Concrete member and method for manufacturing concrete member

Abstract

To provide a concrete member capable of suppressing progress of neutralization, and a method for manufacturing the concrete member.SOLUTION: A concrete member according to the present invention is a concrete member containing a hydraulic powder, a fine aggregate, a coarse aggregate, water, and a hardening accelerator, wherein the hydraulic powder contains a blast-furnace slag fine powder, an expansive additive, and slaked lime, a content of the blast-furnace slag fine powder is 80 parts by mass or more with respect to 100 parts by mass of the hydraulic powder, the hardening accelerator contains at least one of a nitrate ion and a nitrite ion, and the hardening accelerator mixed from surfaces of the concrete member is 0.5 to 1. 6kg / m2.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a concrete member capable of suppressing the progress of carbonation, and a method for manufacturing a concrete member. [Background technology]

[0002] The majority of CO2 emissions from the production of materials such as concrete compositions come from the production of Portland cement. Therefore, using ground granulated blast furnace slag instead of Portland cement can significantly reduce CO2 emissions. However, concrete members that do not use Portland cement (or that use only a small amount of Portland cement) have the problem of being prone to carbonation.

[0003] The following methods can be used to suppress the progress of carbonation of concrete members. For example, there is a method of applying a finishing coating material for architecture to the surface of a concrete member as specified in JISA6909:2014 (hereinafter referred to as the "coating material application method" as appropriate). According to this method, the coating film formed on the surface of the concrete member can suppress the penetration of carbon dioxide and the progression of carbonation. There is also a method of increasing the amount of hardening composition used in the concrete composition (hereinafter referred to as the "hardening composition increasing method" as appropriate). This method makes the concrete member dense overall, thereby suppressing the penetration of carbon dioxide and the progress of carbonation. Furthermore, Patent Document 1 discloses a method using a neutralization inhibitor made of a nitrate compound (referred to as the "method according to Patent Document 1" where appropriate). According to this method, the progress of neutralization can be inhibited by the nitrate compound. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7372159 Summary of the Invention [Problem to be solved by the invention]

[0005] The coating method typically involves applying color or decorative patterns to the surface of the component, which can potentially obscure the unique concrete base material design. Furthermore, coating materials deteriorate over time, requiring maintenance such as repainting. The method of increasing the curing composition requires a large amount of curing composition to densify the entire component, which is economically problematic. In addition, increasing the amount of curing composition used also causes problems such as a decrease in workability due to an increase in viscosity and the occurrence of cracks due to an increase in autogenous shrinkage strain. The method disclosed in Patent Document 1 aims to suppress carbonation throughout the concrete member by mixing an expensive nitrate compound into the concrete when mixing it, but this is not rational because the progress of carbonation is limited to the surface layer. Therefore, more expensive nitrate compounds must be used than necessary, and there is room for economic improvement. In view of these circumstances, the present inventors have wished to create a new concrete member that can inhibit the progress of carbonation, and a method for manufacturing the same.

[0006] Therefore, an object of the present invention is to provide a concrete member that can suppress the progress of carbonation, and a method for manufacturing a concrete member. [Means for solving the problem]

