JP6764702B2 - Hydraulic composition - Google Patents

Description

The present invention relates to hydraulic compositions.

Cement hardens by a hydration reaction with water to become a hardened body. The clinker minerals that make up cement react with water to produce hydrates such as strongly alkaline calcium hydroxide, and the pore solution in the cured product is strongly alkaline.
When the cured product is left in the air, carbon dioxide invades the inside, calcium salts such as calcium hydroxide react with carbon dioxide to generate calcium carbonate, and the pore solution becomes strongly alkaline to neutral. The so-called "neutralization" that degenerates into calcium progresses. Neutralization proceeds from the surface of the cured product. For example, in the case of constructing a reinforced concrete structure using cement, if the neutralization progresses to the vicinity of the reinforcing bar inside the reinforced concrete structure, the passivation film covering the reinforcing bar is destroyed, which contributes to the corrosion of the reinforcing bar. Then, the reinforcing bar expands as compared with that before corrosion, causing cracks, breakage, etc. of the hardened body, and the corrosion causes a cross-sectional defect of the reinforcing bar, resulting in a decrease in the strength of the reinforced concrete structure.

In recent years, environmentally friendly cements that emit less carbon dioxide during production have been proposed. This is 20 to 100% of a mixture of one or more types of cement (Portland cement, blast furnace cement, fly ash cement, silica cement, eco-cement) specified in JIS R5210, R5211, R5212, R5213, R5214. The composition is equivalent to that of slag, fly ash, silica fume, dihydrate cement, semi-water cement, anhydrous cement, limestone fine powder, slaked lime, swelling material, silica mixture, or calcium salt or sodium salt. It is a water-hardening composition. Concrete using environmentally friendly cement is called environmentally friendly concrete. For example, in Patent Document 1, as an environment-friendly cement, a hydraulic composition composed of two or more kinds of stimulants having different elution rates of blast furnace slag fine powder, limestone fine powder and calcium ions is described in Patent Document 2. Has proposed a slag hardening composition containing fine aggregate, coarse aggregate, limestone fine powder, slag fine powder, sodium carbonate, and a chemical admixture as main components as environment-friendly concrete. Non-Patent Document 1 reports an example of concrete construction in which 20 to 80% of Portland cement is replaced with an admixture containing blast furnace slag as a main component as an environment-friendly concrete.
However, hardened bodies using environmentally friendly cement and environmentally friendly concrete using environmentally friendly cement use less Portland cement, and are more neutralized than hardened bodies and concrete using Portland cement. There is a problem that it is easy to proceed.

As a technique for suppressing neutralization, a method is known in which the cured product is made denser to prevent carbon dioxide from entering by reducing the water-cement ratio. However, since the amount of powder used increases, the cost increases. Further, if the water-cement ratio is small, the fluidity is poor and the workability is lowered.

As another neutralization suppressing technique, Patent Document 3 proposes a method for suppressing neutralization of concrete using a modified aggregate obtained by immersing an aggregate in a magnesium silica fluoride solution. However, a process of immersing the aggregate is required, which requires labor. Patent Document 4 describes a mixture for concrete consisting of a substance containing one or more non-hydraulic compounds selected from the group consisting of γ-2CaO · SiO ₂ , α-CaO · SiO ₂ , and calcium magnesium silicate. It is described that the neutralization reaction can be suppressed by the agent. However, Patent Document 4 shows that when γ-2CaO · SiO ₂ or α-CaO · SiO ₂ is absent, the neutralization rate is the same as when no admixture is added.

Japanese Unexamined Patent Publication No. 2014-148434 Japanese Patent No. 5743650 Japanese Unexamined Patent Publication No. 2010-222205 Japanese Unexamined Patent Publication No. 2004-292201 Hiroshi Jinnai, Masaki Kato, Kaori Tateyama, Kenji Kondo: Realization of a building in which the main structural members are constructed of environment-friendly concrete and CO2 reduction effect, concrete engineering, vol. 52, No. 6, pp.528-533, 2014.6.

An object of the present invention is to provide a hydraulic composition that suppresses the progress of the neutralization reaction.

