JP2014148446A - Method of producing concrete and concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide concrete whose fluidity has no possibility of reduction and which can exhibit excellent crack self-healing property at a low cost, and to provide a method of producing the concrete.SOLUTION: The method of producing the concrete includes a coarse aggregate particles making step of making coarse aggregate particles to the surface of which a cement paste is adhered by mixing cement of 100 pts.mass, water of 12 to 35 pts.mass, coarse aggregate of 500 to 1,000 pts.mass and a hardening accelerator of 0.5 to 5 pts.mass, a mortar making step of making a fresh mortar by mixing cement of 100 pts.mass, water of 38 to 65 pts.mass, a fine aggregate of 200 to 400 pts.mass and a setting retarder of 0.05 to 1.5 pts.mass, and a mixing step of mixing the coarse aggregate particles and the flesh mortar with a volume ratio of 3:7 to 5:5.

Description

  The present invention relates to a method for producing concrete and concrete produced by the method.

Cemented hardened bodies such as concrete are hardened by the hydration reaction of the cement contained in the cement composition. However, after hardening, the hardened body is affected by stress or changes in temperature and humidity. Cracks may occur.
Cracked concrete has the problem of causing water leakage and the like in addition to strength reduction and appearance deterioration.

  Therefore, in recent years, a concrete having so-called self-healing properties, in which cracks are naturally closed if moisture is present even when cracks occur after curing, has been studied. In order to obtain such self-healing concrete, various cement mixed materials are blended into the cement composition.

For example, Patent Documents 1 to 3 describe a cement composition in which an expansion material having an action of reacting with calcium hydroxide or the like in cement to generate insoluble crystals is blended.
Patent Document 4 describes a cement composition in which an aluminosilicate having swelling property is further blended in addition to the expansion material.
Patent Document 5 describes a cement mixed material that is granulated by kneading a component such as an expanding material component, a latent hydraulic material, calcium oxide, cement, and water.
In Patent Documents 6 and 7, a bone for cement-cured body loaded with a porous carrier obtained by mixing a waterproofing agent / water-stopping agent / deterioration inhibitor such as water-soluble silicic fluoride with cement. The materials are listed.

  In other words, Patent Documents 1 to 7 describe a component that reacts with a component in a cement composition in the presence of water in the presence of water to generate crystals or the like, or a component that expands (hereinafter, self-healing). It is described that, by blending a component into a cement composition, the concrete is imparted with a crack self-healing property capable of closing the crack and self-healing.

However, since the self-healing components described in Patent Documents 1 to 4 are materials having high water absorption, swelling property, and high reaction activity with water, when mixed into a cement composition as it is, the flow of coarse aggregate particles There is a risk of reducing the performance.
In order to suppress such a decrease in fluidity, it is necessary to increase the amount of water-reducing agent or high-performance water-reducing agent. However, if the amount of water-reducing agent or high-performance water-reducing agent is increased, setting delay or There is a risk that strength will be reduced. In addition, there is a problem that the cost of the self-healing component and the cost for increasing the water reducing agent, the high performance water reducing agent and the like are increased.

  Like the cement admixture described in Patent Document 5, the use of a cement admixture granulated by kneading the self-healing component together with cement can suppress a decrease in fluidity to some extent. However, in the case of a granulated product, since the above components are also present in the central part, the components in the central part may remain unreacted in the granulated product without reacting with water when cracking occurs. . Also in the aggregates described in Patent Documents 6 and 7, since the carrier is a porous body, the components present in the pores may remain unreacted with water. Therefore, in order to obtain sufficient crack self-healing properties, the mixture described in Patent Documents 5 to 7 needs to be added to the cement composition in anticipation of the unreacted residual amount, which increases the material cost. There is a problem.

Japanese Patent No. 3658568 JP 2005-239482 A JP 2007-332010 A JP 2009-190937 A JP 2011-57520 A JP 2003-95715 A Japanese Patent No. 4285675

  In view of the above problems, an object of the present invention is to provide a concrete that can exhibit excellent crack self-healing properties and a method for producing the same without lowering the fluidity and at a low cost.

The method for producing the concrete of the present invention comprises:
Coarse aggregate particles in which cement paste is adhered to the surface by mixing 100 parts by mass of cement, 12 to 35 parts by mass of water, 500 to 1000 parts by mass of coarse aggregate, and 0.5 to 5 parts by mass of a hardening accelerator Coarse aggregate particle production process for producing
A mortar preparation step for preparing a fresh mortar by kneading 100 parts by weight of cement, 38 to 65 parts by weight of water, 200 to 400 parts by weight of fine aggregate, and 0.05 to 1.5 parts by weight of a setting retarder; ,
A mixing step of mixing the coarse aggregate particles and the fresh mortar so as to have a volume ratio of 3: 7 to 5: 5.

According to the present invention, the coarse aggregate particles and the fresh mortar are prepared separately, and then the coarse aggregate particles and the fresh mortar are mixed. A relatively large amount of reactive cement can be present. Moreover, unreacted cement can be made to exist in the cement paste near the surface of the coarse aggregate by mixing coarse aggregate particles and fresh mortar in the volume ratio. Therefore, when a crack occurs in the concrete after hardening, a large amount of unreacted cement can be present in the cross section of the crack. Therefore, when water is supplied to the crack cross section, a hardening reaction occurs due to hydration of the cement, and a concrete having excellent crack self-healing property can be obtained without adding a self-healing component in addition to cement.
Moreover, since cracks are healed by the hydration reaction of unreacted cement, other special self-healing materials are not required, and concrete having self-healing properties can be manufactured at low cost. Furthermore, since it is not necessary to add a self-healing component that inhibits fluidity, it is not necessary to increase the amount of water-reducing agent or high-performance water-reducing agent added to suppress a decrease in fluidity. Therefore, the fall of the fluidity | liquidity of concrete can be suppressed at low cost.

  In the present invention, the coarse aggregate particle preparation step further includes at least one selected from the group consisting of a thickener, calcium sulfate, calcium hydroxide, calcium oxide, aluminum hydroxide, bentonite, iron, and an iron compound. You may mix.

  In the coarse aggregate particle preparation step, by mixing at least one selected from the group consisting of a thickener, calcium sulfate, calcium hydroxide, calcium oxide, aluminum hydroxide, bentonite, iron and iron compounds, These components can be present together with the cement near the surface of the coarse aggregate. Therefore, when cracks occur in the concrete, each of the above components works as a self-healing component together with unreacted cement in the vicinity of the surface of the coarse aggregate, and a concrete with higher self-healing property of cracks can be obtained.

  In the present invention, in the mortar preparation step, at least one selected from the group consisting of fine limestone powder, fine blast furnace slag powder, fly ash, and calcium oxide powder may be further mixed.

  In the mortar preparation step, the coarse aggregate particles and the fresh mortar were mixed by mixing at least one selected from the group consisting of limestone fine powder, blast furnace slag fine powder, fly ash, and calcium oxide powder. The fall of the fluidity at the time can be suppressed. Moreover, it can suppress that the intensity | strength of the concrete after hardening becomes high excessively and a coarse aggregate fractures | ruptures by a crack. In addition, these components promote the hydration reaction of the cement, so if cracking occurs in the concrete, the hydration reaction of the unreacted cement in the crack cross section is promoted, resulting in a concrete that is easier to self-heal the cracks. It is done.

  In the present invention, the curing accelerator may be an inorganic sulfate.

  When the hardening accelerator is an inorganic sulfate, it becomes easier for unreacted cement to exist near the surface of the coarse aggregate.

  In the present invention, the setting retarder may be at least one selected from the group consisting of oxycarboxylic acid and oxycarboxylate.

  When the setting retarder is at least one selected from the group consisting of oxycarboxylic acid and oxycarboxylate, the fluidity is more reduced when the coarse aggregate particles and the fresh mortar are mixed. Can be suppressed.

The coarse aggregate particle production step includes
An adhering step in which cement, water and coarse aggregate are mixed to attach the cement paste to the surface of the coarse aggregate;
A curing step of curing the cement paste by mixing the curing accelerator with the coarse aggregate particles to which the cement paste is adhered in the adhesion step.

  When the coarse aggregate particle preparation step includes the adhesion step and the hardening step, the cement paste can be attached to the surface of the coarse aggregate by mixing cement, water, and the coarse aggregate, Then, by adding and mixing the hardening accelerator, the cement paste adhering to the coarse aggregate particles is hardened, so that there is more reliably a paste containing unhydrated cement on the surface of the coarse aggregate. Can be made. Therefore, even after the coarse aggregate particles and the fresh mortar are mixed, unreacted cement can be surely present in the vicinity of the surface of the coarse aggregate, and exhibits superior crack self-healing properties. sell.

  This invention is the concrete manufactured by the manufacturing method of each said concrete.

  According to the present invention, it is possible to obtain a concrete that can exhibit excellent crack self-healing property at a low cost without any risk of lowering fluidity.

The partial cross section figure which shows the outline of the concrete of this embodiment.

Hereinafter, the concrete manufacturing method and concrete of the present invention will be described.
The concrete production method of this embodiment is:
Coarse aggregate particles in which cement paste is adhered to the surface by mixing 100 parts by mass of cement, 12 to 35 parts by mass of water, 500 to 1000 parts by mass of coarse aggregate, and 0.5 to 5 parts by mass of a hardening accelerator Coarse aggregate particle production process for producing
A mortar preparation step of preparing fresh mortar by mixing 100 parts by weight of cement, 38 to 65 parts by weight of water, 200 to 400 parts by weight of fine aggregate, and 0.05 to 1.5 parts by weight of a setting retarder; ,
A mixing step of mixing the coarse aggregate particles and the fresh mortar within a volume ratio of 3: 7 to 5: 5.

  In the concrete manufacturing method of the embodiment, the coarse aggregate particle preparation step and the fresh mortar preparation step are separately performed, but both steps may be performed in parallel at the same time, and one step is performed. Then, the other step may be performed thereafter.

"Coarse aggregate particle production process"
The coarse aggregate particle preparation step of the present embodiment mixes 100 parts by mass of cement, 12 to 35 parts by mass of water, 500 to 1000 parts by mass of coarse aggregate, and 0.5 to 5 parts by mass of a hardening accelerator. To produce coarse aggregate particles with cement paste on the surface.

  In the coarse aggregate particle creation step of the present embodiment, for example, the method of mixing cement, water, coarse aggregate, and a hardening accelerator may mix all materials at once, or After mixing a part, the remaining ingredients may be added and mixed.

The coarse aggregate particle production process of the present embodiment includes, for example, an adhesion process in which cement, water, and coarse aggregate are mixed and cement paste is adhered to the coarse aggregate surface.
A curing step of curing the cement paste by mixing the curing accelerator with the coarse aggregate particles to which the cement paste is adhered in the adhesion step.

