JP2000095554A - Ultrahigh early-strength cement composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ultrahigh early-strength cement composition excellent in strength, durability, watertightness and flowability, not causing the separation of materials, having good adhesion and optimum for covered concrete by blending a kneaded cement composition (base composition) excellent in suitability to conveyance under pressure with a low alkali set accelerating agent having a specified alkali content and a soluble calcium salt. SOLUTION: The base composition is mortar or concrete containing Portland cement. A compound having a polyoxyalkylene whose polymerization degree of a 2-5C oxyalkylene is 20-500 in a part of its molecular structure is added as a dispersant to the cement. A low alkali set accelerating agent (e.g. silica- alumina sol) having <=2 wt.% alkali content (expressed in terms of oxide) based on the solid content is added by 0.5-1 pts.wt. based on 100 pts.wt. cement and a soluble calcium salt (e.g. calcium chloride) is also added by 0.1-5 pts.wt. based on 100 pts.wt. cement.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-high strength cement composition obtained by adding a quick-setting material to cement paste, mortar, concrete and the like. More specifically, a cement composition produced by adding a quick-setting material to a cement composition (referred to as a base composition) obtained by mixing water and, if necessary, aggregate and the like with cement, and kneading the cement composition. Excellent in quick setting and initial strength that cures in a short time,
The present invention relates to an ultra-high strength cement composition used as lining concrete or the like.

[0002]

2. Description of the Related Art An ultra-high-strength cement composition using a quick-setting material is used for lining concrete on a tunnel or an underground cavity excavation surface, or an injection paste for preventing water leakage in a tunnel,
Injection material for ground stable injection material before tunnel excavation, backfill material for shield tunnel, backfill material for retaining wall or slope, injecting material under railway track support plate, injecting material for jointing concrete material, repair of structures It is used as an injection material such as an injection material.

In this cement composition, cement is set in a short time by a quick-setting material, and contributes to ground stability, adhesion to an excavated surface, and development of strength in an extremely short time. The initial strength and long-term strength of about 7 days are insufficient, and it is necessary to provide reinforcement or high-strength secondary lining for use as a permanent structure.

Conventionally, in order to secure long-term strength, attempts have been made to increase the strength by adding a water reducing agent to the base composition to lower the water-cement ratio, but this method improves long-term strength. Efficiency of construction is a problem, such as poor initial strength and early release after construction. On the other hand, accelerators are generally used to improve the initial strength, but although there is an effect in a cement composition not using a quick-setting material, when a quick-setting material is used, an accelerator may be added. The initial strength is not always improved,
Rather, there was a problem that the initial strength was reduced.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and provides an ultra-high-strength cement composition having good quick-setting properties and excellent initial strength. Things. INDUSTRIAL APPLICABILITY The cement composition of the present invention is suitable as a material for lining concrete by spraying concrete, various injecting materials, a material for early stabilization of a tunnel excavation surface, a slope, and ground, and can shorten a construction period.

[0006]

That is, the present invention provides:
(1) An ultra-high strength cement composition obtained by adding a quick-setting material to a kneaded cement composition (base composition),
The quick-setting material is a low-alkali quick-setting material having an alkali content of less than 2% by weight (calculated as an oxide with respect to solid content).
The present invention relates to an ultra-high-strength cement composition containing 10 parts by weight and further containing 0.1 to 5 parts by weight of a soluble calcium salt as a solid content based on 100 parts by weight of cement.

[0007] The ultra-high strength cement composition of the present invention comprises:
(2) a quick-setting material whose main component is silica sol;
(3) a base composition containing a dispersant having a polyoxyalkylene having 20 to 500 oxyalkylene having a degree of polymerization of 2 to 5 carbon atoms (n) in a part of the molecular structure;
(4) Includes cement used as early-strength Portland cement, and (5) cement used as lining concrete.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments. The ultra-high strength cement composition of the present invention comprises a base composition containing a low alkali quick-setting material having an alkali content of less than 2% by weight (in terms of oxide based on solid content) and a solid content of 100 parts by weight of cement. And 0.5 to 10 parts by weight of a soluble calcium salt based on 100 parts by weight of cement.

The base composition is a cement paste obtained by mixing and adding water to cement, or a mortar or concrete obtained by mixing fine aggregate or coarse aggregate with the cement paste as required. As the cement of the base composition, it is possible to use each of Portland cements such as ordinary, early-strength, moderate heat, low heat, and white. Further, a mixed cement obtained by adding blast furnace slag, silica fume, fly ash, limestone, or the like, which is a fine powder of a mineral substance, to these cements may be used. Further, these several kinds of cement may be used in combination. Particularly, it is preferable to use a cement that conforms to the quality of the early-strength Portland cement specified in Japanese Industrial Standards (JIS R 5210-1997), because the effect of improving the initial strength is remarkably improved in the present invention. This is considered to be because the soluble calcium salt increases the effect of promoting hydration of alite in cement, and therefore, in the present invention, it is advantageous to use an early-strength Portland cement having a high content of alite.

