JP7514639B2 - How concrete is manufactured - Google Patents

Description

The present invention relates to a method for producing concrete by mixing cement, aggregate, admixtures, and water in a specified ratio.

Conventionally, concrete is manufactured in a manufacturing plant by mixing cement, aggregate, admixtures, and water in a specified ratio. For example, when manufacturing concrete in the summer when the outside temperature is high, the temperature of the concrete when unloaded at the construction site may exceed the acceptable limit, the mixed concrete may set early, or the concrete may dry out early, causing a deterioration in the quality of the concrete.

In light of these points, for example, Patent Document 1 discloses a method for producing concrete in which ice blocks are used to substitute for part of the water in a concrete manufacturing plant, and cement, aggregate, admixtures, water, and ice blocks are mixed to produce concrete.

JP 2002-11709 A

However, when cement, aggregate, water, admixtures, and ice blocks are mixed directly in a manufacturing plant, if the ice blocks do not melt completely during mixing, fresh concrete testing cannot be performed immediately after mixing. If the presence of these ice blocks makes it impossible to perform fresh concrete testing immediately after mixing, there is a risk that the quality of the concrete cannot be confirmed at an early stage. In addition, the temperature of the concrete increases between the time when the concrete is poured into the mixer of the agitator vehicle and the time when the concrete is transported to the construction site, and the ice blocks melt completely early, causing a slump loss of the concrete or the temperature of the concrete when it arrives at the construction site exceeding the upper limit of the temperature for acceptance, which may result in a deterioration in the quality of the concrete poured at the construction site. Therefore, for example, a cooling device for cooling the water and aggregate may be installed in the concrete manufacturing plant, and a cooling device for cooling the concrete may be installed in the agitator vehicle, but installing such a cooling device in each agitator vehicle increases the equipment costs of the concrete manufacturing plant.

The present invention was made in consideration of these points, and aims to provide a method for producing concrete that can supply concrete of more stable quality to construction sites at low cost, without incurring equipment costs at a concrete manufacturing plant, without the temperature of the concrete exceeding the upper limit temperature when it is unloaded from an agitator truck that arrives at the construction site.

In view of the above problem, the method for producing concrete according to the present invention is a method for producing concrete by mixing cement, aggregate, admixtures, and water, and is characterized by including at least a first mixing step in which, in the concrete production plant, water corresponding to a unit water volume less than the unit water volume of the concrete is mixed with the cement, aggregate, and admixtures to produce base concrete; an inspection step in which a fresh concrete test is performed on the base concrete after the first mixing step to check whether the base concrete satisfies a predetermined physical property value; and a second mixing step in which, after the inspection step, ice blocks of a weight corresponding to the difference in water volume between the unit water volume of the concrete and the unit water volume of the base concrete are added to a mixer of an agitator vehicle into which the base concrete determined to satisfy the predetermined physical property value has been added between before departure from the production plant and arrival at the construction site, and the base concrete and the ice blocks are mixed in the mixer during transportation to the construction site.

According to the present invention, in the inspection process, in the first mixing process, it is possible to check whether the base concrete satisfies the predetermined physical property values. Therefore, by inspecting the base concrete, it is possible to predict with greater accuracy in advance the properties of the concrete when a pre-measured weight of ice blocks is added to the base concrete and mixed during subsequent transportation to the construction site. This makes it possible to supply concrete of more stable quality.

Furthermore, in the present invention, base concrete that has been determined to satisfy the predetermined physical property values in the inspection process is loaded into the mixer of the agitator vehicle before departure from the manufacturing plant and arrival at the construction site, and ice blocks are further loaded into this mixer, for example, by human power. The weight (total weight) of the loaded ice blocks is a weight according to the difference in water volume between the unit water volume of the concrete to be cast at the construction site and the unit water volume of the base concrete. By loading the ice blocks, ice blocks are present in the agitator vehicle along with the base concrete during transportation from the manufacturing plant to the construction site. Therefore, the agitator vehicle can produce concrete (concrete after the ice blocks have completely melted (final mix concrete)) from the base concrete while melting the ice blocks in a state cooled by the ice blocks, and transport it to the construction site. As a result, concrete can be supplied (unloaded) to the construction site at a lower temperature than concrete not produced using ice blocks, without adding new equipment to the agitator vehicle or incurring equipment costs at the manufacturing plant.

