Lightweight cellular concrete

Abstract

To provide lightweight cellular concrete that maintains acceptable mechanical properties while reducing CFP (carbon fiber concentration). [Solution] Lightweight cellular concrete containing 5% to 25% by weight of calcium carbonate. The above lightweight cellular concrete has pores A having a peak in the range of pore radius 0.004 μm to 2 μm in the differential pore distribution measured on the penetration side of a mercury porosimeter, and when the amount of calcium carbonate is c by weight, the volume of the above pores A is v A However, -1.98 × 10 -3 ×c + 0.600 [mL / g] or higher.

Description

[Technical Field]

[0001] This disclosure relates to lightweight cellular concrete. [Background technology]

[0002] Autoclaved lightweight aerated concrete (ALC) offers numerous advantages over conventional concrete, including superior lightness, moisture control, strength-to-weight ratio, and thermal insulation. Furthermore, ALC is highly durable, easy to maintain, and its lightweight yet high strength makes it easy to handle and efficiently assemble, even in relatively large composite structures, making it a very user-friendly material. The compressive strength of ALC is 3 N / mm² according to JIS A 5416. 2 As defined above, it fully meets the strength requirements for building materials and also has uniform physical properties, making it easy to design as a building component or structure.

[0003] However, the raw materials used in the manufacture of ALC include siliceous materials such as silica sand and silica (SiO2), calcareous materials such as cement and quicklime (CaO), and metallic aluminum as a foaming agent. In particular, because calcareous raw materials are used, there is a need to reduce the carbon footprint (hereinafter also referred to as CFP). Therefore, in recent years, attempts have been made to reduce the CFP by replacing the main raw materials such as cement in ALC with fillers such as calcium carbonate.

[0004] Patent Document 1 describes a method for producing lightweight aerated concrete, which is manufactured using a mixture of powdered siliceous raw materials and calcareous raw materials in predetermined proportions as the main raw materials, with the aim of easily and inexpensively providing ALC with excellent physical properties such as compressive strength and Young's modulus. This method is characterized by producing lightweight aerated concrete by replacing 5 to 20% by weight of the siliceous raw materials with calcium carbonate in equal amounts.

[0005] Patent Document 2 aims to provide an inorganic foam panel with improved durability when used over a long period of time, and describes an inorganic foam panel containing calcium carbonate. The inorganic foam panel is an inorganic foam panel having a panel body made of inorganic foam and formed in the shape of a flat plate, and is characterized by comprising an iron panel reinforcing material embedded in the panel body and a protective film covering the iron panel reinforcing material, and containing calcium carbonate. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2011-020908 [Patent Document 2] Japanese Patent Publication No. 2016-164097 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] However, conventional ALC containing calcium carbonate tends to have decreasing mechanical properties such as compressive strength and elastic modulus as the calcium carbonate content increases.

[0008] One of the objectives of this disclosure is to provide lightweight cellular concrete in which the CFP is reduced while maintaining acceptable mechanical properties. [Means for solving the problem]

[0009] Examples of embodiments of this disclosure are listed below. [1] Lightweight aerated concrete containing 5% to 25% by weight of calcium carbonate, The lightweight aerated concrete has pores A having a peak in the range of pore radius 0.004 μm to 2 μm in the differential pore distribution measured on the penetration side of a mercury porosimeter, and when the amount of calcium carbonate is c by weight, the volume of pores A is vA is -1.98×10 -3 ×c + 0.600 [mL / g] or more, lightweight cellular concrete. [2] The lightweight cellular concrete has pore B having a peak in the range of pore radius of 0.004 μm or more and 2 μm or less in the differential pore distribution measured on the discharge side of a mercury porosimeter, when the amount of the calcium carbonate is c% by weight, the volume v of the pore B B is 9.80×10 -4 ×c + 0.285 [mL / g] or less, the lightweight cellular concrete according to Item 1. [3] The lightweight cellular concrete has pore A having a peak in the range of pore radius of 0.004 μm or more and 2 μm or less in the differential pore distribution measured on the intrusion side of a mercury porosimeter, and the pore radius r of the maximum peak of the pore A A is 8.08×10 -4 ×c + 0.014 [μm] or less, the lightweight cellular concrete according to Item 1 or 2. [4] The total peak intensity T5 including the background of the (002), (201), (220), (222), (400) planes of tobermorite crystals in the X-ray diffraction of the lightweight cellular concrete is -317×c + 2.03×10 4 or more, the lightweight cellular concrete according to any one of Items 1 to 3. [5] The calcium carbonate is light calcium carbonate, the lightweight cellular concrete according to any one of Items 1 to 4. [6] The volume v of the pore A A is -1.98×10 -3 ×c + 0.610 [mL / g] or more, the lightweight cellular concrete according to any one of Items 1 to 5. [7] The lightweight cellular concrete has pore B having a peak in the range of pore radius of 0.004 μm or more and 2 μm or less in the differential pore distribution measured on the discharge side of a mercury porosimeter, the volume v of the pore BB However, 9.80 × 10 -4 Lightweight aerated concrete as described in any one of items 1 to 6, with a concentration of ×c + 0.270 [mL / g] or less. [8] The lightweight aerated concrete has pores A having peaks in the range of pore radii between 0.004 μm and 2 μm in the differential pore distribution measured on the penetration side of a mercury porosimeter, and the pore radius r of the largest peak of pores A A However, 8.08 × 10 -4 Lightweight cellular concrete as described in any one of items 1 to 7, with a thickness of ×c + 0.013 [μm] or less. [9] The lightweight aerated concrete has pores B having a peak in the range of pore radius 0.004 μm to 2 μm in the differential pore distribution measured on the discharge side of a mercury porosimeter. The pore radius r of the pore B with the largest peak B However, 1.37 × 10 -3 Lightweight cellular concrete as described in any one of items 1 to 8, with a thickness of ×c + 0.092 [μm] or less.