The base composition contains a water reducing agent, an AE agent, a high-performance AE water reducing agent, a setting retarder, an antifoaming agent, a foaming agent, a fluidizing agent,
A thickener, a shrinkage reducing agent, a rust preventive, an admixture material such as a foaming material and an expanding material, and an aggregate such as blast furnace slag aggregate, molten slag aggregate, iron ore, and the like may be blended. In particular, the addition of a water reducing agent and a high-performance AE water reducing agent increases the fluidity of the base composition, lowers the pressure at which the base composition is pumped by a transport hose, and lowers the water-cement ratio, thereby increasing the initial strength and long-term strength. Can be improved. Water reducing agents and high-performance AE water reducing agents include lignin sulfonic acid type, amino sulfonic acid type,
Naphthalenesulfonic acid (aromatic sulfonic acid), polycarboxylic acid, and the like can be used.

The water reducing agent and the high-performance AE water reducing agent preferably have a polyoxyalkylene compound in the molecular structure. Specifically, an acrylic acid-based monomer such as acrylate or methacrylate or a derivative thereof, and a copolymer having a compound having a polyoxyalkylene group copolymerizable with the monomer as an essential component, and / or A copolymer of maleic anhydride and a polyoxyalkylene compound copolymerizable with maleic anhydride, and / or a formaldehyde co-condensate of an aromatic compound with a compound having a polyoxyalkylene group capable of co-condensing formaldehyde, etc. Is exemplified.

Although dispersants containing these polyoxyalkylene compounds as essential components are conventionally known, in the present invention, the combination of the base composition with the quick-setting material and the soluble calcium salt is particularly preferred. 2-5 carbon atoms
The number of moles (degree of polymerization n) of the oxyalkylene group of 20 to
Those having 500 polyoxyalkylenes are preferable, and may be those obtained by copolymerizing or co-condensing a polyoxyalkylene compound.

Among the dispersants containing a polyoxyalkylene compound as an essential component, examples of acrylic acid copolymers are described in JP-A-58-74552, JP-A-1-226757 and JP-A-7-109156.
No., JP-A-7-126053, JP-A-8-12396, JP-A-9-278
No. 505, etc. Examples of the maleic anhydride copolymer are described in JP-A-63-285140, JP-A-5-310458 and JP-A-9-255740. Further, examples of formaldehyde co-condensates with aromatic compounds are disclosed in
No. 340459 and JP-A-7-109158. However, these are all related to the components of the dispersant, and do not show an effect on the base composition of the present invention in which a specific quick-setting material and a soluble calcium salt are blended.

By containing the above-mentioned dispersant, the polyoxyalkylene group in the dispersant not only disperses the cement in the base composition to impart fluidity, but also makes the polyoxyalkylene group adsorbed on the cement particles not only disperse. Increase the friction of the cement particles to increase the viscosity of the base composition,
Suppresses separation of the base composition during pump or airflow transport. If the number of added moles n of the oxyalkylene group is smaller than 20, the effect of suppressing separation is not obtained, and the effect of retarding the setting of cement is increased, whereby the effect of promoting the initial strength by the soluble calcium salt in the base composition is suppressed. Furthermore, the slump loss of the base composition may increase, and the fluidity of the base composition may decrease during construction, causing clogging of the conveying pipe. On the other hand, if the number of moles added exceeds 500, the viscosity of the base composition becomes too high and a large transport pressure is required for transport, and the base composition and the quick-set material can be uniformly mixed when the quick-set material is added. In some cases, a predetermined rapid effect may not be obtained.

The amount of the dispersant added is preferably 0.01 to 1 part by weight in terms of solids based on 100 parts by weight of cement.
If the amount is less than 0.01 parts by weight, fluidity cannot be imparted to the base composition, and if the amount is more than 1 part by weight, the base composition separates and water floats from the base composition,
Alternatively, it is not preferable because the sand of the aggregate is settled and a uniform cement composition is not obtained, and the strength is locally reduced.

