Additive for concrete composition and concrete composition

Abstract

To provide a concrete additive capable of suppressing a decrease in the amount of air contained in a fresh concrete composition even under conditions where vibration is applied, and capable of suppressing shrinkage without impairing freeze-thaw resistance even in the hardened concrete, and to provide a concrete composition using the same.SOLUTION: An additive for a concrete composition comprises: (A) an alkane polyol represented by the formula CnH2n+2-mOHm (wherein n is an integer of 2 to 8, m is an integer of 2 to 8, and n≥m); and (B) at least one anionic surfactant selected from the group consisting of (b1) an alkyl sulfate ester salt and / or a polyoxyethylene alkyl sulfate ester salt, (b2) a resin acid and / or its salt, and (b3) a higher fatty acid and / or its salt, wherein the mass ratio ((A) / (B)) of the alkanepolyol (A) to the anionic surfactant (B) is 1,000 or more and 10,000 or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an additive for a concrete composition containing a shrinkage-reducing agent and an air content adjuster, and a concrete composition containing the additive. More specifically, the present invention relates to an additive for a concrete composition that can provide a concrete composition with excellent frost resistance (particularly, freeze-thaw resistance) in addition to excellent shrinkage reduction properties by stably securing fine air bubbles with a bubble diameter of less than 0.15 mm in the concrete composition even under vibration conditions, and a concrete composition containing the additive. The present invention also relates to a method for using a specific shrinkage-reducing agent contained in such an additive for a concrete composition in combination with a specific air content adjuster. [Background technology]

[0002] Suppressing shrinkage and cracking in concrete structures is a very important issue from the viewpoint of suppressing corrosion of reinforcing bars and ensuring durability. Conventional methods include reducing the unit water content, setting a low water-cement ratio, or reducing the paste content, which is the total amount of water and cement, but these mixing methods affect other properties such as strength and freeze-thaw resistance, so they are not necessarily effective.

[0003] In addition, air adjusters are generally added to fresh concrete to ensure a certain amount of air. It is known that by ensuring an adequate amount of air in fresh concrete, the ball-bearing effect improves the fluidity of the fresh concrete, which in turn improves workability, and that the presence of fine air bubbles increases resistance to material separation and suppresses bleeding caused by free water in the concrete. Furthermore, fine air bubbles with a diameter of less than 0.15 mm mitigate the increase in pressure (freezing pressure) that accompanies the expansion of water in concrete due to freezing at low temperatures, and are particularly effective in increasing the freeze-thaw resistance of hardened concrete.

[0004] As a method for suppressing shrinkage of concrete, a method for compensating shrinkage by adding an expansive inorganic mineral as an admixture to a concrete composition is also known. However, such a method not only affects other performances such as hardening, but also has the risk of promoting cracks in a concrete structure due to excessive expansion of the admixture. Another method is known in which a nonionic surfactant containing an alkylene oxide that reduces the surface tension in liquid is added to a concrete composition as a shrinkage reducing agent. However, it has been reported that adding a shrinkage reducing agent to a concrete composition may adversely affect the air entrainment property of an air content adjusting agent (Non-Patent Document 1), and in such a case, there is a concern that it may become difficult to entrain good quality air bubbles in the concrete composition.

[0005] In response to this, Patent Document 1 discloses a technology for suppressing the decrease in freeze-thaw resistance even when a shrinkage-reducing agent is used, by using a shrinkage-reducing agent such as an alkylene oxide adduct of a lower alcohol, solid paraffin having a particle size of 1 μm or less, and a freeze damage inhibitor for concrete that contains at least a nitrite. Also, Non-Patent Document 2 discloses a technology for maintaining freeze-thaw resistance while obtaining an excellent shrinkage-reducing effect by using a multi-component system such as a hydrocarbon compound and a glycol ether derivative as a shrinkage-reducing agent.

[0006] In addition, to ensure that concrete is densely packed as a structural material, it needs to be lightly vibrated and compacted by external forces. However, when vibration compaction is applied to fresh concrete, the air bubbles in the concrete coalesce and become coarse, and in some cases, the strength of the coarsened parts is weakened, not only causing air bubble marks on the concrete surface, but also reducing the amount of air in the concrete, which is known to have a negative effect on freeze-thaw resistance. Therefore, the amount and quality of air in concrete that is assumed to be compacted by vibration is one of the important properties required of concrete, and the quality of the air is required not only to be the size of the air bubbles, but also to have an evenly dispersed distribution of air bubbles without uneven distribution.