[10] Lightweight cellular concrete as described in any one of items 1 to 9, containing 5% by weight or more and 22% by weight or less of the aforementioned calcium carbonate.

[11] Lightweight cellular concrete as described in any one of items 1 to 10, containing 5% by weight or more and 15% by weight or less of the aforementioned calcium carbonate. [Effects of the Invention]

[0010] According to this disclosure, lightweight cellular concrete is provided in which the mechanical properties are maintained to an acceptable degree while the CFP is reduced. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 shows the pore distribution of the lightweight aerated concrete of Example 1, with pore radius (μm) on the horizontal axis and differential pore volume on the vertical axis. [Figure 2]Figure 2 shows the pore distribution of the lightweight aerated concrete of Example 1, with pore radius (μm) on the horizontal axis and integrated pore volume on the vertical axis. [Figure 3] Figure 3 is a graph showing the relationship between the amount of calcium carbonate (weight (%)) and the volume of pore A vA [mL / g] in Examples 1-8 and Comparative Examples 1-6. [Figure 4] Figure 4 is a graph showing the relationship between the amount of calcium carbonate (weight (%)) and the pore radius rA [μm] of the peak of pore A in Examples 1-8 and Comparative Examples 1-6. [Figure 5] Figure 5 is a graph showing the relationship between the amount of calcium carbonate (weight (%)) and the volume of pore B vB [mL / g] in Examples 1-8 and Comparative Examples 1-6. [Figure 6] Figure 6 is a graph showing the relationship between the amount of calcium carbonate (weight (%)) and the pore radius rB [μm] of the peak of pore B in Examples 1-8 and Comparative Examples 1-6. [Figure 7] Figure 7 is a graph showing the relationship between the amount of calcium carbonate (by weight (%)) and the sum of five strong lines (cps) of X-ray diffraction in Examples 1-8 and Comparative Examples 1-6. [Modes for carrying out the invention]

[0012] The embodiments of this disclosure will be described in detail below, but this disclosure is not limited to the embodiments described below. The upper and lower limits in each numerical range of the embodiments described below can be arbitrarily combined to form any numerical range.

[0013] Lightweight cellular concrete The lightweight aerated concrete of this disclosure is lightweight aerated concrete containing 5% to 25% by weight of calcium carbonate. The above lightweight aerated concrete has pores A having a peak in the range of pore radius 0.004 μm to 2 μm in the differential pore distribution measured on the penetration side of a mercury porosimeter (MIP). When the amount of the above calcium carbonate is c by weight, the volume of the above pores A is v A However, -1.98 × 10 -3×c + 0.600 [mL / g] or more. Since the calcium carbonate content is 5% by weight or more, the amount of main raw materials such as cement can be reduced, thus providing lightweight cellular concrete with reduced CFP. Furthermore, when the calcium carbonate content is 25% by weight or less, and the amount of calcium carbonate is c% by weight, the volume of pore A is v A However, -1.98 × 10 -3 By having a calcium carbonate content of ×c + 0.600 [mL / g] or higher, mechanical properties, such as compressive strength, can be maintained to an acceptable degree. Here, "maintaining" mechanical properties to an acceptable degree means maintaining mechanical properties to a level that is usable as a product of the intended purpose, compared to lightweight aerated concrete that does not contain calcium carbonate. For example, when used as a building material, the compressive strength of lightweight aerated concrete is 3.0 N / mm² according to JIS A 5416. 2 The above is preferable as it is considered to meet the strength requirements for building materials. The compressive strength is more preferably 3.12 N / mm². 2 More preferably 3.4 N / mm 2 More preferably, 3.9 N / mm 2 That's all.

[0014] Volume v of pore A AHowever, the reason why the mechanical properties can be maintained if the value is greater than or equal to the value expressed by the specific formula above is not limited to a specific theory, but the inventors of this invention have considered the following. That is, lightweight cellular concrete is generally produced by mixing a slurry of raw materials containing calcareous raw materials, siliceous raw materials, and a foaming agent such as aluminum powder with water, causing foaming (volume expansion) by the reaction of the foaming agent, and pre-hardening it into a pre-hardened body by the hydration reaction of the calcareous raw materials, and then hardening the pre-hardened body using a hydrothermal reaction under high temperature and pressure by autoclave curing. During this curing process, the calcareous and siliceous raw materials dissolve once, and after passing through various intermediate products, a mineral called tobermorite is ultimately produced. The inventors of this invention have analyzed the pore structure of lightweight cellular concrete containing calcium carbonate and have found that it is preferable to have pores (referred to as "pore A" in this disclosure) that have the largest peak in the range of pore radius 0.004 μm to 2 μm, as observed by measurement on the penetration side of a mercury porosimeter. These pores A are thought to be truss (cell) structures formed by tobermorite crystals, and it is believed that this truss (cell) structure gives ALC high mechanical strength despite its light weight. Pores A can be observed on the entry side but not on the discharge side, so they are thought to be voids with an ink bottle shape. The presence of pores A in lightweight aerated concrete suggests that the truss (cell) structure of tobermorite is well formed. And, after diligent investigation, the volume v of pores A A -1.98 × 10 -3 By adjusting the concentration to ×c + 0.600 [mL / g] or higher, a large number of truss (cell) structures can be present in tobermorite, thereby maintaining its mechanical properties, particularly its compressive strength and elastic modulus. This is surprising, considering that at the time of filing this disclosure, attention had not been paid to the pores A measured on the entry side of the mercury porosimeter.