[0007] The above problems can be solved by the following means. The concrete member according to the present invention is a concrete member containing hydraulic powder, fine aggregate, coarse aggregate, water, and a hardening accelerator, wherein the hydraulic powder includes ground granulated blast furnace slag, an expansive material, and slaked lime, and the content of the ground granulated blast furnace slag is 80 parts by mass or more per 100 parts by mass of the hydraulic powder, and the hardening accelerator includes at least one of nitrate ions and nitrite ions, and the hardening accelerator mixed into the surface of the concrete member is 0.5 to 1.6 kg / m 2 is. According to the present invention, the content of ground granulated blast furnace slag per 100 parts by mass of hydraulic powder is 80 parts by mass or more, which allows for a reduction in CO2 emissions compared to conventional blast furnace cement (30 to 70 parts by mass). Furthermore, according to the present invention, a predetermined amount of hardening accelerator is mixed into the surface of the concrete member, thereby improving the resistance to carbonation on the surface where carbonation is likely to progress, thereby rationally suppressing the progress of carbonation. Therefore, the carbonation suppression effect can be appropriately achieved while reducing the amount of expensive hardening accelerator used. In addition, unlike conventional coating application methods, the present invention does not require maintenance work such as repainting, and the concrete base can be utilized as a design (exposed finish).Furthermore, unlike conventional methods of increasing the hardening composition, the present invention does not cause problems such as a decrease in workability due to an increase in viscosity or the occurrence of cracks due to an increase in autogenous shrinkage strain. The concrete member according to the present invention contains calcium carbonate, and the content of the ground granulated blast furnace slag is 40 to 80 parts by mass, the content of the calcium carbonate is 5 to 50 parts by mass, and the total content of the hydraulic powder and the calcium carbonate powder in the concrete member is 0.35 to 0.70 ton / m 3 Furthermore, the concrete member according to the present invention preferably has a water to powder ratio of 30% or less when it does not contain calcium carbonate, and a water to powder ratio of 41% or less when it contains calcium carbonate. According to the present invention, since the content of materials, etc. is specified, the concrete that forms the concrete member can more reliably exhibit the carbonation suppression effect of suppressing the progress of carbonation. The method for manufacturing a concrete member according to the present invention includes a casting step of mixing and casting a concrete composition containing hydraulic powder, fine aggregate, coarse aggregate, and water, and a mixing step of mixing a hardening accelerator into the surface of the cast concrete member, wherein the hydraulic powder includes ground granulated blast furnace slag, an expansive material, and hydrated lime, and the content of the ground granulated blast furnace slag is 80 parts by mass or more per 100 parts by mass of the hydraulic powder, and the hardening accelerator includes at least one of nitrate ions and nitrite ions, and the hardening accelerator mixed into the surface of the concrete member is 0.5 to 1.6 kg / m 2 The hardening accelerator is mixed in the mixing step within 7 days after mixing in the casting step. According to the present invention, the above-mentioned concrete member that exhibits the carbonation suppression effect can be manufactured. [Effects of the Invention]

[0008] The concrete member according to the present invention can suppress the progress of carbonation. According to the method for manufacturing a concrete member of the present invention, a concrete member capable of suppressing the progress of carbonation can be manufactured. [Brief explanation of the drawings]

[0009] [Figure 1A] FIG. 2 is a diagram showing the shape and dimensions of a test specimen in Example 1. [Figure 1B] FIG. 1 is a diagram showing the shape and dimensions of test specimens in Examples 2 and 3. [Figure 2] 1 is a graph showing the measurement results of the neutralization depth in Example 1. [Figure 3] 1 is a graph showing the carbonation rate ratio in Example 1 relative to a test specimen (Comparative Example a1) in which no hardening accelerator was mixed. [Figure 4A]1 is a graph showing the measurement results of the carbonation depth in Example 2, which is a graph for the test specimens formulated as shown in Table 4. [Figure 4B] 1 is a graph showing the measurement results of the carbonation depth in Example 2, which is a graph for the test specimens formulated as shown in Table 5. [Figure 5] 10 is a graph showing the measurement results of the neutralization depth in Example 3. [Figure 6] 1 is a graph showing the relationship between the neutralization rate ratio and the amount of hardening accelerator mixed in in Examples 1 to 3. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention relates to a concrete member that has an excellent carbonation suppression effect, which suppresses the progress of carbonation of concrete, while reducing CO2 emissions compared to conventional blast furnace cement (30 to 70 parts by mass), and a method for manufacturing such a concrete member. Hereinafter, a description will be given of a concrete member and a method for manufacturing a concrete member according to the present invention in accordance with an embodiment. In this specification, the process of applying or penetrating a hardening accelerator into the concrete surface to enhance the concrete's carbonation suppression effect is defined as the "hardening accelerator mixing process." The amount of hardening accelerator to be mixed in during this process is also explained in detail. [Concrete members] The concrete member according to the present embodiment is a member made of a concrete composition containing hydraulic powder, fine aggregate, coarse aggregate, water, etc., and is a hardened concrete body formed by hardening the concrete composition. The concrete member according to the present embodiment may also contain calcium carbonate. The concrete member according to this embodiment has a hardening accelerator mixed into the surface portion. Below, each of the constituent elements of the concrete member according to this embodiment will be described in detail.

