Surface modifier for adjusting the setting of concrete, concrete composition, and method for preparing the concrete composition.

Abstract

To provide a surface modifier for concrete setting adjustment, a concrete composition, and a method for preparing the concrete composition, which can suppress bleeding while ensuring a sufficient pot life even in a hot environment.SOLUTION: A surface modifier for concrete setting adjustment of the invention contains at least one of oxycarboxylic acids except gluconic acid and salts of oxycarboxylic acids except gluconic acid.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a concrete setting-regulating surface modifier, a concrete composition, and a method for preparing a concrete composition. [Background technology]

[0002] In recent years, the number of days with outside temperatures exceeding 30°C or even 35°C has been increasing, and it has been observed that the temperature of concrete at the time of unloading is also tending to rise (see, for example, Non-Patent Document 1). Although factors such as the presence or absence of ventilation at the pouring site also play a role, situations have occurred where the outside temperature at the construction site exceeds 40°C. Such increases in outside temperature can lead to a further increase in the temperature of the concrete during transportation, which can reduce the fluidity of the concrete. There are concerns that this will result in a decrease in workability due to the reduced fluidity of the concrete, and a deterioration in the surface quality of the concrete after hardening due to bleeding.

[0003] As a general measure against hot weather concrete construction, modified standard mix designs are used for ready-mixed concrete, and the details of these designs vary from factory to factory. As an example of a measure against hot weather concrete construction, methods such as changing the type of water-reducing agent from a standard type to a retarder type, or in some cases increasing the unit water content, are taken to compensate for slump retention (see, for example, Non-Patent Document 2). In addition to these measures against hot weather concrete construction during manufacturing at the factory, another measure is to add superplasticizers and retarders to the ready-mixed concrete on-site to ensure fluidity retention. However, for finishing work such as floors, even if compaction is carried out without problems, the timing for setting suitable for finishing is shorter compared to the standard period. As a result, there is often little leeway in working time, and the surface dries out quickly, raising concerns about a decline in the quality of the finished surface (see, for example, Non-Patent Document 3). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Hiroshi Jinnai: Heat countermeasures during construction and curing in building works, Concrete Engineering, pp. 459-464, Vol. 51, No. 5, 2013.5 [Non-Patent Document 2] Kondo, Kihei: Measures to take into account for concrete construction in hot weather as a design and supervision engineer, Concrete Engineering, pp. 407-411, Vol. 51, No. 5, 2013.5 [Non-Patent Document 3] Japan Concrete Institute (ed.): Concrete Basic Technology Research Committee Concrete Construction WG Report, Guidelines for Finishing the Top Surface of Cast Concrete, 2020.11 [Overview of the project] [Problems that the invention aims to solve]

[0005] Based on the above, the present invention aims to provide a concrete setting-adjusting surface modifier, a concrete composition, and a method for preparing a concrete composition that can suppress bleeding while ensuring sufficient pot life even in hot environments. [Means for solving the problem]

[0006] The inventors of the present invention have made various efforts to solve the above problems and have found that by using a concrete setting-adjusting surface modifier containing at least one of an oxycarboxylic acid other than gluconic acid, or a salt of an oxycarboxylic acid other than gluconic acid, bleeding can be suppressed while ensuring sufficient pot life even in hot environments, and have completed the present invention. In other words, the present invention is as follows.

[0007] [1] A concrete setting modifier and surface modifier containing at least one of an oxycarboxylic acid other than gluconic acid, and a salt of an oxycarboxylic acid other than gluconic acid. [2] The concrete setting adjustment surface modifier according to [1], further containing a carbonate, wherein the carbonate content is 40 to 90% by mass. [3] A concrete setting-adjusting surface modifier as described in [1] or [2] above, wherein the residue on a sieve with a mesh size of 300 μm, as determined by the sieving test method specified in JIS K 0069:1992, is 40% or less. [4] A concrete composition containing a concrete setting-adjusting surface modifier described in any of [1] to [3] above and cement, wherein the proportion of the concrete setting-adjusting surface modifier is 0.05 to 0.4 parts by mass per 100 parts by mass of cement. [5] A method for preparing a concrete composition, comprising the step of adding and mixing a concrete setting-adjusting surface modifier described in any of [1] to [3] above into ready-mixed concrete. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a concrete setting adjustment surface modifier, a concrete composition, and a method for preparing a concrete composition that can suppress bleeding while ensuring sufficient pot life even in hot environments. [Modes for carrying out the invention]

[0009] The present invention will be described in detail below. In this specification, "parts" and "%" refer to mass unless otherwise specified. Furthermore, the term "concrete" in this invention refers collectively to cement paste, cement mortar, and cement concrete.

