin condensate salt of naphthalenesulfonic acid that also functions as a water reducing agent to a cement composition has also been proposed (Patent Document 1).
[0005]
The use of polymer cement and anticorrosion coating is not only expensive, but it cannot be said to be general-purpose because a special process is involved in manufacturing or construction. In addition, in the method of adding a water-soluble organic compound having an alkali metal sulfonic acid group, it is necessary to increase the amount of the water-soluble organic compound having an alkali metal sulfonic acid in order to obtain high acid resistance. The water reduction performance becomes excessive, and even if the unit water amount is reduced, a large amount of bleeding may occur. Therefore, the workability in the production of a concrete molded body using the hydraulic composition containing the cement composition is not always good.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-236860
[Problems to be solved by the invention]
The present invention is a concrete molded body having high sulfuric acid resistance without causing excessive bleeding even when a large amount of the above-described formalin condensate salt water reducing agent of naphthalene sulfonic acid is added for the purpose of improving sulfuric acid resistance. It is an object of the present invention to provide a cement composition and a hydraulic composition capable of imparting water.
[0008]
[Means for Solving the Problems]
The inventor of the present invention is that a cement composition obtained by adding a material having a thickening action to a composition of cement and a formalin condensate salt of naphthalenesulfonic acid is a sulfate-resistant cement composition that solves the above-mentioned problems. And found the present invention.
[0009]
The present invention relates to a composition of 5:95 to 90:10 in a mass part ratio of cement and limestone powder, 4.0 to 10 parts by mass with respect to 100 parts by mass of the composition, and cement in the composition 4.0 parts by weight or more of a formalin condensate salt of naphthalenesulfonic acid and 0.005 to 0.1 parts by weight (preferably 0.08 parts by weight or less) thickener are added to 70 parts by weight. It is in a sulfuric acid resistant cement composition.
[0010]
Examples of the intensifying Nebazai, water-soluble, high molecular cellulose, acrylic water-soluble polymers, biopolymers, thickeners preferred arbitrarily selected from the group consisting of glycol-based water-soluble polymer and inorganic thickeners.
[0012]
The present invention also resides in a hydraulic composition obtained by mixing the above-described sulfuric acid resistant cement composition of the present invention and an aggregate with water.
[0013]
The present invention also resides in sulfate resistant concrete which is a cured product of the hydraulic composition of the present invention.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the cement used in the present invention include 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 the like. , And mixed cements such as fly ash cement, blast furnace cement, silica cement and the like, and white cement, oil well cement, grout cement and the like.
[0015]
Generally, as the amount of naphthalene sulfonic acid formalin condensate salt or thickener added to the cement increases, the setting of the cement composition will be delayed. These cements are also preferred in that they have a small particle size and are less likely to cause bleeding.
[0016]
The cement composition of the present invention, cement and limestone powder, about in parts by weight ratio 5: to use a mixture of 95 to 90:10. This limestone powder is desirably a limestone powder having a maximum particle size of less than 500 μm (more preferably 250 μm or less) and a specific surface area of less than 8000 cm ² / g. If the amount of the fine limestone powder is larger than 95 parts by weight, the effect for is less Portland cement content of the cement with reduced, condensation and strength leading to undesirable results such as reduced.
[0017]
The mechanism of the development of sulfuric acid resistance of limestone powder has not been clarified, but it is considered that it is related to the fact that gypsum serving as a barrier is easily generated, and the expansion during the generation of gypsum is small. In addition, when limestone ultrafine powder (brane specific surface area of 8000 cm ² / g or more) is used as limestone powder, a cement composition having excellent sulfuric acid resistance and workability can be obtained without using a thickener. Such a composition is preferable in that the composition becomes simple.
[0018]
As the formalin condensate salt of naphthalene sulfonic acid, for example, the trade name of Mighty 100 or 150 from Kao Co., Ltd., the trade name of Accelerate 550 from Nissan Chemical Industries, Ltd., or Sun Flow Co., Ltd. Products sold under the trade name of Flow PS can be used. These products are marketed as high-performance water reducing agents for concrete, but it is known that cement compositions with excellent sulfuric acid resistance can be obtained when adding more than the amount normally used as water reducing agents. It is what.
[0019]
The addition amount of the formalin condensate salt of naphthalenesulfonic acid is 1 to 10 parts by mass in terms of solid content with respect to 100 parts by mass of the mixture of cement and limestone powder. If the addition amount of the formalin condensate salt of naphthalene sulfonic acid is less than 1 part by mass, water reduction is exhibited, but sulfuric acid resistance cannot be expected. Further, although the sulfuric acid resistance is improved with the addition amount, the improvement effect reaches a peak at 10 parts by mass or more.