In the adhesion step, first, a material other than the hardening accelerator, cement, water, coarse aggregate, and other ingredients that can be blended as necessary are mixed on the surface of the coarse aggregate. Adhere cement paste.
Further, in the hardening step, a hardening accelerator is added to and mixed with the coarse aggregate having the cement paste attached to the surface in the attaching step, and the cement paste attached to the surface of the coarse aggregate is hardened.
In this way, the cement paste is attached to the surface of the coarse aggregate and then the hardening paste is added to harden the cement paste, so that the unreacted cement is present on the surface of the coarse aggregate particles more reliably. Can do.

  In the concrete production method of the present embodiment, as a mixing device used in the coarse aggregate particle preparation step, the fresh mortar preparation step, and the mixing step, for example, a forced biaxial type, a forced uniaxial type, a tilted barrel type, Examples thereof include actual mixers of known ready-mixed concrete production facilities such as a pan-type forced type, truck agitator vehicles, and small test mixers.

The mixing apparatus used in the coarse aggregate particle preparation process of the present embodiment, for example, 0.1m ³ ~6m ³ about the capacity of the mixer is preferred.
First, coarse aggregate, cement, water, and a hardening accelerator are put into the mixer and mixed at a rotation speed of about 10 to 60 rpm for about 30 seconds to 120 seconds.
The kneading time is preferably about 60 to 240 seconds in total before and after adding the curing accelerator.
Thereafter, the cement paste on the surface of the coarse aggregate may be hardened while the mixer is further rotated at a rotational speed of about 10 to 60 rpm for about 30 seconds to 120 seconds.
Alternatively, first, coarse aggregates other than the curing accelerator, cement, and water are put into the mixer and mixed at a rotational speed of about 10 to 60 rpm for 30 seconds to 120 seconds. Thereafter, a paste accelerator containing cement on the surface of the coarse aggregate may be hardened while adding a hardening accelerator and further rotating the mixer at a rotational speed of about 10 to 60 rpm for about 60 seconds to 240 seconds.

In addition, you may implement the said adhesion process and the said hardening process using another apparatus.
For example, after mixing coarse aggregate, cement, and water with the mixer, the mixture is put into another mixing device, and a hardening accelerator is added to the mixing device at a rotation speed of about 1 to 10 rpm. The coarse aggregate particles may be obtained by mixing for about 1 minute to 120 minutes and curing the paste layer containing the unhydrated cement on the surface of the coarse aggregate.
As the other mixing device, for example, a truck agitator vehicle for transporting ready-mixed concrete may be used. In this case, the fresh mortar obtained in the fresh mortar preparation step described later is mixed with the coarse aggregate particles by being put into the agitator car, and then moved to the concrete construction place to perform the concrete construction. May be.

The coarse aggregate particles produced in the coarse aggregate particle production step are adhered so that the cement paste forms a layer on the surface. The thickness of the cement paste layer is preferably an average thickness of 0.1 mm to 0.5 mm, and more preferably 0.2 mm to 0.3 mm.
When the thickness of the layer is within the above range, higher crack self-healing performance can be obtained in the crack cross section.

The method for measuring the thickness of the cement paste layer of the coarse aggregate particles is as follows.
1 kg of coarse aggregate particles are collected, spread thinly in a polyethylene bag having a size of 900 mm × 500 mm × thickness 0.1 mm, and sealed and stored for one day, and then the collected coarse aggregate particles are added to JIS Z 8801. -1 is a test sieve specified in “Test Net Sieve Part 1: Metal Net Sieve”, which is passed through a sieve with a nominal aperture of 4.75 mm, and optionally 10 particles are removed from the particles remaining on the sieve. The taken coarse aggregate particles are crushed with a hammer, and a cross-sectional image of the paste layer on the fracture surface of the coarse aggregate particles is taken using an optical microscope or a digital microscope. The average of the measured values at a total of 20 points where the thickness of the layer was measured is calculated and set as the layer thickness.

  Each material used in this coarse aggregate particle preparation step is as follows.

(cement)
Although it does not specifically limit as said cement, Portland cement, the mixed cement based on Portland cement, a super-hard-hardening cement, other well-known cements, etc. are mentioned.
Examples of the Portland cement include various Portland cements defined in JIS R 5210 “Portland cement” such as normal, early strength, very early strength, moderate heat, low heat, very early strength, and sulfate resistance.
As the mixed cement based on Portland cement, types A, B and C of blast furnace cement specified in JIS R 5211 “Blast Furnace Cement”, and Class A of silica cement specified in JIS R 5212 “Silica Cement”. , B type, C type, A type, B type, C type of fly ash cement specified in JIS R 5213 “Fly ash cement”.
The ultra-fast curing cement, alumina cement meets the specifications of the old JIS R 2511 "alumina cement refractories" or _{11CaO · 7Al 2 O 3 · CaX} 2 ( halogen element such as X is F) based ultra rapid setting cement, Auin = calcium sulfoaluminate (3CaO.3Al ₂ O ₃ .CaSO ₄ ) type super-hard cement, etc.
Examples of the other cements include ordinary ecocements defined in JIS R 5214 “Ecocement”.
The cement may be used alone or in any combination.

Among these cements, early-strength Portland cement and super-early-strength Portland cement have a high Blaine specific surface area and a high alite (3CaO · SiO ₂ ) content, so that they harden in a short time on the surface of the coarse aggregate. This is preferable because unreacted cement is easily present.
Further, early-strength Portland cement, super-early-strength Portland cement and alumina cement are preferable because the cement paste can be cured in a short time because the curing time is fast.
Among these, early-strength Portland cement is preferable because it is inexpensive and easily available.
When alumina cement is used, high alumina type alumina cement containing 55% by mass or more of alumina (Al ₂ O ₃ ) can produce a large amount of hydrates such as expansive ettringite. The self-healing performance can be further improved, which is preferable.

(water)
Water used in the coarse aggregate particle production process of the present embodiment includes tap water, industrial water, ground water, river water, rain water, distilled water, high-purity water for chemical analysis (ultra pure water, pure water, ion exchange) Water).
It is preferable that water does not contain impurities such as organic substances, chloride ions, sodium ions, potassium ions and the like that adversely affect cement hydration reaction, mortar and concrete hardened bodies.
Of these, tap water or industrial water is preferable because it is inexpensive and stable in quality.

  The amount of water is preferably in the range of 12 to 35 parts by mass with respect to 100 parts by mass of cement. When the amount of water is within the above range, unreacted cement is likely to be present on the surface of the coarse aggregate.

(Coarse aggregate)
In this embodiment, the coarse aggregate used in the process of producing coarse aggregate particles includes land gravel (mountain gravel), sea gravel, river gravel, crushed stone, blast furnace slag coarse aggregate, artificial lightweight coarse aggregate, regenerated coarse bone Material, molten slag coarse aggregate and the like.
Among them, crushed stones suitable for various gravels and JIS A 5005 “crushed stone for concrete and crushed sand” are preferable because they are inexpensive and easily available.
Further, among crushed stones, limestone crushed stones are particularly preferable because they reduce the drying shrinkage of concrete, suppress the occurrence of cracks themselves, or reduce the width of cracks.
In addition, as for coarse aggregate, the particle size measured according to the screening test of JISA1102 is preferable about 5-40 mm, for example.

The amount of the coarse aggregate is preferably 500 to 1000 parts by mass with respect to 100 parts by mass of the cement for coarse aggregate particles.
When the amount of coarse aggregate is within the above range, unreacted cement is likely to be present on the surface of the coarse aggregate.
The coarse aggregate may be in any state of an air-dried state, a surface-dried state, and a state having surface water.

(Fine aggregate)
The coarse aggregate particles of this embodiment may further contain fine aggregate.
As the fine aggregate, land sand (mountain sand), sea sand, river sand, crushed sand, quartz sand, blast furnace slag fine aggregate, ferronickel slag fine aggregate, copper slag fine aggregate, electric furnace oxidation slag fine aggregate, Examples include ferrochrome fine aggregate, artificial light-weight fine aggregate, recycled fine aggregate, and molten slag fine aggregate.
Among them, land sand, crushed sand suitable for JIS A 5005 “crushed stone for concrete and crushed sand” is preferable because it is inexpensive and easily available.
Furthermore, among the crushed sand, limestone crushed sand is particularly preferable because it can reduce drying shrinkage of concrete, suppress the occurrence of cracks themselves, or reduce the width of cracks.
The fine aggregate preferably has a particle size measured according to a screening test of JIS A 1102 of, for example, about 0.15 to 5 mm.
When a fine aggregate is added to the coarse aggregate particles, it is preferable to perform internal substitution by about 1 to 10% by mass of the coarse aggregate particles.

(Curing accelerator)
The coarse aggregate particles of this embodiment contain a hardening accelerator.
The curing accelerator is not particularly limited, and can be selected from known curing accelerators for concrete. Examples of the curing accelerator include inorganic curing accelerators and organic curing accelerators.
For example, inorganic curing accelerators include inorganic sulfates such as aluminum sulfate, lithium sulfate, sodium sulfate, potassium sulfate, and sodium potassium sulfate; sodium carbonate, potassium carbonate, lithium carbonate, sodium bicarbonate, potassium bicarbonate, carbonate Alkali carbonates such as lithium hydrogen; sodium silicates such as water glass; aluminates such as sodium aluminate, potassium aluminate and calcium aluminate; cyanates; strong alkalis such as sodium hydroxide and potassium hydroxide Can be mentioned.
Examples of organic curing accelerators include amines such as diethanolamine and triethanolamine; calcium salts of organic acids such as calcium formate, calcium acetate, and calcium salts of acrylic acid.
Among these, inorganic curing accelerators are preferable because they are inexpensive and have high safety.
Among the inorganic curing accelerators, inorganic sulfates, alkali carbonates, sodium silicates, and aluminates are preferable, and inorganic sulfates are more preferable. By using an inorganic sulfate, it becomes easier for unreacted cement to exist near the surface of the coarse aggregate.
In addition, when using an inorganic sulfate as a hardening accelerator, it is preferable to use early-strength Portland cement among the above-mentioned cements because the curability is improved by using it together with the inorganic sulfate.
The curing accelerators may be used alone or in any combination.

  Among the inorganic sulfates, aluminum sulfate, lithium sulfate, and sodium sulfate are particularly preferable.

《Aluminum sulfate》
Examples of aluminum sulfate include a general powdered or flaky industrial sulfuric acid band (aluminum sulfate = Al ₂ (SO ₄ ) ₃ ), a liquid sulfuric acid band dissolved in water, and the like.
These aluminum sulfates may be either aluminum sulfate having crystal water or anhydrous aluminum sulfate.
Among them, powdered anhydrous aluminum sulfate containing no crystallization water is preferable because it is easily pulverized, and a powder whose maximum particle size is adjusted to 0.1 mm or less is particularly preferable because it is easily dissolved in water.

