JP2005213102A - Production method of expansive additive, and expansive additive - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing, from a quicklime-based clinker, an expansive additive which is produced easily with a high production yield without setting strict pulverization control or detailed pulverization conditions and without increasing the production process and of which the particle size is suitable for giving itself a hydration reactivity capable of imparting a stable expansion action to mortar or concrete and does not allow pop out to occur. <P>SOLUTION: In the method for producing an expansive additive, 100 pts.wt. free quicklime and 1-25 pts.wt. inorganic substance having a hardness higher than that of the free quicklime are generated in a clinker, and this clinker is pulverized. The expansive additive contains, as the main component, a pulverized clinker which contains, as a generated phase, 100 pts.wt. free quicklime and 1-25 pts.wt. inorganic substance having a hardness higher than that of the free quicklime. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing an expandable admixture that imparts expansibility to a material containing a hydraulic substance such as cement paste, mortar, concrete, and the expandable admixture.

  Cement paste, mortar, concrete, etc. often use expansive admixtures to prevent cracking due to shrinkage and prevent changes in shape. Among admixtures imparting expansibility, those containing quick lime as an expansion component (for example, see Patent Document 1) exhibit very high expansion by hydration. However, since the reaction activity is quite high, if it is left as it is, the hydration reaction proceeds rapidly after water injection, and most of the expansion pressure is expressed before the cement sets. In order to provide an effective expansion action, attempts have been made to obtain a sustained expansion by suppressing the rapid hydration reaction of quicklime by causing other components to coexist with quicklime. By using a clinker fired product produced by encapsulating quicklime in crystals such as alite for the admixture, it suppresses the rapid hydration reaction and the progress of weathering, and stable expansion action from the beginning of cement setting It is known that can be applied to mortar and concrete. (For example, see Patent Document 2.)

  As the expandable admixture, if it is not uniformly dispersed in the mortar or concrete, the expansion action is unevenly distributed. Therefore, a powdery material having good dispersibility is usually used. Therefore, it is necessary to grind the clinker obtained as a molded product or a coarse lump. However, if pulverization is not performed under sufficient control, over-pulverized particles are likely to appear, and fine particles with a large specific surface area have a higher reaction activity. There is a possibility that expansion pressure is expressed, and an expansion action that can be a resistance to shrinkage during setting and curing cannot be obtained. In addition, the quick lime-based expansion material with fewer coexisting components has a more sensitive relationship between the particle size and the hydration reaction activity, and a slight decrease in particle size may cause a rapid increase in reaction activity. On the other hand, coarse particles tend to be generated when pulverization is loosened, and when an expandable admixture containing some coarse particles is used, it remains as unhydrated particles on the mortar and concrete surface after curing, and is called pop-out. Cause surface degradation. For this reason, the particle size of the pulverized product must be specified more strictly, but it is necessary to set the pulverization conditions in detail to prevent excessive pulverization without leaving coarse particles, and to operate and operate the pulverizer based on it. Management is not easy. As a practical countermeasure, classification processing is performed in addition to pulverization, or the pulverized product is sieved to collect only particles constituting the required particle size distribution. In addition to the increase, removal particles are generated, which causes various problems such as a decrease in manufacturing yield and treatment.

JP 2002-252919 A JP 2001-63847 A

  In view of the above problems, the present invention is obtained from a quicklime clinker having a particle size suitable for having a hydration reaction activity capable of imparting a stable expansion action to mortar or concrete, and having a particle size that does not cause pop-out. The present invention provides a method for producing the expandable admixture easily and at a high production yield without setting strict grinding management and detailed grinding conditions and without increasing the number of production steps.

  Ball mill pulverization is generally widely performed in cement clinker pulverization and the like, and the reduction of the shape and size of the object to be pulverized by such a normal pulverization means is generally dominated by impact crushing at the initial stage. When the shape dimension is considerably reduced, the action of abrasion between the pulverized materials or between the pulverized medium and the pulverized material becomes dominant. From this, the present inventors can reduce the surface area of quick lime exposed on the particle surface and suppress a rapid hydration reaction if co-generated lime and a substance having a hardness higher than that of the quick lime are co-produced in the clinker. The higher the hardness, the harder it is to wear, the particles containing free quick lime are less likely to be over-ground, and thus the appearance of fine, high specific surface area particles with high activity can be avoided, and expandability with moderate reaction activity The present inventors have obtained the knowledge that the admixture can be easily obtained without particularly requiring a manufacturing process such as classification and sieving, and have completed the present invention.

