JP2006283335A - Dry mortar spraying method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dry mortar spraying method simple with excellent field workability as well as excellent working environment property by effectively reducing dust rising in spraying to reduce a rebound rate, and holding strength exhibiting property over a long period of time by suppressing crack initiation while reducing drying shrinkage after spray is hardened. <P>SOLUTION: In the dry mortar spraying method, a powder mixture comprising cement, aggregate, an expansion material and a nonaqueous water reducing agent, and liquid containing a polymer dispersion for cement mixing, are separately prepared, and both are uniformly mixed and sprayed. Particularly the powder mixture is prepared with at least cement mixed in a state of being uniformly sprinkled with the nonaqueous water reducing agent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  TECHNICAL FIELD The present invention relates to a dry mortar spraying method, and in particular, repairing and reinforcing a deterioration of a concrete structure which reduces dust generation in a dry spraying method used in the civil engineering and construction fields and has a low rebound rate. The present invention relates to a dry-type spraying method used for a construction method, for example, a viaduct such as a railway or a road, or a cross-sectional repair method such as a tunnel.

In recent years, dry spraying using fiber reinforced mortar using ultra-fast hardened cement, which is a special cement with the greatest initial strength, has been implemented as one of the repair and reinforcement methods for deterioration of concrete structures. ing.
This construction method is a repair / reinforcement method that combines the initial strength development of super-hard cement, the workability of the spraying method, and the reinforcement effect due to fiber mixing. It is widely used as a cross-section repair method.

  Originally, the fiber-reinforced dry spraying method using super-hard cement has been used as one of the major features of initial strength development as described above, but the amount of dust generated during spraying is large, and the working environment While reduction of dust for improvement has been demanded, mortar using ultra-fast hard cement has a problem that the repaired part is quickly neutralized, and the reinforcing bars in the mortar rust and re-deteriorate.

  Currently, in order to improve the environment by reducing the dust in the spraying method, adding a water-based dust reducing agent to the sprayed concrete and mortar, JP-A 62-59560, There are some which are indicated by JP, 62-17057, A, etc. Various dust reducing agents are sold and can be easily obtained in the market.

  The dry spray method is a system in which water is added in a spray nozzle that discharges material, and this is sprayed onto the spray surface with high-pressure air. The time from the addition of the spray nozzle to the injection with high-pressure air is extremely short, and even if dry spraying method is used with spray concrete or mortar to which these dust reducing agents are added, within the time required Dust cannot be aggregated and reduced, and the effect of reducing dust during spraying is not sufficient. In addition, since a water-based dust reducing agent is used, hydraulic substances such as cement are hydrated and cannot be uniformly mixed with the powder in advance.

Furthermore, in order to effectively suppress dust generation during construction of mortar using a water-based dust reducing agent, it is not effective unless a large amount of dust scattering agent is used because it is desired to mix uniformly. When used in large quantities, there was a problem that the strength was significantly reduced.
In order to reduce dust, JP-A-60-144466 discloses a powder mixture composed of cement and aggregate, and a liquid mixture composed of a synthetic resin emulsion and water, respectively, A dry-type spraying method is disclosed in which both are mixed in front of the nozzle for spraying, and the mixed slurry is sprayed onto the surface to be coated.
However, when the mortar is sprayed by the dry spraying method, cracks due to drying shrinkage of the cured body cannot be effectively prevented.

  In JP-A-11-322390, a mixture of cement, fine aggregate, and fiber is pneumatically fed, and an aqueous polymer dispersion melt-containing liquid is added to the mixture and sprayed before the spray nozzle. Further, in Japanese Patent Application Laid-Open No. 2000-96824, a mixture of cement, fine aggregate, powder emulsion, and fiber is pneumatically fed, and water is added to the mixture before spraying and sprayed. The mortar spraying method characterized by this is disclosed, and fibers are added to these mortars to prevent cracks in the cured body.

