Cement admixture for suppressing expansion, cement composition and method for producing the same, alkali-silica reaction inhibitor, method for inhibiting alkali-silica reaction, and binder for inhibiting alkali-silica reaction

Abstract

To provide an expansion-inhibiting cement admixture while sufficiently reducing the flowability of cement composition slurry and the adverse effect of the hardened material of the composition on intensity in the beginning of material age.SOLUTION: An alkali silica reaction-depressing cement composition is obtained by making an expansion-inhibiting cement admixture including an FCC catalyst include in cement, aggregate and water. The addition amount of the FCC catalyst into the cement is preferably 1 mass% or more but 30 mass% or less. The mixed cement by Portland cement, blast furnace cement, silica cement, fly-ash cement and the like, and the special cement such as eco-cement or alumina cement can be used as the cement.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a cement admixture for suppressing expansion, a cement composition and a method for producing the same, an alkali-silica reaction inhibitor, a method for suppressing alkali-silica reaction, and a binder for suppressing alkali-silica reaction. [Background technology]

[0002] The durability of concrete is a crucial issue in Japan, a country prone to earthquakes. One cause of concrete deterioration is cracking due to concrete expansion. One of the causes of this expansion is the alkali-silica reaction. The alkali-silica reaction is a phenomenon in which alkali silica gel, produced by a chemical reaction between alkali metals mainly supplied from cement and amorphous silica in reactive aggregates, absorbs water and expands, causing cracks in the concrete. As the reaction progresses, these cracks often occur throughout the entire concrete structure, leading to a decrease in the durability of the structure. Therefore, suppressing the alkali-silica reaction is desirable, and methods for doing so include using silica fume or fly ash as cement admixtures.

[0003] For example, Non-Patent Document 1 clarifies the influence of the quality characteristics of silica fume on various properties of concrete, and also describes the effect of silica fume on suppressing alkali-silica reaction.

[0004] Non-patent document 2 evaluates the relationship between the physical and chemical properties of fly ash and its effect in suppressing alkali-silica reactions, and discusses the mechanism by which fly ash suppresses alkali-silica reactions. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Proceedings of the Japan Society of Civil Engineers Vol.520 / V-28,87-98,1995.8 [Non-Patent Document 2] Proceedings of the Japan Society of Civil Engineers E Vol.63 No.3,379-395,2007.7 [Overview of the project] [Problems that the invention aims to solve]

[0006] By using silica fume or fly ash as cement admixtures, it is possible to suppress the alkali-silica reaction and, to some extent, the expansion of the cement composition. However, it is known that when silica fume or fly ash are used as cement admixtures, the fluidity of the cement composition slurry and the strength of the hardened product of the composition in the early stages of curing are reduced.

[0007] Therefore, the object of the present invention is to provide a cement admixture that can suppress alkali-silica reaction while sufficiently reducing adverse effects on the fluidity of the cement composition slurry and the strength of the hardened product of the composition in the early stages of its lifespan. [Means for solving the problem]

[0008] This invention provides a cement admixture for suppressing expansion, which includes an FCC catalyst.

[0009] The present invention provides a cement admixture for suppressing expansion, wherein the composition of the FCC catalyst has an SiO2 content of 30 to 85% by mass and an Al2O3 content of 10 to 60% by mass. The SiO2 or Al2O3 content referred to here is measured and calculated by converting the Si or Al component in the FCC catalyst composition to SiO2 or Al2O3.

[0010] The present invention provides a cement composition comprising the aforementioned cement admixture, cement, aggregate, and water.

[0011] The present invention provides a cement composition having an FCC catalyst content of 1% by mass or more and 30% by mass or less relative to the cement.

[0012] The present invention provides a cement composition comprising the aforementioned cement admixture, cement, aggregate, and water, wherein the expansion rate of the aggregate at 26 weeks of age, as measured in accordance with JIS A1146:2017, is 0.05% or more.

[0013] The present invention provides a method for producing a cement composition, which includes the step of mixing the aforementioned cement admixture, cement, aggregate, and water.

[0014] The present invention provides an alkali-silica reaction inhibitor for cement compositions, comprising an FCC catalyst.

