cement composition
By increasing the air volume ratio and reducing the water-cement ratio, the cement composition effectively decreases CO2 emissions while ensuring structural integrity and workability.
Patent Information
- Authority / Receiving Office
- JP Β· JP
- Patent Type
- Applications
- Current Assignee / Owner
- OHBAYASHI GUMI LTD
- Filing Date
- 2024-12-02
- Publication Date
- 2026-06-12
Smart Images
Figure 2026095857000001_ABST
Abstract
Description
[Technical Field]
[0001] This invention relates to a cement composition. [Background technology]
[0002] When designing the mix design for concrete (an example of a cement composition) used in structures, the water-cement ratio, unit water content, unit cement content, and other mix properties are determined based on the required design strength of the structure and the fluidity required for workability. While the air content is usually set to a constant value, for example, Patent Document 1 discloses a practical concrete with a higher-than-usual air content. [Prior art documents] [Patent Documents]
[0003] [Patent Document 1] Japanese Patent Publication No. 2020-176018 [Overview of the project] [Problems that the invention aims to solve]
[0004] The amount of carbon dioxide (CO2) emitted during concrete production depends on the amount of cement per unit. In typical mix design, the amount of cement per unit (and thus the CO2 emissions) is determined by the predetermined strength and fluidity, so there are no mix options that can reduce CO2 emissions, and there is a risk of high CO2 emissions. Furthermore, Patent Document 1 does not describe how to reduce the amount of cement per unit (i.e., reduce CO2 emissions) while ensuring the predetermined strength and fluidity.
[0005] This invention has been made in view of the above-mentioned problems, and its purpose is to reduce CO2 emissions. [Means for solving the problem]
[0006] The main invention for achieving the above objective is a cement composition containing water, cement, and aggregate, wherein, in the mix design, the volume ratio of air in the cement composition is 6% or more and 40% or less, and the unit cement content is 336 kg / mΒ³. 3 It is less than 170 kg / mΒ³ of water. 3 This cement composition is characterized by having a water-cement ratio of less than 55%.
[0007] Other features of the present invention will be revealed in the specification and drawings described below. [Effects of the Invention]
[0008] According to the present invention, it is possible to reduce CO2 emissions. [Brief explanation of the drawing]
[0009] [Figure 1] This figure shows the materials used in the examples. [Figure 2] This figure shows the formulation conditions and quality test results for the example. [Modes for carrying out the invention]
[0010] The following information will become clear from the description in the specification and drawings described later.
[0011] (Aspect 1) A cement composition containing water, cement, and aggregate, wherein in the mix design, the volume ratio of air in the cement composition is 6% or more and 40% or less, and the unit cement content is 336 kg / mΒ³. 3 It is less than 170 kg / mΒ³ of water. 3 A cement composition characterized by having a water-cement ratio of less than 55%.
[0012] According to the cement composition of Embodiment 1, the amount of cement per unit can be reduced compared to a cement composition formulated with an air volume ratio of 4.5%. Therefore, CO2 emissions during the manufacture of the cement composition can be reduced.
[0013] (Aspect 2) A cement composition containing water, cement, and aggregates, wherein in the mix design, the air volume ratio in the cement composition is 6% or more and less than 8%, and the unit cement amount is less than 336 kg / m 3 and does not contain an air volume adjusting concrete admixture composed of a polyalkylene glycol-based compound.
[0014] According to the cement composition of Aspect 2, the unit cement amount can be reduced as compared with the cement composition having an air volume ratio of 4.5% in the mix design. Therefore, it is possible to reduce the CO2 emissions during the production of the cement composition.
[0015] ===First Embodiment=== Before explaining this embodiment, a general cement composition will be explained. Hereinafter, concrete will be taken as an example of the cement composition for explanation.
[0016] <Regarding General Concrete> Concrete is composed of water, cement, aggregates (fine aggregates, coarse aggregates), admixtures, etc. Also, air is contained in the concrete.
[0017] When designing the mix of concrete used for a structure, the mix such as the water-cement ratio, unit water amount, and unit cement amount is determined based on the design strength required for the structure and the fluidity conditions required for workability. Note that "mix design" means a series of operations for determining the materials and their mixes so as to satisfy the performance of the cement composition (here, concrete). Also, "mix" means the ratio or usage amount of each material when producing the cement composition.