[0011] (hydraulic powder) The hydraulic powder is a powder that hardens by reacting with water and includes ground granulated blast furnace slag, an expansive material, and slaked lime. Note that the hydraulic powder does not include calcium carbonate, which will be described later. Ground granulated blast furnace slag is dried and crushed granulated blast furnace slag, or gypsum added to this, and is specified in JISA6206:2013. The content of ground granulated blast furnace slag is preferably 80 parts by mass or more per 100 parts by mass of hydraulic powder. By having the content of ground granulated blast furnace slag be equal to or greater than a predetermined value, the amount of Portland cement used can be reduced (or eliminated), thereby reducing CO2 emissions. The upper limit of the content of ground granulated blast furnace slag is not particularly limited, and is, for example, 93 parts by mass or less, 90 parts by mass or less, or 88 parts by mass or less relative to 100 parts by mass of the hydraulic powder.

[0012] An expansive additive is an admixture that has the effect of expanding concrete or mortar, and is specified in JISA6202:2017. Preferred examples of the expansive additive include lime-based expansive additives that release calcium ions and calcium sulfoaluminate-based expansive additives. The content of the expansion agent is not particularly limited, but is, for example, 2 parts by mass or more, 3 parts by mass or more, 4 parts by mass or more, and 15 parts by mass or less, 12 parts by mass or less, 10 parts by mass or less, per 100 parts by mass of the hydraulic powder. Slaked lime is calcium hydroxide (Ca(OH)2). The content of slaked lime is not particularly limited, but is, for example, 5 parts by mass or more, 6 parts by mass or more, 7 parts by mass or more, and 15 parts by mass or less, 12 parts by mass or less, or 10 parts by mass or less, relative to 100 parts by mass of the hydraulic powder.

[0013] (fine aggregate, coarse aggregate) Examples of fine and coarse aggregates include crushed stone and crushed sand, slag aggregate, artificial lightweight aggregate, recycled aggregate, gravel and sand, and all of these can be used in accordance with JISA5308 Appendix A:2024. The content of fine aggregate in the concrete member is not particularly limited, but for example, 400 kg / m 3 More than 500kg / m 3 More than 520kg / m 3 or more, 1000 kg / m 3 Below 900kg / m 3 Below 800kg / m 3 The following is the result. The content of coarse aggregate in the concrete member is not particularly limited, but is, for example, 400 kg / m 3 More than 600kg / m 3 More than 800kg / m 3 More than 830kg / m 3 or more, 1200 kg / m 3 Below 1100kg / m 3 Below 1000kg / m 3 The following is the result.

[0014] (Calcium carbonate) Calcium carbonate is a calcium carbonate with the chemical formula CaCO3. Calcium carbonate can be heavy calcium carbonate, which is obtained by crushing and classifying limestone, or light calcium carbonate, which is produced by recovering CO2 contained in exhaust gases. However, when light calcium carbonate is used as calcium carbonate, CO2 can be fixed inside the concrete member, further reducing CO2 emissions.

[0015] (Content of each ingredient in an embodiment containing calcium carbonate) In the concrete member according to this embodiment, calcium carbonate is not essential, but when calcium carbonate is contained, the content of each material (ground granulated blast furnace slag, calcium carbonate, powder) is as follows. The content of the ground blast furnace slag is preferably 40 to 80 parts by mass, and more preferably 45 to 77 parts by mass (rounded to one decimal place), relative to 100 parts by mass of the total of the hydraulic powder and calcium carbonate powder. The content of calcium carbonate is preferably 5 to 50 parts by mass, and more preferably 9 to 45 parts by mass (rounded to one decimal place) relative to 100 parts by mass of the total of the hydraulic powder and calcium carbonate powder. The total content of hydraulic powder and calcium carbonate powder in concrete members is 0.35 to 0.70 ton / m 3 It is preferable that the density is 0.37 to 0.68 ton / m 3 It is more preferable that: By setting the content of each material within a predetermined range, in an embodiment containing calcium carbonate, the carbonation suppression effect can be more reliably exhibited.

