JP2014213479A - Water for concrete production, and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide water for concrete production with which superior freshly mixed concrete can be obtained, the water for concrete production using a concrete recovery water as a raw material, and to provide a method of producing the same.SOLUTION: Water for concrete production is used that: is obtained by injecting gas containing carbon dioxide while stirring concrete recovery water; and has a concentration of dissolved calcium ions of 700-1,000 ppm. Also, a method of producing the water for concrete production includes a stirring injection process of injecting gas containing the carbon dioxide while stirring the concrete recovered water. In the stirring injection process, the stirring and the gas injection are carried out so that the concentration of the dissolved calcium ions becomes 700-1,000 ppm.

Description

  The present invention relates to concrete production water and a method for producing concrete production water.

  In a ready-mixed concrete factory, a concrete product factory, and the like, a large amount of sewage containing cement and aggregate is generated by washing a mixer truck.

  Conventionally, as processing of this wastewater, the aggregate part was separated and recovered, and the concrete recovered water which is the remaining residue was sometimes reused as kneaded water. Further, the cement content was further separated and removed to obtain sludge water containing no solid content, and then neutralized with an acid and discharged.

  However, if the aggregate part is separated and recovered, and the concrete recovered water containing cement is reused as kneaded water, the workability of the resulting ready-mixed concrete will be reduced, or the ready-mixed concrete will be solidified. There were drawbacks, such as reducing the strength of concrete. In addition, the method of neutralizing sludge water from which cement has been removed and discharging it has the disadvantages of complicated equipment and processes, as well as cost.

  Specific examples of the treatment of sewage include the techniques described in Patent Document 1 and Patent Document 2.

  Patent Document 1 describes a system that treats waste water by guiding boiler exhaust gas to a waste water storage tank for concrete production by a blower and forcibly diffusing it.

In Patent Document 2, exhaust gas containing a CO ₂ gas component, which is also generated in the manufacturing process of ceramic products, is introduced into a wastewater storage tank generated in the manufacturing process of ceramic products, and ejected into the drainage. A wastewater treatment system for ceramic wastewater is described.

Japanese Utility Model Publication No. 7-21194 Japanese Patent Laid-Open No. 10-314758

  According to Patent Document 1, it is disclosed that calcium hydroxide in wastewater becomes calcium carbonate and precipitates, and wastewater that exhibits strong alkalinity is also neutralized and falls within a pH range of 6-7.

According to Patent Document 2, the calcium component, which is an alkaline causative substance contained in ceramic wastewater, can be neutralized with CO ₂ gas, NOx gas, etc. in the exhaust gas, and settled and fixed as calcium carbonate or calcium nitrate. The effect is disclosed.

  Patent Document 1 and Patent Document 2 also describe that the neutralized water is reused.

  However, when neutralized water as described in Patent Document 1 and Patent Document 2 is used as concrete production water, workability and the like of the obtained ready-mixed concrete are reduced, or the ready-mixed concrete is solidified. In some cases, such as the strength of the concrete obtained in this way is insufficient.

  In view of such circumstances, an object of the present invention is to provide concrete production water using concrete recovered water as a raw material, and a method for producing the same, from which excellent ready-mixed concrete can be obtained.

  The concrete production water according to one aspect of the present invention is characterized in that the concentration of dissolved calcium ions obtained by injecting a gas containing carbon dioxide while stirring concrete recovered water is 700 to 1000 ppm. And

  According to such a configuration, as described above, even if it is water for concrete production using concrete recovered water as a raw material, when ready-mixed concrete is produced using this concrete-produced water, ready-made concrete excellent in workability and the like. Can be obtained. That is, it is possible to provide concrete production water using concrete recovered water as a raw material from which excellent ready-mixed concrete can be obtained.

  Moreover, the excellent concrete is obtained by using this ready-mixed concrete.

  Moreover, in the said water for concrete manufacture, it is preferable that pH is 10-11.

  According to such a structure, the water for concrete manufacture which can obtain a more excellent ready-mixed concrete can be provided.

  In the concrete production water, the gas is preferably air.

