Description:[TECHNICAL FIELD]
[0001]
An embodiment of the present invention relates to a manufacturing method of a concrete product and a jig for manufacturing the concrete product.

[BACKGROUND ART]
[0002]
Concrete is mainly composed of cement hydrate, aggregate, water, and additives and has been widely used in various fields as one of the important structural materials to create social production and economic infrastructure due to its excellent mechanical properties, weather resistance, ease of handling, and economic efficiency. Concrete without reinforcing steel has also been widely used not only as lining concrete but also as walls, curbs, slide blocks serving as pedestals of a variety of large equipment, small concrete products such as anchor blocks, drainage channels, safety blocks, parking blocks, and bricks, and the like.
[0003]
It has been known that cement serving as the raw material for concrete emits a large amount of carbon dioxide during its production, which has been represented as one of the causes of the greenhouse effect. In order to contribute to solving this problem, a method has been known in which ready-mixed concrete, which is the raw material of concrete, is made to contact with carbon dioxide to fix carbon dioxide in the concrete (see patent documents 1 and 2, for example).

[CITATION LIST]
[PATENT LITERATURE]
[0004]
[Patent Document 1] Japanese Patent No. 5957283
[Patent Document 2] Japanese Patent Application Publication No. 2009-149456

[SUMMARY OF INVENTION]
[TECHNICAL PROBLEM]
[0005]
An object of an embodiment of the present invention is to provide a novel method for manufacturing a concrete product and a jig applicable in this method. Alternatively, an object of an embodiment of the present invention is to provide a method for safely and efficiently manufacturing a concrete product in which carbon dioxide is fixed and a jig which can be used in this method.

[MEANS FOR SOLVING PROBLEM]
[0006]
An embodiment of the present invention is a manufacturing method of a concrete product. The method includes: injecting first ready-mixed concrete into a mold; forming an opening portion in the first ready-mixed concrete located in the mold; monitoring at least one of a weight of the first ready-mixed concrete, a temperature of the first ready-mixed concrete, and a carbon dioxide concentration, while introducing a carbon dioxide-containing gas into the opening portion; stopping the introduction of the carbon dioxide-containing gas after at least one of the weight of the first ready-mixed concrete, the temperature of the first ready-mixed concrete, and the carbon dioxide concentration becomes constant; and curing the first ready-mixed concrete after stopping the introduction of the carbon dioxide-containing gas.
[0007]
An embodiment of the present invention is a jig for manufacturing a concrete product. The jig includes: a scale including a main body and a weighing pan over the main body; and a mold over the scale.
[0008]
An embodiment of the present invention is a jig for manufacturing a concrete product. The jig includes a mold and a sensor. The mold includes a side plate and a partition wall. The partition wall is surrounded by the side plate and divides a space formed by the side plate into a plurality of chambers. The sensor is arranged in at least one of the plurality of chambers and is configured to measure a temperature or a carbon dioxide concentration.

[BRIEF DESCRIPTION OF DRAWINGS]
[0009]
[FIG. 1] A flowchart for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 2] A schematic perspective view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 3A] A schematic perspective view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 3B] A schematic cross-sectional view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 4A] A schematic perspective view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 4B] A schematic cross-sectional view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 5A] A schematic perspective view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 5B] A schematic cross-sectional view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 6] A schematic view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 7A] A schematic perspective view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 7B] A schematic cross-sectional view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 7C] A schematic cross-sectional view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 8A] A schematic perspective view of a jig which can be used in a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 8B] A schematic perspective side view of a jig which can be used in a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 9A] A schematic perspective side view of a jig which can be used in a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 9B] A schematic cross-sectional view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 9C] A schematic cross-sectional view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 10] A schematic view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 11A] A schematic perspective side view of a jig which can be used in a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 11B] A schematic cross-sectional view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.
[FIG. 11C] A schematic view for showing a manufacturing method of a concrete product according to an embodiment of the present invention.

