JP6076722B2 - Concrete material - Google Patents

Description

  The present invention relates to a concrete material produced by a mixed cement containing at least 70% by weight of an admixture.

  With the consumption of a large amount of fossil fuel, the problem of global warming has become serious. In order to suppress this global warming, each industry is required to suppress the emission of carbon dioxide. Also in the construction industry, cement (Portland cement) widely used as a concrete material uses a huge amount of fossil fuel in its production process and generates a large amount of carbon dioxide. In addition, limestone decarboxylation occurs in the production process, and carbon dioxide is generated. For this reason, how to reduce the amount of cement used in concrete is a big problem.

  In recent years, in order to reduce the amount of cement used, a mixed cement in which an admixture is mixed with cement has been used (see, for example, Patent Documents 1 and 2). As admixtures, blast furnace slag, which is a by-product generated when producing pig iron in the blast furnace, is rapidly cooled with water and air and pulverized, and when pulverized coal is burned at a thermal power plant. Fly ash that is a by-product generated in the process, silica fume that is a by-product generated when silicon is refined in an electric furnace, and the like are used.

JP 2011-168436 A JP 2010-285664 A

  In this way, by using an admixture material such as blast furnace slag fine powder and increasing the substitution rate of the admixture material with respect to cement, the amount of carbon dioxide emission can be greatly reduced. However, since the concrete material substituted with the admixture at a high substitution rate tends to have an excessive slump, it is necessary to greatly reduce the amount of unit water and the amount of admixture used.

Here, the slump is a value indicating the fluidity of the concrete before solidification, and the unit water volume is the aggregate in the dry state where there is no water adhering to the surface but the internal voids are filled with water. is the weight of water used in making concrete 1 m ³ using. Admixtures are materials other than cement, water, and aggregate that are added to give special properties to concrete. For example, AE (Air Entraining) agent, AE water reducing agent, fluidizing agent, quick setting agent, rust prevention Agents.

  On the other hand, the decrease in the unit water amount and the admixture decreases the dispersibility of the cement and the admixture, and the slump decreases with the elapsed time from the kneading, resulting in a construction problem.

  Therefore, it has been desired to provide a concrete material that can reduce the decrease in slump due to the elapsed time from kneading while ensuring the unit water amount and the amount of admixture used are almost the same as when only cement is used. .

  In view of the above problems, the present invention is a concrete material manufactured by mixing a mixed cement containing at least 70% by mass of an admixture, an aggregate, water, and an admixture, wherein the blending of the concrete material is performed. Predetermined water cement ratio, unit water volume, fine aggregate ratio and admixture addition amount required when producing concrete material using only cement, containing a certain amount of thickener as admixture A concrete material is provided, characterized in that the admixture is used.

  By providing the concrete material of the present invention, even when the content of the admixture is as large as 70% by mass or more, the amount of unit water and the amount of admixture used are almost the same as when only cement is used. While securing, the degree of slump reduction due to the elapsed time from kneading can be reduced, and the degree of reduction can be made equal to or less than that when only cement is used. As a result, it is possible to achieve workability equivalent to or higher than that when using a cement-only concrete material.

The figure showing the specification of the material used for concrete material. The figure which showed the compounding table | surface of the material used. The figure which showed the result of the slump test done using the concrete material manufactured based on the mixing | blending shown in FIG. The figure which showed the relationship between elapsed time and slump.

  The concrete material of the present invention is manufactured by mixing a mixed cement containing at least 70% by mass of an admixture, aggregate, water, and an admixture. The mixed cement includes an admixture and a general cement, Portland cement.

Portland cement as a main component, tricalcium silicate (alite, 3CaO · _SiO 2), dicalcium silicate (belite, 2CaO · _SiO 2), calcium aluminate (aluminate, 3CaO _· Al _{2 O} 3) , Iron calcium tetraaluminate (ferrite, 4CaO.Al ₂ O ₃ .Fe ₂ O ₃ ), calcium sulfate (gypsum, CaSO ₄ .2H ₂ O).

  Portland cement includes ordinary Portland cement, early-strength Portland cement, ultra-early strong Portland cement, moderately hot Portland cement, sulfate-resistant Portland cement, and low heat Portland cement.