  According to such a configuration, unlike the exhaust gas or the like, as the gas containing carbon dioxide, air having a stable component is used, so that it is possible to provide concrete production water having stable performance. Moreover, cost can be suppressed rather than using the gas containing only a carbon dioxide as a gas containing a carbon dioxide.

  Moreover, the method for producing water for producing concrete according to another aspect of the present invention includes a stirring and injecting step of injecting a gas containing carbon dioxide while stirring the concrete recovered water, and the stirring and injecting step includes dissolved calcium. The stirring and the gas injection are performed so that the concentration of ions is 700 to 1000 ppm.

  According to such a configuration, it is possible to provide a method for producing concrete production water capable of producing concrete production water capable of obtaining excellent ready-mixed concrete using concrete recovered water as a raw material.

  Moreover, it is a manufacturing method of the said water for concrete manufacture, Comprising: It is preferable that the said stirring injection process is a process which performs the said stirring and injection | pouring of the said gas intermittently every predetermined time.

  According to such a structure, the water for concrete manufacture which can obtain the outstanding ready-mixed concrete can be manufactured efficiently.

  Moreover, it is a manufacturing method of the said water for concrete manufacture, Comprising: It is preferable to further provide the process of removing the solid substance which floats on the said concrete collection | recovery water.

  According to such a structure, the water for concrete manufacture which can obtain the outstanding ready-mixed concrete can be manufactured efficiently.

  Moreover, it is a manufacturing method of the said concrete manufacturing method water, Comprising: It further has the stationary process which leaves the obtained liquid after the said stirring injection | pouring process, and a stationary process is a container which accommodates the said obtained liquid. It is preferable that it is the process of sealing and leaving still.

  According to such a structure, the performance of the water for concrete manufacture which can obtain the outstanding ready-mixed concrete can be maintained suitably, without performing the said stirring and injection | pouring of the said gas.

  ADVANTAGE OF THE INVENTION According to this invention, the water for concrete manufacture using the concrete recovery water as a raw material which can obtain the outstanding ready-mixed concrete, and its manufacturing method can be provided.

It is a figure for demonstrating the method to manufacture the water for concrete manufacture which concerns on embodiment of this invention.

  Hereinafter, although the embodiment concerning the present invention is described, the present invention is not limited to these.

  The concrete production water according to the embodiment of the present invention has a dissolved calcium ion concentration of 700 to 1000 ppm obtained by injecting a gas containing carbon dioxide while stirring the concrete recovered water. Even if such concrete production water is concrete production water obtained from concrete recovered water, excellent concrete can be obtained by producing concrete using this concrete production water. This is considered to be due to the fact that the concentration of dissolved calcium ions is higher than that of concrete recovered water and the stability of the state is high.

  Moreover, when trying to use the supernatant liquid of the concrete recovered water as it is, it is in a state where precipitates containing calcium are likely to be generated, so that excellent ready-mixed concrete cannot be obtained. In addition, when using a supernatant liquid obtained by precipitating the calcium component of the concrete recovered water into calcium carbonate or the like, not only the concentration of dissolved calcium ions is low, but also the interface originally contained in the concrete recovered water. Components such as activators hindered the production of excellent ready-mixed concrete. On the other hand, when the concrete production water according to the present embodiment is used, excellent ready-mixed concrete can be obtained.

  Moreover, even if the water for concrete manufacture which concerns on this embodiment has the high density | concentration of the calcium ion to melt | dissolve, it is thought that the reason which can fully suppress generation | occurrence | production of the precipitate containing calcium is based on the following.

  First, it is considered that calcium hydroxide is dissolved in the concrete recovered water. When a gas containing carbon dioxide is added to the concrete recovered water, the concrete recovered water becomes a cloudy liquid. This is considered to be due to the fact that calcium hydroxide dissolved in the concrete recovered water becomes poorly water-soluble calcium carbonate by carbon dioxide. When the supernatant obtained after the white turbid liquid is allowed to stand is used for the production of concrete, as described above, there are cases where problems such as insufficient strength of the obtained concrete occur. Further, when a gas containing carbon dioxide is further added to the clouded liquid, the liquid becomes transparent. This is considered to be due to the fact that calcium carbonate becomes water-soluble calcium hydrogen carbonate by carbon dioxide.