[0015] The present invention provides a method for suppressing the alkali-silica reaction of a cement composition, wherein a cement admixture containing an FCC catalyst is mixed in one of the steps of manufacturing a cement composition containing cement, aggregate, and water.

[0016] The present invention provides a binder for inhibiting alkali-silica reactions in cement compositions, which includes an FCC catalyst. [Effects of the Invention]

[0017] According to the cement admixture of the present invention, alkali-silica reaction can be suppressed while sufficiently reducing adverse effects on the fluidity of the cement composition slurry and the strength of the hardened product of the composition in the early stages of curing. [Modes for carrying out the invention]

[0018] (FCC catalyst) FCC catalysts are catalysts containing clays such as zeolite, alumina, silica, and kaolin, and are a general term for catalysts used in the process of catalytic cracking of feedstock oil in a fluidized bed (FCC process). For example, in the process of fractionating gasoline and LCO from low-grade heavy feedstock oil, they are used for cracking high-molecular-weight residual oil and as metal trapping agents for metals such as V and Ni. In FCC catalysts, ion-exchanged zeolite is usually appropriately distributed on a substrate composed of the aforementioned alumina, silica, kaolin, etc., forming spherical small-particle-size powder.

[0019] In addition, various grades exist depending on differences in function. Specifically, commercially available FCC catalysts, FCC catalysts used in the FCC process (hereinafter referred to as spent FCC catalysts) and the like can be used. In particular, the use of spent FCC catalysts is excellent in terms of cost reduction effects and being environmentally friendly through the reuse of waste.

[0020] The Al₂O₃ content relative to the total amount of the FCC catalyst is 10 to 60% by mass, preferably 15 to 55% by mass, more preferably 20 to 55% by mass, still more preferably 25 to 55% by mass, and even more preferably 25 to 50% by mass. In addition, the SiO₂ content relative to the total amount of the FCC catalyst is 30 to 85% by mass, preferably 35 to 80% by mass, more preferably 40 to 75% by mass, still more preferably 40 to 70% by mass, and even more preferably 45 to 63% by mass.

[0021] As an example of an FCC catalyst, the average particle diameter is preferably 20 to 90 μm, more preferably 40 to 90 μm, and still more preferably 50 to 80 μm. In addition, the FCC catalyst may be pulverized before use.

[0022] As an example of an FCC catalyst, the specific surface area is 50 m 2 / g or more, preferably 50 to 300 m 2 / g, more preferably 80 to 250 m 2 / g, and even more preferably.

[0023] The average particle size is measured by the sieving method, and the specific surface area is measured by the BET adsorption method.

[0024] (Cement admixture for preventing expansion) FCC catalysts can suppress the expansion of cement compositions. Therefore, the FCC catalyst itself, when used as a cement admixture, can also be referred to as an expansion-suppressing cement admixture. Furthermore, the FCC catalyst can be mixed with known expansion-suppressing materials to the extent that its properties are not lost compared to when it is used alone, and this mixture can also be referred to as an expansion-suppressing cement admixture. For example, silica fume, fly ash, or other components mentioned above can be mixed with the FCC catalyst and used as a cement admixture.

[0025] (Other ingredients) Other examples of components include blast furnace slag, lithium nitrite, lithium-containing minerals, dicarboxylic acids or their salts, dicarboxylic acid esters, and acetic acid or its salts.

[0026] (Cement composition) The cement composition of the present invention comprises cement, aggregate, and water. In addition, it comprises the aforementioned cement admixture. The form of the cement composition also includes slurry, hardened material, structure, etc.

[0027] As a result of diligent research, the inventors discovered that by incorporating the FCC catalyst into cement, which is a hydraulic component, it is possible to suppress the occurrence of alkali-silica reaction, which is one of the causes of deterioration of cement compositions, while sufficiently reducing the adverse effects on the fluidity of the cement composition slurry and the strength of the hardened product in the early stages of its lifespan.

[0028] Due to the functions of the FCC catalyst described above, the FCC catalyst used in this invention functions as an alkali-silica reaction inhibitor for cement admixtures and cement compositions that suppress expansion.