[0010] [Concrete setting adjustment and surface modifier] The concrete setting-adjusting surface modifier of the present invention contains at least one of an oxycarboxylic acid other than gluconic acid, and a salt of an oxycarboxylic acid other than gluconic acid. The concrete setting-adjusting surface modifier of the present invention can delay the initial setting time, thereby ensuring sufficient pot life even in hot environments. Furthermore, the concrete setting-adjusting surface modifier of the present invention can increase water retention, thereby suppressing bleeding and improving the surface quality of the concrete.

[0011] The oxycarboxylic acids excluding gluconic acid and salts of oxycarboxylic acids excluding gluconic acid used in this invention enhance water retention, suppress bleeding, improve the surface quality of concrete, delay setting to ensure pot life in hot environments, and improve initial strength. Examples of oxycarboxylic acids excluding gluconic acid include citric acid, tartaric acid, malic acid, salicylic acid, and lactic acid, and examples of salts of oxycarboxylic acids excluding gluconic acid include salts of these. One or more of the above oxycarboxylic acids excluding gluconic acid and salts of oxycarboxylic acids excluding gluconic acid may be used in combination. Among these, citric acid is preferred.

[0012] The content of oxycarboxylic acids excluding gluconic acid, and salts of oxycarboxylic acids excluding gluconic acid, is preferably 10 to 60% by mass, more preferably 15 to 55% by mass, and even more preferably 20 to 50% by mass. By having the content of oxycarboxylic acids excluding gluconic acid and salts of oxycarboxylic acids excluding gluconic acid within the above range, it is possible to increase water retention, suppress bleeding, improve the surface quality of the concrete, delay setting, and ensure a longer pot life in hot environments.

[0013] The concrete setting-adjusting surface modifier of the present invention can contain carbonates along with oxycarboxylic acids other than gluconic acid, and salts of oxycarboxylic acids other than gluconic acid, from the viewpoint of delaying setting and ensuring a longer pot life in hot environments. The carbonate used in the present invention is not particularly limited as long as it can delay coagulation and ensure a pot life in hot environments. Examples include potassium carbonate, sodium carbonate, sodium bicarbonate, lithium carbonate, and potassium bicarbonate, and one or more of these may be used in combination. Among these, potassium carbonate and sodium carbonate are preferred, and potassium carbonate is more preferred, as they are good at delaying coagulation and ensuring a pot life.

[0014] The content ratio of the carbonate is preferably 40 to 90 mass%, more preferably 45 to 85 mass%, and even more preferably 50 to 80 mass%. When the content ratio of the carbonate falls within the above range, setting can be retarded to easily secure the pot life.

[0015] Regarding the particle size of the setting-adjusting surface modifier for concrete, the residue on a sieve with an opening of 300 μm according to the sieve test method specified in JIS K 0069:1992 is preferably 40% or less, more preferably 35% or less, and even more preferably 30% or less. When the particle size of the setting-adjusting surface modifier for concrete is not more than the above upper limit, it can be stably and uniformly mixed into concrete, the water retention capacity is enhanced to suppress bleeding, the surface layer quality of concrete is improved, and setting is retarded to easily secure the pot life in a high-temperature environment.

[0016] [Concrete Composition] The concrete composition of the present invention contains the aforementioned setting-adjusting surface modifier for concrete of the present invention and cement.

[0017] The content ratio of the setting-adjusting surface modifier for concrete is preferably 0.05 to 0.4 parts by mass, more preferably 0.07 to 0.35 parts by mass, and even more preferably 0.1 to 0.3 parts by mass, relative to 100 parts by mass of cement. When the content ratio of the setting-adjusting surface modifier for concrete is at least the above lower limit, setting can be retarded, bleeding is suppressed, and the surface layer quality of concrete can be easily improved. In addition, when the content ratio of the setting-adjusting surface modifier for concrete is not more than the above upper limit, the strength development at the early material age becomes favorable.