[DESCRIPTION OF EMBODIMENTS]
[0010]
Hereinafter, each embodiment of the present invention is explained with reference to the drawings. The invention can be implemented in a variety of different modes within its concept and should not be interpreted only within the disclosure of the embodiments exemplified below.
[0011]
The drawings may be illustrated so that the width, thickness, shape, and the like are illustrated more schematically compared with those of the actual modes in order to provide a clearer explanation. However, they are only an example, and do not limit the interpretation of the invention. In the specification and the drawings, the same reference number is provided to an element that is the same as that which appears in preceding drawings, and a detailed explanation may be omitted as appropriate.
[0012]
In the specification and the claims, an expression “a structure is exposed from another structure” means a mode in which a part of the structure is not covered by the other structure and includes a mode where the part uncovered by the other structure is further covered by another structure.
[0013]
In this specification, concrete refers to as a cured product which does not exhibit fluidity and is obtained by curing cement hydrate formed by the reaction of cement, one of the raw materials, with water. Thus, cured cement paste without aggregate is also included in the category of concrete. Concrete may contain fine aggregate with a diameter of 5 mm or less and/or coarse aggregate with a diameter greater than 5 mm (e.g., greater than 5 mm and equal to or less than 20 mm or equal to or more than 10 mm and equal to or less than 20 mm). On the other hand, pre-cured concrete, i.e., a mixture containing cement and water and having fluidity before completely being cured, is called ready-mixed concrete (also called fresh concrete). Ready-mixed concrete may contain additives such as AE agents (air bubble dispersants), fluidizers, and thickeners in addition to aggregate. Ready-mixed concrete may have fluidity so that it can free-stand. Free-standing means that the ready-mixed concrete maintains its three-dimensional structure without being deformed only by an action of gravity, although it is deformed when an external force is applied.

[0014]
In this specification, "curing" refers to a process of curing ready-mixed concrete, and curing ready-mixed concrete forms hardened ready-mixed concrete, i.e., concrete.
[0015]