[0015] <Calcium carbonate> Calcium carbonate is generally classified into heavy calcium carbonate and light calcium carbonate from the viewpoint of its manufacturing method. Heavy calcium carbonate is produced by crushing limestone and is also called natural calcium carbonate (GCC: Ground Calcium Carbonate). On the other hand, light calcium carbonate is produced by precipitating fine calcium carbonate crystals in a liquid through a chemical reaction and is also called synthetic calcium carbonate or precipitated calcium carbonate (PCC: Precipitated Calcium Carbonate). Either heavy calcium carbonate or light calcium carbonate may be used, but light calcium carbonate is preferred. Light calcium carbonate can be produced, for example, by reacting carbon dioxide (CO2) emitted from industrial facilities such as boilers with highly alkaline wastewater, and since CO2 can be fixed, carbon dioxide production (CFP) can be further reduced.

[0016] From the viewpoint of reducing CFP and maintaining mechanical properties, the calcium carbonate content in lightweight aerated concrete is 5% by weight or more and 25% by weight or less, preferably 5% by weight or more and 22% by weight or less, more preferably 5% by weight or more and 15% by weight or less, and more preferably 5% by weight or more and 12% by weight or less, based on the total mass of the lightweight aerated concrete.

[0017] The Braine value of calcium carbonate is not limited, but for example, 1000 cm 2 / g or more 50000cm 2 / g or less, 2000cm 2 / g or more 30000cm 2 / g or less, or 3000cm 2 / g or more 20000cm 2 It may be less than / g. The BET specific surface area of ​​calcium carbonate is not limited, but for example, 1m 2 / g or more 50m 2 / g or less, 2m 2 / g or more 30m 2 / g or less, or 3m 2 / g or more 20m 2It may be less than or equal to / g. When the Blaine value and / or BET specific surface area of ​​calcium carbonate are within the above range, the fluidity of the slurry obtained by mixing the raw material solids with water is good, and it is easier to maintain mechanical properties, such as compressive strength, to an acceptable level. Regarding the specific surface area of ​​calcium carbonate, the Blaine specific surface area is the value measured by the fineness test based on JIS R 5201:2015. The BET specific surface area is the value measured by the nitrogen adsorption method based on JIS Z 8830:2013.

[0018] <Pore structure> As mentioned above, lightweight aerated concrete has pores A, which have the largest peak in the range of pore radius 0.004 μm to 2 μm, as observed in measurements on the ingress side of a mercury porosimeter. These pores A are thought to be truss (cell) structures formed by tobermorite crystals, and it is believed that this truss (cell) structure gives ALC high mechanical strength despite its light weight. Since pores A can be observed on the ingress side but not on the discharge side, they are thought to be voids with an ink bottle shape. The presence of pores A in lightweight aerated concrete suggests that the tobermorite truss (cell) structure is well formed, which is desirable from the viewpoint of maintaining mechanical properties.

[0019] Volume v of pore A A is -1.98 × 10 -3 ×c + 0.600 [mL / g] or higher, preferably -1.98 × 10 -3 ×c + 0.610 [mL / g] or higher, for example, -1.98 × 10 -3 ×c + 0.680 [mL / g] or higher, or -1.98 × 10 -3 ×c + 0.691 [mL / g] or greater. Volume of pore A v A When the volume v of pore A exceeds the value expressed by the specific formula above, it becomes easier to maintain the mechanical properties. Although not limited to a specific theory, the volume v of pore A AA large value suggests the presence of many truss (cell) structures in tobermorite, which is considered desirable from the viewpoint of maintaining mechanical properties, particularly compressive strength and elastic modulus. Volume v of pore A A A larger value is better, so it is not particularly limited, but considering that the addition of calcium carbonate may cause structural defects in the pore structure, volume V is better than when calcium carbonate is not added. A It is unlikely that it will become larger. Then the volume V of pore A A The upper limit is preferably 0.691 [mL / g] or less.

[0020] In lightweight cellular concrete, when the amount of calcium carbonate is c by weight, the maximum peak of pore A observed in the mercury porosimeter on the penetration side has a pore radius r A However, 8.08 × 10 -4 The thickness is less than or equal to ×c + 0.014 [μm], preferably 8.08 × 10 -4 ×c + 0.013 or less, for example, 8.08 × 10 -4 The diameter is less than or equal to ×c + 0.010 [μm]. The pore radius r of the maximum peak in pore A. A If the value is less than or equal to the value expressed by the specific formula above, it is easier to maintain the mechanical properties. Although not limited to a specific theory, the pore radius r of the pore A is the maximum peak. A This is thought to accurately represent the size of the opening diameter of the ink bottle-shaped void, and the pore radius r of the maximum peak of pore A A A small value suggests the formation of a dense truss (cell) structure, which is considered desirable from the viewpoint of maintaining mechanical properties, particularly compressive strength and elastic modulus. The pore radius r of the maximum peak of pore A. A A smaller value is preferable, so it is not particularly limited, but considering that the addition of calcium carbonate may cause structural defects in the pore structure, the pore radius r of the maximum peak of pore A is better than when calcium carbonate is not added. A It is unlikely that it will become smaller. Then the pore radius r of the maximum peak of pore A A The lower limit is preferably 0.010 [μm] or more.