[0020]
The reason why sulfuric acid resistance is improved by the formalin condensate salt of naphthalene sulfonic acid is not clear, but in the SEM observation of the cured product immersed in the sulfuric acid solution, a dense layer of gypsum that is not normally seen on the surface is recognized. Therefore, it is conceivable that this layer acts as a barrier to suppress the permeation of sulfuric acid. The cement composition dissolves in the sulfuric acid solution and precipitates gypsum, but the gypsum precipitation mechanism was changed by the formalin condensate salt of naphthalene sulfonic acid, and it was assumed that the above-mentioned dense layer was formed. The However, in this state, bleeding often occurs, and for example, there is a problem in workability when concrete is used. As described above, in the present invention, a thickener and / or ultrafine silica, fly By adding ash or blast furnace slag fine powder, or by using ultrafine limestone powder, a cement composition in which the problem of bleeding is solved can be obtained.
[0021]
The following mechanism can be considered as a factor which improves workability | operativity when a thickener forms concrete from a hydraulic composition.
[0022]
The hydraulic composition is manufactured by kneading a chemical admixture such as cement and water reducing agent, aggregate, and water, and the workability when the chemical admixture is constant can generally be improved by increasing the amount of water. However, when a large amount of a formalin condensate salt of naphthalene sulfonic acid is added, the cement particles are easily separated from water, so that the amount of water cannot be increased to the amount necessary for workability. If a thickener is added here, the viscosity of water will increase and the separation of water will be suppressed, so it will be possible to increase the amount of water and improve workability.
[0023]
For thickeners, high-fluidity concrete production such as cellulose water-soluble polymers, acrylic water-soluble polymers, biopolymers, glycol water-soluble polymers and inorganic thickeners, or to improve the workability of plastering mortar. One or more selected from those used is used in an amount within the above range. If the amount used is small, a sufficient workability improvement effect is not exhibited, and if it is excessive, the viscosity becomes too high, the workability is lowered and the setting is delayed. Even in the case of a mixed cement using limestone ultrafine powder, it is economical that both the thickener and the limestone ultrafine powder can be added by using a thickener in combination.
[0024]
In the production of ordinary concrete, the use of a thickener formalin condensate salt of naphthalene sulfonic acid is not added in such an amount that the cement and water are separated. It is a method that applies only to things. This is why the amount of thickener used is small compared to the general amount used in high fluid concrete. In general, it is said that the formalin condensate salt of naphthalene sulfonic acid is not compatible with the cellulose-based water-soluble polymer, but a small amount of cellulose-based water-soluble is added to the formalin condensate salt of naphthalene sulfonic acid of the present invention. In a cement composition to which a polymer is added, the combination of both can be performed without any problem.
[0025]
Materials such as cement, limestone powder, formalin condensate salt of naphthalene sulfonic acid, thickener or silica ultrafine powder (or fly ash or blast furnace slag fine powder) constituting the sulfate resistant cement composition of the present invention are cement. Although it can be used by adding to the composition or the cement composition paste, it can be used by mixing a part or all of them 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 addition amount or ultrafine powder that is difficult to mix with a concrete mixer.
[0026]
The sulfuric acid resistant cement composition of the present invention is a paste molded product having an erosion depth of 5 mm or less when immersed in a 5% sulfuric acid aqueous solution at 20 ° C. for 6 months by kneading with water and curing, with a bleeding rate of 2%. It can be obtained as follows.
[0027]
Further, by using the sulfate-resistant cement composition of the present invention, kneading with aggregate and water, molding and curing, the erosion depth when immersed in a 5% sulfuric acid aqueous solution at 20 ° C. for 28 days is 3 mm or less. Can be obtained at a bleeding rate of 10% or less.
[0028]
When mortar or concrete is targeted, the use of limestone aggregate as the aggregate further improves the sulfuric acid resistance. This seems to be due to the same factor as the effect of adding limestone powder to cement, but using limestone as an aggregate is very preferable because the amount of limestone can be increased while maintaining the amount of cement.
