Cement concrete and its manufacturing method

Abstract

To provide a cement concrete with reduced CO2 emissions and improved strength development while containing food materials, and a method for producing the same.SOLUTION: A cement concrete is produced by hardening and carbonation-curing a cement composition containing cement, an admixture and food materials. A production method of the cement concrete includes a process of kneading a cement composition containing cement, admixtures and food materials with water to make cement slurry, a process of filling the cement slurry into a form, a process of curing the cement slurry filled in the form and then removing the form to make a hydrated hardened body, and a process of carbonation-curing the hydrated hardened body.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to cement concrete and a method for manufacturing the same.

Background Art

[0002] Cement concrete is used as a material for construction and civil engineering works. As cement concrete, a cement composition containing cement, calcium aluminate, and gypsum is described (Patent Document 1). However, Patent Document 1 does not describe food ingredients.

[0003] Patent Documents 2 to 3 describe seaweed reefs. These documents describe concrete blocks as a place for forming seaweed. However, since concrete blocks emit a large amount of CO2 during their production, the seaweed reefs described in Patent Documents 2 to 3 have a problem of a large CO2 emission amount.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made to solve the above-described problems of the prior art, and an object thereof is to provide a cement concrete having a reduced CO2 emission amount and improved strength development property while containing food ingredients, and a method for manufacturing the same.

Means for Solving the Problems

[0006] In order to achieve the above object, the inventors of the present invention have conducted intensive research and found that the above problems can be solved by carbonating and curing concrete containing food ingredients. The present invention is based on the above findings and has the following gist. [1] Cement concrete obtained by curing and carbonating a cement composition containing cement, admixture, and food ingredients. [2] The cement concrete according to [1] above, having a pH of 8 to 10.5. [3] The cement concrete according to [1] or [2] above, which is porous concrete. [4] The cement concrete according to any one of [1] to [3] above, having a porosity of 5 to 40%. [5] The cement concrete according to any one of [1] to [4] above, having a compressive strength of 0.5 to 20 N / mm 2 [6] The cement concrete according to any one of [1] to [5] above, wherein the food ingredient is at least one food ingredient selected from seaweed and vegetables. [7] The cement concrete according to [6] above, wherein the seaweed is leafy seaweed and the vegetable is leafy vegetable. [8] The cement concrete according to any one of [1] to [7] above, wherein the cement composition further contains slag aggregate. [9] The cement concrete according to any one of [1] to [8] above, having a CO2 emission intensity of 300 kg / m 3

[10] A method for producing cement concrete, comprising the steps of kneading a cement composition containing cement, admixture, and food ingredients with water to produce a cement slurry, filling the cement slurry into a mold, curing the cement slurry filled in the mold, removing the mold to produce a hydrated hardened body, and carbonating and curing the hydrated hardened body.

[11] The method for producing cement concrete according to

[10] above, wherein the food ingredient is at least one food ingredient selected from seaweed and vegetables.

[12] The method for manufacturing cement concrete according to

[11] above, wherein the seaweed is leafy seaweed and the vegetable is leafy vegetable.

[13] The method for manufacturing cement concrete according to any one of

[10] to

[12] above, wherein the water-cement binder ratio (W / B), which is the ratio of water to the cement binder composed of cement and admixture when kneading the cement composition and water, is 100 to 300%.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide cement concrete with reduced CO2 emissions and improved strength development while containing food ingredients, and a method for manufacturing the same.

Embodiments for Carrying Out the Invention

[0008] [Cement Concrete] The cement concrete of the present invention is obtained by curing and carbonating a cement composition containing cement, an admixture, and a food ingredient. Thereby, it is possible to improve the strength development while containing the food ingredient. Further, since the cement concrete of the present invention absorbs carbon dioxide by carbonation curing, the CO2 emissions are reduced. Furthermore, since the pH of the cement concrete of the present invention can be reduced by carbonation curing, the adverse effect on the habitat and growth environment of aquatic organisms can be suppressed.

[0009] (Cement) In this specification, "cement concrete" collectively refers to cement paste, cement mortar, and concrete. Examples of the cement used in the cement concrete of the present invention include various Portland cements such as ordinary, early-strength, super-early-strength, low-heat, and medium-heat Portland cements, various blended cements obtained by mixing blast furnace slag, fly ash, or silica with these Portland cements, filler cements obtained by mixing limestone powder, finely ground blast furnace slag, etc. with these Portland cements, and environmentally friendly cements (eco-cements) manufactured using municipal solid waste incineration ash or sewage sludge incineration ash as raw materials. These cements can be used alone or in combination of two or more. Among these cements, ordinary Portland cement is preferred from the viewpoint of being able to easily contain food ingredients.