[0021] It is preferable that lightweight aerated concrete further contains pores (hereinafter referred to as "pore B") having a peak in the range of pore radius between 0.004 μm and 2 μm in the differential pore distribution measured on the discharge side of a mercury porosimeter. Pore B is observed on both the inlet (injection) and discharge sides of the mercury porosimeter and is considered to be a continuous void formed by disrupting the truss (cell) structure of the tobermorite crystal. On the inlet side, pore B has a peak in the range of pore radius greater than 0.004 μm and less than or equal to 2 μm, and is distinguished from the truss (cell) structure (pore A) made of the tobermorite crystal described above. Volume v of pore B B We found that as the value increases, the mechanical strength tends to decrease. Furthermore, after diligent investigation, we found that the volume of pore B, which has a peak in the range of pore radius 0.004 μm to 2 μm, is measured in the differential pore distribution on the discharge side of the mercury porosimeter. B However, 9.80 × 10 -4 It was found that it is preferable for the volume to be less than or equal to ×c + 0.285 [mL / g]. Volume v of pore B B By adjusting the value to be less than or equal to the value expressed by the specific formula above, it is thought that the structural defects that disrupt the truss (cell) structure formed by the continuous tobermorite crystals can be reduced, thereby maintaining the mechanical properties, particularly the compressive strength and elastic modulus. This is surprising considering that, at the time of filing this disclosure, attention had not been paid to the pore B measured on the discharge side of the mercury porosimeter.

[0022] In lightweight cellular concrete, when the amount of calcium carbonate is c by weight, the volume of pores B observed in the discharge side measurement of a mercury porosimeter is v B However, more preferably 9.80 × 10 -4 ×c + 0.270 [mL / g] or less, for example, 9.80 × 10 -4 ×c+0.259[mL / g] or less, 9.80×10 -4 The volume of pore B is less than or equal to ×c + 0.239 [mL / g]. B If the value is less than or equal to the value expressed by the specific formula above, the mechanical properties can be maintained at a higher level. The reason for this is as stated above. Volume v of pore B BA smaller value is preferable, so it is not particularly limited, but the volume V of pore B B The lower limit is preferably 9.80 × 10 -4 ×c + 0.231 [mL / g] or higher.

[0023] In lightweight aerated concrete, when the amount of calcium carbonate is c by weight, the maximum peak of pore B observed in the discharge side measurement of a mercury porosimeter is the pore radius r. B is 1.37 × 10 -3 A value of ×c + 0.092 or less is preferred, and more preferably 1.37 × 10 -3 ×c + 0.089 [μm] or less, for example, 1.37 × 10 -3 ×c+0.085[μm] or less, or 1.37×10 -3 It is less than or equal to ×c + 0.068. While not limited to a specific theory, the pore radius r of the pore B peak... B However, a value less than or equal to the value expressed by the specific formula above suggests that the structural defects that disrupt the truss (cell) structure formed by the tobermorite crystal are small, which is considered desirable from the viewpoint of maintaining mechanical properties, particularly compressive strength and elastic modulus. The value of the peak of pore B is not particularly limited as a smaller value is preferable, but considering that the addition of calcium carbonate may cause structural defects in the pore structure, the pore radius r of the maximum peak of pore B is considered preferable to the value when calcium carbonate is not added. B It is unlikely that it will become smaller. Then the pore radius r of the maximum peak of pore B B The lower limit is preferably 0.068 [μm] or greater.

[0024] <Tobermorite crystal structure> When the amount of calcium carbonate in lightweight aerated concrete is c by weight, the sum of peak intensities T5 (hereinafter also referred to as "5-strong line sum T5") including the background of the (002), (201), (220), (222), and (400) planes of the tobermorite crystal in X-ray diffraction is -317 × c + 2.03 × 10 4 The above is preferable, and more preferably -317×c+2.08×10 4 The above is -317 × c + 2.12 × 10 4The above, or -317 × c + 2.17 × 10 4 That concludes the report. A high value of the 5-strong line sum T5 suggests the formation of many dense tobermorite crystals, which is considered desirable from the viewpoint of maintaining mechanical properties, particularly compressive strength and elastic modulus. The value of the 5-strong line sum T5 is particularly important among the pore structure parameters mentioned above, especially the pore radius r of pore A. A The value of is strongly correlated with the pore radius r of pore A. A As the value of decreases, the value of the 5-strong sum T5 tends to increase. A larger value of the 5-strong sum T5 is desirable, so it is not particularly limited, but considering that the addition of calcium carbonate may cause structural defects in the pore structure, it is unlikely that the 5-strong sum T5 will be larger than when calcium carbonate is not added. Then the upper limit of the 5-strong sum T5 is, for example, 2.17 × 10 4 The following applies:

[0025] <cement> Examples of cement include Portland cement, blast furnace cement, and alumina cement, with Portland cement being the most representative. Portland cement is a fine powder mainly composed of hydraulic substances such as alite and belite, and in water it gradually generates an amorphous gel hydrate called calcium silicate hydrate (CSH, or CASH when focusing on aluminum), which thickens and hardens. Depending on the rate at which Portland cement develops its hydraulic properties (rapid strength), there are types such as rapid-strength, normal, and low-heat in Japan. Similarly, there are multiple types outside of Japan, and they are widely used.

[0026] The raw materials for lightweight aerated concrete contain cement, preferably at a concentration of 10% to 30% by weight, more preferably 15% to 30% by weight, and even more preferably 15% to 25% by weight, based on the total mass of the raw material solids. If the cement is within the above range, it is easy to adjust the volume and pore radius of pores A and B to the preferred range of this disclosure.

[0027] <Silicate raw materials> The raw materials for lightweight aerated concrete generally contain siliceous raw materials. Examples of siliceous raw materials include crystalline silica, silica sand, quartz, and rocks with high concentrations of these materials. Preferably, the quartz crystal component of the siliceous raw material used is 80% by weight or more, and more preferably 90% by weight or more. Using a siliceous raw material with a high quartz crystal component promotes the growth of tobermorite crystals, forming a truss (cell) structure surrounded by tobermorite crystals.

[0028] The raw materials for lightweight aerated concrete contain siliceous raw materials in an amount of 20% to 50% by weight, more preferably 20% to 45% by weight, and even more preferably 25% to 40% by weight, based on the total mass of the raw material solids. If the siliceous raw materials are within the above range, it is easy to adjust the volume and pore radius of pores A and B to the preferred range of this disclosure.

