JP2010105870A - Expansive composition and expansive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an expansive composition which exhibits a high expansion amount even in a use amount smaller than that which has been mixed and used heretofore without causing pop out and can suppress shrinkage cracks in a cement-based hardened body structure as well as cracks generated by large-scale initial shrinkage appearing in a concrete structure or the like, and to provide an expansive material. <P>SOLUTION: The expansive composition contains quicklime as an effective component, and is composed of grains in which the content of grains with a grain size of >300 μm is <1 mass%, the content of grains with a grain size of 300 to 150 μm is <7 mass% and the content of grains with a grain size of 150 to 10 μm is 55 to 80 mass%, and the balance grains with a grain size of <10 μm, and also, the content of grains with a grain size of ≥90 μm is 15 to <40 mass%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an expansible composition and an expansive material that are used for the purpose of suppressing cracking of mortar, concrete, cement paste, or the like used for building structures.

  In order to improve the durability of various components and buildings such as mortar, concrete or cement paste with cement as the binder phase, especially concrete building structures, it occurs due to cracking and drying shrinkage that occur with hardening shrinkage. It is essential to suppress cracking. A particularly effective means of suppressing cracking is the use of an expanding component. Such swelling components are roughly classified into those having quick lime as an active ingredient and those having a substance that produces ettringite through a hydration reaction such as calcium sulfoaluminate. Among these, those containing quicklime as an active ingredient are generally excellent in early-stage expansion due to their high reaction activity and can be expected to have a relatively large expansion amount. Is suitable.

The expansion component can express a larger expansion amount as the mixing amount of concrete and mortar per unit volume increases, but in recent years, in order to reduce the economic burden of the building structure, it is necessary to mix the expensive expansion component. There is a demand for a material that tends to reduce the amount used, and that can express a desired expansion amount with a smaller amount of mixing. In the expansion substance containing quicklime as an active ingredient, when the hydration reaction activity is increased, a high initial expansion can be expressed even with a small amount of use. In order to increase the hydration reaction activity, it is a simple means to increase the specific surface area (brane) of the quicklime-containing particles. Moreover, by increasing the quick lime particle size, a larger expansion amount can be expressed even with a small amount of use. On the other hand, quicklime-containing particles having a large particle size tend to cause partial popping (pop-out) on the mortar or concrete surface due to internal expansion pressure. It is known that the prevention of pop-out is effective when the maximum particle size is defined to a specific value. (For example, Patent Documents 1 and 2)
JP 2007-14567 A JP 2008-201592 A

  By preventing the occurrence of pop-out by defining the maximum particle size of quicklime, etc., it is difficult to express high expansion with a small amount of mixing, and the initial expansion amount is also sluggish. It becomes difficult to sufficiently prevent initial shrinkage on a scale. The present invention is an expansible composition capable of suppressing the shrinkage cracking of a cement-based cured body structure such as a concrete structure, without causing pop-out, and exhibiting a high expansion amount even when the amount is less than that conventionally used. It is an object to provide an object and an expansion material.

  As a result of repeated investigations to solve the above problems, the present inventors have obtained a large amount of expansion, particularly high initial expansion expression, so that quick lime is used as the active ingredient and the particle size configuration of the entire active ingredient is specified. Even if the amount used is less than that of conventional quicklime-based expansion materials, it has the ability to express expansion performance comparable to that of the conventional product, and expandability with sufficiently suppressed pop-out The knowledge that a composition can be obtained was obtained, and the present invention was completed.

  That is, the present invention is an expansible composition containing quicklime as an active ingredient, a particle content exceeding 300 μm in particle size of less than 1% by mass, a particle content of 300 to 150 μm in particle content of less than 7% by mass, and a particle size of 150 It is an expandable composition consisting of particles having a particle content of 10 to 10 μm and a residual particle size of less than 10 μm, and a particle content of 90 μm or more is 15% by mass or more.

  Moreover, this invention is an expansion material formed by containing gypsum or gypsum and cement in the said expansible composition.