[0029] The content of the FCC catalyst in the cement is preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 25% by mass or less, and even more preferably 5% by mass or more and 20% by mass or less. By setting the content of the FCC catalyst in the cement to the above range, it is possible to further sufficiently reduce the adverse effects on the fluidity of the slurry of the cement composition and the strength of the hardened product of the composition in the early stages of age, while further sufficiently reducing the occurrence of alkali-silica reaction, which is one of the causes of deterioration of the cement composition.

[0030] Cement composition 1 m 3 The total alkali (Na2Oeq) content per unit is preferably 1 to 10 kg, more preferably 2 to 7 kg, and even more preferably 3 to 5 kg. This range allows the hardened cement composition to develop sufficient strength.

[0031] Total alkalinity can be measured using a finely ground powder of the hardened cement composition as the measurement target, according to the measurement method described in JIS R5202:2015. If the amount of alkali in each material used in the cement composition is known, the alkalinity may be calculated by summing the alkalis in each material according to Annex B of JIS A5308:2019. Methods to adjust the total alkalinity to the above range include adding metal hydroxides such as sodium hydroxide or potassium hydroxide.

[0032] The cement used can include various types of Portland cement such as ordinary Portland cement, rapid-hardening Portland cement, ultra-rapid-hardening Portland cement, moderate-heat Portland cement, low-heat Portland cement, and sulfate-resistant Portland cement; blended cements such as blast furnace cement, silica cement, and fly ash cement; and special cements such as eco-cement and alumina cement. These can be used individually or in combination. As these cements, for example, cements specified in JIS R5210:2019, JIS R5211:2009, JIS R5212:2009, JIS R5213:2009, and JIS R5214:2019 can also be used.

[0033] Examples of aggregates include fine aggregate and coarse aggregate. Depending on the properties of the desired composition, these aggregates can be used in the form of mortar using only fine aggregate, or in the form of concrete using both fine and coarse aggregate.

[0034] Examples of fine aggregates include natural aggregates such as river sand, mountain sand, land sand, and sea sand; artificial aggregates such as crushed sand, silica sand, blast furnace slag aggregate, ferronickel slag aggregate, and electric furnace oxidized slag aggregate; recycled aggregates; and glass cullet. These can be used individually or in combination. Examples of these fine aggregates include those specified in JIS A1102:2014.

[0035] Examples of coarse aggregates include river gravel, sea gravel, mountain gravel, crushed stone, and crushed slag. These can be used individually or in combination. Examples of these coarse aggregates include those specified in JIS A5005:2020.

[0036] From the viewpoint of obtaining a hardened cement composition with increased density and sufficient strength, the fine aggregate content is preferably 50 to 450 parts by mass, more preferably 100 to 350 parts by mass, and even more preferably 150 to 300 parts by mass, per 100 parts by mass of cement.

[0037] From a similar viewpoint, if coarse aggregate is included, the content of the coarse aggregate is preferably 100 to 450 parts by mass, more preferably 150 to 400 parts by mass, and even more preferably 200 to 350 parts by mass, per 100 parts by mass of cement.

[0038] The aggregate contained in the cement composition preferably has an expansion rate within a predetermined range. Specifically, the expansion rate of the aggregate at 26 weeks of age, as measured in accordance with JIS A1146:2017, is preferably 0.05% or more, more preferably 0.05 to 5%, even more preferably 0.10 to 3%, even more preferably 0.20 to 2%, and most preferably 0.40 to 1%. By having an expansion rate within this range, the alkali-silica reaction suppression effect in the resulting cement composition can be fully exhibited.

[0039] There is a correlation between the expansion rate of aggregate and the occurrence of alkali-silica reaction. With this expansion rate, alkali-silica reaction can be sufficiently suppressed even when using aggregate with an expansion rate considered "not harmless" (0.1% or more at 26 weeks of age). Furthermore, since the expansion rate of aggregate can vary depending on its origin, harvesting time, or the raw materials used, this eliminates the need to spend excessive time and cost on selecting the aggregate to be used, and allows for the efficient use of resources.

[0040] The aforementioned aggregate expansion rate is preferably met in at least the fine aggregate from the viewpoint of suppressing alkali-silica reaction, and more preferably in both the fine and coarse aggregate when coarse aggregate is used.

