JP2001039756A - Low environmental load type concrete - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low environmental load type concrete not only small in carbon output basic unit, but high in compressive strength, having the effect of small calorific value of hydration, or the like and exhibiting a large contribution for environmental problems. SOLUTION: This low environmental load type concrete is prepared by blending cement, anhydrous gypsum generated as an industrial by-product and having pH <=4.5 and lime stone powder and has >=30 N/mm2 compressive strength in 28 day material age and <=70 kg/m3 carbon output basic unit. Further, siliceous fine powder generated as the industrial by-product is desirably blended and the unit quantity of cement is <=280 kg/m3.

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 concrete used mainly in the field of civil engineering and construction.

[0002]

2. Description of the Related Art In recent years, environmental problems have become apparent,
For example, the Third Conference of the Parties to the United Nations Framework Convention on Climate Change was held in Kyoto in December 1997, and the Kyoto Protocol, which stipulates legally binding targets for greenhouse gas emissions in developed countries, was adopted. Was. As a result, each industry has been required to reduce carbon dioxide emissions.However, the ratio of civil engineering and construction industries to the total carbon dioxide emissions of all industries is extremely large, and while satisfying the required performance, the environmental load is reduced. The development of small concrete has been eagerly awaited. In particular, mass concrete cast at a dam or the like uses a large amount of cement and therefore emits a large amount of carbon dioxide, which has a large impact on the environment. Also, mass concrete tends to crack due to temperature stress, so it is necessary to reduce the amount of heat generated by hydration. However, it has been difficult to maintain the strength required for the structure, for example, a strength level of 30 N / mm ² or more, and to suppress the hydration calorific value.

[0003]

The development of concrete that satisfies all of the requirements of reducing the environmental load, reducing the calorific value of hydration and developing the strength has been awaited. In addition, recycling industrial by-products is extremely important in countries with few resources such as Japan, which leads to effective use of resources. The present inventors have conducted various studies in order to solve these problems, and as a result, concrete with a specific industrial by-product will be a low-environmental load type concrete with low carbon dioxide emission while satisfying required performance. With the knowledge described above, the present invention has been completed.

[0004]

That is, the present invention provides a method of mixing cement, anhydrous gypsum produced as an industrial by-product having a pH of 4.5 or less, and limestone fine powder, and having a compressive strength of 30 N / day at 28 days of age. mm ² or more, and wherein the carbon emissions intensity is low environmental load type concrete, characterized in that at 70kgC / m ³ or less, formed by blending the siliceous fine powder further generated as industrial by-products The low environmental load type concrete, wherein the unit cement amount is 280 kg / m ³ or less, and the low environmental load type concrete is characterized in that an adiabatic temperature rise amount is 40 ° C. or less. This is a low environmental load concrete.

[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.
Since the limestone fine powder is obtained by pulverizing limestone, the same unit of carbon emission as crushed stone can be used. In addition, since the carbon emission when recycling industrial by-products is considered to be zero, it is extremely important to use industrial by-products. When crushing for adjusting the particle size of industrial by-products, the fuel consumption required for crushing is taken into account.

The low-environmental load type concrete of the present invention has a compressive strength of 30 N / mm ² or more at 28 days of age, and is based on the above-mentioned LCA subcommittee recommended by the Japan Society of Civil Engineers Global Environment Committee. The basic unit of the calculated carbon emission is 70 kgC / m ³ or less.

[0008] The cement of the present invention is not particularly limited, and includes various portland cements such as ordinary, early strength, moderate heat and low heat, and various mixed cements such as blast furnace cement and fly ash cement.

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. 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 environmentally-friendly concrete of the present invention cannot be obtained.

[0010] The particle size of the anhydrous gypsum industry byproduct of the present invention, but are not particularly limited, is preferably 3000~10000cm ² / g in Blaine specific surface area, 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 usually 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.

The fine limestone powder of the present invention is obtained by pulverizing limestone, and its particle size is not particularly limited. However, it is generally preferable that the specific surface area of the limestone be 2000 to 10000 cm ² / g, and 3000 to 9000 cm ² / g is more preferred. If it is less than 2000 cm ² / g, the workability (workability) of the concrete is not sufficient, and if it exceeds 10,000 cm ² / g, further improvement of the effect cannot be expected.

The mixing ratio of the limestone fine powder of the present invention is not particularly limited, but is usually preferably in the range of 20 to 120 kg / m ³ , more preferably ³⁰ to 100 kg / m ³ in concrete mixing. If it is less than 20 kg / m ³ , workability (workability) of concrete is not sufficiently ensured, and even if it exceeds 120 kg / m ³ , further improvement of the effect cannot be expected.

