JP2001039758A - Low environmental load type ultra high early strength concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a low environmental load type ultra high early strength concrete having excellent high early strength property at a temp. ranging from a low temp. to the normal temp. and remarkably reduced in carbon output. SOLUTION: This low environmental load type ultra high early strength concrete is prepared by blending high early strength Portland cement, anhydrous gypsum having pH <=4.5 and generated as an industrial by-product and a setting accelerator and has >=10 N/mm2 compressive strength at 5 deg. in 1 day material age and >=35 N/mm2 compressive strength at 20 deg.C in 1 day material age and <=95 kg/m3 carbon output basic unit. Further, siliceous fine powder generated as the industrial by-product is desirably blended.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low environmental load type high strength concrete used mainly in the field of civil engineering and construction.

[0002]

2. Description of the Related Art In recent years, the performance required for concrete has been diversified, and in particular, needs for increasing the strength of concrete have been increasing. On the other hand, environmental issues are becoming more apparent. For example, in December 1997, the
The Third Conference of the Parties was held in Kyoto, and the Kyoto Protocol was adopted, setting out legally binding targets for greenhouse gas emissions in developed countries. As a result, it has become necessary for each industry to reduce carbon dioxide emissions.
The contribution of the civil engineering and construction industry to the carbon dioxide emissions of all industries is extremely large, and there is an urgent need to develop concrete that satisfies the required performance and has a low environmental load.

[0003]

SUMMARY OF THE INVENTION High performance concrete,
Particularly, ultra-high strength concrete is a concrete with a large environmental load because a large amount of cement that emits a large amount of carbon dioxide is used during production. In addition, recycling of industrial by-products in countries with few resources such as Japan,
It leads to effective use of resources and is extremely important. The present inventors have conducted various studies in order to solve these problems, and as a result, in concrete containing a specific industrial by-product, excellent early strength, low carbon dioxide emission, low environmental load type ultra early strength. The present invention has been completed based on the knowledge that concrete will be obtained.

[0004]

That is, the present invention provides a method of blending early-strength Portland cement, anhydrous gypsum generated as an industrial by-product having a pH of 4.5 or less, and a setting accelerator,
Water / cement ratio of 35% or more, compressive strength per day at 5 ° C is 10N / mm ² or more, compressive strength at 20 ° C per day is 35%
N / mm ² or more, carbon intensity of concrete is 95kgC
/ m ³ or less, which is a low-environmental load type ultra-high-strength concrete characterized by comprising silica fine powder generated as an industrial by-product. Concrete, unit cement amount 400k
It is low environmental load type super early strength concrete, characterized in g / m ³ or less, set accelerators is calcium formate, calcium nitrite, calcium nitrate, selected from among calcium thiocyanate and calcium thiosulfate The low-environmental load type ultra-high-strength concrete is characterized in that it is at least one or more types, and the low-environmental load type ultra-high-strength concrete is characterized by containing a polyether-based water reducing agent.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The basic unit of carbon emission of the concrete of the present invention means the weight of carbon emitted when producing 1 m ³ of concrete, and the unit is expressed in (kgC / m ³ ). The basic unit of carbon emissions of concrete is calculated from the concrete composition using the basic unit of carbon emissions of materials used when manufacturing concrete, that is, cement, sand, gravel, admixture (material), etc. I do. The basic unit of carbon emissions for each material is calculated and determined by the LCA (Life Cycle Assessment) method. Here, the LCA method is a method of expressing the carbon dioxide emissions that occur in the life cycle of raw material procurement, transportation, manufacturing, consumption, and disposal when manufacturing materials as carbon emissions. . The basic unit of carbon emissions of materials used in the civil engineering and construction industries is:
For example, proposals have been made by various academic organizations and research institutions such as the Japan Society of Civil Engineers, the Japan Aerospace Exploration Association, the Ministry of Construction, the Institute of Construction and the Ministry of Construction. As a specific example, for example,
According to the values recommended by the LCA Subcommittee of the Global Environment Committee of the Japan Society of Civil Engineers, the basic unit of carbon emission of ordinary Portland cement is 0.228 kgC / kg, blast furnace cement is 0.135 kgC / kg, and sand is 0.00154 kgC. / kg, gravel is 0.00189kg for crushed stone
C / kg and quarrying are set at 0.00154kgC / kg.
Early strength Portland cement has a slightly larger amount of limestone (calcium carbonate) as a raw material than ordinary Portland cement, but considering the firing and crushing processes, the basic unit of carbon emission of early strength Portland cement is: Usually the value of Portland cement can be applied.
Also, the carbon emissions from recycling industrial by-products are:
Utilizing industrial by-products is extremely important because it is considered zero.

