JPH0651597B2 - Concrete coating - Google Patents

Description

TECHNICAL FIELD The present invention relates to a concrete coating material used for repairing or preventing deterioration of a concrete structure, and more specifically, corrosion of rebar such as water vapor, chlorine ion, oxygen, carbon dioxide gas. The present invention relates to a concrete covering material having an excellent barrier performance against harmful substances.

[Prior Art] Concrete structures are inherently excellent in durability. However, if the materials used, the mixing ratio, or the construction method are not appropriate, cracks may occur and the reinforcing bar may rust, or it may develop into deep cracks and must be repaired.

Conventionally, various materials and construction methods have been used for repairing concrete structures depending on the degree of deterioration, but the point is that water vapor, chlorine ions, oxygen, which are harmful components that block the deteriorated part of concrete and promote the corrosion of rebar. , To shut off carbon dioxide, etc.

Conventionally, such materials include organic paints, cement mortar and polymer cement mortar.

[Problems to be solved by the invention]

However, the method of applying organic paint to the concrete surface to form a coating film to block harmful components is a very effective method in the short term, but it is not possible to expect that effect over a long period of time. Can not. The reason is that the organic coating film has a coefficient of thermal expansion largely different from that of the base concrete, and the coating film itself is cracked or peeled off due to deterioration due to ultraviolet rays or the like. Further, when the coating is applied, if the base concrete is not sufficiently dried, the adhesion between the coating film and the base becomes incomplete, resulting in swelling, peeling and the like.

On the other hand, cement mortar and polymer cement mortar have good weather resistance, but they have a drawback that they do not sufficiently block harmful components. That is, the generally required blocking performance of harmful components is, for example, 10 g / m ^{2 in} terms of water vapor transmission rate.
It is said that it is necessary to be 1 × 10 ^-2 g / m ² day or less for the day or less and the amount of chlorine ion permeation, but this is not satisfied. It is possible to increase the coating thickness of the coating material to improve the barrier performance, but since conventional cement mortar and polymer cement mortar have a high kneading capacity, for example, a single coating of 15 mm thick on the lower surface of the ceiling (below If it is simply referred to as thick coating, it will peel off due to its own weight. Therefore, for thick coating, a construction method of applying about 5 mm at a time for several times is adopted, but according to this method, the next construction must be performed after a single construction with a gap of several hours or more. Therefore, the evaporation of water from the polymer cement mortar progresses during this time and dryout occurs, and the hydration reaction of the hydraulic binder is insufficient and a dense hardened body structure is not formed, so a harmful component In addition to the fact that a concrete covering that sufficiently blocks the above could not be obtained, there was a drawback that the construction was troublesome.

Therefore, for example, a method of using a lightweight fine aggregate such as pearlite or a method of mixing a large amount of air with a foaming agent to obtain a lightweight mortar can be considered. In this case, thick coating is possible, but on the other hand, these mortar-cured products have a large number of continuous ventilation holes, so that they have a drawback that the ability to block harmful components deteriorates.

[Means for solving problems]

Therefore, the present inventors have conducted various studies to obtain a concrete coating material having good durability and excellent shielding performance against harmful components, and as a result, a polymer cement mortar using a specific fly ash that floats when immersed in water as a fine aggregate. Can be applied thickly, and by applying it thickly, the normal hydration reaction of the hydraulic binder proceeds inside the coating material to form a dense hardened body structure, so concrete with excellent blocking performance against harmful components The inventors have found that a coating material can be obtained and completed the present invention.

That is, the present invention is a hydraulic binder, the maximum particle size is 0.3 ~ 0.4 mm
It is a hollow sphere with an average particle size of 50-150 μm, an apparent specific gravity of 0.3-0.8 g / ml by an air-comparison hydrometer, and a water absorption of 5 volume% or less from fly ash balloons and polymer dispersions. It is to provide a concrete covering material.

Examples of the hydraulic binder used in the present invention include Portland cement, various mixed cements, and alumina cement.

The fly ash balloon as a fine aggregate used in the present invention has a maximum particle size of 0.3 to 0.4 mm and an average particle size of 50 to 150 μm.
It is a hollow sphere with the apparent specific gravity measured by an air-comparison hydrometer.
It is 0.3 to 0.8 g / ml, has a water absorption of 5% by volume or less, and floats when immersed in water. Therefore, the fly ash that precipitates when immersed in water is not suitable for the purpose of the present invention because it has open pores or has a specific gravity of more than 1.0 g / ml. The fly ash balloon of the present invention, for example, collects fly ash contained in the exhaust gas with a dust collector when coal is burned in a thermal power plant, etc., immerses it in water, and collects the floating fly ash. Obtained by collecting and drying.

The polymer dispersion used in the present invention is an emulsion obtained by dispersing organic polymer particles in water, and when mixed with a hydraulic binder, causes aggregation or entrains a large amount of air. What is adjusted with an emulsifier, a stabilizer, an antifoaming agent, etc. so that there is no such thing. Examples thereof include rubber emulsions such as styrene-butadiene rubber and chloroprene rubber, and thermoplastic resin emulsions such as polyethylene, polyvinyl chloride, polyvinyl acetate, and polyacrylic acid ester. Alternatively, a powder obtained by spray-drying these emulsions may be used.

