JP2013095624A - Quick-hardening agent and quick-hardening cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a quick-hardening agent to be used for cement compositions, having a high initial strength developability, further being excellent in a mid/long-term strength developability, and being capable of obtaining a pot life securing enough working hours of construction and placing.SOLUTION: The quick-hardening agent includes β type gypsum hemihydrate (B) and anhydrous gypsum (C) by a mass ratio (C/B) of 2 to 20, and contains calcium aluminate of 70 to 200 pts.mass to 100 pts.mass of the to a total content of the β type gypsum hemihydrate and the anhydrous gypsum. Moreover, the quick-hardening cement composition contains 10 to 150 pts.mass of the quick-hardening agent 100 pts.mass of cement.

Description

  The present invention relates to a quick hardening agent for imparting fast hardening to a cementitious composition and a fast hardening cement composition using the same.

  In order to shorten the time required for the setting of the cement composition such as mortar and concrete and to make a hardened material capable of developing high strength in a short time from the water injection, the cement composition may contain, for example, calcium aluminate or sodium aluminate. A quick hardener as an active ingredient is added. In cement compositions containing quick hardening agents, the time from water injection to the start of setting is also short, and if the start time is too short, the work time required for placing mortar or concrete may not be secured, There is a problem that long-term strength development is low, and it is difficult to obtain a satisfactory product from the viewpoint of durability. In order to solve such problems, it is known that the setting time can be delayed and the pot life can be extended by adding a setting retarder in a neutral to weakly acidic range such as oxycarboxylic acids such as citric acid and tartaric acid. . (For example, refer to Patent Document 1) In order to ensure a long pot life, it is sufficient to increase the blending amount of such an organic setting retarder, but the initial strength develops rapidly with the increase. Decrease, and quick hardening is easily lost. In addition, by adding anhydrous gypsum, medium and long-term strength development is improved, and although it is not as much as oxycarboxylic acids, the pot life can be secured to some extent. As for this person, securing the pot life becomes somewhat easier as the blending amount is increased, but it expands as the blending amount increases, so when trying to obtain the pot life to secure enough work time A considerable amount must be used, resulting in overexpansion and cracking. (For example, see Patent Document 2.)

JP 60-108352 A JP 2006-62888 A

  As described above, in a system in which a fast curing agent is blended with a cement composition, prolonged use time and expression of fast curing are incompatible properties, and when one of the properties is increased to a satisfactory level, Characterization is inhibited. The present invention solves such a problem, that is, has a high initial strength development property, has a good medium- to long-term strength development property, and can sufficiently secure, for example, work time during construction and placing. It is an object of the present invention to provide a quick hardener capable of obtaining a pot life.

  As a result of diligent study to solve the above problems, the present inventor has surprisingly found that a quick hardener blended with calcium aluminate having a crystal structure of β-type hemihydrate gypsum and anhydrous gypsum in a specific amount ratio. It has been found that such problems can be solved as a whole, and the present invention has been made.

  That is, this invention is the quick-hardening agent represented by following (1), and the quick-hardening cement composition represented by (2)-(3). (1) β-type hemihydrate gypsum (B) and anhydrous gypsum (C) are contained at a mass ratio (C / B) = 2 to 20 and the total content of β-type hemihydrate gypsum and anhydrous gypsum is 100 parts by mass. On the other hand, a quick hardener containing 70 to 200 parts by mass of calcium aluminate. (2) A quick-hardening cement composition containing 10 to 150 parts by weight of the quick-hardening agent (1) and 100 parts by weight of cement. (3) The fast-setting cement composition according to (2) above, which does not contain a setting delay component other than gypsum.

  If the rapid curing agent of the present invention is used in a cement composition such as mortar or concrete, it is possible to ensure the working time required for construction and placing without using an organic setting retarder, so that a high initial Strength can be expressed without hindrance, and medium and long-term strength development can also be improved.

  The anhydrous gypsum and β-type hemihydrate gypsum contained in the rapid curing agent of the present invention can suppress the initial hydration of calcium aluminate after water injection and delay the initial setting time. Therefore, in the present invention, the inclusion of the gypsum is indispensable as a means for securing the pot life. Of these, anhydrous gypsum, which is a component of the quick-hardening agent of the present invention, may be any one, and is type II anhydrous gypsum from the standpoint of availability. Use of anhydrous gypsum greatly contributes to obtaining a pot life, and improves strength development in the medium to long term.

