AU2017399309B2

AU2017399309B2 - Geopolymer composition, and mortar and concrete using same

Info

Publication number: AU2017399309B2
Application number: AU2017399309A
Authority: AU
Inventors: Minoru Morioka; Masataka USHIRO
Original assignee: Denka Co Ltd
Current assignee: Denka Co Ltd
Priority date: 2017-02-14
Filing date: 2017-12-27
Publication date: 2023-02-23
Anticipated expiration: 2037-12-27
Also published as: JP2020055696A; MY196681A; CN110167901A; WO2018150753A1; AU2017399309A1

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

DESCRIPTION

Title of Invention GEOPOLYMER COMPOSITION, AND MORTAR AND CONCRETE USING SAME

Technical Field

[0001] The present invention relates to a geopolymer composition, and a mortar and a concrete using the same.

Background Art

[0002] In recent years, the rapid progression of the global warming due to the carbon dioxide (C0 2 ) emission is being recognized as a social problem. Under the circumstances, concretes have been used as one of the construction materials, and the production volume thereof is becoming huge. The worldwide production volume of cement, which is a major raw material of the concrete, is 2.84 billion tons (2008), and in the production of cement, a huge amount of carbon dioxide is emitted due to the chemical decomposition of limestone and the use of heat energy. In Japan, the production of 1 ton of cement emits 0.725 ton of carbon dioxide, and the carbon dioxide emission of the cement industry occupies 4% of the national total emission (2008). Therefore, the reduction of the amount of cement used for the production of concrete is considered to be a significantly important approach for the solution of the global warming problem and the establishment of a sustainable society.

[0003] For that approach, in order to promote the reduction of the CO 2 emission and the effective use of industrial wastes, a fly ash cement containing a portland cement having mixed therein a fly ash as an industrial waste is defined in JIS R5213 as the type A (more than 5% and 10% or less), the type B (more than 10% and 20% or less), and the type C (more than 20% and 30% or less), and is being produced.

[0004] The fly ash is a fine ash recovered with a dust collector from the exhaust gas of a coal ash by-produced through coal combustion in a coal fired electric power plant or the like. The fly ash contains silica (Si 2 ) and alumina (A1 2 0 3) as major components, and is standardized to the types I to IV based on the grain size and the flow value in JIS A6201, and utilized as an admixture material for a cement and an admixture material for a concrete.

[0005]

However, the main raw material of the mixed cement is a portland cement, and in the ordinary techniques, there is a practical difficulty from the standpoint of strength in increasing the mixing ratio of the fly ash in the fly ash cement beyond 30%. Furthermore, the utilization as a raw material of a concrete predominantly occupies the use of the fly ash. Accordingly, such a technique has been demanded that can produce a concrete containing a large amount of the fly ash used therein without the use of a cement.

[0006]

Under the circumstances, in order to promote the reduction of the C02 emission and the effective use of industrial wastes, as a technique producing a concrete without the use of a portland cement, a geopolymer method is receiving attention, which is a technique for producing artificial rocks through binding powder by utilizing a condensation polymer of silicic acid as a binder.

[0007]

The geopolymer method is a technique for producing artificial rocks through binding powder, which is referred to as an active filler, by utilizing a condensation polymer of silicic acid as a binder. The geopolymer is generally produced through reaction of active filler powder and an alkali silicate solution (such as liquid glass).

[0008]

There have been some proposals for the production technique of the geopolymer using the fly ash as the active filler, but the geopolymer is poor in strength exhibition and generally requires steam curing (see, for example, PTL 1). For enhancing the strength exhibition and the compactness, there have been some reports on studies about the use of a mixture of a blast furnace slag and a fly ash (see, for example, PTL 2, PTL 3, NPL 1, and NPL 2). There have also been proposals of a method of hardening acceleration of a geopolymer composition by adding a hardening accelerator containing a calcium aluminate compound as an active ingredient to a geopolymer composition containing a fly ash, an alkali solution, and an aggregate (see, for example, PTL 4), and a method for improving the workability and the good appearance by the particular additive without impairing the fluidity and the strength exhibition (see, for example, PTL 5). PTL 6 proposes a hydraulic composition having a combination of a large amount of a blast furnace slag and limestone fine powder, and using, as a stimulant, two or more kinds of stimulants different in elution rate of calcium ion.

