Hydraulic composition and formulation design thereof
A hydraulic composition with a CH/W ratio of 1% or more addresses the slow compressive strength issue by enabling rapid strength development and stability, enhancing construction efficiency.
Patent Information
- Application Number
- JP2024035075
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-03-07
- Publication Date
- 2025-09-19
AI Technical Summary
Hydraulic compositions containing blast furnace slag powder and slaked lime exhibit a slow increase in compressive strength in the early stages after casting, which can impact subsequent construction processes.
A hydraulic composition with a mass ratio of slaked lime to water (CH/W) of 1% or more, ensuring rapid compressive strength development after casting.
The composition achieves early strength development and maintains stable strength over time, facilitating efficient construction processes and reducing the risk of design changes due to ongoing strength increases.
Smart Images
Figure 2025136470000001_ABST
Abstract
Description
[Technical Field]
[0001] The present invention relates to a hydraulic composition and its formulation design. [Background technology]
[0002] In order to reduce carbon dioxide emissions, hydraulic compositions that do not use cement are being investigated. Non-Patent Document 1 discloses concrete containing blast furnace slag powder, gypsum, and slaked lime. The smaller the amount of slaked lime, the better, with 0.5% or less being desirable. Non-Patent Document 2 discloses cement containing blast furnace slag powder and slaked lime. It states that the optimal amount of slaked lime to be added is 0.2 to 0.4%. [Prior art documents] [Non-patent literature]
[0003] [Non-Patent Document 1] Akira Watanabe, Takashi Idemitsu, Shunichi Takayama, "Study on concrete using slag cement", Materials, March 1980, Vol. 29, No. 318, pp. 47-53 [Non-patent document 2] Song, Zongze, Jinawas Supatla, Daimon, Masaki, Kondo, Renichi, "Hydration Reaction of High Sulfate Slag Cement", Gypsum & Lime, 1979, No.163, pp.2-6 Summary of the Invention [Problem to be solved by the invention]
[0004] The inventors of the present application have found that hydraulic compositions containing blast furnace slag powder and slaked lime may exhibit a slow increase in compressive strength in the early stages after casting. A slow increase in compressive strength has a significant impact on subsequent construction processes. However, Non-Patent Documents 1 and 2 do not describe anything about the relationship between material age and compressive strength.
[0005] An object of the present invention is to provide a hydraulic composition containing blast furnace slag powder and slaked lime, which increases in compressive strength in a short period of time after casting. [Means for solving the problem]
[0006] The hydraulic composition of the present invention contains powder and water, the powder containing blast furnace slag powder and slaked lime, and the mass ratio of the slaked lime to the water is 1% or more. [Effects of the Invention]
[0007] According to the present invention, it is possible to provide a hydraulic composition which contains blast furnace slag powder and slaked lime and whose compressive strength increases in a short period of time after casting. [Brief explanation of the drawings]
[0008] [Figure 1] 1 is a graph showing the relationship between age and compressive strength of the hydraulic composition of Example 1. [Figure 2] 1 is a graph showing the relationship between age and compressive strength of the hydraulic composition of Example 2. [Figure 3] 1 is a graph showing the relationship between age and compressive strength of the hydraulic composition of Example 3. [Figure 4] 1 is a graph showing the relationship between CH / W and compressive strength ratio in Examples 1 to 4. DETAILED DESCRIPTION OF THE INVENTION
[0009] The present invention will be described below with reference to examples. Table 1 shows an overview of the materials used in the examples. The hydraulic composition of the present invention contains ground blast furnace slag and slaked lime. The hydraulic composition of the present invention does not contain cement, but may contain a trace amount of cement, for example, a mass ratio of cement in the powder less than that of slaked lime. Water may be tap water, groundwater, seawater, or water generated during the preparation of the hydraulic composition (sludge water, etc.). Furthermore, although the hydraulic composition of each example contains water, water does not have to be added as mixing water. For example, when the hydraulic composition of the present invention is used for ground improvement, at least a portion of the water may be water contained in the soil. Furthermore, the hydraulic composition of the present invention may or may not contain a chemical admixture.