However, in these mortars, fibers are mixed with inorganic powder to prevent cracking of the cured body, but usually the fibers are converged in units of thousands by a sizing agent. It is difficult to solve the convergence in a short time to the tip and to be uniformly dispersed in the mortar.
Furthermore, the mortar described in JP-A No. 2000-96824 is obtained by adding a powder resin to a powder mixture in advance, but it takes several tens of seconds for the powder resin to re-disperse in water and re-emulsify. It takes several minutes from the beginning, and it is difficult to uniformly re-emulsify in a short time from the front of the spray nozzle to the tip of the nozzle.

  Therefore, it is desired to develop a dry mortar spraying method that can effectively prevent cracks due to drying shrinkage after curing and that can be used for repair work using the dry method and that sufficiently reduces the generation of dust. ing.

The object of the present invention has been made in view of the above problems. Specifically, it is possible to effectively reduce the dust generated during spraying, reduce the rebound rate, and improve the work environment. It is to provide a dry mortar spraying method that is excellent, simple and excellent on site construction.
Furthermore, another object of the present invention is to provide a dry mortar spraying method that can reduce drying shrinkage after spray hardening and suppress cracking, and thus can maintain strength development over a long period of time.

  As a result of various researches on the dry mortar spraying method, the present inventors have mixed a powdered material pre-coated with cement with a non-aqueous shrinkage reducing agent and a separately prepared liquid material. The present inventors have found that the rebound rate during construction can be reduced, the generation of dust can be reduced and the drying shrinkage rate can be reduced, and the present invention has been completed.

In the dry mortar spraying method of the present invention, a powder mixture composed of cement, aggregate, expansion material and non-aqueous shrinkage reducing agent and a liquid containing a polymer dispersion for cement mixing are separately prepared, and both are mixed and sprayed. It is characterized by attaching.
Preferably, in the dry mortar spraying method of the present invention, the powder mixture is prepared by mixing at least cement in a state of being uniformly coated with a non-aqueous shrinkage reducing agent.

  More preferably, in the dry mortar spraying method of the present invention, the powder mixture and the polymer dispersion-containing liquid for mixing with cement are mixed in front of the spray nozzle to perform spraying. It is an attachment method.

The dry mortar spraying method of the present invention can greatly reduce the dust during on-site dry spraying, reduce the rebound rate, and thus significantly improve the working environment, and further from the early age of the material It has excellent compressive strength enhancement stability over a long period of time.
In addition, the dry mortar spraying method of the present invention suppresses drying shrinkage after spraying, and thus can prevent cracking, and can be effectively used as a repair and reinforcement method for deterioration of concrete structures. It is.

The present invention will be described with reference to the following preferred examples, but is not limited thereto.
The dry mortar spraying method of the present invention is a powder mixture comprising cement, an aggregate, an expansion material and a non-aqueous shrinkage reducing agent, and particularly at least the cement is uniformly coated with a non-aqueous shrinkage reducing agent. Is a method of separately preparing a powder mixture prepared to be coated with a non-aqueous shrinkage reducing agent and a polymer dispersion-containing liquid for cement admixture, and uniformly mixing and spraying both. Mixing is performed before the spray nozzle, and spraying is performed.

  In this way, powders such as cement, aggregate, and expansion material are mixed with a non-aqueous shrinkage reducing agent in advance, and preferably at least cement is covered with the non-aqueous shrinkage reducing agent, thereby reducing non-aqueous shrinkage. The agent is adsorbed on the cement surface, the suction force works between the cement particles, the particles generated from the cement used for spraying are granulated, and the generation of dust during construction can be suppressed It is guessed.

