Method for manufacturing precast concrete products and precast mortar products using crushed andesite aggregate

Abstract

This invention provides a method for manufacturing precast concrete products and precast mortar products using crushed andesite aggregate. [Solution] The method for manufacturing precast concrete products uses andesite crushed stone coarse aggregate and andesite crushed stone fine aggregate and cement as the main raw materials to produce concrete products with a water absorption rate of 0.3% or less. Specifically, it includes a mixing step to obtain a fluidized cement composition with a mixed temperature of 15°C to 45°C, which is higher than the temperature in the heat-insulated curing room; a molding step to pour the fluidized cement composition into a molding mold and mold it; and a heat-insulated curing step to harden the fluidized cement composition that constitutes the concrete product body without external heating until demolding strength is ensured.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing precast concrete products and a method for manufacturing precast mortar products with a water absorption rate of 0.3% or less.

Background Art

[0002] Generally, precast residual formwork panels are made using concrete or mortar. Conventionally, methods for manufacturing precast residual formwork panels have been disclosed, and the water absorption rate of precast concrete residual formwork panels manufactured by conventional methods is in the range of about 5.0 to 10%. Therefore, precast concrete residual formwork panels have, as a result, the same volume of voids.

[0003] When cracks occur in precast residual formwork panels, for example, frost damage, salt damage, efflorescence phenomenon, etc. of the residual formwork occur. In order to suppress such cracks, frost damage, salt damage, efflorescence phenomenon, etc., the inventor has proposed a method for manufacturing precast residual formwork panels for closing voids formed in precast residual formwork panels such as capillary voids (for example, Patent Document 1).

[0004] The method for manufacturing a precast permanent formwork panel described in Patent Document 1 includes the steps of: pouring a fluidized cement composition, obtained by mixing concrete raw materials containing cement, gravel, and sand, limestone fine powder in an amount of 5% to 40% by weight relative to the cement in the concrete raw materials, and mixing water, into a molding formwork; molding the fluidized cement composition poured into the molding formwork; and curing the fluidized cement composition. In this method for manufacturing a precast permanent formwork panel, in the molding and curing steps, excess water containing calcium hydroxide dissolved from the cement in the mixing water is pushed up to the back side, accumulating over the entire back surface of the panel body. The excess water covers the back surface of the panel body and fills capillary voids and the like that formed inside the panel body. Furthermore, as the cement in the fluidized cement composition hardens, a waterproof layer is formed across the entire back surface of the panel body. This prevents the formation of a permeable fine powder layer of calcium carbonate across the entire back surface of the panel body through a chemical reaction between carbon dioxide in the outside air and calcium hydroxide, while simultaneously sealing capillary voids and other gaps naturally with the waterproof layer. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 7314430 [Overview of the project] [Problems that the invention aims to solve]

[0006] Conventional manufacturing methods benefit from sealing capillary voids, but they cannot completely seal them, potentially allowing moisture to penetrate the precast formwork panels. Furthermore, continuous moisture penetration can lead to cracking after several years. Against this backdrop, there is a need for the development of a manufacturing method for precast formwork panels that reduces water absorption by sealing capillary voids and other structures formed in precast concrete panels, thereby preventing moisture from penetrating the panels and resulting in extremely low water absorption.

[0007] Therefore, the present invention aims to provide a method for manufacturing precast concrete products and a method for manufacturing precast mortar products utilizing andesite crushed aggregate. [Means for solving the problem]