Since the expansible composition and the expansive material according to the present invention can express a high expansive amount at an early stage after hydration even with a smaller amount of mixing (for example, 15 kg / m ³ ) than conventional quicklime-based expansive materials, concrete is particularly preferred. The large-scale initial shrinkage seen in the structure can be sufficiently prevented. And since generation | occurrence | production of popout is fully suppressed, the mortar and concrete surface after hardening tend to be in the state which generally has a smooth aesthetics.

  The expansible composition of the present invention contains quick lime as an active ingredient, and an expansion action is expressed by an increase in volume due to hydration of quick lime. Since the quick lime in an expansible composition can express a comparatively big expansion | swelling amount, it is preferable to exist with free quick lime. More preferably, the free quicklime content is 50% by mass or more because a high expansion amount can be easily obtained even with a low mixing amount. The expansible composition of the present invention may contain components other than free quicklime. Containing components other than free quicklime are not particularly limited as long as they can be contained in mortar, concrete or the like without affecting the expansion effect of the present invention. Specifically, calcium aluminate (C3A), calcium silicate (C3S), Irwin and the like can be exemplified, but the invention is not limited to these, and further, for example, normal production of oxides of alkali metals and alkaline earth metals In operation, impurities unavoidable may be mixed. Generally, these components are phases that coexist with free quick lime when the expandable composition of the present invention is to be obtained as a fired product containing free quick lime, for example, by heating the raw material at a high temperature. In addition, the manufacturing method of the expandable composition of the present invention is not limited to the above-described manufacturing method, and any method may be used. preferable.

  Moreover, the expansible composition of this invention is an active ingredient as mentioned above, Comprising: It is a thing of the following specific particle size structures. That is, the expandable composition of the present invention has a particle content exceeding 300 μm in particle size of less than 1% by mass (including 0% by mass), preferably less than 0.5% by mass, more preferably no content. . When the particle content exceeding 300 μm is more than 1% by mass, pop-out tends to occur, which is not preferable. The content rate of particles having a particle size of 300 to 150 μm is less than 7% by mass (including 0% by mass). If the particle content of particles with a particle size of 300-150μm exceeds 7% by mass, the surface of concrete and mortar will become too rough, so it will take time to finish the surface, and the appearance will be lost, and depending on the environmental conditions such as construction temperature, pop out It is not preferable because the occurrence is also a concern. The content of particles having a particle size of 150 to 10 μm is 55 to 80% by mass. If the particle content of particles having a particle size of 150 to 10 μm is less than 55% by mass, the content of fine particles having a particle size of less than 10 μm is relatively increased, the number of particles that do not substantially contribute to expansion increases, the expansion amount decreases, and weathering. Since resistance also falls, it is not preferable. When the particle content of particles having a particle size of 150 to 10 μm exceeds 80% by mass, the particle size distribution pattern of the entire constituent particles becomes too sharp, which may affect the uniformity and workability of mortar and concrete kneaded material. Therefore, it is not preferable. The particles having a particle size of less than 10 μm are contained in the remaining amount excluding the content of the particles of 10 μm or more, and preferably at least about 5% by mass.

  The expansible composition of the present invention comprises quick lime as an active ingredient and has the above-mentioned particle size constitution (particle size distribution), and the proportion of particles having a particle size of 90 μm or more in the contained particles is 15% by mass or more. The amount is less than 40% by mass. If the particle size is less than 15% by mass, the hydration reaction activity becomes too high, and there is a possibility that an expansion force will be expressed before the hydraulic binder phase such as cement is condensed. Since shrinkage cannot be suppressed sufficiently, it is not preferable. On the other hand, when the content ratio of particles having a particle size of 90 μm or more exceeds 15% by mass, the early expansion property is deteriorated, so that, for example, large-scale initial shrinkage of concrete cannot be sufficiently suppressed, and cracking may occur.

