JPH0475178B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a repair method for salt-damaged objects such as concrete, steel structures, ships, etc. that have been damaged by salt damage. [Prior Art] Conventionally, materials such as resin, cement mortar, and polymer cement have been used as a repair method for salt-damaged objects. However, resins have drawbacks such as curing being inhibited or significantly delayed when the repaired area is in a wet state, and furthermore, they are subject to ultraviolet deterioration and weather resistance is significantly reduced. In addition, because cement mortar is porous, it has high permeability to chlorine ions, and because it has a high water absorption rate, it has poor freeze-thaw resistance, and even if areas damaged by salt damage are repaired, they will not deteriorate again due to salt damage. There was a drawback that this occurred. Polymer cement is said to cover the above drawbacks of cement mortar because the polymer fills the porous parts.
The polymer commonly used as polymer cement is latex, and the filling effect of the polymer cannot be expressed unless it is in a dry state, and there are also problems in terms of weather resistance. Therefore, there has been a strong desire for a more complete repair method for deteriorating salt-damaged structures such as marine, underwater, and coastal structures and ships. [Problems to be Solved by the Invention] After conducting various studies to meet the above requirements, the present inventors found that the main components are cement, ultrafine powder, high performance water reducing agent, and water, and after curing, the material has a specific porosity. If necessary, aggregate and/or fibers are added to the compound shown above, and if the salt-damaged materials are covered with these materials, it is possible to perform repair work with high durability and low permeability to Cl ^- ions. They have discovered that this is the case, and have completed the present invention. [Means for Solving the Problems] That is, the present invention converts salt-damaged materials into materials whose main components are cement, ultrafine powder, a high-performance water reducer, and water, and which has a porosity of 31 at the age of 3 days. %
This is a repair method for salt-damaged materials, which is characterized by adding aggregates and/or fibers, etc., as needed to the following composition, and covering the materials with the mixture. The present invention will be explained in more detail below. In the present invention, the salt-damaged objects are reinforced concrete and steel structures built on the coast, in the ocean, and under the sea. Specifically, structures built near the coast, such as buildings, bridges, piers, oil drilling barges, artificial islands, laser facilities, and ship chimneys and decks, have rusted and deteriorated due to the action of chlorine ions. . It is said that the reinforcing bars in reinforced concrete do not rust because they are placed in an alkaline region and form a passive film, but when Cl ^- ions penetrate, this passive film is destroyed and rust occurs. Therefore, it is important to prevent the penetration of Cl ^- ions in order to repair the deteriorated and damaged parts and prevent subsequent deterioration. The compounding part according to the present invention contains cement, ultrafine powder, high performance water reducing agent, and water as necessary components, and the porosity of the cured product after 3 days of age is 31%. The cement used in the present invention generally includes ordinary Portland cement, early-strength, ultra-early-strength or white Portland cement, sulfate-resistant Portland cement, and mixed cements such as slag and fly ash. It is also possible to compensate for shrinkage using expansive cement, to develop the required strength in a short time with rapid hardening cement, and to use a gypsum-based high-strength admixture. As the expanding component of the expanding cement, ettringite-based materials such as "CSA" manufactured by Denki Kagaku Kogyo Co., Ltd.
#20” and calcined CaO are preferable, and even among calcined CaO
Particularly preferred are those which are fired at 1100 to 1300°C and have an average crystal diameter of 10 μm or less. Rapid-hardening cement contains calcium aluminate-based rapid-hardening components, such as various types of calcium aluminate alone or a mixture of calcium aluminate and calcium sulfate.
Cement containing the product name “Denka ES”,
Product name: “Jet Cement” manufactured by Onoda Cement Co., Ltd.
and so on. In addition, high-strength admixtures include gypsum-based ones such as "Denka-1000" manufactured by Denki Kagaku Kogyo Co., Ltd., "Asano Super Mix" manufactured by Nippon Cement Co., Ltd., and "Nonclave" manufactured by Osaka Cement Co., Ltd. ” can be given. The ultrafine powder is one whose average particle size is at least one order of magnitude lower than that of the above-mentioned cement, and in particular, one whose average particle diameter is two orders of magnitude lower is preferable from the viewpoint of the fluidity properties of the kneaded product. Specifically, silica dust (silica fume) and siliceous dust, which are produced as by-products during the production of silicon, silicon-containing alloys, and zirconia, are particularly suitable.In addition, calcium carbonate, silica gel, opalescent silica, fly ash, Ultrafine powders such as slag, titanium oxide, and aluminum oxide can also be used. In particular, the use of ultrafine powder obtained by pulverizing opalescent silica, fly ash, or slag using a jet mill equipped with a classifier is effective in improving curing shrinkage. The amount of ultrafine powder used is preferably 5 to 40 parts by weight, more preferably 60 to 95 parts by weight of cement.
The amount is 10 to 35 parts by weight relative to 65 to 90 parts by weight, and if it is less than 5 parts by weight, the effect of reducing the porosity is small;