[0010] From the viewpoint of an appropriate hydration rate of the cement, the Blaine specific surface area of the cement used in the cement concrete of the present invention is preferably 2500 to 4800 cm 2 / g, more preferably 2800 to 4000 cm 2 / g, and even more preferably 3000 to 3600 cm 2 / g. The Blaine specific surface area can be measured in accordance with JIS R 5201-1997 "Physical Testing Methods for Cement".

[0011] The cement used in the cement concrete of the present invention preferably contains cement clinker and gypsum. This can prevent flash setting of the cement, increase the strength of the cement concrete to a certain level or higher, and also increase the chemical resistance. From such a viewpoint, the mineral composition of the cement clinker calculated using the Bogue formula is preferably C3S (tricalcium silicate) of 40 to 70% by mass, C2S (dicalcium silicate) of 7 to 40% by mass, C3A (tricalcium aluminate) of 1 to 15% by mass, and C4AF (tetracalcium ferroaluminate) of 5 to 20% by mass. Also, the content of gypsum in the cement is preferably 0.5 to 4% by mass in terms of SO3 conversion, and more preferably 1.5 to 3% by mass.

[0012] In the cement composition used for the cement concrete of the present invention, the cement content is preferably 10 to 95 parts by mass, more preferably 10 to 70 parts by mass, based on 100 parts by mass in total of cement, admixture and food ingredient, from the viewpoint of maintaining the strength of the cement concrete at a certain level or higher. Further, from the viewpoint of form maintenance in the sea, the cement content in the above cement composition is more preferably 20 to 70 parts by mass based on 100 parts by mass in total of cement, admixture and food ingredient.

[0013] (Food ingredient) The food ingredient used for the cement concrete of the present invention is a material for human food. Also, the food ingredient may be waste. Thereby, the food ingredient that has been discarded can be effectively utilized, and the food ingredient can be easily obtained. Examples of the discarded food ingredient include food ingredients discarded because they do not meet the standards as a product, food ingredients discarded to suppress the price decline of food ingredients due to excessive bumper crops, and food ingredient waste generated when harvesting or processing food ingredients.

[0014] From the viewpoint of easy availability, the food ingredient is preferably at least one kind of food ingredient among seaweed and vegetables. Commonly available seaweed is sufficient for the seaweed. For example, the leaf part or stem part of leafy seaweed such as kombu, wakame, arame, and kajime can be used. The shape of the seaweed is not particularly limited as long as it can be mixed with cement and hardened. Commonly available vegetables are sufficient for the vegetables. For example, leafy vegetables such as cabbage, lettuce, and Chinese cabbage can be used. The shape of the vegetables is not particularly limited as long as it can be mixed with cement and hardened.

[0015] The food ingredients may contain materials other than the above-mentioned food ingredients, as long as the effects of the present invention are not inhibited. Materials other than food ingredients are, for example, materials other than food ingredients such as soil, sand, and stones mixed in discarded food ingredients. However, from the viewpoint of further enhancing the effects of the cement concrete of the present invention, the content of the above-mentioned food ingredients in the food ingredients is preferably 80 to 100% by mass, more preferably 90 to 100% by mass, still more preferably 95 to 100% by mass, and particularly preferably 100% by mass.

[0016] From the viewpoint of maintaining the strength of the cement concrete at a certain level or higher, the content of the food ingredients in the cement composition used in the cement concrete of the present invention is preferably 15 to 70 parts by mass, more preferably 25 to 70 parts by mass, based on 100 parts by mass in total of cement, admixture, and food ingredients. Further, from the viewpoint of the form-maintaining property of the cement concrete in the sea, the content of the food ingredients is more preferably 25 to 60 parts by mass based on 100 parts by mass in total of cement, admixture, and food ingredients. Alternatively, from the viewpoint of further enhancing the effects of the cement concrete of the present invention, the content of the food ingredients is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, still more preferably 15 parts by mass or more, based on 100 parts by mass in total of the total mass (cement and food ingredients, water, aggregate, admixture).

[0017] (Water) The cement composition used in the cement concrete of the present invention preferably further contains water. The amount of water used in the above cement composition is preferably 10 to 200 parts by mass, more preferably 40 to 150 parts by mass, still more preferably 60 to 130 parts by mass, and even more preferably 80 to 110 parts by mass, based on 100 parts by mass in total of cement, admixture, and food ingredients, from the viewpoints of the workability of the cement composition and the porosity of the cement concrete.