In this embodiment, a manufacturing method of a concrete product according to an embodiment of the present invention is explained. An example of the concrete product produced by this manufacturing method is a concrete block. Since the concrete block is manufactured by curing ready-mixed concrete, it can be recognized as a sort of unfired brick. The concrete product may be, for example, a concrete block laid on roads and slopes or a concrete brick used for walls and fences. Alternatively, the concrete block may be a concert block utilized for curbs, sliding blocks for various facilities, anchor blocks, safety blocks, parking blocks, wave-dissipating blocks, or the like. Thus, there is no restriction on the shape and size of the concrete products manufactured by this manufacturing method, and the shape and size may be determined according to the intended use.
[0016]
1. Preparation of Ready-Mixed Concrete
As shown in the flowchart (FIG. 1) showing an example of this manufacturing method, ready-mixed concrete is first prepared. The ready-mixed concrete is prepared by mixing cement, water, and aggregates. As the aggregates, sand, gravel, cobble, rock, crushed stone, crushed sand, and the like are represented. In addition, additives such as AE agents (bubble dispersants), fluidizing agents, thickening agents, and quickening agents may be further added. There are no restrictions on the type of cement, and it is possible to use ordinary Portland cement, white Portland cement containing iron oxide, alumina cement containing alumina, blast furnace cement added with blast furnace slag formed as a byproduct during the steel manufacturing process, fly ash cement added with a fly ash formed as a byproduct during coal ash combustion, eco cement containing waste materials such as incinerator ash and sludge, and the like. Sand, gravel, pumice stone, and the like may be used as the aggregates, or recycled crushed stone obtained by crushing discarded concrete may also be used. The mass ratio of cement to aggregate may also be set appropriately in consideration of the characteristics required for the resulting concrete block, and aggregate with a weight of 3 to 10 times that of cement may be used, for example. The water-cement ratio is also not restricted and may be selected from a range of 10% to 100%.
[0017]
Furthermore, fly ash, slag, ash such as biomass ash and incineration ash, silica fume, or the like may be added as admixture along with or instead of aggregate. The amount of admixture may also be determined as appropriate and may be adjusted so that the water to binder ratio (W/B) is equal to or more than 35% and equal to or less than 70%. Here, the binder refers to cement and admixture, and the water-binder ratio is the mass of water with respect to the total mass of cement and admixture.
[0018]
Through the above process, ready-mixed concrete with fluidity can be obtained. It is preferred that the ready-mixed concrete obtained here have a degree of fluidity which allows it to free-stand.
[0019]
2. Molding of Ready-Mixed Concrete
Next, the ready-mixed concrete is processed into the shape of the concrete product. Specifically, the ready-mixed concrete is placed in a mold 100 shown in FIG. 2. The mold 100 has side plates 100a, a partition wall 100b, and a bottom plate which is not illustrated in FIG 2. The side plates 100a are provided over the bottom plate and form a closed rectangle over the bottom plate. The partition wall 100b is also provided over the bottom plate and is surrounded by the side plates 100a, dividing the space formed by the bottom plate and the side plates 100a into a plurality of chambers 100c. The partition wall 100b is designed and arranged as appropriate so that the shapes of the chambers 100c conform to the shape of the concrete product. Each of the side plates 100a and the partition wall 100b may be composed of a plurality of components or as a single integrated component. Moreover, the side plates 100a and the partition wall 100b may be integrated or fixed to each other, or may be configured to be separable from each other. The side plates 100a, the partition wall 100b, and the bottom plate are configured to include wood, a metal such as iron or stainless steel, or a resin such as polypropylene.
[0020]
FIG. 3A shows a schematic perspective view of a state where the ready-mixed concrete 102 is injected into the mold 100. The ready-mixed concrete 102 is injected into the plurality of chambers 100c so that a top surface thereof matches the top surface of the side plates 100a or the partition wall 100b or is higher or lower than the top surface of the side plates 100a or the partition wall 100b. Furthermore, pressure may also be applied to the ready-mixed concrete 102 in the mold 100 using a compaction device 104 as shown in a schematic view of a cross section along a chain line A-A' in FIG. 3A (FIG. 3B). The pressure during pressurization may be selected from a range equal to or larger than 1 MPa and equal to or lower than 10 MPa, for example. Vibration may be applied during or before the pressurization to remove a part of the air mixed into the mold 100 so that the entire interior of the mold 100 is filled with the ready-mixed concrete 102 at a high density. Processing the ready-mixed concrete while applying pressure increases the strength of the finally obtained concrete product and reduces variations in strength and shape.
[0021]
3. Formation of Carbon Dioxide Introduction Hole
Next, as shown in FIG. 4A, an opening portion (hereinafter, referred to as an introduction hole) 106 for introducing carbon dioxide into the ready-mixed concrete 102 filled in each chamber 100c is formed in the state where the ready-mixed concrete is not cured and has a degree of fluidity so as to self-stand. As shown in a schematic view of a cross section along a chain line B-B' in FIG. 4A (FIG. 4B), the introduction hole 106 may be a bottomed hole which does not pass through the ready-mixed concrete 102 (i.e., which has a bottom) or a through hole passing through the ready-mixed concrete 102 to expose the bottom plate 100d. There is no restriction on the shape of the introduction hole (a shape of the surface parallel to the top surface of the ready-mixed concrete 102), and the shape may be, for example, a circle, an ellipse, a polygon, or a shape formed by both a curve and a line. The size of the introduction hole 106 is also not limited, and the introduction hole 106 may be formed so that the area of its shape is equal to or larger than 0.5 cm2 and equal to or smaller than 80 cm2, for example, in order for the concrete product to maintain a certain level of strength. When the shape of the introduction hole 106 is a circle, the introduction hole 106 may be formed so that its diameter is equal to or larger than 1 cm and equal to or smaller than 5 cm. When the introduction hole 106 is a bottomed hole, its depth may be, for example, equal to or more than 50% and equal to or less than 90% of the height of the ready-mixed concrete (a length in the direction in which the introduction hole 106 extends). Although not illustrated, the introduction hole 106 may be formed to diagonally extend from the surface of the ready-mixed concrete 102.
[0022]
4. Introduction of Carbon Dioxide
Carbon dioxide is subsequently introduced through the introduction hole 106. The carbon dioxide is introduced before the ready-mixed concrete 102 is cured in the mold 100. For example, as shown in a schematic perspective view of FIG. 5A and a schematic cross-sectional view (FIG. 5B) corresponding to a portion of FIG. 4B, an introduction tube 110 connected to a carbon dioxide supply source, which is not illustrated, is arranged over the mold 100. A plurality of apertures 110a overlapping the introduction holes 106 is provided in the introduction tube 110, and a carbon dioxide-containing gas may be supplied to the introduction holes 106 from the carbon dioxide supply source through the apertures 110a.
[0023]
The carbon dioxide-containing gas may be pure carbon dioxide (e.g., 99% purity or higher) or a mixture of carbon dioxide and other gases. The other gases may be air, oxygen, an inert gas such as nitrogen and argon, or water. When a mixed gas is used, its carbon dioxide concentration is higher than the atmospheric carbon dioxide concentration and is appropriately selected from the concentration equal to or higher than 400 ppm and equal to or less than 100%. When a carbon dioxide-containing gas including water is used, the carbon dioxide-containing gas may be prepared so that the humidity is equal to or higher than 40% and equal to or lower than 100%. There are no restrictions on the temperature of the carbon dioxide-containing gas, and the temperature may be room temperature or above room temperature (e.g., equal to or higher than 25°C and equal to or lower than 50°C). The pressure of the introduced carbon dioxide-containing gas is preferred to be equal to or higher than 1 atm (0.10 MPa) and equal to or lower than 1.3 atm (0.13 MPa) in order to prevent deformation of the uncured ready-mixed concrete 102. For this purpose, a pressure gauge or a flow meter (not illustrated) may be installed in the introduction tube 110 to monitor the pressure.
