JP5069044B2 - Cement admixture and cement composition - Google Patents

Description

  The present invention mainly relates to a cement admixture and a cement composition for use in the civil engineering and construction fields.

Zeolite generally has a skeletal structure formed of condensed acid of silicate or aluminosilicate, and forms various three-dimensional skeletons. Therefore, various cations can be taken into cavities inside the skeleton. Since it is possible to provide various functions, it is used in a wide range of fields. Typical applications include removal of ammonia nitrogen from wastewater using cation exchange capacity, softening of hard water, water removal using adsorption capacity, synthesis of various organic compounds using catalytic capacity, etc. ( Non-patent document 1).
Nobuyoshi Hara, Hiroshi Takahashi: Zeolite-Fundamentals and Applications, pp. 113-218, Kodansha, 1995

In the civil engineering / architecture field, technologies for removing heavy metals such as hexavalent chromium (Patent Documents 1 and 2), technologies for adsorbing and reducing chlorine ions (Patent Document 3), and technologies for purifying water and air (Patent Document 4) ), Technology that lowers the viscosity of concrete by combining with a high-performance water reducing agent and improves finishability and handling (Patent Document 5), technology that removes sodium and potassium caused by alkali-aggregate reaction (Patent Document 6, 7, 8) etc. are known.
JP-A-2005-112706 JP-A-2005-232341 JP 2005-225706 A JP 2004-337822 A Japanese Patent Application Laid-Open No. 07-277795 Japanese Patent Laid-Open No. 02-208250 Japanese Patent Laid-Open No. 04-92844 JP 2003-306372 A

On the other hand, in the civil engineering / architecture field, attention has recently been paid to various repair / reinforcing materials and construction methods for deteriorated concrete structures. One of them is a repair method for deterioration caused by alkali aggregate reaction. Alkali-aggregate reaction is a deterioration phenomenon in which an alkali component contained in concrete reacts with aggregate to generate an expansive gel substance and cracks are generated in the concrete. As a countermeasure, it is necessary to remove alkali components (sodium and potassium), but it is very difficult to remove until there is no adverse effect in the existing structure, and there is still no sufficient countermeasure work.
In addition, the use of aggregates having no alkali aggregate reactivity is demanded to develop technology capable of suppressing the reaction even when alkali reactive aggregates are used in a situation where aggregate resources are limited.
At present, the method of mixing pozzolanic material in concrete (Non-patent Document 2), the method of mixing lithium nitrite and lithium hydroxide in concrete, or the method of impregnating them from the surface (Patent Document 9), the concrete surface A method of forming a waterproof layer with a water repellent or a surface coating material is known (Patent Document 10). Further, it is known that even when the same alkali metal is present, if lithium is present, expansion can be suppressed and deterioration due to an alkali aggregate reaction can be suppressed (Non-patent Document 3).
Miki Kawamura, Kunio Takemoto, Shigemasa Kayaba: Suppressive effect on expansion of alkali and silica caused by external alkali infiltration of fly ash and blast furnace slag, 42nd Annual Conference of Japan Society of Civil Engineers, V-206, pp. 450-451, September 1987 JP-A 61-256951 JP-A-63-50380 Mitsuru Saito, Akio Kitagawa, Shigemasa Kiba: Suppression of alkaline aggregate expansion by lithium nitrite, materials, Vol. 41, no. 486, pp. 1375-1381, 1992

  The cement admixture of the present invention contains a zeolite synthesized from allophane that ion-exchanges with sodium or potassium, which are causative substances of alkali aggregate reaction in the cement composition, and releases lithium. All conventional zeolites that suppress alkali-aggregate reaction are zeolites that have alkaline earth metal (calcium) as an exchangeable cation. They take up sodium and potassium in the cement composition and release calcium, so the suppression effect is It was insufficient.

  The present invention provides a cement admixture and a cement composition that not only take in sodium and potassium, but also release lithium which has an effect of suppressing the alkali-aggregate reaction.