[0007] Thus, there is a need for the development of an additive for a concrete composition that can maintain not only the quantity and quality of air in fresh concrete, but also the quantity and quality of air in hardened concrete after vibration compaction, and that can impart a high shrinkage reduction effect and high freeze-thaw resistance to hardened concrete. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6964415 [Non-patent literature]

[0009] [Non-Patent Document 1] Yuji Nishi et al., “Effect of Water-Soluble Shrinkage-Reducing Agents on Drying Shrinkage and Freezing-Thawing”, Proceedings of the Japan Concrete Institute, Vol. 31, No. 1, pp. 1099-1104, 2009 [Non-Patent Document 2] Nishi, Yuji, et al., “Development of a shrinkage reducing agent with improved freeze-thaw resistance”, Proceedings of the Japan Concrete Institute, Vol. 32, No. 1, pp. 143-148, 2010. Summary of the Invention [Problem to be solved by the invention]

[0010] In view of the above circumstances, the present invention aims to provide a concrete additive that can suppress a decrease in the amount of air contained in a fresh concrete composition even when vibration is applied, and that can suppress shrinkage without impairing the freeze-thaw resistance even in hardened concrete, and a concrete composition using the same. [Means for solving the problem]

[0011] The gist of the configuration of the present invention is as follows. [1](A)C n H 2n+2-m OH m(n=an integer of 2 to 8, m=an integer of 2 to 8, n≧m), and (B) at least one anionic surfactant selected from the group consisting of (b1) an alkyl sulfate ester salt and / or a polyoxyethylene alkyl sulfate ester salt, (b2) a resin acid and / or a salt thereof, and (b3) a higher fatty acid and / or a salt thereof, A concrete composition additive, characterized in that the mass ratio ((A) / (B)) of the alkane polyol (A) to the anionic surfactant (B) is 1,000 or more and 10,000 or less. [2] The additive for a concrete composition according to [1], wherein the (A) alkane polyol is an alkane diol. [3] The additive for a concrete composition according to [1], wherein the (A) alkane polyol is hexylene diol. [4] A concrete composition comprising the additive for a concrete composition according to any one of [1] to [3], a hydraulic powder, a cement dispersant, aggregate, and water. [5] The concrete composition according to [4], wherein Xa, which is the ratio of the air content of fresh concrete immediately after mixing to the air content of fresh concrete after 5 minutes of standing ([air content after 5 minutes of standing] / [air content immediately after mixing]), satisfies the following formula (1): 0.9≦Xa≦1.1 (1) [6] The concrete composition according to [4], wherein Xv, which is the ratio of the air volume in fresh concrete after being left to stand for 5 minutes to the air volume when the concrete is vibrated by the vibration method described below ([air volume after 90 seconds of vibration] / [air volume after being left to stand for 5 minutes]), satisfies the following formula (2): 0.5≦Xv≦1.0 (2) Vibration method and method for measuring the air volume after vibration: Fresh concrete that had been left to stand for 5 minutes was packed into a container with a nominal capacity of 7 L, placed in the center of a vibration table (table surface: 90 cm x 90 cm), and subjected to 50 Hz vibration in four stages (after 15 seconds, 30 seconds, 60 seconds, and 90 seconds), and the air volume in the concrete at each stage was measured based on JIS A 1116:2019. [7] The concrete composition according to [4], wherein the ratio of the amount of air having bubbles with a diameter of less than 0.15 mm in the upper, middle and lower parts of a hardened body having a material age of 28 days, which is prepared by the method described below, to the total amount of air in the upper, middle and lower parts ([amount of air having bubbles with a diameter of less than 0.15 mm] / [total amount of air]), Xu (upper part), Xm (middle part), and Xl (lower part) are all 0.23 or more and 1.00 or less. Method for preparing hardened concrete and method for measuring air volume in each part of the hardened concrete: Based on JIS A 1132:2020, concrete was packed into a cylindrical formwork of 150mm (diameter) x 300mm (height) by compacting it with a ram, then placed in the center of a vibration table and subjected to vibration compaction for 30 seconds to harden the resulting specimen. Air volume was measured based on JIS A 1116:2019 at three positions of the hardened concrete: top (within 5mm ± 2.5mm from the top of the cylinder), middle (within 150mm ± 2.5mm from the top of the cylinder), and bottom (within 5mm ± 2.5mm from the bottom of the cylinder). [8](A)C n H 2n+2-m OH m (n=an integer of 2 to 8, m=an integer of 2 to 8, n≧m) is used in combination with at least one anionic surfactant selected from the group consisting of (B) (b1) an alkyl sulfate ester salt and / or a polyoxyethylene alkyl sulfate ester salt, (b2) a resin acid and / or a salt thereof, and (b3) a higher fatty acid and / or a salt thereof, The method, characterized in that the mass ratio ((A) / (B)) of the alkane polyol (A) to the anionic surfactant (B) is 1,000 or more and 10,000 or less. Effect of the Invention

[0012] The present invention can provide a concrete additive that can suppress a decrease in the amount of air contained in a fresh concrete composition even when vibration is applied, and that can suppress shrinkage without impairing the freeze-thaw resistance of the hardened concrete, and a concrete composition using the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The concrete additive of the present invention and the concrete composition using the same will be described in detail below.

