JP2011001243A - Sulfuric acid-resistant cement composition for spraying process, and spraying process using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sulfuric acid-resistant cement composition for a spraying process which can prevent the spalling and sagging of cement mortar directly after spraying, can thicken a spraying thickness, remarkably reduce a rebound amount, has increased adhesion, and also has excellent sulfuric acid resistance, and to provide a spraying process.SOLUTION: The sulfuric acid-resistant cement composition for a spraying process is composed of an A material and a B agent, in which the A material comprises calcium aluminate and the B agent comprises an acrylic ester copolymer emulsion. Further, in the sulfuric acid-resistant cement composition for a spraying process, the A material comprises granulated blast furnace slag and/or silica fume, and the calcium aluminate is alumina cement. Further, the A material preferably comprises a polymer. The spraying process uses the sulfuric acid-resistant cement composition for a spraying process.

Description

  The present invention mainly relates to a cement composition excellent in sulfuric acid resistance for repairing a deteriorated portion of a concrete structure due to sulfuric acid in a sewer or a hot spring area, and a spraying method using the same.

In sewers and hot spring areas, hydrogen sulfide is generated due to the influence of microorganisms and volcanic gas, and when water intervenes, it becomes sulfuric acid. In such places, corrosion of concrete structures due to sulfuric acid or sulfate is a problem. When a cemented body such as concrete is brought into contact with an acid such as sulfuric acid, dihydrate gypsum is generated by reaction with calcium hydroxide present in the cured body, and ettringite is further generated and deteriorated.
As a method for repairing such a deteriorated portion, a method of performing resin lining after removing the deteriorated portion with a water jet and repairing the cross section is often performed. As the cross-sectional restoration material used for this, materials blended with polymer in blast furnace granulated slag (Patent Document 1), materials made of alumina cement (Patent Documents 2 and 3), fly ash, granulated blast furnace slag, silica fume, etc. Cement mortar containing a large amount of powder is used (Patent Document 4). In addition, a material using alumina cement and fine powder of blast furnace slag, alumina cement particles of 5 μm or less are 25 wt% or less, a material containing lithium salt (Patent Document 5), an alkali metal salt of sulfonic acid as a substituent A material (Patent Document 6) containing a water-soluble organic compound has been proposed.

  As a construction method, finishing is often performed by applying with a trowel. However, this finishing method has a problem that it requires skill and is difficult to apply thickly and requires a lot of labor.

  For this reason, methods have been proposed in which mortar is pumped and sprayed (Patent Documents 7, 8, and 9).

  In order to prevent peeling and sagging, it is necessary to spray in several layers. When spraying in several layers, after spraying the first layer, to spray the second layer Further, since the first mortar is condensed (usually said that the mortar is tightened), the construction takes time and the workability is very poor.

In recent years, early deterioration of concrete has become a problem, and improvement in durability such as adhesion to existing concrete and freeze-thaw resistance is required for sprayed mortar for repair.
When performing spraying mortar with a large cross section, it is difficult to make the properties and performance of the spraying mortar constant, and there is a problem that adhesion to some existing concrete structures, strength development, and freeze-thaw resistance are inferior There was also.

Japanese Patent Laid-Open No. 03-290348 JP 2003-89565 A JP 2004-292245 A JP 2000-128618 A JP 2002-293603 A JP 2003-292362 A JP 09-012379 A JP 09-296453 A JP-A-10-216628

  As a result of intensive studies, the present inventor has obtained the knowledge that the above problem can be solved by using a specific spray cement composition, and has completed the present invention.