[0024]
The source of carbon dioxide may be a cylinder filled with carbon dioxide or a facility which emits a large amount of carbon dioxide (chemical plants, waste incineration facilities, thermal power plants, and various other types of plants). In the latter case, the gas emitted from the facility or purified carbon dioxide obtained by performing dust removal, desulfurization, denitrification, or the like on the emitted gas may be used. When a facility which emits a large amount of carbon dioxide and is located near the site where this manufacturing method is implemented is used as the source of carbon dioxide, not only is the cost of transporting carbon dioxide reduced, but further emissions of carbon dioxide associated with the transportation is prevented.
[0025]
Carbon dioxide reacts with the cement hydrate generated by the reaction of the cement with water included in the ready-mixed concrete 112. When Portland cement is used as the cement, for example, the contact of the minerals constituting the main components, namely alite (tricalcium silicate: 3CaO-SiO2) and belite (dicalcium silicate: 2CaO-SiO2), with water results in calcium silicate hydrate (3CaO-2SiO2-3H2O) and calcium hydroxide (Ca(OH)2). The calcium silicate hydrate and calcium hydroxide correspond to the cement paste of concrete. The reaction (carbonation) of the calcium silicate hydrate and the calcium hydroxide with carbon dioxide generates silicon dioxide and calcium carbonate. As the carbonation proceeds, the calcium silicate hydrate grows calcium carbonate crystals to fill the voids in the ready-mixed concrete 102, resulting in a needle-like network. As a result, a strong cured product is produced in which silicon oxide is fixed within the network of the calcium carbonate crystals. That is, the ready-mixed concrete 102 is cured, and concrete with high compressive strength is obtained. Furthermore, when admixture containing silicon oxide and aluminum oxide such as fly ash, blast furnace slag, or silica fume is used during the preparation of the ready-mixed concrete 102, a reaction with calcium hydroxide (pozzolanic reaction) also proceeds. Stable calcium silicate hydrate and calcium aluminate hydrate formed by the pozzolanic reaction fills the voids existing in the concrete, thereby increasing the density of the concrete.
[0026]
As described above, because aggregates are included in the ready-mixed concrete 102, the ready-mixed concrete 102 contains a large number of voids formed by the gaps between the aggregates. Therefore, when carbon dioxide-containing gas is introduced, carbon dioxide is not only injected into the introduction holes 106, but also gradually permeates into the voids (see FIG. 5B). Thus, in the manufacturing method of the concrete products according to an embodiment of the present invention, the amount of carbon dioxide introduced is controlled in order to more efficiently progress the carbonation described above and to prevent the use of excessive amounts of carbon dioxide. Specifically, the weight change of the ready-mixed concrete 102 is monitored while introducing the carbon dioxide-containing gas. The weight change may be monitored by monitoring the weight of the mold 100 and the ready-mixed concrete 102 using a measuring device such as a scale. There are no restrictions on the specifications of the measuring device to be used, and a known scale or the like may be used as appropriate.
[0027]
Before the carbon dioxide-containing gas is introduced, air is present in the voids of the ready-mixed concrete 102. When the carbon dioxide-containing gas is introduced, the air is replaced with carbon dioxide. Therefore, due to the difference in molecular weight between air (28.8) and carbon dioxide (44), the apparent weight of the ready-mixed concrete 102 increases from the initial weight W0 when the introduction of the carbon dioxide-containing gas is started as schematically shown in FIG. 6. When the air in the voids of the ready-mixed concrete 102 and the introduction holes 106 is completely replaced with the carbon dioxide-containing gas, no weight change is observed, and the weight of the ready-mixed concrete 102 reaches a weight W1 (W1>W0) and then becomes constant or substantially constant. The introduction of the carbon dioxide-containing gas is stopped after the time t when the weight becomes constant, by which not only is a sufficient amount of carbon dioxide introduced inside the ready-mixed concrete 102, but also the introduction of more carbon dioxide than necessary is prevented. As a result, not only can the danger caused by carbon dioxide leakage be significantly reduced, but carbon dioxide can be used more efficiently, enabling the safe and low-cost production of the concrete products with high strength.
[0028]
5. Demolding, Filling of Introduction Hole, and Curing (Carbonation)
After the weight of the ready-mixed concrete 102 becomes constant and the supply of the carbon dioxide-containing gas is stopped, the ready-mixed concrete 102 is ejected from the mold 100 (demolding) as shown by the route (a) in FIG. 1. At this time, a cap 112 may be attached to the introduction hole 106 before demolding to prevent carbon dioxide from leaking from the introduction hole 106 (FIG. 7A and FIG. 7B).
[0029]
After that, curing is carried out without supplying the carbon dioxide-containing gas to allow the concrete to be subjected to hydration and carbonation. As described above, the present manufacturing method allows carbon dioxide to be sufficiently supplied not only into the introduction holes 106 but also into the voids in the ready-mixed concrete 102. Therefore, carbonation efficiently proceeds without continuously supplying carbon dioxide to the introduction holes 106 during curing after demolding or without exposing the ready-mixed concrete 102 after demolding to a highly concentrated carbon dioxide environment by using facilities for curing.
[0030]
After curing is completed and the ready-mixed concrete 102 is hardened, the introduction hole 106 is filled. Specifically, ready-mixed concrete 114 is injected into the introduction hole 106 and then cured (FIG. 7C). The ready-mixed concrete 114 may have the same composition as the ready-mixed concrete 102 or a different composition. For example, the ready-mixed concrete 114 may not contain any aggregate. In addition, pressure may be applied using the compaction device 104 and/or vibration may be applied to remove air mixed into the ready-mixed concrete 114 in order that the whole of the introduction hole 106 is densely filled with the ready-mixed concrete 114. Moreover, in order to flatten the surfaces of the resulting concrete product, the top surface of the ready-mixed concrete 114 may be leveled so that the top surfaces of the ready-mixed concrete 102 and 114 exist in the same plane.
[0031]
Through the above processes, high-strength concrete products can be provided. Note that the order of the processes after stopping the introduction of the carbon dioxide-containing gas may be changed as appropriate, and the demolding may be carried out after the introduction holes 106 is filled and then curing may be conducted (FIG. 1, route (b)), for example. Alternatively, the introduction hole 106 may be filled after demolding, and then curing may be conducted (FIG. 1, route (c)).
[0032]
As described above, in the manufacturing method of concrete products according to an embodiment of the present invention, the carbonation is not monitored, but the amount of carbon dioxide required for carbonation is controlled by monitoring the weight change of the ready-mixed concrete 102. Hence, since the necessary and sufficient amount of carbon dioxide can be supplied to the ready-mixed concrete 102 before curing, it is possible to prevent an excessive supply of carbon dioxide and safely provide concrete products at a low-cost.
[0033]
Furthermore, according to the present manufacturing method, the calcium hydroxide in the concrete paste reacts with carbon dioxide to provide calcium carbonate when curing proceeds. Namely, carbon dioxide is fixed in the concrete product as calcium carbonate. Therefore, it can be recognized that this manufacturing method is one of the effective methods for fixing carbon dioxide.
[0034]