  Β-type hemihydrate gypsum, which is a component of the quick-hardener of the present invention, has the fastest dissolution rate in water among the crystals of gypsum (semihydrate gypsum, dihydrate gypsum and anhydrous gypsum). It is possible to release sulfate ions immediately after water injection, accelerate the formation of ettringite phase from the initial hydrate of calcium aluminate, and enhance the initial strength development. Such effects are considerably weakened with hemihydrate gypsum and dihydrate gypsum having crystal structures other than β-type. In other words, β-type hemihydrate gypsum can avoid a long period from the beginning to the end of setting due to the use of anhydrous gypsum. On the other hand, as with anhydrous gypsum, etc. It also has the function of facilitating securing the above. As described above, since the relationship between β-type hemihydrate gypsum and anhydrous gypsum is deeply related to securing the pot life and expression of fast setting, the content of both gypsum in the quick-curing agent of the present invention is also β-type hemihydrate gypsum. (B) and anhydrous gypsum (C) need to satisfy | fill the relationship from which mass ratio (C / B) = 2-20. If the mass ratio (C / B) is less than 2, the pot life cannot be secured sufficiently, which is not preferable. If the mass ratio (C / B) exceeds 20, not only the initial strength is lowered, but also the medium- to long-term strength developability. Since it may decrease, it is not preferable.

In addition, the calcium aluminate that is a component of the quick-hardener of the present invention may be any hydration active substance having a crystallized structure or advanced vitrification composed of CaO and Al ₂ O ₃ as chemical components. In addition, any compound, solid solution, glassy material, or a mixture of other chemical components in addition to CaO and Al ₂ O ₃ may be used as long as the effects of the present invention are not substantially lost. The former, for example, _{12CaO · 7Al 2 O 3, CaO} · Al 2 O 3, 3CaO · Al 2 O 3, CaO · 2Al 2 O 3, CaO · 6Al 2 O 3 and the like, the latter, for example, 4CaO · 3Al ₂ O ₃ · SO ₃ , 11CaO · 7Al ₂ O ₃ · CaF ₂ , Na ₂ O · 8CaO · 3Al ₂ O _{3 and the} like. Preferably, since it has excellent strength development at low temperature, it is preferable that it contains at least a part of amorphous 12CaO · 7Al ₂ O ₃ , CaO · Al ₂ O ₃ and / or 3CaO · Al ₂ O _3. . Such a calcium aluminate preparation method can be obtained, for example, by heating and melting a raw material mixture of a CaO source and an Al ₂ O ₃ source having a predetermined blending ratio and quenching, but commercially available alumina cement can also be used. In this fast curing agent, calcium aluminate is used to develop a fast curing action. The mechanism of imparting quick hardening by calcium aluminate is due to the fact that the initial hydrate after water injection reacts with gypsum and rapidly forms a strong ettringite phase. The content of calcium aluminate is determined by a relative relationship with the amount of gypsum serving as a sulfate ion source during the formation of ettringite, and is the sum of β-type hemihydrate gypsum and anhydrous gypsum contained in the rapid curing agent of the present invention. 70 to 200 parts by mass with respect to 100 parts by mass. If it is less than 70 parts by mass, the initial strength developability is lowered, and it is difficult to obtain rapid curing, or there is a risk of overexpansion, which is not preferable. Moreover, since it will become difficult to ensure desired pot life when it exceeds 200 mass parts, it is unpreferable.

The quick-hardener of the present invention can contain components other than the above anhydrous gypsum, β-type hemihydrate, and calcium aluminate as long as the effects of the present invention are not impaired. Examples of components that can be contained include, for example, cellulose derivatives, calcium sulfoaluminate, silica fume, fly ash in addition to setting accelerators such as alkali metal sulfates, carbonates or nitrates, aluminum sulfate, calcium nitrate or calcium nitrate. , Dispersed components and the like. Moreover, it is desirable that the rapid hardening agent of the present invention does not contain a setting delay component other than gypsum. The use of the setting retarding component is effective for securing the pot life, but it is not preferable because the strength development property including the initial strength tends to decrease as a whole. This tendency generally becomes stronger as the setting retarding action such as oxycarboxylic acid and its salt is stronger. Further, the particle size of the fast curing agent of the present invention may be appropriately selected according to the use and the like, and is not particularly limited. As a practical example, it is easy to ensure the pot life, and as a particle size suitable for satisfying the fast curing, it is intended to stably obtain a higher rapid curing with a specific surface area of about 3000 to 9000 cm ² / g in the Blaine specific surface area. In this case, considering the cost, the Blaine specific surface area is 4000 to 8000 cm ² / g.