[0018] (Aggregate) From the perspective of increasing the porosity of cement concrete and improving workability, the cement composition used in the cement concrete of the present invention may further contain aggregates. Examples of the aggregates include slag aggregates, fine aggregates, coarse aggregates, river sand, mountain sand, crushed stone, and the like. These aggregates can be used alone or in combination of two or more. Among these aggregates, slag aggregates are preferred.

[0019] From the above perspective, the maximum particle size of the aggregate is preferably 20 mm or less, more preferably 5 - 13 mm.

[0020] The amount of the aggregate used in the cement composition used in the cement concrete of the present invention is preferably 100 - 1000 parts by mass with respect to a total of 100 parts by mass of the cement and the food ingredients. When the amount of the aggregate used is 100 parts by mass or more, the porosity of the cement concrete can be increased to improve workability, and when the amount of the aggregate used is 1000 parts by mass or less, the strength of the cement concrete can be increased to a certain level or more. From such a perspective, the amount of the aggregate used is more preferably 300 - 750 parts by mass, and even more preferably 400 - 550 parts by mass.

[0021] (Admixture) The cement composition used in the cement concrete of the present invention contains an admixture. An admixture is a material that has a relatively large usage amount among the admixture materials and whose volume itself is included in the volume of the kneaded product such as concrete. Note that the admixture materials are materials other than cement, water, aggregates, and food ingredients, and are materials that are added as necessary before placing to impart special properties to the concrete. Examples of the admixtures include blast furnace slag fine powder, fly ash, silica fume, rapid hardening materials, expansive materials, and the like. Among these admixtures, rapid hardening materials are preferred. When the cement composition contains an admixture, it is possible to suppress the cement concrete from breaking. In addition, demolding can be performed earlier, thereby improving the production efficiency of the cement concrete.

[0022] Among the rapidly hardening materials, ettringite-forming rapidly hardening materials are preferred. Examples of ettringite-forming rapidly hardening materials include those containing calcium aluminate and gypsum as main components, those containing calcium sulfoaluminate and gypsum as main components, and the like. These ettringite-forming rapidly hardening materials can be used alone or in combination of two or more. Among these ettringite-forming rapidly hardening materials, those containing calcium aluminate and gypsum as main components are preferred.

[0023] Calcium aluminate is a general term for substances with hydration activity mainly composed of CaO and Al₂O₃, and it is a material with a short hardening time and high initial strength development. Because it hardens in a short time and has high initial strength development thereafter, amorphous calcium aluminate quenched rapidly after melting is preferred.

[0024] From the viewpoints of initial strength development and hardenability, the molar ratio of CaO to Al₂O₃ (CaO / Al₂O₃ molar ratio) in calcium aluminate is preferably 1.0 to 3.0, more preferably 1.7 to 2.5.

[0025] The Blaine specific surface area of calcium aluminate is preferably 3000 cm 2 / g or more. When the Blaine specific surface area of calcium aluminate is 3000 cm 2 / g or more, it is possible to suppress the decrease in the flash setting power of calcium aluminate. The Blaine specific surface area can be measured in accordance with JIS R 5201-1997 "Physical Test Methods for Cement".

[0026] From the perspective of reaction activity, the vitrification rate of calcium aluminate is preferably 70% or more, more preferably 90% or more. When the vitrification rate of calcium aluminate is 70% or more, the initial strength development and hardening properties can be improved. The measurement of the vitrification rate of calcium aluminate is to measure in advance the main peak area S of the crystalline mineral of the sample before heating by powder X-ray diffraction method, then heat at 1000 °C for 2 hours, and then slowly cool at a cooling rate of 1-10 °C / min. The main peak area S0 of the crystalline mineral after heating is obtained by powder X-ray diffraction method. Using the values of S0 and S, the vitrification rate χ is calculated using the following formula. Vitrification rate χ (%) = 100×(1 - S / S0)

[0027] As the gypsum used as the admixture, for example, hemihydrate gypsum and anhydrous gypsum can be used. From the perspective of strength development, anhydrous gypsum is preferred. As anhydrous gypsum, for example, by-product anhydrous gypsum from hydrofluoric acid and natural anhydrous gypsum can be used. The pH of water when gypsum is immersed in water is preferably 8 or less. That is, the water when gypsum is immersed in water is preferably weakly alkaline to acidic. When the pH of water when gypsum is immersed in water is 8 or less, the solubility of the gypsum component can be suppressed from increasing, and the inhibition of the initial strength development due to the dissolution of the gypsum component can be suppressed. The pH of water when gypsum is immersed in water mentioned here is the pH of the diluted slurry at 20 °C with gypsum / ion-exchanged water = 1 g / 100 g, measured using an ion-exchange electrode or the like.

