Cement composition, repair method and concrete structure

Abstract

The present invention provides: a cement composition which has high fluidity retention effect, low kneading resistance, fast setting properties and higher initial crack resistance; a repair method; and a concrete structure.　A cement composition according to the present invention contains a cement which contains, as chemical components, MnO, TiO2 and P2O5; the total content of MnO, TiO2 and P2O5 in the cement is 0.05% by mass to 2.0% by mass; and the mass ratio ((MnO + TiO2) / P2O5) of the total content of MnO and TiO2 to the content of P2O5 in the cement is 1.5 to 15.

Description

[Technical Field]

[0001] The present invention relates to a cement composition, a repair method, and a concrete structure used primarily in the fields of civil engineering and construction. [Background technology]

[0002] Concrete structures deteriorate due to salt damage, neutralization, freezing and thawing, chemical corrosion, etc., and there is a risk of cracks or loosening on the surface. As a countermeasure, deteriorated areas are identified by hammering tests, etc., and then removed using electric picks, air picks, water jets, etc., and repair work is carried out to fill in the gaps with new repair materials. In small-scale repair work where the cross section to be repaired is small, polymer cement mortar is often mixed and applied with a trowel to repair the cross section (see, for example, Patent Documents 1 and 2).

[0003] In recent years, there has been a growing demand for reducing environmental impact, and mortar and concrete made by mixing large amounts of Portland cement by-products such as blast furnace slag, fly ash, and silica fume have been actively used. Furthermore, repair methods using these by-products are also known (see, for example, Patent Documents 3 and 4). On the other hand, while using such by-products tends to improve fluidity and workability, it also has issues such as slow setting, which delays construction time, and a tendency for cracks to occur in the early stages. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-322858 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-89565 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-128618 [Patent Document 4] JP 2017-226557 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to provide a cement composition, a repair method, and a concrete structure that have a high fluidity retention effect, low mixing resistance, accelerated setting, and improved resistance to early cracking. [Means for solving the problem]

[0006] The present invention has been made to solve the above-mentioned problems, and as a result of various efforts to solve the above-mentioned problems, the inventors discovered that by containing specific amounts of MnO, TiO2, and P2O5, it is possible to improve the fluidity retention effect, accelerate setting, and further increase resistance to early cracking, and have thereby completed the present invention. The gist of the present invention is as follows. [1] A cement composition comprising cement, the cement containing MnO, TiO2, and P2O5 as chemical components, the total content of MnO, TiO2, and P2O5 in the cement being 0.05% by mass or more and 2.0% by mass or less, and the mass ratio of the total content of MnO and TiO2 to the content of P2O5 in the cement ((MnO + TiO2) / P2O5) being 1.5 or more and 15 or less. [2] The cement composition according to [1], further containing a pozzolan substance. [3] The cement composition according to [2], wherein the pozzolanic substance is ground granulated blast furnace slag. [4] The cement composition according to any one of [1] to [3], further containing aggregate. [5] The cement composition according to any one of [1] to [4], further comprising a polymer emulsion. [6] A repair method using the cement composition according to any one of [1] to [5]. [7] A concrete structure repaired using the cement composition described in any one of [1] to [5]. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a cement composition, a repair method, and a concrete structure that have a high fluidity retention effect, low mixing resistance, accelerated setting, and improved resistance to early cracking. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present invention will be described in detail below. In this specification, parts and percentages are by mass unless otherwise specified. Furthermore, the term "concrete" as used in the present invention is a general term for cement paste, mortar, and concrete.

[0009] [Cement composition] The cement composition of the present invention contains cement. The cement used in the present invention is not particularly limited, and examples include various cements such as normal, early strength, extra early strength, low heat, and medium heat, as well as commercially available fine cements and white cements. It is also possible to use various cements and various blended cements in a finely powdered form. It is also possible to use cements that have been adjusted by increasing or decreasing the amount of components (e.g., gypsum) normally used in cement. Furthermore, combinations of two or more of these can also be used. In the present invention, it is preferable to select ordinary Portland cement or high-early-strength Portland cement from the viewpoint of high strength development and suppression of cracking.