[0041] The oven-dry density of the fine aggregate is 2.4-5 g / cm³. 3 Preferably, it is 2.5-4 g / cm³. 3 It is more preferable that the concentration be 2.5-3 g / cm³. 3is even more preferable. When the fine aggregate has such a density, the alkali-silica reaction can be effectively suppressed, and the quality of the obtained cement composition is improved. The absolute dry density can be measured, for example, in accordance with JIS A1109:2020. In addition, in the present specification, the quality of a cement composition means the strength after hardening, durability, watertightness, crack resistance, performance for protecting steel materials, and the like.

[0042] The surface-dry density of the fine aggregate is 2.4 to 5 g / cm 3 , preferably 2.5 to 4 g / cm 3 , more preferably 2.6 to 3 g / cm 3 is even more preferable. When the fine aggregate has such a density, the alkali-silica reaction can be effectively suppressed, and the quality of the obtained cement composition is improved. The surface-dry density can be measured, for example, in accordance with JIS A1109:2020.

[0043] The water absorption of fine aggregate is preferably as low as possible, but it is preferably more than 0% and 4.0% or less, more preferably 0.5 to 3.0%, and even more preferably 1.0% to 2.0%. When the fine aggregate has such a water absorption, the workability of the slurry of the cement composition during placement and pumping is improved, and the quality of the obtained cement composition is improved. The water absorption can be measured, for example, in accordance with JIS A1109:2020.

[0044] The fineness modulus of fine aggregate is preferably 1.0 to 4.5, more preferably 1.5 to 4.0, even more preferably 2.0 to 3.5, and still more preferably 2.5 to 3.0. When the fine aggregate has such a fineness modulus, the effect of improving the workability of the slurry of the cement composition in a fresh state is exhibited. The fineness modulus can be measured, for example, in accordance with JIS A1102:2020.

[0045] The water used can be any water commonly used in this technology, such as tap water, well water, rainwater, distilled water, purified water, or deionized water, without any particular limitations.

[0046] From the viewpoint of further increasing the strength of the hardened cement composition, the water-cement ratio (ratio of water mass to cement mass) is preferably 0.3 to 0.7, more preferably 0.35 to 0.65, and even more preferably 0.4 to 0.6.

[0047] Insofar as the effects of the present invention are achieved, other admixtures other than the cement, aggregate, water, and cement admixture for suppressing expansion described above may be added in any order or simultaneously as needed.

[0048] Other admixtures besides cement admixtures for suppressing expansion include, for example, siliceous admixtures specified in JIS R5212:2009, gypsum, calcium carbonate, limestone or its powder, chemical admixtures, etc.

[0049] Examples of chemical admixtures include those specified in JIS A6204:2011, specifically water-reducing agents, high-performance water-reducing agents, air-entraining agents, air-entraining water-reducing agents, defoaming agents, shrinkage-reducing agents, fluidizing agents, thickeners, and curing accelerators.

[0050] (Method for producing cement composition and method for suppressing alkali-silica reaction) The cement composition of the above-described embodiment is manufactured by mixing cement, aggregate, water, and a cement admixture for suppressing expansion that constitute the cement composition. The cement admixture for suppressing expansion, i.e., the alkali-silica reaction inhibitor for the cement composition, is added to and mixed with the raw materials at any step in the mixing process of these raw materials.

[0051] For example, the cement and the admixture may be placed in the mixer used for mixing, and then the aggregate and water may be added sequentially. Alternatively, the cement and aggregate may be placed in the mixer, then the admixture may be added, and then the water may be mixed. Furthermore, the cement, aggregate, and water may be placed in the mixer, and then the admixture may be added. In addition, if admixtures other than the cement admixture for expansion suppression are used, both may be placed in the mixer separately or at the same time. Furthermore, one may be placed in the mixer and mixed before the other is added.

[0052] By mixing in this manner, a method for suppressing alkali-silica reaction in cement compositions can be provided. Specifically, the alkali-silica reaction suppression method for cement compositions of the present invention involves mixing an expansion-suppressing cement admixture containing an FCC catalyst in one of the steps of manufacturing a cement composition containing cement, aggregate, and water.

[0053] The mixer used for mixing is not particularly limited; chemical mixers, mortar mixers, twin-shaft forced mixers, pan mixers, grout mixers, etc., can be used.