[0007] The low-environmental load type ultra-high-strength concrete of the present invention has a basic unit of carbon emission calculated based on the recommended values of the LCA subcommittee of the Japan Society of Civil Engineers of 95 kgC /
m ³ or less.

[0008] The early-strength Portland cement of the present invention is manufactured by JI
It means the early-strength Portland cement specified in S, and is not particularly limited as long as it is of JIS standard quality, but usually, the content of alite (C ₃ S solid solution) is 60 % Is preferable from the viewpoint of early strength. Although the fineness not particularly limited, is preferably 3000~5000cm ² / g in Blaine specific surface area, 3500~4500cm ² / g is more preferable. In 3000cm less than ² / g may sufficient early strength can not be obtained, 5000 cm ² /
If it exceeds g, concrete slump loss may increase or workability may deteriorate.

[0009] The water / cement ratio (W / C) of the low environmental load type ultra-high strength concrete of the present invention is 35% or more. If it is less than 35%, the workability of fresh concrete is significantly deteriorated, and cracks due to plastic cracks and self-shrinkage after curing are liable to occur.

The low-environmental load type ultra-high-strength concrete of the present invention has a compressive strength of 10 N / mm ² or more per day at 5 ° C.
One day old compressive strength at 35 ° C. is 35 N / mm ² or more. If the strength development is lower than this, it is not enough as an ultra-high strength concrete.

The anhydrous gypsum produced as an industrial by-product of the present invention preferably has a pH of 4.5 or less as measured according to JIS R 9101, and if the pH exceeds 4.5, good strength development cannot be obtained. Gypsum is roughly divided into dihydrate gypsum, hemihydrate gypsum and anhydrous gypsum, but anhydrous gypsum is preferred in the present invention, and good strength development cannot be obtained with dihydrate gypsum or hemihydrate gypsum. Examples of anhydrous gypsum include anhydrous gypsum produced as a by-product during hydrofluoric acid production and anhydrous gypsum produced naturally, but it is preferable to use anhydrous gypsum produced as an industrial by-product in order to reduce the environmental load. Natural anhydrous gypsum has a pH of more than 4.5 and carbon emissions are greater than anhydrous gypsum, an industrial by-product, and the low environmental load type ultra-high strength concrete of the present invention cannot be obtained.

[0012] The particle size of the anhydrous gypsum industry byproduct of the present invention, but are not particularly limited, but usually, is 3000~10000cm ² / g in Blaine specific surface area preferably, 4000~9000cm ² /
g is more preferred. If it is less than 3000 cm ² / g, the strength developability is not sufficient, and if it exceeds 10,000 cm ² / g, further enhancement of the effect cannot be expected. Further, from the viewpoint of developing strength, the average particle size of anhydrous gypsum is preferably 10 μm or less.

The mixing ratio of anhydrous gypsum as an industrial by-product of the present invention is not particularly limited, but is generally preferably in the range of 10 to 50 kg / m ³ in concrete mixing.
~40kg / m ³ is more preferable. If it is less than 10 kg / m ³ , the strength development is not sufficient, and even if it exceeds 50 kg / m ³ , further increase in strength cannot be expected.

It is preferable from the viewpoint of developing strength that silica fine powder generated as an industrial by-product is used in combination with anhydrous gypsum as an industrial by-product of the present invention. The siliceous fine powder generated as an industrial by-product is not particularly limited, but specific examples include silica dust generated when producing silica fume or fused silica, blast furnace slag, fly ash, and the like.

The mixing ratio of the siliceous fine powder of the industrial by-product of the present invention is not particularly limited, but usually, in the case of concrete mixing, anhydrous gypsum and siliceous fine powder are combined to obtain 10 to 100 kg / m ³ . It is preferable to mix in the range. If it is less than 10 kg / m ³ , the strength development is not sufficient, and even if it exceeds 100 kg / m ³ , further increase in strength cannot be expected.

The unit cement amount of the low environmental load type ultra-high strength concrete of the present invention is preferably 400 kg / m ³ or less. If the unit cement amount exceeds 400 kg / m ³ , the basic unit of carbon emission of concrete increases.