That is, the present invention provides (1) a cement admixture that suppresses an alkaline aggregate reaction containing EDI type and / or ABW type lithium zeolite synthesized from allophane, and (2) the cement admixture and cement of (1) A cement composition containing 0.2 to 100 parts by mass of cement admixture with respect to 100 parts by mass of cement, (3) EDI type and / or ABW type lithium zeolite synthesized from allophane and cement A cement composition containing lithium and containing 0.2 to 100 parts by mass of lithium zeolite with respect to 100 parts by mass of cement to suppress an alkali aggregate reaction , (4) (2) or (3) A paste, mortar or concrete produced using

  The cement admixture of the present invention quickly ion-exchanges with sodium and potassium, and lithium is released into the cement composition, so that the effect of suppressing expansion due to the alkali-aggregate reaction is significantly greater than that of conventional zeolites. Repair of mortar or concrete deteriorated by the material reaction or reactive aggregate can be used.

  Hereinafter, the present invention will be described in detail.

The lithium zeolite synthesized from the allophane of the present invention can be synthesized, for example, from natural soil containing allophane as a mineral component. Allophane is typically an aluminosilicate to produce the volcanic ash soil (amorphous silica-alumina gel _{(Al 2 0 3 · mSi0 2} · nH 2 0 + Al (0H) 3).
Lithium zeolite synthesized from the allophane of the present invention is classified according to the type of three-dimensional structure as a skeleton structure, and there are many structures such as A-type, EDI-type, ABW-type, and BIK. The EDI type and / or the ABW type are preferred from the viewpoint of the effect of suppressing the expansion of the alkali aggregate reaction.

An example of the synthesis method of EDI type and ABW type lithium zeolite of the present invention is shown below.
(EDI type) Powdered allophane is placed in a 10 g beaker, and 100 ml of a 1 mol / l aqueous lithium hydroxide solution is added in portions of 50 ml in two portions and mixed. Next, leave at 60 ° C. for 24 hours with occasional mixing. After removing the supernatant, the precipitate is transferred to a beaker and suspended in distilled water. Further, the mixture is neutralized by adding acetic acid, filtered through a Buchner funnel, washed with distilled water, and then dried at 90 ° C. for 24 hours or longer for synthesis.
(ABW type) Powdered allophane is put in a 10 g beaker, and 100 ml of a 1 mol / l lithium hydroxide aqueous solution is added and mixed in 50 ml portions. Then leave it at 90 ° C. for 48 hours with occasional mixing. After removing the supernatant, the precipitate is transferred to a beaker and suspended in distilled water. Further, the mixture is neutralized by adding acetic acid, filtered through a Buchner funnel, washed with distilled water, and then dried at 90 ° C. for 24 hours or longer for synthesis.

  Powdered allophane can be produced by using naturally-occurring allophane-containing soil, which is purified by water to remove impurities in the soil and classify coarse particles. The purified allophane is used after drying at 100 ° C. for 48 hours and then pulverizing with a vibration mill for 1 minute.

  The cement used in the cement composition of the present invention is not particularly limited, but various portland cements defined in JIS R 5210, JIS R 5211, JIS R 5212, and various types defined in JIS R 5213. One or more types selected from mixed cement, blast furnace cement manufactured with an admixture more than specified in JIS, fly ash cement, filler cement mixed with silica cement, limestone powder, alumina cement, etc. Can be used.

  The amount of the cement admixture of the present invention is preferably 0.2 to 100 parts by mass with respect to 100 parts by mass of cement. If the amount is less than 0.2 parts by mass, the effect of suppressing the expansion due to the alkali aggregate reaction is small, and if the amount exceeds 100 parts by mass, the effect of suppressing the expansion is not so much improved. Further, EDI type lithium zeolite and ABW type lithium zeolite may be mixed and used.