  That is, the present invention is (1) sulfuric acid resistance for spraying method comprising A material and B agent, wherein A material contains calcium aluminate and B agent contains acrylate copolymer emulsion. Cement composition, (2) Furthermore, the A material contains blast furnace granulated slag and / or silica fume. (1) Sulfuric acid resistant cement composition for spraying method of (1), (3) Calcium aluminate is alumina cement ( (1) or (2) sulfuric acid resistant cement composition for spraying method, (4) sulfuric acid resistance for spraying method according to any one of (1) to (3), wherein the A material contains a polymer A cement mortar composition for a spraying method comprising a cement composition, a sulfuric acid resistant cement composition for spraying method (5) (1) to (4), and a fine aggregate, wherein the fine aggregate is A Sprayer mixed with wood For mortar composition, (6) Cement mortar prepared by kneading A and aggregates of (1) to (4), water, and pumping, mixing with compressed air and spraying, Spraying method in which B agent is added and mixed within 10 m from the tip of the spray nozzle, (7) Static flow of cement mortar prepared by kneading A material, aggregate and water in (1) to (4) (6) Spraying method with a value of 150 mm or more.

  By the sulfuric acid resistant cement composition for spraying of the present invention and the spraying method, it is possible to prevent the sprayed cement mortar from peeling off and dripping immediately after spraying, to increase the thickness of the spray, greatly reducing the rebound amount, Adhesiveness increases, and there is a remarkable effect that the sulfuric acid resistance is excellent. In addition to shortening the interval between secondary sprays after primary spraying, it is possible to increase the pumping distance and increase the pumping amount because of excellent pumping performance. Furthermore, the surface finish of concrete with good workability and cross-section repair spraying can be performed, and since the strength development is good, the work time is shortened and the burden on the operator is reduced.

The parts and% used in the present invention are based on mass unless otherwise specified.
The cement mortar referred to in the present invention is a general term for mortar and concrete, and contains calcium aluminate, aggregate and water.

The A material referred to in the present invention contains calcium aluminate.
The calcium aluminate of the present invention is a generic term for compounds mainly composed of CaO and Al ₂ O ₃ and is not particularly limited. Specific _{examples, CaO · 2Al 2 O 3,} CaO · Al 2 O 3, 12CaO · 7Al 2 O 3, 11CaO · 7Al 2 O 3 · CaF 2, 3CaO · Al 2 O 3, 3CaO · 3Al 2 O 3 -Crystalline calcium aluminates represented as CaSO _{4 and the} like, and amorphous compounds mainly composed of CaO and Al ₂ O ₃ components. Among these, it is preferable to select one having a CaO / Al ₂ O ₃ molar ratio of 1 to 2 from the viewpoint of pot life and acid resistance. Of these, alumina cement is preferable. Portland cements such as ordinary Portland cement are not included in the calcium aluminate of the present invention.

Examples of a method for obtaining calcium aluminate include a method in which a CaO raw material and an Al ₂ O ₃ raw material are heat-treated with a rotary kiln or an electric furnace.
Examples of the CaO raw material for producing calcium aluminate include calcium carbonate such as limestone and shells, calcium hydroxide such as slaked lime, and calcium oxide such as quick lime. Examples of the Al ₂ O ₃ raw material include aluminum by-products in addition to industrial by-products called bauxite and aluminum residue ash.

When calcium aluminate is obtained industrially, impurities may be contained. Specific examples thereof include SiO ₂ , Fe ₂ O ₃ , MgO, TiO ₂ , MnO, Na ₂ O, K ₂ O, Li ₂ O, S, P ₂ O ₅ , and F.
The presence of these impurities is not particularly problematic as long as the object of the present invention is not substantially impaired. Specifically, there is no particular problem if the total of these impurities is in the range of 10% or less.

Further, as the impurity compounds, calcium alumino ferrite etc. _{4CaO · Al 2 O 3 · Fe} 2 O 3, 6CaO · 2Al 2 O 3 · Fe 2 O 3, 6CaO · Al 2 O 3 · 2Fe 2 O 3, 2CaO · Calcium ferrites such as Fe ₂ O ₃ and CaO · Fe ₂ O ₃ , galenite 2CaO · Al ₂ O ₃ · SiO ₂ , calcium aluminosilicates such as anorthite CaO · Al ₂ O ₃ · 2SiO ₂ , melvinite 3CaO · MgO · 2SiO _2, Akerumanaito 2CaO · MgO · 2SiO _2, calcium magnesium silicate, such as Monte celite CaO · MgO · SiO _2, tri-calcium silicate 3CaO · SiO _2, dicalcium silicate 2CaO · SiO _2, rankinite night 3CaO · 2 in some cases iO _2, calcium silicates, such as wollastonite CaO · SiO _2, calcium titanate CaO · TiO _2, free lime, leucite _{(K 2 O, Na 2 O} ) , etc. · _{Al 2} O 3 · SiO 2 . In the present invention, these crystalline or amorphous materials may be mixed.