In a more preferred embodiment, a standard concrete with a smaller slump value than the slump value of the concrete is selected from among standard concretes of different mixes possessed by the manufacturing plant, and the unit water content of the base concrete is set so that the slump value of the base concrete becomes the slump value of the selected standard concrete. According to this embodiment, the unit water content of the base concrete is determined by referring to the mix of the standard concrete possessed by the manufacturing plant, so that the physical properties of the base concrete can be inspected in the inspection process while referring to the physical properties of the standard concrete.

Here, as long as ice blocks remain inside the agitator vehicle during transport from the manufacturing plant to the construction site, there is no particular limitation, but in a more preferred embodiment, the method includes a setting step of estimating the elapsed time from the time when the ice blocks are put into the mixer until the agitator vehicle arrives at the construction site, before the first kneading step, and setting the weight of the ice blocks to be put in according to the elapsed time.

According to this aspect, the weight of ice blocks to be added is set according to the time elapsed from the manufacturing plant until the agitator truck arrives at the construction site, so the temperature of the concrete when the agitator truck is unloaded at the construction site can be easily adjusted to a predetermined temperature.

Here, if the ice blocks are completely melted when the concrete is poured, ice blocks may remain when the agitator vehicle arrives at the construction site. However, in an even more preferred embodiment, in the setting step, the weight of the ice blocks to be poured is set so that the ice blocks do not remain when the agitator vehicle arrives at the construction site. According to this embodiment, since there are no ice blocks remaining when the vehicle arrives at the construction site, the concrete can be poured quickly at the construction site. In addition, since the agitator vehicle can depart the manufacturing plant without waiting for the ice blocks to melt completely, the concrete manufacturing time can be shortened. In addition, in this specification, "no ice blocks remain" means that no ice blocks remain in the form of ice blocks, and includes not only a state in which the ice blocks have melted completely, but also a state in which a small amount of ice particles are present.

Here, all ice blocks may be loaded into the agitator vehicle before it leaves the manufacturing plant, but in a more preferred embodiment, in the second mixing process, a number of divisions is set for dividing the weight of the ice blocks to be loaded, and multiple input points for the ice blocks according to the set number of divisions are set on the route from the manufacturing plant to the construction site, and the divided weight of the ice blocks is loaded into the mixer of the agitator vehicle at each of the set input points.

According to this embodiment, even if one batch of ice blocks melts completely on the way from the manufacturing plant to the construction site, the temperature of the concrete being mixed will not increase and the concrete will remain cooled for a certain period of time. Furthermore, by adding subsequent batches of ice blocks to the mixer at appropriate times at the set addition point, the concrete can be kept cooled for a longer period of time.

Here, the size (ice diameter) of the ice blocks to be fed is not particularly limited, but in a more preferred embodiment, prior to the first mixing step, the elapsed time from the time the ice blocks are fed into the mixer until the agitator vehicle arrives at the construction site is estimated, and in the second mixing step, ice blocks with larger diameters are fed as the elapsed time becomes longer.

According to this aspect, the longer the estimated elapsed time, the easier the ice blocks will melt, but ice blocks with a larger diameter have a larger specific surface area than ice blocks with a smaller diameter, so the added ice blocks are less likely to melt. This allows the ice blocks to maintain the cooling state of the concrete for a longer period of time, even if the elapsed time is long. Note that "adding ice blocks with a larger diameter as the elapsed time increases" does not only mean adding ice blocks with a larger diameter as the elapsed time increases, but also includes adding ice blocks that contain a predetermined ratio of larger diameter ice blocks to the total ice blocks added.

According to the present invention, the temperature of concrete when unloaded from the agitator truck that arrives at the construction site does not exceed the acceptable limit, and concrete of more stable quality can be supplied to the construction site more cheaply without incurring the equipment costs of a concrete manufacturing plant.

FIG. 2 is a flow diagram for explaining a method for producing concrete according to the present embodiment. FIG. 2 is a conceptual diagram showing a method for producing the concrete shown in FIG. 1. FIG. 3 is a conceptual diagram showing a modified example of the concrete manufacturing method shown in FIG. 2 . 1 is a schematic graph showing the timing of adding ice blocks and the change in temperature of concrete.