The cement admixture of the present invention can be used in combination with any admixture (agent) used in cement.
For example, AE agent, water reducing agent, high performance water reducing agent, high performance AE water reducing agent, foaming agent, foaming agent, separation reducing agent, setting agent, quick setting material (agent), rust inhibitor, waterproofing agent, shrinkage reduction Agent, expansion agent (agent), high-strength admixture (agent), antifreeze agent, polymer dispersion, antifoaming agent, heat of hydration reducing agent, alkali aggregate reaction inhibitor (agent) other than the present invention, prevention of efflorescence Agents, rapid hardeners (agents), fibers, clay minerals, gypsums and the like.

The cement composition of the present invention can be used in any form of paste without adding aggregate and water, or mortar or concrete containing aggregate and water.
The aggregate is not particularly limited, and an aggregate that may show an alkali aggregate reaction may be used as well as an aggregate that is determined to be harmless to the alkali aggregate reaction. For example, natural aggregates produced from rivers, mountains, and seas, lightweight aggregates, and mixed aggregates using a combination of two or more of these can be used. In addition to ordinary sand and gravel, for example, natural aggregates such as silica sand and limestone, artificial aggregates such as blast furnace granulated slag system, blast furnace slow-cooled slag system, and recycled aggregate system can be used. From the viewpoint of acid resistance and the like, it is preferable to select a silica sand system. In addition, a heavy aggregate having a specific gravity of 3.0 g / cm ³ or more can be used, and specific examples thereof include, for example, an electric furnace oxidation period slag-based aggregate, ferronickel slag, ferrochrome slag as an artificial aggregate. Non-ferrous smelted aggregate slag, such as copper slag, zinc slag and lead slag, and natural aggregates include peridotite aggregates, so-called olivine sand, emery ore, etc. It is done.
The aggregate may be mixed at the construction site, but when it is mixed with cement in advance, a dry aggregate obtained by drying the aggregate may be used.

The paste, mortar, or concrete using the cement composition of the present invention can be subjected to a construction method that is usually used in the civil engineering / architectural field.
For example, since a paste obtained by adding water to the cement composition of the present invention is liquid, it has excellent filling properties in narrow gaps and can be used for injection into cracks generated by expansion due to alkali aggregate reaction. In addition, mortar and concrete can be used for restoration of a portion deteriorated by an alkali aggregate reaction in an existing mortar or concrete structure.

  Hereinafter, although it demonstrates in detail based on an Example, it is not limited to this.

  1 g each of EDI type lithium zeolite and ABW type lithium zeolite synthesized from allophane, which is the cement admixture of the present invention, is added to 50 ml each of sodium hydroxide and potassium hydroxide aqueous solution adjusted so that sodium and potassium become 200 mg / l. The mixture was stirred, and the sodium, potassium and lithium concentrations in the solution at each time shown in Table 1 were determined with an atomic absorption photometer. For comparison, an A-type lithium zeolite having a different skeleton structure and an A-type calcium zeolite having calcium as an exchangeable cation were also used. The framework structure of zeolite was identified by a diffraction pattern of powder X-ray diffraction measurement (for example, R. von Ballmoos, Collection of simulated XRD patterns for zeolites, Butter worth Scientific Limited, 1984). The results are shown in Table 1.