Citation List

Patent Literatures

[0009]

PTL 1: JP 8-301639 A

PTL 2: JP 8-301638 A

PTL 3: JP 2015-157731 A

PTL 4: JP 2016-33104 A

PTL 5: JP 2016-79046 A

PTL 6: JP 2014-148434 A

Non-patent Literatures

[0010]

NPL 1: Kazuo ICHIMIYA, et al., "Composition and high-temperature resistance of fly ash-based geopolymers", Proceedings of the Japan Concrete Institute, vol. 36, No. 1, 2014

NPL 2: Runa KAWAJIRI, et al., "Fundamental studies on basic properties and structural utilization of geopolymers", Proceedings of the Japan Concrete Institute, vol. 33, No. 1, 2011

[001Oa]

A reference herein to a patent document or any other matter identified as prior art, is not to be taken as an admission that the document or other matter was known or that the information it contains was part of the common general knowledge as at the priority date of any of the claims.

[001Ob]

Where any or all of the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components.

Summary of Invention

[0011]

However, as described in NPL 2, the geopolymer hardened with a condensation polymer undergoes larger drying contraction due to escape of water than an ordinary concrete hardened through hydration reaction, and has an issue that cracks becoming an invasion pathway of a degradation factor of the concrete tend to occur.

[0012]

PTL 3 describes that a geopolymer having high durability can be obtained by using an active filler containing various calcium compounds, but does not describe the influence of the kind of the calcium compounds on the strength exhibition and the change in length.

[0013]

PTL 4 describes that the strength exhibition of the geopolymer is enhanced by adding a calcium aluminate compound as a hardening accelerator, but does not describe a working example about the change in length.

[0014]

PTL 5 shows that a hardened product excellent in workability and appearance can be obtained without impairing the fluidity and the strength exhibition, by using an additive for a geopolymer formed of a composition containing the particular salt of an aliphatic oxycarboxylic acid, but does not describe the influence on the change in length.

[0015]

PTL 6 notes an expander as a stimulant, and shows the effect of improving the strength exhibition and the neutralization resistance, but does not show the reduction of the drying contraction and the improvement of the good appearance. In addition, it is stated that a pozzolanic substance, such as a fly ash, is contained in the hydraulic composition in an amount of 15% by mass or less, and thus a fly ash cannot be used in a large amount as a major component. Furthermore, what is described is an invention for accelerating hydration of a blast furnace slag with a stimulant, which is different from a geopolymer hardened through polycondensation.

[0016]

As described in the foregoing, while the geopolymer techniques improved in strength exhibition have been variously proposed, it is the current situation that a geopolymer composition that is excellent in the reduction of the drying contraction, the improvement in good appearance (i.e., suppression of efflorescence), and the expansibility, and also in the strength exhibition has not yet been achieved.

[0017]

In view of the above, various embodiments of the present invention provide a geopolymer composition that exhibits good strength exhibition and expansibility and undergoes a small drying contraction in forming a hardened product, and provide a good appearance for the hardened product.

[0018]

The present invention is as follows.

[1] A geopolymer composition containing an active filler containing a fly ash and a blast furnace slag, an alkali solution containing sodium silicate and/or sodium hydroxide, and a cement mineral based expander, wherein the content of the fly ash is from 70 to 90 parts by mass per 100 parts by mass in total of the fly ash and the blast furnace slag.

[2] The geopolymer composition according to the item [1], wherein the cement mineral based expander is an ettringite based expander, a lime based expander, or an ettringite.lime based expander.

[3] The geopolymer composition according to any one of the items [1] to [2], wherein the cement mineral based expander contains free lime, hauyne, and anhydrous gypsum, and contains from 30 to 70 parts by mass of the free lime, from 5 to 30 parts by mass of the hauyne, and from 15 to 40 parts by mass of the anhydrous gypsum.