In the present invention, it is preferable from the viewpoint of developing strength that a silica-based fine powder generated as an industrial by-product is further used in combination. Siliceous fine powder generated as an industrial by-product is not particularly limited, but as a specific example,
Examples include silica fume produced as a by-product when producing metallic silicon or ferrosilicon, silica dust produced when producing fused silica, and the like.

The siliceous fine powder of a particle size of industrial by-product of the present invention, but are not particularly limited, is preferably 10 to 30 m ² / g in Blaine specific surface area, more preferably 15~25m ² / g . It is insufficient strength development is less than 10m ² / g, 30m ²
Even if it exceeds / g, further improvement of the effect cannot be expected.

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

The unit cement amount of the low environmental load concrete of the present invention is preferably 280 kg / m ³ or less. When the unit cement amount exceeds 280 kg / m ³ , the basic unit of carbon emission of concrete increases.

The amount of increase in the adiabatic temperature of the low environmental load concrete of the present invention is preferably 40 ° C. or less. If the adiabatic temperature rise exceeds 40 ° C., heat cracking is likely to occur in concrete due to hydration heat.

In the present invention, a water reducing agent, a high-performance water reducing agent, AE
Water reducing agent, high-performance AE water reducing agent, fluidizing agent, defoaming agent, thickener, rust inhibitor, anti-freezing agent, shrinkage reducing agent, polymer emulsion and setting regulator, cement hardening material, cement expanding material, One or more of clay minerals such as bentonite and anion exchangers such as hydrotalcite can be used within a range that does not substantially hinder the object of the present invention.

In the present invention, the method of kneading 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.

[0021]

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

The p of various gypsum used as an admixture
H 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

[0024]

[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 all exceed 4.5.

A concrete having the composition shown in Table 2 was prepared.
A high performance water reducing agent was added so that the slump of the concrete became 18 ± 1.5 cm, and the air volume was adjusted to 3.0 ± 1.5%. Concrete properties were measured for compressive strength and adiabatic temperature rise on 28 days of age. For those with low cement content, fine limestone powder was blended to improve the workability of concrete. The basic unit of carbon emission of concrete is
Calculated by LCA method. However, as the basic unit of carbon emissions 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 from the power consumed at the time of grinding. Table 2 shows the results.

<Materials used> Limestone fine powder: Commercial product, specific gravity 2.70. Brain specific surface area 50
00 cm ² / g, average particle size 10 μm. Power for grinding is 0.10kwhr / kg.
The basic unit of carbon emissions calculated from the basic unit of power carbon emissions of 0.129 kgC / kwhr is 0.00189 kgC / kg. Siliceous fine powder A: Silica fume, siliceous fine powder as an industrial by-product, specific gravity 2.20. Brain specific surface area 20m 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 of carbon emission 0.014kgC / kg calculated from unit of power carbon emission 0.129kgC / kwhr. Cement (C): Commercial ordinary Portland cement, specific gravity 3.1
Five. Basic unit of carbon emissions: 0.228kgC / kg. Water (W): tap water Sand (S): from Himekawa, Niigata Prefecture, 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. High-performance water reducing agent: Polycarboxylic acid-based commercial product <Measurement method> Compressive strength: Measured according to JIS A 1108, JIS A 1132, and JIS A 1138. Adiabatic temperature rise: Measured at a casting temperature of 20 ° C using an adiabatic temperature rise measuring device manufactured by Tokyo Riko Co., Ltd.

[0028]

[Table 2]

The low environmental load type high-strength concrete of the present invention has a small unit of carbon emission (70 kgC / m ³ or less), a high compressive strength (30 N / mm ² or more), and a small increase in adiabatic temperature. (40 ° C. or less). On the other hand, in each of the comparative examples, the carbon emission intensity and the adiabatic temperature rise amount are larger or the compressive strength is lower than the low environmental load type high-strength concrete of the present invention.

[0030]

According to the present invention, not only a small unit of carbon emission but also a high compressive strength and a small calorific value of hydration are produced, thereby producing a low environmental load concrete which greatly contributes to environmental problems. can do.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 14:28)

Claims (4)

[Claims] 1. A blend of cement, anhydrous gypsum produced as an industrial by-product having a pH of 4.5 or less, and limestone fine powder, a compressive strength of 28 days of age of 30 N / mm ² or more, and a basic unit of carbon emission. Low environmental load concrete characterized in that the concrete is 70 kgC / m ³ or less. 2. The low environmental load concrete according to claim 1, further comprising a silica fine powder generated as an industrial by-product. 3. The low environmental load concrete according to claim 1, wherein a unit cement amount is 280 kg / m ³ or less. 4. The low environmental load concrete according to claim 1, wherein an adiabatic temperature rise amount is 40 ° C. or less.