[0010] [Table 1]
[0011] Example 1 Table 2 shows the composition of Example 1. Example 1 (Samples 1-1 to 1-5) is a paste in which ground granulated blast furnace slag and slaked lime are used as the powder, and aggregate is omitted. All Samples 1-1 to 1-5 contain ground granulated blast furnace slag and gypsum as the powder. Sample 1-1 does not contain slaked lime, while Samples 1-2 to 1-5 contain slaked lime. Ground granulated blast furnace slag is the material that forms the framework of the hydraulic composition, and gypsum and slaked lime are used as alkaline activators. Samples 1-2 to 1-5 use the mass ratio of slaked lime as a parameter. Samples 1-3 to 1-4 have the same composition but different lots. Compressive strength was measured in accordance with JIS A 1108 at 3, 7, and 28 days (curing conditions: sealed curing at 20°C).
[0012] [Table 2]
[0013] Table 2 shows the compressive strength. Figure 1 also shows the change in compressive strength over time and an overview of the composition of each sample. Sample 1-1, which does not contain slaked lime, exhibits low compressive strength at 3 days old. Samples 1-2 to 1-5 generally show a higher strength in the early stages after pouring (at 3 days old) than Sample 1-1. Furthermore, for Samples 1-2 to 1-5, the increase in strength at 7 and 28 days old is more gradual than at 3 days old. This is thought to be because the slaked lime contained in the powder not only activates the latent hydraulic properties of the ground granulated blast furnace slag, enabling early strength development, but also has the effect of stabilizing the strength thereafter. These findings confirm that a minimum amount of slaked lime is necessary to achieve a certain level of strength development early after pouring and then stabilize the strength after reaching a predetermined strength.
[0014] Example 2 Table 3 shows the blending ratio of Example 2. In all samples 2-1 to 2-22, the powder contained ground granulated blast furnace slag. In samples 2-1 to 2-4 and samples 2-11 to 2-14, the powder did not contain slaked lime, while in samples 2-5 to 2-10 and samples 2-15 to 2-22, the powder contained slaked lime. In addition, samples 2-1 to 2-10 used ground granulated blast furnace slag containing gypsum, while samples 2-11 to 2-22 used ground granulated blast furnace slag without gypsum. Sample 2-11 contained neither slaked lime nor gypsum, and samples 2-15 to 2-17 contained slaked lime but no gypsum. In Example 2, the mass ratio of ground granulated blast furnace slag to slaked lime and gypsum was also used as a parameter. Samples 2-3 to 2-4 had the same blending ratio but different lots. Compressive strength was measured using the same method as in Example 1. For samples 2-1 to 2-10, the compressive strength was measured on the 3rd, 7th, and 28th days, and for samples 2-11 to 2-22, the compressive strength was measured on the 3rd, 7th, 28th, and 91st days.
[0015] [Table 3]
[0016] Table 3 shows the compressive strength. Figure 2 also shows the change in compressive strength over time and an overview of the composition of each sample. For convenience, samples 2-1 to 2-4, 2-5 to 2-10, 2-11 to 2-14, and 2-15 to 2-22 are shown on separate graphs, with the vertical and horizontal scales aligned. Samples 2-1 to 2-4 and 2-11 to 2-14, which do not contain hydrated lime, showed trends roughly similar to those of sample 1-1. Although samples 2-1 to 2-4 contain gypsum, their strength at three days old is generally low. This confirms that when hydrated lime is not included, i.e., when gypsum is the only alkaline stimulant, it is difficult for the initial strength to be developed.
[0017] In contrast, samples 2-5 to 2-10 and 2-15 to 2-22, which contain slaked lime, showed a similar tendency to samples 1-2 to 1-5. Because the tendency did not differ significantly between samples 2-5 to 2-10 and samples 2-15 to 2-22, it is believed that whether gypsum-containing ground granulated blast furnace slag is used (samples 2-5 to 2-10) or whether gypsum is added separately (samples 2-15 to 2-22) does not have a significant effect on strength.