[0016] (water) The water is not particularly limited, and tap water, groundwater, sludge water, etc. can be used. If the concrete does not contain calcium carbonate, the water-to-powder ratio (= water content (kg / m 3 ) / powder content (kg / m 3 )×100) is preferably 30% or less. When the concrete member contains calcium carbonate, the water-powder ratio is preferably 41% or less. If the water-powder ratio exceeds a predetermined value, the neutralization will become even faster, and the neutralization suppression effect of the present invention may not be obtained. The powder not containing calcium carbonate is a hydraulic powder, and the powder containing calcium carbonate is a hydraulic powder and calcium carbonate.

[0017] (curing accelerator) A hardening accelerator is a type of chemical admixture specified in JISA6204:2011, which accelerates the hydration of cement and increases its strength at early ages. The hardening accelerator is nitrate ions (NO3 - ), and nitrite ions (NO2 - ) The hardening accelerator contains at least one of these components, and when mixed into the surface of a concrete member, it can exhibit the effect of suppressing carbonation that progresses from the surface. The hardening accelerator is applied to the surface of the concrete by brushing or spraying at a rate of 0.5 to 1.6 kg / m 2 It is preferable that it is mixed. If the amount of curing accelerator mixed in is less than the predetermined value, the effect of suppressing carbonation may not be fully exerted, whereas if the amount of curing accelerator mixed in exceeds the predetermined value, the increased amount may result in an increase in costs, and the increased number of applications may result in a longer manufacturing time. Instead of the amount of hardening accelerator mixed in, the amount of hardening accelerator converted to nitrate ions (0.12 to 0.384 kg / m on the surface of the concrete member) was used. 2 ) may be specified.

[0018] (Other ingredients) The concrete member according to this embodiment may contain, as appropriate, conventionally known materials used in general concrete (for example, hydraulic powders such as fly ash and silica fume, and chemical admixtures other than the hardening accelerators described above) to the extent that the desired effects of the present invention are not impaired. Examples of chemical admixtures include air-entraining agents, high-performance water-reducing agents, water-reducing agents, air-entraining water-reducing agents, high-performance air-entraining water-reducing agents, and superplasticizers, as specified in JISA6204:2011.

[0019] [Method of manufacturing concrete components] The method for manufacturing a concrete member according to this embodiment includes a pouring step and a mixing step. Each step of the method for manufacturing a concrete member according to this embodiment will be described below. (Pouring process) In the casting process, a concrete composition containing hydraulic powder, fine aggregate, coarse aggregate, water, and calcium carbonate (optional) is mixed and cast. In this casting process, the content of each material may be adjusted so as to fall within the above-mentioned ranges. The mixing conditions and pouring conditions in the pouring step may be conventionally known conditions.

[0020] (mixing process) In the mixing process, the hardening accelerator is mixed into the surface of the poured concrete member. The method of mixing in the mixing step is not particularly limited, but examples include (1) a method in which the formwork for pouring is removed from the concrete member after the pouring step, and the hardening accelerator is applied to the surface of the concrete member, and (2) a method in which a surface material containing the hardening accelerator is attached to the inner surface of the formwork used in the pouring step, and the hardening accelerator is mixed into the surface of the concrete member through this surface material. The application of (1) may be carried out using a roller or by brushing or spraying. Alternatively, a surface material containing the hardening accelerator may be applied to the surface of the concrete member after demolding. The surface material used to mix the hardening accelerator is not particularly limited as long as it allows the hardening accelerator to be mixed into the surface of the concrete member, but nonwoven fabrics or woven fabrics made from chemical fibers or pulp may be used. In the case of method (2), it is preferable to remove the formwork and surface material after the concrete member has developed enough strength to prevent the surface from peeling off.

[0021] The amount of hardening accelerator to be mixed in during the mixing process is 0.5 to 1.6 kg / m of concrete surface area. 2 is. The hardening accelerator mixed in during the mixing process is unlikely to decrease due to evaporation at room temperature, and will be mixed directly into the surface of the concrete member. Therefore, the amount of hardening accelerator mixed in during the mixing process will be approximately the same as the amount of hardening accelerator mixed into the surface of the concrete member after hardening.

