JP7198281B2 - Cement composition for bolt fixation and bolt fixation method - Google Patents

Description

The present invention is a cement composition used in the field of civil engineering and construction, particularly in tunnels such as roads, railways and waterways, as a bolt anchoring material for rock bolt construction, an injection material for excavation, and a bolt for anchor construction on slopes. The present invention relates to a cement composition that can be used as a fixing material and a bolt fixing method using the same.

In the tunnel rock bolt method and the slope anchor method, after drilling, cement, fine aggregate, and water are mixed to prepare mortar, which is then pumped to fill the hole with mortar and bolts are inserted. method is being carried out.

In this construction method, if the water/cement ratio of the mortar is reduced, the strength of the mortar and the fixing force of the bolts will increase, but the fluidity will decrease, making it difficult to pump and fill the holes. Conversely, if the water/cement ratio of the mortar is increased, pumping and filling into the holes become easier, but there is the problem that reliable bolt fixing cannot be achieved due to leakage and material separation after filling. there were.

Especially in recent years, in the rock bolt construction method, after drilling a hole, a bolt is inserted, and mortar is filled from the hole in the center of the bolt or from the gap on the side of the bolt to fix the bolt. In this case, filling is very difficult unless the water/cement ratio is increased, and the above-mentioned problem has become conspicuous. Furthermore, if cracks do not need to be repaired or can be easily repaired after the spring is filled with water, it is very significant from the viewpoint of maintenance.
Therefore, a cement composition obtained by blending the cement shown in Patent Document 1 with an expansive material, an alkali metal aluminate and an alkali metal carbonate, or the cement shown in Patent Document 2, fine aggregate and an anti-separation agent. A cement composition for fixing bolts has been proposed.

JP-A-2005-112648 JP-A-2008-88040

In Patent Document 1 and Patent Document 2, there is a problem that the cement composition has low viscosity and initial strength development after being filled into the hole, and the cement composition flows out under high seepage water.
As described above, according to the present invention, it is possible to produce a bolt fixing mortar that maintains good fluidity when filled into holes, shows a rapid viscosity increase when left to stand after filling, and has high initial strength development. It is an object of the present invention to provide a cement composition for bolt fixation that exhibits excellent repairing action on cracks formed after bolt fixation.

As a result of various investigations, the present inventors have found that a mortar that maintains good fluidity when filled into pores, shows a rapid viscosity increase when left to stand after filling, and has high initial strength development. and found that it can exert an excellent repairing effect on cracks, thereby completing the present invention. That is, the present invention is as follows.

[1] A cement composition for fixing bolts, comprising cement, an expansive material, sodium silicate, and alum and/or an alkali metal carbonate.
[2] The bolt fixing cement composition according to [1], wherein the sodium silicate has a molar ratio of SiO ₂ to Na ₂ O (SiO ₂ /Na ₂ O) of 0.5 to 1.5.
[3] The cement composition for bolt fixing according to [1] or [2], wherein the sodium silicate has 9 or less waters of hydration.
[4] The cement composition for bolt fixation according to any one of [1] to [3], further comprising fine aggregate.
[5] A bolt fixing mortar obtained by kneading the bolt fixing cement composition according to any one of [1] to [4] with water is injected into the drilled hole, and then the bolt is inserted into the drilled hole. A bolt fixing method that is inserted and fixed in the
[6] With the bolt inserted in the drilled hole, the bolt-fixing mortar obtained by kneading the bolt-fixing cement composition according to any one of [1] to [4] with water is drilled. A bolt fixation method in which the bolt is fixed by injecting into the hole.

According to the present invention, it is possible to produce a bolt fixing mortar that maintains good fluidity when filled into holes, shows a rapid increase in viscosity when left to stand after filling, and has high initial strength development. It is possible to provide a cement composition for bolt fixing that can exhibit excellent repairing action against cracks formed after fixing.

Although the present invention will be described in detail below, the present invention is not limited thereto. Parts and percentages in this specification are shown on a mass basis unless otherwise specified.

[Cement composition for bolt fixing]
One aspect (this embodiment) of the bolt fixing cement composition of the present invention comprises cement, an expansive agent, sodium silicate, and alum and/or an alkali metal carbonate. Moreover, it is preferable to further contain a fine aggregate.
A bolt fixing mortar is obtained by kneading the bolt fixing cement composition of the present embodiment with water.