1. 1. A hydraulic composition comprising cement and a neutralization inhibitor composed of a sparingly soluble magnesium compound.
2. 1. The neutralization inhibitor is contained in an amount of 2 mass% or more and 15 mass% or less in terms of magnesium oxide with respect to the total amount of powder. The hydraulic composition according to.
3. 3. The cement is one of Portland cement, blast furnace cement, fly ash cement, silica cement, eco-cement, and environment-friendly cement. Or 2. The hydraulic composition according to.
4. 1. The neutralization inhibitor contains at least one of magnesium oxide, magnesium hydroxide, magnesium carbonate, and magnesium carbonate. ~ 3. The hydraulic composition according to any one of.
5.1. ~ 4. A cured product comprising the hydraulic composition according to any one of.
6. Includes hydrotalcite 5. The cured product described in.
7. A neutralization inhibitor composed of a sparingly soluble magnesium compound.
8. A method for suppressing neutralization of a cured product, which comprises incorporating a neutralization inhibitor composed of a sparingly soluble magnesium compound into cement.

The hydraulic composition of the present invention can suppress the progress of the neutralization reaction in the cured product by containing a neutralization inhibitor composed of a poorly soluble magnesium compound. By replacing a part of the cement with a neutralization inhibitor, the neutralization reaction can be suppressed without increasing the amount of powder. In the hydraulic composition of the present invention, the strength of the cured product does not change with or without the neutralization inhibitor. Therefore, the hydraulic composition of the present invention in which a part of the conventional composition is replaced with a neutralization inhibitor can be used as it is without newly calculating the strength.
The hydraulic composition of the present invention exhibits a neutralization-suppressing effect on various cements, and can be particularly preferably used for blast furnace cements, fly ash cements, and environment-friendly cements in which the neutralization reaction easily proceeds.
By adjusting the blending amount of the neutralization inhibitor in the range of 2 mass% or more and 15 mass% or less in terms of magnesium oxide, the progress of neutralization can be controlled according to the required performance of the structure.
The neutralization inhibitor of the present invention comprises a poorly soluble magnesium compound. The sparingly soluble magnesium compounds such as magnesium hydroxide, magnesium oxide, magnesium carbonate, and magnesium carbonate are commercially available. Neutralization inhibitors such as γ-2CaO · SiO ₂ or α-CaO · SiO ₂ described above are generally difficult to obtain, but commercially available neutralization inhibitors are inexpensive and have a certain quality. Can be easily obtained.

The figure which shows the result of the accelerated neutralization test in Experiment 1. The figure which shows the result of the accelerated neutralization test in Experiment 1. X-ray diffraction pattern of the cured product of the present invention. The figure which shows the result of the accelerated neutralization test in Experiment 2. The figure which shows the result of the accelerated neutralization test in Experiment 3. The figure which shows the result of the accelerated neutralization test in Experiment 4.

The hydraulic composition of the present invention contains cement and a neutralization inhibitor composed of a sparingly soluble magnesium compound.

"cement"
As the cement contained in the hydraulic composition of the present invention, a hydraulic powder that hardens by causing a hydration reaction with water can be used without particular limitation. For example, Portland cement, blast furnace cement, fly ash cement, silica cement, and eco-cement, which are cements specified by JIS, can be mentioned. It is also possible to use environmentally friendly cement. Among these, the neutralization inhibitor of the present invention can be suitably used for blast furnace cement, fly ash cement, and environment-friendly cement, in which neutralization is likely to proceed.

"Neutralization inhibitor"
The neutralization inhibitor of the present invention comprises a poorly soluble magnesium compound. In the present invention, poor solubility means that the solubility in water at 25 ° C. is 100 mg or less with respect to 100 mL of water, and does not mean that it is completely insoluble in water. The poorly soluble magnesium compound, magnesium hydroxide (Mg _(OH) 2), magnesium oxide (MgO), magnesium carbonate (MgCO _3), magnesium carbonate hydroxide _{(mMgCO 3 · Mg (OH)} 2 · nH 2 O, m = 3 to 5, n = 3 to 7), and the like. Two or more of these poorly soluble magnesium can be used in combination.

"Hydraulic composition"
The hydraulic composition of the present invention contains cement and a neutralization inhibitor. In addition to cement and a neutralization inhibitor, the water-hardening composition of the present invention includes an AE agent, a water reducing agent, an AE water reducing agent, a high-performance AE water reducing agent, a retarding agent, a foaming agent, a waterproofing agent, a coloring agent, and a cold resistant agent. , Chemical admixtures such as fast-strengthening agents and thickeners, fine aggregates such as gravel, sand, sea sand, crushed stone, crushed sand, various slag aggregates, heavy aggregates, lightweight aggregates, recycled aggregates and coarse bones. Materials, additives such as vinylon fiber, polypropylene fiber, glass fiber, steel fiber, carbon fiber, tap water, river water, lake water, groundwater, recovered water in ready mixed concrete factory, water contained in chemical admixture, etc. Can contain water.

