HYDRAULIC COMPOSITE MATERIALS

Abstract

The invention relates to a hydraulic composite material comprising at least a suspension of carbonated cement hydrate with a water / carbonated cement hydrate ratio (expressed on the basis of solids) of 50% to 1000%, a pH of 11 or less, and a viscosity at 20 ± 3°C of 1.0 mPa·s to 6.5 mPa·s, or a powder of carbonated cement hydrate, and together with cement, aggregate, and water, wherein the aggregate is only fine aggregate, or fine aggregate and coarse aggregate. The invention also relates to a hydraulic composite material containing at least 5 parts by mass to 50 parts by mass of carbonated cement hydrate (in terms of solids content) in a suspension of carbonated cement hydrate or powder of carbonated cement hydrate (in terms of solids content), 250 parts by mass to 750 parts by mass of aggregate, and 25 parts by mass to 60 parts by mass of water, per 100 parts by mass of cement.

Description

hydraulic composite

[0001] The present invention relates to concrete and mortar (hereinafter referred to as "hydraulic composite") having high strength development and fluidity.

[0002] Conventionally, agents such as calcium nitrite have been used to improve the strength of hydraulic composites. For example, the invention described in Patent Document 1 is a hydraulic material (hydraulic composite) containing more than 60% blast furnace slag powder, and the hydraulic material contains one or more of calcium nitrite, calcium chloride, magnesium carbonate, and magnesium chloride. Furthermore, from the perspective of reducing carbon dioxide emissions, the inorganic salts are said to compensate for the decrease in strength caused by reducing the proportion of Portland cement used in the hydraulic material.

[0003] Furthermore, the invention described in Patent Document 2 is a strength improver for cement, which contains a cyclic iminoether group-containing compound (A) having a cyclic iminoether group represented by general formula (1). The strength of concrete using this improver is said to be significantly improved over a long period of time. In general formula (1), X independently represents a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, and n represents an integer of 1 to 5. However, inorganic compounds such as calcium nitrite described in Patent Document 1 reduce the fluidity of hydraulic composites, and chlorides corrode reinforcing bars in hydraulic composites. Furthermore, the cyclic imino ether group-containing compound described in Patent Document 2 is expensive.

[0004] Various polymeric compounds have also been proposed as agents for improving the fluidity of concrete. For example, the invention described in Patent Document 3 is a copolymer cement dispersant obtained by copolymerizing the following (a), (b), and (c), which is said to exhibit high fluidity and workability. (a): Polyalkylene glycol mono(meth)acrylate monomer represented by general formula (2): In general formula (2), R1 represents a hydrogen atom or a methyl group, R2O represents an oxyethylene group or an oxypropylene group, m represents an integer of 1 to 25, and R3 represents hydrogen or an alkyl group having 1 to 3 carbon atoms. (b): Carboxylic acid monomers represented by general formula (3). In general formula (3), R4, R5, and R6 represent hydrogen, a methyl group, or (CH2)nCOOM (n represents an integer of 0 to 2), and M represents a hydrogen atom, a monovalent metal atom, a divalent metal atom, an ammonium group, or an organic amine group. (c): Other monomers copolymerizable with (a) and / or (b).

[0005] The invention described in Patent Document 4 is a cement additive comprising 100 parts by weight of a compound mainly containing a naphthalene sulfonic acid formaldehyde condensate or the like, and 5 to 30 parts by weight of a water-soluble salt of polyvinyl alcohol sulfate, which is said to improve the fluidity of cement mixtures, prevent a decrease in fluidity over time, and also improve workability and ease of application. However, both of the polymer compounds described in Patent Documents 3 and 4 are expensive.

[0006] Currently, measures to reduce greenhouse gases such as carbon dioxide are being sought on a global scale to prevent global warming. In particular, reducing carbon dioxide emissions is an urgent issue in the cement manufacturing industry, which accounts for approximately 4% (400 million tons) of total carbon dioxide emissions in Japan's entire industry. Currently, carbon dioxide reduction technologies employed in the cement manufacturing industry mainly involve reducing production energy and separating and capturing carbon dioxide from factory exhaust gases. Furthermore, recently, there has been active development of technologies that utilize the property of cement hydrates in concrete to absorb and fix carbon dioxide, thereby fixing carbon dioxide using concrete containing such hydrates.