Moreover, the expansion | swelling material of this invention is either the thing containing the said expansible composition and gypsum, or the thing containing the said expansible composition, gypsum, and cement. Gypsum has an effect of adjusting expansion performance, and also has an effect of improving strength development at a low temperature of about 5 ° C. and a long-term drying shrinkage suppressing effect. As the gypsum, anhydrous gypsum, hemihydrate gypsum, or dihydrate gypsum may be used, or any two or more of these may be used. Preferably, anhydrous gypsum is preferable because the above action can be expressed relatively stably, and type II anhydrous gypsum is particularly preferable. Gypsum having a specific surface area of 3000 cm ² / g or more is desirable because it exhibits good reaction activity and a desired effect. The upper limit of the specific surface area of the brane is not particularly limited, but about 15000 cm ² / g is appropriate in view of the economy and the tendency of improving the reaction activity. Although content of gypsum in this expansion | swelling material is not specifically limited, 3-20 mass parts is preferable with respect to 100 mass parts of said expansible compositions. If the amount is less than 3 parts by mass, the desired content cannot be obtained substantially. If the amount exceeds 20 parts by mass, the content of the expansible composition is relatively lowered, making it difficult to obtain the desired amount of expansion.

  The cement contained in the expansion material of the present invention is not particularly limited, but preferably C3S content is high because early strength or very early strength Portland cement greatly contributes to strength development in the hydration process of mortar and concrete in the early to middle period. It is recommended from that. On the other hand, low heat Portland cement and blast furnace cement, which are delayed in setting, are not suitable for expansion materials such as concrete for which initial shrinkage is large because strength development is delayed. In the present expansion material, cement is contained in combination with the gypsum, and imparts effects such as adjustment of the amount of expansion expressed and adjustment of the hydration reaction to the expandable composition. The content of cement is not particularly limited. Preferably, 5 to 15 parts by mass of cement is contained in combination with 5 to 15 parts by mass of gypsum with respect to 100 parts by mass of the expandable composition. If the amount is less than 5 parts by mass of cement, the inclusion effect is not substantially observed. On the other hand, when the content exceeds 20 parts by mass of cement, the content of the expansible composition is relatively lowered, and thus it is difficult to obtain a desired expansion amount, which is not appropriate.

  The expandable material of the present invention may contain components other than the expandable composition, gypsum, and cement as long as the effects of the present invention are not substantially lost. Examples of such components include water reducing agents (water reducing agents, high-performance water reducing agents, AE water reducing agents, high-performance AE water reducing agents, dispersing agents, etc.), shrinkage reducing agents, setting modifiers and the like that can be used for mortar and concrete. .

The expandable composition of the present invention can be used as a mixture directly in a hydraulic inorganic powder such as cement, or in a unit amount of mortar, concrete or cement paste containing cement as a binder phase forming component. Even if it is mixed and used at a low addition amount of 10 to 20 kg / m ^3, the desired expansibility can be sufficiently expressed. Moreover, the expansion | swelling material of this invention can express desired expansibility even if it mix | blends with mortar and concrete with the low usage-amount substantially equivalent to the expansible composition of this invention.

[Preparation of expandable composition]
A dry mixture composed of the raw materials shown in Table 1 was heated and held in an electric furnace at a firing temperature of 1300 ° C. for about 1 hour, and then naturally cooled in the furnace from the temperature to obtain a fired lump having a capacity of 1.65 g / cm ² . . As a result of examining the product phase of the calcined mass by powder X-ray diffraction by an internal standard method (internal standard material; high-purity silicon), free quick lime: 62.2% by mass, C3S; 22.8% by mass, CaSO ₄ ; 4 It was 0.5% by mass, ferrite (C4AF); 3.4% by mass, calcium aluminate (C3A); 2.2% by mass, and other 2.1% by mass. The fired lump is pulverized with a pin mill pulverizer, classified with a separator and adjusted for particle size, whereby an expandable composition having a particle size composition shown in Table 2 (present product: A1 to A3, reference product; B1 to B5). Was made.