One embodiment of the concrete manufacturing method according to the present invention will now be described in detail with reference to the drawings. FIG. 1 is a flow diagram for explaining the concrete manufacturing method according to this embodiment. FIG. 2 is a conceptual diagram that shows a typical example of the concrete manufacturing method shown in FIG. 1. FIG. 3 is a conceptual diagram that shows a modified example of the concrete manufacturing method shown in FIG. 2. FIG. 4 is a schematic graph showing the timing of adding ice blocks and the change in concrete temperature.

The method for producing concrete according to this embodiment involves mixing cement C, aggregate B, water W, and admixture AD. During mixing, ice blocks F are mixed in place of some of the water, and concrete A2 is produced while the ice blocks F melt. The method for producing concrete A2 according to this embodiment will be explained according to the flow shown in Figure 1 below.

First, in step S11, the mix proportions of concrete A2 and the amount of ice blocks F to be added, which will be described later, are set. This step S11 corresponds to the "setting process." First, the target slump value of concrete A2 to be poured at the construction site G is set, and the weights of each material, such as cement C, aggregate B, admixture AD, and water W, are set to a mix (unit amount) that corresponds to this target slump value.

In this embodiment, the cement C of the concrete A2 to be set is Portland cement, mixed cement, etc., the aggregate B is composed of fine aggregate S and coarse aggregate H, and the admixture AD is a chemical admixture for concrete as specified by JIS A 6204.

For example, the nominal strength of concrete A2 is set to 33 N/ ^mm2 , the target slump value is set to 21 cm, and the mix proportion of concrete A2 is set according to this target slump value. In this case, as shown in Table 1, the mix proportion of concrete A2 is set as follows: the unit amount of cement C is set to 394 kg/ ^m3 , the unit amount of fine aggregate S is set to 809 kg/ ^m3 , the unit amount of coarse aggregate H is set to 869 kg/ ^m3 , the unit amount of admixture AD is set to 3.86 kg/ ^m3 , and the unit amount (unit water amount) of water W is set to 185 kg/ ^m3 . In Table 1 below, the target slump value *1 of base concrete A1 is a value determined by test mixing. In Table 1 below, the unit amount of admixture *2 of base concrete A1 is a value determined by test mixing. However, if the target slump value is not obtained when the ice block F has completely melted, admixture may be re-added to the concrete in the mixer 11 of the agitator truck 10 at the construction site G.

First, before step S11, the mix proportions of concrete A2 (final mix concrete) in which the ice blocks F have completely melted (i.e. completely dissolved) are set. Next, in step S11, the amount of ice blocks F to be added, which will be described later, is set. Specifically, first, the mix proportions of base concrete A1 are determined to be smaller than the target slump value of concrete A1. At this time, a test mix of base concrete A1 is performed, and physical property values such as values corresponding to *1 and *2 in Table 1 are determined. Using the values obtained in this way as standards, pre-shipment inspection of base concrete A1 in step S13, which will be described later, can be performed.

In this embodiment, the base concrete A1 is a mixture of cement C, aggregate B, admixture AD, and water W, with a composition similar to that of the standard concrete B1 managed at the manufacturing plant A. Specifically, among the standard concretes B1 with different compositions possessed by the manufacturing plant A, a standard concrete B1 with a target slump value smaller than the target slump value of concrete A2 is selected. Next, the unit water content of the base concrete A1 is set so that the target slump value of the base concrete A1 becomes the target slump value of the selected standard concrete B1, and so that the fresh properties of the base concrete A1 are similar to the fresh properties of the standard concrete B1. The slump value of the base concrete A1 obtained by setting the unit water content in this way is smaller than the slump value of concrete A2, the unit water content of the base concrete A1 is smaller than the unit water content of concrete A2, and the fresh properties of the base concrete A1 are similar to the fresh properties of the standard concrete B1. Next, the weight of the ice block F is set to a weight corresponding to the difference in water volume between the unit water volume of concrete A2 and the unit water volume of base concrete A1.