Moreover, if it exceeds 40 parts by weight, the fluidity of the kneaded product will be significantly reduced, making it difficult to carry out repair work, and the development of strength will also become insufficient. A high-performance water reducing agent is a surfactant with a large dispersion ability that does not cause too much delay in setting or excessive air entrainment even when added to cement in large quantities. Examples include salts of formaldehyde condensates, high molecular weight lignin sulfonates, polycarboxylate salts, etc. as main components. A high-performance water reducing agent is necessary to obtain a kneaded product with a low water ratio, and the conventional amount used is 0.3 to 1% by weight as a solid content based on cement, but in the present invention, , it is preferable to add it in a larger amount than that. Specifically, a mixture of cement and ultrafine powder
It is used up to about 10 parts by weight as a solid content per 100 parts by weight, and if it is added in a larger amount, it will adversely affect the curing reaction. A particularly preferable addition amount is 1 to 5 parts by weight. By using such a high-performance water reducing agent, even if the water-cement ratio is lowered and the porosity is 31% or less, it is possible to obtain a fluid kneaded material that can be worked with by normal methods. . Water is necessary to provide fluidity for repair work. In order to reduce the porosity, it is best to use as little amount as possible, preferably 12.5 to 30 parts by weight, more preferably 15 to 28 parts by weight, per 100 parts by weight of the mixture of cement and ultrafine powder. If the amount of water exceeds 30 parts by weight, it is difficult to reduce the porosity to 31% or less, and if it is less than 12.5 parts by weight, it is difficult to carry out repair work using normal methods. However, when used as a pad, it is possible to use less than 12.5 parts by weight. The above-mentioned materials may be mixed and kneaded by any method as long as they can be mixed and kneaded uniformly, and the order of addition is not particularly limited. By using the above combination, a compound having a porosity of 31% or less at 3 days old can be prepared. In the present invention, this formulation is used as it is,
Alternatively, aggregates and/or fibers may be further added as needed. Aggregates that have been conventionally used when mixing general concrete may be used, but harder ones, specifically, those with a Mohs hardness of 6 or more, preferably 7 or more, or a Knoop indenter hardness of 700 kg/mm It is preferable to use one selected based on the criteria of ² or more, more preferably 800 Kg/mm ² or more, because the strength can be significantly improved. Examples of materials that meet this standard include silica, emery, pyrite, magnetite, yellow jade, lawsonite, corundum, fenacite, spinel, beryl, gold-cut stone, tourmaline, granite, andalusite, cross stone, zircon, and fired stone. Bauxite, boron carbide, tungsten carbide, ferrosiliconitride, silicon nitride, fused silica, fused magnesia, silicon carbide, cubic boron nitride, etc. Repairs are often made of thin materials, and from the standpoint of improving crack resistance and bending strength, it is preferable to use fibers or nets. Synthetic and natural organic fibers and nets such as polypropylene, vinylon, aromatic polyamide, acrylonitrile, and cellulose can be used, but in terms of weather resistance and adhesion, steel, stainless steel fibers, asbestos, alumina, carbon, glass fibers,
Wire mesh, glass cloth, etc. are preferable. Moreover, steel rods can also be used for reinforcement purposes.
Furthermore, it is also possible to use conventionally used polymer latexes, water-soluble polymers, water-dispersed polymers, and the like. There are various methods of coating a salt-damaged damaged object with the repair material described above. Examples include troweling, brushing, spraying, injection, and pre-packed. After coating, epoxy, acrylic urethane, polymer cement, or inorganic paint can be applied as a surface coating. As described above, the composition according to the present invention contains cement, ultrafine powder, high performance water reducing agent, and water as necessary components, and the porosity of the cured product after 3 days of age is 31%. It must be something that shows the following: In the present invention, the reason why the porosity is measured at the age of 3 days is because it is in the initial stage that salt damage becomes a problem, and it is measured as follows. That is, the mixture was kneaded in a mortar mixer for 3 minutes, vacuum degassed under 600 mmHg for 10 minutes, and then immediately formed into a φ2 x 5 cm specimen, sealed in a plastic bag and placed in water at 20°C. Take care of yourself.
Three days after molding, it is taken out, dried at 105°C for 4 hours, returned to room temperature, and weighed to 10 ^-4 g. Let the weight at that time be (A). Next, the voids are filled with water by a suction method or a boiling method, the weight in water (B) and the weight in air (C) are measured, and the porosity is calculated using the following formula. Porosity (%) = (C - A) / B × 100 In the present invention, the porosity at 3 days old is 31
% or less is as follows. Ordinary Portland cement, ultrafine powder (silica hume, manufactured by Japan Heavy Chemical Industry Co., Ltd.), high-performance water reducer (Daiichi Kogyo Seiba Co., Ltd. product name "Cellflow 110P"), and water were mixed in various proportions to form specimens. The porosity of the material after 3 days of age and the presence or absence of Cl ^- ion penetration when immersed in a 10% NaCl aqueous solution for 14 days were determined using the fluorescein method.
The results shown in the table were obtained, and for specimens with a porosity of 31% or less,
This is because no penetration of Cl ^- ions was observed.