The particle size of the calcium aluminate of the present invention is not particularly limited, but is usually in the range of 3000 to 9000 cm ² / g in terms of Blaine specific surface area, and more preferably about 4000 to 8000 cm ² / g. If it is less than 3000 cm ² / g, strength development may not be sufficient, and if it exceeds 9000 cm ² / g, handling may be difficult.

As the aggregate used in the present invention, normal coarse aggregate or fine aggregate can be used, but it can be used for repairing existing concrete and is difficult to rebound when sprayed to the existing concrete. Aggregates with an aggregate ratio of 70 to 100% are preferable, and aggregates with a fine aggregate ratio of 100% are more preferable. Aggregates having a density of 2.5 g / cm ³ or more are preferred because of their high stability.
River sand, mountain sand, lime sand, and quartz sand can be used as the fine aggregate, and river gravel, mountain gravel, lime gravel, and the like can be used as the coarse aggregate. In particular, it is preferable to use quartz sand from the viewpoint of sulfuric acid resistance. The maximum aggregate size of the aggregate is preferably 10 mm below.

  The blending ratio of the cement mortar used in the present invention is preferably C (cement) / S (aggregate) = 1/1 to 1/4, and more preferably 1 / 1.5 to 1/3. If it is less than 1/1, the sprayed cement mortar may easily crack, and if it exceeds 1/4, the amount of unit cement decreases, W / C (water cement ratio) increases, and short-term strength and long-term strength are increased. In addition to the decrease, the pumping ability may be deteriorated and spraying may be difficult. It is preferable that the aggregate is mixed with the A material containing the calcium aluminate of the present invention.

  The acrylate copolymer emulsion used in the present invention is used to prevent the cement mortar from peeling off or dripping at the time of spraying by causing agglomeration instantaneously by mixing with the cement mortar. The B agent referred to in the present invention contains an acrylate copolymer emulsion.

  Acrylic ester copolymer emulsion (hereinafter referred to as emulsion) is an emulsion polymerization, suspension polymerization, solution polymerization, or bulk polymerization of an unsaturated carboxylic acid and an ethylenically unsaturated compound copolymerizable with the unsaturated carboxylic acid. It is a polymer emulsion obtained by copolymerization using a method such as polymerization.

  Examples of unsaturated carboxylic acids include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and maleic acid, unsaturated carboxylic acid anhydrides such as maleic anhydride and citraconic anhydride, and unsaturated carboxylic acid half compounds such as monoethyl maleate. Examples include esters. Among these, unsaturated carboxylic acid is preferable and acrylic acid and / or methacrylic acid is more preferable in terms of large setting properties.

  Examples of ethylenically unsaturated compounds copolymerizable with unsaturated carboxylic acids include cyanovinyl monomers such as ethylene and acrylonitrile, acrylic acid ester monomers such as methyl acrylate, ethyl acrylate, and butyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate. And polyfunctional vinyl monomers such as methacrylic acid ester monomers and aliphatic carboxylic acid vinyl esters and vinyl ether monomers. Among these, an acrylate monomer and / or a methacrylic acid ester monomer are preferable in that a more excellent effect is exhibited.

  In the emulsion, the copolymerization ratio (mass ratio) between the unsaturated carboxylic acid and the ethylenically unsaturated compound is preferably 20: 1 to 1:20, preferably 5: 1 to 1:20. 5 is more preferable. Outside this range, the setting effect may be deteriorated.

