concrete

Abstract

To provide concrete capable of reducing a setting time, and providing restricted expansion strain within a standard value of a shrinkage compensation concrete, as well as having small dry-shrinkage strain.SOLUTION: A concrete comprises a shrinkage-reducing agent and a cement admixture containing an expansion material and aluminum sulfate, wherein: the expansion material is 80-99 pts.mass and aluminum sulfate is 1-20 pts.mass based on 100 pts.mass of the cement admixture; and an admixture volume of the cement admixture is 20-30 kg / m3.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to concrete using a shrinkage-reducing agent. [Background technology]

[0002] It is generally known that hardened mortar and concrete that use cement undergo drying shrinkage due to a decrease in volume caused by drying. Drying shrinkage-reducing agents for cement have been proposed as a means of suppressing this drying shrinkage (Patent Document 1, etc.). However, concrete that uses shrinkage-reducing agents has the problem of delayed setting time. While the delayed setting time can be avoided by reducing the amount of shrinkage-reducing agent, this increases the drying shrinkage strain, which may result in cracks due to drying shrinkage. Another method is to use an expansive additive and a shrinkage-reducing agent in combination to reduce drying shrinkage strain, but this increases the expansion strain, so the restrained expansion strain must be greater than the standard value for shrinkage-compensated concrete (the restrained expansion strain of concrete at 7 days of age is 150 to 250 × 10 -6 ) and in that case, the compressive strength is likely to decrease. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 59-184753 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention provides a concrete that can shorten the setting time even when a shrinkage-reducing agent is used, that can obtain a restrained expansion strain within the standard value for shrinkage-compensating concrete, and that also has small drying shrinkage strain. [Means for solving the problem]

[0005] That is, the present invention provides the following [1] to [3]. [1] Concrete containing a shrinkage reducing agent and a cement admixture containing an expanding material and aluminum sulfate, wherein the expanding material is 80 to 99 parts by mass, the aluminum sulfate is 1 to 20 parts by mass, and the amount of the cement admixture is 20 to 30 kg / m 3 A concrete characterized by: [2] The concrete according to [1], wherein the aluminum sulfate has a 150 μm sieve residue of 10 to 100 mass %. [3] The amount of the shrinkage reducing agent added is 1.5 to 12 kg / m 3 Concrete of [1] or [2]. [Effects of the Invention]

[0006] According to the present invention, it is possible to shorten the setting time, obtain a restrained expansion strain within the standard value of shrinkage-compensating concrete, and obtain concrete with small drying shrinkage strain. DETAILED DESCRIPTION OF THE INVENTION

[0007] The concrete of the present invention contains a shrinkage-reducing agent and a cement admixture containing an expansive material and aluminum sulfate, and the amount of the expansive material is 80 to 99 parts by mass and 1 to 20 parts by mass of aluminum sulfate per 100 parts by mass of the cement admixture, and the amount of the cement admixture in the concrete is 20 to 30 kg / m 3 This will be explained in detail below.

[0008] The expansive additive in the cement admixture of the present invention can be any of those containing free quicklime (f-CaO) as the active ingredient, those containing calcium sulfoaluminate such as 3CaO·3Al2O3·CaSO4 (aluminium), and those containing both free quicklime and calcium sulfoaluminate as active ingredients. In particular, those that exhibit expansion properties due to the increase in volume caused by hydration of free quicklime are preferred. The free quicklime content in the expansive additive is preferably 30 to 80% by mass, more preferably 40 to 70% by mass.

[0009] In addition to the above components, the expansive material of the present invention contains hydraulic compounds such as calcium silicates such as CaO·2SiO2 (C2S) and CaO·3SiO2 (C3S), CaO·Al2O3 (CA), 12CaO·7Al2O3 (C 12 A7), calcium aluminates such as 3CaO·Al2O3 (C3A), and calcium aluminoferrites such as 4CaO·Al2O3·Fe2O3 (C4AF) and 6CaO·2Al2O3·Fe2O3 (C6A2F) may be included. The content of the hydraulic compound in the expansive material is preferably 3 to 40 mass%, more preferably 5 to 30 mass%.

[0010] The expansive material may further contain gypsum. Examples of gypsum include gypsum hemihydrate, gypsum dihydrate, and anhydrous gypsum, with anhydrous gypsum being particularly preferred. The gypsum content in the expansive material is preferably 2 to 30% by mass, more preferably 3 to 25% by mass.

[0011] The fineness of the expansive material is 2000 to 7000 cm in terms of Blaine specific surface area. 2 / g is preferred, and 3000 to 6500 cm 2 / g is more preferable, 4000~6000cm 2 / g is more preferred.

