JP2005047771A - Cement composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cement composition which is obtained by using waste glass powder of which the effective utilization is not found out and prevents the conversion that is the defect of a calcium aluminate-based compound and also prevents the alkali silica reaction that is the defect of the waste glass. <P>SOLUTION: The cement composition contains the calcium aluminate-based compound and the waste glass powder. The cement composition is suitable for civil engineering and building application because the cement composition prevents deterioration in the strength of the calcium aluminate due to the conversion thereof though the calcium aluminate is mainly used, and because the cement composition is excellent in flowability and acid resistance and suppresses the expansion due to the alkali silica reaction caused by alkali metals contained in waste glass powder in large quantity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention mainly relates to a cement composition used in the civil engineering and construction industry.

  In the present invention, “parts” and “%” are based on mass unless otherwise specified. Moreover, the cement concrete said by this invention is a general term for cement paste, mortar, and concrete.

  In recent years, environmental problems have been greatly highlighted. In particular, various attempts have been made for effective use of industrial by-products. However, many of these by-products have not yet been established for effective use. One example is waste glass powder.

  There is a current situation in which the effective use of dust generated when glass waste such as glass bottles is crushed and recycled as glass cullet, so-called waste glass powder, has not been fully studied. Since waste glass powder is currently disposed of as waste, the processing cost of glass cullet obtained by recycling waste glass is very high. Therefore, finding an effective utilization method of waste glass powder is extremely important in constructing a recycling system for waste glass. As an effective utilization method of waste glass powder, a method of using it as an exhaust gas treatment material (Patent Document 1) and a method of mixing with Portland cement (Patent Document 2) have been proposed.

  However, the method used as an exhaust gas treatment material has an extremely large amount of use, and a large amount of residue is generated after the exhaust gas treatment. As a result, there is a fundamental problem that the amount of waste generated cannot be reduced. In addition, in the method of mixing with Portland cement, waste glass contains a large amount of alkali components (Na and K), so that it exhibits an alkali silica reaction called “concrete gun”, resulting in durability and reliability of the concrete. There has been a problem of significantly impairing the performance. Thus, the effective use of waste glass powder is still in search.

  On the other hand, aluminum cement is known along with Portland cement. Alumina cement is a hydraulic material mainly composed of a calcium aluminate compound. Compared with Portland cement, calcium aluminate compounds are excellent in initial strength development, and are excellent in resistance to chloride penetration and acid resistance. However, on the other hand, there has been a problem that the strength is remarkably lowered in the long term due to conversion of hydrate. As a method for preventing the conversion of the calcium aluminate compound, a method using blast furnace granulated slag, fly ash, silica fume and the like in combination has been proposed (Patent Document 3 and Patent Document 4).

  Here, blast furnace granulated slag, fly ash, silica fume, etc. have already been used in many effective ways, and can be used in a large amount mixed with Portland cement until today JIS is established. It has become. There is a strong demand for the establishment of a recycling-oriented society to establish an effective use method for by-products other than these by-products that have not been found yet.

Therefore, as a result of examining the effective utilization method of waste glass powder for which effective utilization method has not yet been established, the present inventor has an effect of preventing conversion of calcium aluminate compound, and calcium aluminate compound In combination, the present inventors have found a completely new fact that the alkali silica reaction, which is a drawback of waste glass, does not occur, and have completed the present invention.
Japanese Patent Laid-Open No. 14-253956 JP-A-12-233961 JP-A-60-180945 Japanese Patent Laid-Open No. 01-141844

  INDUSTRIAL APPLICABILITY The present invention uses a waste glass powder for which no effective utilization method has been found, and prevents the conversion, which is a defect of the calcium aluminate compound, and also prevents the alkali silica reaction, which is a defect of the waste glass. A composition is provided.

The present invention is a cement composition comprising a calcium aluminate compound and waste glass powder, wherein the waste glass powder has a brain specific surface area of 3000 cm ² / g or more. The cement composition is characterized by containing one or more selected from blast furnace granulated slag, fly ash, and silica fume.