[0014] <Additives for concrete> The concrete additive of the present invention includes components (A) and (B), and the components (A) and (B) are blended at a predetermined mass ratio ((A) / (B)). Specifically, by combining an alkane polyol having a predetermined structural formula as the component (A) with at least one anionic surfactant selected from a predetermined type as the component (B) at a mass ratio ((A) / (B)) of 1,000 to 10,000, it is possible to provide a concrete additive and a concrete composition using the same that maintain the air content in fresh concrete, particularly suppress a decrease in the air content even when vibration is applied, and ensure stable fine air bubbles, and suppress shrinkage in hardened concrete while exhibiting high durability without impairing freeze-thaw resistance even in cold regions. The components (A) and (B) may be added to the concrete composition as a one-part additive containing them together, or the components (A) and (B) may each be added separately to the concrete composition (e.g., used to combine the component (A) with the component (B)), or the components (A) and / or (B) may be blended with other additives (e.g., a dispersant) and then added to the concrete.

[0015] (A) Alkane polyol The additive for concrete of the present invention is a shrinkage reducing agent. n H 2n+2-m OH m The alkane polyol contains an alkane structure represented by C n H 2n+2is a residue of a saturated hydrocarbon, and at least two hydroxyl groups are substituted in this alkane structure. In the alkane polyol, n is an integer of 2 to 8, preferably n is an integer of 4 to 8, and more preferably n is an integer of 4 to 7. The alkane polyol has such an alkane structure, and due to its appropriate hydrophobicity, it can reduce the surface tension in the liquid while being dissolved in an aqueous solution.

[0016] The number m of hydroxyl groups in the alkane polyol is an integer of 2 to 8, preferably an integer of 2 to 6, more preferably 2 or 3, and even more preferably 2. If the number m is greater than 8, it is undesirable because it may delay the hydration of the cement. n H 2n+2-m OH m In the structural formula, n≧m.

[0017] C n H 2n+2-m OH m Examples of the alkane polyol represented by the formula (I) include diols such as ethanediol, propanediol, butanediol, pentanediol, hexanediol, heptanediol, and octanediol, and triols such as propanetriol, butanetriol, pentanetriol, and hexanetriol. The alkane moiety may be linear or branched. The alkane polyol used is preferably liquid at room temperature and water-soluble, and if it is poorly water-soluble, a small amount of a solubilizing component may be appropriately combined. Furthermore, an alkane polyol having 4 or more hydroxyl groups may be included, but sugar alcohols and sugar derivatives such as pentaerythritol and sorbitol are not preferred because they may inhibit the hydration of cement. These can be applied alone or in combination of two or more. Ethylene glycol, propylene glycol, glycerin, and hexylene glycol are preferred because they are readily available as commercial products, and these can be appropriately combined.

[0018] The molecular weight of the alkane polyol is 62-242, preferably 62-162, and most preferably 90-132.

[0019] The alkane polyol is preferably contained in an amount of 0.3 parts by mass or more and 2.9 parts by mass or less, more preferably 0.4 parts by mass or more and 2.4 parts by mass or less, and even more preferably 0.6 parts by mass or more and 1.8 parts by mass or less, per 100 parts by mass of cement.

[0020] (B) Anionic surfactants The concrete additive of the present invention contains at least one anionic surfactant selected from the group consisting of (b1) alkyl sulfate salts and / or polyoxyethylene alkyl sulfate salts, (b2) resin acids and / or their salts, and (b3) higher fatty acids and / or their salts as an air content regulator (air entraining component). By using such a specific anionic surfactant in combination with the above-mentioned component (A), it is possible to suppress a decrease in the amount of air contained in the fresh concrete composition even under conditions where vibration is applied. This maintains the material separation resistance of fresh concrete, improves workability, and is also effective in reducing bleeding. In addition, the freeze-thaw resistance of the hardened concrete is not impaired, and drying shrinkage can be suppressed.