[0018] The cement used in the present invention is not particularly limited, and examples thereof include various cements such as ordinary, high-early-strength, ultra-high-early-strength, low-heat, and moderate-heat cements, various blended cements obtained by mixing these cements with blast furnace slag, fly ash, silica fume, etc., environment-friendly cement (eco-cement) produced using municipal waste incineration ash and sewage sludge incineration ash as raw materials, and commercially available fine particle cements, and it is also possible to use various cements or various blended cements after pulverizing them into fine powder. In addition, cements adjusted by increasing or decreasing the amount of components usually used in cement (such as gypsum) can also be used. In the present invention, it is preferable to select ordinary Portland cement or high-early-strength Portland cement from the viewpoints of high fluidity, salt damage resistance, adhesion strength with reinforcing bars, and rust prevention.

[0019] The cement used in the present invention preferably has a Blaine specific surface area value of 2,500 cm from the viewpoints of production cost and strength development 2 / g or more and 7,000 cm 2 / g or less, more preferably 2,750 cm 2 / g or more and 6,000 cm 2 / g or less, and even more preferably 3,000 cm 2 / g or more and 4,500 cm 2 / g or less. The Blaine specific surface area value is determined in accordance with JIS R 5201 (Physical testing methods for cement).

[0020] In the present invention, one or more of the following materials can be used, within a range that does not adversely affect performance: fine aggregate, coarse aggregate, water-reducing agent, expanding agent, siliceous fine powder, coagulation regulator, air-entraining agent, rust inhibitor, water-repellent agent, antibacterial agent, colorant, antifreeze, limestone fine powder, blast furnace slow-cooling slag fine powder, sewage sludge incineration ash and its molten slag, municipal solid waste incineration ash and its molten slag, and pulp sludge incineration ash and other admixtures, defoaming agents, thickeners, shrinkage reducing agents, fibrous materials such as steel fiber, vinylon fiber, carbon fiber, and wollastonite fiber, polymers, clay minerals such as bentonite and sepiolite, and anion exchangers such as hydrotalcite, within a range that does not substantially hinder the objective of the present invention.

[0021] [Method for preparing concrete compositions] An embodiment of the method for preparing the concrete composition of the present invention is obtained by adding and mixing a concrete setting-adjusting surface modifier to ready-mixed concrete containing the aforementioned cement. In this step, the concrete setting-adjusting surface modifier is mixed with mixing water in a mixing container to form a base concrete. By going through this step, the concrete composition can be prepared by simply, safely, and stably uniformly mixing the concrete setting-adjusting surface modifier into the base concrete. The mixing water mentioned above is supplied, for example, from a ready-mix concrete plant or similar facility. Furthermore, in the mixing process, transportation often occurs simultaneously with the mixing.

[0022] As described above, the concrete setting-adjusting surface modifier of the present invention is suitable for use as a material added after the concrete has been mixed, transported to the construction site, and placed into place.

[0023] The concrete setting-adjusting surface modifier of this embodiment may be directly added to the concrete in the concrete mixer and / or agitator truck, or it may be added to the concrete mixer and / or agitator truck by air pressure. When loading the material into an agitator truck, specifically, the material can be manually loaded into the truck immediately upon arrival, or it can be pumped using compressed air from a compressor via a hose of approximately 5 to 10 meters. In this case, for example, the "Lineback" pneumatic conveyor manufactured by Exair Corporation can be used.

[0024] In this embodiment, the ready-mixed concrete is mixed at a ready-mix concrete plant or similar facility, then transported by a concrete mixer and / or agitator truck, and shipped to construction sites such as civil engineering sites and building sites. The ready-mixed concrete specifies the performance of the transport vehicle and, in principle, limits the time from the start of mixing to unloading to within 1.5 hours. The Standard Specifications for Concrete stipulate that when the ambient temperature exceeds 25°C, the standard time from mixing to the end of placement is within 1.5 hours. The transport time from the factory to the site should be approximately within 1 hour. This embodiment is specifically intended for use in hot environments. In this specification, a hot environment means an environment in which the concrete setting adjustment surface modifier and concrete composition are used at a temperature of 25°C or higher. [Examples]

[0025] The present invention will be described in more detail below based on experimental examples, but the present invention is not limited to these examples.