In the example shown in Table 1, the set target slump value of concrete A2 is 21 cm, while the target slump values of standard concrete B1 and base concrete A1 are 8 cm, and the target slump value of base concrete A1 is smaller than the target slump value of concrete A2. Since the unit water amount of concrete A2 is set to 185 kg/ ^m3 and the unit water amount of base concrete A1 is set to 165 kg/ ^m3 , the unit amount of ice blocks F is 20 kg/ ^m3 , and the weight of ice blocks F is set according to this unit amount of ice blocks F.

The mix proportions managed at manufacturing plant A are those of standard concrete B1 shown in Table 1, and the mix proportions of base concrete A1 are close to those of standard concrete B1. After the production of base concrete A1, which will be described later, base concrete A1 can be inspected by fresh concrete testing to ensure that it satisfies the physical property values determined in the test mix of base concrete A1, as described above.

The following describes the setting of the weight of the ice blocks F. When concrete A1 is manufactured at manufacturing plant A, the temperature is likely to rise during transport from manufacturing plant A to construction site G. Therefore, in this embodiment, concrete A2 is manufactured from base concrete A1 while melting ice blocks F that have been put into mixer 11 during transport of concrete A2 from manufacturing plant A to construction site G, as described below.

In this embodiment, in step S11, before step S12, the elapsed time from the timing when ice blocks F are put into the mixer 11 of the agitator vehicle 10 described later until the agitator vehicle 10 arrives at the construction site G is estimated, and the weight of ice blocks F to be put in is set according to the elapsed time. Specifically, the weight of ice blocks F to be put in is increased as the elapsed time increases. This allows the temperature of the concrete A2 when it arrives at the construction site G to be adjusted to a predetermined temperature. At this time, the weight of ice blocks F to be put in may be set by further taking into account the outside air temperature of the manufacturing plant A or the area including the construction site G on the day of transportation. In this case, the temperature of concrete A2 at which it is desired to supply to the construction site G is set by how many degrees lower than the temperature of the concrete at the time of unloading that is expected in advance, and the weight of ice blocks F to be put in is set based on the amount of temperature reduction relative to the outside air temperature and the elapsed time.

The weight of ice blocks F to be poured can be easily calculated based on the temperature and specific heat of each material that makes up concrete A2, experimental results, etc. For example, it is known that lowering the temperature of aggregate B by 2°C will lower the temperature of concrete A2 by approximately 2°C, and lowering the temperature of water W by 4°C will lower the temperature of concrete A2 by approximately 1°C, so it can be calculated using these results and general heat capacity calculations. Additionally, the weight of ice blocks F to be poured can also be determined based on the actual temperature rise of the concrete from manufacturing plant A to construction site G.

Furthermore, in this embodiment, in step S11, the weight of the ice blocks F to be poured is set so that none of the poured ice blocks F remain until the concrete A2 arrives at the construction site G. This allows the concrete A2 to be used promptly at the construction site G, since no ice blocks F remain when the concrete A2 arrives at the construction site G.

Furthermore, the mix ratio of base concrete A1 can be set based on the unit water content with the smallest slump value among the standard concrete B1 managed (i.e., available for shipment) at manufacturing plant A, and the weight of ice blocks F to be added can be set from the mix ratio of base concrete A1. This makes it possible to maintain the quality of base concrete A1 while fully exerting the cooling effect of adding ice blocks F.

Next, in step S12, water W corresponding to the unit water volume of base concrete A1 is mixed with cement C, aggregate B, and admixture AD corresponding to the unit amount of concrete A2 to produce base concrete A1. This step is the "first mixing step" of the present invention. When mixing by the mixing device 20 is completed, the process proceeds to step S13.

Next, in step S13, the manufactured base concrete A1 is put into the mixer 11 of the agitator vehicle 10, and a fresh concrete test (pre-shipment inspection) is performed on the base concrete A1 discharged from the agitator vehicle 10. In this fresh concrete test, the base concrete A1 is inspected to see if it satisfies predetermined physical property values that have been set in advance. This process is the "inspection process" of the present invention. Here, it is inspected to see if the physical property values of the base concrete A1 satisfy the standards determined by test mixing at the manufacturing plant A.