5a

[4] The geopolymer composition according to any one of the items [1] to [3], wherein the content of the cement mineral based expander is from 5 to 15 parts by mass per 100 parts by mass of the active filler.

[5] A mortar containing the geopolymer composition according to any one of the items [1] to [4] and a fine aggregate.

[6] A concrete containing the geopolymer composition according to any one of the items [1] to [4], a fine aggregate, and a coarse aggregate.

Advantageous Effects of Invention

[0019]

According to various embodiments of the present invention, a geopolymer composition that exhibits good strength exhibition and expansibility and undergoes a small drying contraction in forming a hardened product, and provides a good appearance for the hardened product can be provided.

Description of Embodiments

[0020]

Embodiments of the present invention will be described in detail below, but the present invention is not limited to the embodiments. In the description herein, "part" and "%" are based on mass unless otherwise indicated.

[0021]

[1] Geopolymer Composition An embodiment relating to the geopolymer composition of the present invention contains an active filler containing a fly ash and a blast furnace slag, an alkali solution containing sodium silicate and/or sodium hydroxide, and a cement mineral based expander.

[0022] In the geopolymer composition of the present invention, the expansion occurs along with the enhancement in strength with crystals derived from expanders, such as calcium hydroxide and ettringite, formed through the hydration reaction of the cement mineral based expander. It is considered that as a result, such effects as good strength exhibition, expansibility, reduction in drying contraction can be obtained, and excellent durability can be finally obtained. Furthermore, it is considered that a good appearance (i.e., an appearance with less efflorescence) can be obtained due to the combined effect of the cement mineral based expander and the active filler in the present embodiment.

[0023] (Active Filler) The active filler contained used in the geopolymer composition of the present embodiment is a fly ash and a blast furnace slag. In the case where one of them is not contained, there may be a case where a sufficient strength cannot be exhibited and a case where a sufficient workability cannot be obtained.

[0024] The fly ash used in the active filler is a fine ash recovered with a dust collector from the exhaust gas of a coal ash by-produced through coal combustion in a coal fired electric power plant or the like. The fly ash contains silica (SiO 2 )

and alumina (A120 3) as major components, and is standardized to the types I to IV based on the grain size and the flow value in JIS A6201. The fly ash is not particularly limited in terms of standard, and the type I and the type II, which have a small grain size and high reactivity, are preferred.

[0025]

The blast furnace slag used in the active filler is by-produced in the formation of a pig iron in a blast furnace, and contains CaO, SiO 2 , A1203 , and MgO as major components according to JIS A6206.

[0026] The content of the fly ash is preferably from 70 to 90 parts by mass, and more preferably from 75 to 85 parts by mass, per 100 parts by mass in total of the fly ash and the blast furnace slag. In the case where the content is 70 parts or more, the fluidity can be favorably retained to facilitate the sufficient workability. This is also preferred from the standpoint of the enhancement of the effective utilization of the fly ash. In the case where the content is 90 parts or less, the strength exhibition and the expansion amount can be further enhanced.

[0027] The active filler may contain, in addition to the fly ash and the blast furnace slag, an additional active filler, such as a molten slag from municipal waste incineration ash, a molten slag from sewage sludge, a rice husk ash, a clinker ash, a fluidized bed coal combustion ash, a silica fume, a metakaolin, and a volcanic ash. The total amount of the additional active filler is preferably 30% or less, and more preferably 15% or less, based on the total amount of the active filler.

[0028] (Cement Mineral based Expander) The cement mineral based expander used may be a commercially available product, examples of which include an ettringite based expander, an ettringite.lime based expander, and a lime based expander, and an ettringitelime based expander is preferred from the standpoint of the good strength exhibition, the good appearance, and the expansibility. Specifically, the cement mineral based expander is preferably a heat-treated material that contains free lime, hauyne, and anhydrous gypsum as a major constitutional compound composition, and contains from 10 to 80 parts (preferably from 30 to 70 parts) of the free lime, from 15 to 45 parts (preferably from 5 to 30 parts) of the hauyne, and from 10 to 50 parts (preferably from 15 to 40 parts) of the anhydrous gypsum, per 100 parts in total of the free lime, the hauyne, and the anhydrous gypsum, and/or a mixture of the heat-treated materials.

