JP2006151772A - Liquid expansive admixture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid expansive admixture free from problems that (1) dusting occurs easily in preparation work, (2) the long term storage is difficult because of its high hygroscopicity, (3) it is hard to be dispersed after water is fed or the like which are observed in a hydration expansive admixture, exhibiting high expansive performance and hardly causing the fluctuation of the expansive performance. <P>SOLUTION: The liquid expansive admixture is particles having free quick lime as an active ingredient and contains 100 pts.wt. particles having a coating film layer comprising calcium hydroxide (CH) and magnesium hydroxide (MH) in the ratio (MH/CH) of 0.01-0.1 and 30-100 pts.wt. organic liquid substantially inactive against calcium oxide. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention mainly relates to a liquid expansion material for suppressing shrinkage during curing and drying, in addition to a hydraulic cement-based material.

In the production of hydraulic cement-based materials such as cement paste, mortar, concrete, etc., the expansion material that is mixed to suppress shrinkage during curing and shrinkage during drying is, for example, ettringite mineral-forming substances such as calcium sulfoaluminate, Free quicklime-containing substances have been put into practical use. Since these expansion materials are essentially powders with high hydration reaction activity, they are (1) easy to be dusted during preparation, (2) very hygroscopic and difficult to store for a long time, (3) There are problems such as difficulty in dispersion after water injection. On the other hand, quick lime, among hydrated and expansive substances, has a very high expansibility, so that a high shrinkage suppressing effect can be obtained even with a small amount of mixing with cementitious materials. On the other hand, the hydration reaction activity is remarkably high, and the problems (1) to (3) are more serious than other hydration-swelling substances because of the strong alkali. In particular, in the problem of (3), even if kneading is sufficiently performed during water injection, a hydration reaction occurs abruptly immediately after water injection, and the particles are crosslinked and aggregated by the formed hydrate, so that it is difficult to disperse and dispersion is not possible. Sufficient mortar or concrete causes defects due to local expansion failure called pop-out on the surface. It is known that when a specific amount of calcium hydroxide is contained in a hydrated expansive substance, a radical hydration reaction is suppressed, dispersibility is improved, and pop-out can be prevented. (For example, refer to Patent Document 1.) In this case, the following problems may occur depending on the method of containing calcium hydroxide. In other words, in the method of leaving the simplest quicklime-based expansion substance in the atmosphere and absorbing moisture to form a hydroxide from the surface layer, it is difficult to control the amount of calcium hydroxide produced from (2), and the production scale is expanded. It is not suitable for obtaining an expansion material having stable quality such as performance. In addition, in the method of adding calcium hydroxide powder to the hydrated and expansive powder, even if careful adjustment is made, it is not possible to prevent the water itself from reacting directly with the hydrated and expansive powder at the time of water injection. Is not expensive. In addition, in the method of adding a predetermined amount of water to the quicklime-based expansion material to form calcium hydroxide, the powder particles made of the expansion material tend to aggregate due to the added water, and a treatment for redispersing this is necessary. become. If it is a liquid expansion material, the above problems (1) to (3) may be eliminated or alleviated, but at least hydration-expandable chemical substances that are liquid at room temperature are in a daily available range. Then it is not known. Therefore, it is possible to obtain a practical liquid expandable material by slurrying a solid hydrated expandable substance. However, due to its high hydration reaction activity, aqueous liquids are extremely difficult to use and expandable. A method of slurrying the powdered material with a non-aqueous liquid has been studied. (For example, refer to Patent Document 2.) However, even if a quicklime-based swelling substance exhibiting high hydration reaction activity is simply slurried with a non-aqueous liquid, if water is poured into the cement-based material mixed with the slurry, initial rapid water The sum reaction is hardly suppressed. For this reason, the expansion | swelling substance disperse | distributed before water injection may aggregate, and it is difficult to acquire the remarkable improvement effect with respect to the problem of (3). In order to solve this problem, using the quick lime-based expansion material containing calcium hydroxide as in the past, even if this is slurried, there are problems in terms of quality and manufacturing work due to the calcium hydroxide content. Remain.
JP 11-302047 A JP 2002-226243 A

  The present invention is intended to solve the above-described problems, that is, a liquid expansion material that can obtain high expansion performance without causing the problems (1) to (3), and that hardly causes fluctuations in expansion performance. It is an issue to provide.

