JP7260998B2 - Expansive composition, cement composition and cement-concrete - Google Patents

Description

The present invention mainly relates to expansive compositions, cement compositions and cement-concrete used in the fields of civil engineering and construction.

Cement is an excellent material that is inexpensive and can be used to build large structures in arbitrary shapes. Furthermore, by using a cement admixture together, it is possible to improve the strength and durability of the structure. Although many cement admixtures have been proposed so far, the most widely used one is a cement admixture (expanding composition) that imparts expandability to concrete.

Expanding compositions are widely used to reduce cracking in concrete. For example, the Japan Society of Civil Engineers has set a standard of 150 to 250×10 ⁻⁶ for shrinkage compensation applications of expansive concrete. There are concrete that cracks easily and concrete that does not easily crack even when an expansion strain that falls within this standard is applied. While meeting the shrinkage compensation standards, the development of an expandable composition that is more excellent in crack resistance has been eagerly awaited.

Cement admixtures that impart expandability to concrete structures include, for example, two types: ettringite-based expansive materials containing ettringite-forming substances such as calcium sulfoaluminate as active ingredients, and quicklime-based expansive materials containing free quicklime as active ingredients. used as a representative (Patent Document 1 and Patent Document 2).

A concrete expansive material having excellent expansive properties even when added in a small amount (Patent Document 3) and an expansive material for cement in which the surface of quicklime is coated with calcium carbonate (Patent Document 4) have also been proposed.

JP-A-2004-210551 JP-A-2001-316147 Japanese Patent No. 4244261 JP-A-54-93020

However, Patent Documents 1 to 4 are silent about defining the pH of the swelling composition.

A conventional swelling composition containing free lime as a main component has a problem that its swelling performance deteriorates when stored for a long period of time. That is, an object of the present invention is to provide an expanding composition that is excellent in storage stability and capable of exhibiting appropriate expansion performance.

As a result of intensive studies to solve the above problems, the present inventors have arrived at the following invention and found that the problems can be solved. That is, the present invention is as follows.

[1] A swelling composition containing free lime, a hydraulic compound and anhydrite, and having a maximum pH of 11.5 to 13.0 as measured by the Fuchs method test.
[2] The swelling composition according to [1], which reaches pH 3.0 within 10 seconds as measured by the Fuchs method test.
[3] The expanding composition according to [1] or [2], which maintains a pH of 3.0 or higher as measured by the Fuchs method test for more than 100 minutes and less than 130 minutes.
[4] The expanding composition according to any one of [1] to [3], which has a Blaine specific surface area of 2,000 to 6,000 cm ² /g and a content of particles having a diameter of more than 180 μm of 5% by mass or less.
[5] The content of particles with a diameter of 10 μm or less (W _D10 ) is 30 to 60% by mass, and the content of particles with a diameter of 100 μm or less (W _D100 ) and the content of particles with a diameter of 10 μm or less The expanding composition according to any one of [1] to [4], wherein the ratio (W _D100 /W _D10 ) to the content (W _D10 ) is 1.5 to 4.0.
_{[ 6} ] The hydraulic compound _{is 3CaO.3Al2O3.CaSO4 , 3CaO.SiO2 , 2CaO.SiO2 , 4CaO.Al2O3.Fe2O3 , 6CaO.2Al2O3.Fe2} The expansion according to any one of [ ₁ ] to [5], which is one or more selected from the group consisting of O 3 , 6CaO.Al ₂ O ₃ .Fe ₂ O ₃ , and 2CaO.Fe ₂ O ₃ Composition.
[7] A cement composition containing the expansion composition according to any one of [1] to [6].
[8] Cement-concrete containing the cement composition according to [7].

ADVANTAGE OF THE INVENTION The expansion composition of this invention is excellent in storage stability, and provides the expansion composition which can express appropriate expansion|swelling performance.

The present invention will be described in detail below.
Parts and percentages used in the present invention are based on mass unless otherwise specified. Cement-concrete is a general term for cement paste, mortar and concrete.

[1. Expansion composition]
The swelling composition of the present invention contains free lime, a hydraulic compound and anhydrite. The inclusion of free lime, hydraulic compounds, and anhydrite provides proper swelling performance.

The swelling composition of the present invention has a maximum pH of 11.5 to 13.0, preferably 11.8 to 12.8, and 12.2 to 12.6 as measured by the Fuchs method test. is more preferred.
In the Fuchs method test, 50 ml of 0.1 N hydrochloric acid is taken in a beaker, 1 g of the expansion composition is added, and immediately after stirring, the pH is measured (initial pH), and after 10 minutes from the start of stirring, 1 N Add 2 ml of hydrochloric acid every 10 minutes, read the pH, and continue adding hydrochloric acid and measuring the pH until the initial pH is reached. The time from the first pH measurement until the pH reaches 3.0 is defined as the "reaching time", and this "reaching time", the highest pH after the reaching time, and the duration of maintaining pH 3.0 or higher ( (sometimes simply referred to as "duration") evaluates the swelling performance of the swelling composition.