  In general, the amount of the emulsion used is preferably 0.01 to 2 parts, more preferably 0.1 to 1 part in terms of solid content, based on 100 parts of cement (calcium aluminate). If it is less than 0.01 part, the setting during spraying of the sprayed cement mortar is weak, the adhesive force is reduced, rebound reduction, and the effect of promoting the setting of cement mortar after spraying may not be expected. If it exceeds, not only the improvement of the effect cannot be expected, but the short and long-term strength may deteriorate.

  The method of mixing the emulsion is preferably a method in which the emulsion is press-fitted and mixed with pressurized air for spraying, and is mixed with Y-tube or shower ring and mixed with cement mortar sent by a pump.

The granulated blast furnace slag of the present invention bears the effect of preventing strength reduction due to conversion of calcium aluminate and acid resistance. Although the fineness of granulated blast furnace slag is not particularly limited, it is usually in the range of about 3000 to 9000 cm ² / g in terms of Blaine specific surface area.

In the present invention, pozzolanes such as silica fume can be used in addition to latent hydraulic substances such as granulated blast furnace slag.
Pozzolana plays a role of promoting the effect of preventing strength reduction due to conversion of calcium aluminate and the effect of improving acid resistance. The pozzolan is not particularly limited, and examples include fly ash, silica fume, pulp sludge incineration ash, sewage sludge incineration ash, and waste glass powder. Among these, use of fly ash or silica fume is preferable.
These finenesses are not particularly limited, but usually silica fume is in the range of about 2 to 200,000 m ² / g in terms of BET specific surface area, and fly ash is 3000 to 9000 cm ² in terms of brain specific surface area. / G.

The polymer used in the present invention is used for the purpose of improving adhesion at the time of spraying existing concrete and spray cement mortar, reducing the rebound amount, and improving the durability of spray cement mortar. Examples thereof include, but are not limited to, aqueous polymer disversion, re-emulsifying powder resin, water-soluble polymer, and liquid polymer.
Examples of the aqueous polymer dispersion include natural rubber latex, synthetic rubber latex such as acrylic rubber, styrene butadiene rubber (SBR), and chloroprene rubber (CR), ethylene vinyl acetate copolymer (EVA), and polyacrylic acid. Examples thereof include resin emulsions such as esters (PAE).

As the polymer form, there are a re-emulsification type powder type, a liquid type, and the like, which are used for reducing the rebound amount of spray cement mortar, improving adhesion with existing concrete, and improving durability.
The amount of the polymer used is preferably 15 parts or less, more preferably 3 to 10 parts in terms of solid content with respect to 100 parts of cement (calcium aluminate). If it exceeds 15 parts, not only improvement in the adhesion of existing concrete and sprayed cement mortar, improvement in rebound amount, and improvement in durability of sprayed cement mortar cannot be expected. It may not be economical.

  The mixing method of the polymer is not particularly limited. However, in the case of powder, it is mixed with material A in advance, or added simultaneously with other materials at the time of kneading, suspended in water or dissolved. In the case of a liquid, there are methods such as adding simultaneously with other materials at the time of kneading or mixing with water in advance. It is preferable to use it mixed with the A material.

  In the present invention, various admixtures and fibers such as cement water reducing agent and AE agent are added for the purpose of improving durability such as freeze-thaw property of spray cement mortar, improving bending toughness, and preventing cracks. It is possible to use together.

  The amount of water used in the present invention is preferably 30 to 60% in terms of a water cement ratio (W / C) which is a ratio of water and cement. If it is less than 30%, the viscosity of the cement mortar becomes high, the fluidity is poor and the pumpability may be hindered, and if it exceeds 60%, the strength development may be reduced.

  In the present invention, the stationary flow of the kneaded mortar is preferably 150 to 300 mm, more preferably 200 to 250 mm. If it is 150 mm or less, the mortar pumpability is poor, and if it is 300 mm or more, the material may be separated.