  In order to solve the above problems, the present inventors used, as a hydrated and expansive substance, particles containing free calcined lime having high expansibility as an active ingredient, and the particles were converted to calcium hydroxide having extremely poor hydration activity. , By coating with magnesium hydroxide, which has significantly lower solubility than calcium hydroxide and calcium oxide and does not hinder the setting of cement, and slurrying the coated particles, Completion of the present invention is achieved by preventing formation of a cross-linked structure between particles due to precipitation of a hydrate, ensuring excellent dispersibility without impairing expansion properties, and eliminating the problems (1) to (3). It came to do.

  That is, the present invention is a particle containing free quick lime as an active ingredient, and calcium hydroxide (CH) and magnesium hydroxide (MH) on the surface have a weight ratio (MH / CH) of 0.01 to 0.1. It is a liquid expansion material comprising 100 parts by weight of particles having a coating layer and 30 to 100 parts by weight of an organic liquid substantially inert to calcium oxide. Moreover, this invention is the said liquid expansion | swelling material whose coating layer of calcium hydroxide and magnesium hydroxide is 1 to 10 weight% of particle | grains.

  According to the present invention, an expandable material that is remarkably excellent in dispersibility, has a sufficient mixing effect even when mixed for a short time, and can impart high expansibility. Moreover, this expandable material is suitable for long-term storage, and there is almost no variation in the expression of properties including expansion performance.

  The expansion component used in the liquid expansion material of the present invention contains free quick lime, which is a hydrated expansion material, as an active ingredient, and is preferably calcium oxide or a clinker composition whose main product phase is free quick lime. Among these, the clinker composition is obtained, for example, by using limestone, gypsum, etc. as a raw material and calcining it at about 1000 to 1600 ° C. If free quick lime is present as the main product phase, other products are For example, calcium silicate, calcium sulfate, calcium aluminate, calcium aluminosilicate, calcium ferrite, calcium aluminoferrite, Irwin and the like may coexist. The content of free lime in the clinker composition is preferably 40% by weight or more and less than 100% by weight. If it is less than 40% by weight, high expansion may not be obtained. Calcium oxide (CaO) is not limited to a reagent purified to a high purity. For example, calcium oxide (CaO) obtained by ordinary industrial means such as calcining natural limestone can be suitably used. The impurities are allowed to be mixed. More preferably, quick lime containing about 1 to 10% by weight of magnesium oxide is preferable, such as a calcined calcite limestone. In the present invention, powder particles are used for such an expanding component, and this is dispersed in a liquid to be liquefied. Therefore, sizing and sizing treatment is performed, and the average particle size is set to 5 to 50 μm. preferable. If the average particle size is less than 5 μm, expansion force is expressed before the setting of the cement, and high expansion may not be obtained. If the average particle size exceeds 50 μm, the expansion component becomes sparsely dispersed. Since the unreacted portion tends to remain in the particles for a long period of time even after the injection of water, pop-out or the like may occur.

  In the liquid expansion material of the present invention, particles containing hydrated and expandable free quicklime as an active ingredient are liquefied, and the particles have a coating layer of calcium hydroxide and magnesium hydroxide on the surface thereof. And The amount of calcium hydroxide and magnesium hydroxide in the coating layer is such that the weight ratio (MH / CH) of calcium hydroxide (CH) and magnesium hydroxide (MH) is 0.01 to 0.1. If it is good. If the weight ratio (MH / CH) is less than 0.01, the effect of suppressing particle aggregation after water injection cannot be obtained, and if the weight ratio exceeds 0.1, the hydration reaction of the hydrated swelling component is excessively suppressed, Since strength reduction may be caused, it is not preferable. The amount of the coating layer in each particle is not particularly limited, but is preferably about 1 to 10% by weight of the particle including the coating layer. If the amount is less than 1% by weight, variations in expansion characteristics such as the onset of expansion and expansion force are difficult to eliminate, and if it exceeds 10% by weight, the amount of hydrated expansion component is relatively reduced, making it difficult to secure a desired expansion amount. Sometimes. The coating layer is preferably composed only of calcium hydroxide and magnesium hydroxide, but may contain components other than calcium and magnesium hydroxides within a range not losing the effects of the present invention. Up to about 0.5% by weight may contain calcium carbonate, dolomite, and other components inactive to water.