In addition, the arrival time measured by the Fuchs method test is preferably within 30 seconds, more preferably within 10 seconds, and even more preferably within 5 seconds, from the viewpoint of improving expansion performance.

The duration of maintaining pH 3.0 or higher as measured by the Fuchs method test is preferably over 60 minutes and within 130 minutes, more preferably over 100 minutes and within 130 minutes. When the duration is more than 60 minutes and 130 minutes or less, it is possible to achieve both an improvement in expandability and storage stability of the expandable composition.

(free lime)
Free lime according to the present invention is usually called f-CaO.

(hydraulic compound)
The hydraulic compound according to the present invention is a substance that has the property of _hardening by reacting with water, and includes irimite _represented by _{3CaO.3Al.sub.2O.sub.3.CaSO.sub.4} , _{3CaO.SiO.sub.2} (abbreviated as C3S) and 2CaO. Calcium silicate represented by SiO ₂ (abbreviated as C2S), 4CaO.Al ₂ O ₃ .Fe ₂ O ₃ (abbreviated as C4AF), 6CaO.2Al ₂ O _{3.Fe 2} O ₃ (abbreviated as C6A2F), 6CaO · A calcium aluminoferrite represented by Al ₂ O ₃ · Fe ₂ O ₃ (abbreviated as C6AF), a calcium ferrite such as 2CaO · Fe ₂ O ₃ (abbreviated as C2F), etc., one or two of these It preferably contains more than one species.

(anhydrous gypsum)
The anhydride gypsum of the present invention is not particularly limited, but it is preferable to use type II anhydride gypsum, and it is particularly preferable to use an acidic anhydride gypsum having a pH of 4.5 or less.
Here, the pH of anhydrous gypsum means the pH of the supernatant when 1 g of anhydrous gypsum is added to 100 mL of pure water and stirred.

The expansion composition of the present invention is prepared by appropriately mixing CaO raw material, Al ₂ O ₃ raw material, Fe ₂ O ₃ raw material, SiO ₂ raw material, and CaSO ₄ raw material, and heating it at 1100 to 1600 ° C. using an electric furnace or kiln. Preferably, it is heat-treated at 1200 to 1500° C. to obtain clinker, or the clinker is pulverized to obtain a clinker pulverized product.
By setting the heat treatment temperature to 1,100 to 1,600° C., it becomes easier to obtain sufficient expansibility, and the decomposition of the anhydride gypsum can be suppressed.

Here, in order to adjust the maximum pH to 11.5 to 13.0, it is sufficient to change the component ratio of the expansion composition and the chemical composition of each component. In addition, the arrival time can be adjusted by controlling the component ratio of the expansion composition, the grain growth of f-CaO, and the grain size distribution. Also, the duration can be adjusted by controlling the ratio of components in the swelling composition and the chemical composition of each component.

Examples of CaO raw materials include limestone and slaked lime, examples of Al ₂ O ₃ raw materials include bauxite and aluminum residual ash, examples of Fe ₂ O ₃ raw materials include copper sludge and commercially available iron oxide, and SiO ₂ raw materials such as silica stone. etc., but _CaSO4 raw materials include gypsum dihydrate, gypsum hemihydrate and gypsum anhydrite.

Although these raw materials may contain impurities, they pose no particular problem as long as they do not impair the effects of the present invention. Impurities include MgO, TiO ₂ , MnO, P ₂ O ₅ , Na ₂ O, K ₂ O, Li ₂ O, sulfur, fluorine, chlorine and the like.

The ratio of each mineral contained in the expanding composition of the present invention is preferably within the following range. The free lime content is preferably 10 to 93 parts, more preferably 40 to 90 parts, per 100 parts of clinker. The content of the hydraulic compound is preferably 3 to 50 parts, more preferably 20 to 30 parts, per 100 parts of clinker. The content of anhydrite is preferably 1-50 parts, more preferably 20-30 parts, per 100 parts of clinker. Moreover, when the content of anhydrite in the clinker is small, it is preferable to separately add anhydride gypsum as an expanding agent. Outside the above range, the amount of expansion may become extremely large and the compressive strength may decrease, or the amount of expansion may decrease between days 2 and 7 of material age and between days 5 and 7 of material age. be.

The content of each mineral can be confirmed by a conventional general analysis method. For example, a pulverized sample is subjected to a powder X-ray diffractometer to confirm the produced minerals, and the data can be analyzed by the Rietveld method to quantify the minerals. Also, the amount of minerals can be determined by Borg's formula based on the identification results of chemical components and powder X-ray diffraction. In the present invention, it is preferable to obtain by Borg's formula.