[0010] The cement used in the present invention has a Blaine specific surface area (hereinafter also referred to as the Blaine value) of 2,500 cm from the viewpoint of production cost and strength development. 2 / g or more 7,000cm 2 / g or less, and 2 / g or more 6,000cm 2 / g or less is more preferable, and 2 / g or more 4,500cm 2The Blaine value is determined in accordance with JIS R 5201 (physical testing methods for cement).

[0011] The cement composition of the present invention contains MnO, TiO2, and P2O5 as chemical components in the cement, which can accelerate setting and suppress early cracking. The MnO content in the cement is preferably 0.008% by mass or more and 0.35% by mass or less, and more preferably 0.03% by mass or more and 0.25% by mass or less. The content of TiO2 in the cement is preferably 0.01% by mass or more and 1.4% by mass or less, and more preferably 0.03% by mass or more and 1.0% by mass or less. The P2O5 content in the cement is preferably 0.008% by mass or more and 0.35% by mass or less, and more preferably 0.01% by mass or more and 0.3% by mass or less.

[0012] In the present invention, "cement containing MnO, TiO2, and P2O5 as chemical components" refers to a state in which peaks sufficient to identify MnO, TiO2, and P2O5 are not observed in X-ray diffraction measurement, but the content of each can be measured by X-ray fluorescence measurement. Structurally, it is presumed that MnO, TiO2, and P2O5 are each present in solid solution in the cement.

[0013] In the cement composition of the present invention, the total content of MnO, TiO2, and P2O5 in the cement is 0.05% by mass or more and 2.0% by mass or less. If the total content of MnO, TiO2, and P2O5 in the cement is less than 0.05% by mass, the cement composition will have a low fluidity retention effect and will have problems such as high mixing resistance. If the total content of MnO, TiO2, and P2O5 in the cement exceeds 2.0% by mass, setting will be slow and initial crack resistance will be low. The total content of MnO, TiO2 and P2O5 in the cement is preferably 0.07% by mass or more and 1.7% by mass or less, and more preferably 0.1% by mass or more and 1.5% by mass or less, from the viewpoints of improving the effect of retaining the fluidity of the cement composition, reducing resistance to mixing, accelerating setting, and further improving resistance to initial cracking. To set the amounts of MnO, TiO2, and P2O5, respectively, and the total content thereof, within the above ranges, for example, the contents of each element in the raw materials may be measured in advance, and the amounts of the raw materials containing MnO, TiO2, and P2O5 mixed may be adjusted so that the desired amounts of each element and the desired total content are achieved.

[0014] An example of a raw material containing MnO is manganese oxide. An example of a raw material containing TiO2 is titanium oxide. An example of a raw material containing P2O5 is tricalcium phosphate.

[0015] In the cement composition of the present invention, the mass ratio ((MnO + TiO2) / P2O5) of the total content of MnO and TiO2 to the content of P2O5 in the cement is 1.5 or more and 15 or less. If the mass ratio ((MnO + TiO2) / P2O5) is less than 1.5, the setting of the cement composition will be delayed and the resistance to initial cracking will be reduced. If the mass ratio ((MnO + TiO2) / P2O5) is more than 15, the effect of retaining the fluidity of the cement composition will be reduced, and problems such as increased resistance to mixing will arise. The mass ratio of the total content of MnO and TiO2 to the content of P2O5 in the cement ((MnO + TiO2) / P2O5) is preferably 2 or more and 13 or less, and more preferably 3 or more and 10 or less, from the viewpoints of achieving a high effect of retaining the fluidity of the cement composition, low resistance to mixing, accelerated setting, and further improved resistance to initial cracking. The amounts of MnO, TiO2, and P2O5 in cement can be measured by X-ray fluorescence diffraction (XRF), and the mass ratio ((MnO+TiO2) / P2O5) can be calculated from the measured values.