The setting accelerator of the present invention is not particularly restricted but includes, for example, inorganic sulfates such as aluminum sulfate, alum, sodium sulfate and potassium sulfate, carbonates such as sodium carbonate and potassium carbonate, and alumina. Alkaline aluminates such as sodium citrate and potassium aluminate, nitrates such as sodium nitrate, potassium nitrate and calcium nitrate, nitrites such as sodium nitrite, potassium nitrite and calcium nitrite, formic acid, sodium formate, potassium formate and formic acid Formates such as calcium, lactic acid, sodium lactate, lactate such as potassium lactate and calcium lactate, acetates such as acetic acid, sodium acetate, potassium acetate and calcium acetate, sodium thiocyanate, potassium thiocyanate and calcium thiocyanate Osocyanates, thiosulfates such as sodium thiosulfate, potassium thiosulfate and calcium thiosulfate, and alkanolamines such as monoethanolamine, diethanolamine, triethanolamine and triisopropanolamine, and the like. One or more can be used. Among the setting accelerators of the present invention, in particular, it is preferable to use at least one or more selected from calcium formate, calcium nitrite, calcium nitrate, calcium thiocyanate and calcium thiosulfate for early strength and long-term durability. It is preferable from the viewpoint of.

The amount of the setting accelerator is not particularly limited, but is usually preferably 0.1 to 5%, more preferably 0.3 to 2%, based on the cement.
If it is less than 0.1%, the effect of accelerating the setting may not be sufficient, and even if it exceeds 5%, further enhancement of the effect cannot be expected.

In the present invention, a water reducing agent, a high-performance water reducing agent, AE
It is preferable to use a water reducing agent, a high-performance AE water reducing agent, a fluidizing agent, and the like (hereinafter, these are collectively referred to as a water reducing agent) in view of securing fluidity and developing strength. The water reducing agent of the present invention is not particularly limited, but is usually referred to as naphthalene-based, melamine-based, polycarboxylic acid-based, aminosulfonic acid-based, and more recently, polyether-based. The liquid type and the powder type can be used. Specific examples include Kao Corporation's product names “Mighty 2000WH”, “Mighty 100” and “Mighty 150”, and Denka F
"T-500" and "DENKA FT-80", brand name "Cell Flow 110P" manufactured by Daiichi Kogyo Seiyaku Co., Ltd., brand name "Melment" manufactured by Showa Denko
F-10 "," Mole Master 10 "and" Mole Master 2 "
0 "and" Sikament 1000H "(trade name, manufactured by Sika Japan Co., Ltd.). Examples of polycarboxylic acids include" Darex Super 200 "(trade name, manufactured by Grace Chemicals), NM
Company B brand name “Leo Build SP-8HS”, Takemoto Yushi Company brand name “Tupole HP-11” and “Pole Fine 510”
N ", trade names" Palick FP-100U "and" Palick FP-200 "manufactured by Fujisawa Pharmaceutical Company, Ltd., and" Sunflow PS "and" Sunflow HS700 "manufactured by Nippon Paper Industries.
In addition, as the polyether type, the product name “CAD900
0P "and the like. Various other water reducing agents are commercially available from other companies. In the present invention, it is preferable to mix a naphthalene-based, polycarboxylic acid-based, and polyether-based water reducing agent from the viewpoint of maintaining fluidity and developing strength, and particularly to mix a polyether-based water reducing agent. preferable.

In the present invention, an early Portland cement,
In addition to anhydrous gypsum, silica fine powder, setting accelerator and water reducing agent generated as industrial by-products, defoaming agents, thickeners, rust inhibitors, antifreezing agents, shrinkage reducing agents, polymer emulsions and setting retarders, It is also possible to use at least one or more of cement hardened materials, cement expanding materials, clay minerals such as bentonite, and anion exchangers such as hydrotalcite, as long as the object of the present invention is not substantially inhibited. It is possible.

In the present invention, the method of kneading the concrete is not particularly limited, and the respective materials may be mixed at the time of kneading, or some of them may be mixed in advance.
Alternatively, all may be mixed. As the kneading apparatus, any existing apparatus can be used, and examples thereof include a twin-screw forced mixer, a pan-type forced mixer, a planetary mixer, a tilted mixer, an omni mixer, and the like.

[0022]

The present invention will be described below in detail with reference to examples.

Example 1 The pH of various gypsums used as an admixture was measured. Table 1 shows the results. In addition, the basic unit of carbon emission of the admixture was calculated by the LCA method. However, when an industrial by-product was used, the basic unit of carbon emission of the material was calculated from the power consumed at the time of grinding.