[0029] <Calcareous raw materials> The raw materials for lightweight aerated concrete preferably contain calcareous raw materials. Examples of calcareous raw materials include quicklime (CaO) and slaked lime (Ca(OH)2). Quicklime is preferable because, when mixed with water, it produces crystalline hydrate (Ca(OH)2) and generates heat, thus promoting the hydration of cement.

[0030] The raw materials for lightweight aerated concrete contain calcareous raw materials, preferably in an amount of 1% to 10% by weight, and more preferably 1% to 5% by weight, based on the total mass of the raw material solids. If the calcareous raw materials are within the above range, it is easy to adjust the volume and pore radius of pores A and B to the preferred range of this disclosure.

[0031] <Sulfuric acid compounds> The raw materials for lightweight aerated concrete preferably contain a sulfate compound. Examples of sulfate compounds include gypsum. Gypsum mainly consists of calcium sulfate (CaSO4), and examples include calcined gypsum (basani stone) (CaSO4·1 / 2H2O) and dihydrate gypsum (CaSO4·2H2O).

[0032] The raw materials for lightweight aerated concrete contain sulfate compounds, preferably 1% to 10% by weight, more preferably 1% to 5% by weight, and even more preferably 1% to 4% by weight, based on the total mass of the raw material solids. Increasing the amount of sulfate compounds can promote the formation of tobermorite during the hydrothermal reaction (autoclave curing). Conversely, decreasing the amount of sulfate compounds tends to result in a more appropriate pore structure and highly crystalline tobermorite, making it easier to adjust the volume and pore radius of pores A and B to the preferred range of this disclosure.

[0033] <C / S> The mixing ratio of siliceous raw materials and calcareous raw materials is preferably 0.3 to 0.8, more preferably 0.4 to 0.7, and even more preferably 0.4 to 0.6, in terms of CaO / SiO2 molar ratio (C / S), from the viewpoint of productivity and mechanical strength. If the C / S is within the above range, it is easy to adjust the volume and pore radius of pores A and B to the preferred range of this disclosure. The C / S molar ratio is calculated from the mixing ratio of each raw material, the CaO and SiO2 content in the chemical analysis values ​​of each raw material, and the molecular weights of CaO and SiO2, but the Ca content of added gypsum and calcium carbonate is not included in the CaO.

[0034] <Recycled materials> The raw materials for lightweight aerated concrete can be recycled materials, such as recovered materials generated during the manufacturing process of lightweight aerated concrete. Examples of recycled materials include crushed waste from pre-hardened scraps (hereinafter also referred to as "pre-hardened material crushed waste") and ALC powder obtained by crushing scraps after autoclave curing (hereinafter also referred to as "ALC powder"). Among the recycled materials, ALC powder may contain calcium carbonate due to partial carbonation, in which case the calcium carbonate content (c wt%) includes the amount of calcium carbonate derived from the filler material. The recycled materials themselves may also contain calcium carbonate derived from the blending process.

[0035] The raw materials for the lightweight aerated concrete preferably contain recycled materials in an amount of 10% to 40% by weight, more preferably 15% to 35% by weight, and even more preferably 20% to 30% by weight, based on the total mass of the raw material solids. The raw materials for the lightweight aerated concrete preferably contain pre-hardened crushed waste in an amount of 1% to 30% by weight, more preferably 5% to 25% by weight, and even more preferably 15% to 20% by weight, based on the total mass of the raw material solids. The raw materials for the lightweight aerated concrete preferably contain ALC powder in an amount of 1% to 20% by weight, more preferably 1% to 15% by weight, and even more preferably 5% to 10% by weight, based on the total mass of the raw material solids. If the filler is within the above range, it is easy to adjust the volume and pore radius of pores A and B to the preferred range of this disclosure.

[0036] <Additives> The raw materials for lightweight aerated concrete can suitably contain additives such as foaming agents, rheological property modifiers, surfactants, shrinkage reducing agents, and water repellents. The amount of each additive is adjusted as appropriate according to the desired effect, and is usually between 0.01% and 5% by weight based on the total mass of the raw material solids.

[0037] For example, aluminum powder can be used as a foaming agent. The amount of foaming agent can be adjusted according to the density of the foamed composite material to be obtained, and can be added in a range of, for example, 0.01% to 1% by weight relative to the total mass of the raw material solids. For example, when obtaining lightweight foamed concrete with a bulk density of 0.45 to 0.55, the amount is adjusted to about 0.05% to 0.15% by weight, preferably 0.055% to 0.070% by weight.

[0038] Examples of rheological property modifiers include commercially available water-reducing agents, lignin sulfonic acid-based water-reducing agents, and polycarboxylic acid-based water-reducing agents. Examples of surfactants include alkaline soaps (alkaline salts of fatty acids, e.g., potassium oleate), potassium alkylene sulfosuccinate, polyoxyethylene alkyl ethers, alkyl betaines, and fatty acid alkanolamides. Examples of shrinkage-reducing agents include polyether-based shrinkage-reducing agents. Examples of water-repellent agents include silicone-based water-repellent agents and fluorine-based water-repellent agents.

[0039] Method for manufacturing lightweight aerated concrete The method for producing lightweight cellular concrete according to this disclosure is as follows: The process involves mixing necessary materials such as calcium carbonate, cement, silicate raw materials, and calcareous raw materials with water to prepare a raw material slurry; A step of causing volume expansion of the raw material slurry with a foaming agent, thereby pre-curing the resulting pre-cured material to a desired hardness; The process includes curing the obtained pre-cured material in a high-temperature, high-pressure steam atmosphere using an autoclave or the like.