[0007] For example, the technology described in Non-Patent Document 1 involves forcibly carbonating a molded concrete product in a curing tank to fix a large amount of carbon dioxide in the concrete. Furthermore, the invention described in Patent Document 5 is a method for producing a cement composition, including the steps of kneading a portion of cement with water to obtain a cement slurry with a specific water-cement ratio, supplying carbon dioxide into the cement slurry to obtain a carbon dioxide-containing slurry, and kneading the carbon dioxide-containing slurry, the remainder of the cement, and aggregate to obtain a cement composition. This production method has the advantage of being able to fix more carbon dioxide than a method for producing a cement composition obtained by adding cement all at once.

[0008] Incidentally, in the process of obtaining a carbon dioxide-containing slurry according to the invention described in Patent Document 5, a large amount of cement hydrate that has absorbed and fixed carbon dioxide (hereinafter referred to as "carbonated cement hydrate") is produced. However, the effect of the carbonated cement hydrate on the physical properties of concrete is unknown. However, since the carbonated cement hydrate is hydrated and carbonated, it has been commonly believed that the hydrate is merely a substance with reduced hydration activity and that its only use is as a filler (extender).

[0009] JP 2022-179954 A JP 2021-46338 A JP 2009-242197 A JP 61-83659 A JP 2023-6313 A

[0010] Torichigaya et al., "CO2 Balance and Quality Evaluation of Carbonated Cured Concrete," Proceedings of the Japan Concrete Institute, 2012, 34(1), pp. 1450-1455

[0011] Therefore, an object of the present invention is to provide a new use of the carbonated cement hydrate other than as a filler.

[0012] The present inventors have investigated the properties of the carbonated cement hydrate in order to develop new applications for the hydrate, and have found that hydraulic composites containing the hydrate have improved strength development and fluidity, leading to the completion of the present invention. That is, the present invention relates to a hydraulic composite having the following configuration:

[0013] [1] A hydraulic composite comprising at least a carbonated cement hydrate slurry or a powder of the carbonated cement hydrate having a water / carbonated cement hydrate (solid content equivalent) ratio of 50 to 1000%, a pH of 11 or less, and a viscosity at 20±3°C of 1.0 to 6.5 mPa s, cement, aggregate, and water. [2] The hydraulic composite according to [1] above, wherein the aggregate is fine aggregate alone, or fine aggregate and coarse aggregate. [3] The hydraulic composite according to [1] or [2] above, comprising at least 5 to 50 parts by mass of the carbonated cement hydrate (solid content equivalent) in the carbonated cement hydrate slurry or the powder of the carbonated cement hydrate (solid content equivalent), 250 to 750 parts by mass of aggregate, and 25 to 60 parts by mass of water, per 100 parts by mass of cement. [4] The hydraulic composite according to [3] above, wherein the fine aggregate accounts for 35 to 65% by mass, with the total aggregate being 100% by mass. [5] The hydraulic composite according to [1] or [2] above, comprising at least 100 parts by mass of cement, 250 to 750 parts by mass of aggregate, a carbonated cement hydrate slurry or powder of the carbonated cement hydrate, and water, wherein the hydraulic composite according to [1] or [2] above contains at least 5 to 30 parts by mass of the carbonated cement hydrate (solid content equivalent) in the carbonated cement hydrate slurry or powder of the carbonated cement, and 25 to 60 parts by mass of water relative to 100 parts by mass of the fine aggregate in the aggregate. [6] The hydraulic composite according to [1] or [2] above, wherein the compressive strength of the hydraulic composite at ages of 3 days, 28 days, and 91 days is 0.5% or more higher than the compressive strength of a hydraulic composite not containing the carbonated cement hydrate slurry or powder of the carbonated cement. [7] The hydraulic composite according to [1] or [2] above, which has a slump flow of 350 to 700 mm as measured in accordance with JIS A 1150 "Testing method for slump flow of concrete." [8] The hydraulic composite according to [1] or [2] above, which contains a carbonated cement hydrate slurry or a powder of the carbonated cement hydrate obtained by fixing carbon dioxide emitted in the cement manufacturing process.