[0026] (Experiments No. 1-1 to 1-13, 2-1 to 2-2, 3-1 to 3-4) The concrete setting-adjusting surface modifier was obtained by mixing oxycarboxylic acids excluding gluconic acid, salts of oxycarboxylic acids excluding gluconic acid, and carbonates in the proportions shown in Table 1. The obtained concrete setting-adjusting surface modifier was added to ready-mixed concrete and mixed in the proportions shown in Tables 1 to 3 relative to 100 parts by mass of cement to obtain a concrete composition. The relative bleeding and initial setting time of the obtained concrete composition were measured as follows. The results are shown in Tables 1 to 3.

[0027] <Materials used for the setting-regulating surface modifier for concrete> ·Citric acid: Commercial product, manufactured by Fujifilm Wako Pure Chemical Corporation ·Sodium citrate: Commercial product, manufactured by Fujifilm Wako Pure Chemical Corporation ·Gluconic acid (50% aqueous solution): Commercial product, manufactured by Fujifilm Wako Pure Chemical Corporation ·Sodium gluconate: Commercial product, manufactured by Fujifilm Wako Pure Chemical Corporation ·Tartaric acid: Commercial product, manufactured by Fujifilm Wako Pure Chemical Corporation ·Malic acid: Commercial product, manufactured by Fujifilm Wako Pure Chemical Corporation ·Potassium carbonate: Commercial product, manufactured by Fujifilm Wako Pure Chemical Corporation ·Sodium carbonate: Commercial product, manufactured by Fujifilm Wako Pure Chemical Corporation

[0028] <Materials used for concrete> ·Cement: Commercially available ordinary Portland cement, manufactured by Denka Co., Ltd., Blaine specific surface area 3,200 cm 2 / g, density 3.15 g / cm 3 ·Fine aggregate: Crushed sand, density 2.61 g / cm 3 ·Coarse aggregate: Crushed stone, density 2.66 g / cm 3 . ·Water: Tap water ·Water reducing agent: Lignin-based water reducing agent, manufactured by GCP Chemicals Co., Ltd.

[0029] <Measurement methods> ·Relative bleeding: In accordance with JIS A 1123:2012 "Test method for bleeding of concrete", the bleeding rate was measured in a constant temperature bath at 30°C for ready-mixed concrete with the setting-regulating surface modifier for concrete added and that without the additive, and the relative value was calculated. ·Initial setting time: In accordance with JIS R 5201:2015 "Physical testing methods for cement", the initial setting time was measured by the Proctor penetration test in a constant temperature bath at 30°C for ready-mixed concrete with the setting-regulating surface modifier for concrete added and that without the additive. • Sieve residue: In accordance with JIS K 0069:1992 "Test methods for sieving chemical products," the sieve residue of the concrete setting adjustment surface modifier was measured using a sieve with a mesh size of 300 μm.

[0030] [Table 1]

[0031] [Table 2]

[0032] [Table 3] [Industrial applicability]

[0033] The concrete setting-adjusting surface modifier and concrete composition of the present invention can suppress bleeding while ensuring sufficient pot life even in hot environments, and is therefore particularly suitable for use in the civil engineering and construction fields.

Claims

1. A concrete setting-adjusting surface modifier for suppressing bleeding, containing at least one of an oxycarboxylic acid excluding gluconic acid, or a salt of an oxycarboxylic acid excluding gluconic acid, and having a sieve residue of 40% or less when sieved using the sieving test method specified in JIS K 0069:1992 with a mesh size of 300 μm (excluding those containing alumina cement or jet cement).

2. Furthermore, it contains carbonates, The concrete setting-adjusting surface modifier for suppressing bleeding, according to claim 1, wherein the content of the carbonate in the concrete setting-adjusting surface modifier for suppressing bleeding is 40 to 90% by mass.

3. A concrete setting-adjusting surface modifier for suppressing bleeding as described in claim 1 or 2, and cement, A concrete composition in which the proportion of a concrete setting-adjusting surface modifier for suppressing the aforementioned bleeding is 0.05 to 0.4 parts by mass per 100 parts by mass of cement.

4. A method for preparing a concrete composition, comprising the step of adding and mixing a concrete setting-adjusting surface modifier for suppressing bleeding, as described in claim 1 or 2, into ready-mixed concrete.

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