《Lithium sulfate》
Examples of the lithium sulfate include general powdered or flaky industrial lithium sulfate (Li ₂ SO ₄ ), an aqueous lithium sulfate solution dissolved in water, and the like.
These lithium sulfates may be either lithium sulfate having crystal water or anhydrous lithium sulfate.
Among them, powdery lithium sulfate monohydrate having low hygroscopicity is preferable because it is easily pulverized, and one having a maximum particle size adjusted to 0.1 mm or less is particularly preferable because it is easily dissolved in water.

《Sodium sulfate》
Examples of sodium sulfate include general powdered or flaky anhydrous sodium sulfate (Na ₂ SO ₄ ), sodium sulfate hydrate (Na ₂ SO ₄ .10H ₂ O), and an aqueous sodium sulfate solution dissolved in water. Can be mentioned.
These sodium sulfates may be either sodium sulfate having crystal water or anhydrous sodium sulfate.
Among these, powdered anhydrous sodium sulfate containing no crystallization water is preferable because it is easy to grind, and a powder whose maximum particle size is adjusted to 0.1 mm or less is particularly preferable because it is easily dissolved in water.

The amount of the hardening accelerator contained in the coarse aggregate particles is preferably 0.5 to 5 parts by mass, preferably 1 to 3 parts by mass in terms of solid content with respect to 100 parts by mass of the cement for coarse aggregate particles. Is more preferable.
When the amount of the hardening accelerator in the coarse aggregate particles is within the above range, unreacted cement is more likely to be present in the vicinity of the surface of the coarse aggregate, and the hardening delay of the coarse aggregate particles and the freshness described later. In the process of mixing with mortar, false setting (stiffness) of concrete can be suppressed.

As the curing accelerator, a powdery one may be used, or a liquid one (for example, an aqueous solution) may be used. In the case of using a liquid curing accelerator, the moisture contained in the curing accelerator is converted into the amount of the water, that is, the moisture contained in the curing accelerator is mixed with water for producing coarse aggregate particles. Is preferably deducted from.
In addition, solid content conversion of a hardening accelerator means the value converted from the solid content rate computed from the solid content obtained by heating until it becomes constant weight at 105 degreeC.

Furthermore, the curing accelerator may be impregnated (supported) in a carrier such as an artificial lightweight aggregate in advance. When a curing accelerator is used by impregnating such a carrier, it is preferable because the handling of the curing accelerator becomes easy. In this case, it is preferable to use a liquid accelerator as the hardening accelerator because the hardening accelerator can be easily supported on the carrier by immersing the carrier in the hardening accelerator.
The carrier is preferably an artificial lightweight aggregate. Since the artificial lightweight aggregate has internal voids, it can be easily impregnated with a hardening accelerator. As the artificial lightweight aggregate, the absolute dry density conforming to JIS A 5002 “lightweight concrete aggregate for structure” = around 1.6 g / cm ³ , 24-hour water absorption = about 10% by mass, coarse particle ratio = FM is 2 About .75 is preferable because it is inexpensive and easily available.
When the curing accelerator is used by impregnating the carrier, the amount of the carrier is, for example, from 10 parts by mass to 30 parts by mass with respect to 1 part by mass of the curing accelerator (solid content conversion). preferable.

(Self-healing aid)
In the coarse aggregate particle production step of the present embodiment, at least one selected from the group consisting of thickeners, calcium sulfate, calcium hydroxide, calcium oxide, aluminum hydroxide, bentonite, iron, and iron compounds is further added. You may mix as a healing aid.
Thickeners, calcium sulfate, calcium hydroxide, calcium oxide, aluminum hydroxide, bentonite, iron, and iron compounds can function as self-healing aids that increase self-healing properties together with unreacted cement.
These self-healing aids may be used alone or in any combination.

<Thickener>
The thickener is not particularly limited, and can be selected from known thickeners for concrete. Examples of the thickener include cellulose thickeners such as methylcellulose (MC), hydroxypropylmethylcellulose (HPMC), and hydroxyethylmethylcellulose (HEMC); synthetic resin thickeners such as polyacrylic acid and polyacrylamide Agents: thickeners of natural thickening polysaccharides (glucan) such as guar gum derivatives such as biogum, guar gum, hydroxypropyl guar gum, cationized guar gum, guar gum hydrolyzate such as welan gum, diyutan gum, xanthan gum, gellan gum Is mentioned.
Among them, the cellulose-based thickener is particularly preferable because it is easily available and has high safety.
The thickeners may be used alone or in any combination.

The amount of the thickening agent is preferably 0.05 to 1 part by mass with internal substitution with respect to 100 parts by mass of the cement for coarse aggregate particles.
When the amount is within the above range, the viscosity of the cement paste increases moderately, and the cement paste easily adheres to the surface of the coarse aggregate. As a result, self-cracking due to unreacted cement occurs. The healing ability can be used effectively.
Furthermore, when the viscosity of the cement paste is increased moderately, the cement paste hardly remains in the mixer after the kneading and the loss of raw materials and the cleaning effort can be reduced.
As the thickener, a powdery one or a soluble one may be used. When using a liquid thickener, it is preferable to convert the water contained in the thickener to the amount of water.

<Calcium sulfate>
Examples of the calcium sulfate source include general industrial gypsum such as anhydrous gypsum, dihydrate gypsum, and hemihydrate gypsum. The industrial gypsum is any of by-products such as natural products, by-product gypsum during flue gas desulfurization, by-product gypsum during hydrofluoric acid production, by-product gypsum during phosphoric acid production, and by-product gypsum during titanium oxide production. Also good.
Among these, anhydrous gypsum is preferable because it has an SO ₃ content of 55% by mass or more, does not contain moisture, and is easily pulverized.
It is preferable to use the anhydrous gypsum adjusted to a maximum particle size of 0.1 mm or less. Further, among the above anhydrous gypsum, it is particularly preferable to use one that has been finely pulverized until the Blaine specific surface area becomes 5000 cm ² / g or more.
Calcium sulfate sources may be used alone or in any combination.

The calcium sulfate source is preferably mixed so as to be contained in an amount of 1 to 10 parts by mass as CaSO ₄ by internal substitution with respect to 100 parts by mass of the cement for coarse aggregate particles.
When the amount is in the above range, the presence of calcium sulfate together with unreacted cement in the vicinity of the surface of the coarse aggregate causes a calcium aluminate derived from cement in the vicinity of the surface of the coarse aggregate when cracking occurs. It is preferable to generate a sufficient amount of hydrate such as ettringite that reacts with the self-healing cracks to enhance the self-healing effect of the cement.

"Calcium hydroxide"
Examples of the calcium hydroxide source include slaked lime. Preferably, commercially available products such as special slaked lime, No. 1 slaked lime and No. 2 slaked lime that conform to JIS R 9001 “industrial slaked lime” and the like.
Among them, it is preferable to use special slaked lime, No. 1 slaked lime, etc., which are inexpensive industrial slaked lime having a Ca (OH) ₂ content of 70% by mass or more and a maximum particle size of 0.1 mm or less. .
Each of the calcium hydroxide sources may be used alone or in any combination.

The calcium hydroxide source is preferably mixed so that 1 to 30 parts by mass of Ca (OH) ₂ is contained by internal substitution with respect to 100 parts by mass of the cement for coarse aggregate particles.
When the amount is in the above range, the presence of calcium hydroxide along with the unreacted cement near the surface of the coarse aggregate, and when cracking occurs, the calcium aluminum derived from cement is near the surface of the coarse aggregate. Calcium aluminate hydrate such as hydrocalumite can be produced by reacting with the carbonate, and when water is supplied to the cracked part, it reacts with carbonate ions supplied from the water to react with water such as calcium carbonate. Japanese products can be produced. Therefore, it is preferable because the self-healing effect can be further enhanced.

<Calcium oxide>
Examples of the calcium oxide source include quick lime for manufacturing steel pellets mainly composed of f-CaO (free calcium oxide), quick lime for steel making converter, hard calcined quick lime (dead calcined quick lime), super hard calcined quick lime, quick lime for soil improvement. Commercial lime, such as agricultural or horticultural lime, or shell ash produced by firing shells, steelmaking slag, calcia clinker, expansion material for concrete conforming to JIS A 6202 (Etringite expansion material, ettringite-lime Composite expansion material, quicklime expansion material) and the like.
Among these, concrete expansion materials (ettringite-based expansion material, ettringite-quick lime-based expansion material, quick-lime-based expansion material) conforming to JIS A 6202 that generates expansive ettringite are preferable.
The calcium oxide source may be used alone or as a mixture in any combination.

The calcium oxide source is preferably mixed so as to be contained in an amount of 1 to 10 parts by mass as CaO by internal substitution with respect to 100 parts by mass of the cement for coarse aggregate particles.
When the amount is in the above range, sulfate ions supplied from water can react with calcium aluminate derived from cement near the surface of the coarse aggregate to produce calcium aluminate hydrate such as hydrocalumite. To form hydrates such as ettringite. Alternatively, when water is supplied to the cracked portion, it can react with carbonate ions supplied from the water to produce a hydrate such as calcium carbonate. Therefore, it is preferable because the self-healing effect can be further enhanced.

<Aluminum hydroxide>
Examples of the aluminum hydroxide source include commercially available aluminum hydroxide for industrial use.
Among them, it is preferable to use inexpensive industrial aluminum hydroxide having an Al (OH) ₃ content of 60% by mass or more and a maximum particle size of 0.1 mm or less.
The aluminum hydroxide source may be used alone or mixed in any combination.

The aluminum hydroxide source is preferably mixed so as to be contained in an amount of 1 to 10 parts by mass as Al (OH) ₃ by internal substitution with respect to 100 parts by mass of the cement for coarse aggregate particles.
When the amount is within the above range, calcium aluminate hydrate can be gradually produced by reacting gradually with calcium hydroxide, which is a strong alkaline substance derived from cement, near the surface of the coarse aggregate. When water is supplied to the cracked portion, it can react with sulfate ions supplied from the water to form a hydrate such as ettringite. Therefore, it is preferable because the self-healing ability of cracks can be exhibited for a long time.

《Bentonite》
Examples of the bentonite include Na-bentonite and Ca-bentonite. Among these, Na-bentonite is preferable because it is excellent in swelling property, and Na-bentonite produced in Wyoming, North America is particularly preferable.
Each of the bentonites may be used alone or in any combination.

It is preferable that the amount of the bentonite is 0.5 to 30 parts by mass by internal substitution with respect to 100 parts by mass of the cement for coarse aggregate particles.
By being the quantity of the said range, when water is supplied to a crack location, a crack can be obstruct | occluded by swelling.