[0012] Next, commercially available powdered aluminum sulfate can be used as the aluminum sulfate in the cement admixture of the present invention. For example, powdered aluminum sulfate (aluminum sulfate) commercially available for use as a flocculant is in the form of a hydrate (Al2(SO4)3·xH2O), but anhydrous or amorphous aluminum sulfate can also be used. From the standpoint of storage in powder form, aluminum sulfate containing octahydrate to octadecahydrate water of crystallization is preferred.

[0013] Regarding the particle size of aluminum sulfate, from the viewpoint of the slump properties of fresh concrete, the 150 μm sieve residue is preferably 10 to 100 mass%, more preferably 20 to 90 mass%, and even more preferably 40 to 80 mass%.

[0014] The contents of the expanding agent and aluminum sulfate in the cement admixture are 80 to 99 parts by mass of the expanding agent and 1 to 20 parts by mass of aluminum sulfate per 100 parts by mass of the cement admixture. If the aluminum sulfate content is less than 1 part by mass, the setting time will be long, while if the aluminum sulfate content exceeds 20 parts by mass, there is a risk that the restrained expansion performance will not be ensured and the fresh properties will be reduced. The aluminum sulfate content is more preferably 3 to 18 parts by mass, and even more preferably 5 to 15 parts by mass. The expanding agent and aluminum sulfate are thoroughly mixed in a mixer to prepare the cement admixture.

[0015] In addition to the above-mentioned components, the cement admixture of the present invention may contain small amounts of various additives, provided that the advantages of the present invention are not impaired. Examples of such additives include air-entraining agents, water-reducing agents, foaming agents, setting regulators, hardening accelerators, waterproofing agents, water-repellents, water-retaining agents, rust inhibitors, thickeners, pigments, and anti-efflorescence agents.

[0016] The amount of cement admixture in the concrete of the present invention is 20 to 30 kg / m from the viewpoint of compensation for shrinkage of the concrete. 3 25~30kg / m 3 is more preferred.

[0017] The shrinkage reducing agent in the present invention is not particularly limited as long as it is one generally used in concrete. Examples of the components include alkylene oxide adducts of alcohols, polyethers, polyoxyalkylene alcohol ethers, glycol ether amino alcohol derivatives, alkylene oxide copolymers, etc., and it is preferable to use one or more selected from these.

[0018] The amount of shrinkage reducing agent added to the concrete of the present invention is 1.5 to 12 kg / m from the viewpoint of minimizing drying shrinkage strain. 3 It is preferable that the density is 2 to 9 kg / m. 3 More preferably, it is 3 to 6 kg / m 3 It is more preferable that:

[0019] In addition to the above materials, the concrete of the present invention uses cement, aggregate, and water, but there are no particular limitations, and the cement, aggregate, and water used in ordinary concrete can be used. Note that the concrete of the present invention also includes mortar that uses only fine aggregate.

[0020] The cement used in the concrete of the present invention may be one or more selected from the group consisting of ordinary Portland cement, high-early-strength Portland cement, ultra-high-early-strength Portland cement, low-heat Portland cement, moderate-heat Portland cement, ecocement, and mixed cements obtained by mixing the Portland cement with blast furnace slag powder, fly ash, silica powder, silica fume, limestone powder, etc. The unit cement amount is preferably 270 to 500 kg / m 3 , more preferably 300 to 500 kg / m 3 is.

[0021] The aggregate used in the concrete of the present invention is not particularly limited as long as it is an aggregate generally used for mortar concrete. Specifically, the fine aggregate may be one or more selected from river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, lightweight fine aggregate, etc., and the coarse aggregate may be one or more selected from river gravel, mountain gravel, crushed stone, lightweight coarse aggregate, etc. Furthermore, the aggregate is not limited to natural aggregates, and artificial aggregates such as slag aggregate and recycled aggregates can also be used. Furthermore, the unit amount of the fine aggregate and coarse aggregate is preferably 500 to 1100 kg / m for both aggregates from the viewpoint of good workability. 3 , more preferably 600 to 1000 kg / m 3 is.

[0022] The water used in the concrete of the present invention is not particularly limited, and any water that does not affect the strength development or fluidity of the concrete, such as tap water, treated sewage water, or supernatant water from ready-mixed concrete, can be used. From the viewpoint of good workability, the unit water content is preferably 100 to 200 kg / m 3, more preferably 120 to 180 kg / m 3 is.