  Moreover, the quick-hardening cement composition of this invention contains a cement and the above-mentioned quick-hardening agent. The cement may be any hydraulic cement, for example, normal, early strength, super early strength, moderate heat, low heat, etc. Portland cement, mixed cement such as blast furnace cement and silica cement, white cement, alumina cement, eco cement, etc. 2 or more types may be used in combination. Preferably, ordinary or early-strength Portland cement is preferable because high initial strength is obtained in combination with calcium aluminate and workability is relatively good. Content of the said quick hardening agent in the cement composition of this invention shall be 10-150 mass parts with respect to 100 mass parts of cement. If it is less than 10 parts by mass, it is not preferable because rapid curing may not be obtained substantially.

  The fast-curing cement composition of the present invention can contain components other than cement and the above-mentioned fast-curing agent as long as the effects of the present invention are not substantially lost. Examples of such components include aggregates, various water reducing agents (dispersing agents), shrinkage reducing agents, expansion materials, fibers, cement polymers, thickeners, air entraining agents, antifoaming agents, white flower preventing agents, Examples thereof include water repellents, water retention agents, pigments, pozzolanic reactive substances, and curing accelerators. In addition, the cement composition of the present invention does not contain any setting delay components other than gypsum, including in the quick-hardening agent as a constituent material, when it is desired to sufficiently obtain higher strength. good. Further, the amount of water used for water injection of the cement composition of the present invention is not particularly limited. When a recommended example is shown, if it is 15-100 mass parts with respect to 100 mass parts of cement, it will be easy to obtain high intensity | strength developability, without affecting workability etc.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to the described examples.

[Preparation of fast curing agent]
A mixture of pulverized limestone and shale shale is heated in an electric furnace at 1550 ± 50 ° C. for 1 hour, and the fired product is rapidly cooled from the temperature into the room temperature chamber to the chemical component content shown in Table 1. Two types of calcium aluminate were prepared. Any calcium aluminate was adjusted to a specific surface area of about 5000 cm ² / g by pulverization and classification. These calcium aluminates were mixed with various gypsums listed in Table 2 (all of which were adjusted to a brain specific surface area of about 6000 cm ² / g with a commercially available reagent), and a quick hardener (this product 1-9, reference product). 1-9) were produced.

[Preparation of cement composition (mortar)]
Fast-curing agent prepared as described above, ordinary Portland cement (commercially available), fine aggregate (corresponding to “standard sand for cement strength test” defined in JIS R 5201 “Cement physical test method”) and water the use of citric acid as necessary (commercially available reagent), blast furnace slag powder (commercial product, Blaine specific surface area of about 8000 cm ² / g) or fly ash powder (Blaine specific surface area of about 6000 cm ² / g) was used added, tables A mortar was prepared by kneading in a Hobart mixer for about 4 minutes at room temperature so as to achieve the composition shown in FIG.

[Evaluation of cement composition (mortar)]
The produced mortar was subjected to a flow test defined in JIS R 5201 “Physical test method for cement”, and measured so that a time range in which a 15-stroke flow value was 120 mm or more was regarded as a usable time. However, the measurement was censored when the time range was up to 90 minutes, and the usable time “> 90 (minutes)” was written for those that surely exceeded 90 minutes. In addition, the mortar immediately after kneading is filled into a cylinder forming mold having an inner diameter of 50 mm and an inner dimension height of 100 mm, followed by demolding / curing means specified in JIS R 5201 “Cement physical testing method” and compressed. A specimen for strength measurement was prepared. The uniaxial compressive strength was measured at room temperature for specimens with a material age of 24 hours and 7 days. The above results are summarized in Table 3.

  From the results in Table 3, the mortars (Examples 1 to 9) using an appropriate amount of the quick-curing agent of the present invention all exhibit a high initial strength and are sufficient to be required during normal construction and placing. It can be seen that the usage time is secured. In addition, it is sufficiently observed that a high strength development property can be obtained regardless of the period by confirming the tendency to improve the strength in the medium term (7-day body). On the other hand, mortars that are outside the scope of the present invention have a pot life that is considerably shorter than those of the present invention (Comparative Examples 1 to 3). It was not provided (Comparative Examples 6 to 9), or the pot life and strength development were sluggish (Comparative Examples 4 to 5).

Claims (3)

β-type hemihydrate gypsum (B) and anhydrous gypsum (C) are contained at a mass ratio (C / B) = 2 to 20 and calcium is added to 100 parts by mass of the total content of β-type hemihydrate gypsum and anhydrous gypsum. A hardener containing 70 to 200 parts by weight of aluminate. A fast-hardening cement composition containing 10 to 150 parts by weight of the quick-hardening agent according to claim 1 and 100 parts by weight of cement. The fast-setting cement composition according to claim 2, which does not contain a setting delay component other than gypsum.