<Iron or iron compounds>
Examples of the iron or iron compound include metallic iron or iron oxide such as maghemite (γ-Fe ₂ O ₃ ) and magnetite (Fe ₃ O ₄ ).
Metallic iron or iron oxides (for example, maghemite (γ-Fe ₂ O ₃ ), magnetite (Fe ₃ O ₄ )) coexist with water and oxygen to cause oxidation and hydration reactions and expand. Hematite (α-Fe ₂ O ₃ ) and goethite (goethite; α-FeOOH), which are rusts, are generated, and the cracked portion can be closed. Among them, it is particularly preferable to use inexpensive industrial iron powder having an Fe (zero-valent metallic iron) content of 90% by mass or more and a maximum particle size of 0.1 mm or less.
The iron or iron compound may be used alone or in any combination.

The amount of iron or iron compound is preferably 0.5 to 5 parts by mass as FeO (in terms of divalent iron oxide) by internal substitution with respect to 100 parts by mass of the cement for coarse aggregate particles.
When the amount is in the above range, when water is supplied to the cracked portion, an oxidation reaction of iron occurs together with oxygen in the air, and the swelling can be blocked by generating swelling rust.

(Other ingredients)
The coarse aggregate particles of the present embodiment may contain other components as necessary, for example. For example, various chemical admixtures for reducing the amount of water may be included.
As the chemical admixture, known ones such as liquid or powder water reducing agents, AE water reducing agents, high performance water reducing agents, and high performance AE water reducing agents commercially available for concrete or mortar can be used.
The chemical admixture is preferably contained in an amount of about 0.1 to 3.0 parts by mass in terms of solid content with respect to 100 parts by mass of cement used in the coarse aggregate particles or the mortar.
When a liquid chemical admixture is used, it is preferable to convert the water contained in the chemical admixture into the amount of water, that is, subtract the water content contained in the chemical admixture from the water.
In addition, solid substance conversion of a chemical admixture means the value converted from the solid content rate computed from solid content obtained by heating until it becomes constant weight at 70 degreeC.

Other ingredients include clay minerals (sepiolite, attapulgite), talc, anorthite, alunite, calcium phosphate, magnesium carbonate, amorphous siliceous fine powder (silica fume), natural pozzolans (silicic acid clay, tuff, shirasu). Etc.), and powder materials such as carbonic acid diamide may be included as auxiliary materials.
By adding these auxiliary materials, the self-healing performance of cracks can be further improved.
The auxiliary material can be used alone or in an arbitrary mixing amount within a range that does not adversely affect the fluidity of the concrete of the present embodiment.

"Fresh mortar production process"
In the fresh mortar preparation process of the present embodiment, 100 parts by mass of cement, 38 to 65 parts by mass of water, 200 to 400 parts by mass of fine aggregate, and 0.05 to 1.5 parts by mass of a setting retarder are mixed. To make fresh mortar.

In the fresh mortar production process of the present embodiment, for example, cement, water, fine aggregate, and setting retarder are charged at once into a known mixing apparatus as described above, and the rotational speed is about 10 to 60 rpm. The fresh mortar may be obtained by mixing for about 30 seconds to 120 seconds.
Alternatively, a fresh mortar may be produced by mixing a part of each of the materials and then adding and mixing the remaining materials.

  Each material used in the fresh mortar production process is as follows.

(cement)
The cement used for the fresh mortar can be the same as the cement for the coarse aggregate particles.
Among these, mixed cements such as ordinary Portland cement, moderately hot Portland cement, low heat Portland cement, blast furnace cement, fly ash cement and the like are preferably used as the cement for the fresh mortar of the present embodiment because the setting time is slow. Portland cement and blast furnace cement are particularly preferable because they are inexpensive and easily available.
In addition, low heat Portland cement and medium heat Portland cement contain a large amount of belite (2CaO · SiO ₂ ), which has a slow hydration reaction. This is preferable because it is possible.

(water)
As water used in the fresh mortar preparation process of this embodiment, the same water as that used in the coarse aggregate particle preparation process can be used.
The amount of water is preferably in the range of 38 to 65 parts by mass with respect to 100 parts by mass of cement for fresh mortar. If the amount of water is within the above range, the fluidity of the mortar can be kept moderate.

(Fine aggregate)
The fresh mortar of the present embodiment includes fine aggregate.
As the fine aggregate, the same fine aggregate that can be used for the coarse aggregate particles can be used.
Among them, land sand, crushed sand suitable for JIS A 5005 “crushed stone for concrete and crushed sand” is preferable because it is inexpensive and easily available.
Furthermore, among the crushed sand, limestone crushed sand is particularly preferable because it can reduce drying shrinkage of concrete, suppress the occurrence of cracks themselves, or reduce the width of cracks.
Alternatively, since granulated slag sand suitable for blast furnace slag fine aggregate of JIS A 501-2-2 “Slag aggregate for concrete: Part 2: Blast furnace slag aggregate” has latent hydraulic properties, the cracks are self-healing. Since it is easy, it is especially preferable.

(Setting retarder)
Examples of the setting retarder include organic and inorganic ones. Examples of organic setting retarders include oxycarboxylic acids such as citric acid, gluconic acid, tartaric acid, malic acid and lactic acid; oxycarboxylic acid salts such as sodium citrate, sodium gluconate, sodium tartrate and sodium malate; Aminocarboxylic acids such as glutamic acid and salts thereof such as sodium glutamate; sugars; sugar alcohols; high molecular organic acids such as lignin sulfonic acid, humic acid and tannic acid and salts thereof; water-soluble acrylic acid such as polyacrylic acid and its Examples include salt.
Examples of the inorganic setting retarder include silicofluoride, boric acid and its compound, phosphate, zinc compound, lead compound, copper compound and the like.
Among them, oxycarboxylic acids such as citric acid, gluconic acid and tartaric acid, oxycarboxylates such as sodium citrate and sodium gluconate are preferable because they are inexpensive and highly safe.
The setting retarder may be used alone or mixed in any combination.

The amount of the setting retarder is 0.05 to 1.5 parts by mass, preferably 0.1 to 1 part by mass in terms of solid content with respect to 100 parts by mass of the cement for fresh mortar.
This is because when the amount of the setting retarder is within the above range, the setting delay of the concrete can be suppressed to an appropriate time in the mixing step with the coarse aggregate particles described later.
The setting retarder may be in the form of powder or in the form of a solution. When using a liquid setting retarder, it is preferable to convert the contained moisture into the amount of water, that is, subtract the amount of moisture contained in the set retarder from the water.
In addition, solid content conversion of a setting retarder means the value converted from the solid content rate computed from solid content obtained by heating until it becomes constant weight at 70 degreeC.

"citric acid"
Examples of citric acid include general powdered or flaky industrial or food additive anhydrous citric acid or citric acid monohydrate, aqueous citric acid solution dissolved in water, and the like.
These citric acids may be either anhydrous citric acid (C ₆ H ₈ O ₇ ) or citric acid monohydrate (C ₆ H ₈ O ₇ .H ₂ O).
Of these, anhydrous citric acid containing no water of crystallization is preferable because it is easy to handle and easily pulverized, and one having a maximum particle size adjusted to 0.1 mm or less is particularly preferable because it is easily dissolved in water.

《Sodium gluconate》
Examples of sodium gluconate include general powdered or flaky industrial or food additive gluconic anhydride (C ₆ H ₁₁ NaO ₇ ), liquid sodium gluconate aqueous solution dissolved in water, and the like.
Among these, those having a maximum particle size adjusted to 0.1 mm or less are particularly preferable because they are easy to handle and easily dissolved in water.

When the hardening accelerator used for the coarse aggregate particles is an inorganic sulfate (such as aluminum sulfate), the setting retarder used for the fresh mortar may be oxycarboxylic acid or / and oxycarboxylate. preferable.
By combining such a curing accelerator and a setting retarder, a particularly excellent self-healing effect of cracks can be exhibited, and a concrete having an excellent effect of suppressing a decrease in fluidity in the mixing process can be obtained. it can.

Specific examples of preferable combinations of the setting retarders include the following combinations.
For example, when an oxycarboxylic acid such as citric acid and an oxycarboxylic acid salt such as sodium gluconate are used in combination as a setting retarder, a high fluidity reduction suppressing effect can be achieved by adding a small amount compared to using each of them alone. can get.
When a large amount of oxycarboxylic acid is added alone to the cement composition, the cement may be corroded (neutralization reaction) by the oxycarboxylic acid, or the fluidity of fresh mortar may be reduced due to its viscosity. In addition, if a large amount of oxycarboxylate containing sodium or potassium alone is added to the cement composition, the fluidity of fresh mortar may decrease due to the viscosity of oxycarboxylate, or it may cause alkali aggregate reaction in concrete. The harmful sodium ions and potassium ions may increase.
By using both in combination, the above-described problems are unlikely to occur, and a better fluidity reduction suppressing effect can be obtained.

In addition, when the comparison was made with the change over time of 15 shot flow values measured according to the flow test using the mortar of JIS R 5201 “Cement physical method”, only the oxycarboxylic acid (citric acid) was used. Compared with mortar using only (sodium gluconate), mortar combined with citric acid and sodium gluconate was able to suppress a decrease in fluidity.
Specifically, mortar formulation: 100 parts by weight of early strength Portland cement, 300 parts by weight of fine aggregate, 50 parts by weight of water, water cement ratio = 50% by weight, oxycarboxylic acid (citric acid) as a setting retarder and What mix | blended oxycarboxylate (sodium gluconate) with the following combination was prepared.
(1) No setting retarder (2) 1 part by mass of citric acid (3) 1 part by mass of sodium gluconate (4) 0.4 part by mass of citric acid and 0.4 part by mass of sodium gluconate The above (1) to (4 ) Under the temperature conditions of the material temperature and the environmental temperature of 30 ° C., the 15-stroke flow value was measured immediately after kneading and after 30 minutes from water injection.
As a result, the flow was as follows, that is, (4) compared with (2) and (3), although the total addition amount of setting retarder was 0.8 parts by mass, The value was large and the flow value after 30 minutes was the largest.
(1): 241 mm immediately after mixing → 141 mm after 30 minutes
(2): 253 mm immediately after mixing → 198 mm after 30 minutes
(3): 261 mm immediately after mixing → 189 mm after 30 minutes
(4): 267 mm immediately after mixing → 201 mm after 30 minutes

(Mixed material)
In the fresh mortar production process of the present embodiment, at least one selected from the group consisting of limestone fine powder, blast furnace slag fine powder, fly ash, and calcium oxide powder may be mixed as a mixture.
The mixed material is mixed with the mortar cement by internal substitution.
When the said mixed material is mixed, the fluidity | liquidity fall of the concrete after mixing coarse aggregate particle | grains and fresh mortar in the mixing process mentioned later can be prevented, and it can prevent that an intensity | strength becomes high too much. When cracking occurs in the concrete after hardening, the exposed portion (interface) of the coarse aggregate having a crack cross section is likely to undergo a hydration reaction, and the crack is likely to be blocked. Therefore, a higher crack self-healing effect can be exhibited.