[0028] The Blaine specific surface area of gypsum is preferably 3000 cm 2 / g or more. From the perspective of initial strength development and obtaining an appropriate working time, it is more preferably 5000 cm 2 / g or more. The Blaine specific surface area can be measured in accordance with JIS R 5201-1997 "Physical Test Methods for Cement".

[0029] The amount of gypsum used in the admixture is not particularly limited, but is preferably 50 to 250 parts by mass with respect to 100 parts by mass of calcium aluminate. When the amount of gypsum used is 50 parts by mass or more, sufficient working time can be taken and the strength development property can be improved. When the amount of gypsum used is 250 parts by mass or less, sufficient working time and sufficient initial strength can be obtained.

[0030] From the viewpoint of maintaining the strength of the cement concrete of the present invention at a certain level or more, the content of the admixture in the cement concrete of the present invention is preferably 3 to 50 parts by mass, more preferably 5 to 40 parts by mass, with respect to a total of 100 parts by mass of cement, admixture and food ingredients. Further, from the viewpoint of form maintenance in the sea, the content of the admixture is more preferably 10 to 35 parts by mass.

[0031] (Admixture) The cement composition used in the cement concrete of the present invention may further contain an admixture. An admixture is a material in the admixture that is used in a small amount and its own volume is not included in the kneaded volume such as cement concrete. Examples of the admixture include an AE agent, a water reducing agent, an AE water reducing agent, a high performance AE water reducing agent, a high performance water reducing agent, a fluidizing agent, a quick setting agent, a thickening agent, and the like. For example, in order to further improve the production efficiency of cement concrete, an admixture may be used for the purpose of early demolding. When an admixture is used in the cement concrete of the present invention, the amount of the admixture used in the cement composition used in the cement concrete of the present invention is preferably 0.01 to 10 parts by mass, more preferably 0.1 to 1 part by mass, with respect to 100 parts by mass of cement.

[0032] In the present specification, the cement binder is composed of the above-mentioned cement and admixture.

[0033] (Curing and carbonation curing) As described above, the cement concrete of the present invention is obtained by curing and carbonating the above cement composition. Details of the curing and carbonation curing of the above cement composition will be described in the explanation of the manufacturing method of the cement concrete described later.

[0034] The pH of the cement concrete of the present invention is preferably 8 to 10.5. The pH of normal seawater is about 7.8 to 8.4. When the pH of the cement concrete is 8 to 10.5, it is possible to suppress an increase in the pH of the seawater around the cement concrete. Note that when the pH of the seawater is 10 or less, the settlement and growth of larvae and eggs are not inhibited. Therefore, seawater with a pH of 10 or less is an environment in which larvae and eggs are extremely likely to settle and grow, and it can be said that it is an environment in which aquatic organisms are likely to inhabit and grow. From such a viewpoint, the pH of the cement concrete of the present invention is more preferably 8 to 9.5. The pH of the cement concrete can be measured by the method described in the examples below.

[0035] The cement concrete of the present invention is preferably porous concrete. In this specification, porous concrete means cement concrete having porosity. Therefore, in this specification, porous concrete is not limited to porous concrete in which coarse aggregates are bonded together with cement paste or mortar containing a small amount of fine aggregate. When the cement concrete of the present invention is porous concrete, the light weight and workability of the cement concrete can be improved.

[0036] From the viewpoint of maintaining the strength of the cement concrete at a certain level or higher, the porosity of the cement concrete of the present invention is preferably 5 to 40%, more preferably 10 to 35%, and even more preferably 15 to 30%.

[0037] Since the cement concrete of the present invention absorbs carbon dioxide by carbonation curing, the amount of CO2 emissions can be reduced. As a result, the CO2 emission intensity of the cement concrete of the present invention is preferably 300 kg / m3 More preferably, it is 250 kg / m or less 3 Even more preferably, it is 200 kg / m or less 3 and can be made to be such hereinafter.

[0038] The shape of the cement concrete of the present invention is not particularly limited. Examples of the shape of the cement concrete include shapes such as a cylinder, a prism, a rectangular parallelepiped, a cone, a sphere, and a tetra-pot body. It is preferable to determine the size and shape of the cement concrete according to conditions such as the sea area where it is installed. For example, in a sea area with a fast tidal current, by combining a plurality of cement concretes in the shape of a tetra-pot body, it is possible to prevent the cement concrete from being washed away and fix it at the target location.

