WO2018150753A1 - Geopolymer composition, and mortar and concrete using same - Google Patents

Abstract

Provided is a geopolymer composition comprising: an active filler containing fly ash and a blast furnace slag; an alkaline solution containing a sodium silicate and/or a sodium hydroxide; and a cement mineral-based expanding material.

Description

Geopolymer composition, and mortar and concrete using the same

The present invention relates to a geopolymer composition, and mortar and concrete using the same.

In recent years, global warming due to carbon dioxide (CO ₂ ) emission has rapidly progressed and has become a social problem. Among them, concrete is used as a construction material, and its production volume is enormous. The world's total production of cement, the main raw material for concrete, is 2.84 billion tons (2008), and in the production of cement, a large amount of carbon dioxide is emitted by chemical decomposition of limestone and the use of thermal energy. Yes. If 1 ton of cement is produced in Japan, 0.725 ton of carbon dioxide is generated, and the carbon dioxide emissions of the cement industry account for 4% of the total nationwide emissions (2008). Therefore, it can be said that reducing the amount of cement used in the production of concrete is an extremely important approach to solving the global warming problem and building a sustainable society.

Therefore, for the purpose of reducing CO ₂ emissions and effective utilization of industrial waste, fly ash cement, which is a mixture of Portland cement and fly ash, which is industrial waste, is Class A (exceeding 5% and exceeding 10%) in JIS R 5213. ), B type (over 10% and 20% or less), and C type (over 20% and 30% or less).

Fly ash is fine ash recovered from exhaust gas by a dust collector among coal ash by-produced during coal combustion in a coal-fired power plant or the like. Fly ash is mainly composed of silica (SiO ₂ ) and alumina (Al ₂ O ₃ ), and is standardized to JIS A6201 based on particle size and flow value. Has been used.

However, the main raw material in the mixed cement is Portland cement, and it has been practically problematic to increase the mixing ratio of fly ash in the fly ash cement to more than 30% from the viewpoint of strength. Fly ash is overwhelmingly used as a raw material for concrete. Therefore, there has been a demand for a technique for producing concrete that does not use cement and uses a large amount of fly ash.

Under such circumstances, as a technology for producing concrete without using Portland cement for the purpose of reducing CO ₂ emissions and effective utilization of industrial waste, a polycondensation polymer of silicic acid is used as a binder and the powders are joined together. Thus, the geopolymer method, which is a technique for producing artificial rocks, has attracted attention.

The geopolymer method is a technique for making artificial rock by joining powders called active fillers using a condensation polymer of silicic acid as a binder. Generally, it is produced by reacting an active filler powder with an alkali silicate solution (water glass or the like).

Several geopolymer production techniques using fly ash for this active filler have been proposed, but the geopolymer has poor strength development and generally requires steam curing (for example, patents) Reference 1). In view of this, in order to enhance strength development and denseness, several examples of studies using a mixture of blast furnace slag and fly ash have been reported (for example, Patent Document 2, Patent Document 3, Non-Patent Document 1, and Non-Patent Document). Reference 2). Moreover, the hardening acceleration | stimulation method of the geopolymer composition by which the hardening accelerator which contains calcium aluminate as an active ingredient is added to the geopolymer composition containing fly ash, an alkaline solution, and an aggregate (for example, patent document 4). And a method for improving workability and aesthetics without impairing fluidity and strength development with a specific additive (for example, see Patent Document 5). Moreover, the hydraulic composition which uses 2 or more types of irritation | stimulation agents from which the speed | rate which elutes calcium ion as a irritation | stimulation agent is combined as a irritation | stimulation agent in combination with a lot of blast furnace slag like patent document 6 is proposed.