[0029] The mixing ratio of the cement mineral based expander is preferably from

5 to 15 parts, and more preferably from 8 to 12 parts, per 100 parts of the active filler. With the mixing ratio of 5 parts or more, the strength exhibition and the expansion amount can be increased, and with the mixing ratio of 15 parts or less, the expansion can be prevented from becoming excessive to facilitate the sufficient workability.

[0030] (Alkali Solution) The alkali solution is a solution for kneading the active filler, the expander, and an aggregate. Examples of the alkali solution include a sodium silicate solution (liquid glass), a potassium silicate solution, a sodium hydroxide solution, and a potassium hydroxide solution. One kind or two or more kinds thereof may be used. In particular, a combination use of a sodium silicate solution and a sodium hydroxide solution is preferred.

[0031] The geopolymer composition of the present embodiment may contain various admixtures and admixture materials in such a range that does not impair the effects of the present invention. Examples thereof include a fluidizer, a contraction reducing agent, a rust inhibitor, a waterproofing material, a setting retarder, an anti-foaming agent, a dust reducing agent, a pigment, and calcium carbonate powder.

[0032] The geopolymer composition of the present embodiment may be produced, for example, in such a manner that the active filler, the alkali solution, the cement based expander, and also various additives depending on necessity are simultaneously or sequentially mixed in the prescribed amounts, and appropriately kneaded with a kneader. The kneader is not particularly limited, and examples thereof include a forced biaxial mixer used for kneading a concrete. There may be a case where the geopolymer composition of the present embodiment exists as a part of the raw materials in the production of a mortar or a concrete.

[0033]

[2] Mortar and Concrete Am embodiment of the mortar of the present invention contains the geopolymer composition of the present invention and a fine aggregate. An embodiment of the concrete of the present invention contains the geopolymer composition of the present invention, a fine aggregate, and a coarse aggregate. The aggregates are not particularly limited, as far as the aggregates are those generally used in the ordinary mortars and concretes. Examples thereof include a natural aggregate, such as river gravel, mountain gravel, coastal gravel, crushed rock, and a lapilli lightweight aggregate, and an artificial aggregate, such as a slag aggregate, an artificial lightweight aggregate, and a heavyweight aggregate.

[0034] The mixing amount of the fine aggregate in the production of the mortar is preferably from 50 to 500 parts, and more preferably from 100 to 300 parts, per 100 parts of the geopolymer composition.

[0035] The mixing amount of the fine aggregate and the coarse aggregate in the production of the concrete is preferably from 200 to 1,000 parts, and more preferably from 300 to 600 parts, per 100 parts of the geopolymer composition.

[0036] A hardened product of the mortar or the concrete of the present embodiment can exhibit the various characteristics derived from the geopolymer composition of the present invention in hardening thereof, and can have, as an appearance after hardening, a good appearance with substantially no efflorescence on the surface thereof.

Examples

[0037] The contents will be described in more detail with reference to examples and comparative examples below, but the present invention is not limited thereto.

[0038] (Raw Materials) (1) Fly ash: fly ash type II (according to JIS A6201) (2) Blast furnace slag: blast furnace slag fine powder 6000 (according to JIS A6206) (3) Sodium silicate solution: sodium silicate solution No. 1, reagent (produced by Kanto Chemical Co., Inc.) (4) Sodium hydroxide solution: 48% sodium hydroxide aqueous solution, reagent (produced by Kanto Chemical Co., Inc.)

(5) Aggregate: fine aggregate (sand according to JIS) (6) Water: tap water (7) CaO raw material: calcium carbonate (limestone fine powder), 100 mesh, commercially available product (8) A120 3 raw material: bauxite, 90 pm mesh pass rate: 100%, commercially available product (9) CaSO4 raw material: dehydrated gypsum, commercially available product

[0039] (Expanders A to G) The CaO raw material, the A1203 raw material, and the CaSO 4 raw material described in the aforementioned (Raw Materials) were mixed to make the prescribed composition shown in Table 1 below for the mineral after the heat treatment. The mixture was heat-treated at 1,350°C for 0.5 hour with an electric furnace, and the resulting heat-treated product was pulverized with a ball mill to a Blaine specific surface area of 3,500 cm 2 /g, so as to prepare expanders A to G. The Blaine specific surface area is a value that is measured with a Blaine air permeability apparatus according to JIS R5201 "Physical test methods for cements".