(cement)
The cement used in the present embodiment is not particularly limited, and various cements such as normal, early-strength, ultra-early-strength, low heat and moderate heat, and blast furnace slag, fly ash, silica fume, etc. are added to these cements. There are various mixed cements, environment-friendly cement (eco-cement) manufactured from municipal waste incineration ash and sewage sludge incineration ash, and commercially available fine particle cement. It is also possible to convert and use it. In addition, those adjusted by increasing or decreasing the amount of components (for example, gypsum, etc.) normally used in cement can also be used.

(expanding material)
The expansive material used in this embodiment is not particularly limited, and any material can be used as long as it produces an expansive hydrate and suppresses bleeding. Examples of expansive materials include free lime, free magnesia, calcium ferrite, ettringite, lime, ettringite-lime composite, and awine, and are not particularly limited.

The particle size of the expanding material is preferably 2,000 to 9,000 cm ² /g, more preferably 3,000 to 8,000 cm ² /g in Blaine specific surface area. When it is 2,000 cm ² /g or more, the hydration reaction proceeds favorably, and when it is 9,000 cm ² /g or less, the hydration reaction does not become too fast, making it easier to obtain a predetermined expansion.
In this specification, the Blaine specific surface area can be determined according to JIS R 5201.

The amount of expansive material used is preferably 1-20 parts, more preferably 2-15 parts, and even more preferably 3-7 parts, per 100 parts of cement. In particular, when it is 1 part or more (especially 2 parts or more), the effect of reducing shrinkage is easily obtained, and when it is 20 parts or less (especially 15 parts or less), the amount of expansion becomes too large and the strength is prevented from decreasing. can be prevented.

(sodium silicate)
The sodium silicate used in the present invention mainly exerts the effect of promoting the loss of fluidity in the very initial stage, and also, for example, when the bolt fixing material during bolt fixing construction cracks over a long period of time. For example, a 0.1 mm crack can be repaired under running water conditions. It is considered that this is because the sodium silicate gelled by water acts to repair the crack itself and reduce the width of the crack. From the viewpoint of efficiently exhibiting the above effects, the sodium silicate is preferably in the form of powder.

As a cement composition for fixing bolts, for example, as a composition that promotes loss of fluidity in the very initial stage, the molar ratio of SiO ₂ and Na ₂ O (SiO ₂ /Na ₂ O) in sodium silicate is 0.5 to 1.5. It is preferably 5, more preferably 0.9 to 1.3.
When the molar ratio is 0.5 or more, the handleability as a powder is good, and when it is 1.5 or less, it becomes easy to obtain significant loss of fluidity and initial strength development immediately after addition to mortar. .

Examples of sodium silicate include sodium orthosilicate, sodium metasilicate, sodium sesquisilicate, etc. Among them, sodium metasilicate is preferable. Examples of sodium silicate include sodium silicate No. 1 [Na ₂ Si ₂ O ₅ (Na ₂ O.2SiO ₂ : n=2)], sodium silicate No. 2 [Na ₄ Si ₅ O ₁₂ (Na ₂ O.2. 5SiO ₂ : n=2.5)], sodium silicate No. 3 [Na ₂ Si ₃ O ₇ (Na ₂ O.3SiO ₂ : n=3)], and sodium silicate No. 4 [Na ₂ Si ₄ O ₉ (Na ₂ O.4SiO ₂ : n=4)] and the like.

The sodium silicate is not particularly limited whether it is a hydrate or an anhydride, but the number of waters of hydration is preferably 9 or less, more preferably 5 or less, and more preferably an anhydrate.

The Blaine specific surface area of sodium silicate is preferably 300 to 1000 cm ² /g, more preferably 500 to 800 cm ² /g. When it is 300 to 1000 cm ² /g, it is easy to obtain initial strength development.

The amount of sodium silicate used is preferably 0.05 to 8 parts, more preferably 0.1 to 5 parts, and even more preferably 0.2 to 1 part per 100 parts of cement. . If it is 0.05 parts or more (especially 0.1 parts or more), the thickening effect after filling tends to be sufficient, and if it is 8 parts or less (especially 5 parts or less), the thickening effect is too large and pumping is difficult. Difficulty can be prevented, and long-term strength development can be improved.