(Materials used)
EDI type lithium zeolite: It was carried out in the same manner as the synthesis method shown in paragraph [0011]. First, powdered allophane (SiO ₂ : 33.6% by mass, Al ₂ O ₃ : 33.1% by mass, Fe ₂ O ₃ : 2.3% by mass, CaO 0.4% by mass, MgO 0.13% by mass) In a 10 g beaker, 100 ml of a 1 mol / l lithium hydroxide aqueous solution is added in portions of 50 ml in two portions and mixed. Next, leave at 60 ° C. for 24 hours with occasional mixing. After removing the supernatant, the precipitate is transferred to a beaker and suspended in distilled water. Further, the mixture was neutralized by adding acetic acid, filtered through a Buchner funnel, washed with distilled water, dried at 90 ° C. for 24 hours or more and synthesized (lithium content: 3.3 mass%).
ABW type lithium zeolite: It is considered to be a type in which the bonding force between lithium in the cavity and oxygen forming a skeleton is stronger than that of EDI type lithium zeolite. In the synthesis method, powdered allophane is put into a 10 g beaker, and 100 ml of a 1 mol / l lithium hydroxide aqueous solution is added and mixed in 50 ml portions. Then leave it at 90 ° C. for 48 hours with occasional mixing. After removing the supernatant, the precipitate is transferred to a beaker and suspended in distilled water. Further, the mixture was neutralized by adding acetic acid, filtered through a Buchner funnel, washed with distilled water, dried at 90 ° C. for 24 hours or more, and synthesized (lithium content: 4.0 mass%).
A-type lithium zeolite: 10 g of commercially available A-type synthetic sodium zeolite in 100 ml of a 7.5 mass% lithium chloride solution at 90 ° C. for 3 hours, filtered through a Buchner funnel, washed with distilled water, and then at 90 ° C. for at least 24 hours What was synthesize | combined after drying was used (lithium content 3.5 mass%).
Type A calcium zeolite: commercial product, manufactured by Nippon Chemical Industry Co., Ltd., trade name “ARCAT S”

  From Table 1, it can be seen that the cement admixture of the present invention has higher ion exchange capacity with sodium or potassium than A type lithium zeolite or A type calcium zeolite.

  The cement admixture used in Example 1 was added in the amount shown in Table 2 with respect to 100 parts by mass of cement to prepare a cement composition. Furthermore, a predetermined amount of water was added and kneaded to prepare a mortar, and the amount of expansion appearing due to the alkali silica reaction was measured for the cured body subjected to the predetermined curing. For comparison, the same procedure was performed for the A-type lithium zeolite and the A-type calcium zeolite used in Example 1. The results are shown in Table 2.

(Contains mortar)
Cement composition: water: aggregate (mass ratio) = 1: 0.5: 2.5

(Materials used)
Cement: Ordinary Portland cement, total alkali amount 0.52% by mass
Fine Aggregate: Aggregate having alkali aggregate reactivity (Pyroxene andesite), specific gravity 2.61, maximum particle size 5 mm, the amount of fused silica in the alkali silica reactivity test (chemical method) of aggregate of JIS A 1145 Aggregate determined to be harmless at 520 mmol / l with a decrease in alkali concentration of 211 mmol / l.
Water: distilled water

(Test method)
Length change: Conforms to JIS A 1146 alkali silica reactivity test (mortar bar method). The test body size was 4 × 4 × 16 cm with measurement plugs embedded at both ends, the environmental temperature during the measurement period was 40 ° C., and the humidity was 90%.

  From Table 2, it can be seen that by using the cement admixture of the present invention, the amount of expansion is suppressed even when an aggregate having alkali silica reactivity is used. Moreover, it turns out that it is larger than an A type lithium zeolite or an A type calcium zeolite as an inhibitory effect.

  The cement admixture of the present invention not only rapidly ion-exchanges with sodium or potassium, but also releases lithium into the cement composition, so the effect of suppressing expansion due to alkali aggregate reaction is significantly greater than conventional zeolites. Since it becomes possible to repair mortar or concrete structures deteriorated by alkali aggregate reaction or to use reactive aggregate, it can be widely used in the civil engineering and construction fields.

Claims (4)

A cement admixture containing an EDI-type and / or ABW-type lithium zeolite for suppressing an alkali aggregate reaction . A cement composition comprising the cement admixture according to claim 1 and cement , wherein the cement admixture is blended in an amount of 0.2 to 100 parts by mass with respect to 100 parts by mass of cement. Alkaline aggregate characterized by containing EDI type and / or ABW type lithium zeolite synthesized from allophane and cement, and containing 0.2 to 100 parts by mass of lithium zeolite with respect to 100 parts by mass of cement. Cement composition that suppresses reaction . A paste, mortar, or concrete produced using the cement composition according to claim 2 or 3.