  Ordinary Portland cement is the most versatile cement and is used for general construction and construction of structures. Early-strength Portland cement and Super-early-strength Portland cement are cements that increase the content of alite and develop strong strength in a short time, and are used in emergency repair work. Medium heat Portland cement and low heat Portland cement are cements with high belite content and excellent long-term strength, and are used in construction of large-volume structures such as dams and piers. Sulfate-resistant Portland cement is a cement that has a low aluminate phase and excellent chemical durability, and is used in revetments that contact seawater and construction in hot springs. In the present invention, an appropriate Portland cement can be used depending on the content of the construction.

Examples of admixtures mixed with Portland cement include blast furnace slag fine powder, fly ash, and silica fume. Blast furnace slag fine powder is a mineral in a glass state, mainly composed of silicon dioxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), calcium oxide (CaO), magnesium oxide (MgO), iron oxide (Fe ₂ O). ₃ ) A small amount of titanium oxide (TiO ₂ ) or the like is contained.

Fly ash contains SiO ₂ and Al ₂ O ₃ as main components and contains a small amount of Fe ₂ O ₃ , CaO, sodium oxide (Na ₂ O), potassium oxide (K ₂ O), and the like. Silica fume contains SiO ₂ as a main component, contains a small amount of Al ₂ O ₃ , Fe ₂ O ₃ , CaO, TiO _{2 and the} like and has high pozzolanic reactivity. In the pozzolanic reaction, SiO ₂ contained as a main component in the admixture reacts with calcium hydroxide (Ca (OH) ₂ ) produced by the hydration reaction, resulting in dense and durable calcium silicate hydration. This is a reaction for producing a product (nCaO.SiO ₂ .mH ₂ O, n and m are arbitrary natural numbers).

  The admixture material is not limited to these materials, and any material can be used as long as it can be used as an alternative material for cement. Further, the admixture may be a mixture of two or all of fine blast furnace slag powder, fly ash, and silica fume at an arbitrary ratio.

  Aggregates are sand, gravel, crushed sand, crushed stone, etc., and are classified into coarse aggregate and fine aggregate according to the particle size. The coarse aggregate is an aggregate containing 85% by mass or more of particles having a particle size of 5 mm or more, and the fine aggregate is an aggregate that passes through all of the 10 mm sieve and passes through the 5 mm sieve by 85% by mass or more.

  Admixtures include AE agents, water reducing agents, AE water reducing agents, fluidizing agents, quick setting agents, rust preventives and the like. The AE agent is a material for uniformly distributing minute bubbles in the concrete and is also called an air entraining agent. For example, oleic acid soap, alkyl allyl sulfonate, alkylol amide, polyethylene glycol sulfate, etc. can be used.

  The water reducing agent is a material for reducing the required unit water amount. For example, a material mainly composed of a polyol complex, lignin sulfonate, oxycarboxylate, or the like can be used. The AE water reducing agent is a material having both functions of the AE agent and the water reducing agent. The fluidizing agent is a material for increasing the fluidity of concrete. For example, a material based on naphthalene sulfonate and melamine sulfonate can be used.

  The quick setting agent is a material for accelerating the setting of cement, and for example, calcium chloride, sodium silicate, or the like can be used. The rust preventive agent is a material for preventing the reinforcing bars embedded in the concrete from being rusted, and silicates, phosphates, amines, oxidants and the like that form a film on the metal surface can be used.

  As the admixture, a necessary one can be selected and used according to the use and purpose of the concrete material. Therefore, for example, if only the amount of unit water is reduced, only the AE water reducing agent can be used.

  The concrete material of the present invention is blended with a predetermined water-cement ratio, unit water amount, fine aggregate ratio and admixture that are required when the concrete material is produced using only cement (Portland cement). As an admixture, an admixture containing a certain amount of thickener is used.

  Here, the water-cement ratio is a ratio of cement and water contained in the concrete immediately after kneading, and is a value obtained by multiplying the denominator by the mass of cement and the numerator by 100. When mixed cement is used instead of cement, the ratio of mixed cement to water is obtained. This water-cement ratio is determined in consideration of the strength and durability of the concrete, and the strength, durability, and water tightness are improved as the ratio is reduced. Usually, the required concrete strength, durability, and water tightness are determined, and the water-cement ratio is determined so as to achieve the determined strength and the like.