[0008] The present invention relates to a method for manufacturing precast concrete products, in which a concrete product with a water absorption rate of 0.3% or less is manufactured using as the main raw materials coarse aggregate of crushed andesite with a water absorption rate of 1.9% to 7.5%, fine aggregate of crushed andesite with a water absorption rate of 1.9% to 7.5%, and cement. The method for manufacturing this precast concrete product comprises a mixing step in which concrete raw materials consisting of the cement, the coarse aggregate of crushed andesite and the fine aggregate of crushed andesite are mixed with mixing water for the hydration reaction heated to a temperature of 20°C to 85°C in a water heater to obtain a fluidized cement composition with a mixed temperature of 15°C to 45°C, which is higher than the temperature in the heat-insulated curing room, and after the mixing step, the fluidized cement composition is poured into a mold for forming the concrete product body and compacted during the compaction process, in which the fluidized cement compositionA molding process that suppresses the generation of bleeding water on the surface of the concrete product body by allowing the pores of the andesite crushed stone coarse aggregate and the andesite crushed stone fine aggregate to absorb excess alkaline water containing calcium hydroxide generated internally, and after the molding process, without external heating of the fluidized cement composition constituting the concrete product body, the temperature of the fluidized cement composition is allowed to naturally decrease to the temperature of the heat-insulated curing chamber over a period of 3 hours or more, thereby suppressing the bleeding phenomenon that occurs when the mixing water for the hydration reaction containing calcium hydroxide leached from the fluidized cement composition expands in volume, thereby preventing bleeding of the fluidized cement composition. The method includes a heat-curing step of hardening the fluidized cement composition until demolding strength is ensured without the formation of voids in the small tubes, and a demolding step of removing the molding formwork after the heat-curing step, wherein, in the heat-curing step, when the fluidized cement composition hardens, the alkaline water contained in the fluidized cement composition, the andesite crushed coarse aggregate, and the silica contained in the andesite crushed fine aggregate undergo a chemical reaction to produce alkali silica gel, thereby sealing the pores of the andesite crushed coarse aggregate and the andesite crushed fine aggregate with the alkali silica gel, resulting in a water absorption rate of 0.3% or less of the concrete product body.

[0009] In this method of manufacturing precast concrete products, andesite No. 6 crushed stone coarse aggregate is used to produce concrete products with a thickness of 35 mm, a height of 300 mm, and a width of 900 mm. The allowable particle size of the andesite crushed stone coarse aggregate is 8.75 mm (35 mm / 4 plate thickness). In the mixing process of this precast concrete product manufacturing method, concrete raw materials consisting of 450 kg of cement, 450 kg of andesite crushed stone coarse aggregate, and 900 kg of andesite crushed stone fine aggregate are mixed with 248 kg of mixing water for the hydration reaction, which has been heated to a temperature of 20°C to 85°C using a water heater, to obtain a fluidized cement composition with a mixed temperature of 15°C to 45°C, which is higher than the temperature in the insulated curing room.

[0010] The present invention relates to a method for manufacturing precast mortar products, which involves using andesite crushed stone fine aggregate with a water absorption rate of 1.9% to 7.5% and cement as the main raw materials to produce a mortar product with a water absorption rate of 0.3% or less. The method for manufacturing this precast mortar product involves a mixing step in which the mortar raw materials consisting of the cement and the andesite crushed stone fine aggregate are mixed with mixing water for the hydration reaction, which has been heated to a temperature of 20°C to 85°C in a water heater, to obtain a fluidized cement composition with a mixed temperature of 15°C to 45°C, which is higher than the temperature in the heat-insulated curing room, and after the mixing step, the fluidized cement composition is poured into a molding mold to form the main body of the mortar product, and during the compaction process, the fluidized cement composition A molding process that suppresses the generation of bleeding water on the surface of the mortar product body by allowing excess alkaline water containing calcium hydroxide generated internally to be absorbed into the pores of the andesite crushed stone fine aggregate, and after the molding process, without external heating of the fluidized cement composition constituting the mortar product body, the temperature of the fluidized cement composition is allowed to naturally decrease to the temperature of the heat-insulated curing chamber over a period of 3 hours or more, thereby suppressing the bleeding phenomenon that occurs when the mixing water for the hydration reaction containing calcium hydroxide dissolved from the fluidized cement composition expands in volume, thereby preventing the fluidized cement from being absorbed into the pores of the andesite crushed stone fine aggregate, and The method includes a heat-curing step of hardening the fluidized cement composition until demolding strength is ensured without the formation of capillary voids in the composition, and a demolding step of removing the molding formwork after the heat-curing step, wherein, in the heat-curing step, when the fluidized cement composition hardens, the alkaline water contained in the fluidized cement composition and the silica contained in the andesite crushed aggregate chemically react to produce alkali silica gel, thereby sealing the pores of the andesite crushed aggregate with alkali silica gel, and the water absorption rate of the mortar product body becomes 0.3% or less.