  The cement composition of the present invention can prevent a decrease in strength due to conversion of a calcium aluminate compound, and can also prevent an alkali silica reaction caused by waste glass, so that it can be widely used in the civil engineering and construction fields and is an industrial byproduct. Enables effective use of waste glass powder.

The waste glass powder referred to in the present invention is not particularly limited. It is dust generated when waste glass such as glass bottles is crushed and regenerated as glass cullet, and its component is mainly composed of SiO ₂ and its content is about 70%. In addition, CaO, Na ₂ O, Al ₂ O ₃ , Fe ₂ O ₃ , K ₂ O, MgO, SO ₃ , TiO _{2 and the} like are included. The content of CaO and Na ₂ O is about 10%, and other components are often within 3%.

The particle size of the waste glass powder is not particularly limited. Usually, the particle size of dust generated when waste glass is crushed and regenerated as glass cullet is about 2000 cm ² / g in terms of Blaine specific surface area. Although this may be used as it is, it is preferable to further pulverize and classify to make a fine powder. The particle size of the waste glass powder is preferably at least 3000 cm ² / g in Blaine specific surface area, 4000 cm ² / g or more is more preferable. When the particle size of the waste glass powder is less than 3000 cm ² / g, the effect of suppressing the reduction in strength due to conversion may not be sufficient, or the alkali silica reaction may become apparent.

The calcium aluminate compound of the present invention is a generic term for compounds mainly composed of CaO and Al ₂ O ₃ and is not particularly limited. Specific examples _{thereof, CaO · 2Al 2 O 3,} CaO · Al 2 O 3, 12CaO · 7Al 2 O 3, 11CaO · 7Al 2 O 3 · CaF 2, 3CaO · Al 2 O 3, 3CaO · 3Al 2 Examples thereof include crystalline calcium aluminates represented as O ₃ · CaSO ₄ , and amorphous compounds mainly composed of CaO and Al ₂ O ₃ components. Among these, it is preferable to select one having a CaO / Al ₂ O ₃ molar ratio of 1 to 2 from the viewpoint of securing the pot life and from the viewpoint of preventing the alkali silica reaction.

Examples of a method for obtaining calcium aluminate include a method in which a CaO raw material and an Al ₂ O ₃ raw material are heat-treated with a rotary kiln or an electric furnace. Examples of the CaO raw material for producing calcium aluminate include calcium carbonate such as limestone and shells, calcium hydroxide such as slaked lime, and calcium oxide such as quick lime. Examples of the Al ₂ O ₃ raw material include aluminum by-products in addition to industrial by-products called bauxite and aluminum residual ash.

When calcium aluminate is obtained industrially, impurities may be contained. Specific examples _{thereof, SiO 2, Fe 2 O 3} , MgO, TiO 2, MnO, Na 2 O, K 2 O, Li 2 O, S, like P ₂ O _5, and F or the like. The presence of these impurities is not particularly problematic as long as the object of the present invention is not substantially impaired. Specifically, there is no particular problem if the total of these impurities is 10% or less.

The compounds include 4CaO · Al ₂ O ₃ · Fe ₂ O ₃ , 6CaO · 2Al ₂ O ₃ · Fe ₂ O ₃ , 6CaO · Al ₂ O ₃ · 2Fe ₂ O ₃ and other calcium aluminoferrites, 2CaO · Fe ₂ O ₃ and calcium ferrite, such CaO · Fe ₂ O _3, gehlenite _{2CaO · Al 2 O 3 · SiO} 2, calcium aluminosilicate, such as anorthite _{CaO · Al 2 O 3 · 2SiO} 2, Merubinaito 3CaO · MgO · 2SiO ₂ , Akerumanaito 2CaO · MgO · 2SiO _2, calcium magnesium silicate, such as Monte celite CaO · MgO · SiO _2, tri-calcium silicate 3CaO · SiO _2, dicalcium silicate 2CaO · SiO _2, rankinite night 3CaO · 2SiO _2, wollastonite CaO calcium silicates such as SiO _2, calcium titanate CaO-TiO _2, free lime may include a leucite _{(K 2 O, Na 2 O} ) · Al 2 O 3 · SiO 2 or the like. In the present invention, these crystalline or amorphous materials may be mixed.

