JP7836766B2 - Two-component ready-mix concrete shipping type rapid-hardening concrete material and ready-mix concrete shipping type rapid-hardening concrete composition - Google Patents

Description

This invention relates to a two-component type ready-mix concrete shipping rapid-hardening concrete material and a ready-mix concrete shipping rapid-hardening concrete composition.

Globally, cement production is increasing, and infrastructure development is progressing rapidly. In particular, the construction boom in China and Southeast Asia continues. Among infrastructure developments, road construction holds a crucial position. Because early opening is desired for both new road construction and repairs, materials that enable rapid use are required. One example of this is rapid-hardening concrete.

For rapidly hardening concrete, pot life is also an important performance requirement. Considering the time required for manufacturing ready-mix concrete at a concrete plant, transporting it to the construction site, and the time needed for construction and cleaning the concrete transport trucks (agitator trucks), it is desirable to secure a pot life of at least 120 minutes, and preferably 180 minutes or more. However, securing a longer pot life delays the hardening time, making it impossible to meet the required strength at the early stages of hardening. Therefore, with conventional technology, it has been difficult to ensure sufficient pot life while meeting the necessary strength development at the initial stages of hardening.

Currently, rapid-hardening concrete is typically prepared on-site. For small-volume projects, rapid-hardening concrete is mixed in a mixer of about 0.1 to 0.2 ^m³ , and the preparation and placement are done manually. This method requires a large amount of manpower, resulting in high labor costs and limited supply volume of rapid-hardening concrete. For larger-volume projects, rapid-hardening concrete is continuously supplied using concrete mobiles. However, this method requires arranging concrete mobiles, and also involves the labor of preparing fine and coarse aggregates with controlled moisture content in flexible containers (FIBCs) beforehand, as well as preparing rapid-hardening cement in FIBCs and transporting it to the site. This significantly increases the cost of rapid-hardening concrete. Furthermore, there are limitations to the availability of concrete mobiles.

Today, there is a strong demand for the development of rapid-hardening concrete that can be shipped directly from ready-mix concrete plants. If rapid-hardening concrete can be shipped from ready-mix concrete plants, large quantities of it can be supplied to construction sites using existing mixing equipment and transport systems.

For example, Patent Document 1 discloses a ready-mix concrete-type rapid-hardening concrete material that uses a hardening agent for ready-mix concrete-type rapid-hardening concrete, comprising at least one selected from the group consisting of calcium hydroxide, calcium carbonate, calcium aluminate compounds, calcium silicate compounds, colloidal silica, Portland cement, calcium sulfoaluminate cement, and blast furnace slag.

International Publication No. 2018/154890

According to the ready-mix concrete-type rapid-hardening concrete material described in Patent Document 1, it is possible to manufacture a ready-mix concrete-type rapid-hardening concrete composition that has excellent initial strength development while ensuring a sufficient pot life. However, Patent Document 1 shows that if aluminum sulfate is used as a rapid-setting agent, it sets instantly, making it impossible to ensure a sufficient pot life. Furthermore, there was room for further improvement regarding the initial strength development in low-temperature environments.

Therefore, the present invention aims to provide a highly practical two-component type ready-mix concrete-type rapid-hardening concrete material that ensures sufficient pot life even in low-temperature environments while exhibiting excellent initial strength development. Furthermore, the present invention aims to provide a ready-mix concrete-type rapid-hardening concrete material suitable for manufacturing the said ready-mix concrete-type rapid-hardening concrete composition.

Therefore, in order to solve the above problems, the inventors of the present invention have made various efforts and have found that by preparing concrete by mixing material A, which contains rapid-hardening cement and a stimulant, at a ready-mix concrete plant, transporting it to the site, and then adding and mixing material B, which consists of a hardening accelerator containing aluminum, sulfur, sodium, and fluorine, it is possible to prepare a practical rapid-hardening concrete composition that has excellent initial strength development while ensuring sufficient pot life even in low-temperature environments, and have completed the present invention. In other words, the present invention is as follows.