[0014] The hydraulic composite of the present invention has high strength development and fluidity. In addition, the carbonated cement hydrate slurry and the carbonated cement hydrate powder contained in the hydraulic composite of the present invention absorb and fix carbon dioxide, which contributes to reducing carbon dioxide.

[0015] FIG. 1 is a schematic diagram of an apparatus for producing carbonated cement hydrate slurry.

[0016] As described above, the present invention relates to a hydraulic composite containing at least a carbonated cement hydrate slurry having a water / carbonated cement hydrate (solid content equivalent) ratio of 50 to 1000%, a pH of 11 or less, and a viscosity at 20±3° C. of 1.0 to 6.5 mPa s, or a powder of the carbonated cement hydrate, cement, aggregate, and water. Below, the carbonated cement hydrate slurry, the carbonated cement hydrate powder, the hydraulic composite, and methods for producing the carbonated cement hydrate powder will be described.

[0017] 1. Carbonated cement hydrate slurry and powder of the carbonated cement hydrate The water / carbonated cement hydrate (solid content equivalent) ratio used in the present invention is 50 to 1000%. When this ratio is within the above range, the hydraulic composite has high strength development and fluidity. The ratio is preferably 80 to 900%, more preferably 100 to 800%. The water is the water in the carbonated cement hydrate slurry, and the mass of the carbonated cement hydrate (solid content equivalent) is the mass of the solid content in the slurry. However, as will be described later, the carbonated cement hydrate slurry may be decanted, and in this case, the water / carbonated cement hydrate (solid content equivalent) ratio after decantation [in Table 3 shown later, W ２ / C ２The above-mentioned carbonated cement hydrate slurry has a pH of 11 or less. When the pH is 11 or less, the carbon dioxide content in the carbonated cement hydrate is 125 kg or more per ton of cement, and similarly, the strength development and fluidity of the hydraulic composite are high. The pH is preferably 6 to 10, more preferably 7 to 9. The viscosity of the carbonated cement hydrate slurry at 20±3°C is 1.0 to 6.5 mPa·s. When the viscosity is within the above range, similarly, the strength development and fluidity of the hydraulic composite are high. The viscosity is preferably 2.0 to 6.0 mPa·s, more preferably 3.0 to 5.0 mPa·s.

[0018] The Blaine specific surface area of ​​the carbonated cement hydrate powder is preferably 5000 to 15000 cm ２ If the Blaine specific surface area is in the above range, the hydraulic composite has high strength development and fluidity. The Blaine specific surface area is more preferably 6000 to 14500 cm ２ / g, more preferably 7000 to 14000 cm ２ / g.

[0019] The cement is at least one selected from ordinary Portland cement, high-early-strength Portland cement, extra-high-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, blast-furnace cement, and fly ash cement, and the cement hydrate is at least one selected from cement hydrate contained in fresh concrete sludge, cement hydrate contained in waste concrete, and cement hydrate contained in scraps of lightweight aerated concrete (ALC). The carbonated cement hydrate is calcium silicate hydrate (CaO—SiO ２ -H ２ O), calcium hydroxide (Ca(OH) ２ ), ettringite (3CaO·Al ２ O ３ 3CaSO ４ ・32H ２ O), calcium aluminate hydrate (3CaO.Al ２ O ３ ・6H２ O), and monosulfate hydrate (3CaO·Al ２ O ３ CaSO ４ ・12H ２ O) and the like.

[0020] 2. Hydraulic Composite The hydraulic composite of the present invention is made of cement (referred to as C in Table 3 below). １ ) in the carbonated cement hydrate slurry (solid content equivalent, C in Table 3 shown later) ２ ) or the powder of the carbonated cement hydrate (solid content equivalent, C in Table 3 below) ２ 5 to 50 parts by mass of aggregate, 250 to 750 parts by mass of water (referred to as W in Table 3 below). １ +W ２ The carbonated cement hydrate slurry contains at least 25 to 60 parts by mass of the carbonated cement hydrate (equivalent to solids content). If the carbonated cement hydrate (equivalent to solids content) in the carbonated cement hydrate slurry or the carbonated cement hydrate powder (equivalent to solids content) is 5 to 50 parts by mass per 100 parts by mass of cement, the hydraulic composite has high strength development and fluidity. Furthermore, if the aggregate is 250 to 750 parts by mass per 100 parts by mass of cement, the hydraulic composite has high fluidity.