(alkali metal carbonate)
Alkali metal carbonates (hereinafter referred to as carbonates) used in the present embodiment include sodium carbonate, potassium carbonate, lithium carbonate, sodium bicarbonate, potassium bicarbonate, sodium sesquicarbonate, and the like. You may use 2 or more types. Among these, potassium carbonate is preferable because it has a large thickening effect after filling.

The amount of alkali metal carbonate used is preferably 0.03 to 4 parts, more preferably 0.05 to 3 parts, and 0.1 to 1.0 parts per 100 parts of cement. is more preferred. When it is 0.03 parts or more (especially 0.05 parts or more), the thickening effect after filling is sufficiently easily obtained, and when it is 4 parts or less (3 parts or less), the thickening effect becomes too large. It can prevent the pumping and keep the pumping in good condition.

(Alum)
Alum is effective in promoting loss of fluidity of the cement composition for fixing bolts and in promoting strength development for about one day. The alum is not particularly limited, but any alum such as potassium alum, chrome alum, iron alum, ammonium alum, sodium alum, and natural alum can be used or used in combination. In particular, it preferably contains at least one selected from the group consisting of potassium alum, sodium alum, and ammonium alum as a substance that eliminates the fluidity of cement mortar and cement concrete.

The amount of alum used is preferably 0.05 to 18 parts, more preferably 0.1 to 15 parts, and even more preferably 0.2 to 10 parts per 100 parts of cement. . By setting the amount to be 0.05 to 18 parts (especially 0.1 to 15 parts), loss of fluidity is not delayed, and strength development at one day of age can be improved.

Alkali metal carbonate and alum may be used in combination, and in that case, the total amount used is preferably 0.03 to 25 parts, preferably 0.05 to 20 parts, per 100 parts of cement. is more preferred, and 0.1 to 18 parts is even more preferred. When the amount used is 0.03 to 25 parts, loss of fluidity is not delayed, and good strength development can be achieved at a material age of 1 day.
From the viewpoint of loss of fluidity or development of strength, the Blaine specific surface area of alum is preferably 400 to 1000 cm ² /g.

(fine aggregate)
The fine aggregate used in this embodiment is not particularly limited, and any of river sand, mountain sand, lime sand, silica sand, etc. can be used.
The maximum dimension of the fine aggregate is preferably 1.2 mm or less, more preferably 0.6 mm or less. When it is 1.2 mm or less, even if the filling port is narrow during construction on site, particularly in the post-filling method of the rock bolt method, it can be filled satisfactorily without clogging.
The fine aggregate is preferably used by mixing dry sand such as lime sand or silica sand with the present cement composition in advance, since there is little variation in workability and physical properties during on-site construction.
The amount of fine aggregate used is preferably 10 to 300 parts, more preferably 50 to 200 parts, per 100 parts of cement. When it is 10 to 300 parts, it can be filled satisfactorily without clogging.

In this embodiment, a water reducing agent, a thickening agent, or the like may be further used as necessary.
The water reducing agent used in this embodiment is an agent used to improve the fluidity of cement concrete, and can be used in liquid or powder form. Examples of water reducing agents include polyol derivatives, lignin sulfonates and their derivatives, high performance water reducing agents, and the like, and one or more of these may be used in combination. Among these, high-performance water reducing agents are preferred because they have a large effect of improving strength and fluidity.

Examples of high-performance water reducing agents include formalin condensates of alkylallylsulfonates, formalin condensates of naphthalenesulfonates, formalin condensates of melaminesulfonates, polycarboxylic acid-based polymer compounds, and the like. You may use a seed|species or 2 or more types together. Among these, a sodium methacrylate-methoxypolyoxyethylene methacrylate copolymer is preferred because of its large fluidity-improving effect.

The amount of superplasticizer used is preferably 0.05 to 3 parts, more preferably 0.1 to 2 parts, per 100 parts of cement. If it is 0.05 parts or more, a sufficient fluidity improving effect is likely to be obtained, and if it is 3 parts or less, the fluidity is not too large, the thickening effect after filling is hindered, and the material separation occurs, resulting in strength. It is possible to prevent a decrease in expression.
A liquid or powdery high-performance water reducing agent can be used, but it is preferable to mix a powdery water reducing agent with the cement composition of the present invention in advance, since there is little change in workability and physical properties when used on site. preferable.