[1] A two-component ready-mix concrete material for rapid hardening, comprising material A containing rapid hardening cement and a sedative, and material B consisting of a hardening accelerator containing aluminum, sulfur, sodium, and fluorine, wherein the sodium lunite content in material B is 0.3 to 5% by mass.
[2] The two-component ready-mix concrete shipping type rapid-hardening concrete material according to [1], wherein the stoichiometric ratio of the hypnotic agent represented by the following formula (1) to the B material is 0.5 to 5.
Formula (1): Stoichiometric ratio = [Amount of aluminum in material B (mol)] × Number of aluminum particles × Valence of aluminum ions / (Amount of oxycarboxylic acid contained in the sleeping pill (mol) × Valence of oxycarboxylic acid contained in the sleeping pill)
[3] A two-component ready-mix concrete ready-mix type rapid-hardening concrete material according to [1] or [2], wherein the content of natroalnite in the B material is 5% by mass or less after being stored at 0 to 40°C for 48 hours immediately after the preparation of the B material.
[4] The two-component ready-mix concrete shipping type rapid-hardening concrete material according to any one of [1] to [3], wherein the natroalnite contained in the B material is derived from cryolite.
[5] A two-component ready-mix concrete material for rapid hardening according to any one of [1] to [4], wherein the pH of material B is 1 to 4.
[6] A _two- component ready-mix concrete material for rapid hardening according to any one of [ ₁ ] to [5], wherein the aluminum in the B material is 0.1 to 20 parts by mass in terms of Al₂O₃, the sulfur is 0.1 to 30 parts by mass in terms of _SO₃ , the sodium is 0.01 to 5 parts by mass in terms of _Na₂O , and the fluorine is 0.01 to 10 parts by mass.
[7] A two-component ready-mix concrete material for rapid hardening according to any one of [1] to [6], wherein the solid content concentration of material B is 20 to 70% by mass.
[8] A two-component ready-mix concrete material for rapid hardening according to any one of [1] to [7], wherein the viscosity of material B at 20°C is 1,400 mPa·s or less.
[9] A two-component ready-mix _concrete material for rapid hardening according to any one of [1] to [8], wherein the mass ratio of aluminum in terms of _Al₂O₃ to _sulfur in terms of _SO₃ ( _Al₂O₃ / _SO₃ ) is 0.05 to 1.0.
[10] A ready-mix concrete-type rapid-hardening concrete composition comprising material A, which contains rapid-hardening cement and a sedative, and material B, which consists of a hardening accelerator containing aluminum, sulfur, sodium, and fluorine, wherein the content of natroalnite in material B is 0.3 to 5% by mass.

According to the present invention, it is possible to provide a highly practical ready-mix, rapid-hardening concrete composition that ensures sufficient pot life even in low-temperature environments while exhibiting excellent initial strength development. Furthermore, it is possible to provide a two-component ready-mix, rapid-hardening concrete material suitable for manufacturing the said ready-mix, rapid-hardening concrete composition.

The embodiments of the present invention will be described in detail below, but the present invention is not limited to these embodiments. In this specification, "parts" and "%" refer to mass unless otherwise specified. Furthermore, in this specification, "composition" refers collectively to cement compositions, mortar compositions, and concrete compositions.

[1] Two-component ready-mix concrete shipment type rapid-hardening concrete material The two-component ready-mix concrete shipment type rapid-hardening concrete material of this embodiment is composed of at least two components, including component A which contains rapid-hardening cement and a stimulant, and component B which consists of a hardening accelerator containing aluminum, sulfur, sodium, and fluorine.

In this embodiment, "ready-mix concrete-type rapid-hardening concrete" refers to concrete that is mixed at a ready-mix concrete plant or similar facility, transported by agitator truck or the like, and shipped to construction sites such as civil engineering sites or building sites, and hardens relatively quickly after placement. In the case of ready-mix concrete-type rapid-hardening concrete, due to transportation time, a minimum pot life of 120 minutes or more is required from shipment to completion of work, and it is desirable to secure a pot life of 180 minutes or more if the transportation distance is long. This embodiment is specifically designed for use in such applications.
The "agitator truck" mentioned above is a cargo truck equipped with a mixing drum (a container for mixing) in its cargo bed, which allows it to transport ready-mix concrete while stirring it. Although there is no significant difference in their functions, they come in various sizes with maximum load capacities ranging from 2 to 26 tons, and are used differently depending on the application.

In this embodiment, the dormant agent in Material A puts the ready-mix, rapid-hardening concrete into a dormant state, meaning that hydration hardening is almost completely stopped. This ensures a longer pot life. Furthermore, the addition of hardening accelerators containing aluminum, sulfur, sodium, and fluorine in Material B reawakens the hydration hardening of the rapid-hardening concrete, which had been put into a dormant state by the addition of a large amount of dormant agent, at the construction site. Then, other components such as the rapid-hardening agent provide excellent initial strength development.
Adding material B promotes setting and hardening, but it is necessary to ensure sufficient working time after adding material B, with a pot life of at least 15 minutes required. However, if the amount of natroalnite in material B exceeds a certain level, the rapid hardening effect that the hardening accelerator can exert is inhibited, making it difficult to achieve good workability. In contrast, in this embodiment, the amount of natroalnite in material B was examined and set to a range of 0.3 to 5%, thereby ensuring a sufficient pot life even in low-temperature environments and achieving excellent initial strength development.
Furthermore, Material B is easy to handle and can be used in either liquid or solid (preferably powder) form, making it highly practical as the form can be selected according to the construction site and conditions.
The following provides a detailed explanation of material B and material A.

