JPH10330140A - Cement accelerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cement accelerator not containing an alkali, good in bond performance on spraying the cement and developing an excellent setting performance in a short period of time by blending aluminum sulfate with a calcined material of a calcium sulfoalminate in a specific weight ratio. SOLUTION: This cement accelerator is obtained by adding 5-100 pt.wt. one or more kinds of additives selected from <=50 pt.wt. gypsum, <=50 pt.wt. lime and <=50 pt.wt. aluminum hydroxide into 100 pts.wt. mixture of 99-22 wt.% aluminum sulfate composed of Al2 (SO4 )3 .xH2 O (x is 15-18) and/or Al2 (SO4 )3 .yH2 O (y is 8-10) with 1-80 wt.% calcined material of a calcium sulfoaluminate of which chemical composition is CaO: 30-50 wt.%, Al2 O3 ; 30-55 wt.%, SO3 ; 7-32 wt.%, SiO2 ; <=14 wt.% anf Fe2 O3 ; <=14 wt.%, and having 2000-7500 cm<2> /g, preferably 3500-6500 cm<2> /g specific surface area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for spraying cement mortar or concrete onto a ceiling or a wall such as a tunnel or a pier, which allows the mortar or concrete to harden rapidly without giving any room for peeling off by its own weight, and for a long time. Of quick-setting materials to give strength over
Particularly, the present invention relates to an alkali-free quick-setting material containing no alkali or having a very small content.

[0002]

2. Description of the Related Art Conventionally, in a so-called shotcrete method in which mortar or concrete is sprayed to reinforce a tunnel excavation surface and is instantaneously hardened, water glass (sodium silicate) and sodium aluminate have been used as quick-setting materials. Or a substance containing a large amount of alkali by adding an alkali salt such as sodium carbonate to amorphous calcium aluminate. However, they are strongly alkaline, and it has been pointed out that they have an adverse effect on the human body, especially the skin, respiratory organs, eyes, etc. of the spraying construction worker, and there is a risk that the surrounding environment may be contaminated by the alkali. In addition, alkali metal ions cause a so-called alkali-aggregate reaction with aggregates in mortar and concrete, particularly silica-based aggregates, for a long period of time, and in some cases, there is a risk that the strength of concrete will be significantly reduced.

Under such circumstances, silica sol and alumina sol-based quick-setting materials have been devised as quick-setting materials containing no alkali. However, these quick-setting materials have a low quick-setting property, and are still far from being practically used as quick-setting materials. There are many issues. In other words, these silica sol and alumina sol quick-setting materials have a thickening effect after mixing with mortar and concrete, and although they adhere to a certain extent by suppressing fluidity, their subsequent curing is slow and the sprayed thickness becomes thick. Then, it cannot withstand its own weight and tends to peel off. In order to exhibit good performance as a quick-setting material, it is necessary to improve the initial hardening performance, especially after mixing with mortar and concrete.
It is necessary to ensure that the curing proceeds within minutes.

[0004]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a quick-setting material containing substantially no alkali, exhibiting good adhesion when spraying, and exhibiting excellent curing performance in a short time. To provide quick setting material.

[0005]

The inventors of the present invention have conducted intensive studies on a material containing aluminum sulfate and a calcined calcium sulfoaluminate, and as a result, have found that a quick-setting material containing both of them at an appropriate mixing ratio is obtained. It has been found that the composition has good quick-setting performance even in an alkali-free condition and has excellent adhesion performance when sprayed, and has completed the present invention.

That is, the present invention provides that (a) aluminum sulfate and (b) a calcined product of calcium sulfoaluminate are contained in a weight ratio of (a) :( b) = 99: 1 to 20:80. It is intended to provide a quick-setting material for cement which is characterized.

The aluminum sulfate (a) used in the present invention is represented by a basic chemical formula of aAl ₂ O ₃ .bSO ₃ .cH ₂ O. In particular, a: b = 1: 3, that is, Al ₂ ( Those based on SO ₄ ) ₃ are stable and easy to manufacture. This aluminum sulfate may contain impurities such as iron components which are mixed as a chemical component in a range normally produced.

(B) The calcined product of calcium sulfoaluminate is a clinker obtained by calcining a CaO—Al ₂ O ₃ —SO ₃ composition mainly containing aauin (3CaO.3Al ₂ O ₃ .CaSO ₄ ). There, and vice minerals such as _{2CaO · SiO 2, 4CaO · Al} 2 O 3 · Fe 2 O 3,
Although other minor components may be included, the higher the ratio of the outer parts, the more desirable the rapid hardening performance.