[0011] This method for manufacturing precast mortar products produces concrete products with a thickness of 25 mm, a height of 300 mm, and a width of 900 mm. In the mixing process of this method, mortar raw materials consisting of 450 kg of cement and 1500 kg of crushed andesite aggregate are mixed with 248 kg of mixing water for the hydration reaction, which has been heated to a temperature of 20°C to 85°C using a water heater, to obtain a fluidized cement composition with a mixed temperature of 15°C to 45°C, which is higher than the temperature in the insulated curing room. [Effects of the Invention]

[0012] The method for manufacturing precast concrete products according to the present invention is used to manufacture precast concrete products using coarse aggregate andesite crushed stone with a water absorption rate of 1.9% to 7.5%, fine aggregate andesite crushed stone with a water absorption rate of 1.9% to 7.5%, and cement as the main raw materials. This method for manufacturing precast concrete products is a mixing step in which concrete raw materials consisting of cement, coarse aggregate andesite crushed stone and fine aggregate and mixing water for the hydration reaction heated to a temperature of 20°C to 85°C in a hot water heater are mixed to obtain a fluidized cement composition with a mixed temperature of 15°C to 45°C, which is higher than the temperature in the heat-insulated curing room. After the mixing step, the fluidized cement composition is poured into a mold for forming the concrete product body and compacted during the compaction process. compositionThe method includes a molding step that suppresses the generation of bleeding water on the surface of the concrete product body by allowing excess alkaline water containing calcium hydroxide generated internally to be absorbed into the pores of the andesite crushed stone coarse aggregate and andesite crushed stone fine aggregate; a heat-insulating curing step after the molding step in which the fluidized cement composition is hardened until demolding strength is ensured; and a demolding step after the heat-insulating curing step in which the molding formwork is removed. During the heat-insulating curing step, as the fluidized cement composition hardens, the alkaline water contained in the fluidized cement composition reacts chemically with the silica contained in the andesite crushed stone coarse aggregate and andesite crushed stone fine aggregate to produce alkali silica gel. As a result, the pores of the andesite crushed stone coarse aggregate and andesite crushed stone fine aggregate are blocked by the alkali silica gel, and the water absorption rate of the concrete product body becomes 0.3% or less. Since the water absorption rate of marble is approximately 0.3%, the precast concrete product manufactured by the precast concrete product manufacturing method according to the present invention has an extremely low water absorption rate.

[0013] Similarly, the method for manufacturing precast mortar products according to the present invention can also be used to produce precast mortar products with extremely low water absorption rates. [Brief explanation of the drawing]

[0014] [Figure 1] This figure shows a precast permanent formwork panel (concrete product) according to an embodiment of the present invention. (a) shows a cross-sectional view, and (b) shows a rear view. [Figure 2] This figure illustrates the manufacturing process of a precast permanent formwork panel according to an embodiment of the present invention. (a), (b), and (c) show the respective steps. [Figure 3] This figure shows a permanent formwork constructed using precast permanent formwork panels according to an embodiment of the present invention. (a) shows a cross-sectional view, and (b) shows a rear view. [Figure 4] This image shows the condition of the test specimen before the start of the water absorption test. [Figure 5] This image shows the results of a water absorption test (immediately after dropping). [Figure 6]An image showing the results of the water absorption test (37 minutes after 6 hours from the start of the test). [Figure 7] An image showing the results of the water absorption test (13 minutes after 9 hours from the start of the test). [Figure 8] An image showing the results of the water absorption test (51 minutes after 9 hours from the start of the test).

Mode for Carrying Out the Invention

[0015] In this embodiment, the manufacturing method of precast concrete products will be described by taking the manufacturing method of precast residual formwork panels as an example and referring to FIGS. 1 to 3. Also, on the drawings, the horizontal direction of the precast residual formwork is denoted as the left - right direction X, the vertical direction as the up - down direction Y, and the thickness direction as the front - back direction Z.