《Limestone fine powder》
Examples of the limestone fine powder include limestone fine powder (heavy calcium carbonate) used for general industrial product production such as glass production use, filler use, agricultural chemical carrier use, and flue gas desulfurization use, JIS A 5003 “ Examples include limestone powder suitable for “paving limestone powder”.
Among them, limestone fine powder for producing high-fluidity concrete having a fineness of about Blaine specific surface area of 3000 to 7000 cm ² / g is preferable.
The limestone fine powders may be used alone or mixed in any combination.

As for the quantity of the said limestone fine powder contained in the fresh mortar of this embodiment, 5-30 mass parts of limestone fine powder is preferable by internal substitution with respect to 100 mass parts of cement for fresh mortar.
When the amount of the limestone fine powder is within the above range, the flowability of the mortar becomes good in the mixing step described later, the strength of the concrete after hardening is prevented from becoming too high, and drying shrinkage can be further reduced.

《Blast furnace slag fine powder》
As the blast furnace slag fine powder, various blast furnace slag such as blast furnace slag fine powder 3000, blast furnace slag fine powder 4000, blast furnace slag fine powder 6000, blast furnace slag fine powder 8000 conforming to JIS A 6206 “Blast furnace slag fine powder for concrete”. A fine powder is mentioned.
Among them, blast furnace slag fine powder 4000 which is inexpensive and easily available is preferable.
The blast furnace slag fine powder may be used alone or as a mixture in any combination.

It is preferable that the quantity of the said blast furnace slag fine powder contained in the fresh mortar of this embodiment is 5-60 mass parts of blast furnace slag fine powder by internal substitution with respect to 100 mass parts of cement for fresh mortar.
When the amount of the blast furnace slag fine powder is within the above range, the flowability of the mortar becomes good in the mixing step described later, and the compressive strength of the concrete can be prevented from becoming too high.

《Fly Ash》
Examples of the fly ash include various types of fly ash such as Class I fly ash, Class II fly ash, Class III fly ash, and Class IV fly ash that conform to JIS A 6201 “Fly Ash for Concrete”.
Among these, type II fly ash which is inexpensive and easily available is preferable.
The blast furnace slag fine powder may be used alone or as a mixture in any combination.

It is preferable that the amount of the fly ash contained in the fresh mortar of the present embodiment is 5 to 30 parts by mass of fly ash by internal substitution with respect to 100 parts by mass of the cement for fresh mortar.
When the amount of fly ash is within the above range, the mortar has good fluidity in the mixing step described later, and the pozzolanic reactivity of fly ash enables the self-healing performance of cracks for a long time after the concrete is cured. Since it can be given, it is preferable.

<Calcium oxide powder>
As a raw material of the said calcium oxide powder, the thing similar to the said calcium oxide source which can be used for coarse aggregate particle | grains is mentioned.
Among these, concrete expansion materials (ettringite-based expansion material, ettringite-quick lime-based expansion material, quick-lime-based expansion material) conforming to JIS A 6202 that generates expansive ettringite are preferable.
The calcium oxide source may be used alone or as a mixture in any combination.

The amount of the calcium oxide source is preferably 1 to 10 parts by mass as CaO by internal substitution with respect to 100 parts by mass of cement for fresh mortar.
For example, when a concrete expansion material conforming to JIS A 6202 is used as the calcium oxide source, about 2 to 20 parts by mass may be mixed by 100% substitution with 100 parts by mass of fresh mortar cement. preferable.
When the amount falls within the above range, when water is supplied to the cracked portion, swellable ettringite or / and calcium hydroxide can be generated and the crack can be closed.

(Other optional ingredients)
The fresh mortar of this embodiment may contain other components as necessary. As another component, the component similar to the other component of the said coarse aggregate particle | grains can be mix | blended, for example.

"Mixing process"
In the concrete manufacturing method of the present embodiment, the mixing step of mixing the coarse aggregate particles and the fresh mortar in a volume ratio of 3: 7 to 5: 5 is performed.
The volume ratio between the coarse aggregate particles and the fresh mortar is 3: 7 to 5: 5, preferably 3: 7 to 4: 6.

  By mixing separately prepared coarse aggregate particles and fresh mortar at the volume ratio, the cement paste on the surface of the coarse aggregate particles and the cement paste of the fresh mortar are prevented from being mixed and uniformed. be able to. Therefore, it is possible to leave a cement paste in which a small amount of water cement, that is, a large amount of unreacted cement can remain on the surface of the coarse aggregate so that cracks in the concrete can be easily healed.

In particular, when the coarse aggregate particle preparation step includes the adhesion step and the curing step, a paste having a small water-cement ratio (unreacted cement) can be more reliably present on the surface of the coarse aggregate. Since it can, self-healing performance can be improved more.
In the concrete of this embodiment, the cement paste portion of the coarse aggregate particles is preferably a cement paste having a water cement ratio of 12 to 35 parts by mass, for example.

In the mixing step in the present embodiment, for example, the coarse aggregate particles and the fresh mortar may be fed into a mixing device that performs the mixing step by a predetermined amount and mixed.
Or you may implement a mixing process by mixing the said fresh mortar with the mixing apparatus which produced the said coarse aggregate particle | grains, and also mixing.
Alternatively, the coarse aggregate particle preparation step and the mixing step may be continuously performed using a truck agitator vehicle for transporting ready-mixed concrete.
In this case, first, coarse aggregate particles other than the hardening accelerator are mixed with a mixer of a ready-mixed concrete production facility, and cement paste is attached to the surface of the coarse aggregate, and then the hardening is accelerated on the agitator car. Add the agent and mix. Then, mixing is performed while rotating the drum of the agitator wheel until the cement paste on the surface of the coarse aggregate particles is hardened. Then, the fresh mortar produced with another mixer etc. is thrown into the said agitator vehicle, and the mixing process is implemented by rotating the drum of an agitator vehicle further.
Thus, when concrete is manufactured using an agitator vehicle, the concrete can be transported to the construction site as it is, and the work efficiency is good.

Or you may perform the mixing process of this embodiment in the construction site of concrete.
That is, by transporting coarse aggregate particles and fresh mortar separately to the concrete construction site, first implanting coarse aggregate particles into the construction site, and then implanting fresh mortar, so-called prepacked concrete placement method, Coarse aggregate particles and fresh mortar may be mixed (integrated) to obtain concrete.

  Next, the concrete obtained by the concrete manufacturing method of the present invention will be described.

The concrete obtained by the manufacturing method of the present embodiment is in a state where a large amount of unreacted cement exists near the surface of the coarse aggregate. For example, as shown in FIG. 1, the concrete 10 includes a mortar (with a setting retarder) 3 and a coarse bone having a cement paste (with a hardening accelerator) 2 attached to the surface of the coarse aggregate 1 so as to form a layer. Material particles 4.
The cement paste 2 of the coarse aggregate particles 4 is composed of a cement paste having a water cement ratio of 12 to 35 parts by mass as described above, and even after the concrete is hardened by the cement paste having the water cement ratio, Unreacted cement is present in the cement paste 2.

In the concrete obtained by the concrete production method of the present embodiment, it is preferable that each component is contained in the following range per 1 m ³ of the cured body.
That is, the amount of coarse aggregate is 500 to 1000 kg, preferably 600 to 800 kg. The amount of fine aggregate is 700 to 1200 kg, preferably 800 to 900 kg.
The amount of cement (including auxiliary materials, hardening accelerators, mixed materials, setting retarders and carriers) is 300 to 600 kg, preferably 400 to 500 kg.
The amount of water (including water in liquid components such as chemical admixtures) is 160 to 240 kg, preferably 180 to 200 kg.
The amount of air contained in the concrete is preferably about 4.5% (tolerance ± 1.5%), which is the amount of air in ordinary concrete as defined in JIS A5308.
If it is the range of the said air quantity, the basic physical properties of concrete, such as fluidity | liquidity or intensity | strength, frost damage resistance, can be adjusted to an appropriate range.

  For example, cracks may occur after the concrete of the present embodiment is hardened. Generally, as shown in FIG. 1, the cracks generated in the concrete may pass through the interface between C and coarse aggregate particles 4 and mortar 3. It is thought that there are many.

When the crack passes through the interface between the coarse aggregate and the mortar, there is usually a portion where the surface of the coarse aggregate is exposed in the crack cross section.
Incidentally, the exposed area of the coarse aggregate in the cross section of the crack is the unit amount of the coarse aggregate (for example, water cement ratio = 50%, design standard strength = 30 N / mm ² , target slump = 12 ± 2.5 cm, air weight = 4.5 for a ± 1.5% concrete: unit coarse aggregate weight = about 950 kg / m ^3, often in proportion to the coarse aggregate unit volume = 0.36m ³ / m ^3). That is, since the volume occupied by the coarse aggregate reaches 36% of the concrete volume, the exposed portion of the coarse aggregate in the crack cross section increases.
Even if the self-healing component is mixed in the mortar cement composition (cement + admixture with self-healing property) in the cracked section, the self-healing component is present in the exposed part of the coarse aggregate surface. No or few. And since the coarse aggregate has a very large particle diameter of 5 mm to several tens of mm, it may be a portion that is difficult to self-heal in places where the coarse aggregate exists. Therefore, there is a problem that the self-healing performance is lowered in a crack cross section where there are many exposed portions of the coarse aggregate.
On the other hand, in order to ensure that self-healing performance is imparted to concrete, increase the self-healing ability of the cement composition by adding a lot of self-healing admixtures to the cement composition constituting the mortar. Etc. are considered. However, when many admixtures with self-healing properties are added to the cement composition, there are problems such as a decrease in concrete fluidity, an excessive increase in concrete strength after hardening, an increase in self-shrinkage, and a cost increase. There is.

As described above, the concrete according to the present embodiment includes coarse aggregate particles adhered to the surface of the coarse aggregate so that the cement paste forms a layer. Therefore, the concrete is unreacted on the surface of the coarse aggregate present in the cracked cross section. Cement can be present. Therefore, in the cross section of a crack, when water is supplied by rain water, ground water, etc., the unreacted cement in the paste layer causes a hydration reaction, and the crack can be closed.
In addition, since cracks are blocked by the hydration reaction of unreacted cement, self-healing of cracks can be achieved without the addition of special admixtures with self-healing ability other than cement, or even in the absence of a large amount. Can demonstrate performance. Therefore, problems such as a decrease in fluidity due to a special admixture having self-healing ability, an excessive increase in concrete strength after curing, an increase in self-shrinkage, and an increase in cost can be suppressed.
In addition, if no special admixtures with self-healing ability other than cement are blended, storage devices and supply devices for special admixtures with self-healing ability become unnecessary, and the production cost of concrete is further reduced. Can be reduced.