[0022] (Mixing process: timing of mixing) The hardening accelerator is preferably mixed in the mixing step within seven days of mixing in the pouring step (in other words, it is preferably mixed into a concrete member whose age is seven days or less). By mixing the hardening accelerator into the surface of the concrete member within a predetermined period of time, the desired effect (carbonation suppression effect) can be more reliably achieved. [Example]

[0023] [Example 1] (Example 1: Test specimen) FIG. 1A is a diagram showing the shape and dimensions of a test specimen in Example 1. FIG. As shown in FIG. 1A, the test specimen prepared in Example 1 was a rectangular parallelepiped with dimensions of 40 mm high x 160 mm wide x 88 mm deep. The specimens in Example 1 were prepared by using the materials shown in Table 1 and by preparing mortar members based on the mix shown in Table 2 (each table shows the mix of the target concrete composition, but in Example 1, coarse aggregate (G) is excluded). The amount of high-performance AE water-reducing agent used for each test specimen shown in Table 2 was adjusted so as to obtain the fluidity of the mortar suitable for pouring.

[0024] Example 1: Experimental conditions As shown in Table 2, two comparative examples were prepared: a test specimen without any hardening accelerator (Comparative Example a1) and a specimen in which the hardening accelerator was mixed during the kneading of the mortar using the usual mixing method (Comparative Example a2). The amount of hardening accelerator mixed in for Comparative Example a2 was within the range of the standard amount used for the product. As shown in Table 2, examples were prepared with different mixing methods and different ages of the material at the time of mixing. In all examples, the hardening accelerator was impregnated into or applied to one side of a 40 mm x 160 mm mortar. The ages of the material at the time of mixing were 0, 3, and 7 days. Example a1 was prepared by placing a nonwoven fabric (material: polyester, nylon) impregnated with a hardening accelerator on one side of a 40 mm x 160 mm formwork used in the casting process, and pouring mortar into it. Examples a2 and a3 were prepared by demolding at the material age when each mixture was added, and applying a hardening accelerator to one surface of a 40 mm x 160 mm sample.

[0025] [Table 1]

[0026] [Table 2]

[0027] (Example 1: Curing method) The curing method was sealed curing at 20°C until the material was aged 7 days. The test specimens to which the hardening accelerator was applied at aged 3 and 7 days (Examples a2 and a3) were sealed again after application. After the age of 7 days, the material was cured in air at 20°C and 60% RH.

[0028] (Example 1: Neutralization Acceleration Test) The accelerated carbonation test was conducted in a test environment of 20°C, 60% RH, and 5% CO2 concentration. A 40mm x 160mm surface was left open, and the other surfaces were covered with aluminum tape. The accelerated carbonation test began at 12 days old, and the carbonation depth was measured at 2, 4, and 13 weeks after acceleration. The measurement method was in accordance with JISA1152 "Method for measuring the depth of neutralization of concrete," with measurements taken at four locations per fracture surface (88 mm depth direction), and one test specimen per experimental condition.

[0029] Example 1: Experimental Results FIG. 2 is a graph showing the measurement results of the carbonation depth in Example 1. From the results in FIG. 2, it was confirmed that Examples a1 to a3 had a smaller carbonation depth than Comparative Example a1, in which no hardening accelerator was mixed, and that carbonation was suppressed in all cases. Fig. 3 is a graph showing the carbonation rate ratio of the test specimen (Comparative Example a1) in Example 1 to which no hardening accelerator was added. The carbonation rate was calculated from the slope of the approximation line in Fig. 2. The carbonation rate ratio was calculated as "carbonation rate of the test specimen / carbonation rate of Comparative Example a1 in which no hardening accelerator was added." From the results in FIG. 3, it was confirmed that the neutralization rate ratios of Examples a1 to a3 were 0.9 or less, which was similar to that of Comparative Example a2 in which the hardening accelerator was mixed during kneading. Furthermore, according to the approximation line (solid line in Fig. 3) of the carbonation rate ratios of Examples a1 to a3 shown in Fig. 3, the carbonation rate ratio tended to approach 0.9 as the material age at the time of mixing the hardening accelerator increased. It was also confirmed that if the material age at the time of mixing the hardening accelerator exceeds 7 days, the carbonation rate ratio may exceed 0.9, and the carbonation suppression effect may not be obtained.