【table】

〔Example〕

A test specimen measuring 100 x 100 x 30 cm with embedded reinforcing bars was prepared and exposed to a coastal area for two years. The degree of corrosion was measured using the corrosion potential method, and deteriorated concrete was removed from areas where corrosion had progressed significantly or where cracks had occurred due to corrosion of reinforcing bars, and the following repairs were carried out. The figure shows its cross section. In the drawing, 1 is old concrete, 2 is reinforcing steel (SD35-
D25), 3 to 5 are deteriorated parts. Part 3 shows particularly significant deterioration. After removing the area and cleaning the reinforcing steel, repairs were carried out using the pre-packed construction method. First, place the formwork and
Fill with 13mm aggregate and fill the remaining area with Table 2 No.1
The mortar shown in was grouted. The compressive strength of this prepacked concrete (test method according to Japan Society of Civil Engineers standards) was 927 kgf/cm ² at 28 days old. Next, mortar shown in Table 2 No. 2 was applied with a trowel to the deteriorated portion No. 4. After applying one layer of troweling, a wire mesh was set, and another layer of troweling was applied on top of that. GRC was sprayed onto the deteriorated portion of No. 5 using the spray-up method using the mortar shown in Table 2 No. 3 to form a GRC surface coating layer 6. After the repair, the test specimen was exposed to the coastal area again, but even after two years, no changes in corrosion potential or appearance due to rusting of the reinforcing bars were observed.

〔Effect of the invention〕

According to the present invention, it is possible to perform repair work on damaged items due to salt damage, which has high durability and reduces penetration of Cl ^- ions.

[Brief explanation of drawings]

The drawing is a cross-sectional view of repair concrete used in Examples. 1: old concrete, 2: reinforcing bars, 3-5: deteriorated parts, 6: GRC surface coating layer.

Claims (1)

[Claims] 1 Salt-damaged materials are converted into a mixture containing cement, ultrafine powder, high-performance water reducer, and water as the main components, and with a porosity of 31% or less at 3 days old, as required, with aggregate and/or water. Or, a method for repairing salt-damaged materials, which is characterized by blending fibers, etc., and covering them with the same.