JP-A-8-301039 JP-A-8-301638 JP2015-157731A JP 2016-33104 A JP 2016-79046 A JP 2014-148434 A

Kazuo Ichinomiya et al., Fly ash-based geopolymer formulation and high temperature resistance, concrete engineering annual papers, Vol. 36, no. 1,2014 Rina Kawajiri et al., Basic research on geophysical properties and structural utilization of geopolymers, Annual report on concrete engineering, Vol. 33, no. 1,2111

However, as described in Non-Patent Document 2, a geopolymer cured by a condensation polymer has a large drying shrinkage due to the dissipation of water compared to general concrete cured by a hydration reaction. There has been a problem that cracks are likely to occur.

Patent Document 3 also describes that a highly durable geopolymer can be obtained by using an active filler containing various calcium compounds, but the effect of the type of calcium compound on strength development and length change. Is not listed.

Even in Patent Document 4, although it has been shown that the addition of calcium aluminates as a curing accelerator improves the strength of the geopolymer, there is no description of the results of the change in length.

Also in Patent Document 5, by using a geopolymer additive comprising a composition containing a salt of a specific aliphatic oxycarboxylic acid, curing excellent in workability and appearance without impairing fluidity and strength development. Although it shows that the body can be obtained, the effect on the length change is not described.

In addition, Patent Document 6 mentions an expansion material as a stimulant, and although it shows an effect of improving strength development and neutralization resistance, it shows a reduction in drying shrinkage and an improvement in aesthetics. It has not been. In addition, a pozzolanic material such as fly ash is contained in the hydraulic composition in an amount of 15% by mass or less, and cannot be used in large quantities with fly ash as a main component. Moreover, it is an invention that promotes hydration of blast furnace slag with a stimulant, and is different from a geopolymer that is cured by condensation polymerization.

As described above, various technologies have been proposed for the geopolymer technology with improved strength development. However, along with strength development, reduction of drying shrinkage, improvement of aesthetics (inhibition of white flower), and expandability. The present situation is that no excellent geopolymer composition is shown.

From the above, the present invention has an object to provide a geopolymer composition that exhibits good strength development and expandability when used as a cured product, has a small drying shrinkage, and has a good appearance when used as a cured product. And

That is, the present invention is as follows.
[1] A geopolymer composition comprising an active filler containing fly ash and blast furnace slag, an alkaline solution containing sodium silicate and / or sodium hydroxide, and a cement mineral expansion material.
[2] The geopolymer composition according to [1], wherein a content of the fly ash is 70 to 90 parts by mass with respect to a total of 100 parts by mass of the fly ash and the blast furnace slag.
[3] The geopolymer composition according to [1] or [2], wherein the cement mineral expansion material is an ettringite expansion material, a lime expansion material, or a lime / ettringite expansion material.
[4] The cement mineral expansive material includes free lime, Auin and anhydrous gypsum, the free lime is 30 to 70 parts by mass, the Auin is 5 to 30 parts by mass, and the anhydrous gypsum is 15 to 40 parts by mass. The geopolymer composition according to any one of [1] to [3].
[5] The geopolymer composition according to any one of [1] to [4], wherein a content of the cement mineral expansion material is 5 to 15 parts by mass with respect to 100 parts by mass of the active filler.
[6] A mortar comprising the geopolymer composition according to any one of [1] to [5] above and a fine aggregate.
[7] A concrete comprising the geopolymer composition according to any one of the above [1] to [5], a fine aggregate, and a coarse aggregate.

According to the present invention, it is possible to provide a geopolymer composition that exhibits good strength development and expandability when used as a cured product, has small drying shrinkage, and has a good appearance when used as a cured product.

Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the embodiments. In the present specification, “part” and “%” are based on mass unless otherwise specified.

[1] Geopolymer composition An embodiment of the geopolymer composition of the present invention includes an active filler containing fly ash and blast furnace slag, an alkaline solution containing sodium silicate and / or sodium hydroxide, and a cement mineral-based expansion material. Including.