[0030] Note that Example 1 is a result related to mortar members, not concrete members. However, since carbonation progresses in mortar members (because the progress of carbonation is hardly related to coarse aggregate), the results of Example 1 related to mortar members are considered to be similar to those of concrete members.

[0031] [Example 2] Example 2: Test specimen FIG. 1B is a diagram showing the shape and dimensions of the test specimen in Example 2. As shown in FIG. 1B, the test specimen prepared in Example 2 was a rectangular parallelepiped with dimensions of 85 mm high x 255 mm wide x 87 mm deep. The specimens of Example 2 were made of concrete members using the materials shown in Table 3 and based on the mix proportions shown in Tables 4 and 5 (two types of mix proportions). The amount of high-performance water-reducing agent used for each test specimen shown in Tables 4 and 5 was adjusted so as to obtain concrete with fluidity suitable for pouring.

[0032] Example 2: Experimental conditions As shown in Tables 4 and 5, comparative examples were prepared: specimens without any hardening accelerator (Comparative Examples b1 and c1), and specimens in which the hardening accelerator was mixed during the kneading of the mortar using the usual mixing method (Comparative Examples b2 and c2). The amount of hardening accelerator mixed in for Comparative Examples b2 and c2 was within the range of the standard amount used for the product. As shown in Tables 4 and 5, examples were prepared in which the amount of hardening accelerator mixed in and applied to the concrete surface was varied. All examples were prepared by removing the formwork after one day of age and applying the hardening accelerator to one surface of an 85 mm x 255 mm size on the same day.

[0033] [Table 3]

[0034] [Table 4]

[0035] [Table 5]

[0036] (Example 2: Curing method) The curing method was sealed curing at 20°C until the material was 7 days old. The test specimens to which the hardening accelerator was applied on day 1 (Examples b1, b2, c1, c2) were sealed again after application.

[0037] (Example 2: Neutralization Acceleration Test) The accelerated carbonation test was conducted in a test environment of 20°C, 60% RH, and 5% CO2 concentration. One 85mm x 255mm surface was left open, and the other surfaces were covered with aluminum tape. The accelerated carbonation test began at 7 days old, and the carbonation depth was measured at 4, 8, and 13 weeks after acceleration. The measurement method was in accordance with JISA1152 "Method for measuring the depth of neutralization of concrete," with measurements taken at five locations per fracture surface (85 mm depth direction), and one test specimen per experimental condition.

[0038] Example 2: Experimental Results 4A and 4B are graphs showing the measurement results of the carbonation depth in Example 2, where FIG. 4A is a graph for the test specimen with the formulation in Table 4, and FIG. 4B is a graph for the test specimen with the formulation in Table 5. From the results of Figures 4A and 4B, the amount of curing accelerator mixed in was 0.5 kg / m 2It was confirmed that Examples b2 and c2, in which a hardening accelerator was added, had a smaller carbonation depth than Comparative Examples b1 and c1, in which no hardening accelerator was added. Furthermore, the carbonation depth of Examples b2 and c2 was similar to that of Comparative Examples b2 and c2, in which a hardening accelerator was added during kneading, and it was also confirmed that carbonation was suppressed in both of the formulations in Tables 4 and 5. On the other hand, the amount of hardening accelerator mixed is 0.2 kg / m 2 Although Examples b1 and c1, which contained only a small amount of hardening accelerator, had a smaller carbonation depth than Comparative Examples b1 and c1, which contained no hardening accelerator, the amount of hardening accelerator mixed was 0.5 kg / m 2 It was confirmed that the effect of inhibiting neutralization was small compared with Examples b2 and c2.