[0029]
When the cement composition is kneaded, the water / cement ratio, which is defined as the mass percentage of the amount of water relative to the amount of the inorganic component in the sulfuric acid resistant cement composition of the present invention, is preferably 30 to 60% by mass. When the water / cement ratio is less than 30% by mass, the sulfuric acid resistance tends to be lowered, and when it exceeds 60% by mass, the setting is delayed and the water tightness tends to be lowered. The amount of unit water at the time of 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 the concrete molding is likely to deteriorate. On the other hand, when the amount exceeds 175 kg / m ³ , the amount of aggregate in the concrete decreases, so the properties as concrete. It is easy to lead to decline. The total amount of water and cement in 1 m ^{3 of} concrete is preferably 160 to 300 L.
[0030]
The hydraulic composition using the sulfuric acid resistant cement composition of the present invention is used in sewerage treatment plants and sewerage related facilities such as pipes, hot springs, chemical factories, etc. where excellent sulfuric acid resistance is required. It can be advantageously applied as a structure, secondary product, or repair material.
[0031]
【Example】
Hereinafter, the present invention will be described in more detail with specific examples.
(1) Raw materials The following raw materials were used in carrying out each example.
(I) Cement:
(1) Portland cement / ordinary Portland cement (N)
・ Early strength Portland cement (H)
(2) Mixed material:
Limestone powder (LS): specific surface area 6400 cm ² / g (measured by the brain method)
・ Limestone ultra fine powder (FLS): specific surface area 25000cm ² / g (Brain method)
Silica fume (SF): specific surface area 182000 cm ² / g (BET method)
[0032]
(Ii) Admixture:
・ (I) Naphthalenesulfonic acid formalin condensate salt (NS)
・ (B) Lignin sulfonic acid-based water reducing agent ・ (c) Thickener: Cellulose-based water-soluble polymer (iii) Aggregate:
(1) Fine aggregate:
・ Sea sand: Density 2.59g / cm ³ , coarse grain ratio 2.57, Fukuoka City Hakata ・ Limestone fine aggregate: Density 2.67g / cm ³ , coarse grain ratio 2.77, Bibai production ▲ 2 ▼ Coarse aggregate:
- crushed stone 2005: density 2.69g / cm ^3, Sotsuburitsu 6.68, Yamaguchi Miyano assets and limestone coarse aggregate: Density 2.70g / cm ^3, Sotsuburitsu 6.72, Mine City Omine production (iv ) Mixing water: tap water [0033]
(2) Paste test (i) Preparation of paste A paste shown in Table 1 was mixed with a predetermined amount of admixture and water to prepare a paste. The kneading was performed according to JIS R 5201 “Physical testing method of cement” (8.31 cement paste kneading).
(Ii) Bleeding rate test The bleeding rate test was carried out in accordance with Japan Society of Civil Engineers standard JSCE-F 522-1999 "Testing method for bleeding rate and expansion rate of mortar of prepacked concrete (polyethylene bag method)". Table 1 shows the bleeding rate after 3 hours.
[0034]
(Iii) Sulfuric acid resistance test specimens were prepared by filling the kneaded paste into a cylindrical polyethylene container of φ37 × 60 mm, capping, sealing and curing for 20 hours at 20 ° C. with the casting surface facing down, and up to 60 ° C. The temperature was raised at 20 ° C./hour (95% RH constant), held at 60 ° C. for 5 hours, then the lid was removed, and the product was cured in water at 20 ° C. until the age of 7 days. After measuring the base length of the specimen with a dial gauge (1/100 mm) with a cylindrical polyethylene container attached, it was immersed in a 5% sulfuric acid aqueous solution (pH of about 0.3), and the sulfuric acid aqueous solution was completely exchanged every two weeks. After 6 months, the layer was taken out from the sulfuric acid aqueous solution and washed with water, and then the defect portion was measured with a dial gauge (1/100 mm), further cut perpendicular to the immersion surface, and the thickness of the layer discolored from the immersion surface on the cut surface. The thickness was measured with calipers (5/100 mm), and the sulfuric acid resistance was evaluated using the length obtained by adding the thickness of the layer changed to the length of the defect portion as the erosion depth. The results are shown in Table 1.