The thickening agent used in the present embodiment is an agent that imparts viscosity to cement concrete, and further enhances the thickening effect after filling. Thickeners include celluloses such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose and hydroxyethylethylcellulose; alginic acid, sodium alginate, β-1,3-glucan, pullulan, guar gum, casein And polysaccharides such as dutan gum and welan gum; vinyl acetate, ethylene, vinyl chloride, methacrylic acid, acrylic acid, sodium acrylate and vinyl polymers such as unsaturated carboxylic acids and copolymers thereof, and vinyl acetate polymers Emulsions such as those obtained by modifying the copolymer to a saponified polyvinyl alcohol skeleton may be mentioned, and one or more of these may be used in combination. Among these, celluloses are preferable because they have a large thickening effect after filling.

The amount of thickening agent used is preferably 0.005 to 0.1 parts, more preferably 0.008 to 0.05 parts, per 100 parts of cement. When the amount is 0.005 parts or more, a sufficient thickening effect is likely to be obtained, and when the amount is 0.1 part or less, the thickening effect does not become too large, making pumping difficult and reducing strength development. can prevent you from doing it.

Further, in this embodiment, organic acids or their salts, mixtures of organic acids or their salts and carbonates, phosphates, boron salts are used to retard the viscosity rise time and setting time of the cement composition of the present invention at elevated temperatures. Set retarders such as acid salts or salts thereof and alcohols may also be used.

According to the cement composition of the present embodiment as described above, in the rock bolt construction method in tunnels such as roads, railways, and waterways, the injection method during excavation, and the anchor construction method for slopes, during pumping with a pump It maintains good fluidity, and when left to stand after pumping stops, the viscosity rises sharply, and the rapid viscosity rise and early strength development are high, and it is possible to prevent leakage and material separation. Since the effect can be exerted, reliable bolt fixation is possible.

[Bolt fixing method]
In the first bolt fixing construction method of the present embodiment, a bolt fixing mortar obtained by kneading the bolt fixing cement composition of the present embodiment with water is injected into the drilled hole, and then the bolt is inserted into the drilled hole. It is a method of inserting and fixing.

In the second bolt fixing method of the present embodiment, the bolt fixing mortar obtained by kneading the bolt fixing cement composition of the present embodiment with water while the bolt is inserted into the drilled hole is removed. In this method, the bolt is fixed by injecting it into the drilled hole.

The amount of water used in the cement composition of the present embodiment is preferably 45 to 75%, more preferably 50 to 70%, in water/cement ratio. When it is 45% or more, good fluidity is likely to be obtained, and pumping becomes good. When it is 75% or less, it is possible to prevent material separation and a decrease in strength development.

The rock bolt construction method, the anchor construction method, and the like are known as construction methods for reinforcing fragile ground, and the present invention is very effective for anchoring bolts in these construction methods.

The anchoring method is a treatment for sliding soil masses that are about to move. For example, one end of a tension member called a tendon is placed on the stable ground (anchor anchorage portion) of the borehole to absorb the reaction force, and the other end of the tension member is placed on the ground surface. It is fixed to a concrete structure or a pressure plate to suppress sliding activity. The bolt fixing construction method of the present embodiment can be applied when installing the tension member.
In addition, in the ground where it is difficult for the boring hole to stand on its own, a sheath tube may be inserted between the ground and the anchor fixing portion.

The rock bolt method involves drilling a cylindrical hole in a slope (slope) using an excavator, inserting a long cylindrical rock bolt (deformed steel, etc.) into the hole. After that, the rock bolt is fixed (fixed) inside the excavated hole, and the bolt fixing method of the present embodiment can be applied during this fixation.

EXAMPLES The present invention will be described in detail below with reference to Examples, but the present invention is not limited to these.

(Experimental example 1)
100 parts of cement A, the amount of expansive material shown in Table 1, sodium silicate, alum, and alkali metal carbonate, and 0.1 part of sodium methacrylate-methoxypolyoxyethylene methacrylate copolymer were blended for bolt fixing. A cement composition was obtained. Furthermore, 50 parts of fine aggregate α and 65 parts of water were mixed to prepare a mortar for fixing bolts, and the viscosity, expansion rate, compressive strength, and crack repair rate were measured for each elapsed time. The results are shown in Table 2 below.