  That is, the present invention is a method for producing an expandable admixture represented by the following (1) to (3) and an expandable admixture represented by (4). (1) A method for producing an expandable admixture, characterized in that 100 parts by weight of free quick lime and 1 to 25 parts by weight of an inorganic substance having a higher hardness than the free quick lime are produced in the clinker and then the clinker is pulverized. (2) The method for producing an expandable admixture according to (1), wherein an inorganic substance equivalent to and / or lower in hardness than free quick lime is generated in the clinker. (3) The method for producing an expandable admixture according to (1) or (2), wherein the pulverization is performed using a rod mill. (4) An expandable admixture mainly composed of a clinker pulverized product containing 100 parts by weight of free quick lime and 1 to 25 parts by weight of an inorganic substance having a hardness higher than that of the free quick lime as a product phase.

  The method for producing an expandable admixture according to the present invention comprises a quick lime-based expandable admixture whose expansion action varies greatly depending on the size of the particle size. There is no need for management and operation, and it can be easily made into a particle size suitable for providing a stable expansion effect effective in suppressing shrinkage of mortar and concrete, etc., and without increasing the production process, Furthermore, since the production yield is also high, the method can be produced at a very low cost.

  In the method for producing an expandable admixture of the present invention, first, free quick lime and an inorganic substance having higher hardness than the free quick lime are generated in a clinker. The inorganic substance having higher hardness than quick lime is not particularly limited as long as it is an inorganic substance having a Mohs hardness of more than 3 and can be co-produced with free quick lime in a clinker. Any of crystalline may be sufficient. Preferably, the grindability is lower than that of quicklime, and examples thereof include calcite, dolomite, periclase, calcium aluminate, calcium silicate, calcium sulfoaluminate and the like. The amount of the inorganic substance having higher hardness than the free quick lime generated in the clinker is 1 to 25 parts by weight, preferably 1 to 20 parts by weight of the inorganic substance having higher hardness than the free quick lime with respect to 100 parts by weight of the free quick lime. Preferably it is 2 to 12 parts by weight. If the inorganic substance having a hardness higher than that of free quick lime exceeds 25 parts by weight, the expansion action may be insufficient as an expandable admixture, and less than 1 part by weight may prevent overcrushing of free quick lime in the clinker. Since it becomes difficult, it is not preferable.

  As long as the effects of the present invention are not largely impaired, an inorganic substance having a hardness equal to or lower than that of free quick lime may be produced together with free quick lime and an inorganic substance having higher hardness than quick lime in the clinker. In this case, the amount of inorganic substance having a hardness equal to or lower than that of free quick lime is 100% by weight of free quick lime, and the total amount of inorganic substance having a hardness higher than that of free quick lime and free quick lime is equal to or lower than that of free quick lime. A range of 1 to 25 parts by weight is desirable. Although such a substance is not specifically limited, For example, various portlandite, calcium sulfate, brucite etc. are mentioned.

The raw material for producing free quick lime in clinker may be any material that can produce quick lime by heating, for example, quick lime, calcium hydroxide and calcium carbonate for small-scale production, and natural limestone for industrial scale production. Further, a viscous mineral composed of CaO and other chemical components can be used as long as it can produce free quick lime by thermal decomposition. In addition, the raw material for generating an inorganic substance having a hardness higher than that of free quick lime in the clinker is not particularly limited as long as it does not significantly inhibit the formation of free quick lime in the clinker. You may react with a part of quicklime source material. Specific examples of each raw material include, for example, when calcium aluminate is produced as the inorganic substance, alumina (α-alumina), boehmite, aluminum hydroxide, porphyry shale, etc. are produced, for example, calcium silicate. In this case, add silica, etc., for example, to produce calcium sulfoaluminate, add gypsum, etc., to produce calcium aluminoferrite, for example, to an Al ₂ O ₃ source such as alumina, boehmite, aluminum hydroxide, or clay shale. In the case of generating Fe ₂ O ₃ sources such as ferric oxide, for example, galenite, kaolin and the like can be mentioned. Also, the raw material is one kind of composition or compound, such as dolomite limestone, which is pyrolyzed into quick lime and inorganic substances other than quick lime at the time of clinker firing and produces free hard lime and an inorganic substance with higher hardness than quick lime as a production phase. It can also be used. Although the particle size of the raw material used is not limited, a material having a particle size of 10 mm or less is recommended in order to improve the mixing efficiency and firing reaction before clinker firing. The mixing ratio of each raw material is not particularly limited, but preferably, the amount of free quick lime generated in the clinker and the amount of inorganic substance harder than the free quick lime is higher than that of free quick lime with respect to 100 parts by weight of free quick lime. The blending amount of the raw material is determined so as to be 1 to 20 parts by weight of the inorganic substance. The firing temperature for clinker preparation varies depending on the raw materials used and the product phase to be obtained. Firing can be performed in the air, but is not particularly limited as long as it is an atmosphere other than a strong reducing atmosphere. Any firing apparatus can be used as long as it can be fired under such conditions, and examples thereof include a rotary kiln, a fluidized furnace, a vertical kiln, and an annular or box-shaped electric furnace.