[0023] Furthermore, the concrete of the present invention can contain admixtures used in ordinary concrete, such as air-entraining agents, water-reducing agents, air-entraining water-reducing agents, high-performance water-reducing agents, and high-performance air-entraining water-reducing agents. In addition to these admixtures, foaming agents, foaming agents, waterproofing agents, rust inhibitors, thickeners, water-retaining agents, pigments, water-repellents, efflorescence inhibitors, fibers, and re-emulsified powdered resins can also be used depending on the purpose of the concrete. [Example]

[0024] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0025] Example 1 First, the expansive material and aluminum sulfate were mixed to prepare a cement admixture. The expansive material used was a quicklime-based expansive material (free quicklime content: 50% by mass, Blaine specific surface area: 5,130 cm). 2 / g). The aluminum sulfate used was a commercially available aluminum sulfate (17% alumina) with particle size adjusted (150 μm sieve residue 60% by mass). The expansive additive and aluminum sulfate were thoroughly mixed in a blend mixer to prepare a cement admixture.

[0026] [Table 1]

[0027] Concrete was produced using the prepared cement admixture in a 20°C environment. The concrete mix is ​​shown in Table 2. Ordinary Portland cement (manufactured by Taiheiyo Cement Corporation) was used as the cement, mountain sand from Kakegawa was used as the fine aggregate, and crushed stone from Sakuragawa was used as the coarse aggregate. Two types of shrinkage-reducing agents were used: shrinkage-reducing agent A (commercially available product; polyoxyethylene alkyl ether) and shrinkage-reducing agent B (commercially available product; alkylene oxide adduct of lower alcohol). An admixture (commercially available product; AE water-reducing agent) was added at 0.6% by mass relative to the total amount of cement and cement admixture (symbol P).

[0028] [Table 2]

[0029] <Evaluation test> The concrete thus prepared was tested for slump, setting time, restrained expansion strain, drying shrinkage strain and compressive strength using the following test methods. (1) Slump The test was conducted in accordance with "JIS A 1101 Slump Test for Concrete." (2) Coagulation test The test was conducted in accordance with "JIS A 1147 Concrete Setting Test Method." (3) Restrained expansion test In accordance with "JIS A 6202 Expansive Material for Concrete Appendix B," the restrained expansion strain was measured after 7 days of material age. (4) Drying shrinkage test The test was conducted in accordance with "JIS A 1129 Method for measuring changes in length of mortar and concrete." The concrete was demolded after 24 hours and cured in water at 20°C for 7 days, after which the base length was measured, and the amount of strain after 6 months was measured to calculate the drying shrinkage strain. The concrete specimens were stored in a constant temperature room at 20°C and 60% humidity throughout the aging period. (5) Compression strength test The compressive strength of the concrete was tested at 28 days of age in accordance with JIS A 1108 "Testing Method for Compressive Strength of Concrete." The curing temperature was kept at 20°C until just before the test.

[0030] <Test Results> The test results are shown in Table 3. The concrete in the present invention is within the standard value of shrinkage-compensating concrete (150 to 250 × 10 -6 ) and drying shrinkage strain is small, and it is found that concrete with good compressive strength can be obtained.

[0031] [Table 3]

[0032] Example 2 Next, the effect of particle size of aluminum sulfate used in cement admixture was evaluated. Table 4 shows cement admixtures using particle-sized aluminum sulfate.

[0033] [Table 4]

[0034] The prepared cement admixture was added, concrete was prepared in the same manner as in Example 1, and each evaluation test was carried out. The concrete mix is ​​shown in Table 5, and the test results are shown in Table 6. When the 150 μm residual content of aluminum sulfate was 0 mass%, the slump tended to be smaller. Also, the restrained expansion strain at 7 days of age tended to be smaller, although it was within the standard value for shrinkage-compensated concrete.

[0035] [Table 5]

[0036] [Table 6]

Claims

【Request Item 1】 A concrete having a unit cement amount of 300 to 500 kg / m 3 containing a shrinkage-reducing agent, and a cement admixture containing an expansive agent having free quicklime and / or calcium sulfoaluminate as an active ingredient, and aluminum sulfate having a 150 μm sieve residue of 10 to 100% by mass, wherein, per 100 parts by mass of the cement admixture, the expansive agent having free quicklime and / or calcium sulfoaluminate as an active ingredient is 82 to 97 parts by mass, and the aluminum sulfate having a 150 μm sieve residue of 10 to 100% by mass is 3 to 18 parts by mass, and the amount of the cement admixture is 20 to 30 kg / m 3 A concrete characterized by: 【Request Item 2】 The amount of the shrinkage reducing agent added is 1.5 to 12 kg / m 3 2. The concrete according to claim 1, wherein

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