[0039] Table 6 below shows the carbonation rate and carbonation rate ratio for the test specimens with the formulations in Table 4, as well as the amount of hardening accelerator used when assuming a pillar or wall. Similarly, Table 7 below shows the carbonation rate and carbonation rate ratio for the test specimens with the formulations in Table 5, as well as the amount of hardening accelerator used when assuming a pillar or wall. The carbonation rate ratio in Table 6 was calculated as "carbonation rate of test specimen / carbonation rate of comparative example b1 in which no hardening accelerator was added," and the carbonation rate ratio in Table 7 was calculated as "carbonation rate of test specimen / carbonation rate of comparative example c1 in which no hardening accelerator was added." The dimensions of the columns and walls assumed in Tables 6 and 7 are as follows: (Column dimensions): Width 600mm x Thickness 600mm x Height 4000mm (Area where hardening accelerator is mixed into the column): 600mm x 4000mm x 4 surfaces (Wall dimensions): Width 6000mm x Thickness 200mm x Height 4000mm (Wall surface where hardening accelerator is mixed): 6000mm x 4000mm x 2 surfaces

[0040] [Table 6]

[0041] [Table 7]

[0042] From the results in Tables 6 and 7, it was confirmed that the amount of hardening accelerator used could be significantly reduced in Examples b1 to b2 and c1 to b2 compared to Comparative Examples b2 and c2, in which the hardening accelerator was mixed during kneading. In addition, from the results of Tables 6 and 7, when the amount of hardening accelerator mixed in was 0.2 kg / m 2 It was also confirmed that Examples b1 and c1, in which the amount of carbon dioxide is as small as that of carbon dioxide, have a higher neutralization rate ratio than Examples b2 and c2, and in some cases, as in Example c1, the neutralization rate ratio exceeds 0.9.

[0043] [Example 3] Example 3: Test specimen FIG. 1B is a diagram showing the shape and dimensions of the test specimen in Example 3. As shown in FIG. 1B, the test specimen prepared in Example 3 was a rectangular parallelepiped with dimensions of 85 mm high x 255 mm wide x 87 mm deep. The specimens of Example 3 were prepared by using the materials shown in Table 8 and by preparing concrete members based on the mix proportions shown in Table 9. The amount of high-performance water-reducing agent used for each test specimen shown in Table 9 was adjusted so as to obtain concrete with fluidity suitable for pouring.

[0044] Example 3: Experimental conditions As shown in Table 9, a test specimen (Comparative Example d1) containing no curing accelerator was prepared as a comparative example. As shown in Table 9, the examples are those under the conditions where the carbonation rate ratio was 0.9 or less in Examples 1 and 2, that is, the age of the material when the hardening accelerator was mixed was 7 days or less, and the amount of hardening accelerator mixed was 0.5 kg / m 2 The above items were prepared. Example d1 was prepared by placing a nonwoven fabric (material: pulp, polypropylene) impregnated with a hardening accelerator on one side of a 85 mm x 255 mm formwork used in the casting process, and then pouring concrete into it. Examples d2 and d3 were produced by demolding the material at 7 days of age and coating one surface of an 85 mm x 255 mm sample with a hardening accelerator on the same day.

[0045] [Table 8]

[0046] [Table 9]

[0047] (Example 3: Curing method) The curing method was sealed curing at 20°C until the material was 7 days old, and in Examples d2 and d3, a hardening accelerator was applied after the sealed curing and demolding. After the age of 7 days, the material was cured in air at 20°C and 60% RH.

[0048] (Example 3: Neutralization Acceleration Test) The accelerated carbonation test was conducted in a test environment of 20°C, 60% RH, and 5% CO2 concentration. One 85mm x 255mm surface was left open, and the other surfaces were covered with aluminum tape. The accelerated carbonation test began at 51 days old, and the carbonation depth was measured at 4, 13, and 26 weeks after the accelerated test. The measurement method was in accordance with JISA1152 "Method for measuring the depth of neutralization of concrete," with measurements taken at five locations per fracture surface (85 mm depth direction), and one test specimen per experimental condition.

[0049] Example 3: Experimental Results FIG. 5 is a graph showing the measurement results of the carbonation depth in Example 3. From the results in FIG. 5, it was confirmed that in all of Examples d1 to d3, the carbonation was suppressed compared to Comparative Example d1 in which no hardening accelerator was mixed.