[0018] Specifically, in mix design, the water-cement ratio (W / C) is determined from the target design strength. The design strength (fc) is an index used in structural calculations for determining allowable stress, and specifically refers to the compressive strength of the concrete.
[0019] Furthermore, in the mix design, the unit water content is determined based on the target fluidity (slump). The unit water content is set to an upper limit (175 kg / mΒ³ unless otherwise specified). 3 The water content is set so as not to exceed a certain limit. Furthermore, the unit water content must be at least greater than the sum of the water content constrained on the cement surface and the water content constrained on the fine aggregate surface (constrained water content) (constraint condition).
[0020] Then, the unit cement quantity that satisfies the design strength (compressive strength) and fluidity (slump) requirements is determined.
[0021] Unless otherwise specified, the air content (air volume ratio) of concrete is set at 4.5% (tolerance Β±1.5%) (JIS A 5308).
[0022] Incidentally, the amount of carbon dioxide (CO2) emitted during concrete production depends on the amount of cement per unit. If the amount of air is constant, as mentioned above, the amount of cement per unit (CO2 emissions) is determined by the predetermined compressive strength and fluidity, so there is a risk that the amount of cement per unit (CO2 emissions) cannot be reduced.
[0023] As a result of diligent research to solve the above problems, the inventors have found a mix design that can ensure compressive strength and fluidity (slump) even when the unit cement amount is reduced by increasing the amount of air.
[0024] <Concrete of this embodiment> In this embodiment, the concrete has an air content (air volume ratio) of 6% to 40% (preferably 7% to 20%) in its mix design. Furthermore, the unit cement content is 336 kg / mΒ³. 3 Less than (preferably 300 kg / mΒ³) 3less than), and the amount of water per unit volume is less than 170 kg / m 3 less than (preferably less than 155 kg / m 3 less than), and the water-cement ratio is less than 55% (preferably less than 53%).
[0025] In the concrete produced based on such a mix design, while satisfying the compressive strength and slump required for the structure, the amount of cement per unit can be reduced compared to general concrete (see the examples described later for details). That is, the CO2 emissions during the production of concrete can be reduced.
[0026] ===Second Embodiment=== In the second embodiment, the range of the air content (designed air content) is different from that of the first embodiment. Specifically, in the mix design of the concrete of the second embodiment, the air content (air content volume ratio) in the concrete is 6% or more and less than 8% (preferably 7% or more and less than 8%). Also, the amount of cement per unit is less than 336 kg / m 3 less than (preferably less than 300 kg / m 3 less than), and as an admixture, it does not contain an air content adjusting concrete admixture (an air content adjusting concrete admixture composed of a polyalkylene glycol-based compound).
[0027] Even in the concrete of the second embodiment, while satisfying the compressive strength and slump required for the structure, the amount of cement per unit can be reduced compared to general concrete (see the examples described later for details).
[0028] <<Examples>> The air content was increased from the general 4.5% to perform the mix design of the cement composition (here, concrete), and the quality test of the produced concrete was carried out. Also, as a comparative example, the concrete with a fixed air content (designed air content) of 4.5% was also evaluated.
[0029] <Materials Used> Figure 1 is a diagram showing the materials used in the examples.
[0030] Concrete was prepared using cement (C), fine aggregate (S), coarse aggregate (G), admixtures (HWR, SP, AE1, Ad1), and water (W) as shown in Figure 1. Note that the admixtures used were not air-content regulating concrete admixtures (polyalkylene glycol-based admixtures).
[0031] <Formulation conditions and quality test results> Figure 2 shows the formulation conditions and quality test results for the example.
[0032] Note that the air content in the mix design table in Figure 2 (hereinafter referred to as "set air content") is the volume ratio of air in the concrete in the mix design, and the air content in the quality test results shows the measured air content in the manufactured concrete.
[0033] Furthermore, in the mix design table in Figure 2, s / a represents the fine aggregate ratio, where a = fine aggregate (S) + coarse aggregate (G). If Vs is the volume ratio of fine aggregate and Vg is the volume ratio of coarse aggregate, then the fine aggregate ratio s / a is expressed as Vs / (Vs+Vg).