[0021] The aggregate is fine aggregate alone when the hydraulic composite is mortar, and fine and coarse aggregates when the hydraulic composite is concrete. The fine aggregate may be one or more selected from river sand, mountain sand, land sand, sea sand, crushed sand, silica sand, slag fine aggregate, lightweight fine aggregate, etc., while the coarse aggregate may be one or more selected from gravel, crushed stone, slag coarse aggregate, lightweight coarse aggregate, etc. Both the fine and coarse aggregates may be natural aggregates or recycled aggregates. The content of fine aggregate in the total aggregate is preferably 35 to 65% by mass, based on 100% by mass of the total aggregate. This range of fine aggregate content ensures good fluidity of the hydraulic composite. The content of fine aggregate is more preferably 40 to 60% by mass, based on 100% by mass of the total aggregate.

[0022] The hydraulic composite of the present invention is a hydraulic composite containing at least 100 parts by mass of cement, 250 to 750 parts by mass of aggregate, a carbonated cement hydrate slurry or powder of the carbonated cement hydrate, and water, and contains at least 5 to 30 parts by mass of the carbonated cement hydrate (in terms of solids) in the carbonated cement hydrate slurry or powder of the carbonated cement hydrate, and 25 to 60 parts by mass of water, relative to 100 parts by mass of fine aggregate in the aggregate. If the carbonated cement hydrate (in terms of solids) in the carbonated cement hydrate slurry or powder of the carbonated cement hydrate is 5 to 30 parts by mass relative to 100 parts by mass of fine aggregate, the hydraulic composite has high strength development and fluidity.

[0023] The water can be any water that does not adversely affect the physical properties such as strength and fluidity of the hydraulic composite, and examples thereof include one or more types selected from tap water, industrial water, supernatant water of ready-mixed concrete, and recovered water. １ +W ２ The water content is preferably 25 to 60 parts by mass per 100 parts by mass of cement. If the water content is within this range, the hydraulic composite has good fluidity. The water content is more preferably 30 to 50 parts by mass per 100 parts by mass of cement.

[0024] As shown in Table 3 below, the compressive strengths of the hydraulic composite of the present invention at ages of 3 days, 28 days, and 91 days are 0.5% or more higher than the compressive strength of a hydraulic composite that does not contain carbonated cement hydrate slurry or carbonated cement hydrate powder.

[0025] The hydraulic composite of the present invention has a slump flow of 350 to 700 mm as measured in accordance with JIS A 1150 "Testing Method for Slump Flow of Concrete." In the present invention, the carbon dioxide used for carbonation of the cement slurry is preferably carbon dioxide emitted during the cement production process, in order to reduce the amount of carbon dioxide emitted during cement production.

[0026] In addition to the above essential components, the hydraulic composite of the present invention may contain one or more admixtures such as a shrinkage reducing agent, a water reducing agent, and an air-entraining water reducing agent, or an expansive agent, blast furnace slag, fly ash, coal ash, silica fume, silica powder, and limestone powder, depending on the required durability performance such as suppressing cracking, preventing salt damage, and improving freeze-thaw resistance.

[0027] 3. Method for Producing Carbonated Cement Hydrate Powder The method for producing carbonated cement hydrate powder of the present invention includes the steps of kneading cement and water having a water / cement ratio of 50 to 1000%, or cement hydrate and water having a water / cement hydrate ratio of 50 to 1000%, to obtain a cement hydrate slurry, supplying carbon dioxide into the cement hydrate slurry to obtain a carbonated cement hydrate slurry, and drying the carbonated cement hydrate slurry to obtain a carbonated cement hydrate powder. The cement is one or more selected from ordinary Portland cement, high-early-strength Portland cement, ultra-high-early-strength Portland cement, moderate-heat Portland cement, low-heat Portland cement, blast-furnace cement, and fly ash cement, and the cement hydrate is one or more selected from cement hydrate contained in ready-mixed concrete sludge, cement hydrate contained in waste concrete, and cement hydrate contained in scraps of lightweight aerated concrete (ALC).