[0039] <Effect> Hereinafter, an example of the effect of the cement concrete of the present invention will be described. The cement concrete of the present invention can improve strength development, workability, and light weight. Furthermore, since the cement concrete of the present invention absorbs carbon dioxide by carbonation curing, it is possible to reduce the amount of CO2 emissions. Furthermore, since the pH of the cement concrete of the present invention is reduced by carbonation curing, it is possible to suppress the adverse effects of the cement concrete on the habitat and growth environment of aquatic organisms.

[0040] The cement concrete of the present invention can further reduce the labor of removing herbivores. This is because the cement concrete of the present invention contains food ingredients. This is because the food ingredients of the present invention have the effect of attracting herbivores.

[0041] In coastal waters, there are seaweed beds where seaweed thrives, which play important roles such as a feeding ground and a spawning ground for marine organisms. However, in recent years, a phenomenon called "seashore burning" in which the seaweed beds disappear has been observed. The causes of seashore burning are various, but the damage caused by herbivores such as fish is particularly regarded as a problem (Fisheries Agency, Revised Guidelines for Combating Seashore Burning, 2015).

[0042] Various techniques for reducing damage caused by the removal of herbivores have been proposed so far (Fisheries Agency, Revised Guide for Countermeasures against Rock Burn, 2015, Patent No. 3311339, JP-A-2011-167083). However, the removal of herbivores mainly relies on manual work by divers, which is difficult to continue due to the large amount of labor, and has not led to an improvement in rock burn.

[0043] Furthermore, when cement concrete is installed in water, Ca eluted from the cement concrete raises the pH of the surrounding water, which has an adverse effect on the habitat and growth environment of aquatic organisms. Therefore, the seaweed reefs described in Patent Documents 2 to 3 also have the problem of raising the pH of the water around the seaweed reef and having an adverse effect on the habitat and growth environment of aquatic organisms.

[0044] The present invention can solve the above problems. The present invention can reduce the labor of removing herbivores and suppress the adverse effects on the habitat and growth environment of aquatic organisms. With the cement concrete of the present invention, at least a part of the herbivores can be gathered in a predetermined area, and the gathered herbivores can be captured, so that the labor of removing the herbivores can be reduced. Herbivores are mainly animals that eat seaweed. Examples of herbivores include abalone, sea slugs, small snails, predatory fish (such as sea bream, red sea bream, black porgy, and yellowtail). When the cement composition contains an admixture, it is possible to suppress the cement concrete from breaking when storing the cement concrete in the cage for collecting herbivores. The cement concrete of the present invention has the effect of gradually releasing the attracting component in the food material. For example, when the cement concrete is porous cement concrete, the attracting component that attracts herbivores can be efficiently released from the cement concrete, and the attracting effect of the cement concrete can be improved.

[0045] When the cement concrete of the present invention is stored in a cage for collecting herbivores, the herbivores are attracted to the cement concrete of the present invention and enter the cage for collecting herbivores. Then, by lifting the cage for collecting herbivores, the labor for removing herbivores can be reduced. However, the appropriate size of the cement concrete for storage in the cage for collecting herbivores varies depending on the size of the entrance of the cage for collecting herbivores and the size of the mesh opening. For this reason, it is preferable that the cement concrete can be easily processed by manually breaking the cement concrete so that it has an appropriate size for the cage for collecting herbivores. From such a viewpoint, the compressive strength of the cement concrete of the present invention is preferably 0.5 to 20 N / mm 2 and more preferably 1 to 15 N / mm 2 and even more preferably 2 to 10 N / mm 2 is. The compressive strength of the cement concrete of the present invention can be measured by the method described in the examples.

[0046] [Method for manufacturing cement concrete] Hereinafter, the method for manufacturing the cement concrete of the present invention will be described. Note that the cement and food materials used in the method for manufacturing the cement concrete of the present invention are the same as those described for the cement concrete of the present invention, so the description of the cement and food materials used in the method for manufacturing the cement concrete of the present invention will be omitted.

[0047] The method for manufacturing the cement concrete of the present invention includes a step (A) of kneading a cement composition containing cement, admixture, and food material with water to produce a cement slurry, a step (B) of filling the cement slurry into a mold, a step (C) of curing the cement slurry filled in the mold and then removing the mold to produce a hydrated hardened body, and a step (D) of carbonating and curing the hydrated hardened body. Hereinafter, each step will be described in detail.