  A means for forming a coating layer of calcium hydroxide and magnesium hydroxide on particles containing free quick lime as an active ingredient is not limited. For example, calcium hydroxide particles mixed with calcium oxide particles mixed with calcium oxide particles or calcium oxide particles containing about 1 to 10% by weight of magnesium oxide while sprinkling water using a sprayer or the like are mixed. A coating layer in which magnesium oxide coexists can be easily formed. In such a method, the amount of water sprinkled and the amount of calcium or magnesium hydroxide produced are generally proportional to the amount of hydroxide produced up to about 10% by weight. What is necessary is just to determine the amount of water sprinkling suitably so that 1-10 weight% of the particle | grains which use as an active ingredient may become a hydroxide.

  Further, the organic liquid used for liquefying the hydrated and expanded component subjected to the coating treatment is not particularly limited as long as it is substantially inert to calcium oxide and is liquid at least at room temperature. Substantially inactive to calcium oxide does not necessarily need to be completely inactive, and the reaction action on calcium oxide is extremely slow. For example, calcium oxide used for alteration or reaction even if it coexists for one month at room temperature. Mention may be made of less than about 1% by weight. Desirably, it contains as little water as possible. Examples of organic liquids that can be used in the present invention include alcohols, ethers, oils, and the like that are liquid at room temperature. Preferably, an alkylene oxide adduct or oil of lower alcohol can be expressed without loss of expansion force.

  The amount of the organic liquid used is 30 to 100 parts by weight with respect to 100 parts by weight of the coated particles containing free quick lime as an active ingredient. If it is less than 30 parts by weight of the organic liquid, it may not be a sufficiently fluid liquid, which is not preferable. If the amount of the organic liquid exceeds 100 parts by weight, solid-liquid separation may occur, and dispersion in the cementitious composition may occur. This is not preferable because the organic properties may deteriorate or the organic liquid may become excessive, which may impair the condensation and strength development. In addition, as a method for liquefying the hydrated expansion component, the coated particles containing the above-mentioned amount of free quicklime as an active ingredient and the organic liquid may be appropriately mixed with a mixer such as a pan type or biaxial forced kneading.

  The liquid expandable material of the present invention may contain other admixtures / materials that can be used for cement, mortar, and concrete as long as the effects of the present invention are not affected. Examples of such admixtures / materials include dispersants, antifoaming agents, air entraining agents, shrinkage reducing agents and the like, all of which are non-hydrated or have extremely low reaction activity with quicklime.

  In addition, the method of using the liquid expandable material of the present invention is not particularly limited, and can be mixed and used in cement paste, mortar, concrete, etc. in substantially the same manner as powdered expandable materials used in mortar and concrete. . The mixing amount can be arbitrarily determined, but preferably about 3 to 15 parts by weight as a liquid expansion material per 100 parts by weight of cement is recommended.

[Adjustment of hydrated expandable particles]
The limestone produced in Kamiiso, Hokkaido was baked in an electric furnace at about 1100 ° C., allowed to cool naturally, and then crushed to a specific surface area of 35002 ± 200 cm ² / g by a rod mill. The cooling and pulverization were performed in an environment with a humidity of 10% or less. Table 1 shows chemical analysis values of the pulverized grains after firing. From the analysis value, it was confirmed that the pulverized grains contained 2.5% by weight of magnesium oxide, and the remainder could be regarded as substantial calcium oxide.