<Materials> Admixture a: anhydrous gypsum by-produced during the production of hydrofluoric acid, specific gravity
2.96. Pulverized to a specific surface area of 5000 cm ² / g, average particle size 10
μm. Power for grinding 0.06kwhr / kg. Basic unit of carbon emissions calculated from 0.129 kgC / kwhr
0.008kgC / kg. Admixture b: anhydrous gypsum by-product during hydrofluoric acid production, specific gravity
2.95. Pulverized to a specific surface area of 5000 cm ² / g, average particle size 8μ
m. Power for grinding 0.07kwhr / kg. Power unit carbon emissions 0.129kg C / kwhr Unit carbon emissions calculated from 0.0 / 0.0hr 0.0
09kgC / kg. Admixture c: natural anhydrous gypsum, specific gravity 2.96. Pulverized to a Blaine specific surface area of 5000 cm ² / g, average particle size 18 μm. Power for grinding
0.17kwhr / kg. 0.129kgC / kwhr per unit of power carbon emissions
The basic unit of carbon emissions calculated from the above is 0.022kgC / kg. Admixture d: Natural dihydrate gypsum heated at about 130 ° C. to form hemihydrate gypsum. Specific gravity 2.65. Brain specific surface area 5000cm
² / g, average particle size 12μm. Power for heating 0.15kwhr / k
g. Power for grinding is 0.10kwhr / kg. Basic unit of carbon emissions of power 0.129kgC / kwhr Unit of carbon emissions calculated from 0.032kgC / kwhr
kgC / kg. Admixture e: flue gas desulfurized dihydrate gypsum, specific gravity 2.32. Pulverized to a Blaine specific surface area of 5000 cm ² / g, average particle size 11 μm. Power for grinding 0.06kwhr / kg. Basic unit of carbon emissions of power 0.129kgC /
Basic unit of carbon emission calculated from kwhr 0.008kgC / kg. <Measurement method> Specific gravity, Blaine specific surface area: Measured according to JIS R 5201 Average particle size: Measured by laser type particle size distribution analyzer pH: Measured according to JIS R 9101

[0025]

[Table 1]

The pH of anhydrous gypsum, an industrial by-product used in the present invention, is 4.5 or less, and the pH of natural anhydrous gypsum, hemihydrate gypsum and dihydrate gypsum is all over 4.5.

A concrete having the composition shown in Table 2 was prepared.
The compressive strength at 5 ° C and 20 ° C for one day of age was measured. or,
The unit of carbon emission of concrete was calculated by LCA method. However, as the basic unit of carbon emission of each material, the values recommended by the LCA subcommittee of the Global Environment Committee of the Japan Society of Civil Engineers were used. When using industrial by-products,
The basic unit of carbon emission of the material was calculated. The concrete fine aggregate ratio (s / a) is 42%, and the slump value is 18 ± 1.5.
cm, air volume 4.5 ± 1.5%, high performance water reducing agent and AE
The agent was added. Table 2 shows the results.

<Materials used> Silica fine powder A: Silica fume, siliceous fine powder as an industrial by-product, specific gravity 2.20. Brain specific surface area 200000
cm ² / g, average particle size 0.2 μm. Admixture f: 50 parts by weight of admixture b and 50 parts by weight of siliceous fine powder A mixed and ground to a Blaine specific surface area of 9000 cm ² / g,
Specific gravity 2.58. Power at the time of grinding 0.08kwhr / kg. Unit carbon emission 0.010kgC / kg calculated from unit carbon emission 0.129kgC / kwhr of power. Cement (C): Commercial Portland cement, specific gravity 3.1
Four. Blaine specific surface area 4250cm ² / g. Basic unit of carbon emissions0.
228kgC / kg. Setting accelerator A: Reagent grade 1 calcium formate Water (W): Tap water Sand (S): Himekawa, Niigata, specific gravity 2.62. Basic unit of carbon emissions
0.00154kgC / kg. Gravel (G): From Himekawa, Niigata Prefecture, specific gravity 2.64. Basic unit of carbon emissions: 0.00189kgC / kg. Water reducing agent a: Commercially available polyether type <Measurement method> Compressive strength: Measured according to JIS A 1108, JIS A 1132, and JIS A 1138.