In this embodiment, a jig which can be used in the manufacturing method of concrete products described in the First Embodiment is explained. An explanation of the structures the same as or similar to those described in the First Embodiment may be omitted.
[0035]
Schematic perspective and side views of the jig 120 are respectively shown in FIG. 8A and FIG. 8B. As shown in these drawings, the jig 120 includes a scale 122 and a mold 100 arranged over the scale 122. The scale 122 has a main body 124 and a weighing pan 126 over the main body 124. Although not illustrated, a spring, a strain gauge, a combination of an electromagnetic coil and a magnet, a tuning fork vibration sensor, or the like is provided in the main body 124 as a mechanism for measuring the weight of objects. The main body 124 may be equipped with a display 128 for showing measured values and a level 132. The mold 100 may have the same configuration as the mold 100 described in the First Embodiment. The mold 100 is fixed to the weighing pan 126 so as to be detachable from the weighing pan 126.
[0036]
The jig 120 further includes a plurality of fixing mechanisms 130 for fixing the weighing pan 126 to prevent vertical movement or vertical vibration. There are no restrictions on the configuration of the fixing mechanisms 130. For example, the fixing mechanisms 130 may be an outrigger fixed to the weighing pan 126 as shown in FIG. 8A and FIG. 8B. In this case, the fixing mechanism 130 is extendable and retractable in the vertical direction and is configured so that a lower end is positioned below a lower surface of the main body 124 in a retracted state, while the lower end is positioned above the lower surface of the main body 124 in an extended state. The weighing pan 126 is fixed by extending the fixing mechanism 130 when applying pressure to the ready-mixed concrete 102 in the mold 100 using the compaction device 104, by which excessive pressure can be prevented from being applied to the main body 124 so that damage of the measuring mechanism due to the pressure from the compaction device 104 can be prevented. Conversely, the weighing pan 126 can undergo vertical movement by retracting the fixing mechanism 130, allowing the weight of the mold 100 and ready-mixed concrete 102 to be measured.