[0016] (pozzolanic substances) The cement composition of the present invention preferably further contains a pozzolanic substance. The pozzolanic substance used in the present invention is a by-product that, when mixed with cement, helps maintain the fluidity of the cement. The pozzolanic substance is not particularly limited, and examples thereof include ground granulated blast furnace slag, fly ash, silica fume, pulp sludge incineration ash, sewage sludge incineration ash, and waste glass powder. One or more of these can be used. Among these, ground granulated blast furnace slag and fly ash are preferred, and ground granulated blast furnace slag is more preferred.

[0017] The fineness of the ground granulated blast furnace slag is not particularly limited, but is usually 3,000 to 9,000 cm in Blaine value. 2 / g range. The fineness of fly ash and silica fume is not particularly limited, but usually, the fineness of fly ash is 3,000 to 9,000 cm in Blaine value. 2 / g, and for silica fume, the BET specific surface area is in the range of 2 to 20 m 2 / g range.

[0018] The blending ratio of cement and pozzolanic substance is not particularly limited, but is preferably 30 to 80 parts cement, more preferably 40 to 70 parts, per 100 parts of binder consisting of cement and pozzolanic substance. The amount of pozzolanic substance is preferably 20 to 70 parts, more preferably 30 to 60 parts, per 100 parts of binder consisting of cement and pozzolanic substance. Having the cement content at or above the lower limit and the pozzolanic substance content at or below the upper limit reduces mixing resistance, accelerates setting, and improves initial crack resistance. Furthermore, having the cement content at or below the upper limit and the pozzolanic substance content at or above the lower limit ensures sufficient fluidity retention.

[0019] (aggregate) The cement composition of the present invention preferably further contains aggregate. The aggregate used in the present invention can be the same fine aggregate or coarse aggregate as that used in ordinary cement mortar or concrete. That is, river sand, river gravel, mountain sand, mountain gravel, crushed stone, crushed sand, limestone aggregate, lime sand, silica sand, colored sand, artificial aggregate, blast furnace slag aggregate, sea sand, sea gravel, artificial lightweight aggregate, heavy aggregate, etc. can be used, and combinations of these are also possible. In particular, for applications where high fluidity retention and low mixing resistance are desired, the use of siliceous silica sand, limestone aggregate, or lime sand is preferred.

[0020] The content of the aggregate is preferably 50 to 350 parts, more preferably 70 to 200 parts, relative to 100 parts of the cement composition. When the content of the aggregate is within the above range, it is possible to further improve the initial crack resistance.

[0021] (polymer emulsion) The cement composition of the present invention preferably further contains a polymer emulsion. The polymer emulsion used in the present invention is not particularly limited, but examples thereof include rubber latexes such as acrylonitrile-butadiene rubber, styrene-butadiene rubber, chloroprene rubber, and natural rubber; resin emulsions such as ethylene-vinyl acetate copolymers, polyacrylates, styrene-acrylate copolymers, and acrylic ester copolymers such as acrylonitrile-acrylate copolymers; and vinyl acetate-vinyl versatate copolymers. The polymer is available in a re-emulsifiable powder form or a liquid form, either of which can be used to improve adhesion to the substrate and to increase the durability of the mortar.

[0022] The content of the polymer emulsion is preferably 1 to 15 parts by solid content, more preferably 3 to 10 parts, per 100 parts of the cement composition. When the content of the polymer emulsion is within the above range, fluidity can be increased and initial cracking can be suppressed.

[0023] (fiber) Fibers may also be used in the present invention to further improve incipient crack resistance. The type of fiber is not particularly limited, but examples include polymer fibers such as vinylon fiber, propylene fiber, acrylic fiber, nylon fiber, and aramid fiber, and inorganic fibers such as steel fiber, glass fiber, carbon fiber, and fibers made by melt-spinning rocks such as basalt.