[0016] The manufacturing method of the precast residual formwork panel according to this embodiment is used to manufacture the precast residual formwork panel 1 made of concrete shown in FIG. 1. Specifically, andesite No. 6 crushed stone coarse aggregate is used to manufacture a concrete product with a plate thickness of 35 mm, a height of 300 mm, and a width of 900 mm. The andesite crushed stone coarse aggregate with an allowable particle size of 8.75 mm (35 mm of plate thickness / 4) is used.

[0017] As shown in FIG. 1(a), the precast residual formwork panel 1 includes a precast residual formwork panel main body 2 (hereinafter also referred to as the panel main body 2), and a plurality of connecting metal fittings 3 provided at predetermined positions on the back surface 2a of the panel main body 2. This precast residual formwork panel 1 uses andesite crushed stone coarse aggregate with a water absorption rate of 1.9% to 7.5%, andesite crushed stone fine aggregate with a water absorption rate of 1.9% to 7.5%, and cement as the main raw materials. The JIS water absorption standard value of the crushed stone aggregate is 3.0%.

[0018] [Panel Main Body 2] As shown in Figs. 1(a) and (b), the panel body 2 is rectangular, and on the back surface 2a of the panel body 2, two connecting brackets 3 are provided in each of the left - right direction X and the up - down direction Y. This connecting bracket 3 is provided so as to protrude from the back surface 2a of the panel body 2. Also, in the left - right direction X and the up - down direction Y inside the panel body 2, a plurality of reinforcing bars 5 are provided to ensure the strength of the panel body 2. Note that the size (height and width) of the panel body 2 can be changed as appropriate.

[0019] [Connecting Bracket 3] The connecting bracket 3 includes a hook portion 6 and embedding portions 7 connected to both ends of this hook portion 6 (Fig. 1(a)). The connecting bracket 3 is provided such that the embedding portions 7 are embedded inside the panel body 2, the hook portion 6 protrudes from the back surface 2a of the panel body 2, and it is provided on the panel body 2. For this connecting bracket 3, a metal one can be used, and it is preferable to use a material with excellent corrosion resistance. For example, a stainless steel material (SUS304) can be used.

[0020] Next, the manufacturing method of the precast residual formwork panel will be described.

[0021] [Precast Concrete Product] The manufacturing method for the precast concrete product (precast permanent formwork panel 1) according to this embodiment includes a mixing step of mixing concrete raw materials consisting of cement, andesite crushed coarse aggregate and andesite crushed fine aggregate with mixing water for hydration reaction heated by a hot water heater to obtain a fluidized cement composition; a molding step of pouring the fluidized cement composition into a molding formwork to form the concrete product body and molding the concrete product body; a heat-curing step of hardening the fluidized cement composition that constitutes the concrete product body without external heating until demolding strength is ensured; and a demolding step of removing the molding formwork. Furthermore, during the heat-insulating curing process, as the fluidized cement composition hardens, a chemical reaction occurs between the alkaline water contained in the fluidized cement composition and the silica contained in the andesite crushed coarse aggregate and andesite crushed fine aggregate, generating alkali silica gel. This seals the pores of the andesite crushed coarse aggregate and andesite crushed fine aggregate, resulting in a concrete product body with a water absorption rate of 0.3% or less. In the manufacturing method of the precast concrete product according to this embodiment, no heating is performed in the mixing process other than heating and raising the temperature of the mixing water for the hydration reaction.

[0022] [Mixing process] In the mixing process, concrete raw materials consisting of cement, andesite crushed coarse aggregate, and andesite crushed fine aggregate are mixed with mixing water for the hydration reaction, which has been heated to a temperature of 20°C to 85°C using a water heater. A fluidized cement composition with a mixed temperature of 15°C to 45°C, which is higher than the temperature in the insulated curing room, is obtained. The mixed temperature is preferably 15°C higher than 0°C when the outside temperature in winter is 0°C, and preferably 5°C higher than 40°C when the outside temperature in summer is 40°C. For the andesite crushed coarse aggregate and andesite crushed fine aggregate, for example, those derived from Mt. Asama in Nagano Prefecture are used. The andesite crushed coarse aggregate and andesite crushed fine aggregate used are porous and have many fine voids (pores) inside. In this embodiment, the pores in the andesite crushed coarse aggregate and andesite crushed fine aggregate are called porosity parts.