[0037]
[Table 1]
Table 1
────────────────────────────────────
Cement limestone powder admixture breedy erosion depth
NHLS FLS SF Iro hang rate% (mm)
────────────────────────────────────
Comparative Example 1 100 0 0 0 0 0 0.25 0 2.2 16.0
2 70 0 30 0 0 2.0 0 0 7.8 5.0
────────────────────────────────────
Reference example 1 70 0 30 0 0 2.0 0 0.03 0.4 3.0
2 0 70 30 0 0 2.0 0 0.03 0.1 0.16
3 0 70 30 0 0 2.0 0 0.02 0.3 0.20
4 0 70 30 0 0 2.0 0 0.04 0.0 0.20
5 0 70 0 30 0 2.0 0 0 0.3 0.19
6 0 70 15 15 0 2.0 0 0.01 0.1 0.19
7 0 70 15 0 15 2.0 0 0 0.1 0.57
8 0 90 10 0 0 2.0 0 0.03 0.1 2.80
9 0 60 40 0 0 2.0 0 0.03 0.1 0.16
10 0 40 60 0 0 2.0 0 0.03 0.0 0.16
11 0 10 90 0 0 2.0 0 0.03 0.0 1.20
Example 12 0 70 30 0 0 4.0 0 0.03 0.0 0.12
13 0 70 30 0 0 8.0 0 0.08 0.0 0.05
────────────────────────────────────
1) Numerical values of cement, limestone, SF and admixture represent parts by mass.
2) The amount of water / [cement + limestone powder + SF] is 0.3 in Comparative Examples 1-2 and Example 12, and 0.4 in other reference examples and Examples.
[0039]
Compared with Comparative Example 1 which is a normal cement composition paste using ordinary cement (N), a part of the cement is replaced with limestone powder (LS), and the formalin condensate salt (NS) of naphthalene sulfonic acid is used. In Comparative Example 2 added in a large amount, the erosion depth of the paste is 5 mm or less and the sulfuric acid resistance is improved, but the bleeding rate is increased. However, the composition further added with a thickener not only improves bleeding at 2% or less, but also improves the sulfuric acid resistance of the paste [ Reference Example 1].
[0040]
In addition, when ordinary cement is replaced with early-strength Portland cement (H) in the presence of limestone powder, the bleeding rate remains small, and the sulfuric acid resistance of the paste is further improved [ Reference Examples 2 to 4]. The addition of limestone powder improves the sulfuric acid resistance of the paste by adding 10 to 90 parts by mass per 100 parts by mass of the total amount of cement and limestone powder [ Reference Examples 8 to 11]. Moreover, the paste with the highest sulfuric acid resistance is given in the region of 30 to 60 parts by mass [ Reference Examples 2, 8 to 11]. The amount of naphthalenesulfonic acid formalin condensate (NS) added is preferably in the range of 1 to 10 parts by mass per 100 parts by mass of the total amount of cement and limestone powder [Examples 12 and 13].
[0041]
When limestone powder (LS) is replaced with limestone ultrafine powder (FLS) or silica fume (SF), a paste with excellent sulfuric acid resistance can be used with a small bleeding rate without using or reducing the thickener. Obtained [ Reference Examples 5 to 7].
[0043]
【The invention's effect】
The sulfuric acid resistant cement composition according to the present invention not only enables the production of a concrete product excellent in sulfuric acid resistance, but also has good workability equivalent to or higher than that of a general-purpose hydraulic composition. It enables construction of acid-resistant repair paste, mortar, and sulfate-resistant concrete structures by on-site casting. In addition, the materials used are only easily available, and can be easily and inexpensively manufactured in a facility for manufacturing ordinary concrete and concrete products.
Therefore, the cement composition according to the present invention is not only applied to hot springs, sewer facilities, etc., where it is likely to be exposed to sulfuric acid, but also has a concrete structure capable of exhibiting high durability against acid rain, which has become a problem in recent years. It can be advantageously used in the manufacture of products and concrete products.

Claims (6)

In a composition of 5:95 to 90:10 by mass part ratio of cement and limestone powder, 4.0 to 10 parts by mass with respect to 100 parts by mass of the composition, and 70 parts by mass of cement in the composition On the other hand, a sulfuric acid resistant cement composition comprising 4.0 parts by mass or more of a formalin condensate salt of naphthalenesulfonic acid and 0.005 to 0.1 parts by mass of a thickener.   The sulfate-resistant cement composition according to claim 1, wherein the thickener is a cellulose-based water-soluble polymer.   The sulfuric acid resistant cement composition according to claim 1 or 2, wherein the cement is an early strong cement or an ultra early strong cement.   A hydraulic composition obtained by mixing the sulfuric acid resistant cement composition according to any one of claims 1 to 3 with water.   A hydraulic composition comprising the sulfuric acid resistant cement composition according to any one of claims 1 to 3 and an aggregate mixed with water.   A sulfuric acid resistant concrete which is a cured product of the hydraulic composition according to claim 4 or 5.