[0024] The fiber content is preferably 0.02 to 1.5 parts, more preferably 0.05 to 1.0 parts, relative to 100 parts of the cement composition. When the fiber content is within the above range, the initial crack resistance can be further improved while maintaining the fluidity of the cement composition. From the viewpoint of the aesthetic appearance of the trowel-finished surface, the length of the fibers is preferably 15 mm or less, more preferably 12 mm or less, and even more preferably 10 mm or less.

[0025] (Antifoaming agent) In the present invention, it is possible to use an antifoaming agent within a range that does not adversely affect performance. The antifoaming agent is used for the purpose of suppressing the amount of air entrained during kneading. The type of defoaming agent is not particularly limited as long as it does not significantly adversely affect the strength properties of the cement composition, and either liquid or powder form can be used. Examples include polyether-based defoaming agents, polyhydric alcohol-based defoaming agents such as polyhydric alcohol esters and alkyl ethers, alkyl phosphate-based defoaming agents, and silicone-based defoaming agents.

[0026] The content of the antifoaming agent is preferably 0.002 to 0.5 parts, more preferably 0.01 to 0.4 parts, per 100 parts of the cement composition. By having the content of the antifoaming agent be 0.002 parts or more, the antifoaming effect can be fully exerted. Furthermore, by having the content of the antifoaming agent be 0.5 parts or less, a decrease in fluidity and early cracking can be suppressed.

[0027] (Other additives) In the present invention, one or more of the following may be used to the extent that they do not adversely affect performance: hardening accelerators, accelerators, setting retarders, gas foaming substances, expansion agents, water reducing agents, setting adjusters, shrinkage reducing agents, air-entraining agents, rust inhibitors, water repellents, antibacterial agents, colorants, antifreeze agents, admixtures such as fine limestone powder, slowly cooled blast furnace slag powder, sewage sludge incineration ash and its molten slag, municipal waste incineration ash and its molten slag, and pulp sludge incineration ash; thickeners; shrinkage reducing agents; polymers; clay minerals such as bentonite and sepiolite; and anion exchangers such as hydrotalcite.

[0028] In the cement composition of the present invention, the method for mixing the materials is not particularly limited, and the materials may be mixed at the time of application, or some or all of the materials may be mixed in advance. As the mixing device, any existing device such as a tilting mixer, an omni mixer, a Henschel mixer, a V-type mixer, or a Nauta mixer can be used.

[0029] [Repair method] Repair methods using the cement composition of the present invention include adding a predetermined amount of water, mixing the mixture, and applying it to the repair area with a trowel, or, in some cases, using a pump to pump the mixed mortar to an extent that does not interfere with construction, blowing it off to the repair area with compressed air, and finishing it with a trowel. The mixing method may be a method of putting the materials into a container such as a pail and mixing it with a hand mixer, or a method of mixing it with a pan-type mixer, etc.

[0030] As an example of a specific repair method, the deteriorated concrete is removed with a water jet, and then a primer is applied. Next, the mixed mortar is applied with a trowel or sprayed on. For wall and ceiling surfaces, if the repair thickness is around 30 mm, it can be applied in one go, so the surface can be finished with a trowel. For repair thicknesses exceeding 30 mm, the repair is carried out in multiple layers. In this case, the joint surfaces are not troweled smoothly, but rather left with a rough finish to ensure adhesion. The timing of pouring the joints varies depending on factors such as the outside temperature, but it is sufficient to do so when the previously applied mortar has hardened enough to touch with your finger and not dent. Finally, the surface is troweled to make it smooth. For more thorough construction, it is preferable to take measures to prevent drying, such as using a protective sheet or curing agent.

[0031] [Concrete Structures] By the repair method as described above, a concrete structure repaired using the cement composition of the present invention can be obtained. [Example]

[0032] The present invention will be further described below based on examples, but the present invention is not limited to these examples.

[0033] (Preparation of cement composition) Manganese oxide (reagent), titanium oxide (reagent), and tricalcium phosphate (reagent) were added to ordinary Portland cement so that the amounts of MnO, TiO2, and P2O5 were in the proportions shown in Table 1 to prepare cement compositions.