[0054] (Binding agent for inhibiting alkali-silica reaction) The binder is a substance that reacts with water to produce a material that contributes to the strength development of the hardened cement composition. Specifically, this includes cement, blast furnace slag powder, fly ash, etc. The alkali-silica reaction inhibitory binder of the present invention comprises an FCC catalyst, and the binder further comprises cement. Examples of cement include the types of cement described above. One of these may be used alone, or two or more may be used in combination. In addition, the FCC catalyst and other admixtures may be added to the cement as appropriate. The alkali-silica reaction-inhibiting binder of the present invention contains an FCC catalyst, and therefore can suppress the alkali-silica reaction.

[0055] The cement admixtures and binders of the present invention, by containing an FCC catalyst, can suppress the alkali-silica reaction of cement compositions, and therefore function as alkali-silica reaction inhibitors for cement compositions.

[0056] The cement compositions of the above embodiments can suppress alkali-silica reactions while exhibiting fluidity in the slurry and strength in the hardened product. Since these cement compositions contain an FCC catalyst, which is one of the features for suppressing alkali-silica reactions, they are also advantageous in that they can preventively suppress alkali-silica reactions. Furthermore, by using, for example, FCC waste catalysts, manufacturing costs can be reduced, and the technology can contribute to global environmental protection by promoting the effective utilization of industrial waste. [Examples]

[0057] The present invention will be described in detail below with reference to examples. The present invention is not limited to these examples. In the following examples, unless otherwise specified, "%" means mass%.

[0058] [1. Materials used] The materials used are shown in Table 1 below. For the sake of evaluation, in this example, mortar containing only fine aggregate was used for evaluation. Each alkali content is a value measured according to JIS R5202:2015.

[0059] [Table 1]

[0060] [2. Mortar Mixing] Table 2 shows the composition of the cement (mortar) used in the alkali-silica reaction inhibition test. The composition conformed to JIS A1146:2017, and the admixtures were added in the proportions shown in Table 3, using the materials shown in Table 1. Glass cullet and river sand, known as reactive aggregates that promote alkali-silica reactions, were used as aggregates. The particle size adjustment of the glass cullet and river sand conformed to JIS A1146:2017 and is shown in Table 2. The total alkali content of the cement was adjusted to 1.2% by adding an aqueous sodium hydroxide solution. Separately, a sample without admixtures was also prepared.

[0061] [Table 2]

[0062] The cement composition (mortar) used in the flow value and compressive strength tests consisted of a mass ratio of 1 part cement or cement-admixture mixture, 2.25 parts standard sand, and 0.5 parts water. The admixture was added in the proportions shown in Table 4.

[0063] [3. Evaluation of the rate of expansion] Using cement compositions with the materials mixed as shown in Table 2, test specimens were prepared according to the method described in JIS A1146:2017, and the expansion rate of the test specimens was measured at 4 weeks (28 days) or 8 weeks (56 days) of age. Curing was carried out by covering the test specimens with absorbent paper that kept moisture constantly retained to prevent leakage, placing them in a sealed plastic bag, and maintaining an environment of 40±2℃ and relative humidity of 95%RH or higher. The results are shown in Table 3. The criteria for judgment shown in Table 3 are also shown below. ○: Expansion rate is less than 0.1%. △: Expansion rate is 0.1% or more, but less than 0.2%. ×: Expansion rate is 0.2% or higher. However, the "%" here represents the rate of change in length, not the percentage of mass.

[0064] [4.15 mortar flow evaluation] Mortar flow was evaluated in accordance with "12.2 Measurement of Flow Value" described in JIS R5201:2015. The results are shown in Table 4 below. The criteria for evaluation shown in Table 4 are also shown below. ○: Flow value is 185 mm or more. △: Flow value is 155mm or more but less than 185mm. ×: Flow value is less than 155 mm.

[0065] [5. Evaluation of compressive strength] The compressive strength was evaluated according to "11.5 Preparation of specimens" in JIS R5201:2015. After sealing and curing at 23±3℃ for 24±2 hours, the specimen was demolded to obtain the specimen, and then cured in water at 23±3℃ until the material was 28 days old. The compressive strength (N / mm²) was then measured according to "11.6 Measurement" in JIS R5201:2015. 2 ) was measured.