[0028] In the step of obtaining the carbonated cement hydrate slurry, carbon dioxide is supplied so that the pH of the carbonated cement hydrate slurry becomes 11 or less. If the pH of the carbonated cement hydrate slurry is within the above range, the carbon dioxide content in the carbonated cement hydrate slurry becomes 125 kg or more per ton of cement, as described above, and the amount of fixed carbon dioxide increases.

[0029] Furthermore, in the step of obtaining the carbonated cement hydrate slurry, carbon dioxide is supplied so that the viscosity of the carbonated cement hydrate slurry measured with a rotational viscometer (ambient temperature during measurement is 20±3°C) is preferably 1.0 to 6.5 mPa·S. If the viscosity is within the above range, the amount of fixed carbon dioxide also increases. In adjusting the viscosity of the slurry, if the viscosity of the slurry is less than 1.0 mPa·S, water may be removed from the slurry by drying, decantation, or the like, or if the viscosity exceeds 6.5 mPa·S, water may be added to the slurry.

[0030] In the step of obtaining the carbonated cement hydrate slurry, it is preferable to fix 80 mass % or more of the carbon dioxide supplied. If the amount of fixed carbon dioxide is 80 mass % or more, the fixation efficiency of carbon dioxide is high, which can contribute to reducing carbon dioxide.

[0031] In the step of obtaining the carbonated cement hydrate powder, the method for drying the carbonated cement hydrate slurry can be one or more methods selected from natural drying, hot air drying, vacuum drying, cooling drying, infrared drying, freeze drying, and contact drying. The drying methods can dry the carbonated cement hydrate without decarbonating the carbon dioxide fixed in the carbonated cement hydrate.

[0032] The present invention will be described below with reference to examples, but is not limited to these examples. 1. Materials Used The materials used are shown in Table 1.

[0033]

[0034] 2. Example of using carbonated cement hydrate slurry as a partial cement replacement (1) Production of carbonated cement hydrate slurry Ten batches (batches) of cement hydrate slurry were prepared by kneading 10 kg of ordinary Portland cement and 30 kg of tap water for 120 seconds using a hand mixer. The temperature of the slurry was 23°C (ambient temperature: 20°C). Next, as shown in Figure 1, the cement hydrate slurry was circulated using a pump between a carbon dioxide reaction tank filled with carbon dioxide gas and a slurry tank, and the cement hydrate in the slurry was carbonated until the pH of the slurry reached the value shown in Table 2. Next, the carbonated cement hydrate slurry was left to stand for one day in an environment of 20°C, and the supernatant water was decanted off, and the water / carbonated cement hydrate (solid content equivalent) ratio [W in Table 3] was calculated. ２ / C ２ The mass of the water removed by decantation was calculated by multiplying the mass of the carbonated cement hydrate (solid content) obtained by drying the carbonated cement hydrate slurry at 105°C for 24 hours by the water / carbonated cement hydrate (solid content equivalent) ratio [W in Table 3]. ２ / C ２ The physical properties (pH and viscosity) of the carbonated cement hydrate slurry thus obtained are shown in Table 2. The temperature of the carbonated cement hydrate slurry during the viscosity measurement was 21°C (ambient temperature: 20°C).

[0035]

[0036] As shown in Table 2, carbonated cement hydrate slurries a1 to a9 have a pH of 6.83 to 10.10 and a viscosity of 1.60 to 4.23 mPa·s. In comparison, carbonated cement hydrate slurry b1 has a viscosity of 1.40 mPa·s, which is similar to the above slurries, but a pH of 11.10, which is higher than the above slurries. Conversely, carbonated cement hydrate slurry b2 has a pH of 8.94, which is similar to the above slurries, but a viscosity of 7.21 mPa·s, which is higher than the above slurries.

[0037] (2) Production of Concrete (Hydraulic Composite) Concrete was produced in accordance with JIS A 1138 "Laboratory Concrete Production Method" according to the formulations shown in Table 3. That is, in Examples 1 to 9 and Comparative Examples 2 and 3, concrete was produced by mixing carbonated cement hydrate slurry according to the formulations in Table 3, while in Comparative Example 1, concrete was produced using cement alone without blending the carbonated cement hydrate slurry.

