Alkali aggregate reaction retarder for cement concrete

Abstract

To develop a new alkali aggregate reaction retarder that has other useful functions in cement concrete while having an alkali aggregate reaction inhibition function.SOLUTION: An alkali aggregate reaction retarder for cement concrete includes a basic organic acid aluminum. The alkali aggregate reaction retarder can exhibit a strength improvement function, a water-reducing effect function, and an antirust effect function for steel bars useful in cement concrete, while having an alkali aggregate reaction inhibition function.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an alkali-aggregate reaction inhibitor for cement concrete. [Background technology]

[0002] One of the alkali aggregate reactions in cement concrete is the alkali-silica reaction. Various alkali-silica reaction inhibitors for cement concrete have been developed so far. For example, Patent Document 1 discloses a dicarboxylic acid, Patent Document 2 discloses a combination of acetic acid and silica fume, and Patent Document 3 discloses an FCC catalyst. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-134234 A [Patent Document 2] JP 2023-109331 A [Patent Document 3] JP 2023-111238 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to develop a new alkali-aggregate reaction inhibitor which has an alkali-aggregate reaction inhibitor function while also having other functions that are useful in cement concrete. [Means for solving the problem]

[0005] As a result of intensive research into the above-mentioned problems, the inventors have found that a basic organic aluminum salt has a function of inhibiting an alkali-aggregate reaction, while also exhibiting a strength improving function, a water reducing effect, and a rust-preventing effect for reinforcing bars, which are useful in cement concrete, and have completed the present invention based on this finding.

[0006] The present invention is as follows. [1] An alkali-aggregate reaction inhibitor for cement concrete, containing a basic organic aluminum salt. [2] A method for manufacturing cement concrete using a basic organic aluminum salt as an alkali-aggregate reaction inhibitor. [Brief description of the drawings]

[0007] [Figure 1] 1A and 1B are photographs and schematic diagrams showing the rust-preventive effect of a basic organic aluminum salt on an iron plate in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present invention will be described in detail below based on preferred embodiments, but the present invention is not limited to the following embodiments and various modifications are possible within the scope of the claims. In addition, in the present invention, the expression "numeric value 1 to numerical value 2" regarding a numerical range means a numerical range including both the numerical values ​​1 and 2, with numerical value 1 being the lower limit and numerical value 2 being the upper limit, and is synonymous with "numerical value 1 or more and numerical value 2 or less."

[0009] The present invention relates to an alkali-aggregate reaction inhibitor for cement concrete, which contains a basic organic aluminum acid.

[0010] A basic aluminum organic acid salt is an aluminum organic acid salt having basicity. The basicity is defined as {(the number of chemical equivalents of aluminum in a certain amount of compound)-(the number of chemical equivalents of organic acid in a certain amount of compound)} / (the number of chemical equivalents of aluminum in a certain amount of compound)×100(%). For example, in the case of basic aluminum succinate in which the organic acid is succinic acid, when 4.6 g of aluminum and 15 g of succinic acid are contained, the basicity is {(4.6 / 27)×3-(15 / 118)×2} / {(4.6 / 27)×3}×100=50.3%.

[0011] Preferred examples of organic acids constituting basic organic acid aluminum include monocarboxylic acids, dicarboxylic acids, and oxycarboxylic acids. Examples of monocarboxylic acids include formic acid, acetic acid, propionic acid, n-butyric acid, and valeric acid. Examples of dicarboxylic acids include oxalic acid, succinic acid, maleic acid, malonic acid, phthalic acid, and glutaric acid. Examples of oxycarboxylic acids include glycolic acid, lactic acid, tartaric acid, malic acid, and citric acid. Among these, oxycarboxylic acids are preferred, and among oxycarboxylic acids, glycolic acid, lactic acid, and malic acid are preferred. Lactic acid is particularly preferred. Also preferred is a combination of lactic acid and an oxycarboxylic acid other than lactic acid.

[0012] One example of a method for producing basic organic aluminum salt is a method in which a soluble aluminum salt such as aluminum chloride, aluminum sulfate, basic aluminum chloride, or aluminum nitrate is reacted with an alkali metal or ammonium carbonate or bicarbonate, and the precipitated alumina hydrate is dissolved in an organic acid. Another example is a method in which an alkali aluminate is reacted with carbon dioxide gas, and the precipitated alumina hydrate is dissolved in an organic acid.

[0013] The alkali-aggregate reaction inhibitor is preferably made of a basic organic aluminum salt, but may contain other compounds as long as the alkali-aggregate reaction inhibitor function is not impaired.