[0037]
The use of the jig 120 allows the weight of the ready-mixed concrete 102 injected into the mold 100 to be monitored as needed, by which a necessary and sufficient amount of carbon dioxide for carbonation can be supplied and the use of an excessive amount of carbon dioxide can be avoided. In addition, since the mold 100 can be detached from the weighing pan 126, demolding can also be readily performed.
[0038]

In this embodiment, a manufacturing method and a jig different from the manufacturing method and the jig for concrete products respectively described in the First and Second Embodiments are explained. An explanation of the structures the same as or similar to those described in the First and Second Embodiments may be omitted.
[0039]
1. Control of Amount of Carbon Dioxide by Monitoring Temperature
In the manufacturing method for concrete products according to the present embodiment, the amount of carbon dioxide required for carbonation is controlled by monitoring the temperature change of the ready-mixed concrete 102. Hence, the jig 140 available for the manufacturing method of concrete products according to the present embodiment includes, in addition to the mold 100, a temperature sensor 142 for measuring temperature in at least one of the plurality of chambers 100c as shown in FIG. 9A. The jig 140 may include the temperature sensor 142 in each of two or more of the plurality of chambers 100c. When the temperature sensors 142 are provided in the plurality of chambers 100c, it is preferred to arrange the temperature sensors 142 so as to be uniformly distributed within the mold 100. For example, the temperature sensors 142 may be arranged to measure the temperatures of the chambers 100c located at the center of the mold 100 and at the four corners of the mold 100. The temperature sensor 142 may be arranged in the chamber 100c as shown in FIG. 9A or outside the chamber 100c although not illustrated. When the temperature sensor 142 is provided in the chamber 100c, the temperature sensor 142 is arranged so as to be in contact with the bottom plate 100d, the partition wall 100b, or the side plate 100a. When the temperature sensor 142 is provided outside the chamber 100c, the temperature sensor 142 may be disposed so as to be in contact with the bottom plate 100d or the side plate 100a. The temperature sensor 142 may or may not be fixed to the bottom plate 100d, the partition wall 100b, or the side plate 100a.
[0040]
There are no restrictions on the configuration of the temperature sensor 142, and any known temperature sensor may be used. For example, a contact-type temperature sensor equipped with a side temperature resistor or a thermocouple may be used. The temperature sensor 142 is wirelessly connected or wire-connected through a wiring 144 to a communication terminal which is not illustrated, by which the information from the temperature sensor 142 can be obtained using a display portion provided to the communication terminal. There are no restrictions on the communication terminal, and stationary (desktop) computers, notebook computers, or portable communication terminals such as portable phones, tablets, and smart phones are exemplified as the communication terminal.
[0041]
When the temperature sensor 142 is placed in the chamber 100c, the ready-mixed concrete 102 is injected into the mold 100 so that the temperature sensor 142 is embedded as shown in FIG. 9B. Furthermore, the introduction hole 106 formed in the ready-mixed concrete 102 injected into the chamber 100c in which the temperature sensor 142 is disposed is formed as a bottomed hole. With this configuration, the temperature sensor 142 is not exposed from the ready-mixed concrete 102, allowing the temperature sensor 142 to be in direct contact with the introduced carbon dioxide-containing gas. In the chamber 100c in which the temperature sensor 142 is not arranged, the introduction hole 106 may be a bottomed hole or a through hole. Moreover, when the temperature sensor 142 is arranged outside the chamber 100c, the introduction hole 106 may be a bottomed hole or a through hole.
[0042]
Furthermore, in the manufacturing method of concrete products according to the present embodiment, the carbon dioxide-containing gas having a temperature higher than room temperature is used. The temperature of the carbon dioxide-containing gas may be set at 30 °C or higher and 60 °C or lower, 40 °C or higher and 60 °C or lower, or 40°C or higher and 50 °C or lower.
[0043]
Once the introduction of the carbon dioxide-containing gas into the introduction hole 106 is started, the carbon dioxide-containing gas spreads from the inner wall of the introduction hole 106 into the voids in the ready-mixed concrete 102 (see FIG. 9C). The temperature of the carbon dioxide-containing gas is higher than room temperature, i.e., the temperature of the ready-mixed concrete 102 at the time when it is injected. Therefore, when the introduction of the carbon dioxide-containing gas is started, the temperature of the ready-mixed concrete 102 increases from the initial temperature T0 (see FIG. 10). When the air in the voids of the ready-mixed concrete 102 is completely replaced with the carbon dioxide-containing gas, the rate of the temperature increase of the ready-mixed concrete 102 gradually decreases, and the temperature then becomes constant or substantially constant at temperature T1 (T1 > T0). The temperature T1 is the same or substantially the same as the temperature of the introduced carbon dioxide-containing gas. The introduction of the carbon dioxide-containing gas is stopped after a time t at which the temperature becomes constant, by which the introduction of an excessive amount of carbon dioxide is prevented and a necessary and sufficient amount of carbon dioxide can be introduced into the ready-mixed concrete 102. Therefore, by implementing this embodiment, concrete products with increased strength due to the fixation of carbon dioxide can be safely and efficiently produced.
[0044]
2. Controlling Amount of Carbon Dioxide by Monitoring Carbon Dioxide Concentration
Instead of monitoring the weight or the temperature changes of the ready-mixed concrete 102, the carbon dioxide concentration may be monitored to control the amount of the introduced carbon dioxide. A schematic cross-sectional view of a jig 150 which can be used in this method is shown in FIG. 11A. FIG. 11A is a cross-sectional view corresponding to FIG. 4B. As shown in FIG. 11A, the jig 150 includes, in addition to the mold 100, a carbon dioxide concentration sensor 152 measuring the carbon dioxide concentration in at least one of the plurality of chambers 100c of the mold 100. The jig 150 may have carbon dioxide concentration sensors152 in each of two or more of the plurality of chambers 100c. Similar to the arrangement of the temperature sensor 142, when the carbon dioxide concentration sensors 152 are arranged in the plurality of chambers 100c, the carbon dioxide concentration sensors 152 are preferably arranged so as to be uniformly distributed within the mold 100. For example, the carbon dioxide concentration sensors 152 may be arranged in the chambers 100c at the center of the mold 100 and at the four corners of the mold 100.
[0045]
There are no restrictions on the configuration of the carbon dioxide concentration sensor 152. For example, a sensor equipped with an infrared source and a detector capable of measuring its intensity may be used. The carbon dioxide concentration can be measured by measuring the amount of infrared absorbed by carbon dioxide with the detector. Similar to the temperature sensor 142, the carbon dioxide concentration sensor 152 is provided so as to be in contact with the bottom plate 100d, the partition wall 100b, or the side plate 100a. The carbon dioxide concentration sensor 152 may or may not be fixed to the bottom plate 100d, the partition wall 100b, or the side plate 100a. The carbon dioxide concentration sensor 152 is also wirelessly connected or wire-connected to a communication terminal which is not illustrated, by which the information from the carbon dioxide concentration sensor 152 can be obtained using a display portion provided to the communication terminal.
[0046]
As shown in FIG. 11B, the ready-mixed concrete 102 is injected into the mold 100 so that the carbon dioxide concentration sensor 152 is embedded. Moreover, the introduction hole 106 formed in the ready-mixed concrete 102 injected into the chamber 100c where the carbon dioxide concentration sensor 152 is placed is formed as a bottomed hole. With this configuration, the carbon dioxide concentration sensor 152 is not exposed from the ready-mixed concrete 102 and is allowed to be in direct contact with the introduced carbon dioxide-containing gas. Note that the introduction hole 106 formed in the ready-mixed concrete 102 injected into the chamber 100c where the carbon dioxide concentration sensor 152 is not disposed may be a bottomed hole or a through hole.