  50 kg of the obtained calcium oxide pulverized particles were transferred to a Laedige mixer and mixed for about 2 minutes while adding distilled water by spraying using an accumulator. The amount of distilled water spray added is 0, 0.3, 1.0, or 2.0 parts by weight with respect to 100 parts by weight of the mixture, and is shown in Table 2. The particles after mixing with distilled water were left in a desiccator for 30 days. As a result of quantitative analysis of the particles after standing by thermogravimetric analysis, it was confirmed that magnesium hydroxide (MH) and calcium hydroxide (CH) were newly generated, and the generation ratio of hydroxide in the particles and The production ratio (MH / CH) between magnesium hydroxide and calcium hydroxide was the value shown in Table 2. For reference, calcium oxide particles not containing magnesium oxide (commercially available reagent, purity 99.9%) were subjected to the same spraying treatment with distilled water as described above, and were coated with calcium hydroxide (A0). Got.

[Production of liquid admixture]
A liquid (B1 to B8) 5.0 kg described below is put in a 18 liter bale can, and the particles (A1 to A4 and A0) shown in Table 1 are mixed in a weight ratio of 100 parts by weight of the liquid shown in Table 3. It poured into the liquid in a bale can over about 30 seconds, and then stirred for 5 minutes with a hand mixer to prepare liquid admixtures (C1 to C10 and C11 to C15). A dry powder admixture (C16) not added to the liquid was also prepared for reference. The temperature at the time of preparing the liquid admixture was 20 ± 1 ° C.
B1; soybean oil (commercially available, moisture content 0%)
B2: alkylene oxide adduct of lower alcohol (Tetragard AS20 manufactured by Taiheiyo Materials Co., Ltd., moisture content 0%)
B3; rapeseed oil (commercial product, moisture content 0%)
B4; oleic acid (commercially available reagent, water content 0%)
B5: Linoleic acid (commercially available reagent, water content 0%)
B6: Equal weight mixed oil of soybean oil and palm oil (commercial product, moisture content 0%)
B7: Tap water

[Evaluation of liquid admixture]
From 300 parts by weight of fine aggregate (mixed crushed sand from Kokura Minami Ward and Noura sea sand in Iki-gungo at a weight ratio of 3: 7), 100 parts by weight of ordinary Portland cement (manufactured by Taiheiyo Material Co., Ltd.) and 50 parts by weight of water Add 8 parts by weight of the liquid admixture (C1 to C15) prepared above or 5 parts by weight of the dry powder admixture (C16) to the base mortar having the above composition to make a total amount of about 1 liter with a Hobart mixer. Slow mixing. The mixing time was set to the time shown in Table 3 in the range of 0.5 to 10 minutes. The mixture was immediately poured into a mold having an inner size of 4 × 4 × 16 cm, and demolded after 16 hours to prepare a specimen comprising a mortar composition. The shape dimension of the specimen immediately after demolding was measured as the initial length, the specimen was cured in water at 20 ° C. for 7 days, and then the length of the same part was measured again. The expansion rate of the specimen for each liquid admixture used was calculated from the initial length and the length after underwater curing. Also, the variation (variation) in the amount of expansion varies from the standard deviation of the expansion rate; the average value of E; the ratio of S; R (= E / S) for each liquid admixture used Rate: M (= 100 × R) was calculated, and the difficulty of fluctuation was evaluated with this value. That is, it is evaluated that the smaller the value of M, the smaller the variation. (If M = 0, there is no variation.)

  From Table 4, the specimens (D1 to D11) using the liquid expansion material (C1 to C10) of the present invention are compared with the specimens (D21 to D25) using the admixture (C11 to C15) outside the present invention. It can be seen that the amount of expansion was large, and the liquid admixture of the present invention could exhibit high expansion performance accurately. It can also be seen that the variation in the amount of expansion is remarkably reduced as compared with the case where the conventional powdery expansion material (C16) is mixed (D26 and D27). In addition, the dispersibility in the base mortar is remarkably excellent, and a sufficient mixing effect can be obtained by mixing in a shorter time than when a powdery expansion material is mixed and used.

Claims (2)

Particles having free quick lime as an active ingredient, and having a coating layer of 0.01 to 0.1 on the surface of calcium hydroxide (CH) and magnesium hydroxide (MH) in a weight ratio (MH / CH) 100 A liquid expanding material comprising 30 parts by weight of an organic liquid substantially inactive to calcium oxide and parts by weight. The liquid expansion material according to claim 1, wherein the coating layer of calcium hydroxide and magnesium hydroxide is 1 to 10% by weight of the particles.