The hydraulic composition of the present invention preferably contains a neutralization inhibitor in an amount of 2 mass% or more and 15 mass% or less in terms of magnesium oxide with respect to the total amount of powder. Here, in the present invention, the powder refers to cement and a neutralization inhibitor. If the amount of the neutralization inhibitor is less than 2 mass% in terms of magnesium oxide, the effect of suppressing the progress of neutralization may not be sufficient. If the amount of the neutralization inhibitor is more than 15 mass% in terms of magnesium oxide, the viscosity after kneading is high and the workability may be lowered.

The hydraulic composition of the present invention may be used as a paste using water or a chemical admixture, or as a mortar or concrete using a fine aggregate, coarse aggregate or chemical admixture. Can be done.
Concrete can be used for on-site concrete, ready-mixed concrete, and concrete products such as concrete blocks, box culverts, and segments.

The method for producing the hydraulic composition of the present invention may be carried out by a conventional method. That is, when used as a paste or mortar or concrete, the neutralization inhibitor and some or all of the other constituent materials except water can be premixed prior to water injection, or in a concrete mixer. The neutralization inhibitor may be kneaded while mixing other constituent materials including water, or other constituent materials other than the neutralization inhibitor may be kneaded to produce a paste or mortar or concrete and then neutralized. It is also possible to add an anti-formation agent and knead again.

The hydraulic composition of the present invention can suppress the neutralization of the cured product. The neutralization inhibitor composed of a sparingly soluble magnesium compound does not increase the compressive strength of the cured product. Since the increase in the compressive strength of the cured product indicates that the microstructure of the cured product has become denser, the neutralization inhibitor composed of the sparingly soluble magnesium compound does not make the microstructure of the cured product denser. Is suggested. Generally, when the cured product becomes dense, carbon dioxide is less likely to penetrate and the neutralization reaction is suppressed, but the cured product made of the hydraulic composition of the present invention is unknown because the microstructure is not densified. It is presumed that the progress of the neutralization reaction is suppressed by the mechanism of. The mechanism by which the hydraulic composition of the present invention suppresses the progress of the neutralization reaction is unknown.

"Experiment 1" Environmentally friendly cement For environmentally friendly cement containing 77 mass% of blast furnace slag with respect to the total amount of powder, any of magnesium hydroxide, magnesium oxide, and magnesium carbonate carbonate, which are neutralization inhibitors, And water were blended in the mass ratios shown in Table 1 to obtain a cement paste. The preparation was carried out by pouring water into the premixed powder and thoroughly kneading with a scoop for 3 minutes or more. Among the materials, JIS A 6206 for blast furnace slag, JIS A 6202 for expansion material, JIS R 9001 for slaked lime, and JIS A 5008 for fine limestone powder are satisfied, and magnesium hydroxide, magnesium oxide, and magnesium hydroxide (4 MgCO) are satisfied. _{3 · Mg (OH) 2 ·} 5H 2 O) was used to grade reagent or deer first grade reagent manufactured by Kanto Chemical Co., Inc..

Water: Yokohama Waterworks Bureau, tap water blast furnace slag (with gypsum): Made by DC Co., Ltd., Product name: Cerament A
(SO ₃ = 2.1%, anhydrous gypsum additive)
Expansion material: Made by Pacific Material Co., Ltd., Product name: Expanded slaked lime: Made by Okutama Kogyo Co., Ltd., Product name: Special issue Slaked limestone Fine powder: Made by Miyagi limestone Co., Ltd.

A specimen having a diameter of about 3 cm and a height of about 5 cm was prepared from this cement paste and cured by sealing. The material was demolded at 28 days of age, and stored at 20 ° C. and 60% RH for 7 days after demolding. Then, the surface other than the bottom surface was coated with aluminum tape, and an accelerated neutralization test was conducted at 20 ° C., 60% RH, and a CO ₂ concentration of 5%.
After a lapse of a predetermined period, the specimen was split and the cross section was sprayed with an alcohol solution of phenolphthalein having a concentration of 1%, and the neutralization depth was measured. The results are shown in FIGS. 1 and 2. In Comparative Example 1, the entire range of the observation surface was neutralized during the neutralization period of 91 days.