[0047]
Once the introduction of the carbon dioxide-containing gas into the introduction hole 106 is started, the carbon dioxide-containing gas spreads from the inner wall of the introduction hole 106 into the voids in the ready-mixed concrete 102 and then reaches the carbon dioxide concentration sensor 152 (see FIG. 11B). Hence, when the introduction of the carbon dioxide-containing gas is started, the carbon dioxide concentration detected by the carbon dioxide concentration sensor 152 gradually increases from an initial concentration of C0 (FIG. 11C). When the air in the voids of the ready-mixed concrete 102 is completely replaced with the carbon dioxide-containing gas, the carbon dioxide concentration reaches a concentration C1 (C1 > C0) and then becomes constant or substantially constant. The concentration C1 is the same or substantially the same as the carbon dioxide concentration of the introduced carbon dioxide-containing gas. The introduction of the carbon dioxide-containing gas is stopped after a time t at which the carbon dioxide concentration becomes constant, by which the introduction of an excessive amount of carbon dioxide is prevented and a necessary and sufficient amount of carbon dioxide can be introduced into the ready-mixed concrete 102. Therefore, by implementing this embodiment, concrete products with increased strength due to the fixation of carbon dioxide can be safely and efficiently produced.
[0048]
Although the introduced amount of the carbon dioxide-containing gas is controlled by monitoring the temperature or the carbon dioxide concentration of the ready-mixed concrete 102 in this embodiment, the introduction of the carbon dioxide-containing gas may be controlled by monitoring at least one of the weight of the ready-mixed concrete 102 described in the First Embodiment, the temperature of the ready-mixed concrete 102, and the carbon dioxide concentration described in this embodiment. Therefore, the introduction of the carbon dioxide-containing gas may be controlled by combining the monitoring of the weight and the temperature of the ready-mixed concrete 102 and the carbon dioxide concentration as appropriate.
[0049]
The aforementioned modes described as the embodiments of the present invention can be implemented by appropriately combining with each other as long as no contradiction is caused. Furthermore, any mode which is realized by persons ordinarily skilled in the art through the appropriate addition, deletion, or design change of elements or through the addition, deletion, or condition change of a process is included in the scope of the present invention as long as they possess the concept of the present invention.
[0050]
It is understood that another effect different from that provided by each of the aforementioned embodiments is achieved by the present invention if the effect is obvious from the description in the specification or readily conceived by persons ordinarily skilled in the art.
[Reference Sign List]
[0051]
100: Mold, 100a: Side plate, 100b: Partition wall, 100c: Chamber, 100d: Bottom plate, 102: Ready-mixed concrete, 104: Compaction device, 106: Introduction hole, 110: Introduction tube, 110a: Opening, 112: Cap, 114: Ready-mixed concrete, 120: Jig, 122: Scale, 124: Main body, 126: Weighing pan, 128: Display, 130: Fixing mechanism, 132: Level, 140: Jig, 142: Temperature sensor, 144: Wiring, 150: Jig, 152: Carbon dioxide concentration sensor
, Claims:[Claim 1]
A manufacturing method of a concrete product, the method comprising:
injecting first ready-mixed concrete into a mold;
forming an opening portion in the first ready-mixed concrete located in the mold;
monitoring at least one of a weight of the first ready-mixed concrete, a temperature of the first ready-mixed concrete, and a carbon dioxide concentration, while introducing a carbon dioxide-containing gas into the opening portion;
stopping the introduction of the carbon dioxide-containing gas after at least one of the weight of the first ready-mixed concrete, the temperature of the first ready-mixed concrete, and the carbon dioxide concentration becomes constant; and
curing the first ready-mixed concrete after stopping the introduction of the carbon dioxide-containing gas.