[0034] (Comparative example) In the comparative examples (Comparative Examples A-I) in Figure 2, the set air content is 4.5%, and the mix conditions (water-cement ratio W / C, unit water content W, unit cement content C) are determined according to the slump and compressive strength.
[0035] For example, with the same amount of air, the higher the water-cement ratio (W / C), the lower the compressive strength. Here, the compressive strength of the comparative examples is Comparative Examples A-E < Comparative Example F < Comparative Example G < Comparative Example H < Comparative Example I (see quality test results). In other words, the water-cement ratio (W / C) is Comparative Examples A-E > Comparative Example F > Comparative Example G > Comparative Example H > Comparative Example I.
[0036] Similarly, for the same amount of air, the slump increases as the unit water volume increases. Here, for example, in Comparative Examples A to D, the slump is Comparative Example A < Comparative Example B < Comparative Example C < Comparative Example D (see quality test results). In other words, the magnitude of the unit water volume is Comparative Example A < Comparative Example B < Comparative Example C < Comparative Example D.
[0037] Furthermore, for each of Comparative Examples A to I, the unit cement quantity (C) that satisfies the compressive strength and slump is determined.
[0038] (Examples) In the examples, the amount of air (set air amount) is used as a variable. More specifically, it is set to be larger than the 4.5% in the comparative example. The mix design conditions (water-cement ratio, unit water content, unit cement content, etc.) are then determined to satisfy the compressive strength and slump requirements.
[0039] Examples 1 to 11 represent mix designs corresponding to the second embodiment. Specifically, in the mix design, the target air content in the concrete is 6.0% or more and less than 8.0%. Furthermore, the unit cement content is 336 kg / mΒ³. 3 It is less than [amount missing]. Furthermore, as mentioned above, it does not contain concrete admixtures for air content adjustment consisting of polyalkylene glycol compounds.
[0040] Furthermore, Examples 12 to 23 represent mix designs corresponding to the first embodiment. In other words, in the mix design, the set air content in the concrete is 10.0% to 40.0% (6.0% to 40.0%). Also, the unit cement content is 336 kg / mΒ³. 3 It is less than 170 kg / mΒ³, and the unit water volume (W) is 170 kg / mΒ³. 3 The water-cement ratio (W / C) is less than 55%.
[0041] As can be seen from Figure 2, the unit cement content is smaller in the example than in the comparative example. For example, when comparing Comparative Example A and Example 5, the unit cement content is smaller in Comparative Example A than in Example 5, but this is because the target slump values ββare different.
[0042] When comparing examples and comparative examples (e.g., Example 5 and Comparative Example B) with nearly identical slump (and compressive strength), the unit cement content is smaller in Example 5 than in Comparative Example B. The same is true in other cases. Therefore, the unit cement content can be reduced in the examples compared to the comparative examples.
[0043] As explained above, the concrete in the example has a higher air content (set air content) than the comparative example (typical 4.5%). This allows for a smaller unit cement amount to satisfy the required strength and slump compared to the comparative example. Therefore, it is possible to reduce CO2 emissions during concrete production.
[0044] ===Other=== The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit its interpretation. The present invention can be modified and improved without departing from its spirit, and it goes without saying that the present invention includes equivalents thereof.
[0045] In the embodiments described above, concrete was used as an example, but the method is not limited to concrete and can be applied to other cement compositions (for example, mortar that does not contain coarse aggregate).
Claims
1. A cement composition containing water, cement, and aggregate, In the mix design, the air volume ratio in the cement composition is 6% to 40%, and the unit cement content is 336 kg / mΒ³. οΌ It is less than 170 kg / mΒ³ of water. οΌ It is less than 55%, and the water-cement ratio is less than 55%. A cement composition characterized by the following features.
2. A cement composition containing water, cement, and aggregate, In the mix design, the air volume ratio in the cement composition is 6% or more and less than 8%, and the unit cement content is 336 kg / mΒ³. οΌ It is less than and does not contain concrete admixtures for air content adjustment consisting of polyalkylene glycol compounds. A cement composition characterized by the following features.