[B material]
The B material according to this embodiment of the present invention is a hardening accelerator containing aluminum, sulfur, sodium, and fluorine. By including these in the B material as a hardening accelerator, good rapid hardening and strength development can be achieved even in low-temperature environments.

Furthermore, in this embodiment, the sodium nitrite content of material B is 5% or less. If the sodium nitrite content exceeds 5%, the rapid hardening effect that the hardening accelerator can exert is inhibited, making it difficult to achieve good workability. The sodium nitrite content is preferably 4% or less, and more preferably 3% or less. Although it is preferable that sodium nitrite be absent, it may actually be present at a concentration of about 0.3% because it is generated by thermal hydrolysis.

It is preferable that the natroalnite content becomes 5% or less at least after storing the B material at 0-40°C for 48 hours immediately after its preparation. If the natroalnite content is 5% or less at this point, the inhibition of rapid hardening by natroalnite will be suppressed during subsequent storage at 0-40°C. Note that "0-40°C" is the temperature range assumed for actual use of the B material. The natroalnite content can be measured by the method described in the examples.

Here, natroalunite, also known as soda alum, is represented as ( _NaAl3 ( _SO4 ) ₂ (OH) ₆ , (Na,K) _Al3 ( _SO4 ) ₂ (OH) ₆ , or [Na ⁺ ][Al3 ⁺ ][Al3 ⁺ ₂ ][(OH) ₆ |( _SO4 ) ₂ ] ^10- ). According to the inventors, natroalunite mainly originates from cryolite, _{the raw material, and in particular, they have found that it originates from thiolite (Na5Al3F14) and elpasolite (K2NaAlF6 ) in cryolite .}
Therefore, to reduce the natroalnite content in material B to 5% or less, treatments such as reducing the thiolite and elpasolite in cryolite can be applied. Furthermore, as described later, the temperature conditions during the production of material B may be adjusted.

The B material according to this embodiment is preferably acidic, and more preferably has a pH of 1 to 4. The acidity of the B material improves handling compared to basic curing accelerators. To adjust the pH of the B material within the above range, water and sulfuric acid can be added.

The content of aluminum, sulfur, sodium, and fluorine in material B is not particularly limited, but from the viewpoint of rapid hardening, it is preferable that the amount of aluminum is 0.1 to ₂₀ parts in terms of _Al₂O₃ , the amount of sulfur is 0.1 to 30 parts in terms of _SO₃ , the amount of sodium is 0.01 to 5 parts in terms of _Na₂O , and the amount of fluorine is 0.01 to 10 parts. It is more preferable that _the amount of aluminum is 0.1 to 10 parts in terms of _Al₂O₃ . It is more preferable that the amount of sulfur is 0.1 to 10 parts in terms of _SO₃ . It is more preferable that the amount of sodium is 0.01 to 2 parts in terms of _Na₂O . It is more preferable that the amount of fluorine is 0.01 to 2 parts.

Furthermore, from the viewpoint of storage stability of material B and mixability when added to paste, mortar, and concrete, the mass ratio of aluminum in terms of _Al₂O₃ to sulfur in terms of _SO₃ ( _{Al₂O₃ / SO₃} ) is preferably 0.05 to _1.0 , and more preferably 0.1 to 0.8.

The solid content concentration of material B according to this embodiment is preferably 20 to 70%, and more preferably 23 to 60%, from the viewpoint of storage stability of the hardening accelerator and mixability when added to paste, mortar, and concrete.

Furthermore, the viscosity of material B according to this embodiment at 20°C is preferably 1,400 mPa·s or less, and more preferably 1 to 1,000 mPa·s. A viscosity of 1,400 mPa·s or less enhances miscibility and provides stable physical properties. Viscosity can be measured by the method described in the examples.