[0038] (3) Measurement of Compressive Strength and Slump Flow of Concrete The compressive strength of the concrete was measured in accordance with JIS A 1108 "Test Method for Compressive Strength of Concrete" using concrete specimens cured underwater for ages of 3 days, 28 days, and 91 days. The slump flow of the concrete was measured in accordance with JIS A 1150 "Test Method for Slump Flow of Concrete." The results are shown in Table 3.

[0039]

[0040] As shown in Table 3, Examples 1 to 9 of the present invention all have higher compressive strengths in the short term (3 days old), medium term (28 days old), and long term (91 days old) and a larger slump flow than Comparative Examples 1 to 3. Therefore, the hydraulic composite of the present invention has improved strength development and fluidity, and the present invention can open up new uses for carbonated cement hydrate. Furthermore, because the carbonated cement hydrate absorbs and fixes carbon dioxide, the present invention contributes to reducing carbon dioxide emissions.

[0041] 3. Example using carbonated cement hydrate slurry as partial replacement for fine aggregate Concrete was produced using carbonated cement hydrate slurry a5 according to the formulation shown in Table 4 and in accordance with JIS A 1138 "Laboratory concrete production method." The slump flow of the concrete was measured in accordance with JIS A 1150 "Test method for slump flow of concrete." The compressive strength of the concrete was measured in accordance with JIS A 1108 "Test method for compressive strength of concrete" using concrete specimens cured underwater for ages of 3 days, 28 days, and 91 days. The results are shown in Table 4.

[0042]

[0043] As shown in Table 4, Examples 10 to 13 of the present invention all have higher compressive strengths in the short term (3 days old), medium term (28 days old), and long term (91 days old) and a larger slump flow than Comparative Example 4. Therefore, as in the above, the hydraulic composite of the present invention has improved strength development and fluidity, and the present invention can open up new uses for carbonated cement hydrate. Furthermore, since the carbonated cement hydrate absorbs and fixes carbon dioxide, the present invention contributes to reducing carbon dioxide.

Claims

1. A hydraulic composite comprising at least a carbonated cement hydrate slurry having a water / carbonated cement hydrate (in terms of solid content) ratio of 50 to 1000%, a pH of 11 or less, and a viscosity of 1.0 to 6.5 mPa·s at 20±3°C, or a powder of said carbonated cement hydrate, cement, aggregate, and water.

2. The hydraulic composite according to claim 1, wherein the aggregate is fine aggregate alone or a combination of fine aggregate and coarse aggregate.

3. The hydraulic composite according to claim 1 or 2, comprising at least 5 to 50 parts by mass of carbonated cement hydrate (in terms of solid content) in a carbonated cement hydrate slurry or a powder of said carbonated cement hydrate (in terms of solid content), 250 to 750 parts by mass of aggregate, and 25 to 60 parts by mass of water, per 100 parts by mass of cement.

4. The hydraulic composite according to claim 3, wherein the fine aggregate is 35 to 65% by mass, with the total aggregate being 100% by mass.

5. A hydraulic composite according to claim 1 or 2, comprising at least 100 parts by mass of cement, 250 to 750 parts by mass of aggregate, a carbonated cement hydrate slurry or a powder of the carbonated cement hydrate, and water, the hydraulic composite comprising at least 5 to 30 parts by mass of the carbonated cement hydrate (converted into solid content) in the carbonated cement hydrate slurry or the powder of the carbonated cement hydrate, and 25 to 60 parts by mass of water relative to 100 parts by mass of fine aggregate in the aggregate.

6. The hydraulic composite according to claim 1 or 2, wherein the compressive strength of the hydraulic composite at an age of 3 days, 28 days, and 91 days is 0.5% or more higher than the compressive strength of a hydraulic composite not containing a carbonated cement hydrate slurry or powder of the carbonated cement hydrate slurry.

7. The hydraulic composite according to claim 1 or 2, which has a slump flow of 350 to 700 mm as measured in accordance with JIS A 1150 "Test method for slump flow of concrete".

8. The hydraulic composite according to claim 1 or 2, which contains a carbonated cement hydrate slurry produced by fixing carbon dioxide discharged during the cement manufacturing process, or a powder of said carbonated cement hydrate.

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