hydraulic components

Abstract

To provide a hydraulic composition with suppressed propagation of neutralization reaction.SOLUTION: Disclosed is a hydraulic composition including a hydraulic powder including Portland cement and a neutralization suppression agent including calcium nitrate. A blending ratio of the Portland cement in all powders is 10 mass% or over and 70 mass% or under. Preferably, to all powder amounts, the neutralization suppression agent in nitrate ion (NO3-, formula weight 62) conversion of 0.8 mass% or over and 5.0 mass% or under is included therein. Preferably, the hydraulic powder further includes at least one of a blast furnace slag and a fly ash.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a hydraulic composition.

Background Art

[0002] Cement hardens through a hydration reaction with water to form a hardened body. The clinker minerals that make up part or all of the cement react with water to produce hydrates such as strongly alkaline calcium hydroxide, and the pore solution in the hardened body exhibits strong alkalinity. When the hardened body is left in the atmosphere, carbon dioxide that has penetrated into the interior reacts with calcium salts such as calcium hydroxide to form calcium carbonate, and the pore solution变性from strongly alkaline to neutral, so-called "neutralization" proceeds. Neutralization proceeds from the surface of the hardened body in contact with the atmosphere. When constructing a reinforced concrete structure using cement, when neutralization proceeds to near the reinforcing bars inside the reinforced concrete structure, the passive film covering the reinforcing bars is destroyed, which contributes to the corrosion of the reinforcing bars. Then, the reinforcing bars expand compared to before corrosion, causing cracks and destruction of the hardened body, and also causing cross-sectional loss of the reinforcing bars due to corrosion, reducing the strength of the reinforced concrete structure.

[0003] In recent years, environmentally friendly cements that produce less carbon dioxide during manufacturing have been proposed. Environmentally friendly cement is a hydraulic composition having a composition equivalent to that of a mixture of one or more types of cement specified in JIS R5210, R5211, R5212, R5213, and R5214 (Portland cement, blast furnace cement, fly ash cement, silica cement, eco-cement), in which 20 to 100% is replaced with slag, fly ash, silica fume, dihydrate gypsum, hemihydrate gypsum, anhydrous gypsum, limestone powder, slaked lime, expansive agents, siliceous admixtures, or calcium salts or sodium salts. Concrete made using environmentally friendly cement is called environmentally friendly concrete. For example, Patent Document 1 proposes a hydraulic composition as an environmentally friendly cement, consisting of blast furnace slag powder, limestone powder, and two or more stimulants with different rates of calcium ion elution. Patent Document 2 proposes a slag-hardening composition as an environmentally friendly concrete, mainly composed of fine aggregate, coarse aggregate, limestone powder, slag powder, sodium carbonate, and chemical admixtures. Non-Patent Document 1 reports an example of concrete construction as an environmentally friendly concrete, in which 20-80% of Portland cement is replaced with an admixture mainly composed of blast furnace slag. However, hardened materials and concrete made using environmentally friendly cement have the problem that they use less Portland cement and are more prone to carbonation compared to hardened materials and concrete made using only Portland cement. For example, the environmentally friendly cement shown in Patent Document 1 is said to have suppressed carbonation by selecting the reaction stimulant necessary for hardening blast furnace cement, but the rate of carbonation of this environmentally friendly cement is greater than the rate of carbonation of hardened materials made using only Portland cement.

[0004] One known technique to suppress carbonation is to increase the amount of cement, thereby reducing the water-cement ratio and making the hardened material denser, which makes it more difficult for carbon dioxide to penetrate. However, this increases the amount of cement used, thus increasing costs. Also, a low water-cement ratio results in poor fluidity and reduced workability. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2014-148434 [Patent Document 2] Patent No. 5743650 [Non-patent literature]

[0006] [Non-Patent Document 1] Hiroshi Jinnai, Masaki Kato, Kaori Tateyama, and Kenji Kondo: Realization of a building constructed with environmentally friendly concrete for its main structural members and its CO2 reduction effect, Concrete Engineering, vol. 52, No. 6, pp. 528-533, 2014.6. [Overview of the project] [Problems that the invention aims to solve]

[0007] The objective is to provide a hydraulic composition in which the progress of the neutralization reaction is suppressed. [Means for solving the problem]