  And, when adding a gas containing carbon dioxide, it is considered that fine, so-called micro-sized bubbles are maintained in a state where the particle size is highly uniform in the liquid (water for producing concrete) by stirring. It is done. This is considered to be due to the presence of a surfactant such as an air entraining agent (AE agent) originally contained in the concrete recovered water. And it is considered that not only the AE agent but also calcium carbonate and calcium hydrogen carbonate exist at the interface between the micro-sized bubbles and the liquid, and a relatively stable state can be maintained.

  From the above, it is considered that the water for producing concrete according to this embodiment can sufficiently suppress the generation of precipitates containing calcium even when the concentration of dissolved calcium ions is high. Therefore, when this concrete production water is used for the production of concrete, an excellent ready-mixed concrete can be obtained. Moreover, the excellent concrete is obtained by using this ready-mixed concrete. That is, excellent concrete can be obtained by solidifying the ready-mixed concrete. Furthermore, ready-mixed concrete with good workability can be used sufficiently even if the workability is somewhat sacrificed, and the composition such as the mixing ratio of ready-mixed concrete is adjusted according to the concrete usage conditions. Cheap. From this, the ready-mixed concrete obtained using the water for producing concrete according to the present embodiment can provide excellent concrete according to the use condition of the concrete. That is, the concrete production water obtained by injecting a gas containing carbon dioxide while stirring the concrete recovered water and having a dissolved calcium ion concentration of 700 to 1000 ppm can obtain excellent concrete. Water for concrete production.

  In addition, when adding the gas containing a carbon dioxide, even if the liquid obtained without stirring was transparent, a white solid precipitated immediately. This is considered to be an unstable state even if calcium hydrogen carbonate is present in the liquid because the uniformity of the particle size of the bubbles in the liquid is low and the bubbles are not in a stable state. In addition, since an AE agent is not included in a simple calcium bicarbonate aqueous solution, calcium bicarbonate is not present at the interface of the bubbles, so even if calcium bicarbonate is present in the liquid, it is in an unstable state. It is believed that there is.

  As described above, when a gas containing carbon dioxide is added, a liquid obtained without stirring or a simple calcium hydrogen carbonate aqueous solution causes crystal precipitation on the entire interface between the liquid and the container. It can also be seen from the fact that in the concrete production water according to the embodiment, precipitation occurs not from the entire interface between the liquid and the container but from the vicinity of the water surface. It is considered that this is because the bubbles in the concrete production water according to the present embodiment are stable and collapse only near the water surface.

  In addition, when concrete is produced using the water for producing concrete according to this embodiment, the reason why excellent concrete is obtained is not only high calcium ion concentration, but also breathing, which is a phenomenon in which water is pushed out to the concrete surface. Can also be effective. This is considered to be due to the fact that the water for producing concrete according to the present embodiment stably has air bubbles in which the AE agent is present at the interface as described above.

  In addition, the calcium ion density | concentration of the water for concrete manufacture can be measured using a well-known concentration meter, a water quality measuring device, etc., for example.

  Moreover, as for the water for concrete manufacture which concerns on this embodiment, it is preferable that the pH is 10-11. At such a pH, most of the calcium components are calcium bicarbonate, and the state is considered to be stable, so it can be water for concrete production that can provide a better ready-mixed concrete. .

  Moreover, the manufacturing method of the concrete manufacturing water which concerns on this embodiment will not be specifically limited if said concrete manufacturing water can be manufactured. Specifically, the water for concrete production includes a stirring / injecting step of injecting a gas containing carbon dioxide while stirring the concrete recovered water, and the stirring / injecting step has a concentration of dissolved calcium ions of 700. The manufacturing method which performs the said stirring and injection | pouring of the said gas so that it may become -1000 ppm is mentioned. More specifically, the following methods are mentioned.

  In addition, the calcium ion density | concentration of the water for concrete manufacture can be measured using a well-known pH meter, pH test paper, etc., for example.