In this embodiment, the stoichiometric ratio of the hypnotic agent and material B, described later, was examined, and by setting the range to 0.5 to 5, sufficient pot life was ensured and excellent initial strength development was achieved. This stoichiometric ratio is expressed by the following formula (1). Formula (1) represents the ratio of material B, which is a hardening accelerator, to the hypnotic agent in concrete containing the hypnotic agent and material B. The fact that this ratio is in the range of 0.5 to 5 means that if the ratio is too low, there will be an excess of the hypnotic agent and rapid hardening will not be achieved, and if the ratio is too high, there will be an excess of material B and instantaneous hardening will occur.
Formula (1): Stoichiometric ratio = [Amount of aluminum in material B (mol)] × Number of aluminum particles × Valence of aluminum ions / (Amount of oxycarboxylic acid contained in the sleeping pill (mol) × Valence of oxycarboxylic acid contained in the sleeping pill)

The following explanation of stoichiometric ratios will be given using the example of material B containing aluminum sulfate and material A using potassium carbonate and citric acid (potassium carbonate:citric acid = 75:25 (mass ratio)) as sedatives.
First, the molar masses of aluminum sulfate and citric acid are as follows:
Aluminum sulfate ( _Al₂ ( _SO₄ ) _₃ ) Molecular weight (M.W.) = 342.2
Citric acid ( _C6H8O7 ) Molecular weight ₍ M.W.) ₌ 192.1
If 1% aluminum sulfate and 1.5% sedative are added to 500 kg of binder in concrete, the respective components per unit of concrete will be as follows. Component B acts on citric acid, which is a retarder for the sedative.
Aluminum sulfate: 500,000g of binder × 0.01 (=1%) ÷ 342.2 = 14.6 mol
Citric acid: 500,000g binder × 0.015 (=1.5%) × 0.25 (=25%) ÷ 192.1 = 9.7 mol
Since aluminum ions act as trivalent acids, aluminum sulfate contains two Al atoms, and citrate ions are trivalent bases (valence of retarder ions = 3), the aforementioned equation (1) is calculated as follows.
Formula (1): Stoichiometric ratio = (14.6 x 2 x 3) / (9.7 x 3) = 3.0

Material B according to this embodiment can be produced by mixing raw materials such as aluminum sulfate, various types of alum, aluminum hydroxide, sodium hydroxide, sulfuric acid, natural or synthetic cryolite, sodium fluoride, and aluminum fluoride in a liquid and heating at 80 to 95°C for 30 to 120 minutes. From the viewpoint of good productivity, it is preferable to use sulfuric acid, aluminum hydroxide, aluminum sulfate, or various types of alum and natural or synthetic cryolite as raw materials. Furthermore, it is preferable to use water or the like as the liquid.

In this embodiment, when cryolite is used as the raw material for producing material B, insoluble precipitates tend to form. In particular, it is presumed that thiolite and erpasolite contained in cryolite contribute to the formation of insoluble precipitates. Furthermore, it has been found that the formation of insoluble precipitates can be suppressed by performing certain operations when producing the hardening accelerator. Taking either of these into consideration, it is preferable to perform operations such as (1) or (2) below in order to keep the natroalnite content in material B to 5% or less.

(1) When using cryolite as the raw material, use cryolite in which the amount of thiolite and elpasolite contained is 5% or less.
(2) After heating at 80-95°C as described above, rapidly cool to room temperature (e.g., 25°C) within 60 minutes.

The B material produced in the manner described above is suitable for use in ready-mix concrete shipments, as described later.

[Material A]
Material A contains rapid-hardening cement and a sedative.
(Sleeping pills)
The sedative used in this embodiment has the function of putting rapid-hardening concrete to sleep (almost stopping hydration hardening) after it has been shipped from the ready-mix concrete plant, thereby avoiding rapid-hardening problems at the ready-mix concrete plant and during transport by agitator truck. Examples of sedatives include oxycarboxylic acids, their salts, or a combination of these with alkali metal carbonates, sugars, and boric acid. The combination of oxycarboxylic acid and alkali metal carbonate is preferred because it has a greater effect in putting rapid-hardening concrete to sleep and because it allows for good strength development after the addition of material B. However, it is preferable to select an alkali metal carbonate other than lithium. It is necessary to ensure a sufficient pot life for the base concrete, a certain pot life after the addition of material B, and good strength development, and from this viewpoint, the application of lithium carbonate is undesirable. Also, alkali metal carbonate alone, without the combination of oxycarboxylic acid, does not act as a sedative.
In this specification, "base concrete" refers to concrete prepared by mixing at least rapid-hardening cement, a stimulant, aggregate, and mixing water.