Examples 1 to 7 containing 3.0 to 11.1 mass% of the neutralization inhibitor in terms of magnesium oxide as compared with Comparative Example 1 which is an environment-friendly cement containing no neutralization inhibitor. , The neutralization depth is less than half. In addition, it was confirmed that the neutralization depth became smaller by containing a large amount of the neutralization inhibitor. In addition, the effect of suppressing neutralization was confirmed in any of the poorly soluble magnesium of magnesium hydroxide, magnesium oxide, and magnesium carbonate.

Of the hardened cement paste compounded in Example 2 after the accelerated neutralization period of 56 days, the neutralized portion at a distance of 3 cm or more from the exposed surface was crushed to reduce the particle size to 75 μm or less, and then 10 mass of alumina. % Was added, and an X-ray diffraction pattern was obtained by the powder method. The measurement conditions are shown in Table 2, and the diffraction pattern is shown in FIG.

From the diffraction pattern, and Mg _{(OH) 2,} hydrotalcite _{(Mg 6 Al 2 CO 3 (} OH) 16 · 4 (H 2 O)) were identified. It was confirmed that the neutralization inhibitor of the present invention reacts with the cement component to form hydrotalcite.

"Experiment 2" Environmentally Friendly Cement-Mortar A 4 x 4 x 16 cm mortar specimen was prepared by adding fine aggregate to the cement paste containing the formulations of Example 2 and Comparative Example 1 shown in Table 1. The fine aggregate was crushed sand having a density of 2.63 g / cm ³ satisfying JIS A 5308 Annex A, and the mass ratio of the fine aggregate to the powder was 1: 2 and the water powder ratio was 0.36. A mortar mixer (manufactured by Marui Co., Ltd., device name: MIC-362-1-01) was used for kneading.
After kneading, it was driven into a mold having a size of 4 × 4 × 16 cm. After 3 days, the mold was removed and cured in water at 20 ° C. until the age of 28 days. After that, it was stored at 20 ° C. and 60% RH until the age of 56 days, and the surface other than one side surface of 4 × 16 cm was coated with aluminum tape, and promoted neutralization at 20 ° C., 60% RH and CO ₂ concentration of 5%. The test was conducted.

After a lapse of a predetermined period, the specimen was split and the cross section was sprayed with an alcohol solution of phenolphthalein having a concentration of 1%, and the neutralization depth was measured. The results are shown in FIG.
It was confirmed that even in mortar containing fine aggregate, neutralization can be suppressed by the neutralization inhibitor. The hydraulic composition of Example 2 had a neutralization depth of about half that of the hydraulic composition of Comparative Example 1.

"Experiment 3" Environmentally Friendly Cement-Concrete A 10 x 10 x 40 cm concrete specimen was prepared by adding fine aggregate and coarse aggregate to the cement paste containing the formulations of Example 2 and Comparative Example 1 shown in Table 1. .. The fine aggregate used was the same as in Experiment 2, and the coarse aggregate used was crushed stone satisfying JIS A 5005 with a density of 2.66 g / cm ³ and a Gmax of 20 mm, and the fine aggregate ratio was 43%. The water powder ratio was set to 0.36, and an appropriate amount of an AE agent and a high-performance AE water reducing agent was added to adjust the amount of air to 6.0%. A forced twin-screw kneader (manufactured by Pacific Machinery & Engineering Co., Ltd., device name: SD-55 type) was used for kneading.
It was demolded at the age of 3 days and cured in water at 20 ° C. until the age of 28 days. After that, it was stored at 20 ° C. and 60% RH until the age of 56 days, and the surface other than one side surface was coated with aluminum tape, and an accelerated neutralization test was conducted at 20 ° C., 60% RH and a CO ₂ concentration of 5%. ..

After a lapse of a predetermined period, the specimen was split and the cross section was sprayed with an alcohol solution of phenolphthalein having a concentration of 1%, and the neutralization depth was measured. The results are shown in FIG.
It was confirmed that even in concrete containing coarse aggregate, neutralization can be suppressed by the neutralization inhibitor. The hydraulic composition of Example 2 had a neutralization depth of about half that of the hydraulic composition of Comparative Example 1.