[0023] In the manufacturing method of the precast concrete product according to this embodiment, andesite No. 6 crushed coarse aggregate is used to manufacture a concrete product with a plate thickness of 35 mm, a height of 300 mm, and a width of 900 mm. The allowable particle size of the andesite crushed coarse aggregate is 8.75 mm (plate thickness 35 mm / 4). Specifically, concrete raw materials consisting of 450 kg of cement, 450 kg of andesite crushed coarse aggregate, and 900 kg of andesite crushed fine aggregate are mixed with 248 kg of mixing water for the hydration reaction (55% of the cement) heated to a temperature of 20°C to 85°C using a water heater. The above ratio of cement, andesite crushed coarse aggregate, andesite crushed fine aggregate, and heated mixing water has been found to be optimal.

[0024] [Molding process] After the mixing process, a molding process is carried out. In the molding process, as shown in Figure 2, the panel body 2 is molded using a molding formwork 22. The molding formwork 22 is designed so that the back surface 2a of the panel body 2 is kept facing upward and horizontal. The upper side of the molding formwork 22 is the back surface 2a side of the panel body 2. Specifically, as shown in Figure 2(a), a mixture of the fluidized cement composition C is poured into the molding formwork 22, which is installed on a stand 21 equipped with a vibrator 20. Then, the fluidized cement composition C is vibrated by the vibrator 20. At this time, alkaline water containing excess calcium hydroxide generated in the fluidized cement composition C during the compaction process is absorbed into the pores of the andesite crushed stone coarse aggregate and andesite crushed stone fine aggregate. This suppresses the generation of bleeding water on the surface of the panel body (concrete product body).

[0025] [Burial process] After the molding process, as shown in Figures 2(b) and (c), the connecting fittings 3 attached to the reinforcing bars 5 are embedded in the fluidized cement composition C poured into the molding mold 22. Specifically, the connecting portion of the hook portion 6 and the embedded portion 7 are pushed to a predetermined position in the fluidized cement composition C, and the connecting fittings 3 are embedded so that the hook portion 6 of the connecting fittings 3 protrudes from the back surface 2a of the panel body 2. Note that if the connecting fittings 3 are not integrally formed with the panel body 2, the embedding process is not performed.

[0026] [Thermal curing process] After the molding and embedding processes, a heat-insulating curing process is performed. In the heat-insulating curing process, the fluidized cement composition C is hardened until sufficient demolding strength is ensured. Specifically, without external heating of the fluidized cement composition C, the temperature of the fluidized cement composition C is allowed to naturally decrease to the temperature of the heat-insulating curing room over a period of 3 hours or more. At this time, the bleeding phenomenon caused by the volume expansion of the mixing water for the hydration reaction containing calcium hydroxide leached from the fluidized cement composition C is suppressed, preventing the formation of capillary voids in the fluidized cement composition C, and allowing the fluidized cement composition C to harden until sufficient demolding strength is ensured. Furthermore, as the fluidized cement composition C hardens, the alkaline water contained in the fluidized cement composition C reacts chemically with the silica contained in the andesite crushed coarse aggregate and andesite crushed fine aggregate to produce alkali silica gel. This alkali silica gel then seals the pores of the andesite crushed coarse aggregate and andesite crushed fine aggregate, resulting in an extremely low water absorption rate for the panel body 2.

[0027] [Demolding process] The demolding process involves removing the molding formwork 22 after a predetermined time for heat retention and curing, thereby obtaining the desired precast remaining formwork panel 1.

[0028] Next, a construction method using the precast permanent formwork panel 1 manufactured by the manufacturing method described above will be explained. The cement-based consolidating material used in the permanent formwork construction method can be any material that contains moisture and hardens over time; for example, concrete, mortar, or aerated mortar can be used. In this embodiment, an example using ready-mixed concrete 12 as the cement-based consolidating material will be described.