[0018] Among samples 2-15 to 2-22, samples 2-15 to 2-17 contain slaked lime but no gypsum, while samples 2-18 to 2-22 contain both slaked lime and gypsum. Compared with samples 2-15 to 2-17, which do not contain gypsum, samples 2-18 to 2-22, which contain gypsum, exhibit higher strength at 3 days (see Table 3), and the strength increase thereafter is also gradual (see Figure 2). This trend is consistent with Example 1. This indicates that the presence of gypsum is highly effective in achieving both the aforementioned early strength development and long-term strength stability. Furthermore, a comparison of samples 2-5 to 2-10 reveals that the greater the CH / W, the lower the strength at 91 days.
[0019] A hardening pattern in which the initial strength after pouring is low and then the strength increases rapidly is not necessarily desirable for the construction and design of structures. For example, paste or mortar is sometimes injected into the ground for ground improvement. This increases the ground strength, preventing collapse of the surrounding ground during excavation and enabling the placement of heavy machinery on the ground. Therefore, early development of high strength is important for early implementation of subsequent processes. However, excessive increase in ground strength may reduce the efficiency of, for example, excavating the improved ground. Furthermore, when constructing a structure using hydraulic compositions such as concrete, subsequent processes often cannot be carried out until the hydraulic composition has hardened to a certain extent in the previous process. Therefore, low initial strength after pouring may affect the entire construction process. Furthermore, in the ultimate strength design of concrete structures, the cross section is designed so that the structure will reach its ultimate state when a load exceeding the design ultimate load is applied. Therefore, if the concrete strength continues to increase over a long period of time, the failure mode assumed in the design may change. Therefore, it is generally preferable that a hydraulic composition develops a certain degree of strength early after pouring, and that the strength remains stable (does not increase significantly) after reaching a predetermined strength. From this perspective, it can be said that among Samples 2-11 to 2-22, which were measured for strength up to 91 days, Samples 2-15 to 2-22 have preferable properties.
[0020] Example 3 Table 4 shows the mix proportions for Example 3. Example 3 is a mortar containing fine aggregate. In all samples 3-1 to 3-32, the powder contains ground granulated blast furnace slag, fly ash, and silica fume. In sample 3-1, the powder contains neither slaked lime nor gypsum, while in samples 3-2 to 3-5, the powder contains gypsum but not slaked lime. In samples 3-6 to 3-13, the powder contains slaked lime but not gypsum. In samples 3-14 to 3-32, the powder contains slaked lime and gypsum. In samples 3-14 to 3-32, the mass ratio of gypsum is the main parameter. Compressive strength was measured using the same method as in Example 1.
[0021] [Table 4]
[0022] Table 4 shows the compressive strength. Figure 3 shows the change in compressive strength over time and an overview of the composition of each sample. For convenience, samples 3-1 to 3-5, 3-7 to 3-13, 3-14 to 3-23, and 3-24 to 3-32 are plotted on separate graphs, with the vertical and horizontal scales aligned. Sample 3-6 was not prepared as it was deemed difficult to fill the formwork after mixing. Samples 3-1 to 3-5, which do not contain slaked lime, showed a tendency similar to that of sample 1-1. Samples 3-7 to 3-13, which contain slaked lime but no gypsum, tended to have low early strength. Samples 3-14 to 3-23 belong to the group with a relatively low CH / W ratio (CH / W less than 1%), while samples 3-24 to 3-32 belong to the group with a relatively high CH / W ratio (CH / W greater than 1%). As an overall trend, it was confirmed that the higher the CH / W, the higher the initial strength and the lower the strength on day 91. The mass ratio of gypsum to powder may be any value between 1% and 15%.
[0023] Table 5 shows the relationship between the CH / W and gypsum mass ratio and compressive strength for samples containing anhydrous gypsum and gypsum-free ground granulated blast furnace slag (samples 3-1 to 3-4, 3-14, 3-15, 3-17 to 3-19, 3-21 to 3-26, 3-29, and 3-31 to 3-32) by day. Focusing on the strength at days 3 and 7, a significant difference in compressive strength was observed between CH / W = 0.8 and 1.7. In contrast, there was no significant difference between CH / W = 0.8 and 1.7 at days 28 and 90. This indicates that ground granulated blast furnace slag hardens sufficiently over time even without hydrated lime or gypsum, but the initial hardening rate is largely due to the contribution of CH / W. Furthermore, focusing on the compressive strength at CH / W = 1.7, the higher the gypsum mass ratio, the higher the strength. Since similar trends in strength development were confirmed for samples 2-15 to 2-22, which do not contain fly ash or silica fume, and samples 3-7 to 3-32, which contain fly ash and silica fume, it is possible to use both fly ash and silica fume, either alone, or neither.