The sleep aid preferably contains an oxycarboxylic acid, an alkali metal carbonate other than lithium, and a mixture of the oxycarboxylic acid, and more preferably a mixture of an alkali metal carbonate other than lithium and an oxycarboxylic acid. The mixing ratio (mass ratio) of the alkali metal carbonate other than lithium and the oxycarboxylic acid is preferably 10/90 to 90/10, and more preferably 20/80 to 80/20, in terms of alkali metal carbonate/oxycarboxylic acid.

The oxycarboxylic acid includes oxycarboxylic acids or their salts. Examples of oxycarboxylic acids include citric acid, gluconic acid, tartaric acid, malic acid, etc. Examples of their salts include sodium salts, potassium salts, calcium salts, magnesium salts, etc. One or more of these may be used in combination.

The amount of sedative is preferably 0.3 to 5 parts, and more preferably 0.3 to 4.5 parts, per 100 parts of rapid-hardening cement. A concentration of 0.3 to 5 parts makes it easier to ensure sufficient working time in addition to the transportation time to the site. Furthermore, it makes it easier to re-induce hydration hardening when material B is added.

(Rapid-hardening cement)
Rapid-hardening cement is a type of cement for rapid-hardening concrete that achieves a compressive strength of 24 N/mm² or ^higher after 3 hours of use. Based on its rapid-hardening component, it is broadly classified into calcium fluoroaluminate type, hauyne type, and calcium aluminate type. Among these, calcium aluminate type rapid-hardening cement is preferable in terms of reducing slump loss.

Calcium aluminate-based rapid-setting cement is a compound of cement, a rapid-setting agent, and a setting regulator, with the rapid-setting agent consisting of calcium aluminate compounds and gypsum.

(cement)
The term "cement" in this embodiment is not particularly limited, but includes, for example, various types of Portland cement (ordinary, rapid-hardening, moderate-heat, and low-heat) as defined by the Japanese Industrial Standards (JIS), various blended cements mixed with blast furnace slag, fly ash, and silica, filler cements mixed with limestone powder and blast furnace slow-cooled slag fine powder, and all types of cement, including environmentally friendly cement (eco-cement) manufactured using municipal solid waste incineration ash and sewage sludge incineration ash as raw materials. In addition, it can refer to all types of cement defined in the international EN197-2000 standard and the Chinese GB standard, and one or more of these types can be used.

Portland cement is composed of alite (3CaO・_SiO₂ ), belite ₍ 2CaO・_SiO₂ ), aluminate (3CaO・_{Al₂O₃ )} , ferrite (4CaO・_Al₂O₃・_Fe₂O₃ ), and dihydrate gypsum (a portion of which may change to hemihydrate gypsum). In this embodiment, from the viewpoint of strength development _, it is desirable to select a cement that does not contain admixtures such as blast furnace slag, fly ash, silica, and limestone powder, and among these, it is preferable to select a cement with a high alite content and high fineness (fine particle size). Examples of cements that fit this description include, for example, early-strength cement and ordinary cement from Japan. Examples of cements from China include PII 52.5 and PII 42.5.

(Sudden hardwood)
The rapidly hardening material of this embodiment preferably consists of a calcium aluminate compound and gypsum. Here, the term "calcium aluminate compound" is a general term for compounds mainly composed of CaO _{and Al₂O₃} , and is not particularly limited. Specific examples include _CaO・_Al₂O₃ , 12CaO・_7Al₂O₃ , 11CaO・_{7Al₂O₃ ・ CaF₂} , _{3CaO・Al₂O₃ ,} 3CaO・_3Al₂O₃・_CaSO₄ , and also amorphous materials mainly composed of CaO and _Al₂O₃ (for example, CaO- _{Al₂O₃ -SiO₂ compounds ) .} Among these, selecting _an amorphous material is preferable from the viewpoint of strength development.

In this embodiment, amorphousness is defined as follows: The target material is annealed at 1000°C for 2 hours, then slowly cooled at a cooling rate of 5°C/min to induce crystallization. The crystallized material is then measured by powder X-ray diffraction to determine the area _S0 of the main peak of the crystalline mineral. Subsequently, the amorphousness X is calculated from the main peak area S of the crystal of the material before annealing using the following formula.
X (%) = 100 x (1-S/S ₀ )

In general, industrial raw materials contain impurities such as _SiO₂ , MgO, _Fe₂O₃ , _TiO₂ , _K₂O , and _{Na₂O .} These impurities also contribute to the amorphous formation of calcium aluminate compounds, and their total amount can be as low as 20%. In particular, the presence of _SiO₂ is preferable, and it can be included in amounts ranging from 1% to 18% for the purpose of obtaining amorphous materials.