  Furthermore, the concrete according to the present embodiment is mainly composed of coarse aggregate and cement, which are materials that are always provided in the ready-mix factory, and the mixing process is performed using a mixer, a truck agitator vehicle, and the like in the ready-mix factory. be able to. Therefore, in addition to not having to use special materials and equipment, it is possible to produce concrete with continuous self-healing performance in a normal ready-mixed plant without bringing in processed materials, It is possible to suppress an increase in cost due to the trouble of delivery, storage, and supply of special admixtures (eg, granulated materials) having healing ability.

  Since the concrete of this embodiment can exhibit high self-healing performance, it can self-heal even if the crack width is 0.2 to 0.3 mm, which was difficult to self-heal in the past. It becomes.

The concrete of this embodiment is, for example, a concrete viaduct superstructure, floor slab bottom and pier / abutment side, tunnel lining concrete, concrete bottom and side such as agricultural waterway, slab / wall such as office building or apartment, tunnel Leaked wall products such as segments, box culverts, retaining walls such as L-shaped retaining walls, U-shaped structures, fume pipes, utility poles, concrete blocks, concrete panels, etc., and it was difficult to repair cracks It can be suitably used for a structure.
If cracks occur in these structures and water is supplied to the cracked parts by rainfall, snowfall, groundwater infiltration, river water, seawater flow, water spraying, water injection, etc. The unreacted cement and other components cause a hydrate formation reaction with water and components in the cement, so that cracks can be effectively self-healed.

In the case where cracks occur in the concrete as described above, conventionally, repair work in which an organic or inorganic filler is injected into the cracks, or even if cracks occur, the structure is not adversely affected. Measures are taken such as waterproofing and waterproofing of concrete. However, such repair work, waterproof work, water stop work, etc. require a large cost, and if the waterproof work or water stop work is performed simultaneously with the concrete work, the construction period of the structure will be lengthened. Invite. In particular, when concrete is a structure such as a tunnel, railway viaduct, or automobile viaduct, it is necessary to take measures such as traffic regulation and suspension of operation to repair these cracks after the start of operation of the structure. It was very difficult.
Therefore, when the concrete of this embodiment is used for such a structure, the above-described repair work, waterproof work, water stop work, etc. are unnecessary or reduced by self-healing cracks. There is.

  In addition, although the concrete concerning this embodiment and its manufacturing method are as mentioned above, embodiment disclosed this time is an illustration in all the points, Comprising: It should be thought that it is not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

The equipment used in the concrete of this example is as follows.
[Used equipment]
・ Agitator (for mixing in the laboratory = coarse aggregate particles and fresh mortar are alternately produced with one mixer: SUPER DOUBLE MIXER SD-55, manufactured by Taiyo Kiko Co., Ltd., forced biaxial mixer, capacity 55 liters, rotation (Several 50rpm, 200V three-phase motor output 3.7kW)
・ Inclined mixer for concrete (simulation of agitator vehicle in test room = for concrete production, capacity 100 liter, 200V three-phase motor output 2.2 kW)
-Plastic boat (produced coarse aggregate particles, fresh mortar, for concrete cradle, manufactured by Risu Kogyo Co., Ltd., made of impact-resistant polypropylene, outer dimensions 866 mm x 522 mm x height 207 mm, capacity 60 liters)
-Ready-mixed concrete production equipment (for coarse aggregate particles and fresh mortar production with actual equipment = alternating production of coarse aggregate particles and fresh mortar with one mixer: JIS A 5308 certified factory in Chiba Prefecture, installed mixer = Nikko (Compulsory biaxial type, capacity 3.0m ³ , rotation speed 33rpm)
・ Truck agitator car (for concrete production using actual equipment: medium-sized car, manufactured by Shin Meiwa Kogyo Co., Ltd.) Vehicle dimensions: Length 6.4m x Width 2.2m x Height 3.4m, Proper load capacity 5-8t, Proper load capacity (2.5 to 4.0 m ³ , drum rotation speed 1 to 10 rpm)
・ Concrete pressure tester (manufactured by Shimadzu Corporation, maximum loading capacity 3000KN)
Digital microscope (manufactured by Keyence Corporation, body = VHX-1000, lens = VH-Z100R wide range lens (magnification 100-1000 times))

The materials used for each concrete shown in Table 1 are as follows.
[material]

(1) Cement i) Ordinary poldoland cement (manufactured by Sumitomo Osaka Cement Co., Ltd., JIS R 5210 compliant product, density = 3.15 g / cm ³ , C ₃ S content = 56 mass%, C ₂ S content = 17 mass% Al ₂ O ₃ content = 5.2% by mass, SO ₃ content = 1.9% by mass, Blaine specific surface area = 3400 cm ² / g, maximum particle size = 45 μm or less)
B) Blast furnace cement type B (manufactured by Sumitomo Osaka Cement Co., Ltd., JIS R 5211 compliant, density = 3.04 g / cm ³ , MgO content = 3.2% by mass, SO ₃ content = 1.9% by mass, brane) Specific surface area = 3750 cm ² / g, maximum particle size = 45 μm or less)
C) Hayashi Portland Cement (manufactured by Sumitomo Osaka Cement Co., Ltd., JIS R 5210 compliant, density = 3.13 g / cm ³ , C ₃ S content = 65 mass%, Al ₂ O ₃ content = 5.0 mass%) SO ₃ content = 2.8% by mass, Blaine specific surface area = 4400 cm ² / g, maximum particle size = 45 μm or less)
D) Low heat Portland cement (manufactured by Sumitomo Osaka Cement Co., Ltd., JIS R 5210 compliant product, density = 3.24 g / cm ³ , C ₂ S content = 56 mass%, Al ₂ O ₃ content = 2.7 mass%, SO ₃ content = 2.0 mass%, Blaine specific surface area = 3400 cm ² / g, maximum particle size = 45 μm or less)

(2) Water: Tap water (produced in Funabashi City, Chiba Prefecture)

(3) Other components: chemical admixture / high performance AE water reducing agent (Reobuild SP8SV, manufactured by BASF Japan, polycarboxylic acid type, JIS A 6204 high performance water reducing agent standard type II compatible product)

(4) Coarse aggregate / Coarse aggregate: Hard sandstone crushed stone from Sakuragawa City, Ibaraki Prefecture 2005 (surface dry density = 2.65 g / cm ³ , water absorption = 0.6%, FM = 6.67, JIS A 5005 Crushed stone 2005 compatible product)

(5) Fine aggregate / fine aggregate: land sand from Futtsu, Chiba (surface dry density = 2.58 g / cm ³ , water absorption = 2.1%, FM = 2.65, Annex A of JIS A 5308 Suitable for gravel and sand)

(6) Self-healing aid (The amount of blending in Table 1 is internal substitution for cement)
a) Thickener (Metroze SCH-300L, manufactured by Shin-Etsu Chemical Co., Ltd., methylcellulose, powder, maximum particle size = 0.1 mm or less)
b) Calcium sulfate (finely pulverized product of natural anhydrous gypsum, manufactured by Sumitomo Osaka Cement Co., Ltd., density = 2.97 g / cm ³ , CaO content = 41.1 mass%, Al ₂ O ₃ content = 0.1 mass) %, SO ₃ content = 56.7% by mass, Blaine specific surface area = 6800 cm ² / g, maximum particle size = 45 μm or less)
c) Calcium hydroxide (special slaked lime, manufactured by Yoshizawa Lime Industry Co., Ltd., JIS R 9001 compliant product, CaO content = 74.0% by mass, Al ₂ O ₃ content = 0.45% by mass, SO ₃ content = (Less than 0.1% by mass, density = 2.34 g / cm ³ , brain specific surface area = 5000 cm ² / g, maximum particle size = 45 μm or less)
d) calcium oxide (carbide sintered lime, Yoshizawasekkaikogyo Co., CaO content = 95.2 wt%, Al ₂ O ₃ content = 0.78 wt%, SO ₃ content = less than 0.1 wt% Density = 3.32 g / cm ³ , specific surface area of brane = 4500 cm ² / g, maximum particle size = 45 μm or less)
e) Aluminum hydroxide (reagent grade 1: pulverized aluminum hydroxide, manufactured by Kanto Chemical Co., Ltd., density = 2.4 g / cm ³ , Al ₂ O ₃ content = 60% by mass or more, SO ₃ content = 0. (Less than 1% by mass, maximum particle size = 0.1 mm or less)
f) Na-bentonite (Western gel, manufactured by Bentonite Sangyo Co., Ltd., Wyoming, USA, density = 2.24 g / cm ³ , Al ₂ O ₃ content = 20.8 mass%, SO ₃ content = 0.1 mass% Less than, maximum particle size = 0.1 mm or less)
g) Expansion material conforming to JIS A 6202 (Sachs: Ettlingite expansion material, manufactured by Sumitomo Osaka Cement Co., Ltd., density = 2.98 g / cm ³ , CaO content = 52.2 mass%, Al ₂ O ₃ content = 13.9% by mass, SO ₃ content = 30.2% by mass, Blaine specific surface area = 3200 cm ² / g, maximum particle size = 45 μm or less)
h) Iron powder (reagent: pulverized iron powder, manufactured by Kanto Chemical Co., Ltd., density = 7.6 g / cm ³ , Fe content = 90% by mass or more, maximum particle size = 0.1 mm or less)

(7) Curing accelerator promotion 1) Aluminum sulfate (reagent: ground product of aluminum sulfate 13-14 hydrate, manufactured by Kanto Chemical Co., Ltd., density = 2.71 g / cm ³ , Al ₂ O ₃ content = 14% by mass SO ₃ content = 33 mass%, maximum particle size = 0.1 mm or less)
Promotion 2) Lithium sulfate (reagent: ground product of lithium sulfate monohydrate, manufactured by Kanto Chemical Co., Inc., density = 2.21 g / cm ³ , SO ₃ content = 61 mass%, maximum particle size = 0.1 mm or less)
Promotion 3) Sodium sulfate (reagent: ground product of sodium sulfate decahydrate, manufactured by Kanto Chemical Co., Inc., density = 2.71 g / cm ³ , SO ₃ content = 53 mass%, maximum particle size = 0.1 mm or less)

(8) Artificial lightweight aggregate for carrier Mesalite fine aggregate (manufactured by Nippon Mesalite Co., Ltd., absolute dry density = 1.61 g / cm ³ , 24-hour water absorption = 10.1% by mass, coarse particle ratio (FM) = 2. 77, maximum particle size = 5 mm or less)

(9) Mixed material (The amount of blending in Table 2 is the amount of internal substitution for the cement in Table 2)
i) Limestone fine powder (Calfinder CF-90, manufactured by Omi Mining Co., Ltd., density = 2.68 g / cm ³ , CaCO ₃ content = 91.2% by mass, brane specific surface area = 5200 cm ² / g, maximum particle size = 45μm or less)
j) Blast furnace slag fine powder (JIS A 6206 blast furnace slag fine powder 4000 compatible product, manufactured by SMENT Co., Ltd., density = 2.76 g / cm ³ , brain specific surface area = 4200 cm ² / g, maximum particle size = 45 μm or less)
k) Fly ash (JIS A 6201 type II conformity product, manufactured by J-Pec Co., Ltd., density = 2.46 g / cm ³ , SiO ₂ content = 62% by mass, brane specific surface area = 4250 cm ² / g, maximum particle size = 45μm or less)
l) Expansion material conforming to JIS A 6202 (Sax: Ettlingite expansion material, manufactured by Sumitomo Osaka Cement Co., Ltd., density = 2.98 g / cm ³ , CaO content = 52.2 mass%, Al ₂ O ₃ content = 13.9% by mass, SO ₃ content = 30.2% by mass, Blaine specific surface area = 3200 cm ² / g, maximum particle size = 45 μm or less)

(10) Setting retarder slow 1) oxycarboxylic acid (reagent citrated anhydrous product, manufactured by Kanto Chemical Co., Ltd., maximum particle size = 0.1 mm or less)
Slow 2) Salt of oxycarboxylic acid (reagent sodium gluconate ground product, manufactured by Kanto Chemical Co., Ltd., maximum particle size = 0.1 mm or less)

"Coarse aggregate particles"
Coarse aggregate particles P-1 to P-38 were produced using the materials of each formulation shown in Table 1.
The manufacturing method is as follows.