[0024] [Table 5] Example 4 Table 6 shows the mix proportions for Example 4. Example 4 is concrete containing fine aggregate and coarse aggregate. The same trends as in Examples 1 to 3 were observed. That is, even when the hydraulic composition is concrete, it was confirmed that a compressive strength that does not pose a practical problem can be obtained when CH / W is 1% or more (CH / W = 5.6%, 6.0%).
[0025] [Table 6]
[0026] FIG. 4 shows the relationship between CH / W and compressive strength ratio in Examples 1 to 4. FIG. 4(a) shows the relationship between CH / W and compressive strength ratio (ratio of strength at 7 days to strength at 3 days), and FIG. 4(b) shows the relationship between CH / W and compressive strength ratio (ratio of strength at 7 days to strength at 91 days). The compressive strength ratio in FIG. 4(a) is an index of strength development in the early period after pouring, with a smaller value indicating that strength is more likely to develop in the early period after pouring. The compressive strength ratio in FIG. 4(b) is an index of strength development over the long term after pouring, with a larger value indicating that strength is more stable (less significant fluctuations) over the long term after pouring. In FIG. 4(a), over a wide range of CH / W of 1% or more, the compressive strength ratio (ratio of strength at 7 days to strength at 3 days) is 10% or less. Furthermore, over a range of CH / W of 1% to 25% or less, the compressive strength ratio (ratio of strength at 7 days to strength at 3 days) is 6% or less. In Figure 4(b), over a wide range of CH / W values above 1%, the compressive strength ratio (the ratio of the strength at 7 days to the strength at 3 days) exceeds 0.07%. From the above, the relationship between CH / W and compressive strength ratio indicates that a CH / W of 1% or more is sufficient, and there is no need to specify an upper limit. However, as CH / W increases, the amount of carbon dioxide emitted during the production of slaked lime increases. Therefore, as a guideline, it is preferable to keep CH / W below 30%.
[0027] In this example, CH / W is used as an index. Conventionally, the mass ratio of slaked lime to powder (CH / P) has been used to specify the content of slaked lime, and this is thought to be the case in Non-Patent Documents 1 and 2. When evaluating materials that harden in an alkaline environment, evaluation based on the water volume conditions and the level of alkalinity is important. In this example, in order to comprehensively evaluate the water volume conditions and the level of alkalinity, a new index, the mass ratio of slaked lime to water (CH / W), is used to evaluate whether the composition will harden and its compressive strength. Therefore, using CH / W in the mix design (method) of hydraulic compositions is also novel.
Claims
1. A hydraulic composition comprising a powder and water, wherein the powder comprises blast furnace slag powder and slaked lime, and the mass ratio of the slaked lime to the water is 1% or more.
2. 2. The hydraulic composition according to claim 1, wherein the mass ratio of said slaked lime to said water is 1% or more and less than 10%.
3. The hydraulic composition according to claim 1 , wherein the powder further comprises gypsum.
4. The hydraulic composition according to claim 3, wherein a mass ratio of the gypsum to the powder is 1% or more and 15% or less.
5. The hydraulic composition according to claim 3 , wherein the powder further comprises silica fume.
6. 2. The hydraulic composition according to claim 1, wherein the ratio of the compressive strength at 7 days to the compressive strength at 3 days is 10 or less, and the ratio of the compressive strength at 7 days to the compressive strength at 91 days is greater than 0.
07.
7. The hydraulic composition according to claim 1 , wherein the powder does not contain cement.
8. A formulation design for a hydraulic composition comprising powder and water, the powder comprising blast furnace slag powder and slaked lime, A formulation design for a hydraulic composition, comprising a mass ratio of the slaked lime to the water being 1% or more.