Therefore, the rapidly hardening material preferably contains a CaO- _{Al₂O₃ -SiO₂ compound} and gypsum, wherein the amorphousness of the CaO- _Al₂O₃ - _SiO₂ compound is 70% or more and the _SiO₂ content is in the range of 1 to ₁₈ %. More preferably, the amorphousness of the CaO- _{Al₂O₃ -SiO₂ compound} is 80% or more and the _SiO₂ content is in the range of 2 to 13%.

The calcium aluminate compound is preferably adjusted to a Blaine specific surface area of 3,000 to 9,000 ^cm² /g by grinding, and more preferably to 4,000 to 8,000 ^cm² /g. A powderiness (Blaine specific surface area) of 4,000 to 9,000 ^cm² /g of the calcium aluminate compound makes it easier to obtain sufficient rapid hardening and also facilitates strength development at low temperatures.

Furthermore, the rapid-hardening material of this embodiment is preferably adjusted to a Blaine specific surface area of 3,000 to 9,000 ^cm² /g by pulverization, and more preferably to 4,000 to 8,000 ^cm² /g. Having a powderiness of 3,000 to 9,000 ^cm² /g in the rapid-hardening material makes it easier to obtain sufficient ultra-rapid hardening properties and also makes it easier to obtain strength development at low temperatures.

The content of the rapid hardening agent is preferably 10 to 35 parts, more preferably 15 to 30 parts, and even more preferably 20 to 25 parts, out of a total of 100 parts of cement and rapid hardening agent. A content of 10 to 35 parts makes it easier to obtain good initial strength development and reduces the likelihood of long-term strength degradation.

In this embodiment, any type of gypsum can be used: anhydrous gypsum, hemihydrate gypsum, or dihydrate gypsum. Furthermore, natural gypsum, chemical gypsum such as phosphate-derived gypsum, exfoliated gypsum, and hydrofluoric acid-derived gypsum, or gypsum obtained by heat treatment of these can also be used. Among these, anhydrous gypsum and/or hemihydrate gypsum are preferred in terms of strength development, but from a cost perspective, it is desirable to select anhydrous gypsum, and Type II anhydrous gypsum and/or natural anhydrous gypsum are preferred. The particle size of the gypsum is preferably 3,000 ^cm² /g or more in Blaine value, and more preferably 4,000 to 7,000 ^cm² /g. A particle size of ^{3,000 cm²} /g or more allows for good initial strength development.

The amount of gypsum used is preferably 10 to 200 parts, more preferably 15 to 150 parts, and even more preferably 20 to 130 parts, per 100 parts of the calcium aluminate compound. Using gypsum within these ranges allows for good strength development.

In this embodiment, in addition to the previously described hardening agent, sedative, aluminum, sulfur, sodium, and hardening accelerator containing fluorine, one or more of the following can be used in material A and/or material B, to the extent that they do not substantially hinder the objective of the present invention: expansive agents, water-reducing agents, AE water-reducing agents, high-performance water-reducing agents, slag such as blast furnace slow-cooling slag powder, admixtures such as limestone powder, fly ash, silica fume, defoaming agents, thickeners, rust inhibitors, antifreeze agents, shrinkage-reducing agents, polymers, clay minerals such as bentonite, and anion exchangers such as hydrotalcite.

[2] Rapid-hardening concrete composition for ready-mix concrete shipment The rapid-hardening concrete composition for ready-mix concrete shipment according to this embodiment is a mixture of material A, which contains rapid-hardening cement and a hardening agent, and material B, which consists of a hardening accelerator containing aluminum, sulfur, sodium, and fluorine. The content of natroalnite in material B is 0.3 to 5%. The preferred range and other details are the same as those mentioned in "Two-component type rapid-hardening concrete material for ready-mix concrete shipment".

At a ready-mix concrete plant, it is necessary to prepare various types of base concrete mixed with material A, and material B must be added and mixed to these base concretes after being transported to the construction site. If material B is mixed with the various base concretes at the ready-mix concrete plant rather than at the construction site, the pot life cannot be ensured. Also, if both the rapid-setting agent and material B are added at the ready-mix concrete plant, the pot life becomes extremely short, forcing the concrete to be discarded during transport.
If material B is added at the ready-mix concrete plant and the rapid-setting agent is added at the construction site, the pot life after adding the rapid-setting agent becomes extremely short, less than 10 minutes, making construction impossible. If the rapid-setting agent and material B are added at the construction site, the pot life is shortened, the compressive strength is low, and only about 30% of the agitator drum volume can be transported. Thus, the timing of adding material A and material B is extremely important.