[Claim 2]
The manufacturing method according to claim 1, further comprising:
ejecting the first ready-mixed concrete from the mold before curing the first ready-mixed concrete.

[Claim 3]
The manufacturing method according to claim 1, further comprising:
filling the opening portion with second ready-mixed concrete; and
curing the second ready-mixed concrete.

[Claim 4]
The manufacturing method according to claim 1,
wherein the weight of the first ready-mixed concrete is monitored using a scale arranged under the mold.

[Claim 5]
The manufacturing method according to claim 1,
wherein the temperature of the first ready-mixed concrete and the carbon dioxide concentration are monitored with a sensor arranged in the mold, and
wherein the first ready-mixed concrete is injected into the mold so that the monitor is embedded.

[Claim 6]
A jig for manufacturing a concrete product comprising:
a scale comprising a main body and a weighing pan over the main body; and
a mold over the scale.

[Claim 7]
The jig according to claim 6, further comprising a fixing mechanism to fix the weighing pan.

[Claim 8]
A jig for manufacturing a concrete product comprising:
a mold comprising side plates and a partition wall surrounded by the side plates and dividing a space formed by the side plates into a plurality of chambers; and
a sensor arranged in at least one of the plurality of chambers,
wherein the sensor is configured to measure a temperature or a carbon dioxide concentration.