[Production of expansion material]
Using a material selected from the expandable composition (A1 to A3, B1 to B5), type II anhydrous gypsum (Brain specific surface area of about 7100 cm ² / g), early strength Portland cement (manufactured by Taiheiyo Cement Co., Ltd.), The mixture was dry-mixed with a ball mill so as to have the composition shown in Table 3 to prepare an expansion material (product of the present invention; E1 to E5, reference product; F1 to F5).

[Production of evaluation concrete]
Composition A1 produced above, expansion material produced above (E1 to E5, F1 to F5), commercially available low-added quicklime expansion material (manufactured by Taiheiyo Materials Co., Ltd .; abbreviated as F6), commercially available low-additive type Ettringite / lime composite expansion material (manufactured by Denki Kagaku Kogyo Co., Ltd., abbreviated as F7), fine aggregate (land sand from Ogasa), coarse aggregate (crushed stone from Iwase), lignin sulfonic acid AE water reducing agent (BASF) Pozzolith Co., Ltd. is manufactured by a company), ordinary Portland cement (manufactured by Taiheiyo Cement Co., Ltd.) and water, and kneaded in a forced pan mixer so that the composition shown in Table 4 is obtained. Produced.

[Characteristic evaluation]
The following characteristics evaluation was performed with respect to the produced concrete kneaded material. Each evaluation result is also summarized in Table 4.
(1) Evaluation of expansion performance: Concrete constrained expansion rate at 7 days of age was measured by a method based on the method of restraint expansion and contraction test (Method A) described in JIS A 6202 Expansive Material Annex 2 for Concrete. Evaluated by whether or not the concrete constrained expansion rate at the age of 7 days: 150 to 250 × 10 ⁻⁶ , which is the standard specified in the “Construction Guidelines for Expanded Concrete” of the Japan Society of Civil Engineers.
(2) Strength evaluation: Preparation of a specimen to be used for a strength test was performed by a method based on JIS A 1132, and the strength measurement was performed by measuring the compressive strength measured based on the compressive strength test method for JIS A 1108 concrete. Or it represents with the ratio (Y / X) of the compressive strength (Y) of each concrete with respect to the compressive strength (X) of the concrete (equivalent to the comparative example 1 of Table 4) in which none of the expansible composition is mixed.
(3) Evaluation of surface condition (skin surface) of hardened concrete body; concrete mixture was poured into a 100 × 100 × 400 mm formwork and molded underwater until the seventh day of age. Visually observe the surface of the cured concrete molded body cured at room temperature in the air (humidity 70%) until 28th, and whether there is pop-out marks or rough skin (due to occurrence of rash-like projections) due to finger touch. Evaluation was made, and only those that were not seen were regarded as “None”.

From Table 4, mixing concrete expansion material a (E1 to E5) of the added concrete and the invention composition (A1) of the present invention, than was done conventional unit concrete volume per 10~18kg / m ³ It can be seen that even with a low addition amount (mixing amount), a constrained expansion coefficient satisfying the Japan Society of Civil Engineers standard was obtained, and there was no pop-out or rough skin. On the other hand, concrete added with an expansion material that deviates from the present invention shows pop-out and rough skin (F1 and F2), or Japan with a low addition amount (mixing amount) of 12 to 17 kg / m ³ per unit. The constrained expansion rate that met the Japan Society of Civil Engineers standards was not obtained, and was a lower value. (F3-F7)

Claims (2)

An expansible composition containing quicklime as an active ingredient, a particle content of less than 1% by mass exceeding 300 μm in particle size, a particle content of less than 7% by mass of 300 to 150 μm, and a particle content of 150 to 10 μm in particle size An expandable composition comprising particles having a particle size of 55 to 80% by mass and a remaining particle size of less than 10 μm, and having a particle content of 90 μm or more in particle size of 15 to 40% by mass. An expandable material comprising the expandable composition according to claim 1 and containing gypsum or gypsum and cement.