[0050] [Summary of Examples 1 to 3] FIG. 6 is a graph showing the relationship between the neutralization rate ratio and the amount of hardening accelerator mixed in Examples 1 to 3. From the results in Figure 6, the age of the material when the hardening accelerator is mixed should be within 7 days, and the amount of hardening accelerator mixed should be 0.5 to 1.6 kg / m 2 It was confirmed that by doing so, the carbonation rate ratio compared to when no hardening accelerator was added was 0.9 or less. If too much hardening accelerator is mixed in, not only will costs increase, but the number of times it needs to be applied to the surface will also increase, requiring more time and effort (when applying to vertical surfaces, it is necessary to apply the coating in separate applications to prevent sagging). Therefore, the amount of hardening accelerator mixed in is 1.6 kg / m 2 It is best to set the upper limit at this level.

[0051] The component compositions of powders, hardening accelerators, etc. in Examples 1 to 3 are summarized in Table 10 below.

[0052] [Table 10]

[0053] As shown in Table 10, in each example where the carbonation suppression effect was confirmed to be exerted, the content of ground granulated blast furnace slag per 100 parts by mass of hydraulic powder was 80 parts by mass or more. In other words, it was confirmed that the present invention can exert the carbonation suppression effect while reducing CO2 emissions. Furthermore, as shown in Table 10, among the examples in which the carbonation suppression effect was confirmed, the examples containing calcium carbonate (examples shown in Tables 2 and 5) met the requirements that "the content of ground granulated blast furnace slag is 40 to 80 parts by mass and the content of calcium carbonate is 5 to 50 parts by mass per 100 parts by mass of powder" and "the total content of hydraulic powder and calcium carbonate powder in the concrete member is 0.35 to 0.70 ton / m 3 It was confirmed that the requirements were met. In addition, as shown in Table 10, among the examples in which the carbonation suppression effect was confirmed, the examples that did not contain calcium carbonate (examples shown in Tables 4 and 9) were confirmed to satisfy the requirement of "water-powder ratio of 30% or less." On the other hand, the examples that contained calcium carbonate (examples shown in Tables 2 and 5) were confirmed to satisfy the requirement of "water-powder ratio of 41% or less."

Claims

1. A concrete member containing hydraulic powder, fine aggregate, coarse aggregate, water, and a hardening accelerator, The hydraulic powder includes ground granulated blast furnace slag, an expanding material, and slaked lime, The content of the ground granulated blast furnace slag is 80 parts by mass or more relative to 100 parts by mass of the hydraulic powder, The hardening accelerator contains at least one of a nitrate ion and a nitrite ion, The hardening accelerator mixed into the surface of the concrete member is 0.5 to 1.6 kg / m ２ A concrete member characterized by:

2. Contains calcium carbonate, the content of the ground granulated blast furnace slag is 40 to 80 parts by mass and the content of the calcium carbonate is 5 to 50 parts by mass relative to 100 parts by mass of the total of the hydraulic powder and the calcium carbonate powder; The total content of the hydraulic powder and the calcium carbonate powder in the concrete member is 0.35 to 0.70 ton / m ３ 2. The concrete member according to claim 1, wherein

3. 3. The concrete member according to claim 1, wherein the water-to-powder ratio is 30% or less when calcium carbonate is not contained, and 41% or less when calcium carbonate is contained.

4. A casting process of mixing and casting a concrete composition containing hydraulic powder, fine aggregate, coarse aggregate, and water; A method for manufacturing a concrete member, comprising: a mixing step of mixing a hardening accelerator into the surface of the poured concrete member; The hydraulic powder includes ground granulated blast furnace slag, an expanding material, and slaked lime, The content of the ground granulated blast furnace slag is 80 parts by mass or more relative to 100 parts by mass of the hydraulic powder, The hardening accelerator contains at least one of a nitrate ion and a nitrite ion, The hardening accelerator mixed into the surface of the concrete member is 0.5 to 1.6 kg / m ２ and A method for manufacturing a concrete member, characterized in that the hardening accelerator is mixed in the mixing step within 7 days of mixing in the pouring step.

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