[0040] Table 1 Free lime Hauyne Anhydrous gypsum A 80parts 20parts B 70 parts 20 parts 10 parts C 70 parts 15 parts 15 parts Expander D 50 parts 15 parts 35 parts E 50 parts -_50 parts F 40 parts 20 parts 40 parts G 10 parts 45 parts 45 parts

[0041] (Production of Geopolymer Mortar) A mixture of 600 parts by mass of the powder containing the active filler and the expander (having the composition and the proportions shown in Experimental Examples 1 to 3), 100 parts by mass of the sodium silicate solution having been diluted twice with water, 100 parts by mass of the sodium hydroxide aqueous solution, 100 parts by mass of water, and 1,350 parts by mass of the fine aggregate was prepared indoors at 200C, and subjected to sealed curing to a material age of one day, followed by demolding.

[0042] (Measurement Methods) (1) Compression strength: According to JIS R5201, a test piece of 4 x 4 x 16 cm was produced and subjected to underwater curing to the prescribed material age, and then measured for the compression strength.

[0043] (2) Change rate of length and drying contraction rate: According to the expansibility test method for expanders with mortars of JIS A6202, Appendix 1, the change rate of length in underwater curing (200C) was measured until a material age of 7 days, and based on a material age of 7 days as the base length, the drying contraction rate in atmospheric aging (200C, 60%RH) of from 7 days to 28 days was measured. The sign "-" in the change rate of length and the drying contraction rate means contraction, and the numeral without the sign means expansion. A larger change rate of length under the same condition is economical and preferred since the amount of the expander required for providing the prescribed expansion amount is smaller. The contraction rate is preferably smaller since the drying contraction may be a factor of crack formation.

[0044] (3) Appearance (good appearance): After the demolding, the test piece was subjected to atmospheric curing at a temperature of 200 C and a humidity of 60% until a material age of 7 days, and the dried surface of the test piece was observed and evaluated by the following standard. A: No efflorescence was observed on the surface of the test piece. B: Slight efflorescence was observed on the surface of the test piece (less than approximately 2% of the surface area). C: Noticeable efflorescence was observed on the surface of the test piece (approximately 2% or more of the surface area).

[0045] (Experimental Example 1) A mortar was prepared according to (Production of Geopolymer Mortar) with 10 parts of the expander D per 100 parts of the active filler having a composition shown in Table 2, and the compression strength and the change rate of length were measured. For comparison, mortars produced without the use of the blast furnace slag or the fly ash or without the use of the expander were also evaluated.

[0046] Table 2 Active filler Compression 2strength (N/mm ) Change Drying Experiment Fly Blast Expander Appearance rate of contraction Note No. Fly furnace D 1 7 28 length rate a slag day days days (x 10-6) (x 10-6) (%) C -78 -475 comparative none - 1 8.2 1-1 100 0 10comparatie 12 -488 comparative 1-2 used - 1.2 9.4 A comptie 1-3 none 0.6 1.6 11.9 C -91 -621 comparative

1-4 used 1.2 2.8 13.2 A 192 -531 example 90 10 none 4.6 16.4 31.1 C -112 -815 comparative 1-5 1-6 used 13.4 28.4 41.2 A 580 -443 example 1-7 80 20 none 8.5 22.3 38.6 C -167 -980 comparative

1-8 used 18.7 34.7 47.1 A 720 -371 example 1-9 70 30 none 14.7 28.8 46.3 C -221 -897 comparative

1-10 used 23.1 39.1 50.2 A 766 -365 example 1-11 60 40 none 16.5 26.5 44.2 C -195 -921 comparative

1-12 used 24.6 40.7 48.9 A 693 -405 example 1-13 none comparative

1-14 0 100 used unable to produce specimen due to immediate setting comparative example

[0047] It is understood from Table 2 that the use of the geopolymer composition within the scope of the present invention containing the active filler formed of the fly ash and the blast furnace slag, the expander, and the alkali solution can provide a mortar using a geopolymer composition that is excellent in strength exhibition and good appearance, has expansibility, and is reduced in drying contraction.