[0008] The means for solving the problems of the present invention are as follows. 1. As a hydraulic material Contains Portland cement and blast furnace slag. ru powder The material contains a body and a neutralization inhibitor containing calcium nitrate, and the proportion of Portland cement in the total powder is 10% by mass or more and 32.7% by mass or less. The proportion of blast furnace slag in the total powder is 60.8% by mass or more and 85% by mass or less. The neutralization inhibitor is added to the total amount of powder using nitrate ions (NO3 - A hydraulic composition characterized by containing 0.8% to 5.0% by mass of a powder (calculated on a formula weight of 62), wherein the powder does not contain limestone fine powder or fly ash. 2. As a hydraulic material Contains Portland cement and blast furnace slag. ru powderThe material contains Portland cement and a neutralization inhibitor containing calcium nitrate, wherein the proportion of Portland cement in the total powder is 10% by mass or more and 32.7% by mass or less, and the neutralization inhibitor is contained in proportion to the total amount of powder, with nitrate ions (NO3 - A hydraulic composition characterized by containing 0.8% to 5.0% by mass of a powder (calculated on a formula weight of 62), wherein the powder further contains at least one of silica fume and anhydrous gypsum. [Effects of the Invention]

[0009] The hydraulic composition of the present invention can suppress the progression of neutralization in the hardened body by containing a neutralization inhibitor containing calcium nitrate. Neutralization of the resulting hardened body can be suppressed by replacing a portion of the water added during hardening with an aqueous solution of a nitrate compound, dissolving a portion or all of the water added during hardening with a nitrate compound, or simply adding or mixing a nitrate compound as a solid. The hydraulic composition of the present invention only requires the addition of a nitrate compound in aqueous or solid form to the hydraulic composition to be neutralized, and neutralization can be suppressed while maintaining the conventional composition without changing the composition, individual amounts, or total amount of powders consisting of cement and admixtures other than the nitrate compound.

[0010] The amount of neutralization inhibitor added is determined by the amount of neutralization inhibitor relative to the total amount of powder, specifically by the amount of nitrate ions (NO3) - The effect can be obtained by adding 0.8 mass% or more (calculated as formula weight 62). While a higher addition rate increases the inhibitory effect, exceeding 5.0 mass% results in a sufficient effect, but the rate of decrease in the carbonation rate with increasing addition rate becomes smaller, and the cost increases. Therefore, it is preferable to adjust the amount within the range of 0.8 mass% to 5.0 mass%. By adding a carbonation inhibitor, the progression of carbonation can be controlled to match the required performance of the structure. [Brief explanation of the drawing]

[0011] [Figure 1]Figure showing the results of the accelerated neutralization test in Experiment 1. [Figure 2] Figure showing the results of the accelerated neutralization test in Experiment 2. [Figure 3] Figure showing the neutralization depth after 3.8 years of exposure in Experiment 2. [Figure 4] Figure showing the results of the accelerated neutralization test in Experiment 4.

Embodiments for Carrying Out the Invention

[0012] "Hydraulic composition" The hydraulic composition of the present invention contains cement and a neutralization inhibitor composed of a nitrate compound. The hydraulic composition of the present invention only needs to contain a neutralization inhibitor composed of cement and a nitrate compound, and a admixture can be contained herein. Here, in this specification, cement and the admixture are collectively referred to as powder, and the total amount thereof is referred to as the total powder amount. In addition to cement and a neutralization inhibitor, or cement, a admixture, and a neutralization inhibitor, the hydraulic composition of the present invention can contain chemical admixtures such as an AE agent, a water reducing agent, an AE water reducing agent, a high-performance water reducing agent, a high-performance AE water reducing agent, a retarder, a foaming agent, a waterproof agent, a coloring agent, a cold-resistant agent, an early strength agent, a thickening agent, etc., fine aggregates and coarse aggregates such as gravel, sand, sea sand, crushed stone, crushed sand, various slag aggregates, heavy aggregates, lightweight aggregates, recycled aggregates, etc., additives such as vinylon fiber, polypropylene fiber, glass fiber, steel fiber, carbon fiber, etc., and water such as tap water, river water, lake water, groundwater, recovered water in a ready-mixed concrete plant, water contained in a chemical admixture, crystal water contained in a neutralization inhibitor, etc.