In the geopolymer composition of the present embodiment, expansion occurs with improvement in strength due to crystals caused by an expansion material such as calcium hydroxide and ettringite produced by a hydration reaction of a cement mineral expansion material. As a result, it is considered that effects such as good strength development, expandability, and reduction in drying shrinkage are obtained, and finally excellent durability is obtained. Moreover, it is thought that a favorable aesthetic appearance (appearance with less white flower) can be obtained due to the combined effect of the cement mineral expansion material and the active filler according to the present embodiment.

(Active filler)
As the active filler contained in the geopolymer composition of the present embodiment, fly ash and blast furnace slag are used. If one of these is not contained, sufficient strength may not be exhibited or sufficient workability may not be obtained.

Fly ash used for the active filler is fine ash recovered from the exhaust gas by a dust collector among coal ash produced as a by-product during coal combustion in a coal-fired power plant or the like. Silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) are the main components, and in JIS A 6201, they are specified as I to IV types based on the particle size and flow value. The specifications of fly ash are not particularly limited, but type I and type II are preferred because of their fine particle size and high reactivity.

The blast furnace slag used for the active filler is by-produced when producing pig iron in the blast furnace and conforms to JIS A 6206 mainly composed of CaO, SiO ₂ , Al ₂ O ₃ , and MgO.

The content of fly ash with respect to 100 parts by mass in total of fly ash and blast furnace slag is preferably 70 to 90 parts by mass, and more preferably 75 to 85 parts. By being 70 parts or more, fluidity can be maintained well and sufficient workability can be easily obtained. Moreover, it is preferable also from a viewpoint of effective utilization expansion of fly ash. By being 90 parts or less, strength development property and expansion amount can be further increased.

Other active fillers such as municipal waste incineration ash molten slag other than fly ash and blast furnace slag, sewage sludge molten slag, rice husk ash, clinker ass, fluidized bed coal ash, silica fume, metakaolin, and volcanic ash may be included as active fillers. Good. The total amount of these other active fillers is preferably 30% or less and more preferably 15% or less in the total amount of the active fillers.

(Cement mineral expansion material)
Commercially available products can be used as the cement mineral expansion material, including ettringite, ettringite / lime, lime, etc. Ettringite / lime expansion materials have better strength development, aesthetics, and expansibility. It is preferable from the viewpoint. Specifically, free lime, Auin and anhydrous gypsum are the main constituent compound compositions, and 10 to 80 parts (preferably 30 to 70 parts) of free lime out of 100 parts in total of free lime, Auin and anhydrous gypsum, Auin Is preferably 15 to 45 parts (preferably 5 to 30 parts) and 10 to 50 parts (preferably 15 to 40 parts) of anhydrous gypsum, and / or a mixture of heat treated products.

The blending ratio of the cement mineral expansion material with respect to 100 parts of the active filler is preferably 5 to 15 parts, more preferably 8 to 12 parts. When it is 5 parts or more, it is possible to increase the strength development and the amount of expansion, and when it is 15 parts or less, the expansion does not become excessive, and sufficient workability is easily obtained.

(Alkaline solution)
The alkaline solution is a solution in which the active filler, the expansion material and the aggregate are kneaded. Examples of the alkaline solution include sodium silicate solution (water glass), potassium silicate solution, sodium hydroxide aqueous solution, potassium hydroxide aqueous solution and the like. These 1 type (s) or 2 or more types can be used. In particular, the combined use of a sodium silicate solution and an aqueous sodium hydroxide solution is preferred.

In addition to the above, various types of admixtures and admixtures can be added to the geopolymer composition in the present embodiment as long as the effects of the present invention are not impaired. Examples thereof include a fluidizing agent, a shrinkage reducing agent, a rust preventive agent, a waterproofing material, a setting retarder, an antifoaming agent, a dust reducing agent, a pigment, and calcium carbonate powder.