[0048] (Experimental Example 2) The amount of the fly ash was 80 parts per 100 parts of the active filler. A mortar was prepared according to (Production of Geopolymer Mortar) with 10 parts of the expander shown in Table 3 per 100 parts of the active filler, and the compression strength and the change rate of length were measured.

[0049] Table 3 Compression strength Change rate of Drying contraction Experiment Expander (N/mm 2) Appearance length rate Note No. 1 day 7days 28 days (x 10-6) (x 10-6)

2-1 A 12.1 25.2 40.4 B 891 -541 example 2-2 B 16.6 31.9 45.7 B 781 -532 example 2-3 C 17.1 31.8 47.2 A 710 -411 example 1-8 D 18.7 34.7 47.1 A 720 -371 example 2-4 E 13.3 29.6 41.1 A 549 -563 example 2-5 F 16.6 32.5 46.2 A 680 -429 example 2-6 G 10.9 27.6 42.8 B 380 -449 example

[0050] It is understood from Table 3 that the use of the expander having the prescribed mineral composition can provide a mortar that is further excellent in strength exhibition and good appearance, has expansibility, and is reduced in drying contraction.

[0051] (Experimental Example 3) The amount of the fly ash was 80 parts per 100 parts of the active filler. A mortar was prepared according to (Production of Geopolymer Mortar) with the expander D in the amount shown in Table 4 per 100 parts of the active filler, and the compression strength and the change rate of length were measured.

[0052] Table 4 Compression strength Change Drying Experiment Expander D (N/mm 2) Appearance rate of contraction Note No. (paArt) length rate N. (1daydays 28days (x 10-6) (x 10-6)

1-7 0 8.5 22.3 38.6 C -167 -980 coexampltive 3-1 2 9.9 22.9 40.1 B 15 -780 example 3-2 5 13.9 25.9 42.9 A 276 -665 example 1-8 10 18.7 34.7 47.1 A 720 -371 example 3-3 15 22.5 38.1 50.1 A 1,321 -355 example 3-4 20 24.1 29.1 41.9 A 2,185 -332 example

[0053] It is understood from Table 4 that the use of the expander in the prescribed amount with respect to the active filler can provide a mortar using a geopolymer composition that is excellent in strength exhibition and good appearance, has expansibility, and is reduced in drying contraction.

Industrial Applicability

[0054] According to the present invention, a mortar and a concrete using a geopolymer composition, which not only are excellent in strength exhibition and good appearance and have expansibility, but also have small drying expansion can be provided, and can be favorably applied to the civil engineering and construction fields.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

[Claim 1] A geopolymer composition comprising an active filler containing a fly ash and a blast furnace slag, an alkali solution containing sodium silicate and/or sodium hydroxide, and a cement mineral based expander, wherein the content of the fly ash is from 70 to 90 parts by mass per 100 parts by mass in total of the fly ash and the blast furnace slag.
[Claim 2] The geopolymer composition according to claim 1, wherein the cement mineral based expander is an ettringite based expander, a lime based expander, or an ettringitelime based expander.
[Claim 3] The geopolymer composition according to claim 1 or claim 2, wherein the cement mineral based expander contains free lime, hauyne, and anhydrous gypsum, and contains from 30 to 70 parts by mass of the free lime, from 5 to 30 parts by mass of the hauyne, and from 15 to 40 parts by mass of the anhydrous gypsum.
[Claim 4] The geopolymer composition according to any one of claims 1 to 3, wherein the content of the cement mineral based expander is from 5 to 15 parts by mass per 100 parts by mass of the active filler.
[Claim 5] A mortar comprising the geopolymer composition according to any one of claims 1 to 4 and a fine aggregate.
[Claim 6] A concrete comprising the geopolymer composition according to any one of claims 1 to 4, a fine aggregate, and a coarse aggregate.