In the present invention, (a) aluminum sulfate reacts with calcium ions eluted from cement kneaded with water to form acicular ettringite (usually 3CaO.Al ₂ O).
₃ · 3CaSO ₄ · 32H generates ₂ O and the notation), contributes to curing, prone to concentrate in a short time as a reaction of the reaction liquid phase due to the high solubility of aluminum sulfate. On the other hand, (b) Auin, which is the main component in the calcined product of calcium sulfoaluminate, reacts with calcium ions eluted from the cement similarly kneaded with water to form acicular ettringite, and at the same time, alumina gel (Al (OH) ₃
Gel). However, Auin has a lower solubility than aluminum sulfate, and the hydration reaction occurs on the surface of the Auin particles, and the formed ettrine guide or alumina gel covers the particle surfaces and functions to suppress the progress of hydration thereafter. For this reason, the production of ettrine guides is not as abrupt as aluminum sulfate and proceeds relatively mildly. Further, the generated alumina gel imparts a moderately thixotropic viscosity to the fluid mortar or concrete, thereby improving the adhesion to the wall surface.

[0010] Sprayed concrete does not simply involve instantaneous setting after the quick-setting material has been mixed. Insufficient mixing of concrete results in hardening and non-hardening parts. In addition, even if mixed well, if it is hardened before it reaches the wall surface, it is poorly held on the wall surface and rebounds, so-called rebound increases, resulting in a decrease in spraying efficiency. In other words, mortar and concrete having good spray properties have a certain degree of viscosity immediately after mixing of the quick-setting material, but do not undergo remarkable hardening and must be hardened over time.

In the present invention, by mixing (a) aluminum sulfate and (b) calcined calcium sulfoaluminate in an appropriate ratio, a quick-setting material having good adhesion performance and good quick-setting property. It is what it was. That is,
The weight ratio of (a): aluminum sulfate and (b) calcined calcium sulfoaluminate [(a) :( b)] is 9 by weight.
The range of 9: 1 to 20:80 is appropriate, and more preferably the range of 90:10 to 40:60. (A) If the amount of aluminum sulfate is too large, the viscosity immediately after mixing is too high, so that the spraying property is poor and the curing speed is not sufficient. on the other hand,
(B) If the calcined calcium sulfoaluminate is too large, the curing rate is undesirably reduced.

Further, (a) as aluminum sulfate,
It is preferable that the amount of water of crystallization is large. When aluminum sulfate having water of crystallization of 6 or less is used, the curing rate tends to be insufficient. When the amount of water of crystallization is 8 or more, that is, Al ₂ (SO ₄ ) ₃ .xH ₂
O (x = 15-18) and / or Al ₂ (SO ₄ ) ₃ .yH ₂ O (y =
8-10), better quick-setting performance can be obtained.

(B) The calcined product of calcium sulfoaluminate has a chemical composition range of 30 to 5% by weight of CaO.
0, Al ₂ O ₃ 30-55, SO ₃ 7-32, SiO ₂ ≦ 14, F
Excellent quick-setting performance is obtained by setting e ₂ O ₃ ≦ 14,
More preferably, CaO 33-43, Al ₂ O ₃ 40-53,
SiO ₃ 10 to 23, a _{SiO 2 ≦ 7, Fe 2 O} 3 ≦ 7.

Further, the performance of the calcined calcium sulfoaluminate (b) can be further improved by adjusting the particle size. That is, the specific surface area is 2000
７7500 cm ² / g, more preferably 3500 to 650
By setting it to 0 cm ² / g, a quick setting material having an appropriate setting and hardening rate can be obtained.

Further, in the present invention, in addition to (a) aluminum sulfate and (b) calcined calcium sulfoaluminate, at least one selected from gypsum, lime and aluminum hydroxide is mixed in an appropriate amount. Thereby, a quick-setting material having better performance can be obtained. That is, gypsum is effective for supplementing sulfate ions in mortar and concrete cement paste mixed with water, and lime keeps the initial calcium ion concentration high and activates the reaction of the quick-setting material. Aluminum hydroxide is effective in supplementing the aluminum component. However, excessive addition of these subcomponents will reduce the amount of the calcined product of aluminum sulfate and calcium sulfoaluminate, and as a result, the rapid hardening will be reduced. In addition, as a component in the cement paste, a balance of calcium ion, sulfate ion, and aluminum component is also required, so that addition of a single component in a large amount is not effective. That is, the total amount of (a) aluminum sulfate and (b) calcined calcium sulfoaluminate is 1
With respect to 00 parts by weight, the addition amount of these components is suitably 5 to 100 parts by weight, and more preferably 50 parts by weight or less as an individual amount.

As gypsum, gypsum dihydrate, hemihydrate gypsum and anhydrous gypsum can be used, but anhydrous gypsum is most preferable in terms of dissolution rate. As the lime, quick lime or slaked lime having high solubility can be used. As aluminum hydroxide, besides crystalline aluminum hydroxide such as gibbsite and boehmite, amorphous aluminum hydroxide can be used. In particular, amorphous aluminum hydroxide exhibits good performance.

When the quick-setting material of the present invention is used for mortar and concrete, various admixtures such as a water-reducing agent and an AE agent used for ordinary spray mortar and concrete, a strength-enhancing material and a thickening material are used. Admixtures such as may be used in combination.