[0014] Cement concrete is made by mixing and hardening cement, water, aggregate, and optionally adding admixtures.

[0015] Examples of cement include Portland cement, blended cement, etc. Examples of Portland cement include normal Portland cement, high-early-strength Portland cement, extra-high-early-strength Portland cement, sulfate-resistant Portland cement, moderate-heat Portland cement, low-heat Portland cement, white Portland cement, etc. Blended cement is a cement in which various admixtures are mixed with Portland cement, and examples thereof include blast-furnace cement, silica cement, fly ash cement, etc.

[0016] Examples of aggregates are fine aggregate and coarse aggregate. Only fine aggregate may be used, or both fine and coarse aggregates may be used. Examples of fine aggregates are sand, crushed sand, blast furnace slag aggregate, ferronickel slag aggregate, copper slag fine aggregate, electric furnace oxidized slag aggregate, molten slag aggregate, recycled aggregate, etc. Examples of coarse aggregates are gravel, crushed stone, blast furnace slag aggregate, ferronickel slag aggregate, electric furnace oxidized slag aggregate, molten slag aggregate, recycled aggregate, etc. The recycled aggregate includes modified recycled aggregate in which CO2 is fixed and carbonated.

[0017] Examples of admixtures include admixtures, additives, etc. Examples of admixtures include air-entraining agents, air-entraining water-reducing agents, water-reducing agents, high-performance air-entraining water-reducing agents, superplasticizers, separation-reducing agents, foaming agents, setting and hardening regulators, quick-setting agents, rust inhibitors, waterproofing agents, etc. Examples of admixtures include ultrafine powders (ground granulated blast furnace slag, fly ash, silica fume, etc.), polymers for mixing with cement, expansive agents, etc.

[0018] There are no particular restrictions on the method of using the alkali aggregate reaction inhibitor in the production of cement concrete, and it may be kneaded together with various raw materials in the production of cement concrete by a conventional method. When the amount of the alkali aggregate reaction inhibitor used is expressed in terms of basic organic aluminum salt, it is preferable that the amount of basic organic aluminum salt is in the range of 0.05 to 10 parts by mass per 100 parts by mass of aggregate. The lower limit of this range is more preferably 0.1 parts by mass, and the upper limit is more preferably 7.5 parts by mass, and even more preferably 5 parts by mass.

[0019] Known alkali-aggregate reactions include alkali-silica reaction, alkali carbonate reaction, and alkali silicate reaction. For example, the alkali-silica reaction is a phenomenon in which alkali silicate hydrate is generated by the reaction of alkali metals derived mainly from cement with reactive silica derived from aggregate. The alkali-carbonate reaction is a phenomenon in which magnesium in dolomite aggregate is converted to hydroxide in an alkaline environment caused by cement hydration, and this reacts with silica to generate magnesium silicate. The alkali-silicate reaction is said to be a reaction between clayey rock and alkali. Although there are various theories on these reactions, in recent years they have all come to be considered to be a type of alkali-silica reaction. In these reactions, it is believed that the reactants produced absorb water and expand, causing cracks. The mechanism by which basic organic acid aluminum inhibits the alkali-aggregate reaction in cement concrete is not clear, but the following is speculated. In other words, due to the pH change in concrete, the organic acid component in the basic organic aluminum salt dissociates from the aluminum component, and the organic acid component inhibits the bonding between the alkaline component and silica by coordinating and bonding with alkali metals and alkaline earth metals. In addition, the aluminum component precipitates as fine aluminum hydrate due to the pH change, and these fine aluminum hydrate particles also inhibit contact between the alkaline component and silica. It is speculated that these factors inhibit the alkali-aggregate reaction. EXAMPLES

[0020] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these.

[0021] (Basic organic aluminum salt) The commercially available "Taxeram M-160P" was used as the basic organic aluminum acid salt. "Taxeram M-160P" is a powder made of basic aluminum lactate manufactured by Taki Chemical Industry Co., Ltd., and contains 35.0% by mass of Al2O3 and 48.0% by mass of lactic acid.

[0022] The raw material mix is ​​shown in Table 1. In addition to the actual mix amounts, Table 1 also shows the relative mix amounts in parentheses when the total amount of aggregate (sintered alumina + river sand + magnesia aggregate) is 400g, which is 100 parts.