[0013] · Cement As the cement contained in the hydraulic composition of the present invention, a hydraulic powder that reacts with water and hardens can be used without particular limitation. For example, those defined by JIS Examples of the cement include Portland cement, blast furnace cement, fly ash cement, silica cement, and eco-cement. Environmentally considerate cement can also be used. Among these, cement in which the blending ratio of Portland cement in the total powder amount where neutralization easily progresses is 80% by mass or less, blast furnace cement, fly ash cement, and environmentally considerate cement are preferable.

[0014] · Admixture Slag, fly ash, silica fume, gypsum dihydrate, gypsum hemihydrate, anhydrous gypsum, fine limestone powder, slaked lime, expansive agent, and siliceous admixture are mixtures or minor mixtures of cement defined by JIS or environmentally considerate cement, but can also be used as an admixture when making mortar or concrete using cement.

[0015] · Neutralization inhibitor The hydraulic composition of the present invention contains a neutralization inhibitor composed of a nitrate compound. As the nitrate compound, those that can be blended into the hydraulic composition can be used without particular limitation. For example, calcium nitrate, magnesium nitrate, sodium nitrate, potassium nitrate, ammonium nitrate, aluminum nitrate, etc. can be used. Further, as long as the effects of the present invention are not hindered, a neutralization inhibitor composed of other than nitrate compounds can be used in combination.

[0016] The hydraulic composition of the present invention preferably contains 0.8% by mass or more and 5.0% by mass or less of the neutralization inhibitor in terms of nitrate ions (NO3 - , formula weight 62) based on the total powder amount. When the amount of the neutralization inhibitor is less than 0.8% by mass in terms of nitrate ions, the effect of suppressing the progress of neutralization may not be sufficient. When the amount of the neutralization inhibitor is more than 5.0% by mass in terms of nitrate ions, a sufficient neutralization suppression effect can be obtained, but the improvement of the neutralization suppression effect with respect to the increase in the neutralization inhibitor reaches a plateau, and the cost becomes high.

[0017] The hydraulic composition of the present invention can be used as a paste with water, or further with chemical admixtures, or as mortar or concrete with further fine aggregate, coarse aggregate, and chemical admixtures. Concrete can be used in the form of site-mixed concrete, ready-mixed concrete, and concrete products such as concrete blocks, box culverts, and segments for shield tunnels.

[0018] The hydraulic composition of the present invention is hardened by mixing it with water and kneading it. The carbonation inhibitor may be mixed in advance as part of the hydraulic composition of the present invention, or mixed in advance with the water to be mixed, or the carbonation inhibitor may be added and mixed when mixing the hydraulic composition other than the carbonation inhibitor with water. When the nitrate compound is mixed into the hydraulic composition in solid form, it is preferable that it be in powder form so that it can be mixed uniformly. Also, when the nitrate compound is mixed into the water for hardening, it is preferable that the nitrate compound is dissolved so that it can be mixed uniformly. The method for producing the hydraulic composition of the present invention can be carried out by conventional methods, except for the addition of the nitrate compound. In other words, when using it as a paste, mortar, or concrete, the water containing the carbonation inhibitor and the other constituent materials may be mixed together in a concrete mixer or mortar mixer, or the carbonation inhibitor may be mixed together with water and the other constituent materials, or the other constituent materials excluding the carbonation inhibitor may be mixed together to produce a paste, mortar, or concrete, after which the carbonation inhibitor may be added and mixed again. When producing a paste, mortar, or concrete, the hydraulic composition of the present invention may have some or all of the other constituent materials excluding water premixed before adding water. [Examples]

[0019] "Experiment 1" Environmentally friendly cement Environmentally friendly cement, in which blast furnace slag accounts for 77.2% by mass of the total powder content, was hardened using aqueous solutions of calcium nitrate, a neutralization inhibitor, dissolved at different concentrations. Of the materials, the blast furnace slag satisfied JIS A 6206, the expansive agent satisfied JIS A 6202, the slaked lime satisfied JIS R 9001, and the limestone fine powder satisfied JIS A 5008. The calcium nitrate used was a special grade reagent (calcium nitrate tetrahydrate (Ca(NO3)2·4H2O)) manufactured by Kanto Chemical Co., Ltd. Examples 1 and 2 are for reference only.