The ultra-high strength cement composition of the present invention contains a specific amount of a soluble calcium salt together with the above base composition. The soluble calcium salt may be added to the base composition, or may be added to the quick-setting material,
If the soluble calcium salt causes the quick-setting material to gel, it may be added to the base composition. The inclusion of the soluble calcium salt improves the initial strength of concrete and the like. The higher the solubility of the soluble calcium salt, the greater the effect of increasing the initial strength, and the soluble calcium salt preferably has a solubility in water at 0 ° C. of 5 g / 100 ml or more. Such soluble calcium salts include calcium chloride, calcium nitrate,
Calcium nitrite, calcium formate, calcium bromide,
Examples thereof include calcium iodide and calcium sulfamate. These may be used in combination of a plurality of types. In addition, although calcium chloride is economical, it induces rust on the reinforcing steel, and therefore, it is appropriate that calcium chloride is not used. On the other hand, calcium nitrite has an antirust effect and is one of the most suitable for use in the present invention. In addition, if calcium chloride is used together with calcium nitrite, even if it is used in a case where a reinforcing bar is provided, it is possible to suppress the induction of rust of the reinforcing bar and to improve the economic efficiency.

The amount of the soluble calcium salt added is
The range of 0.1 to 5 parts by weight relative to 00 parts by weight is suitable, and 0.5 to 3 parts by weight is preferable. If the amount is less than 0.1 part by weight, the effect of increasing the initial strength is insufficient. On the other hand, if the amount is more than 5 parts by weight, the effect of increasing the initial strength does not increase. Is unfavorable because it impairs fluidity.

The ultra-high strength cement composition of the present invention is obtained by adding a specific quick-setting material to the above base composition. As the quick setting material, a low alkali quick setting material having an alkali content of less than 2% by weight based on the solid content of the quick setting material in terms of oxide (R ₂ O) is used. If the quick-setting material has an alkali content of 2% by weight or more, the effect of increasing the initial strength by the above-mentioned soluble calcium salt is lost, and the long-term strength is further reduced.
This is because, when a large amount of alkali metal ions such as Νa ⁺ and K ⁺ are present in the liquid phase of the cement composition, the solubility of Ca ²⁺ is suppressed, and therefore the hydration reaction of the cement is suppressed and the strength does not increase. This is because, in some cases, the strength is reduced.

As long as the alkali content is a low alkali quick setting material having an alkali content of less than 2% by weight, either a liquid quick setting agent or a mineral quick setting material may be used. As a liquid quick-setting agent, silica sol, silica sol or precipitated silica obtained by gelling water glass with an acid,
Examples thereof include silica-alumina sol containing alumina, and those mainly containing aluminum sulfate. Note that alkali metal aluminate, which is usually used as a liquid quick-setting agent, is not preferable as the quick-setting material of the present invention because of its high alkali content. As a mineral quick setting material, C ₁₂ A ₇ (12Ca
O · 7Al ₂ O _3), calcium aluminate minerals such as _{C 11 A 7 · 7CaF 2 (} 11CaO · Al 2 O 3 · 7CaF 2) or C ₃ A ₃ · C,
_{aSO 4 (3CaO · 3A 2 O} 3 · CaSO 4) as a main component calcium sulfoaluminate minerals such as are exemplified.

The amount of the quick-setting material added is suitably 0.5 to 10 parts by weight as the solid content of the quick-setting material with respect to 100 parts by weight of the cement. If the addition amount is less than 0.5 part by weight, early strength (rapid effect) cannot be obtained, and particularly when used as lining concrete, adhesion to construction surfaces such as excavated surfaces and slopes is not sufficient. When the amount of the quick-setting material is more than 10 parts by weight, the setting of the cement composition after the addition of the quick-setting material becomes too fast, and the adhesive force is reduced. It is not suitable because it causes root clogging.

To add the quick setting material to the base composition,
For example, in lining concrete, it is added as a wet spraying method. Specifically, while the base composition is blown out from the spray nozzle by a concrete pump or air flow conveyance using a transport hose, the quick-setting material is conveyed by another system and added to the base composition at the nozzle port or near the nozzle port. Then, it is sprayed on the tunnel excavation surface or slope. Further, for example, when using the ultra-high strength cement composition of the present invention as an injection material, the base composition and the quick-setting material are pressure-fed to each tip using a double pipe, and both are injected at the injection tip. And inject it into the construction area.

[0022] In the ultra-high strength cement composition of the present invention, a regulator can be added to the base composition or the quick setting material in order to suppress rapid hardening when the quick setting material is added. Examples of the regulator include alkali metal salts of carbonic acid such as Na ₂ CO ₃ and NaHCO ₃ , citric acid, galactonic acid, gluconic acid, glucoheptonic acid, tartaric acid, malic acid, pyruvic acid, organic acids such as oxycarboxylic acid, glucose,
Examples include sugars or sugar alcohols such as mannose, fructose, saccharose, maltose, dextrin, sorbitol and the like.