In this fresh concrete test, a slump test (JIS A 1101), or a slump flow test, an air content test (for example, JIS A 1128), and concrete temperature measurements are performed to check whether these values satisfy predetermined physical property values. Here, the predetermined physical property values may be the physical property values of concrete B1 manufactured in manufacturing plant A and whose quality is controlled. If base concrete A1 satisfies the predetermined physical property values, the process proceeds to step S14, and if it does not satisfy the standard physical property values, the process returns to step S12 and base concrete A1 is manufactured again.

In step S13, a fresh concrete test can be performed to check whether the mixed base concrete A1 meets the required physical properties. By inspecting the base concrete A1, it is possible to predict in advance the properties of the concrete when a pre-measured weight of ice blocks F is added to and mixed with the base concrete A1 during subsequent transportation to the construction site G.

In step S14, the agitator vehicle 10 is moved to the location where the ice blocks F are to be added, and in step S15 the weight of the ice blocks F to be added is inspected, and in step S16 the inspected weight of the ice blocks F is added. This makes it possible to determine whether an optimal amount of water (reference weight) has been added. If the weight of the ice blocks F to be added is the weight of the ice blocks F set in step S11, the process proceeds to step S16, and if the weight of the ice blocks F added is significantly different from the set weight of the ice blocks F, the process returns to step S12 and the base concrete A1 is manufactured again.

In step S17, the agitator vehicle 10 is departed from the manufacturing plant A, and the ice blocks F are melted while being mixed into the base concrete A1, and the agitator vehicle 10 is transported from the manufacturing plant A to the construction site G. In step S18, the agitator vehicle 10 arrives at the construction site G.

In this embodiment, in step S16, ice blocks F are loaded into the mixer 11 of the agitator vehicle 10 before departure from the manufacturing plant A. However, for example, an input point for ice blocks F may be set between departure from the manufacturing plant A and arrival at the construction site G, that is, on the route from the manufacturing plant A to the construction site G, and ice blocks F may be loaded into the mixer 11 of the agitator vehicle 10 at this input point.

Furthermore, as shown in FIG. 3, the number of divisions by which the weight of ice blocks F is to be input is set (three divisions in FIG. 3), and multiple input points T1, T2, and T3 for ice blocks F according to the set number of divisions are set on the route from the manufacturing plant A to the construction site G, and the divided weights of ice blocks F are input into the mixer 11 of the agitator vehicle 10 at the set input points T1, T2, and T3. In this embodiment, point T1 is the manufacturing plant A, and points T2 and T3 are supply stations R1 and R2. Note that in FIG. 3, supply stations R1 and R2 are inside a building, but supply stations R1 and R2 may be outdoors. In addition, during transportation, admixture AD may be re-added to the concrete in the mixer 11 of the agitator vehicle 10 as necessary.

As shown in FIG. 4, even if one batch of ice blocks F melts completely on the route from the manufacturing plant A to the construction site G, the temperature of the concrete being mixed does not increase and the concrete is temporarily kept in a cooled state. Furthermore, the second and subsequent batches of ice blocks F can be added to the mixer 11 at appropriate times at the set addition points T2 and T3, allowing the concrete to maintain a cooled state for a longer period of time.

Furthermore, the size (ice diameter) of the ice blocks F to be poured is not particularly limited as long as it can be cooled while producing the concrete A2, but for example, the ice diameter is about 2 to 4 cm, and the shape is not particularly limited, such as a rectangular parallelepiped or spherical shape. Here, as a more preferred embodiment, ice blocks F with larger ice diameters are poured as the elapsed time from the time when the ice blocks F are poured into the mixer 11 to the time when the agitator vehicle 10 arrives at the construction site G increases. In this case, the ice diameter of all ice blocks F may be increased as the elapsed time increases, but the ice diameter of a predetermined proportion (proportion of the weight of the ice blocks F) of ice blocks F may also be increased. Here, the ice diameter of the ice blocks F may be set, for example, based on the maximum length of the ice blocks F.

As time passes, the ice blocks F tend to melt more easily, but ice blocks F with larger diameters have a larger specific surface area than ice blocks F with smaller diameters, so the ice blocks F that are poured in are less likely to melt. This allows the ice blocks F to keep the concrete A2 cooled for a longer period of time, even if the transportation time is long.