The geopolymer composition in the present embodiment is prepared, for example, by mixing predetermined amounts of active filler, alkaline solution, cement-based expansion material, and various additives simultaneously or sequentially as necessary, and kneading with a kneader as appropriate. it can. The kneading apparatus is not particularly limited, and examples thereof include a forced biaxial mixer used for kneading concrete.
Moreover, when producing mortar and concrete, the geopolymer composition in this embodiment may exist as a part of raw material.

[2] Mortar and Concrete An embodiment according to the mortar of the present invention includes the geopolymer composition of the present invention and a fine aggregate. Moreover, embodiment which concerns on the concrete of this invention contains the geopolymer composition of this invention, a fine aggregate, and a coarse aggregate. The various aggregates are not particularly limited as long as they are generally used for ordinary mortar and concrete. Examples include natural aggregates such as river gravel, mountain gravel, sea gravel, crushed stone, and volcanic gravel lightweight aggregates, and artificial aggregates such as slag aggregates, artificial lightweight aggregates, and heavy aggregates.

The blending amount of the fine aggregate in the preparation of the mortar is preferably 50 to 500 parts, more preferably 100 to 300 parts with respect to 100 parts of the geopolymer composition.

The blending amount of the fine aggregate and the coarse aggregate at the time of producing the concrete is preferably 200 to 1000 parts, more preferably 300 to 600 parts with respect to 100 parts of the geopolymer composition.

The cured product of mortar or concrete of this embodiment exhibits various characteristics resulting from the geopolymer composition of the present invention during the curing, and the appearance after curing is almost entirely white. Do not have a good aesthetic.

Hereinafter, the contents will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these.

(raw materials)
(1) Fly ash: Fly ash type II (conforms to JIS A 6201)
(2) Blast furnace slag: blast furnace slag fine powder 6000 (conforms to JIS A 6206)
(3) Sodium silicate solution: Sodium silicate solution No. 1, reagent (manufactured by Kanto Chemical Co., Inc.)
(4) Aqueous sodium hydroxide solution: 48% aqueous sodium hydroxide solution, reagent (Kanto Chemical Co., Inc.)
(Made by company)
(5) Aggregate: Fine aggregate (JIS sand)
(6) Water: Tap water (7) CaO raw material: Calcium carbonate (limestone fine powder), 100 mesh, commercial product (8) Al ₂ O ₃ raw material: bauxite, 90 μm sieve passage rate 100%, commercial product (9) CaSO ₄ raw materials: dihydrate gypsum, commercial product

(Expandable materials A to G)
The CaO raw material, the Al ₂ O ₃ raw material, and the CaSO ₄ raw material described in the above (raw materials) were mixed so that the mineral after the heat treatment had a predetermined composition shown in Table 1 below. This mixture was heat-treated at 1350 ° C. for 0.5 hours using an electric furnace, and the obtained heat-treated product was pulverized with a ball mill to a Blaine specific surface area of 3,500 cm ² / g to prepare expansion materials A to G.
In addition, a brane specific surface area is the value measured using the brane air permeation | transmission apparatus based on JISR5201 "cement physical test method".

(Preparation of geopolymer mortar)
Powder composed of active filler and expansion material (see Experimental Examples 1 to 3 for composition and ratio): 600 parts by weight, sodium silicate solution diluted twice with water: 100 parts by weight, aqueous sodium hydroxide solution: 100 parts by weight, water : 100 parts by mass, fine aggregate: 1350 parts by mass were prepared in a room at 20 ° C., sealed up to 1 day of age, and demolded.

(Measuring method)
(1) Compressive strength: A 4 × 4 × 16 cm specimen was prepared according to JIS R 5201, cured under water until a predetermined age, and the compressive strength was measured.