(Production in test room: P-1 to P3, P-5 to P-20, P-22 to P-34)
First, coarse aggregate particles of P-1 to P3, P-5 to P-20, and P-22 to P-34 were produced in a concrete test chamber (test chamber; constant temperature of 20 ° C.). Amount of cement, coarse aggregate, water, hardening accelerator, high-performance AE water reducing agent, and self-healing aid in a total volume of 10-30 liters for the agitator (inclined mixer = for mixing in a test room) Was added and kneaded. The curing accelerator was dissolved in water and added simultaneously with water. The kneading time was initially 15 seconds with cement, coarse aggregate, and self-healing aid added, and then 120 seconds after adding water and high-performance AE water reducing agent.
The produced coarse aggregate particles were discharged from the agitator to a plastic boat and temporarily stored for 10 minutes each.

(Production (support) in actual machine: P-4, P-21)
Coarse aggregate particles of P-4 and P-21 were produced in an actual machine (fresh concrete manufacturing factory; temperature 30 ° C.).
First, a curing accelerator (solid content 2 kg) was dissolved in water in advance to prepare 5 kg of an aqueous solution having a solid content of 40% by mass, and this aqueous solution was placed in a polypropylene container having a capacity of 60 liters. An artificial lightweight fine aggregate carrying a curing accelerator was prepared by impregnating 60 kg of the artificial lightweight fine aggregate. Thereafter, the artificial lightweight fine aggregate was stored for 24 hours with stirring every 6 hours in order to uniformly impregnate the aqueous solution of the hardening accelerator without leaving (artificial lightweight fine aggregate 60 kg + water 3 kg + setting accelerator 2 kg = supported). Artificial lightweight aggregate 65kg).
Cement forced biaxial mixer capacity 3m ³ of the raw concrete production facility (for actual production), coarse aggregate, water, high AE water reducing agent, an artificial lightweight aggregate impregnated bearing a curing accelerator, a self-healing aid All materials were added and kneaded so that the total capacity was 1 m ³ . The mixing time is 120 seconds after first adding water and high-performance AE water reducing agent for 15 seconds after adding cement, coarse aggregate, artificial lightweight aggregate impregnated and loaded with a hardening accelerator, and self-healing aid. Seconds.
The produced coarse aggregate particles were discharged from the actual mixer of the ready-mix factory, respectively (incorporated) into the agitator car, and kept waiting while rotating the drum of the agitator car for 15 minutes at a rotation speed of 1 rpm.
The mass parts of the curing accelerator and carrier in Table 1 are values measured by heating at 105 ° C. until a constant weight is reached.

(Manufacturing in actual machine (simultaneous): P-35, P-36)
First, in a forced biaxial mixer similar to P-4 and P-21, cement, coarse aggregate, water, high-performance AE water reducing agent, hardening accelerator, and self-healing aid are added in an amount such that the total capacity is 1 m ^3. It was added and kneaded. The curing accelerator was dissolved in water and added simultaneously with water. The mixing time was 15 seconds after adding cement, coarse aggregate, and self-healing aid first, and 120 seconds after adding water and a high-performance AE water reducing agent.
The produced coarse aggregate particles were discharged from the actual mixer of the ready-mix factory, respectively (incorporated) into the agitator car, and kept waiting while rotating the drum of the agitator car for 15 minutes at a rotation speed of 1 rpm.

(Production in actual machine (post-addition): P-37, P-38)
Cement, coarse aggregate, water, high-performance AE water reducing agent, and self-healing aid were added to the forced biaxial mixer similar to P-4 and P-21 in an amount of 1 m ³ in total capacity and kneaded. The mixing time was 15 seconds after adding cement, coarse aggregate, and self-healing aid first, and 120 seconds after adding water and a high-performance AE water reducing agent. Thereafter, the mixture was put into the agitator wheel, the curing accelerator was added in a powder state, and the drum was put on standby for 15 minutes at a rotation speed of 1 rpm.

"Fresh Mortar"
Fresh mortars M-1 to M-21 were prepared using the materials of each formulation shown in Table 2.
The manufacturing method is as follows.

(Production in test room: M-1 to M-20)
First, mortars of M-1 to M-20 were produced in a concrete test room (test room; constant temperature of 20 ° C.). Cement, fine aggregate, water, high-performance AE water reducing agent, setting retarder, and mixed material were added to the agitator (for kneading in a test room) in an amount of 15 to 35 liters in total volume. The mixing time was 15 seconds after adding cement, fine aggregate, setting retarder and mixed material, and 120 seconds after adding water and high-performance AE water reducing agent.
The produced fresh mortar was discharged from the agitator to a plastic boat and temporarily stored for 15 minutes.

(Production with actual machine: M-21)
M-21 mortar was produced in an actual machine (a fresh concrete manufacturing factory: outside temperature 30 ° C.).
First, the amount of the total capacity of 1.63m ³ of cement, fine aggregate, water, high-performance AE water reducing agent, mixed material) to the 3m ³ forced biaxial mixer of the ready-mixed concrete production facility (for actual machine production) Was added and kneaded. The kneading time was initially 15 seconds after adding cement, fine aggregate, and mixed material, and 120 seconds after adding water and a high-performance AE water reducing agent.
The prepared fresh mortar is discharged from the actual mixer of the ready-mix factory, put into the agitator car loaded with the aforementioned coarse aggregate particles, and mixed by rotating the drum of the agitator car for 3 minutes at 10 rpm. Concrete was manufactured.

"Manufacture of concrete"
Using the coarse aggregate particles and fresh mortar shown in Tables 1 and 2, concretes of Examples 1 to 38 and Comparative Examples 1 to 14 shown in Table 3 were produced by the following method.
Note that the density of the cement paste containing the self-healing aid adhered to the coarse aggregate was regarded as the same as that of the coarse aggregate, and the formulation was not modified. Similarly, the density of the mixed material of fresh mortar was regarded as the same as that of cement, and the formulation was not modified. The high performance AE water reducing agent was considered part of the water.

(Examples 1 to 32 and Comparative Examples 1 to 14)
In the test room, the coarse aggregate particles temporarily stored in the plastic boat were put into the concrete tilting barrel mixer, and the cement paste adhered to the surface of the coarse aggregate while rotating for 15 minutes at 1 rpm. Was cured.
Thereafter, fresh mortar temporarily stored in another plastic boat is put into the tilting barrel mixer, and the tilting barrel mixer is rotated for 3 minutes at a rotation speed of 10 rpm to be mixed, and coarse aggregate particles and fresh mortar are mixed. Were mixed to obtain concretes of Examples 1 to 32 and Comparative Examples 1 to 14.
The amount of each coarse aggregate particle and fresh mortar was adjusted so that the total amount of concrete in the test room was 40 liters.

(Examples 33 to 38)
Coarse aggregate particles are loaded on the agitator car with the actual machine, and the drum of the agitator car is kept waiting for 15 minutes while rotating the drum of the agitator car for 15 minutes to harden the cement paste adhered to the surface of the coarse aggregate. It was.
Next, fresh mortar kneaded with an actual mixer was put into the agitator car, and the drum of the agitator car was rotated for 3 minutes at a rotation speed of 10 rpm to mix, and coarse aggregate particles and fresh mortar were mixed to give Example 33. ~ 38 concretes were obtained.
In addition, the mixing amount of each coarse aggregate particle and fresh mortar was adjusted so that the total amount of concrete kneaded was 2.63 m ³ .

(Comparative Examples 15 and 16)
Concretes of Comparative Examples 15 to 16 having the formulations shown in Table 4 were produced in a test room.
Comparative Example 15 is plain concrete (design standard strength 30 N / mm ² , target slump = 12.0 ± 2.5 cm, target air amount = 4.5 ± 1.5%, W / C = 50% (water = 175 kg). / M ³ , cement = 350 kg / m ³ ), s / a = 45.3% (fine aggregate = 800 kg / m ³ , coarse aggregate = 950 kg / m ³ ), reduced cement, water, high-performance AE The agent, coarse aggregate, and fine aggregate were all put into a biaxial forced mixer and kneaded for 120 seconds.
Comparative Example 16 uses the same materials and blends as in Example 2, and does not mix coarse aggregate particles and mortar separately. Cement, water, high-performance AE water reducing agent, coarse aggregate, fine aggregate, hardened The accelerator and the setting retarder were all put into a biaxial forced mixer and kneaded for 120 seconds.
The concrete kneading amount of Comparative Examples 15 and 16 was 40 liters.

<Measurement of slump and air volume>
The slump and air amount were measured for the concrete of each example and comparative example.
The slump was measured according to the method described in JIS A 1101 “Concrete slump test method”.
The amount of air was measured in accordance with the method described in JIS A 1128 “Test Method by Pressure of Air Volume of Fresh Concrete”. The results are shown in Table 3.

《Concrete compressive strength test》
Using the concrete of each Example and Comparative Example, it was driven into a simple steel mold having a diameter of 10 cm and a height of 20 cm to prepare six concrete column specimens. The prepared cylindrical specimen was sealed with a head (opening) of a simple steel mold using a polyethylene film and a rubber band, and sealed and cured in a thermostatic chamber at 20 ° C. for 91 days. After curing for 28 days, all six specimens were removed from the mold, and three of them were tested using a pressure tester, and the material was 91 days old in accordance with the method described in JIS A 1108 “Concrete compressive strength test method”. The compressive strength was measured. The results are shown in Tables 3 and 4.