[0029]

[Table 2]

The low-environmental load type ultra-high-strength concrete of the present invention has a basic unit of carbon emission of 95 kgC / m ³ or less at 5 ° C.
Compressive strength of 1 day age of at the 10 N / mm ² or more, the compressive strength age of 1 day at 20 ° C. is 35N / mm ² or more. On the other hand, in each of the comparative examples, the unit of carbon emission is larger or the compressive strength is lower than the low environmental load type ultra-high strength concrete of the present invention.

Example 2 Table 3 shows the unit cement amount of concrete at 350 kg / m ³ , the water / cement ratio is 40%, the unit amount of the admixture f is 50 kg / m ³ , the type of the setting accelerator and the compounding amount to the cement. Except having changed as above, it carried out similarly to Example 1. Table 3 shows the results.
Shown in

<Materials Used> Setting accelerator A: Reagent primary calcium formate Setting accelerator B: Reagent primary calcium nitrite Setting accelerator C: Reagent primary calcium nitrate Setting accelerator D: Reagent primary calcium thiocyanate 4 Hydrate Setting accelerator E: Reagent 1st grade calcium thiosulfate Setting accelerator F: 50 parts by weight of setting accelerator A and setting accelerator B50
Parts by weight of a mixture of setting accelerator G: 50 parts by weight of setting accelerator A and 50 parts of setting accelerator C50
Parts by weight of a mixture set accelerator H: set accelerator A 40 parts by weight and set accelerator B30
Mixture of parts by weight and 30 parts by weight of setting accelerator C

[0033]

[Table 3]

[0034] Low environmental load type ultra-high strength concrete of the present invention
Means that the basic unit of carbon emissions is 95kgC / m^Three5 ℃ below
Compressive strength of 10N / mm per day^TwoAt 20 ° C
Compressive strength of 35N / mm per day^TwoThat is all. Meanwhile, compare
In the example (Experiment No.2-1), the compressive strength of one day old at 5 ℃
Is 2N / mm^TwoThe compressive strength of one day of age at 20 ° C is 34N / mm ^TwoWhen
It shows a low value.

Example 3 The unit cement amount of concrete was 350 kg / m ³ , the water / cement ratio was 40%, the unit amount of the admixture f was 50 kg / m ³ , and the setting accelerator H was used at 1% to the cement to reduce water. The procedure was performed in the same manner as in Example 1 except that the type of the agent was changed as shown in Table 4.
The same test was also conducted when no water reducing agent was added. However, the slump value is not constant. Table 4 shows the results.

<Materials used> Water reducing agent a: Commercially available polyether-based product, 0.10% added to cement in terms of solid content. Water reducer b: Commercially available naphthalene-based product, 0.60% added to cement in terms of solid content. Water reducer c: Melamine-based commercial product, 0.60% added to cement in terms of solid content. Water reducer d: Aminosulfonic acid commercial product, 0.65% added to cement in terms of solid content. Water reducing agent E: Polycarboxylic acid-based commercial product, 0.14% added to cement in terms of solid content.

[0037]

[Table 4]

The low-environmental load type ultra-high-strength concrete of the present invention has a carbon emission intensity of 95 kgC / m ³ or less, a compressive strength per day at 5 ° C. of 10 N / mm ² or more, and 20 ° C. Is 1 day or more compressive strength of 35 N / mm ² or more. Among them, those containing the water reducing agent i (polyether type) have good strength developability.

[0039]

Industrial Applicability According to the present invention, concrete having excellent early strength in a range from low temperature to normal temperature and having a significantly reduced carbon emission and a small environmental load can be obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 24:04)

Claims (5)

[Claims] (1) An early-strength Portland cement having a pH of 4.5
Anhydrous gypsum which occurs as the following industrial byproducts, blended and setting accelerator, water / cement ratio of 35% or more, 5 compressive strength of 1 day age of at ° C. is 10 N / mm ² or more, the age at 20 ° C. Low environmental impact type ultra-high-strength concrete characterized by a daily compressive strength of 35 N / mm ² or more and a carbon unit of concrete of 95 kgC / m ³ or less. 2. The low environmental load type ultra-high strength concrete according to claim 1, further comprising a silica fine powder generated as an industrial by-product. 3. The low environmental load type ultra-high strength concrete according to claim 1, wherein a unit cement amount is 400 kg / m ³ or less. 4. The method according to claim 1, wherein the setting accelerator is at least one selected from calcium formate, calcium nitrite, calcium nitrate, calcium thiocyanate and calcium thiosulfate. Low environmental load type ultra-high strength concrete described in Crab. 5. The low environmental load type ultra-high strength concrete according to claim 1, further comprising a polyether-based water reducing agent.