  FIG. 1 is a diagram for explaining a method for producing water for producing concrete according to the present embodiment. Concrete production water is produced using four tanks 11, 21, 31, 41 as shown in FIG.

  First, as shown in FIG. 1, drainage is supplied from a drainage supply device 15 to the drainage storage tank 11. The waste water supplied into the waste water storage tank 11 is sufficiently stirred by the stirring device 14. Then, it leaves still, the supernatant liquid 12 is supplied to the collection | recovery water tank 21, and the deposit 13 is supplied to the deposit storage tank 41. FIG.

  Here, the drainage refers to the drainage generated by the production of ready-mixed concrete, the use of ready-mixed concrete, etc. For example, separated and recovered water of concrete (residual concrete). Moreover, the supernatant liquid in the drainage storage tank 11 is concrete recovered water from which aggregates and the like are removed from the drainage. In other words, the recovered concrete water contains cement, such as cleaning wastewater from ready-mixed concrete production facilities (ready-mixed concrete factories), cleaning wastewater from agitator cars, and separation / recovery water of unused concrete (residual concrete) The sludge water etc. which are the water which removed the aggregate etc. from the water to do are mentioned.

  Moreover, the drainage storage tank 11 will not be specifically limited if it is a water tank which can store wastewater. The drainage supply device 15 is not particularly limited as long as the drainage can be supplied to the drainage storage tank 11. Moreover, the stirring apparatus 14 will not be specifically limited if it can stir the waste_water | drain stored in the waste water storage tank 11. FIG.

  Next, as shown in FIG. 1, a gas containing carbon dioxide is injected into the concrete recovery water by the gas supply device 25 while stirring the concrete recovery water supplied to the recovery water tank 21 by the stirring device 24. Then, it leaves still, the supernatant liquid 22 is supplied to the water tank 31 for manufacture, and the deposit 23 is supplied to the deposit storage tank 41. FIG. The stirring and gas injection are performed so that the calcium ion concentration of the supernatant liquid 22 supplied to the production water tank 31 is 700 to 1000 ppm. This process corresponds to the stirring injection process. The supernatant liquid 22 is concrete production water. That is, water for concrete production can be produced by this stirring and pouring step.

  Moreover, it is preferable to perform stirring and gas injection so that the pH of the supernatant liquid 22 is 10-11.

  Moreover, it is preferable to perform this stirring and gas injection intermittently every predetermined time. Specifically, for example, it is preferable to repeat the process of performing stirring and gas injection for 1 to 3 hours and then allowing to stand for 20 minutes to 1 hour. By performing intermittently in this way, it can be achieved in a shorter time than when stirring and gas injection are continuously performed so that the calcium ion concentration of the supernatant liquid 22 falls within the above range. That is, the water for concrete production which can obtain the outstanding ready-mixed concrete can be efficiently manufactured by performing stirring and gas injection intermittently every predetermined time.

  Moreover, the recovery water tank 21 will not be specifically limited if it is a water tank which can store concrete recovery water. The gas supply device 25 is not particularly limited as long as it can supply a gas containing carbon dioxide to the recovery water tank 21 and inject the gas into the concrete recovery water stored in the recovery water tank 21. The stirring device 24 is not particularly limited as long as it can stir the concrete recovered water stored in the recovered water tank 21.

  The gas supplied by the gas supply device 25 is not particularly limited as long as it contains carbon dioxide. Examples of the gas include air, a gas composed only of carbon dioxide, and exhaust gas. Among these, air is preferable. Unlike exhaust gas or the like, the gas containing carbon dioxide uses air with a stable component, so that the water for producing concrete has stable performance. Moreover, cost can be suppressed rather than using the gas containing only a carbon dioxide as a gas containing a carbon dioxide.

  In addition, concrete recovered water contains cement, such as cleaning wastewater from ready-mixed concrete production facilities (ready-mixed concrete factories), cleaning wastewater from agitator cars, and separation / recovery water of unused concrete (residual concrete). Sludge water, which is water from which aggregates and the like have been removed from the water to be obtained by the method as described above. Moreover, in the manufacturing method according to the present embodiment, sludge water obtained by another method may be used as concrete recovery water.