  In the present invention, the mixing method of the cement mortar containing the A material and the aggregate and the emulsion (B agent) is not particularly limited, but an additive machine for forcibly mixing the emulsion of the B agent with the cement mortar, For example, a pump that pumps emulsion, such as a diaphragm pump, a squeeze pump, a piston pump, and a snake pump, is pumped at a pressure of 10 Mpa or less, and a position in front of the tip of the spray nozzle, preferably within 10 m from the tip of the spray nozzle. Preferably, a spray cement mortar is prepared by mixing with cement mortar at a position 5 m before, and this spray cement mortar is used as a repair spray material and sprayed to repair sites. If the position where the cement mortar and the emulsion are mixed exceeds 10 m from the tip of the spray nozzle, the pumpability in the pumping tube may be lowered.

  The emulsion is sent by a pump, mixed with compressed air in the middle, sent to a Y-tube or shower ring via a hose, discharged from the Y-tube or shower ring, mixed with cement mortar, and sprayed. As the cement mortar, the most preferable method is one that is sprayed for surface finishing or cross-sectional repair of concrete.

The compressed air is 1 Mpa or less, preferably 0.4 to 0.7 Mpa, the amount of air is 0.2 to 1 m ³ / min, and is sent to a Y-tube or shower ring via a hose, It is discharged from a Y-shaped tube or a shower ring and mixed with cement mortar, and is sprayed as a sprayed cement mortar for surface finishing and cross-sectional repair of concrete.

  The sulfuric acid-resistant cement composition for spraying of the present invention can be preferably used as a cross-sectional restoration material for a deteriorated portion of a concrete structure due to sulfuric acid in a sewer or a hot spring area. In the spraying method using this, the spraying method can be used once. The spray thickness is preferably about 10 to 30 mm at the ceiling and about 10 to 50 mm at the side wall.

  Hereinafter, it demonstrates in detail based on an experiment example.

"Experiment 1"
50 parts of alumina cement, 200 parts of fine aggregate, 50 parts of granulated blast furnace slag, 4 parts of polymer (A) (in terms of solid content) (8 parts for 100 parts of alumina cement), 0.03 part of water reducing agent, Cement mortar (A material) composed of W / C = 50% was prepared by kneading with a trade name “Damacut mixer” manufactured by Okasan Kiko with a capacity of 50 liters. The prepared cement mortar is pumped with a squeeze pump, and the emulsion (agent B) in the amount shown in Table 1 is forced against 100 parts of alumina cement from the spray nozzle shower ring 15 cm before the tip of the spray nozzle with a tip of 10 mmφ. Into the compressed air. The pressure of the compressed air was 0.7 Mpa, and the amount of air was 0.4 m ³ / min. Cement mortar for this spraying method was sprayed onto the concrete wall at a discharge rate of 1.0 m ³ / h. As a comparison, an experiment was conducted using aluminum sulfate or lithium silicate instead of the emulsion.
In addition, the pressure feeding hose which conveys cement mortar used the pressure hose of 1.5 inch diameter, and the air hose which sends compressed air used the hose of 0.5 inch diameter.
The compressive strength of the sprayed cement mortar, the rebound rate of the sprayed cement mortar, adhesion, and sulfuric acid resistance were measured. Further, as a comparative example, ordinary Portland cement was used instead of alumina cement. The results are also shown in Table 1.

<Materials used>
Cement (1): Alumina cement, Blaine specific surface area 4000 cm ² / g, commercial cement (2): Normal Portland cement, Blaine specific surface area 3200 cm ² / g, commercial fine aggregate: Aomi lime sand from Itoigawa, Niigata Prefecture, Maximum aggregate size 2.5 mm or less Blast furnace granulated slag: Blaine specific surface area 4000 cm ² / g, commercial product polymer (A): styrene butadiene rubber (SBR), commercial product emulsion: polymer emulsion copolymerized with ethyl acrylate / methacrylic acid (Mass ratio 1/1), solid content 30%
Aluminum sulfate: Commercial product, solid content 27%
Lithium silicate: commercial product, SiO ₂ / Li ₂ O (molar ratio 4.5 / 1), solid content 20%
Water reducing agent: Polycarboxylic acid, commercial product