[0021] (b1) (Polyoxyethylene) alkyl sulfate ester salt Alkyl sulfate ester salts are classified as R in the commonly known classification of cleaning ingredients. 1 -O-SO3M1 (in the formula, R 1 represents an alkyl group, and M1 represents an alkali metal, an alkaline earth metal, or an ammonium ion), and polyoxyethylene alkyl sulfate refers to a higher alcohol sulfate (AS) represented by the formula: R 2 -O-(CH2CH2O) a -SO3M2 (in the formula, in the formula, R 2represents an alkyl group, a is an integer of 1 to 4, and M2 represents an alkali metal, an alkaline earth metal, or an ammonium ion). Note that alkylbenzenesulfonates (ABS, LAS), α-olefinsulfonates, and alkanesulfonates (SAS) are not included in the alkyl sulfate ester salts. Here, in the alkyl sulfate ester salts and polyoxyethylene alkyl sulfate ester salts having the above-mentioned structures, R 1 and R 2 is preferably an alkyl group having 10 to 16 carbon atoms, and for example, as an alkyl sulfate salt, R 1 dodecyl sulfate, where R is an alkyl group having 12 carbon atoms; and polyoxyethylene alkyl ether sulfate, where R 2 lauryl ether sulfate, in which the alkyl group has 12 carbon atoms. The alkyl sulfate and polyoxyethylene alkyl sulfate are preferably at least one selected from alkali metal salts, alkaline earth metal salts and ammonium salts, and more preferably alkali metal salts. These salts may contain unneutralized acid. This allows high air entrainment even when the amount of anionic surfactant added is small.

[0022] (b2) Resin acid and / or its salt Resin acids are natural resins extracted and purified from trees, and include various carboxylic acids, such as abietic acid. Examples of such resin acids include rosin, which is the residue remaining after extracting pine resin, which is the sap of the pine family, and distilling turpentine. Here, resin acids include gum rosin, wood rosin, etc., but do not include tall oil rosin produced in papermaking processes, etc. The resin acid salt is a salt of such a resin acid, and is preferably at least one selected from alkali metal salts, alkaline earth metal salts, and ammonium salts, and is more preferably an alkali metal salt. The resin acid salt is most preferably an alkali metal salt of abietic acid. The resin acid salt may contain an unneutralized acid. This makes it possible to entrain independent fine air bubbles even in a concrete composition to which component (A) is added, and suppresses the disappearance of air bubbles over time, allowing sufficient good quality air bubbles (air bubbles with a bubble diameter of 150 μm or less) to remain in the hardened concrete.

[0023] (b3) Higher fatty acid and / or its salt The higher fatty acid is a chain monocarboxylic acid having a large number of carbon atoms, and examples thereof include palmitic acid (C16), stearic acid (C18), oleic acid (C18), linoleic acid (C18), and mixtures thereof. Among such higher fatty acids, it is preferable to include unsaturated fatty acids such as oleic acid or linoleic acid, and more preferable to include tall oil fatty acid. The higher fatty acid salt is a salt of such a higher fatty acid, and is preferably at least one selected from alkali metal salts, alkaline earth metal salts, and ammonium salts, and more preferably an alkali metal salt. The higher fatty acid salt may contain unneutralized acid.

[0024] The anionic surfactant may contain any one of (b1), (b2) and (b3) alone, or may contain them in appropriate combination. The total active ingredients of (b1), (b2) and (b3) are preferably contained in an amount of 0.0001 to 0.0050 parts by mass, more preferably 0.0005 to 0.0040 parts by mass, and even more preferably 0.0010 to 0.0030 parts by mass, per 100 parts by mass of cement. By containing the total active ingredients of (b1), (b2) and (b3) in an amount of 0.0001 to 0.0050 parts by mass per part by mass of cement, a predetermined amount of air is entrained in the concrete, and a certain degree of freeze-thaw resistance is imparted to the hardened concrete.

[0025] In addition, the anionic surfactant may appropriately contain various other surfactant components, thickening components, components for enhancing the film thickness of air bubbles, pH adjusting components, coloring components, etc., within the scope of not impairing the effects of the present invention.

[0026] The mass ratio ((A) / (B)) of the alkane polyol as component (A) to the at least one anionic surfactant as component (B) is from 1000 to 10000, preferably from 1000 to 9000, and more preferably from 1100 to 8000. By having the mass ratio ((A) / (B)) be from 1000 to 10000, it is possible to suppress a decrease in the amount of air contained in fresh concrete even under conditions where vibration is applied, and the freeze-thaw resistance of the hardened concrete is not impaired, and the effect of suppressing drying shrinkage can be obtained.