The particle size of the calcium aluminate compound of the present invention is not particularly limited, but is usually in the range of 3000 to 9000 cm ² / g in terms of Blaine specific surface area, and more preferably about 4000 to 8000 cm ² / g. preferable. If it is less than 3000 cm ² / g, strength development may not be sufficient, and if it exceeds 9000 cm ² / g, handling may be difficult.

The fineness of ground granulated blast furnace slag, fly ash and silica fume (hereinafter referred to as pozzolanic for convenience) is not particularly limited. Is about 3000 to 9000 cm ² / g, and silica fume has a BET specific surface area of about 2 to 200,000 m ² / g.

  The pozzolan plays a role of promoting the effect of preventing the strength reduction due to the conversion of the calcium aluminate compound and the effect of preventing the alkali silica reaction.

  The blending ratio of each material in the cement composition of the present invention is not particularly limited, but usually 30 to 80 parts of calcium aluminate is preferable, and 40 to 70 parts is more preferable. The waste glass powder is preferably 70 to 20 parts, more preferably 60 to 30 parts. In addition, pozzolana can be used by replacing it with part of the waste glass powder as necessary. If calcium aluminate is less than 30 parts or waste glass powder exceeds 70 parts, strength development may not be sufficient, calcium aluminate exceeds 80 parts, waste glass powder is less than 20 parts If it exists, the prevention effect of the intensity | strength fall by conversion may not be enough.

The particle size of the cement composition of the present invention is not particularly limited since it depends on the purpose and application of use, generally preferably 3,000~8,000cm ^{2 /} g in Blaine specific surface area value, 4,000～6,000Cm ² / g is more preferred. If it is less than 3,000 cm ² / g, sufficient strength development may not be obtained, and if it exceeds 8,000 cm ² / g, workability may deteriorate.

  In this invention, you may use together well-known cement other than the cement composition of this invention. Known cements include various portland cements such as normal, early strength, super early strength, low heat, and moderate heat, various mixed cements obtained by mixing these portland cements with blast furnace slag, fly ash, or silica, and limestone powder. Etc., filler cement mixed with blast furnace slow-cooled slag fine powder, waste-use cement, so-called eco-cement, and the like, and one or more of them can be used in combination.

  In the present invention, in addition to aggregates such as sand and gravel, limestone fine powder, blast furnace slow-cooled slag fine powder, sewage sludge incinerated ash and its molten slag, municipal waste incinerated ash and its molten slag, pulp sludge incinerated ash, etc. Admixture, water reducing agent, AE water reducing agent, high performance water reducing agent, high performance AE water reducing agent, antifoaming agent, thickener, rust inhibitor, antifreeze agent, shrinkage reducing agent, polymer, setting modifier, steel fiber, vinylon In the range which does not substantially impair the object of the present invention, one or more of fiber materials such as fibers, carbon fibers, clay minerals such as bentonite, and anion exchangers such as hydrotalcite. It is possible to use.

  In the present invention, the mixing method of each material is not particularly limited, and the respective materials may be mixed at the time of construction, or a part or all of them may be mixed in advance.

  Any existing device can be used as the mixing device, and for example, a tilting barrel mixer, an omni mixer, a Henschel mixer, a V-type mixer, and a Nauta mixer can be used.

A cement composition was prepared by blending calcium aluminate and waste glass powder as shown in Table 1. Subsequently, a mortar was prepared according to JIS R 5201, and a reduction rate of compressive strength due to accelerated conversion was confirmed and an alkali silica reactivity test was performed. However, when the alkali silica reactivity test was performed, an experiment was conducted by replacing a part of the fine aggregate (30 parts with respect to 100 parts of the cement composition) with the reactive aggregate. For comparison, the same procedure was performed when ordinary Portland cement was used instead of calcium aluminate. The results are also shown in Table 1.