  Moreover, it is preferable to remove the solid matter floating in the concrete recovery water stored in the recovery water tank 21. It is preferable to remove solid substances floating in the liquid stored in another water tank. By removing such solid matter, it can be achieved in a shorter time than when the removal is not performed so that the calcium ion concentration of the supernatant liquid 22 falls within the above range. That is, the water for concrete manufacture which can obtain the outstanding ready-mixed concrete can be efficiently manufactured by removing the above solid matter. This is thought to be because the floating solid contains free calcium and the like, and by removing it, the transition to calcium bicarbonate can be further advanced. Further, by removing the solid matter, separation of large floating matters such as fine sand is promoted, and separation of the supernatant liquid 22 and the precipitate 23 is promoted. Also from this, the water for concrete manufacture which can obtain the outstanding ready-mixed concrete can be manufactured efficiently.

  Next, as shown in FIG. 1, a gas containing carbon dioxide is injected into the concrete production water by the gas supply device 35 while stirring the concrete production water supplied to the production water tank 31 by the stirring device 34. Then, when using the concrete production water stored in the production water tank 31, the concrete production water is taken out from the production water tank 31 using the production water suction device 36.

  As described above, in the production water tank 31, as in the case of the recovered water tank 21, the quality of the concrete production water can be maintained by performing the stirring with the stirring device 34 and injecting the gas with the gas supply device 35.

  Moreover, the manufacturing water tank 31 will not be specifically limited if it is a water tank which can store the water for concrete manufacture. The gas supply device 35 is not particularly limited as long as it can supply a gas containing carbon dioxide to the production water tank 31 and inject the gas into the concrete production water stored in the production water tank 31. Moreover, the stirring apparatus 34 will not be specifically limited if it can stir the water for concrete manufacture stored in the water tank 31 for manufacture.

  Moreover, although the water for concrete manufacture obtained at the said stirring injection | pouring process may be stored as mentioned above, it can also be stored by sealing the container which stored the water for concrete manufacture. Thus, by storing in a closed container, the performance of the water for producing concrete can be suitably maintained without performing the stirring and the injection of the gas. That is, the concrete production method water production method further includes a stationary step of allowing the obtained liquid to stand after the stirring and injecting step, and the stationary step seals a container containing the obtained liquid. It is preferable that it is the process of leaving still. By doing so, the performance of the water for concrete manufacture which can obtain the outstanding ready-mixed concrete can be maintained suitably, without performing the said stirring and the injection | pouring of the said gas.

  Finally, as shown in FIG. 1, the precipitate 42 supplied to the precipitate storage tank 41 is stored while being stirred by the stirring device 44. This precipitate may be disposed of by a known method or may be reused.

  The concrete manufacturing water which concerns on this embodiment is concrete manufacturing water which can manufacture the outstanding ready-mixed concrete by setting it as said structure. Moreover, the said manufacturing method can also manufacture the said concrete manufacture water by setting it as said structure.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(Manufacture of concrete production water 1)
First, as the waste water, cleaning waste water of a ready-mixed concrete manufacturing facility (Ready Mixed Concrete Factory) was prepared. Concrete water for concrete production was produced from this washing wastewater by the method for producing water for concrete production shown in FIG. Specifically, the stirring and gas injection were performed so that the calcium ion concentration of the supernatant was 700 to 1000 ppm. At that time, the agitation and gas injection were performed intermittently at predetermined time intervals of 2 hours and then allowed to stand for 30 minutes. Moreover, the solid substance which floats in concrete collection | recovery water was removed as needed. Moreover, the time until the calcium ion concentration of the supernatant liquid reached 700 to 1000 ppm was about 24 hours including the time of the stirring and gas injection and the standing.

  And the calcium ion density | concentration of the obtained water for concrete manufacture was 800 ppm, and pH was 10.5. The calcium ion concentration was measured using a water quality measuring device (pack test manufactured by Kyoritsu Riken Corporation). Moreover, pH was measured using pH test paper (made by Merck Co., Ltd.).