[0027] Furthermore, the concrete additive may optionally contain various auxiliary components within the scope of the present invention, such as a nonionic surfactant component for stabilizing bubbles, a chelating component, a detergent builder component, an alkali metal salt component for adjusting the degree of acid neutralization, and the like.

[0028] A concrete composition according to another embodiment of the present invention includes the above-mentioned additive for a concrete composition, and further includes a hydraulic powder, a cement dispersant, an aggregate, and water. The content of the additive for a concrete composition contained in the concrete composition is preferably 0.04% by mass or more and 0.44% by mass or less, more preferably 0.08% by mass or more and 0.35% by mass or less, and particularly preferably 0.20% by mass or more and 0.30% by mass or less.

[0029] The hydraulic powder is a powder containing cement and cement components. Examples of such hydraulic powder include portland cement, calcium aluminate cement, magnesium phosphate cement, magnesium potassium phosphate cement, sulfoaluminate cement, pozzolana cement, slag cement, fly ash cement, and silica fume cement. Among these, the hydraulic cement is preferably portland cement, slag cement, or fly ash cement. It is even more preferable to apply the present invention to slag cement or fly ash cement, since it is difficult to maintain a good air content.

[0030] The cement dispersant may be a known cement dispersant, for example, a polycarboxylic acid dispersant, a naphthalene dispersant, a melamine dispersant, a lignin dispersant, an oxycarboxylic acid dispersant, etc. The content of the cement dispersant contained in the concrete composition is preferably 0.05 parts by mass or more and 1.00 parts by mass or less in terms of the amount of active ingredient of the cement dispersant relative to 100 parts by mass of cement. In addition, a commercially available cement dispersant may be used, and examples of the dispersant include the Polyhed 15 series and Mastergranium series manufactured by Pozzolith Solutions, the Floric S series and SV series manufactured by Floric, and the Chupol EX series and HP series manufactured by Takemoto Oil Co., Ltd. The amount of such a commercially available cement dispersant added can be appropriately adjusted according to the manufacturer's recommended value, and is preferably 0.5 parts by mass or more and 2.0 parts by mass or less relative to 100 parts by mass of cement.

[0031] Examples of aggregates include coarse aggregates and fine aggregates such as silica, quartz, sand, crushed marble, glass spheres, granite, limestone, calcite, feldspar, alluvial sand, any other durable aggregates, and mixtures thereof. In particular, in aggregates containing a large amount of clay components (for example, aggregates containing 20% ​​by mass or more of a viscosity component), the above-mentioned (A) and (B) components contained in the additive for a concrete composition may not be effective. Therefore, the content of the clay component contained in the aggregate is preferably 10% by mass or less in the concrete composition, and more preferably 0% by mass, that is, no clay component is contained. In addition, the content of the aggregate contained in the concrete composition is preferably 52% by mass or more and 96% by mass or less, and more preferably 70% by mass or more and 90% by mass or less.

[0032] The content of water in the concrete composition is not particularly limited, but is preferably from 4.3 mass % to 9.5 mass %, and more preferably from 6.5 mass % to 8.3 mass %.

[0033] In the concrete composition of the present invention, it is preferable that Xa, which is the ratio of the air content of fresh concrete immediately after mixing to the air content of fresh concrete after 5 minutes of standing ([air content after 5 minutes of standing] / [air content immediately after mixing]), satisfies the following formula (1). By setting Xa in the range of 0.9 to 1.1, high fluidity that imparts excellent workability to the concrete can be obtained, and excellent freeze-thaw resistance can be obtained. Xa is more preferably 0.95 to 1.05.

[0034] 0.9≦Xa≦1.1 (1)

[0035] In the concrete composition of the present invention, it is preferable that Xv, which is the ratio of the air volume of fresh concrete after being left to stand for 5 minutes to the air volume when the concrete is vibrated by the vibration method described below ([air volume after 90 seconds of vibration] / [air volume after being left to stand for 5 minutes]), satisfies the following formula (2). When the value of Xv satisfies the following formula (2), an excess increase in air is prevented, and even when the concrete is subjected to vibration compaction during construction, a certain amount of air remains in the concrete, thereby obtaining excellent fluidity and excellent freeze-thaw resistance.

[0036] 0.5≦Xv≦1.0 (2)

[0037] (Vibration method and method for measuring air volume after vibration) After leaving the concrete for 5 minutes, the fresh concrete is packed into a container with a nominal capacity of 7 L, placed in the center of a vibration table (table surface: 90 cm x 90 cm), and subjected to 50 Hz vibration in four stages (after 15 seconds, 30 seconds, 60 seconds, and 90 seconds). The amount of air in the concrete at each stage is measured based on JIS A 1116:2019.

