JP6289897B2 - Swelling composition and hydraulic composition - Google Patents

Description

  The present invention relates to a technique for increasing the expansion force of a hydraulic composition using an expansion material containing quicklime as an active ingredient.

  Among the expanding materials that expand by the hydration reaction, an expanding material containing quicklime as an active ingredient (referred to as a quicklime-based expanding material) can exhibit a high expansion force. Due to its high expansion force, this expandable material is widely used as a static crushing material for concrete structures and bedrock, and as an admixture for suppressing shrinkage when hardening hydraulic compositions such as concrete and mortar. ing. However, when an expansion material having a high expansion force is mixed with the hydraulic composition, distortion and minimal cracks may occur due to expansion during curing, and it becomes difficult to increase the strength. Also, hydraulic compositions such as concrete and mortar cause excessive volume expansion in the process of quicklime-based expandable particles becoming hydrates due to water contact, and the surface of concrete and mortar is partially expanded (pop-out) ) Is likely to occur, and fine irregularities due to overexpanded particles may remain on the surface, resulting in a loss of aesthetics. In order to suppress pop-out, it has been proposed that adjusting the particle size so as to reduce the coarse particle content ratio of the quicklime-based expansion material is effective. (For example, see Patent Documents 1 and 2.)

  By the technique disclosed in Patent Document 1 or 2, it is possible to suppress the occurrence of pop-out of the hydraulic composition when using the quicklime expansion material. And a popout suppression effect increases, so that a coarse grain content rate is decreased. However, with the decrease in the coarse particle content ratio of the quicklime-based expansion material, there is a tendency that the expression of expansion force is lost. For example, when an expansion material adjusted to a coarse particle content ratio that can sufficiently suppress the occurrence of pop-out is used, it becomes difficult to prevent large-scale initial shrinkage as seen in a concrete structure.

JP 2007-145670 A JP 2008-201592 A

  The present invention provides an expansion composition that greatly increases the expansion force of a conventional expansion material without causing any trouble in the curing properties such as the strength of the hydraulic composition and without causing pop-out. It is an object of the present invention to provide a hydraulic composition in which large-scale initial shrinkage is suppressed without reducing the provision and strength.

  As a result of repeated studies, the present inventor has found that an expansion composition in which a specific inorganic salt is added to an expansion material containing at least quick lime as an active ingredient can express a higher expansion force than an additive-free one. Since the hydraulic composition using the expansion composition can solve the above problems as a whole, the present invention has been completed.

That is, the present invention is an expansion composition represented by the following [1] to [2] and a hydraulic composition represented by [3].
[1] An expansion composition comprising 80 to 95% by mass of an expansion material containing at least quick lime as an active ingredient and 5 to 20% by mass of calcium nitrite.
[2] An expanded composition in which the expanded material of [1] has a quicklime content of 25 to 80% by mass.
[3] A hydraulic composition containing 100 parts by mass of cement and 4 to 12 parts by mass of the expansion composition of [1] or [2].

  According to the present invention, it is sufficiently possible to suppress the large-scale initial shrinkage seen in a hydraulic composition such as concrete without causing any trouble in the curable properties such as strength.

The expansion composition of the present invention comprises 80 to 95% by mass of an expansion material containing at least quick lime as an active ingredient and 5 to 20% by mass of calcium nitrite. The expansion material containing at least quick lime as an active ingredient is not particularly limited as long as it contains at least free quick lime as an active ingredient for expression of expansion. Preferably, an expansion material having a quicklime content of 25 to 80% by mass is easy to obtain an expansion amount that can sufficiently suppress shrinkage of a concrete structure or the like, and is also relatively easy to obtain. More preferably, an expansion material having a quicklime content of 30 to 60% by mass is used. The expansion material containing at least quick lime as an active ingredient is not particularly limited to contain components other than quick lime. For example, in addition to expansive components such as anhydrous or hemihydrate gypsum, ettringite phase forming substances such as calcium sulfoamate, calcium silicate and It may contain clinker porosity. In addition, the expansive material containing at least quick lime as an active ingredient to be used preferably has a particle size of 300 μm or less, so that delayed expansion is likely to occur due to a delay in hydration, and a significant pop-out or strength reduction may occur. It is good in that it can be reduced. Moreover, the particle size of the expansion | swelling material which uses the quick lime used as an active ingredient at least is not restrict | limited. In consideration of the mixing property, reaction activity, and economic efficiency, it is sufficient that at least a value close to the particle size of commercially available cement can be secured. For example, a grain specific surface area of about 3000 to 5000 cm ² / g can be mentioned, but the particle size deviating from the description example Values can be used.

  Any calcium nitrite can be used as the calcium nitrite constituting the expansion composition of the present invention, and for example, it may be in the form of an aqueous solution. By combining the expansion material containing at least quick lime as an active ingredient and calcium nitrite, the expansion force of the expansion material can be increased without causing deterioration in properties such as strength. If the content of calcium nitrite in the expansion composition of the present invention is less than 5% by mass, it is difficult to increase the expansion force, which is not preferable. In addition, when the content of calcium nitrite exceeds 20% by mass, the action as a hardening accelerator for hydraulic substances such as cement becomes too strong, workability is reduced, and hydration heat generation becomes large and cracks occur during shrinkage. Is not preferable because it is likely to occur. When the calcium nitrite used is an aqueous solution, the solid content in the aqueous solution is used as the content. The expansion composition of the present invention can be suitably used in cement paste, mortar or concrete containing a hydraulic substance such as cement as a main binding component. In addition, those in which the expansion composition exhibits an extremely high expansion pressure can be diverted to a static crushed material or the like.