[0040] <Raw material slurry preparation process> First, a raw material slurry is prepared by mixing raw material solids, including calcium carbonate, cement, siliceous raw materials, calcareous raw materials, sulfate compounds, and recycled raw materials, with water and additives such as foaming agents and water-reducing agents. The amounts of each raw material and additive contained in the solid content of the raw material slurry are as described above. The mass ratio (W / S) of water to solid content is preferably 1.0 or less, more preferably 0.65 to 0.95, and even more preferably 0.70 to 0.90.

[0041] <Pre-curing process> In the pre-curing process, the raw material slurry is poured into a mold, and the volume of the raw material slurry expands within the mold to obtain a pre-cured body. If necessary, reinforcing materials can be placed in the mold beforehand. For example, it is preferable to embed reinforcing bars or reinforcing wire mesh to increase bending strength, shear strength, and toughness. Reinforcing bars refer to bars arranged in a desired shape and welded at the intersections. Reinforcing wire mesh is made by processing iron into a mesh, and typical examples include lath mesh. The shape, dimensions, thickness of the bars, mesh size, and embedding location of the reinforcing bars or reinforcing wire mesh are not limited, and it is preferable to select them appropriately depending on the size and application of the cured product.

[0042] The slurry poured into the formwork is pre-hardened over a period of at least one hour, preferably between 40°C and 85°C, by foaming due to the foaming agent and the self-heating of quicklime and cement. Pre-hardening is preferably carried out in an environment where moisture evaporation is suppressed, such as a steam curing room.

[0043] The degree of pre-hardening should be sufficient to allow the pre-hardened material to be removed from the mold and moved. After the pre-hardening process, the obtained pre-hardened material may be cut into the desired product shape according to the final size of the aerated concrete, if necessary. Cutting can be done using a wire cutting method commonly used in the manufacture of aerated concrete.

[0044] <Curing process> In the curing process, the pre-hardened material is cured with high-temperature, high-pressure steam using an autoclave or the like to obtain lightweight aerated concrete. Autoclave conditions include, for example, 160°C (gauge pressure: approximately 5.3 kgf / cm²). 2 ) Above 220℃ (gauge pressure: approximately 22.6 kgf / cm²) 2 The following are preferable.

[0045] <Method for adjusting the volume and pore radius of pores A and B> To adjust the volume and pore radius of pores A and B to the preferred range of this disclosure, the mass ratio (W / S) of water to solids is preferably 0.65 to 0.95, and more preferably 0.70 to 0.85. The gypsum addition rate is preferably 1.0% to 4.0% by weight, and more preferably 1.5% to 3.0% by weight. The recycled material preferably consists of 10% to 20% by weight of pre-hardened material pulverized debris and 5.0% to 15.0% by weight of ALC powder. It is thought that a larger amount of recycled material increases the number of continuous voids formed by the disruption of the truss (cell) structure of the tobermorite crystals. In particular, it is thought that this tendency becomes more pronounced when the proportion of ALC powder in the recycled material increases. [Examples]

[0046] Examples and comparative examples of the present disclosure are described below, but the present disclosure is not limited to the following examples and comparative examples.

[0047] Measurement and Evaluation Methods <Volume and pore radius of pore A and pore B> The volume and radius of pores A and B are measured using the Mercury Intrusion Porosimetry method. The Mercury Intrusion Porosimetry method involves injecting mercury into the hardened material and measuring the distribution of pore diameters from the relationship between the pressure and the amount of mercury injected or released. This method is calculated assuming that the pores are cylindrical. The measurable range for pore diameters using the Mercury Intrusion Porosimetry is from a few nanometers to several hundred micrometers. However, this value does not represent the actual size of the pores, but rather serves as an indicator of the size of the gaps between constituent materials. It is a particularly effective analytical method when examining the pore structure of the lightweight cellular concrete of the present invention. The differential pore distribution measured by the Mercury Intrusion Porosimetry method is obtained by taking the first derivative of the integration curve of pore volume with respect to the measured pore radius.

[0048] The particles with a size of 2 mm to 4 mm obtained by classifying the cured body after autoclave curing and pulverizing were dried at 105 °C for 24 hours to obtain measurement samples. The pore size distribution of these measurement samples was measured using a mercury porosimeter (POREMASTER 60GT manufactured by Anton Paar GmbH). At this time, the contact angle between mercury and the cured body was 130 degrees, and the surface tension of mercury was 484 dyn / cm for calculation. Among the integrated curves of the pore volume with respect to the measured pore radius, the integrated volume of the portion with a pore radius of 0.004 μm or more and 2 μm or less obtained from the intrusion-side curve was defined as the total pore volume V, and the integrated volume of the portion with a pore radius of 0.004 μm or more and 2 μm or less obtained from the discharge-side curve was defined as the volume v of pore B. B Subtracting the volume v of pore B from the total pore volume V B gave the value (V - v B ), which was defined as the volume v of pore A. A Also, the maximum peak existing in the range of a pore radius of 0.004 μm or more and 2 μm or less in the intrusion-side curve was defined as the pore radius r of the peak of pore A A , and the peak existing in the range of a pore radius of 0.004 μm or more and 2 μm or less in the discharge-side curve was defined as the pore radius r of the peak of pore B B .

[0049] As an example of the measurement results, Fig. 1 shows the pore distribution with the pore radius (μm) of the lightweight cellular concrete of Example 1 on the horizontal axis and the differential pore volume on the vertical axis. In Fig. 1, the intrusion-side curve is shown by a solid line, and it can be read that there is a peak of pore A at 0.019 μm and a small peak of pore B on the right shoulder thereof. Also, the discharge-side curve is shown by a dashed line, and it can be read that there is a peak of pore B at 0.099 μm. Fig. 2 shows the pore distribution with the pore radius (μm) of the lightweight cellular concrete of Example 1 on the horizontal axis and the integrated pore volume on the vertical axis. In Fig. 2, the intrusion-side curve is shown by a solid line, representing the total pore volume V obtained by combining the volume v of pore A A and the volume v of pore B B . Also, the discharge-side curve is shown by a dashed line, representing the volume v of pore B B .