  The unit amount of water is determined so as to be the smallest slump within the possible range. This unit water amount can be adjusted using a water reducing agent or an AE water reducing agent. The fine aggregate ratio is determined in consideration of the shape and particle size of the aggregate, the maximum size of the coarse aggregate, the presence or absence of an admixture, and the like. The maximum size of the coarse aggregate is preferably large in order to improve the quality of the concrete, but is generally 20 to 25 mm. The addition amount of the admixture is determined by performing test mixing or the like so that a required effect can be obtained according to the use and purpose.

  In addition, parameters required for the concrete material include air amount, slump, unit cement amount, aggregate amount, type of admixture and the amount used. The amount of air can be determined in consideration of concrete workability and freeze-thaw resistance. Since increasing the amount of air leads to a decrease in strength, it is desirable to select a value as small as possible within a range where predetermined freeze-thaw resistance can be obtained. The amount of air can be 4 to 6% by volume with respect to the concrete material, for example.

  The slump can be selected in the smallest possible range in consideration of various conditions in construction. In general, slump is affected by the unit amount of water, and a smaller value means less unit water and improves quality. The unit cement amount is determined from the water cement ratio and the unit water amount. The aggregate amount is determined as the remaining amount after the unit cement amount, the unit water amount, and the air amount are determined. The kind of admixture and the amount of the admixture are determined by conducting test mixing so that the required effect can be obtained according to the use and purpose of the concrete material.

  The thickener contained in the admixture is a material having an action of increasing the viscosity of fresh concrete and increasing the material separation resistance. For example, cellulose derivatives, polyacrylamides, polyvinyl alcohol, polysaccharides, β-1,3-glucan and the like can be used. Examples of the cellulose derivative include methyl cellulose, ethyl cellulose, and hydroxyethyl cellulose. The material separation resistance is a property that resists relative movement caused by a difference in mass between constituent materials. Since the content of the thickener varies depending on the type of admixture and the substitution rate in the mixed cement, it can be determined accordingly.

  When the AE water reducing agent is used as an admixture, the content of the thickener is about 0.05% to 0.2% by mass with respect to the unit cement amount (0.025% by mass for the AE water reducing agent). -0.4 mass%). If it is smaller than this, the decrease in slump due to the elapsed time becomes larger than that in the case of cement alone, and if it is larger than this, the viscosity is too high and molding becomes difficult and the workability deteriorates.

  In the present invention, by adding an admixture containing a certain amount of thickener determined as described above, only the cement is used even if the admixture in the mixed cement contains 70% by mass or more. As the unit water volume, water cement ratio, fine aggregate ratio, admixture addition amount almost the same as the case, it can be the degree of slump reduction due to the elapsed time equal to or more than when using only cement, Moreover, workability equivalent to or higher than that of a concrete material manufactured using only cement can be realized.

Here, a preferable blending example of the concrete material is shown. For example, the mixed cement is 70 to 90% by mass of blast furnace slag fine powder and 10 to 30% by mass of ordinary Portland cement, the maximum particle size of the coarse aggregate is 20 to 25 mm, and the fine aggregate ratio of the aggregate is 45 to 50% by volume, water cement ratio is 45 to 50% by mass, unit water amount is 160 to 175 kg / m ^3, and AE water reducing agent containing a certain amount of thickener is 0.5 to the mixed cement. It can mix | blend so that it may contain -2 mass%. This is merely an example, and these numerical values may vary if the type of admixture, the shape and particle size of the aggregate, and the like are different.

The results of a slump test using a specific material and a specific composition are shown below. First, the used material is shown in FIG. As materials used, ordinary Portland cement was used as cement (OPC), and ground granulated blast furnace slag (BFS) was used as an admixture. The cement having a density of 3.16 g / cm ³ was used, and the blast furnace slag fine powder having a density of 2.89 g / cm ³ and a specific surface area of 4180 cm ² / g was used.

The fine aggregate (S) used is mountain sand from Kakegawa, Shizuoka Prefecture, with a density of 2.59 g / cm ³ , and the coarse aggregate (G) is a hard sandstone crushed stone from Ome, Tokyo, with a density of 2.65 g / cm ^3. I used one. Two types of admixtures are prepared for comparison with the conventional case. One is a commercially available AE water reducing agent standard form (Type I) which is conventionally used, and the other is used in the present invention. An AE water reducing agent containing a certain amount of thickener was used.