Further, a specimen of Φ10 × 20 cm was prepared from concrete using the cement paste of the formulations of Example 2 and Comparative Example 1 prepared above, and the specimen was demolded at the age of 3 days and 20 ° C. until the age of 28 days. After curing in water, the compression strength was measured using a universal testing machine (manufactured by Tokyo Kouki Seisakusho Co., Ltd., device name: RU-30) in accordance with JIS A 1108. The results are shown in Table 3.

Even when the neutralization inhibitor was added, the compression strength was almost unchanged. The cured product of the hydraulic composition has a higher compressive strength as the microstructure becomes denser. For this reason, the neutralization inhibitor composed of a sparingly soluble magnesium compound suppresses the progress of the neutralization reaction by a mechanism different from the general neutralization suppression method that compacts the tissue and prevents the invasion of carbon dioxide. It was suggested that they were doing.

"Experiment 4" Various cements A neutralization inhibitor was added to various cements in the mass ratio shown in Tables 4 to 8 to prepare a cement paste. The materials used are shown below. Among the materials, JIS A 6206 for blast furnace slag, JIS R 5210 for early-strength Portland cement and ordinary Portland cement, JIS R 5211 for blast furnace cement type B, JIS A 6207 for silica fume, and JIS A 6201 for fly ash. did. For magnesium hydroxide, a special grade reagent manufactured by Kanto Chemical Co., Inc. was used.

Water: Yokohama City Waterworks Bureau, tap water blast furnace slag (without slag): Made by DC Co., Ltd., Product name: Cerament Hayako Portland cement: Taiheiyo Cement Co., Ltd. Ordinary Portland cement: Taiheiyo Cement Co., Ltd. Made by Cement Co., Ltd., Class B (ordinary Portland
40-70 mass% of cement,
(Including 30-60 mass% of blast furnace slag)
Silica fume: Made by DC Co., Ltd. Fly ash: Made by Techno Chubu Co., Ltd., Type II anhydrous gypsum: Made by DC Co., Ltd.

In Tables 4 to 8, Comparative Examples 2, 3, 8, 9, and 10 are environmentally friendly cements, and Comparative Examples 4 to 7 are ordinary Portland cement, blast furnace cement type B, blast furnace cement type C, and fly ash cement C, respectively. It is a seed.

Using each of the hydraulic compositions shown in Tables 4 to 8, an accelerated neutralization test was carried out in the same manner as in Experiment 1.
The neutralization rate coefficient was calculated from the results up to the neutralization period of 91 days. The relationship between the amount of the neutralization inhibitor converted to magnesium oxide and the neutralization rate coefficient was determined.
FIG. 6 shows the neutralization results of the formulations obtained by performing the neutralization test as Examples 1 to 24 and Comparative Examples 1 to 5.

It was confirmed that in various cements, the progress of neutralization can be suppressed by a neutralization inhibitor composed of a poorly soluble magnesium compound. It was also confirmed that the progress of neutralization can be further suppressed by increasing the amount of the neutralization inhibitor.
Even if the composition of the powder in the paste, mortar, and concrete was changed, the neutralization depth could be reduced by the neutralization inhibitor. That is, it was confirmed that the neutralization inhibitor of the present invention can suppress the progress of neutralization of various types and formulations of cement paste, mortar, and concrete.

Claims (5)

And cement, and a neutralization inhibitor consisting of a poorly soluble magnesium compound observed including,
The cement is one of blast furnace cement, fly ash cement, silica cement, eco-cement, and environment-friendly cement.
The neutralization inhibitor is at least one of magnesium oxide, magnesium hydroxide, magnesium carbonate, and magnesium carbonate.
A hydraulic composition characterized in that a part of the cement is replaced with a neutralization inhibitor . The hydraulic composition according to claim 1, wherein the neutralization inhibitor is contained in an amount of 2 mass% or more and 15 mass% or less in terms of magnesium oxide with respect to the total amount of powder. The cement, blast furnace cement, fly ash cement, hydraulic composition according to claim 1 or 2, characterized in that either environmentally friendly cement. A cured product comprising the hydraulic composition according to any one of claims 1 to 3 . A method for suppressing neutralization of a cured product, which comprises replacing a part of cement with a neutralization inhibitor composed of a poorly soluble magnesium compound.