[0023] [Table 1]

[0024] For each of the Examples and Comparative Examples, a kneaded product was prepared by kneading the raw materials shown in Table 1. This kneaded product was subjected to the following evaluation tests. The amount of water in Table 1 was adjusted so that each Example and Comparative Example would have the same mixing feel. In both the Portland cement and blast-furnace cement systems, the Examples had lower values ​​than the Comparative Examples, which shows that the amount of added water can be reduced by adding basic organic aluminum salt. In other words, the water-reducing effect was confirmed.

[0025] [Evaluation test] Pot life: The kneaded material was molded into a sphere with a diameter of 3 cm in a mold, and the time until it lost its plasticity was measured by palpation. Strength: The mixture was poured into a mold (8cm long, 2cm wide, 2cm high) and then cast using a vibration molding machine. After curing for 7 days at room temperature, the mold was removed to obtain a cement concrete body. A three-point bending tester was used to measure strength. A universal strength testing machine manufactured by Marubishi Scientific Machinery Works was used as the three-point bending tester. The distance between the supports was 50mm, and the molded body was placed horizontally on the support (the 8cm length was horizontal). The surface that was on top when placed was defined as the top surface, and the entire part of the top surface that was perpendicular to the long side at the midpoint of the long side was pressed from above vertically with the suspension part, and the force at which the molded body broke was defined as the strength. · Digestion time: The kneaded material was poured into a mold (8 cm long, 2 cm wide, 2 cm high), and then poured into a vibration molding machine. After curing at 25°C for 24 hours, it was removed from the mold and dried at 80°C for 15 hours to obtain a molded body. This molded body was placed horizontally (8 cm long horizontally) in an autoclave (under saturated steam at 135°C), and then taken out at regular intervals to measure its length. The length was measured by measuring the length of the long side of each side, with the surface that was on the top when placed statically as the top surface, the opposite surface as the bottom surface, and the surface that was imaginary between the top and bottom surfaces as the middle surface. It was considered to have been digested when the length of two of the three surfaces exceeded an elongation rate of 0.3% (if the length was 8 cm before the test, it exceeded 8.024 cm). If the molded body warped, the length of the remaining two surfaces, excluding the minimum value of the three surfaces, was used. The digestion time was calculated by proportionally calculating the time it took for the elongation rate to reach 0.3% from the elongation rate at the first measurement point after the elongation rate exceeded 0.3% for the top, middle, and bottom surfaces, and then averaging these values.

[0026] Table 2 shows the results of the evaluation test.

[0027] [Table 2]

[0028] The results in Table 2 are discussed below. Regarding pot life, there was no difference between the Examples and Comparative Examples for the Portland cement system, but for the blast-furnace cement system, Example 3 showed a higher value than Comparative Example 2. When the pot life is longer, it becomes easier to secure the working time from mixing to pouring into a formwork, etc. Regarding strength, the examples showed higher values ​​than the comparative examples in both the Portland cement-based and blast-furnace cement-based concretes, confirming that the addition of basic organic aluminum salt provided a strength-enhancing function. In terms of digestion time, the examples showed higher values ​​than the comparative examples in all systems. A longer digestion time means that water absorption and expansion are less likely to occur. In other words, it means that the alkali-aggregate reaction is less likely to occur. Therefore, it was confirmed that the addition of basic organic aluminum salt suppressed the alkali-aggregate reaction.

[0029] The following tests were carried out to evaluate the rust prevention effect of rebar. The raw materials shown in Table 3 were mixed and kneaded, and an iron plate was inserted to represent rebar, to create a hardened cement product with the iron plate inserted. This was cured at 40°C for one month, and then left at room temperature for three months. After that, part of the hardened cement product was peeled off to expose the iron plate, and the state of rust was confirmed. Note that NaCl in Table 3 was added for the purpose of supplying chloride ions to generate rust.

[0030] [Table 3]

[0031] The results are shown in Figure 1. Figure 1(a) is a photograph of the actual product, and (b) is its schematic diagram. The iron plate of the comparative example had rust all over, whereas the iron plate of the example had no rust in the areas where the hardened cement was in close contact. Therefore, it was confirmed that the addition of basic organic aluminum salt provides an anti-corrosion effect for reinforcing bars. [Industrial Applicability]

[0032] According to the present invention, the basic organic aluminum salt can exhibit not only an alkali-aggregate reaction inhibitory function but also a strength improving function, a water reducing effect function, and a rust inhibitory effect function for reinforcing bars in cement concrete, and therefore the industrial applicability thereof can be said to be extremely high.

Claims

1. An alkali-aggregate reaction inhibitor for cement concrete, which contains a basic organic aluminum salt.

2. A method for producing cement concrete using a basic organic aluminum salt as an inhibitor for alkali aggregate reaction.

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