<Materials used>
Calcium aluminate (1): Commercially available alumina cement, manufactured by Denki Kagaku Kogyo Co., Ltd., mainly composed of CaO · Al ₂ O ₃ . Blaine specific surface area 5000 cm ² / g.
Calcium aluminate (2): 12CaO · 7Al ₂ O ₃ , reagent primary calcium carbonate and aluminum oxide mixed in a molar ratio of 12 to 7 and baked at 1350 ° C for 3 hours, synthesized twice . Blaine specific surface area 5000 cm ² / g.
Calcium aluminate (3): Amorphous 12CaO · 7Al ₂ O ₃ , 3% of reagent grade 1 silica added to calcium aluminate (2), melted at 1650 ° C, and then rapidly cooled to synthesize. Blaine specific surface area 5000 cm ² / g.
Calcium aluminate (4): A mixture of equal amounts of calcium aluminate (1) and calcium aluminate (2). Blaine specific surface area 5000 cm ² / g.
Waste glass powder A: Dust generated from a factory that recycles waste glass as glass cullet is pulverized to a specific surface area of 3000 cm ² / g.
Waste glass powder B: Waste glass powder A is further pulverized to a Blaine specific surface area of 4000 cm ² / g.
Waste glass powder C: Waste glass powder A further pulverized to a Blaine specific surface area of 6000 cm ² / g.
Waste glass powder D: Waste glass powder A further pulverized to a Blaine specific surface area of 8000 cm ² / g.
Ordinary Portland cement: A mixture of three commercial products in equal amounts.
Water: Tap water fine aggregate: Standard sand used in JIS R 5201.
Reactive fine aggregate: Opal quartzite.

<Measurement method>
Compressive strength: Mortar was packed in a mold to form a 4 cm × 4 cm × 16 cm compact, and the compressive strength at 28 days of age was measured according to JIS R 5201.
Accelerated conversion test: Specimens subjected to 20 ° C water curing until the age of 28 days were placed in 50 ° C warm water for 28 days for accelerated conversion. The ratio of the intensity after the acceleration conversion to the compression intensity before the acceleration conversion was expressed as a relative value and evaluated.
Alkali-silica reactivity test: Evaluated by the expansion rate after 6 months by the mortar bar method.

The same procedure as in Example 1 was conducted except that 60 parts of calcium aluminate (1), waste glass powder B, and various pozzolans were blended as shown in Table 2 to obtain a cement composition. The results are also shown in Table 2.
<Materials used>
Pozzolana α: Commercially ground granulated blast furnace slag, Blaine specific surface area 4000 cm ² / g.
Pozzolana β: Commercially available fly ash, brain specific surface area 4000 cm ² / g.
Pozzolana γ: Commercially available silica fume, BET specific surface area of 150,000 m ² / g.
Pozzolanic Δ: An equal mixture of pozzolanic α and pozzolanic β. Blaine specific surface area 4000cm ² / g.

Calcium aluminate (1), waste glass powder B, and various pozzolans were blended as shown in Table 3, and a cement composition was used to conduct an acid resistance experiment. The results are also shown in Table 3.
<Measurement method>
Acid resistance experiment: The specimen was immersed in a solution having a sulfuric acid concentration of 5%, and the weight change and the sulfuric acid penetration depth were confirmed and evaluated. X when the weight change is ± 5% or more and the sulfuric acid penetration depth is 5 mm or more, Δ when the weight change is ± 5% or more, or the sulfuric acid penetration depth is 5 mm or more, and the weight change is ± 5. % When the sulfuric acid penetration depth is less than 5 mm, and ◎ when the weight change is less than ± 3% and the sulfuric acid penetration depth is less than 3 mm.

The cement composition of the present invention effectively prevents strength reduction due to conversion of calcium aluminate compounds, is excellent in fluidity and acid resistance, and is caused by an alkali silica reaction caused by alkali metals contained in a large amount of waste glass powder. It has features such as suppression of expansion, and is suitable for civil engineering and construction applications.

Claims (3)

A cement composition comprising a calcium aluminate compound and waste glass powder. The cement composition according to claim 1, wherein the glass surface area of the waste glass powder is 3000 cm ² / g or more. The cement composition according to claim 1 or 2, comprising one or more selected from blast furnace granulated slag, fly ash, and silica fume.