[0029] In the construction method using the precast permanent formwork panels 1, as shown in Figure 3(b), the precast permanent formwork panels 1 are stacked to construct the permanent formwork 10. When constructing the permanent formwork 10, as shown in Figure 3(a), the precast permanent formwork panels 1 are fixed to the front of the wooden formwork 13 by connecting them with the connecting fittings 3 and steel connecting fittings (separators) 11 connected to the wooden formwork (plywood) 13.

[0030] Next, the cement-based hardening agent placement process is carried out. Specifically, after placing fresh concrete 12 between the precast remaining formwork panel 1 (panel body 2) and the wooden formwork 13 (Figure 3(a)), more fresh concrete 12 is placed and allowed to harden (cement-based hardening agent hardening process). Because the water absorption rate of the entire panel body 2 is extremely low, moisture from the fresh concrete 12 is prevented from penetrating into the interior of the panel body 2. As a result, the release and evaporation of moisture from the fresh concrete 12 is suppressed, and drying shrinkage cracks in the fresh concrete 12 are prevented.

[0031] <Precast mortar products> The manufacturing method for precast mortar products according to this embodiment is used to manufacture mortar products with a water absorption rate of 0.3% or less, using andesite crushed aggregate with a water absorption rate of 1.9% to 7.5% and cement as the main raw materials. Furthermore, the manufacturing process for this precast mortar product is carried out in the same manner as the manufacturing process for the precast permanent formwork panel described above.

[0032] The manufacturing method for this precast mortar product involves a mixing step in which mortar raw materials consisting of cement and crushed andesite fine aggregate are mixed with mixing water for the hydration reaction, which has been heated to a temperature of 20°C to 85°C in a hot water heater, to obtain a fluidized cement composition with a mixed temperature of 15°C to 45°C, which is higher than the temperature in the heat-insulated curing room. In the process of pouring the fluidized cement composition into a molding mold to form the main body of the mortar product and compacting it, the fluidized cement compositionThe method includes: a molding step in which excess alkaline water containing calcium hydroxide generated internally is absorbed into the pores of the andesite crushed stone fine aggregate to suppress the generation of bleeding water on the surface of the mortar product body; a heat-insulating curing step in which, after the molding step, the temperature of the fluidized cement composition constituting the mortar product body is allowed to naturally decrease to the temperature of the heat-insulating curing room over a period of 3 hours or more without external heating of the fluidized cement composition, thereby suppressing the bleeding phenomenon caused by the volume expansion of the mixing water for the hydration reaction containing calcium hydroxide dissolved from the fluidized cement composition, and hardening the fluidized cement composition until demolding strength is ensured without the formation of capillary voids in the fluidized cement composition; and a demolding step in which the molding formwork is removed after the heat-insulating curing step.

[0033] During the heat-insulating curing process, as the fluidized cement composition hardens, the alkaline water contained in the fluidized cement composition reacts chemically with the silica contained in the andesite crushed aggregate to produce alkali silica gel. As a result, the pores of the andesite crushed aggregate are sealed by the alkali silica gel, and the water absorption rate of the mortar product itself becomes 0.3% or less.

[0034] This method for manufacturing precast mortar products produces concrete products with a thickness of 25 mm, a height of 300 mm, and a width of 900 mm. In the mixing process of this method, concrete raw materials consisting of 450 kg of cement and 1500 kg of crushed andesite fine aggregate are mixed with 248 kg of mixing water for the hydration reaction, which has been heated to a temperature of 20°C to 85°C using a hot water heater, to obtain a fluidized cement composition with a mixed temperature of 15°C to 45°C, which is higher than the temperature in the insulated curing room.

[0035] [Comparative test of water absorption rate] A comparative water absorption test was conducted using test specimens produced by each manufacturing method. Test specimen 1, with a thickness of 35 mm, was prepared using the concrete mix described in the mixing step of the manufacturing method for precast concrete products, and test specimen 2, with a thickness of 25 mm, was prepared using the mix described in the mixing step of the manufacturing method for premortar products. For comparison, marble with a water absorption rate of 0.30% and a thickness of 15 mm was also used.