[0020] [Table 1]

[0021] Water: Yokohama City Waterworks Bureau, tap water Blast furnace slag (containing gypsum): Manufactured by Day-C Co., Ltd., Product name: Cerament A (anhydrous) Gypsum additive: SO3 equivalent amount = 2.1%) Expanding material: Manufactured by Taiheiyo Material Co., Ltd., Product name: Expan Slaked lime: Manufactured by Okutama Kogyo Co., Ltd., Product name: Special Grade Slaked Lime Limestone fine powder: Manufactured by Miyagi Limestone Industry Co., Ltd. Calcium nitrate tetrahydrate: Manufactured by Kanto Chemical Co., Ltd., special grade reagent.

[0022] Using this cement paste, specimens approximately 3 cm in diameter and 5 cm in height were prepared and sealed and cured. After 28 days, they were demolded and stored for 7 days at 20°C and 60% RH. Subsequently, all sides except one of the bottom surfaces were coated with aluminum adhesive tape, and an accelerated carbonation test was conducted by leaving them undisturbed in an environment of 20°C, 60% RH, and a CO2 concentration of 5%. After a predetermined period, the specimen was split open, and a 1% phenolphthalein alcohol solution was sprayed onto the cross-section. The area where no color change occurred was considered the area where neutralization had progressed, and the accelerated neutralization depth was measured. The results are shown in Figure 1. It is known that neutralization progresses in proportion to the square root of the neutralization period, and the slope of the straight line obtained by approximating the relationship between the change in accelerated neutralization depth and the square root of the neutralization period (linear approximation) can be defined as the neutralization rate. In other words, the neutralization rate represents the ratio of the change in neutralization depth to the change in the square root of the accelerated neutralization period.

[0023] For pastes using environmentally friendly cement, the ratio of the neutralization rate when a neutralization inhibitor was added to the neutralization rate of Comparative Example 1, which did not contain a neutralization inhibitor, was determined. Comparative Example 2, which contained 0.5% by mass of the total powder amount (converted to 0.5 nitrate ions), had a neutralization rate ratio of 1.7, and no effect of the addition was observed. On the other hand, in Example 1, which contained 1.0% by mass of the total powder amount (converted to 1.0 nitrate ions), the neutralization rate was suppressed, and the neutralization rate ratio was approximately 0.78. In Example 2, which contained 2.0% by mass of the neutralization inhibitor (converted to 2.0 nitrate ions), the neutralization rate ratio was 0.59, confirming that neutralization was suppressed.

[0024] "Experiment 2" For Example 2 described above, instead of calcium nitrate, a concrete chemical admixture containing calcium nitrate (BASF Japan, product name: Masterset FZP99, nitrate ion content: 24% by mass) was used at a concentration of 8.3% by mass (2.0% by mass in terms of nitrate ions) relative to the total amount of powder. Fine aggregate and coarse aggregate were added to this paste to prepare concrete. This mixture is designated as Example 3. Comparative Example 3 is a mixture obtained by removing the concrete chemical admixture containing calcium nitrate from Example 3. For both Example 3 and Comparative Example 3, the fine aggregate was 2.63 g / cm³ in density according to JIS A 5308 Annex A. 3 For the crushed sand and coarse aggregate, crushed stone conforming to JIS A 5005 with a Gmax of 20 mm was used, with a fine aggregate ratio of 43% and a water-to-powder ratio of 0.36. Note that Example 3 is for reference only.