(Manufacture of concrete production water 2)
It is the same as the manufacturing method of the water 1 for concrete manufacture except performing the said stirring and gas injection | pouring continuously.

  The time until the calcium ion concentration of the supernatant became 700 to 1000 ppm, that is, the time for stirring and gas injection was about 72 hours.

  And the calcium ion density | concentration of the obtained water for concrete manufacture was 800 ppm, and pH was 10.5.

(Manufacture of concrete production water 3)
The method is the same as the method for manufacturing the concrete manufacturing water 1 except that the solid matter floating in the concrete recovered water is not removed.

  The time until the calcium ion concentration of the supernatant reached 700 to 1000 ppm was about 48 hours, including the time of stirring and gas injection and the standing.

  And the calcium ion density | concentration of the obtained water for concrete manufacture was 800 ppm, and pH was 10.5.

(Manufacture of concrete recovered water 1)
It is the same as that of the manufacturing method of the water 1 for concrete manufacture except not performing the said stirring and injection | pouring of gas. That is, the obtained liquid is concrete recovered water.

  The calcium ion concentration of this concrete recovered water was 400 ppm, and the pH was 10.5.

  Next, concrete was produced using the above concrete production water and concrete recovered water.

[Example]
First, ready-mixed concrete was manufactured by blending so as to have the following blending composition (mass%).

  12.91% by mass of cement, 42.97% by mass of coarse aggregate (crushed stone), 35.86% by mass of fine aggregate (crushed stone powder and granulated slag), 8.13% by mass of water for concrete production 1, It mixed so that an admixture (AE water reducing agent Floric SV-10 made from Floric Co., Ltd.) might be 0.13 mass%. By doing so, ready-mixed concrete was obtained.

[Comparative Example 1]
It is the same as that of an Example except having used concrete recovery water instead of the water for concrete manufacture.

[Comparative Example 2]
It is the same as that of an Example except having used tap water instead of the water for concrete manufacture. The tap water used had a calcium ion concentration of 10 ppm and a pH of 7.

  Next, using the ready-mixed concrete, it was tested by a known method so that the nominal strength was 21 N and the target slump was 15 cm. Note that the ready-mixed concrete of the above is a standard blend in the above test. Specifically, the following evaluation was performed. The evaluation results are shown in Table 1 below.

(Liquidity)
The fluidity of the obtained ready-mixed concrete was confirmed visually. The fluidity of ready-mixed concrete is one of the indicators of workability on site, and it was evaluated as “◎” if 9-10 out of 10 workers on site were judged to have good fluidity. . Further, if 6 to 8 out of 10 workers on site were judged to have good fluidity, it was evaluated as “◯”. Further, if 3 to 5 out of 10 workers on site were judged to have good fluidity, it was evaluated as “Δ”. If 0 to 2 out of 10 workers on site were judged to have good fluidity, it was evaluated as “x”.

(slump)
The slump evaluation of ready-mixed concrete was performed according to JIS A1101. Specifically, as described above, the height of the slump was measured immediately after the slump was formed. Moreover, the difference (slump difference) of the measured height with respect to 15 cm which is the height of a target slump was evaluated.

  The slump height was evaluated using ready-mixed concrete immediately after manufacture and ready-mixed concrete after 30 minutes from manufacture.

(flow)
The flow evaluation of the ready-mixed concrete was performed according to JIS A1101. Specifically, as described above, the spread of the slump immediately after forming the slump was evaluated as “standard”, “large”, and “small” in accordance with the criteria in JIS A 1101.

(Air volume)
The amount of air in the ready-mixed concrete was measured by a method according to JIS A 1101. The amount of air was evaluated as “standard”, “large”, and “small” in accordance with the criteria in JIS A 1101. Specifically, when the ratio of the volume of air mixed with ready-mixed concrete to the volume of ready-mixed concrete is 4 to 5% by volume, it is evaluated as “standard”. And less than 4% by volume is evaluated as “less”. In Comparative Example 1, the air amount was 6.5% by volume.