[0036] Manufacturing conditions for test specimen 1 Ambient temperature: 15°C, Mixing water temperature: 45°C, Fluidized cement composition temperature: 31°C

[0037] Manufacturing conditions for test specimen 2 Ambient temperature: 15°C, Mixing water temperature: 45°C, Fluidized cement composition temperature: 34°C

[0038] Test specimens 1 and 2 were placed on a marble table, and a comparative water absorption test was conducted as follows. 1.0 ml of water was dropped onto each test specimen, and observation was conducted for approximately 10 hours from immediately after dropping. The state of the dropped water (water droplets) on each test specimen was photographed with a digital camera. The results of the water absorption test are shown in Figures 4 to 8.

[0039] In test specimens 1 and 2, and in the marble, no water absorption was observed immediately after dropping (Figure 5). Six hours and 37 minutes after dropping the water droplets, the water had disappeared in the marble, while in test specimen 1, the water remained until 9 hours and 13 minutes, and in test specimen 2, until 9 hours and 51 minutes (Figures 6 to 8).

[0040] These results indicate that test specimens 1 and 2 possess water absorption performance equal to or less than that of marble (0.30%).

[0041] Next, the effects and advantages of the manufacturing method for precast permanent formwork panels according to this embodiment will be explained.

[0042] The manufacturing method for a precast permanent formwork panel according to this embodiment uses coarse aggregate andesite crushed stone with a water absorption rate of 1.9% to 7.5%, fine aggregate andesite crushed stone with a water absorption rate of 1.9% to 7.5%, and cement as the main raw materials to manufacture a precast permanent formwork panel 1. In the molding process of this manufacturing method, excess mixing water for the hydration reaction that becomes available during the compaction process is absorbed into the pores of the coarse aggregate and fine aggregate andesite crushed stone, thereby suppressing the generation of bleeding water on the surface of the panel body 2. Furthermore, in the heat-insulating curing process, when the temperature of the fluidized cement composition C is allowed to naturally decrease to the temperature of the curing chamber over a period of 3 hours or more, the bleeding phenomenon caused by the volume expansion of the mixing water for the hydration reaction containing calcium hydroxide dissolved from the fluidized cement composition C is prevented, thereby suppressing the formation of capillary voids in the fluidized cement composition C that constitutes the panel body 2.

[0043] Furthermore, during the heat-insulating curing process, as the fluidized cement composition C hardens, the alkaline water contained in the fluidized cement composition C reacts chemically with the silica contained in the andesite crushed coarse aggregate and andesite crushed fine aggregate to produce alkali silica gel, which then seals the pores of the andesite crushed coarse aggregate and andesite crushed fine aggregate. The precast formwork panel 1 manufactured using andesite aggregate has a water absorption rate lower than that of marble (0.30%), preventing moisture from penetrating the precast formwork panel 1. Therefore, water and other substances are extremely difficult to penetrate into the panel body 2 of the precast formwork panel 1, preventing deterioration over time such as cracking.

[0044] Although this embodiment has been described above, it is possible to select or replace the configurations listed in the above embodiment, or to change them to other configurations as appropriate, as long as they do not deviate from the spirit of the present invention.

[0045] The manufacturing method for precast concrete products of the present invention can also be used to manufacture precast concrete products other than precast permanent formwork panels, such as Hume pipes. Specifically, in the molding process, a fluidized cement composition is poured into a cylindrical molding formwork while it is rotating, and a rotational centrifugal force is applied to the poured fluidized cement composition to form the Hume pipe body. Hume pipes manufactured using the manufacturing method for precast concrete products of the present invention are subjected to large loads during or after construction, and even if minute cracks occur, the calcium hydroxide dissolved in the water immersed in the cement reacts with the silica contained in the aggregate, filling the minute cracks and providing semi-permanent healing. Therefore, the service life of the Hume pipe can be improved. [Explanation of symbols]

[0046] 1. Precast permanent formwork panels (precast concrete products) 2. Precast permanent formwork panel body (panel body) 2a Back (back side) 3. Connecting fittings 5 Reinforcement bars 6. Hook section 7. Buried section 10. Permanent formwork 11. Connecting fittings (separators) 12. Ready-mix concrete (cement-based binder) 13. Wooden formwork (plywood) 20 Vibration device 21 units 22. Molding molds C. Flowable cement composition X Left / right direction Y vertical direction Z front and rear direction