  Moreover, the hydraulic composition of this invention contains the said expansion | swelling composition and cement. As the cement, any hydraulic cement can be used. Specifically, for example, various ordinary portland cements such as normal, early strength, very early strength, moderate heat, or low heat generation, various mixed cements such as blast furnace cement and fly ash cement, and special cements such as alumina cement and white cement. Two or more kinds may be used in combination. When using alumina cement, it is recommended to use it with other cement.

  Although content of the said expansion | swelling composition contained in the hydraulic composition of this invention is not restrict | limited in particular, Preferably it is 4-12 mass parts with respect to 100 mass parts of cement contents. More preferably 5 to 11 parts by mass. When the content of the expansion composition is in the above range, a high expansion force that can sufficiently suppress the large-scale initial shrinkage seen in concrete and the like is obtained, and there is no decrease in strength and there is no risk of overexpansion. Recommended because it is suitable for

  In addition, the hydraulic composition of the present invention can be used within a range in which components other than the expansion composition and cement do not substantially lose the effects of the present invention. As such components, for example, all can be used for mortar and concrete, fine aggregate, coarse aggregate, water reducing agent (dispersing agent), high performance water reducing agent, AE water reducing agent, high performance AE water reducing agent, drying shrinkage reduction Agents, antifoaming agents, pozzolanic reactive materials, fibers, fast-curing / hardening agents, setting modifiers, thickeners, water retention agents, curing agents, rust preventives, water repellents, etc. It is not limited to examples.

  The amount of kneading water added to the hydraulic composition of the present invention is not particularly limited. Preferably, the kneading water addition amount is 40 to 65 parts by mass with respect to 100 parts by mass of the total content of cement and the expansion composition in the hydraulic composition. By using such a kneading water amount, there is almost no risk of self-shrinkage and temperature cracking, and there is no risk of large-scale drying shrinkage and strength reduction, and an amount of water suitable for the hydration reaction can be provided. In addition, when using the thing of aqueous solution for a mixing | blending component, it is desirable to consider the water | moisture content contained in it as kneading | mixing water.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples described. Further, the preparation and property evaluation tests of the expansion composition and mortar described below were performed in an environment of 20 ° C. (± 2 ° C.) unless otherwise specified.

[Preparation of expansion composition]
Using the materials A1 to A3 and B shown below, an expansion composition having the composition shown in Table 1 was prepared.
A1; low-addition type expansion material containing quick lime as an active ingredient (commercial product name: Pacific Hyperexpan K, maximum particle size of about 350 μm, Blaine specific surface area of 3450 cm ² / g, quick lime content of 50% by mass)
A2; low-addition type expansion material containing calcium sulfoaluminate and quicklime as active ingredients (commercial product name: Denka Power CSA, maximum particle size of about 150 μm, Blaine specific surface area of 3800 cm ² / g, quicklime content of 50% by mass)
A3: Low-addition type expansion material containing quicklime as an active ingredient (commercial product name: Pacific Hyperexpan winter coating, maximum particle size of about 150 μm, Blaine specific surface area of 4800 cm ² / g, quicklime content of 50% by mass)
A4: Expansion material containing quick lime as an active ingredient (commercial product name: Pacific Expan K, maximum particle size of about 300 μm, Blaine specific surface area of 3500 cm ² / g, quick lime content of 30% by mass)
B: Calcium nitrite (30% strength aqueous solution, commercial product)

[Mortar preparation]
The expanded composition prepared above, ordinary Portland cement (commercially available), fine aggregate (standard sand for cement strength test manufactured by Cement Association) and kneaded water (including water derived from aqueous material). A mortar was prepared by kneading by a method according to JIS A 6202 with the formulation shown in Table 2, and the mortar was molded to obtain a mortar specimen. However, the addition amount of the expansion composition is less than the value specified in the “Expansion test method with mortar of expansion material” in view of the fact that the expansion material used in the expansion composition is of a low addition type. Although it was set as 6.7 mass% of a compounding quantity, it was set as addition amount other than this addition ratio about a part of mortar (this invention products 7 and 8).

[Characteristic evaluation]
The amount of expansion of the prepared mortar specimen was measured by a method in accordance with “Expansion test method using mortar of expansion material” defined in JIS A 6202, Annex 1 of the expansion material for concrete. Moreover, the measurement of the compressive strength of the produced mortar test body was performed by the method according to the mortar compressive strength test of the concrete expansion material of JIS A6202, and the expansion composition of the present invention was used for the expansion material for concrete. The change in the compressive strength due to the expansion of was confirmed. In addition, the surface condition (skin surface) of the cured mortar body is evaluated by visually checking the surface of the mortar specimen used for the mortar expansibility test and the mortar compressive strength test, and by palpating with a finger. The presence or absence of rough skin due to the occurrence was examined. Only those that were not detected were judged as “no”, and those that were in other situations were judged as “present”. The above results are summarized in Table 3.

  From the results of Table 3, it can be seen that the expansion composition of the present invention shows a larger rate of change in length by the addition of calcium nitrite than in the case of no calcium nitrite addition, and the amount of expansion increases. Moreover, since the hydraulic composition containing the expansion composition of the present invention exhibited a compressive strength comparable to that of a mortar that does not contain an expansion component, the combination impedes curable properties such as strength reduction. It turns out that there is nothing. Further, it can be seen that the hydraulic composition of the present invention has substantially no pop-out.

Claims (3)

An inflating composition comprising 80 to 95% by mass of an expansion material containing at least quick lime as an active ingredient and 5 to 20% by mass of calcium nitrite. The expansion | swelling material which uses at least quick lime of Claim 1 as an active ingredient is a free quick lime content rate of 25-80 mass%, The expansion | swelling composition characterized by the above-mentioned. A hydraulic composition comprising 100 parts by mass of cement and 4 to 12 parts by mass of the expansion composition according to claim 1 or 2.