[0038] In the concrete composition of the present invention, the ratios of the amount of air with bubbles having a diameter of less than 0.15 mm in each of the upper, middle and lower parts of a hardened concrete body having an age of 28 days, which are prepared by the following method, to the total amount of air in each of the upper, middle and lower parts ([amount of air with bubbles having a diameter of less than 0.15 mm] / [total amount of air]) are preferably 0.23 or more and 1.00 or less. More preferably, Xu, Xm and Xl are each 0.29 or more and 1.00 or less.

[0039] (Method of producing hardened body and method of measuring air content in each part of hardened body) In accordance with JIS A 1132:2020, concrete is packed into a cylindrical formwork of 150 mm (diameter) x 300 mm (height) using a ram to compact it, and then vibration compaction is performed for 30 seconds on a vibration table. The air volume of the hardened specimen is measured in accordance with JIS A 1116:2019 at three positions: the top (within 5 mm ± 2.5 mm from the top of the cylinder), the middle (within 150 mm ± 2.5 mm from the top of the cylinder), and the bottom (within 5 mm ± 2.5 mm from the bottom of the cylinder).

[0040] In addition, in the concrete composition of the present invention, the freeze-thaw resistance of the hardened body obtained can be estimated by the values ​​of Xu (upper part), Xm (middle part), and Xl (lower part), which are the ratios of the amount of air with a bubble diameter of less than 0.15 mm in each part of the hardened body prepared by the above-mentioned method to the total amount of air in each part of the upper, middle, and lower parts ([amount of air with a bubble diameter of less than 0.15 mm] / [total amount of air]). For example, if the values ​​of Xu (upper part), Xm (middle part), and Xl (lower part) are 0.29 or more and 1.00 or less, it can be estimated that the durability index, which is an index showing freeze-thaw resistance, is 90 or more.

[0041] <Production of concrete composition> The concrete composition according to the present invention can be manufactured by a known method. The mixing method and the mixer used are not particularly limited as long as the concrete composition is mixed uniformly. For example, the mixing method may be a procedure in which cement, admixtures, fine aggregates, and water are mixed in advance, and then coarse aggregates are added (pre-mixing mortar), or a procedure in which cement, admixtures, fine aggregates, and coarse aggregates are mixed in advance (dry mixing), and then water is added (mixed together). In this case, it is preferable that the additive for a concrete composition according to the present invention is mixed with water in advance, or is added at the same time as the addition of water. In this case, the additive for a concrete composition according to the present invention containing components (A) and (B) may be added as one additive, or the shrinkage reducing agent containing component (A) and the air content adjusting agent containing component (B) in the additive for a concrete composition according to the present invention may be added separately. The time required for mixing can also be appropriately selected. For example, the mixer used may be a pan type, forced twin-axis type, tilting barrel type, paddle type, batch type, continuous type line mixer, static mixer, etc. From the viewpoint of easy understanding of the kneading and mixing state, a batch type mixer is preferred, and from the viewpoint of high mixing efficiency, a forced twin-axis mixer is preferred.

[0042] By appropriately controlling the bubbles in the fresh concrete composition using the additive for concrete composition of the present invention, it is possible to obtain hardening properties that do not impair the freeze-thaw resistance even in cold regions while suppressing shrinkage after hardening. Furthermore, by appropriately controlling the bubbles in the fresh concrete, it is also possible to predict the freeze-thaw resistance of the hardened concrete. Therefore, the concrete composition containing the additive for concrete composition of the present invention is effective when concrete containing clay minerals or concrete using moderate heat cement, fly ash cement, slag cement, or a mixture thereof with relatively low strength development is applied to cold regions. EXAMPLES

[0043] The additive for a concrete composition of the present invention and a concrete composition using the same will be described in detail below with reference to examples. However, the present invention is not limited to the examples shown below.

[0044] To prepare a concrete composition, the materials shown in Tables 1 and 2 were used. A cement composition was produced under the mixing conditions shown in Table 3. The slump, slump flow, and air content of the obtained concrete were measured. In Table 1, the cement dispersant and shrinkage reducing agent 2 were commercially available products. The cement dispersant contains a polycarboxylic acid ether copolymer as a main component, and the shrinkage reducing agent 2 contains an alkylene glycol compound as a main component, and does not correspond to the alkane polyol of the above-mentioned component (A). The anionic surfactant is an aqueous solution in which the following b1, b2, and b3 are mixed in the mixing ratio shown in Table 1. In Table 3, W / C means the water-cement ratio, and s / a means the fine aggregate volume ratio.