  FIG. 2 shows a recipe. Four cases are shown in the recipe. Case 1 is a case where only conventional OPC is used. Case 2 and Case 3 are cases where a conventional commercially available AE water reducing agent is used and a mixed cement containing 30% by mass of OPC and 70% by mass of BFS is used. In Case 2, the unit water amount is smaller than others, and in Case 3, the amount of AE water reducing agent added is small. Case 4 is a case using the improved AE water reducing agent used in the present invention. In this blending, the slump immediately after kneading was adjusted to 10.0 cm ± 2.5 cm and the amount of air was adjusted to 4.5 ± 1.5%, and the addition amount of the AE water reducing agent was adjusted.

  FIG. 3 shows the results of a slump test performed on three conventional cases (Case 1 to Case 3) and the case (Case 4) of the present invention. In the slump test, a concrete material manufactured by the blend shown in FIG. 2 is put into a slump cone, which is a test container, and after stirring with a projecting rod, the slump cone is lifted in the vertical direction to remove the slump cone. This was done by measuring how much the height fell.

  As shown in FIG. 3, in Case 1, the slump became −3.5 cm after 30 minutes and −5.5 cm after 60 minutes. On the other hand, in Case 2, it significantly decreased to −4.7 cm after 30 minutes and −8.1 cm after 60 minutes. In Case 3, it further decreased to −5.7 cm after 30 minutes and −9 cm after 60 minutes. As described above, in the conventional AE water reducing agent, when the substitution rate of the admixture is increased, the degree of slump reduction due to the elapsed time is large even if the unit water amount is reduced or the amount of AE water reducing agent added is reduced. became.

  In Case 4, it was -1.6 cm even after 30 minutes and -4.1 cm after 60 minutes, and the degree of decrease in slump due to elapsed time was smaller than in Case 1. For this reason, it has been found that even if the amount of unit water and the amount of AE water reducing agent are not reduced, the degree of the reduction can be made equal to or less than that when only cement is used. Thereby, it turns out that workability equivalent to or more than the case where the concrete material only of cement is used can be realized.

  FIG. 4 is a graph showing the result of FIG. 3, and shows the relationship between elapsed time and slump. Referring to FIG. 4, it can be seen that Case 4 showing an example of the concrete material of the present invention has the slowest slump drop due to the elapsed time, and improves the temporal retention of fresh properties that are important in terms of construction.

It is estimated that the amount of CO ₂ emission, which is a warming gas, can be reduced by about 66% by setting the blast furnace slag fine powder to 70% by mass and lowering the cement to 30% by mass. For this reason, by using the concrete material of the present invention, in addition to improving the retention over time, the amount of CO ₂ emission can be significantly reduced.

  The concrete material of the present invention has been described in detail with reference to the embodiments shown in the drawings, but the present invention is not limited to the above-described embodiments, and other embodiments, additions, and modifications are made. It is possible to make modifications within the range that can be conceived by those skilled in the art, such as deletion, and any aspect is included in the scope of the present invention as long as the effects and advantages of the present invention are exhibited.

Claims (4)

A concrete material produced by mixing a mixed cement containing at least 70% by weight of an admixture, an aggregate, water and an admixture,
Formulation of the concrete material is a predetermined water-cement ratio, unit water amount, fine aggregate ratio and additive amount required when producing concrete material using only cement, and as the admixture, A concrete material characterized in that an AE water reducing agent containing a certain amount of thickener is used. The admixture is ground granulated blast furnace slag, concrete material according to claim 1. The mixed cement is composed of 70% by mass to 90% by mass of the blast furnace slag fine powder and 10% by mass to 30% by mass of ordinary Portland cement, and the maximum particle size of the aggregate is 20 mm to 25 mm. The fine aggregate ratio is 45% by volume to 50% by volume, the water cement ratio is 45% by mass to 50% by mass, the unit water amount is 160 kg / m ^{3 to} 175 kg / m ³ , The concrete material of Claim 2 mix | blended so that the said AE water reducing agent containing a thickener may be contained 0.5 mass%-2 mass% with respect to the said mixed cement. The said thickener is a concrete material of any one of Claims 1-3 contained 0.025 mass%-0.4 mass% with respect to the said AE water reducing agent.