  An expandable admixture can be obtained by grinding the clinker. The clinker pulverization is preferably performed by a ball mill or the like that can sufficiently exert an abrasion action, rather than the one mainly composed of impact crushing, and more preferably by a rod mill because the particle size distribution range can be narrowed. In the present invention, it is not particularly necessary to strictly set and manage the pulverizing operation conditions. However, in order to prevent pop-out, the pulverized product may be pulverized until the maximum particle size is approximately 80 to 100 μm. As long as this level of pulverization is performed, there are almost no fine particles that cause a rapid hydration reaction activity. Furthermore, the narrower the particle size distribution range is, the more desirable it is because the proportion of hydrated and expandable particles that effectively act on the expansion of mortar and concrete increases. Further, other components can be mixed with the clinker pulverized product as long as the effects of the present invention are not substantially impaired. Such a mixed component may have any hardness. Examples of the components that can be mixed include gypsum, limestone fine powder, various slag fine powders such as blast furnace slag and molten slag, various cements such as coal ash, ordinary Portland cement and mixed cement, dispersants, shrinkage reducing agents and the like.

  The expandable admixture of the present invention produces 100 parts by weight of free quick lime and 1 to 25 parts by weight of an inorganic substance having a hardness higher than that of free quick lime, preferably 1 to 20 parts by weight, more preferably 2 to 12 parts by weight. It is a pulverized product of clinker included as a phase. The inorganic substance having a hardness higher than that of free quick lime is not particularly limited as long as it is an inorganic substance having a Mohs hardness of more than 3, and can be co-produced with free quick lime in a clinker. Any of crystalline may be sufficient. When the inorganic substance whose hardness is higher than that of free quick lime exceeds 20 parts by weight, the expansion action as the expandable admixture may be insufficient. Further, if the content of the inorganic substance having a hardness higher than that of free quick lime is less than 1 part by weight, it is difficult to prevent overcrushing of the free quick lime in the clinker. The expandable admixture of the present invention can be preferably obtained by the above production method. The expandable admixture of the present invention may be a clinker pulverized product in which an inorganic substance having a hardness lower than that of free quick lime and an inorganic substance having a hardness higher than that of free quick lime are coexisting with free quick lime. Furthermore, the expandable admixture of the present invention may be one obtained by mixing other components with the clinker pulverized product as described above as long as the effects of the present invention are not lost. Examples of components that can be mixed include gypsum, limestone fine powder, various slag fine powders such as blast furnace slag and molten slag, various cements such as coal ash, ordinary Portland cement and mixed cement, dispersants, shrinkage reducing agents, and the like. . The mixing amount is preferably 75 parts by weight or less from 100 parts by weight of the clinker pulverized product from the viewpoint of providing an effective expansion pressure that can resist shrinkage after the start of cement setting.

Hereinafter, the present invention will be described in detail by way of examples.
The raw material selected from the following A or B was used as a raw material for quicklime production.
A: Calcium carbonate (Brain specific surface area: 4250 cm ² / g, commercially available reagent)
B: Quicklime (Blaine specific surface area; 4330 cm ² / g, commercially available reagent)

The raw material selected from the following C-F was used as a raw material which produces | generates inorganic substances other than quicklime.
C: Ferric oxide (Brain specific surface area; 8030 cm ² / g, commercially available reagent)
D: Type II anhydrous gypsum (Brain specific surface area: 4120 cm ² / g, commercially available reagent)
E: Quartz powder (Blaine specific surface area; 4320 cm ² / g; commercially available reagent)
F: Aluminum oxide powder (Blaine specific surface area; 4240 cm ² / g, commercially available reagent)