The method for producing the ultra-high strength cement composition of the present invention, the construction method, the construction machine, the quick-setting material, and the method for adding the soluble calcium salt are not limited. If the above-mentioned constituents of the present invention and the amount of addition thereof are achieved, an ultra-high strength cement composition of the present invention having excellent initial strength can be obtained.

[0024]

The cementitious composition of the present invention is excellent in strength, durability, watertightness, fluidity, pumpability of the base composition, does not cause material separation, and is suitable for excavation and slopes. It has good adhesion and is most suitable as lining concrete. Further, when the mortar or the injection paste is used, the filling property and the permeability to the ground are good, and the initial strength is significantly improved, and the construction period can be shortened.

[0025]

Examples and Comparative Examples Hereinafter, the present invention will be specifically described with reference to Examples. In addition, these are illustrations and do not limit this invention.

Example 1 An early-strength Portland cement was used as a cement, and fine aggregate (land sand from Ogasa), a soluble calcium salt and a dispersant were kneaded at 20 ° C. using a pan-type mixer in accordance with the composition shown in Table 1. A composition was prepared. After 1 hour from the mixing, 10 kg of the base composition was separated, and 3
Add quick-setting material of seed (X, Y, Z) and add 30
After kneading for seconds, it was immediately filled into a simple mold (5 cmφ × 10 cmH) and molded. The molded sample was sealed and cured at 20 ° C. As an evaluation of the fluidity of this cement composition, the mortar flow immediately after kneading and after 60 minutes had elapsed was measured in accordance with the standard (JIS R 5201). Further, as an evaluation of the development of strength, the compressive strength of the cured product was measured for 1, 3, and 7 days. Table 2 shows the results. In addition, as a comparison, a test was similarly performed on the quick-setting material, the soluble calcium salt, and the cement composition without using the dispersant.
The results are summarized in Table 2. As shown in the results, all of the samples of this example have high compressive strength, and particularly excellent initial strength from 12 hours to 3 days of age. In addition, the fluidity after 60 minutes has little decrease and the fluidity is excellent.

[0027]

[Table 1]

[0028]

[Table 2]

Example 2 Using early-strength Portland cement as cement, fine aggregate (sand from Kashima), coarse aggregate (5-10 mm crushed stone), soluble calcium salt (calcium nitrite), and a dispersing agent as shown in Table 3 The mixture was kneaded with a pan-type mixer at 20 ° C. according to the above to prepare a base composition. The dispersant used was a copolymer of maleic anhydride and polyoxyethylene allyl ether having an added mole number of 34. On the other hand, a wet spraying machine that uses a silica sol (SI-30, manufactured by Kasei Kasei Kogyo Co., Ltd., solid content 30% by weight, Na ₂ O: 0.4% by weight) as a quick-setting material and mixes the quick-setting material with the base composition at the nozzle tip The above-mentioned base composition and the quick-setting material were mixed using, and sprayed to a thickness of about 20 cm on the excavation slope. The amount of the quick setting material was 5 parts by weight based on 100 parts by weight of the base composition. Immediately after spraying, a sample was collected, filled into a steel mold (10 cmφ × 20 cmH) while shaking, and molded, and the compressive strength at the age of 24 hours was measured. Further, as a comparative example, the compressive strength of a sample not using calcium nitrite was measured in the same manner. The results are shown in Table 3. As shown in Table 3, the sample of this example (No. 10) has much higher initial strength than the comparative sample (No. 11). Further, the sample of this example had little rebound during spraying and did not peel off from the slope.

[0030]

[Table 3]

Claims (5)

[Claims] 1. An ultra-high strength cement composition comprising a kneaded cement composition (base composition) and a quick-setting material, wherein the quick-setting material has an alkali content of less than 2% by weight (solids content). Is a low alkali quick setting material having a solid content of 0.5 to 10 parts by weight based on 100 parts by weight of cement, and a soluble calcium salt is added to 100 parts by weight of cement. On the other hand, the solid content is 0.1 ~
An ultra-high strength cement composition comprising 5 parts by weight. 2. The ultra-high strength cement composition according to claim 1, wherein the quick-setting material is mainly composed of silica sol. 3. The base composition according to claim 1, wherein the molecular structure has a degree of polymerization of oxyalkylene having 2 to 5 carbon atoms (n) of 20 to 50.
The ultra-high strength cement composition according to claim 1 or 2, comprising a dispersant having 0 polyoxyalkylene. 4. The ultra-high strength cement composition according to claim 1, wherein the cement is a high strength Portland cement. 5. The ultra-high strength cement composition according to claim 1, which is used as lining concrete.