(Mixed state)
The mixed state of the obtained ready-mixed concrete was evaluated by the stickiness of ready-made concrete. For example, soft but sticky ready concrete is good ready concrete. The mixed state of ready-mixed concrete was evaluated as “◎” when 9-10 out of 10 workers on site were judged to be in a good mixed state. Further, if 6 to 8 out of 10 workers on site were judged to be in a good mixed state, it was evaluated as “◯”. Moreover, if 3 to 5 out of 10 workers on site were judged to be in a good mixed state, it was evaluated as “Δ”. Moreover, if 0 to 2 out of 10 workers on site were judged to be in a good mixed state, it was evaluated as “x”.

  As described above, soft but sticky ready concrete is good ready concrete. For this reason, this mixed state is more important than the above fluidity for evaluation of ready-mixed concrete.

(Strength)
The strength of the concrete obtained by solidifying the obtained ready-mixed concrete was measured by a method according to JIS A 1108. The amount of air was evaluated as “standard” and “bad” in accordance with the standard in JIS A 1108.

(Comprehensive evaluation)
From the above evaluations, as the evaluation of ready-mixed concrete, those that can be judged to be very good are evaluated as `` ○ '', and those that are inferior to that but can be judged usable are evaluated as `` △ '', The raw concrete that was judged to be difficult to use was evaluated as “×”.

  As can be seen from Table 1, when using concrete production water obtained by injecting a gas containing carbon dioxide while stirring the concrete recovered water, the concentration of dissolved calcium ions is 700 to 1000 ppm ( Example) is excellent in all the above evaluations. Moreover, it turned out that an Example is excellent also compared with the case (comparative example 1 and comparative example 2) when concrete collection water and tap water are used.

  Moreover, the change in the slump height in Comparative Example 1 was greater than in other cases. That is, the ready-mixed concrete according to Comparative Example 1 had a large slump loss. This is considered to be due to the large amount of air in the ready-mixed concrete according to Comparative Example 1. Since the ready-mixed concrete is solidified, it hardens with time. Even in the ready-mixed concrete according to the example, a slump loss of 1 cm was generated. This value suggests that the ready-mixed concrete is sufficiently excellent.

  In addition, ready-mixed concrete with good workability can be used sufficiently even if the workability is somewhat sacrificed, and it is easy to adjust the composition of the ready-mixed concrete, etc., depending on the use of the concrete. Excellent concrete can be obtained according to the situation. From this, it can be said that the ready-mixed concrete according to the example can obtain excellent concrete. That is, the concrete production water obtained by injecting a gas containing carbon dioxide while stirring the concrete recovered water and having a dissolved calcium ion concentration of 700 to 1000 ppm can obtain excellent concrete. Water for concrete production.

DESCRIPTION OF SYMBOLS 11 Wastewater storage tank 12,22 Supernatant liquid 13,23,42 Precipitate 14,24,34,44 Agitation apparatus 15 Wastewater supply apparatus 21 Recovery water tank 25,35 Gas supply apparatus 31 Water tank for manufacture 36 Water suction apparatus for manufacture 41 Precipitate Storage tank

Claims (7)

  Concrete manufacturing water obtained by injecting a gas containing carbon dioxide while stirring concrete recovered water, and having a dissolved calcium ion concentration of 700 to 1000 ppm.   The water for producing concrete according to claim 1, wherein the pH is 10 to 11.   The water for concrete production according to claim 1 or 2, wherein the gas is air. While stirring the concrete recovery water, equipped with a stirring injection step of injecting a gas containing carbon dioxide,
The said stirring and injection process performs the said stirring and injection | pouring of the said gas so that the density | concentration of the calcium ion to melt | dissolve will be 700-1000 ppm, The manufacturing method of the water for concrete manufacture characterized by the above-mentioned.   The method for producing water for producing concrete according to claim 4, wherein the agitation injection step is a step of intermittently injecting the agitation and the gas every predetermined time.   The method for producing water for concrete production according to claim 4 or 5, further comprising a step of removing solid matter floating in the concrete recovery water. After the stirring and injecting step, further comprising a standing step of standing the obtained liquid,
The method for producing water for producing concrete according to any one of claims 4 to 6, wherein the stationary step is a step of sealing and leaving the container containing the obtained liquid.

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