The raw material selected from the following GL was used as a raw material which produces | generates inorganic substances other than quicklime and quicklime simultaneously.
G: Dolomite limestone (MgO; 0.3 wt%, CaO; 55.5 wt%, SiO ₂ ; 0.2 wt%, Ig. Loss; 43.9 wt%, Blaine specific surface area; 4220 cm ² / g)
H: Dolomite limestone (MgO; 1.1 wt%, CaO; 54.5 wt%, SiO ₂ ; 0.3 wt%, Ig. Loss; 44.1 wt%, Blaine specific surface area; 4310 cm ² / g)
I: Dolomite limestone (MgO; 2.8 wt%, CaO; 52.7 wt%, SiO ₂ ; 0.1 wt%, Ig. Loss; 44.4 wt%, Blaine specific surface area; 4230 cm ² / g)
J: Dolomite limestone (MgO; 5.5% by weight; CaO; 49.5% by weight; SiO ₂ ; 0.1% by weight; Ig. Loss; 44.9% by weight; specific surface area of brane; 4160 cm ² / g)
K: Dolomite limestone (MgO; 8.2% by weight; CaO; 46.2% by weight; SiO ₂ ; 0.2% by weight; Ig. Loss; 45.4% by weight; Blaine specific surface area; 4250 cm ² / g)
L: Dolomite limestone (MgO; 13.4% by weight, CaO; 40.1% by weight, SiO ₂ ; 0.3% by weight, Ig. Loss; 46.2% by weight, Blaine specific surface area; 4190 cm ² / g)

  The raw materials A to G were dry-mixed with a Redige mixer so as to obtain the blending amounts shown in Table 1. Each mixture or a molded product obtained by press-molding each of the raw materials of HM was fired in an electric furnace at the firing temperature and firing time shown in Table 1, and allowed to cool naturally to obtain a clinker. As a result of examining the generation phase of each obtained clinker using a polarizing microscope, powder X-ray diffraction and EPMA, it was confirmed that the generation phase of any clinker was a solid solution almost maintaining the crystal phase or the original crystal structure. The components produced and the amounts produced were determined. The amount of the produced component was measured by a point microscope method using a polarizing microscope and EPMA. Moreover, the high / low judgment of the hardness of the free quick lime produced | generated in the clinker and each component were rubbed against free quick lime, and the hardness in which the streak produced was judged to be lower than the other. The above results are shown in Table 2.

  Each of the obtained clinker was put in a ball mill having an internal volume of 2.5 liters together with 15,000 g of φ10 mm pulverized balls and pulverized at a rotational speed of 60 rpm for 20 minutes. A pulverized product having an average particle diameter was obtained. (Examples 1 to 7 and Comparative Examples 1 to 5) However, only Example 8 was pulverized with a rod mill (manufactured by Yoshida Seisakusho Co., Ltd.) for 20 minutes without using a ball mill. The particle size was measured with a laser diffraction particle size distribution measuring device. The pulverized product is 30% by weight of fine aggregate (crushed sand from Kokura Minami-ku (specific gravity 2.69) 30% by weight, so that it becomes 3 parts by weight per 100 parts by weight of cement (ordinary Portland cement, Taiheiyo Cement Co., Ltd.). It was put in a Hobart mixer together with 300 parts by weight of Gungo Noura offshore sea sand (mixed sand of 70% by weight of specific gravity 2.59) and 50 parts by weight of water, and kneaded at a low speed for about 10 minutes. A 4 × 4 × 16 cm mortar specimen was prepared from the kneaded product using a mold. A mortar specimen cured in water at about 20 ° C. for 7 days was measured for a change in length by a method according to JIS A 1129, and an expansion coefficient (= length change of specimen / specimen) Base length) was calculated. The results are shown in Table 3. In addition, the presence or absence of pop-out was visually observed. The results are also shown in Table 3.

  From Table 3, it can be seen that the mortars using the admixture produced according to the present invention all exhibited high expansibility and were imparted with expansibility sufficient to counter shrinkage. On the other hand, the admixture produced by the method not according to the present invention contains over-pulverized fine particles unless the pulverization conditions are specified finely or the particle size adjustment such as classification and sieving after pulverization is not performed. It can be seen that coarse particles that cause pop-out are likely to remain, and that effective expansibility against mortar shrinkage cannot be imparted, or that the mortar surface tends to deteriorate.

Claims (4)

A method for producing an expandable admixture, characterized in that 100 parts by weight of free quick lime and 1 to 25 parts by weight of an inorganic substance having a hardness higher than that of the free quick lime are produced in the clinker and then the clinker is pulverized. The method for producing an expandable admixture according to claim 1, wherein an inorganic substance equivalent to and / or having a lower hardness than free quick lime is also produced in the clinker. The method for producing an expandable admixture according to claim 1 or 2, wherein the pulverization is performed using a rod mill. An expandable admixture comprising as a main component a clinker pulverized product containing 100 parts by weight of free quick lime and 1 to 25 parts by weight of an inorganic substance having a hardness higher than that of the free quick lime as a generated phase.