[0050] 〈Calcium Carbonate Content in Lightweight Cellular Concrete〉 The calcium carbonate content in lightweight aerated concrete is measured by the acid dissolution method. The acid dissolution method utilizes the carbon dioxide gas produced by the reaction between the hardened material and the calcium carbonate contained in the material when hydrochloric acid is added: CaCO3 + 2HCl → CaCl2 + H2O + CO2. Since the mass of the carbon dioxide gas produced in this reaction is proportional to the mass of the calcium carbonate contained in the hardened material, the flow rate of carbon dioxide gas from the calcium carbonate alone can be measured beforehand, and the calcium carbonate content (weight %) can be determined from the flow rate of carbon dioxide gas CO2.

[0051] The hardened body cured in an autoclave was pulverized to obtain a powder, which was then completely dried in a 105°C oven. Using this sample or calcium carbonate, the sample was reacted with 5 mol / L hydrochloric acid in a container, and the cumulative flow rate was measured using a gas flow meter (Beijing Horiba Metron Mass Flow Controller S48 series, MT-51). The amount of calcium carbonate in the hardened body was determined from the cumulative flow rate [ml], and the calcium carbonate content of the hardened body was calculated by dividing this by the weight of the sample and multiplying by 100.

[0052] <T5 strong linear sum of tobermorite crystals> The five-strong line sum T5 of tobermorite crystals is measured by X-ray diffraction of lightweight aerated concrete. After curing in an autoclave, the hardened concrete was dried at 105°C, and the sample was pulverized in a mortar. The measurement was then performed using Cu's Kα rays with an Empyrean X-ray analyzer manufactured by Malvern Panalytical Co., Ltd. The measurement conditions were: acceleration voltage 45kV, acceleration current 40mA, receiving slit width 0.1mm, scanning speed 2.5° / min, and sampling 0.02°. The diffraction lines were monochromatized using a graphite monochromator and counted. The sum of peak intensities including the background of the (002), (201), (220), (222), and (400) planes of the tobermorite crystal was defined as the five-strong line sum T5 (cps) of the tobermorite crystal.

[0053] 〈Absolute dry specific gravity〉 The cured material, after autoclaving, was placed in a 105°C dryer, and its specific gravity (absolute dry) was determined from the weight at which it reached a constant weight.

[0054] <Compressive strength and elastic modulus> After autoclaving, the cured material was cut to a size of 100φ × 100mm perpendicular to the foaming direction and placed in a constant temperature and humidity chamber at 20℃ and 60%RH. The cured material with a moisture content of 10±2% relative to the completely dry state was used as the measurement sample. Compressive strength was determined by applying a uniform load to the 100φ side as the pressure surface and measuring the maximum load until failure. The elastic modulus was determined by attaching strain gauges to the cylindrical side surface of the test specimen and measuring the strain-load gradient from 5% to 20% of the maximum load.

[0055] Example 1 78.8 parts by weight of 50℃ water, 37.5 parts by weight of silica (quartz crystal content 92%) as a siliceous raw material, 4.6 parts by weight of quicklime, 20.2 parts by weight of rapid-hardening Portland cement, 1.9 parts by weight of gypsum dihydrate, heavy calcium carbonate (Blaine specific surface area 4180 cm²) 2 10 parts by weight of ALC powder (D50=43μm in Microtrac MT3000II) obtained by crushing the scraps from the hardened body after autoclave curing, 8.0 parts by weight of ALC powder obtained by crushing the scraps that remained after pre-curing, and 18.0 parts by weight of pre-hardened body pulverized scraps obtained by crushing the scraps that remained after pre-curing were added and mixed and stirred for 2 minutes. Subsequently, an aqueous slurry obtained by mixing 0.0012 parts by weight of surfactant with 2.0 parts by weight of water was added, and 0.058 parts by weight of metallic aluminum powder was added, stirred for 30 seconds, and injected into a mold to foam and pre-cured. The slurry temperature at the time of injection into the mold was 45°C. The hardness of the top surface of the block was 0.303 N / mm after 4 hours of injection. 2 The resulting pre-hardened material was placed in an autoclave and cured at 180°C for 4 hours under a saturated steam atmosphere. After being removed from the autoclave, it was dried to obtain lightweight aerated concrete. The siliceous raw materials, cement, and calcareous raw materials were in a CaO / SiO2 molar ratio of 0.476.

[0056] Examples 2-8 As shown in Table 1, lightweight cellular concrete was manufactured and evaluated in the same manner as in Example 1, except that the mix design was changed.

[0057] Comparative Example 1 78.2 parts by weight of 50℃ water, 36.7 parts by weight of siliceous raw material, 3.0 parts by weight of quicklime, 22.3 parts by weight of rapid-hardening Portland cement, 5.1 parts by weight of dihydrate gypsum, light calcium carbonate (Blaine specific surface area 4180 cm²) 2 10 parts by weight of the mixture (10 parts by weight) and 22.9 parts by weight of ALC powder (average particle size 43 μm), which was obtained by crushing scraps from autoclaved lightweight aerated concrete, were added and mixed, and stirred for 2 minutes. Subsequently, an aqueous slurry, which had been prepared by mixing 0.0012 parts by weight of surfactant with 2.0 parts by weight of water, was added, and 0.058 parts by weight of metallic aluminum powder was added, stirred for 30 seconds, and then injected into a mold to allow foaming and pre-harden. The slurry temperature at the time of injection into the mold was 45°C and the viscosity was 576 g·cm. The hardness of the top surface of the block 4 hours after injection was 0.763 N / mm 2 The pre-hardened material was placed in an autoclave and cured in a saturated steam atmosphere at 180°C for 4 hours. After being removed from the autoclave, it was dried to obtain lightweight aerated concrete. The siliceous raw materials, cement, and calcareous raw materials were in a CaO / SiO2 molar ratio of 0.477.