In the present invention, a part of the fly ash balloon may be used by replacing it with a fine aggregate such as river sand and silica sand used in general polymer cement mortar. The particle size of the fine aggregate may be within the range used for general mortar.

The mixing ratio of each material may be determined by the ease of mixing each material during kneading, the iron coating property of the kneaded material, the adhesiveness, the blocking property of harmful components, etc., but as a rough guideline, the hydraulic binder The mixing ratio of fly ash balloon to fly ash is 1: 0 by weight.
It is 2-1: 1. When substituting and mixing the fly ash balloon with fine aggregate such as silica sand, the weight ratio of fly ash balloon to silica sand is preferably in the range of 100: 0 to 12.5: 87.5. Outside this range, the capacity of the kneaded product becomes too large and the thick coatability deteriorates.

The addition amount of the polymer dispersion is such that it is used in general polymer cement mortar, and specifically, it is 5 to 30% by weight as a solid content with respect to the hydraulic binder.
If it is less than 5% by weight, the adhesion between the concrete coating material and the base concrete and the ability to block harmful substances become insufficient. On the other hand, if it exceeds 30% by weight, the viscosity of the kneaded product becomes too large and the workability deteriorates. A more preferred range is 10 to 25% by weight.

When the surface of concrete is coated with the concrete coating material of the present invention, water may be added to a mixture of the above-mentioned materials and kneaded, followed by trowel coating or spraying.

The working thickness is determined depending on the deterioration state of the concrete and environmental conditions, but generally 5 to 20 mm is appropriate, and it is desirable to set it to 10 mm or more to sufficiently block harmful components.

〔Example〕

Examples 1 to 3 Ordinary Portland cement (trade name Asano Portland Cement manufactured by Nippon Cement Co., Ltd.) as a hydraulic binder,
Fly ash balloon (Philite 52/7 (FG) made by Nippon Philite Co., Ltd.), silica sand as fine aggregate (a mixture of silica sand No. 4 and silica sand No. 7 manufactured by Nihon Kogyo Co., Ltd. 2: 1).
And styrene-butadiene rubber emulsion as polymer dispersion (product name Nipol manufactured by Nippon Zeon Co., Ltd.)
Defoamer (TSA730 manufactured by Toshiba Silicone Co., Ltd.) is added to LX206 1.5
1% by weight) was blended as shown in Table 1 and kneaded to obtain a kneaded product.

The kneaded product was troweled once at a thickness of 15 mm on the lower surface of a horizontally placed 60 cm × 60 cm × 8 cm concrete flat plate. There was no one part peeled off after the iron coating, and the adhesion was good.

The test piece after ironing is 28 in a room at a temperature of 20 ° C and 65% RH.
I was left to cure for a day. After curing, a core drill with a 65 mmφ core was used to remove the core together with the base concrete, and then the boundary between the base concrete and the iron coating was cut with a concrete cutter to obtain a disk specimen for the harmful component blocking test.

This sample was tested according to JIS Z0208 "Moisture Permeability Test Method for Moisture-Proof Materials (Up Method)" to determine the amount of water vapor permeation at 20 ° C and 90% RH.

The chlorine ion permeation amount is such that one side contains distilled water and the other side contains a 3% saline solution, and the disc sample is sandwiched between the disc samples. After one month, chlorine ions pass through the disc sample and move to the distilled water side. It was calculated from the amount. The obtained results are shown in Table 1.

Comparative Examples 1 to 3 As fine aggregates, the same materials as those in the examples, except that the same silica sand, pearlite (Asano pearlite No. 4 manufactured by Asano pearlite Co., Ltd.) or normal fly ash as the examples are used, are shown in Table 1. The mixture was blended at a blending ratio and kneaded to obtain a kneaded product. This kneaded material was troweled and cured on a base concrete by the same operation as in Example to obtain a disk test piece.

In addition, a disc specimen could not be obtained because silica sand and fly ash alone were used as fine aggregates because they fell off immediately after ironing.

The other disk specimens were subjected to the same tests as in the example, and the water vapor permeation amount and the chlorine ion permeation amount were obtained. The results are shown in Table 1.

[Effect of the invention] The concrete coating material of the present invention can be applied thickly because it uses a fly ash balloon, which is hollow inside but has almost no open pores, as an aggregate, and can be obtained with a conventional polymer cement mortar. It has excellent blocking performance that could not be achieved.

Therefore, the concrete covering material of the present invention is not limited to the floor surface,
Deteriorated concrete structures including wall surfaces and ceiling surfaces can be easily and efficiently repaired, and their performance is maintained over a long period of time, which greatly contributes to improving the durability of reinforced concrete structures.

Claims (1)

[Claims] 1. A hydraulic binder, which is a hollow sphere having a maximum particle size of 0.3 to 0.4 mm and an average particle size of 50 to 150 μm, and an apparent specific gravity by an air-comparison hydrometer of 0.3 to 0.8 g / m, Concrete coating material consisting of fly ash balloon having a water absorption of 5% by volume or less and polymer dispersion