[0045] b1: Sodium salt of alkyl (C=10-16) ether of α-sulfo-ω-hydroxypoly(oxyethylene) b2: Rosin acid mainly composed of abiotic acid and its sodium salt b3: Na and K salts of tall oil fatty acids

[0046] [Table 1]

[0047] [Table 2]

[0048] [Table 3]

[0049] The concrete tests were carried out according to the following procedure.

[0050] <Mixing method> A cement composition containing cement, fine aggregate, and coarse aggregate in the ratios shown in Table 3 was added to a forced twin-shaft mixer for practical testing, and dry mixing was carried out for 10 seconds. Then, in order to obtain the concrete compositions shown in Tables 4 to 7, water containing the materials shown in Table 1 was added and mixed for 90 seconds to prepare fresh concrete.

[0051] The test items of the obtained concrete composition are as follows. All of the following tests were carried out at an environmental temperature of 20°C.

[0052] <Slump> The slump immediately after mixing was measured according to JIS A 1101:2020.

[0053] <Air volume> The air content was measured immediately after mixing in accordance with JIS A 1116:2019.

[0054] <Rate of change in length> The length change rate was measured in accordance with JIS A 1129-3:2010. The measurement period was six months.

[0055] <Air bubble spacing factor> The spacing factor (SF) was measured according to ASTM C457 / C457M:2010.

[0056] <Durability index> The durability index (DF) was measured according to JIS A 1148:2010 Method A. The underwater curing period was 28 days, and the number of freeze-thaw cycles was 300.

[0057] <Change in air volume (standing still)> In accordance with JIS A 1116:2019, the air volume immediately after mixing and the air volume after 5 minutes of standing were measured, and Xa, which is the ratio of the air volume immediately after mixing to the air volume after 5 minutes of standing ([air volume after 5 minutes of standing] / [air volume immediately after mixing]), was calculated.

[0058] <Changes in air volume: static and vibration tests> After 5 minutes of standing, the fresh concrete was packed into a Maruto Seisakusho air meter with a nominal capacity of 7 L, which was placed in the center of a vibration table (table surface: 90 cm x 90 cm), and vibrations of 50 Hz were applied in four stages (after 15 seconds, 30 seconds, 60 seconds, and 90 seconds), and the air volume in the concrete at each stage was measured according to JIS A 1116: 2019. In addition, Xv, which is the ratio of the air volume after 5 minutes of standing to the air volume when the concrete was subjected to vibration using the above vibration method ([air volume after 90 seconds of vibration] / [air volume after 5 minutes of standing]), was calculated.

[0059] <Uneven distribution of air in hardened body> Based on JIS A 1132:2020, concrete was packed into a cylindrical formwork of 150 mm (diameter) x 300 mm (height) by compacting it with a ram, and then placed in the center of the vibration table and subjected to vibration compaction for 30 seconds to harden the resulting specimen. The total air volume (%) and the air volume with bubbles less than 0.15 mm in diameter (%) of the hardened specimen were measured at three positions: the top (50 mm from the top of the cylinder), the middle (150 mm from the top of the cylinder), and the bottom (50 mm from the bottom of the cylinder) based on JIS A 1116:2019. In addition, the ratio of the total air volume in each of the top, middle, and bottom parts ([air volume with bubbles less than 0.15 mm in diameter] / [total air volume]), Xu (top), Xm (middle), and Xl (bottom), were calculated.

[0060] The test results for slump, air content, and length change rate are shown in Table 4. In Table 4, C×% means the parts by mass of the cement dispersant, shrinkage reducing agent, and anionic surfactant relative to 100 parts by mass of cement, and for the cement dispersant or shrinkage reducing agent, it means the parts by mass of the material shown in Table 1, and for the anionic surfactant, it means the parts by mass of each active ingredient. The same applies to Tables 5 and 6.

[0061] [Table 4]

[0062] Table 5 shows the test results for slump, air content, air content of hardened body, air space factor SF (μm) and durability index DF (%).

[0063] [Table 5]

[0064] The test results regarding slump, air content, and change in air content are shown in Table 6, and the test results regarding uneven distribution of air content in the hardened body are shown in Table 7.

[0065] [Table 6]

[0066] [Table 7]

[0067] From Table 4, it was shown that in the concrete composition prepared in Example 1, the length change rate was smaller than that in Comparative Example 1, and the shrinkage of the concrete composition was smaller.