The quick-setting material of the present invention is used for the purpose of spraying cement mortar or concrete onto a ceiling or a wall such as a tunnel or a pier, and the method of use is not particularly limited. What is necessary is just to mix and spray the quick-setting material of the present invention and mortar, concrete or the like.

[0019]

Hereinafter, the present invention will be described with reference to examples.
The present invention is not limited by these.

Production Example After crushing industrial materials such as limestone, alumina, gypsum, silica sand, and iron oxide, they are mixed so as to have the chemical composition of (a) or (b) shown in Table 1, respectively, and then mixed with a rotary kiln. Calcination was performed at a firing point of 1300 ° C. to obtain a calcium sulfoaluminate clinker. After crushing this with a roll crusher, the specific surface area of the clinker is 2,000, 5,000, or 8,000 cm ² / g by a ball mill.
The clinker (b) was pulverized to 5000 cm ² / g to obtain a calcined calcium sulfoaluminate. On the other hand, commercially available aluminum sulfate (a mixture of 18 and 9 hydrates, average 13 hydrates) as aluminum sulfate (c), and partially dehydrated by heating (5.3 hydrate on average) (d) It was used. Further, anhydrous gypsum was used as gypsum, slaked lime commercially available as lime, and gibbsite was used as aluminum hydroxide.

The aluminum sulfate (AS), calcined calcium sulfoaluminate (CSA), and anhydrous gypsum (C
S), slaked lime (CH) and aluminum hydroxide (AH)
Were mixed at the weight ratios shown in Table 2. In Table 2, as Comparative Example 4, a conventionally known silica sol was used.

[0022]

[Table 1]

[0023]

[Table 2]

Test Example As an evaluation of quick-setting performance, the penetration resistance of a proctor with a cement paste having a water / cement ratio of 0.4 was measured. The addition amount of the quick setting material was 12 parts by weight with respect to 100 parts by weight of the cement. Further, the properties of the paste up to 10 seconds after kneading with water were visually observed and evaluated on a four-point scale. Table 3 shows the obtained results.

[0025]

[Table 3]

As is evident from Table 3, the quick-setting material of the present invention has good properties of the paste immediately after kneading and excellent quick-setting performance. In particular, the quick-setting performance when using 8 to 10 hydrates and 16 to 18 hydrates was remarkable as compared with the case where 5.3 hydrate was used as aluminum sulfate.

On the other hand, silica sol hardly exhibited a proctor penetration resistance, and other Comparative Examples 2 and 3
In addition, the resistance to penetration of the proctor was very low, and none of them were sufficient as quick-setting materials. In Comparative Example 1 using only aluminum sulfate, the resistance to penetration by the proctor was exhibited, but the fluidity was greatly reduced due to the initial stiffness, and it was very difficult to use.

[0028]

According to the present invention, even if the alkali-free quick-setting material contains no alkali or has a very small content, a quick-setting material exhibiting good short-term curing performance and excellent in spraying properties can be obtained. can get.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Koichi Soeda, Inventor 2-4-2 Daisaku, Sakura-shi, Chiba Prefecture Chinobu Onoda Noda Central Research Laboratory (72) Inventor Waki Nishi 2-4-2, Daisaku, Sakura-shi, Chiba Prefecture No. Inside the Onoda Sakura Research Laboratories

Claims (5)

[Claims] (1) A weight ratio of (a) aluminum sulfate and (b) a calcined product of calcium sulfoaluminate:
(B) A quick-setting material for cement, which is contained in the range of 99: 1 to 20:80. 2. The method according to claim 1, wherein (a) the aluminum sulfate is Al ₂ (SO ₄ ) _{3
· XH 2 O (x = 15~18} ) and / or _{Al 2 (SO 4) 3 ·} yH 2 O
The quick-setting material for cement according to claim 1, wherein (y = 8 to 10). The chemical composition of wherein (b) Calcium sulfoaluminate baked product, CaO 30 to 50 wt% Al ₂ O ₃ 30 to 55 wt% SO ₃ seven to thirty-two wt% SiO ₂ ≦ 14 wt% Fe ₂ O _{3. The} quick setting material for cement according to claim 1, wherein the content is in a range of ₃ ≦ 14% by weight. 4. The fineness of the calcined product of (b) calcium sulfoaluminate has a specific surface area of 2,500 to 7,500 cm ² /
The quick-setting material for cement according to any one of claims 1 to 3, which is in a range of g. 5. A total of 5 to 100 components of at least one selected from lime, gypsum and aluminum hydroxide, based on 100 parts by weight of the total of (a) aluminum sulfate and (b) calcined calcium sulfoaluminate. Parts by weight,
The quick-setting material for cement according to any one of claims 1 to 4, wherein each of gypsum, lime and aluminum hydroxide alone is 50 parts by weight or less.