《Concrete splitting test》
For the three specimens that were not used in the compression test, the cylindrical specimen was split into two pieces in accordance with the method described in JIS A 1113 “Method for splitting tensile strength of concrete”. The split tensile strength at age 91 days was measured.
The results are shown in Tables 3 and 4.

《Concrete water-stop (water permeability test)》
Using the specimens for which the split tensile strength was measured, a water-stopping test for concrete was performed.
After splitting (breaking) the cylindrical specimen, two pieces of paraffin film having a length of 200 mm, a width of 5 mm, and a thickness of 0.2 mm were sandwiched between both end portions of the cylinder, and the two fracture surfaces were accurately aligned. Two steel binding bands of 95 to 115 mm variable × width 12 mm × thickness 0.8 mm are used to constrain the outside (side portion) of the cylindrical specimen, and are introduced into the cylindrical specimen using a digital microscope. While observing the crack width of the cracked part (measurement of the upper and lower surfaces of the specimen two at a time), the crack width of the upper and lower surfaces of the cylindrical specimen was adjusted to about 0 by adjusting the tension of the steel binding band. It adjusted so that it might become 2-0.3 mm. Thereafter, a vinyl chloride pipe having an inner diameter of 95 mm × height of 80 mm for water passage test is connected to the upper surface of the cylindrical specimen (on the upper side of the mold at the time of specimen preparation). Sealing was performed by applying a commercially available sealing material (silicone rubber) to the cracked portion on the side of the specimen.
Such specimens were placed vertically on a steel grating laid in a constant temperature room at 20 ° C., and from the age of 91 days when cracks were introduced by splitting, tap water was supplied to the PVC pipe connected to the upper part of the cylindrical specimen. Water injection was performed, a water head of 8 cm was always given, the amount of water leakage from the cracks of the cylindrical specimen was measured for 7 days, and the water-stopping evaluation was evaluated using the following five grades.
In addition, water-stop evaluation was evaluated using the average value of three cylindrical specimens.

[Evaluation of water stoppage by self-healing of cracks]
Initial amount of water leak = amount of water leaked for 5 minutes immediately after the start of water flow Evaluation A: When the amount of water leaked for 5 minutes on the 7th day from the start of the water flow test is 1% or less of the initial amount of water leak Evaluation B: Start of water flow test When the amount of water leakage per 5 minutes on the 7th day is larger than 1% of the initial water leakage amount and 5% or less Evaluation C: The amount of water leakage per 5 minutes on the 7th day of the water flow test is 5% of the initial water leakage amount. Evaluation D: Case where the amount of water leakage per 5 minutes on the 7th day from the start of the water flow test is greater than 10% of the initial water leakage amount and 25% or less Evaluation E: Water flow test started When the amount of water leakage per 5 minutes on the 7th day cannot be less than 25% of the initial amount of water leakage

<Measurement of cement paste layer thickness>
Immediately after preparation of the coarse aggregate particles, 1 kg was collected and thinned in a polyethylene bag having a size of 900 mm × 500 mm × thickness 0.1 mm so that the coarse aggregates to which the cement paste was adhered in layers were not adhered to each other. After spreading and sealing for one day, coarse aggregates were collected and tested according to JIS Z8801-1 “Test Screen Sieve Part 1: Metal Screen Sieve”. Pass through an open 4.75 mm sieve and arbitrarily remove 10 particles from the particles that remain on the sieve. The extracted coarse aggregate is crushed with a hammer, the cross-section of the paste layer on the fracture surface of the coarse aggregate is taken using an optical microscope or a digital microscope, and a paste layer at any two positions of the cross-sectional image is taken. The average value of the measured values at a total of 20 locations where the thickness of each was measured was obtained. Table 3 shows the average value of each thickness.

  From Table 3 and Table 4, in each example, both the slump and the air amount were good, and there was no problem in the compressive strength and split tensile strength at the age of 91 days. Further, the evaluation of water-stopping was as good as B or higher.

On the other hand, each comparative example had the following results.
In Comparative Example 1, the water-cement ratio of the coarse aggregate particles was too low so that the cement paste was not formed, the cement paste did not adhere to the coarse aggregate, and the coarse aggregate particles could not be produced. For this reason, no subsequent concrete production was performed, and the subsequent tests and measurements were not performed.
In Comparative Example 2, the water-cement ratio of the coarse aggregate particles was too high, and the sag of the cement paste occurred, the paste did not adhere stably to the coarse aggregate surface, and coarse aggregate particles could not be produced. For this reason, no subsequent concrete production was performed, and the subsequent tests and measurements were not performed.
In Comparative Example 3, the amount of coarse aggregate is insufficient with respect to the cement paste (the amount of paste is excessive), so the coarse aggregate is embedded in the paste and integrated, and the coarse aggregate particles themselves cannot be produced. It was. For this reason, no subsequent concrete production was performed, and the subsequent tests and measurements were not performed.
In Comparative Example 4, the amount of coarse aggregate is excessive with respect to the cement paste (the amount of paste is insufficient), so the cement paste is not sufficiently adhered to the surface of the coarse aggregate, and coarse aggregate particles cannot be produced. It was. For this reason, no subsequent concrete production was performed, and the subsequent tests and measurements were not performed.
In Comparative Example 5, because no hardening accelerator was added to the coarse aggregate particles, after mixing with fresh mortar, uncured cement paste dropped off from the surface of the coarse aggregate, and the amount of cement in the mortar increased. The concrete slump was extremely small. In addition, since the amount of cement in the mortar increased, the strength of the concrete was excessively high, and the coarse aggregate was present in a cracked cross section. Therefore, the self-healing performance was low because the cement paste layer containing unreacted cement contributing to self-healing was hardly exposed on the cracked fracture surface.
In Comparative Example 6, since the hardening accelerator for the coarse aggregate particles was excessive, after mixing with fresh mortar, the hydration reaction of the cement in the mortar was affected, and false setting (stiffness) occurred in the concrete. Therefore, a cylindrical specimen could not be produced, and each subsequent test and measurement could not be performed.
In Comparative Example 7, the water cement ratio of the fresh mortar was too low and the fluidity of the mortar was low, so the concrete slump after mixing with the coarse aggregate particles was too small. Therefore, a cylindrical specimen could not be produced, and each subsequent test and measurement could not be performed.
In Comparative Example 8, because the water cement of fresh mortar was too high, material separation and bleeding of the mortar were intense. For this reason, no subsequent concrete production was performed, and the subsequent tests and measurements were not performed.
In Comparative Example 9, since the fine aggregate of fresh mortar was insufficient, the slump of the concrete after mixing with coarse aggregate particles became extremely small. In addition, the strength of the concrete was excessively high, and the coarse aggregate was present in a cracked cross section. Therefore, the self-healing performance was low because the cement paste layer containing unreacted cement contributing to self-healing was hardly exposed on the cracked fracture surface.
In Comparative Example 10, since the fine aggregate of fresh mortar was excessive, the slump of concrete after mixing with coarse aggregate particles was significantly reduced. Therefore, a cylindrical specimen could not be produced, and each subsequent test and measurement could not be performed.
In Comparative Example 11, since the setting retarder was not added to the fresh mortar, the concrete slump was reduced by the influence of the hardening accelerator remaining on the coarse aggregate particles after mixing with the coarse aggregate particles. Therefore, a cylindrical specimen could not be produced, and each subsequent test and measurement could not be performed.
In Comparative Example 12, since the setting retarder of the fresh mortar was excessive, the concrete was poorly cured (insufficiently cured) after being mixed with the coarse aggregate particles. Therefore, a cylindrical specimen could not be produced, and each subsequent test and measurement could not be performed.
In Comparative Example 13, since the amount of fresh mortar was excessive, the strength of the concrete after mixing with the coarse aggregate particles was excessively high, and the coarse aggregate was present in a cracked cross section. Therefore, the self-healing performance was low because the cement paste layer containing unreacted cement contributing to self-healing was hardly exposed on the cracked fracture surface.
In Comparative Example 14, since the amount of coarse aggregate particles was excessive, the concrete slump was too small. Therefore, a cylindrical specimen could not be produced, and each subsequent test and measurement could not be performed.
Since Comparative Example 15 was a plain concrete for comparison, the evaluation of water stoppage due to self-healing was low.
Comparative Example 16 is the case where the same materials and blends as in Example 2 were used, and all the materials were added together and the concrete was mixed, but the concrete was stiff due to the effect of the directly added curing accelerator, and the slump was greatly increased. It became small. For this reason, it was judged that there was a problem in workability because it hindered pumping and the like. Further, since the amount of cement is large, the strength of the concrete is excessively high, and the coarse aggregate exists in a cracked cross section. Therefore, the self-healing performance was low because the cement paste layer containing unreacted cement contributing to self-healing was hardly exposed on the cracked fracture surface.

1: Coarse aggregate, 2: Cement paste, 3: Mortar, 4: Coarse aggregate particle, 10: Concrete, C: Crack.

Claims (7)

Coarse aggregate particles in which cement paste is adhered to the surface by mixing 100 parts by mass of cement, 12 to 35 parts by mass of water, 500 to 1000 parts by mass of coarse aggregate, and 0.5 to 5 parts by mass of a hardening accelerator Coarse aggregate particle production process for producing
A mortar preparation step of preparing fresh mortar by mixing 100 parts by weight of cement, 38 to 65 parts by weight of water, 200 to 400 parts by weight of fine aggregate, and 0.05 to 1.5 parts by weight of a setting retarder; ,
A method for producing concrete comprising a mixing step of mixing the coarse aggregate particles and the fresh mortar so as to have a volume ratio of 3: 7 to 5: 5.   The coarse aggregate particle production step further comprises mixing at least one selected from the group consisting of a thickener, calcium sulfate, calcium hydroxide, calcium oxide, aluminum hydroxide, bentonite, iron, and an iron compound. The method for producing concrete according to 1.   The method for producing concrete according to claim 1 or 2, wherein at least one selected from the group consisting of limestone fine powder, blast furnace slag fine powder, fly ash, and calcium oxide powder is further mixed in the mortar production step.   The method for producing concrete according to any one of claims 1 to 3, wherein the curing accelerator is an inorganic sulfate.   The method for producing concrete according to any one of claims 1 to 4, wherein the setting retarder is at least one selected from the group consisting of oxycarboxylic acid and oxycarboxylate. The coarse aggregate particle production step includes
An adhering step in which cement, water and coarse aggregate are mixed to attach the cement paste to the surface of the coarse aggregate;
The method for producing concrete according to any one of claims 1 to 5, further comprising: a curing step of curing the cement paste by mixing the curing accelerator with the coarse aggregate particles to which the cement paste is adhered in the adhesion step.   Concrete produced by the method for producing concrete according to any one of claims 1 to 6.

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