[0068] From Table 5, it was shown that the concrete compositions prepared in Examples 2 to 4 had an air bubble spacing factor SF of less than 300 μm, indicating an excellent state in which minute air bubbles are dispersed. In addition, the durability index DF was 92% or more, indicating high freeze-thaw resistance even when subjected to frost damage.

[0069] Furthermore, from Tables 6 and 7, it was inferred that the concrete compositions of Examples 5 and 6, in which the concrete composition additive of the present invention was applied, had high freeze-thaw resistance because Xa was in the range of 0.9 to 1.1, Xv was in the range of 0.5 to 1.0, and Xu, Xm, and Xl were all in the range of 0.29 to 1.00. In contrast, the concrete compositions of Comparative Examples 3 and 4, in which a concrete additive other than the present invention was applied, had low Xa of 0.83 or less, low Xv of 0.25 or less, and high Xu, Xm, and Xl of 0.22 or less.

Claims

1. (A) C ｎ H ２ｎ＋２－ｍ O.H. ｍ (n=an integer of 2 to 8, m=an integer of 2 to 8, n≧m), and (B) at least one anionic surfactant selected from the group consisting of (b1) an alkyl sulfate ester salt and / or a polyoxyethylene alkyl sulfate ester salt, (b2) a resin acid and / or a salt thereof, and (b3) a higher fatty acid and / or a salt thereof, A concrete composition additive, characterized in that the mass ratio ((A) / (B)) of the alkane polyol (A) to the anionic surfactant (B) is 1,000 or more and 10,000 or less.

2. 2. The additive for a concrete composition according to claim 1, wherein the alkane polyol (A) is an alkane diol.

3. 2. The additive for a concrete composition according to claim 1, wherein the alkane polyol (A) is a hexylene diol.

4. A concrete composition comprising the additive for concrete compositions according to any one of claims 1 to 3, a hydraulic powder, a cement dispersant, aggregate and water.

5. 5. The concrete composition according to claim 4, wherein Xa, which is the ratio of the air content of fresh concrete immediately after mixing to the air content of fresh concrete after 5 minutes of standing ([air content after 5 minutes of standing] / [air content immediately after mixing]), satisfies the following formula (1): 0.9≦Xa≦1.1 (1)

6. 5. The concrete composition according to claim 4, wherein Xv, which is a ratio of the air volume after 5 minutes of standing in fresh concrete to the air volume when the concrete is vibrated by the vibration method described below ([air volume after 90 seconds of vibration] / [air volume after 5 minutes of standing]), satisfies the following formula (2): 0.5≦Xv≦1.0 (2) Vibration method and method for measuring the air volume after vibration: Fresh concrete after 5 minutes of standing was packed into a container with a nominal capacity of 7 L, placed in the center of a vibration table (table surface: 90 cm x 90 cm), and subjected to 50 Hz vibration in four stages (after 15 seconds, 30 seconds, 60 seconds, and 90 seconds), and the air volume in the concrete at each stage was measured based on JIS A 1116:2019.

7. The concrete composition according to claim 4, wherein the ratios of the amount of air having bubbles with a diameter of less than 0.15 mm in each of the upper, middle and lower parts of a hardened body having an age of 28 days, which are produced by the method described below, to the total amount of air in each of the upper, middle and lower parts ([amount of air having bubbles with a diameter of less than 0.15 mm] / [total amount of air]), Xu (upper part), Xm (middle part), and Xl (lower part) are all 0.23 or more and 1.00 or less. Method for preparing hardened body and method for measuring air volume in each part of the hardened body: Based on JIS A 1132:2020, concrete was packed into a cylindrical formwork of 150 mm (diameter) x 300 mm (height) by compacting it with a ram, which was then placed in the center of the vibration table and subjected to vibration compaction for 30 seconds. The air volume of the obtained test specimen was measured in accordance with JIS A 1116:2019 at three positions of the top (within 5 mm ± 2.5 mm from the top surface of the cylinder), middle (within 150 mm ± 2.5 mm from the top surface of the cylinder), and bottom (within 5 mm ± 2.5 mm from the bottom surface of the cylinder).

8. (A) C ｎ H ２ｎ＋２－ｍ O.H. ｍ (n=an integer of 2 to 8, m=an integer of 2 to 8, n≧m) is used in combination with at least one anionic surfactant selected from the group consisting of (B) (b1) an alkyl sulfate ester salt and / or a polyoxyethylene alkyl sulfate ester salt, (b2) a resin acid and / or a salt thereof, and (b3) a higher fatty acid and / or a salt thereof, The method, characterized in that the mass ratio ((A) / (B)) of the alkane polyol (A) to the anionic surfactant (B) is 1,000 or more and 10,000 or less.

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