Therefore, in this embodiment, by using a two-component type consisting of material A and material B, specifically, by transporting the base concrete mixed with material A at the ready-mix concrete plant to the construction site and mixing material B at the construction site, the ready-mix concrete shipment type rapid-hardening concrete composition of this embodiment can be obtained.

[Preparation method for ready-mix, rapid-hardening concrete]
An embodiment of the method for preparing ready-mixed, rapidly hardened concrete according to the present invention includes, in order, a step of mixing at least material A with mixing water in a mixing container to form a base concrete (mixing step), and further a step of mixing material B, for example, at the construction site.
The mixing water mentioned above is supplied, for example, from a ready-mix concrete plant or similar facility. Furthermore, transportation often occurs simultaneously with the mixing process.

In the mixing process, it is preferable that the volume of the base concrete, including material A and mixing water, be at least 40% of the internal volume of the mixing (transport) container, and more preferably 50% or more.
Here, a mixing (transport) container refers to a container that is attached to a ready-mix concrete transport vehicle, such as the drum of an agitator truck, and is capable of holding and agitating ready-mix concrete.

Furthermore, it is preferable to determine the type of material B and the aforementioned stoichiometric ratio within an appropriate range so that a pot life of 10 minutes or more, preferably 15 minutes or more, is ensured after mixing material B.

As described above, the two-component ready-mix concrete material according to this embodiment is suitable for use as a material added after the concrete is poured, after the ready-mix concrete has been mixed and the mixture has been transported to the construction site. Furthermore, the pot life can be set to, for example, 120 minutes or more, preferably 180 minutes or more.

The present invention will be described in more detail below based on experimental examples, but the present invention is not limited to these examples.

(Experiments No. 1-1 to 1-29)
Aluminum sulfate and cryolite were mixed with water so that the proportions of aluminum (in _Al₂O₃ equivalent ₎ , sulfur (in _SO₃ equivalent), sodium (in _Na₂O equivalent), and fluorine were as shown in Table 1, and the mixture was heated at 90°C for 60 minutes. After heating, the mixture was rapidly cooled to 25°C in 50 minutes using a circulating cooling device to produce material B as a hardening accelerator. The solid content concentration and viscosity of material B at 20°C were measured as described below. The pH of material B was also measured using a pH meter. The results are shown in Table 1.

<Materials used>
Water: Tap water; Aluminum sulfate: Aluminum sulfate powder (14-18 aqueous solution), reagent; Cryolite: Reagent; Thiolite: 2%, Elpasolite: 0.5% (measured by XRD)

- Solid content concentration: The total amount of _SO₃ , _Al₂O₃ , _and cryolite from the raw materials was calculated.
Viscosity (20°C): Measured using a rotational viscometer.

50g of material B was stored at 20°C for 48 hours. Afterward, the amount of natroalnite precipitated was measured as described below. The results are shown in Table 1.

- Natroalnite content: 50g of stored material B was passed through a glass filter, filtered by suction, and then dried in a vacuum desiccator for 24 hours. X-ray diffraction measurements were performed on the resulting sample. The peak intensity of natroalnite alone was compared with the peak intensity of natroalnite in the sample to determine its content.

Rapid-hardening concrete was prepared with 375 kg/ ^m³ of cement, 125 kg/ ^m³ of rapid-hardening agent, a water/binder ratio of 32%, s/a = 42%, and an air content of 2.0 ± 1.5 volume%. At this time, 1.5 parts of a stimulant was added to 100 parts of the binder (cement and rapid-hardening agent) to prevent hydration and hardening for more than 24 hours (A component). Assuming transportation time to the site and waiting time after arrival at the construction site, A component B, as a hardening accelerator, was added 120 minutes later in the stoichiometric ratio shown in Table 1 below. The pot life after adding A component B was measured, and the compressive strength was measured 6 hours after adding A component B (8 hours after mixing). s/a is the fine aggregate ratio, expressed as a percentage of the absolute volume ratio of fine aggregate to the total aggregate in the concrete. The ambient temperature was 20°C. The stoichiometric ratio was calculated from the previously described formula (1).