[0048] (Step (A)) In step (A), a cement slurry is prepared by kneading a cement composition containing cement, admixture, and cementitious materials with water. The formulation of the cement slurry is preferably determined in consideration of the forming and curing methods so that the required quality is satisfied after the cement slurry hardens. Note that the required quality after the cement slurry hardens can be determined by a test conducted using a cement concrete specimen manufactured under the same conditions as cement concrete. Also, the workability of the cement concrete is preferably determined in consideration of the shape, dimensions, forming method, etc. of the cement concrete. To facilitate quality stabilization, it is preferable to use a batch mixer for kneading the cement composition and water.

[0049] In order to make the porosity of the cement concrete fall within the above range, the water-to-cementitious material ratio (W / B) when kneading the cement composition and water is preferably 100 to 300%, more preferably 100 to 200%.

[0050] (Step (B)) In step (B), the cement slurry is filled into a mold. The mold preferably has a robust structure, can obtain the shape and dimensions required for cement concrete, and is easy to assemble and disassemble. When the number of molds is small, a wooden mold may be used, but a steel mold is preferred. In step (B), after filling the cement slurry into the mold, mechanical compaction may be performed. Examples of mechanical compaction include vibration compaction, centrifugal compaction, vibration-pressure compaction, vacuum compaction, and compaction using a combination thereof.

[0051] (Step (C)) In step (C), after curing the cement slurry filled in the formwork, the formwork is removed to produce a hydrated hard body. It is preferable to determine the curing method and period of the cement slurry filled in the formwork so as to obtain the required quality. The cement slurry filled in the formwork is preferably cured sufficiently while paying attention not to be affected by harmful factors such as low temperature, drying, rapid temperature change, load, and impact. Although the curing method is not particularly limited, it is preferable to perform steam curing from the viewpoint of improving the initial strength development property and enhancing productivity. Steam curing generally means piping the steam generated by a boiler and sending it to a steam curing chamber, and heating and humidifying the cement slurry in the formwork under normal pressure to accelerate the strength development. Although the steam curing conditions are not particularly limited, after ensuring a predetermined preheating time, the heating rate is set to 1 to 20 °C / hr, steam is applied, the maximum reaching temperature is in the range of 20 to 60 °C, and the holding time at the maximum reaching temperature is 1 hour to 2 weeks. When each condition is within the above range, the effect of improving the initial strength development property by steam curing and enhancing productivity can be obtained, and a hardened body with predetermined characteristics can be obtained. After maintaining the maximum reaching temperature, it is preferable to gradually lower the temperature in the curing chamber so that the hydrated hard body does not crack. It is preferable to determine the cooling time so that the hydrated hard body can be taken out after the temperature difference from the outside air becomes small. In addition, in order to further improve the quality of the cement concrete, wet curing may be carried out after steam curing. Demolding is preferably performed after the strength of the hydrated hard body reaches a strength that does not hinder handling. The hydrated hard body removed from the formwork needs to be handled so that its shape and dimensions are not impaired.

[0052] (Step (D)) In step (D), the hydrated hardening body is carbonated. Carbonation curing involves sending a gas containing carbon dioxide into a carbonation curing chamber and heating and humidifying the hydrated hardening body in a carbon dioxide atmosphere at normal pressure or under a pressure of 10 MPa or less to accelerate the carbonation of the hydrated hardening body. Note that the carbonation of the hydrated hardening body proceeds by the diffusion of carbon dioxide into the voids in the hydrated hardening body and the carbonation of the cement hydrate. As a supply source of the carbon dioxide used for carbonation curing, combustion exhaust gas discharged from factories or facilities can be utilized. The combustion exhaust gas may be directly fed into the curing chamber for carbonation curing, or it may be fed after being mixed with other gases. Carbonation curing is preferably carried out at a carbon dioxide concentration of 5 to 100% by volume, a temperature of 20 to 80°C, a humidity of 30 to 70% RH, and over a period of 1 day to 2 weeks, although it depends on the size of the hydrated hardening body.

[0053] Note that in the cement concrete of the present invention, the hardening of the cement composition can be carried out, for example, as in steps (B) and (C), by filling the cement slurry into a mold and then curing the cement slurry filled in the mold. Also, in the cement concrete of the present invention, the carbonation curing of the cement composition can be carried out, for example, after hardening, by carbonation curing the demolded cement composition as in step (D).

Examples

[0054] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples.

[0055] [pH Evaluation Test] The pH evaluation test of the present invention is a value measured using a glass electrode type pH meter (manufactured by Horiba, Ltd.) at 25°C for the test solution obtained by filtering the mixed solution after adding water 10 times the mass ratio of the material to the pulverized powder of the prepared concrete solidified body as the material and stirring at 500 rpm.

[0056] [Porosity Evaluation Test] The porosity was calculated using the liquid weighing method. This porosity means the open porosity without closed pores, which is measured by the Archimedes method.