[0034] 100 parts by mass of the resulting cement composition was mixed with pozzolan substance A, pozzolan substance B, aggregate A, aggregate B, polymer emulsion A, and polymer emulsion B in the proportions shown in Table 1, and 25 parts by mass of water was added to 100 parts by mass of the cement composition, followed by measuring the fluidity retention effect, mixing resistance, setting, and crack resistance. The results are also shown in Table 1.

[0035] <Materials used> Pozzolanic material A: Granulated blast furnace slag powder, Blaine value 4,000 cm 2 / g, commercially available Pozzolanic material B: Fly ash, Blaine value 4,300 cm 2 / g, commercially available Aggregate A: Fine aggregate, lime sand less than 0.6 mm 50% mixed with 0.6-1.2 mm 50% Aggregate B: Coarse aggregate, river gravel, maximum size 20mm Polymer emulsion A: styrene-butadiene rubber (solid content 45%), commercially available Polymer emulsion B: Polyacrylic ester, re-emulsified powder type, commercially available Water: Tap water

[0036] <Measurement items> Fluidity retention effect: In accordance with JIS R 5201, the flow values ​​were measured immediately after mixing and 20 minutes later in a 20°C environment, and the fluidity retention effect was determined by subtracting the flow value after 20 minutes from the flow value immediately after mixing. Mixing resistance: Using a mortar hand mixer in a 20°C environment, the mixture was mixed for 90 seconds, and the current value at this time was measured with a clamp meter. The maximum value was used as an index of mixing resistance. Setting: The time until setting was completed was measured according to JIS A 1171. Crack resistance: A 40cm x 40cm x 2cm cement composition was poured onto an existing 40cm x 40cm x 30cm concrete structure, and the surface was exposed to wind at a speed of 4m / s for 5 days, after which the occurrence (number of cracks) of surface cracks was confirmed.

[0037] [Table 1]

[0038] The results in Table 1 confirm that using a cement composition containing specific amounts of MnO, TiO2, and P2O5 has the effect of maintaining fluidity, reducing mixing resistance, accelerating setting, and increasing resistance to initial cracking. [Industrial Applicability]

[0039] The cement composition of the present invention, which contains specific amounts of MnO, TiO2, and P2O5, has high fluidity retention, low mixing resistance, accelerated setting, and increased resistance to initial cracking. Therefore, it can be widely used in the fields of civil engineering and architecture, including concrete structures used in ground improvement, water supply and sewage systems, agriculture and water supply, railways, electricity, roads, and construction, as well as repair methods, gap filling, and anchoring of reinforcing steel bars.

Claims

1. Contains cement and a pozzolanic substance, The cement contains MnO and TiO as chemical components. ２ and P ２ O ５ Contains MnO and TiO in the cement ２ and P ２ O ５ The total content is 0.05% by mass or more and 2.0% by mass or less, P in the cement ２ O ５ MnO and TiO relative to the content ２ The mass ratio of the total content of (MnO + TiO ２ ) / P ２ O ５ ) is 1.5 or more and 15 or less, The pozzolanic substance is present in an amount of 50 to 200 / 3 parts per 100 parts of the binder consisting of the cement and the pozzolanic substance, A cement composition wherein the pozzolanic material is ground granulated blast furnace slag.

2. The mass ratio ((MnO + TiO ２ ) / P ２ O ５ 2. The cement composition according to claim 1, wherein the mass ratio is 5 or more and 15 or less (excluding those in which the mass ratio is 5.5, 6.1, 6.7, 7.5, or 8.0).

3. The cement composition according to claim 1 or 2, further comprising aggregate.

4. The cement composition according to claim 1 or 2, further comprising a polymer emulsion.

5. A repair method using the cement composition according to claim 1 or 2.

6. A concrete structure repaired with the cement composition according to claim 1 or 2.

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