  The cement used in the mortar spraying method of the present invention is not limited as long as it is a cement mainly composed of a hydraulic calcium silicate compound, and usually, various portland cements such as early strength, blast furnace cement, silica cement and Various cements available in the market, such as various mixed cements of fly ash cement, white Portland cement, alumina cement, and super-hard cements such as calcium aluminate, calcium sulfoaluminate and calcium fluoroaluminate These can be exemplified, and these can be used alone or in combination. Preferably, it is preferable to use ordinary cement, early-strength cement, or the like that has a slow neutralization.

In addition, the fine aggregate used in the method of the present invention is not particularly limited, and fine particles having a relatively small particle size such as river sand, mountain sand, land sand, crushed sand, sea sand, silica sand No. 3-7 and the like. Aggregates or fine powders such as quartzite powder and limestone powder can be used.
Although the compounding quantity is not specifically limited, Usually, it is preferable that it is 100-300 weight part with respect to 100 mass parts of the said cement, and it is more preferable to set it as 150-250 mass part. This is because in such a range, the filling property to the repaired portion, particularly the reinforcing bar back, is good.

Furthermore, examples of the expansion material used in the method of the present invention include calcium sulfoaluminate, quicklime, or a mixture of both.
The expansion material has a function of reducing drying shrinkage of the sprayed mortar.

  Although the compounding quantity is not specifically limited, Usually, it is preferable that it is 1-10 mass parts with respect to 100 mass parts of the said cement, and it is more preferable to set it as 3-7 mass parts. This is because the drying shrinkage of the sprayed mortar can be effectively reduced within this range.

The non-aqueous liquid drying shrinkage reducing agent in the powder mixture used in the method of the present invention is generally an alkylene oxide and an adduct thereof, and a composition that does not inhibit cement hydration. if, it can be used., available in any market, as the _{composition, R 1 O (AO) nR} 2 (R 1, R 2: H, alkyl group, phenyl group, a: an alkylene group, n : Degree of polymerization) and is soluble in water or alcohol.
The non-aqueous liquid dry shrinkage reducing agent has a function of reducing the dry shrinkage of sprayed mortar.

  Although the compounding quantity is not specifically limited, Usually, it is preferable that it is 0.1-1.5 mass parts with respect to 100 mass parts of the said cement, and it is more preferable to set it as 0.5-1 mass part. This is because the drying shrinkage of the sprayed mortar can be effectively reduced within this range.

Examples of the cement-mixing polymer used in the method of the present invention include polyacrylates exemplified in JIS A 6203, styrene butadiene, ethylene vinyl acetate, vinyl acetate / vinyl versatate, vinyl acetate / vinyl versatate / acrylic. Examples thereof include polymer dispersions mainly composed of acid esters, and these can be used alone or in combination.
Re-emulsifying powder resin takes several tens of seconds to several minutes for the powder resin to re-disperse in water and re-emulsify, and it is difficult to uniformly re-emulsify in a short time from the front of the spray nozzle to the nozzle tip. This is not preferable.
Particularly preferably, an acrylic polymer can be used, and it is preferable from the viewpoint of durability to use a dispersion of the acrylic polymer.

  The admixture polymer has a polymer hydraulic substance (cement + expansion material) ratio (solid content ratio) of 1-15% by mass, preferably 3 between the polymer dispersion for cement admixture and the hydraulic substance (cement + expansion material). It is desirable that it is added and mixed in an amount of 10% by mass. This is because, within such a range, the strength of the sprayed mortar is not lowered, the viscosity can be maintained well, and the adhesion is excellent.

Next, the construction method of the dry spraying method of the present invention will be exemplified.
The mortar used in the dry mortar spraying method of the present invention is first made of cement, aggregate, expansion material, non-aqueous drying-reducing shrinkage agent, admixture added as necessary (for example, water reducing agent, thickener, A dry mix mortar is prepared by mixing a foaming agent and the like. The dry-mix mortar may be mixed on site, but it is desirable to premix in advance for simplification of equipment and work.