The fineness of the expanding composition of the present invention is preferably 2,000 to 6,000 cm ² /g, more preferably 2,500 to 5,000 cm ² /g in Blaine specific surface area. If it is less than 2,000 cm ² /g ^, expansion may occur over a long period of time and the structure of the concrete may be destroyed. The Blaine specific surface area can be measured according to JIS R 5201 (physical test method for cement).
In addition, from the viewpoint of suppressing pop-out due to post-expansion, the content of particles with a diameter of more than 180 μm is preferably 5% or less, more preferably 0.1 to 0.5%.

The content of particles with a diameter of 10 μm or less (W _D10 ) is 30 to 60%, and the content of particles with a diameter of 100 μm or less (W _D100 ) and the content of particles with a diameter of 10 μm or less (W _D10 ) ratio (W _D100 /W _D10 ) is preferably 1.5 to 4.0. By doing so, it is possible to both ensure effective expandability and suppress pop-out due to post-expansion.
More preferably, the content of particles with a particle size of 10 μm or less is 40 to 50%. The ratio of the content of particles with a particle size of 100 μm or less to the content of particles with a particle size of 10 μm or less is more preferably 2.0 to 3.5. The content of particles having a particle size of 100 μm or less is preferably 60 to 90%.
The content of particles with a particle size of 10 μm or less and the content of particles with a particle size of 100 μm or less can be measured by controlling the pulverization method and classification method.

[2. cement composition]
The cement composition of the invention comprises the expanding composition of the invention.
The amount of the expansive composition of the present invention is not particularly limited because it varies depending on the composition of the concrete. part is more preferred. By using 3 parts or more, it becomes easy to obtain sufficient expansion performance. Further, by setting the amount to 12 parts or less, it is possible to prevent the occurrence of expansion cracks in the concrete due to excessive expansion.

As the cement of the cement composition, various Portland cements such as normal, high-early strength, ultra-early strength, low heat, and moderate heat, various mixed cements obtained by mixing these Portland cements with blast furnace slag, fly ash, or silica, limestone powder, etc. Examples include filler cement mixed with ground granulated blast furnace slow-cooled slag, and environment-friendly cement (eco-cement) manufactured from municipal waste incineration ash and sewage sludge incineration ash as raw materials.

[2. Cement/Concrete]
The cement-concrete of the present invention contains the cement composition of the present invention.

The cement-concrete of the present invention can be produced by kneading the above-mentioned cement composition, aggregate, water, and optional admixtures (excluding the expansion composition of the present invention).
Aggregates are not particularly limited, and both fine aggregates and coarse aggregates commonly used in the production of concrete can be used.

The expansion performance (expansibility) according to the present invention can be evaluated by measuring the length change according to the method described in Appendix 1 and Appendix 2 of JIS A 6202 "Expansion material for concrete". Shows expansion strain.

EXAMPLES The present invention will be described in detail below with reference to Examples, but the present invention is not limited to these.

A test according to the Fuchs method was performed using expansion compositions A, B, C, D and E shown in the following materials used. Storage stability was then determined. Table 1 shows the results.
The expansion compositions (a), (b), (c), (d), and (e) are prepared by blending the CaO raw material, the CaSO ₄ raw material, and the Al ₂ O ₃ raw material, and mixing the raw materials so as to obtain a predetermined mineral composition as shown in the materials used. and clinker by heat treatment using a small electric furnace, and then pulverized by a ball mill.

(Material used)
Expansion composition A: ettringite-lime composite expansion material. 50% free lime, 10% ellimite, 21% anhydrogypsum in the leavening composition. Density 3.10 g/cm ³ . Blaine specific surface area of 4,000 cm ² /g.
Expanding composition b: Lime-based expanding material. 30% free lime, 25% calcium silicate, 26% anhydrogypsum, density 3.20 g/cm ³ in the swelling composition. Blaine specific surface area of 4,000 cm ² /g.
Intumescent composition C: Lime-based intumescent material. 90% free lime, 4% calcium silicate, 3% anhydrogypsum, density 3.28 g/cm ³ in the swelling composition. Blaine specific surface area of 3,500 cm ² /g. Firing temperature 1350°C. Small electric furnace fired product.
Expanding composition D: Lime-based expanding material. 90% free lime, 4% calcium silicate, 3% anhydrous gypsum, density 3.27 g/cm ³ in the swelling composition. Blaine specific surface area of 3,500 cm ² /g. Firing temperature 1250°C. Small electric furnace fired product.
Expanding composition E: Lime-based expanding material. 90% free lime, 4% calcium silicate, 3% anhydrous gypsum, density 3.26 g/cm ³ in the swelling composition. Blaine specific surface area of 3,500 cm ² /g. Firing temperature 1150°C. Small electric furnace fired product.
Expanding composition F: Lime-based expanding material. 90% free lime, 4% calcium silicate, 3% anhydrous gypsum, density 3.26 g/cm ³ in the swelling composition. Blaine specific surface area of 7,000 cm ² /g. Firing temperature 1350°C. Small electric furnace fired product.