[0025] [Table 2]

[0026] In Example 3 and Comparative Example 3, a high-performance AE water-reducing agent, a retarder, and an AE agent were added, and it was confirmed that the slump and air volume satisfied the target values ​​of 15±2.5 cm and 6.0±1.5%, respectively. The high-performance AE water-reducing agent used was a polycarboxylic acid ether (BASF Japan, product name: Master Glenium SP8SV), the retarder was a complex of a modified lignin sulfonic acid compound and an oxycarboxylic acid compound (BASF Japan, product name: Master Pozzolith No. 89), and the AE agent was a high alkylcarboxylic acid anionic surfactant (BASF Japan, product name: Master Air 775). Test specimens were prepared by casting Example 3 and Comparative Example 3 into molds with internal dimensions of 100 × 100 × 400 mm. The specimens were demolded after 3 days and cured in water at 20°C until 28 days of age. After that, they were stored in an environment of 20°C and 60% RH until 56 days of age, and then covered with aluminum adhesive tape except for one side of the 100 × 400 mm specimens. After covering, the specimens were left to stand in an environment of 20°C, 60% RH, and 5% CO2 concentration, and an accelerated carbonation test was performed. After the prescribed accelerated testing period, the specimens were fractured, and a 1% phenolphthalein alcohol solution was sprayed onto the cross-section to measure the neutralization depth. The results are shown in Figure 2.

[0027] Furthermore, specimens prepared using the same method as described above and cured until 56 days old were coated with epoxy resin, except for one side of a 100 × 400 mm specimen. After coating, the specimens were exposed to rain outdoors for 3.8 years, with the exposed surface vertical and facing outward relative to the building, and the carbonation depth of the exposed surface was measured. The average annual precipitation during the exposure period was 1777 mm / year, and the atmospheric carbon dioxide concentration was 0.041%. The results are shown in Figure 3.

[0028] The neutralization inhibitor is added to the total amount of powder using nitrate ions (NO3). -By adding 2.0% by mass (calculated as formula weight 62), the carbonation rate ratio of Example 3 to Comparative Example 3 was approximately 0.36, and approximately 0.43 in the exposed environment. From this, the carbonation suppression effect was confirmed not only in paste but also in concrete containing fine and coarse aggregates, and not only in the accelerated environment but also in the actual environment.

[0029] "Experiment 3" Various types of cement Cement pastes were prepared by blending various types of cement or mixtures of cement and admixtures with the materials listed below in the mass ratios shown in Tables 3 to 9. Of the materials, ordinary Portland cement and rapid-hardening Portland cement conformed to JIS R 5210, blast furnace cement to JIS R 5211, blast furnace slag to JIS A 6206, silica fume to JIS A 6207, fly ash to JIS A 6201, and anhydrous gypsum to JIS R 9151. For calcium nitrate, special grade reagent (calcium nitrate tetrahydrate (Ca(NO3)2·4H2O)) manufactured by Kanto Chemical Co., Ltd. was used, and the crystal water contained in the calcium nitrate tetrahydrate was counted as water in Tables 3 to 9. The calcium nitrate was pre-dissolved in water added to harden the hydraulic composition before being added to the hydraulic composition. Note that Example 4 is a reference example.

[0030] Water: Yokohama City Waterworks Bureau, tap water Ordinary Portland Cement: Manufactured by Taiheiyo Cement Corporation Early-hardening Portland cement: Manufactured by Taiheiyo Cement Corporation Blast furnace slag (without gypsum): Manufactured by Day-C Corporation, Product name: Cerament Blast furnace slag (containing gypsum): Manufactured by Day-C Corporation, Product name: Cerament A (anhydrous gypsum) Kou was added, and the amount added was equivalent to 2.1% of SO3. Silica Fume: Manufactured by Day-C Co., Ltd. Fly ash: Manufactured by Techno Chubu Co., Ltd., Type II Anhydrous gypsum: Manufactured by Day-C Co., Ltd. Calcium nitrate: Manufactured by Kanto Chemical Co., Ltd., special grade reagent, tetrahydrate.

[0031] Ordinary Portland cement [Table 3]

[0032] Equivalent to blast furnace cement (Type C), 30% by mass of Portland cement [Table 4]

[0033] Equivalent to fly ash cement (Type C), 70% by mass of Portland cement [Table 5]

[0034] Environmentally friendly cement (1), Portland cement 10% by mass [Table 6]

[0035] Environmentally friendly cement (2), Portland cement 25% by mass [Table 7]

[0036] Environmentally friendly cement (3), Portland cement 25% by mass [Table 8]

[0037] Environmentally friendly cement (4), Portland cement 32.7% by mass [Table 9]

[0038] In Tables 3-9, Table 3 represents ordinary Portland cement, Table 4 represents a mixture of ordinary Portland cement and blast furnace slag equivalent to blast furnace cement type C, Table 5 represents a mixture of ordinary Portland cement and fly ash equivalent to fly ash cement type C, and Tables 6-9 represent environmentally friendly cements.