<Materials used>
• Rapid-hardening material: Equimolar mixture of CaO- _Al₂O₃ - _{SiO₂ amorphous} material and anhydrous gypsum. The CaO- _{Al₂O₃ - SiO₂} amorphous material consists of 43% CaO, 44% _Al₂O₃ , 10% _SiO₂ , and 3 _% other components. Density: 2.85 g/ ^cm³ , Blaine specific surface area: 5,000 ^cm² /g, Amorphousness: 90%
• Sleeping pill: A mixture of 75 parts reagent-grade potassium carbonate and 25 parts reagent-grade citric acid. • Cement: Commercially available ordinary Portland cement (manufactured by Denka Co., Ltd., density 3.15 g/ ^cm³ )
Anhydrous gypsum: Type II anhydrous gypsum, pH 3.0, Blaine specific surface area 5,000 ^cm² /g
Water: Tap water; Fine aggregate: Natural river sand; Coarse aggregate: Crushed stone

<Measurement method>
- Pot life: The pot life was determined by measuring the time of initial condensation in accordance with JIS A 1147.
- Compressive strength: Measured in accordance with JIS A 1108.

The two-component ready-mix concrete-type rapid-hardening concrete material and ready-mix concrete-type rapid-hardening concrete composition of the present invention are particularly suitable for use in the civil engineering and construction fields because they ensure sufficient pot life even in low-temperature environments while exhibiting excellent initial strength development.

Claims (9)

Material A, which contains rapid-hardening cement and a sedative,
The material comprises a curing accelerator containing aluminum, sulfur, sodium, and fluorine,
The aforementioned sleeping agent comprises an oxycarboxylic acid or an alkali metal carbonate other than lithium and a mixture of oxycarboxylic acids,
The sodium nitrite content in material B is 0.3 to 5% by mass.
A two- _component ready-mix concrete material for rapid hardening, wherein, per 100 parts by mass of material B, the aluminum in material B is 0.1 to 20 parts by mass in terms of _Al₂O₃ , the sulfur is 0.1 to 30 parts by mass in terms of _SO₃ , the sodium is 0.01 to 5 parts by mass in terms of _Na₂O , and the fluorine is 0.01 to 10 parts by mass. The two-component type ready-mix concrete shipping type rapid-hardening concrete material according to claim 1, wherein the stoichiometric ratio of the hypnotic agent and the B material, represented by the following formula (1), is 0.5 to 5.
Formula (1): Stoichiometric ratio = [Amount of aluminum in material B (mol)] × Number of aluminum particles × Valence of aluminum ions / (Amount of oxycarboxylic acid contained in the sleeping pill (mol) × Valence of oxycarboxylic acid contained in the sleeping pill) The two-component type ready-mix concrete shipment type rapid-hardening concrete material according to claim 1 or 2, wherein the content of natroalnite in the aforementioned B material is 5% by mass or less after being stored at 0 to 40°C for 48 hours immediately after the preparation of the B material. The two-component _{type ready-mixed concrete material for rapid hardening according to any one of claims 1 to 3, wherein the natroalnite contained in the B material is represented as NaAl 3 (SO 4) 2 ( OH) 6 , ( Na , K} )Al 3 (SO 4) 2 (OH) 6, or [Na ⁺ ][Al ³ +][Al ³⁺ ₂ ][(OH) ₆ | (SO ₄ ) ₂ ] ^10- . The two-component type ready-mix concrete shipment type rapid-setting concrete material according to any one of claims 1 to 4, wherein the pH of the aforementioned component B is 1 to 4. A two-component, ready-mix concrete-type rapid-setting concrete material according to any one of claims 1 to 5, wherein the solid content concentration of the aforementioned component B is 20 to 70% by mass. The two-component, ready-mix concrete shipment type rapid-setting concrete material according to any one of claims 1 to 6, wherein the viscosity of component B at 20°C is 1,400 mPa·s or less. _A two-component ready-mix _concrete material for rapid hardening according to any one of claims 1 to 7, wherein the mass ratio of aluminum in terms of _Al₂O₃ and sulfur in terms of _SO₃ ( _Al₂O₃ / _SO₃ ) in the B component is 0.05 to 1.0. Material A, which contains rapid-hardening cement and a sedative,
The material comprises a curing accelerator containing aluminum, sulfur, sodium, and fluorine,
The aforementioned sleeping agent comprises an oxycarboxylic acid or an alkali metal carbonate other than lithium and a mixture of oxycarboxylic acids,
The sodium nitrite content in material B is 0.3 to 5% by mass.
A ready-mix concrete-type rapid-hardening concrete composition, wherein, per 100 _parts by mass of material B, the aluminum in material B is 0.1 to 20 parts by mass in terms of _Al₂O₃ , the sulfur is 0.1 to 30 parts by mass in terms of _SO₃ , the sodium is 0.01 to 5 parts by mass in terms of _Na₂O , and the fluorine is 0.01 to 10 parts by mass.