Claims

1. A method for manufacturing precast concrete products, in which coarse aggregate andesite crushed stone with a water absorption rate of 1.9% to 7.5%, fine aggregate andesite crushed stone with a water absorption rate of 1.9% to 7.5%, and cement are used as the main raw materials to produce concrete products with a water absorption rate of 0.3% or less, A mixing step involves mixing concrete raw materials consisting of the cement, the andesite crushed coarse aggregate, and the andesite crushed fine aggregate with mixing water for the hydration reaction, heated to a temperature of 20°C to 85°C in a water heater, to obtain a fluidized cement composition with a mixed temperature of 15°C to 45°C, which is higher than the temperature in the heat-insulated curing room. After the mixing step, the molding step involves pouring the fluidized cement composition into a mold to form the concrete product body and compacting it, during which excess alkaline water containing calcium hydroxide generated in the fluidized cement composition is absorbed into the pores of the andesite crushed coarse aggregate and the andesite crushed fine aggregate, thereby suppressing the generation of bleeding water on the surface of the concrete product body. After the molding process, the temperature of the fluidized cement composition constituting the concrete product body is allowed to naturally decrease to the temperature of the heat-insulated curing chamber over a period of three hours or more without external heating, thereby suppressing the bleeding phenomenon caused by the volume expansion of the mixing water for the hydration reaction containing calcium hydroxide dissolved from the fluidized cement composition, and hardening the fluidized cement composition until sufficient demolding strength is ensured, without the formation of capillary voids in the fluidized cement composition. The process includes a demolding step of removing the molding frame after the heat-insulating curing step, In the heat-insulating curing process, as the fluidized cement composition hardens, the alkaline water contained in the fluidized cement composition, the silica contained in the andesite crushed coarse aggregate, and the andesite crushed fine aggregate undergo a chemical reaction to generate alkali silica gel. As a result, the pores of the andesite crushed coarse aggregate and the andesite crushed fine aggregate are blocked by the alkali silica gel, and the water absorption rate of the concrete product body becomes 0.3% or less. A method for manufacturing precast concrete products characterized by the following:

2. A method for manufacturing precast mortar products, in which fine aggregate andesite crushed stone with a water absorption rate of 1.9% to 7.5% and cement are used as the main raw materials to produce mortar products with a water absorption rate of 0.3% or less, A mixing step is to mix the mortar raw materials consisting of the cement and the andesite crushed stone fine aggregate with mixing water for the hydration reaction, which has been heated to a temperature of 20°C to 85°C in a water heater, in order to obtain a fluidized cement composition with a mixed temperature of 15°C to 45°C, which is higher than the temperature in the heat-insulated curing room. After the mixing step, the molding step involves pouring the fluidized cement composition into a mold to form the mortar product body and compacting it, during which excess alkaline water containing calcium hydroxide generated in the fluidized cement composition is absorbed into the pores of the andesite crushed stone fine aggregate, thereby suppressing the generation of bleeding water on the surface of the mortar product body. After the molding process, the temperature of the fluidized cement composition constituting the mortar product body is allowed to naturally decrease to the temperature of the heat-insulated curing chamber over a period of 3 hours or more without external heating, thereby suppressing the bleeding phenomenon caused by the volume expansion of the mixing water for the hydration reaction containing calcium hydroxide dissolved from the fluidized cement composition, and hardening the fluidized cement composition until sufficient demolding strength is ensured, without the formation of capillary voids in the fluidized cement composition. The process includes a demolding step of removing the molding frame after the heat-insulating curing step, In the heat-insulating curing process, as the fluidized cement composition hardens, the alkaline water contained in the fluidized cement composition and the silica contained in the andesite crushed aggregate chemically react to produce alkali silica gel. As a result, the pores of the andesite crushed aggregate are blocked by the alkali silica gel, and the water absorption rate of the mortar product becomes 0.3% or less. A method for manufacturing precast mortar products, characterized by the following features.

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