At that time, the non-aqueous drying-reducing shrinkage agent is mixed and prepared so as to dust at least the cement powder, and preferably so as to dust other powders.
As described above, the cement powder is previously coated with the non-aqueous drying-reducing shrinkage agent, whereby the rebound rate at the time of spraying can be reduced, and crack shrinkage due to drying after curing can be suppressed.

  Next, use this dry mix mortar for dry spraying equipment, pneumatically feed, separately inject the pre-mixed polymer dispersion and water at the front part of the nozzle, mix both at the nozzle part, and mix both The obtained slurry is obtained, and the spraying method is applied to the surface to be coated.

  The amount of water to be mixed with the polymer dispersion is not particularly limited depending on the location where spraying is performed or the case where a trowel finish is applied after spraying, but the polymer hydraulic substance (cement + expansion material) cement ratio (solid content ratio) ) Is 1 to 15% by mass, preferably 3 to 10% by mass, and it is possible to prepare a dilution liquid of the polymer dispersion so as to be added and mixed in the spraying mortar. From the point of view is desirable.

The mixing position of the dry mix powder, the polymer dispersion and the water is the front part of the nozzle, and it is particularly desirable that the mixing is performed at a position of 0.4 to 1.2 m before the nozzle spraying port. Is mixed uniformly, for example, a mixing method such as showering is used. This is because if the mixing position is less than 0.4 m, mixing may be insufficient, and if it exceeds 1.2 m, the pressure hose of the spraying device may be blocked.
In this way, dry mix mortar, polymer dispersion and water are uniformly mixed at the front of the nozzle to form a slurry and sprayed with mortar to reduce dust generation and rebound rate. It can be effectively used for repairing and reinforcing methods for deterioration of concrete structures having a low profile, for example, viaducts such as railways and roads, and cross-sectional repair methods such as tunnels.

The present invention is illustrated by the following examples and test examples, but is not limited thereto.
In carrying out the spraying method of the used material mortar, the following materials were used to prepare the mortar.
・ Cement: Early strong Portland cement (manufactured by Sumitomo Osaka Cement Co., Ltd.)
・ Fine aggregate: Silica sand No. 1, No. 2, No. 4, No. 5 ・ Expandable material: Brand name
-Non-aqueous liquid drying shrinkage reducing agent: Tester F (manufactured by Sumitomo Osaka Cement Co., Ltd.)
・ Polymer dispersion for cement: Brand name Lion Bond A (styrene acrylic polymer emulsion; solid content 45% by weight, water 55% by weight, manufactured by Sumitomo Osaka Cement Co., Ltd.)

(Examples 1-2)
Using each of the materials described above, two types of dry mix powders were prepared at the blending ratios shown in Table 1, and designated as dry mix powder (1) and dry mix powder (2), respectively.
As a standard blending ratio of the mortar, 0.89 kg of Lion Bond A (polymer dispersion for cement admixture) and 1.5 kg of water are mixed with 20 kg of each of the dry mix powders (1) and (2).

  When spraying, each dry mix powder is compressed with compressed air, and the inside of the hose is pumped using a Towa rotary gun sprayer. A liquid material in which the polymer dispersion for water is premixed with water is press-fitted and mixed, and the dry mix powder and the liquid material in which the polymer dispersion for cement mixing is premixed with water are combined in the nozzle to form a slurry. And sprayed on the mold body 1 shown in FIG.

Specifically, the protruding portion 3 is provided on the 50 cm square frame 1, and the protruding portion 3 is directed upward by using a test mold arranged so that the reinforcing bar 2 intersects the frame 1. The test piece was prepared by spraying to a thickness of 12 cm by performing a dry spraying operation in the mold from above and into the mold. The specimen was prepared according to JSCE-F561 (How to make a specimen for compressive strength test of shotcrete).
1A is a cross-sectional view at A in FIG. 1A, and FIG. 1B is a cross-sectional view at B in FIG.
Liquid (water + cement dispersion polymer dispersion) / powder (dry mix powder) ratio, P / C (polymer solids / cement) ratio, W / C (water / cement) ratio when spraying mortar Are also shown in Table 1.