(Test method)
Arrival time: Fuchs method test. Take 50 ml of 0.1 N hydrochloric acid in a beaker, add 1 g of the expansion composition, stir, and measure the pH to obtain the initial pH. 2 ml of 1 N hydrochloric acid was added every 10 minutes from the start of stirring until the initial pH was reached, and the time from the addition of the swelling composition until the pH reached 3.0 was defined as the reaching time.
Maximum pH: Fuchs method test. Highest pH between arrival time and pH 3.0.

Storage stability: The ratio (%) of the weight after storage for 7 days and 28 days to 100% of the weight of the expanded composition immediately after preparation was determined. The expanded material was placed in a plastic cup, left to stand, and stored in an open state in a constant temperature room at a temperature of 20° C. and a humidity of 60% RH for 7 days and 28 days.

From Table 1, the maximum pH measured by the Fuchs method test is 11.5 to 13.0, and the duration of maintaining pH 3.0 or more measured by the Fuchs method test is more than 100 minutes and within 130 minutes. It can be seen that the composition is particularly excellent in storage stability.

A mortar with 420 g of cement, 30 g of inflating composition, 1350 g of fine aggregate, and a water/binder (cement) ratio of 50% was prepared using the types of swelling materials shown in Table 2, and the length change was measured. Table 2 shows the results.

(Material used)
Cement: Ordinary Portland cement, commercial product, Blaine specific surface area 3,200 cm ² /g.
Fine aggregate: Standard sand for cement strength test. Density 2.64 g/cm ³ .
Water: tap water.

(Test method)
Length change measurement: The length change was measured at 3 days and 7 days of age according to JIS A 6202.

From Table 2, the maximum pH measured by the Fuchs method test is 11.5 to 13.0, and the duration of maintaining pH 3.0 or more measured by the Fuchs method test is more than 60 minutes and within 130 minutes. It can be seen that the composition has a large rate of change in length and can effectively impart swelling.

The inflatable composition of the present invention can be widely used in the fields of civil engineering and construction.

Claims (6)

It contains free lime, hydraulic compounds other than gypsum, and anhydrous gypsum, and has a maximum pH of 11.5 to 13.0 as measured by the Fuchs method test,
The hydraulic compound is 3CaO.3Al ₂ O ₃ .CaSO ₄ , 2CaO.SiO ₂ , 6CaO.2Al 2 O _{3 .Fe 2} O ₃ , 6CaO.Al ₂ O ₃ .Fe ₂ O ₃ , and 2CaO.Fe ₂ An expanding composition that is one or more selected from the group consisting of _O3 ,
The swelling composition is clinker or a clinker pulverized product obtained by pulverizing the clinker,
The free lime content is 10 to 93 parts by mass in 100 parts by mass of the clinker,
The content of the hydraulic compound is 3 to 50 parts by mass in 100 parts by mass of the clinker,
An expanding composition in which the content of the anhydride gypsum is 1 to 50 parts by mass per 100 parts by mass of the clinker (excluding the expanding compositions (A) to (C) having the following composition).
Expansion composition (A): 50 parts by mass of free lime, 10 parts by mass of Auin, 5 parts by mass of calcium aluminoferrite (4CaO·Al ₂ O ₃ ·Fe ₂ O ₃ ), 5 parts by mass of calcium silicate (2CaO·SiO ₂ ), Anhydrous gypsum 30 parts by mass
Expansion composition (B): 10 parts by mass of free lime, 30 parts by mass of Auin, 5 parts by mass of calcium aluminoferrite (4CaO·Al ₂ O ₃ ·Fe ₂ O ₃ ), 10 parts by mass of calcium silicate (2CaO·SiO ₂ ), Anhydrous gypsum 45 parts by mass
Expansion composition (C): 70 parts by mass of free lime, 10 parts by mass of Auin, 5 parts by mass of calcium aluminoferrite (4CaO·Al 2 O 3 ·Fe 2 O 3 ), ₅ parts _by mass _of calcium _silicate ( 2CaO·SiO ₂ ), 10 parts by mass of anhydrous gypsum 2. The swelling composition according to claim 1, wherein the time to reach pH 3.0 as measured by the Fuchs method test is within 10 seconds. 3. The swelling composition according to claim 1 or 2, wherein the duration of maintaining a pH of 3.0 or more as measured by the Fuchs method test exceeds 100 minutes and is within 130 minutes. The expanding composition according to any one of claims 1 to 3, having a Blaine specific surface area of 2000 to 6000 cm ² /g. A cement composition comprising the expanding composition according to any one of claims 1-4. Cement-concrete containing the cement composition according to claim 5.