In step S19, a fresh concrete test (acceptance inspection) is performed on the concrete (final mix concrete) A2 discharged from the agitator truck 10 at the construction site G. In this fresh concrete test, the concrete A2 is inspected to see if it satisfies the predetermined physical property values that have been set in advance.

In addition to the above tests, this fresh concrete test also includes a chloride ion concentration test. At this time, it is visually confirmed that no ice blocks F remain in the concrete A2. If the concrete A2 satisfies the specified physical properties, the process proceeds to step S20, where the concrete A2 is poured. On the other hand, if the concrete A2 does not satisfy the specified physical properties, the concrete A2 is discarded.

According to this embodiment, before the agitator truck 10, which has been charged with base concrete A1 that has been determined to satisfy the predetermined physical property values, departs from the manufacturing plant A and arrives at the construction site G, ice blocks F of a weight corresponding to the difference in water volume between the unit water volume of concrete A2 and the unit water volume of base concrete A1 are charged into the agitator truck 10. After the ice blocks F are charged, the base concrete A1 and the ice blocks F are mixed and transported to the construction site G by the agitator truck 10.

As a result, ice blocks F are present on the agitator vehicle 10 during transport from the manufacturing plant A to the construction site G. Therefore, while being cooled by the ice blocks F, the agitator vehicle 10 can produce concrete A2 from the base concrete A1 while melting the ice blocks F, and transport the concrete A2 to the construction site G. As a result, without adding new equipment to the agitator vehicle 10 and without incurring equipment costs at the manufacturing plant A, the concrete A2 can be unloaded at the construction site G at a lower temperature than concrete not produced using ice blocks F, and concrete A2 of more stable quality can be poured.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various design changes can be made without departing from the spirit of the present invention described in the claims.

A1: base concrete, A2: concrete, A: manufacturing plant, C: cement, B: aggregate, AD: admixture, F: ice block, G: construction site, W: water, 10: agitator vehicle, 20: kneading device

Claims (3)

A method for producing concrete by mixing cement, aggregate, admixtures, and water, comprising the steps of:
A first mixing step of mixing the cement, the aggregate, and the admixture with water corresponding to a unit water amount less than the unit water amount of the concrete in the concrete manufacturing plant to produce a base concrete;
An inspection step of inspecting whether the base concrete satisfies predetermined physical property values by performing a first fresh concrete test on the base concrete after the first kneading step;
a second mixing step of adding ice blocks having a weight corresponding to the difference in water volume between the unit water volume of the concrete and the unit water volume of the base concrete to a mixer of an agitator vehicle into which the base concrete determined to satisfy the predetermined physical property values was added after the inspection step, between before departure from the manufacturing plant and arrival at the construction site, and mixing the base concrete and the ice blocks in the mixer during transportation to the construction site;
After the second mixing step, a second fresh concrete test is performed on the concrete produced by the mixer from the base concrete and the ice blocks at the construction site to inspect whether the concrete satisfies predetermined physical property values.
Prior to the first mixing step, a standard concrete having a slump value smaller than the slump value of the concrete is selected from among standard concretes of different compositions possessed by the manufacturing plant, and the unit water content of the base concrete is set so that the slump value of the base concrete becomes the slump value of the selected standard concrete;
A method for manufacturing concrete, characterized in that in the second mixing process, a number of divisions into which the weight of the ice blocks to be charged is divided is set, a plurality of input points for the ice blocks according to the set number of divisions are set on the route from the manufacturing plant to the construction site, and a divided weight of the ice blocks is charged into the mixer of the agitator vehicle at each of the set input points. The method for producing concrete according to claim 1, further comprising a setting step of estimating the time elapsed from the time the ice blocks are put into the mixer until the agitator vehicle arrives at the construction site before the first mixing step, and setting the weight of the ice blocks to be put in according to the elapsed time. Before the first kneading step, an elapsed time from the time when the ice blocks are put into the mixer until the time when the agitator vehicle arrives at the construction site is estimated;
3. The method for producing concrete according to claim 1, wherein in the second mixing step, ice blocks having a larger diameter are added as the elapsed time becomes longer.