[0058] Comparative Examples 2-6 Lightweight aerated concrete was manufactured and evaluated in the same manner as in Comparative Example 1, except that the mix design was changed as shown in Table 2.

[0059] [Table 1]

[0060] [Table 2]

[0061] Figure 3 shows the amount (by weight (%)) of calcium carbonate and the volume of pore A in Examples 1-8 and Comparative Examples 1-6. A This graph shows the relationship with [mL / g]. Figure 4 shows the amount of calcium carbonate (weight (%)) and the pore radius r of the peak of pore A in Examples 1-8 and Comparative Examples 1-6. AThis graph shows the relationship with [μm]. Figure 5 shows the amount (weight (%)) of calcium carbonate and the volume of pore B in Examples 1-8 and Comparative Examples 1-6. B This graph shows the relationship with [mL / g]. Figure 6 shows the amount of calcium carbonate (weight (%)) and the pore radius r of the peak of pore B in Examples 1-8 and Comparative Examples 1-6. B This graph shows the relationship with [μm]. Figure 7 is a graph showing the relationship between the amount of calcium carbonate (weight (%)) and the sum of five strong lines (cps) of X-ray diffraction in Examples 1-8 and Comparative Examples 1-6. In these graphs, examples are indicated by circles and comparative examples by crosses. From these graphs, it can be seen that by satisfying the preferred pore volume and pore radius of pores A and B in this disclosure, lightweight cellular concrete can be obtained that contains 5% by weight or more of calcium carbonate while maintaining mechanical properties. [Industrial applicability]

[0062] The lightweight cellular concrete of this disclosure can reduce CFP by containing 5% by weight or more of calcium carbonate, and when it contains 25% by weight or less of calcium carbonate and the amount of calcium carbonate is c% by weight, the volume of a specific pore A is v A However, -1.98 × 10 -3 By having a concentration of ×c + 0.600 [mL / g] or higher, the mechanical properties can be maintained. As a result, the lightweight aerated concrete of this disclosure can replace conventional ALC and is suitable for use in various applications such as exterior walls, interior materials, ceiling materials, roofing materials, flooring materials, insulation materials, humidity control materials, sound absorbing materials, and corner panels.

Claims

1. Lightweight aerated concrete containing 5% to 25% by weight of calcium carbonate, The lightweight aerated concrete has pores A having a peak in the pore radius range of 0.004 μm to 2 μm in the differential pore distribution measured on the penetration side of a mercury porosimeter, and when the amount of calcium carbonate is c by weight, the volume of pores A is v Ａ However, -1.98 × 10 －３ Lightweight aerated concrete with a concentration of ×c + 0.600 [mL / g] or higher.

2. The lightweight aerated concrete has pores B having a peak in the range of pore radius 0.004 μm to 2 μm in the differential pore distribution measured on the discharge side of a mercury porosimeter. When the amount of calcium carbonate is c by weight, the volume of the pore B is v Ｂ However, 9.80 x 10 －４ Lightweight cellular concrete according to claim 1, wherein the concentration is ×c + 0.285 [mL / g] or less.

3. The lightweight aerated concrete has pores A having peaks in the range of pore radii from 0.004 μm to 2 μm in the differential pore distribution measured on the penetration side of a mercury porosimeter, and the pore radius r of the largest peak of pores A Ａ However, 8.08 x 10 －４ Lightweight cellular concrete according to claim 1 or 2, wherein the thickness is ×c + 0.014 [μm] or less.

4. The sum of peak intensities T, including the background of the (002), (201), (220), (222), and (400) planes of the tobermorite crystal in the X-ray diffraction of the aforementioned lightweight aerated concrete. ５ However, -317 × c + 2.03 × 10 ４ The lightweight cellular concrete according to claim 1 or 3.

5. The lightweight cellular concrete according to claim 1 or 2, wherein the calcium carbonate is light calcium carbonate.

6. The volume v of the pores A Ａ is -1.98×10 －３ ×c + 0.610 [mL / g] or more, the lightweight cellular concrete according to claim 1 or 2.

7. The lightweight aerated concrete has pores B having a peak in the range of pore radius 0.004 μm to 2 μm in the differential pore distribution measured on the discharge side of a mercury porosimeter. Volume v of the pore B Ｂ However, 9.80 x 10 －４ Lightweight cellular concrete according to claim 1 or 2, wherein the concentration is ×c + 0.270 [mL / g] or less.

8. The lightweight aerated concrete has pores A having peaks in the range of pore radii from 0.004 μm to 2 μm in the differential pore distribution measured on the penetration side of a mercury porosimeter, and the pore radius r of the largest peak of pores A Ａ However, 8.08 x 10 －４ Lightweight cellular concrete according to claim 1 or 2, wherein the thickness is less than or equal to ×c + 0.013 [μm].

9. The lightweight aerated concrete has pores B having a peak in the range of pore radius 0.004 μm to 2 μm in the differential pore distribution measured on the discharge side of a mercury porosimeter. The pore radius r of the pore B with the largest peak Ｂ However, 1.37 × 10 －３ Lightweight cellular concrete according to claim 1 or 2, wherein the thickness is ×c + 0.092 [μm] or less.

10. The lightweight cellular concrete according to claim 1 or 2, comprising 5% by weight or more and 22% by weight or less of the calcium carbonate.

11. The lightweight cellular concrete according to claim 1 or 2, comprising 5% by weight or more and 15% by weight or less of the calcium carbonate.

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