[0066] The compressive strength of the material without admixtures was set to 100, and the compressive strength with each admixture was expressed as a relative value. The results are shown in Table 4 below. The criteria for evaluation shown in Table 4 are also shown below. ○: Relative compressive strength value of 96 or higher. △: Relative compressive strength value is 93 or higher but less than 96. ×: Relative compressive strength is less than 93.

[0067] [Table 3]

[0068] [Table 4]

[0069] As shown in Table 3, the expansion rate of Example 1 is smaller than that of Comparative Example 1, indicating that the alkali-silica reaction can be suppressed. Furthermore, from Example 2, it can be seen that the alkali-silica reaction can be further suppressed by increasing the amount of FCC catalyst. From Examples 1 and 3, it can be seen that the alkali-silica reaction can be similarly suppressed even when using FCC catalysts with different SiO2 and Al2O3 content. From Examples 1 and 2 and Comparative Examples 2 and 4, it can be seen that the FCC catalyst can suppress the alkali-silica reaction more effectively than fly ash. Furthermore, from Examples 4 and Comparative Examples 5 and 6, it can be seen that the FCC catalyst can suppress the alkali-silica reaction even when reactive aggregate is used, and that its effect is even greater than that of fly ash. Both FCC catalysts and fly ash are compositions mainly composed of SiO2 and Al2O3, and there is no significant difference in their content, but since their alkali-silica reaction suppression effects differ greatly, it is thought that the difference in alkali-silica suppression effect between FCC catalysts and fly ash is due to the difference in their synthesis processes.

[0070] Furthermore, as can be seen from Example 5 and Comparative Examples 7 to 9 shown in Table 4, the FCC catalyst does not significantly reduce the fluidity of the cement composition slurry, and moreover, the compressive strength of the hardened product of the composition can be maintained at the strength of the product without the admixture. Since silica fume has a significant adverse effect on the fluidity of the cement composition slurry when added, and fly ash has a significant drawback in that it reduces the compressive strength of the hardened product of the cement composition when added, the FCC catalyst is a well-balanced and excellent admixture that is superior in its ability to suppress the alkali-silica reaction, while also having little impact on the fluidity of the cement composition slurry and the strength development of the hardened product of the composition.

[0071] Furthermore, by using FCC waste catalyst as an FCC catalyst, this technology offers excellent cost reduction benefits and can contribute to global environmental protection by promoting the effective utilization of industrial waste.

Claims

1. Includes FCC spent catalyst, SiO in the composition of the FCC waste catalyst ２ The content is 57.8 to 85% by mass, Al ２ O ３ A cement admixture for suppressing expansion, having a content of 15 to 29.6% by mass.

2. A cement composition comprising the cement admixture, cement, aggregate, and water described in claim 1.

3. The cement composition according to claim 2, wherein the content of the FCC waste catalyst relative to the cement is 1% by mass or more and 30% by mass or less.

4. The aggregate was measured at 26 weeks of age in accordance with JIS A1146:2017. The cement composition according to claim 2 or 3, wherein the expansion rate is 0.05% or more.

5. A method for producing a cement composition, comprising the step of mixing the cement admixture, cement, aggregate, and water described in claim 1.

6. Includes FCC spent catalyst, SiO in the composition of the FCC waste catalyst ２ The content is 57.8 to 85% by mass, Al ２ O ３ An alkali-silica reaction inhibitor for cement compositions, having a content of 15 to 29.6% by mass.

7. A method for suppressing the alkali-silica reaction of a cement composition, comprising a process for manufacturing a cement composition containing cement, aggregate, and water, wherein a cement admixture containing FCC waste catalyst is mixed in one of the processes, In the composition of the FCC spent catalyst, SiO ２ has a content of 57.8 to 85% by mass, and Al ２ O ３ has a content of 15 to 29.6% by mass. The present invention relates to a method for inhibiting alkali-silica reaction of a cement composition.

8. Includes FCC spent catalyst, SiO in the composition of the FCC waste catalyst ２ The content is 57.8 to 85% by mass, Al ２ O ３ A binder for inhibiting alkali-silica reaction in cement compositions, having a content of 15 to 29.6% by mass.

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