<Measurement method>
Compressive strength: A molded body of 4 cm × 4 cm × 16 cm was prepared by filling a mortar into a mold, and the compressive strength at a material age of 3 days / 28 days was measured according to JIS R 5201.
Rebound rate: Measure the mass of spray cement mortar sprayed on top concrete and the mass of spray cement mortar dropped after rebound, and the amount of spray cement mortar dropped (kg) / spray cement sprayed The mortar amount (kg) × 100 (%) was used.
Adhesiveness: Sprayed cement mortar was sprayed on the top concrete in a circular shape of approximately 10 cm, and the spraying thickness until peeling was measured.
Sulfuric acid resistance: A molded body of φ7.5 cm × 15 cm is prepared by filling a mortar into a mold, cured in water from a material age of 1 day to a material age of 28 days, and then immersed in a 5% strength sulfuric acid solution for 28 days. The mass after immersion (g) / the mass before immersion (g) × 100 (%).

  From Table 1, it can be seen that the sprayed cement mortar sprayed according to the present invention has high compressive strength, low rebound rate, and high adhesion. Furthermore, it turns out that it is excellent in sulfuric acid resistance.

"Experimental example 2"
Example 1 with the exception that 0.5 part of emulsion was added to the binder containing 50 parts of alumina cement and 50 parts of granulated blast furnace slag, and the type and addition rate of the polymer were changed as shown in Table 2. Similarly, spraying was performed to measure the compressive strength, rebound rate, adhesion, and adhesion strength. The results are also shown in Table 2.

<Materials used>
Polymer (B): ethylene vinyl acetate copolymer, commercially available polymer (C): polyacrylate ester, commercially available product

<Measurement method>
Adhesive strength: measured according to JIS A 1171.

  From Table 2, it can be seen that according to the present invention, the sprayed cement mortar has high compressive strength, low rebound rate, high adhesion, and high adhesion strength.

"Experiment 3"
Except that the water-cement ratio was changed as shown in Table 3, spraying was performed in the same manner as in Experiment No. 1-6 in Experimental Example 1, and the static mortar flow and pumpability were measured.

<Measurement method>
Static mortar flow: Stir mortar into a flow cone, and measure the diameter of the mortar that has spread 30 seconds after the flow cone is removed.
Pumpability: The kneaded mortar was pumped 100 m with a squeeze pump, and the pressure at the outlet of the squeeze pump was measured with a pressure gauge.

  By using the cement composition for spraying method and the spraying method of the present invention, it becomes possible to prevent the spraying mortar from coming off and dripping immediately after spraying, and to increase the spraying thickness of the spraying cement mortar. In addition to being able to reduce the amount of rebound by suppressing the blowing air, the strength development is good and the sulfuric acid resistance is excellent, so the bottom surface of the bridge, pier, road, railway, and It is extremely useful for repairing concrete structures such as tunnels, buildings, and marine / harbor structures such as waterways and repairs and preventive maintenance.

Claims (7)

A sulfuric acid resistant cement composition for a spraying method, comprising an A material and a B agent, wherein the A material contains calcium aluminate and the B agent contains an acrylate copolymer emulsion. Furthermore, A material contains a blast furnace granulated slag and / or a silica fume, The sulfuric-resistant cement composition for spraying methods of Claim 1 characterized by the above-mentioned. The sulfuric acid-resistant cement composition for spraying method according to claim 1 or 2, wherein the calcium aluminate is alumina cement. Furthermore, the sulfuric acid-resistant cement composition for spraying methods of any one of Claims 1-3 in which A material contains a polymer. In the cement mortar composition for spraying construction method containing the sulfuric acid-resistant cement composition for spraying construction method according to claim 1 and fine aggregate, the fine aggregate is mixed with the A material. A mortar composition for spraying method characterized by the above. Cement mortar prepared by kneading A material, aggregate and water according to claims 1 to 4 is pumped, mixed with compressed air, and sprayed, within 10 m from the tip of the spray nozzle. A spraying method characterized by adding and mixing agent B. The spraying method according to claim 6, wherein the static flow value of the cement mortar prepared by kneading the A material, the aggregate, and water according to claims 1 to 4 is 150 mm or more.