[0039] Using each of the hydraulic compositions listed in Tables 3-9, accelerated neutralization tests were conducted in the same manner as in Experiment 1. From the results up to 28 days of accelerated neutralization, the neutralization rate was calculated, and for each, the neutralization rate ratio was determined compared to the comparative example (where the number following the "Example" is the same as the "Comparative Example" number, and the combinations of corresponding Examples and Comparative Examples are shown in the same table. For example, Example 4 corresponds to Comparative Example 4, and that combination is shown in Table 3) without the addition of the corresponding neutralization inhibitor. For each hydraulic composition, the neutralization rate of the Comparative Example and the corresponding Example, and the calculated neutralization rate ratio are shown in Table 10.

[0040] [Table 10]

[0041] It was confirmed that the progression of carbonation can be suppressed in hydraulic compositions with a low proportion of Portland cement, which are prone to carbonation. While it is expected that the progression of carbonation is also suppressed for Portland cement, it is presumed that measurement errors significantly affect the measured carbonation rate ratio because Portland cement is inherently resistant to carbonation.

[0042] Experiment 4: Types of Nitrate Compounds To the formulation of Comparative Example 1, magnesium nitrate (hexahydrate), ammonium nitrate, sodium nitrate, and potassium nitrate were added in the proportions shown in Table 11 to form a cement paste. All of these nitrates were special grade reagents manufactured by Kanto Chemical Co., Ltd. Examples 11 to 14 are for reference only.

[0043] [Table 11]

[0044] Using each of the hydraulic compositions listed in Table 11, accelerated neutralization tests were conducted in the same manner as in Experiment 1. The neutralization rate coefficient was calculated from the results up to 28 days of the neutralization period. The relationship between the amount of neutralization inhibitor converted to nitrate ions and the neutralization rate coefficient was determined. Figure 4 shows the ratio of the neutralization rate coefficients of Examples 11-14 to the neutralization rate coefficient of Comparative Example 1, which did not contain any neutralization inhibitor.

[0045] By adding magnesium nitrate, ammonium nitrate, sodium nitrate, and potassium nitrate, the rate of neutralization could be reduced to 0.4 to 0.9 times its original rate. It has been confirmed that the progression of carbonation can be suppressed in various types of cement using a carbonation inhibitor consisting of nitrate compounds. Furthermore, it has been confirmed that the progression of carbonation can be further suppressed by increasing the amount of carbonation inhibitor added. Even when the composition of powders in the paste, mortar, and concrete was changed, the carbonation depth could be reduced by the carbonation inhibitor. In other words, it was confirmed that the carbonation inhibitor of the present invention can suppress the progression of carbonation in various types and formulations of cement paste, mortar, and concrete.

Claims

1. A powder containing Portland cement and blast furnace slag as hydraulic materials, and a neutralization inhibitor containing calcium nitrate, The proportion of Portland cement in the total powder is 10% by mass or more and 32.7% by mass or less. The proportion of blast furnace slag in the total powder is 60.8% by mass or more and 85% by mass or less. The neutralization inhibitor is added to the total amount of powder using nitrate ions (NO ３ － , when converted to formula weight 62), it contains 0.8% by mass or more and 5.0% by mass or less. The aforementioned powder is a hydraulic composition characterized by not containing limestone fine powder and fly ash.

2. A powder containing Portland cement and blast furnace slag as a hydraulic material, and a neutralization inhibitor containing calcium nitrate, The proportion of Portland cement in the total powder is 10% by mass or more and 32.7% by mass or less. The proportion of blast furnace slag in the total powder is 60.8% by mass or more and 85% by mass or less. The neutralization inhibitor is added to the total amount of powder using nitrate ions (NO ３ － , when converted to formula weight 62), it contains 0.8% by mass or more and 5.0% by mass or less. The hydraulic composition is characterized in that the powder further contains at least one of silica fume and anhydrous gypsum.

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