[0057] [Evaluation Test of Compressive Strength] In accordance with JIS R 5201-1997 "Physical Testing Methods for Cement", the compressive strength of the concrete was measured 28 days after mixing the cement paste and aggregates. Those that could not maintain their shape after 28 days were not measured.

[0058] [Calculation of CO2 Emission Intensity] The CO2 emission intensity of concrete means the mass of CO2 emitted when manufacturing 1 m 3 of concrete, and its unit is expressed as (kg-CO2 / m 3 ). The CO2 emission intensity of concrete is calculated from the concrete mix using the emission intensities of the materials used in manufacturing concrete, namely, cement, sand, gravel, admixtures (materials), etc. The emission intensity of each material is calculated and determined by the LCA (Life Cycle Assessment) method. Here, the LCA method is a method that expresses the amount of carbon dioxide emissions generated in the life cycle from raw material procurement, transportation, manufacturing, consumption, to disposal as carbon emissions when manufacturing materials. The emission intensities of materials used in the civil engineering and construction industries have been proposed by various academic societies and research institutions such as the Japan Society of Civil Engineers, the Japan Society of Aerial and Sanitary Architecture, the Building Research Institute of the Ministry of Construction, and the Civil Engineering Research Institute of the Ministry of Construction. As a specific example, for instance, according to the recommended values of the LCA Subcommittee of the Earth Environment Committee of the Japan Society of Civil Engineers, the emission intensity of ordinary Portland cement is 0.228 kgC / kg, that of blast furnace cement is 0.135 kgC / kg, that of sand is 0.00154 kgC / kg, that of gravel is 0.00189 kgC / kg in the case of crushed stone and 0.00154 kgC / kg in the case of quarrying. Also, the carbon emission of the admixture used is proposed in the following reference and is determined to be 0.153 kgC / kg. Furthermore, the amount of CO2 absorbed by carbonation of the concrete solidified body was measured by the coulometric titration method using a carbon analyzer (manufactured by International Electric Co., Ltd., coulometric C, model VK-1C). It was confirmed that the concrete solidified body after carbonation curing had carbonated to the center by the coloring reaction using the phenolphthalein method. References: Kenji Yamamoto, Minoru Morioka, Satoru Teramura, Etsuro Sakai: Mix Design of Sprayed Concrete with Low Environmental Impact, Proceedings of the Cement Concrete Society, No. 56, pp. 148-155, 2002

[0059] [Example 1] 100 parts by mass of cement, 80 parts by mass of admixture, 180 parts by mass of food ingredients, and 288 parts by mass of tap water were put into a concrete mixer (Omni Mixer, manufactured by Chiyoda Machinery Co., Ltd.) and kneaded to prepare a cement composition, which was then poured into a mold of 10 cm × 10 cm × 9 cm. Then, steam curing was carried out under the conditions of a pre-curing time of 2 days (20 °C), a heating rate of 5 °C / hr, a maximum reaching temperature of 40 °C, a holding time at the maximum reaching temperature of 7 days, and a cooling rate of 5 °C / hr. Immediately after steam curing, the mold was removed, and carbonation curing was carried out for 14 days under the conditions of 50 °C, 40% RH, and a carbon dioxide gas concentration of 20% by volume to produce the concrete of Example 1.

[0060] [Example 2] Concrete of Example 2 was produced in the same manner as Example 1, except that 100 parts by mass of cement, 80 parts by mass of admixture, 77.1 parts by mass of food ingredients, and 233 parts by mass of tap water were put into the concrete mixer.

[0061] [Example 3] Concrete of Example 3 was produced in the same manner as Example 1, except that 100 parts by mass of cement, 80 parts by mass of admixture, 270 parts by mass of food ingredients, and 450 parts by mass of tap water were put into the concrete mixer.

[0062] [Comparative Example 1] 100 parts by mass of cement and 40 parts by mass of tap water were put into a concrete mixer (Omni mixer, manufactured by Chiyoda Machinery Co., Ltd.) and kneaded to prepare a cement composition, which was then poured into a mold of 10 cm × 10 cm × 9 cm. Then, steam curing was carried out under the conditions of a preconditioning time of 2 days (20 °C), a heating rate of 5 °C / hr, a maximum temperature reached of 40 °C, a holding time at the maximum temperature reached of 7 days, and a cooling rate of 5 °C / hr to produce the concrete of Comparative Example 1.