<Materials used>
(1) Cement Cement A: Ordinary Portland cement, Blaine specific surface area value 3340 cm ² /g
(2) Expanding material Expanding material a: Auin system, Blaine specific surface area 6110 cm ² /g
Expanding material b: "Denka Power CSA Type S" manufactured by Denka, ettringite-lime composite type, Blaine specific surface area 3000 cm ² /g
(3) Sodium silicate Sodium silicate: SiO ₂ /Na ₂ O molar ratio 1.0, Blaine specific surface area value 600 cm ² /g, commercial product, anhydrous salt

(4) Alum Alum a: potassium alum dodecahydrate, commercial product, Blaine specific surface area value 600 cm ² /g
Alum b: sodium aluminum sulfate dodecahydrate, commercial product, Blaine specific surface area value 700 cm ² /g
Alum c: ammonium alum dodecahydrate, commercial product, Blaine specific surface area value 600 cm ² /g
(5) Alkali metal carbonate Alkali metal carbonate a: Potassium carbonate, commercially available Alkali metal carbonate b: Sodium carbonate, commercially available

(6) Fine aggregate Fine aggregate α: Silica sand, commercial product, maximum size 0.5 mm

<Test method>
(1) Viscosity: The mortar obtained in each example was placed in a cup and measured with a Brookfield viscometer. Measurement times were immediately after kneading (0 minute) and after 15 minutes. The viscosity immediately after kneading is preferably 7500 mPa·s or less, more preferably 6500 mPa·s or less, and the viscosity after 15 minutes is preferably 10000 mPa·s or more.
By measuring the viscosity, it is possible to evaluate the fluidity at the time of filling into the pores and the viscosity increase at the time of standing after filling.

(2) Expansion rate: The mortar obtained in each example was placed in a standard φ50 mm polyethylene bag of the Japan Society of Civil Engineers and measured at 20 hours of age according to JSCE-F 522-1999. The expansion rate is preferably -3.0% or more.

(3) Compressive strength: The mortar obtained in each example was collected in a formwork of 40 x 40 x 160 mm, and measured according to JIS R 5201 at 1 day and 28 days of age. The strength (initial strength) at one day of age is preferably 5 N/mm ² or more.

(4) Crack repair rate: According to JIS A 6202-1997, the mortar obtained in each example was poured into a mold of 10 cm x 10 cm x 40 cm under the condition of uniaxial restraint to prepare a test specimen. After 7 days of material age, a bending test was performed so that the crack width was 0.1 mm, and then underwater curing was performed at 20 ° C. for 6 months. asked. The crack repair rate is preferably 50% or more.

By using the cement composition for bolt fixation of the present invention, the initial viscosity is low, and then the viscosity increases to improve the fixation effect, and it can be seen that the strength development and crack repair rate are excellent.

(Experimental example 2)
Experiment No. 1 was carried out except that sodium silicate having a SiO ₂ /Na ₂ O molar ratio shown in Table 3 below was used. A mortar for bolt fixing was prepared in the same manner as in 1-3. After that, various tests were conducted in the same manner as in Experimental Example 1. Table 3 shows the results.

By using the cement composition for fixing bolts of the present embodiment, the initial viscosity is low, and then the viscosity increases, thereby improving the fixing effect.

The present invention is a cement composition used in the field of civil engineering and construction, particularly in tunnels such as roads, railways and waterways, as a bolt anchoring material for rock bolt construction, an injection material for excavation, and a bolt for anchor construction on slopes. It can be suitably used as a fixing material and the like.

Claims (5)

It contains cement, an expanding material, sodium silicate, and alum and/or an alkali metal carbonate, and the molar ratio of SiO ₂ and Na ₂ O in the sodium silicate (SiO ₂ /Na ₂ O ) is 0.5 to 1.5 . 2. The bolt fixing cement composition according to claim 1 , wherein the sodium silicate has 9 or less waters of hydration. 3. The bolt anchoring cement composition according to claim 1, further comprising fine aggregate. After injecting a bolt-fixing mortar obtained by kneading the bolt-fixing cement composition according to any one of claims 1 to 3 with water into the drilled hole, a bolt is inserted into the drilled hole. bolt fixing method. With a bolt inserted into the drilled hole, a bolt-fixing mortar obtained by kneading the bolt-fixing cement composition according to any one of claims 1 to 3 with water is applied to the drilled hole. A bolt fixing construction method in which the bolt is fixed by injection.