Test Examples 1-7
Each specimen subjected to the above-described spray construction was subjected to the following test, and the results are shown in Table 2.
(1) Rebound rate (%)
It is a value indicated by (mass of mortar material rebounded during spraying / total used mass of material during spraying) × 100 (%) at the time of spraying.
(2) Core hardened body specific gravity After the above-mentioned spraying, each specimen was cured by curing at 20 ° C. and 60% RH for 1 week, and then the core was removed, and the apparent specific gravity of the core hardened body was determined as the core. It is a value measured by mass / core volume.

(3) Compressive strength Compressive strength was measured in accordance with JIS R 5201 for the same core cured product as used in the core cured product specific gravity measurement of (2).
(4) Adhesive strength Sub-attached mortar is sprayed onto JIS A 5304 pavement concrete board (300 x 300 x 60 mm) with a thickness of 4 cm, and the surface is smoothed with a trowel and covered with a vinyl sheet up to the measurement material example. did. The test method is the bond strength by the Building Research Institute type tensile tester, and the depth of biting about 2 mm from the surface of each mortar to the concrete surface of the foundation at each age. The steel attachment was bonded with an epoxy resin, and the adhesion strength was measured at each age.

(5) Length change rate After the above-mentioned spray construction, each specimen was cured by curing at 20 ° C. and 60% RH for one week, or after curing in water at 20 ° C. Two restraint bands each having a measuring chip attached thereto were attached to each core hardened body, and the rate of change in length at each subsequent age was measured using a contact gauge with this point as the base length.

(6) Accelerated neutralization After the spraying, each specimen was cured at 20 ° C. and 60% RH for 1 week, then cored, and the end face of each core cured body was epoxy-coated according to JIS A 1171 Sealed with resin and accelerated neutralization was performed in an accelerated neutralization tank (30 ° C., 60% RH, CO ₂ 5%).
After the start of the acceleration test, the material was split at a predetermined age, and a phenolphthalein alcohol solution was sprayed to measure the thickness of the portion that did not react with red.

(7) Reinforcing bar back filling After each spraying, each specimen was cured at 20 ° C. and 60% RH for 1 week, then demolded and cut with a concrete cutter, and voids and unfilled parts on the cut surface were removed. This is a value obtained by tracing and calculating the area ratio of the trace by the image analysis apparatus.

From the above table, it can be seen that, according to the construction method of the present invention, the rebound rate is remarkably reduced even in the top surface construction, and from the measurement result of the core hardened body specific gravity, there is no void and it is well sprayed.
Furthermore, it is excellent in compressive strength and adhesive strength, the rate of change in length is small, it can be seen that high strength and good dimensional stability.
Furthermore, from the results of the accelerated neutralization test, it became clear that there is a high resistance to neutralization and that the filling property is better than the void ratio of the reinforcing steel back.

  The mortar spraying method of the present invention can be effectively used as a cross-sectional restoration material in the field of repair and reinforcement of concrete structures, especially for top surface construction such as cross-section repair methods such as viaducts for railways and roads, tunnels, etc. It can be used appropriately.

It is the schematic which shows an example of the mold body used in order to implement the mortar spraying construction of this invention.

Explanation of symbols

1 Frame 1
2 Reinforcing bar 3 Protrusion

Claims (3)

  A powder mixture composed of cement, aggregate, expansion material and non-aqueous shrinkage reducing agent and a polymer dispersion-containing liquid for cement mixing are separately prepared, mixed and sprayed before the spray nozzle. Dry mortar spraying method.   The dry mortar spraying method according to claim 1, wherein the powder mixture is prepared by mixing at least cement in a state of being uniformly coated with a non-aqueous shrinkage reducing agent. Attaching method. 3. The dry mortar spraying method according to claim 1, wherein the cement used is Portland cement.

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