[0063] [Comparative Example 2] 100 parts by mass of cement and 40 parts by mass of tap water were put into a concrete mixer (Omni mixer, manufactured by Chiyoda Machinery Co., Ltd.) and kneaded to prepare a cement composition, which was then poured into a mold of 10 cm × 10 cm × 9 cm. Then, steam curing was carried out under the conditions of a preconditioning time of 2 days (20 °C), a heating rate of 5 °C / hr, a maximum temperature reached of 40 °C, a holding time at the maximum temperature reached of 7 days, and a cooling rate of 5 °C / hr. After the steam curing, the mold was removed immediately, and carbonation curing was carried out for 14 days under the conditions of 50 °C, 40% RH, and a carbon dioxide gas concentration of 20% by volume to produce the concrete of Comparative Example 2.

[0064] [Comparative Example 3] 100 parts by mass of food ingredients and 200 parts by mass of tap water were put into a concrete mixer (Omni mixer, manufactured by Chiyoda Machinery Co., Ltd.) and kneaded, and then poured into a mold of 10 cm × 10 cm × 9 cm. Then, steam curing was carried out under the conditions of a preconditioning time of 2 days (20 °C), a heating rate of 5 °C / hr, a maximum temperature reached of 40 °C, a holding time at the maximum temperature reached of 7 days, and a cooling rate of 5 °C / hr to produce the solidified body of Comparative Example 3.

[0065] [Comparative Example 4] The concrete of Comparative Example 4 was produced in the same manner as Comparative Example 2, except that 90 parts by mass of cement, 10 parts by mass of food ingredients, and 60 parts by mass of tap water were put into a concrete mixer.

[0066] [Comparative Example 5] The solidified body of Comparative Example 5 was produced in the same manner as Comparative Example 3, except that 10 parts by mass of cement, 90 parts by mass of food ingredients, and 180 parts by mass of tap water were put into a concrete mixer.

[0067] (Raw materials used) In the above Examples and Comparative Examples, the following raw materials were used. Cement: Ordinary Portland cement, commercially available, Blaine specific surface area 3300 cm 2 / g, density 3.15 g / cm 3 In the cement clinker, the cement mineral composition was 56% by mass of C3S, 26% by mass of C2S, 9% by mass of C3A, and 9% by mass of C4AF. The content of gypsum in the cement was 2.1% by mass in terms of SO3. Admixture: 100 parts by mass of calcium aluminate (CaO / Al2O3 molar ratio 2.2, vitrification rate 97%, Blaine specific surface area 5000 cm 2 / g) and 100 parts by mass of gypsum (natural anhydrous gypsum, Blaine specific surface area 6000 cm 2 / g, pH 7.2), a mixture thereof. Food ingredient: Wakame stems discarded from a wakame farm, density 1.73 g / cm 3 Water: Tap water

[0068]

Table 1

[0069] The concrete of the Example is obtained by hardening and carbonating a cement composition containing cement, an admixture, and a food ingredient, so it has sufficient strength while containing a food ingredient and has a small CO2 emission per unit.

Claims

1. A cement concrete obtained by hardening and carbonating a cement composition containing cement, admixture, and food ingredients, wherein the food ingredients are at least one kind of food ingredient selected from seaweed and vegetables.

2. The cement concrete according to Claim 1, having a pH of 8 to 10.

5.

3. The cement concrete according to Claim 1 or 2, which is porous concrete.

4. The cement concrete according to any one of Claims 1 to 3, having a porosity of 5 to 40%.

5. The compressive strength is 0.5 to 20 N / mm ２ The cement concrete according to any one of claims 1 to 4, which is such that

6. The cement concrete according to any one of Claims 1 to 5, wherein the seaweed is leafy seaweed and the vegetables are leafy vegetables.

7. The cement concrete according to any one of Claims 1 to 6, wherein the cement composition further contains slag aggregate.

8. CO ２ The discharge rate per unit is 300 kg / m ３ The cement concrete according to any one of claims 1 to 7, wherein the discharge rate per unit is 300 kg / m or less.

9. A step of kneading a cement composition containing cement, admixture, and food ingredients with water to produce a cement slurry, a step of filling the mold with the cement slurry, a step of curing the cement slurry filled in the mold and then removing the mold to produce a hydrated hardened body, and a step of carbonating and curing the hydrated hardened body, wherein the food ingredients are at least one kind of food ingredient selected from seaweed and vegetables. A method for producing cement concrete.

10. The method for producing cement concrete according to Claim 9, wherein the seaweed is leafy seaweed and the vegetables are leafy vegetables.

11. The method for producing cement concrete according to Claim 9 or 10, wherein the water-cement binder ratio (W / B), which is the ratio of water to the cement binder composed of cement and admixture when kneading the cement composition and water, is 100 to 300%.

Images