(2) Length change rate, drying shrinkage rate: JIS A 6202 appendix 1 Measure the rate of change in length in water (20 ° C) curing up to 7 days of age curing according to the expansibility test method with mortar of expanding material. The drying shrinkage rate in the air (20 ° C., 60 RH%) curing from 7 to 28 days was measured with the material age of 7 days as the base length.
In the length change rate and the drying shrinkage rate, “−” represents shrinkage, and those without a sign represent expansion.
Further, it is more preferable that the rate of change in length is larger under the same conditions because the amount of expansion material added for obtaining a predetermined expansion amount is reduced, which is more economical. Furthermore, since drying shrinkage causes cracking, it is preferable that the amount of shrinkage is small.

(3) Appearance (aesthetic appearance): After demolding, air curing was performed at a temperature of 20 ° C. and a humidity of 60% until the age of 7 days, and the surface of the dried specimen was observed and evaluated according to the following criteria.
A: No white flower is observed on the surface of the specimen.
○: Slight whiteness is observed on the surface of the specimen (less than about 2% of the surface area).
X: White flower is conspicuously observed on the surface of the specimen (2% or more of the surface area).

(Experimental example 1)
With respect to 100 parts of the active filler having the composition shown in Table 2, the expansion material D was 10 parts, and the mortar was prepared according to (Production of Geopolymer Mortar), and the compression strength and the rate of change in length were measured. For comparison, mortars prepared without using blast furnace slag or fly ash or without using an expanding material were also evaluated.

From Table 2, the use of the geopolymer composition included in the present invention consisting of fly ash and blast furnace slag, an expansion material, and an alkaline solution provides excellent strength development and aesthetics, expandability, and drying. It can be seen that a mortar using the geopolymer composition with reduced shrinkage is obtained.

(Experimental example 2)
80 parts of fly ash in 100 parts of active filler was used. Mortar was prepared according to (Production of geopolymer mortar) with 10 parts of the expansion material shown in Table 3 with respect to 100 parts of active filler, and the compressive strength and the rate of change in length were measured.

From Table 3, it can be seen that by using an expanding material having a predetermined mineral composition, a mortar having more excellent strength development and aesthetics, expandability, and reduced drying shrinkage can be obtained.

(Experimental example 3)
80 parts of fly ash in 100 parts of active filler was used. Mortar was prepared according to (Production of geopolymer mortar) as a ratio shown in Table 4 with respect to 100 parts of the active filler, and the compressive strength and the rate of change in length were measured.

From Table 4, the mortar using the geopolymer composition which is excellent in strength development and aesthetics, has expansibility, and has reduced drying shrinkage by making the amount of the expansion material used relative to the active filler a predetermined ratio. It turns out that it is obtained.

According to the present invention, it is possible to provide mortar and concrete using a geopolymer composition that is excellent in strength development and aesthetics, has not only expansibility but also small drying shrinkage, and is suitable in the civil engineering and construction fields. Can be used for

Claims (7)

A geopolymer composition comprising an active filler containing fly ash and blast furnace slag, an alkaline solution containing sodium silicate and / or sodium hydroxide, and a cement mineral-based expansion material. The geopolymer composition according to claim 1, wherein a content of the fly ash is 70 to 90 parts by mass with respect to a total of 100 parts by mass of the fly ash and the blast furnace slag. The geopolymer composition according to claim 1 or 2, wherein the cement mineral expansion material is an ettringite expansion material, a lime expansion material, or a lime / ettringite expansion material. The cement mineral-based expansion material includes free lime, Auin and anhydrous gypsum, wherein the free lime is 30 to 70 parts by mass, the Auin is 5 to 30 parts by mass, and the anhydrous gypsum is 15 to 40 parts by mass. The geopolymer composition according to any one of 1 to 3. The geopolymer composition according to any one of claims 1 to 4, wherein a content of the cement mineral expansion material is 5 to 15 parts by mass with respect to 100 parts by mass of the active filler. A mortar comprising the geopolymer composition according to any one of claims 1 to 5 and a fine aggregate. A concrete comprising the geopolymer composition according to any one of claims 1 to 5, a fine aggregate, and a coarse aggregate.